Coarsening Dynamics of Granular Heaplets in Tapped Granular Layers

A semi-continuum model is introduced to study the dynamics of the formation of granular heaplets in tapped granular layers. By taking into account the energy dissipation of collisions and screening effects due to avalanches, this model is able to reproduce qualitatively the pattern of these heaplets. Our simulations show that the granular heaplets are characterised by an effective surface tension which depends on the magnitude of the tapping intensity. Also, we observe that there is a coarsening effect in that the average size of the heaplets, V grows as the number of taps k increases. The growth law at intermediate times can be fitted by a scaling function V ~ k^z but the range of validity of the power law is limited by size effects. The growth exponent z appears to diverge as the tapping intensity is increased.Comment: 4 pages, 4 figure

Spin transport in a unitary Fermi gas close to the BCS transition

We consider spin transport in a two-component ultracold Fermi gas with attractive interspecies interactions close to the BCS pairing transition. In particular, we consider the spin-transport relaxation rate and the spin-diffusion constant. Upon approaching the transition, the scattering amplitude is enhanced by pairing fluctuations. However, as the system approaches the transition, the spectral weight for excitations close to the Fermi level is decreased by the formation of a pseudogap. To study the consequence of these two competing effects, we determine the spin-transport relaxation rate and the spin-diffusion constant using both a Boltzmann approach and a diagrammatic approach. The former ignores pseudogap physics and finite lifetime effects. In the latter, we incorporate the full pseudogap physics and lifetime effects, but we ignore vertex corrections, so that we effectively calculate single-particle relaxation rates instead of transport relaxation rates. We find that there is qualitative agreement between these two approaches although the results for the transport coefficients differ quantitatively.Comment: 9 pages, 10 figure

Affective iconic words benefit from additional sound–meaning integration in the left amygdala

Recent studies have shown that a similarity between sound and meaning of a word (i.e., iconicity) can help more readily access the meaning of that word, but the neural mechanisms underlying this beneficial role of iconicity in semantic processing remain largely unknown. In an fMRI study, we focused on the affective domain and examined whether affective iconic words (e.g., high arousal in both sound and meaning) activate additional brain regions that integrate emotional information from different domains (i.e., sound and meaning). In line with our hypothesis, affective iconic words, compared to their non‐iconic counterparts, elicited additional BOLD responses in the left amygdala known for its role in multimodal representation of emotions. Functional connectivity analyses revealed that the observed amygdalar activity was modulated by an interaction of iconic condition and activations in two hubs representative for processing sound (left superior temporal gyrus) and meaning (left inferior frontal gyrus) of words. These results provide a neural explanation for the facilitative role of iconicity in language processing and indicate that language users are sensitive to the interaction between sound and meaning aspect of words, suggesting the existence of iconicity as a general property of human language

The dynamical behaviour of shallow-marine dunes

In the period 1995-1999, a detailed morpho- and sediment dynamical investigation was carried out in the western Belgian near coastal area, in water depths of -3 to -15 m MLLWS. Through chronosequential bathymetrical and digital side-scan sonar registrations supplemented by intensive samplings, a quantitative monitoring of the most dynamic zones was accomplished. Although, the area is generally devoid of bedforms, well-constraint zones of very large dunes occur where the bed shear stresses are highest. Since, suspended load accounts for more than 80 %, the dimensions seem to be largely controlled by the amount of the total load actually taking part in bedform development. A clear differentiation exists between the morphology of the dunes and their surficial sediments, the troughs being up to 0.30 phi finer than the crests. During the observation period, the similarities in crestline positions were more striking than the differences and showed a maximum shift of only 20 m. The data set allowed to differentiate the vulnerability of the area to varying hydro-meteorological conditions and showed that the area recovers fairly quickly from stormy periods

Shock tunnel studies of scramjet phenomena

Commissioning of the new T4 shock tunnel at the University of Queensland implied that it was no longer necessary to focus the work of the research group about an annual test series conducted in the T3 shock tunnel in Canberra. Therefore, it has been possible to organize a group for work to proceed along lines such that particular personnel are associated with particular project areas. The format of this report consists of a series of reports on specific project areas, with a brief general introduction commenting on each report. The introduction is structured by project areas, with the title of the relevant report stated under the project area heading. The reports themselves follow in the order of the project area headings

Shock tunnel studies of scramjet phenomena, supplement 5

A series of reports are presented on SCRAMjet studies, shock tunnel studies, and expansion tube studies. The SCRAMjet studies include: (1) Investigation of a Supersonic Combustion Layer; (2) Wall Injected SCRAMjet Experiments; (3) Supersonic Combustion with Transvers, Circular, Wall Jets; (4) Dissociated Test Gas Effects on SCRAMjet Combustors; (5) Use of Silane as a Fuel Additive for Hypersonic Thrust Production, (6) Pressure-length Correlations in Supersonic Combustion; (7) Hot Hydrogen Injection Technique for Shock Tunnels; (8) Heat Release - Wave Interaction Phenomena in Hypersonic Flows; (9) A Study of the Wave Drag in Hypersonic SCRAMjets; (10) Parametric Study of Thrust Production in the Two Dimensional SCRAMjet; (11) The Design of a Mass Spectrometer for use in Hypersonic Impulse Facilities; and (12) Development of a Skin Friction Gauge for use in an Impulse Facility. The shock tunnel studies include: (1) Hypervelocity flow in Axisymmetric Nozzles; (2) Shock Tunnel Development; and (3) Real Gas Efects in Hypervelocity Flows over an Inclined Cone. The expansion tube studies include: (1) Investigation of Flow Characteristics in TQ Expansion Tube; and (2) Disturbances in the Driver Gas of a Shock Tube

Do Hospital Boards matter for better, safer, patient care?

Manifest failings in healthcare quality and safety in many countries have focused attention on the role of hospital Boards. While a growing literature has drawn attention to the potential impacts of Board composition and Board processes, little work has yet been carried out to examine the influence of Board competencies. In this work, we first validate the structure of an established ‘Board competencies’ self-assessment instrument in the English NHS (the Board Self-Assessment Questionnaire, or BSAQ). This tool is then used to explore in English acute hospitals the relationships between (a) Board competencies and staff perceptions about how well their organisation deals with quality and safety issues; and (b) Board competencies and a raft of patient safety and quality measures at organisation level. National survey data from 95 hospitals (334 Board members) confirmed the factor structure of the BSAQ, validating it for use in the English NHS. Moreover, better Board competencies were correlated in consistent ways with beneficial staff attitudes to the reporting and handling of quality and safety issues (using routinely collected data from the NHS National Staff Survey). However, relationships between Board competencies and aggregate outcomes for a variety of quality and safety measures showed largely inconsistent and non-significant relationships. Overall, these data suggest that Boards may be able to impact on important staff perceptions. Further work is required to unpack the impact of Board attributes on organisational aggregate outcomes