A major element, PGE and Re-Os isotope study of Middle Atlas (Morocco) peridotite xenoliths : evidence for coupled introduction of metasomatic sulphides and clinopyroxene

We present major element and PGE (platinum-group-element) abundances in addition to Re–Os isotope data for 11 spinel-facies whole rock peridotites from a single maar from the Middle Atlas Mountains, Morocco. Major element systematics of these xenoliths are generally correlated with indices of depletion. FeO–MgO systematics appear to suggest spinel-facies melting in the range of 5 to 25%. However, Al2O3 abundances in these xenoliths appear elevated relative to primitive mantle (Prima). The Al2O3 abundances in conjunction with other major elements require distinct re-enrichment of the Middle Atlas continental mantle root due to melt/rock reaction and precipitation of amphibole and/or clinopyroxene from passing silicate melts akin to MORB or OIB that evolved in reverse direction along the melting curves in e.g. FeO–MgO space. Sc and V confirm the range of apparent depletion and also indicate that the currently preserved fO2 in these peridotites is distinctly different from fO2 conditions observed in subduction zones. The majority of these xenoliths have low Os and Ir (I-PGEs) concentrations relative to Prima and modelled sulphide- and clinopyroxene-depleted residues of mantle melting under low fO2, mid-ocean ridge-like conditions. Moreover, Pt and Pd (P-PGE) abundances are elevated when compared to their expected abundances after substantial melt extraction. Importantly, the systematically low Ir abundances in the majority of samples show well-correlated trends with Al2O3, MgO and Cu that are inconsistent with established melting trends. Os isotopes in the Middle Atlas xenoliths range from 187Os/188Os = 0.11604 to 0.12664 although most samples are close to chondritic. The Os isotope ratios are decoupled from 187Re/188Os but, together with Re abundances, also exhibit a good correlation with Al2O3, MgO and Cu. The major element, I-PGE and Os isotope correlations suggest that the initial melt depletion led to the exhaustion of sulphide and clinopyroxene (20 to 30%) without significant stabilization of I-PGE-rich alloys. During later modal metasomatism of the refractory Middle Atlas continental mantle root with silicate melts akin to MORB or OIB the introduction of clinopyroxene/amphibole reduced the volume of the melt inducing sulphur saturation in these melts causing precipitation of secondary sulphides. This coupled crystallization of pyroxenes and sulphides (chalcopyrite) resulted in the two-component mixing systematics exhibited by I-PGEs, Os isotopes with major elements and Cu preserved in the Middle Atlas continental mantle root

Tracing the metasomatic and magmatic evolution of continental mantle roots with Sr, Nd, Hf and Pb isotopes : a case study of Middle Atlas (Morocco) peridotite xenoliths

We studied clinopyroxenes from spinel-facies peridotite xenoliths sampled by the Quaternary intra-plate volcanism of the Middle Atlas (Morocco) and present new trace element and Sr–Nd–Hf isotope data. However, we focus in particular on Pb isotope data and 238U/204Pb and 232Th/204Pb ratios of these clinopyroxenes. This data allows us to investigate: (a) the timing of metasomatic events, (b) the prevalence and persistence of elevated 238U/204Pb, 232Th/238U and 232Th/204Pb in continental mantle roots and (c) the 238U/204Pb and 232Th/204Pb composition of putative basaltic melts generated from such metasomatised sub-continental lithospheric mantle (SCLM). Incompatible trace element concentrations in these clinopyroxenes are elevated, marked by high-field strength element depletion and fractionated elemental ratios (e.g., U/Nb, Zr/Hf) most consistent with enrichment due to carbonatitic liquids. Sr, Nd and Hf isotopes have an affinity to HIMU. U, Th and Pb abundances in the clinopyroxenes generally exceed estimates of primitive mantle clinopyroxene. Pb isotope compositions of these clinopyroxenes are radiogenic and vary between 206Pb/204Pb = 19.93–20.25, 207Pb/204Pb = 15.63–15.66 and 208Pb/204Pb = 39.72–40.23. These Pb isotope systematics result in generally negative Δ7/4 but positive Δ8/4; setting these samples distinctly apart from typical HIMU. These Pb isotope compositions are also distinct from the associated host volcanic rocks. 238U/204Pb and 232Th/204Pb of these clinopyroxenes, which range from 26 to 81 and 136 to 399, respectively, are elevated and more extreme than estimates of MORB- and HIMU-source mantle. The Pb isotope evolution of the clinopyroxenes suggests that the metasomatic enrichment is younger than 200 Ma, which discounts the volcanic activity due to the opening of the Atlantic and the onset of the collision of the African and Eurasian plates as processes generating the lithophile element and isotope composition of this continental mantle root. Instead, the enrichment is thought to be associated with the Quaternary intra-plate volcanism in the Middle Atlas. However, the erupted mafic melts have unradiogenic Pb isotopes and lower 238U/204Pb, 232Th/204Pb and 232Th/238U relative to the clinopyroxene and do not seem to have equilibrated with the clinopyroxenes. The high Th abundances and the high 232Th/238U also suggest that the metasomatism was due to carbonatitic liquids. When literature data for Pb isotopes in mantle minerals are considered, the Pb isotope range of Archean, Proterozoic and Phanerozoic continental mantle roots is remarkable in that they are similar to the convecting mantle. This observation does not support the existence of sub-continental lithospheric mantle with high 238U/204Pb and 232Th/204Pb for long periods of time. Consequently, the narrow range of Pb isotopes in SCLM worldwide suggests that only the youngest metasomatic events are recorded by incompatible elements such as U, Th and Pb. Numerical modelling of putative magmas generated from Middle Atlas SCLM by fractional, non-modal melting calculations yield extremely high 238U/204Pb and 232Th/204Pb ratios. For example, pure SCLM magmas generated from 0.5% to 10% melting are anticipated to have 232Th/204Pb ratios exceeding those known from terrestrial basalts

Ecological and temperature controls on Mg/Ca ratios of Globigerina bulloides from the southwest Pacific Ocean

We present Mg/Ca data for Globigerina bulloides from 10 core top sites in the southwest Pacific Ocean analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Mg/Ca values in G. bulloides correlate with observed ocean temperatures (7 degrees C-19 degrees C), and when combined with previously published data, an integrated Mg/Ca-temperature calibration for 7 degrees C-31 degrees C is derived where Mg/Ca (mmol/mol) = 0.955 x e(0.068 x T) (r(2) = 0.95). Significant variability of Mg/Ca values (20%-30%) was found for the four visible chambers of G. bulloides, with the final chamber consistently recording the lowest Mg/Ca and is interpreted, in part, to reflect changes in the depth habitat with ontogeny. Incipient and variable dissolution of the thin and fragile final chamber, and outermost layer concomitantly added to all chambers, caused by different cleaning techniques prior to solution-based ICPMS analyses, may explain the minor differences in previously published Mg/Ca-temperature calibrations for this species. If the lower Mg/Ca of the final chamber reflects changes in depth habitat, then LA-ICPMS of the penultimate (or older) chambers will most sensitively record past changes in near-surface ocean temperatures. Mean size-normalized G. bulloides test weights correlate negatively with ocean temperature (T = 31.8 x e(-30.5xwtN); r(2) = 0.90), suggesting that in the southwest Pacific Ocean, temperature is a prominent control on shell weight in addition to carbonate ion levels

Healthy babies through infant-centered feeding protocol: an intervention targeting early childhood obesity in vulnerable populations

<p>Abstract</p> <p>Background</p> <p>Poor feeding practices during infancy contribute to obesity risk. As infants transition from human milk and/or formula-based diets to solid foods, these practices interfere with infant feeding self-regulation and healthy growth patterns. Compared with other socioeconomic groups, lower-income mothers are more likely to experience difficulty feeding their infants. This may include misinterpreting feeding cues and using less-than-optimal feeding styles and practices, such as pressuring infants during mealtimes and prematurely introducing solid food and sweetened beverages. The Healthy Babies trial aims to determine the efficacy of a community-based randomized controlled trial of an in-home intervention with economically and educationally disadvantaged mother-infant dyads. The educational intervention is being conducted during the infant's first 6 months of life to promote healthy transition to solids during their first year and is based on the theory of planned behavior.</p> <p>Methods/Design</p> <p>We will describe our study protocol for a multisite randomized control trial being conducted in Colorado and Michigan with an anticipated sample of 372 economically and educationally disadvantaged African American, Hispanic, and Caucasian mothers with infants. Participants are being recruited by county community agency staff. Participants are randomly assigned to the intervention or the control group. The intervention consists of six in-home visits by a trained paraprofessional instructor followed by three reinforcement telephone contacts when the baby is 6, 8, and 10 months old. Main maternal outcomes include a) maternal responsiveness, b) feeding style, and c) feeding practices. Main infant outcome is infant growth pattern. All measures occur at baseline and when the infant is 6 and 12 months old.</p> <p>Discussion</p> <p>If this project is successful, the expected outcomes will address whether the home-based early nutrition education intervention is effective in helping mothers develop healthy infant feeding practices that contribute to improving infant health and development and reducing the risk of early-onset childhood obesity.</p> <p>Trial Registration</p> <p>Current Controlled Trials <a href="http://www.anzctr.org.au/ACTRN126100000415000.aspx">ACTRN126100000415000</a></p

Chronological Age-Grading of House Flies by Using Near-Infrared Spectroscopy

The sensitivity and accuracy of near-infrared spectroscopy (NIRS) was compared with that of the pteridine fluorescence technique for estimating the chronological age of house flies, Musca domestica (L.). Although results with both techniques were significantly correlated with fly age, confidence limits on predicted ages generally were smaller with NIRS. Young flies could be readily differentiated from old flies by using NIRS. Age predictions using the pteridine method are dependent upon size, sex, and temperature at which adult flies are exposed. In contrast, those factors do not need to be determined for age-grading using NIRS. Classification accuracy using the NIRS method was similar for whole flies, fresh heads, dried heads, and ethanol-preserved heads. The NIRS method was also suitable for predicting age of stable flies, Stomoxys calcitrans (L.), and face flies, Musca autumnalis De Geer. NIRS has several advantages over the measurement of pteridine levels for age-grading field-collected flies, including speed and portability of instrumentation, and not needing to determine sex, size, and temperatures to which adult flies were exposed

100% RAG: Syracuse School of Architecture, Student Newspaper, Volume 2, Number 2

100% RAG: Syracuse School of Architecture, Student Newspaper, Volume 2, Number 2. Student newsletter from student contributors of Syracuse School of Architecture in 1976

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

L-Edge Spectroscopy of Dilute, Radiation-Sensitive Systems Using a Transition-Edge-Sensor Array

We present X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS) measurements on the iron L-edge of 0.5 mM aqueous ferricyanide. These measurements demonstrate the ability of high-throughput transition-edge-sensor (TES) spectrometers to access the rich soft X-ray (100-2000eV) spectroscopy regime for dilute and radiation-sensitive samples. Our low-concentration data are in agreement with high-concentration measurements recorded by conventional grating-based spectrometers. These results show that soft X-ray RIXS spectroscopy acquired by high-throughput TES spectrometers can be used to study the local electronic structure of dilute metal-centered complexes relevant to biology, chemistry and catalysis. In particular, TES spectrometers have a unique ability to characterize frozen solutions of radiation- and temperature-sensitive samples.Comment: 19 pages, 4 figure

Impact of thermal oxidation uniformity on 150 mm GaAs- and Ge-substrate VCSELs

Vertical cavity surface emitting laser (VCSEL) devices and arrays are increasingly important in meeting the demands of today’s wireless communication and sensing systems. Understanding the origin of non-uniform wet thermal oxidation across large-area VCSEL wafers is a crucial issue to ensure highly reliable, volume-manufactured oxide-confined VCSEL devices. As VCSEL wafer diameters approach 200 mm, germanium (Ge) is emerging as an alternative substrate solution. To this end, we investigate the uniformity of 940 nm-emitting VCSEL performance across 150 mm diameter GaAs- and Ge-substrates, comparing the oxidation method in each case. Nominally identical epitaxial structures are used to evaluate the strain induced wafer bow for each substrate type with Ge exhibiting a reduction of over 100 μm in the peak-to-valley distortion when compared with GaAs. This wafer bow is found to be the principal cause of centre-to-edge oxidation non-uniformity when utilising a conduction-heated chuck furnace, in comparison to a convection-heated tube furnace. Using on-wafer testing of threshold current, differential resistance, and emission wavelength, device performance is demonstrated for the first time across a 150 mm Ge wafer, and is shown to be comparable to performance on GaAs substrates, when the effects of oxidation uniformity are removed. These results provide evidence that there is a realistic path to manufacturing high yield VCSELs, over wafer diameters approaching those used in Si-photonics, via Ge substrates