| 1. |
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| 2. |
- Newton-Cheh, Christopher, et al.
(författare)
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Genome-wide association study identifies eight loci associated with blood pressure
- 2009
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 41:6, s. 666-676
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Tidskriftsartikel (refereegranskat)abstract
- Elevated blood pressure is a common, heritable cause of cardiovascular disease worldwide. To date, identification of common genetic variants influencing blood pressure has proven challenging. We tested 2.5 million genotyped and imputed SNPs for association with systolic and diastolic blood pressure in 34,433 subjects of European ancestry from the Global BPgen consortium and followed up findings with direct genotyping (N <= 71,225 European ancestry, N <= 12,889 Indian Asian ancestry) and in silico comparison (CHARGE consortium, N 29,136). We identified association between systolic or diastolic blood pressure and common variants in eight regions near the CYP17A1 (P = 7 x 10(-24)), CYP1A2 (P = 1 x 10(-23)), FGF5 (P = 1 x 10(-21)), SH2B3 (P = 3 x 10(-18)), MTHFR (P = 2 x 10(-13)), c10orf107 (P = 1 x 10(-9)), ZNF652 (P = 5 x 10(-9)) and PLCD3 (P = 1 x 10(-8)) genes. All variants associated with continuous blood pressure were associated with dichotomous hypertension. These associations between common variants and blood pressure and hypertension offer mechanistic insights into the regulation of blood pressure and may point to novel targets for interventions to prevent cardiovascular disease.
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| 3. |
- Barrera Rolla, Leandro, et al.
(författare)
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Implementation of the forward-advancing wave expansion method (FWEM) for numerical solution of three dimensional large-scale sound propagation problems
- 2007
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Ingår i: 36th International Congress and Exposition on Noise Control Engineering, INTER-NOISE. - 9781605603858 ; , s. 4796-4805
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper a “one-way” wave based field discretization method for solving the Helmholtz equation in large-scale problems is proposed and is referred to as the Forward Wave Expansion Method (FWEM). The FWEM is derived from a highly efficient discretization procedure based on the interpolation of wave functions known as the Wave Expansion Method (WEM) and computes the propagated sound field by means of an exclusively forward advancing solution. This technique does not require the inversion of large system matrices and thus enables the solution of large scale acoustic problems where backscatter is not of interest. A computationally light model is thus formulated which retains many advantages of WEM. Accurate results were obtained for a free field sound propagation benchmarking problem. The method was also implemented to successfully model some diffraction effects. The FWEM offers a simple, flexible and efficient discretization method to solve the Helmholtz equation for extensive domains with mesh densities as low as 3 nodes per wavelength. This makes the FWEM a promising method for long range sound propagation problems.
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| 4. |
- Bennett, Gareth J., et al.
(författare)
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Modelling multi-modal sound transmission from point sources in ducts with flow using a wave-based method
- 2009
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Ingår i: 16th International Congress on Sound and Vibration, ICSV16. - 9781615677368 ; , s. 4685-4693
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An understanding of the multi-modal propagation of acoustic waves in ducts is of practical interest for use in the control of noise in, for example, aero-engines, automotive exhaust and ventilation systems. In this paper, the propagation of sound from point sources in hard-walled ducts is modelled using a numerical wave-based approach, referred to as the wave expansion method. This is a highly efficient full-domain discretisation method, which requires as few as two-to-three mesh points per wavelength. An inhomogeneous potential flow may be easily included in the method. The numerical solution for point sources embedded in the wall of a circular duct with non-reflective end-conditions and a uniform axial flow is compared with an analytical Green's function solution. A modal decomposition technique is used to provide detailed information about the modal content of the sound field. This study provides an insightful comparison between an analytical and numerical solution to the acoustic field in a duct. The accuracy and robustness of the wave expansion method is assessed for this benchmark problem before its versatility is demonstrated with examples.
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| 5. |
- Bharath, G., et al.
(författare)
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Iterative solutions of the three-dimensional Helmholtz equation using the wave expansion method for high frequency acoustic scattering problems
- 2007
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Ingår i: 36th International Congress and Exposition on Noise Control Engineering, INTER-NOISE. - 9781605603858 ; , s. 4788-4795
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Modelling sound propagation over large domains presents severe challenges with respect to computational requirements. In general, direct solutions of system equations resulting from the full field discretization of many three-dimensional problems of practical interest cannot be attempted. The present study investigates iterative solutions for solving a Three-Dimensional Helmholtz equation. The discretization of the Helmholtz equation is done by a Wave Based Finite Difference scheme known as the Wave Expansion Method (WEM). The WEM requires only 2-3 nodes per wavelength to obtain accurate solutions which offers a potential for major improvement in efficiency compares to conventional techniques such as the Finite Element/Finite Difference approaches which require around 8-10 nodes per wavelength. The solver employed here is the standard Bi-Conjugate Gradient Stabilized (Bi-CGSTAB) algorithm. Results are presented for high frequency acoustic scattering problems occurring in aircrafts. Investigations are also carried out to check the effectiveness of the standard preconditioning strategies such as the Incomplete LU decomposition with drop tolerance method. The influence of the scatterer is also studied in this paper.
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| 6. |
- O'Reilly, Ciarán J., et al.
(författare)
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An investigation into the effects of engine body reflections and flow refraction on jet noise shielding predictions
- 2007
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Ingår i: 36th International Congress and Exhibition on Noise Control Engineering, INTER-NOISE. - 9781605603858 ; , s. 733-742
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Airframe acoustic shielding predictions, using simple point sources located over an isolated wing, tend to over-predict shielding effects, when compared with full-model test data. The study presented in this paper investigates the effects of the inclusion of the engine body and the jet flow on shielding predictions. A wave expansion method (WEM), is used to efficiently model the sound propagation, in a small domain which includes the wing and engine body. In this model the jet is still represented as point sources. A 2d model is examined, in which the mean jet flow has been included. The point source locations and strengths are determined using a RANS solution of a hot coaxial jet and Goldstein's interpretation of the acoustic analogy. The near-field WEM results are then propagated to the far-field using the Helmholtz-Kirchhoff integral equation, which assumes a uniform flow external to the Kirchhoff surface. Results presented here are very encouraging as they clearly indicate that with the inclusion of engine body reflections, and the refractive effects of the jet flow, predicted shielding values are much more consistent with observed levels both in terms of magnitude and variation over observation angle.
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| 7. |
- O'Reilly, Ciarán J., et al.
(författare)
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Jet noise modelling for shielding calculations using RANS solution source localisation and WEM propagation
- 2006
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Ingår i: 22nd International Conference on Noise and Vibration Engineering, ISMA. - : Leuven University Press. - 9789073802834 ; , s. 667-676
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, a method to determine the jet noise source input for shielding calculations is described. The method involves three steps - localisation, propagation and simplification. Firstly, for the frequency of interest, a small localised source region is determined, using Goldstein-Rosenbaum's acoustic model, with a numerical RANS solution providing local flow properties. A number of distinct incoherent noise sources may be located in this region, using the turbulence length scales. In the second step, each source is propagated out through the jet flow using the wave expansion method (WEM) to solve the Helmholtz equation, with local Mach values acquired from the RANS solution. The third step is to define a Kirchhoff surface outside the jet flow, from which the sound may be propagated further by simply using the Helmholtz-Kirchhoff integral, which can account for any mean flow present. Although the method is quite crude, it is relatively robust as it is a shielding factor or ratio, rather than an absolute value, which is of interest in design evaluation. Preliminary results, presented in this paper, provide encouragement that this new three-step jet noise source modelling method can be used to provide a source input for use in airframe shielding calculations, that is equivalent - in terms of source frequency, distribution and directivity - to the noise produced by a jet flow.
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| 8. |
- O'Reilly, Ciarán J., et al.
(författare)
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Jet noise modelling for shielding calculations using RANS source localisation and WEM propagation
- 2006
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Ingår i: 8th International Symposium Transport Noise and Vibration.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, a method to determine the jet noise source input for shielding calculations is described. The method involves three steps – localisation, propagation and simplification. Firstly, for the frequency of interest, a small, localised source region is determined, using Goldstein-Rosenbaums’ acoustic model, with a numerical RANS solution providing local flow properties. A number of distinct incoherent noise sources may be located in this region, using the turbulence length scales. In the second step, each source is propagated out through the jet flow using the wave expansion method (WEM) to solve the Helmholtz equation, with local Mach values acquired from the RANS solution. The third step is to define a Kirchhoff surface outside the jet flow, from which, the sound may be propagated further by simply using the Helmholtz-Kirchhoff integral equation, which, can account for any mean flow present. This method is relatively robust, as it is a shielding factor or ratio, rather than an absolute value, which is of interest in acoustic design evaluation. Preliminary results, presented in this paper, provide encouragement that this new three-step jet noise source modelling method can be used to provide a source input for use in airframe shielding calculations, that is equivalent – in terms of source frequency, distribution and directivity – to the noise produced by a jet flow.
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| 9. |
- O'Reilly, Ciarán J., et al.
(författare)
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Jet noise shielding : Mean flow convection and refraction effects on jet noise source propagation
- 2008
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Ingår i: 23rd International Conference on Noise and Vibration Engineering, ISMA. - : Leuven University Press. - 9789073802865 ; , s. 525-533
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Positioning aircraft engines on the rear of the fuselage above a U-shaped empennage, is an aircraft configuration, which could possibly reduce the engine noise emitted towards the ground during take-off and approach. In order to acoustically assess the shielding effect attained from such a configuration, the complicated physical noise sources must, firstly, be represented in a manner appropriate for input into propagation / shielding prediction methods. In this paper, the development of an innovative methodology for providing such a source for jet noise is described. Convecting point sources are located using Lighthill's analogy with a Reynolds-Averaged Navier Stokes (RANS) solution to provide mean flow properties. The refractive effect of the mean jet flow on sound propagation is determined using a Wave Expansion Method (WEM) to efficiently numerically propagate monopole noise sources in a small domain, which includes the sheared jet flow. This near-field WEM result is then propagated to the far-field using the Helmholtz-Kirchhoff integral equation, assuming a uniform flow external to the Kirchhoff surface. The refractive flow effect on omnidirectional sources is superimposed on the convecting sources. These directional point sources may be used as a sound source input for shielding prediction methods. In this present study, jet noise sources have been created for a range of frequencies. The isolated sound pressure level and the shielding effect, resultant from separating these sources from an arc of receivers, with a flat plate, have been evaluated and results compared with test data. Results presented here are very encouraging, as they clearly indicate that with the inclusion of both the convective and the refractive effects of the jet flow on the propagation of point sources, simple jet noise sources may be defined for use in shielding prediction methods, however, using the present approximations, the predicted sound pressure levels are greater than the measured values at downstream receiver angles.
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| 10. |
- Pereira, M A, et al.
(författare)
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Dietary fiber, folate, and vitamin E with coronary risk : A pooled analysis of cohort studies
- 2006
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Ingår i: Circulation. - Univ Minnesota, Minneapolis, MN USA. Harvard Univ, Boston, MA 02115 USA. Karolinska Inst, Stockholm, Sweden. Loma Linda Univ, Loma Linda, CA 92350 USA. Neufeld Cardiac Res Inst, Tel Hashomer, Israel. Copenhagen Univ Hosp, Copenhagen, Denmark. Umea Univ, Umea, Sweden. Natl Publ Hlth Inst, Helsinki, Finland. Inst Publ Hlth, Helsinki, Finland. Inst Publ Hlth, Helsinki, Finland. Univ N Carolina, Chapel Hill, NC USA. : LIPPINCOTT WILLIAMS & WILKINS. - 0009-7322 .- 1524-4539. ; 113:8, s. E374-E375
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 11. |
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| 12. |
- Bennett, Gareth J., et al.
(författare)
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Noise source location in turbomachinery using coherence based modal decomposition
- 2009
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Ingår i: 15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference). - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781563479748
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Coherence based source analysis techniques can be used to identify the contribution of turbomachinery core noise sources to pressure measurements in the far-field. The usual approach is to locate a measurement sensor within the engine and to calculate the ordinary coherence function between this and the far-field pressure measurement. If the internal measurement is close to a dominant noise source, the technique will identify this sources' contribution to the overall far-field energy. Modal decomposition is an advanced technique which can provide detailed information as to the modal content of sound propagating in ducts. When applied to aero-engines, the technique can be used as a diagnostic to determine which of the many rotor-stator stages contribute most to the overall radiated sound power. The method developed in this paper discusses how the two techniques can be combined to locate the plane at which a mode is generated within an aeroengine. A proof of concept of the technique is successfully demonstrated with the use of simulated data.
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| 13. |
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| 14. |
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| 15. |
- Jakobsen, Marianne U, et al.
(författare)
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Major types of dietary fat and risk of coronary heart disease : a pooled analysis of 11 cohort studies.
- 2009
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165 .- 1938-3207. ; 89:5, s. 1425-1432
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Saturated fatty acid (SFA) intake increases plasma LDL-cholesterol concentrations; therefore, intake should be reduced to prevent coronary heart disease (CHD). Lower habitual intakes of SFAs, however, require substitution of other macronutrients to maintain energy balance. OBJECTIVE: We investigated associations between energy intake from monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and carbohydrates and risk of CHD while assessing the potential effect-modifying role of sex and age. Using substitution models, our aim was to clarify whether energy from unsaturated fatty acids or carbohydrates should replace energy from SFAs to prevent CHD. DESIGN: This was a follow-up study in which data from 11 American and European cohort studies were pooled. The outcome measure was incident CHD. RESULTS: During 4-10 y of follow-up, 5249 coronary events and 2155 coronary deaths occurred among 344,696 persons. For a 5% lower energy intake from SFAs and a concomitant higher energy intake from PUFAs, there was a significant inverse association between PUFAs and risk of coronary events (hazard ratio: 0.87; 95% CI: 0.77, 0.97); the hazard ratio for coronary deaths was 0.74 (95% CI: 0.61, 0.89). For a 5% lower energy intake from SFAs and a concomitant higher energy intake from carbohydrates, there was a modest significant direct association between carbohydrates and coronary events (hazard ratio: 1.07; 95% CI: 1.01, 1.14); the hazard ratio for coronary deaths was 0.96 (95% CI: 0.82, 1.13). MUFA intake was not associated with CHD. No effect modification by sex or age was found. CONCLUSION: The associations suggest that replacing SFAs with PUFAs rather than MUFAs or carbohydrates prevents CHD over a wide range of intakes.
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| 16. |
- Massa, J, et al.
(författare)
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Plasma titers of antibodies against Epstein-Barr virus BZLF1 and risk of multiple sclerosis
- 2007
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Ingår i: Neuroepidemiology. - : S. Karger AG. - 1423-0208 .- 0251-5350. ; 28:4, s. 214-215
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Tidskriftsartikel (refereegranskat)abstract
- <i>Background/Aims:</i> Results of recently conducted prospective studies have demonstrated that the presence of high titers of anti-EBNA-1 or anti-EBNA complex IgG antibodies in healthy individuals is a strong risk factor for multiple sclerosis (MS). Antibodies to BZLF1, the product of the homonymous early lytic gene, have been found to be related to risk of nasopharyngeal carcinoma, but have not been previously measured in MS studies. <i>Methods:</i> We examined whether high levels of anti-BZLF1 IgG antibodies also predict MS risk in a nested case-control study among women in the Nurses Health Study and Nurses Health Study II cohorts. <i>Results:</i> Results of this prospective study suggest that antibody titers to EBNAs are the strongest predictor of MS risk. <i>Conclusion:</i> Little further contribution may be provided by measuring anti-BZLF1 antibodies in regard to MS risk.
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| 18. |
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