Colour Metallography of Ferrous Alloys and its Applications to iron and Steel Making

Reagents used to show the structure of metallographie samples may give reaction products which dissolve in the reagent; or, on the contrary , products may be insoluble and remain in the place, forming thin films, more or less adherent. Both kinds of reagents attack the various const-ituents,at least in the initial stage, at different rates ; namely, they are selective with respect to: 1. The different phases in the sample. 2. Heterogeneity of solid solutions. 3. Crystallographic orientation of the phases. 4. Internal stress in the lattices. In boundaries between crystal grains of a, metal aggregate, these different heterogeneities accumulate in large measure, and, therefore, boundaries are gen-erally etched by reagents more quickly than the core of the grains, consequently, reagents of the first kind, at the first steps of attack, develop on the sur-face of the sample a network of grooves, more or less deep, which shows the granular pattern of the aggregate. Therefore, the surface of the sample, which was mirrorlike before etching, becomes uneven and, at the microroscope, through the contrast of lights and shadows, reveals the structure of the metal. With the second kind of reagents, on the other hand, the products of reaction form, at least in the first steps of attack, films which are more or less epitassic, and whose thickness is a function of etching rate, and, therefore, of the above mentioned heterogeneities. When etching goes on for a longer time, the first layers formed protect to some extent the underlaying metal, and the rate of subsequent etching is influenced also by other factors, as for instance, diffusion rate of the reagent through the first layers formed

Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy

Near exit plane non-resonant light induced fluorescence spectroscopy is performed in a Hall effect low-power Xenon thruster at discharge voltage of 250V and anode flow rate of 0.7mg/sec. Measurement of the axial and radial velocity components are performed, exciting the 6s[3/2]_2-->6p[3/2]_2 transition at 823.16nm in XeI and the 5d[4]_(7/2)-->6p[3]_(5/2) transition at 834.724nm in XeII. No significant deviation from the thermal velocity is observed for XeI. Two most probable ion velocities are registered at a given position with respect to the thruster axis, which are mainly attributed to different areas of creation of ions inside the acceleration channel. The spatial resolution of the set-up is limited by the laser beam size (radius of the order of 0.5mm) and the fluorescence collection optics, which have a view spot diameter of 8mm.Comment: 6 pages, 8 figure

Ion dynamic characterization using phase-resolved laser-induced fluorescence spectroscopy in low power Hall effect thruster

Valuable information on the dynamics of the plasma constituents in Hall effect thrusters can be extracted with minimally intrusive means such as time-resolved light-induced fluorescence diagnostics. In general, maps of the ion velocity distribution function are built for plasma characterization using different techniques. One of the most relevant phenomena under investigation is the so called breathing mode that is characterized by intense and quasi-periodic oscillation of the discharge current. The goal of this work is to propose a new approach for plasma dynamic studies based on parallelized laser-induced fluorescence spectroscopy with phase-resolution within the breathing period.Comment: 6 pages, 11 figures, 29 reference

Base Excision Repair in Sugarcane – A New Outlook

The base excision repair (BER) pathway has been associated with genome integrity maintenance. Owing to its central role, BER is present in all three domains of life. The studies in plants, considering BER, have been conducted using Arabidopsis and rice models. Therefore, future studies regarding BER are required in other organisms, particularly in crops such as sugarcane, to understand its mechanism, which may reflect the uniqueness of DNA repair in monocots. Our previous results have revealed that sugarcane is an interesting plant for studying this pathway considering the polyploidy genome and genome evolution. This chapter aimed to characterize the BER pathway in sugarcane by using different bioinformatics tools, for example, screening for BER homologs in the sugarcane genome to identify its members. Each sequence obtained was subjected to structural analysis, and certain differences were identified when Arabidopsis was compared to other monocots, including sugarcane. Moreover, ROS1, DEM, and DML3 were not identified as a complete sequence in the sugarcane EST database. Furthermore, FEN1 is present as two sequences, namely FEN1A and FEN1B, both featuring different amino acid sequence and motif presence. Furthermore, FEN1 sequence was selected for further characterization considering its evolutionary history, as sequence duplication was observed only in the Poaceae family. Considering the importance of this protein for BER pathway, this sequence was evaluated using protein models (3D), and a possible conservation was observed during protein–protein interaction. Thus, these results help us understand the roles of certain BER components in sugarcane, and may reveal the aspects and functions of this pathway beyond those already established in the literature

advanced electric propulsion diagnostic tools at iom

Abstract Recently, we have set up an Advanced Electric Propulsion Diagnostic (AEPD) platform [1] , which allows for the in-situ measurement of a comprehensive set of thruster performance parameters. The platform utilizes a five-axis-movement system for precise positioning of the thruster with respect to the diagnostic heads. In the first setup (AEPD1) an energy-selective mass spectrometer (ESMS) and a miniaturized Faraday probe for ion beam characterization, a telemicroscope and a triangular laser head for measuring the erosion of mechanical parts, and a pyrometer for surface temperature measurements were integrated. The capabilities of the AEPD1 platform were demonstrated with two electric propulsion thrusters, a gridded ion thruster RIT 22 (Airbus Defence & Space, Germany, [13]) and a Hall effect thruster SPT 100D EM1 (EDB Fakel, Russia, [1] , [4] ), in two different vacuum facilities