486 research outputs found
Local Meteoric Water Line of Northern Chile (18° S–30° S): An Application of Error-in-Variables Regression to the Oxygen and Hydrogen Stable Isotope Ratio of Precipitation
No full textIn this study, a revision of the previously published data on hydrogen (2H/1H) and oxygen (18O/16O) stable isotope ratio of precipitation in northern Chile is presented. Using the amount-weighted mean data and the combined standard deviation (related to both the weighted mean calculation and the spectrometric measurement), the equation of the local meteoric line calculated by error-in-variables regression is as follows: Northern Chile EIV-LMWL: δ2H = [(7.93 ± 0.15) δ18O] + [12.3 ± 2.1]. The slope is similar to that obtained by ordinary least square regression or other types of regression methods, whether weighted or not (e.g., reduced major axis or major axis) by the amount of precipitation. However, the error-in-variables regression is more accurate and suitable than ordinary least square regression (and other types of regression models) where statistical assumptions (i.e., no measurement errors in the x-axis) are violated. A generalized interval of δ2H = ±13.1‰ is also proposed to be used with the local meteoric line. This combines the confidence and prediction intervals around the regression line and appears to be a valid tool for distinguishing outliers or water samples with an isotope composition significantly different from local precipitation. The applicative examples for the Pampa del Tamarugal aquifer system, snow samples and the local geothermal waters are discussed
The Roman Marble artefacts from the Lapidario Romano (Museo Civico Archeologico Etnologico di Modena): Archeometrical evidence for italian sources
No full text
Morphoecology in larval fin-fish: A new candidate species for aquaculture, Diplodus puntazzo (Sparidae)
No full textThis study was aimed to acquire information on trophic behavior of Diplodus
puntazzo larvae and juveniles, by studing the ontogenetic sensory development, except vision.
D. puntazzo specimens were observed using a scanning electron (n = 67) and a light microscope
(n = 7). The results concerned four ontogenetical stages of sharpsnout seabream: larval,
post-larval, transitional, and juvenile stages. The yolk-sac larval stage was not detected as
the smallest larvae at our disposal (3.1 mm TL; 2nd day from hatching) showed no external
appearance of the yolk. During the larval stage (3.1–4.7 mm TL), sharpsnout seabream is
equipped with free neuromasts and olfactory ciliated receptor cells. In the post-larval stage (5–
28.6 mm TL), mechano- and chemo-reception is implemented: the inner and outer taste buds
differentiation, the nasal formation, the lateral line system canalization occur. The precocious
differentiation of chemo-receptors makes post-larvae particularly sensitive to the organoleptic
properties of administered preys. D. puntazzo, at the end of this phase, could be considered
a juvenile (complete squamation is acquired), except for the mouth and pharyngeal teeth.
During the subsequent phase (‘transitional’), in fact, eight chisel-type and two lateral series
of molar-like teeth progressively substituted the conical ones on each jaw, and three different
types of teeth on the upper and lower pharynx differentiated. So, the juvenile phase is reached
in individuals longer than 58 mm TL
Aragonite to calcite transformation in speleothems (Grotte de Clamouse, France): environment, textures and carbonate geochemistry
No full textIn Grotte de Clamouse (France), aragonite forms in a variety of crystal habits whose properties reflect the conditions of formation. Prolonged degassing and evaporation yield needle aragonite, which is more enriched in 18O and 13C than aragonite ray crystals, which form near isotopic equilibrium. At present, aragonite ray crystals form at the tops of stalagmites at very low discharge (0.00035 ml/ min), and when fluid Mg/Ca ratio is \u3e 1.1. Temperature and evaporation do not seem to have a significant role in their formation. The presence of aragonite in stalagmites should be indicative of a decrease in drip rate related to either dry climate conditions or local hydrology. Fossil aragonite was in part replaced by calcite in a time frame \u3c 1.0 ka, possibly through the combined effects of dissolution of aragonite, and precipitation of calcite, which preferentially nucleated on calcite cements that had previously formed between aragonite rays. Commonly, the replacement phase inherited the textural and chemical characteristics of the precursor aragonite prisms and needles (and in particular the δ13C signal and U content), and preserved aragonite relicts (up to 16 weight %). The isotope signal of different aragonite habits may reflect conditions of formation rather than climate parameters. The real extent of aragonite-to-calcite transformation may be underestimated when replacement calcite inherits both textural and chemical properties of the precursor
An Oceanic Cold Reversal during the last deglaciation
No full textA detailed deuterium excess proÞle measured along the Dome C EPICA (European Project for Ice Coring in Antarctica) core reveals the timing and strength of the sea surface temperature changes at the source regions for Dome C precipitation. We infer that an Oceanic Cold Reversal took place in the southern Indian Ocean, 800 years after the Antarctic Cold Reversal. The temperature gradient between the oceanic moisture source and Antarctica is similar to the Dome C sodium proÞle during the deglaciation, illustrating the strong link between this gradient and the strength of the atmospheric circulation
nanowires
No full textThe thermal resistance along the thickness of In3SbTe2 crystalline nanowires was measured using the scanning thermal microscopy in 3ω mode. The nanowires were grown by metal organic vapor deposition, exploiting the VLS mechanism induced by Au metal-catalyst nanoparticles and harvested on a SiO2/Si substrate. Two nanowires with different thickness (13 and 23 nm) were investigated. The thermal resistance of the nanowires was determined using two different approaches; the first one exploits the experimental data, whereas the second one is more sophisticated, since it involves a minimization procedure. Both methods led to comparable values of the thermal resistance along the transverse direction (thickness) of the nanowire. The obtained results were explained starting from the mean free path of phonons calculated in the In3SbTe2 bulk
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