On surface radiation conditions for high-frequency wave scattering

A new approximation of the logarithmic derivative of the Hankel function is derived and applied to high-frequency wave scattering. We re-derive the on surface radiation condition (OSRC) approximations that are well suited for a Dirichlet boundary in acoustics. These correspond to the Engquist–Majda absorbing boundary conditions. Inverse OSRC approximations are derived and they are used for Neumann boundary conditions. We obtain an implicit OSRC condition, where we need to solve a tridiagonal system. The OSRC approximations are well suited for moderate wave numbers. The approximation of the logarithmic derivative is also used for deriving a generalized physical optics approximation, both for Dirichlet and Neumann boundary conditions. We have obtained similar approximations in electromagnetics, for a perfect electric conductor. Numerical computations are done for different objects in 2D and 3D and for different wave numbers. The improvement over the standard physical optics is verified.     

Self-phase modulation in slow-wave structures: A comparative numerical analysis

Self-phase modulation effects in 1D optical slow-wave structures made of Fabry–Pérot cavities coupled by Distributed Bragg Reflectors (DBRs) are discussed. The nonlinear response of the structure is investigated by a comparative analysis of several numerical methods operating either in time or frequency-domain. Time-domain methods include two Finite-Difference Time-Domain approaches, respectively, optimized to compensate for numerical dispersion and to model nonlinearity at any order. In the frequency-domain an efficient method based on a numerical integration of Maxwell’s equations and an iterative nonlinear extension of the Eigenmode Expansion method are discussed. A Nonlinear Equivalent Circuit of DBRs is also presented as a useful model to reduce computational efforts. Numerical results show that bistable effects and self-pulsing phenomena can occur when either the optical power or the number of coupled cavities of the structure are sufficiently increased.     

Antioxidant and antimutagenic polyisoprenylated benzophenones and xanthones from Rheedia acuminata

Dichloromethane extract of the stem bark of Rheedia acuminata yielded three benzophenones with antioxidant activity, the new one named acuminophenone A (1), guttiferone K (2) and isoxanthochymol (3), along with the known xanthones formoxanthone C (4) and macluraxanthone (5). The structures were established through interpretation of their spectroscopic data, the stereochemistry of compounds (1) and (2) were resolved by experimental and computational experiments and their antioxidant activities were measured using the DPPH, ABTS and TEAC assays. The antioxidant results showed that metabolites 1, 4 and 5 had a better antioxidant activity than the reference compound quercetin. In addition, we evaluate the mutagenicity and antimutagenicity of the CH2Cl2 extract as well as of the free radical scavenger compounds 1, 4 and 5 by the AMES Salmonella/microsomal test. No mutagenicity was found in the CH2Cl2 extract using Salmonella typhimurium strains TA98, TA100, TA102, TA1537 and TA1538, with or without S9 metabolic activation. The pure compounds neither showed mutagenicity in TA 102 strain and the most important result was the strong reduction of mutagenic effect induced by hydrogen peroxide in S. typhimurium TA102, with or without S9, showed by the compounds 1 (more than 93%) and 4 (more than 88%) at 0.02 microg/plate.     

The use of 3D-laser scanning in assessing the safety of masonry vaults—A case study on the church of Saint-Jacobs

Safety and stability of historical structures are of key importance when dealing with a restoration project. The stability of masonry vaults very much depends on its overall geometry and the analysis results strongly depend on the accuracy in which this geometry can be measured in practice. To obtain an accurate estimate of the geometry of the vaults, 3D-laser scanning was performed. Based on the 3D-point cloud, a 3D-model of the vaults allows determining the lines of thrust in the structure as well as the reaction forces (application point and magnitude) at the abutments. This contribution gives a critical appraisal of the process used in the preliminary research phase: gathering the point clouds, 3D-modelling, structural analysis calculating thrust lines and the consolidation requirements that are obtained. The focus is on the added value of the methodology, its applicability, cost-effectiveness, overall advantages and drawbacks.     

Properties of Removable Singularities for Hardy Spaces of Analytic Functions

Removable singularities for Hardy spaces H^p() = {f Hol(): |f|^p u in for some harmonic u}, 0 < p < are studied. A setE = is a weakly removable singularity for H^p(\E) if H^p(\E) Hol(), and a strongly removable singularity for H^p(\E) if H^p(\E)= H^p(). The two types of singularities coincide for compactE, and weak removability is independent of the domain . The paper looks at differences between weak and strong removability,the domain dependence of strong removability, and when removabilityis preserved under unions. In particular, a domain and a setE that is weakly removable for all H^p, but not strongly removablefor any H^p(\E), 0 < p < , are found. It is easy to show that if E is weakly removable for H^p(\E)and q > p, then E is also weakly removable for H^q(\E). Itis shown that the corresponding implication for strong removabilityholds if and only if q/p is an integer. Finally, the theory of Hardy space capacities is extended, anda comparison is made with the similar situation for weightedBergman spaces.     

Torsion Packets on Curves

Let X be a curve of genus g2 over a field of characteristic zero. Then X has at most finitely many torsion packets of size greater than 2. Moreover, X has infinitely many torsion packets of size 2 if and only if either g=2, or g=3 and X is both hyperelliptic and bielliptic.     

Siamang gibbons exceed the saccular threshold: intensity of the song of Hylobates syndactylus

Measurements are reported of the intensity of the siamang gibbon loud call obtained from the vocal bouts of three family groups at Twycross Zoo, UK. Across 25 samples the maximum intensity ranged from 95 to 113 dB SPL (linear frequency-weighting and fast time-weighting) and exhibited three frequency modes of 250-315 Hz, 630-800 Hz and 1.2-1.6 kHz. The lowest frequency mode, which may correspond to the "boom" sound produced by resonance of the siamang inflated vocal sac, had a mean maximum intensity of 99 dB SPL. These values, which are in excess of the saccular acoustic threshold of about 90 dB at 300 Hz for air conducted sound, suggest that primate loud calls recruit a primitive mode of acoustic sensitivity furnished by the sacculus. Thus reproductive vocal behavior of primates may be influenced by a primitive acoustical reward pathway inherited from a common ancestor with anamniotes. In humans such a pathway could explain the compulsion for exposure to loud music.     

Novel Selectivity-Based Forensic Toxicological Validation of a Paper Spray Mass Spectrometry Method for the Quantitative Determination of Eight Amphetamines in Whole Blood

Paper spray tandem mass spectrometry is used to identify and quantify eight individual amphetamines in whole blood in 1.3 min. The method has been optimized and fully validated according to forensic toxicology guidelines, for the quantification of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-methylamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA), and 4-fluoroamphetamine (4-FA). Additionally, a new concept of intrinsic and application-based selectivity is discussed, featuring increased confidence in the power to discriminate the amphetamines from other chemically similar compounds when applying an ambient mass spectrometric method without chromatographic separation. Accuracy was within ±15% and average precision was better than 15%, and better than 20% at the LLOQ. Detection limits between 15 and 50 ng/mL were obtained using only 12 μL of whole blood.

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