Basement-cover relations and internal structure of the Cape Smith klippe: A 1.9 Ga greenstone belt in northern Quebec, Canada

The Cape Smith Belt is a 380x60 km tectonic klippe composed of greenschistto amphibolite-grade mafic and komatiitic lava flows and fine-grained quartzose sediment, intruded by minor syn- to post-tectonic granitoids. Previously studied transects in areas of relatively high structural level show that the belt is constructed of seven or more north-dipping thrust sheets which verge toward the Superior Province (Archean) foreland in the south and away from an Archean basement massif (Kovik Antiform) external to the Trans-Hudson Orogen (Early Proterozoic) in the north. A field project (mapping and structural-stratigraphic-metamorphic studies) directed by MRS was begun in 1985 aimed at the structurally deeper levels of the belt and underlying basement, which are superby exposed in oblique cross-section (12 km minimum structural relief) at the west-plunging eastern end of the belt. Mapping now complete of the eastern end of the belt confirms that all of the metavolcanic and most of the metasedimentary rocks are allochthonous with respect to the Archean basement, and that the thrusts must have been rooted north of Kovik Antiform. The main findings follow

Optimizing the Optoelectronic Properties of Conjugated Polymers Through Metal-Ligand Coordination

From the phones at our fingertips to the solar panels on our roofs, humans are becoming increasingly dependent on electronics for information, entertainment, and to power their daily lives. Further advancements are paving the way for a new age of high-performance, flexible devices. Organic electronics made from conjugated semiconducting polymers are showing great potential as a softer and more processable material than brittle silicon used in today’s devices, while exhibiting comparable charge transport to silicon. However, one key challenge with these organic polymers is the difficulty to control their optical properties and charge transport in devices. Electronics must interact with and alter their lighting while efficiently conducting electricity. Therefore, the desired material must be tuneable to precisely control these important properties. In this research, a novel organic diketopyrrolopyrrole-based conjugated polymer is presented as a leading candidate for optoelectronics. This polymer uses noncovalent metal-ligand interactions, enabled by using specific terpyridine ligands, to fine-tune its ability to emit light and transport electrons. Various transition metal ions, including Fe2+, Co2+, Zn2+, and Mn2+, were introduced into the polymer to determine which species would coordinate most efficiently with the ligand, altering its optical nature. Results from fluorescence and absorption spectroscopies showed that the manganese ion coordinated the weakest to the ligand, while iron and cobalt ions bound the most efficiently and optimally altered emission intensity. Thus, iron and cobalt were identified as great candidates for metal-ligand coordination within the polymer for optimal optoelectronic capabilities. These findings contribute to the continued pursuit of creating efficient organic optoelectronics through the promising technique of metal-ligand interactions. Keywords: organic electronics, conjugated polymer, optoelectronics, metal-ligand interaction

Influence of the n-p asymmetry on decay properties of palladium isotopes

The INDRA 4 π-array was coupled with the high acceptance spectrometer VAMOS to study the decay of palladium isotopes with a large range of N/Z = 1–1.26, produced in the 34,36,40Ar + 58,60,64Ni reactions at E/A = 13 .3MeV. The coupling of both apparatuses gives the opportunity to detect complete events with light charged particles identified in INDRA and the compound nucleus residue in VAMOS. The detailed studies of this experiment put constraints on the N/Z effects in the statistical models

Crustal-Lithospheric structure, geological evolution and continental extrusion of Tibet

Abstract HKT-ISTP 2013 A

Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question

Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a ∆ R of 140 ± 30 14C years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25 are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full ice-shelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; ∆ R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge. At the end of HS1, IP25, brassicasterol and benthic forams indicative of sea-ice edge productivity increase, indicating warming interstadial conditions. Within the Bølling/Allerød interstadial a strong rise in IP25 content and IRD spikes rich in detrital carbonate from northern Baffin Bay indicate that northern Baffin Bay ice streams were retreating and provides evidence for increased open water, advection of Atlantic Water in the West Greenland Current, and formation of an IRD belt along the W. Greenland margin

Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective from Kane Basin

A radiocarbon-dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that provide new insight into the evolution of ice sheet configuration in Nares Strait. Proglacial marine sedimentation at the core site initiated ca. 9.0&thinsp;cal&thinsp;ka&thinsp;BP following the retreat of grounded ice. Varying contributions of sand and clasts suggest unstable sea ice conditions and glacial activity, which subsisted until ca. 7.5&thinsp;cal&thinsp;ka&thinsp;BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. An interval rich in ice-rafted debris (IRD) is interpreted as the collapse of the ice saddle in Kennedy Channel ca. 8.3&thinsp;cal&thinsp;ka&thinsp;BP that marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between ca. 8.3 and ca. 7.5&thinsp;cal&thinsp;ka&thinsp;BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at about 8.1&thinsp;cal&thinsp;ka&thinsp;BP as evidenced by a noticeable change in sediment geochemistry in our core. The gradual decrease in carbonate inputs to Kane Basin between ∼8.1 and ∼4.1&thinsp;cal&thinsp;ka&thinsp;BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Reduced iceberg delivery from 7.5 to 1.9&thinsp;cal&thinsp;ka&thinsp;BP inferred by our dataset may be linked to the retreat of the bordering ice sheets on land that decreased their number of marine termini.</p

Source-sink cooperation dynamics constrain institutional evolution in a group-structured society

Societies change through time, entailing changes in behaviors and institutions. We ask how social change occurs when behaviors and institutions are interdependent. We model a group-structured society in which the transmission of individual behavior occurs in parallel with the selection of group-level institutions. We consider a cooperative behavior that generates collective benefits for groups but does not spread between individuals on its own. Groups exhibit institutions that increase the diffusion of the behavior within the group, but also incur a group cost. Groups adopt institutions in proportion to their fitness. Finally, cooperative behavior may also spread globally. As expected, we find that cooperation and institutions are mutually reinforcing. But the model also generates behavioral source-sink dynamics when cooperation generated in institutional groups spreads to non-institutional groups, boosting their fitness. Consequently, the global diffusion of cooperation creates a pattern of institutional free-riding that limits the evolution of group-beneficial institutions. Our model suggests that, in a group-structured society, large-scale change in behavior and institutions (i.e. social change) can be best achieved when the two remain correlated, such as through the spread successful pilot programs