935 research outputs found

    The atomisation of detergent slurries

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    A study was made to determine the conditions under which the optimum droplet size distribution (ie., narrowest size range with a minimum of fines and over-sized agglomerates), is generated in sprays from centrifugal pressure nozzles. A range of non-Newtonian detergent slurries were tested but the results are of wider application and parallel work was undertaken with water, ionic solutions and chalk slurries. Six centrifugal pressure nozzles were used and the drop-size distributions correlated as a function of fluid properties, pressure, fiowrate, feed temperature, and nozzle characteristics. Measurements were made using a Malvern Particle Size Anayser slung across a specially-designed transparent tower section of approximately 1.2m diameter in order to reduce obscuration caused by the spray and improve existing droplet sizing techniques. The results obtained were based upon the Rosin-Rammler distribution model and the Size Analyser provided a direct print-out of size distribution and the parameters characterising it. A Spraying System nozzle, AAASSTC8-8, produced the optimum spray distribution with the detergent slurry at a temperature of 60°C whilst operating at 1200 psi. With other fluids the Delevan 2.2SJ nozzle produced the optimum spray distribution operating at 1200 psi but with the Spraying Systems nozzles there was no clear-cut optimum set of conditions, ie. the nozzle and pressure varied depending upon the fluid being sprayed. The mechanisms of liquid sheet break-up and droplet dispersion were investigated in specially-constructed, scaled-up, transparent nozzles. A mathematical model of centrifugal pressure nozzle atomisation was developed based upon fundamental operating parameters rather than resorting to empirical correlations. This enabled theoretical predictions to be made over a wide range of operating conditions and nozzle types. The model predictions for volumetric fiowrate, liquid sheet length and air core diameter showed good agreement with the experimentally determined results. However, the model predicted smaller droplet sizes than were produced experimentally due to inaccuracies identified in the initial assumptions

    Drug prescriptions and dementia incidence: a medication-wide association study of 17000 dementia cases among half a million participants

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    Previous studies have suggested that some medications may influence dementia risk. We conducted a hypothesis-generating medication-wide association study to investigate systematically the association between all prescription medications and incident dementia. We used a population-based cohort within the Secure Anonymised Information Linkage (SAIL) databank, comprising routinely-collected primary care, hospital admissions and mortality data from Wales, UK. We included all participants born after 1910 and registered with a SAIL general practice at ≤60 years old. Follow-up was from each participant's 60th birthday to the earliest of dementia diagnosis, deregistration from a SAIL general practice, death or the end of 2018. We considered participants exposed to a medication if they received ≥1 prescription for any of 744 medications before or during follow-up. We adjusted for sex, smoking and socioeconomic status. The outcome was any all-cause dementia code in primary care, hospital or mortality data during follow-up. We used Cox regression to calculate hazard ratios and Bonferroni-corrected p values. Of 551 344 participants, 16 998 (3%) developed dementia (median follow-up was 17 years for people who developed dementia, 10 years for those without dementia). Of 744 medications, 221 (30%) were associated with dementia. Of these, 217 (98%) were associated with increased dementia incidence, many clustering around certain indications. Four medications (all vaccines) were associated with a lower dementia incidence. Almost a third of medications were associated with dementia. The clustering of many drugs around certain indications may provide insights into early manifestations of dementia. We encourage further investigation of hypotheses generated by these results. [Abstract copyright: © Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.
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