U/Pb zircon, strontium, and oxygen isotopic and geochronological study of the southernmost Sierra Nevada Batholith, California

The southernmost Sierra Nevada offers a view into the deep levels of the Mesozoic batholithic belt which constitutes much of the range to the north, and represents one of the major tectonic features of western North America. The main crystalline rocks of the study area are (1) the intrusive suite of Bear Valley, a middle Cretaceous tonalite batholith complex with coeval gabbroic intrusives, and (2) the gneiss complex of the Tehachapi Mountains, which consists of Early Cretaceous orthogneiss and subordinate paragneiss, with local domains having granulite facies metamorphic assemblages. The orthogneisses are dominantly tonalitic in composition, with significant layers of granodioritic to granitic and lesser dioritic to gabbroic gneiss. Quartz-rich and psammitic metasedimentary rocks with subordinate marble constitute the main framework assemblage into which the plutonic rocks were emplaced. Field relations demonstrate assimilation of metasedimentary material into the orthogneiss and tonalite batholith magmas, and magma mixing between mafic, tonalitic, and granitic materials. Significant domains of both homogenization and inhomogenization are recognized isotopically within the mixed rocks. U/Pb zircon studies have resolved two major igneous suites and a third suite of postdeformational intrusives, all lying between 90 and 120 Ma. The first suite (gneiss complex of the Tehachapi Mountains) was emplaced at ∼115 Ma, and exhibits penetrative high-temperature deformation developed at or near solidus conditions. A number of discordance patterns, along with the physical properties of the zircon, suggest minor inheritance of Proterozoic zircon and limited open system behavior in response to a major 100 Ma plutonic event. The 100 ± 3 Ma intrusive suite of Bear Valley crosscuts the older suite, but also exhibits significant synplutonic deformation. Mainly concordant zircon ages indicate the igneous crystallization age, but some discordances occur due to inheritance or entrainment of Proterozoic zircon. The high-temperature deformation fabrics in these suites and within the metasedimentary framework rocks were crosscut by the granodiorite of Claraville (90 Ma) and pegmatite dikes (∼95 Ma). The granodiorite of Claraville shows strong inheritance of Proterozoic zircon and high initial ^(87)Sr/^(86)Sr and δ^(18)O. Zircon populations from paragneiss and quartzite samples are dominated by Proterozoic detrital grains. Strontium and oxygen isotopic data on the zircon geochronology sample suite suggest simple twocomponent mixing of mantle-derived gabbroic to tonalitic magmas with partial to complete melt products from the metasedimentary framework rocks. Sedimentary admixtures for some granitic rocks may be as high as 45%, but for the tonalitic batholithic complex are no higher than about 15%. Modeled values of 10–20% metasediment are typical for the orthogneisses. Initial ^(87)Sr/^(86)Sr correlates directly with δ^(18)O, and generally correlates inversely with Sr content. Some subtle complexities in the Sr and O isotopic data suggest the involvement of a third cryptic component. Such a component could be early Phanerozoic ensimatic accretionary terranes that were structurally beneath the observed metasedimentary sequence, or altered oceanic crust and sediments introduced into the mantle magma source area by subduction. One of the initial aims of this study was to seek out remnants of Proterozoic sialic crystalline rocks within the gneiss complex of the Tehachapi Mountains. No such remnants were found, and our studies strongly suggest that sialic components within this link of the Mesozoic batholithic belt were introduced into mantle-derived magraatic systems by anatexis of continent-derived sedimentary rocks

Review of world experience and properties of materials for encapsulation of terrestrial photovoltaic arrays

Published and unpublished information relating to encapsulation systems and materials properties was collected by searching the literature and appropriate data bases (over 1,300 documents were selected and reviewed) and by personal contacts including site and company visits. A data tabulation summarizing world experience with terrestrial photovoltaic arrays (50 installations) is presented in the report. Based on criteria of properties, processability, availability, and cost, candidate materials were identified which have potential for use in encapsulation systems for arrays with a lifetime of over 20 years high reliability, an efficiency greater than 10 percent, a total price less than $500/kW, and a production capacity of 500,000 kW/yr. The recommended materials (all commercially available) include, depending upon the device design, various borosilicate and soda-lime glasses and numerous polymerics suitable for specific encapsulation system functions

Methodology for designing accelerated aging tests for predicting life of photovoltaic arrays

A methodology for designing aging tests in which life prediction was paramount was developed. The methodology builds upon experience with regard to aging behavior in those material classes which are expected to be utilized as encapsulant elements, viz., glasses and polymers, and upon experience with the design of aging tests. The experiences were reviewed, and results are discussed in detail

Replacing the Transfusion of 1-2 Units of Blood with Plasma Expanders that Increase Oxygen Delivery Capacity: Evidence from Experimental Studies.

At least a third of the blood supply in the world is used to transfuse 1-2 units of packed red blood cells for each intervention and most clinical trials of blood substitutes have been carried out at this level of oxygen carrying capacity (OCC) restoration. However, the increase of oxygenation achieved is marginal or none at all for molecular hemoglobin (Hb) products, due to their lingering vasoactivity. This has provided the impetus for the development of "oxygen therapeutics" using Hb-based molecules that have high oxygen affinity and target delivery of oxygen to anoxic areas. However it is still unclear how these oxygen carriers counteract or mitigate the functional effects of anemia due to obstruction, vasoconstriction and under-perfusion. Indeed, they are administered as a low dosage/low volume therapeutic Hb (subsequently further diluted in the circulatory pool) and hence induce extremely small OCC changes. Hyperviscous plasma expanders provide an alternative to oxygen therapeutics by increasing the oxygen delivery capacity (ODC); in anemia they induce supra-perfusion and increase tissue perfusion (flow) by as much as 50%. Polyethylene glycol conjugate albumin (PEG-Alb) accomplishes this by enhancing the shear thinning behavior of diluted blood, which increases microvascular endothelial shear stress, causes vasodilation and lowering peripheral vascular resistance thus facilitating cardiac function. Induction of supra-perfusion takes advantage of the fact that ODC is the product of OCC and blood flow and hence can be maintained by increasing either or both. Animal studies suggest that this approach may save a considerable fraction of the blood supply. It has an additional benefit of enhancing tissue clearance of toxic metabolites

Spiking Neurons Learning Phase Delays

Time differences between the two ears are an important cue for animals to azimuthally locate a sound source. The first binaural brainstem nucleus, in mammals the medial superior olive, is generally believed to perform the necessary computations. Its cells are sensitive to variations of interaural time differences of about 10 μs. The classical explanation of such a neuronal time-difference tuning is based on the physical concept of delay lines. Recent data, however, are inconsistent with a temporal delay and rather favor a phase delay. By means of a biophysical model we show how spike-timing-dependent synaptic learning explains precise interplay of excitation and inhibition and, hence, accounts for a physical realization of a phase delay

Astronomical Site Ranking Based on Tropospheric Wind Statistics

We present comprehensive and reliable statistics of high altitude wind speeds and the tropospheric flows at the location of five important astronomical observatories. Statistical analysis exclusively of high altitude winds point to La Palma as the most suitable site for adaptive optics, with a mean value of 22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have found a clear annual periodicity of high altitude winds for the five sites in study. We have also explored the connection of high to low altitude atmospheric winds as a first approach of the linear relationship between the average velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001). We may conclude that high and low altitude winds show good linear relationships at the five selected sites. The highest correlation coefficients correspond to Paranal and San Pedro Martir, while La Palma and La Silla show similar high to low altitude wind connection. Mauna Kea shows the smallest degree of correlation, which suggests a weaker linear relationship. Our results support the idea of high altitude winds as a parameter for rank astronomical sites in terms of their suitability for adaptive optics, although we have no evidence for adopting the same linear coefficient at different sites. The final value of this linear coefficient at a particular site could drastically change the interpretation of high altitude wind speeds as a direct parameter for site characterization.Comment: 18 pages, 5 figures. Accepted in MNRA

The Star Formation Rate in the Reionization Era as Indicated by Gamma-ray Bursts

High-redshift gamma-ray bursts (GRBs) offer an extraordinary opportunity to study aspects of the early Universe, including the cosmic star formation rate (SFR). Motivated by the two recent highest-z GRBs, GRB 080913 at z = 6.7 and GRB 090423 at z = 8.1, and more than four years of Swift observations, we first confirm that the GRB rate does not trace the SFR in an unbiased way. Correcting for this, we find that the implied SFR to beyond z = 8 is consistent with LBG-based measurements after accounting for unseen galaxies at the faint end of the UV luminosity function. We show that this provides support for the integrated star formation in the range 6 < z < 8 to have been alone sufficient to reionize the Universe.Comment: 4 pages, 4 figures; modified to match version accepted for publication in ApJ Letter