Investigation of static zones and wall slip through sequential ram extrusion of contrasting micro-crystalline cellulose-based pastes

The shape and size of static regions in the extrusion flow of a viscoplastic material through axisymmetric square entry dies was studied experimentally using a simple flow field analysis technique. A white micro-crystalline cellulose/water paste was extruded sequentially with a graphite-stained black analogue paste, revealing static regions in the corners of the system extending less than 30% of the barrel radius into the centre of the channel. Slow (relative to the bulk) slip flow along the die face was evident in the experiments, implying the existence of a stick-slip transition on this surface. Finite element simulations using the Papanastasiou regularised Bingham plastic viscosity model and the linear Navier wall slip law were found to reproduce the experimental results poorly, capturing only separately the slip dominated bulk flow and the static corner region for different values of the slip coefficient _. The effect of severe wall slip was to reduce the distinction between unyielded and yielded material making the definition of the yield surface challenging. Investigation and implementation of a stick-slip wall condition is believed to be required for further work in this area.This is the author's accepted manuscript. The final version is available from Elsevier in the Journal of Non-Newtonian Fluid Mechanics here: http://www.sciencedirect.com/science/article/pii/S0377025714001207

Flow visualisation and modelling of solid soap extrusion

Ram extrusion of a solid granular soap was studied using three geometrically identical but differently-scaled extruders. The experimental design revealed deviation from the Benbow and Bridgwater (1993) extrusion model due to nonideal, scale-dependent effects. Typically these effects, linked to the shear rate in the extruder, are absorbed into the model's material pseudo-properties. The data were able to be represented using the Basterfield et al. (2005) model for extrusion flow which does include a shear rate as a variable. Flow visualisation in conjunction with fluid dynamics-based simulations showed, however, that the assumptions underlying the Basterfield et al. model are not appropriate for soap extrusion, despite the good agreement of the model with the experimental extrusion data. This highlights a need for care in interpretation of extrusion data, in that the limited information gathered about any given experiment, typically just the extrusion pressure, can lead to the generation of spurious parameters if the wrong model is applied.This work was funded by Ceratizit GmbH Austria and Sandvik Hyperion U

Research preparedness in undergraduate property and construction curriculum: the student experience

This study investigates the student experience of undergraduate research in order to develop a “research preparedness framework” that can be applied to the development of undergraduate curriculum design within a case study organisation. This research utilises built environment students from a Higher Education Institution in the UK. The study adopts a multi-method qualitative design using focus groups with various student cohorts, including Building Surveying, Real Estate Management and Quantity Surveying, followed by face-to-face interviews with industry representatives. This study highlights a discrepancy between student’s research preparedness and their understanding of its importance and perceived impact. It establishes areas for improvement within the curriculum to enhance students’ research preparedness throughout their undergraduate career. There are numerous benefits for students from being involved in research, such as developing a critical mind-set through the appraisal, collection, analysis and interpretation of complex information. However, students often do not see the tangible benefit of developing research skills to help them succeed and differentiate once they make their transition from higher education to employment. This study provides intriguing findings for anyone involved in property and construction curriculum across the globe, and will also appeal to any institution where students are undertaking research activities/projects

Early versus delayed antiretroviral treatment in HIV-positive people with cryptococcal meningitis.

BACKGROUND: There remains uncertainty about the optimum timing of antiretroviral therapy (ART) initiation in HIV-positive people with cryptococcal meningitis. This uncertainty is the result of conflicting data on the mortality risk and occurrence of immune reconstitution inflammatory syndrome (IRIS) when ART is initiated less than four weeks after cryptococcal meningitis treatment is commenced. OBJECTIVES: To compare the outcomes of early initiation of ART (less than four weeks after starting antifungal treatment) versus delayed initiation of ART (four weeks or more after starting antifungal treatment) in HIV-positive people with concurrent cryptococcal meningitis. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase for trials published between 1 January 1980 and 7 August 2017. We additionally searched international trial registries, including ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP), and conference abstracts from the International AIDS Society (IAS) and the Conference on Retroviruses and Opportunistic Infections (CROI) for ongoing or unpublished studies between 2015 and 2017. We reviewed reference lists of included studies to identify additional studies. SELECTION CRITERIA: We included randomized controlled trials (RCTs) that compared early versus delayed ART initiation in HIV-positive people with cryptococcal meningitis. Children, adults, and adolescents from any setting were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Two review authors independently applied the inclusion criteria and extracted data. We presented dichotomous outcomes as risk ratios (RR) with 95% confidence intervals (CIs). We presented time-to-death data as hazard ratios with 95% CIs. We assessed the certainty of the evidence using the GRADE approach. MAIN RESULTS: Four trials including 294 adult participants met the inclusion criteria of this review. Participants were predominantly from low- and middle-income countries. Two trials treated cryptococcal meningitis with amphotericin B and fluconazole; a third trial used fluconazole monotherapy; and the fourth trial did not specify the antifungal used.Early ART initiation may increase all-cause mortality compared to delayed ART initiation (RR 1.42, 95% CI 1.02 to 1.97; 294 participants, 4 trials; low-certainty evidence). Early ART initiation may reduce relapse of cryptococcal meningitis compared to delayed ART initiation (RR 0.27, 95% CI 0.07 to 1.04; 205 participants, 2 trials, low-certainty evidence). We are uncertain whether early ART initiation increases or reduces cryptococcal IRIS events compared to delayed ART initiation (RR 3.56, 95% CI 0.51 to 25.02; 205 participants, 2 trials; I2 = 54%; very low-certainty evidence). We are uncertain if early ART initiation increases or reduces virological suppression at six months compared to delayed ART initiation (RR 0.93, 95% CI 0.72 to 1.22; 205 participants, 2 trials; I2 statistic = 0%; very low-certainty evidence).We were unable to pool results related to rate of fungal clearance for the two trials that reported this outcome; individual trial results indicated that there was no difference in cerebrospinal fluid fungal clearance between trial arms. Similarly, we were unable to pool results on adverse events for the trials reporting on this outcome; individual trial results indicated no difference in the occurrence of grade 3 to 5 adverse events between trial arms.Three of the four included trials had an overall low or unclear risk of bias related to the primary outcome of all-cause mortality. However, we assessed one trial as at high risk of bias due to selective outcome reporting and other bias. This, in addition to the few clinical events and imprecision of effect estimates, led to downgrading of the evidence to low or very low certainty. AUTHORS' CONCLUSIONS: The results of this review are relevant to HIV-positive adults with cryptococcal meningitis in low- and middle-income countries. These data suggest a higher risk of mortality among people who initiate ART within four weeks of cryptococcal meningitis diagnosis. However, it is unclear if this higher mortality risk is related to cryptococcal meningitis-IRIS

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

Extrusion–spheronisation is a widely used technique for the manufacture of pellets with high sphericity and narrow size distribution. A dimensionless framework for describing the evolution of pellet shape with spheronisation time is presented for the first time and is validated using new experimental data obtained with two families of materials: (i) microcrystalline cellulose (MCC)/water-based pastes with loadings of up to 15 wt.% calcium carbonate representing a ‘hard’ active pharmaceutical ingredient, and (ii) a lactose/MCC/water paste. The dimensional analysis of the pellet rounding stage identified the paste density and bulk yield strength, σY, as scaling quantities: σY was measured in separate extrusion tests and found to increase with increasing carbonate content. Larger paste strength gave longer spheronisation times and less spherical pellets for a given set of spheronisation conditions. The pellet aspect ratio was found to increase in a linear manner with the logarithm of spheronisation time, progressing towards an asymptotic final value. This behaviour, which is evident in old data sets but has not been discussed previously, is compared with two simple models. High speed imaging was also used to examine the collision behaviour of pellets during the breakage and rounding stages in spheronisation. This confirmed that the rounding phase was the rate-determining step. The velocities of a number of tracked pellets were consistently lower than the tip speed of the rotating friction plate, confirming previous findings in studies of beds of pellets.Microcrystalline cellulose for this final year student research project was kindly provided by MSD Devlab, Hoddesdon, UK. Support for M.P. Bryan from CERATIZIT GmbH and Sandvik Hyperion is gratefully acknowledged.This is the author accepted manuscript. The final version is available from Elsevier via https://doi.org/10.1016/j.powtec.2016.05.00

Measurement of the wall slip behaviour of a solid granular soap in ram extrusion

The wall slip behaviour of a solid granular soap was investigated in the context of ram extrusion, with particular focus on determining the sensitivity of the wall shear stress to the pressure within the soap, as well as the slip velocity. Two novel slip measurement devices were used to infer the shear stress: a two stage extrusion die with inbuilt pressure gradient measurement; and a combined compression-translation assembly to measure the frictional force between the soap and the wall. Both devices provided differing measurements of the pressure sensitivity, and gave shear stress estimates in agreement with a Benbow and Bridgwater (1993) analysis of the extrusion behaviour, which cannot gauge pressure dependence. The influence of the wall material on the slip and extrusion behaviour was also investigated, using three geometrically identical extruders constructed from polycarbonate, stainless steel and tungsten carbide. There was found to be a non-negligible relationship between wall material, wall surface roughness, and the Benbow-Bridgwater extrusion parameters, in which the wall shear stress was greatest against the smoothest, cemented tungsten carbide wall in contrast to a rougher stainless steel and rougher-still polycarbonate wall. Keywords: extrusion, wall slip, soft solid

Behavioural syndrome in a solitary predator is independent of body size and growth rate.

Models explaining behavioural syndromes often focus on state-dependency, linking behavioural variation to individual differences in other phenotypic features. Empirical studies are, however, rare. Here, we tested for a size and growth-dependent stable behavioural syndrome in the juvenile-stages of a solitary apex predator (pike, Esox lucius), shown as repeatable foraging behaviour across risk. Pike swimming activity, latency to prey attack, number of successful and unsuccessful prey attacks was measured during the presence/absence of visual contact with a competitor or predator. Foraging behaviour across risks was considered an appropriate indicator of boldness in this solitary predator where a trade-off between foraging behaviour and threat avoidance has been reported. Support was found for a behavioural syndrome, where the rank order differences in the foraging behaviour between individuals were maintained across time and risk situation. However, individual behaviour was independent of body size and growth in conditions of high food availability, showing no evidence to support the state-dependent personality hypothesis. The importance of a combination of spatial and temporal environmental variation for generating growth differences is highlighted

Developing the return on workplace investment (ROWI) tool

Facilities managers and the wider corporate real estate (CRE) community have increasingly become focused on cost reduction, with organisations typically viewing property as a cost burden rather than an investment. Consequently, it remains rare for organisations to include performance benefits in financial investment appraisals of workplace projects. A change in narrative is required to one where value can be demonstrated rather than simply costs reduced. Previous attempts have been made to quantify workplace performance, but a tangible tool to assist in recommending major decisions regarding changes to the workplace has eluded discovery. Therefore, the authors joined forces with the Institute of Workplace and Facilities Management (IWFM) to create the Return on Workplace Investment (ROWI) tool. The ROWI tool is a ready reckoner for calculating the impact of workplace projects (including planning, design or operation) on people performance. It can be used as part of a cost-benefit analysis to help professionals build a business case which accounts for positive factors other than cost alone. The initial step to developing the ROWI tool was to conduct an extensive literature review to determine the performance metrics that could be used to calculate a return on workplace investment. Some 105 unique and robust literature sources, with a total of 194 individual assessments of performance, were selected. Five dominant and recurring performance metrics were identified, along with nine recurring broad workplace design elements affecting task performance. Previously, there was little confidence in productivity research due to the range in performance data that various studies produce. A unique aspect of the ROWI tool, however, is that the performance data for each study was weighted to make it more relevant to real office work. The corresponding, more realistic, potential impact of workplace design on each of the performance metrics was calculated using the weighted results from all the research studies

Development of a variational flux inversion system (INVICAT v1.0) using the TOMCAT chemical transport model

We present a new variational inverse transport model, named INVICAT (v1.0), which is based on the global chemical transport model TOMCAT, and a new corresponding adjoint transport model, ATOMCAT. The adjoint model is constructed through manually derived discrete adjoint algorithms, and includes subroutines governing advection, convection and boundary layer mixing, all of which are linear in the TOMCAT model. We present extensive testing of the adjoint and inverse models, and also thoroughly assess the accuracy of the TOMCAT forward model's representation of atmospheric transport through comparison with observations of the atmospheric trace gas SF6. The forward model is shown to perform well in comparison with these observations, capturing the latitudinal gradient and seasonal cycle of SF6 to within acceptable tolerances. The adjoint model is shown, through numerical identity tests and novel transport reciprocity tests, to be extremely accurate in comparison with the forward model, with no error shown at the level of accuracy possible with our machines. The potential for the variational system as a tool for inverse modelling is investigated through an idealised test using simulated observations, and the system demonstrates an ability to retrieve known fluxes from a perturbed state accurately. Using basic off-line chemistry schemes, the inverse model is ready and available to perform inversions of trace gases with relatively simple chemical interactions, including CH4, CO2 and CO