Stability of a Gaussian pancake vortex in a stratified fluid

International audienceVortices in stably stratified fluids generally have a pancake shape with a small vertical thickness compared with their horizontal size. In order to understand what mechanism determines their minimum thickness, the linear stability of an axisymmetric pancake vortex is investigated as a function of its aspect ratio alpha, the horizontal Froude number F-h, the Reynolds number Re and the Schmidt number Sc. The vertical vorticity profile of the base state is chosen to be Gaussian in both radial and vertical directions. The vortex is unstable when the aspect ratio is below a critical value, which scales with the Froude number: alpha(c) similar to 1.1F(h) for sufficiently large Reynolds numbers. The most unstable perturbation has an azimuthal wavenumber either m = 0, vertical bar m vertical bar = 1 or vertical bar m vertical bar = 2 depending on the control parameters. We show that the threshold corresponds to the appearance of gravitationally unstable regions in the vortex core due to the thermal wind balance. The Richardson criterion for shear instability based on the vertical shear is never satisfied alone. The dominance of the gravitational instability over the shear instability is shown to hold for a general class of pancake vortices with angular velocity of the form (Omega) over tilde (r, z) = Omega(r)f(z) provided that r partial derivative Omega/partial derivative r < 3 Omega everywhere. Finally, the growth rate and azimuthal wavenumber selection of the gravitational instability are accounted well by considering an unstably stratified viscous and diffusive layer in solid body rotation with a parabolic density gradient

Fostering Apprentice Beauticians’ Visual Expertise Through Annotations: A Design Experiment Using the Platform Realto

Professional beauticians regularly perform skin analyses and should be skilled at observing small skin anomalies and skin damages. However, little is done directly for improving their observation skills at school, during their training. In order to foster apprentices’ observation skills of skin anomalies, a new training scheme exploiting annotations and attention-guiding methods through the use of the platform Realto was developed and tested.A second year class of apprentice beauticians (N=9) was given a pre-test on the visual expertise of skin anomalies. Then, for a semester they attended multiple training sessions where firstly teachers explained skin anomaly images with the help of annotations (attention-guiding) and secondly, students were asked to observe other images of the same anomalies, annotate them, and then provide a textual description of the identified anomaly.At the end of the semester, the trained class completed a post-test and a questionnaire, and group interview have been collected. Another group of apprentices (N=19) of the third year who already completed the skin anomaly course was used as baseline. Results showed that the group who participated in the treatment mentioned almost double the amount of details noticed by the baseline group in the post-test; being trained using annotations and the Realto platform proved effective in developing observation skills, compared to normal lessons. Furthermore, apprentices confirmed, both through the questionnaire and the interviews, that they considered annotations useful for improving their observation skills and that using Realto and its annotation facilities was a good way to achieve this result

Computer aided modelling of low density polyethylene pyrolysis to produce synthetic fuels

The pyrolysis of waste low-density polyethylene (LDPE) is an excellent method of converting waste materials into useful products. Aspen HYSYS 2006 was used to develop a computational steady-state model to simulate the pyrolysis of LDPE. The Peng-Robinson fluid package was used for the simulation. A continuous stirred tank reactor with an Arrhenius kinetic expression was used to predict reaction extent and product yield. At a pyrolysis temperature of 4500C and atmospheric pressure, 92.88% liquid yield was obtained. From the given feedstock, the char obtained was composed of only elemental carbon. The synthesis gas was composed mainly Hydrogen and C1-C4 hydrocarbons with traces of n-C5 and n-C6. The Pyrolysis oil was composed of higher hydrocarbon fractions (C8-C24). The conversion temperature relationships from the simulation are in good agreement with experimental results. This proved that pyrolysis of waste LDPE can give an excellent yield of liquid product and is a viable recycling technique.Keywords: Pyrolysis, Simulation, LDPE, Synthetic fuels, Aspen HYSY

Legal Regime of Trademark in the Nigeria Sports Industry

A trademark is a distinctive sign that identifies certain goods or services produced or provided by an individual or a company and distinguishing same from others. Trade mark is a symbol or sign which differentiates the goods and services of one business from another one although they may operate in horizontal business within or without same community. Trademark is an indicative medium relied upon by consumers to create an imaginary link between a product on which such mark is used and its seller. Its major hallmark is its ability to differentiate the goods of one seller from those of others in the same line of business from one another. Trademark in Nigeria is governed by the Trade Marks Act, Cap T 13, Laws of the Federation of Nigeria 2004 (hereinafter referred to as Trademark Act) and the Trademark Regulations 1990. In contributing to existing literature, the paper examines the economic aspect of mark registration in the sports industry. It examines registrable marks and identifies the possibility of registration under existing treatise globally. The paper concludes with salient recommendations toward harnessing the economic aspect of trade mark registration in the Nigeria sports industry. Keywords: Legal Regime, Trademark, Nigeria, Sports Industry. DOI: 10.7176/JLPG/124-03 Publication date:September 30th 2022

Physico-chemical characterisation of some ground water supply in a school environment in Ilorin, Nigeria

The water quality assessment of some ground water supply to a school in Ilorin City was carried out over a year. The concentration of nitrates in the samples were determined using a UV - visible spectrophotometer. The wells located within the student hostels were found to be high in nitrate with concentrations ranging from 7.11 - 8.54 mg/l. This is close to the World Health Organization (WHO) limit of 10 mg/l allowed in drinking water. The concentrations in the boreholes ranged between 0.43 - 1.34 mg/l. The trace metal analysis was carried out using Atomic Absorption Spectrophotometer. Lead (Pb) and cadmium (Cd) concentrations were found to be below detection limit. The concentration of copper (Cu) ranged between 0.017 - 0.065 mg/l, the concentration of magnesium (Mg) ranged between 4.29 - 16.28 mg/l while calcium (Ca) concentration ranged between 26.60-235.60 mg/l. The metal concentrations were all within WHO recommended concentrations in drinking water. A linear regression carried out using the polymath software gave a negative slope

A Broad Study to Develop Maternity Units Design Knowledge Combining Spatial Analysis and Mothers' and Midwives' Perception of the Birth Environment

Objectives: This article investigates how the physical birth environment is perceived by the users (women and midwives) in different settings, a midwife-led unit and an obstetric-led unit, placed in Italy. Background: In the field of birth architecture research, there is a gap in the description of the spatial and physical characteristics of birth environments that impact users' health, specifically for what concerns the perception by women. Methods: The study focuses on multi-centered mixed methods design, employing both quantitative and qualitative research methods (questionnaire, spatial analysis) and covering different disciplines (architecture, environmental psychology, and midwifery). Results: The results revealed significant differences between the two settings and some associations between perceived and spatial data concerning: calm atmosphere, greater intimacy, spacious birth room, clarity of service points, clarity in finding midwives, sufficient space for labor, noise, privacy, and the birth room adaptability. Conclusions: The findings confirm the importance of the spatial layout and indicate documented knowledge as an input to consider when designing birth spaces in order to promote user well-being

Challenges of Otolaryngologic Referral in a Nigerian Tertiary Hospital

Background: The referral system offers one strategy for making the best use of hospitals and tertiary healthcare services. The aim of this study was to analyze the referral system of patients to the otorhinolaryngologist and to examine the use of in-house referral system in the teaching hospital set up.Methods: This was a retrospective review of all patients referred to the ENT Department between January 2000 and December 2007. Data retrieved from all referral notes included the review of referral letter, demographic, referral status, clinical presentations and examination findings. These data were entered into the SPSS computer software version 11.0 and analysedResults: A total of 1402 cases were analyzed. The patients’ ages ranged from 3weeks to 90yrs, with 70.4% of cases being below 40yrs of age while 25.9% were between 40-64yrs and 3.7% were above 65yrs. The Male to female sex ratio was 1:1. The majority (70.4%) of the patients had at least primary school education. The rest (29.6%) had no formal education. Slight over half (51.5%) of the patients were unemployed. The rest were either civil servants or self employed. Out of the 1402 patients that were referred to the hospital, in-house referral accounted for 74.1%, 7.2% of came from private health facility and 4.3% were self referrals. Out of the 1038 in-house referrals, 42.8% were from GOPD, 5.0% from Staff clinic, 13.3% from surgery, 4.7% from medicine, 3.5% from Obstetrics and Gynaecology, 10% from paediatrics and 10.4% from ophthalmology and 10.3% from ENT staffs such as residents, ENT Nurse Practitioner and ENT supporting staffs such as speech therapist and audiologist.Conclusion: The challenges of referral to the otolaryngologists are enormous thus the need to organize continuous medical education for the family physician, to make patients have confidence in the primary care physician, early referral of patients and to allow the otorhinolaryngologist to focus on the cutting edge issues of the specialt

Neuro-Identification of Some Commonly Used Volatile Organic Compounds Using Electronic Nose

Electronic nose system comprising of three Figaro sensors (TGS2602, TGS832 and TGS816)  arrayed in a chamber interfaced through  PICO ADC11/10 card to a computer system loaded with artificial neural network (ANN) was used to identify three  volatile organic compounds (Formaldehyde, Acetone and Chloroform). The back propagated ANN had four layers having positive linear, logsigmodal, logsigmidal  and tansigmodal transfer functions  with 10, 20, 20, 1 neurons, respectively. 60% of the acquired data was used for training and 20% each for testing and validation.TGS832 had the highest average sensitivity (1.3639 volts) while TGS816 had the least (0.0420 volts) for formaldehyde with similar trend for chloroform and acetone. Sensors’ sensitivities were significantly different from the control at p &lt; 0.05. Mean square error of 0.0006, 0.0001 and 0.0003(R2:0.996, 0.997 and 0.996) were obtained for the ANN training of formaldehyde, chloroform and acetone respectively. Validation run gave correct identification of the VOCs. Key Words: Sensors, Neurons, Normalization, Electronic nose, Data car