Reflection of sound from random distributions of semicylinders on a hard plane: models and data

A new analytical theory for multiple scattering of cylindrical acoustic waves by an array of finite impedance semi-cylinders embedded in a smooth acoustically hard surface is derived by extending previous results for plane waves [Linton and Martin, J. Acoust. Soc. Am. 117 (6) 3413 – 3423 (2005)]. Although the computational demands of the new theory increase as the number of the semi-cylinders in the arrays and/or the frequency increases, the theory offers an improvement on analytical boss theories since the latter (i) are restricted to non-deterministic (infinite) random distributions of semi-cylinders with spacing/radii small compared to the incident wavelength and (ii) are derived only for plane waves. The influence on prediction accuracy of truncation of the infinite system of equations introduced by the new theory is explored empirically. Laboratory measurements have been made over deterministic random arrays of identical varnished wooden semi-cylinders on a glass plate. The agreement between predictions and measured relative sound pressure level spectra is very good both for single deterministic random distributions and for averages representing non-deterministic random distributions. The analytical theory is found to give identical results to a boundary element calculation but is much faster to compute

Generation of flexural waves in infinite plates by laser-initiated air shock waves

Controlled explosions that take place above ground surface during military testing generate not only shock waves in air but also strong ground vibrations. It is convenient and much less expensive to study the associated sound and vibration phenomena using reduced-scale laboratory simulations, with a laser as a source of air shock waves interacting with large elastic plates modelling the ground1,2. Earlier, a semi-analytical model describing interaction of air shock waves with an elastic half space has been suggested by one of the present authors to describe generation of Rayleigh surface waves by electric spark discharge near the surface3. The aim of the present paper is to further develop the above-mentioned semi-analytical model3 and to apply it to the interaction of laser-initiated air shock waves with an infinite elastic plate. The impact of the incident shock wave is to be approximated by an equivalent cylindrically diverging surface force resulting from the surface pressure of the incident and reflected shock waves. The well-known analytical expressions for air particle velocity and pressure in the front of a shock wave are used to describe this surface force as a function of time and distance from the epicentre. The problem is then solved using the Green’s function method applied to an infinite plate. The resulting frequency spectra and time shapes of the generated flexural wave pulses are calculated for different values of the height of the laser-generated spark above the plate surface. The obtained theoretical results for time histories and frequency spectra of generated flexural waves are compared with the results of the reduced-scale model experiments on shock wave interaction with a large plastic plate

Generation of Rayleigh-type edge waves by laser-initiated airborne shocks

This paper presents a semi-analytical model of the interaction of laser-initiated airborne shocks with the edge of an infinite vertically mounted elastic plate. The impact of the shock wave on the plate edge is approximated by an equivalent edge force resulting from the combined pressure of the incident and reflected shock waves. The problem is then solved using the Green’s function method. The resulting predictions are compared with the results of the laboratory experiments on laser-initiated air shock wave interaction with an edge of a large vertically mounted Perspex plate that is used for reduced-scale modelling of blast wave interaction with the ground surface. The resulting frequency spectra and time histories of generated Rayleigh-type wave pulses propagating along the plate edge are calculated for different heights of the laser beam focusing above the plate edge. The comparisons show that the obtained semi-analytical predictions are in good agreement with the experiments

Generation of rayleigh-type waves on plate edges by laser-initiated airborne shock waves

The present paper describes the results of the semi-analytical modelling of the interaction of laser-initiated air shock waves with the edge of an infinite vertically mounted elastic plate. The impact of the shock wave on the plate edge is approximated by an equivalent edge force resulting from the combined pressure of the incident and reflected shock waves. This force is then represented in the wavenumber-frequency domain by means of Fourier transforms that are carried out numerically. After that the problem is solved using the Green’s function method. The resulting frequency spectra and time histories of generated Rayleigh-type wave pulses propagating along the plate edge are calculated for different heights of the laser beam focusing above the plate edge. The obtained theoretical results are compared with the results of the laboratory experiments on laser-initiated air shock wave interaction with an edge of a large vertically mounted Perspex plate that is used for reduced-scale modelling of blast wave interaction with the ground surface. The resonant properties of the accelerometer have been taken into account to describe the received signals. The comparison shows that the obtained semi-analytical results are in good agreement with the experiments

Generation of flexural waves in plates by laser-initiated airborne shock waves

Results of the semi-analytical modelling of the interaction of laser-initiated airborne shock waves with an infinite horizontally positioned elastic plate are presented. The impact of the airborne shock waves on the plate is approximated by a cylindrically diverging surface force resulting from the pressure of the incident and reflected shock waves. This force is then represented in the wavenumber-frequency domain by means of Hankel and Fourier transforms that are carried out numerically so that the interaction problem can be solved using the Green’s function method. The resulting frequency spectra and time histories of generated 2 flexural wave pulses are calculated for different values of laser pulse energy and for different heights of the laser beam focusing above the plate surface. The theoretical results obtained are compared with the results of laboratory measurements of the interaction of laser-generated acoustic shocks with a large plastic plate. The comparison shows reasonably good agreement between the semi-analytical predictions and data

Wicket: A Versatile Tool for the Integration and Optimization of Exogenous Pathways in <i>Saccharomyces cerevisiae</i>

Yeast can be used as a microbial cell factory to produce valuable chemicals. However, introducing an exogenous pathway into particular or different chromosomal locations for stable expression is still a daunting task. To address this issue, we designed a DNA cassette called a “wicket”, which can be integrated into the yeast genome at designated loci to accept exogenous DNA upon excision by a nuclease. Using this system, we demonstrated that, in strains with “wickets”, we could achieve near 100% efficiency for integration of the β-carotene pathway with no need for selective markers. Furthermore, it allowed independent and simultaneous integration of different genes in a pathway, resulting in a large variety of strains with variable copy numbers of each gene. This system could be a useful tool to modulate the integration of multiple copies of genes within a metabolic pathway and to optimize the yield of the target products

Semi-analytical modelling of plate flexural waves generated by laser-initiated air shock waves

Semi-analytical modelling of plate flexural waves generated by laser-initiated air shock wave

Derivation and Osmotolerance Characterization of Three Immortalized Tilapia (<i>Oreochromis mossambicus</i>) Cell Lines

<div><p>Fish cell cultures are becoming more widely used models for investigating molecular mechanisms of physiological response to environmental challenge. In this study, we derived two immortalized Mozambique tilapia (<i>Oreochromis mossambicus</i>) cell lines from brain (OmB) and lip epithelium (OmL), and compared them to a previously immortalized bulbus arteriosus (TmB) cell line. The OmB and OmL cell lines were generated without or with Rho-associated kinase (ROCK) inhibitor/3T3 feeder layer supplementation. Although both approaches were successful, ROCK inhibitor/feeder layer supplementation was found to offer the advantages of selecting for epithelial-like cell type and decreasing time to immortalization. After immortalization (≥ passage 5), we characterized the proteomes of the newly derived cell lines (OmB and OmL) using LCMS and identified several unique cell markers for each line. Subsequently, osmotolerance for each of the three cell lines following acute exposure to elevated sodium chloride was evaluated. The acute maximum osmotolerance of these tilapia cell lines (>700 mOsm/kg) was markedly higher than that of any other known vertebrate cell line, but was significantly higher in the epithelial-like OmL cell line. To validate the physiological relevance of these tilapia cell lines, we quantified the effects of acute hyperosmotic challenge (450 mOsm/kg and 700 mOsm/kg) on the transcriptional regulation of two enzymes involved in biosynthesis of the compatible organic osmolyte, <i>myo</i>-inositol. Both enzymes were found to be robustly upregulated in all three tilapia cell lines. Therefore, the newly established tilapia cells lines represent valuable tools for studying molecular mechanisms involved in the osmotic stress response of euryhaline fish.</p></div

Heat map representing comparative proteomics data for newly derived OmB and OmL cell lines.

<p>Data presented are significantly different ratios of protein abundances (relative to OmB abundance) for four technical replicates of OmB and OmL generated with a proteomics software package (PEAKS suite 7, BSI, Inc.). Protein accession numbers and relationships are given on the left side of the heat map.</p

Cell morphology of tilapia cell lines.

<p>Images depicting differences in cell morphology of two newly immortalized cell lines derived from brain (OmB) (A+D) and lip (OmL) (B+E) and the previously established bulbus arteriosus (TmB) (C+F) cell line. OmB cells are fibroblast-like, OmL cells are epithelial-like, and TmB cells are endothelial. Images were taken on an inverted or fluorescent microscope at 100X (A–B) and 250X (C), and 400X (D–F) magnification. Cells (D–F) were stained with MitoTracker Red to visualize mitochondria (red) and with Hoechst 33342 for nuclei (blue).</p