Archean crust-mantle geochemical differentiation

Isotope measurements on carbonatite complexes and komatiites can provide information on the geochemical character and geochemical evolution of the mantle, including the sub-continental mantle. Measurements on young samples establish the validity of the method. These are based on Sr, Nd and Pb data from the Tertiary-Mesozoic Gorgona komatiite and Sr and Pb data from the Cretaceous Oka carbonatite complex. In both cases the data describe a LIL element-depleted source similar to that observed presently in MORB. Carbonatite data have been used to study the mantle beneath the Superior Province of the Canadian Shield one billion years (1 AE) ago. The framework for this investigation was established by Bell et al., who showed that large areas of the province appear to be underlain by LIL element-depleted mantle (Sr-85/Sr-86=0.7028) at 1 AE ago. Additionally Bell et al. found four complexes to have higher initial Sr ratios (Sr-87/Sr-86=0.7038), which they correlated with less depleted (bulk earth?) mantle sources, or possibly crustal contamination. Pb isotope relationships in four of the complexes have been studied by Bell et al

Metallic Xenon, Molecular Condensates, and Superconductivity

A possibility of explaining the light absorption observed to occur under pressure-induced xenon metallization as due to the transition to the superconducting state is analyzed. The mechanism of the van der Waals bonding is discussed.Comment: LaTeX 2.09 (RevTeX), 4 pages, 4 PostScript figures included in tex

Decay Constants of K40 as Determined by the Radiogenic Argon Content of Potassium Minerals

It is shown that the potassium-argon age of young minerals depends almost linearly on the decay constant for electron capture in K40 and is very insensitive to the decay constant for beta emission. This fact permits calculation of λe by comparing the concordant uranium-lead age of cogenetic uraninite with A40/K40 ratios found in young samples of mica. It is found that λe=(0.557±0.026)×10^-10 yr^-1. Similar comparisons with older mica samples indicate that satisfactory agreement with the uraninite ages are obtained by use of this value of λe together with λβ=(0.472±0.05)×10^-9 yr^-1. It is concluded that there is no conflict between the decay constants inferred by this geological method and those found by direct counting experiments

Roles of IL-6-gp130 Signaling in Vascular Inflammation

Interleukin-6 (IL-6) is a well-established, independent indicator of multiple distinct types of cardiovascular disease and all-cause mortality. In this review, we present current understanding of the multiple roles that IL-6 and its signaling pathways through glycoprotein 130 (gp130) play in cardiovascular homeostasis. IL-6 is highly inducible in vascular tissues through the actions of the angiotensin II (Ang II) peptide, where it acts in a paracrine manner to signal through two distinct mechanisms, the first being a classic membrane receptor initiated pathway and the second, a trans-signaling pathway, being able to induce responses even in tissues lacking the IL-6 receptor. Recent advances and new concepts in how its intracellular signaling pathways operate via the Janus kinase (JAK)-Signal Transducer and Activator of Transcription (STAT) are described. IL-6 has diverse actions in multiple cell types of cardiovascular importance, including endothelial cells, monocytes, platelets, hepatocytes and adipocytes. We discuss central roles of IL-6 in endothelial dysfunction, cellular inflammation by affecting monocyte activation/differentiation, cellular cytoprotective functions from reactive oxygen species (ROS) stress, modulation of pro-coagulant state, myocardial growth control, and its implications in metabolic control and insulin resistance. These multiple actions indicate that IL-6 is not merely a passive biomarker, but actively modulates adaptive and pathological responses to cardiovascular stress

Incorporating expression data in metabolic modeling: a case study of lactate dehydrogenase

Integrating biological information from different sources to understand cellular processes is an important problem in systems biology. We use data from mRNA expression arrays and chemical kinetics to formulate a metabolic model relevant to K562 erythroleukemia cells. MAP kinase pathway activation alters the expression of metabolic enzymes in K562 cells. Our array data show changes in expression of lactate dehydrogenase (LDH) isoforms after treatment with phorbol 12-myristate 13-acetate (PMA), which activates MAP kinase signaling. We model the change in lactate production which occurs when the MAP kinase pathway is activated, using a non-equilibrium, chemical-kinetic model of homolactic fermentation. In particular, we examine the role of LDH isoforms, which catalyze the conversion of pyruvate to lactate. Changes in the isoform ratio are not the primary determinant of the production of lactate. Rather, the total concentration of LDH controls the lactate concentration.Comment: In press, Journal of Theoretical Biology. 27 pages, 9 figure

Effect of acute copper sulfate exposure on olfactory responses to amino acids and pheromones in goldfish (Carassius auratus)

Exposure of olfactory epithelium to environmentally relevant concentrations of copper disrupts olfaction in fish. To examine the dynamics of recovery at both functional and morphological levels after acute copper exposure, unilateral exposure of goldfish olfactory epithelia to 100 μM CuSO4 (10 min) was followed by electro-olfactogram (EOG) recording and scanning electron microscopy. Sensitivity to amino acids (L-arginine and L-serine), generally considered food-related odorants, recovered most rapidly (three days), followed by that to catecholamines(3-O-methoxytyramine),bileacids(taurolithocholic acid) and the steroid pheromone, 17,20 -dihydroxy-4-pregnen- 3-one 20-sulfate, which took 28 days to reach full recovery. Sensitivity to the postovulatory pheromone prostaglandin F2R had not fully recovered even at 28 days. These changes in sensitivity were correlated with changes in the recovery of ciliated and microvillous receptor cell types. Microvillous cells appeared largely unaffected by CuSO4 treatment. Cilia in ciliated receptor neurones, however, appeared damaged one day post-treatment and were virtually absent after three days but had begun to recover after 14 days. Together, these results support the hypothesis that microvillous receptor neurones detect amino acids whereas ciliated receptor neurones were not functional and are responsible for detection of social stimuli (bile acidsandpheromones).Furthermore, differences in sensitivity to copper may be due to different transduction pathways in the different cell types

Numerical Investigation of Boundary Conditions for Moving Contact Line Problems

When boundary conditions arising from the usual hydrodynamic assumptions are applied, analyses of dynamic wetting processes lead to a well-known nonintegrable stress singularity at the dynamic contact line, necessitating new ways to model this problem. In this paper, numerical simulations for a set of representative problems are used to explore the possibility of providing material boundary conditions for predictive models of inertialess moving contact line processes. The calculations reveal that up to Capillary number Ca=0.15, the velocity along an arc of radius 10Li (Li is an inner, microscopic length scale! from the dynamic contact line is independent of the macroscopic length scale a for a.103Li , and compares well to the leading order analytical ‘‘modulated-wedge’’ flow field [R. G. Cox, J. Fluid Mech. 168, 169 (1986)] for Capillary number Ca,0.1. Systematic deviations between the numerical and analytical velocity field occur for 0.1168, 169 (1986)] is used as a boundary condition along an arc of radius R=10-2a from the dynamic contact line, agree well with those using two inner slip models for Ca\u3c0.1, with a breakdown at higher Ca. Computations in a cylindrical geometry reveal the role of azimuthal curvature effects on velocity profiles in this vicinity of dynamic contact lines. These calculations show that over an appropriate range of Ca, the velocity field and the meniscus slope in a geometry-independent region can potentially serve as material boundary conditions for models of processes containing dynamic contact lines

Technological Change in Resource Extraction and Endogenous Growth

We add an extractive sector to an endogenous growth model of expanding varieties and directed technological change. Extractive firms reduce the stock of non-renewable resources through extraction, but also increase the stock through R&D investment in extraction technology. Our model replicates long-term trends in non-renewable resource markets, namely stable prices and exponentially increasing extraction, for which we present data from 1792 to 2009. The model suggests that the development of new extraction technologies neutralizes the increasing demand for non-renewable resources in industrializing countries like China in the long term

Global Food Security Support Analysis Data (GFSAD) at Nominal 1 km (GCAD) Derived from Remote Sensing in Support of Food Security in the Twenty-First Century: Current Achievements and Future Possibilities

The precise estimation of the global agricultural cropland— extents, areas, geographic locations, crop types, cropping intensities, and their watering methods (irrigated or rain-fed; type of irrigation)—provides a critical scientific basis for the development of water and food security policies (Thenkabail et al., 2010, 2011, 2012). By year 2100, the global human population is expected to grow to 10.4 billion under median fertility variants or higher under constant or higher fertility variants (Table 6.1) with over three-quarters living in developing countries and in regions that already lack the capacity to produce enough food. With current agricultural practices, the increased demand for food and nutrition would require about 2 billion hectares of additional cropland, about twice the equivalent to the land area of the United States, and lead to significant increases in greenhouse gas productions associated with agricultural practices and activities (Tillman et al., 2011). For example, during 1960–2010, world population more than doubled from 3 to 7 billion. The nutritional demand of the population also grew swiftly during this period from an average of about 2000 calories per day per person in 1960 to nearly 3000 calories per day per person in 2010. The food demand of increased population along with increased nutritional demand during this period was met by the “green revolution,” which more than tripled the food production, even though croplands decreased from about 0.43 ha per capita to 0.26 ha per capita (FAO, 2009). The increase in food production during the green revolution was the result of factors such as: (1) expansion of irrigated croplands, which had increased in 2000 from 130 Mha in the 1960s to between 278 Mha (Siebert et al., 2006) and 467 Mha (Thenkabail et al., 2009a,b,c), with the larger estimate due to consideration of cropping intensity; (2) increase in yield and per capita production of food (e.g., cereal production from 280 to 380 kg/person and meat from 22 to 34 kg/person (McIntyre, 2008); (3) new cultivar types (e.g., hybrid varieties of wheat and rice, biotechnology); and (4) modern agronomic and crop management practices (e.g., fertilizers, herbicide, pesticide applications)..