Quenching of acoustic bandgaps by flow noise

Copyright (2009) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics along with the following message: The following article appeared in Appl. Phys. Lett. 94, 134104 (2009) and may be found at http://dx.doi.org/10.1063/1.3111797. Authors own version of final article on e-print serversWe report an experimental study of acoustic effects produced by wind impinging on noise barriers based on two-dimensional sonic crystals with square symmetry. We found that the attenuation strength of sonic-crystal bandgaps decreases for increasing values of flow speed. A quenching of the acoustic bandgap appears at a certain speed value that depends of the barrier filling ratio. For increasing values of flow speed, the data indicate that the barrier becomes a sound source because of its interaction with the wind. We conclude that flow noise should be taken into account in designing acoustic barriers based on sonic crystals.This work was supported by the Spanish Agency of International Cooperation (AECI), the Spanish Ministry of Science and Innovation (MICIIN), and the Spanish Ministry of Public Works (MF). J.S.-D. acknowledges useful conversations with A. Broatch.Elnady, T.; Elsabbagh, A.; Akl, W.; Mohamady, O.; Garcia Chocano, VM.; Torrent Martí, D.; Cervera Moreno, FS.... (2009). Quenching of acoustic bandgaps by flow noise. Applied Physics Letters. 94(13). doi:10.1063/1.3111797S9413Sánchez-Pérez, J. V., Caballero, D., Mártinez-Sala, R., Rubio, C., Sánchez-Dehesa, J., Meseguer, F., … Gálvez, F. (1998). Sound Attenuation by a Two-Dimensional Array of Rigid Cylinders. Physical Review Letters, 80(24), 5325-5328. doi:10.1103/physrevlett.80.5325Rubio, C., Caballero, D., Sanchez-Perez, J. V., Martinez-Sala, R., Sanchez-Dehesa, J., Meseguer, F., & Cervera, F. (1999). The existence of full gaps and deaf bands in two-dimensional sonic crystals. Journal of Lightwave Technology, 17(11), 2202-2207. doi:10.1109/50.803012Caballero, D., Sánchez-Dehesa, J., Rubio, C., Mártinez-Sala, R., Sánchez-Pérez, J. V., Meseguer, F., & Llinares, J. (1999). Large two-dimensional sonic band gaps. Physical Review E, 60(6), R6316-R6319. doi:10.1103/physreve.60.r6316Caballero, D., Sánchez-Dehesa, J., Martínez-Sala, R., Rubio, C., Sánchez-Pérez, J. V., Sanchis, L., & Meseguer, F. (2001). Suzuki phase in two-dimensional sonic crystals. Physical Review B, 64(6). doi:10.1103/physrevb.64.064303Chen, Y.-Y., & Ye, Z. (2001). Acoustic Attenuation by Two-Dimensional Arrays of Rigid Cylinders. Physical Review Letters, 87(18). doi:10.1103/physrevlett.87.184301Sanchez-Perez, J. V., Rubio, C., Martinez-Sala, R., Sanchez-Grandia, R., & Gomez, V. (2002). Acoustic barriers based on periodic arrays of scatterers. Applied Physics Letters, 81(27), 5240-5242. doi:10.1063/1.1533112Goffaux, C., Maseri, F., Vasseur, J. O., Djafari-Rouhani, B., & Lambin, P. (2003). Measurements and calculations of the sound attenuation by a phononic band gap structure suitable for an insulating partition application. Applied Physics Letters, 83(2), 281-283. doi:10.1063/1.1592016Goffaux, C., & Vigneron, J. P. (2001). Theoretical study of a tunable phononic band gap system. Physical Review B, 64(7). doi:10.1103/physrevb.64.075118Zhong, L., Wu, F., Zhang, X., Zhong, H., & Zhong, S. (2005). Effects of orientation and symmetry of rods on the complete acoustic band gap in two-dimensional periodic solid/gas systems. Physics Letters A, 339(1-2), 164-170. doi:10.1016/j.physleta.2005.03.025Umnova, O., Attenborough, K., & Linton, C. M. (2006). Effects of porous covering on sound attenuation by periodic arrays of cylinders. The Journal of the Acoustical Society of America, 119(1), 278-284. doi:10.1121/1.2133715Martínez-Sala, R., Rubio, C., García-Raffi, L. M., Sánchez-Pérez, J. V., Sánchez-Pérez, E. A., & Llinares, J. (2006). Control of noise by trees arranged like sonic crystals. Journal of Sound and Vibration, 291(1-2), 100-106. doi:10.1016/j.jsv.2005.05.030Sanchis, L., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2003). Acoustic interferometers based on two-dimensional arrays of rigid cylinders in air. Physical Review B, 67(3). doi:10.1103/physrevb.67.03542

Burden of rotavirus gastroenteritis in the Middle Eastern and North African pediatric population

<p>Abstract</p> <p>Background</p> <p>Rotavirus gastroenteritis (RVGE) is the most common cause of severe childhood diarrhea worldwide. Objectives were to estimate the burden of RVGE among children less than five years old in the Middle East (Bahrain, Iran, Iraq, Israel, Jordan, Kuwait, Oman, Qatar, Saudi Arabia, Syria, UAE, Yemen), North Africa (Algeria, Egypt, Libya, Morocco, Tunisia) and Turkey.</p> <p>Methods</p> <p>A comprehensive literature search was conducted in major databases on the epidemiology and burden of rotavirus among children less than five years old between 1999 and 2009. Data from each country was extracted and compared.</p> <p>Results</p> <p>The search identified 43 studies. RVGE was identified in 16-61% of all cases of acute gastroenteritis, with a peak in the winter. RVGE-related hospitalization rates ranged from 14% to 45%, compared to 14%-28% for non-RVGE. Annually, RVGE caused up to 112 fatalities per 100,000 in certain countries in the region. Hospitalization costs ranged from $1.8 to$4.6 million annually, depending on the country. The most recent literature available showed that G1P[8] was the most prevalent genotype combination in 8 countries (range 23%-56%). G2P[4] was most prevalent in 4 countries (26%-48%). G9P[8] and G4P[8] were also frequently detected.</p> <p>Conclusions</p> <p>RVGE is a common disease associated with significant morbidity, mortality, and economic burden. Given the variety and diverse rotavirus types in the region, use of a vaccine with broad and consistent serotype coverage would be important to help decrease the burden of RVGE in the Middle East and North Africa.</p

Mild and Highly Flexible Enzyme-Catalyzed Modification of Poly (ethersulfone) Membranes

Poly(ethersulfone) (PES) membranes are widely used in industry for separation and purification purposes. However, the drawback of this type of membranes is fouling by proteins. For that reason, modification of PES membranes has been studied to enhance their protein repellence. This paper presents the first example of enzyme-catalyzed modification of PES membranes. Various phenolic acids (enzyme substrates) were bound to a membrane under very mild conditions (room temperature, water, nearly neutral pH) using only laccase from Trametes versicolor as catalyst. The extent of modification, monitored, for example, by the coloration of the modified membranes, can be tuned by adjusting the reaction conditions. The most significant results were obtained with 4-hydroxybenzoic acid and gallic acid as substrates. The presence of a covalently bound layer of 4-hydroxybenzoic acid on the grafted membranes was confirmed by X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and NMR. In the case of gallic acid, PES membrane modification is mainly caused by adsorption of enzymatically formed homopolymer. The ionization potential of the substrates, and the electronic energies and spin densities of the radicals that are intermediates in the attachment reaction were calculated (B3LYP/6-311G(d,p)) to determine the reactive sites and the order of reactivity of radical substrates to couple with the PES membrane. The calculated order of reactivity of the substrates is in line with the experimental observations. The calculated spin densities in the phenolic radicals are highest at the oxygen atom, which is in line with the formation of ether linkages as observed by IRRAS. The liquid fluxes of the modified membranes are hardly influenced by the grafted layers, in spite of the presence of a substantial and stable new layer, which opens a range of application possibilities for these modified membrane