Search results for "MINERALOGY"
showing 10 items of 1516 documents
Observations of high concentrations of I2and IO in coastal air supporting iodine-oxide driven coastal new particle formation
2010
[1] Theoretical studies have predicted that concentrations of gaseous I2 and IO of the order of 80–100 ppt and 40–50 ppt, respectively, are required in coastal air to account for photochemically-driven coastal new-particle formation events to occur. However, measurements reported to date (i.e., ∼20 ppt I2, ≤ 10 ppt IO) have not supported the required model predictions. Here, we present measurements of high concentrations of I2 and IO in N.E. Atlantic marine air on the west coast of Ireland. The maximum mixing ratios of daytime I2 and IO over the seaweed beds during low tide were 302 ppt and 35 ppt, respectively. The I2 distribution was rather inhomogeneous, even at the inter-tidal zone, but…
Correlation between ball milling conditions and planar effects on Cu-nanostructured powders
2002
It is most often proposed that the process of ball milling introduces a variety of defects (vacancies, dislocations, grain boundaries, stacking faults,...) which raise the free energy of the system making it possible to produce metastable phases. But there are very few investigations that deal with the characterization and quantification of the defects produced in milled powders. XRD is really a valuable technique for a characterization in terms of size and morphology of crystallites and imperfections. In this paper, a new line profile analysis method is proposed in order to take into account the dependence of the crystallite size, of the residual strains as well as of the planar defects, o…
Cooling and stabilization by collisions in a mixed ion–atom system
2012
In mixed systems of trapped ions and cold atoms, the ions and atoms can coexist at different temperatures. This is primarily due to their different trapping and cooling mechanisms. The key questions of how ions can cool collisionally with cold atoms and whether the combined system allows stable coexistence, need to be answered. Here we experimentally demonstrate that rubidium ions cool in contact with magneto-optically trapped rubidium atoms, contrary to the general experimental expectation of ion heating. The cooling process is explained theoretically and substantiated with numerical simulations, which include resonant charge exchange collisions. The mechanism of single collision swap cool…
Specific features of the electronic structure of III–VI layered semiconductors: recent results on structural and optical measurements under pressure …
2003
In this paper we review some recent results on the electronic structure of III-VI layered semiconductors and its dependence under pressure, stressing the specific features that differentiate their behaviour from that of tetrahedrally coordinated semiconductors. We will focus on several unexpected results that have led to changes in the image that was currently accepted a few years ago. Intralayer bond angles change under pressure and the layer thickness remains virtually constant or increases. As a consequence, models based in intra- and inter-layer deformation potentials fail in explaining the low pressure nonlinearity of the band gap. Numerical-atomic-orbital/density-functional-theory ele…
Study of the pyroelectricity in LiIns2 crystal
2002
Abstract Pyroelectric current measurements performed on a LiInS2 monodomain single crystal show a linear variation of the current between 120 and 260 K. Near room temperature, a space charge relaxation screens pyroelectricity. The pyroelectric coefficient follows a linear thermal dependence leading to an extrapolated value of 6×10−10 C K−1 cm−2 at 300 K. As for other oxide-type pyroelectric compounds, this value is shown to be proportional to the electro-optic coefficient r333 of LiInS2.
Critical Exponents and Randomness in SrTiO3 : Ca
1994
Since its discovery, the SrTiO3: Ca system is known to exhibit a number of features which were thought to arise from an impurity induced disorder. Non-linear dielectric measurements are used to obtain a more quantitative insight into this disorder. For 0.001 < xCa < 0.05, it is found that the non-linear susceptibility diverges at low temperatures. This is similar to what was previously reported in the dielectric random system KTaO3: Na. A method is proposed to quantify the contribution of the disorder to the non-linearities. It is found that the deviation from a true ferroelectric behaviour is not enough to call the low-temperature phase of SrTiO3: Ca a glass one. The maximum non-linearity …
Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of the wooden part
2020
Abstract: This work follows a previous one dealing with the state of conservation study of the wooden part of the roman Acqualadroni rostrum soon after its finding in the seabed of Acqualadroni (Messina, Italy). The archaeological survey and recovery were particularly relevant since this artefact is one of the two rostrums, nowadays known,found together with its wooden part. Following the recovery, it was consolidated by immersion in a melamine-formaldehyde resin (Kauramin) aqueous solution for eight months at the “Centro di Restauro del Legno Bagnato” (Pisa, Italy). The present investigation is aimed to determine at microscopic scale the wood state of conservation and to highlight interact…
Evaluating the protecting effects of two consolidants applied on Pietra di Lecce limestone: A neutronographic study
2020
Abstract In this work a combined laboratory-based and neutronographic investigation was carried out on a type of limestone, known as Pietra di Lecce stone, widely used in Italian Baroque as construction material. The limestone was treated with two different commercially-available coatings, namely nanosilica and nanolime, and artificially weathered by salt crystallization and temperature/relative humidity jumps. The aim was to provide an experimental evidence of the protective and consolidating effectiveness of the two treatments by looking at the water absorption process occurring inside the pore network of the analyzed stones. The analysis of the wetting front position revealed significant…
One dimensional consolidation of Opalinus Clay from shallow depth
2017
First experimental results on Opalinus Clay from shallow depth (< 30 m depth) are presented and compared to results on cores from Mont Terri Underground Rock Laboratory (~ 300 m depth). Samples were tested in one dimensional condition using an advanced experimental technique. The samples from the two sites show similar properties in terms of geotechnical characterization and one dimensional compressibility/swelling indexes, despite the different source depths.
Characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the Erzgebirge, Germany
2003
About 1000 zircon grains from a diamondiferous quartzofeldspathic rock of the Saxonian Erzgebirge were investigated for inclusions using optical microscopy and confocal laser-Raman spectroscopy. Cathodoluminescence imagery was applied to characterize the growth zone of zircon where the inclusions occurred. The most abundant inclusion minerals are microdiamonds. Coesite was not detected. However, garnet and jadeite occur as rare inclusions in zircon cores where diamonds are lacking. Jadeite was detected for the first time in quartzofeldspathic rocks from the crystalline complex of the Erzgebirge. The compositions of the pristine garnets in the zircons are similar to those of core areas of mi…