Scattering of sound waves by a canonical acoustic hole

This is a study of a monochromatic planar perturbation impinging upon a canonical acoustic hole. We show that acoustic hole scattering shares key features with black hole scattering. The interference of wave fronts passing in opposite senses around the hole creates regular oscillations in the scattered intensity. We examine this effect by applying a partial wave method to compute the differential scattering cross section for a range of incident wavelengths. We demonstrate the existence of a scattering peak in the backward direction, known as the glory. We show that the glory created by the canonical acoustic hole is approximately 170 times less intense than the glory created by the Schwarzschild black hole, for equivalent horizon-to-wavelength ratios. We hope that direct experimental observations of such effects may be possible in the near future.

New Measurement of the pi(0) Radiative Decay Width

High precision measurements of the differential cross sections for pi(0) photoproduction at forward angles for two nuclei, (12)C and (208)Pb, have been performed for incident photon energies of 4.9-5.5 GeV to extract the pi(0) -> gamma gamma decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The pi(0) -> gamma gamma decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is Gamma(pi(0) -> gamma gamma) = 7.82 +/- 0.14(stat) +/- 0.17(syst) eV. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current Particle Data Group average of this fundamental quantity, and it is consistent with current theoretical predictions.

Experimental and theoretical study of two-photon absorption in nitrofuran derivatives: Promising compounds for photochemotherapy

We report experimental and theoretical studies of the two-photon absorption spectrum of two nitrofuran derivatives: nitrofurantoine, (1-(5-nitro-2-furfurilideneamine)-hidantoine) and quinifuryl, 2-(5`-nitro-2`-furanyl) ethenyl-4-{N-[4`-(N,N-diethylamino)-1`-methylbutyl]carbamoyl} quinoline. Both molecules are representative of a family of 5-nitrofuran-ethenyl-quinoline drugs that have been demonstrated to display high toxicity to various species of transformed cells in the dark. We determine the two-photon absorption cross-section for both compounds, from 560 to 880 nm, which present peak values of 64 GM for quinifuryl and 20 GM for nitrofurantoine (1 GM = 1 x 10(-50) cm(4).s.photon(-1)). Besides, theoretical calculations employing the linear and quadratic response functions were carried out at the density functional theory level to aid the interpretations of the experimental results. The theoretical results yielded oscillator strengths, two-photon transition probabilities, and transition energies, which are in good agreement with the experimental data. A higher number of allowed electronic transitions was identified for quinifuryl in comparison to nitrofurantoine by the theoretical calculations. Due to the planar structure of both compounds, the differences in the two-photon absorption cross-section values are a consequence of their distinct conjugation lengths. (c) 2011 American Institute of Physics. [doi:10.1063/1.3514911]

Theoretical study of one- and two-photon absorption spectra of azoaromatic compounds

In this study, the one- and two-photon absorption spectra of seven azoaromatic compounds (five pseudostilbenes-type and two aminoazobenzenes) were theoretically investigated using the density functional theory combined with the response functions formalism. The equilibrium molecular structure of each compound was obtained at three different levels of theory: Hartree-Fock, density functional theory (DFT), and Moller-Plesset 2. The effect of solvent on the equilibrium structure and the electronic transitions of the compounds were investigated using the polarizable continuum model. For the one-photon absorption, the allowed pi ->pi(*) transition energy showed to be dependent on the molecular structures and the effect of solvent, while the n ->pi(*) and pi ->pi(*)(n) transition energies exhibited only a slight dependence. An inversion between the bands corresponding to the pi ->pi(*) and n ->pi(*) states due to the effect of solvent was observed for the pseudostilbene-type compounds. To characterize the allowed two-photon absorption transitions for azoaromatic compounds, the response functions formalism combined with DFT using the hybrid B3LYP and PBE0 functionals and the long-range corrected CAM-B3LYP functional was employed. The theoretical results support the previous findings based on the three-state model. The model takes into account the ground and two electronic excited states and has already been used to describe and interpret the two-photon absorption spectrum of azoaromatic compounds. The highest energy two-photon allowed transition for the pseudostilbene-type compounds shows to be more effectively affected (similar to 20%) by the torsion of the molecular structure than the lowest allowed transition (similar to 10%). In order to elucidate the effect of the solvent on the two-photon absorption spectra, the lowest allowed two-photon transition (dipolar transition) for each compound was analyzed using a two-state approximation and the polarizable continuum model. The results obtained reveal that the effect of solvent increases drastically the two-photon cross-section of the dipolar transition of the pseudostilbene-type compounds. In general, the features of both one- and two-photon absorption spectra of the azoaromatic compounds are well reproduced by the theoretical calculations.

Low-energy electron scattering from methanol and ethanol

Measured and calculated differential cross sections for elastic (rotationally unresolved) electron scattering from two primary alcohols, methanol (CH(3)OH) and ethanol (C(2)H(5)OH), are reported. The measurements are obtained using the relative flow method with helium as the standard gas and a thin aperture as the collimating target gas source. The relative flow method is applied without the restriction imposed by the relative flow pressure conditions on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV and for scattering angles of 5 degrees-130 degrees. There are no previous reports of experimental electron scattering differential cross sections for CH(3)OH and C(2)H(5)OH in the literature. The calculated differential cross sections are obtained using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons. Comparison between theory and experiment shows that theory is able to describe low-energy electron scattering from these polyatomic targets quite well.

Analytical formulae for electromechanical effective properties of 3-1 longitudinally porous piezoelectric materials

A unidirectional fiber composite is considered here, the fibers of which are empty cylindrical holes periodically distributed in a transversely isotropic piezoelectric matrix, The empty-fiber cross-section is circular and the periodicity is the same in two directions at an angle pi/2 or pi/3. Closed-form formulae for all electromechanical effective properties of these 3-1 longitudinally periodic porous piezoelectric materials are presented. The derivation of such expressions is based on the asymptotic homogenization method as a limit of the effective properties of two-phase transversely isotropic parallel fiber-reinforced composites when the fibers properties tend to zero. The plane effective coefficients satisfy the corresponding Schulgasser-Benveniste-Dvorak universal type of relations, A new relation among the antiplane effective constants from the solutions of two antiplane strains and potential local problems is found. This relation is valid for arbitrary shapes of the empty-fiber cross-sections. Based on such a relation, and using recent numerical results for isotropic conductive composites, the antiplane effective properties are computed for different geometrical shapes of the empty-fiber cross-section. Comparisons with other analytical and numerical theories are presented. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DESIGN OF CONCRETE PLATFORMS OFFSHORE USING THE THREE-LAYER SHELL THEORY

The concrete offshore platforms, which are subjected a several loading combinations and, thus, requires an analysis more generic possible, can be designed using the concepts adopted to shell elements, but the resistance must be verify in particular cross-sections to shear forces. This work about design of shell elements will be make using the three-layer shell theory. The elements are subject to combined loading of membrane and plate, totalizing eight components of internal forces, which are three membrane forces, three moments (two out-of-plane bending moments and one in-plane, or torsion, moment) and two shear forces. The design method adopted, utilizing the iterative process proposed by Lourenco & Figueiras (1993) obtained from equations of equilibrium developed by Gupta (1896) , will be compared to results of experimentally tested shell elements found in the literature using the program DIANA.

Experimental investigation of Vortex-Induced Vibration on rigid, smooth and inclined cylinders

This paper presents new experimental results of Vortex-Induced Vibration (VIV) on inclined cylinders. Models are mounted on a low damping air-bearing elastic base with one degree-of-freedom, constrained to oscillate only in the transverse direction to a free stream. The Reynolds number varied in the range 2000 less than or similar to Re less than or similar to 8000. New measurements on the dynamic response oscillations of inclined cylinders, due to VIV, are compared with previous experiments of a vertical cylinder. Models with circular and elliptical cross sections have been tested. The purpose of this work is to check the validity of the normal velocity correction of VIV studies of inclined structures. The results show that the reduced velocity range, in which the upper and lower branches of VIV occurs, is similar to the vertical cylinder case if the proper projected velocity is considered. Tests have been conducted to support this observation with inclinations up to 45 degrees. We have also observed that the amplitudes of oscillation of the inclined circular cylinder are comparable, but slightly lower than, to the amplitudes observed in the vertical cylinder experiments. Measured forces and added mass also show similar behaviour. However, for cases with an elliptical cylinder, the amplitudes of oscillation are considerably lower than those observed for a circular cylinder. This difference is explained by the higher added mass of the elliptical cylinder. (C) 2009 Elsevier Ltd. All rights reserved.

Animated solid model of the lung constructed from unsynchronized MR sequential images

This work discusses a 4D lung reconstruction method from unsynchronized MR sequential images. The lung, differently from the heart, does not have its own muscles, turning impossible to see its real movements. The visualization of the lung in motion is an actual topic of research in medicine. CT (Computerized Tomography) can obtain spatio-temporal images of the heart by synchronizing with electrocardiographic waves. The FOV of the heart is small when compared to the lung`s FOV. The lung`s movement is not periodic and is susceptible to variations in the degree of respiration. Compared to CT, MR (Magnetic Resonance) imaging involves longer acquisition times and it is not possible to obtain instantaneous 3D images of the lung. For each slice, only one temporal sequence of 2D images can be obtained. However, methods using MR are preferable because they do not involve radiation. In this paper, based on unsynchronized MR images of the lung an animated B-Repsolid model of the lung is created. The 3D animation represents the lung`s motion associated to one selected sequence of MR images. The proposed method can be divided in two parts. First, the lung`s silhouettes moving in time are extracted by detecting the presence of a respiratory pattern on 2D spatio-temporal MR images. This approach enables us to determine the lung`s silhouette for every frame, even on frames with obscure edges. The sequence of extracted lung`s silhouettes are unsynchronized sagittal and coronal silhouettes. Using our algorithm it is possible to reconstruct a 3D lung starting from a silhouette of any type (coronal or sagittal) selected from any instant in time. A wire-frame model of the lung is created by composing coronal and sagittal planar silhouettes representing cross-sections. The silhouette composition is severely underconstrained. Many wire-frame models can be created from the observed sequences of silhouettes in time. Finally, a B-Rep solid model is created using a meshing algorithm. Using the B-Rep solid model the volume in time for the right and left lungs were calculated. It was possible to recognize several characteristics of the 3D real right and left lungs in the shaded model. (C) 2007 Elsevier Ltd. All rights reserved.

Assessment of the differential linear coherent scattering coefficient of biological samples

New differential linear coherent scattering coefficient, mu(CS), data for four biological tissue types (fat pork, tendon chicken, adipose and fibroglandular human breast tissues) covering a large momentum transfer interval (0.07 <= q <= 70.5 nm(-1)), resulted from combining WAXS and SAXS data, are presented in order to emphasize the need to update the default data-base by including the molecular interference and the large-scale arrangements effect. The results showed that the differential linear coherent scattering coefficient demonstrates influence of the large-scale arrangement, mainly due to collagen fibrils for tendon chicken and fibroglandular breast samples, and triacylglycerides for fat pork and adipose breast samples at low momentum transfer region. While, at high momentum transfer, the mu(CS) reflects effects of molecular interference related to water for tendon chicken and fibroglandular samples and, fatty acids for fat pork and adipose samples. (C) 2009 Elsevier B.V. All rights reserved.

Preliminary study of human breast tissue using synchrotron radiation combining WAXS and SAXS techniques

Using synchrotron radiation, we combined simultaneously wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) techniques to obtain the scattering profiles of normal and neoplastic breast tissu-es samples at the momentum transfer range 6.28 nm(-1) <= Q(=4 pi.sin(theta/2)lambda) <= 50.26 nm(-1) and 0.15 nm(-1) <= Q <= 1.90 nm(-1), respectively. The results obtained show considerable differences between the scattering profiles of these tissues. We verified that the combination of some parameters (ratio between glandular and adipose peak intensity and third-order axial peak intensity) extracted from scattering profiles can be used for identifying breast cancer. (c) 2009 Elsevier Ltd. All rights reserved.

Activated satellite cells in medial rectus muscles of patients with strabismus

PURPOSE. The goal of this study was to determine whether the medial rectus muscles of patients with a history of medial rectus underaction or overaction show alterations in the process of satellite cell activation when compared with normal age-matched control muscles. METHODS. Medial rectus muscles were obtained with consent from adult patients undergoing surgical resection due to medial rectus underaction or overaction and were prepared for histologic examination by fixation and paraffin embedding. Control muscles were obtained from cornea donor eyes of adults who had no history of strabismus or neuromuscular disease. Cross sections were obtained and stained immunohistochemically for the presence of activated satellite cells, as identified by MyoD immunoreactivity, and the presence of the total satellite cell population, as identified by Pax7 immunoreactivity. The percentages of MyoD- and Pax7-positive satellite cells per 100 myofibers in cross section were calculated. RESULTS. As predicted from results in the literature, MyoD-positive satellite cells, indicative of activation, were present in both the control and resected muscles. In the underacting medial rectus muscles, the percentages of MyoD- and Pax7-positive satellite cells, based on the number of myofibers, were approximately twofold higher than the percentages in the control muscles. In the overacting medial rectus muscles, the percentage of MyoD- positive satellite cells was twofold less than in the control muscles, whereas the percentage of Pax7-positive satellite cells significantly increased compared with that in the control specimens. CONCLUSIONS. The presence of an increased number of activated satellite cells in the resected underacting medial rectus muscles and the decreased numbers of activated satellite cells in the overacting muscles was unexpected. The upregulation in the number of MyoD- positive satellite cells in underacting muscles suggests that there is potential for successful upregulation of size in these muscles, as the cellular machinery for muscle repair and regeneration, the satellite cells, is retained and active in patients with medial rectus underaction. The decreased number of activated satellite cells in overacting MR muscle suggests that factors as yet unknown in these overacting muscles are able to affect the number of satellite cells and/or their responsiveness compared with normal age-matched control muscles. These hypotheses are currently being tested.

Analysis of the gutta-percha filled area in C-shaped mandibular molars obturated with a modified MicroSeal technique

To analyse the gutta-percha filled area of C-shaped molar teeth root filled with the modified MicroSeal technique with reference to the radiographic features and the C-shaped canal configuration. Twenty-three mandibular second molar teeth with C-shaped roots were classified according to their radiographic features as: type I - merging, type II - symmetrical and type III - asymmetrical. The canals were root filled using a modified technique of the MicroSeal system. Horizontal sections at intervals of 600 mu m were made 1 mm from the apex to the subpulpal floor level. The percentage of gutta-percha area from the apical, middle and coronal levels of the radiographic types was analysed using the Kruskal-Wallis test. Complementary analysis of the C-shaped canal configurations (C1, C2 and C3) determined from cross-sections from the apical third was performed in a similar way. No significant differences were found between the radiographic types in terms of the percentage of gutta-percha area at any level (P > 0.05): apical third, type I: 77.04%, II: 70.48% and III: 77.13%, middle third, type I: 95.72%, II: 93.17%, III: 91.13% and coronal level, type I: 98.30%, II: 98.25%, III: 97.14%. Overall, the percentage of the filling material was lower in the apical third (P < 0.05). No significant differences were found between the C-shaped canal configurations apically; C1: 72.64%, C2: 79.62%, C3: 73.51% (P > 0.05). The percentage of area filled with gutta-percha was similar in the three radiographic types and canal configuration categories of C-shaped molars. These results show the difficulty of achieving predictable filling of the root canal system when this anatomical variation exists. In general, the apical third was less completely filled.

Experimental Surgical and Orthodontic Extrusion of Teeth in Dogs

The purpose of this study was to evaluate histologically the root surfaces of teeth submitted to orthodontic and surgical extrusion procedures in a dog model. Eighteen adult male dogs, divided into six groups of three dogs each, were used in the study Each animal underwent two procedures: rapid orthodontic extrusion and surgical extrusion of the maxillary lateral incisors. The animals were sacrificed to produce samples at 7, 14, 45, 90, 120, and 180 days after surgery for assessment of cross sections of the coronal, medial, and apical thirds of the treated teeth. At early time points, some active surface and inflammatory resorption was observed exclusively in the surgical extrusion group; however, samples collected at later times demonstrated functional repair of the resorption gaps in both groups. Ankylosis was observed as a minor event and was apparently of a transient nature in samples of the surgical extrusion group. The results demonstrate the importance of maintaining the periodontal ligament and cementum surface; both are vital for the prevention of root resorption. It may be postulated that orthodontic extrusion is more conservative and physiologic than surgical extrusion; however the results showed that function was restored in both groups. (Int J Periodontics Restorative Dent 2009;29:435-443.)

Comparative Internal Structure of Dorsal Lips and Radiolar Appendages in Sabellidae (Polychaeta) and Phylogenetic Implications

Fan worms (Sabellidae) possess paired modified prostomial structures at the base of the radiolar crown, dorso-lateral to the mouth, called dorsal lips. The dorsal lips are involved in the sorting of particles collected by the radiolar crown. The range of variation in the morphology of dorsal lips is extensive, and probably this is not only due to adaptations to different environments and feeding preferences but also due to phylogenetic constraints. In this study, we describe and compare the morphology of dorsal lips in a range of sabellid taxa based on histological cross-sections of these structures, and compare our data and terminology with those of previous studies. Dorsal lips are maintained erect in most taxa by a modified radiole fused to them known as dorsal radiolar appendage. We suggest that dorsal radiolar appendages with an internal supporting axis (cellular or acellular) and probably also the ventral lips are synapomorphies of the family. J. Morphol. 272: 302-319, 2011. (C) 2010 Wiley-Liss, Inc.