Application of orthogonality-relation for the separation of Lamb modes at a plate edge: numerical and experimental predictions.

In this study the orthogonality relation-based method for post-processing finite element (FE) predictions and experimental measurements is applied in order to separate Lamb modes at a plate edge at normal incidence. The scattered wave field from the free edge is assumed to be a superposition of all the eigenmodes of an infinite plate. The eigenmode amplitudes of the reflected wave field are determined by implementing the orthogonality-based method on the measured plate edge displacements. Overlapping wavepackets of Lamb modes at a plate edge are simulated by using the FE model and the experiment in the case of an incident S0 mode in a plate with a notch. In the experiment a 3D Scanning Laser Doppler Vibrometer (3D SLDV) (Johansmann and Sauer, 2005) is used to measure 3 dimensional vibrations and thus the edge two-dimensional displacement components simultaneously. It is demonstrated that it is possible to extract signals of various propagating and non-propagating modes in time-domain. The influences of the errors in practical measurements on the extraction procedure have also been studied.

Technology-driven dietary assessment: a software developer's perspective.

Dietary researchers need new software to improve nutrition data collection and analysis, although the creation of information technology is difficult. Software development projects may be unsuccessful as a result of an inadequate understanding of needs, management problems, technology barriers or legal hurdles. Cost over-runs and schedule delays are common. Barriers facing scientific researchers developing software include workflow, cost, schedule and team issues. Different methods of software development and the role that intellectual property rights play are discussed. A dietary researcher must carefully consider multiple issues to maximise the likelihood of success when creating new software.

Acoustic scattering from a finite plate: generation of guided Lamb waves S(0), A(0) and A.

In the domain of renewable energies, marine current turbines constitute one of the possibilities of producing electrical energy. Naked-eye inspection, or with the aid of video monitoring systems of these machines to ensure their perfect working order, can be difficult in a turbid environment. Acoustic methods are conceivable. The study focuses on the blades of these machines, by considering rectangular plates. The propagation of Lamb waves in a plate is studied by analyzing experimental time signals obtained from acoustic scattering. These signals are analyzed employing the ray theory. In vacuum, the flexural wave is the A(0) Lamb wave, whilst in water this wave splits in a bifurcation: the A wave with a phase velocity always smaller than the sound speed in water, and the A(0) wave with a phase velocity always higher than the sound speed in water. In the central bandpass of the transducers used in the experiments, mainly the A and S(0) waves exist. However, signals observed in the third harmonic bandpass of the transducers are also analyzed. In order to complement these results, resonance frequencies of the plate studied are calculated taking into account the boundary conditions and compared with the resonance frequencies of the experimental spectra.

Edge resonance in semi-infinite thick pipe: numerical predictions and measurements.

This paper presents theoretical and experimental studies of axisymmetric longitudinal guided wave L(0,2) interaction with the free edge of the pipe. A numerical method based on normal mode superposition is applied to predict the edge resonance by an analysis of dispersion relations of separate modes. In parallel, the finite element analysis and experimental measurements prove the existence of edge resonance in the pipe in case of L(0,2) wave incidence. It is shown that the edge resonance is mainly caused by the first pair of complex modes. Additionally the behavior of edge resonance phenomenon as a function of the curvature of the pipe is studied. The displacement amplitudes measured at the edge demonstrate that the edge resonance is affected by the frequency and thickness to midradius ratio of the pipe, and it is losing its strength in thicker pipes, as the growing difference between the outer and inner radii destroys symmetry. The reflected energy amplitudes show that at the resonance frequencies the incident wave is strongly converted to L(0,1) and L(0,3) modes, depending also on the curvature parameter of the pipe.

Prediction of the acoustic form function by neural network techniques for immersed tubes.

A new approach is used to predict the acoustic form function (FF) for an infinite length cylindrical shell excited perpendicularly to its axis using the artificial neural network (ANN) techniques. The Wigner-Ville distribution is used like a comparison tool between the FF calculated by the analytical method and that predicted by the ANN techniques for a stainless steel tube. During the development of the network, several configurations are evaluated for various radius ratios ba (a: outer radius: b: inner radius of the tube). The optimal model is a network with one hidden layer. It is able to predict the FF with a mean relative error about 1.61% for the cases studied in this paper.

Behavior of first guided wave on finite cylindrical shells of various lengths: experimental investigation.

Acoustic backscattering from elastic cylindrical shells of finite lengths, immersed in water, is investigated. These objects, characterized by the ratio of length over diameter (L/2a = 9.76, 4.88, 2.44, a: outer radius), are excited by an obliquely incident plane acoustic wave. In the three cases studied here, the radii ratio b/a (b: inner radius) is fixed at 0.97. The investigated dimensionless frequency range extends over 10 k1a < or = 50 (k1 : wave number in water). The first guided wave, T0, is of particular interest here. The influence of the shell's length on the backscattered pressure is experimentally observed in the time-angle and frequency-angle representations. In support of this experimental study, a time-domain representation is used by extending a theoretical model that provides a geometrical description of the helical propagation of the surface waves around the shell [Bao, J. Acoust. Soc. Am. 94, 1461-1466 (1993)]. Theoretical results on cylindrical shells considered as infinitely long, with identical characteristics, are compared with both experimental representations.

Coupled guided acoustic modes in water-filled thin-walled tubes.

Recent results [J. D. N. Cheeke et al., J. Acoust. Soc. Am. 104, 3678 (1998)] reported a 20% decrease in group velocity for flexural mode circumferential waves propagating around water-filled thin-walled stainless-steel tubes. In the present work, the full theory of such modes is developed to explain the structure modes which originates from the coupling between the water filler and stainless tube. Calculated values of the group velocity for the first two coupled modes are in excellent agreement with experiment. The results are of interest for the physics of acoustic waves in fluid-loaded structures and have potential application for liquid level detection.

Analysis of the acoustic scattering at variable incidences from an extra thin cylindrical shell bounded by hemispherical endcaps

Through an experimental approach, in this paper we investigate the acoustic wave scattering processes involved in the acoustic backscattering at variable incidences from an air-filled submerged cylindrical shell with hemispherical endcaps. Given the 1% shell thickness and the explored low frequency domain, the wave types studied are the circumferential or helical S0 wave and the helical T0 wave only. Between the axial (in the direction of the main axis of the object) and the normal incidences (normal to the main axis), two distinct angular zones can be observed depending on hemispherical or cylindrical excitation. In these zones, after a pressure wave excitation, different series of echoes on the echo wave forms are identified by their arrival times and related wave types. From results in the time domain and those obtained in the frequency domain, each acoustic response from the target corresponding to the two zones of excitation is compared with the acoustic response of canonical objects (spherical shell for axial excitation and tube for normal excitation). This analysis of the acoustic response from the target at various incidences, highlights the influence of both the endcaps and the finite length for a cylindrical shell on scattering. The study is intended to make a contribution to the knowledge of the identification of such geometrically complex objects.

Acoustic scattering from complex elastic shells: visualization of S0, A0 and A waves

Acoustic scattering phenomena from complex immersed elastic shells are studied by high-speed Schlieren visualization for spark-generated spherical quasi-Dirac excitations. The situations considered are air-filled cylindrical shells under normal insonification and air-filled cylindrical shells soldered at one end with a hemispherical endcap under axial and non-axial incidences. The results are compared with those provided by the Methode d'Isolement et d'Identification des Resonances (MIIR) method and corresponding analytical theoretical solutions. The combination of these complementary approaches better highlights some of the behaviors of the symmetric S0- and antisymmetric A0-Lamb waves, as well was the Scholte-Stoneley A-wave, on the considered targets. In particular, the influence of the internal solder inhomogeneities on the creation and/or the conversion of these modes is demonstrated.

Acoustic scattering from fluid-loaded stiffened cylindrical shell: analysis using elasticity theory

The acoustic scattering from a fluid-loaded stiffened cylindrical shell is described by using elasticity theory. The cylindrical shell is reinforced by a thin internal plate which is diametrically attached along the tube. In this model, cylindrical shell displacements and constraints expressed from elasticity theory are coupled to those of the plate at the junctions, where plate vibrations are described by using plate theory. The present model is first validated at low frequency range (k1a approximately 5-40) by comparison with a previous model based on the Timoshenko-Mindlin thin shell theory and by experimental results. Theoretical and experimental resonance spectra are then analyzed in a high frequency range (k1a approximately 120-200). Only resonances due to the S0 wave are clearly observed in this frequency range, and their modes of propagation are identified. Furthermore, A0 wave propagation is detected, because of the presence of the reflection of this wave at the shell-plate junctions.

Polymicrobial cholangitis and liver abscess in a patient with the acquired immunodeficiency syndrome.

Cholangitis/cholangiopathy associated with the human immunodeficiency virus (HIV) infection is characterized by chronic abdominal pain, low-grade fever, cholestasis, and sometimes areas of focal or diffuse dilatation of the bile ducts that may be apparent on noninvasive imaging studies. Although the etiology of this biliary disease may be multifactorial, it appears to be the result of immunosuppression and/or secondary opportunistic infections rather than a direct cytopathic effect of HIV itself. Various opportunistic pathogens, including cytomegalovirus, Cryptosporidium, Campylobacter fetus, and Candida albicans, have been implicated as causes of HIV-associated cholangitis. We report an unusual case of polymicrobial cholangitis and liver abscess in a patient with HIV infection.

Inflammatory pseudotumor of the liver and pregnancy.

Inflammatory pseudotumor of the liver (IPL) is a rare, nonneoplastic entity of unknown etiology. Our patient represents the first reported case of IPL that was managed conservatively during an intrauterine pregnancy.

Ultrasonic characterization of the quality of an epoxy resin polymerization.

This work concerns monitoring the polymerization of an epoxy resin and its hardener. An ultrasonic pulse echo technique was used to monitor the attenuation, the phase velocity, and the acoustic impedance of the resin as a function of time. The first two parameters give information about the average state of the hardening of the resin itself. The third parameter, acoustic impedance, indicates the state of the hardening of the resin at the interface with the vessel. These parameters are determined from spectral properties of echoes extracted from the experimental echo waveforms. Experiments were made for different proportions of hardener and allowed a determination of the best mixture (10% of hardener) that corresponds to the manufacturer's recommended value. Analysis of the results shows a progressive hardening from the center of the resin toward the walls of the vessel.

Intrusion phenomenon in combination tooth-implant restorations: a review of the literature.

STATEMENT OF PROBLEM: Controversy regarding the connection of implants to natural teeth in fixed partial dentures has emerged in response to clinical reports of intrusion of the natural teeth. Although theories have been proposed to explain this phenomenon, the cause of the intrusion remains unknown. Numerous longitudinal studies have demonstrated that teeth can be successfully connected to implants. The use of rigid connectors, or nonrigid connectors with the keyway on the implant, are described as mechanisms to prevent intrusion of the natural tooth. PURPOSE: This article reviews the literature that pertains to this subject and includes treatment modalities that may be helpful in preventing intrusion.

Treatment options for the radicular lingual groove: a review and discussion.

The radicular lingual groove (RLG) is a developmental anomaly in which an infolding of the inner enamel epithelium and Hertwig's epithelial root sheath create a groove that passes from the cingulum of maxillary incisors apically onto the root. Radicular lingual grooves can create periodontal and pulpal pathology, but they may be difficult to identify as an etiological factor. This article identifies the diagnostic and treatment modalities for the various forms of RLGs and describes the prognosis that can be anticipated with each treatment modality.

Age-dependent sensitization to oxidative stress by dietary fatty acids.

Experiments were designed to test the hypothesis that short-term feeding of a high polyunsaturated fatty acid (PUFA) diet would increase susceptibility to lipid peroxidation in an age-dependent manner. Young (6 month) and old (24 month) male B6C3F1 mice were fed modified AIN-76 diets containing either 5% corn oil (CO, N = 5 per age group) or 19% fish oil plus 1% corn oil (FO, N = 20 per age group) for two weeks. Five CO and five FO diet mice per age received an intraperitoneal injection of normal saline and were sacrificed one hour later; the remaining FO diet mice (N = 15 per age) were challenged with an acute systemic oxidative stress by intraperitoneal injection of 125 mg iron/kg body weight as iron dextran, and were sacrificed 1, 5, and 24 hours post-injection. Microsomal membrane fatty acid analysis revealed that increased age and a FO diet significantly increased membrane PUFA content. Serum iron levels increased significantly following iron treatment, peaking at 5 hours in both age groups. Formation of microsomal malondialdehyde (MDA), a product of lipid peroxidation, was significantly greater in the livers of the young mice. The temporal patterns of serum iron and microsomal MDA concentrations were significantly correlated in young mice, but not in old mice. Histochemical examination showed that liver iron accumulation following iron injection was similar in both age groups, but was associated with a significant temporal increase in liver apoptotic cells in young mice, but not in old mice. Thus, both age groups had similar iron exposure and iron accumulation, and the liver microsomal membranes of old mice were more unsaturated, yet there was significantly greater peroxidative damage (MDA formation) and cell death (apoptosis) in the young mouse livers. These findings suggest that the older animals have upregulated antioxidant defenses.

Properties of Sm 3 + ions in fluorozirconate fiber.

The spectroscopic properties of Sm3 + ions in fluorozirconate fiber are presented. We found that our results were not in full agreement with previous research on Sm3 +doped silica. We observed that the visible emission bands have a relative strength closer to unity, and we measured a fluorescence lifetime that is three times longer than previously reported. The implications of these findings on the role of Sm3 + in zirconium barium fluoride glass and on the operation of Sm3 + doped fiber devices are discussed.

Gingival fluid tetracycline release from bioerodible gels.

Intracrevicular antimicrobial therapy is consistent with the site-specific nature of periodontitis. Considerable research has focused on the use of nonresorbable fibers. However, a bioerodible system is desirable. The purpose of this study was to assess tetracycline release and safety following a single application of a syringable 35% tetracycline hydrochloride in a lactic-glycolic acid gel. 31 generally healthy adult volunteers (mean age = 59 years) were enrolled in and completed this randomized, double-blind eight day study. 2, 6-10 mm non-adjacent interproximal pockets that bled on pocket probing were chosen as experimental sites in each subject. I experimental site and the surrounding gingival crevice received small particle size tetracycline in gel while the other site received larger particle size tetracycline in gel. Gingival crevicular fluid (GCF) was collected prior to treatment and 15 min, 1, 2, 3, 4 and 8 days post-treatment. GCF tetracyline concentrations were determined by agar diffusion bioassay and GCF volume measurements. 61% and 71% of sites had > or = 100 micrograms/ml tetracycline 3 days following application of large (mean concentration = 430 +/- 92 micrograms/ml) and small particle gels (mean concentration = 418 +/- 70 micrograms/ml), respectively. 37% and 55% of sites had measurable tetracycline 8 days after placement of large (mean concentration = 86 +/- 31 micrograms/ml) and small particle gels (mean concentration = 293 +/- 79 micrograms/ml), respectively. The most common adverse event was "bitter taste" (10% of subjects). Based upon the reduction in probing depths and % of sites bleeding on probing at 8 days relative to pretreatment, and the absence of any serious adverse events, it is concluded that these bioerodible gels are safe, and since the bacteriostatic range for most putative periodontopathogens is in the 2-10 micrograms/ml range, the tetracycline levels observed at days 3 and 8 likely represent significant antimicrobial efficacy.

Inhibition of a fast inwardly rectifying potassium conductance by barbiturates.

Whole cell voltage clamp recordings were used to study the effects of two barbiturates, methohexital and pentobarbital, on inwardly rectifying K+ currents in the plasma membrane of a rat basophilic granulocyte cell line (RBL-1). Inwardly rectifying K+ currents are responsible for maintaining the resting membrane potential in a variety of cell types including skeletal and cardiac muscle, neurons, glia, blood cells, and endothelial cells. RBL-1 cells are unusual because the inward rectifier is the only apparent voltage-dependent current in these cells. Steps to command potentials between + 80 and -120 mV evoked only this strongly rectifying, rapidly developing current at membrane potentials more hyperpolarized than the reversal potential for K' ions. Extracellular Cs+ (10 mM) and Ba2+ (100 microM and 1 mM) blocked this current in a reversible and voltage-dependent manner. The voltage threshold for activation of the inwardly rectifying K+ current is dependent on the extracellular K+ concentration as predicted by the Nernst equation. Methohexital and pentobarbital reversibly inhibited the current in a concentration-dependent fashion with 50% inhibitory concentration (IC50) values of 145 microM and 218 microM respectively. The Hill slopes for both of these effects were approximately 1. The inhibition was not voltage dependent. These results indicate that fast inwardly rectifying K+ channels are potential molecular targets for barbiturates and could explain some of the diverse clinical effects of these drugs.