Roughness and waviness requirements for laminar flow surfaces

Many modern metal and composite airframe manufacturing techniques can provide surface smoothness which is compatible with natural laminar flow (NLF) requirements. An important consideration is manufacturing roughness of the surface in the form of steps and gaps perpendicular to the freestream. The principal challenge to the design and manufacture of laminar flow surfaces today appears to be in the installation of leading-edge panels on wing, nacelle, and empennage surfaces. A similar challenge is in the installation of access panels, doors, windows, fuselage noses, and engine nacelles. Past work on roughness and waviness manufacturing tolerances and comparisons with more recent experiments are reviewed

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

Using System Dynamics to Explore the Water Supply and Demand Dilemmas of a Small South African Municipality

This paper explores the challenges faced by small municipalities in providing water services in a developing world context of increasing urban demand. The paper uses a case study of the Sundays River Valley Municipality (SRVM) in South Africa. The municipality faces multiple dilemmas in reconciling its available water supply with growing demand for potable water in the primary urban settlement in the area, in a struggle that is typical of the broad category of South African municipalities to which the SRVM belongs. These dilemmas are explored using a system dynamics model, referred to as the ‘Kirkwood water demand system dynamics model’ (K-DEM). This paper specifically introduces the K-DEM structure,which is aimed at investigating the impacts of households progressively receiving full water and sanitation services; the use of rainwater harvesting as an alternative form of water supply; and the possible effect of a household-level water conservation / water demand management programme. Baseline results are discussed, and areas for future research identified. Paper presented at the 32nd International Conference of the System Dynamics Society, 21-24 July 2014, in Delft, the Netherlands.WordMac OS X 10.8.5 Quartz PDFContex

A functional variant of the myeloperoxidase gene is associated with cardiovascular disease in end-stage renal disease patients

A functional variant of the myeloperoxidase gene is associated with cardiovascular disease in end-stage renal disease patients. Cardiovascular disease (CVD) is the leading cause of mortality in end-stage renal disease (ESRD) patients and there is emerging evidence that genetic factors may contribute to the development of atherosclerosis. Myeloperoxidase (MPO) is an abundant enzyme involved in the production of free radicals. A functional G→A single nucleotide polymorphism (SNP) has been identified at position -463, where the A allele is associated with lower MPO expression. To analyze the association between this SNP and inflammation, oxidative stress, and CVD, we studied a cohort of 155 ESRD patients (52 ± 1 years, 62% males, 22% diabetics) shortly before the initiation of dialysis treatment. CVD was defined by medical history criteria; plasma interleukin-6 (IL-6) was used as a marker of inflammation, and plasma pentosidine as an estimation of oxidative protein damage. DNA from leukocytes was used for genotyping, performed by the pyrosequencing reaction. Only five patients (3%) had the genotype AA at the -463 position, whereas 38 (25%) had the GA and 112 (72%) had the GG genotype. No differences were noted in plasma IL-6 levels between the genotype groups, whereas the pentosidine levels were higher in the GG group (28.4 pmol/mg albumin [range, 8.5 to 123 pmol/mg albumin]) compared to the other two groups (21.4 pmol/mg albumin [range, 7.6 to 384 pmol/mg albumin; P < 0.05]). Patients with the GG genotype had a higher prevalence of positive serology for Chlamydia pneumoniae (51%) when compared to the carriers of the A allele (24%) (P < 0.05). The prevalence of CVD was lower in the AA (0%) and GA genotypes (18%), compared to the GG genotype (35%). The GG genotype was still associated with CVD after correction for age, diabetes, smoking, malnutrition, and inflammation. Our findings suggest that the -463 G→A SNP, which supposedly results in lower MPO activity, is associated with a lower prevalence of CVD in ESRD patients. It could be speculated that this effect is mediated by a decreased oxidative stress due to lower production of free radicals

State of the field: What can political ethnography tell us about anti-politics and democratic disaffection?

This article adopts and reinvents the ethnographic approach to uncover what governing elites do, and how they respond to public disaffection. Although there is significant work on the citizens’ attitudes to the governing elite (the demand side) there is little work on how elites interpret and respond to public disaffection (the supply side). We argue that ethnography is the best available research method for collecting data on the supply side. In doing so, we tackle long-standing stereotypes in political science about the ethnographic method and what it is good for. We highlight how the innovative and varied practices of contemporary ethnography are ideally suited to shedding light into the ‘black box’ of elite politics. We demonstrate the potential pay-off with reference to important examples of elite ethnography from the margins of political science scholarship. The implications from these rich studies, we argue, suggest a reorientation of how we understand the drivers of public disaffection and the role that political elites play in exacerbating cynicism and disappointment. We conclude by pointing to the benefits to the discipline in embracing elite ethnography both to diversify the methodological toolkit in explaining the complex dynamics of disaffection,and to better enable engagement in renewed public debate about the political establishment

Principles for transformative ocean governance

With a focus on oceans, we collaborated across ecological, social and legal disciplines to respond to the United Nations call for transformation in the ‘2030 Agenda for Sustainable Development’. We developed a set of 13 principles that strategically and critically connect transformative ocean research to transformative ocean governance (complementing the UN Decade for Ocean Science). We used a rigorous, iterative and transparent consensus-building approach to define the principles, which can interact in supporting, neutral or sometimes conflicting ways. We recommend that the principles could be applied as a comprehensive set and discuss how to learn from their interactions, particularly those that reveal hidden tensions. The principles can bring and keep together partnerships for innovative ocean action. This action must respond to the many calls to reform current ocean-use practices which are based on economic growth models that have perpetuated inequities and fuelled conflict and environmental decline

Adapting effects of emotional expression in anxiety: evidence for an enhanced late positive potential

An adaptation paradigm was used to investigate the influence of a previously experienced visual context on the interpretation of ambiguous emotional expressions. Affective classification of fear-neutral ambiguous expressions was performed following repeated exposure to either fearful or neutral faces. There was a shift in the behavioural classification of morphs towards ‘fear’ following adaptation to neutral compared to adaptation to fear with a non-significant trend towards the high anxiety group compared to the low being more influenced by the context. The event-related potential (ERP) data revealed a more pronounced late positive potential (LPP), beginning at ~400 ms post-stimulus onset, in the high but not the low anxiety group following adaptation to neutral compared to fear. In addition, as the size of the behavioural adaptation increased there was a linear increase in the magnitude of the late-LPP. However, context-sensitivity effects are not restricted to trait anxiety, with similar effects observed with state anxiety and depression. These data support the proposal that negative moods are associated with increased sensitivity to visual contextual influences from top-down elaborative modulations, as reflected in an enhanced late positive potential deflection

Categorical encoding of color in the brain

The areas of the brain that encode color categorically have not yet been reliably identified. Here, we used functional MRI adaptation to identify neuronal populations that represent color categories irrespective of metric differences in color. Two colors were successively presented within a block of trials. The two colors were either from the same or different categories (e.g., “blue 1 and blue 2” or “blue 1 and green 1”), and the size of the hue difference was varied. Participants performed a target detection task unrelated to the difference in color. In the middle frontal gyrus of both hemispheres and to a lesser extent, the cerebellum, blood-oxygen level-dependent response was greater for colors from different categories relative to colors from the same category. Importantly, activation in these regions was not modulated by the size of the hue difference, suggesting that neurons in these regions represent color categorically, regardless of metric color difference. Representational similarity analyses, which investigated the similarity of the pattern of activity across local groups of voxels, identified other regions of the brain (including the visual cortex), which responded to metric but not categorical color differences. Therefore, categorical and metric hue differences appear to be coded in qualitatively different ways and in different brain regions. These findings have implications for the long-standing debate on the origin and nature of color categories, and also further our understanding of how color is processed by the brain

Guidelines for restoring Lowland Sand Fynbos ecosystems

CITATION: Holmes, P.M., et al. 2022. Guidelines for restoring Lowland Sand Fynbos ecosystems. Stellenbosch: Stellenbosch Univesity, Department of Conservation Ecology and Entomology.The original publication is available at http://biodiversityadvisor.sanbi.org/planning-and-assessment/ecological-restoration/Lowland Sand Fynbos ecosystems are among the most threatened terrestrial systems in South Africa. Of the ten Sand Fynbos veld types, seven are Critically Endangered or Endangered according to the IUCN Red List of Ecosystems. They are all either poorly protected, or not protected at all in the conservation network. Sand Fynbos ecosystems harbour unique biodiversity, but owing to their lowland locations experience extensive losses to other land uses. Some natural pockets remain scattered within agricultural or urban developments. They are, however degraded due to invasive alien plants, inappropriate fire regimes or pollution and are an urgent priority to restore. National biodiversity targets aim for a minimum proportion of an ecosystem type to be retained in a natural or near-natural state. The minimum target for Sand Fynbos ecosystems is mostly 30% of the original extent – a target no longer attainable for several of these ecosystems, such as Cape Flats Sand Fynbos. For many of these precious systems, this means a necessary focus on their restoration. The purpose of these guidelines is to assist managers and landowners of degraded Sand Fynbos vegetation to restore biodiversity and contribute to the conservation of these threatened ecosystems. The guidelines outline appropriate methods to restore degraded Sand Fynbos ecosystems, based on the latest research and field trial outcomes.Hans Hoheisen Charitable TrustBiodiversity Management Branch, City of Cape TownSANBI - South African National Biodiversity InstituteHans Hoheisen Charitable TrustPublishers versio

Progression and regression of incident cervical HPV 6, 11, 16 and 18 infections in young women

<p>Abstract</p> <p>Background</p> <p>We describe type-specific progression, regression and persistence of incident human papillomavirus (HPV)-6-11-16 and -18 infections, along with type distribution in cervical intra-epithelial neoplasia (CIN) lesions.</p> <p>Methods</p> <p>The study population consisted of 16–23 year-old women undergoing Pap testing and cervical swab polymerase chain reaction testing for HPV DNA at approximate 6 month intervals for up to 4 years in the placebo arm of a clinical trial of an HPV 16-vaccine. HPV types in incident infections were correlated with types in lesion biopsy specimens.</p> <p>Results</p> <p>56.7% of CIN-1 and nearly one-third of CIN-2/3 lesions following incident HPV-6-11-16 or -18 infections did not correlate with the incident infection HPV type. Cumulative 36-month progression rates to CIN-2/3 testing positive for the relevant HPV type were highest for HPV-16 infections (16.5%), followed by HPV-18 (8.2%). Overall, 26.0% of CIN-1, 50.0% of CIN-2 and 70.6% of CIN-3 biopsies tested positive for HPV-6-11-16-18 infections.</p> <p>Conclusion</p> <p>Women with a given HPV type may often be co-infected or subsequently infected with other types which may lead to subsequent cervical lesions. This issue has been addressed in this study reporting data for the natural history of HPV-6-11-16 and -18 infections and is a relevant consideration in designing future studies to evaluate the incidence/risk of CIN following other type-specific HPV infections.</p