Search results for "Lamb"
showing 10 items of 745 documents
Receptor identification and physiological characterisation of glucagon-like peptide-2 in the rat heart.
2010
Abstract Background and aims The anorexigenic glucagon-like peptide (GLP)-2 is produced by intestinal L cells and released in response to food intake. It affects intestinal function involving G-protein-coupled receptors. To verify whether GLP-2 acts as a cardiac modulator in mammals, we analysed, in the rat heart, the expression of GLP-2 receptors and the myocardial and coronary responses to GLP-2. Methods and results GLP-2 receptors were detected on ventricular extracts by quantitative real-time polymerase chain reaction (Q-RT-PCR) and Western blotting. Cardiac GLP-2 effects were analysed on Langendorff perfused hearts. Intracellular GLP-2 signalling was investigated on Langendorff perfuse…
Beyond Viner: Smoothed Cost Curves and Co-Detetermination of Output and Production Capacity
2017
We address two problems of traditional cost functions: the discontinuity caused by the production capacity (the marginal cost abruptly becomes infinite when production capacity is reached) and the production capacity is artificially exogenous. So, we introduce a smoothed form of marginal cost function. It progressively tends to infinity when it approaches to the production capacity. Then, we prove that it is perfectly possible to determine directly output, fixed costs and production capacity simultaneously, even if this could lead to a system of equations that is not so elementary to solve because it includes a Lambert function. We also show that the smoothed cost function prevails in both …
Klasiskas un robustas MANOVA analīzes metodes
2019
Daudzdimensiju dispersiju analīze (MANOVA) tiek pielietota situācijās, kad tiek mērīti vairāki mainīgie katrai eksperimentālai vienībai. Darbā aplūkota teorija par klasisko MANOVA metodi un robusto MANOVA metodi, to pieņēmumiem un pielietojumiem. Bieži datos tiek novēroti izlēcēji, kuri atšķiras no pārējiem datiem. Analizējot datus, šie izlēcēji var būtiski ietekmēt parametru novērtējumus, šādās situācijās ieteicams izmantot robustas statistikas metodes. Tika secināts, ka robustā MANOVA metode ne vienmēr dod precīzākus rezultātus par klasisko MANOVA metodi. Atslēgas vārdi: Daudzdimensiju analīze, MANOVA, robusta MANOVA, Vilksa Lambda statistika
Photo-acoustic excitation and optical detection of fundamental flexural guided wave in coated bone phantoms.
2013
Abstract Photo-acoustic (PA) imaging was combined with skeletal quantitative ultrasound (QUS) for assessment of human long bones. This approach permitted low-frequency excitation and detection of ultrasound so as to efficiently receive the thickness-sensitive fundamental flexural guided wave (FFGW) through a coating of soft tissue. The method was tested on seven axisymmetric bone phantoms, whose 1- to 5-mm wall thickness and 16-mm diameter mimicked those of the human radius. Phantoms were made of a composite material and coated with a 2.5- to 7.5-mm layer of soft material that mimicked soft tissue. Ultrasound was excited with a pulsed Nd:YAG laser at 1064-nm wavelength and received on the s…
Defect characterization in Al welded joints by non-contact Lamb wave technique
2006
Abstract The use of air-coupled sensors to detect flaws in Al welded joints and the advantage of Lamb wave for their characterization has been proved. Ultrasonic waves were generated by a pulsed laser and by contact angle-beam transducer, and received by an air-coupled capacitive transducer. Laser-based configuration was used to quickly locate the defect, whereas the angle-beam contact probe configuration to characterize it thanks to the dispersive behavior of Lamb waves. Guided waves allow inspection of the complete thickness with only one scan, permitting to detect and to size both internal and surface defects; their high flexibility in the measurement is due to the various parameters cha…
Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy
2016
International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…
Coded excitation speeds up the detection of the fundamental flexural guided wave in coated tubes
2016
The fundamental flexural guided wave (FFGW) permits ultrasonic assessment of the wall thickness of solid waveguides, such as tubes or, e.g., long cortical bones. Recently, an optical non-contact method was proposed for ultrasound excitation and detection with the aim of facilitating the FFGW reception by suppressing the interfering modes from the soft coating. This technique suffers from low SNR and requires iterative physical scanning across the source-receiver distance for 2D-FFT analysis. This means that SNR improvement achieved by temporal averaging becomes time-consuming (several minutes) which reduces the applicability of the technique, especially in time-critical applications such as…
TeO2 liquid phase: Viscosity measurements and evaluation of the thermal conductivity from crystal growth experiments
2008
Current applications of paratellurite TeO{sub 2} in optics and nuclear physics require improving the yield and optical quality of synthesized single crystals. Modelling of the growth process is a useful tool for such purpose, however, involving the knowledge of several thermodynamic parameters of both solid and liquid phase of the compound. This work describes the determination of two main unknown ones, namely dynamic viscosity {eta} and thermal conductivity {lambda}{sub l} of the liquid phase. Measurements of {eta} are performed by means of a specifically designed apparatus; over a 40 K temperature interval above the melting point we find a mean value of 0.028 Pa.s. This data is used in co…
Non-contact ultrasonic inspection of skin/core bond in honeycomb with lamb waves
2003
The assessment of skin/core bond in honeycomb samples was carried out by a bistatic ultrasonic non-contact system. Lamb waves were generated by a Nd:YAG pulsed laser and detected by an air-coupled capacitance transducer located in pitch-catch configuration. Periodically spaced line sources, generated on the sample surface using a four element lenticular array, allowed generation of narrow-band directional Lamb waves. Changes in amplitude of the transmitted signal permitted detection of skin/core disbonds.
Lattice-Matched GaN–InAlN Waveguides at $\lambda=1.55\ \mu$m Grown by Metal–Organic Vapor Phase Epitaxy
2008
We report on the demonstration of low-loss, single-mode GaN-InAlN ridge waveguides (WGs) at fiber-optics telecommunication wavelengths. The structure grown by metal-organic vapor phase epitaxy contains AlInN cladding layers lattice-matched to GaN. For slab-like WGs propagation losses are below 3 dB/mm and independent of light polarization. For 2.6-mum-wide WGs the propagation losses in the 1.5- to 1.58-mum spectral region are as low as 1.8 and 4.9 dB/mm for transverse-electric- and transverse-magnetic-polarization, respectively. The losses are attributed to the sidewall roughness and can be further reduced by the optimization of the etching process.