Granular Rheology in Zero Gravity

We present an experimental investigation on the rheological behavior of model granular media made of nearly elastic spherical particles. The experiments are performed in a cylindrical Couette geometry and the experimental device is placed inside an airplane undergoing parabolic flights to cancel the effect of gravity. The corresponding curves, shear stress versus shear rate, are presented and a comparison with existing theories is proposed. The quadratic dependence on the shear rate is clearly shown and the behavior as a function of the solid volume fraction of particles exhibits a power law function. It is shown that theoretical predictions overestimate the experiments. We observe, at intermediate volume fractions, the formation of rings of particles regularly spaced along the height of the cell. The differences observed between experimental results and theoretical predictions are discussed and related to the structures formed in the granular medium submitted to the external shear.Comment: 10 pages, 6 figures to be published in Journal of Physics : Condensed Matte

Masses, Oxygen and Carbon abundances in CHEPS dwarf stars

Reproduced with permission from Astronomy & Astrophysics. © 2019 ESOContext. We report the results from the determination of stellar masses, carbon, and oxygen abundances in the atmospheres of 107 stars from the Calan-Hertfordshire Extrasolar Planet Search (CHEPS) programme. Our stars are drawn from a population with a significantly super-solar metallicity. At least 10 of these stars are known to host orbiting planets. Aims. In this work, we set out to understand the behaviour of carbon and oxygen abundance in stars with different spectral classes, metallicities, and V sin i within the metal-rich stellar population. Methods. Masses of these stars were determined using data from Gaia DR2. Oxygen and carbon abundances were determined by fitting the absorption lines. We determined oxygen abundances with fits to the 6300.304 Å O I line, and we used 3 lines of the C I atom and 12 lines of the C 2 molecule for the determination of carbon abundances. Results. We determine masses and abundances of 107 CHEPS stars. There is no evidence that the [C/O] ratio depends on V sin i or the mass of the star within our constrained range of masses, i.e. 0.82 5 km s -1) are massive stars.Peer reviewedFinal Published versio

Shocks in supersonic sand

We measure time-averaged velocity, density, and temperature fields for steady granular flow past a wedge and calculate a speed of granular pressure disturbances (sound speed) equal to 10% of the flow speed. The flow is supersonic, forming shocks nearly identical to those in a supersonic gas. Molecular dynamics simulations of Newton's laws and Monte Carlo simulations of the Boltzmann equation yield fields in quantitative agreement with experiment. A numerical solution of Navier-Stokes-like equations agrees with a molecular dynamics simulation for experimental conditions excluding wall friction.Comment: 4 pages, 5 figure

An Inversion Disrupting FAM134B Is Associated with Sensory Neuropathy in the Border Collie Dog Breed

Sensory neuropathy in the Border Collie is a severe neurological disorder caused by the degeneration of sensory and, to a lesser extent, motor nerve cells with clinical signs starting between 2 and 7 months of age. Using a genome-wide association study approach with three cases and 170 breed matched controls, a suggestive locus for sensory neuropathy was identified that was followed up using a genome sequencing approach. An inversion disrupting the candidate gene FAM134B was identified. Genotyping of additional cases and controls and RNAseq analysis provided strong evidence that the inversion is causal. Evidence of cryptic splicing resulting in novel exon transcription for FAM134B was identified by RNAseq experiments. This investigation demonstrates the identification of a novel sensory neuropathy associated mutation, by mapping using a minimal set of cases and subsequent genome sequencing. Through mutation screening, it should be possible to reduce the frequency of or completely eliminate this debilitating condition from the Border Collie breed population

Hyperon Nonleptonic Decays in Chiral Perturbation Theory Reexamined

We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic decays in chiral perturbation theory. Our results partially disagree with those calculated before, and include new terms previously omitted in the P-wave amplitudes. Although these modifications are numerically significant, they do not change the well-known fact that good agreement with experiment cannot be simultaneously achieved using one-loop S- and P-wave amplitudes.Comment: 14 pages, latex, 3 figures, uses axodraw.sty, minor additions, to appear in Phys. Rev.

Conversion of solid waste to activated carbon to improve landfill sustainability

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Landfills’ heterogeneous composites waste were evaluated as precursors for generation of activated carbon (AC). A single step chemical activation process was applied involving irradiation with microwave energy and impregnation with KOH. The average percentage yield of AC from active landfill precursor was higher than that from closed landfill for all depths sampled. Increase in impregnation ratio and irradiation power decreased the average percentage yield for both landfill precursors (Active: 38.1 to 33.1%) (Closed 42.1: to 33.3%). The optimum pH range for adsorption of methylene blue was pH 6-7, while adsorption increased with increase in temperature over the range 30 to 50oC. Carbonyl and hydroxyl groups were the major functional groups on the surface of AC. The properties of the AC are potentially suitable for the removal of cationic dyes and pollutants. AC generated from the landfill composite were comparable to that from some other biomass being managed through AC generation. This is the first report to demonstrate the possible reuse of landfill composite as AC. The reuse option of landfill composite could provide a means of sustainable management of landfilled municipal waste

Multivariate analysis of the effects of age, particle size and landfill depth on heavy metals pollution content of closed and active landfill precursors

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Multivariate analysis of a heavy metal pollution survey of closed and active landfill precursors was carried out in order to compare environmental risk levels in relation to age, particle size and depth of the precursors. Landfill precursors (77) were collected and analyzed for 15 USEPA toxic heavy metals using ICP-MS. Heavy metals concentrations in closed landfill precursors were significantly higher than those in the active landfill for 11 of 15 heavy metals investigated (closed landfill order: Fe > Al > Mn > Cu > Pb > Ba> Co > Cr > Ni > Cd > As > Se > Ti). Cluster analysis and correlation studies indicated the distribution of the metals was more influenced by landfill precursor size than by depth of the sample. Principal component analysis (PCA) showed that 10 of 15 of heavy metals of both landfill precursors were from similar anthropogenic sources. Heavy metals pollution indices (Igeo > 5, EF > 40 and CF > 7) of both active and closed landfill precursors exceeded limits in the order of Zn > Cd > Pb > Cu > Ag, indicating a major potential health risk influenced by age and particle size of precursor. Zn, Cd, Cu and Pb of both landfill precursors exceeded the USEPA set standard for assessment of human health risk for each of the metals (1×10 -4 to 1× 10-3). This study highlights the need for the integration of a clean-up process for precursors from both types of landfill to reduce possible environmental pollution during a reuse process

Chemical pretreatment of cells for enhanced MALDI-TOF-MS discrimination of clinical staphylococci including MRSA

BACKGROUND: Limited success has been reported for matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) differentiation of staphylococci, including methicillin resistant Staphylococcus aureus (MRSA) strains. Chemical pretreatment of cells prior to MALDI-TOF-MS analysis has not been systematically investigated for enhanced discrimination of S.aureus strains. OBJECTIVES: To evaluate various chemical pretreatment of cells for MALDI-TOF-MS discrimination of clinical staphylococcal isolates, with a focus on differentiation of MRSA from methicillin sensitive S. aureus (MSSA) strains and from other staphylococcal species. METHOD: MALDI-TOF-MS of a well-characterised S. aureus strain(s) was optimised with respect to matrix chemical(s), matrix solvent and target plating method. Various chemical pretreatments (solvents, reductants, detergents) and pretreatment application methods were then evaluated for enhancement of spectral richness. The three most promising pretreatments were applied to MALDI-TOF-MS discrimination of three set of clinical isolates comprising non-S.aureus staphylococci (77 isolates ), MSSA (36) and MRSA (43), with analysis by total or set specific resolved peaks. RESULTS: The optimized MALDI-TOF-MS protocol involved α-cyano-4-hydroxycinnamic acid (CHCA) as matrix chemical (in 1:2 acetonitrile:H2O and 2% trifluoroacetic acid), with application as an overlay onto smeared cells (on-probe). On-probe application of chemical pretreatment was most effective at enhancing MALDI-TOF-MS spectral richness. Use of reductants and detergents as pretreatments were ineffective. The three most effective solvents/acid pretreatments - ethanol:formate, ethanol:acetate and formate:isopropanol - each generated reproducible and distinct spectra over the 2,000 -10,000 m/z range. For the combined sets of clinical isolates (114), all three of these pretreatments increased the total number of resolved peaks in comparison with no pretreatment controls. The ethanol:formate pretreatment gave 100% clustering of non-S. aureus staphylococci, based on total resolved peaks. The formate:isopropanol pretreatment generated the largest increase in number of MRSA set specific peaks (from 18 to 32; 78% increase) and clustered the majority (77%) of the MRSA strains together, although compete discrimination of the MSSA and MRSA was not achieved. CONCLUSION: MALDI-TOF-MS discrimination of clinical isolates of staphylococci is enhanced through chemical pretreatment of cells. Three chemical pretreatments, not previously applied to staphylococci, are highlighted for enhancing spectral richness and offering new opportunities for improved discrimination of staphylococci, including MRSA and MSSA strains