A-posteriori error estimation in axisymmetric geotechnical analyses

In this paper, an a-posteriori error estimator suitable for use in axisymmetric geotechnical analyses has been developed. The consolidation superconvergent patch recovery with equilibrium and boundaries (CSPREB) method, developed for plane-strain coupledconsolidation problems, is extended to axisymmetric analyses. The use of pore pressures in the error estimator was found to improve results when predicting consolidation. Collapse loads under undrained soil conditions are known to be over-predicted due to “locking”, especially in axial symmetry where there are further displacement constraints. The proposed solution technique reduced locking slightly, but could not eliminate it, as it is inherent in the displacement formulation for lower order elements

Dark Matter Contraction and the Stellar Content of Massive Early-type Galaxies: Disfavoring "Light" Initial Mass Functions

We use stellar dynamics, strong lensing, stellar population synthesis models, and weak lensing shear measurements to constrain the dark matter (DM) profile and stellar mass in a sample of 53 massive early-type galaxies. We explore three DM halo models (unperturbed Navarro Frenk & White [NFW] halos and the adiabatic contraction models of Blumenthal and Gnedin) and impose a model for the relationship between the stellar and virial mass (i.e., a relationship for the star-formation efficiency as a function of halo mass). We show that, given our model assumptions, the data clearly prefer a Salpeter-like initial mass function (IMF) over a lighter IMF (e.g., Chabrier or Kroupa), irrespective of the choice of DM halo. In addition, we find that the data prefer at most a moderate amount of adiabatic contraction (Blumenthal adiabatic contraction is strongly disfavored) and are only consistent with no adiabatic contraction (i.e., a NFW halo) if a mass-dependent IMF is assumed, in the sense of a more massive normalization of the IMF for more massive halos.Comment: 6 pages, 3 figures; submitted to ApJL, including revisions based upon the referee repor

A Relationship between Supermassive Black Hole Mass and the Total Gravitational Mass of the Host Galaxy

We investigate the correlation between the mass of a central supermassive black hole and the total gravitational mass of the host galaxy (M_tot). The results are based on 43 galaxy-scale strong gravitational lenses from the Sloan Lens ACS (SLACS) Survey whose black hole masses were estimated through two scaling relations: the relation between black hole mass and Sersic index (M_bh - n) and the relation between black hole mass and stellar velocity dispersion (M_bh - sigma). We use the enclosed mass within R_200, the radius within which the density profile of the early type galaxy exceeds the critical density of the Universe by a factor of 200, determined by gravitational lens models fitted to HST imaging data, as a tracer of the total gravitational mass. The best fit correlation, where M_bh is determined from M_bh - sigma relation, is log(M_bh) = (8.18 +/- 0.11) + (1.55 +/- 0.31) (log(M_tot) - 13.0) over 2 orders of magnitude in M_bh. From a variety of tests, we find that we cannot reliably infer a connection between M_bh and M_tot from the M_bh - n relation. The M_bh - M_tot relation provides some of the first, direct observational evidence to test the prediction that supermassive black hole properties are determined by the halo properties of the host galaxy.Comment: 29 pages, 10 figures, Accepted for publication in Ap

Golden gravitational lensing systems from the Sloan Lens ACS Survey. II. SDSS J1430+4105: A precise inner total mass profile from lensing alone

We study the SLACS strong lensing system SDSSJ1430+4105 at z=0.285. The lensed source (z=0.575) of this system has a complex morphology with several subcomponents. Its subcomponents span a radial range from 4 to 10kpc in the lens plane. Therefore we can constrain the slope of the total projected mass profile around the Einstein radius (R_E) from lensing alone. We measure a density profile that is slightly but not significantly shallower than isothermal at R_E. We decompose the mass of the lensing galaxy into a de Vaucouleurs (deV) component to trace the stars and an additional dark component. The spread of multiple image components over a large radial range also allows us to determine the amplitude of the deV and dark matter components separately. We get a mass to light ratio of M_deV/L_B~5.5\pm1.5M/L_sun,B and a dark matter fraction within R_E of ~20 to 40%. Modelling the star formation history assuming composite stellar populations at solar metallicity to the galaxy's photometry yields a mass to light ratio of M_star,salp/L_B~4.0_{-1.3}^{+0.6}M/L_sun,B and M_star,chab/L_B~2.3_{-0.8}^{+0.3}M/L_sun,B for Salpeter and Chabrier IMFs, respectively. Hence, the mass to light ratio derived from lensing is more Salpeter-like, in agreement with results for massive Coma galaxies and other nearby massive early type galaxies. We examine the consequences of the galaxy group in which the lensing galaxy is embedded, showing that it has little influence on the mass to light ratio obtained for the deV component of the lensing galaxy. Finally, we decompose the projected, azimuthally averaged 2D density distribution of the deV and dark matter component of the lensing signal into spherically averaged 3D density profiles. We can show that the 3D dark and luminous matter density within R_E~0.6R_eff of this SLACS galaxy is similar to the values of Coma galaxies with the same velocity dispersions.Comment: 24 pages, 21 figures, 11 tables, accepted for publication by MNRA

Social preferences and agricultural innovation: An experimental case study from Ethiopia

We run an experiment in Ethiopia where farmers can use their own money to decrease the money of others (money burning). The data support the prediction from an inequality aversion model based on absolute income differences; but there is no support for an inequality aversion model based on comparison with mean payoff of others. Experimentally measured money burning on the village level is negatively correlated to real-life agricultural innovations. This result is robust even when data from another independent survey than the current research are used. This underscores the importance of social preferences in agricultural innovations in developing countries

Exploring students’ reflective writing on Facebook

[EN] According to our experience, facilitating online reflective writing via Facebook motivates students to improve their writing skills and reflective thinking. Six students and a teacher from an urban school in the northern region of Malaysia were involved in this study. The qualitative data in the form of online archives were categorized as reflection-in-action (feedback and self-correction) based on Garrison et al.'s (2000) cognitive presence. Additionally, reflection-on-action which comprised the students’ reflective journal demonstrated their thoughts and feelings while engaged in the Facebook environment. Data suggested that feedback only related to grammar and sentence structures (micro aspects). There was no feedback relating to organization and content (macro aspects). The reflective journal revealed that Facebook can be considered as a successful platform to enhance students’ narrative writing. The findings of this study have implications for teaching and learning activities in web-based environments.Annamalai, N.; Jaganathan, P. (2017). Exploring students’ reflective writing on Facebook. The EuroCALL Review. 25(2):3-17. doi:10.4995/eurocall.2017.7750SWORD31725

PubChem3D: Similar conformers

<p>Abstract</p> <p>Background</p> <p>PubChem is a free and open public resource for the biological activities of small molecules. With many tens of millions of both chemical structures and biological test results, PubChem is a sizeable system with an uneven degree of available information. Some chemical structures in PubChem include a great deal of biological annotation, while others have little to none. To help users, PubChem pre-computes "neighboring" relationships to relate similar chemical structures, which may have similar biological function. In this work, we introduce a "Similar Conformers" neighboring relationship to identify compounds with similar 3-D shape and similar 3-D orientation of functional groups typically used to define pharmacophore features.</p> <p>Results</p> <p>The first two diverse 3-D conformers of 26.1 million PubChem Compound records were compared to each other, using a shape Tanimoto (ST) of 0.8 or greater and a color Tanimoto (CT) of 0.5 or greater, yielding 8.16 billion conformer neighbor pairs and 6.62 billion compound neighbor pairs, with an average of 253 "Similar Conformers" compound neighbors per compound. Comparing the 3-D neighboring relationship to the corresponding 2-D neighboring relationship ("Similar Compounds") for molecules such as caffeine, aspirin, and morphine, one finds unique sets of related chemical structures, providing additional significant biological annotation. The PubChem 3-D neighboring relationship is also shown to be able to group a set of non-steroidal anti-inflammatory drugs (NSAIDs), despite limited PubChem 2-D similarity.</p> <p>In a study of 4,218 chemical structures of biomedical interest, consisting of many known drugs, using more diverse conformers per compound results in more 3-D compound neighbors per compound; however, the overlap of the compound neighbor lists per conformer also increasingly resemble each other, being 38% identical at three conformers and 68% at ten conformers. Perhaps surprising is that the average count of conformer neighbors per conformer increases rather slowly as a function of diverse conformers considered, with only a 70% increase for a ten times growth in conformers per compound (a 68-fold increase in the conformer pairs considered).</p> <p>Neighboring 3-D conformers on the scale performed, if implemented naively, is an intractable problem using a modest sized compute cluster. Methodology developed in this work relies on a series of filters to prevent performing 3-D superposition optimization, when it can be determined that two conformers cannot possibly be a neighbor. Most filters are based on Tanimoto equation volume constraints, avoiding incompatible conformers; however, others consider preliminary superposition between conformers using reference shapes.</p> <p>Conclusion</p> <p>The "Similar Conformers" 3-D neighboring relationship locates similar small molecules of biological interest that may go unnoticed when using traditional 2-D chemical structure graph-based methods, making it complementary to such methodologies. The computational cost of 3-D similarity methodology on a wide scale, such as PubChem contents, is a considerable issue to overcome. Using a series of efficient filters, an effective throughput rate of more than 150,000 conformers per second per processor core was achieved, more than two orders of magnitude faster than without filtering.</p

The Density Profiles of Massive, Relaxed Galaxy Clusters. II. Separating Luminous and Dark Matter in Cluster Cores

We present stellar and dark matter (DM) density profiles for a sample of seven massive, relaxed galaxy clusters derived from strong and weak gravitational lensing and resolved stellar kinematic observations within the centrally-located brightest cluster galaxies (BCGs). In Paper I of the series, we demonstrated that the total density profile derived from these data, which span 3 decades in radius, is consistent with numerical DM-only simulations at radii >~ 5-10 kpc, despite the significant contribution of stellar material in the core. Here we decompose the inner mass profiles of these clusters into stellar and dark components. Parametrizing the DM density profile as a power law rho_DM ~ r^{-\beta} on small scales, we find a mean slope = 0.50 +- 0.10 (random) +0.14-0.13 (systematic). Alternatively, cored Navarro-Frenk-White (NFW) profiles with = 1.14 +- 0.13 (random) +0.14-0.22 (systematic) provide an equally good description. These density profiles are significantly shallower than canonical NFW models at radii <~ 30 kpc, comparable to the effective radii of the BCGs. The inner DM profile is correlated with the distribution of stars in the BCG, suggesting a connection between the inner halo and the assembly of stars in the central galaxy. The stellar mass-to-light ratio inferred from lensing and stellar dynamics is consistent with that inferred using stellar population synthesis models if a Salpeter initial mass function is adopted. We compare these results to theories describing the interaction between baryons and DM in cluster cores, including adiabatic contraction models and the possible effects of galaxy mergers and active galactic nucleus feedback, and evaluate possible signatures of alternative DM candidates.Comment: Updated to matched the published version in Ap

Universal IMF vs dark halo response in early-type galaxies: breaking the degeneracy with the fundamental plane

We use the relations between aperture stellar velocity dispersion (\sigma_ap), stellar mass (M_sps), and galaxy size (R_e) for a sample of \sim 150,000 early-type galaxies from SDSS/DR7 to place constraints on the stellar initial mass function (IMF) and dark halo response to galaxy formation. We build LCDM based mass models that reproduce, by construction, the relations between galaxy size, light concentration and stellar mass, and use the spherical Jeans equations to predict \sigma_ap. Given our model assumptions (including those in the stellar population synthesis models), we find that reproducing the median \sigma_ap vs M_sps relation is not possible with {\it both} a universal IMF and a universal dark halo response. Significant departures from a universal IMF and/or dark halo response are required, but there is a degeneracy between these two solutions. We show that this degeneracy can be broken using the strength of the correlation between residuals of the velocity-mass (\Delta log \sigma_ap) and size-mass (\Delta log R_e) relations. The slope of this correlation, d_vr \equiv \Delta log \sigma_ap/\Delta log R_e, varies systematically with galaxy mass from d_vr \simeq -0.45 at M_sps \sim 10^{10}M_sun, to d_vr \simeq -0.15 at M_sps \sim 10^{11.6} M_sun. The virial fundamental plane (FP) has d_vr=-1/2, and thus we find the tilt of the observed FP is mass dependent. Reproducing this tilt requires {\it both} a non-universal IMF and a non-universal halo response. Our best model has mass-follows-light at low masses (Msps < 10^{11.2}M_sun) and unmodified NFW haloes at M_sps \sim 10^{11.5} M_sun. The stellar masses imply a mass dependent IMF which is "lighter" than Salpeter at low masses and "heavier" than Salpeter at high masses.Comment: 19 pages, 16 figures, accepted to MNRAS. More extensive discussion, 4 new figures, conclusions unchange