Shear-induced segregation of particles by material density.

Recently, shear rate gradients and associated gradients in velocity fluctuations (e.g., granular temperatures or kinetic stresses) have been shown to drive segregation of different-sized particles in a manner that reverses at relatively high solids fractions (〈f〉>0.50). Here we investigate these effects in mixtures of particles differing in material density through computational and theoretical studies of particles sheared in a vertical chute where we vary the solids fraction from 〈f〉=0.2 to 0.6. We find that in sparse flows, 〈f〉=0.2 to 0.4, the heavier (denser) particles segregate to lower shear rates similarly to the heavier (larger) particles in mixtures of particles differing only in size. However, there is no segregation reversal at high f in mixtures of particles differing in density. At all solids fractions, heavier (denser) particles segregate to regions of lower shear rates and lower granular temperatures, in contrast with segregation of different-sized particles at high f, where the heavier (larger) particles segregate to the region of higher shear rates. Kinetic theory predicts well the segregation for both types of systems at low f but breaks down at higher f's. Our recently proposed mixture theory for high f granular mixtures captures the segregation trends well via the independent partitioning of kinetic and contact stresses between the two species. In light of these results, we discuss possible directions forward for a model framework that encompasses segregation effects more broadly in these systems.

Bonamia exitiosa transmission among, and incidence in, Asian oyster Crassostrea ariakensis under warm euhaline conditions.

Previously reported in Australia, New Zealand, and more recently in Europe, the protistan parasite Bonamia exitiosa was also reported in the mid-Atlantic region of the USA after causing serious mortalities there in the Asian oyster Crassostrea ariakensis. At the time, this oyster was being considered for introduction, and the potential consequences of introducing this species were being assessed using field and laboratory studies. B. exitiosa emerged as the most serious disease threat for this oyster species, especially under warm euhaline conditions and for oysters <50 mm in size. To better evaluate how quickly this parasite may be able to spread among C. ariakensis, we investigated B. exitiosa transmission and incidence in C. ariakensis. During a first trial, potential direct transmission of B. exitiosa was evaluated by cohabitating infected C. ariakensis with uninfected C. ariakensis under in vivo quarantine conditions. In a second experiment, B. exitiosa incidence was estimated in situ by determining its prevalence in C. ariakensis deployed in an enzootic area after 4, 7, 14, 21 and 28 d of exposure. Results suggest that under warm euhaline conditions B. exitiosa can be transmitted among C. ariakensis without requiring any other parasite source and that parasite incidence may be at least as high as 40% after only 4 d exposure to an enzootic area. These results underscored the severity of the bonamiasis disease threat to C. ariakensis and provided further evidence that efforts to build an aquaculture industry based on C. ariakensis in the eastern USA might have been thwarted by parasitic disease.

Racial differences in cortical bone and their relationship to biochemical variables in Black and White children in the early stages of puberty.

UNLABELLED: Osteoporotic fracture rates differ according to race with Blacks having up to half the rate of Whites. The current study demonstrates that racial divergence in cortical bone properties develops in early childhood despite lower serum 25-hydroxyvitamin D in Blacks. INTRODUCTION: Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of Black and White children in the early stages of puberty and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties. METHODS: A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n = 155 males; n = 164 Blacks) in the early stages of puberty. RESULTS: Blacks had greater cortical volumetric bone mineral density, mass, and size compared to Whites (all p < 0.01), contributing to Blacks having 17.0 % greater tibial strength (polar strength-strain index (SSIP)) (p < 0.001). Turnover markers indicated that Blacks had higher bone formation (osteocalcin (OC) and bone-specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than Whites (all p < 0.01). Blacks also had lower 25-hydroxyvitamin D (25(OH)D) and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) (all p < 0.05). There were no correlations between tibial bone properties and 25(OH)D and PTH in Whites (all p ≥ 0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in Blacks, respectively (all p ≤ 0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH, and OC. CONCLUSIONS: Divergence in tibial cortical bone properties between Blacks and Whites is established by the early stages of puberty with the enhanced cortical bone properties in Black children possibly being explained by higher PTH and OC.

Stroke management: updated recommendations for treatment along the care continuum.

The Australian Clinical Guidelines for Stroke Management 2010 represents an update of the Clinical Guidelines for Stroke Rehabilitation and Recovery (2005) and the Clinical Guidelines for Acute Stroke Management (2007). For the first time, they cover the whole spectrum of stroke, from public awareness and prehospital response to stroke unit and stroke management strategies, acute treatment, secondary prevention, rehabilitation and community care. The guidelines also include recommendations on transient ischaemic attack. The most significant changes to previous guideline recommendations include the extension of the stroke thrombolysis window from 3 to 4.5 h and the change from positive to negative recommendations for the use of thigh-length antithrombotic stockings for deep venous thrombosis prevention and the routine use of prolonged positioning for contracture management.

Phase transitions in shear-induced segregation of granular materials.

We computationally study shear-induced segregation of different-sized particles in vertical chute flow. We find that, for low solid fractions, large particles segregate toward regions of low shear rates where the granular temperature (velocity variance) is low. As the solid fraction increases, this trend reverses, and large particles segregate toward regions of high shear rates and temperatures. We find that this is a global phenomenon: local segregation trends reverse at high system solid fractions even where local solid fractions are small. The reversal corresponds to the growth of a single enduring cluster of 30%-60% of the particles that we propose changes the segregation dynamics.

Rheology of dense granular mixtures: boundary pressures.

Models for dense sheared granular materials indicate that their rheological properties depend on particle size, but the representative size for mixtures is not obvious. Here, we computationally study pressure on a boundary due to sheared granular mixtures to determine its dependence on particle size distribution. We find that the pressure does not depend monotonically on average particle size. Instead it has an additional dependence on a measure of the effective free volume per particle we adapt from an expression for packing of monosized particles near the jammed state.

Shear-driven segregation of dense granular mixtures in a split-bottom cell.

Shear-driven segregation of dense granular mixtures has been associated with a number of interesting pattern formation problems. We use experimental and computational split-bottom cells to isolate segregation effects associated with shear gradients from those associated with gravity. We find the effect of shear gradients much less dramatic than initial observations of segregation suggest. While a segregation pattern emerges in a circular split-bottom cell that appears coincident with the shear gradient, we find the pattern is orthogonal to the active segregation flux. We measure a toroidal convection roll that, in conjunction with gravity-driven segregation, is likely responsible for the dramatic horizontal segregation pattern. On the other hand, computational results from a parallel split-bottom cell indicate a subtle segregation flux associated with the shear gradient. The nature of the driving mechanism is unknown. A current predictive form of kinetic theory based on binary collisions dominating the particle dynamics predicts segregation in the opposite direction from observed trends. This indicates the direction of shear-driven segregation depends on the nature of the flow itself, collisional or frictional.

Collapse of a rectangular well in a quasi-two-dimensional granular bed.

We report on an experimental and numerical study of the collapse under gravity of a rectangular well in a quasi-two-dimensional granular bed. For comparison, we also perform experiments on the collapse of a single vertical step. Experiments are conducted in a vertical Hele-Shaw cell, which allows the flow to be recorded from the side using high-speed video. If the rectangular well is sufficiently narrow, the collapsing sidewalls collide at the center of the well and the dynamics of the collapse are dependant on the aspect ratio of the initial well. We follow the evolution of the free surface from the video images, and use particle image velocimetry to determine the subsurface velocity field. From these data, the potential and kinetic energy of the system are calculated. We observe two stages to the collapse flow: an initial gravity-dominated stage, during which the kinetic energy increases, and a later dissipation-dominated phase during which the kinetic energy decreases. We find that although both the width and depth of the depression that remains after the well has collapsed depend on the initial aspect ratio, the surface profiles are self-similar; that is, the shape of the final profile is independent of the aspect ratio of the initial well. We model the collapse of the well using a depth-averaged continuum model with basal friction and with a discrete element model. Both models give results which agree well with experiment. The discrete element model indicates that friction between the particles is the most important source of dissipation over the course of the collapse.

Rheology of dense granular mixtures: particle-size distributions, boundary conditions, and collisional time scales.

We computationally investigate the dependence of the rheology of dense sheared granular mixtures on their particle size distribution. We consider the simplest case of a binary mixture of two different sized particles where the fraction of large particles is varied from one simulation to the next while the total solid mass is kept constant. We find that the variation of the rheology with the particle size distribution depends on the boundary conditions. For example, under constant pressure conditions the effective friction coefficient µ(∗) (the ratio between shear and pressure stresses at the boundary) increases mildly with the average particle size. On the other hand, under constant volume conditions, µ(∗) has a nonmonotonic dependence on the average particle size that is related to the proximity of the system solid fraction to the maximum packing fraction. Somewhat surprisingly, then, µ(∗) scales with a dimensionless shear rate (a generalized inertial number) in the same way for either boundary condition. We show that, for our system of relatively hard spheres, these relationships are governed largely by the ratio between average collision times and mean-free-path times, also independent of boundary conditions.

Acute stroke and transient ischaemic attack management--time to act fast.

Stroke is Australia's second single greatest killer with 53 000 new events each year at a rate of 1 every 10 min. Stroke services should be organized to enable people to access proven therapies, such as stroke unit care and thrombolysis, to reduce the impact of stroke. Timely, efficient and coordinated care from ambulance services, emergency services and stroke services will maximize recovery and prevent costly complications and subsequent strokes. Efficient management of patients with transient ischaemic attack can produce significant reductions in subsequent stroke events and risk stratification using the ABCD2 tool can aid management decisions. Evidence for acute stroke care continues to evolve and it is crucial that health professionals are aware of, and implement, best practice clinical guidelines for stroke care.

How useful is an online tool to facilitate guideline implementation? Feasibility study of using eGLIA by stroke clinicians in Australia.

BACKGROUND: The success of guidelines is determined by their use in the real world. The GuideLine Implementability Appraisal (GLIA) tool was developed as a quality-improvement tool to assist guideline developers and guideline users identify potential problems in implementing recommendations. The objective of this study was to assess the feasibility of using the electronic version of GLIA (eGLIA) by implementers of a clinical guideline for acute stroke management in Australia. METHODS: Health professionals who had no previous experience with the eGLIA tool but who are involved in implementing guidelines volunteered for the study. These health professionals were provided background information about the tool and were provided a short training session (<30 min). The participants were asked to consider at least two recommendations from the guideline document. Time spent, numbers of recommendations reviewed and subjective feedback of the process were used for evaluation. RESULTS: 40 participants completed the study, representing nursing and allied health professions from different geographical regions of Australia. The median number of recommendations per participant completed was 2 (range 2-10), taking an average of 47 min (range 15-120 min) to complete or about 22 min per recommendation. Ninety-four per cent of participants agreed or strongly agreed that eGLIA was useful, while 77% indicated they would use the tool again. eGLIA helped participants think systematically about implementation, although only 72% agreed that the tool allowed them to clearly identify potential barriers to implementation. CONCLUSION: This study suggests that eGLIA may be a useful tool which is relatively easy to use for implementers of guidelines. eGLIA enables a detailed, systematic evaluation of guidelines. Further refinement of the tool is recommended to better assist implementers to clearly identify barriers to implementation and therefore facilitate greater implementation. Further work is also warranted to determine the effect of using eGLIA as part of an implementation strategy and if it improves health outcomes.

Isolating segregation mechanisms in a split-bottom cell.

We study the segregation of mixtures of particles in a split-bottom cell to isolate three possible driving mechanisms for segregation of densely sheared granular mixtures: gravity, porosity, and velocity gradients. We find that gravity alone does not drive segregation associated with particle size without a sufficiently large porosity or porosity gradient. A velocity gradient, however, appears to be capable of driving segregation associated with both particle size and material density. In all cases, the final segregation state is approached exponentially.

Kinematics of densely flowing granular mixtures.

We measure the kinematics of segregating granular mixtures in dense free-surface boundary-layer flow in a rotated drum. We find that in a segregating mixture, the different components move with roughly the same velocities, except for a relatively small segregation velocity perpendicular to the direction of flow. On the other hand, the mean variance of the velocities--often associated with a granular temperature--may differ for the two components. In the majority of the high-density boundary layer, the difference is driven by relative particle size and may be understood considering a geometrically motivated model. In the low-density region at the top of the boundary layer, the difference is driven by relative particle mass, similar to observations in more energetic systems.

Fluctuating velocity and momentum transfer in dense granular flows.

We show experimentally that in a free-surface granular flow the fluctuating velocity brings about momentum transfer at a considerable rate only very close to the free surface. Away from the free surface, where the flow is dense and stratified (or laminar), the fluctuating velocity plays no prominent dynamic role and stems passively from a kinematic constraint: The strata of particles must shake laterally as they slip past one another in the direction of the mean flow. Based on this insight, we formulate a simple model for the fluctuating velocity of dense granular flows. The predictions of the model agree well with our experimental measurements.

Radial segregation patterns in rotating granular mixtures: waviness selection.

We model the radial segregation patterns that form in a thin rotating drum partially filled with beads of two sizes. We predict that the waviness (or amplitude-to-wavelength ratio, denoted w) of a pattern should be subjected to low-pass filtering with a cutoff waviness w(c) that depends strongly on the fill level of the drum. Then we perform experiments and find that w

Structure and kinematics in dense free-surface granular flow.

We show that the structure of a dense, free-surface boundary layer granular flow is similar to the structure of a laminar liquid flow: There is a strong component of order (stratification parallel to the mean flow) superposed with a mild component of disorder (self-diffusion perpendicular to the mean flow). We also show that the self-diffusion coefficient scales with the mean velocity and propose a model that relates this scaling to the ordered structure of the flow. Last, we show that the structure of the flow imprints an oscillatory signature (similar to that found in confined granular flow) on the mean velocity profile.

Do newly diagnosed lung cancer patients feel their concerns are being met?

Lung cancer is the leading cause of cancer death worldwide. It has a poor prognosis and the majority of those affected are elderly. Evidence suggests that providing clear, relevant information and addressing patients' concerns can make a worthwhile difference to patients. This study aimed to: explore the concerns of lung cancer patients shortly after diagnosis; and enquire whether these concerns had been discussed by their care teams. Eighty patients with a new diagnosis of primary lung cancer were interviewed 14-28 days after the date on which they were told the diagnosis. Interviews were conducted either in the hospital ward, outpatient clinic or at home. Participants were asked to rate 17 specific items of concern from 1 = 'not a worry' to 5 = 'extremely worried', plus one non-specific item. Patients rated at least two items as worrying them to some degree with a median of nine concerns being reported. Major concerns for patients were the illness itself; the future relating to the illness and concerns about the family. Overall, patients in the study felt that less than half of their concerns (43%) had been discussed by the care team. Although levels of concern about physical symptoms were relatively low, these had been more frequently addressed than the psychosocial issues, which were rated higher by patients. There were some differences in the number of concerns reported between males/females and younger/older age groups, but the pattern of concerns was similar. There were no differences in the level of concerns between treatment groups; the location of the interview nor in the interval between diagnosis and delivery of the checklist. This study supports previous findings that there is a need for health professionals to provide emotional support and respond to the psychosocial needs of patients by eliciting their concerns and attempting to address them in the early stages of the disease process.

Modes of granular segregation in a noncircular rotating cylinder.

Axial segregation is a well-known example of segregation of granular materials. However, at present, there is no conclusive explanation as to why it occurs. Most studies of axial segregation to date are based on cylinders with circular cross sections, and models focus on the character of the surface flow without accounting explicitly for the influence of any subsurface detail. The present experiments demonstrate that the cross section of the mixer has a significant influence on axial segregation and that subsurface dynamics are, in fact, important. Unlike circular mixers, in square mixers the subsurface segregation patterns change with filling level, as does the time dependence of axial segregation. Furthermore, when radial segregation patterns in noncircular mixers most closely resemble that observed for circular cylinders, the time dependence for axial band formation deviates the most. These results challenge segregation theories of axial segregation that ignore subsurface effects.

Living with severe COPD. A qualitative exploration of the experience of patients in Leeds.

A sample of 37 patients with severe chronic obstructive pulmonary disease (COPD) drawn from a larger group of 64 patients being studied in a randomized trial of nebulizer versus high-dose inhaler therapy, and similar in age and gender mix, was interviewed in depth, with a view to illuminating standardized outcome measures and improving the understanding of these patients' needs. Three patients are described in detail. The interview material was analysed using non-computerized methods. Quality of life was seen as depending mainly on family relationships, opportunities afforded locally for neighbourliness and freedom from fear, mobility and independence in the activities of daily living, and the absence or successful mitigation of symptoms of concomitant disease. Disease-specific, symptom-oriented outcome measures may miss these. Additionally, the near and repeatedly threatening approach of death recommended extension of a palliative approach to endstage COPD.

N-terminal domains of the class ia phosphoinositide 3-kinase regulatory subunit play a role in cytoskeletal but not mitogenic signaling.

Phosphoinositide (PI) 3-kinases are required for the acute regulation of the cytoskeleton by growth factors. We have shown previously that in the MTLn3 rat adenocarcinoma cells line, the p85/p110alpha PI 3-kinase is required for epidermal growth factor (EGF)-stimulated lamellipod extension and formation of new actin barbed ends at the leading edge of the cell. We have now examined the role of the p85alpha regulatory subunit in greater detail. Microinjection of recombinant p85alpha into MTLn3 cells blocked both EGF-stimulated mitogenic signaling and lamellipod extension. In contrast, a truncated p85(1-333), which lacks the SH2 and iSH2 domains and does not bind p110, had no effect on EGF-stimulated mitogenesis but still blocked EGF-stimulated lamellipod extension. Additional deletional analysis showed that the SH3 domain was not required for inhibition of lamellipod extension, as a construct containing only the proline-rich and breakpoint cluster region (BCR) homology domains was sufficient for inhibition. Although the BCR domain of p85 binds Rac, the effects of the p85 constructs were not because of a general inhibition of Rac signaling, because sorbitol-induced JNK activation in MTLn3 cells was not inhibited. These data show that the proline-rich and BCR homology domains of p85 are involved in the coupling of p85/p110 PI 3-kinases to regulation of the actin cytoskeleton. These data provide evidence of a distinct cellular function for the N-terminal domains of p85.