Cervelleite, Ag4TeS: solution and description of the crystal structure

Copyright: Springer-Verlag Wien 2015. This is the final, post refereeing version. You are advised to consult the publisher's version if you wish to cite from it, http://link.springer.com/article/10.1007%2Fs00710-015-0384-

Secondary Electron Emission Induced by Electron Bombardment of Polycrystalline Metallic Targets

The aim of the present paper is the analysis of the backward secondary electron emission phenomenon, under electron bombardment, on the basis of experimental and theoretical results. Among the theoretical models, we will mention the phenomenological models, those which use a Monte-Carlo type simulation method, and those based on the numerically solved Boltzmann transport equation. To correlate experimental and theoretical results on all the data characterizing this phenomenon, it is necessary to use an appropriate description for the excitation process of the internal secondary electrons; it also needs a complete description of the transport process for the excited electrons, which incorporates the elastic and inelastic interactions, as well as the energy and angular distribution of the incident primary beam. From this, it follows that it will be necessary, either to use a direct Monte-Carlo simulation method, or, in the case of the transport model, to carry out a preliminary treatment of the primary electron dispersion; this treatment is also based upon a Boltzmann equation resolution. The results of such an analysis will be useful in electron microscopy and in quantitative Auger spectroscopy

Transport Models for Backscattering and Transmission of Low Energy ( \u3c 3 Kilovolts) Electrons from Solids

This paper deals with the backscattering and the transmission of electrons with energy \u3c 3 keV through thin self supporting films, or on bulk metals. We present the main theoretical models used in such problems, and we analyse mainly the models based on the Boltzmann transport equation, similar to those developed in our laboratory. For any model shown here, we try to give the precise domain in which they give reliable results as well as the limitations connected to the simplifying assumptions. In the case of the most sophisticated model, we give original results for copper. The models are presented in a comparative form, and when it is possible we compare our results with the experimental ones. The theoretical models were applied to Al and Cu. We give, for bulk metals, the values of the backscattering yield, and the energy distributions of backscattered electrons. In the case of thin self supporting films, we studied mainly the backscattering and transmission coefficients, as well as the energy distributions of transmitted and backscattered electrons

Detection of variations in precipitation at different time scales of twentieth century at three locations of Italy

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Shock Synthesis of Decagonal Quasicrystals

Abstract The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al71Ni24Fe5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al73Ni19Fe4Cu2Mg0.6Mo0.4Mn0.3 with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe alloy with the B2 (CsCl-type) structure and the metastable Al9Ni2 phase. We present chemical (scanning electron microscopy and electron microprobe) and structural (electron backscatter diffraction and transmission electron microscopy) characterization of the recovered phases and discuss the implications of this shock synthesis for the stability of quasicrystals during high-pressure shocks and for the interpretation of the phase assemblage found in Khatyrka

Eliopoulosite, V7S8, A New Sulfide from the Podiform Chromitite of the Othrys Ophiolite, Greece

The new mineral species, eliopoulosite, V7S8, was discovered in the abandoned chromium mine of Agios Stefanos of the Othrys ophiolite, located in central Greece. The investigated samples consist of massive chromitite hosted in a strongly altered mantle tectonite, and are associated with nickelphosphide, awaruite, tsikourasite, and grammatikopoulosite. Eliopoulosite is brittle and has a metallic luster. In plane-reflected polarized light, it is grayish-brown and shows no internal reflections, bireflectance, and pleochroism. It is weakly anisotropic, with colors varying from light to dark greenish. Reflectance values of mineral in air (Ro, Re’ in %) are: 34.8–35.7 at 470 nm, 38–39 at 546 nm, 40–41.3 at 589 nm, and 42.5–44.2 at 650 nm. Electron-microprobe analyses yielded a mean composition (wt.%) of: S 41.78, V 54.11, Ni 1.71, Fe 1.1, Co 0.67, and Mo 0.66, totali 100.03. On the basis of Σatoms = 15 apfu and taking into account the structural data, the empirical formula of eliopoulosite is (V6.55Ni0.19Fe0.12Co0.07Mo0.04)Σ = 6.97S8.03. The simplified formula is (V, Ni, Fe)7S8 and the ideal formula is V7S8, which corresponds to V 58.16%, S 41.84%, total 100 wt.%. The density, based on the empirical formula and unit-cell volume refined form single-crystal structure XRD data, is 4.545 g·cm−3. The mineral is trigonal, space group P3221, with a = 6.689(3) Å, c = 17.403(6) Å, V = 674.4(5) Å3, Z = 3, and exhibits a twelve-fold superstructure (2a × 2a × 3c) of the NiAs-type subcell with V-atoms octahedrally coordinated by S atoms. The distribution of vacancies is discussed in relation to other pyrrhotite-like compounds. The mineral name is for Dr. Demetrios Eliopoulos (1947–2019), a geoscientist at the Institute of Geology and Mineral Exploration (IGME) of Greece and his widow, Prof. Maria Eliopoulos (nee Economou, 1947), University of Athens, Greece, for their contributions to the knowledge of ore deposits of Greece and to the mineralogical, petrographic, and geochemical studies of ophiolites, including the Othrys complex. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association (No. 2019-96).© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

The AMS-02 Time of Flight System. Final Design

The AMS-02 detector is a superconducting magnetic spectrometer that will operate on the International Space Station. The time of flight (TOF) system of AMS-02 is composed by four scintillator planes with 8, 8, 10, 8 counters each, read at both ends by a total of 144 phototubes. This paper describes the new design, the expected performances, and shows preliminary results of the ion beam test carried on at CERN on October 2002.Comment: 4 pages, 6 EPS figures. Proc. of the 28th ICRC (2003