Bio-inspired canopies for the reduction of roughness noise

This work takes inspiration from the structure of the down covering the flight feathers of larger species of owls, which contributes to their ability to fly almost silently at frequencies above 1.6 kHz. Microscope photographs of the down show that it consists of hairs that form a structure similar to that of a forest. The hairs initially rise almost perpendicular to the feather surface but then bend over in the flow direction to form a canopy with an open area ratio of about 70 percent. Experiments have been performed to examine the noise radiated by a large open area ratio canopy suspended above a surface. The canopy is found to dramatically reduce pressure fluctuations on the underlying surface. While the canopy can produce its own sound, particularly at high frequencies, the reduction in surface pressure fluctuations can reduce the noise scattered from an underlying rough surface at lower frequencies. A theoretical model is developed which characterizes the mechanism of surface pressure reduction as a result of the mixing layer instability of flow over forest canopies.Office of Naval Research (Grant IDs: N00014-13-1-0244, N00014-14-1-0242

AGI and the Knight-Darwin Law: why idealized AGI reproduction requires collaboration

Can an AGI create a more intelligent AGI? Under idealized assumptions, for a certain theoretical type of intelligence, our answer is: “Not without outside help”. This is a paper on the mathematical structure of AGI populations when parent AGIs create child AGIs. We argue that such populations satisfy a certain biological law. Motivated by observations of sexual reproduction in seemingly-asexual species, the Knight-Darwin Law states that it is impossible for one organism to asexually produce another, which asexually produces another, and so on forever: that any sequence of organisms (each one a child of the previous) must contain occasional multi-parent organisms, or must terminate. By proving that a certain measure (arguably an intelligence measure) decreases when an idealized parent AGI single-handedly creates a child AGI, we argue that a similar Law holds for AGIs

Excitation of airborne acoustic surface modes driven by a turbulent flow

This is the author accepted manuscript. The final version is available from AIAA via the DOI in this recordThis experiment demonstrated the generation of trapped acoustic surface waves excited by a turbulent flow source through the coupling of pressure fluctuations at the interface between an acoustic metamaterial and a flow environment. The turbulent flow, which behaves as a stochastic pressure source, was produced using a fully developed turbulent wall jet. The plate in the wall jet was perforated with a single cavity. On the flow-side it was capped by a Kevlar weave to ensure the cavity did not significantly disturb the flow, whilst on the adjacent side the cavity was open to the quiescent (static) environment. The through-cavity opening, on the quiescent side, was flush with an acoustic metasurface waveguide, which, through evanescent diffractive coupling of the pressure field, produced an acoustic surface mode. This acoustic mode was trapped at the plate surface, with its mode dispersion determined by the surface geometry. The results of two different metasurface geometries are discussed; (1) a slotted cavity array, and (2) a meander connected cavity array, each demonstrating a different trapped surface wave dispersion behavior. Fourier transform and correlation analyses of spatially-resolved temporal acoustic signals, measured close to the metamaterial surface, were used to construct the frequency and wave vector-dependent acoustic mode dispersion. Results demonstrated the flow can indeed be used to excite these acoustic modes and that their mode dispersion can be tailored towards realizing novel control of turbulent flow through acoustic-flow interactionsDefence Science and Technology Laboratory (DSTL

Equity and justice in climate change adaptation : Policy and practical implication in Nigeria

Over the past decade, justice and equity have become a quasi-universal answer to problems of environmental governance. The principles of justice and equity emerged as a useful entry point in global governance to explore the responsibilities, distribution, and procedures required for just climate change adaptation. These principles are designed primarily through the establishment of funding mechanisms, top-down guides, and frameworks for adaptation, and other adaptation instruments from the UNFCCC process, to ensure effective adaptation for vulnerable countries like Nigeria that have contributed least to the issue of climate change but lack adaptive capacity. Global adaptation instruments have been acknowledged for adaptation in Nigeria. Climate change has a detrimental impact on Nigeria as a nation, with the burden falling disproportionately on the local government areas. As Nigeria develop national plans and policies to adapt to the consequences of climate change, these plans will have significant consequences for local government areas where adaptation practices occur. Although the local government’s adaptation burden raises the prospects for justice and equity, its policy and practical implication remains less explored. This chapter explores the principles of justice and equity in national adaptation policy and adaptation practices in eight local government areas in southeast Nigeria. The chapter argues that some factors make it challenging to achieve equity and justice in local adaptation practices. With the use of a qualitative approach (interview (n = 52), observation, and document analysis), this chapter identified some of the factors that constraints equity and justice in local government adaptation in southeast Nigeria.publishedVersio

Land Law, Property Ideologies and the British-Irish relationship

English and Irish land law are deeply influenced by the historical context of the British-Irish relationship, yet property scholarship comparing the two jurisdictions is surprisingly rare. The current Brexit negotiations provide a timely reminder of the strategic importance of property and trade relations between the two countries; and of their related-but-different legal cultures. In this article we examine how the property cultures of England and Ireland were shaped by the politics and practices of land tenure, by competing economic and property ideologies, and by the influence of both on national identity and statehood in both jurisdictions. The article reveals the role of local contexts and events in shaping land reform, and demonstrates the fertile potential of the comparative frame to contextualise each jurisdiction’s doctrines and practices. As domestic land law systems are drawn together in the context of emerging EU jurisdiction over areas like mortgage credit, each jurisdiction’s underpinning ideological commitments have important implications for the ease – or not – of attempts to harmonize member state practices. We explain the alignments and divergences between domestic underpinnings of Irish and English law, and reflect on the implications of our findings for contemporary property problems in the context of evolving economic and political relationships between the UK and Ireland

NuStar observations of WISE J1036+0449, a galaxy at z ∼ 1 obscured by hot dust

Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer’s all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z> 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z˜ 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 ({L}{Bol}≃ 8× {10}46 {erg} {{{s}}}-1). We find evidence of a broadened component in Mg II, which would imply a black hole mass of {M}{BH}≃ 2× {10}8 {M}⊙ and an Eddington ratio of {λ }{Edd}≃ 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of {N}{{H}}≃ (2{--}15)× {10}23 {{cm}}-2. The source has an intrinsic 2-10 keV luminosity of ˜ 6× {10}44 {erg} {{{s}}}-1, a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z≲ 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio

Haematogenous Staphylococcus aureus meningitis. A 10-year nationwide study of 96 consecutive cases

BACKGROUND: Haematogenous Staphylococcus aureus meningitis is rare but associated with high mortality. Knowledge about the disease is still limited. The objective of this study was to evaluate demographic and clinical prognostic features of bacteraemic S. aureus meningitis. METHODS: Nationwide surveillance in Denmark from 1991 to 2000 with clinical and bacteriological data. Risks of death were estimated by Cox proportional hazards regression analysis. RESULTS: Among 12480 cases of S. aureus bacteraemia/sepsis, we identified 96 cases of non-surgical bacteraemic S. aureus meningitis (0.8%). Incidence rates were 0.24 (95% confidence interval [CI], 0.18 to 0.30)/100 000 population between 1991–1995 and 0.13 (CI, 0.08 to 0.17)/100 000 population between 1996–2000. Mortality was 56%. After adjustment, only co morbidity (hazard ratio [HR], 3.45; CI, 1.15 to 10.30) and critical illness (Pitt score ≥ 4) (HR, 2.14; CI, 1.09 to 4.19) remained independent predictors of mortality. CONCLUSION: The incidence, but not mortality of bacteraemic S. aureus meningitis decreased during the study period. Co morbidity and critical illness were independent predictors of a poor outcome

Chronic disease risk factors, healthy days and medical claims in South African employees presenting for health risk screening

<p>Abstract</p> <p>Background</p> <p>Non-communicable diseases (NCD) accounts for more than a third (37%) of all deaths in South Africa. However, this burden of disease can be reduced by addressing risk factors. The aim of this study was to determine the health and risk profile of South African employees presenting for health risk assessments and to measure their readiness to change and improve lifestyle behaviour.</p> <p>Methods</p> <p>Employees (n = 1954) from 18 companies were invited to take part in a wellness day, which included a health-risk assessment. Self-reported health behaviour and health status was recorded. Clinical measures included cholesterol finger-prick test, blood pressure and Body Mass Index (BMI). Health-related age was calculated using an algorithm incorporating the relative risk for all case mortality associated with smoking, physical activity, fruit and vegetable intake, BMI and cholesterol. Medical claims data were obtained from the health insurer.</p> <p>Results</p> <p>The mean percentage of participation was 26% (n = 1954) and ranged from 4% in transport to 81% in the consulting sector. Health-related age (38.5 ± 12.9 years) was significantly higher than chronological age (34.9 ± 10.3 yrs) (p < 0.001). Both chronological and risk-related age were significantly different between the sectors (P < 0.001), with the manufacturing sector being the oldest and finance having the youngest employees. Health-related age was significantly associated with number of days adversely affected by mental and physical health, days away from work and total annual medical costs (p < 0.001). Employees had higher rates of overweight, smoking among men, and physical inactivity (total sample) when compared the general SA population. Increased health-related expenditure was associated with increased number of risk factors, absenteeism and reduced physical activity.</p> <p>Conclusion</p> <p>SA employees' health and lifestyle habits are placing them at increased risk for NCD's, suggesting that they may develop NCD's earlier than expected. Inter-sectoral differences for health-related age might provide insight into those companies which have the greatest need for interventions, and may also assist in predicting future medical expenditure. This study underscores the importance of determining the health and risk status of employees which could assist in identifying the appropriate interventions to reduce the risk of NCD's among employees.</p