Manufacturing requirements

In recent years, natural laminar flow (NLF) has been proven to be achievable on modern smooth airframe surfaces over a range of cruise flight conditions representative of most current business and commuter aircraft. Published waviness and boundary layer transition measurements on several modern metal and composite airframes have demonstrated the fact that achievable surface waviness is readily compatible with laminar flow requirements. Currently, the principal challenge to the manufacture of NLF-compatible surfaces is two-dimensional roughness in the form of steps and gaps at structural joints. Results of recent NASA investigations on manufacturing tolerances for NLF surfaces, including results of a flight experiment are given. Based on recent research, recommendations are given for conservative manufacturing tolerances for waviness and shaped steps

Global Lifetime of Elemental Mercury Against Oxidation by Atomic Bromine in the Free Troposphere

We calculate the global mean atmospheric lifetime of elemental mercury (Hg0) against oxidation by atomic bromine (Br) in the troposphere by combining recent kinetic data for the Hg-Br system with modeled global concentrations of tropospheric Br. We obtain a lifetime of 0.5–1.7 years based on the range of kinetic data, implying that oxidation of Hg0 by Br is a major, and possibly dominant, global sink for Hg0. Most of the oxidation takes place in the middle and upper troposphere, where Br concentrations are high and where cold temperatures suppress thermal decomposition of the HgBr intermediate. This oxidation mechanism is consistent with mercury observations, including in particular high gaseous Hg(II) concentrations in Antarctic summer. Better free-tropospheric measurements of bromine radicals and further kinetic study of the Hg-Br system are essential to more accurately assess the global importance of Br as an oxidant of atmospheric Hg0.Earth and Planetary SciencesEngineering and Applied Science

Surface alignment control of nematodynamics

The primary study of this thesis is the response of the nematic director to pressure driven flow. Dynamic flow experiments using optical conoscopy and pressure gradient measurements are used to explore the physics behind the flow alignment seen to occur for some nematic liquid crystals. New research into the techniques and methods for aligning the director at a glass interface is also presented, the results of which are used towards the latter end of this thesis in the production of a highly novel flow cell. A bespoke technique for fabricating robust liquid crystal flow cells is also presented. The observation of flow alignment for the nematic liquid crystal 5CB is detailed for pressure driven flow via optical conoscopy when the director is initially aligned planar homogeneously at 45◦ to the direction of flow. The results of this experiment are compared to the theory of Ericksen and Leslie through a one dimensional dynamic model that provides simulated director profiles and corresponding simulated conoscopic images. Good agreement between the data and simulation is observed, whereby the director is seen to rotate to become parallel to the flow direction whilst exhibiting no net tilt distortion at all flow rates. The presence of small surface pretilt from a rubbed planar aligning polyimide layer and its effect on director rotation is also examined for cells that are rubbed in both the parallel and anti-parallel directions. The result observed is a striking difference in the mean director rotation when initially aligned close to normal to the direction of flow. The results of these experiments are also compared to the theory of Ericksen and Leslie through the one dimensional dynamic model. Good agreement is seen, highlighting the dramatic effect that a small amount of surface pretilt can have on the overall director orientation, whilst also demonstrating the need for caution when assuming that rubbed conventional alignment techniques provide true planar orientation. Two methods for producing intermediate or large pretilt angles at liquid crystal align- ment surfaces are also examined. Here, two recipes involving the commercial polyimides Nissan SE-1211, Nissan SE-130 and Nissan SE-4811 are experimentally investigated, with results showing the ability to tune the director pretilt angle as a function of the rubbing strength used to align the sample. The results also show an interesting depen- dance on the material upon which the aligning layer is deposited for the recipe involving Nissan SE-1211. Here, vastly different pretilt angles are observed for cells constructed with glass and indium tin oxide (ITO) layers. Finally, the large pretilt angles produced from the recipes mentioned above are also used to fabricate pressure driven flow cells exhibiting large pretilt angles on both sur- faces, constraining the director to align in a splayed state. When aligned parallel to the flow direction, experiments examining the valve-like nature of the director profile suggest that a preferential flow direction exists in what here is termed the ‘diode cell’. Measurements of the pressure gradient required to achieve a constant volumetric flow rate through the cell are compared for flow in both directions relative to the splayed di- rector profile. A striking difference is observed for flow ‘with’ the splay and ‘against’ the splay, leading to the realisation of a cell exhibiting a preferential flow direction through surface treatment. Again, results are compared to the theory of Ericksen and Leslie through the one dimensional dynamic model, showing good agreement.H

Quantitative analysis of epithelial cells in urine from men with and without urethritis: implications for studying epithelial: pathogen interactions in vivo

<p>Abstract</p> <p>Background</p> <p>Epithelial cells in first catch urine (FCU) specimens from 87 men with and without urethritis were quantified. Epithelial cells were broadly categorised into transitional and squamous populations using morphological characteristics and immunostaining with anti-pan leukocyte and anti-cytokeratin monoclonal antibodies.</p> <p>Findings</p> <p>The majority (77/87 = 89%) of samples contained both transitional (76/87 = 87%; range 1 × 10⁴– 6 × 10⁵, median 6 × 10⁴) and squamous (57/87 = 66%; range 1 × 10⁴– 8 × 10⁵, median 2 × 10⁴) epithelial cells. The number of transitional cells correlated with the number of squamous cells (Spearman's rho = 0.697 p < 0.001). Squamous, but not transitional, cell numbers correlated with leukocyte numbers (Spearman's rho = 0.216 p = 0.045 and rho = 0.171 and p = 0.113, respectively). However there was no significant difference in epithelial cell numbers between men with and without urethritis. Nevertheless, some men with urethritis had relatively high numbers of transitional cells in their FCU. Transitional cells were morphologically heterogeneous and appeared to display complex cytokeratin phenotypes.</p> <p>Conclusion</p> <p>Further studies are required to explore the complexity of epithelial cell populations in urine. These would provide novel opportunities for studying cellular interactions of <it>C. trachomatis </it>in male urethral infections, about which little is currently known.</p

Poland: a successful transition to budget sustainability?

In this paper we evaluate the sustainability of the current fiscal policy regime in Poland, which has been in place for almost 10 years since the start of the economic reform process. We use the intertemporal budget constraint (IBC) as a framework, and evaluate the sustainability of current policies. Consistency of fiscal policy with the IBC is evaluated using unit root and cointegration tests. In contrast to much previous research on fiscal sustainability in western economies, we explicitly take account of the possible role of seignorage from money creation as a source of government revenue. Sustainability tests are conducted excluding and then including seignorage. We find firm evidence that Polish fiscal policy is sustainable, and that the fiscal regime is "expenditure-led", adjusting tax revenues to the planned levels of government expenditures. This would appear to bode well for Poland's prospective entry to the EU and possible subsequent consideration of membership of the monetary union

Initial test results on bolometers for the Planck high frequency instrument

We summarize the fabrication, flight qualification, and dark performance of bolometers completed at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2009. The HFI is a multicolor focal plane which consists of 52 bolometers operated at 100 mK. Each bolometer is mounted to a feedhorn-filter assembly which defines one of six frequency bands centered between 100-857 GHz. Four detectors in each of five bands from 143-857 GHz are coupled to both linear polarizations and thus measure the total intensity. In addition, eight detectors in each of four bands (100, 143, 217, and 353 GHz) couple only to a single linear polarization and thus provide measurements of the Stokes parameters, Q and U, as well as the total intensity. The measured noise equivalent power (NEP) of all detectors is at or below the background limit for the telescope and time constants are a few ms, short enough to resolve point sources as the 5 to 9 arc min beams move across the sky at 1 rpm

Sources and Deposition of Reactive Gaseous Mercury in the Marine Atmosphere

Observations of reactive gaseous mercury (RGM) in marine air show a consistent diurnal cycle with minimum at night, rapid increase at sunrise, maximum at midday, and rapid decline in afternoon. We use a box model for the marine boundary layer (MBL) to interpret these observations in terms of RGM sources and sinks. The morning rise and midday maximum are consistent with oxidation of elemental mercury (Hg0) by Br atoms, requiring <2 ppt BrO in most conditions. Oxidation of Hg0 by Br accounts for 35–60% of the RGM source in our model MBL, with most of the remainder contributed by oxidation of Hg0 by ozone (5–20%) and entrainment of RGM-rich air from the free troposphere (25–40%). Oxidation of Hg0 by Cl is minor (3–7%), and oxidation by OH cannot reproduce the observed RGM diurnal cycle, suggesting that it is unimportant. Fitting the RGM observations could be achieved in the model without oxidation of Hg0 by ozone (leaving Br as the only significant oxidant) by increasing the entrainment flux from the free troposphere. The large relative diurnal amplitude of RGM concentrations implies rapid loss with a lifetime of only a few hours. We show that this can be quantitatively explained by rapid, mass-transfer-limited uptake of RGM into sea-salt aerosols as HgCl3− and HgCl42−. Our results suggest that 80–95% of HgII in the MBL should be present in sea-salt aerosol rather than gas-phase, and that deposition of sea-salt aerosols is the major pathway delivering HgII to the ocean.Earth and Planetary SciencesEngineering and Applied Science

Prenatal dexamethasone ‘programmes’ hypotension, but stress-induced hypertension in adult offspring

Low birth weight in humans is predictive of hypertension in adult life. Although the mechanisms underlying this link remain unknown, fetal overexposure to glucocorticoids has been implicated. We previously showed that prenatal dexamethasone (DEX) exposure in the rat lowers birth weight and programmes adult hypertension. The current study aimed to further investigate the nature of this hypertension and to elucidate its origins. Unlike previous studies, we assessed offspring blood pressure (BP) with radiotelemetry, which is unaffected by stress artefacts of measurement. We show that prenatal DEX during the last week of pregnancy results in offspring of low birth weight (14% reduction) that have lower basal BP in adulthood (∼4–8 mmHg lower); with the commonly expected hypertensive phenotype only being noted when these offspring are subjected to even mild disturbance or a more severe stressor (up to 30 mmHg higher than controls). Moreover, DEX-treated offspring sustain their stress-induced hypertension for longer. Promotion of systemic catecholamine release (amphetamine) induced a significantly greater rise of BP in the DEX animals (77% increase) over that observed in the vehicle controls. Additionally, we demonstrate that the isolated mesenteric vasculature of DEX-treated offspring display greater sensitivity to noradrenaline and other vasoconstrictors. We therefore conclude that altered sympathetic responses mediate the stress-induced hypertension associated with prenatal DEX programming