The Two Phases of Galaxy Formation

Cosmological simulations of galaxy formation appear to show a two-phase character with a rapid early phase at z>2 during which in-situ stars are formed within the galaxy from infalling cold gas followed by an extended phase since z<3 during which ex-situ stars are primarily accreted. In the latter phase massive systems grow considerably in mass and radius by accretion of smaller satellite stellar systems formed at quite early times (z>3) outside of the virial radius of the forming central galaxy. These tentative conclusions are obtained from high resolution re-simulations of 39 individual galaxies in a full cosmological context with present-day virial halo masses ranging from 7e11 M_sun h^-1 < M_vir < 2.7e13 M_sun h^-1 and central galaxy masses between 4.5e10 M_sun h^-1 < M_* < 3.6e11 M_sun h^-1. The simulations include the effects of a uniform UV background, radiative cooling, star formation and energetic feedback from SNII. The importance of stellar accretion increases with galaxy mass and towards lower redshift. In our simulations lower mass galaxies ($M_* < 9e10 M_sun h^-1) accrete about 60 per cent of their present-day stellar mass. High mass galaxy ($M_* > 1.7e11 M_sun h^-1) assembly is dominated by accretion and merging with about 80 per cent of the stars added by the present-day. In general the simulated galaxies approximately double their mass since z=1. For massive systems this mass growth is not accompanied by significant star formation. The majority of the in-situ created stars is formed at z>2, primarily out of cold gas flows. We recover the observational result of archaeological downsizing, where the most massive galaxies harbor the oldest stars. We find that this is not in contradiction with hierarchical structure formation. Most stars in the massive galaxies are formed early on in smaller structures, the galaxies themselves are assembled late.Comment: 13 pages, 13 figures, accepted for publication in Ap

Investigation of reactivity of launch vehicle materials with liquid oxygen Quarterly report, 23 Jul. - 22 Oct. 1968

Reactivity of launch vehicle organic materials with liquid oxyge

Investigation of Reactivity of Launch Vehicle Materials with Liquid Oxygen

Impact sensitivity and ignition mechanism of organic compounds in liquid oxygen correlated with chemical and physical propertie

Methylation age acceleration does not predict mortality in schizophrenia.

Schizophrenia (SCZ) is associated with high mortality. DNA methylation levels vary over the life course, and pre-selected combinations of methylation array probes can be used to estimate "methylation age" (mAge). mAge correlates highly with chronological age but when it differs, termed mAge acceleration, it has been previously associated with all-cause mortality. We tested the association between mAge acceleration and mortality in SCZ and controls. We selected 190 SCZ cases and 190 controls from the Sweden Schizophrenia Study. Cases were identified from the Swedish Hospital Discharge Register with ≥5 specialist treatment contacts and ≥5 antipsychotic prescriptions. Controls had no psychotic disorder or antipsychotics. Subjects were selected if they had died or survived during follow-up (2:1 oversampling). Extracted DNA was assayed on the Illumina MethylationEPIC array. mAge was regressed on age at sampling to obtain mAge acceleration. Using Cox proportional hazards regression, the association between mAge acceleration and mortality was tested. After quality control, the following were available: n = 126 SCZ died, 63 SCZ alive, 127 controls died, 62 controls alive. In the primary analyses, we did not find a significant association between mAge acceleration and SCZ mortality (adjusted p &gt; 0.005). Sensitivity analyses excluding SCZ cases with pre-existing cancer demonstrated a significant association between the Hannum mAge acceleration and mortality (hazard ratio = 1.13, 95% confidence interval = 1.04-1.22, p = 0.005). Per our pre-specified criteria, we did not confirm our primary hypothesis that mAge acceleration would predict subsequent mortality in people with SCZ, but we cannot rule out smaller effects or effects in patient subsets

Spatial processing is frequency-specific in auditory cortex but not in the midbrain

The cochlea behaves like a bank of band-pass filters, segregating information into different frequency channels. Some aspects of perception reflect processing within individual channels, but others involve the integration of information across them. One instance of this is sound localization, which improves with increasing bandwidth. The processing of binaural cues for sound location has been extensively studied. However, while the advantage conferred by bandwidth is clear we currently know little about how this additional information is combined to form our percept of space. We investigated the ability of cells in the auditory system of guinea pigs to compare interaural level differences (ILDs), a key localization cue, between tones of disparate frequencies in each ear. Cells in auditory cortex, believed to be integral to ILD processing (Excitatory from one ear, Inhibitory from the other: EI cells), separately compare ILDs over restricted frequency ranges, not consistent with their monaural tuning. In contrast, cortical EE (Excitatory from both ears) cells showed no evidence of frequency-specific processing. Both cell types are explained by a model in which ILDs are computed within separate frequency channels and subsequently combined in a single cortical cell. Interestingly, ILD processing in all inferior colliculus cell types (EE and EI) is largely consistent with processing within single matched frequency channels from each ear. Our data suggests a clear constraint on the way that localisation cues are integrated: cortical ILD tuning to broadband sounds is a composite of separate frequency-specific binaurally sensitive channels. This frequency-specific processing appears after the midbrain

3D multiphysics model for the simulation of electrochemical machining of stainless steel (SS316)

In Electrochemical Machining (ECM) - a method that uses anodic dissolution to remove metal - it is extremely difficult to predict material removal and resulting surface finish due to the complex interaction between the numerous parameters available in the machining conditions. In this paper, it is argued that a 3D coupled multiphysics finite element model is a suitable way to further develop the ability to model the ECM process. This builds on the work of previous researchers and further claims that the over-potential available at the surface of the workpiece is a crucial factor in ensuring satisfactory results. As a validation example, a real world problem for polishing via ECM of SS316 pipes is modelled and compared to empirical tests. Various physical and chemical effects, including those due to electrodynamics, fluid dynamic, and thermal and electrochemical phenomena were incorporated in the 3D geometric model of the proposed tool, workpiece and electrolyte. Predictions were made for current density, conductivity, fluid velocity, temperature, and crucially, with estimates of the deviations in over-potential. Results revealed a good agreement between simulation and experiment and these were sufficient to solve the immediate real problem presented but also to ensure that future additions to the technique could in the longer term lead to a better means of understanding a most useful manufacturing process