Do Jet-Driven Shocks ionize the Narrow Line Regions of Seyfert Galaxies?

We consider a model in which the narrow line regions (NLRs) of Seyfert galaxies are photoionized ``in situ'' by fast (300 -- 1,000 km/s), radiative shock waves driven into the interstellar medium of the galaxy by radio jets from the active nucleus. Such shocks are powerful sources of soft X-rays. We compute the expected ratio of the count rates in the ROSAT PSPC and Einstein IPC detectors to the [OIII] \lambda 5007 flux as a function of shock velocity, and compare these ratios with observations of type 2 Seyferts. If most of the observed soft X-ray emission from these galaxies originates in the NLR and the absorbing hydrogen column is similar to that inferred from the reddening of the NLR, a photoionizing shock model with shock velocity $\simeq$ 400 -- 500 km/s is compatible with the observed ratios. High angular resolution observations with AXAF are needed to isolate the X-ray emission of the NLR and measure its absorbing column, thus providing a more conclusive test. We also calculate the expected coronal iron line emission from the shocks. For most Seyfert 2s, the [Fe X] \lambda 6374/H \beta$ ratio is a factor of 2 -- 14 lower than the predictions of 300 -- 500 km/s shock models, suggesting that less hot gas is present than required by these models.Comment: Astrophys J. Letters 1999 March 10 issue, Vol. 51

The effect of corrugation on heat transfer and pressure drop in channel flow with different Prandtl numbers

Large Eddy Simulation and Direct Numerical Simulation are applied to study the turbulent flow field in a wavy channel at two Prandtl numbers, Pr = 0.71 and Pr = 3.5, and Reynolds number Re b = 10,000. The characteristics of the separated shear layer and the near wall recirculating zone are discussed in relation to the turbulent heat transfer. Special attention is paid to the behavior of the flow and thermal boundary layers and various turbulent characteristics and their effects on the distribution of the Nusselt number and friction coefficient in the separation and reattachment regions. The results indicate that the thickness of the thermal boundary layer rather than the turbulent fluctuations has a significant effect on the local variation of the averaged Nusselt number. The results are compared with Direct Numerical Simulation results of a plane channel at the same Reynolds number. \ua9 2013 Elsevier Ltd. All rights reserved

Experimental and computational investigation of droplet-particle interactions

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An experimental study of droplet-particle collisions

When spray drying a liquid slurry such as milk, collisions between droplets, partially dried particles and completely dry particles are important because coalescence, agglomeration and breakup events influence the size and morphology of the produced powder. When modelling such a spray drying process, it is therefore important to be able to predict the outcomes of individual binary collisions. Both binary dry particle collisions and binary droplet collisions have individually been thoroughly researched over the years due to their widespread occurrence. The importance of understanding binary particle-droplet collisions has been emphasized more recently. However, the number of available studies is limited and simulation studies usually focus on relatively high capillary number. A theory explaining the transition between different regimes is still lacking. The goal of this study is to provide an experimental data set at low capillary number. These results can be used to validate future theories and simulations. To produce and record particle-droplet collisions, an experimental setup that enables synchronized release of both a particle and a droplet was used. One single hanging droplet was released from above onto a particle that initially was held in place by vacuum suction. A high speed camera was synchronized with the setup, and recorded the collisions. Image files were then analysed in Matlab to find velocities and sizes of the particle and droplet before and after impact. The contrast of particle and droplet against the illuminated background was a key factor in succeeding with this. Different collision outcomes were identified as either agglomeration (merging), where the whole droplet would stick to the surface of the particle, or a stretching separation (breaking), where the droplet collides with the particle in an oblique position and stretches out until a part of the droplet detaches from the liquid sticking to the particle. The formation of satellite droplets, i.e. droplets with a radius significantly smaller than the leaving droplet, was also detected. The relation of these collision outcomes to impact conditions such as Weber number and impact parameter was reviewed and put into regime maps

Experimental study of the heat transfer in a falling film evaporator: influence of the co-flowing vapor

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.A large number of industrial processes are based on the concentration of liquid products by means of falling-film evaporation. In the dehydration of dairy products, concentrating a fluid by evaporating represents one of the most important steps of the whole drying process. Among the advantages of this technology is that it is possible to operate within small temperature differences which results in low heat consumption. In this sense, it is necessary to increase the amount of removed water during the falling-film evaporation to reduce the energy cost of the overall process. However, reducing the fraction of the solvent leads to an increase in viscosity of the product which can show non-Newtonian features. This aspect significantly affects the heat transfer, that is to say, the higher the solid content, the lower the heat transfer coefficient. One of the possible solutions to this drawback consists in drawing maximum benefit from the interaction between the fluid film and the co-flow of the gaseous phase resulting from the evaporation process. Unfortunately, accurate studies of the effect of co-flow on evaporative falling films are very rare and difficult to perform because of the high costs of the implementation of a suitable experimental apparatus. In this work, the experimental study of the influence of the co-flow on the heat transfer coefficient is presented as a function of both the solid content and the mass flow rate of the feed. The experimental set-up, consisting in a unique industrial pilot scale evaporator, provides the possibility to obtain results useful for realistic industrial conditions. Tests were conducted with varying dry solid content from 10 to 50%. The results show that the co-flow has the effect to decrease the potential for fouling/poor wetting. Above this, the influence on the heat transfer is not as large as expected because of the dominant influence of the viscosity.cf201

New Strategy for Rapid Diagnosis and Characterization of Fungal Infections: The Example of Corneal Scrapings

PURPOSE: The prognosis of people infected with Fungi especially immunocompromised depends on rapid and accurate diagnosis to capitalize on time administration of specific treatments. However, cultures produce false negative results and nucleic-acid amplification techniques require complex post-amplification procedures to differentiate relevant fungal types. The objective of this work was to develop a new diagnostic strategy based on real-time polymerase-chain reaction high-resolution melting analysis (PCR-HRM) that a) detects yeasts and filamentous Fungi, b) differentiates yeasts from filamentous Fungi, and c) discriminates among relevant species of yeasts. METHODS: PCR-HRM detection limits and specificity were assessed with a) isolated strains; b) human blood samples experimentally infected with Fungi; c) blood experimentally infected with other infectious agents; d) corneal scrapings from patients with suspected fungal keratitis (culture positive and negative) and e) scrapings from patients with suspected bacterial, viral or Acanthamoeba infections. The DNAs were extracted and mixed with primers diluted in the MeltDoctor® HRM Master Mix in 2 tubes, the first for yeasts, containing the forward primer CandUn (5'CATGCCTGTTTGAGCGTC) and the reverse primer FungUn (5'TCCTCCGCTT ATTGATATGCT) and the second for filamentous Fungi, containing the forward primer FilamUn (5'TGCCTGTCCGAGCGTCAT) and FungUn. Molecular probes were not necessary. The yields of DNA extraction and the PCR inhibitors were systematically monitored. RESULTS: PCR-HRM detected 0.1 Colony Forming Units (CFU)/µl of yeasts and filamentous Fungi, differentiated filamentous Fungi from yeasts and discriminated among relevant species of yeasts. PCR-HRM performances were higher than haemoculture and sensitivity and specificity was 100% for culture positive samples, detecting and characterizing Fungi in 7 out 10 culture negative suspected fungal keratitis. CONCLUSIONS: PCR-HRM appears as a new, sensitive, specific and inexpensive test that detects Fungi and differentiates filamentous Fungi from yeasts. It allows direct fungal detection from clinical samples and experimentally infected blood in less than 2.30 h after DNA extraction

The role of micro-organisms (Staphylococcus aureus and Candida albicans) in the pathogenesis of breast pain and infection in lactating women: study protocol

Background: The CASTLE (Candida and Staphylococcus Transmission: Longitudinal Evaluation) study will investigate the micro-organisms involved in the development of mastitis and &ldquo;breast thrush&rdquo; among breastfeeding women. To date, the organism(s) associated with the development of breast thrush have not been identified. The CASTLE study will also investigate the impact of physical health problems and breastfeeding problems on maternal psychological health in the early postpartum period.Methods/Design: The CASTLE study is a longitudinal descriptive study designed to investigate the role of Staphylococcus spp (species) and Candida spp in breast pain and infection among lactating women, and to describe the transmission dynamics of S. aureus and Candida spp between mother and infant. The relationship between breastfeeding and postpartum health problems as well as maternal psychological well-being is also being investigated. A prospective cohort of four hundred nulliparous women who are at least thirty six weeks gestation pregnant are being recruited from two hospitals in Melbourne, Australia (November 2009 to June 2011). At recruitment, nasal, nipple (both breasts) and vaginal swabs are taken and participants complete a questionnaire asking about previous known staphylococcal and candidal infections. Following the birth, participants are followed-up six times: in hospital and then at home weekly until four weeks postpartum. Participants complete a questionnaire at each time points to collect information about breastfeeding problems and postpartum health problems. Nasal and nipple swabs and breast milk samples are collected from the mother. Oral and nasal swabs are collected from the baby. A telephone interview is conducted at eight weeks postpartum to collect information about postpartum health problems and breastfeeding problems, such as mastitis and nipple and breast pain.Discussion: This study is the first longitudinal study of the role of both staphylococcal and candidal colonisation in breast infections and will help to resolve the current controversy about which is the primary organism in the condition known as breast thrush. This study will also document transmission dynamics of S. aureus and Candida spp between mother and infant. In addition, CASTLE will investigate the impact of common maternal physical health symptoms and the effect of breastfeeding problems on maternal psychological well-being.<br /

Drop Break-up in High-Pressure Homogenisers

The overall aim of this project was to investigate the drop break-up process in milk homogenisers. This was done by measurements and calculations of the flow fields in the gap region and by visualisation of drops being broken up. To make visualisation and measurements possible, two scale models of a homogeniser gap were developed. The full-scale model was a direct copy of the gap in a production-scale homogeniser, but with optical access. Normal operational homogenisation pressures could be tested, and drops down to 5µm in diameter could be visualised. The second model was scaled-up about 100 times ensuring that the relevant dimensionless groups were kept constant, so that the same factors governed the drop break-up process. The scaled-up model was made of transparent plastic and was used for both velocity field measurements and drop visualisation. From these measurements it was concluded that the drops did not break up in the entrance of the gap. Larger drops were elongated to some extent and smaller ones remained spherical. Not much happens in the gap itself. The velocity profile is very flat throughout the gap in a production-scale homogeniser. In a pilot-scale homogeniser the boundary layers have time to grow and the velocity profile is almost developed at the gap exit. The growing shear layers seem to have a limited effect on the drops. During passage through the gap small drops will have time to relax back to their spherical shape, while large ones will leave the gap with almost the same aspect ratio as when they entered it. This study shows that drop break-up takes place in the turbulent jet at the gap outlet. The flow velocity measurements show a very unsteady jet breaking down faster than a jet in a free liquid. Depending on the geometry of the chamber at the gap outlet, the jet can attach to either of the 45-degree walls and become a wall jet. The turbulence in the jet is very high, with turbulence intensities of 50-100%. Indications were found that flow structures of the size of, or slightly smaller than, the gap height, have very high intensities. Drop deformation experiments and theoretical analyses show that the eddies breaking up the drops range in size from much larger than, to just smaller than, the drop. The larger eddies deform the drop viscously by the velocity gradient created by the eddy. The smaller eddies deform the drop by fluid inertia. The critical phase of the drop break-up process is the initial deformation. If the drop is deformed to an aspect ratio of 3-5, the drop is then very quickly elongated into one or more filaments which may be bent, coiled and further deformed before they break up into many small droplets

Visualization of the drop deformation and break-up process in a high pressure homogenizer

For the creation of sub-micron emulsions in fluids of low viscosity the high pressure homogenizer (HPH) is usually chosen. One way of obtaining deeper knowledge of exactly what happens in the active region is to visualize it. In this work, a drop deformation and break-up visualization system based on a modified Particle Image Velocimetry (PIV) system is described. The system reproduces the gap in a HPH and has been used with pressures up to 18 MPa and drops as small as 5 mu m. The optics of the system are analyzed taking into account limiting factors such as the lens resolving power, the focal depth, and the duration of the laser pulses. It is shown that it is possible to resolve drops down to a few mu m moving in excess of 100 m/s, and that the main limitations are the resolving power and in the focal depth of the objectives. Examples are shown from capillary drop creation and from the deformation and break-up of drops in a HPH. It can be concluded that in a HPH, the drops are only deformed to a limited extent in the inlet of the gap, and that all drop break-up occurs far downstream of the gap