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

Regolith-atmosphere exchange of water in Mars' recent past

We investigate the exchange of water vapour between the regolith and atmosphere of Mars, and how it varies with different orbital parameters, atmospheric dust contents and surface water ice reservoirs. This is achieved through the coupling of a global circulation model (GCM) and a regolith diffusion model. GCM simulations are performed for hundreds of Mars years, with additional one-dimensional simulations performed for 50 kyr. At obliquities ε = 15° and 30°, the thermal inertia and albedo of the regolith have more control on the subsurface water distribution than changes to the eccentricity or solar longitude of perihelion. At ε = 45°, atmospheric water vapour abundances become much larger, allowing stable subsurface ice to form in the tropics and mid-latitudes. The circulation of the atmosphere is important in producing the subsurface water distribution, with increased water content in various locations due to vapour transport by topographically-steered flows and stationary waves. As these circulation patterns are due to topographic features, it is likely the same regions will also experience locally large amounts of subsurface water at different epochs. The dustiness of the atmosphere plays an important role in the distribution of subsurface water, with a dusty atmosphere resulting in a wetter water cycle and increased stability of subsurface ice deposits

Magnetically levitated mesenchymal stem cell spheroids cultured with a collagen gel maintain phenotype and quiescence

Multicellular spheroids are an established system for three-dimensional cell culture. Spheroids are typically generated using hanging drop or non-adherent culture; however, an emerging technique is to use magnetic levitation. Herein, mesenchymal stem cell spheroids were generated using magnetic nanoparticles and subsequently cultured within a type I collagen gel, with a view towards developing a bone marrow niche environment. Cells were loaded with magnetic nanoparticles, and suspended beneath an external magnet, inducing self-assembly of multicellular spheroids. Cells in spheroids were viable and compared to corresponding monolayer controls, maintained stem cell phenotype and were quiescent. Interestingly, core spheroid necrosis was not observed, even with increasing spheroid size, in contrast to other commonly used spheroid systems. This mesenchymal stem cell spheroid culture presents a potential platform for modelling in vitro bone marrow stem cell niches, elucidating interactions between cells, as well as a useful model for drug delivery studies

Being Bad in a Video Game can Make Us Morally Sensitive

Several researchers have demonstrated that the virtual behaviors committed in a video game can elicit feelings of guilt. Researchers have proposed that such guilt could have prosocial consequences. However, this proposition has not been supported with empirical evidence. The current study examined this issue in a 2 2 (video game play vs. real world recollection guilt vs. control) experiment. Participants were first randomly assigned to either play a video game or complete a memory recall task. Next, participants were randomly assigned to either a guilt-inducing condition (game play as a terrorist/recall of acts that induce guilt) or a control condition (game play as a UN soldier/recall of acts that do not induce guilt). Results of the study indicate several important findings. First, the current results replicate previous research indicating that immoral virtual behaviors are capable of eliciting guilt. Second, and more importantly, the guilt elicited by game play led to intuition-specific increases in the salience of violated moral foundations. These findings indicate that committing "immoral" virtual behaviors in a video game can lead to increased moral sensitivity of the player. The potential prosocial benefits of these findings are discussed.Advertisin

Future Type Ia Supernova Data as Tests of Dark Energy from Modified Friedmann Equations

In the Cardassian model, dark energy density arises from modifications to the Friedmann equation, which becomes H^2 = g(\rhom), where g(\rhom) is a new function of the energy density. The universe is flat, matter dominated, and accelerating. The distance redshift relation predictions of generalized Cardassian models can be very different from generic quintessence models, and can be differentiated with data from upcoming pencil beam surveys of Type Ia Supernovae such as SNAP. We have found the interesting result that, once $\Omega_m$ is known to 10% accuracy, SNAP will be able to determine the sign of the time dependence of the dark energy density. Knowledge of this sign (which is related to the weak energy condition) will provide a first discrimination between various cosmological models that fit the current observational data (cosmological constant, quintessence, Cardassian expansion). Further, we have performed Monte Carlo simulations to illustrate how well one can reproduce the form of the dark energy density with SNAP. To be concrete we study a class of two parameter ($n$,$q$) generalized Cardassian models that includes the original Cardassian model (parametrized by $n$ only) as a special case. Examples are given of MP Cardassian models that fit current supernovae and CMB data, and prospects for differentiating between MP Cardassian and other models in future data are discussed. We also note that some Cardassian models can satisfy the weak energy condition $w>-1$ even with a dark energy component that has an effective equation of state $w_X < -1$.Comment: revised version accepted by Ap

Phosphine Functionalization of GaAs(111)A Surfaces

Phosphorus-functionalized GaAs surfaces have been prepared by exposure of Cl-terminated GaAs(111)A surfaces to triethylphosphine (PEt3) or trichlorophosphine (PCl3), or by the direct functionalization of the native-oxide terminated GaAs(111)A surface with PCl3. The presence of phosphorus on each functionalized surface was confirmed by X-ray photoelectron spectroscopy. High-resolution, soft X-ray photoelectron spectroscopy was used to evaluate the As and Ga 3d regions of such surfaces. On PEt3 treated surfaces, the Ga 3d spectra exhibited a bulk Ga peak as well as peaks that were shifted to 0.35, 0.92 and 1.86 eV higher binding energy. These peaks were assigned to residual Cl-terminated Ga surface sites, surficial Ga2O and surficial Ga2O3, respectively. For PCl3-treated surfaces, the Ga 3d spectra displayed peaks ascribable to bulk Ga(As), Ga2O, and Ga2O3, as well as a peak shifted 0.30 eV to higher binding energy relative to the bulk signal. A peak corresponding to Ga(OH)3, observed on the Cl-terminated surface, was absent from all of the phosphine-functionalized surfaces. After reaction of the Cl-terminated GaAs(111)A surface with PCl3 or PEt3, the As 3d spectral region was free of As oxides and As0. Although native oxide-terminated GaAs surfaces were free of As oxides after reaction with PCl3, such surfaces contained detectable amounts of As0. Photoluminescence measurements indicted that phosphine-functionalized surfaces prepared from Cl-terminated GaAs(111)A surfaces had better electrical properties than the native-oxide capped GaAs(111)A surface, while the native-oxide covered surface treated with PCl3 showed no enhancement in PL intensity