Processing of Silicon Carbide by Laser Micro Sintering

Silicon carbide – a solid with covalent bonds - is conventionally synthesized via the Acheson process. Usually solid bodies of silicon carbide with definite shapes are generated from the grained material via hot isostatic pressing or liquid phase sintering. Both processes are conducted under well-controlled temperature regimes. Applying the freeform fabrication technique “Laser Micro Sintering” poses a big challenge to experimental skill due to the nonequilibrium conditions that are characteristic features of laser material processing. Successive layers SiC layers with a thickness of 1μm were processed with coherent radiation of 1064 nm. The specific behavior of two different silicon carbide powders - one of them blended with additives - are reported along with interpretational approaches.Mechanical Engineerin

A mosaic maternal splice donor mutation in the EHMT1 gene leads to aberrant transcripts and to Kleefstra syndrome in the offspring

The euchromatic histone-lysine N-methyltransferase 1 (EHMT1) gene was examined in a 3-year-old boy with characteristic clinical features of Kleefstra syndrome. Sequencing of all 27 EHMT1 exons revealed a novel mutation, NM_024757.4:c.2712+1G>A, which affects the splice donor of intron 18. Whereas the index patient is heterozygous for that mutation, his phenotypically normal mother shows tissue-specific mosaicism. Sequencing of EHMT1 RT-PCR products revealed two aberrant transcript variants: in one variant, exon 18 was skipped; in the other, a near-by GT motif was used as splice donor and intronic sequence was inserted between exons 18 and 19. Both transcript variants were found in the patient and his mother. The latter had lower amounts of these transcripts consistent with mosaic status. This is the first description of an EHMT1 point mutation being inherited from a parent with verified mosaicism. The constitutive c.2712+1G>A splice site mutation in EHMT1 is fully pathogenic, and the transcript variants produced do not attenuate the severity of the disease.European Journal of Human Genetics advance online publication, 12 December 2012; doi:10.1038/ejhg.2012.267

Thermodynamic Models for the Temperature and Pressure Variations Within Adiabatic Caverns of Compressed Air Energy Storage Plants

The temperature and pressure variation limits within the cavern of a compressed air energy storage (CAES) plant affect the compressor and turbine works, the required fuel consumption and therefore the overall plant performance. In the present work, the thermodynamic response of adiabatic cavern reservoirs to charge/discharge cycles of CAES plants are studied. Solutions for the air cavern temperature and pressure variations were derived from the mass and energy conservation equations, and applied to three different gas state equations, namely, ideal, real, and a self-developed simplified gas models. Sensitivity analyses were conducted to identify the dominant parameters that affect the storage temperature and pressure fluctuations. It is demonstrated that a simplified gas model can adequately represent the air thermodynamic properties. The stored air maximal to minimal temperature and pressure ratios were found to depend primarily on, both the ratio of the injected to the initial cavern air mass, and the reservoir mean pressure. The results also indicate that the storage volume is highly dependent on the air maximum to minimum pressure ratio. Its value should preferably be in between 1.2 and 1.8, where the exact selection should account for design and economic criteria

The impact of corporate philanthropy on reputation for corporate social performance

This study seeks to examine the mechanisms by which a corporation’s use of philanthropy affects its reputation for corporate social performance (CSP), which the authors conceive of as consisting of two dimensions: CSP awareness and CSP perception. Using signal detection theory (SDT), the authors model signal amplitude (the amount contributed), dispersion (number of areas supported), and consistency (presence of a corporate foundation) on CSP awareness and perception. Overall, this study finds that characteristics of firms' portfolio of philanthropic activities are a greater predictor of CSP awareness than of CSP perception. Awareness increases with signal amplitude, dispersion, and consistency. CSP perception is driven by awareness and corporate reputation. The authors’ contention that corporate philanthropy is a complex variable is upheld, as we find that CSP signal characteristics influence CSP awareness and perception independently and asymmetrically. The authors conclude by proposing avenues for future research

The 63^{63}Ni(n,γ\gamma) cross section measured with DANCE

The neutron capture cross section of the s-process branch nucleus $^{63}$Ni affects the abundances of other nuclei in its region, especially $^{63}$Cu and $^{64}$Zn. In order to determine the energy dependent neutron capture cross section in the astrophysical energy region, an experiment at the Los Alamos National Laboratory has been performed using the calorimetric 4$\pi$ BaF$_2$ array DANCE. The (n,$\gamma$) cross section of $^{63}$Ni has been determined relative to the well known $^{197}$Au standard with uncertainties below 15%. Various $^{63}$Ni resonances have been identified based on the Q-value. Furthermore, the s-process sensitivity of the new values was analyzed with the new network calculation tool NETZ.Comment: 11 pages, 13 page

Non-Statistical Effects in Neutron Capture

There have been many reports of non-statistical effects in neutron-capture measurements. However, reports of deviations of reduced-neutron-width distributions from the expected Porter-Thomas (PT) shape largely have been ignored. Most of these deviations have been reported for odd-A nuclides. Because reliable spin (J) assignments have been absent for most resonances for such nuclides, it is possible that reported deviations from PT might be due to incorrect J assignments. We recently developed a new method for measuring spins of neutron resonances by using the DANCE detector at LANSCE. Measurements made with a 147Sm sample allowed us to determine spins of almost all known resonances below 1 keV. Furthermore, analysis of these data revealed that the reduced-neutron-width distribution was in good agreement with PT for resonances below 350 eV, but in disagreement with PT for resonances between 350 and 700 eV. Our previous (n,alpha) measurements had revealed that the alpha strength function also changes abruptly at this energy. There currently is no known explanation for these two non-statistical effects. Recently, we have developed another new method for determining the spins of neutron resonances. To implement this technique required a small change (to record pulse-height information for coincidence events) to a much simpler apparatus: A pair of C6D6 gamma-ray detectors which we have employed for many years to measure neutron-capture cross sections at ORELA. Measurements with a 95Mo sample revealed that not only does the method work very well for determining spins, but it also makes possible parity assignments. Taken together, these new techniques at LANSCE and ORELA could be very useful for further elucidation of non-statistical effects.Comment: 8 pages, 3 figures, for proceedings of CGS1