Petrography and petrology of the Hawaii Scientific Drilling Project lavas: Inferences from olivine phenocryst abundances and compositions

The Mauna Loa (ML) and Mauna Kea (MK) lavas recovered by the Hawaii Scientific Drilling Project (HSDP) include aphyric to highly olivine-phyric basalts. The average olivine phenocryst abundance in the reference suite of ML flows is 14.5 vol % (vesicle-free and weighted by the flow thickness), while the average abundances of olivine in the reference suites of the MK alkalic and tholeiitic basalts are 1.1 and 14.0 vol %, respectively. Plagioclase and augite phenocrysts are rare in the ML and MK tholeiites, but the MK alkalic basalts can have up to 4 vol % plagioclase phenocrysts. Strained olivine grains, thought to represent disaggregated dunite xenoliths from the cumulate pile within the magma chamber(s), are ubiquitous in the drill core lavas. These deformed grains can comprise up to 50 % of the modal olivine in a given rock. Olivine core compositions in the lavas span forsterite contents of 80.4–90.7 (median 88.8, ML tholeiites), 75.8–86.6 (median 85.8, MK alkalic basalts), and 76.3–90.5 (median 88.0 mol %, MK tholeiites). Olivines with core compositions in the range Fo_(89–90.5) are present in tholeiitic lavas with a wide range of whole-rock MgO contents (9–30 wt %). Strained and unstrained olivines completely overlap in composition as do the compositions of spinels (100*Cr/(Cr+Al) ∼59–72; Mg# = 100*Mg/(Mg+Fe^(2+)) ∼40–66) present as inclusions in the olivine phenocrysts. The presence of Fo_(90.5) olivine in the HSDP lavas requires magmas with ∼16 wt % MgO in the ML and MK plumbing systems. Rare dunite xenoliths are also present in the drill core lavas. While compositionally homogeneous within a given xenolith, the six xenoliths contain olivines that span a wide range of forsterite contents (78.3–89.2 mol %). Spinels in these xenoliths are chrome-rich, have Mg# between 31 and 66, and define two populations on the basis of TiO_2 contents. Whole-rock compositions for the ML and MK tholeiites define olivine control lines on MgO-oxide diagrams, and the relationship between whole-rock MgO and olivine phenocryst abundance in these lavas suggests that the lavas with >12 wt % MgO have accumulated olivine. Comparing the weighted bulk composition of all of the MK tholeiites in the drill core with a calculated parental magma suggests that, on average, the MK tholeiites entrained most of the olivine phenocrysts that crystallized from their parental liquids. Although deformed olivines in Hawaiian lavas are widely thought to represent disaggregated dunite xenoliths, none of the majoror minor-element data on the strained or unstrained olivine phenocrysts suggest that the strained olivines in the HSDP lavas are exotic. We suggest that most of the olivine phenocrysts in a given flow, whether strained or unstrained, are closely related to the evolved liquid that now forms the groundmass. This is consistent with observed correlations between isotopic systems measured on olivine separates (e.g., O, He) and isotopic systems dominated by groundmass (e.g., Nd, Pb)

Intercropping for Water Conservation: Environmental and Economic Implications of a Sustainable Farming Practice in California\u27s Central Valley

California’s agricultural sector is the biggest water consumer in the state and faces intense pressure to reduce its overall water usage. Industrialized monoculture systems dominate the industry and often disregard long-term environmental and economic externalities for short-term profit maximization. To maintain longstanding food security and economic stability as well as protect the state’s water supply, it is critical that these systems transition to more sustainable and resilient production mechanisms. As an alternative to monoculture, intercropping affords greater potential to conserve water, protect soil quality, and increase crop yields, among other metrics of sustainability. However, there has been much controversy over intercropping’s true potential to maintain the high crop yields of current commercial agriculture and whether it can effectively decrease water consumption in semi-arid and arid climates. Through meta-analysis and literature review of research completed in similar environments, this paper determines that if properly implemented, the methodologies of intercropping can be effective for long-term economic success in the Central Valley, while simultaneously increasing water conservation and protecting California’s valuable resources. To encourage the transition to these systems, potential policies and strategies are provided as mechanisms to stimulate positive growth towards a sustainable future

Measurement of deuterons at LHCb

A first measurement of deuteron production at the LHCb experiment is presented. The measurement is performed as a function of momentum, using proton-proton collision data from the 2018 data taking period, at a centre-of-mass energy √s =13 TeV. The simulation of deuteron production in proton-proton collisions, which is used extensively in the development of the measurement strategy, is described. The deuteron production cross-section measurement uses a neural network variable, ProbNNd, to discriminate between deuterons and other charged particles, in the momentum range 20 < p < 100 GeV/c, for pseudorapidities 1.89 < η < 4.89. Measurements of deuterons produced in high energy collisions provide important information for the calibration of models used in indirect dark matter searches. Some of these searches use antideuteron signals in cosmic-rays to look for evidence for dark matter annihilation. The measurement at LHCb is found not to be sensitive to a deuteron signal. The steps that should be followed to compute a deuteron production cross-section at LHCb are detailed.Open Acces

Long-lasting insecticide-treated net usage in eastern Sierra Leone - the success of free distribution.

Summary Objective Médecins Sans Frontières (MSF) runs a malaria control project in Bo and Pujehun districts (population 158 000) that includes the mass distribution, routine delivery and demonstration of correct use of free, long-lasting insecticide-treated nets (LLINs). In 2006/2007, around 65 000 LLINs were distributed. The aim of this follow-up study was to measure LLIN usage and ownership in the project area. Methods Heads of 900 randomly selected households in 30 clusters were interviewed, using a standardized questionnaire, about household use of LLINs. The condition of any LLIN was physically assessed. Results Of the 900 households reported, 83.4% owning at least one LLIN. Of the 16.6% without an LLIN, 91.9% had not participated in the MSF mass distribution. In 94.1% of the households reporting LLINs, the nets were observed hanging correctly over the beds. Of the 1135 hanging LLINs, 75.2% had no holes or 10 or fewer finger-size holes. The most common source of LLINs was MSF (75.2%). Of the 4997 household members, 67.2% reported sleeping under an LLIN the night before the study, including 76.8% of children under 5 years and 73.0% of pregnant women. Conclusion Our results show that MSF achieved good usage with freely distributed LLINs. It is one of the few areas where results almost achieve the new targets set in 2005 by Roll Back Malaria to have at least 80% of pregnant women and children under 5 years using LLINs by 2010

Degenerate boundaries for multiple-alternative decisions

Integration-to-threshold models of two-choice perceptual decision making have guided our understanding of human and animal behavior and neural processing. Although such models seem to extend naturally to multiple-choice decision making, consensus on a normative framework has yet to emerge, and hence the implications of threshold characteristics for multiple choices have only been partially explored. Here we consider sequential Bayesian inference and a conceptualisation of decision making as a particle diffusing in n-dimensions. We show by simulation that, within a parameterised subset of time-independent boundaries, the optimal decision boundaries comprise a degenerate family of nonlinear structures that jointly depend on the state of multiple accumulators and speed-accuracy trade-offs. This degeneracy is contrary to current 2-choice results where there is a single optimal threshold. Such boundaries support both stationary and collapsing thresholds as optimal strategies for decision-making, both of which result from stationary representations of nonlinear boundaries. Our findings point towards a normative theory of multiple-choice decision making, provide a characterisation of optimal decision thresholds under this framework, and inform the debate between stationary and dynamic decision boundaries for optimal decision making

The ethnic density effect in psychosis: a systematic review and multilevel meta-analysis

Background: An 'ethnic' or 'group' density effect in psychosis has been observed, whereby the risk of psychosis in minority group individuals is inversely related to neighbourhood-level proportions of others belonging to the same group. However, there is conflicting evidence over whether this effect differs between minority groups and limited investigation into other moderators. Aims: To conduct a comprehensive systematic review and meta-analysis of the group density effect in psychosis and examine moderators. Method: Four databases were systematically searched. A narrative review was conducted and a three-level meta-analysis was performed. The potential moderating effect of crudely and specifically defined minority groups was assessed. Country, time, area size and whether studies used clinical or non-clinical outcomes were also tested as moderators. Results: Thirty-two studies were included in the narrative review and ten in the meta-analysis. A 10 percentage-point decrease in own-group density was associated with a 20% increase in psychosis risk (OR = 1.20, 95% CI 1.09-1.32, P < 0.001). This was moderated by crudely defined minority groups (F-6,F-68 = 6.86, P < 0.001), with the strongest associations observed in Black populations, followed by a White Other sample. Greater heterogeneity was observed when specific minority groups were assessed (F-25,F-49 = 7.26, P < 0.001). Conclusions: This is the first review to provide meta-analytic evidence that the risk of psychosis posed by lower own-group density varies across minority groups, with the strongest associations observed in Black individuals. Heterogeneity in effect sizes may reflect distinctive social experiences of specific minority groups. Potential mechanisms are discussed, along with the implications of findings and suggestions for future research