Solar generated quasi-biennial geomagnetic variation

The existence of highly correlated quasi-biennial variations in the geomagnetic field and in solar activity is demonstrated. The analysis uses a numerical filter technique applied to monthly averages of the geomagnetic horizontal component and of the Zurich relative sunspot number. Striking correlations are found between the quasi-biennial geomagnetic variations determined from several magnetic observatories located at widely different longitudes, indicating a worldwide nature of the obtained variation. The correlation coefficient between the filtered Dst index and the filtered relative sunspot number is found to be -0.79 at confidence level greater than 99% with a time-lag of 4 months, with solar activity preceding the Dst variation. The correlation between the unfiltered data of Dst and of the sunspot number is also high with a similar time-lag. Such a timelag has not been discussed in the literature, and a further study is required to establish the mode of sun-earth relationship that gives this time delay

Negotiating employability: migrant capitals and networking strategies for Zimbabwean highly skilled migrants in the UK

In this paper we focus on highly skilled migration from Zimbabwe to the UK, exploring these migrants’ social capital sources/structures and content. In doing so we pay attention to routes of migration and how they shape migrants’ networking capabilities and patterns. We further take a Bourdieusian perspective and explore the intersection between social capital and cultural capital in the process of migrants’ negotiation of employment opportunities, giving closer attention to how the distinctive habitus associated with being highly skilled migrants from Zimbabwe shape migrants’ attitudes towards work. By exploring the interplay between external processes and internalised structures, we bring to the fore the multiple positioning of our participants, who we see not as simply depending on social networks, but as complex actors whose negotiation of employability in the UK is shaped by various factors including intersecting aspects of differentiation

Hydrothermal dolomitization of basinal deposits controlled by a synsedimentary fault system in Triassic extensional setting, Hungary

Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow

Sustained Large-Amplitude Chemomechanical Oscillations Induced by the Landolt Clock Reaction

International audienceSynergetic chemomechanical oscillators represent a fundamentally new class of oscillators, where a clock reaction, owning no oscillatory chemical kinetics, generates shrinking−swelling cycles in a chemoresponsive gel under appropriate fixed nonequilibrium boundary conditions. Sufficiently large size-changes are a condition for continually switching between a reacted and an unreacted chemical state in the gel through sufficiently large differences in the diffusion time between the environment and the core of the gel. Two former experimental demonstrations with acid autocatalytic reactions were frustrated either by complex behaviors (chlorite−tetrathionate system) or by side reactions with the gel matrix (bromate−sulfite system)....

Migrant networks and integration: The transatlantic field of communication of German immigrant families in the US

Basierend auf einer Sammlung von 1000 Briefen deutscher Auswanderer in den USA analysiert dieser Aufsatz die Entwicklung und Bedeutung transatlantischer und deutsch-amerikanischer migrantischer Netzwerke über einen Zeitraum von 150 Jahren. Wir unterscheiden zwischen „starken“ und „schwachen“ Beziehungen, die diesen Netzwerken zugrunde liegen, und untersuchen die politischen Faktoren, die die verschiedenen Formen von Netzwerken prägen. Unsere Studie konzentriert sich auf die Schnittstellen zwischen den transatlantischen und deutsch-amerikanischen migrantischen Netzwerken. Sie kontrastiert dabei Elemente des 19. Jahrhunderts, ein Zeitalter dichter migrantischer Netzwerke, die sich weitestgehend ohne staatliche Einwirkung entfalteten, mit der schrittweisen Auflösung und geringeren Verbindlichkeit deutsch-amerikanischer und transatlantischer Netzwerke im 20. Jahrhundert. Die Bandbreite der bisher nur punktuell erforschten Auswandererbriefe veranschaulicht sowohl die Diversität von Integrationserfahrungen als auch die Gleichzeitigkeit von kultureller Anbindung ans Heimatland und wirtschaftlicher und gesellschaftlicher Integration in den USA über einen langen Zeitraum hinweg