3D Particle Tracking Velocimetry Method: Advances and Error Analysis

A full three-dimensional particle tracking system was developed and tested. By using three separate CCDs placed at the vertices of an equilateral triangle, the threedimensional location of particles can be determined. Particle locations measured at two different times can then be used to create a three-component, three-dimensional velocity field. Key developments are: the ability to accurately process overlapping particle images, offset CCDs to significantly improve effective resolution, allowance for dim particle images, and a hybrid particle tracking technique ideal for three-dimensional flows when only two sets of images exist. An in-depth theoretical error analysis was performed which gives the important sources of error and their effect on the overall system. This error analysis was verified through a series of experiments, which utilized a test target with 100 small dots per square inch. For displacements of 2.54mm the mean errors were less than 2% and the 90% confidence limits were less than 5.2 μm in the plane perpendicular to the camera axis, and 66 μm in the direction of the camera axis. The system was used for flow measurements around a delta wing at an angle of attack. These measurements show the successful implementation of the system for three-dimensional flow velocimetry

On imploding cylindrical and spherical shock waves in a perfect gas

The problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest is studied without the use of the strong-shock approximation. Dimensional arguments are first used to show that this flow admits a general solution where an infinitesimally weak shock from infinity strengthens as it converges towards the origin. For a perfect-gas equation of state, this solution depends only on the dimensionality of the flow and on the ratio of specific heats. The Guderley power-law result can then be interpreted as the leading-order, strong-shock approximation, valid near the origin at the implosion centre. We improve the Guderley solution by adding two further terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion, valid where the shock is still weak and very far from the origin, is also constructed. With an appropriate change of variables and using the exact shock-jump conditions, a numerical, characteristics-based solution is obtained describing the general shock motion from almost infinity to very close to the reflection point. Comparisons are made between the series expansions, the characteristics solution, and the results obtained using an Euler solver. These show that the addition of two terms to the Guderley solution significantly extends the range of validity of the strong-shock series expansion

Accelerated Microbial Degradation of Nematicides in Vineyard and Orchard Soils

Accelerated microbial degradation (AMD) of organophosphate and carbamate nematicides is aphenomenon whereby biodegradation in the soil is increased, leading to a dramatically shortenedpersistence of nematicides. More intensified agriculture practices in South Africa in response to the futuredemand for food may lead to increased pest and disease pressure, which in turn will lead to more frequentpesticide application. The same principle applies to plant-parasitic nematode control practices, and theoveruse and misuse will have a pronounced effect on the enhancement of AMD. With limited managementoptions available, the responsible use of nematicides becomes more pertinent. Producers should beaware of the problems associated with multiple soil applications of organophosphates and carbamatesagainst plant-parasitic nematodes. This article reviews factors contributing to the AMD of carbamate andorganophosphate nematicides in soil and makes practical recommendations to avoid the occurrence ofAMD in vineyard and orchards

Tableau de Bord Géographique des Parcs nationaux : un outil cartographique d'aide à la gestion.

Objectif : donner aux gestionnaires des parcs nationaux un outil permettant d'accéder rapidement à une information synthétique : description du territoire, diagnostics, suivi des actions. Deux exemples sont donnés dans le P.N. du Mercantour

Efficacy, safety and tolerance of parenteral piperacillin/tazobactam in the treatment of patients with lower respiratory tract infections

Contains fulltext : 4772.pdf (publisher's version ) (Open Access

COVID-19 coronavirus: recommended personal protective equipment for the orthopaedic and trauma surgeon

PURPOSE: With the COVID-19 crisis, recommendations for personal protective equipment (PPE) are necessary for protection in orthopaedics and traumatology. The primary purpose of this study is to review and present current evidence and recommendations for personal protective equipment and safety recommendations for orthopaedic surgeons and trauma surgeons. METHODS: A systematic review of the available literature was performed using the keyword terms “COVID-19”, “Coronavirus”, “surgeon”, “health-care workers”, “protection”, “masks”, “gloves”, “gowns”, “helmets”, and “aerosol” in several combinations. The following databases were assessed: Pubmed, Cochrane Reviews, Google Scholar. Due to the paucity of available data, it was decided to present it in a narrative manner. In addition, participating doctors were asked to provide their guidelines for PPE in their countries (Austria, Luxembourg, Switzerland, Germany, UK) for consideration in the presented practice recommendations. RESULTS: World Health Organization guidance for respiratory aerosol-generating procedures (AGPs) such as intubation in a COVID19 environment was clear and included the use of an FFP3 (filtering face piece level 3) mask and face protection. However, the recommendation for surgical AGPs, such as the use of high-speed power tools in the operating theatre, was not clear until the UK Public Health England (PHE) guidance of 27 March 2020. This guidance included FFP3 masks and face protection, which UK surgeons quickly adopted. The recommended PPE for orthopaedic surgeons, working in a COVID19 environment, should consist of level 4 surgical gowns, face shields or goggles, double gloves, FFP2-3 or N95-99 respirator masks. An alternative to the mask, face shield and goggles is a powered air-purifying respirator, particularly if the surgeons fail the mask fit test or are required to undertake a long procedure. However, there is a high cost and limited availabilty of these devices at present. Currently available surgical helmets and toga systems may not be the solution due to a permeable top for air intake. During the current COVID-19 crisis, it appeared that telemedicine can be considered as an electronic personal protective equipment by reducing the number of physical contacts and risk contamination. CONCLUSION: Orthopaedic and trauma surgery using power tools, pulsatile lavage and electrocautery are surgical aerosol-generating procedures and all body fluids contain virus particles. Raising awareness of these issues will help avoid occupational transmission of COVID-19 to the surgical team by aerosolization of blood or other body fluids and hence adequate PPE should be available and used during orthopaedic surgery. In addition, efforts have to be made to improve the current evidence in this regard