Trace Element Conundrum of Natural Quasicrystals

We report laser ablation inductively coupled plasma mass spectrometry measurements of the trace element contents of the two naturally occurring quasicrystalline minerals, Al₆₃Cu₂₄Fe₁₃ icosahedrite and Al₇₁Ni₂₄Fe₅ decagonite, from their type locality in the Khatyrka meteorite. The isolated quasicrystal fragments were mounted separately from any matrix and are larger than the laser beam diameter. When the elements are sorted in order of volatility, a systematic and unique pattern emerges in both bulk natural quasicrystal specimens. They are highly depleted compared to primitive solar system materials (chondritic meteorites) in moderately refractory elements (those with 50% condensation temperatures near 1350–1300 K; V, Co, Mg, Cr) and significantly enriched in moderately volatile elements (those with 50% condensation temperatures between 1250 and 500 K; Sb, B, Ag, Sn, Bi). We compare the chondrite-normalized trace element patterns and ratios of the quasicrystals to those of scoriaceous cosmic spherules and other meteoritic components. The nonmonotonic shapes of the chondrite-normalized trace element patterns in both icosahedrite and decagonite are incompatible with a single condensation process from the gas of the solar nebula. Previous transmission electron microscopy studies show that the natural quasicrystals contain 3–5 vol % of silicate and oxide nanoparticle inclusions, which we consider to be the main host of the measured trace elements. On this basis, we construct a three-stage model for the formation of the quasicrystals and their inclusions: a high-temperature condensation stage and a low-temperature vapor-fractionation stage to make nanoparticles, followed by a third stage that leads to the formation of quasicrystals incorporating the two different types of nanoparticles and their incorporation into the CV chondrite parent body of the Khatyrka meteorite

A QGIS Tool for Automatically Identifying Asbestos Roofing

Exposure to asbestos fibers implies a long-term risk for human health; therefore, the development of information systems that are able to detect the extent and status of asbestos over a certain territory has become a priority. This work presents a tool (based on the geographic information system open source software, QGIS) that is conceived for automatically identifying buildings with asbestos roofing. The area under investigation is the metropolitan area around Prato (Italy). The performance analysis of this system was carried out by classifying images that were acquired by the WorldView-3 sensor. These images are available at a low cost when compared with those obtained by means of aerial surveys, and they provide adequate resolution levels for roofing classification. The tool, a QGIS plugin, has shown fairly good performance in identifying asbestos roofing, with some false negatives and some false positives when applying a per-pixel classification. A performance improvement is obtainable when considering the percentage of asbestos pixels that are contained in each roof of the analyzed image. This value is also available with the plugin. In the future, this tool should make it possible to monitor the asbestos roof removal process over time in the area of interest, in accordance with other image data that give evidence of such removals

Defects in graphenic materials by EPR and DFT methods

We have used EPR to characterize a series of defects, which are characterized by tipical g-tensors, linewidths, intensity as function of the temperature. Mostly, signals arises from the presence of conduction electrons, and of so-called "edge states", that are unpaired electrons located at the edges of graphenic flakes; the relative molecular orbitals are not very muche extended as for low-lying orbitals, and are located within few atomic rows from edges with zig-zag topology. All the relative EPR signals are naturally and intrinsically generated by all graphitic materials. We now extend our study to the defects that are formed inside the graphenic structure. There is a full zoo of possible defects that can in principle originate EPR signals, like the presence of ad-atoms, holes, dislocation of atoms.We have started to study and analyze each type of defect from an experimental as well as from a theoretical point of view

Combination of Herbicide Band Application and Inter-Row Cultivation Provides Sustainable Weed Control in Maize

Herbicides have facilitated weed management but their incorrect use can lead to environmental contamination. Reducing herbicide use by limiting their application to a band along the crop row can decrease their environmental impact. Three field experiments were conducted in North-eastern Italy to evaluate herbicide band application systems integrated with inter-row hoeing for silage maize. Post-emergence herbicide band application (sprayed area 50% of total field; herbicide dose 50% of that recommended, application with an inter-row cultivator prototype) was compared with pre-emergence band application (sprayed area 33% of total field; herbicide dose 33% of that recommended, application with a seeder) and pre-emergence broadcast application (sprayed area 100% of total field; full recommended herbicide dose, application with a boom sprayer) that is standard management for maize. Weed density and composition were evaluated before and after post-emergence herbicide application and at crop harvest. Crop yield was also recorded. Weed density in untreated areas ranged between 5 and 15 plants m−2 in the different experiments. Optimal weed control and good yields were achieved without significant differences between all treatments. Herbicide band application can provide optimal weed control in silage maize, at the same time allowing a relevant reduction of herbicide input

The dunites of the Balmuccia peridotitic massif

ab

The Dunites in the Balmuccia peridotite massif.

The Balmuccia massif is dominantly lherzolitic. Dunites are a minor lithotype occurring: a) at the contacts of websterite dykes; b) as tabular bodies associated with layers of Cr-rich spinel; c) as large, decametric lenses typically associated with hornblendite pockets and veins. Type a dunites are 15 cm), olivine coexists with clinopyroxene. At a distance of 10-13 cm, clinopyroxene coexists with a \u201cpyribole\u201d (a mineral constituted by a few microns-large lamellae of clinopyroxene and amphibole). At 7-10 cm distance, clinopyroxene disappears and the pyribole coexists with discrete amphibole (kaersutite) crystals. Closer to the pocket, pyribole disappears and only amphibole and spinel (high Ti, low Cr) are present along with olivine. Similar variations occur in thin veins cutting the dunite and ending at the pocket. The pockets, up to 40 cm large, are constituted by giant kaersutitic amphibole, phlogopite, plagioclase, rutile, Al-Mg spinel. Towards the ambient lherzolites, the dunite fades into wehrlite, where orthopyroxene abundance increases outwards and the outer belt is constituted by a granular, undeformed, opx-rich lherzolite.On the basis of petrography, Sr and Nd isotopes and trace element characteristics of clinopyroxene we preliminarily hypothesise that type b dunites are the result of Cr-diopside dykes melting, eventually triggered by percolation of deeper-derived melts, and reactive percolation of these melts into the ambient lherzolite under increasing melt mass conditions. Type c dunites may represent a relatively shallow event (as indicated by the plagioclase stability) of reactive percolation of an hydrous, possibly alkaline, melt under decreasing melt mass

Observation of Thoracic Duct Morphology in Portal Hypertension by Endoscopic Ultrasound

Background:Thoracic duct dilation has been demonstrated in portal hypertension and hepatic cirrhosis by lymphangiography and laparotomy and at autopsy. It is thought to be secondary to increased hepatic lymph flow and has been described in the absence of ascites or esophageal varices. The aim of the present study was to observe thoracic duct morphology by endoscopic ultrasound in various subsets of patients with portal hypertension and hepatic cirrhosis and also to validate existing radiologic/surgical data. Methods:The thoracic duct of 33 patients with cirrhosis and portal hypertension was studied by endoscopic ultrasound. Patients were divided into four groups: 1, patients with ascites and esophageal varices; 2, esophageal varices without ascites; 3, without esophageal varices or ascites; 4, extrahepatic portal hypertension due to pancreatic malignancy. The thoracic duct diameter was also measured in 14 control subjects (group 5). Results:When the thoracic duct diameter for the five groups was compared with analysis of variance, significance was p \u3c 0.0001; by pairwise comparison, group 1 differed from the other four groups (p \u3c 0.05). Thoracic duct dilation (5.61 mm) was seen in group 1 patients, whereas no dilation was present in groups 2 through 4. Additionally, thoracic duct diameter in 33 portal hypertensive and/or cirrhotic patients was significantly different from that in the 14 control subjects (p = 0.003). Conclusion:The thoracic duct can be reliably identified by EUS in patients with hepatic cirrhosis and portal hypertension. Dilation of the duct is seen only in patients with hepatic cirrhosis, ascites, and esophageal varices. No thoracic duct dilation is present in extrahepatic portal hypertension. Contrary to existing radiologic/surgical data, thoracic duct dilation is not seen in all patients with hepatic cirrhosis and portal hypertension signifying advanced disease. A dilated thoracic duct by endoscopic ultrasound should be considered yet another sign of portal hypertension. (Gastrointest Endosc 1998;48:588-92.