Smoothed particle magnetohydrodynamic simulations of protostellar outflows with misaligned magnetic field and rotation axes

We have developed a modified form of the equations of smoothed particle magnetohydrodynamics which are stable in the presence of very steep density gradients. Using this formalism, we have performed simulations of the collapse of magnetised molecular cloud cores to form protostars and drive outflows. Our stable formalism allows for smaller sink particles (< 5 AU) than used previously and the investigation of the effect of varying the angle, {\theta}, between the initial field axis and the rotation axis. The nature of the outflows depends strongly on this angle: jet-like outflows are not produced at all when {\theta} > 30{\deg}, and a collimated outflow is not sustained when {\theta} > 10{\deg}. No substantial outflows of any kind are produced when {\theta} > 60{\deg}. This may place constraints on the geometry of the magnetic field in molecular clouds where bipolar outflows are seen.Comment: Accepted for publication in MNRAS, 13 pages, 14 figures. Animations can be found at http://www.astro.ex.ac.uk/people/blewis/research/outflows_misaligned_fields.htm

Control Force Compensation in Ground-Based Flight Simulators

This paper presents the results of a study that investigated if controller force compensations accounting for the inertial force and moment due to the aircraft motion during flight have a significant effect on pilot control behavior and performance. Seven rotorcraft pilots performed a side-step and precision hovering task in light turbulence in the Vertical Motion Simulator. The effects of force compensation were examined for two different simulated rotorcraft: linear and UH-60 dynamics with two different force gradient of the lateral stick control. Four motion configurations were used: large motion, hexapod motion, fixed-base motion, and fixed-base motion with compensation. Control-input variables and task performance such as the time to translate to the designated hover position, station-keeping position errors, and handling qualities ratings were used as measures. Control force compensation enabled pilot control behavior and performance more similar to that under high- or medium-fidelity motion to some extent only. Control force compensation did not improve overall task performance considering both rotorcraft models at the same time. The control force compensation had effects on the linear model with lighter force gradient, but only a minimal effect on pilots? control behavior and task performance for the UH-60 model, which had a higher force gradient. This suggests that the control force compensation has limited benefits for controllers that have higher stiffness

Smoothed particle magnetohydrodynamic simulations of protostellar outflows with misaligned magnetic field and rotation axes (dataset)

The compressed tarballs in this repository contain the binary output data from the SPMHD (smoothed particle magnetohydrodynamics) simulation presented in the paper. The data is a Fortran binary file in big-endian format. The DAT???? files are dumps of the simulation spaced every 1/100 of a free-fall time and can be read in Splash (Written by Daniel Price, see http://users.monash.edu.au/~dprice/splash/). The Atest_? and Ptest_? files contain information on accreted particles and sink particles respectively (again in big-endian format). The two Fortran programs in utils.tar.xz can read these files and output ASCII data. The tarballs themselves are named according to the following scheme: theta_*.tar.xz are the 1.5 million particle simulations presented as the main result of the paper, where theta_0.tar.xz is a fully aligned model and theta_90.tar.xz is fully misaligned (i.e. theta = 90) &c.; lowres_*.tar.xz are the two low-resolution collapse simulations earlier in the paper and disc_*.tar.xz are the two test models. For both the low-resolution and test models, `clean' denotes the result of using and unmodified code and `hav' denotes the new formalism presented in the paper. All the plots in the paper, except for Figs. 13 and 14, can be produced using Splash and the `DAT' files directly. Figs. 13 and 14 use the data extracted from the `A' and `P' files.The journal article associated with this datast was published in Monthly Notices of the Royal Astronomical Society Vol. 451 (1), pp 288-299. doi: 10.1093/mnras/stv957 and is in ORE at http://hdl.handle.net/10871/19588The article associated with this dataset is available in ORE at http://hdl.handle.net/10871/19588.This is the dataset that was used to produce the paper published in MNRAS. Included are the binary dump files from each of the simulations in the paper and two utilities that can be used to produce an ASCII file detailing accreted particles.Science and Technology Facilities CouncilEuropean Research CouncilAustralian Research Council Discovery Project GrantUniversity of Exeter Supercomputer: jointly funded by Science and Technology Facilities Council (STFC), Large Facilities Capital Fund of BIS, and the University of Exeter DiRac Complexity computer: jointly funded by Science and Technology Facilities Council (STFC) and the Large Facilities Capital Fund of BI

Si/TiO_2 Tandem-Junction Microwire Arrays for Unassisted Solar-Driven Water Splitting

Tandem-junction microwire array photoelectrodes have been fabricated by coating np^+-Si radial homojunction microwire arrays sequentially with fluorine-doped tin oxide (FTO) and titanium dioxide (TiO_2). These photoelectrodes effected unassisted water splitting under simulated 1 Sun conditions with an open-circuit potential (E_(oc)) of −1.5 V vs the formal potential for oxygen evolution, E^(0′)(OH^−/O_2), a current density at E = E^(0′)(OH^−/O_2) of 0.78 mA cm^(−2), a fill factor ( ff ) = 0.51, and a photovoltaic-biased photoelectrochemical ideal regenerative cell efficiency of 0.6%

Vibronic coupling in the superoxide anion: The vibrational dependence of the photoelectron angular distribution

We present a comprehensive photoelectron imaging study of the O₂(X³Σg⁻,v′=0–6)←O₂⁻(X²Πg,v′′=0) and O₂(a¹Δg,v′=0–4)←O₂⁻(X²Πg,v′′=0)photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v′=1–4 data for detachment into the ground electronic state, presented in a recent communication [R. Mabbs, F. Mbaiwa, J. Wei, M. Van Duzor, S. T. Gibson, S. J. Cavanagh, and B. R. Lewis, Phys. Rev. A82, 011401–R (2010)]. Measured vibronic intensities are compared to Franck–Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model [R. M. Stehman and S. B. Woo, Phys. Rev. A23, 2866 (1981)]. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy,β(E), displays the characteristics of photodetachment from a d-like orbital, consistent with the π∗g 2p highest occupied molecular orbital of O₂⁻. However, differences exist between the β(E) trends for detachment into different vibrational levels of the X³Σg⁻ and a ¹Δg electronic states of O₂. The ZCC model invokes vibrational channel specific “detachment orbitals” and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O₂: the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.The authors gratefully acknowledge support by the National Science Foundation Grant No. CHE-0748738 and ANU ARC Discovery Projects under Grant Nos. DP0666267 and DP0880850

O-GlcNAc modification blocks the aggregation and toxicity of the protein α-synuclein associated with Parkinson's disease.

Several aggregation-prone proteins associated with neurodegenerative diseases can be modified by O-linked N-acetyl-glucosamine (O-GlcNAc) in vivo. One of these proteins, α-synuclein, is a toxic aggregating protein associated with synucleinopathies, including Parkinson's disease. However, the effect of O-GlcNAcylation on α-synuclein is not clear. Here, we use synthetic protein chemistry to generate both unmodified α-synuclein and α-synuclein bearing a site-specific O-GlcNAc modification at the physiologically relevant threonine residue 72. We show that this single modification has a notable and substoichiometric inhibitory effect on α-synuclein aggregation, while not affecting the membrane binding or bending properties of α-synuclein. O-GlcNAcylation is also shown to affect the phosphorylation of α-synuclein in vitro and block the toxicity of α-synuclein that was exogenously added to cells in culture. These results suggest that increasing O-GlcNAcylation may slow the progression of synucleinopathies and further support a general function for O-GlcNAc in preventing protein aggregation

Appropriateness of intensive care treatments near the end of life during the COVID-19 pandemic

The patient and family perspective on the appropriateness of intensive care unit (ICU) treatments involves preferences, values and social constructs beyond medical criteria. The clinician’s perception of inappropriateness is more reliant on clinical judgment. Earlier consultation with families before ICU admission and patient education on the outcomes of life-sustaining therapies may help reconcile these provider–patient disagreements. However, global emergencies like COVID-19 change the usual paradigm of end-of-life care, as it is a new disease with only scarce predictive information about it. Pandemics can also bring about the burdensome predicament of doctors having to make unwanted choices of rationing access to the ICU when demand for otherwise life-saving resources exceeds supply. Evidence-based prognostic checklists may guide treatment triage but the principles of shared decision-making are unchanged. Yet, they need to be altered with respect to COVID-19, defining likely outcomes and likelihood of benefit for the patient, and clarifying their willingness to take on the risks inherent to being in an ICU for 2 weeks for those eligible. For patients who are admitted during the prodrome of COVID-19 disease, or those who deteriorate in the second week, clinicians have some lead time in hospital to have appropriate discussions about ceilings of treatments offered based on severity

Spatial Curvature Falsifies Eternal Inflation

Inflation creates large-scale cosmological density perturbations that are characterized by an isotropic, homogeneous, and Gaussian random distribution about a locally flat background. Even in a flat universe, the spatial curvature measured within one Hubble volume receives contributions from long wavelength perturbations, and will not in general be zero. These same perturbations determine the Cosmic Microwave Background (CMB) temperature fluctuations, which are O(10^-5). Consequently, the low-l multipole moments in the CMB temperature map predict the value of the measured spatial curvature \Omega_k. On this basis we argue that a measurement of |\Omega_k| > 10^-4 would rule out slow-roll eternal inflation in our past with high confidence, while a measurement of \Omega_k < -10^-4 (which is positive curvature, a locally closed universe) rules out false-vacuum eternal inflation as well, at the same confidence level. In other words, negative curvature (a locally open universe) is consistent with false-vacuum eternal inflation but not with slow-roll eternal inflation, and positive curvature falsifies both. Near-future experiments will dramatically extend the sensitivity of \Omega_k measurements and constitute a sharp test of these predictions.Comment: 16+2 pages, 2 figure