673 research outputs found
PO-0918: Effects of everyday low-dose pre-irradiation followed by higher dose on cancer and normal cells in vitro
Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer Part II- Experimental Results
In this paper is presented a preceding procedure that should be conducted in order to successfully regenerate damaged forging dies by the hard facing process. After the tool damage types identification, as well as their causes, we have chosen the procedure and the parameters of hard facing that we further corrected by conducting the test hard facings on models. Thus, we were able to relate the experimental results outputs with the repair technology, taking as a criterion the quality of the surface layers wear resistance such as friction coefficient and width of hard faced zone, hardness and its distribution in cross section, then microstructure of characteristic of hard faced zones, etc. This research points out significancy of tribological properties of certain types of carbides and their effects on metal matrix, in which carbides are embedded. Our tribological investigations have shown that the working life of the hard faced tool can be longer than that of the new tool
Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer - Part I - Theoretical Considerations
This paper gives a theoretical review of influence of the most important alloying elements on steel, and review of the most important carbide-forming elements and states the conditions which elements should fulfill in order to be considered as carbide-forming. It primarily involves alloying elements which in the iron-carbon system can form simple, complex or special carbides, i.e. phases of interstitial and substitutive type. It also gives a review of carbide types that are formed during either production or reparatory hard facing of steel parts with different types of filler materials
Multi-phonon scattering and Ti-induced hydrogen dynamics in sodium alanate
We use ab initio methods and neutron inelastic scattering (NIS) to study the
structure, energetics, and dynamics of pure and Ti-doped sodium alanate
(NaAlH_4), focusing on the possibility of substitutional Ti doping. The NIS
spectrum is found to exhibit surprisingly strong and sharp two-phonon features.
The calculations reveal that substitutional Ti doping is energetically
possible. Ti prefers to substitute for Na and is a powerful hydrogen attractor
that facilitates multiple Al--H bond breaking. Our results hint at new ways of
improving the hydrogen dynamics and storage capacity of the alanates.Comment: 5 pages, with 4 postscript figures embedded. Uses REVTEX4 and
graphicx macro
Electronic structure and optical properties of lightweight metal hydrides
We study the electronic structures and dielectric functions of the simple
hydrides LiH, NaH, MgH2 and AlH3, and the complex hydrides Li3AlH6, Na3AlH6,
LiAlH4, NaAlH4 and Mg(AlH4)2, using first principles density functional theory
and GW calculations. All these compounds are large gap insulators with GW
single particle band gaps varying from 3.5 eV in AlH3 to 6.5 eV in the MAlH4
compounds. The valence bands are dominated by the hydrogen atoms, whereas the
conduction bands have mixed contributions from the hydrogens and the metal
cations. The electronic structure of the aluminium compounds is determined
mainly by aluminium hydride complexes and their mutual interactions. Despite
considerable differences between the band structures and the band gaps of the
various compounds, their optical responses are qualitatively similar. In most
of the spectra the optical absorption rises sharply above 6 eV and has a strong
peak around 8 eV. The quantitative differences in the optical spectra are
interpreted in terms of the structure and the electronic structure of the
compounds.Comment: 13 pages, 10 figure
Mixed Brain Pathologies in Dementia: The BrainNet Europe Consortium Experience
Background: Dementia results from heterogeneous diseases of the brain. Mixed disease forms are increasingly recognized. Methods: We performed a survey within brain banks of BrainNet Europe to estimate the proportion of mixed disease forms underlying dementia and age- and gender-specific influences. Results: Data collected in 9 centres from 3,303 individuals were analysed. The proportion of patients with mixed diagnoses among all cases with Alzheimer disease (AD), vascular pathology (VP), argyrophilic grain dementia (AGD), and synucleinopathies, such as Lewy body dementia (LBD), Parkinson disease (PD) and synuclein pathology only in the amygdala, was 53.3%. Mixed pathology was more frequently reported with LBD, PD, AGD, and VP than with AD. The percentage of mixed diagnoses for AGD and VP significantly differed between centres. In patients younger than 75 years, synucleinopathies, and pure forms of AD, VP, and AGD were more frequent in men. Above 75 years of age, more women had pure AD and pure AGD. Conclusions: The most obvious neuropathological alteration should not terminate the diagnostic procedure since copathology is likely to be found. Neuropathological interpretation of AGD and VP has not been sufficiently established in a consensus. Pure forms of synucleinopathies are unlikely sole substrates for dementia. Copyright (C) 2008 S. Karger AG, Base
Structure and Thermodynamics of the Mixed Alkali Alanates
The thermodynamics and structural properties of the hexahydride alanates
(M2M'AlH6) with the elpasolite structure have been investigated. A series of
mixed alkali alanates (Na2LiAlH6, K2LiAlH6 and K2NaAlH6) were synthesized and
found to reversibly absorb and desorb hydrogen without the need for a catalyst.
Pressure-composition isotherms were measured to investigate the thermodynamics
of the absorption and desorption reactions with hydrogen. Isotherms for
catalyzed (4 mol% TiCl3) and uncatalyzed Na2LiAlH6 exhibited an increase in
kinetics, but no change in the bulk thermodynamics with the addition of a
dopant. A structural analysis using synchrotron x-ray diffraction showed that
these compounds favor the Fm-3m space group with the smaller ion (M') occupying
an octahedral site. These results demonstrate that appropriate cation
substitutions can be used to stabilize or destabilize the material and may
provide an avenue to improving the unfavorable thermodynamics of a number of
materials with promising gravimetric hydrogen densities.Comment: 6 pages, 7 figures,3 tables, submitted to PR
Raman study of insulating and conductive ZnO: (Al, Mn) thin films
Raman spectroscopy results obtained for undoped and Al- and/or Mn-doped ZnO thin films produced by RF-sputtering are reported. The effect of the doping method (either co-sputtering or ion implantation), the dopant type and its concentration on the Raman-active vibrational modes in these films were studied in detail. The results are discussed with focus on the peak shifts and broadening, and on the doping-induced relaxation of the symmetry selection rules. A particular attention is paid to the 520-530 cm-1 Raman band observed in all Mn containing samples and a simple theoretical model and arguments are presented in support of its relation to the local (gap) phonon mode produced by Mn atoms substituting Zn in the cationic sublattice of the ZnO crystal.Karlsruhe Nano Micro Facility (KNMF), a Helmholtz Research Infrastructure at KI
Influence of surface morphology on erosion of plasma-facing components in H-mode plasmas of ASDEX Upgrade
Net erosion of plasma-facing materials was investigated at the low-field-side (outer) strike-point area of the ASDEX Upgrade (AUG) divertor during H-mode discharges with small and frequent ELMs. To this end, Au and Mo marker samples with different surface morphologies and geometries were exposed to plasmas using the DIMII divertor manipulator. The results were compared to existing erosion and deposition patterns from various Land H-mode experiments, in the latter case the main difference was the size and frequency of the ELMs. We noticed that increasing surface roughness reduces net erosion but less than what is the case in L-mode. On the other hand, net-erosion rates in H-mode are generally 2–5 times higher than the corresponding L-mode values, in addition to which exposure in H-mode conditions results in strong local variations in the poloidal and toroidal erosion/deposition profiles. The latter observation we associate with the large migration length, on the order of several cm, of the eroded material, resulting in strong competition between erosion and re-deposition processes especially at poloidal distances > 50 mm from the strike point. Considerable net erosion was measured throughout the analysed poloidal region unlike in L-mode where the main erosion peak occurs in the vicinity of the strike point. We attribute this qualitative difference to the slow decay lengths of the plasma flux and electron temperature in the applied H-mode scenario. Both erosion and deposition require detailed analyses at the microscopic scale and the deposition patterns may be drastically different for heavy and light impurities. Generally, the rougher the surface the more material will accumulate on locally shadowed regions behind protruding surface features. However, rough surfaces also exhibit more non-uniformities in the quality or even integrity of marker coatings produced on them, thus complicating the analyses of the experimental data. We conclude that local plasma parameters have a huge impact on the PFC erosion rates and, besides incident plasma flux, surface morphology and its temporal evolution have to be taken into account for quantitative estimates of erosion rates and PFC lifetime under reactor-relevant conditions
Massive Black Hole Binary Inspirals: Results from the LISA Parameter Estimation Taskforce
The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007
to provide the LISA Project with vetted codes, source distribution models, and
results related to parameter estimation. The Taskforce's goal is to be able to
quickly calculate the impact of any mission design changes on LISA's science
capabilities, based on reasonable estimates of the distribution of
astrophysical sources in the universe. This paper describes our Taskforce's
work on massive black-hole binaries (MBHBs). Given present uncertainties in the
formation history of MBHBs, we adopt four different population models, based on
(i) whether the initial black-hole seeds are small or large, and (ii) whether
accretion is efficient or inefficient at spinning up the holes. We compare four
largely independent codes for calculating LISA's parameter-estimation
capabilities. All codes are based on the Fisher-matrix approximation, but in
the past they used somewhat different signal models, source parametrizations
and noise curves. We show that once these differences are removed, the four
codes give results in extremely close agreement with each other. Using a code
that includes both spin precession and higher harmonics in the
gravitational-wave signal, we carry out Monte Carlo simulations and determine
the number of events that can be detected and accurately localized in our four
population models.Comment: 14 pages, 2 figures, 5 tables, minor changes to match version to be
published in the proceedings of the 7th LISA Symposium. For more information
see the Taskforce's wiki at http://www.tapir.caltech.edu/dokuwiki/lisape:hom
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