3,790 research outputs found
The effect of an axial magnetic field on periodic growth rate fluctuations in Czochralski crystal growth
No full textIn this paper we develop a mathematical model to investigate the effect of growth rate fluctuations in magnetic Czochralski crystal growth. The pull rate is assumed constant and the growth rate fluctuates with frequency ω rad/s, the crystal rotation rate. We explore the effect of the magnetic field and the crucible rotation on fluid flow and mass transfer in the vicinity of the crystal/melt interface. Numerical results are obtained for 0≤N≤32 and -0.1≤s≤1.0, where N is the magnetic interaction parameter and s is the ratio of crucible to crystal rotation. Asymptotic results are obtained for the velocity field for large N and agreement is good for N>4. The analysis is extended to the concentration field to give asymptotic results for N→∞, Sc→∞, N/Sc2→∞ where Sc is the Schmidt number. Again the asymptotic results agree well with the numerical solutions. We conclude that the phase of the resulting concentration fluctuations appears to be independent of N and s. The spatially averaged effective distribution coefficient, keff and the amplitude of the concentration oscillations, Ac, are linked. As keff→1, Ac increases and so improved macrosegregation is accompanied by a deterioration in microsegregation
Children's personal exposure to particulate matter in a UK urban environment - preliminary results
No full textMarriage record of Green, R. A. and Wheeler, Hettie
No full textMarriage license for R.A. Green and Hettie Wheeler. J. Allen Rankin was the Notary Public
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No full textHere is a curious book. Its title-page declares "The Artist's Book of Fables" but its pre-title-page has "Fables, Original and Selected, with a Memoir of the Author." After that title-page, it is identical with "Fables, Original and Selected" as in our copy printed by John Murray in 1833. There is again an AI at the front and an index of engravings and engravers at the back. I found that copy twenty years ago. I had found an inferior copy twenty-two years before that. At that time, I noted Aesopic fables here including "Stone Broth" and "The Mouse and the Oyster."This is a hardbound book (hard cover)James Northcote, R.A
Characterisation of particulate matter sampled during a study of children's personal exposure to airborne particulate matter in a UK urban environment
No full textThe personal exposure of children aged 9 – 11 years to particulate matter (PM10 and PM2.5) was carried out between January and September 1997 in the London Borough of Barnet. Personal sampling along with home, garden and classroom microenvironmental monitoring was completed for all ten children. Each child was monitored for five days during winter, spring and summer. All children completed daily time activity diaries to provide information on any potential activities that could influence their exposure to particulate matter. Each evening a household activity questionnaire was also completed by the parents. Personal Environmental Monitors were used to sample personal exposure to PM10 and PM2.5. Harvard Impactors were used for the microenvironmental sampling of both size fractions. The children's mean personal exposure concentrations for PM10 during winter, spring and summer were 72, 54 and 35 µg/m3 respectively and for PM2.5 22, 17 and 18 µg/m3 respectively. In order to determine the potential sources of particulate matter, analysis of the Teflon filters has been undertaken. The physical characteristics of the particles have been identified using Scanning Electron Microscopy. The relationships between personal exposure concentrations and the different microenvironments will be discussed
Scope and feasibility of operating on the neonatal intensive care unit: 312 cases in 10 years
No full textPurposeTo report the scope, feasibility and learning experience of operating on neonates on the neonatal intensive care unit (NICU).Methods(1) Review of all NICU operations performed by general neonatal surgeons over 10 years; (2) 6-month prospective comparison of procedures performed in NICU or operating room; (3) structured interviews with five surgeons with 1–13 years experience of operating on NICU.Results312 operations were performed in 249 infants. Median birth weight was 1,494 g (range 415–4,365), gestational age 29 weeks (22–42), and age at operation 25 days (0–163). Nearly half (147) were laparotomy for acute abdominal pathology in preterm, very low birth-weight infants There were no surgical adverse events related to location of surgery. Surgeon satisfaction with operating on NICU for this population was high (5/5). Several factors contribute to making this process a success.ConclusionsThis is the largest reported series of general neonatal surgical procedures performed on NICU. Operating on NICU is feasible and safe, and a full range of neonatal operations can be performed. It removes risks associated with neonatal transfer and is likely to reduce physiological instability. We recommend this approach for all ventilated neonates and urge neonatal surgeons to operate at the cotside of unstable infants
Repair of Oseophageal atrisia by consultants and supervised trainees results in similar outcomes
No full textAims: consultants and trainees require exposure to complex cases for maintainingand gaining operative experience. Oesophageal atresia (OA) repair is a neonatalsurgical case with indicative numbers for completion of training. A conflict of interestmay exist between adequate training, maintaining consultant experience andachieving good outcomes. We aimed to review outcomes of cases performedprimarily by trainees compared to those by a consultant. Methods: retrospective casenote review of all consecutive infants who underwentsurgical repair of OA with distal Tracheo-Oesophageal Fistula (TOF) between Jan1994 and Dec 2014. Only cases that underwent primary oesophageal anastomosiswere included. Surgical Outcomes were compared between cases that had trainee orconsultant listed as primary operator. Results:one hundred and twenty-two cases were included. Fifty-two cases were operated by a trainee, 68 by a consultant (2 cases undeterminable and excluded). Infant demographics, clinical characteristics and duration of f ollow-up were similarbetween groups. All infants survived to discharge. C ases operated by a trainee andconsultant as primary operator had a similar incidence of postoperative pneumothorax (trainee 4 vs consultant 3; p=0.46), anastomotic leak (5vs 3; p=0.29) and recurrentTOF (0vs 2; p=0.5). Overall 52% of cases had an anastomotic dilatation during follow-up with no difference between trainee and consultant groups (50%vs 53%;p=0.85). Conclusion: surgical outcomes for repair of OA/TOF are not adversely affected by trainee operating. Trainees with a ppropriate skills should perform supervised OA/TOF repair. These data are important for understanding the inter-relationship between provision of training and surgical outcome
Turbulent entrainment in a shearless mixing layer at the edge of a cloud
No full textThree-dimensional direct numerical simulations which combine the Eulerian description of temperature, vapor content and velocity with a Lagrangian ensemble of cloud water droplets are used to study the turbulent entrainment and subsequent mixing of clear air with a cloudy air filament. The study is conducted in a shearless mixing layer setup which is adjusted to realistic conditions at a cumulus cloud boundary. The magnitude of turbulent velocity fluctuations in- and outside the cloud can be varied independently. We find that the evolution of the cloud water droplet ensemble depends slightly only on the contrast of turbulent velocity fluctuations in- and outside the cloud filament. The buoyancy feedback on the flow via the evaporating droplets causes a transient amplification of all fluctuations before the turbulence eventually decays. We study the evolution of the probability density functions of droplet size as well as of supersaturation, temperature and vorticity at the droplet positions
Flyleaf of The Village Politicians, signed by author and publisher R.A. Parsons, and printed by Guardian Ltd.
No full textNewIntroduction. Flyleaf of the The Village Politicans by R.A. Parsons and printed by Guardian Ltd.DA vol. 15 no.
Non-Linear Time Series Analysis of Deep Groundwater Levels: An application to the Veluwe
No full textThe objective of this study is to improve the simulation of deep groundwater levels by time se- ries models with pre-defined impulse response functions. This is attempted by adding a conceptual non-linear root zone model to simulate the recharge series to the model and by testing the use of a separate response function for the percolation zone. Three root zone models are developed based on two different recharge mechanisms: preferential flow, percolation, and a combination of the two. The performance of these models is compared to a linear model that is commonly used in time se- ries models to simulate the recharge. The approach is applied to groundwater level measurements in the Veluwe, a largely forested area in the Netherlands characterized by thick unsaturated zones. The effect of groundwater extractions and land reclamations is added to the model to further im- prove the simulation of the groundwater levels. The models are tested on three observations wells with increasing thickness of the unsaturated zone, varying from 7 m to 29 m to 49 m. The results show that model performance is improved by the implementation of a non-linear root zone model, particularly in simulating the peaks and lows in the groundwater levels. The recharge fluxes simulated by the non-linear models show different patterns that are physically more realistic than those simulated by the linear model. It is shown that different recharge series result in simulated groundwater levels that are very similar. This is a clear example of equifinality and it is recommended to introduce new sources of information to validate the modelled processes (e.g., water content measurements of the percolation zone or actual evaporation data). For the shallow well, the models with a single response function are selected as the best. The largest improvements for the deeper groundwater levels are obtained by the addition of a separate response for the percolation zone. For example, the average deviation from the observed ground- water levels decreased 0.18 m to 0.08 m for the deepest observation well by applying the separate response function. The models with an additional response function were better at simulating the estimated time to peak, the time it takes a recharge pulse to cause a peak in the groundwater levels. The time to peak is introduced in this research as a qualitative indicator to validate the modelled processes. The simulated responses indicate that the groundwater levels respond very quickly to water that leaves the root zone, even though the percolation zone is tens of metres thick. For each of the observations wells it is investigated if adding the effect of groundwater extrac- tions or land reclamations of Flevoland to the models improves the simulation of the groundwater levels. For the shallow well it is concluded that either the effect of land reclamations or groundwater extractions needs to be taken into account. Since these two stresses are correlated, it is concluded that only one of these should be taken into account when no further information is available to con- strain the models. For the medium deep well, the additional stresses did not significantly improve model performance and it is concluded that they do not have to be taken into account for this well. For the deep well, model performance is improved by both stresses. The largest improvements are observed when the effect of groundwater extractions is considered in the model. For implemen- tation of these stresses, the entire simulation period should be used for calibration, or constraints have to be implemented to obtain realistic results.Water ResourcesWater ManagementCivil Engineering and Geoscience
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