Fracture and Back Stress Along the Byrd Glacier Flowband on the Ross Ice Shelf

East Antarctic ice discharged by Byrd Glacier continues as a flowband to the calving front of the Ross Ice Shelf. Flow across the grounding line changes from compressive to extensive as it leaves the fjord through the Transantarctic Mountains occupied by Byrd Glacier. Magnitudes of the longitudinal compressive stress that suppress opening of transverse tensile cracks are calculated for the flowband. As compressive back stresses diminish, initial depths and subsequent growth of these cracks, and their spacing, are calculated using theories of elastic and ductile fracture mechanics. Cracks are initially about one millimeter wide, with approximately 30 in depths and 20 in spacings for a back stress of 83 kPa at a distance of 50 kin beyond the fjord, where floating ice is 600 in thick. When these crevasses penetrate the whole ice thickness, they release tabular icebergs 20 kin to 100 kin wide, spaced parallel to the calving front of the Ross Ice Shelf

Monsoonal Circulation of the McMurdo Dry Valleys, Ross Sea Region, Antarctica: Signal from the Snow Chemistry

McMurdo Dry Valleys (MDV, Ross Sea region, Antarctica) precipitation exhibits extreme seasonality in ion concentration, 3-5 orders of magnitude between summer and winter precipitation. To identify aerosol sources and investigate causes for the observed amplitude in concentration variability, four snow pits were sampled along a coast-Polar Plateau transect across the MDV. The elevation of the sites ranges from 50 to 2400 m and the distance from the coast from 8 to 93 km. Average chemistry gradients along the transect indicate that most species have either a predominant marine or terrestrial source in the MDV. Empirical orthogonal function analysis on the snow-chemistry time series shows that at least 57% of aerosol deposition occurs concurrently. A conceptual climate model, based on meteorological observations, is used to explain the strong seasonality in the MDV. Our results suggest that radiative forcing of the ice-free valleys creates a surface low-pressure cell during summer which promotes air-mass flow from the Ross Sea. The associated precipitating air mass is relatively warm, humid and contains a high concentration of aerosols. During winter, the MDV are dominated by air masses draining off the East Antarctic ice sheet, that are characterized by cold, dry and low concentrations of aerosols. The strong differences between these two air-mass sources create in the MDV a polar version of the monsoonal flow, with humid, warm summers and dry, cold winters.

Das Werk als Feige und als Figur. Ambivalenzen der Rezeption zwischen Valéry, Mallarmé, "Tel Quel" und Francis Ponge

L’œuvre poétique de Valéry est caractérisée par une esthétique de la perfection, de la pureté et de la clôture. La série ouverte et hétérogène des "Cahiers", en revanche, ne se laisse guère ranger dans la catégorie de l’œuvre. Selon Valéry, la réorientation intellectuelle à la base de cette opposition est due au "choc" subi par la découverte de l’œuvre mallarméenne. Les divers écrits valéryens sur Mallarmé nous servent à reconstruire cette relation ambivalente et nous aident à éclairer sa conception non moins ambivalente de l’œuvre d’art. Nous soutenons que ce ne sont pas ses propres travaux, mais les poésies de Mallarmé qui lui semblaient des œuvres achevées à proprement parler. Pour décrire l’expérience de perfection et d’achèvement que lui fournit la lecture du "Coup de dés", Valéry se sert de la notion de figure qui, entre autres, comporte des associations géométriques. Sous la forme d’un hommage ambivalent, Francis Ponge oppose aux concepts valéryens de figure et d’œuvre d’art une poétique de l’objet matériel et concret qui s’incarne dans "La figue (sèche)", publiée en 1960 comme pièce inaugurale de la revue "Tel Quel".

Die neue Rose "William Francis Bennett"

von Gebr. Schultheis

The genomic substrate for adaptive radiation in African cichlid fish

Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand the molecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra (recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), and Astatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification.

Sir Francis Montefiore

Theodor Herzl

Rede von Sir Francis Montefiore

Francis Montefiore

Sir Francis Montefiore über die Colonialbank

Francis Montefiore

Rede Sir Francis Montefiores

Francis Montefiore