Near field structure of wing tip vortices

High spatial resolution experiments in the near field of a trailing vortex using a Stereoscopic Particle Image Velocimetry technique have been carried out. A NACA 0015 model with flat tip has been tested for several Reynolds numbers and angles of attack. An axisymmetric meandering of the vortex is observed and a discussion on the aperiodicity correction method has identified the helicity peak as the most convenient indicator of the vortex centre. The axial velocity in the centre of the vortex has been recorded always as an excess except for low angle of attack cases where intermittent peaks of excess and deficit are superimposed on a large patch of deficit velocity. The double vortex structure and the consequent double inflection in the tangential velocity profiles is also studied with reference to a vortex age parameter. At already 2 chords of distance from the trailing edge the profiles exhibit axisymmetric behaviour. A spiral structure of the vortex core has been reported as effect of the early stage of the rolling up and considerations on the rotation confirmed the high dependency of the initial phase of the rolling up with the tip shape. The square tip produces a strong asymmetry of the vortex core and an intense secondary vortex. Good agreement of the tangential velocity and the circulation profiles between the experiments and analytical vortex expressions has been observed. The results confirm the existence of a three-part vortex structure, namely an inner, a logarithmic and an outer region of the vortex where the former is affected by the initial vortex structure and the latter is not universal but shows a dependence on the angle of attack

Effect of humidity on transonic flow

An experimental investigation of the effects of humidity-induced condensation on shock/boundary-layer interaction has been conducted in a transonic wind-tunnel test. The test geometry considered was a wall-mounted bump model inserted in the test section of the wind tunnel. The formation of a λ-shape condensation shock wave was shown from schlieren visualization and resulted in a forward movement of the shock wave, reduced shock wave strength, and reduced separation. Empirical correlations of the shock wave strength and humidity/dew point temperature were established. For humidity levels below 0.15 or a dew point temperature of 268 K, the effect of humidity was negligible. The unsteady pressure measurements showed that if a condensation shock wave formed and interacted with a main shock wave, the flow becomes unsteady with periodic flow oscillations occurring at 720 Hz

Neuronal post-developmentally acting SAX-7S/L1CAM can function as cleaved fragments to maintain neuronal architecture in C. elegans [preprint]

Whereas remarkable advances have uncovered mechanisms that drive nervous system assembly, the processes responsible for the lifelong maintenance of nervous system architecture remain poorly understood. Subsequent to its establishment during embryogenesis, neuronal architecture is maintained throughout life in the face of the animal’s growth, maturation processes, the addition of new neurons, body movements, and aging. The C. elegans protein SAX-7, homologous to the vertebrate L1 protein family, is required for maintaining the organization of neuronal ganglia and fascicles after their successful initial embryonic development. To dissect the function of sax-7 in neuronal maintenance, we generated a null allele and sax-7S-isoform-specific alleles. We find that the null sax-7(qv30) is, in some contexts, more severe than previously described mutant alleles, and that the loss of sax-7S largely phenocopies the null, consistent with sax-7S being the key isoform in neuronal maintenance. Using a sfGFP::SAX-7S knock-in, we observe sax-7S to be predominantly expressed across the nervous system, from embryogenesis to adulthood. Yet, its role in maintaining neuronal organization is ensured by post-developmentally acting SAX-7S, as larval transgenic sax-7S(+) expression alone is sufficient to profoundly rescue the null mutants’ neuronal maintenance defects. Moreover, the majority of the protein SAX-7 appears to be cleaved, and we show that these cleaved SAX-7S fragments together, not individually, can fully support neuronal maintenance. These findings contribute to our understanding of the role of the conserved protein SAX-7/L1CAM in long-term neuronal maintenance, and may help decipher processes that go awry in some neurodegenerative conditions

Functional Requirements for Heparan Sulfate Biosynthesis in Morphogenesis and Nervous System Development in C. elegans

The regulation of cell migration is essential to animal development and physiology. Heparan sulfate proteoglycans shape the interactions of morphogens and guidance cues with their respective receptors to elicit appropriate cellular responses. Heparan sulfate proteoglycans consist of a protein core with attached heparan sulfate glycosaminoglycan chains, which are synthesized by glycosyltransferases of the exostosin (EXT) family. Abnormal HS chain synthesis results in pleiotropic consequences, including abnormal development and tumor formation. In humans, mutations in either of the exostosin genes EXT1 and EXT2 lead to osteosarcomas or multiple exostoses. Complete loss of any of the exostosin glycosyltransferases in mouse, fish, flies and worms leads to drastic morphogenetic defects and embryonic lethality. Here we identify and study previously unavailable viable hypomorphic mutations in the two C. elegans exostosin glycosyltransferases genes, rib-1 and rib-2. These partial loss-of-function mutations lead to a severe reduction of HS levels and result in profound but specific developmental defects, including abnormal cell and axonal migrations. We find that the expression pattern of the HS copolymerase is dynamic during embryonic and larval morphogenesis, and is sustained throughout life in specific cell types, consistent with HSPGs playing both developmental and post-developmental roles. Cell-type specific expression of the HS copolymerase shows that HS elongation is required in both the migrating neuron and neighboring cells to coordinate migration guidance. Our findings provide insights into general principles underlying HSPG function in development

Adding a quadrivalent human papillomavirus vaccine to the UK cervical cancer screening programme: A cost-effectiveness analysis

<p>Abstract</p> <p>Background</p> <p>We assessed the cost-effectiveness of adding a quadrivalent (6/11/16/18) human papillomavirus (HPV) vaccine to the current screening programme in the UK compared to screening alone.</p> <p>Methods</p> <p>A Markov model of the natural history of HPV infection incorporating screening and vaccination was developed. A vaccine that prevents 98% of HPV 6, 11, 16 and 18-associated disease, with a lifetime duration and 85% coverage, in conjunction with current screening was considered.</p> <p>Results</p> <p>Vaccination with screening, compared to screening alone, was associated with an incremental cost-effectiveness ratio of £21,059 per quality adjusted life year (QALY) and £34,687 per life year saved (LYS). More than 400 cases of cervical cancer, 6700 cases of cervical intraepithelial neoplasia and 4750 cases of genital warts could be avoided per 100,000 vaccinated girls. Results were sensitive to assumptions about the need for a booster, the duration of vaccine efficacy and discount rate.</p> <p>Conclusion</p> <p>These analyses suggest that adding a quadrivalent HPV vaccine to current screening in the UK could be a cost-effective method for further reducing the burden of cervical cancer.</p

Plasma actuator: influence of dielectric surface temperature

Plasma actuators have become the topic of interest of many researchers for the purpose of flow control. They have the advantage of manipulating the flow without the need for any moving parts, a small surface profile which does not disturb the free stream flow, and the ability to switch them on or off depending on the particular situation (active flow control). Due to these characteristics they are becoming very popular for flow control over aircraft wings. The objective of the current study is to examine the effect of the actuator surface temperature on its performance. This is an important topic to understand when dealing with real life aircraft equipped with plasma actuators. The temperature variations encountered during a flight envelope may have adverse effects in actuator performance. A peltier heater along with dry ice are used to alter the actuator temperature, while particle image velocimetry (PIV) is utilised to analyse the flow field. The results show a significant change in the induced flow field by the actuator as the surface temperature is varied. It is found that for a constant peak-to-peak voltage the maximum velocity produced by the actuator depends directly on the dielectric surface temperature. The findings suggest that by changing the actuator temperature the performance can be maintained or even altered at different environmental conditions

Measurement of the spatial distribution of mucilage around roots using infrared spectroscopy

Mucilage is a mixture of polysaccharides and some lipids which is secreted by the root tip. It facilitates plant nutrient acquisition, stabilizes aggregates, reduces lubrication during plant growth and may increase rhizosphere water content due to its high water holding capacity. So far there is no method to measure the spatial distribution of mucilage in soil around roots. The aim of this study was to test whether infrared spectroscopy can be applied to quantify gradients of mucilage around roots in soil. The C-H to C-O ratio obtained from infrared spectroscopy measurements is an indicator of soil hydrophobicity. As Mucilage turns hydrophobic after drying we hypothesized that mucilage can be detected by the C-H to C-O ratio measured with infrared spectroscopy. We grew maize plants in rhizoboxes filled with quartz silt. Before measurement the planted containers were dried and the roots were removed from soil. Infrared spectroscopy measurements were conducted with a spatial resolution of 50x50 µm a) radially with increasing distance from the root channel center and b) axially with increasing distance from the root channel tip. In parallel, the contact angle, which also indicates soil hydrophobicity, was quantified in the same locations. Both measurements were additionally conducted on glass slides covered with quartz silt mixed with given concentrations of mucilage. The measurements on the glass slides revealed that the C-H to C-O ratio and the contact angle measurements correlated well with the mucilage concentration in soil. Similarly, the infrared spectroscopy measurements in in the rhizoboxes revealed that radial profiles of mucilage around roots can be quantified: while the C-H to C-O ratio was highest inside the root channels, it decreased to the bulk soil values 0.7 mm in radial direction from the border of the root channel. In axial direction the C-H to C-O ratio did not change significantly, indicating that those compounds causing hydrophobicity of mucilage are not easily degraded by soil microorganisms. We showed that infrared spectroscopy can be applied to measure profiles of mucilage around roots in soil. The radial profiles of mucilage were narrower than those reported for other rhizodeposits which may be explained by the viscosity of mucilage

Renormalization group approach of itinerant electron systems near the Lifshitz point

Using the renormalization approach proposed by Millis for the itinerant electron systems we calculated the specific heat coefficient $\gamma(T)$ for the magnetic fluctuations with susceptibility $\chi^{-1}\sim |\delta+\omega|^\alpha+f(q)$ near the Lifshitz point. The constant value obtained for $\alpha=4/5$ and the logarithmic temperature dependence, specific for the non-Fermi behavior, have been obtained in agreement with the experimental dat.Comment: 6 pages, Revte

Infection With Strongyloides Stercoralis Among Children In Urban Slums Of Kibera In Nairobi, Kenya

Background: Strongyloidiasis is an intestinal parasitic infection with poorly-defined geographical Endemicity in Africa. It is a Soil-Transmitted Helminths (STH) infection caused by Strongyloides stercoralis and Strongyloides fuelleborni. Aim: To investigate the prevalence of Strongyloides infection among children living in an urban slum in Nairobi, Kenya. Likewise, to assess it's association with other soil - transmitted Helminths. Methodology and Findings: We used the recently-developed Ss-NIE-1-antibody ELISA assay for Strongyloides to evaluate Sera collected during a 2012 study of Soil Transmitted Helminth infection prevalence among children in the Kibera slum of Nairobi, Kenya. A total of 745 samples from School Age Children (SAC) and Pre-school-age children (PSAC) were tested; eight (1.1%) were positive for Strongyloides. Infection was equally common among SAC and PSAC. No association was found between infection with Strongyloides and infection with other Soil Transmitted Helminths. Conclusion: Strongyloides is a rare infection among children living in the urban slum of Kibera. Similar evaluation of exposure to Strongyloides stercoralis across different age groups and environmental, geographical features in Africa are warranted. Keywords: Strongyloides, children, Keny