The metal and dust yields of the first massive stars

We quantify the role of Population (Pop) III core-collapse supernovae (SNe) as the first cosmic dust polluters. Starting from a homogeneous set of stellar progenitors with masses in the range [13 - 80] Msun, we find that the mass and composition of newly formed dust depend on the mixing efficiency of the ejecta and the degree of fallback experienced during the explosion. For standard Pop III SNe, whose explosions are calibrated to reproduce the average elemental abundances of Galactic halo stars with [Fe/H] < -2.5, between 0.18 and 3.1 Msun (0.39 - 1.76 Msun) of dust can form in uniformly mixed (unmixed) ejecta, and the dominant grain species are silicates. We also investigate dust formation in the ejecta of faint Pop III SN, where the ejecta experience a strong fallback. By examining a set of models, tailored to minimize the scatter with the abundances of carbon-enhanced Galactic halo stars with [Fe/H ] < -4, we find that amorphous carbon is the only grain species that forms, with masses in the range 2.7 10^{-3} - 0.27 Msun (7.5 10^{-4} - 0.11 Msun) for uniformly mixed (unmixed) ejecta models. Finally, for all the models we estimate the amount and composition of dust that survives the passage of the reverse shock, and find that, depending on circumstellar medium densities, between 3 and 50% (10 - 80%) of dust produced by standard (faint) Pop III SNe can contribute to early dust enrichment.Comment: Accepted by MNRAS, 22 pages, 12 figures, 12 table

A Follow-Up Study (1970-1972) of the 1969 State Scholarship Program in the State of Rhode Island

Introduction The philosophy and objectives underlying the Rhode Island State Scholarship Program encompassed severa1 basic assumptions about secondary education. Some of these assumptions have changed substantially over the past fifteen years and deserve close consideration. The new emphasis toward equalizing educational opportunities had been reflected in the changing philosophy that guided the administration of student financial aid. The genesis of most aid programs could be found in a concept that fostered the belief in a system built entirely upon meritocracy. This approach provided aid to students with high achievement and measured potential, irrespective of financial need. Educators seeing the inequity and irrationality of this approach developed a more standardized and need-analysis system. High ability students who needed assistance were given scholarships, but as the research over the past .five years had indicated, this kind of approach benefited only a few of the truly financially impoverished students. The overriding criterion of previous academic success has had the effect of excluding the most needy from participation. The review of the literature for this study was divided into three areas: (l) state scholarship or grant programs, {2) federal scholarship grant or loan programs, and (3) general student aid program models. Procedures The procedures followed in the conduct of the study were typical of those used in descriptive research design. A series of questions was identified bearing on important educational concerns; the related literature was reviewed; a survey instrument was designed and tested; follow ups were made; and the collected data were analyzed for significant findings and implications. As a means of assessing the effectiveness ·of the Rhode Island scholarship programs, the investigators conducted a survey of Rhode Island high school seniors in November 1970 and 1971. Four major variables relating to tests for higher education, academic and economic readiness for higher education, and specific demographic characteristics were investigated through a questionnaire administered in the high schools. The pooled responses to the questionnaire totaled 19,313 returns over the two-year period. This return represented 74 per cent of the 25,920 seniors in Rhode Island high schools during 1970 and 1971. Because of this relatively high return, the findings of the study were assumed to be indicative of the larger population and adequately described the characteristics of this total population. The significant finding indicated that a major discrepancy existed between the needs of the students and the delivery system of the Rhode Islan

Halo dust detection around NGC 891

Observations of edge-on galaxies allow us to investigate the vertical extent and properties of dust, gas and stellar distributions. NGC 891 has been studied for decades and represents one of the best studied cases of an edge-on galaxy. We use deep PACS data together with IRAC, MIPS and SPIRE data to study the vertical extent of dust emission around NGC 891. We also test the presence of a more extended, thick dust component. By performing a convolution of an intrinsic vertical profile emission with each instrument PSF and comparing it with observations we derived the scaleheight of a thin and thick dust disc component. For all wavelengths considered the emission is best fit with the sum of a thin and a thick dust component. The scaleheight of both dust components shows a gradient passing from 70 $\mu$m to 250 $\mu$m. This could be due to a drop in dust heating (and thus dust temperature) with the distance from the plane, or to a sizable contribution ($\sim 15 - 80$) of an unresolved thin disc of hotter dust to the observed surface brightness at shorter wavelengths. The scaleheight of the thick dust component, using observations from 70 $\mu$m to 250 $\mu$m has been estimated to be $(1.44\pm 0.12)$ kpc, consistent with previous estimates (extinction and scattering in optical bands and MIR emission). The amount of dust mass at distances larger than $\sim 2$ kpc from the midplane represents $2 - 3.3$ % of the total galactic dust mass and the relative abundance of small grains with respect to large grains is almost halved comparing to that in the midplane. The paucity of small grains high above the midplane might indicate that dust is hit by interstellar shocks or galactic fountains and entrained together with gas. The halo dust component is likely to be embedded in an atomic / molecular gas and heated by a thick stellar disc.Comment: 15 pages, 13 figures, A&A accepte

Photonic mode density effects on single-molecule fluorescence blinking

We investigated the influence of the photonic mode density (PMD) on the triplet dynamics of individual chromophores on a dielectric interface by comparing their response in the presence and absence of a nearby gold film. Lifetimes of the excited singlet state were evaluated in ordet to measure directly the PMD at the molecules position. Triplet state lifetimes were simultaneously determined by statistical analysis of the detection time of the fluorescence photons. The observed singlet decay rates are in agreement with the predicted PMD for molecules with different orientations. The triplet decay rate is modified in a fashion correlated to the singlet decay rate. These results show that PMD engineering can lead to an important suppression of the fluorescence, introducing a novel aspect of the physical mechanism to enhance fluorescence intensity in PMD-enhancing systems such as plasmonic devices

Garnets from Val d&#8217;Ala Rodingites, Piedmont, Italy: An Investigation of Their Gemological, Spectroscopic and Crystal Chemical Properties

In Val d\u2019Ala (Piedmont,Western Alps, Italy), the more interesting rocks for the mineralogical research are represented by rodingites (rich in mineralized veins and fractures) associated with serpentinites in the eclogitized oceanic crust of Piemonte Zone, south of Gran Paradiso Massif. Among the vein-filling minerals, garnets are the most appreciated as mineral specimens and, in less degree despite their vivid and rich colors, for their potential as gem-quality materials. This study provides a complete gemological characterization of five faceted samples and others new information by means of Synchrotron X-ray computed micro-tomography imaging gem features. Electron-probe microanalysis (EMPA) and laser ablation\u2013inductively coupled plasma\u2013mass spectrometry (LA\u2013ICP\u2013MS) established that the chemical composition of garnets from different localities, resulted both close to pure andradite, enriched in light rare earth elements (LREE) with a positive Eu anomaly, and grossular-andradite solid solution (grandite), enriched in heavy rare earth elements (HREE). X-ray powder diffraction analyses indicate the possible coexistence of almost pure grossular and andradite. A spectroscopic approach, commonly used with gem-like material, by Raman and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, completes the characterization of the samples. The new data on the textural and geochemical features of the grandite and andradite garnets suggest local growth processes under various chemical and oxidation conditions of metasomatic and metamorphic fluids interacting with the host-rocks. Garnets represent long-lasting mineral records of the complex geological history of the Val d\u2019Ala rodingitic dikes during their oceanic- and subduction-related metamorphic evolution

Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range

This paper analyses the behaviour of the gas-to-dust mass ratio (G/D) of local Universe galaxies over a large metallicity range. We combine three samples: the Dwarf Galaxy Survey, the KINGFISH survey and a subsample from Galametz et al. (2011) totalling 126 galaxies, covering a 2 dex metallicity range, with 30% of the sample with 12+log(O/H) < 8.0. The dust masses are homogeneously determined with a semi-empirical dust model, including submm constraints. The atomic and molecular gas masses are compiled from the literature. Two XCO are used to estimate molecular gas masses: the Galactic XCO, and a XCO depending on the metallicity (as Z^{-2}). Correlations with morphological types, stellar masses, star formation rates and specific star formation rates are discussed. The trend between G/D and metallicity is empirically modelled using power-laws (slope of -1 and free) and a broken power-law. We compare the evolution of the G/D with predictions from chemical evolution models. We find that out of the five tested galactic parameters, metallicity is the galactic property driving the observed G/D. The G/D versus metallicity relation cannot be represented by a power-law with a slope of -1 over the whole metallicity range. The observed trend is steeper for metallicities lower than ~ 8.0. A large scatter is observed in the G/D for a given metallicity, with a dispersion of 0.37 dex in metallicity bins of ~0.1 dex. The broken power-law reproduces best the observed G/D and provides estimates of the G/D that are accurate to a factor of 1.6. The good agreement of the G/D and its scatter with the three tested chemical evolution models shows that the scatter is intrinsic to galactic properties, reflecting the different star formation histories, dust destruction efficiencies, dust grain size distributions and chemical compositions across the sample. (abriged)Comment: 23 pages, 12 figures, accepted in Astronomy & Astrophysic

Gem-Quality Tourmaline from LCT Pegmatite in Adamello Massif, Central Southern Alps, Italy: An Investigation of Its Mineralogy, Crystallography and 3D Inclusions

In the early 2000s, an exceptional discovery of gem-quality multi-coloured tourmalines, hosted in Litium-Cesium-Tantalum (LCT) pegmatites, was made in the Adamello Massif, Italy. Gem-quality tourmalines had never been found before in the Alps, and this new pegmatitic deposit is of particular interest and worthy of a detailed characterization. We studied a suite of faceted samples by classical gemmological methods, and fragments were studied with Synchrotron X-ray computed micro-tomography, which evidenced the occurrence of inclusions, cracks and voids. Electron Microprobe combined with Laser Ablation analyses were performed to determine major, minor and trace element contents. Selected samples were analysed by single crystal X-ray diffraction method. The specimens range in colour from colourless to yellow, pink, orange, light blue, green, amber, brownish-pink, purple and black. Chemically, the tourmalines range from fluor-elbaite to fluor-liddicoatite and rossmanite: these chemical changes occur in the same sample and affect the colour. Rare Earth Elements (REE) vary from 30 to 130 ppm with steep Light Rare Earth Elemts (LREE)-enriched patterns and a negative Eu-anomaly. Structural data confirmed the elbaitic composition and showed that high manganese content may induce the local static disorder at the O(1) anion site, coordinating the Y cation sites occupied, on average, by Li, Al and Mn2+ in equal proportions, confirming previous findings. In addition to the gemmological value, the crystal-chemical studies of tourmalines are unanimously considered to be a sensitive recorder of the geological processes leading to their formation, and therefore, this study may contribute to understanding the evolution of the pegmatites related to the intrusion of the Adamello pluton

MULTICUBE: Multi-objective design space exploration of multi-core architectures

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Neurochemical Changes in the Mouse Hippocampus Underlying the Antidepressant Effect of Genetic Deletion of P2X7 Receptors.

Recent investigations have revealed that the genetic deletion of P2X7 receptors (P2rx7) results in an antidepressant phenotype in mice. However, the link between the deficiency of P2rx7 and changes in behavior has not yet been explored. In the present study, we studied the effect of genetic deletion of P2rx7 on neurochemical changes in the hippocampus that might underlie the antidepressant phenotype. P2X7 receptor deficient mice (P2rx7-/-) displayed decreased immobility in the tail suspension test (TST) and an attenuated anhedonia response in the sucrose preference test (SPT) following bacterial endotoxin (LPS) challenge. The attenuated anhedonia was reproduced through systemic treatments with P2rx7 antagonists. The activation of P2rx7 resulted in the concentration-dependent release of [3H]glutamate in P2rx7+/+ but not P2rx7-/- mice, and the NR2B subunit mRNA and protein was upregulated in the hippocampus of P2rx7-/- mice. The brain-derived neurotrophic factor (BDNF) expression was higher in saline but not LPS-treated P2rx7-/- mice; the P2rx7 antagonist Brilliant blue G elevated and the P2rx7 agonist benzoylbenzoyl ATP (BzATP) reduced BDNF level. This effect was dependent on the activation of NMDA and non-NMDA receptors but not on Group I metabotropic glutamate receptors (mGluR1,5). An increased 5-bromo-2-deoxyuridine (BrdU) incorporation was also observed in the dentate gyrus derived from P2rx7-/- mice. Basal level of 5-HT was increased, whereas the 5HIAA/5-HT ratio was lower in the hippocampus of P2rx7-/- mice, which accompanied the increased uptake of [3H]5-HT and an elevated number of [3H]citalopram binding sites. The LPS-induced elevation of 5-HT level was absent in P2rx7-/- mice. In conclusion there are several potential mechanisms for the antidepressant phenotype of P2rx7-/- mice, such as the absence of P2rx7-mediated glutamate release, elevated basal BDNF production, enhanced neurogenesis and increased 5-HT bioavailability in the hippocampus