1,782 research outputs found
The Impact of Galactic Disc Environment on Star-Forming Clouds
We explore the effect of different galactic disc environments on the
properties of star-forming clouds through variations in the background
potential in a set of isolated galaxy simulations. Rising, falling and flat
rotation curves expected in halo dominated, disc dominated and Milky Way-like
galaxies were considered, with and without an additional two-arm spiral
potential. The evolution of each disc displayed notable variations that are
attributed to different regimes of stability, determined by shear and
gravitational collapse. The properties of a typical cloud were largely
unaffected by the changes in rotation curve, but the production of small and
large cloud associations was strongly dependent on this environment. This
suggests that while differing rotation curves can influence where clouds are
initially formed, the average bulk properties are effectively independent of
the global environment. The addition of a spiral perturbation made the greatest
difference to cloud properties, successfully sweeping the gas into larger,
seemingly unbound, extended structures and creating large arm-interarm
contrasts.Comment: Accepted to MNRAS on 3rd December, 201
Dislocation arrangement in small crystal volumes determines power-law size dependence of yield strength
postprin
Superplasticity of a nano-grained Mg-Gd-Y-Zr alloy processed by high-pressure torsion
While most of the reports on Mg-Gd-Y-Zr alloys report superplasticity after extrusion or friction stir processing, it is important to investigate superplasticity in these alloys after other severe plastic deformation processes having greater grain refinement capability. Accordingly, superplasticity was studied in an Mgâ9Gdâ4Yâ0.4Zr (GW94) alloy after different high-pressure torsion (HPT) conditions. The HPT was performed at room temperature under an applied pressure of 6.0 GPa for up to 16 turns. TEM microstructural characterization revealed that the grain size was reduced from an initial value of ?8.6 ?m in the extruded condition to ?95±10 and ?85±10 nm after 8 and 16 turns, respectively. A shear punch testing method was used for evaluation of superplasticity at 573, 623, 673 and 723 K. Maximum strain rate sensitivities of ?0.51±0.05 and ?0.48±0.05 were obtained at 623 K for the material processed through 16 and 8 turns, respectively. This strain rate sensitivity and an activation energy of ?100±5 kJ molâ1 suggests the occurrence of grain boundary sliding in the superplastic regio
Comparative methylome analysis in solid tumors reveals aberrant methylation at chromosome 6p in nasopharyngeal carcinoma
© 2015 The Authors. Cancer Medicine published by John Wiley & Sons Ltd. Altered patterns of DNA methylation are key features of cancer. Nasopharyngeal carcinoma (NPC) has the highest incidence in Southern China. Aberrant methylation at the promoter region of tumor suppressors is frequently reported in NPC; however, genome-wide methylation changes have not been comprehensively investigated. Therefore, we systematically analyzed methylome data in 25 primary NPC tumors and nontumor counterparts using a high-throughput approach with the Illumina HumanMethylation450 BeadChip. Comparatively, we examined the methylome data of 11 types of solid tumors collected by The Cancer Genome Atlas (TCGA). In NPC, the hypermethylation pattern was more dominant than hypomethylation and the majority of de novo methylated loci were within or close to CpG islands in tumors. The comparative methylome analysis reveals hypermethylation at chromosome 6p21.3 frequently occurred in NPC (false discovery rate; FDR=1.33 à 10 -9 ), but was less obvious in other types of solid tumors except for prostate and Epstein-Barr virus (EBV)-positive gastric cancer (FDR < 10 -3 ). Bisulfite pyrosequencing results further confirmed the aberrant methylation at 6p in an additional patient cohort. Evident enrichment of the repressive mark H3K27me3 and active mark H3K4me3 derived from human embryonic stem cells were found at these regions, indicating both DNA methylation and histone modification function together, leading to epigenetic deregulation in NPC. Our study highlights the importance of epigenetic deregulation in NPC. Polycomb Complex 2 (PRC2), responsible for H3K27 trimethylation, is a promising therapeutic target. A key genomic region on 6p with aberrant methylation was identified. This region contains several important genes having potential use as biomarkers for NPC detection.published_or_final_versio
Choice of acquisition form in Australia and the post-takeover employment of target firm directors on the acquiring firm board
© 2017 AFAANZ In Australia, a corporate acquisition can be structured as either a scheme of arrangement or a takeover. We investigate the association between deal structure and the retention of target directors on the merged entity board. We find that the odds of a target director subsequently sitting on the merged entity's board are significantly higher in schemes. The results also show that premiums are lower in schemes of arrangement when additional target directors are appointed to the board of the acquiring firm. The findings indicate that target director appointment is unrelated to the merged entity's post-acquisition performance
To scheme or bid? Choice of takeover method and impact on premium
© 2015, © The Author(s) 2015. In recent years there has been an increasing use of membersâ schemes of arrangement to bring about a change in corporate control. This increasing use of schemes has been criticised in public quarters on the basis that unlike takeovers, schemes are not subject to the Eggleston principles and have arguably led to target shareholders receiving lower offer prices. This study provides the first large-sample empirical evidence on differences between schemes and takeovers. We find that the likelihood of the use of schemes significantly increases when target firm ownership concentration is higher and when the bidder has a lower toehold. Scheme usage is also more likely for larger targets and bidders with higher leverage. Consistent with public criticisms of schemes, we find that after controlling for self-selection premiums in schemes are significantly lower than those in takeovers
Report of the QCD Tools Working Group
We report on the activities of the ``QCD Tools for heavy flavors and new
physics searches'' working group of the Run II Workshop on QCD and Weak Bosons.
The contributions cover the topics of improved parton showering and comparisons
of Monte Carlo programs and resummation calculations, recent developments in
Pythia, the methodology of measuring backgrounds to new physics searches,
variable flavor number schemes for heavy quark electro-production, the
underlying event in hard scattering processes, and the Monte Carlo MCFM for NLO
processes.Comment: LaTeX, 47 pages, 41 figures, 10 tables, uses run2col.sty, to appear
in the Proceedings of the Workshop on "QCD and Weak Boson Physics in Run II",
Fermilab, March - November 199
Handheld Standoff Mine Detection System (HSTAMIDS) Operational Field Evaluation in Cambodia
Handheld Standoff Mine Detection System (HSTAMIDS) Operational Field Evaluation in Cambodi
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