Jet-edge interaction tones

Motivated by the problem of jet-flap interaction noise, we study the tonal dynamics that occur when a sharp edge is placed in the hydrodynamic nearfield of an isothermal turbulent jet. We perform hydrodynamic and acoustic pressure measurements in order to characterise the tones as a function of Mach number and streamwise edge position. The distribution of spectral peaks observed, as a function of Mach number, cannot be explained using the usual edge-tone scenario, in which resonance is underpinned by coupling between downstream-travelling Kelvin-Helmholtz wavepackets and upstream-travelling sound waves. We show, rather, that the strongest tones are due to coupling between the former and upstream-travelling jet modes recently studied by Towne et al. (2017) and Schmidt et al. (2017). We also study the band-limited nature of the resonance, showing a high-frequency cut-off to be due to the frequency dependence of the upstream-travelling waves. At high Mach number these become evanescent above a certain frequency, whereas at low Mach number they become progressively trapped with increasing frequency, a consequence of which is their not being reflected in the nozzle plane. Additionally, a weaker, low-frequency, forced-resonance regime is identified that involves the same upstream travelling jet modes but that couple, in this instance, with downstream-travelling sound waves. It is suggested that the existence of two resonance regimes may be due to the non-modal nature of wavepacket dynamics at low-frequency.Comment: 21 pages, 15 figure

Financial Impact of Complex Cancer Surgery in India: A Study of Pancreatic Cancer.

PURPOSE: The rapidly increasing burden of cancer in India has profound impacts on health care costs for patients and their families. High out-of-pocket (OOP) expenditure, lack of insurance, and low government expenditure create a vicious cycle, leading to household impoverishment. Complex cancer surgery is now increasingly important for emerging countries; however, little is understood about the macro- and microeconomics of these procedures. After the Lancet Oncology Commission on Global Cancer Surgery, we evaluated the OOP expenditure for patients undergoing pancreatico-duodenectomy (PD) at a government tertiary cancer center in India. METHODS: Prospective data from 98 patients who underwent PD between January 2014 and June 2015 were collected and analyzed. The time frame for consideration of expenses, including all preoperative investigations, was from the first hospital visit to the day of discharge. Catastrophic expenditure was calculated by assessing the percentage of households in which OOP health payments exceeded 10% of the total household income. RESULTS: The mean expenditure for PD by patients was Rs.295,679.57 (US$74,420, purchasing power parity corrected). This amount was significantly higher among those admitted to a private ward and those with complications. Only 29.6% of the patients had insurance coverage. A total of 76.5% of the sample incurred catastrophic expenditure, and 38% of those with insurance underwent financial catastrophe compared with 93% of those without insurance. The percentage of patients facing catastrophic impact was highest among those in semiprivate wards, at 86.7%, followed by those in public and private wards. CONCLUSION: The cost of PD is high and is often unaffordable for a majority of India's population. A review of insurance coverage policies for better coverage must be considered

Molecular Population Structure for Feral Swine in the United States

Feral swine (Sus scrofa) have invaded most of the United States and continue to expand throughout North America. Given the ecological and economic threats posed by increasing feral swine abundance, it is imperative to develop an understanding of their patterns of natural range expansion and human-mediated introductions. Towards this goal, we used molecular markers to elucidate the genetic structure of feral swine populations throughout the United States and evaluated the association between historical introductions and contemporary patterns of genetic organization. We used STRUCTURE and discriminant analysis of principal components (DAPC) to delineate genetic clusters for 959 individuals genotyped at 88 single nucleotide polymorphism loci. We identified 10 and 12 genetic clusters for the 2 clustering approaches, respectively. We observed strong agreement in clusters across approaches, with both describing clusters having strong geographic association at regional levels reflecting past introduction and range expansion patterns. In addition, we evaluated patterns of isolation by distance to test for and estimate spatial scaling of population structure within western, central, and eastern regions of North America. We found contrasting spatial patterns of genetic relatedness among regions, suggesting differences in the invasion process, likely as a result of regional variation in landscape heterogeneity and the influence of human mediated introductions. Our results indicate that molecular analyses of population genetic structure can provide reliable insights into the invasion processes of feral swine, thus providing a useful basis for management focused on minimizing continued range expansion by this problematic species

Super- and multi-directive acoustic radiation by linear global modes of a turbulent jet

The mean flow stability of a Mach 0.9 turbulent jet is investigated by means of global linear theory with a focus on acoustic effects. A novel class of resonant acoustic modes that are trapped within the potential core, and whose eigenvalues appear as discrete branches in the global stability spectrum, is studied in detail. A dispersion relation is reconstructed from the global modes, and shown to accurately predict energy bands observed in the PSD of a high-fidelity LES. Similarly, the acoustic far-field radiation patterns of the trapped modes are compared to the LES. A favorable agreement between the global mode waveforms and coherent structures educed from the LES is found for both the trapped acoustic wave component inside the core and the far-field radiation

Trapped acoustic waves in the potential core of subsonic jets

The purpose of this paper is to characterize and model waves that are observed within the potential core of subsonic jets and that have been previously detected as tones in the near-nozzle region. Using three models (the linearized Euler equations, a cylindrical vortex sheet, and a cylindrical duct with pressure release boundary conditions), we show that these waves can be described by linear modes of the jet and correspond to acoustic waves that are trapped within the potential core. At certain frequencies, these trapped waves resonate due to repeated reflection between end conditions provided by the nozzle and the streamwise contraction of the potential core. Our models accurately capture numerous aspects the potential core waves that are extracted from large-eddy-simulation data of a Mach 0.9 isothermal jet. Furthermore, the vortex sheet model indicates that this behavior is possible for only a limited range of Mach numbers that is consistent with previous experimental observations

Large eddy simulation for jet noise: azimuthal decomposition and intermittency of the radiated sound

To improve understanding and modeling of jet-noise source mechanisms, extensive experimental and numerical databases are generated for an isothermal Mach 0.9 turbulent jet at Reynolds number Re = 10^6. The large eddy simulations (LES) feature localized adaptive mesh refinement, synthetic turbulence and wall modeling inside the nozzle to match the fully turbulent nozzle-exit boundary layers in the experiments. Long LES databases are collected for two grids with different mesh resolutions in the jet plume. Comparisons with the experimental measurements show good agreement for the flow and sound predictions, with the far-field noise spectra matching microphone data to within 0.5 dB for most relevant angles and frequencies. Preliminary results on the radiated noise azimuthal decomposition and temporal intermittency are also discussed. The azimuthal analysis shows that the axisymmetric mode is dominant at the peak radiation angles and that the first 3 Fourier azimuthal modes of the LES data recover more than 97% of the total acoustic energy at these angles. The temporal analysis highlights the presence of recurring intermittency in the radiated sound for the low-frequency range and main downstream angles. At these frequencies and angles, temporally-localized bursts of noise can reach levels up to 3 or 4 dB higher (or lower) than the long-time average

Quasi-two-dimensional acoustic metamaterial with negative bulk modulus

We present the experimental realization and characterization of an acoustic metamaterial with negative bulk modulus. The metamaterial consists of a two-dimensional array of cylindrical cavities, and the bulk modulus is controlled by their radius size and length. Experiments are performed in a two-dimensional waveguide where a slab of seven layers is used to extract the parameters of the metamaterial. A complete characterization of the constructed structure is reported, including the dispersion relation of the acoustic bands and the skin depth effect, which both have been measured, and the data are well supported by semianalytical models and by finite-element simulations. © 2012 American Physical Society.This work was supported by the Spanish MICINN under Contracts No. TEC2010-19751 and No. CSD2008-0066 (CONSOLIDER program), and by the USA Office of Naval Research. We acknowledge the technical help by A. Diaz-Rubio and A. Climente. J.S.-D. acknowledges useful discussions with A. Broatch and A. Krokhin. D.T. acknowledges the postdoctoral grant provided by the UPV under the program Campus de excelencia internacional.García Chocano, VM.; Graciá Salgado, R.; Torrent Martí, D.; Cervera Moreno, FS.; Sánchez-Dehesa Moreno-Cid, J. (2012). Quasi-two-dimensional acoustic metamaterial with negative bulk modulus. Physical Review B. 85(18). https://doi.org/10.1103/PhysRevB.85.184102S8518Fok, L., Ambati, M., & Zhang, X. (2008). Acoustic Metamaterials. MRS Bulletin, 33(10), 931-934. doi:10.1557/mrs2008.202Norris, A. N. (2009). Acoustic metafluids. The Journal of the Acoustical Society of America, 125(2), 839-849. doi:10.1121/1.3050288Liu, Z. (2000). Locally Resonant Sonic Materials. Science, 289(5485), 1734-1736. doi:10.1126/science.289.5485.1734Yang, Z., Mei, J., Yang, M., Chan, N. H., & Sheng, P. (2008). Membrane-Type Acoustic Metamaterial with Negative Dynamic Mass. Physical Review Letters, 101(20). doi:10.1103/physrevlett.101.204301Yao, S., Zhou, X., & Hu, G. (2008). Experimental study on negative effective mass in a 1D mass–spring system. New Journal of Physics, 10(4), 043020. doi:10.1088/1367-2630/10/4/043020Park, C. M., Park, J. J., Lee, S. H., Seo, Y. M., Kim, C. K., & Lee, S. H. (2011). Amplification of Acoustic Evanescent Waves Using Metamaterial Slabs. Physical Review Letters, 107(19). doi:10.1103/physrevlett.107.194301Fang, N., Xi, D., Xu, J., Ambati, M., Srituravanich, W., Sun, C., & Zhang, X. (2006). Ultrasonic metamaterials with negative modulus. Nature Materials, 5(6), 452-456. doi:10.1038/nmat1644Wang, Z. G., Lee, S. H., Kim, C. K., Park, C. M., Nahm, K., & Nikitov, S. A. (2008). Acoustic wave propagation in one-dimensional phononic crystals containing Helmholtz resonators. Journal of Applied Physics, 103(6), 064907. doi:10.1063/1.2894914Two-dimensional acoustic metamaterial with negative modulus. (2010). Journal of Applied Physics, 108(7), 074911. doi:10.1063/1.3493155Fey, J., & Robertson, W. M. (2011). Compact acoustic bandgap material based on a subwavelength collection of detuned Helmholtz resonators. Journal of Applied Physics, 109(11), 114903. doi:10.1063/1.3595677Li, J., & Chan, C. T. (2004). Double-negative acoustic metamaterial. Physical Review E, 70(5). doi:10.1103/physreve.70.055602Lee, S. H., Park, C. M., Seo, Y. M., Wang, Z. G., & Kim, C. K. (2010). Composite Acoustic Medium with Simultaneously Negative Density and Modulus. Physical Review Letters, 104(5). doi:10.1103/physrevlett.104.054301Torrent, D., & Sánchez-Dehesa, J. (2011). Multiple scattering formulation of two-dimensional acoustic and electromagnetic metamaterials. New Journal of Physics, 13(9), 093018. doi:10.1088/1367-2630/13/9/093018Torrent, D., & Sánchez-Dehesa, J. (2008). Anisotropic mass density by two-dimensional acoustic metamaterials. New Journal of Physics, 10(2), 023004. doi:10.1088/1367-2630/10/2/023004Pendry, J. B., & Li, J. (2008). An acoustic metafluid: realizing a broadband acoustic cloak. New Journal of Physics, 10(11), 115032. doi:10.1088/1367-2630/10/11/115032Torrent, D., & Sánchez-Dehesa, J. (2010). Anisotropic Mass Density by Radially Periodic Fluid Structures. Physical Review Letters, 105(17). doi:10.1103/physrevlett.105.174301Spiousas, I., Torrent, D., & Sánchez-Dehesa, J. (2011). Experimental realization of broadband tunable resonators based on anisotropic metafluids. Applied Physics Letters, 98(24), 244102. doi:10.1063/1.3599849Li, J., Fok, L., Yin, X., Bartal, G., & Zhang, X. (2009). Experimental demonstration of an acoustic magnifying hyperlens. Nature Materials, 8(12), 931-934. doi:10.1038/nmat2561Fokin, V., Ambati, M., Sun, C., & Zhang, X. (2007). Method for retrieving effective properties of locally resonant acoustic metamaterials. Physical Review B, 76(14). doi:10.1103/physrevb.76.144302Torrent, D., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2006). Homogenization of Two-Dimensional Clusters of Rigid Rods in Air. Physical Review Letters, 96(20). doi:10.1103/physrevlett.96.20430

Reproductive Factors and Serum Uric Acid Levels in Females from the General Population: The KORA F4 Study

Hyperuricemia is associated with an increased risk of metabolic and cardiovascular diseases. There are pronounced sex differences in the levels of uric acid. It is largely unknown whether or not reproductive parameters which induce hormonal changes are responsible for this. We examined if there are associations between reproductive parameters and uric acid levels in a female population-based sample. In this cross-sectional analysis, data of 1530 women aged 32 to 81 years participating in the KORA F4 study, conducted between 2006 and 2008 in Southern Germany were used. Reproductive parameters were obtained by standardized interviews. Uric acid levels were tested by the uricase method. The whole study sample and stratified in pre- and postmenopausal women was analyzed. Menopausal status and earlier age at menarche were associated with higher serum uric acid levels (age-adjusted: p-values 0.003, <0.001 respectively; after multivariable adjustment, including BMI: p-values 0.002, 0.036). A history of oral contraceptive use showed an association with uric acid levels only after multivariable adjustment (p-value 0.009). Hot flushes showed an association with uric acid levels only after age-adjustment (p-value 0.038), but lost significance after adding other confounders. Other reproductive factors, including parity, current or ever use of hormone replacement therapy, current use of oral contraceptives, hysterectomy, bilateral oophorectomy, or depressive mood related to menopausal transition were not associated with uric acid levels. Postmenopausal status, earlier age at menarche and a history of oral contraceptive use were independently associated with higher serum uric acid concentrations in women from the general population. Further studies, especially longitudinal population-based studies investigating the relationship of female reproductive parameters with uric acid levels are necessary to confirm our findings