Grain-size analysis of surface sediments, continental margin off NW Africa

The terrigenous fraction of seabed sediments recovered along the north-west African continental margin illustrates spatial variability in grain size attributed to different transport mechanisms. Three subpopulations are determined from the grain-size analyses (n = 78) of the carbonate-free silt fraction applying an end-member modelling algorithm (G. J. Weltje, 1997). The two coarsest end-members are interpreted as representing aeolian dust, and the fine-grained end-member is related to fluvial supply. The end-member model thus allows aeolian fallout to be distinguished from fluvial-sourced mud in this area. The relative contributions of the end-members show distinct regional variations that can be related to different transport processes and pathways. Understanding present-day sediment dispersal and mixing is important for a better understanding of older sedimentary records and palaeoclimate reconstructions in the region.

(Table 1) Stable-isotopes for foraminifers at DSDP Holes 3-16 and 73-519

A stable-isotope stratigraphy was established for planktonic and benthic foraminifers from upper Miocene-lower Pliocene pelagic sediments from the Mid-Atlantic Ridge. A correlation of stable-isotope and biostratigraphic data with magnetostratigraphic age revealed the following: (1) the late Miocene carbon-isotope shift in the South Atlantic bottom waters was minute compared with the shift reported for other deep-sea locations (Haq et al., 1980), (2) a significant cooling or continental ice-volume increase occurred between 5.7 and 5.2 Ma, and (3) a period of warming or ice-volume decrease followed, with the rate of warming increasing beginning at 4.5 Ma and reaching a climax at 4.3 Ma. The timing of these paleoceanographic events is correlated with the onset and termination of the Messinian salinity crisis in the Mediterranean Sea.

Abundance of organic-walled dinoflagellate cysts of sediment core GeoB3603-2

Here, we reconstruct the varying influence of the Agulhas Current (AgC), the South Atlantic Current and the Antarctic Circumpolar Current on the Agulhas Retroflection (AgR) in the eastern South Atlantic Ocean for the last 160,000 years on the basis of the dinoflagellate cysts, pollen and spores present in a sediment core (GeoB 3603-2) from the southeastern Cape Basin offshore South Africa, where the Agulhas Current enters the Atlantic Ocean. Our analyses reveal strong orbital forcing on the heat exchange between the Indian Ocean and the South Atlantic Ocean during the Late Quaternary. Maxima in local productivity appear to be primarily related to a strengthening of the ocean circulation as a result of the high seasonal contrast during precession maxima. During precession minima, seasonal contrast was low and stratified, oligo- to mesotrophic conditions prevailed, notably when these minima coincided with the glacial terminations. The clear presence of periodicities on a sub-Milankovitch scale as well as modulations of the primary frequencies demonstrate that the Agulhas Retroflection furthermore is modulated substantially by complex interactions between the subtropical, 'precession-driven', climate and ocean circulation systems, and the southern, 'obliquity-driven', high latitudes.

(Table 2) Carbonate chemistry and isotopes from northern Cascadia margin samples

Most authigenic carbonates previously recovered from the Cascadia slope have 87Sr/86Sr signatures that reflect shallow precipitation in equilibrium with coeval seawater. There is also evidence for carbonate formation supported by fluids that have been modified by reactions with the incoming Juan de Fuca plate (87Sr/86Sr = 0.7071; Teichert et al., 2005, doi:10.1016/j.epsl.2005.08.002) or with terrigenous turbidites (87Sr/86Sr = 0.70975 to 0.71279; Sample et al., 1993, doi:10.1130/0091-7613(1993)021<0507:CCICFF>2.3.CO;2). We report on the strontium isotopic composition of carbonates and fluids from IODP Site U1329 and nearby Barkley Canyon (offshore Vancouver Island), which have strontium isotope ratios as low as 0.70539. Whereas the strontium and oxygen isotopic compositions of carbonates from paleoseeps in the uplifted Coast Range forearc indicate formation in ambient bottom seawater, several samples from the Pysht/Sooke Fm. show a 87Sr-depleted signal (87Sr/86Sr = 0.70494 and 0.70511) similar to that of the anomalous Site U1329 and Barkley Canyon carbonates. Our data, when analyzed in the context of published elemental and isotopic composition of these carbonates (Joseph et al., 2012, doi:10.1016/j.palaeo.2013.01.012 ), point to two formation mechanisms: 1) shallow precipitation driven by the anaerobic oxidation of methane (AOM) with d13C values as low as -50 per mil and contemporaneous 87Sr/86Sr seawater ratios, and 2) carbonate precipitation driven by fluids that have circulated through the oceanic crust, which are depleted in 87Sr. Carbonates formed from the second mechanism precipitate both at depth and at sites of deep-sourced fluid seepage on the seafloor. The 87Sr-depleted carbonates and pore fluids found at Barkley Canyon represent migration of a deep, exotic fluid similar to that found in high permeability conglomerate layers at 188 mbsf of Site U1329, and which may have fed paleoseeps in the Pysht/Sooke Fm. These exotic fluids likely reflect interaction with the 52-57 Ma igneous Crescent Terrane, which supplies fluids with high calcium, manganese and strontium enriched in the non-radiogenic nucleide. Tectonic compression and dehydration reactions then force these fluids updip, where they pick up the thermogenic hydrocarbons and 13C-enriched dissolved inorganic carbon that are manifested in fluids and carbonates sampled at Barkley Canyon and at Site U1329. The Crescent Terrane may have sourced cold seeps in this margin since at least the late Oligocene.

HDL-C and HDL-C/ApoA-I predict long-term progression of glycemia in established type 2 diabetes

OBJECTIVE: Low HDL cholesterol (HDL-C) and small HDL particle size may directly promote hyperglycemia. We evaluated associations of HDL-C, apolipoprotein A-I (apoA-I), and HDL-C/apoA-I with insulin secretion, insulin resistance, HbA1c, and long-term glycemic deterioration, reflected by initiation of pharmacologic glucose control.

RESEARCH DESIGN AND METHODS: The 5-year Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study followed 9,795 type 2 diabetic subjects. We calculated baseline associations of fasting HDL-C, apoA-I, and HDL-C/apoA-I with HbA1c and, in those not taking exogenous insulin (n = 8,271), with estimated β-cell function (homeostasis model assessment of β-cell function [HOMA-B]) and insulin resistance (HOMA-IR). Among the 2,608 subjects prescribed lifestyle only, Cox proportional hazards analysis evaluated associations of HDL-C, apoA-I, and HDL-C/apoA-I with subsequent initiation of oral hypoglycemic agents (OHAs) or insulin.

RESULTS: Adjusted for age and sex, baseline HDL-C, apoA-I, and HDL-C/apoA-I were inversely associated with HOMA-IR (r = -0.233, -0.134, and -0.230; all P < 0.001; n = 8,271) but not related to HbA1c (all P > 0.05; n = 9,795). ApoA-I was also inversely associated with HOMA-B (r = -0.063; P = 0.002; n = 8,271) adjusted for age, sex, and HOMA-IR. Prospectively, lower baseline HDL-C and HDL-C/apoA-I levels predicted greater uptake (per 1-SD lower: hazard ratio [HR] 1.13 [CI 1.07-1.19], P < 0.001; and HR 1.16 [CI 1.10-1.23], P < 0.001, respectively) and earlier uptake (median 12.9 and 24.0 months, respectively, for quartile 1 vs. quartile 4; both P < 0.01) of OHAs and insulin, with no difference in HbA1c thresholds for initiation (P = 0.87 and P = 0.81). Controlling for HOMA-IR and triglycerides lessened both associations, but HDL-C/apoA-I remained significant.

CONCLUSIONS: HDL-C, apoA-I, and HDL-C/apoA-I were associated with concurrent insulin resistance but not HbA1c. However, lower HDL-C and HDL-C/apoA-I predicted greater and earlier need for pharmacologic glucose control.

El proceso de diseño. En tesis “El taller total, una evaluación formativa”, p. 68-83

Extracto (Parte 1, capítulo 2) de la Tesis Doctoral “El taller total, una evaluación formativa”, Sobresaliente Cum Laude por la Universidad de Sevilla, España 2006 de la Dra. Arq. Graciela Gayetzky de Kuna - Arquitecta (Universidad de Buenos Aires, 1985), Doctora en Educación en Artes Visuales (Universidad de Sevilla, 2006) Diplomada en Estudios Avanzados-Suficiencia Investigativa (Universidad de Sevilla, España, 2003) Magister en Educación por el Arte (Universidad de Misiones, 2002). Profesora titular regular e Investigadora- U.Na.M (Posadas, Argentina); Profesora asociada e investigadora U.C.S.F. (Posadas, Argentina) graciela.kuna@gmail.com -

Przegląd prawodawstwa RPEiS 2, 1922, z. 3

Digitalizacja i deponowanie archiwalnych zeszytów RPEiS sfinansowane przez MNiSW w ramach realizacji umowy nr 541/P-DUN/2016

Procesos hopping a través del modelo difusional en materiales nanocristalinos usados para aplicaciones fotovoltaicas

Se presentan los modelos de hopping de rango variable (variable range hopping; VRH), vecinos cercanos (nearest neighbor hopping; NNH) y barreras de potencial presentes en las fronteras de grano; como mecanismos de transporte eléctrico predominantes en los materiales semiconductores para aplicaciones fotovoltaicas. Las medidas de conductividad a oscuras en función de temperatura fueron realizadas para región de bajas temperaturas entre 120 y 400 K con Si y compuestos Cu3BiS2 y Cu2ZnSnSe4. Siguiendo la teoría de percolación, se obtuvieron parámetros hopping y la densidad de estados cerca del nivel de Fermi, N(EF), para todas las muestras. A partir de los planteamientos dados por Mott para VRH, se presentó el modelo difusional, que permitió establecer la relación entre la conductividad y la densidad de estados de defecto o estados localizados en el gap del material. El análisis comparativo entre modelos, evidenció, que es posible obtener mejora hasta de un orden de magnitud en valores para cada uno de los parámetros hopping que caracterizan el material.