Elastic electron scattering from water vapor and ice at high momentum transfer

We compare the area, peak separation, and width of the H and O elastic peak for light and heavy water, as observed in spectra of keV electrons scattered over large angles. Peak separation is well reproduced by the theory, but the O:H area ratio is somewhat larger than expected and is equal to the O:D area ratio. Thus no anomalous scattering from H was observed. Only minor differences are observed for scattering from a gaseous or a solid target. The extracted mean kinetic energy of H and D agreed within 5% with the calculated ones for ice. For the more difficult vapor measurements agreement was on a 12% level. A preliminary attempt to extract the O kinetic energy in ice agreed within 10% with the calculated values.This work was made possible by financial support of the Australian Research Council

Revised Academic Hardiness Scale Factor Structure in College Students

The construct of academic hardiness has gained attention in recent literature as an antecedent of successful academic performance and enrollment in higher education. Although academic hardiness scales have been validated for use with elementary and high school students, none have been examined in college students. The current study investigated the factor structure of the Revised Academic Hardiness Scale using two college student samples. Exploratory analyses found a five-factor structure in a sample of 454 students at a large university. Confirmatory analyses indicated adequate to good model fit for this solution in a sample of 160 students at a small college

Electron spectroscopy using two-dimensional electron detection and a camera in a single electron counting mode

A brief description is given of an economical implementation of the read out of a two-dimensional detector in an electron spectrometer by a charge coupled device camera, using a pulse counting mode. Count rates up to 10 kHz can be handled in this way. A comparison with results obtained using a resistive anode detector is given for the case of electron scattering from Xe atoms. Good agreement was obtained between both detection techniques, establishing the validity of the method described here.This research was made possible by a grant of the Australian Research Council

Geochemistry and mineralogy of Western Australian salt lake sediments: Implications for Meridiani Planum on Mars

Hypersaline lakes are characteristic for Western Australia and display a rare combination of geochemical and mineralogical properties which make these lakes potential analogues for past conditions on Mars. In our study we focused on the geochemistry and mineralogy of Lake Orr and Lake Whurr. While both lakes are poor in organic carbon (<1%) the sediments’ pH values differ and range from 3.8 to 4.8 in Lake Orr and from 5.4 to 6.3 in Lake Whurr sediments. Lake Whurr sediments were dominated by orange and red sediment zones in which the main Fe minerals were identified as hematite, goethite, and tentatively jarosite and pyrite. Lake Orr was dominated by brownish and blackish sediments where the main Fe minerals were goethite and another paramagnetic Fe(III)-phase that could not be identified. Furthermore, a likely secondary Fe(II)-phase was observed in Lake Orr sediments. The mineralogy of these two salt lakes in the sampling area is strongly influenced by events such as flooding, evaporation and desiccation, processes that explain at least to some extent the observed differences between Lake Orr and Lake Whurr. The iron mineralogy of Lake Whurr sediments and the high salinity make this lake a suitable analogue for Meridiani Planum on Mars and in particular the tentative identification of pyrite in Lake Whurr sediments has implications for the interpretation of the Fe mineralogy of Meridiani Planum sediments

Resource Efficiency of the Robot-Based Hybrid Additive Manufacturing Chain

Combining additive and subtractive metal processes to a hybrid additive manufacturing chain not only enables the production of parts with application-oriented design but also leads to increased resource efficiency especially when combined in an industrial robotic cell. Compared to parts manufactured through subtractive processes from full material the hybrid additive manufacturing chain is considered to be resource efficient due to reduced material consumption. However, the energy consumption of the hybrid additive process is considered higher because of the use of laser for the additive process. It is assumed that the decreased material consumption outweighs the higher energy consumption regarding the resource efficiency but until now it is not investigated. Therefore, in this paper the resource consumption of the robot-based hybrid additive manufacturing chain including the wire based direct energy deposition process and the milling process is analysed through measurements during experiments and compared to subtractive processes using the carbon footprint as a reference.Mechanical Engineerin

Experimental and Theoretical Cross Sections for Molecular-frame Electron-impact Excitation-ionization of D₂

We present both experimental and theoretical results for the dissociative ionization of D2 molecules induced by electron impact. Cross sections are determined in the molecular frame and are fully differential in the energies and emission angles of the dissociation fragments. Transitions are considered from the X1Σg+ electronic ground state of D2 to the 2sσg, 2pπu and 2pσu excited states of D2+. The experimental results are compared to calculations performed within the molecular four-body distorted-wave framework to describe the multicenter nature of the scattering process. The cross sections reveal a dramatic dependence on both the alignment of the internuclear axis with respect to the direction of the projectile momentum and on the symmetry of the excited dissociating state which is energetically resolved

Quasiparticle properties in a density functional framework

We propose a framework to construct the ground-state energy and density matrix of an N-electron system by solving selfconsistently a set of single-particle equations. The method can be viewed as a non-trivial extension of the Kohn-Sham scheme (which is embedded as a special case). It is based on separating the Green's function into a quasi-particle part and a background part, and expressing only the background part as a functional of the density matrix. The calculated single-particle energies and wave functions have a clear physical interpretation as quasiparticle energies and orbitals.Comment: 12 pages, 1 figure, to be published in Phys. Rev.

Fully differential cross-section measurements for electron-impact ionization of argon over the complete in-plane angular range

The triple differential cross section for electron-impact ionization of the 3p orbital of argon by 113.5 eV incident electrons has been measured using a magnetic angle changer in a conventional (e,2e) spectrometer. Results are presented for 2 eV ejected electrons over an extended angular range, and over the complete coplanar scattering plane for 5 eV ejected electrons. The data reveal previously unobserved structures, and are compared with recent distorted-wave Born approximation (DWBA) and hybrid DWBA R-matrix calculations. Large discrepancies exist between experiment and both calculations in the accessed regions.M. A. Stevenson and B. Lohman

Influence of contour scans on surface roughness and pore formation using Scalmalloy® manufactured by laser powder bed fusion (PBF‐LB)

The scandium modified aluminium alloy Scalmalloy® is specifically developed for the use in laser‐based powder bed fusion (PBF‐LB). It is supposed to show potential in the production of lightweight structures due to its high specific strength compared to other aluminium alloys. A limiting factor is the high surface roughness of additively manufactured parts, which has a negative influence on its mechanical properties, especially under cyclic loads. In order to reduce the surface roughness, methods of design of experiments (DoE) are applied to develop contour parameters. Additionally, the formation of pores in keyhole‐mode welding and strategies to reduce the porosity in the contour area are investigated. The surface roughness of vertical walls can be reduced down to Ra 0.9 J mm⁻¹ but keyhole pores start to form applying EL >0.6– 0.75 J mm⁻¹. Two contour parameter sets in different EL‐ranges are developed that can be used to reduce the surface roughness compared to parameter sets without contour scans, without increasing the porosity in the contour area. Their impact on the mechanical properties has to be further investigated