602 research outputs found

    "Ladder" structure in tonal noise generated by laminar flow around an airfoil

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    The presence of a “ladder” structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the scattering of the boundary layer instability noise and the discrete noise produced by an aeroacoustic feedback loop

    Poro-Serrated trailing edge devices for airfoil self-noise reduction

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    This paper represents the continuation of the works previously published in Chong et al. (“Self-Noise Produced by an Airfoil with Nonflat Plate Trailing-Edge Serrations,” AIAA Journal, Vol. 51, No. 11, 2013, pp. 2665–2677), who used several nonflat plate serrated trailing edges for the reduction of airfoil self-noise. The poro-serrated concept developed in the current work improves substantially the overall noise performance of the nonflat plate trailing-edge serration type. The use of porous metal, synthetic foams, or thin brush bundles to fill the gaps between adjacent members of the sawtooth can completely suppress the bluntness-induced vortex shedding tonal noise. Most important, up to 7 dB turbulent boundary layer–trailing-edge broadband noise reduction can simultaneously be achieved without compromising the aerodynamic performances in lift and drag. The poro-serrated trailing edges do not cause any noise increase throughout the frequency range investigated here. The reduction of the turbulent broadband noise is primarily caused by the serration effect, but under a condition that the sawtooth surface must be solid and nonporous. The primary role of the porous metal foams in a poro-serrated trailing edge is to suppress the vortex shedding tonal noise. However, an optimum selection of the porous material is also found to be able to further reduce the broadband noise level. The new serrated trailing-edge concept developed here has the potential to improve the industrial worthiness of the serration technology in achieving low noise radiation in fan and turbine blades.The EPSRC Doctoral Training Grants in the United Kingdo

    Self-noise produced by an airfoil with nonflat plate trailing-edge serrations

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    This paper represents the results of an experimental study aimed at reducing the airfoil self-noise by the trailing edge serration of four different sawtooth geometries (defined in the serration angle and length). These serrations have a common feature: all of the sawtooth patterns are cut directly into the trailing edge of a realistic airfoil. This configuration offers better structural strength and integrity. For the sawtooth trailing edges investigated here, the radiation of the extraneous vortex shedding noise in a narrowband frequency due to the partial bluntness at the serration roots is unavoidable. However, this narrowband component tends to be less significant provided that the serration angle is large and the serration length is moderate. Sound power was measured, and some of the sawtooth geometries have been shown to afford significant boundary-layer instability tonal noise and moderate turbulent broadband noise reductions across a fairly large velocity range. This paper demonstrates that a nonflat plate serrated trailing edge can also be effective in the self-noise reduction. Some experimental results are also presented in order to explain the self-noise mechanisms.This work is partly supported by the Brunel Research Initiative and Enterprise fun

    Three Conceptions of Practical Authority

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    Sustained high prevalence of viral hepatitis and sexually transmissible infections among female sex workers in China: a systematic review and meta-analysis.

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    BACKGROUND: The 1980's economic boom has been associated with a rapid expansion of China's sex industry over the past three decades. Consequently, the spread of sexually transmitted infections (STIs) and hepatitis infections among female sex workers (FSW) has become an important public health issue in China. This study identifies prevalence and risks of hepatitis and STIs in Chinese FSWs. METHOD: Four electronic databases were searched for Chinese and English language peer-reviewed studies conducted between 01/2000-12/2011 that reported prevalence of hepatitis and STIs (excluding HIV) among Chinese FSW. Following the PRISMA guidelines, meta-analysis was used to estimate pooled prevalence and 95% confidence intervals for each infection. RESULT: Three hundred and thirty nine articles (34 in English and 305 in Chinese) investigating 603,647 FSWs in 29 Chinese provinces were included in this review. Over the period 2000-2011, the seroprevalence of active hepatitis B and hepatitis C among FSW were 10.7% (7.3-15.5%) and 1.0% (0.7-1.3%), respectively. The most prevalent STI was human papillomavirus (HPV, 27.0% [10.1-55.1%]), followed by herpes simplex virus-2 (HSV-2, 15.8% [11.7-20.9%]), chlamydia (13.7% [12.1-15.4%]), gonorrhoea (6.1% [5.3-7.0%]), syphilis (5.2% [4.8-5.7%]), genital warts (3.3% [2.5-4.2%]) and Trichomonas vaginitis (2.1% [1.5-24.2%]). Disease burden of both hepatitis and STI among FSW were concentrated in South Central and Southwest China. In particular, chlamydia and syphilis demonstrated a significant declining trend during the studied period (P < 0.05). Compared with the general Chinese population, FSW had significantly higher prevalence of all STIs except Trichomonas vaginitis. Further, compared to the general FSW population, HIV-positive FSW had significantly higher prevalence of syphilis, chlamydia, HSV-2 and Trichomonas vaginitis. CONCLUSION: Prevalence of hepatitis and STIs remained high and mostly stable among Chinese FSW over the period of 2000-2011. Targeted STI and hepatitis surveillance and interventions should be strengthened among Chinese FSWs, especially those who are HIV-positive

    A One Health Framework for the Evaluation of Rabies Control Programmes: A Case Study from Colombo City, Sri Lanka

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    <div><p>Background</p><p>One Health addresses complex challenges to promote the health of all species and the environment by integrating relevant sciences at systems level. Its application to zoonotic diseases is recommended, but few coherent frameworks exist that combine approaches from multiple disciplines. Rabies requires an interdisciplinary approach for effective and efficient management.</p><p>Methodology/Principal Findings</p><p>A framework is proposed to assess the value of rabies interventions holistically. The economic assessment compares additional monetary and non-monetary costs and benefits of an intervention taking into account epidemiological, animal welfare, societal impact and cost data. It is complemented by an ethical assessment. The framework is applied to Colombo City, Sri Lanka, where modified dog rabies intervention measures were implemented in 2007. The two options included for analysis were the control measures in place until 2006 (“baseline scenario”) and the new comprehensive intervention measures (“intervention”) for a four-year duration. Differences in control cost; monetary human health costs after exposure; Disability-Adjusted Life Years (DALYs) lost due to human rabies deaths and the psychological burden following a bite; negative impact on animal welfare; epidemiological indicators; social acceptance of dogs; and ethical considerations were estimated using a mixed method approach including primary and secondary data. Over the four years analysed, the intervention cost US $1.03 million more than the baseline scenario in 2011 prices (adjusted for inflation) and caused a reduction in dog rabies cases; 738 DALYs averted; an increase in acceptability among non-dog owners; a perception of positive changes in society including a decrease in the number of roaming dogs; and a net reduction in the impact on animal welfare from intermediate-high to low-intermediate.</p><p>Conclusions</p><p>The findings illustrate the multiple outcomes relevant to stakeholders and allow greater understanding of the value of the implemented rabies control measures, thereby providing a solid foundation for informed decision-making and sustainable control.</p></div

    A systematic review and meta-analysis of the prevalence, trends, and geographical distribution of HIV among Chinese female sex workers (2000-2011): implications for preventing sexually transmitted HIV.

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    OBJECTIVE: The aim of this meta-analysis was to investigate temporal and geographical trends in the HIV epidemic among female sex workers (FSWs) recruited from various venues in China. METHODS: Chinese and English peer-reviewed articles published between January 2000 and February 2013 were systematically searched. Standard meta-analysis methods were used to calculate the pooled HIV prevalence, in accordance with the PRISMA guidelines. RESULTS: The national HIV prevalence among FSWs declined from 0.74% (95% confidence interval (CI) 0.37-1.49%) in 2000-2002 to 0.40% (95% CI 0.31-0.53%) in 2009-2011. All Chinese regions demonstrated significant declines in HIV prevalence, apart from the East and South Central regions, in which the epidemics stabilized at low/moderate levels. Despite a significant decline from 1.92% (95% CI 0.86-4.24%) to 0.87% (95% CI 0.65-1.18%) during 2000-2011, Southwest China still bore the greatest HIV disease burden. Nationwide, FSWs recruited from detention centres had the highest HIV prevalence (0.92%, 95% CI 0.46-1.88%), followed by voluntary counselling and testing sites (0.80%, 95% CI 0.46-1.67%) and entertainment venues (0.61%, 95% CI 0.47-0.79%). The prevalences among FSWs in high-, middle-, and low-tier entertainment venues were 0.59% (95% CI 0.32-1.45%), 0.92% (95% CI 0.50-1.77%), and 1.10% (95% CI 0.71-2.16%), respectively. High- and middle-tier FSWs had a significantly lower risk of HIV infection than lower-tier FSWs (high/low: odds ratio (OR) 0.48, 95% CI 0.40-0.59; middle/low: OR 0.49, 95% CI 0.37-0.66). CONCLUSIONS: The HIV epidemic has shown a gradual declining or stabilizing trend among Chinese FSWs. Intervention efforts should be diverted to high-risk subgroups of FSWs, such as drug-using and low-tier FSWs

    Recurrent spontaneous hip dislocation in a patient with neurofibromatosis type 1: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>Neurofibromatosis type-1 is a common genetic disorder which often affects the skeleton. Skeletal manifestations of neurofibromatosis type-1 include scoliosis, congenital pseudarthrosis of the tibia and intraosseous cystic lesions. Dislocation of the hip associated with neurofibromatosis type-1 is a rare occurrence and is underreported in the literature.</p> <p>Case presentation</p> <p>We report a case of hip dislocation resulting from an intra-articular neurofibroma in an 18-year-old Caucasian woman following minor trauma. This was originally suggested by the abnormalities on early radiographs of her pelvis and later confirmed with computed tomography and magnetic resonance imaging. Treatment was successful with skeletal traction for six weeks with no further hip dislocations at a 12-year follow-up.</p> <p>Conclusion</p> <p>This case illustrates the radiological features of this rare complication of neurofibromatosis type-1 using the modalities of plain radiograph, magnetic resonance imaging and computed tomography reconstruction. The radiological images give a clear insight into the mechanism by which neurofibromatosis type-1 leads to hip dislocation. It also demonstrates one treatment option with excellent results on long-term follow-up.</p

    Distinct Binding and Immunogenic Properties of the Gonococcal Homologue of Meningococcal Factor H Binding Protein

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    Neisseria meningitidis is a leading cause of sepsis and meningitis. The bacterium recruits factor H (fH), a negative regulator of the complement system, to its surface via fH binding protein (fHbp), providing a mechanism to avoid complement-mediated killing. fHbp is an important antigen that elicits protective immunity against the meningococcus and has been divided into three different variant groups, V1, V2 and V3, or families A and B. However, immunisation with fHbp V1 does not result in cross-protection against V2 and V3 and vice versa. Furthermore, high affinity binding of fH could impair immune responses against fHbp. Here, we investigate a homologue of fHbp in Neisseria gonorrhoeae, designated as Gonococcal homologue of fHbp (Ghfp) which we show is a promising vaccine candidate for N. meningitidis. We demonstrate that Gfhp is not expressed on the surface of the gonococcus and, despite its high level of identity with fHbp, does not bind fH. Substitution of only two amino acids in Ghfp is sufficient to confer fH binding, while the corresponding residues in V3 fHbp are essential for high affinity fH binding. Furthermore, immune responses against Ghfp recognise V1, V2 and V3 fHbps expressed by a range of clinical isolates, and have serum bactericidal activity against N. meningitidis expressing fHbps from all variant groups

    A Comparative Phase I Study of Combination, Homologous Subtype-C DNA, and Env gp 140 Protein/Adjuvant HIV Vaccines in Two Immunization Regimes

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    There remains an urgent need for a prophylactic HIV vaccine. We compared combined MVA and adjuvanted gp140 to sequential MVA/gp140 after DNA priming. We expected Env-specific CD4+ T-cells after DNA and MVA priming, and Env-binding antibodies in 100% individuals after boosting with gp140 and that combined vaccines would not compromise safety and might augment immunogenicity. Forty volunteers were primed three times with DNA plasmids encoding (CN54) env and (ZM96) gag-pol-nef at 0, 4 and 8 weeks then boosted with MVA-C (CN54 env and gag-pol-nef) and glucopyranosyl lipid adjuvant—aqueous formulation (GLA-AF) adjuvanted CN54gp140. They were randomised to receive them in combination at the same visit at 16 and 20 weeks (accelerated) or sequentially with MVA-C at 16, 20, and GLA-AF/gp140 at 24 and 28 weeks (standard). All vaccinations were intramuscular. Primary outcomes included ≥grade 3 safety events and the titer of CN54gp140-specific binding IgG. Other outcomes included neutralization, binding antibody specificity and T-cell responses. Two participants experienced asymptomatic ≥grade 3 transaminitis leading to discontinuation of vaccinations, and three had grade 3 solicited local or systemic reactions. A total of 100% made anti-CN54gp140 IgG and combining vaccines did not significantly alter the response; geometric mean titer 6424 (accelerated) and 6578 (standard); neutralization of MW965.2 Tier 1 pseudovirus was superior in the standard group (82 versus 45% responders, p =  0.04). T-cell ELISpot responses were CD4+ and Env-dominant; 85 and 82% responding in the accelerated and standard groups, respectively. Vaccineinduced IgG responses targeted multiple regions within gp120 with the V3 region most immunodominant and no differences between groups detected. Combining MVA and gp140 vaccines did not result in increased adverse events and did not significantly impact upon the titer of Env-specific binding antibodies, which were seen in 100% individuals. The approach did however affect other immune responses; neutralizing antibody responses, seen only to Tier 1 pseudoviruses, were poorer when the vaccines were combined and while T-cell responses were seen in >80% individuals in both groups and similarly CD4 and Env dominant, their breadth/polyfunctionality tended to be lower when the vaccines were combined, suggesting attenuation of immunogenicity and cautioning against this accelerated regimen