Solar silicon from directional solidification of MG silicon produced via the silicon carbide route

A process of metallurgical grade (MG) silicon production is presented which appears particularly suitable for photovoltaic (PV) applications. The MG silicon is prepared in a 240 KVA, three electrode submerged arc furnace, starting from high grade quartz and high purity silicon carbide. The silicon smelted from the arc furnace was shown to be sufficiently pure to be directionally solidified to 10 to 15 kg. After grinding and acid leaching, had a material yield larger than 90%. With a MG silicon feedstock containing 3 ppmw B, 290 ppmw Fe, 190 ppmw Ti, and 170 ppmw Al, blended with 50% of off grade electronic grade (EG) silicon to reconduct the boron content to a concentration acceptable for solar cell fabrication, the 99% of deep level impurities were concentrated in the last 5% of the ingot. Quite remarkably this material has OCV values higher tham 540 mV and no appreciable shorts due to SiC particles

Drought increases chlorophyll content in stems of Vitis interspecific hybrids

Plants respond to drought stress through different physiological mechanisms. To highlight a specific adaptation strategy related to stem photosynthetic activity, woody tissue pigmentation was studied. In this work, 25 Vitis hybrids were studied in two experimental vineyards: one of them with sufficient water availability and the other showing drought stress. 1500 reflectance spectra of woody tissues were collected. Beside the spectral elaboration and interpretation, indexes for the pigment quantification were calculated. The content and the proportion in chlorophylls (a and b) in stems were significantly modified in response to water stress. Genotypes were classified based on their plasticity/elasticity and adaptive/susceptible behavior. The cluster analysis produced 4 main groups based on their average spectra and on the spectral variations between watered and stress conditions. The most interesting genotypes concerning this trait were pointed out. Nevertheless, this adaptation mechanism could also be due to an increased detoxification necessity related to other physiological disfunctions caused by water stress. A multi-parameter approach is encouraged for phenotyping of abiotic stress tolerant plant selection. In the next future, this work will support the release of new drought tolerant rootstocks for viticulture

THE GENUS URSUS IN EURASIA: DISPERSAL EVENTS AND STRATIGRAPHICAL SIGNIFICANCE

On the basis of the results of former studies by the present authors five main groups of bears are recognized: Ursus gr. minimus - thibetanus (black bears), Ursus gr. etruscus (etruscan bears), Ursus gr. arctos (brown bears), Ursus gr. deningei - spelaeus (cave bears) and Ursus gr. maritimus (white bears). Black bears seem to have disappeared from Europe during the Late Pliocene, immigrated again at the beginning of the Middle Pleistocene, and definitively died out in Europe at the beginning of the Late Pleistocene. Etruscan bears occur more or less contemporaneously in the southern areas of Europe and Asia during the Late Pliocene. The Asian branch apparently became extinct at the end of this period, while the European stock survived, giving rise to more advanced representatives during the Early Pleistocene. Brown bears seem to have originated in Asia. This group dispersed widely in holoarctic areas diversifying into a great number of varieties. They reached Europe presumably at the very end of the Early Pleistocene. The arrival of brown bears in Europe is a crucial event, which approximately coincides with the great faunal turnover which marks the Early-Middle Pleistocene transition. Brown bears replaced the etruscan bears, typical of the Villafranchian faunal assemblages, and gave rise to the cave bear line. Cave bears were very successful in Europe during the Middle and Late Pleistocene and disappeared at the end of the last glaciation or even at the very beginning of the Holocene. White bears presumably originated from northern Eurasian brown bear populations during the Late Pleistocene

The composition of subduction zone fluids and the origin of the trace element enrichment in arc magmas

<jats:title>Abstract</jats:title><jats:p>The partitioning of major and trace elements between eclogite and aqueous fluids with variable salinity was studied at 700–800 °C and 4–6 GPa in piston cylinder and multi anvil experiments. Fluid compositions were determined using the diamond trap technique combined with laser ablation ICP-MS measurements in the frozen state. In addition to NaCl, SiO<jats:sub>2</jats:sub> is the main solute in the fluids. The fluid/eclogite partition coefficients of the large ion lithophile elements (LILE), such as Rb, Cs, Sr, and Ba as well as those of the light rare earths (LREE), of Pb, and of U increase by up to three orders of magnitude with salinity. These elements will therefore be efficiently transported by saline fluids. On the other hand, typical high field strength elements, such as Ti, Nb, and Ta, are not mobilized even at high salinities. Increasing temperature and pressure gradually increases the partitioning into the fluid. In particular, Th is mobilized by silica-rich fluids at 6 GPa already at low salinities. We show that we can fully reproduce the trace element enrichment pattern of primitive arc basalts by adding a few percent of saline fluid (with 5–10 wt% Cl) released from the basaltic slab to the zone of melting in the mantle wedge. Assuming 2 wt% of rutile in the eclogite equilibrated with the saline fluid produces a negative Nb Ta anomaly that is larger than in most primitive arc basalts. Therefore, we conclude that the rutile fraction in the subducted eclogite below most arcs is likely < 1 wt%. In fact, saline fluids would even produce a noticeable negative Nb Ta anomaly without any rutile in the eclogite residue. Metasomatism by sediment melts alone, on the other hand, is unable to produce the enrichment pattern seen in arc basalts. We, therefore, conclude that at least for primitive arc basalts, the release of hydrous fluids from the basaltic part of the subducted slab is the trigger for melting and the main agent of trace element enrichment. The contribution of sediment melts to the petrogenesis of these magmas is likely negligible. In the supplementary material, we provide a “Subduction Calculator” in Excel format, which allows the calculation of the trace element abundance pattern in primitive arc basalts as function of fluid salinity, the amount of fluid released from the basaltic part of the subducted slab, the fluid fraction added to the source, and the degree of melting.</jats:p&gt

Effect of anthocyanin absence on white berry grape (Vitis vinifera L.)

In grapevines, white berried cultivars are characterized by the absence of anthocyanins, which are the main pigments in V. vinifera fruits. These varieties produce berries with a yellowish color. The pigments responsible of this hue are still not well defined. In this paper, spectrophotometric analyzes were carried out using non-invasive methods (reflectance spectra) and destructive quantifications (chlorophyll and carotenoid quantifications) to describe the variation in color of three white grape varieties during ripening. A decrease in chlorophylls and carotenoids was found. Changes in the proportion of blue (450-500 nm) and red (630\u2011700 nm) absorption bands were underlined. The contribution of melanin-like pigments (oxidation products) is also discussed. In general, our results indicate that the yellow color of white cultivars is not related to the activation of specific biosynthetic pathways. It is most likely due to a series of catabolic processes (and to their relative intensity), which become visible and that are possibly stimulated by the anthocyanin absence

Effect of anthocyanin absence on white berry grape (Vitis vinifera L.)

In grapevines, white berried cultivars are characterized by the absence of anthocyanins, which are the main pigments in V. vinifera fruits. These varieties produce berries with a yellowish color. The pigments responsible of this hue are still not well defined. In this paper, spectrophotometric analyzes were carried out using non-invasive methods (reflectance spectra) and destructive quantifications (chlorophyll and carotenoid quantifications) to describe the variation in color of three white grape varieties during ripening. A decrease in chlorophylls and carotenoids was found. Changes in the proportion of blue (450-500 nm) and red (630‑700 nm) absorption bands were underlined. The contribution of melanin-like pigments (oxidation products) is also discussed. In general, our results indicate that the yellow color of white cultivars is not related to the activation of specific biosynthetic pathways. It is most likely due to a series of catabolic processes (and to their relative intensity), which become visible and that are possibly stimulated by the anthocyanin absence

Chlorophyll and carotenoid quantifications in white grape (Vitis vinifera L.) skins by reflectance spectroscopy

In white grapes, chlorophylls and carotenoids play important roles in berry color and environmental interactions (e.g. radiative stresses). In this paper, easy, fast and low cost non-invasive reflectance methods have been tested and developed. Previously published indexes showed good performances for chlorophyll quantifications. However, in this work, new formulas able to discriminate chlorophylls a and b were also proposed. The wavelengths of major interest for the absorption detection were identified. Formulas based on the Gaussians half heights were proposed. In general, chlorophyll quantifications were obtained directly from reflectance spectra, while carotenoid absorption bands did not allow good reflectance correlations. However, the chlorophyll/carotenoid ratio (due to the pigments physiological linked roles) could be used to estimate carotenoid content. Their proportion changes during berry development, thus the index coefficients should be adapted in relation to the BBCH phenological phase. The obtained indexes demonstrated good correlations with the destructive quantifications. These methods could support further researches concerning cultivar classification and physiological studies

A MIOCENE CERVID FROM THE TORRENTE MORRA SEQUENCE (COLLESALVETTI, PISA, ITALY)

A well preserved fossil left tibia of artiodactyl was recently found along Torrente Morra, in the surroundings of Collesalvetti (15 Kms South of Pisa). The bone is embedded in Upper Messinian deltaic sediments which outcrop patchily in the area. The specimen can be referred to a primitive cervid and shows morphological characters and proportions very close to those of the tibiae of extant roe deer, Capreolus capreolus. The find is particularly significant because continental mammals have never been reported before from the Miocene deposits of this area. A possible reference to a primitive roe deer would be consistent with Late Miocene macrofloral and palynological evidence from this area, which attest to a transition from a subtropical forested environment to a temperate Mediterranean one.&nbsp

Optical Properties of Berry Epicuticular Waxes in Four Georgian Grape Cultivars (Vitis vinifera L.)

The epidermis of plant shoot organs is generally covered by epicuticular waxes. The role of this layer isrelated mainly to the protection of the inner tissues from biotic and abiotic stresses. In this study, attentionis focused on the optical properties of the berry epicuticular waxes of the grapevine (Vitis vinifera L.) atfruit ripening. The reflectance of the berry surface was measured before and after chloroform treatmentsin four Georgian grape cultivars grown in northern Italy. Epicarp optical properties were underlinedat different wavelengths (341 to 1025 nm) for each cultivar. The results show that the berry waxes haveseveral optical properties; it is possible that their main eco-physiological effect is to provide specificprotection against different types of radiation. Besides the physiological aspects, the results are interestingalso from a technical point of view in the field of interpretation of reflectance measurements carried out bynon-invasive instruments