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Sample records for acoustoelastic lamb wave

  1. Investigating the thermally induced acoustoelastic effect in isotropic media with Lamb waves

    PubMed Central

    Dodson, Jacob C.; Inman, Daniel J.

    2014-01-01

    Elastic wave velocities in metallic structures are affected by variations in environmental conditions such as changing temperature. This paper extends the theory of acoustoelasticity by allowing thermally induced strains in unconstrained isotropic media, and it experimentally examines the velocity variation of Lamb waves in aluminum plates (AL-6061) due to isothermal temperature deviations. This paper presents both thermally induced acoustoelastic constants and thermally varying effective Young's modulus and Poisson's ratio which include the third order elastic material constants. The experimental thermal sensitivity of the phase velocity (∂vP/∂θ) for both the symmetric and antisymmetric modes are bounded by two theories, the acoustoelastic Lamb wave theory with thermo-acoustoelastic tensors and the thermoelastic Lamb wave theory using an effective thermo-acoustoelastic moduli. This paper shows the theoretical thermally induced acoustoelastic Lamb wave thermal sensitivity (∂vP/∂θ) is an upper bound approximation of the experimental thermal changes, but the acoustoelastic Lamb wave theory is not valid for predicting the antisymmetric (A0) phase velocity at low frequency-thickness values, <1.55 MHz mm for various temperatures. PMID:25373955

  2. Experimental study of the acoustoelastic Lamb wave in thin plates

    NASA Astrophysics Data System (ADS)

    Pei, Ning; Bond, Leonard J.

    2016-02-01

    Many factors can cause residual stresses in industry, like rolling, welding and coating. Residual stresses can have both benefits and shortcomings on components, so it is important to find the residual stresses out and enhance its benefits part and get rid of its harmful part. There are many methods for residual stresses detection and ultrasonic method turns out to be a good one for it is nondestructive, relative cheap and portable. The critically refracted longitudinal (LCR) wave is widely used for it is regarded most sensitive to stress and less sensitive to texture which can influence detection results. Ultrasonic methods for residual stresses detection are based on time of flight (TOF) measurement, but because the measurement should reach nanosecond to show stress change, there are many other factors that can influence TOF, like temperature, texture of the components and even the thickness of the couplant. So increasing the TOF's sensitivity to stress is very important. In this paper the relationships between velocity and frequency are studied experimentally[6] for different Lamb modes, under various stress loadings. The result shows that the sensitivity of different modes various a lot, the A1 mode is the most sensitivity, compared to S0, S1 and A0 modes; if the force is added to 100 MPa, the change stress of A1 mode can be as large to 80 m/s, which is about 10 times more sensitive than the traditional bulk wave. This makes it as a good choice for residual stress detection.

  3. Continuous waves probing in dynamic acoustoelastic testing

    NASA Astrophysics Data System (ADS)

    Scalerandi, M.; Gliozzi, A. S.; Ait Ouarabi, M.; Boubenider, F.

    2016-05-01

    Consolidated granular media display a peculiar nonlinear elastic behavior, which is normally analysed with dynamic ultrasonic testing exploiting the dependence on amplitude of different measurable quantities, such as the resonance frequency shift, the amount of harmonics generation, or the break of the superposition principle. However, dynamic testing allows measuring effects which are averaged over one (or more) cycles of the exciting perturbation. Dynamic acoustoelastic testing has been proposed to overcome this limitation and allow the determination of the real amplitude dependence of the modulus of the material. Here, we propose an implementation of the approach, in which the pulse probing waves are substituted by continuous waves. As a result, instead of measuring a time-of-flight as a function of the pump strain, we study the dependence of the resonance frequency on the strain amplitude, allowing to derive the same conclusions but with an easier to implement procedure.

  4. Ultrasonic Lamb wave tomography

    NASA Astrophysics Data System (ADS)

    Leonard, Kevin R.; Malyarenko, Eugene V.; Hinders, Mark K.

    2002-12-01

    Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our recent work using ultrasonic Lamb wave tomography to address this pressing NDE technology need. Lamb waves are ultrasonic guided waves, which allow large sections of aircraft structures to be rapidly inspected for structural flaws such as disbonds, corrosion and delaminations. Because the velocity of Lamb waves depends on thickness, for example, the travel times of the fundamental Lamb modes can be converted into a thickness map of the inspection region. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. Our work focuses on tomographic reconstruction to produce quantitative maps that can be easily interpreted by technicians or fed directly into structural integrity and lifetime prediction codes. Laboratory measurements discussed here demonstrate that Lamb wave tomography using a square perimeter array of transducers with algebraic reconstruction tomography is appropriate for detecting flaws in aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this paper.

  5. Dynamic acousto-elastic test using continuous probe wave and transient vibration to investigate material nonlinearity.

    PubMed

    Eiras, J N; Vu, Q A; Lott, M; Payá, J; Garnier, V; Payan, C

    2016-07-01

    This study demonstrates the feasibility of the dynamic acousto-elastic effect of a continuous high frequency wave for investigating the material nonlinearity upon transient vibration. The approach is demonstrated on a concrete sample measuring 15×15×60cm(3). Two ultrasonic transducers (emitter and receiver) are placed at its middle span. A continuous high frequency wave of 500kHz propagates through the material and is modulated with a hammer blow. The position of the hammer blow on the sample is configured to promote the first bending mode of vibration. The use of a continuous wave allows discrete time extraction of the nonlinear behavior by a short-time Fourier transform approach, through the simultaneous comparison of a reference non-modulated signal and an impact-modulated signal. The hammer blow results in phase shifts and variations of signal amplitude between reference and perturbed signals, which are driven by the resonant frequency of the sample. Finally, a comprehensive analysis of the relaxation mechanisms (modulus and attenuation recovery) is conducted to untangle the coupled fast and slow hysteretic effects. PMID:27018754

  6. Lamb Wave Tomography for Corrosion Mapping

    NASA Technical Reports Server (NTRS)

    Hinders, Mark K.; McKeon, James C. P.

    1999-01-01

    As the world-wide civil aviation fleet continues to age, methods for accurately predicting the presence of structural flaws-such as hidden corrosion-that compromise airworthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical-waveguide physics. Our work focuses on using a variety of different tomographic reconstruction techniques to graphically represent the Lamb wave data in images that can be easily interpreted by technicians. Because the velocity of Lamb waves depends on thickness, we can convert the travel times of the fundamental Lamb modes into a thickness map of the inspection region. In this paper we show results for the identification of single or multiple back-surface corrosion areas in typical aluminum aircraft skin structures.

  7. A discontinuous Galerkin method with a modified penalty flux for the propagation and scattering of acousto-elastic waves

    NASA Astrophysics Data System (ADS)

    Ye, Ruichao; de Hoop, Maarten V.; Petrovitch, Christopher L.; Pyrak-Nolte, Laura J.; Wilcox, Lucas C.

    2016-05-01

    We develop an approach for simulating acousto-elastic wave phenomena, including scattering from fluid-solid boundaries, where the solid is allowed to be anisotropic, with the discontinuous Galerkin method. We use a coupled first-order elastic strain-velocity, acoustic velocity-pressure formulation, and append penalty terms based on interior boundary continuity conditions to the numerical (central) flux so that the consistency condition holds for the discretized discontinuous Galerkin weak formulation. We incorporate the fluid-solid boundaries through these penalty terms and obtain a stable algorithm. Our approach avoids the diagonalization into polarized wave constituents such as in the approach based on solving elementwise Riemann problems.

  8. Efficient laser generation of Lamb waves.

    PubMed

    Huke, Philipp; Schröder, Martin; Hellmers, Sandra; Kalms, Michael; Bergmann, Ralf B

    2014-10-15

    We report about the efficient generation of Lamb waves for nondestructive testing (NDT) of carbon fiber reinforced plastics (CFRP) with spatially formed laser beams. Therefore we describe the successful introduction of a liquid crystal on silicon (LCoS)-based spatial light modulator (SLM) to create predetermined spatial laser light distributions for a flexible Lamb wave excitation. We investigate the influence of the formed beam profiles of the generation laser to the resulting Lamb wave. The further objective of the study is the close adaptation of the laser-generated guided waves to a specific testing situation and an optimized defect evaluation.

  9. Influence of acoustoelastic coefficient on wave time of flight in stress measurement in piezoelectric self-excited system

    NASA Astrophysics Data System (ADS)

    Kwaśniewki, Janusz; Dominik, Ireneusz; Lalik, Krzysztof; Holewa, Karolina

    2016-10-01

    This paper presents the Self-excited Acoustical System (SAS) in elastic construction stress change measurement. The system is based on the acoustical autoresonance phenomena and enables an indirect measurement of the construction effort level. The essence of the SAS system is to use a piezoelectric vibration emitter and a piezoelectric vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which are operating in a closed loop with a positive feedback. This causes the excitation of the system. The change of the velocity of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the stress change in the examined material. A variable, which determines the change of the acoustic wave velocity, is called an acoustoelastic coefficient β. Such a coefficient allows to determine the absolute stress value in the tested material.

  10. Lamb Wave Response of Fatigued Composite Samples

    NASA Technical Reports Server (NTRS)

    Seale, Michael; Smith, Barry T.; Prosser, William H.; Masters, John E.

    1994-01-01

    Composite materials are being more widely used today by aerospace, automotive, sports equipment, and a number of other commercial industries because of their advantages over conventional metals. Composites have a high strength-to-weight ratio and can be constructed to meet specific design needs. Composite structures are already in use in secondary parts of the Douglas MD-11 and are planned to be used in the new MD-12X. Plans also exist for their use in primary and secondary structures on the Boeing 777. Douglas proposed MD-XX may also incorporate composite materials into primary structures such as the wings and tail. Use of composites in these structures offers weight savings, corrosion resistance, and improved aerodynamics. Additionally, composites have been used to repair cracks in many B-1Bs where traditional repair techniques were not very effective. Plans have also been made to reinforce all of the remaining B-1s with composite materials. Verification of the structural integrity of composite components is needed to insure safe operation of these aerospace vehicles. One aspect of the use of these composites is their response to fatigue. To track this progression of fatigue in aerospace structures, a convenient method to nondestructively monitor this damage needs to be developed. Traditional NDE techniques used on metals are not easily adaptable to composites due to the inhomogeneous and anisotropic nature of these materials. Finding an effective means of nondestructively monitoring fatigue damage is extremely important to the safety and reliability of such structures. Lamb waves offer one method of evaluating these composite materials. As a material is fatigued, the modulus degrades. Since the Lamb wave velocity can be related to the modulus of the material, an effective tool can be developed to monitor fatigue damage in composites by measuring the velocity of these waves. In this work, preliminary studies have been conducted which monitor fatigue damage in

  11. Crack Detection with Lamb Wave Wavenumber Analysis

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Leckey, Cara; Rogge, Matt; Yu, Lingyu

    2013-01-01

    In this work, we present our study of Lamb wave crack detection using wavenumber analysis. The aim is to demonstrate the application of wavenumber analysis to 3D Lamb wave data to enable damage detection. The 3D wavefields (including vx, vy and vz components) in time-space domain contain a wealth of information regarding the propagating waves in a damaged plate. For crack detection, three wavenumber analysis techniques are used: (i) two dimensional Fourier transform (2D-FT) which can transform the time-space wavefield into frequency-wavenumber representation while losing the spatial information; (ii) short space 2D-FT which can obtain the frequency-wavenumber spectra at various spatial locations, resulting in a space-frequency-wavenumber representation; (iii) local wavenumber analysis which can provide the distribution of the effective wavenumbers at different locations. All of these concepts are demonstrated through a numerical simulation example of an aluminum plate with a crack. The 3D elastodynamic finite integration technique (EFIT) was used to obtain the 3D wavefields, of which the vz (out-of-plane) wave component is compared with the experimental measurement obtained from a scanning laser Doppler vibrometer (SLDV) for verification purposes. The experimental and simulated results are found to be in close agreement. The application of wavenumber analysis on 3D EFIT simulation data shows the effectiveness of the analysis for crack detection. Keywords: : Lamb wave, crack detection, wavenumber analysis, EFIT modeling

  12. Lamb Wave Assessment of Fiber Volume Fraction in Composites

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Smith, Barry T.; Prosser, W. H.; Zalameda, Joseph N.

    1998-01-01

    Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.

  13. Pump and probe waves in dynamic acousto-elasticity: Comprehensive description and comparison with nonlinear elastic theories

    NASA Astrophysics Data System (ADS)

    Rivière, J.; Renaud, G.; Guyer, R. A.; Johnson, P. A.

    2013-08-01

    Standard nonlinear ultrasonic methods such as wave frequency mixing or resonance based measurements allow one to extract average, bulk variations of modulus and attenuation versus strain level. In contrast, dynamic acousto-elasticity (DAE) provides the elastic behavior over the entire dynamic cycle including hysteresis and memory effects, detailing the full nonlinear behavior under tension and compression. In this work, we address experimental difficulties and apply new processing methods, illustrating them with a Berea sandstone sample. A projection procedure is used to analyze the complex nonlinear signatures and extract the harmonic content. Amplitude dependences of the harmonic content are compared with existing models. We show that a combination of classical and hysteretic nonlinear models capture most of the observed phenomena. Some differences between existing models and experimental data are highlighted, however. A progressive decrease of the power-law amplitude dependence is found for harmonics larger than the second and for strains larger than 10-6. This observation is related to the phenomenon of acoustic conditioning that brings the material to a metastable state for each new excitation amplitude. Analysis of the steady-state regime provides additional information regarding acoustic conditioning, i.e., a progressive decrease of the amplitude of odd harmonics during excitation time with a log(t)-dependence. This observation confirms that the harmonic content is affected by the conditioning. Experimental challenges addressed include the fact that the compressional mode used for DAE can be affected by bending/torsion modes: their influence is evaluated, and guidances are given to minimize effects.

  14. DETECTION OF DISBONDING IN GLARE COMPOSITES USING LAMB WAVE APPROACH

    SciTech Connect

    Huang Qiaojian; Balogun, Oluwaseyi; Yang Ningli; Regez, Brad; Krishnaswamy, Sridhar

    2010-02-22

    Lamb-waves can be used to detect disbonds in composite plates. In this work, a photoacoustic technique was first applied to measure the dispersive property of a GLAss-REinforced (GLARE) composite panel. The measured phase velocity dispersion curves are consistent with the theoretical calculation using the classical transfer matrix method for layered media. Based on the obtained properties, a finite element method (FEM) model was constructed to study the influence of a disbond void on the Lamb wave propagation in the GLARE plate. It is found that the displacement amplitudes of the A{sub o} mode Lamb wave decrease while its travel time increases as the disbond size increases.

  15. Coherent, data-driven Lamb wave localization under environmental variations

    NASA Astrophysics Data System (ADS)

    Harley, Joel B.; Liu, Chang; Oppenheim, Irving J.; Greve, David W.; Moura, José M. F.

    2015-03-01

    Lamb waves are powerful tools in nondestructive evaluation and structural health monitoring. Researchers use Lamb waves to detect and locate damage across large areas. To best utilize Lamb waves, they are analyzed through two processing steps: baseline subtraction and velocity calibration. Baseline subtraction removes background information from our data and velocity calibration tunes our algorithms. Yet, in many scenarios, these steps are challenging to implement. Baseline subtraction is challenging due to variable environmental conditions. Velocity calibration is challenging due to multi-modal and dispersive velocity behavior in Lamb waves. To address both challenges, we present two approaches that combine environmental compensation with self-calibrating localization. We discuss temperature compensation strategies based on the scale transform and singular value decomposition. We then integrate these with a localization framework known as data-driven matched field processing. We show these combined approaches to be effective in a variety of scenarios.

  16. Lamb wave propagation in negative Poisson's ratio composites

    NASA Astrophysics Data System (ADS)

    Remillat, Chrystel; Wilcox, Paul; Scarpa, Fabrizio

    2008-03-01

    Lamb wave propagation is evaluated for cross-ply laminate composites exhibiting through-the-thickness negative Poisson's ratio. The laminates are mechanically modeled using the Classical Laminate Theory, while the propagation of Lamb waves is investigated using a combination of semi analytical models and Finite Element time-stepping techniques. The auxetic laminates exhibit well spaced bending, shear and symmetric fundamental modes, while featuring normal stresses for A 0 mode 3 times lower than composite laminates with positive Poisson's ratio.

  17. Thermal sensitivity of Lamb waves for structural health monitoring applications.

    PubMed

    Dodson, J C; Inman, D J

    2013-03-01

    One of the drawbacks of the current Lamb wave structural health monitoring methods are the false positives due to changing environmental conditions such as temperature. To create an environmental insensitive damage detection scheme, the physics of thermal effects on Lamb waves must be understood. Dispersion and thermal sensitivity curves for an isotropic plate with thermal stress and thermally varying elastic modulus are presented. The thermal sensitivity of dispersion curves is analytically developed and validated by experimental measurements. The group velocity thermal sensitivity highlights temperature insensitive features at two critical frequencies. The thermal sensitivity gives us insight to how temperature affects Lamb wave speeds in different frequency ranges and will help those developing structural health monitoring algorithms.

  18. Propagation of time-reversed Lamb waves in bovine cortical bone in vitro.

    PubMed

    Lee, Kang Il; Yoon, Suk Wang

    2015-01-01

    The present study aims to investigate the propagation of time-reversed Lamb waves in bovine cortical bone in vitro. The time-reversed Lamb waves were successfully launched at 200 kHz in 18 bovine tibiae through a time reversal process of Lamb waves. The group velocities of the time-reversed Lamb waves in the bovine tibiae were measured using the axial transmission technique. They showed a significant correlation with the cortical thickness and tended to follow the theoretical group velocity of the lowest order antisymmetrical Lamb wave fairly well, consistent with the behavior of the slow guided wave in long cortical bones.

  19. Minimal model for spoof acoustoelastic surface states

    SciTech Connect

    Christensen, J. Willatzen, M.; Liang, Z.

    2014-12-15

    Similar to textured perfect electric conductors for electromagnetic waves sustaining artificial or spoof surface plasmons we present an equivalent phenomena for the case of sound. Aided by a minimal model that is able to capture the complex wave interaction of elastic cavity modes and airborne sound radiation in perfect rigid panels, we construct designer acoustoelastic surface waves that are entirely controlled by the geometrical environment. Comparisons to results obtained by full-wave simulations confirm the feasibility of the model and we demonstrate illustrative examples such as resonant transmissions and waveguiding to show a few examples of many where spoof elastic surface waves are useful.

  20. Amplitude-dependent Lamb wave dispersion in nonlinear plates.

    PubMed

    Packo, Pawel; Uhl, Tadeusz; Staszewski, Wieslaw J; Leamy, Michael J

    2016-08-01

    The paper presents a perturbation approach for calculating amplitude-dependent Lamb wave dispersion in nonlinear plates. Nonlinear dispersion relationships are derived in closed form using a hyperelastic stress-strain constitutive relationship, the Green-Lagrange strain measure, and the partial wave technique integrated with a Lindstedt-Poincaré perturbation approach. Solvability conditions are derived using an operator formalism with inner product projections applied against solutions to the adjoint problem. When applied to the first- and second-order problems, these solvability conditions lead to amplitude-dependent, nonlinear dispersion corrections for frequency as a function of wavenumber. Numerical simulations verify the predicted dispersion shifts for an example nonlinear plate. The analysis and identification of amplitude-dependent, nonlinear Lamb wave dispersion complements recent research focusing on higher harmonic generation and internally resonant waves, which require precise dispersion relationships for frequency-wavenumber matching. PMID:27586758

  1. Experimental study of ultrasonic beam sectors for energy conversion into Lamb waves and Rayleigh waves.

    PubMed

    Declercq, Nico Felicien

    2014-02-01

    When a bounded beam is incident on an immersed plate Lamb waves or Rayleigh waves can be generated. Because the amplitude of a bounded beam is not constant along its wave front, a specific beam profile is formed that influences the local efficiency of energy conversion of incident sound into Lamb waves or Rayleigh waves. Understanding this phenomenon is important for ultrasonic immersion experiments of objects because the quality of such experiments highly depends on the amount of energy transmitted into the object. This paper shows by means of experiments based on monochromatic Schlieren photography that the area within the bounded beam responsible for Lamb wave generation differs from that responsible for Rayleigh wave generation. Furthermore it provides experimental verification of an earlier numerical study concerning Rayleigh wave generation.

  2. Experimental observation of cumulative second-harmonic generation of lamb waves propagating in long bones.

    PubMed

    Zhang, Zhenggang; Liu, Dan; Deng, Mingxi; Ta, Dean; Wang, Weiqi

    2014-07-01

    The experimental observation of cumulative second-harmonic generation of fundamental Lamb waves in long bones is reported. Based on the modal expansion approach to waveguide excitation and the dispersion characteristics of Lamb waves in long bones, the mechanism underlying the generation and accumulation of second harmonics by propagation of the fundamental Lamb waves was investigated. An experimental setup was established to detect the second-harmonic signals of Lamb wave propagation in long bones in vitro. Through analysis of the group velocities of the received signals, the appropriate fundamental Lamb wave modes and the duration of the second-harmonic signals could be identified. The integrated amplitude of the time-domain second-harmonic signal was introduced and used to characterize the efficiency of second-harmonic generation by fundamental Lamb wave propagation. The results indicate that the second-harmonic signal generated by fundamental Lamb waves propagating in long bones can be observed clearly, and the effect was cumulative with propagation distance when the fundamental Lamb wave mode and the double-frequency Lamb wave mode had the same phase velocities. The present results may be important in the development of a new method to evaluate the status of long bones using the cumulative second harmonic of ultrasonic Lamb waves.

  3. Conversion of evanescent Lamb waves into propagating waves via a narrow aperture edge.

    PubMed

    Yan, Xiang; Yuan, Fuh-Gwo

    2015-06-01

    This paper presents a quantitative study of conversion of evanescent Lamb waves into propagating in isotropic plates. The conversion is substantiated by prescribing time-harmonic Lamb displacements/tractions through a narrow aperture at an edge of a semi-infinite plate. Complex-valued dispersion and group velocity curves are employed to characterize the conversion process. The amplitude coefficient of the propagating Lamb modes converted from evanescent is quantified based on the complex reciprocity theorem via a finite element analysis. The power flow generated into the plate can be separated into radiative and reactive parts made on the basis of propagating and evanescent Lamb waves, where propagating Lamb waves are theoretically proved to radiate pure real power flow, and evanescent Lamb waves carry reactive pure imaginary power flow. The propagating power conversion efficiency is then defined to quantitatively describe the conversion. The conversion efficiency is strongly frequency dependent and can be significant. With the converted propagating waves from evanescent, sensors at far-field can recapture some localized damage information that is generally possessed in evanescent waves and may have potential application in structural health monitoring.

  4. Experimental and theoretical study of Rayleigh-Lamb wave propagation

    NASA Technical Reports Server (NTRS)

    Rogers, Wayne P.; Datta, Subhendu K.; Ju, T. H.

    1990-01-01

    Many space structures, such as the Space Station Freedom, contain critical thin-walled components. The structural integrity of thin-walled plates and shells can be monitored effectively using acoustic emission and ultrasonic testing in the Rayleigh-Lamb wave frequency range. A new PVDF piezoelectric sensor has been developed that is well suited to remote, inservice nondestructive evaluation of space structures. In the present study the new sensor was used to investigate Rayleigh-Lamb wave propagation in a plate. The experimental apparatus consisted of a glass plate (2.3 m x 25.4 mm x 5.6 mm) with PVDF sensor (3 mm diam.) mounted at various positions along its length. A steel ball impact served as a simulated acoustic emission source, producing surface waves, shear waves and longitudinal waves with dominant frequencies between 1 kHz and 200 kHz. The experimental time domain wave-forms were compared with theoretical predictions of the wave propagation in the plate. The model uses an analytical solution for the Green's function and the measured response at a single position to predict response at any other position in the plate. Close agreement was found between the experimental and theoretical results.

  5. Acoustoelastic constants in dilute two-phase alloys

    NASA Technical Reports Server (NTRS)

    Salama, K.; Schneider, E.; Chu, S. L.

    1986-01-01

    Acoustoelastic constants are calculated for two-phase alloys containing dilute concentrations of precipitates in a solid-solution matrix, on the basis of a model in which the precipitates are represented as a dilute elastic suspension of spherical particle inclusions in an infinite matrix. The longitudinal propagation velocity in the alloy is thereby obtained in terms of the precipitates' concentration and the elastic moduli of the two phases. Results are presented which indicate that the acoustoelastic constant of longitudinal waves in a dilute two-phase alloy varies linearly with the concentration of second-phase precipitates, in agreement with recent measurements in aluminum and steel alloys where the acoustoelastic constants changed linearly with the second phase's volume fraction.

  6. Detecting Lamb waves with broad-band acousto-ultrasonic signals in composite structures

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.

    1992-01-01

    Lamb waves can be produced and detected in ceramic matrix composites (CMC) and metal matrix composites (MMC) plates using the acousto-ultrasonic configuration employing broadband transducers. Experimental dispersion curves of lowest symmetric and antisymmetric modes behave in a manner analogous to the graphite/polymer theoretical curves. In this study a basis has been established for analyzing Lamb wave velocities for characterizing composite plates. Lamb wave dispersion curves and group velocities were correlated with variations in axial stiffness and shear stiffness in MMC and CMC. For CMC, interfacial shear strength was also correlated with the first antisymmetric Lamb mode.

  7. Temperature effects in ultrasonic Lamb wave structural health monitoring systems.

    PubMed

    Lanza di Scalea, Francesco; Salamone, Salvatore

    2008-07-01

    There is a need to better understand the effect of temperature changes on the response of ultrasonic guided-wave pitch-catch systems used for structural health monitoring. A model is proposed to account for all relevant temperature-dependent parameters of a pitch-catch system on an isotropic plate, including the actuator-plate and plate-sensor interactions through shear-lag behavior, the piezoelectric and dielectric permittivity properties of the transducers, and the Lamb wave dispersion properties of the substrate plate. The model is used to predict the S(0) and A(0) response spectra in aluminum plates for the temperature range of -40-+60 degrees C, which accounts for normal aircraft operations. The transducers examined are monolithic PZT-5A [PZT denotes Pb(Zr-Ti)O3] patches and flexible macrofiber composite type P1 patches. The study shows substantial changes in Lamb wave amplitude response caused solely by temperature excursions. It is also shown that, for the transducers considered, the response amplitude changes follow two opposite trends below and above ambient temperature (20 degrees C), respectively. These results can provide a basis for the compensation of temperature effects in guided-wave damage detection systems.

  8. Temperature effects in ultrasonic Lamb wave structural health monitoring systems.

    PubMed

    Lanza di Scalea, Francesco; Salamone, Salvatore

    2008-07-01

    There is a need to better understand the effect of temperature changes on the response of ultrasonic guided-wave pitch-catch systems used for structural health monitoring. A model is proposed to account for all relevant temperature-dependent parameters of a pitch-catch system on an isotropic plate, including the actuator-plate and plate-sensor interactions through shear-lag behavior, the piezoelectric and dielectric permittivity properties of the transducers, and the Lamb wave dispersion properties of the substrate plate. The model is used to predict the S(0) and A(0) response spectra in aluminum plates for the temperature range of -40-+60 degrees C, which accounts for normal aircraft operations. The transducers examined are monolithic PZT-5A [PZT denotes Pb(Zr-Ti)O3] patches and flexible macrofiber composite type P1 patches. The study shows substantial changes in Lamb wave amplitude response caused solely by temperature excursions. It is also shown that, for the transducers considered, the response amplitude changes follow two opposite trends below and above ambient temperature (20 degrees C), respectively. These results can provide a basis for the compensation of temperature effects in guided-wave damage detection systems. PMID:18646963

  9. Multi-stage temperature compensation method for Lamb wave measurements

    NASA Astrophysics Data System (ADS)

    Dworakowski, Ziemowit; Ambrozinski, Lukasz; Stepinski, Tadeusz

    2016-11-01

    One of the important issues related to the applications of Lamb waves for structural health monitoring is their undesired sensitivity to variation of environmental conditions. Temperature is the main factor that can affect wave propagation and hence significantly reduce performance of a SHM system. Therefore, there is a need for development of robust monitoring methods with low sensitivity to temperature variations. This paper is aimed at verification of efficiency of four methods designed for damage detection using Lamb wave measurements performed in variable environmental conditions. The methods investigated in the comparison are the following: optimal baseline selection approach, the damage index based on a signal alignment with respect to instantaneous phase, and a group measurement approach capable of distinguishing local damage-related changes from temperature-induced global ones. The fourth method relies on fusion all these solutions simultaneously. The methods' ability to damage detection is compared using a specimen that is subjected to large temperature changes. It is found that although all the methods have their strengths and weaknesses, a cooperation of all solutions allows for significant increase of the damage detection efficiency.

  10. Pulse energy evolution for high-resolution Lamb wave inspection

    NASA Astrophysics Data System (ADS)

    Hua, Jiadong; Lin, Jing; Zeng, Liang; Gao, Fei

    2015-06-01

    Generally, tone burst excitation methods are used to reduce the effect of dispersion in Lamb wave inspection. In addition, algorithms for dispersion compensation are required to simplify responses, especially in long-range inspection. However, the resolution is always limited by the time duration of tone burst excitation. A pulse energy evolution method is established to overcome this limitation. In this method, a broadband signal with a long time (e.g. a chirp, white noise signal, or a pseudo-random sequence) is used as excitation to actuate Lamb waves. First of all, pulse compression is employed to estimate system impulse response with a high signal-to-noise ratio. Then, dispersion compensation is applied repeatedly with systemically varied compensation distances, obtaining a series of compensated signals. In these signals, amplitude (or energy) evolution associated with the change of compensation distance is utilized to estimate the actual propagation distance of the interested wave packet. Finally, the defect position is detected by an imaging algorithm. Several experiments are given to validate the proposed method.

  11. Experimental study of A0 Lamb wave tomography

    NASA Astrophysics Data System (ADS)

    Seher, Matthias; Huthwaite, Peter; Lowe, Michael; Cawley, Peter

    2015-03-01

    Corrosion damage in inaccessible regions presents a significant challenge to the petrochemical industry, and determining the remaining wall thickness is important to establish the remaining service life. Guided wave tomography is one solution and involves transmitting Lamb waves through the area of interest and using the received signals to reconstruct the remaining wall thickness. This avoids the need to access all points on the surface, making the technique well suited to inspection beneath supports. For this purpose a tomography system for pipe inspections is developed using low frequency A0 Lamb waves that are excited and detected with two arrays of electromagnetic acoustic transducers (EMATs). Two different defect depths are considered with different contrasts relative to the nominal wall thickness and in a first step, the repeatability of the measurements is demonstrated. Due to the limited view array configuration, the maximum depth of the reconstruction underestimates the true depth. In a second experimental study, the influence of a pipe clamp on the thickness reconstruction is considered, representing an inspection problem with restricted access. Preliminary results have shown that the maximum defect depth is further underestimated when compared to the thickness reconstructions without the clamp. However, it is possible to detect the defect underneath the clamp for all conducted experiments.

  12. Experimental study of A0 Lamb wave tomography

    SciTech Connect

    Seher, Matthias Huthwaite, Peter Lowe, Michael Cawley, Peter

    2015-03-31

    Corrosion damage in inaccessible regions presents a significant challenge to the petrochemical industry, and determining the remaining wall thickness is important to establish the remaining service life. Guided wave tomography is one solution and involves transmitting Lamb waves through the area of interest and using the received signals to reconstruct the remaining wall thickness. This avoids the need to access all points on the surface, making the technique well suited to inspection beneath supports. For this purpose a tomography system for pipe inspections is developed using low frequency A0 Lamb waves that are excited and detected with two arrays of electromagnetic acoustic transducers (EMATs). Two different defect depths are considered with different contrasts relative to the nominal wall thickness and in a first step, the repeatability of the measurements is demonstrated. Due to the limited view array configuration, the maximum depth of the reconstruction underestimates the true depth. In a second experimental study, the influence of a pipe clamp on the thickness reconstruction is considered, representing an inspection problem with restricted access. Preliminary results have shown that the maximum defect depth is further underestimated when compared to the thickness reconstructions without the clamp. However, it is possible to detect the defect underneath the clamp for all conducted experiments.

  13. Numerical and experimental investigation of nonlinear ultrasonic Lamb waves at low frequency

    NASA Astrophysics Data System (ADS)

    Zuo, Peng; Zhou, Yu; Fan, Zheng

    2016-07-01

    Nonlinear ultrasonic Lamb waves are popular to characterize the nonlinearity of materials. However, the widely used nonlinear Lamb mode suffers from two associated complications: inherent dispersive and multimode natures. To overcome these, the symmetric Lamb mode (S0) at low frequency region is explored. At the low frequency region, the S0 mode is little dispersive and easy to generate. However, the secondary mode still exists, and increases linearly for significant distance. Numerical simulations and experiments are used to validate the nonlinear features and therefore demonstrate an easy alternative for nonlinear Lamb wave applications.

  14. A rapid, fully non-contact, hybrid system for generating Lamb wave dispersion curves.

    PubMed

    Harb, M S; Yuan, F G

    2015-08-01

    A rapid, fully non-contact, hybrid system which encompasses an air-coupled transducer (ACT) and a laser Doppler vibrometer (LDV) is presented for profiling A0 Lamb wave dispersion of an isotropic aluminum plate. The ACT generates ultrasonic pressure incident upon the surface of the plate. The pressure waves are partially refracted into the plate. The LDV is employed to measure the out-of-plane velocity of the excited Lamb wave mode at some distances where the Lamb waves are formed in the plate. The influence of the ACT angle of incidence on Lamb wave excitation is investigated and Snell's law is used to directly compute Lamb wave dispersion curves including phase and group velocity dispersion curves in aluminum plates from incident angles found to generate optimal A0 Lamb wave mode. The measured curves are compared to results obtained from a two-dimensional (2-D) Fast Fourier transform (FFT), Morlet wavelet transform (MWT) and theoretical predictions. It was concluded that the experimental results obtained using Snell's law concept are well in accordance with the theoretical solutions. The high degree of accuracy in the measured data with the theoretical results proved a high sensitivity of the air-coupled and laser ultrasound in characterizing Lamb wave dispersion in plate-like structures. The proposed non-contact hybrid system can effectively characterize the dispersive relation without knowledge of neither the materials characteristics nor the mathematical model.

  15. Fan beam and double crosshole Lamb wave tomography for mapping flaws in aging aircraft structures.

    PubMed

    Malyarenko, E V; Hinders, M K

    2000-10-01

    As the worldwide aviation fleet continues to age, methods for accurately predicting the presence of structural flaws-such as hidden corrosion and disbonds-that compromise airworthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. The work summarized here focuses on a variety of different tomographic reconstruction techniques to graphically represent the Lamb wave data in quantitative maps that can be easily interpreted by technicians. Because the velocity of Lamb waves depends on thickness, for example, the traveltimes of the fundamental Lamb modes can be converted into a thickness map of the inspection region. This article describes two potentially practical implementations of Lamb wave tomographic imaging techniques that can be optimized for in-the-field testing of large-area aircraft structures. Laboratory measurements discussed here demonstrate that Lamb wave tomography using either a ring of transducers with fan beam reconstructions, or a square array of transducers with algebraic reconstruction tomography, is appropriate for detecting flaws in multilayer aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this article.

  16. Sensitivity of contact-free fiber Bragg grating sensor to ultrasonic Lamb wave

    NASA Astrophysics Data System (ADS)

    Wee, Junghyun; Hackney, Drew; Peters, Kara; Wells, Brian; Bradford, Philip

    2016-04-01

    Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring (SHM) systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves requires a high signal-to-noise ratio because Lamb waves have a low amplitude. This paper investigates the signal transfer between Lamb waves propagating in an aluminum plate collected by an optical fiber containing a FBG. The fiber is bonded to the plate at locations away from the FBG. The Lamb waves are converted into longitudinal and flexural traveling waves propagating along the optical fiber, which are then transmitted to the Bragg grating. The signal wave amplitude is measured for different distances between the bond location and the Bragg grating. Bonding the optical fiber away from the FBG location and closer to the signal source produces a significant increase in signal amplitude, here measured to be 5.1 times that of bonding the Bragg grating itself. The arrival time of the different measured wave coupling paths are also calculated theoretically, verifying the source of the measured signals. The effect of the bond length to Lamb wavelength ratio is investigated, showing a peak response as the bond length is reduced compared to the wavelength. This study demonstrates that coupling Lamb waves into guided traveling waves in an optical fiber away from the FBG increases the signal-to-noise ratio of Lamb wave detection, as compared to direct transfer of the Lamb wave to the optical fiber at the location of the FBG.

  17. A frequency selective acoustic transducer for directional Lamb wave sensing.

    PubMed

    Senesi, Matteo; Ruzzene, Massimo

    2011-10-01

    A frequency selective acoustic transducer (FSAT) is proposed for directional sensing of guided waves. The considered FSAT design is characterized by a spiral configuration in wavenumber domain, which leads to a spatial arrangement of the sensing material producing output signals whose dominant frequency component is uniquely associated with the direction of incoming waves. The resulting spiral FSAT can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. The analytical expression of the shape of the spiral FSAT is obtained through the theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. Testing is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The discrete array approximates the continuous spiral FSAT geometry, and provides the flexibility to test several configurations. The experimental results demonstrate the strong frequency dependent directionality of the spiral FSAT and suggest its application for frequency selective acoustic sensors, to be employed for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health. PMID:21973344

  18. ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. II. LAMB, SURFACE, AND CENTRIFUGAL WAVES

    SciTech Connect

    Peralta, J.; López-Valverde, M. A.; Imamura, T.; Read, P. L.; Luz, D.; Piccialli, A.

    2014-07-01

    This paper is the second in a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases where the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this second part, we study the waves' solutions when several atmospheric approximations are applied: Lamb, surface, and centrifugal waves. Lamb and surface waves are found to be quite similar to those in a geostrophic regime. By contrast, centrifugal waves turn out to be a special case of Rossby waves that arise in atmospheres in cyclostrophic balance. Finally, we use our results to identify the nature of the waves behind atmospheric periodicities found in polar and lower latitudes of Venus's atmosphere.

  19. Dispersion of Lamb waves in a honeycomb composite sandwich panel.

    PubMed

    Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

    2015-02-01

    Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems. PMID:25287973

  20. Electromagnetomechanical elastodynamic model for Lamb wave damage quantification in composites

    NASA Astrophysics Data System (ADS)

    Borkowski, Luke; Chattopadhyay, Aditi

    2014-03-01

    Physics-based wave propagation computational models play a key role in structural health monitoring (SHM) and the development of improved damage quantification methodologies. Guided waves (GWs), such as Lamb waves, provide the capability to monitor large plate-like aerospace structures with limited actuators and sensors and are sensitive to small scale damage; however due to the complex nature of GWs, accurate and efficient computation tools are necessary to investigate the mechanisms responsible for dispersion, coupling, and interaction with damage. In this paper, the local interaction simulation approach (LISA) coupled with the sharp interface model (SIM) solution methodology is used to solve the fully coupled electro-magneto-mechanical elastodynamic equations for the piezoelectric and piezomagnetic actuation and sensing of GWs in fiber reinforced composite material systems. The final framework provides the full three-dimensional displacement as well as electrical and magnetic potential fields for arbitrary plate and transducer geometries and excitation waveform and frequency. The model is validated experimentally and proven computationally efficient for a laminated composite plate. Studies are performed with surface bonded piezoelectric and embedded piezomagnetic sensors to gain insight into the physics of experimental techniques used for SHM. The symmetric collocation of piezoelectric actuators is modeled to demonstrate mode suppression in laminated composites for the purpose of damage detection. The effect of delamination and damage (i.e., matrix cracking) on the GW propagation is demonstrated and quantified. The developed model provides a valuable tool for the improvement of SHM techniques due to its proven accuracy and computational efficiency.

  1. Dispersion of Lamb waves in a honeycomb composite sandwich panel.

    PubMed

    Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

    2015-02-01

    Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems.

  2. Improved ultrasonic TV images achieved by use of Lamb-wave orientation technique

    NASA Technical Reports Server (NTRS)

    Berger, H.

    1967-01-01

    Lamb-wave sample orientation technique minimizes the interference from standing waves in continuous wave ultrasonic television imaging techniques used with thin metallic samples. The sample under investigation is oriented such that the wave incident upon it is not normal, but slightly angled.

  3. Optimization design of a Lamb wave device for density sensing of nonviscous liquid.

    PubMed

    Chen, Zhijun; Li, Lianger; Shi, Wenkang; Guo, Huawei

    2007-10-01

    A Lamb wave device composed of a piezoelectric plate loaded with a nonviscous liquid layer is presented. The relation between the Lamb wave phase velocity and the liquid density can be used for liquid density sensing. In this paper, utilizing the partial wave theory, the concept of effective permittivity is introduced to analyze the Lamb wave's excitation and the phase velocity calculation under a certain liquid density. The interface between the Lamb wave device and the liquid layer is metallized to eliminate the influence of liquid electrical properties when sensing liquid density. Based on the theory model, the phase difference measurement method is adopted to study the device's sensitivity to liquid density. In order to achieve high sensitivity to liquid density with sufficient excitation efficiency of Lamb wave, the optimal parameters of the Lamb wave device including plate thickness and cut orientation are obtained by numerical calculation. The experimental results are found to be in agreement with the theoretical simulations, verifying the validity of the theory model and the practicability of the optimization design.

  4. Evaluation of an acoustic black hole’s structural characteristics using laser-generated Lamb waves

    NASA Astrophysics Data System (ADS)

    Yan, Shi-Ling; Lomonosov, A. M.; Shen, Zhong-Hua

    2016-02-01

    The interaction of laser-generated Lamb waves propagating in a thin aluminum plate with a two-dimensional (2D) acoustic black hole was studied experimentally and theoretically. The decrease in phase velocity due to the gradual decrease in thickness was validated. The focusing function of the structure was also studied in this work. Experiments were performed using a vibrometer. A scanning laser line source technique was used to generate a series of Lamb wave waveforms to obtain the dispersion spectrum through the 2D fast Fourier transform method. Using this method, the effect of structure on Lamb modes was studied.

  5. Simple Dispersion Equation Based on Lamb-Wave Model for Propagating Pulsive Waves in Human Heart Wall

    NASA Astrophysics Data System (ADS)

    Bekki, Naoaki; Shintani, Seine A.

    2015-12-01

    We consider the Rayleigh-Lamb-type equation for propagating pulsive waves excited by aortic-valve closure at end-systole in the human heart wall. We theoretically investigate the transcendental dispersion equation of pulsive waves for the asymmetrical zero-order mode of the Lamb wave. We analytically find a simple dispersion equation with a universal constant for a small Lamb wavenumber. We show that the simple dispersion equation can qualitatively explain the myocardial noninvasive measurements in vivo of pulsive waves in the human heart wall. We can also consistently estimate the viscoelastic constant of the myocardium in the human heart wall using the simple dispersion equation for a small Lamb wavenumber instead of using a complex nonlinear optimization.

  6. Negative reflection of Lamb waves at a free edge: Tunable focusing and mimicking phase conjugation.

    PubMed

    Gérardin, Benoît; Laurent, Jérôme; Prada, Claire; Aubry, Alexandre

    2016-07-01

    The paper studies the interaction of Lamb waves with the free edge of a plate. The reflection coefficients of a Lamb mode at a plate free edge are calculated using a semi-analytical method, as a function of frequency and angle of incidence. The conversion between forward and backward Lamb modes is thoroughly investigated. It is shown that at the zero-group velocity (ZGV) frequency, the forward S1 Lamb mode fully converts into the backward S2b Lamb mode at normal incidence. Besides, this conversion is very efficient over most of the angular spectrum and remains dominant at frequencies just above the ZGV-point. This effect is observed experimentally on a Duralumin plate. First, the S1 Lamb mode is selectively generated using a transducer array, second the S2b mode is excited using a single circular transducer. The normal displacement field is probed with an interferometer. The free edge is shown to retro-focus the incident wave at different depths depending on the wave number mismatch between the forward and backward propagating modes. In the vicinity of the ZGV-point, wave numbers coincide and the wave is retro-reflected on the source. In this frequency range, the free edge acts as a perfect phase conjugating mirror. PMID:27475181

  7. Negative reflection of Lamb waves at a free edge: Tunable focusing and mimicking phase conjugation

    NASA Astrophysics Data System (ADS)

    Gérardin, Benoît; Laurent, Jérôme; Prada, Claire; Aubry, Alexandre

    2016-07-01

    The paper studies the interaction of Lamb waves with the free edge of a plate. The reflection coefficients of a Lamb mode at a plate free edge are calculated using a semi-analytical method, as a function of frequency and angle of incidence. The conversion between forward and backward Lamb modes is thoroughly investigated. It is shown that, at the zero-group velocity (ZGV) frequency, the forward $S_1$ Lamb mode fully converts into the backward $S_{2b}$ Lamb mode at normal incidence. Besides, this conversion is very efficient over most of the angular spectrum and remains dominant at frequencies just above the ZGV-point. This effect is observed experimentally on a Duralumin plate. Firstly, the $S_1$ Lamb mode is selectively generated using a transducer array, secondly the $S_{2b}$ mode is excited using a single circular transducer. The normal displacement field is probed with an interferometer. The free edge is shown to retro-focus the incident wave at different depths depending on the wave number mismatch between the forward and backward propagating modes. In the vicinity of the ZGV-point, wave numbers coincide and the wave is retro-reflected on the source. In this frequency range, the free edge acts as a perfect phase conjugating mirror.

  8. Sparse recovery of the multimodal and dispersive characteristics of Lamb waves.

    PubMed

    Harley, Joel B; Moura, José M F

    2013-05-01

    Guided waves in plates, known as Lamb waves, are characterized by complex, multimodal, and frequency dispersive wave propagation, which distort signals and make their analysis difficult. Estimating these multimodal and dispersive characteristics from experimental data becomes a difficult, underdetermined inverse problem. To accurately and robustly recover these multimodal and dispersive properties, this paper presents a methodology referred to as sparse wavenumber analysis based on sparse recovery methods. By utilizing a general model for Lamb waves, waves propagating in a plate structure, and robust l1 optimization strategies, sparse wavenumber analysis accurately recovers the Lamb wave's frequency-wavenumber representation with a limited number of surface mounted transducers. This is demonstrated with both simulated and experimental data in the presence of multipath reflections. With accurate frequency-wavenumber representations, sparse wavenumber synthesis is then used to accurately remove multipath interference in each measurement and predict the responses between arbitrary points on a plate.

  9. Increasing signal amplitude in fiber Bragg grating detection of Lamb waves using remote bonding.

    PubMed

    Wee, Junghyun; Wells, Brian; Hackney, Drew; Bradford, Philip; Peters, Kara

    2016-07-20

    Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves using FBG sensors requires a high signal-to-noise ratio because the Lamb waves are of low amplitudes. This paper compares the signal transfer amplitudes between two adhesive mounting configurations for an FBG to detect Lamb waves propagating in an aluminum plate: a directly bonded FBG and a remotely bonded FBG. In the directly bonded FBG case, the Lamb waves create in-plane and out-of-plane displacements, which are transferred through the adhesive bond and detected by the FBG sensor. In the remotely bonded FBG case, the Lamb waves are converted into longitudinal and flexural traveling waves in the optical fiber at the adhesive bond, which propagate through the optical fiber and are detected by the FBG sensor. A theoretical prediction of overall signal attenuation also is performed, which is the combination of material attenuation in the plate and optical fiber and attenuation due to wave spreading in the plate. The experimental results demonstrate that remote bonding of the FBG significantly increases the signal amplitude measured by the FBG.

  10. Increasing signal amplitude in fiber Bragg grating detection of Lamb waves using remote bonding.

    PubMed

    Wee, Junghyun; Wells, Brian; Hackney, Drew; Bradford, Philip; Peters, Kara

    2016-07-20

    Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves using FBG sensors requires a high signal-to-noise ratio because the Lamb waves are of low amplitudes. This paper compares the signal transfer amplitudes between two adhesive mounting configurations for an FBG to detect Lamb waves propagating in an aluminum plate: a directly bonded FBG and a remotely bonded FBG. In the directly bonded FBG case, the Lamb waves create in-plane and out-of-plane displacements, which are transferred through the adhesive bond and detected by the FBG sensor. In the remotely bonded FBG case, the Lamb waves are converted into longitudinal and flexural traveling waves in the optical fiber at the adhesive bond, which propagate through the optical fiber and are detected by the FBG sensor. A theoretical prediction of overall signal attenuation also is performed, which is the combination of material attenuation in the plate and optical fiber and attenuation due to wave spreading in the plate. The experimental results demonstrate that remote bonding of the FBG significantly increases the signal amplitude measured by the FBG. PMID:27463905

  11. Wireless system for structural health monitoring based on Lamb waves

    NASA Astrophysics Data System (ADS)

    Lieske, U.; Dietrich, A.; Schubert, L.; Frankenstein, B.

    2012-04-01

    Structural health monitoring systems are increasingly used for comprehensive fatigue tests and surveillance of large scale structures. In this paper we describe the development and validation of a wireless system for SHM application based on Lamb-waves. The system is based on a wireless sensor network and focuses especially on low power measurement, signal processing and communication. The sensor nodes were realized by compact, sensor near signal processing structures containing components for analog preprocessing of acoustic signals, their digitization and network communication. The core component is a digital microprocessor ARM Cortex-M3 von STMicroelectronics, which performs the basic algorithms necessary for data acquisition synchronization and filtering. The system provides network discovery and multi-hop and self-healing mechanisms. If the distance between two communicating devices is too big for direct radio transmission, packets are routed over intermediate devices automatically. The system represents a low-power and low-cost active structural health monitoring solution. As a first application, the system was installed on a CFRP structure.

  12. Quantitative corrosion monitoring and detection using ultrasonic Lamb waves

    NASA Astrophysics Data System (ADS)

    Gordon, Grant A.; Braunling, Russ

    2005-05-01

    Corrosion is a major problem for airframe operators. For the aircraft industry in general, the direct costs of corrosion are estimated at $2.2 billion. As part of their strategy to control corrosion, airframe operators constantly seek to improve their ability to anticipate, manage and identify corrosion activity. Motivated by the need for an on-line real-time corrosion-monitoring tool for industry and aircraft a prototype system and analysis approach is presented. The tool employs ultrasonic Lamb waves along with a dispersion compensated synthetic aperture focusing technique (SAFT) to detect emerging pitting damage. In order to develop an automated detection approach the noise sources of the SAFT processed defect maps were examined and modeled. The random noise was found to be neither stationary nor normally distributed. Locally varying Weibull distribution parameters are used to characterize the image noise. An algorithm is developed to quantify the uncertainty in the corrosion detection and to allow assignment of a constant false alarm probability to any region of the monitored area.

  13. Non-contact ultrasonic technique for Lamb wave characterization in composite plates.

    PubMed

    Harb, M S; Yuan, F G

    2016-01-01

    A fully non-contact single-sided air-coupled and laser ultrasonic non-destructive system based on the generation and detection of Lamb waves is implemented for the characterization of A0 Lamb wave mode dispersion in a composite plate. An air-coupled transducer (ACT) radiates acoustic pressure on the surface of the composite and generates Lamb waves within the structure. The out-of-plane velocity of the propagating wave is measured using a laser Doppler vibrometer (LDV). In this study, the non-contact automated system focuses on measuring A0 mode frequency-wavenumber, phase velocity dispersion curves using Snell's law and group velocity dispersion curves using Morlet wavelet transform (MWT) based on time-of-flight along different wave propagation directions. It is theoretically demonstrated that Snell's law represents a direct link between the phase velocity of the generated Lamb wave mode and the coincidence angle of the ACT. Using Snell's law and MWT, the former three dispersion curves of the A0 mode are easily and promptly generated from a set of measurements obtained from a rapid ACT angle scan experiment. In addition, the phase velocity and group velocity polar characteristic wave curves are also computed to analyze experimentally the angular dependency of Lamb wave propagation. In comparison with the results from the theory, it is confirmed that using the ACT/LDV system and implementing simple Snell's law method is highly sensitive and effective in characterizing the dispersion curves of Lamb waves in composite structures as well as its angular dependency.

  14. Lamb wave line sensing for crack detection in a welded stiffener.

    PubMed

    An, Yun-Kyu; Kim, Jae Hong; Yim, Hong Jae

    2014-07-18

    This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with multiple reflections from complex waveguides. In particular, crack detection in a welded joint, one of the structural hot spots due to stress concentration, is accompanied by reflections from the welded joint as well as a crack. Extracting and highlighting crack-induced Lamb wave modes from Lamb wave responses measured at multi-spatial points along a single line can be accomplished through a frequency-wavenumber domain analysis. The advantages of the proposed technique enable us not only to enhance the crack detectability in the welded joint but also to minimize false alarms caused by environmental and operational variations by avoiding the direct comparison with the baseline data previously accumulated from the pristine condition of a target structure. The proposed technique is experimentally and numerically validated in vertically stiffened metallic structures, revealing that it successfully identifies and localizes subsurface cracks, regardless of the coexistence with the vertical stiffener.

  15. Lamb Wave Line Sensing for Crack Detection in a Welded Stiffener

    PubMed Central

    An, Yun-Kyu; Kim, Jae Hong; Yim, Hong Jae

    2014-01-01

    This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with multiple reflections from complex waveguides. In particular, crack detection in a welded joint, one of the structural hot spots due to stress concentration, is accompanied by reflections from the welded joint as well as a crack. Extracting and highlighting crack-induced Lamb wave modes from Lamb wave responses measured at multi-spatial points along a single line can be accomplished through a frequency-wavenumber domain analysis. The advantages of the proposed technique enable us not only to enhance the crack detectability in the welded joint but also to minimize false alarms caused by environmental and operational variations by avoiding the direct comparison with the baseline data previously accumulated from the pristine condition of a target structure. The proposed technique is experimentally and numerically validated in vertically stiffened metallic structures, revealing that it successfully identifies and localizes subsurface cracks, regardless of the coexistence with the vertical stiffener. PMID:25046014

  16. A hybrid method based upon nonlinear Lamb wave response for locating a delamination in composite laminates.

    PubMed

    Yelve, Nitesh P; Mitra, Mira; Mujumdar, P M; Ramadas, C

    2016-08-01

    A new hybrid method based upon nonlinear Lamb wave response in time and frequency domains is introduced to locate a delamination in composite laminates. In Lamb wave based nonlinear method, the presence of damage is shown by the appearance of higher harmonics in the Lamb wave response. The proposed method not only uses this spectral information but also the corresponding temporal response data, for locating the delamination. Thus, the method is termed as a hybrid method. The paper includes formulation of the method and its application to locate a Barely Visible Impact Damage (BVID) induced delamination in a Carbon Fiber Reinforced Polymer (CFRP) laminate. The method gives the damage location fairly well. It is a baseline free method, as it does not need data from the pristine specimen. PMID:27115575

  17. Three-dimensional temperature effect modelling of piezoceramic transducers used for Lamb wave based damage detection

    NASA Astrophysics Data System (ADS)

    Kijanka, Piotr; Packo, Pawel; Zhu, Xuan; Staszewski, Wieslaw J.; Lanza di Scalea, Francesco

    2015-06-01

    The paper presents a three-dimensional temperature-dependent model of surface-bonded, low-profile piezoceramic transducers (PZT) used for Lamb wave propagation. The effect of temperature on Lamb wave actuation, propagation and sensing is investigated. The major focus is on the study of actuation and sensing properties of PZT for various temperature levels. These properties are investigated through the electric field analysis of transducers. The temperature effect on transducer bond layers is also investigated. Numerically simulated amplitude responses are analysed for various temperatures and excitation frequencies. Numerical simulations are validated experimentally. The results demonstrate that temperature-dependent physical properties of PZT, bond layers and particularly host structures significantly affect the amplitude and phase of Lamb wave responses.

  18. Baseline Signal Reconstruction for Temperature Compensation in Lamb Wave-Based Damage Detection.

    PubMed

    Liu, Guoqiang; Xiao, Yingchun; Zhang, Hua; Ren, Gexue

    2016-01-01

    Temperature variations have significant effects on propagation of Lamb wave and therefore can severely limit the damage detection for Lamb wave. In order to mitigate the temperature effect, a temperature compensation method based on baseline signal reconstruction is developed for Lamb wave-based damage detection. The method is a reconstruction of a baseline signal at the temperature of current signal. In other words, it compensates the baseline signal to the temperature of current signal. The Hilbert transform is used to compensate the phase of baseline signal. The Orthogonal matching pursuit (OMP) is used to compensate the amplitude of baseline signal. Experiments were conducted on two composite panels to validate the effectiveness of the proposed method. Results show that the proposed method could effectively work for temperature intervals of at least 18 °C with the baseline signal temperature as the center, and can be applied to the actual damage detection. PMID:27529245

  19. Baseline Signal Reconstruction for Temperature Compensation in Lamb Wave-Based Damage Detection

    PubMed Central

    Liu, Guoqiang; Xiao, Yingchun; Zhang, Hua; Ren, Gexue

    2016-01-01

    Temperature variations have significant effects on propagation of Lamb wave and therefore can severely limit the damage detection for Lamb wave. In order to mitigate the temperature effect, a temperature compensation method based on baseline signal reconstruction is developed for Lamb wave-based damage detection. The method is a reconstruction of a baseline signal at the temperature of current signal. In other words, it compensates the baseline signal to the temperature of current signal. The Hilbert transform is used to compensate the phase of baseline signal. The Orthogonal matching pursuit (OMP) is used to compensate the amplitude of baseline signal. Experiments were conducted on two composite panels to validate the effectiveness of the proposed method. Results show that the proposed method could effectively work for temperature intervals of at least 18 °C with the baseline signal temperature as the center, and can be applied to the actual damage detection. PMID:27529245

  20. Ultrasonic Waveguide Sensor Using a Leaky Lamb Wave for Under-Sodium Viewing

    NASA Astrophysics Data System (ADS)

    Joo, Young-Sang; Lee, Jae-Han

    2010-02-01

    A plate-type ultrasonic waveguide sensor using a leaky Lamb wave has been developed for the under-sodium viewing of a reactor core and in-vessel structures of a sodium-cooled fast reactor (SFR). An A0 Lamb wave mode is utilized in the waveguide sensor for the single mode generation and the effective radiation capability in a fluid. A radiation beam steering technique is presented which is achieved by the frequency tuning of the excitation pulse in the frequency range of the A0 Lamb wave mode which the group velocity is not dispersive and the phase velocity is dispersive. The long distance propagation ability and C-scan imaging performance have been demonstrated successfully by experimental feasibility tests of the waveguide sensor.

  1. A hybrid method based upon nonlinear Lamb wave response for locating a delamination in composite laminates.

    PubMed

    Yelve, Nitesh P; Mitra, Mira; Mujumdar, P M; Ramadas, C

    2016-08-01

    A new hybrid method based upon nonlinear Lamb wave response in time and frequency domains is introduced to locate a delamination in composite laminates. In Lamb wave based nonlinear method, the presence of damage is shown by the appearance of higher harmonics in the Lamb wave response. The proposed method not only uses this spectral information but also the corresponding temporal response data, for locating the delamination. Thus, the method is termed as a hybrid method. The paper includes formulation of the method and its application to locate a Barely Visible Impact Damage (BVID) induced delamination in a Carbon Fiber Reinforced Polymer (CFRP) laminate. The method gives the damage location fairly well. It is a baseline free method, as it does not need data from the pristine specimen.

  2. Experimental demonstration of ordered and disordered multiresonant metamaterials for lamb waves.

    PubMed

    Rupin, Matthieu; Lemoult, Fabrice; Lerosey, Geoffroy; Roux, Philippe

    2014-06-13

    We demonstrate the experimental realization of a multiresonant metamaterial for Lamb waves, i.e., elastic waves propagating in plates. The metamaterial effect comes from the resonances of long aluminum rods that are attached to an aluminum plate. Using time-dependent measurements, we experimentally prove that this metamaterial exhibits wide band gaps as well as sub- and suprawavelength modes for both a periodic and a random arrangement of the resonators. The dispersion curve inside the metamaterial is predicted through hybridizations between flexural and compressional resonances in the rods and slow and fast Lamb modes in the plate. We finally underline how the various degrees of freedom of such system paves the way to the design of metamaterials for the control of Lamb waves in unprecedented ways. PMID:24972210

  3. A probabilistic crack size quantification method using in-situ Lamb wave test and Bayesian updating

    NASA Astrophysics Data System (ADS)

    Yang, Jinsong; He, Jingjing; Guan, Xuefei; Wang, Dengjiang; Chen, Huipeng; Zhang, Weifang; Liu, Yongming

    2016-10-01

    This paper presents a new crack size quantification method based on in-situ Lamb wave testing and Bayesian method. The proposed method uses coupon test to develop a baseline quantification model between the crack size and damage sensitive features. In-situ Lamb wave testing data on actual structures are used to update the baseline model parameters using Bayesian method to achieve more accurate crack size predictions. To demonstrate the proposed method, Lamb wave testing on simple plates with artificial cracks of different sizes is performed using surface-bonded piezoelectric wafers, and the data are used to obtain the baseline model. Two damage sensitive features, namely, the phase change and normalized amplitude are identified using signal processing techniques and used in the model. To validate the effectiveness of the method, the damage data from an in-situ fatigue testing on a realistic lap-joint component are used to update the baseline model using Bayesian method.

  4. Modal analysis of Lamb wave generation in elastic plates by liquid wedge transducers

    SciTech Connect

    Jia, X.

    1997-02-01

    A modal analysis is presented to describe the excitation of Lamb waves in an elastic plate using a liquid wedge transducer. Analytical expression for the displacement of a given mode is derived for the excitation by a uniform bounded beam. In contrast to previous studies, the contribution of the reflected wave is included in the input exciting forces using a perturbation theory. The conversion efficiency, defined as the ratio of the guided mode power to the incident power, is related to a single parameter which depends on the rate of attenuation due to leakage from the guided wave into the liquid wedge. Numerical results relevant to the fundamental Lamb modes are obtained as a function of frequency for various incident beam widths and plate thickness. Using optical interferometric detection, direct measurements of the Lamb modes displacements have been carried out in aluminium plates to verify the theoretical analysis. {copyright} {ital 1997 Acoustical Society of America.}

  5. Lamb Wave Characteristics of Composite Plates Including a Diamond Layer with Distinct Electrode Arrangements

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Yu

    2013-07-01

    Diamond films have been utilized to develop surface acoustic wave filters and micromechanical resonators because of the highest acoustic wave velocity and largest product of frequency and quality factor (f.Q) of diamond among all materials. A theoretical analysis of Lamb wave characteristics in multilayer piezoelectric plates including a diamond layer is presented in this paper. Formulae for effective permittivity are derived using the transfer matrix method and are further employed to calculate Lamb wave phase velocity dispersions. The electromechanical coupling coefficients (ECCs) are also calculated exactly by Green's function method. Detailed calculations are carried out for ZnO/diamond and AlN/diamond composite plates with four distinct electrode arrangements. Results show that the ZnO/diamond structure yields a phase velocity of 6420 m/s and a large ECC of 7.41%, which makes it suitable for high-frequency wideband filter applications. Moreover, in the AlN/diamond structure, the S0 mode exhibits a large phase velocity of up to 10.3 km/s and a moderate ECC of 1.97%. Such favorable characteristics are expected to contribute to the development of AlN/diamond Lamb wave oscillators operating at approximately 5-10 GHz without the need for a sub-micrometer-resolution lithographic process. Therefore, both ZnO/diamond and AlN/diamond Lamb wave devices are highly promising candidates for RF devices in modern communication systems with advantages over conventional surface acoustic wave devices.

  6. Damage imaging using Lamb waves for SHM applications

    NASA Astrophysics Data System (ADS)

    Stepinski, Tadeusz; Ambroziński, Łukasz; Uhl, Tadeusz

    2015-03-01

    2-D ultrasonic arrays, due to their beam-steering capability and all azimuth angle coverage are a very promising tool for the inspection of plate-like structures using Lamb waves (LW). Contrary to the classical linear phased arrays (PAs) the 2D arrays enable unequivocal defect localization and they are even capable of mode selectivity of the received LWs . Recently, it has been shown that multistatic synthetic focusing (SF) algorithms applied for 2D arrays are much more effective than the classical phase array mode commonly used in NDT. The multistatic SF assumes multiple transmissions of elements in a transmitting aperture and off-line processing of the data acquired by a receiving aperture. In the simplest implementation of the technique, only a single multiplexed input and a number of output channels are required, which results in significant hardware simplification compared with the PA systems. On the one hand implementation of the multistatic SF to 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process. On the other hand, it enables designing sparse arrays with performance similar to that of the fully populated dense arrays. In this paper we present a general systematic approach to the design and optimization of imaging systems based on the 2D array operating in the multistatic mode. We start from presenting principles of the SF schemes applied to LW imaging. Then, we outline the coarray concept and demonstrate how it can be used for reducing number of elements of the 2D arrays. Finally, efficient tools for the investigation and experimental verification of the designed 2D array prototypes are presented. The first step in the investigation is theoretical evaluation performed using frequency-dependent structure transfer function (STF), which enables approximate simulation of an array excited with a tone-burst in a dispersive medium. Finally, we show how scanning laser vibrometer

  7. Damage imaging using Lamb waves for SHM applications

    SciTech Connect

    Stepinski, Tadeusz Ambroziński, Łukasz Uhl, Tadeusz

    2015-03-31

    2-D ultrasonic arrays, due to their beam-steering capability and all azimuth angle coverage are a very promising tool for the inspection of plate-like structures using Lamb waves (LW). Contrary to the classical linear phased arrays (PAs) the 2D arrays enable unequivocal defect localization and they are even capable of mode selectivity of the received LWs . Recently, it has been shown that multistatic synthetic focusing (SF) algorithms applied for 2D arrays are much more effective than the classical phase array mode commonly used in NDT. The multistatic SF assumes multiple transmissions of elements in a transmitting aperture and off-line processing of the data acquired by a receiving aperture. In the simplest implementation of the technique, only a single multiplexed input and a number of output channels are required, which results in significant hardware simplification compared with the PA systems. On the one hand implementation of the multistatic SF to 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process. On the other hand, it enables designing sparse arrays with performance similar to that of the fully populated dense arrays. In this paper we present a general systematic approach to the design and optimization of imaging systems based on the 2D array operating in the multistatic mode. We start from presenting principles of the SF schemes applied to LW imaging. Then, we outline the coarray concept and demonstrate how it can be used for reducing number of elements of the 2D arrays. Finally, efficient tools for the investigation and experimental verification of the designed 2D array prototypes are presented. The first step in the investigation is theoretical evaluation performed using frequency-dependent structure transfer function (STF), which enables approximate simulation of an array excited with a tone-burst in a dispersive medium. Finally, we show how scanning laser vibrometer

  8. Intelligent feature selection techniques for pattern classification of Lamb wave signals

    SciTech Connect

    Hinders, Mark K.; Miller, Corey A.

    2014-02-18

    Lamb wave interaction with flaws is a complex, three-dimensional phenomenon, which often frustrates signal interpretation schemes based on mode arrival time shifts predicted by dispersion curves. As the flaw severity increases, scattering and mode conversion effects will often dominate the time-domain signals, obscuring available information about flaws because multiple modes may arrive on top of each other. Even for idealized flaw geometries the scattering and mode conversion behavior of Lamb waves is very complex. Here, multi-mode Lamb waves in a metal plate are propagated across a rectangular flat-bottom hole in a sequence of pitch-catch measurements corresponding to the double crosshole tomography geometry. The flaw is sequentially deepened, with the Lamb wave measurements repeated at each flaw depth. Lamb wave tomography reconstructions are used to identify which waveforms have interacted with the flaw and thereby carry information about its depth. Multiple features are extracted from each of the Lamb wave signals using wavelets, which are then fed to statistical pattern classification algorithms that identify flaw severity. In order to achieve the highest classification accuracy, an optimal feature space is required but it’s never known a priori which features are going to be best. For structural health monitoring we make use of the fact that physical flaws, such as corrosion, will only increase over time. This allows us to identify feature vectors which are topologically well-behaved by requiring that sequential classes “line up” in feature vector space. An intelligent feature selection routine is illustrated that identifies favorable class distributions in multi-dimensional feature spaces using computational homology theory. Betti numbers and formal classification accuracies are calculated for each feature space subset to establish a correlation between the topology of the class distribution and the corresponding classification accuracy.

  9. Intelligent feature selection techniques for pattern classification of Lamb wave signals

    NASA Astrophysics Data System (ADS)

    Hinders, Mark K.; Miller, Corey A.

    2014-02-01

    Lamb wave interaction with flaws is a complex, three-dimensional phenomenon, which often frustrates signal interpretation schemes based on mode arrival time shifts predicted by dispersion curves. As the flaw severity increases, scattering and mode conversion effects will often dominate the time-domain signals, obscuring available information about flaws because multiple modes may arrive on top of each other. Even for idealized flaw geometries the scattering and mode conversion behavior of Lamb waves is very complex. Here, multi-mode Lamb waves in a metal plate are propagated across a rectangular flat-bottom hole in a sequence of pitch-catch measurements corresponding to the double crosshole tomography geometry. The flaw is sequentially deepened, with the Lamb wave measurements repeated at each flaw depth. Lamb wave tomography reconstructions are used to identify which waveforms have interacted with the flaw and thereby carry information about its depth. Multiple features are extracted from each of the Lamb wave signals using wavelets, which are then fed to statistical pattern classification algorithms that identify flaw severity. In order to achieve the highest classification accuracy, an optimal feature space is required but it's never known a priori which features are going to be best. For structural health monitoring we make use of the fact that physical flaws, such as corrosion, will only increase over time. This allows us to identify feature vectors which are topologically well-behaved by requiring that sequential classes "line up" in feature vector space. An intelligent feature selection routine is illustrated that identifies favorable class distributions in multi-dimensional feature spaces using computational homology theory. Betti numbers and formal classification accuracies are calculated for each feature space subset to establish a correlation between the topology of the class distribution and the corresponding classification accuracy.

  10. Defect Detection on Carbon Fibre Reinforced Plastics (cfrp) with Laser Generated Lamb Waves

    NASA Astrophysics Data System (ADS)

    Focke, O.; Huke, P.; Hildebrandt, A.

    2011-06-01

    Standard ultrasound methods using a phased-array or a single transducer are commonly used for non-destructive evaluation (NDE) during manufacturing of carbon fiber reinforced plastics (CFRP) parts and certificated testing schemes were developed for individual parts and geometries. However, most testing methods need direct contact, matching gels and remain therefore time consuming. Laser-Ultrasonics is advantageous due to the contactless measurement technology and high accessibility even on complex parts. Despite the non-destructive testing with body waves, we show that the NDE can be expanded using two-dimensional surface (Lamb) waves for detection of delaminations close to the surface or small deteriorations caused by e.g. impacts. Lamb waves have been excited with a single transducer and with a short-pulse Laser with additionally producing A0-and S0-Lamb waves. The waves were detected with a shearography setup that allows for measuring two-dimensionally the displacement of a surface. Short integration times of the camera were realized using a pulsed ruby laser for illumination. As a consequence to the anisotropy the propagation in different directions exhibits individual characteristics like amplitude, damping and velocity. This has motivated to build up models for the propagation of Lamb waves and to compare them with experimental results.

  11. Elliptical trajectory orientation of Lamb wave polarization as a damage localization parameter in aerospace structures

    NASA Astrophysics Data System (ADS)

    Ayers, J.; Owens, C. T.; Swenson, E.; Apetre, N.; Ruzzene, M.; Ghoshal, A.

    2012-05-01

    The ability to measure and quantify the polarization of ultrasonic waves has led to the development of novel non-destructive diagnostic tools, which rely on the sensitivity of polarization to surface roughness, cracks, temperature and residual stresses, among others. In particular, the following paper provides an analytical description of polarized Lamb wave components that yield an elliptical, rotated profile of the particle trajectory. The formulation includes Lamb waves generated by a circular piezoelectric disc, along with descriptions of bi-modal and single mode polarization characteristics. A technique is proposed that utilizes the elliptical orientation as a damage identification parameter for guided wave structural interrogation techniques. The technique is applied to finite element models of aluminum and composite armor-like structures. This analytical formulation is compared to experimental Lamb wave polarization results, where polarized Lamb wave components are extracted from complex, homogenous aluminum specimens using a 3D Scanning Laser Doppler Vibrometry setup. The experimental results show that the proposed technique allows for improved damage characterization.

  12. Visualization of non-propagating Lamb wave modes for fatigue crack evaluation

    NASA Astrophysics Data System (ADS)

    An, Yun-Kyu; Sohn, Hoon

    2015-03-01

    This article develops a non-propagating Lamb wave mode (NPL) imaging technique for fatigue crack visualization. NPL has a great potential for crack evaluation in that it significantly contributes local mode amplitudes in the vicinity of a crack without spatial propagation. Such unique physical phenomenon is theoretically proven and experimentally measured through laser scanning. Although its measurement is a quite challenging work due to the fact that it is quite localized and coexists with complex propagating Lamb wave modes, a NPL filter proposed in this article overcomes the technical challenge by eliminating all propagating Lamb modes from laser scanned full Lamb wavefields. Through the NPL filtering process, only fatigue crack-induced NPLs can be measured and retained. To verify such physical observation and the corresponding NPL filter, a real micro fatigue crack is created by applying repeated tensile loading, and its detectability is tested using a surface-mounted piezoelectric transducer for generating Lamb waves and a laser Doppler vibrometer for measuring the corresponding responses. The experimental results confirm that even an invisible fatigue crack can be instantaneously visualized and effectively evaluated through the proposed NPL measurement and filtering processes.

  13. Data-driven and calibration-free Lamb wave source localization with sparse sensor arrays.

    PubMed

    Harley, Joel B; Moura, José M F

    2015-08-01

    Most Lamb wave localization techniques require that we know the wave's velocity characteristics; yet, in many practical scenarios, velocity estimates can be challenging to acquire, are unavailable, or are unreliable because of the complexity of Lamb waves. As a result, there is a significant need for new methods that can reduce a system's reliance on a priori velocity information. This paper addresses this challenge through two novel source localization methods designed for sparse sensor arrays in isotropic media. Both methods exploit the fundamental sparse structure of a Lamb wave's frequency-wavenumber representation. The first method uses sparse recovery techniques to extract velocities from calibration data. The second method uses kurtosis and the support earth mover's distance to measure the sparseness of a Lamb wave's approximate frequency-wavenumber representation. These measures are then used to locate acoustic sources with no prior calibration data. We experimentally study each method with a collection of acoustic emission data measured from a 1.22 m by 1.22 m isotropic aluminum plate. We show that both methods can achieve less than 1 cm localization error and have less systematic error than traditional time-of-arrival localization methods. PMID:26276960

  14. Fast and accurate analytical model to solve inverse problem in SHM using Lamb wave propagation

    NASA Astrophysics Data System (ADS)

    Poddar, Banibrata; Giurgiutiu, Victor

    2016-04-01

    Lamb wave propagation is at the center of attention of researchers for structural health monitoring of thin walled structures. This is due to the fact that Lamb wave modes are natural modes of wave propagation in these structures with long travel distances and without much attenuation. This brings the prospect of monitoring large structure with few sensors/actuators. However the problem of damage detection and identification is an "inverse problem" where we do not have the luxury to know the exact mathematical model of the system. On top of that the problem is more challenging due to the confounding factors of statistical variation of the material and geometric properties. Typically this problem may also be ill posed. Due to all these complexities the direct solution of the problem of damage detection and identification in SHM is impossible. Therefore an indirect method using the solution of the "forward problem" is popular for solving the "inverse problem". This requires a fast forward problem solver. Due to the complexities involved with the forward problem of scattering of Lamb waves from damages researchers rely primarily on numerical techniques such as FEM, BEM, etc. But these methods are slow and practically impossible to be used in structural health monitoring. We have developed a fast and accurate analytical forward problem solver for this purpose. This solver, CMEP (complex modes expansion and vector projection), can simulate scattering of Lamb waves from all types of damages in thin walled structures fast and accurately to assist the inverse problem solver.

  15. Lamb wave acousto-optic modulator in ZnO/MgO multiple quantum wells and comparison with classical modulator.

    PubMed

    Gryba, T; Lefebvre, J-E; Elmaimouni, L; Ratolojanahary, F E

    2015-10-10

    An analysis of a ZnO/MgO multiple quantum well (MQW) acousto-optic modulator with Lamb waves is performed. With the MQW thickness in the range of 0.2 times the Lamb wavelength, the only observed Lamb modes are the lowest-order symmetric S0 and antisymmetric A0 modes. These modes induce strain and electric field components which influence the absorption coefficient of the modulator by the associated variation of the excitonic energies of MQW. The optical absorption coefficient spectra of the modulator as a function of the Lamb waves' power is presented. The Lamb-wave-based modulator gives a better absorption coefficient than the Rayleigh-wave-based one. An analysis of a classical acousto-optic modulator is also performed for comparison of performance. PMID:26479819

  16. Locating fatigue damage using temporal signal features of nonlinear Lamb waves

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Su, Zhongqing; Lu, Ye; Sohn, Hoon; Qing, Xinlin

    2015-08-01

    The temporal signal features of linear guided waves, as typified by the time-of-flight (ToF), have been exploited intensively for identifying damage, with proven effectiveness in locating gross damage in particular. Upon re-visiting the conventional, ToF-based detection philosophy, the present study extends the use of temporal signal processing to the realm of nonlinear Lamb waves, so as to reap the high sensitivity of nonlinear Lamb waves to small-scale damage (e.g., fatigue cracks), and the efficacy of temporal signal processing in locating damage. Nonlinear wave features (i.e., higher-order harmonics) are extracted using networked, miniaturized piezoelectric wafers, and reverted to the time domain for damage localization. The proposed approach circumvents the deficiencies of using Lamb wave features for evaluating undersized damage, which are either undiscernible in time-series analysis or lacking in temporal information in spectral analysis. A probabilistic imaging algorithm is introduced to supplement the approach, facilitating the presentation of identification results in an intuitive manner. Through numerical simulation and then experimental validation, two damage indices (DIs) are comparatively constructed, based, respectively, on linear and nonlinear temporal features of Lamb waves, and used to locate fatigue damage near a rivet hole of an aluminum plate. Results corroborate the feasibility and effectiveness of using temporal signal features of nonlinear Lamb waves to locate small-scale fatigue damage, with enhanced accuracy compared with linear ToF-based detection. Taking a step further, a synthesized detection strategy is formulated by amalgamating the two DIs, targeting continuous and adaptive monitoring of damage from its onset to macroscopic formation.

  17. Propagation of Lamb waves in an immersed periodically grooved plate: experimental detection of the scattered converted backward waves.

    PubMed

    Harhad, Nadia; El-Kettani, Mounsif Ech-Cherif; Djelouah, Hakim; Izbicki, Jean-Louis; Predoi, Mihai Valentin

    2014-03-01

    Guided waves propagation in immersed plates with irregular surfaces has potential application to detection and assessment of the extent, depth and pattern of the irregularity. The complexity of the problem, due to the large number of involved parameters, has limited the number of existing studies. The simplest case of irregularities of practical interest is the two-dimensional corrosion profile. Even this case is in general so complex, that one can extract several amplitude dominant periodic surfaces only by using a Fourier spectrum of the surface. Guided waves in plates, with one or both free surfaces having periodic perturbations of different shapes, have been presented in specialized literature. In this paper is studied the propagation of Lamb waves in an aluminum plate with a periodic grooved surface on only one side and immersed in water. The interaction between an incident Lamb wave and the grating gives rise to retro-converted waves. Preliminary numerical simulation by the finite element method is performed in order to obtain key parameters for the experiments. It is shown that retro-converted waves radiating into the water are detectable although their amplitudes are small. The phonon relation is verified for the leaky Lamb modes. The damping coefficients of the leaky Lamb modes in the grooved immersed plate are evaluated.

  18. Stiffness matrix determination of composite materials using lamb wave group velocity measurements

    NASA Astrophysics Data System (ADS)

    Putkis, O.; Croxford, A. J.

    2013-04-01

    The use of Lamb waves in Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) is gaining popularity due to their ability to travel long distances without significant attenuation, therefore offering large area inspections with a small number of sensors. The design of a Lamb-wave-based NDE/SHM system for composite materials is more complicated than for metallic materials due to the directional dependence of Lamb wave propagation characteristics such as dispersion and group velocity. Propagation parameters can be theoretically predicted from known material properties, specifically the stiffness matrix and density. However, in practice it is difficult to obtain the stiffness matrix of a particular material or structure with high accuracy, hence introducing errors in theoretical predictions and inaccuracies in the resulting propagation parameters. Measured Lamb wave phase velocities can be used to infer the stiffness matrix, but the measurements are limited to the principal directions due to the steering effect (different propagation directions of phase and corresponding group velocities). This paper proposes determination of the stiffness matrix from the measured group velocities, which can be unambiguously measured in any direction. A highly anisotropic carbon-fibre-reinforced polymer plate is chosen for the study. The influence of different stiffness matrix elements on the directional group velocity profile is investigated. Thermodynamic Simulated Annealing (TSA) is used as a tool for inverse, multi variable inference of the stiffness matrix. A good estimation is achieved for particular matrix elements.

  19. Lamb wave detection in prepreg composite materials with fibre Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Miesen, Nick; Mizutani, Yoshihiro; Groves, Roger M.; Sinke, Jos; Benedictus, Rinze

    2011-04-01

    This paper demonstrates that existing Structural Health Monitoring (SHM) techniques have potential during the production phase in addition to their application for maintenance and for in-flight monitoring. Flaws occur during composite fabrication in industry, due to an imperfect process control and human errors. This decreases production efficiency and increases costs. In this paper, the monitoring of Lamb waves in unidirectional carbon fibre (UD-CFRP) prepreg material is demonstrated using both Fibre Bragg Gratings (FBG)s and piezolectric acoustic sensors, and that these SHM sensors may be used for flaw detection and production monitoring. The detection of Lamb waves in a one ply thick sheet of prepreg UD-CFRP material is demonstrated for an FBG sensor aligned with the carbon fibre orientation and bonded to the surface of the prepreg, Furthermore, the velocity of Lamb waves in prepreg UD-CFRP in different orientations is investigated. Finally the successful detection of a material crack in a prepreg UD-CFRP sheet using the Lamb wave detection method is demonstrated.

  20. Dispersion of Lamb waves under a periodic metal grating in aluminum nitride plates.

    PubMed

    Naumenko, Natalya F

    2014-09-01

    Dispersion of Lamb waves propagating in AlN plates with a periodic Al grating on the top surface and an Al electrode on the bottom surface is investigated using the numerical technique SDA-FEM-SDA, which combines finite element modeling (FEM) analysis of the electrode region with spectral-domain analysis (SDA) of the adjacent multi-layered half-spaces. Characteristics of zero-order and higher-order Lamb waves are presented as functions of plate thickness and spectral frequency, which varies in the first Brillouin zone. The structures of typical Lamb waves are examined via visualization of the instantaneous displacement fields in the AlN plate confined between the grating and the bottom electrode. The mechanism of building hybrid modes, which arise from intermode coupling between the counter-propagating Lamb waves of different symmetry and order, is illustrated by two examples of modes propagating with wavelengths λ = 3p and λ = 4p, where p is the pitch of the grating.

  1. Multiple-mode Lamb wave scattering simulations using 3D elastodynamic finite integration technique.

    PubMed

    Leckey, Cara A C; Rogge, Matthew D; Miller, Corey A; Hinders, Mark K

    2012-02-01

    We have implemented three-dimensional (3D) elastodynamic finite integration technique (EFIT) simulations to model Lamb wave scattering for two flaw-types in an aircraft-grade aluminum plate, a rounded rectangle flat-bottom hole and a disbond of the same shape. The plate thickness and flaws explored in this work include frequency-thickness regions where several Lamb wave modes exist and sometimes overlap in phase and/or group velocity. For the case of the flat-bottom hole the depth was incrementally increased to explore progressive changes in multiple-mode Lamb wave scattering due to the damage. The flat-bottom hole simulation results have been compared to experimental data and are shown to provide key insight for this well-defined experimental case by explaining unexpected results in experimental waveforms. For the rounded rectangle disbond flaw, which would be difficult to implement experimentally, we found that Lamb wave behavior differed significantly from the flat-bottom hole flaw. Most of the literature in this field is restricted to low frequency-thickness regions due to difficulties in interpreting data when multiple modes exist. We found that benchmarked 3D EFIT simulations can yield an understanding of scattering behavior for these higher frequency-thickness regions and in cases that would be difficult to set up experimentally. Additionally, our results show that 2D simulations would not have been sufficient for modeling the complicated scattering that occurred. PMID:21908011

  2. Acoustoelasticity

    NASA Technical Reports Server (NTRS)

    Dowell, E. H.

    1976-01-01

    Internal sound fields are considered. Specifically, the interaction between the (acoustic) sound pressure field and the (elastic) flexible wall of an enclosure is discussed. Such problems frequently arise when the vibrating walls of a transportation vehicle induce a significant internal sound field. Cabin noise in various flight vehicles and the internal sound field in an automobile are representative examples. A mathematical model, simplified solutions, and numerical results and comparisons with representative experimental data are briefly considered. An overall conclusion is that reasonable grounds for optimism exist with respect to available theoretical models and their predictive capability.

  3. Multi Reflection of Lamb Wave Emission in an Acoustic Waveguide Sensor

    PubMed Central

    Schmitt, Martin; Olfert, Sergei; Rautenberg, Jens; Lindner, Gerhard; Henning, Bernd; Reindl, Leonhard Michael

    2013-01-01

    Recently, an acoustic waveguide sensor based on multiple mode conversion of surface acoustic waves at the solid—liquid interfaces has been introduced for the concentration measurement of binary and ternary mixtures, liquid level sensing, investigation of spatial inhomogenities or bubble detection. In this contribution the sound wave propagation within this acoustic waveguide sensor is visualized by Schlieren imaging for continuous and burst operation the first time. In the acoustic waveguide the antisymmetrical zero order Lamb wave mode is excited by a single phase transducer of 1 MHz on thin glass plates of 1 mm thickness. By contact to the investigated liquid Lamb waves propagating on the first plate emit pressure waves into the adjacent liquid, which excites Lamb waves on the second plate, what again causes pressure waves traveling inside the liquid back to the first plate and so on. The Schlieren images prove this multi reflection within the acoustic waveguide, which confirms former considerations and calculations based on the receiver signal. With this knowledge the sensor concepts with the acoustic waveguide sensor can be interpreted in a better manner. PMID:23447010

  4. Reflection of Lamb waves obliquely incident on the free edge of a plate.

    PubMed

    Santhanam, Sridhar; Demirli, Ramazan

    2013-01-01

    The reflection of obliquely incident symmetric and anti-symmetric Lamb wave modes at the edge of a plate is studied. Both in-plane and Shear-Horizontal (SH) reflected wave modes are spawned by an obliquely incident in-plane Lamb wave mode. Energy reflection coefficients are calculated for the reflected wave modes as a function of frequency and angle of incidence. This is done by using the method of orthogonal mode decomposition and by enforcing traction free conditions at the plate edge using the method of collocation. A PZT sensor network, affixed to an Aluminum plate, is used to experimentally verify the predictions of the analysis. Experimental results provide support for the analytically determined results.

  5. Lamb wave propagation modelling and simulation using parallel processing architecture and graphical cards

    NASA Astrophysics Data System (ADS)

    Paćko, P.; Bielak, T.; Spencer, A. B.; Staszewski, W. J.; Uhl, T.; Worden, K.

    2012-07-01

    This paper demonstrates new parallel computation technology and an implementation for Lamb wave propagation modelling in complex structures. A graphical processing unit (GPU) and computer unified device architecture (CUDA), available in low-cost graphical cards in standard PCs, are used for Lamb wave propagation numerical simulations. The local interaction simulation approach (LISA) wave propagation algorithm has been implemented as an example. Other algorithms suitable for parallel discretization can also be used in practice. The method is illustrated using examples related to damage detection. The results demonstrate good accuracy and effective computational performance of very large models. The wave propagation modelling presented in the paper can be used in many practical applications of science and engineering.

  6. 3D numerical simulation of laser-generated Lamb waves propagation in 2D acoustic black holes

    NASA Astrophysics Data System (ADS)

    Yan, Shiling; Lomonosov, Alexey M.; Shen, Zhonghua; Han, Bing

    2015-05-01

    Acoustic black holes have been widely used in damping structural vibration. In this work, the Lamb waves are utilized to evaluate the specified structure. The three-dimensional numerical model of acoustic black holes with parabolic profile was established. The propagation of laser-generated Lamb wave in two-dimensional acoustic black holes was numerically simulated using the finite element method. The results indicated that the incident wave was trapped by the structure obviously.

  7. Lamb waves from airborne explosion sources: Viscous effects and comparisons to ducted acoustic arrivals

    SciTech Connect

    Revelle, D.O.; Whitaker, R.W.

    1996-12-31

    Observations of large explosions in the atmosphere at long range are dominated by a leading pulse of large amplitude and long period that is often followed by a series of higher frequency impulses usually of smaller amplitude. This description can be interpreted using linearized acoustic-gravity wave theory in terms of a Lamb wave arrival followed by ducted acoustic and/or gravity waves. This pattern of arrivals is not the same at all ranges nor is it independent of the source energy or of the altitude of the source. Earlier, Pierce, using an isothermal, windless atmospheric model, theoretically formulated the distances beyond which the Lamb wave would just be discernible and also where it would dominate the arriving signals for a specified explosion source. In this work the authors have evaluated these distances for the cases of both an inviscid and a viscous fluid for the source energies of interest to the CTBT (Comprehensive Test Ban Treaty) R and D work at Los Alamos. Although the inviscid results are analytic, the fully viscous solutions are iterative. For the inviscid solutions, the authors find that the Lamb wave domination distance is proportional to wave frequency at frequencies large with respect to the acoustic waveguide cut-off frequency. Under similar conditions they also find that the computed distances are linearly proportional to the source height. At 1 Hz for example, the Lamb wave must propagate about 200 km before having a significant amplitude. For a viscous fluid they found slight increases in the distances compared to an inviscid fluid with the lower frequencies, near the acoustic cut-off frequency, exhibiting the greatest changes. During the period from 1981--1994 at Los Alamos, they have also observed infrasound from eight point source, near-surface ANFO explosions at White Sands Missile Range events even though the ducted acoustic waves were observed. In this work, they will compare the current theory against some of these observations.

  8. Multi-Mode Lamb Wave Arrival Time Extraction for Improved Tomographic Reconstruction

    SciTech Connect

    Hinders, Mark K.; Hou Jidong; Leonard, Kevin R.

    2005-04-09

    An ultrasonic signal processing technique is applied to multi-mode arrival time estimation from Lamb waveforms. The basic tool is a simplified time-scale projection called a dynamic wavelet fingerprint (DWFP) which enables direct observation of the variation of features of interest in non-stationary ultrasonic signals. The DWFP technique was used to automatically detect and evaluate each candidate through-transmitted Lamb mode. The area of the dynamic wavelet fingerprint was then used as a feature to distinguish false modes caused by noise and other interference from the true modes of interest. The set of estimated arrival times were then used as inputs for tomographic reconstruction. The Lamb wave tomography images generated with these estimated arrival times were able to indicate different defects in aluminum plates.

  9. Combined analytical FEM approach for efficient simulation of Lamb wave damage detection.

    PubMed

    Shen, Yanfeng; Giurgiutiu, Victor

    2016-07-01

    Lamb waves have been widely explored as a promising inspection tool for non-destructive evaluation (NDE) and structural health monitoring (SHM). This article presents a combined analytical finite element model (FEM) approach (CAFA) for the accurate, efficient, and versatile simulation of 2-D Lamb wave propagation and interaction with damage. CAFA used a global analytical solution to model wave generation, propagation, scattering, mode conversion, and detection, while the wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local FEM with non-reflective boundaries (NRB). The analytical procedure was coded using MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The methodology of obtaining WDICs from local FEM was presented. Case studies were carried out for Lamb wave propagation in a pristine plate and a damaged plate. CAFA predictions compared well with full scale multi-physics FEM simulations and experiments with scanning laser Doppler vibrometry (SLDV), while achieving remarkable performance in computational efficiency and computer resource saving compared with conventional FEM. PMID:27085109

  10. Numerical and experimental study of Lamb wave propagation in a two-dimensional acoustic black hole

    NASA Astrophysics Data System (ADS)

    Yan, Shiling; Lomonosov, Alexey M.; Shen, Zhonghua

    2016-06-01

    The propagation of laser-generated Lamb waves in a two-dimensional acoustic black-hole structure was studied numerically and experimentally. The geometrical acoustic theory has been applied to calculate the beam trajectories in the region of the acoustic black hole. The finite element method was also used to study the time evolution of propagating waves. An optical system based on the laser-Doppler vibration method was assembled. The effect of the focusing wave and the reduction in wave speed of the acoustic black hole has been validated.

  11. Nondestructive testing in human teeth using a leaky Lamb wave device.

    PubMed

    Toda, Shinji; Fujita, Takeshi; Arakawa, Hirohisa; Toda, Kohji

    2006-12-22

    A Lamb wave interdigital transducer mounted on a layered substrate composed of two plates, a thin piezoelectric ceramic plate and an acrylic plate, operating at a liquid-solid boundary, is investigated for ultrasonic nondestructive testing of the layer thickness in human teeth. A higher-order mode having a phase velocity higher than the longitudinal wave velocity in the human teeth can be used for nondestructive testing. In the combination of the two layers, the fourth mode of leaky Lamb wave is most favorable for a frequency-controllable radiation angle of an ultrasound beam into a water layer as an acoustic coupler. In the configuration of an acoustic delay line, the layer-thickness measurement in vivo, evaluated from the time interval between two reflected ultrasound echoes, is successfully realized under a thin water layer as the acoustic coupler.

  12. Inspection of lamb waves in carbon fiber composites using shearographic interferometry

    NASA Astrophysics Data System (ADS)

    Focke, O.; Hildebrand, A.; von Kopylow, C.; Calomfirescu, M.

    2008-03-01

    The implementation of structural health monitoring systems in modern aircraft structures requires a deeper understanding of impact and piezoelectric generated lamb wave propagation on carbon fibre reinforced plastics. In this paper a digital shearing interferometry method is presented that visualizes lamb waves excited by impact events or piezoelectric actuators. The contactless full field measurement of these waves is realized by a Mach-Zehnder interferometer which combines spatial phase shifting and Shearography. The latter is a laser based technique whereby the first order derivates of the displacement is indicated. Since a dynamical process is observed the spatial phase shifting technique is required. The optical implementation of both techniques within the interferometically setup and experimental results with the possibility to measure the out of plane displacement are presented. Therefore the underlying wavefield is reconstructed from the measured first order derivatives. Subsequently these results are compared with a one point measuring method and FEM simulation.

  13. Robust decision making in damage detection using piezoelectric transducers and Lamb wave propagation

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Wang, Xin; Tang, Jiong

    2007-04-01

    In this paper, we present a robust quantitative decision-making methodology for structural damage detection using piezoelectric transducers and the Lamb wave approach with the consideration of environmental and operational variances. The features of wave propagation are extracted from multiple signals using an improved adaptive harmonic wavelet transform (AHWT), which are then denoised and highlighted by applying the principal component analysis (PCA) in the wavelet domain. After self-checking and updating the baseline dataset, the Hotelling's T2 analysis provides a statistical indication of damage under a certain given confidence level. The detectability, sensitivity and robustness of the methodology are investigated using experimental as well as numerical studies. As the basis for the detection practice, the propagation of Lamb waves in an aluminum beam is systematically studied in this paper.

  14. Fatigue damage localization using time-domain features extracted from nonlinear Lamb waves

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Su, Zhongqing; Lu, Ye; Cheng, Li

    2014-03-01

    Nonlinear guided waves are sensitive to small-scale fatigue damage that may hardly be identified by traditional techniques. A characterization method for fatigue damage is established based on nonlinear Lamb waves in conjunction with the use of a piezoelectric sensor network. Theories on nonlinear Lamb waves for damage detection are first introduced briefly. Then, the ineffectiveness of using pure frequency-domain information of nonlinear wave signals for locating damage is discussed. With a revisit to traditional gross-damage localization techniques based on the time of flight, the idea of using temporal signal features of nonlinear Lamb waves to locate fatigue damage is introduced. This process involves a time-frequency analysis that enables the damage-induced nonlinear signal features, which are either undiscernible in the original time history or uninformative in the frequency spectrum, to be revealed. Subsequently, a finite element modeling technique is employed, accounting for various sources of nonlinearities in a fatigued medium. A piezoelectric sensor network is configured to actively generate and acquire probing Lamb waves that involve damageinduced nonlinear features. A probability-based diagnostic imaging algorithm is further proposed, presenting results in diagnostic images intuitively. The approach is experimentally verified on a fatigue-damaged aluminum plate, showing reasonably good accuracy. Compared to existing nonlinear ultrasonics-based inspection techniques, this approach uses a permanently attached sensor network that well accommodates automated online health monitoring; more significantly, it utilizes time-domain information of higher-order harmonics from time-frequency analysis, and demonstrates a great potential for quantitative characterization of small-scale damage with improved localization accuracy.

  15. Lamb wave sensing using fiber Bragg grating sensors for delamination detection in composite laminates

    NASA Astrophysics Data System (ADS)

    Takeda, N.; Okabe, Y.; Kuwahara, J.; Kojima, S.

    2005-05-01

    The authors are constructing a damage detection system using ultrasonic waves. In this system, a piezo-ceramic actuator generates Lamb waves in a CFRP laminate. After the waves propagate in the laminate, transmitted waves are received by a fiber Bragg grating (FBG) sensor attached on the laminate using a newly developed high-speed optical wavelength interrogation system. At first, the optimal gauge length of the FBG to detect ultrasonic waves was investigated through theoretical simulations and experiments. Then, the directional sensitivity of the FBG to ultrasonic waves was evaluated experimentally. On the basis of the above results, the 1mm FBG sensors were applied to the detection of Lamb waves propagated in carbon fiber reinforced plastic (CFRP) cross-ply laminates. The piezo-actuator was put on the laminate about 50mm away from the FBG sensor glued on the laminate, and three-cycle sine waves of 300kHz were excited repeatedly. The waveforms obtained by the FBG showed that S0 and A0 modes could be detected appropriately. Then, artificial delamination was made in the laminate by removing of a Teflon sheet embedded in the 0/90 interface after the manufacturing. When the Lamb waves passed through the delamination, the amplitude decreased and a new wave mode appeared. These phenomena could be well simulated using a finite element method. Furthermore, since the amplitude and the velocity of the new mode increased with an increase in the delamination length, this system has a potential to evaluate the interlaminar delamination length quantitatively.

  16. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness

    NASA Technical Reports Server (NTRS)

    Seale, M. D.; Madaras, E. I.

    1999-01-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.

  17. Damage Evaluation of Unsaturated Polyester Resin Using Zero-Group Velocity Lamb Waves in Non-Contact Matter

    NASA Astrophysics Data System (ADS)

    Cho, Hideo; Oka, Daichi; Matsuo, Takuma

    In this study we attempted to evaluate the degree of degradation of an unsaturated polyester resin when it was degraded by exposing it to hot water at 90°C, using the frequency of zero-group-velocity (ZGV) Lamb waves. The energy of ZGV Lamb waves does not propagate while the phase velocity remains finite. We generated ZGV Lamb waves with a Q-switched YAG laser and detected them with a focused air-coupled transducer at the same area of an irradiation point of the YAG laser in con-contact matter. A change in measured frequencies of ZGV Lamb waves decreased with increase of exposed period to hot water and are corresponding to the change in Young's modulus and thickness of the plate near the exposed surface

  18. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness.

    PubMed

    Seale, M D; Madaras, E I

    1999-09-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.

  19. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

    PubMed

    Zhang, Y; Huang, S L; Wang, S; Zhao, W

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals. PMID:27250446

  20. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Huang, S. L.; Wang, S.; Zhao, W.

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

  1. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

    PubMed

    Zhang, Y; Huang, S L; Wang, S; Zhao, W

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

  2. Microstrain-level measurement of third-order elastic constants applying dynamic acousto-elastic testing

    NASA Astrophysics Data System (ADS)

    Renaud, Guillaume; Talmant, Maryline; Marrelec, Guillaume

    2016-10-01

    The nonlinear elasticity of solids at the microstrain level has been recently studied by applying dynamic acousto-elastic testing. It is the analog of conventional quasi-static acousto-elastic experiments but the strain-dependence (or stress-dependence) of ultrasonic wave-speed is measured with an applied strain ranging from 10-7 to 10-5 and produced by a stationary elastic wave. In conventional quasi-static acousto-elastic experiments, the strain is applied in a quasi-static manner; it exceeds 10-4 and can reach 10-2. In this work, we apply dynamic acousto-elastic testing to measure the third-order elastic constants of two isotropic materials: polymethyl methacrylate and dry Berea sandstone. The peak amplitude of the dynamic applied strain is 8 × 10-6. The method is shown to be particularly suitable for materials exhibiting large elastic nonlinearity like sandstones, since the measurement is performed in the domain of validity of the third-order hyperelastic model. In contrast, conventional quasi-static acousto-elastic experiments in such materials are often performed outside the domain of validity of the third-order hyperelastic model and the stress-dependence of the ultrasonic wave-speed must be extrapolated at zero stress, leading to approximate values of the third-order elastic constants. The uncertainty of the evaluation of the third-order elastic constants is assessed by repeating multiple times the measurements and with Monte-Carlo simulations. The obtained values of the Murnaghan third-order elastic constants are l = -73 GPa ± 9%, m = -34 GPa ± 9%, and n = -61 GPa ± 10% for polymethyl methacrylate, and l = -17 000 GPa ± 20%, m = -11 000 GPa ± 10%, and n = -30 000 GPa ± 20% for dry Berea sandstone.

  3. Characteristics of second harmonic generation of Lamb waves in nonlinear elastic plates.

    PubMed

    Müller, Martin F; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J

    2010-04-01

    This paper investigates the characteristics of the second harmonic generation of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal generation of a symmetric second harmonic mode by an antisymmetric primary mode is possible. These solutions also demonstrate that modes showing internal resonance-nonzero power flux to the second harmonic mode, plus phase velocity matching-are most useful for measurements. In addition, when using finite wave packets, which is the case in most experimental measurements, group velocity matching is required for a cumulative increase in the second harmonic amplitude with propagation distance. Finally, five mode types (which are independent of material properties) that satisfy all three requirements for this cumulative increase in second harmonic amplitude-nonzero power flux, plus phase and group velocity matching-are identified. These results are important for the development of an experimental procedure to measure material nonlinearity with Lamb waves.

  4. A micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications

    NASA Astrophysics Data System (ADS)

    Wingqvist, G.; Arapan, L.; Yantchev, V.; Katardjiev, I.

    2009-03-01

    Micromachined thin film plate acoustic wave resonators (FPARs) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2 µm thick aluminium nitride (AlN) membranes have been successfully demonstrated (Yantchev and Katardjiev 2007 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54 87-95). The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900 MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is the non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm K-1 to -25 ppm K-1. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.

  5. Lamb wave-based damage detection of composite shells using high-speed fiber-optic sensing

    NASA Astrophysics Data System (ADS)

    Sotoudeh, Vahid; Black, Richard J.; Moslehi, Behzad; Qiao, Pizhong

    2014-04-01

    A Lamb wave-based damage identification method called damage imaging method for composite shells is presented. A damage index (DI) is generated from the delay matrix of the Lamb wave response signals, and it is used to indicate the location and approximate area of the damage. A piezoelectric actuator is employed to generate the Lamb waves that are subsequently captured by a fiber Bragg grating (FBG) sensor element array multiplexed in a single fiber connected to a high-speed fiber-optic sensor system. The high-speed sensing is enabled by an innovative parallel-architecture optical interrogation system. The viability of this method is demonstrated by analyzing the numerical and experimental Lamb wave response signals from laminated composite shells. The technique only requires the response signals from the plate after damage, and it is capable of performing near real-time damage identification. This study sheds some light on the application of a Lamb wave-based damage detection algorithm for curved plate/shell-type structures by using the relatively low frequency (around 100 kHz) Lamb wave response and the high-speed FBG sensor system.

  6. Structural damage detection in pipeline using Lamb waves and wavelet transform

    NASA Astrophysics Data System (ADS)

    Shoeibi, Fatemeh; Ebrahimi, Afshin; Ghavifekr, Habib Badri

    2011-10-01

    Over the last few decades, damage identification methods of civil and mechanical structures have been drawing much interest from various fields. This article presented a novel time-frequency based approach for detecting structural damage in pipeline. This is done by applying lamb wave technique and wavelet transforms for detection of change in the structural response data. Lamb waves were propagated through pipes and the received signals were subjected to wavelet transforms. The viability of the proposed approach is demonstrated using simulation examples. The pipes were modeled using finite -element method. This damage detection technique may serve the purpose of structural health monitoring because of long -distance inspection capability in situations where spatially distributed measurement of structural response is difficult.

  7. Performance optimization of high-order Lamb wave sensors based on silicon carbide substrates.

    PubMed

    Chen, Zhe; Fan, Li; Zhang, Shu-yi; Zhang, Hui

    2016-02-01

    Silicon carbide (SiC), as a new type of material for substrates in micro-electromechanical system (MEMS), was given high consideration in virtue of the properties of high acoustic velocity, low loss, chemical resistance, and etc. In this work, five performance parameters, which are electromechanical coupling coefficients, mass sensitivities, conductivity sensitivities, insert losses and minimum detectable masses, are theoretically investigated in Lamb wave chemical sensors for gas sensing based on SiC substrates. It is presented that higher performance can be achieved based on high-order modes other than fundamental modes, and the abovementioned five parameters can be simultaneously optimized. Then, according to the optimized operating conditions, operating parameters of the SiC-based high-order Lamb wave sensors are designed, which can be easily realized in MEMS technology. Finally, it is demonstrates that the SiC-based sensor exhibits better performance than that of the sensor with a conventional silicon substrate.

  8. Robust laser-based detection of Lamb waves using photo-EMF sensors

    NASA Astrophysics Data System (ADS)

    Klein, Marvin B.; Bacher, Gerald D.

    1998-03-01

    Lamb waves are easily generated and detected using laser techniques. It has been shown that both symmetric and antisymmetric modes can be produced, using single-spot and phased array generation. Detection has been demonstrated with Michelson interferometers, but these instruments can not function effectively on rough surfaces. By contrast, the confocal Fabry-Perot interferometer can interrogate rough surfaces, but generally is not practical for operation below 300 kHz. In this paper we will present Lamb wave data on a number of parts using a robust, adaptive receiver based on photo-emf detection. This receiver has useful sensitivity down to at least 100 kHz, can process speckled beams and can be easily configured to measure both out-of-plane and in- plane motion with a single probe beam.

  9. Structural health monitoring system based on diffracted Lamb wave analysis by multiresolution processing

    NASA Astrophysics Data System (ADS)

    Lemistre, Michel; Balageas, Daniel

    2001-06-01

    A health monitoring system is presented composed of integrated disc-shaped, 100 µm thick and 5 mm diameter piezoelectric transducers (PZTs) working sequentially as Lamb wave emitters and receivers. The diagnostic is based on the analysis of Lamb wave signals recorded before and after damage. In the composite, delaminations are discontinuities producing mode conversion processes generating various outgoing modes. The multiresolution processing allows the isolation of various propagation modes and their extraction in order to measure, for various propagation paths, the time delay between the arrivals of the main burst and of a specific outgoing mode. This process permits, with good accuracy, the localization of damage and the estimation of its extent. The robustness and portability of this technique is demonstrated by the fact that, after validation in our laboratory, it was successfully applied to data coming from an experiment conducted in another laboratory using its own acousto-ultrasonic health monitoring hardware system.

  10. Rectification of Lamb wave propagation in thin plates with piezo-dielectric periodic structures

    NASA Astrophysics Data System (ADS)

    Iwasaki, Yuhei; Tsuruta, Kenji; Ishikawa, Atsushi

    2016-07-01

    Based on a heterostructured plate consisting of piezoelectric-ceramic/epoxy-resin composites with different periodicities, we design a novel acoustic diode for the symmetrical/asymmetrical (S/A) mode of Lamb wave at audible ranges. The acoustic diode is constructed with two parts, i.e., the mode conversion part and the mode selection part, and the mode conversion mechanism at the interface is applied to the mode hybridization from S to S+A and for the mode conversion from A to S. The phonon band structures for each part are calculated and optimized so that the mode selection is realized for a specific mode at the junction. Finite-element simulations prove that the proposed acoustic diode achieves efficient rectification at audio frequency ranges for both S and A mode incidences of the Lamb wave.

  11. The effects of air gap reflections during air-coupled leaky Lamb wave inspection of thin plates.

    PubMed

    Fan, Zichuan; Jiang, Wentao; Cai, Maolin; Wright, William M D

    2016-02-01

    Air-coupled ultrasonic inspection using leaky Lamb waves offers attractive possibilities for non-contact testing of plate materials and structures. A common method uses an air-coupled pitch-catch configuration, which comprises a transmitter and a receiver positioned at oblique angles to a thin plate. It is well known that the angle of incidence of the ultrasonic bulk wave in the air can be used to preferentially generate specific Lamb wave modes in the plate in a non-contact manner, depending on the plate dimensions and material properties. Multiple reflections of the ultrasonic waves in the air gap between the transmitter and the plate can produce additional delayed waves entering the plate at angles of incidence that are different to those of the original bulk wave source. Similarly, multiple reflections of the leaky Lamb waves in the air gap between the plate and an inclined receiver may then have different angles of incidence and propagation delays when arriving at the receiver and hence the signal analysis may become complex, potentially leading to confusion in the identification of the wave modes. To obtain a better understanding of the generation, propagation and detection of leaky Lamb waves and the effects of reflected waves within the air gaps, a multiphysics model using finite element methods was established. This model facilitated the visualisation of the propagation of the reflected waves between the transducers and the plate, the subsequent generation of additional Lamb wave signals within the plate itself, their leakage into the adjacent air, and the reflections of the leaky waves in the air gap between the plate and receiver. Multiple simulations were performed to evaluate the propagation and reflection of signals produced at different transducer incidence angles. Experimental measurements in air were in good agreement with simulation, which verified that the multiphysics model can provide a convenient and accurate way to interpret the signals in

  12. Monitoring of fatigue crack growth at fastener holes using guided Lamb waves

    NASA Astrophysics Data System (ADS)

    Fromme, P.; Sayir, M. B.

    2002-05-01

    An experimental method for the detection of fatigue cracks at holes in aluminum specimens is investigated. The first anti-symmetric Lamb wave mode A0 is excited. Using a heterodyne laser interferometer, the scattered field close to the hole during crack growth is monitored. The fatigue crack is initiated and propagated by cyclic tensile loading of the test specimen in a servo-hydraulic testing machine. The measurements are compared to finite difference calculations. Good qualitative agreement is found.

  13. Investigations of droplet movement excited by Lamb waves on a non-piezoelectric substrate

    NASA Astrophysics Data System (ADS)

    Liang, Wei; Lindner, Gerhard

    2013-07-01

    A model for the numerical simulation of the movement of liquid droplets excited by Lamb waves propagating on non-piezoelectric substrates was developed, and the results of simulation calculations based on this model were compared with experimental observations. In the experiments antisymmetrical zero order Lamb waves with 1 MHz center frequency were excited on a 1 mm thick glass substrate by piezoelectric single phase transducers, which caused the propulsion of microliter water droplets. The acoustic streaming within the droplet was calculated by solving the incompressible Navier-Stokes equations with an inhomogeneous acoustic streaming force field. These calculations were validated by optical measurements of the streaming effects in the droplet and by measurements of the displacement amplitudes of the Lamb waves with a laser-Doppler-vibrometer. Another part of the numerical simulations was related to the transient motion of acoustically driven droplets by solving the incompressible Navier-Stokes equations using the moving mesh application mode of the comsol software including a weak formulation for the calculation of the surface tension. The corresponding measurements with a high-speed camera revealed a silkworm-like movement of the droplet resulting from the interaction with acoustic force, surface tension, gravity, and inertial force, which was reproduced by the numerical simulations.

  14. Research on sensor technology of Lamb-wave signal acquisition using optical low-coherence

    NASA Astrophysics Data System (ADS)

    Zhu, Y. K.; Yang, C.; Li, X. W.; Chong, B.

    2012-10-01

    Non-destructive testing of composite materials is a key technology issue in equipment testing. Among the emerging new testing methods, Lamb-wave technology is getting more and more attention. This paper proposed a sensing method to acquire the Lamb-wave signal in thin plate based on optical low-coherence principles. Methods to acquire Lamb-wave in thin plate using optical low-coherence technology were analyzed, and the technical path of non-contact, high-precision method was chosen. Complete in-line experimental system and methods were designed and built up for testing. A sensor system based on Michelson low-coherence interferometer was set up. The distributed optical fiber sensors were arranged on the top of sample materials for signal detection. Mirrors to enhance reflection intensity were attached on the sample. The phase of sensing arm was modulated by PZT vibration. Then signals were detected and processed by Daubechies10 wavelet and Gabor wavelet. In-line testing of thin plate with features of high-precision and high signal-noise-ratio was realized, which is meaningful to dynamic testing of large-scale structure.

  15. Broadband Lamb Wave Trapping in Cellular Metamaterial Plates with Multiple Local Resonances

    PubMed Central

    Zhao, De-Gang; Li, Yong; Zhu, Xue-Feng

    2015-01-01

    We have investigated the Lamb wave propagation in cellular metamaterial plates constructed by bending-dominated and stretch-dominated unit-cells with the stiffness differed by orders of magnitude at an ultralow density. The simulation results show that ultralight metamaterial plates with textured stubs deposited on the surface can support strong local resonances for both symmetric and anti-symmetric modes at low frequencies, where Lamb waves at the resonance frequencies are highly localized in the vibrating stubs. The resonance frequency is very sensitive to the geometry of textured stubs. By reasonable design of the geometry of resonant elements, we establish a simple loaded-bar model with the array of oscillators having a gradient relative density (or weight) that can support multiple local resonances, which permits the feasibility of a broadband Lamb wave trapping. Our study could be potentially significant in designing ingenious weight-efficient acoustic devices for practical applications, such as shock absorption, cushioning, and vibrations traffic, etc. PMID:25790858

  16. Effects of adhesive, host plate, transducer and excitation parameters on time reversibility of ultrasonic Lamb waves.

    PubMed

    Agrahari, J K; Kapuria, S

    2016-08-01

    To develop an effective baseline-free damage detection strategy using the time-reversal process (TRP) of Lamb waves in thin walled structures, it is essential to develop a good understanding of the parameters that affect the amplitude dispersion and consequently the time reversibility of the Lamb wave signal. In this paper, the effects of adhesive layer between the transducers and the host plate, the tone burst count of the excitation signal, the plate thickness, and the piezoelectric transducer thickness on the time reversibility of Lamb waves in metallic plates are studied using experiments and finite element simulations. The effect of adhesive layer on the forward propagation response and frequency tuning has been also studied. The results show that contrary to the general expectation, the quality of the reconstruction of the input signal after the TRP may increase with the increase in the adhesive layer thickness at certain frequency ranges. Similarly, an increase in the tone burst count resulting in a narrowband signal does not necessarily enhance the time reversibility at all frequencies, contrary to what has been reported earlier. For a given plate thickness, a thinner transducer yields a better reconstruction, but for a given transducer thickness, the similarity of the reconstructed signal may not be always higher for a thicker plate. It is important to study these effects to achieve the best quality of reconstruction in undamaged plates, for effective damage detection. PMID:27176646

  17. PVDF array sensor for Lamb wave reception: Aircraft structural health monitoring

    NASA Astrophysics Data System (ADS)

    Ren, Baiyang; Lissenden, Cliff J.

    2016-02-01

    Fracture critical structures need structural health monitoring (SHM) to improve safety and reliability as well as reduce downtime and maintenance costs. Lamb waves provide promising techniques for on-line SHM systems because of their large volumetric coverage and good sensitivity to defects. Extensive research has focused on using features derived from time signals obtained at sparse locations distributed across the structure. Commonly used features are wave amplitude, energy, and time of arrival. However, the modal content of received Lamb waves contains valuable information about the existence and characteristics of defects, but cannot be determined from these signal features. Wave scattering at a defect often results in mode conversions in both transmitted and reflected waves. Features like change in time of arrival or amplitude reduction can be interpreted as being a result of mode conversion. This work is focused on the design of a 1D array sensor such that received wave signals at equally spaced locations are available for modal analysis in the wavenumber-frequency domain. PVDF (polyvinylidene fluoride) is selected as the active material of the sensor because of its low interference with wave fields in structures. The PVDF array sensor is fabricated to have 16 independent channels and its capability to detect and characterize different types of defects is demonstrated experimentally.

  18. Wall thickness measurement using resonant phenomena of circumferential Lamb waves generated by plural transducer elements located evenly on girth

    NASA Astrophysics Data System (ADS)

    Nishino, Hideo; Iwata, Kodai; Ishikawa, Masashi

    2016-07-01

    We present a novel method of measuring the pipe wall thickness using the resonance of the circumferential (C-) Lamb wave generated by a piezoelectric ring-shaped sensor (PS). The PS is a special device for an axially propagating torsional wave; however, the C-Lamb waves are generated simultaneously as spurious signals owing to the structure of the PS. Particularly under resonant conditions, the C-Lamb waves are dominantly generated, distorting the axially propagating wave. In this method, these troublesome spurious signals are used effectively for the measurement of the wall thickness under the PS location that is a dead zone of the PS itself. The method can compensate for its drawback, namely, the dead zone problem, without using additional instruments. In this study, the mechanisms of the generation and resonance of the C-Lamb waves were first explained. Secondly, the principle of the wall thickness estimation utilizing the resonance of the C-Lamb waves was proposed. Finally, experimental verifications were carried out. The estimated wall thicknesses agreed very well (maximum 1.5% error) with those measured by a micrometer caliper under suitable resonant conditions.

  19. Lamb wave excitation and propagation in elastic plates with surface obstacles: proper choice of central frequencies

    NASA Astrophysics Data System (ADS)

    Glushkov, Evgeny; Glushkova, Natalia; Lammering, Rolf; Eremin, Artem; Neumann, Mirko N.

    2011-01-01

    Experimental and theoretical investigations of Lamb wave excitation and sensing using piezo patch transducers and the laser vibrometer technique have been performed, aiming at the development of adequate mathematical and computer models for the interpretation of sensing data and for the choice of optimal parameters for structural health monitoring. The proposed models are validated by experimental results. Furthermore, a methodology is presented which allows for the determination of central frequencies at which maximal values of the structural response spectrum can be expected in the case of wave propagation monitoring with laser vibrometry.

  20. Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

    NASA Astrophysics Data System (ADS)

    Shen, Li; Wu, Jiu Hui; Liu, Zhangyi; Fu, Gang

    2015-11-01

    In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

  1. Lamb wave detection of limpet mines on ship hulls.

    PubMed

    Bingham, Jill; Hinders, Mark; Friedman, Adam

    2009-12-01

    This paper describes the use of ultrasonic guided waves for identifying the mass loading due to underwater limpet mines on ship hulls. The Dynamic Wavelet Fingerprint Technique (DFWT) is used to render the guided wave mode information in two-dimensional binary images because the waveform features of interest are too subtle to identify in time domain. The use of wavelets allows both time and scale features from the original signals to be retained, and image processing can be used to automatically extract features that correspond to the arrival times of the guided wave modes. For further understanding of how the guided wave modes propagate through the real structures, a parallel processing, 3D elastic wave simulation is developed using the finite integration technique (EFIT). This full field, technique models situations that are too complex for analytical solutions, such as built up 3D structures. The simulations have produced informative visualizations of the guided wave modes in the structures as well as mimicking directly the output from sensors placed in the simulation space for direct comparison to experiments. Results from both drydock and in-water experiments with dummy mines are also shown.

  2. Time-frequency beamforming for nondestructive evaluations of plate using ultrasonic Lamb wave

    NASA Astrophysics Data System (ADS)

    Han, Je-Heon; Kim, Yong-Joe

    2015-03-01

    The objective of this study is to detect structural defect locations in a plate by exciting the plate with a specific ultrasonic Lamb wave and recording reflective wave signals using a piezoelectric transducer array. For the purpose of eliminating the effects of the direct excitation signals as well as the boundary-reflected wave signals, it is proposed to improve a conventional MUSIC beamforming procedure by processing the measured signals in the time-frequency domain. In addition, a normalized, damped, cylindrical 2-D steering vector is proposed to increase the spatial resolution of time-frequency MUSIC power results. A cross-shaped array is selected to further improve the spatial resolution and to avoid mirrored virtual image effects. Here, it is experimentally demonstrated that the proposed time-frequency MUSIC beamforming procedure can be used to identify structural defect locations on an aluminum plate by distinguishing the defect-induced waves from the excitation-generated and boundary-reflected waves.

  3. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

    SciTech Connect

    Tadesse, Semere A.; Li, Huan; Liu, Qiyu; Li, Mo

    2015-11-16

    Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.

  4. Separation of Lamb waves modes using polarization filter of 3D laser measured signals

    NASA Astrophysics Data System (ADS)

    Ambrozinski, Lukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2015-04-01

    Interpretation of Lamb waves signals can rise serious difficulties due to their multi-modal nature. Different modes propagating with different velocities can be misleading with damage reflected components. As a solution to this problem we propose a technique capable of modes separation based on a polarization filter. Both S0 and A0 Lamb modes exhibit elliptical polarization, however, their polarization parameters, i.e. the ratios of in-plane and out-of-plane displacements and phase-shifts between these components are different. Furthermore, these parameters can be considered constant in a narrow frequency band. Therefore, if the vertical and horizontal components of the wave motion are available, it is possible to apply signal processing technique referred to as oblique polarization filter. This operation is based on phase-shifts and amplifications of the in- and out-of-plane components, which results in orthogonal, linearly polarized A0 and S0 waves signals. In this paper the proposed technique will be illustrated using both numerical simulations and experimental data. The simulations of wave propagation were performed using local interaction simulation approach (LISA) assuming isotropic material. The experiments were performed using 3D laser scanning Doppler vibrometer that allowed to capture the in-plane and out-of-plane wave components.

  5. Non-contact feature detection using ultrasonic Lamb waves

    DOEpatents

    Sinha, Dipen N.

    2011-06-28

    Apparatus and method for non-contact ultrasonic detection of features on or within the walls of hollow pipes are described. An air-coupled, high-power ultrasonic transducer for generating guided waves in the pipe wall, and a high-sensitivity, air-coupled transducer for detecting these waves, are disposed at a distance apart and at chosen angle with respect to the surface of the pipe, either inside of or outside of the pipe. Measurements may be made in reflection or transmission modes depending on the relative position of the transducers and the pipe. Data are taken by sweeping the frequency of the incident ultrasonic waves, using a tracking narrow-band filter to reduce detected noise, and transforming the frequency domain data into the time domain using fast Fourier transformation, if required.

  6. Phase velocities and attenuations of shear, Lamb, and Rayleigh waves in plate-like tissues submerged in a fluid (L).

    PubMed

    Nenadic, Ivan Z; Urban, Matthew W; Bernal, Miguel; Greenleaf, James F

    2011-12-01

    In the past several decades, the fields of ultrasound and magnetic resonance elastography have shown promising results in noninvasive estimates of mechanical properties of soft tissues. These techniques often rely on measuring shear wave velocity due to an external or internal source of force and relating the velocity to viscoelasticity of the tissue. The mathematical relationship between the measured velocity and material properties of the myocardial wall, arteries, and other organs with non-negligible boundary conditions is often complicated and computationally expensive. A simple relationship between the Lamb-Rayleigh dispersion and the shear wave dispersion is derived for both the velocity and attenuation. The relationship shows that the shear wave velocity is around 20% higher than the Lamb-Rayleigh velocity and that the shear wave attenuation is about 20% lower than the Lamb-Rayleigh attenuation. Results of numerical simulations in the frequency range 0-500 Hz are presented. PMID:22225009

  7. Evaluation of layer thickness in human teeth using higher-order-mode leaky Lamb wave interdigital transducers

    SciTech Connect

    Toda, Shinji; Fujita, Takeshi; Arakawa, Hirohisa; Toda, Kohji

    2005-03-01

    An ultrasonic nondestructive evaluation technique of the layer thickness in human teeth is proposed using a leaky Lamb wave device with two arch-shaped interdigital transducers, operating at a plate/water interface. The use of a higher-order-mode leaky Lamb wave with a phase velocity higher than the longitudinal wave velocity in the human tooth is essential to detect reflected ultrasound beams from the tooth section The layer thickness of dentin, estimated from the measured time interval between two reflected echoes, is in good agreement with the optically measured data.

  8. Lamb waves based fast subwavelength imaging using a DORT-MUSIC algorithm

    NASA Astrophysics Data System (ADS)

    He, Jiaze; Yuan, Fuh-Gwo

    2016-02-01

    A Lamb wave-based, subwavelength imaging algorithm is developed for damage imaging in large-scale, plate-like structures based on a decomposition of the time-reversal operator (DORT) method combined with the multiple signal classification (MUSIC) algorithm in the space-frequency domain. In this study, a rapid, hybrid non-contact scanning system was proposed to image an aluminum plate using a piezoelectric linear array for actuation and a laser Doppler vibrometer (LDV) line-scan for sensing. The physics of wave propagation, reflection, and scattering that underlies the response matrix in the DORT method is mathematically formulated in the context of guided waves. The singular value decomposition (SVD) and MUSIC-based imaging condition enable quantifying the damage severity by a `reflectivity' parameter and super-resolution imaging. With the flexibility of this scanning system, a considerably large area can be imaged using lower frequency Lamb waves with limited line-scans. The experimental results showed that the hardware system with a signal processing tool such as the DORT-MUSIC (TR-MUSIC) imaging technique can provide rapid, highly accurate imaging results as well as damage quantification with unknown material properties.

  9. Bayesian separation of Lamb wave signatures in laser ultrasonics

    NASA Astrophysics Data System (ADS)

    Kercel, Stephen W.; Klein, Marvin B.; Pouet, Bruno F.

    2000-03-01

    Laser-based ultrasonic (LBU) measurement shows great promise for on-line monitoring of weld quality in tailor-welded blanks. Tailor-welded blanks are steel blanks made from plates of differing thickness and/or properties butt-welded together; they are used in automobile manufacturing to produce body, frame, and closure panels. LBU uses a pulsed laser to generate the ultrasound and a continuous wave laser interferometer to detect the ultrasound at the point of interrogation to perform ultrasonic inspection. LBU enables in-process measurements since there is no sensor contact or near-contact with the workpiece. The authors are using laser-generated plate waves to propagate from one plate into the weld nugget as a means of detecting defects.

  10. EMAT-generated Lamb waves for volumetric inspection of strip steel

    NASA Astrophysics Data System (ADS)

    Latham, Wayne M.; Latimer, P. J.; MacLauchlan, Daniel T.; Camplin, Kenneth R.; Lang, Dennis D.

    1998-03-01

    The detection of longitudinally oriented defects in steel plate using ultrasonics has been widely reported. Ultrasonic methods are capable of detecting extremely small volume flaws in strip steel, but are limited because of the need to maintain fluid couplant between the transducer and steel strip. At a minimum, this couplant requirement slows the test speeds considerably, can introduce errors in test results, and, in many cases, prevents the test from being performed at all. The purpose of this paper is to present the results of the investigation of EMAT generated Lamb waves for the volumetric inspection of steel strip and subsequent on-line system performance. The strip steel industry has described a manufacturing problem of internal inclusions in their strip steel product for use in the automotive/appliance industry which is manifested after the rolling operation. The 'pencil pipe', a non-metallic inclusion introduced during the continuous casting process, is not detected prior to the roll, and after rolling it is too late to recover. A major midwestern US steel company considers this defect to be their number one quality problem. A method of detecting these inclusions prior to rolling was needed and is the basis of this development. The objective of this evaluation was the selection and implementation of EMAT generated Lamb wave modes that could be used for on-line detection of pencil pipe defects in strip steel before the strip is rolled to its final thickness. In addition, different Lamb waves modes were used to discriminate between the internal pencil pipe and non- deleterious surface scratches.

  11. Tomographic reconstruction of damage images in hollow cylinders using Lamb waves.

    PubMed

    Hu, Bin; Hu, Ning; Li, Leilei; Li, Weiguo; Tang, Shan; Li, Yuan; Peng, Xianghe; Homma, Atsushi; Liu, Yaolu; Wu, Liangke; Ning, Huiming

    2014-09-01

    Lamb wave tomography (LWT) is a potential and efficient technique for non-destructive tomographic reconstruction of damage images in structural components or materials. A two-stage inverse algorithm proposed by the authors for quickly reconstructing the damage images was applied to hollow cylinders. An aluminum hollow cylinder with an internal surface pit and a Carbon Fiber Reinforced Plastic (CFRP) laminated hollow cylinder with an artificial internal surface damage were used to validate the proposed method. The results show that the present method is capable of successfully reconstructing the images of the above damages in a larger inspection area with much less experimental data compared to some conventional ultrasonic tomography techniques.

  12. Measurement of Lamb wave polarization using a one-dimensional scanning laser vibrometer (L).

    PubMed

    Ayers, James; Apetre, Nicole; Ruzzene, Massimo; Sabra, Karim

    2011-02-01

    A single head scanning laser Doppler vibrometer is used for the estimation of the polarization of the first symmetric (S(0)) and antisymmetric (A(0)) Lamb wave modes. The measurements at two known incidence angles are performed in order to resolve the two components of motion. Filtering in the frequency/wavenumber domain of the response recorded along a scan line separates the contributions from each mode and allows the evaluation of the corresponding elliptical trajectories of particle motion. Comparison between measured and analytically estimated trajectories validates the measurement technique and suggests its application for the development of material characterization and diagnostics tools. PMID:21361415

  13. A Lamb waves based statistical approach to structural health monitoring of carbon fibre reinforced polymer composites.

    PubMed

    Carboni, Michele; Gianneo, Andrea; Giglio, Marco

    2015-07-01

    This research investigates a Lamb-wave based structural health monitoring approach matching an out-of-phase actuation of a pair of piezoceramic transducers at low frequency. The target is a typical quasi-isotropic carbon fibre reinforced polymer aeronautical laminate subjected to artificial, via Teflon patches, and natural, via suitable low velocity drop weight impact tests, delaminations. The performance and main influencing factors of such an approach are studied through a Design of Experiment statistical method, considering both Pulse Echo and Pitch Catch configurations of PZT sensors. Results show that some factors and their interactions can effectively influence the detection of a delamination-like damage.

  14. Measurement of Lamb wave polarization using a one-dimensional scanning laser vibrometer (L).

    PubMed

    Ayers, James; Apetre, Nicole; Ruzzene, Massimo; Sabra, Karim

    2011-02-01

    A single head scanning laser Doppler vibrometer is used for the estimation of the polarization of the first symmetric (S(0)) and antisymmetric (A(0)) Lamb wave modes. The measurements at two known incidence angles are performed in order to resolve the two components of motion. Filtering in the frequency/wavenumber domain of the response recorded along a scan line separates the contributions from each mode and allows the evaluation of the corresponding elliptical trajectories of particle motion. Comparison between measured and analytically estimated trajectories validates the measurement technique and suggests its application for the development of material characterization and diagnostics tools.

  15. Lamb wave inspection for large cracks in centrifugally cast stainless steel: Interim report

    SciTech Connect

    Not Available

    1988-08-01

    The objective of the present research project is to develop an inspection technique to detect and size large-scale cracks in centrifugally cast stainless steel (CCSS) pipes. This technique is based on the use of Lamb waves, or generally the resonant modes of propagation in the considered geometry, to circumvent the difficulties encountered when the conventional ultrasonic bulk waves are used to inspect the anisotropic, highly absorptive CCSS material. The research activities in 1987 were focused on probe design, Lamb-wave mode selection and excitation, detection mechanism, and anisotropy and curvature effects. The optimal design of a laboratory search unit was determined to be a tandem dual-element system built on the liquid-wedge principle. A reliable mechanism, which features a strong amplitude reduction when the search unit is scanned over a crack, was identified for crack detection and location. The preliminary experimental and analytical findings indicate that the best resonant modes were identified to be the four lowest modes in light of their excitability and minimization of the anisotropy effect. Finally, for typical geometrical dimensions under consideration, the curvature effect was found to be minimal.

  16. Lamb wave propagation in a restricted geometry composite pi-joint specimen

    NASA Astrophysics Data System (ADS)

    Blackshire, James L.; Soni, Som

    2012-05-01

    The propagation of elastic waves in a material can involve a number of complex physical phenomena, resulting in both subtle and dramatic effects on detected signal content. In recent years, the use of advanced methods for characterizing and imaging elastic wave propagation and scattering processes has increased, where for example the use of scanning laser vibrometry and advanced computational models have been used very effectively to identify propagating modes, scattering phenomena, and damage feature interactions. In the present effort, the propagation of Lamb waves within a narrow, constrained geometry composite pi-joint structure are studied using 3D finite element models and scanning laser vibrometry measurements, where the effects of varying sample thickness, complex joint curvatures, and restricted structure geometries are highlighted, and a direct comparison of computational and experimental results are provided for simulated and realistic geometry composite pi-joint samples.

  17. Calculations of Lamb wave band gaps and dispersions for piezoelectric phononic plates using mindlin's theory-based plane wave expansion method.

    PubMed

    Hsu, Jin-Chen; Wu, Tsung-Tsong

    2008-02-01

    Based on Mindlin's piezoelectric plate theory and the plane wave expansion method, a formulation is proposed to study the frequency band gaps and dispersion relations of the lower-order Lamb waves in two-dimensional piezoelectric phononic plates. The method is applied to analyze the phononic plates composed of solid-solid and airsolid constituents with square and triangular lattices, respectively. Factors that influence the opening and width of the complete Lamb wave gaps are identified and discussed. For solid/solid phononic plates, it is suggested that the filling material be chosen with larger mass density, proper stiffness, and weak anisotropic factor embedded in a soft matrix in order to obtain wider complete band gaps of the lower-order Lamb waves. By comparing to the calculated results without considering the piezoelectricity, the influences of piezoelectric effect on Lamb waves are analyzed as well. On the other hand, for air/solid phononic plates, a background material itself with proper anisotropy and a high filling fraction of air may favor the opening of the complete Lamb wave gaps.

  18. Laser-Generated Lamb Waves Propagation in Multilayered Plates Composed of Viscoelastic Fiber-reinforced Composite Materials

    NASA Astrophysics Data System (ADS)

    Sun, Hong-xiang; Zhang, Shu-yi; Yuan, Shou-qi; Guan, Yi-jun; Ge, Yong

    2016-07-01

    The propagation characteristics of laser-generated Lamb waves in multilayered fiber-reinforced composite plates with different fiber orientations and number of layers have been investigated quantitatively. Considering the viscoelasticity of the composite materials, we have set up finite element models for simulating the laser-generated Lamb waves in two types of the multilayered composite plates. In the first type, different fiber orientations are adopted. In the second one, different number of layers are considered. The results illustrate the occurrence of attenuation and dispersion, which is induced by the viscoelasticity and multilayer structure, respectively.

  19. Statistical updating of finite element model with Lamb wave sensing data for damage detection problems

    NASA Astrophysics Data System (ADS)

    Vanli, O. Arda; Jung, Sungmoon

    2014-01-01

    Health monitoring of large structures with embedded, distributed sensor systems is gaining importance. This study proposes a new probabilistic model updating method in order to improve the damage prediction capability of a finite element analysis (FEA) model with experimental observations from a Lamb-wave sensing system. The approach statistically calibrates unknown parameters of the FEA model and estimates a bias-correcting function to achieve a good match between the model predictions and sensor observations. An experimental validation study is presented in which a set of controlled damages are generated on a composite panel. Time-series signals are collected with the damage condition using a Lamb-wave sensing system and a one dimensional FEA model of the panel is constructed to quantify the damages. The damage indices from both the experiments and the computational model are used to calibrate assumed parameters of the FEA model and to estimate a bias-correction function. The updated model is used to predict the size (extent) and location of damage. It is shown that the proposed model updating approach achieves a prediction accuracy that is superior to a purely statistical approach or a deterministic model calibration approach.

  20. Simulation of Lamb wave propagation for the characterization of complex structures.

    PubMed

    Agostini, Valentina; Delsanto, Pier Paolo; Genesio, Ivan; Olivero, Dimitri

    2003-04-01

    Reliable numerical simulation techniques represent a very valuable tool for analysis. For this purpose we investigated the applicability of the local interaction simulation approach (LISA) to the study of the propagation of Lamb waves in complex structures. The LISA allows very fast and flexible simulations, especially in conjunction with parallel processing, and it is particularly useful for complex (heterogeneous, anisotropic, attenuative, and/or nonlinear) media. We present simulations performed on a glass fiber reinforced plate, initially undamaged and then with a hole passing through its thickness (passing-by hole). In order to give a validation of the method, the results are compared with experimental data. Then we analyze the interaction of Lamb waves with notches, delaminations, and complex structures. In the first case the discontinuity due to a notch generates mode conversion, which may be used to predict the defect shape and size. In the case of a single delamination, the most striking "signature" is a time-shift delay, which may be observed in the temporal evolution of the signal recorded by a receiver. We also present some results obtained on a geometrically complex structure. Due to the inherent discontinuities, a wealth of propagation mechanisms are observed, which can be exploited for the purpose of quantitative nondestructive evaluation (NDE).

  1. Effects of Z-pins on Lamb waves in composite plates

    NASA Astrophysics Data System (ADS)

    Swenson, Eric D.; Kapoor, Hitesh; Soni, Som R.

    2010-04-01

    This experimental research investigates the effects of adding z-pins to a carbon fiber reinforced plate (CFRP) on Lamb wave propagation, such as mode conversion and reflections. The motivation for this study is derived from the current and expected future use of z-pins in aircraft structures coupled with the requirement to design structural health monitoring (SHM) systems for detecting damage in regions of composite structures with z-pins. This experimental study is conducted on two 4.8 mm thick CFRP test articles, where one plate has a 20 by 279 mm2 band of z-pins and the other does not. The z-pins have an average diameter of 0.28 mm and are inserted through the thickness of the panel with an area density of 4% before curing. A three-dimensional (3D) laser Doppler vibrometer (LDV) was employed to collect velocity measurements over a 1 mm uniformly-spaced grid of 17,899 scan points. Time-sequenced 3D LDV scans are presented to show that adding this relatively small amount of z-pins to a 4.8 mm thick CFRP has few measureable effects on Lamb wave propagation.

  2. Detection of thermal fatigue in composites by second harmonic Lamb waves

    NASA Astrophysics Data System (ADS)

    Li, Weibin; Cho, Younho; Achenbach, Jan D.

    2012-08-01

    Composite materials which are widely used in the aerospace industry, are usually subjected to frequent variation of temperature. Thermal cyclic loading may induce material degradation. Considering the long-term service of aircraft composites and the importance of safety in the aircraft industry, even a little damage that may be accumulative via thermal fatigue is often of great concern. Therefore, there is a demand to develop non-destructive approaches to evaluate thermal fatigue damage in an early stage. Due to the sensitivity of acoustic nonlinearity to micro-damage, the nonlinear ultrasonic technique has been explored as a promising tool for early detection of micro-damage. This paper investigates an experimental scheme for characterizing thermal fatigue damage in composite laminates using second harmonic Lamb waves. The present results show a monotonic increase of acoustic nonlinearity with respect to thermal fatigue cycles. The experimental observation of the correlation between the acoustic nonlinearity and thermal fatigue cycles in carbon/epoxy laminates verifies that nonlinear Lamb waves can be used to assess thermal fatigue damage rendering improved sensitivity over conventional linear feature based non-destructive evaluation techniques. Velocity and attenuation based ultrasonic studies are carried out for comparison with the nonlinear ultrasonic approach and it is found that nonlinear acoustic parameters are more promising indicators of thermal fatigue damage than linear ones.

  3. Lamb waves propagation in functionally graded piezoelectric materials by Peano-series method.

    PubMed

    Ben Amor, Morched; Ben Ghozlen, Mohamed Hédi

    2015-01-01

    The Peano-series expansion is used to investigate the propagation of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb wave modes in a functionally graded piezoelectric material (FGPM) plate. Aluminum nitride has been retained for illustration, it is polarized along the thickness axis, and at the same time the material properties change gradually perpendicularly to the plate with an exponential variation. The effects of the gradient variation on the phase velocity and the coupling electromechanical factor are obtained. Appropriate curves are given to reflect their behavior with respect to frequency. The highest value of the electromechanical coupling factor has been observed for S0 mode, it is close to six percent, conversely for A0 mode it does not exceed 1.5%. The coupling factor maxima undergo a shift toward the high frequency area when the corresponding gradient coefficient increases. The Peano-series method computed under Matlab software, gives rapid convergence and accurate phase velocity when analysing Lamb waves in FGPM plate. The obtained numerical results can be used to design different sensors with high performance working at different frequency ranges by adjusting the extent of the gradient property.

  4. Delamination detection in composite laminates using dispersion change based on mode conversion of Lamb waves

    NASA Astrophysics Data System (ADS)

    Okabe, Yoji; Fujibayashi, Keiji; Shimazaki, Mamoru; Soejima, Hideki; Ogisu, Toshimichi

    2010-11-01

    A new ultrasonic propagation system has been constructed using macrofiber composite (MFC) actuators and fiber Bragg grating (FBG) sensors. The MFCs and FBGs can be integrated into composite laminates because of their small size and high fracture strain. The developed system can send and receive broadband Lamb waves. In this research, this system was used to detect delamination damage in composite laminates. First, the multiple modes of Lamb waves in a carbon-fiber-reinforced plastic (CFRP) quasi-isotropic laminate were identified by transmitting and receiving the symmetric and antisymmetric modes separately. Then, the mode conversions at both tips of a delamination were investigated through an experiment and a two-dimensional finite element analysis (FEA). A new delamination detection method was proposed on the basis of the mode conversions, and experiments were carried out on laminates with an artificial delamination. When antisymmetric modes were excited, the frequency dispersion of the received A1 mode changed, depending on the delamination length owing to the mode conversion between the A1 mode and the S0 mode. This phenomenon was confirmed through the FEA and these results prove that this new method is effective in detecting a delamination in CFRP laminates.

  5. Interaction of Guided Lamb Waves with Delaminations and Discontinuities in Composite Plate-Like Structures

    NASA Astrophysics Data System (ADS)

    Balasubramaniam, Krishnan; Ramadas, C.; Padiyar, Janardhan; Krishnamurthy, C. V.

    2011-06-01

    Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in-service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub-laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T-joint. During the interaction of Ao mode with structural discontinuity in a T-joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T-joint have been worked out using D-scan and B-scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non- Contact Ultrasound (NCU) technique.

  6. A novel damage index for fatigue damage detection in a laminated composites using Lamb waves

    NASA Astrophysics Data System (ADS)

    Seki, Daigo

    A well-established structural health monitoring (SHM) technique, the Lamb wave based approach, is used for fatigue damage identification in a laminated composite. A novel damage index, 'normalized correlation moment' (NCM) which is composed of the nth moment of the cross correlation of the baseline and comparison waves, was used as damage index for monitoring damage in composites and compared with the signal difference coefficient (SDC) which is one of the most commonly used damage indices. Composite specimens were fabricated by the hand layup method by followed by compression. Piezo electric disks mounted on composite specimens were used as actuators and sensors. Three point bending fatigue tests were carried out on an intact composite laminate and a delaminated composite laminate with [06/904/06] orientation. Finite element analysis was performed to test the validity of SDC and NCM for fatigue damage.

  7. 2D aperture synthesis for Lamb wave imaging using co-arrays

    NASA Astrophysics Data System (ADS)

    Ambrozinski, Lukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2014-03-01

    2D ultrasonic arrays in Lamb wave based SHM systems can operate in the phased array (PA) or synthetic focusing (SF) mode. In the real-time PA approach, multiple electronically delayed signals excite transmitting elements to form the desired wave-front, whereas receiving elements are used to sense scattered waves. Due to that, the PA mode requires multi channeled hardware and multiple excitations at numerous azimuths to scan the inspected region of interest. To the contrary, the SF mode, assumes a single element excitation of subsequent transmitters and off-line processing of the acquired data. In the simplest implementation of the SF technique, a single multiplexed input and output channels are required, which results in significant hardware simplification. Performance of a 2D imaging array depends on many parameters, such as, its topology, number of its transducers and their spacing in terms of wavelength as well as the type of weighting function (apodization). Moreover, it is possible to use sparse arrays, which means that not all array elements are used for transmitting and/ or receiving. In this paper the co-array concept is applied to facilitate the synthesis process of an array's aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum co-array is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual elements' locations in the sub-arrays used for imaging. The coarray framework will be presented here using two different array topologies, aID uniform linear array and a cross-shaped array that will result in a square coarray. The approach will be discussed in terms of array patterns and beam patterns of the resulting imaging systems. Both, theoretical and experimental results will be given.

  8. In-Process Detection of Weld Defects Using Laser-Based Ultrasonic Lamb Waves

    SciTech Connect

    Kercel, S W

    2001-01-04

    Laser-based ultrasonic (LBU) measurement shows great promise for on-line monitoring of weld quality in tailor-welded blanks. Tailor-welded blanks are steel blanks made from plates of differing thickness and/or properties butt-welded together; they are used in automobile manufacturing to produce body, frame, and closure panels. LBU uses a pulsed laser to generate the ultrasound and a continuous wave (CW) laser interferometer to detect the ultrasound at the point of interrogation to perform ultrasonic inspection. LBU enables in-process measurements since there is no sensor contact or near-contact with the workpiece. The authors have used laser-generated plate (Lamb) waves to propagate from one plate into the weld nugget as a means of detecting defects. This report recounts an investigation of a number of inspection architectures based on processing of signals from selected plate waves, which are either reflected from or transmitted through the weld zone. Bayesian parameter estimation and wavelet analysis (both continuous and discrete) have shown that the LBU time-series signal is readily separable into components that provide distinguishing features, which describe weld quality. The authors anticipate that, in an on-line industrial application, these measurements can be implemented just downstream from the weld cell. Then the weld quality data can be fed back to control critical weld parameters or alert the operator of a problem requiring maintenance. Internal weld defects and deviations from the desired surface profile can then be corrected before defective parts are produced. The major conclusions of this study are as follows. Bayesian parameter estimation is able to separate entangled Lamb wave modes. Pattern recognition algorithms applied to Lamb mode features have produced robust features for distinguishing between several types of weld defects. In other words, the information is present in the output of the laser ultrasonic hardware, and it is feasible to

  9. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness.

    PubMed

    Seale, M D; Madaras, E I

    1999-09-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels. PMID:10489699

  10. Cumulative second-harmonic analysis of ultrasonic Lamb waves for ageing behavior study of modified-HP austenite steel.

    PubMed

    Xiang, Yanxun; Deng, Mingxi; Xuan, Fu-Zhen; Liu, Chang-Jun

    2011-12-01

    The cumulative second-harmonic analysis of ultrasonic Lamb wave has been performed to study the precipitation kinetics and microvoid initiation of ferritic Cr-Ni alloy steel during the ageing process. Ageing of ferritic Cr-Ni alloy materials have been done at 1223 K and 1173 K for different degradation time intervals and air cooled. The results show that the normalized acoustic nonlinearity of Lamb wave increases with the formation of fine precipitates at the early stage of ageing till about 1000 h and keeps as a plateau with the precipitates dynamic balance for a long-term ageing, and then decreases gradually at the final holding time with the coarsening of precipitates and initiation of microvoids. The results also show that the variation of nonlinear Lamb wave follows the same trend as that of hardness in materials. Therefore, the cumulative second-harmonic of ultrasonic Lamb waves has been found to be strongly sensitive to the precipitates behavior and microstructure evolution during the thermal ageing of ferritic Cr-Ni alloy steel.

  11. Imaging of a Defect in Thin Plates Using the Time Reversal of Single Mode Lamb Waves

    NASA Astrophysics Data System (ADS)

    Jeong, Hyunjo; Lee, Jung-Sik; Bae, Sung-Min

    2011-06-01

    This paper presents an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of-flight information on the defect location. One of the side band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free detection of a defect, so that experimental studies are needed to verify the proposed method and to be applied to real structure.

  12. A Baseline-Free Defect Imaging Technique in Plates Using Time Reversal of Lamb Waves

    NASA Astrophysics Data System (ADS)

    Hyunjo, Jeong; Sungjong, Cho; Wei, Wei

    2011-06-01

    We present an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of-flight information on the defect location. One of the side-band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free imaging of a defect.

  13. Transmission of Lamb waves and resonance at an adhesive butt joint of plates.

    PubMed

    Mori, Naoki; Biwa, Shiro

    2016-12-01

    The transmission behavior of Lamb waves and the possible occurrence of resonance at an adhesive butt joint of plates are studied experimentally. To this purpose, two 2.5-mm thick aluminum alloy plates are bonded at their edges using cyanoacrylate-based adhesive. Bonded plate specimens with different joint conditions are prepared by changing the bonding procedure. The measurements are performed for the transmission characteristics of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb modes for the frequency range of 0.4-0.6MHz below the cut-off frequency of the higher-order modes. The experimental results show that the transmission coefficients of the S0 and A0 modes exhibit different frequency-dependent characteristics depending on the joint condition. Furthermore, for the incidence of the S0 mode at the center frequency of 1MHz, the transmitted S0 mode in weakly bonded specimens shows a long oscillation tail due to the resonance effect. The experimental results are discussed in the light of the theoretical results based on the spring-type interface model. The interfacial stiffnesses identified from the transmission coefficients are shown to be correlated with the bonding condition of the joint and give reasonable estimates of the resonance frequencies of weakly bonded specimens. PMID:27490207

  14. Designing of sparse 2D arrays for Lamb wave imaging using coarray concept

    NASA Astrophysics Data System (ADS)

    Ambroziński, Łukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2015-03-01

    2D ultrasonic arrays have considerable application potential in Lamb wave based SHM systems, since they enable equivocal damage imaging and even in some cases wave-mode selection. Recently, it has been shown that the 2D arrays can be used in SHM applications in a synthetic focusing (SF) mode, which is much more effective than the classical phase array mode commonly used in NDT. The SF mode assumes a single element excitation of subsequent transmitters and off-line processing the acquired data. In the simplest implementation of the technique, only single multiplexed input and output channels are required, which results in significant hardware simplification. Application of the SF mode for 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process, however, it enables sparse array designs with performance similar to that of the fully populated dense arrays. In this paper we present the coarray concept to facilitate synthesis process of an array's aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum coarray is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual sub-arrays' elements locations. The coarray framework will be presented here using a an example of a star-shaped array. The approach will be discussed in terms of beampatterns of the resulting imaging systems. Both simulated and experimental results will be included.

  15. Imaging of Lamb Waves in Plates for Quantitative Determination of Anisotropy using Photorefractive Dynamic Holography

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall

    1998-06-01

    Anisotropic properties of sheet materials can be determined by measuring the propagation of Lamb waves in different directions. Electromagnetic acoustic transduction and laser ultrasonic methods provide noncontacting approaches that are often desired for application to industrial and processing environments. This paper describes a laser imaging approach utilizing the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb wave mode in all directions simultaneously. Continuous excitation is employed enabling the data to be recorded and displayed by a CCD camera. Analysis of the image produces a direct quantitative determination of the phase velocity in all directions showing plate anisotropy in the plane. Many optical techniques for measuring ultrasonic motion at surfaces have been developed for use in applications such as vibration measurement and laser ultrasonics. Most of these methods have similar sensitivities and are based on time domain processing using homodyne, Fabry-Perot [1], and, more recently, photorefractive interferometry [2]. Generally, the methods described above do not allow measurement at more than one surface point simultaneously, requiring multiple beam movements and scanning in order to produce images of surface ultrasonic motion over a large area. Electronic speckle interferometry, including shearography, does provide images directly of vibrations over large surface areas. This method has proven very durable in the field for large displacement amplitudes of several wavelengths. In addition, a sensitivity of ë/3000 has been demonstrated under laboratory conditions [3]. Full-field imaging of traveling ultrasonic waves using digital shearography has been recently reported with sensitivity in the nanometer range [4]. With this method, optical interference occurs at the photodetector

  16. Investigation of the Higher Harmonic Lamb Wave Generation in Hyperelastic Isotropic Material

    NASA Astrophysics Data System (ADS)

    Rauter, Natalie; Lammering, Rolf

    Micro-structural damages, such as micro-cracks and voids, give locally rise to stresses and may initiate subsequent failure of structural components. Therefore, the development of methods for the detection of microstructural damage and the observation of their growth is an important and ongoing area of research, especially for thin-walled structures. The proposed method for the detection is based on the nonlinearity caused by the micro-structural damages. Lamb waves are generated which induce simultaneously higher harmonic modes due the inherent nonlinearity. For detailed investigations, numerical simulations are essential. In this work, the nonlinearity is modeled by the material law, which is based on the Neo- Hookean and Mooney-Rivlin material models. In contrast to previous studies, which used third order elastic coefficients, these hyperelastic material models are widely accepted, frequently used, and implemented in commonly available FEM software. In the numerical investigations, Lamb waves are generated in a thin-walled aluminum plate with windowed sine burst signals. Due to the nonlinearity in the material law, the waves are not only observed at the excitation frequency, but also at higher harmonic frequencies. Excitation at especially selected frequencies evoke the cumulative effect, and thus gives rise to the amplitudes of the higher harmonics. Comparing the S1-S2 and S2-S4 mode pairs clearly show the higher sensitivity of the latter to the material nonlinearity. This matches with previous published experimental results. Finally, it is shown that the results obtained agree qualitatively well with numerical analyses, in which the micro-structural damages are modeled directly by a respective finite element discretization.

  17. Numerical Simulation of Nonlinear Lamb Waves Used in a Thin Plate for Detecting Buried Micro-Cracks

    PubMed Central

    Wan, Xiang; Zhang, Qing; Xu, Guanghua; Tse, Peter W.

    2014-01-01

    Compared with conventional linear ultrasonic inspection methods, which are sensitive only to severe defects, nonlinear ultrasonic inspection methods are better for revealing micro-cracks in thin plates. However, most nonlinear ultrasonic inspection methods have only been experimentally investigated using bulk or Rayleigh waves. Numerical studies, especially numerical simulations of Lamb ultrasonic waves, have seldom been reported. In this paper, the interaction between nonlinear S0 mode Lamb waves and micro-cracks of various lengths and widths buried in a thin metallic plate was simulated using the finite element method (FEM). The numerical results indicate that after interacting with a micro-crack, a new wave-packet was generated in addition to the S0 mode wave-packet. The second harmonics of the S0 mode Lamb waves and the new wave-packet were caused by nonlinear acoustic effects at the micro-crack. An amplitude ratio indicator is thus proposed for the early detection of buried micro-cracks. PMID:24834908

  18. COMSOL modelling of the acoustoelastic effect

    NASA Astrophysics Data System (ADS)

    Watson, N. J.; Hazlehurst, T.; Povey, M. J. W.; Drennan, A.; Seaman, P.

    2015-01-01

    Many structural components are subjected to either constant or temporal mechanical loads, such as a suspension bridge bolts and rail tracks. Methods are required to accurately and efficiently measure the stresses experienced by these components to ensure they can continue to operate in an effective and safe manner. Acoustic techniques can be used to monitor the stress in a solid material via the acoustoelastic effect. This is the stress dependence of the acoustic velocity in an elastic media. This work develops a multiphysics computational model to study the acoustoelastic effect in a three point bending system. A simple linear relationship was utilised to represent the stress effect on the acoustic velocity. The simulation results were compared with experimental results and the same general trend was observed. An increase in applied load resulted in a greater difference between the time of flight of two transducers at the top and bottom of a component and perpendicular to the applied load. However, there were quantitative differences between the model and the experiment. The model was used to investigate different ultrasound transducer location and operating frequency, highlighting the benefit of modelling tools for the design of acoustic equipment.

  19. Measurement of beating effects in narrowband multimode Lamb wave displacement fields in aluminum plates by pulsed TV Holography

    NASA Astrophysics Data System (ADS)

    Fernandez, Jose L.; Trillo, Cristina; Doval, Angel F.; Cernadas, Daniel; Lopez, Carlos; Dorrio, Benito V.; Miranda, Marta; Rodriguez, Francisco

    2005-06-01

    Narrowband ultrasonic surface acoustic waves are of the greatest current interest for the nondestructive testing of thin-walled members and shell structures like plates, pipes, bridge girders, cans and many others. The measurement and characterization of ultrasonic displacement fields of Lamb waves by pulsed TV holography (TVH) is presented. Narrowband ultrasound is generated in a few millimeters thick aluminum plate by the prismatic coupling block method using a tone-burst excitation signal in the range of 1MHz. At this frequency, the plate supports only a few Lamb wave modes, mainly the A0 and S0 ones. The simultaneous presence of these modes produces a beating clearly detectable as a spatial amplitude modulation. Our self-developed TVH system performs the optical phase evaluation by the Spatial Fourier Transform Method and renders the instantaneous out-of-plane mechanical displacement field along the whole inspected area. From this field, the wavenumber of each Lamb mode can be obtained and, by combining them with the value of the ultrasound frequency and with the Rayleigh-Lamb theoretical frequency spectrum, information about the elastic constants of the specimen material is obtained.

  20. Numerical and experimental studies of delamination detection in short fiber reinforced composites using Lamb waves

    NASA Astrophysics Data System (ADS)

    Kudela, Pawel; Radzienski, Maciej; Ostachowicz, Wieslaw

    2016-04-01

    The aim of this paper is to present aspects of Lamb wave propagation in randomly oriented short fiber reinforce composites with delamination. Prediction of elastic constants is based on mechanics of composites, rule of mixture and total mass balance tailored to the spectral element mesh composed of 3D brick elements. Piezoelectric excitation as well as glue layer are taken into account. Complex full wave field includes multiple reflections at short fibers. This wave pattern is also obtained by the use of laser vibrometry confirming good quality of the model. Further studies are related to symmetrical and non-symmetrical delamination in respect to the thickness of the composite plate. Square delamination of the side length 10 mm is investigated. It has been found that reflections from delamination are mostly superimposed with reflections coming from short fibers. Hence, delamination detection by direct analysis of wave propagation pattern on the surface of the plate is ineffective. However, adaptive wavenumber filtering method overcome these difficulties and enables not only to detect the delamination but also is helpful for delamination size estimation. Moreover, the method is more effective if the full wavefield measurements are acquired on the surface of the plate which is closer to the delamination.

  1. PZT based tunable Interdigital Transducer for Lamb waves based NDT and SHM

    NASA Astrophysics Data System (ADS)

    Mańka, Michał; Rosiek, Mateusz; Martowicz, Adam; Stepinski, Tadeusz; Uhl, Tadeusz

    2016-10-01

    In this paper a novel concept of a tunable transducer for generation and sensing of the Lamb waves is presented. The proposed transducer is developed based on a commonly applied Interdigital Transducer (IDT). In the proposed design, further referred to as the Tunable IDT (T-IDT), the conventional comb electrodes with fixed pitch are replaced by a series of densely distributed discrete electrode strips. These electrodes can be easily interconnected in different configurations to match the required wavelength without a need of applying physical changes to the electrode layout. In order to verify the properties of the T-IDT, numerical simulations and experimental tests were performed and their results were compared to the ones obtained for the IDT. The outcomes from both the numerical and experimental analyses proved that the beampatterns generated by the T-IDT are similar to those determined for the conventional transducer. Moreover, the changes in electrode connections lead to the changes of phase-amplitude characteristics.

  2. Application of a Lamb waves based technique for structural health monitoring of GFRP undercyclic loading

    NASA Astrophysics Data System (ADS)

    Eremin, A.; Byakov, A.; Panin, S.; Burkov, M.; Lyubutin, P.; Sunder, R.

    2016-04-01

    A Lamb wave based ultrasonic technique as well as optical image characterization was utilized to estimate a current mechanical state of glass fiber reinforced polymers (GFRP) under cyclic tension. The ultrasonic acoustic method was applied in a 'pitch-catch' mode using piezoelectric transducers adhesively bonded onto a specimen surface. Numerical evaluation of acoustic data was performed by calculating two informative parameters: maximum of amplitude of the received signal and variance of signal envelopes. Optical images were registered and then analysed by calculating Shannon entropy that makes it possible to characterize changing of GFRP specimen translucency. The obtained results were treated in order to find out the relation between the current mechanical state of a specimen and informative parameter values being computed from the acoustic and optical signals.

  3. Higher and sub-harmonic Lamb wave mode generation due to debond-induced contact nonlinearity

    NASA Astrophysics Data System (ADS)

    Guha, Anurup; Bijudas, C. R.

    2016-04-01

    Non-cumulative higher and sub-harmonic Lamb wave mode generation as a result of partial-debond of piezoelectric wafer transducers (PWT) bonded onto an Aluminium plate, is numerically investigated and experimentally validated. The influence of excitation frequency on the extent of nonlinearity due to clapping mechanism of the partially-debonded PWTs is discussed. A set of specific frequency range is arrived at based on the Eigen-value and Harmonic analyses of PWTs used in the model. It is found that, at these frequencies, which are integral multiple of the first width-direction mode of a PWT, significantly higher amplitudes of higher-harmonics are observed. It is also seen that at specific debond-positions and lengths, sharp sub-harmonics in addition to higher-harmonics are present. Signal processing is carried out using Fast Fourier transform, which is normalized for comparisons.

  4. Active health system based on wavelet transform analysis of diffracted Lamb waves

    NASA Astrophysics Data System (ADS)

    Lemistre, Michel B.; Osmont, Daniel L.; Balageas, Daniel L.

    2000-08-01

    In composite materials, delaminations are discontinuities producing mode conversion processes generating various out-going modes. The Discrete Wavelet Transform allows isolating various propagation modes and extracting them in order to measure the time delay between the arrivals of the main burst and a specific out-going mode, for various propagation paths. This process permits, with a good accuracy, to localize a damage and to estimate its extension. An active health monitoring system composed of integrated disc-shaped, 100 (mu) m-thick and 5 mm-dia PZT transducers working sequentially as actuators and receives is presented. The diagnostic is based on multiresolution process by wavelet transform applied on recorded Lamb wave signals obtained before and after damage. The robustness and portability of this technique is demonstrated by the fact that, after validation in our laboratory it was successfully applied to data coming from an experiment conducted in an other Laboratory using its own Health Monitoring system.

  5. Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Madaras, Eric I.

    2004-01-01

    The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for

  6. Conjunctive and compromised data fusion schemes for identification of multiple notches in an aluminium plate using Lamb wave signals.

    PubMed

    Lu, Ye; Ye, Lin; Wang, Dong; Wang, Xiaoming; Su, Zhongqing

    2010-09-01

    Conjunctive and compromised data fusion schemes were applied to aggregate perceptions from individual actuator-sensor paths, for the purpose of evaluating positions of multiple notches in an aluminum plate, with the signatures extracted from the scattered Lamb wave signals captured by sensors. An active sensor network consisting of piezoelectric (lead zirconium tantalate, PZT) wafers was employed to activate and capture Lamb wave signals, where two-level configurations hierarchically provided global and local evaluations of the location of damage. A signal processing algorithm featuring signal correlation was proposed to facilitate accurate extraction of the arrival time of damage-scattered waves in the time domain. The diagnostic results demonstrate that the proposed approach is capable of identifying the locations of multiple notches with good accuracy.

  7. Lamb wave dispersion in a PZT/metal/PZT sandwich plate with imperfect interface

    NASA Astrophysics Data System (ADS)

    Kurt, Ilkay; Akbarov, Surkay D.; Sezer, Semih

    2016-07-01

    The Lamb wave dispersion in a PZT/Metal/PZT sandwich plate is investigated by employing the exact linear equations of electro-elastic waves in piezoelectric materials within the scope of the plane-strain state. It is assumed that at the interfaces between the piezoelectric face layers and metal core layer, shear-spring and normal-spring type imperfect conditions are satisfied. The degree of this imperfectness is estimated through the corresponding shear-spring and normal-spring type parameters which appear in the contact condition characterizing the transverse and normal displacements' discontinuity. The corresponding dispersion equation is derived, and as a result of the numerical solution to this equation, the dispersion curves are constructed for the first and second lowest modes in the cases where the material of the face layers is PZT and the material of the middle layer is Steel (St). Consequently, for the PZT/St/PZT sandwich plate, the study of the influence of the problem parameters such as the piezoelectric and dielectric constants, layer thickness ratios, non-dimensional shear-spring, and normal-spring type parameters, is carried out. In particular, it is established that the imperfectness of the contact between the layers of the plate causes a decrease in the values of the wave propagation velocity.

  8. Generation of narrowband antisymmetric lamb waves using a formed laser source in the ablative regime.

    PubMed

    Cosenza, Claudio; Kenderian, Shant; Djordjevic, B Boro; Green, Robert E; Pasta, Antonino

    2007-01-01

    A formed laser source, using a four-element lenticular array, is used in the ablative regime to generate select, narrowband, acoustic plate waves. The arrangement of the array produces acoustical signals that have frequencies compatible with the response of the broadband capacitive air-coupled transducer used in this study. A simplified concept is presented to explain the effect of a line array source on the frequency content of acoustic waves. The analytical model for a point pulse surface displacement is derived from the point load solution to Lamb's problem. The point pulse displacement elements of a line array source are summed mathematically, taking into account all applicable propagation modes and dispersion of plate waves. The model considers only the out-of-plane displacement of the antisymmetric plate modes to represent the detection capability of the broadband receiver. The distribution function of the laser beam energy profile is modified to depict the actual energy distribution that illuminates the surface of the plate. Filtering functions are made compatible with the sensitivity of the broadband receiver so as to retain only the detected frequencies in the model. The theoretical model showed good agreement with experimental results.

  9. Lamb mode selection for accurate wall loss estimation via guided wave tomography

    SciTech Connect

    Huthwaite, P.; Ribichini, R.; Lowe, M. J. S.; Cawley, P.

    2014-02-18

    Guided wave tomography offers a method to accurately quantify wall thickness losses in pipes and vessels caused by corrosion. This is achieved using ultrasonic waves transmitted over distances of approximately 1–2m, which are measured by an array of transducers and then used to reconstruct a map of wall thickness throughout the inspected region. To achieve accurate estimations of remnant wall thickness, it is vital that a suitable Lamb mode is chosen. This paper presents a detailed evaluation of the fundamental modes, S{sub 0} and A{sub 0}, which are of primary interest in guided wave tomography thickness estimates since the higher order modes do not exist at all thicknesses, to compare their performance using both numerical and experimental data while considering a range of challenging phenomena. The sensitivity of A{sub 0} to thickness variations was shown to be superior to S{sub 0}, however, the attenuation from A{sub 0} when a liquid loading was present was much higher than S{sub 0}. A{sub 0} was less sensitive to the presence of coatings on the surface of than S{sub 0}.

  10. Symmetry issues in the hybridization of multi-mode waves with resonators: an example with Lamb waves metamaterial

    PubMed Central

    Rupin, Matthieu; Roux, Philippe; Lerosey, Geoffroy; Lemoult, Fabrice

    2015-01-01

    Locally resonant metamaterials derive their effective properties from hybridization between their resonant unit cells and the incoming wave. This phenomenon is well understood in the case of plane waves that propagate in media where the unit cell respects the symmetry of the incident field. However, in many systems, several modes with orthogonal symmetries can coexist at a given frequency, while the resonant unit cells themselves can have asymmetric scattering cross-sections. In this paper we are interested in the influence of symmetry breaking on the hybridization of a wave field that includes multiple propagative modes. The A0 and S0 Lamb waves that propagate in a thin plate are good candidates for this study, as they are either anti-symmetric or symmetric. First we designed an experimental setup with an asymmetric metamaterial made of long rods glued to one side of a metallic plate. We show that the flexural resonances of the rods induce a break of the orthogonality between the A0/S0 modes of the free-plate. Finally, based on numerical simulations we show that the orthogonality is preserved in the case of a symmetric metamaterial leading to the presence of two independent polariton curves in the dispersion relation. PMID:26333601

  11. Symmetry issues in the hybridization of multi-mode waves with resonators: an example with Lamb waves metamaterial.

    PubMed

    Rupin, Matthieu; Roux, Philippe; Lerosey, Geoffroy; Lemoult, Fabrice

    2015-01-01

    Locally resonant metamaterials derive their effective properties from hybridization between their resonant unit cells and the incoming wave. This phenomenon is well understood in the case of plane waves that propagate in media where the unit cell respects the symmetry of the incident field. However, in many systems, several modes with orthogonal symmetries can coexist at a given frequency, while the resonant unit cells themselves can have asymmetric scattering cross-sections. In this paper we are interested in the influence of symmetry breaking on the hybridization of a wave field that includes multiple propagative modes. The A0 and S0 Lamb waves that propagate in a thin plate are good candidates for this study, as they are either anti-symmetric or symmetric. First we designed an experimental setup with an asymmetric metamaterial made of long rods glued to one side of a metallic plate. We show that the flexural resonances of the rods induce a break of the orthogonality between the A0/S0 modes of the free-plate. Finally, based on numerical simulations we show that the orthogonality is preserved in the case of a symmetric metamaterial leading to the presence of two independent polariton curves in the dispersion relation. PMID:26333601

  12. Lamb wave feature extraction using discrete wavelet transformation and Principal Component Analysis

    NASA Astrophysics Data System (ADS)

    Ghodsi, Mojtaba; Ziaiefar, Hamidreza; Amiryan, Milad; Honarvar, Farhang; Hojjat, Yousef; Mahmoudi, Mehdi; Al-Yahmadi, Amur; Bahadur, Issam

    2016-04-01

    In this research, a new method is presented for eliciting the proper features for recognizing and classifying the kinds of the defects by guided ultrasonic waves. After applying suitable preprocessing, the suggested method extracts the base frequency band from the received signals by discrete wavelet transform and discrete Fourier transform. This frequency band can be used as a distinctive feature of ultrasonic signals in different defects. Principal Component Analysis with improving this feature and decreasing extra data managed to improve classification. In this study, ultrasonic test with A0 mode lamb wave is used and is appropriated to reduce the difficulties around the problem. The defects under analysis included corrosion, crack and local thickness reduction. The last defect is caused by electro discharge machining (EDM). The results of the classification by optimized Neural Network depicts that the presented method can differentiate different defects with 95% precision and thus, it is a strong and efficient method. Moreover, comparing the elicited features for corrosion and local thickness reduction and also the results of the two's classification clarifies that modeling the corrosion procedure by local thickness reduction which was previously common, is not an appropriate method and the signals received from the two defects are different from each other.

  13. Probability-based diagnostic imaging using hybrid features extracted from ultrasonic Lamb wave signals

    NASA Astrophysics Data System (ADS)

    Zhou, Chao; Su, Zhongqing; Cheng, Li

    2011-12-01

    The imaging technique based on guided waves has been a research focus in the field of damage detection over the years, aimed at intuitively highlighting structural damage in two- or three-dimensional images. The accuracy and efficiency of this technique substantially rely on the means of defining the field values at image pixels. In this study, a novel probability-based diagnostic imaging (PDI) approach was developed. Hybrid signal features (including temporal information, intensity of signal energy and signal correlation) were extracted from ultrasonic Lamb wave signals and integrated to retrofit the traditional way of defining field values. To acquire hybrid signal features, an active sensor network in line with pulse-echo and pitch-catch configurations was designed, supplemented with a novel concept of 'virtual sensing'. A hybrid image fusion scheme was developed to enhance the tolerance of the approach to measurement noise/uncertainties and erroneous perceptions from individual sensors. As applications, the approach was employed to identify representative damage scenarios including L-shape through-thickness crack (orientation-specific damage), polygonal damage (multi-edge damage) and multi-damage in structural plates. Results have corroborated that the developed PDI approach based on the use of hybrid signal features is capable of visualizing structural damage quantitatively, regardless of damage shape and number, by highlighting its individual edges in an easily interpretable binary image.

  14. CMOS-compatible ruggedized high-temperature Lamb wave pressure sensor

    NASA Astrophysics Data System (ADS)

    Kropelnicki, P.; Muckensturm, K.-M.; Mu, X. J.; Randles, A. B.; Cai, H.; Ang, W. C.; Tsai, J. M.; Vogt, H.

    2013-08-01

    This paper describes the development of a novel ruggedized high-temperature pressure sensor operating in lateral field exited (LFE) Lamb wave mode. The comb-like structure electrodes on top of aluminum nitride (AlN) were used to generate the wave. A membrane was fabricated on SOI wafer with a 10 µm thick device layer. The sensor chip was mounted on a pressure test package and pressure was applied to the backside of the membrane, with a range of 20-100 psi. The temperature coefficient of frequency (TCF) was experimentally measured in the temperature range of -50 °C to 300 °C. By using the modified Butterworth-van Dyke model, coupling coefficients and quality factor were extracted. Temperature-dependent Young's modulus of composite structure was determined using resonance frequency and sensor interdigital transducer (IDT) wavelength which is mainly dominated by an AlN layer. Absolute sensor phase noise was measured at resonance to estimate the sensor pressure and temperature sensitivity. This paper demonstrates an AlN-based pressure sensor which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications.

  15. Research on a Lamb Wave and Particle Filter-Based On-Line Crack Propagation Prognosis Method.

    PubMed

    Chen, Jian; Yuan, Shenfang; Qiu, Lei; Cai, Jian; Yang, Weibo

    2016-03-03

    Prognostics and health management techniques have drawn widespread attention due to their ability to facilitate maintenance activities based on need. On-line prognosis of fatigue crack propagation can offer information for optimizing operation and maintenance strategies in real-time. This paper proposes a Lamb wave-particle filter (LW-PF)-based method for on-line prognosis of fatigue crack propagation which takes advantages of the possibility of on-line monitoring to evaluate the actual crack length and uses a particle filter to deal with the crack evolution and monitoring uncertainties. The piezoelectric transducers (PZTs)-based active Lamb wave method is adopted for on-line crack monitoring. The state space model relating to crack propagation is established by the data-driven and finite element methods. Fatigue experiments performed on hole-edge crack specimens have validated the advantages of the proposed method.

  16. Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves

    PubMed Central

    Li, Weibin; Xu, Chunguang; Cho, Younho

    2016-01-01

    Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates. PMID:26907283

  17. Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves.

    PubMed

    Li, Weibin; Xu, Chunguang; Cho, Younho

    2016-02-19

    Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates.

  18. Research on a Lamb Wave and Particle Filter-Based On-Line Crack Propagation Prognosis Method.

    PubMed

    Chen, Jian; Yuan, Shenfang; Qiu, Lei; Cai, Jian; Yang, Weibo

    2016-01-01

    Prognostics and health management techniques have drawn widespread attention due to their ability to facilitate maintenance activities based on need. On-line prognosis of fatigue crack propagation can offer information for optimizing operation and maintenance strategies in real-time. This paper proposes a Lamb wave-particle filter (LW-PF)-based method for on-line prognosis of fatigue crack propagation which takes advantages of the possibility of on-line monitoring to evaluate the actual crack length and uses a particle filter to deal with the crack evolution and monitoring uncertainties. The piezoelectric transducers (PZTs)-based active Lamb wave method is adopted for on-line crack monitoring. The state space model relating to crack propagation is established by the data-driven and finite element methods. Fatigue experiments performed on hole-edge crack specimens have validated the advantages of the proposed method. PMID:26950130

  19. Research on a Lamb Wave and Particle Filter-Based On-Line Crack Propagation Prognosis Method

    PubMed Central

    Chen, Jian; Yuan, Shenfang; Qiu, Lei; Cai, Jian; Yang, Weibo

    2016-01-01

    Prognostics and health management techniques have drawn widespread attention due to their ability to facilitate maintenance activities based on need. On-line prognosis of fatigue crack propagation can offer information for optimizing operation and maintenance strategies in real-time. This paper proposes a Lamb wave-particle filter (LW-PF)-based method for on-line prognosis of fatigue crack propagation which takes advantages of the possibility of on-line monitoring to evaluate the actual crack length and uses a particle filter to deal with the crack evolution and monitoring uncertainties. The piezoelectric transducers (PZTs)-based active Lamb wave method is adopted for on-line crack monitoring. The state space model relating to crack propagation is established by the data-driven and finite element methods. Fatigue experiments performed on hole-edge crack specimens have validated the advantages of the proposed method. PMID:26950130

  20. Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves.

    PubMed

    Li, Weibin; Xu, Chunguang; Cho, Younho

    2016-01-01

    Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates. PMID:26907283

  1. Simulation of Detecting Damage in Composite Stiffened Panel Using Lamb Waves

    NASA Technical Reports Server (NTRS)

    Wang, John T.; Ross, Richard W.; Huang, Guo L.; Yuan, Fuh G.

    2013-01-01

    Lamb wave damage detection in a composite stiffened panel is simulated by performing explicit transient dynamic finite element analyses and using signal imaging techniques. This virtual test process does not need to use real structures, actuators/sensors, or laboratory equipment. Quasi-isotropic laminates are used for the stiffened panels. Two types of damage are studied. One type is a damage in the skin bay and the other type is a debond between the stiffener flange and the skin. Innovative approaches for identifying the damage location and imaging the damage were developed. The damage location is identified by finding the intersection of the damage locus and the path of the time reversal wave packet re-emitted from the sensor nodes. The damage locus is a circle that envelops the potential damage locations. Its center is at the actuator location and its radius is computed by multiplying the group velocity by the time of flight to damage. To create a damage image for estimating the size of damage, a group of nodes in the neighborhood of the damage location is identified for applying an image condition. The image condition, computed at a finite element node, is the zero-lag cross-correlation (ZLCC) of the time-reversed incident wave signal and the time reversal wave signal from the sensor nodes. This damage imaging process is computationally efficient since only the ZLCC values of a small amount of nodes in the neighborhood of the identified damage location are computed instead of those of the full model.

  2. Precise Measurement of Pipe Wall Thickness in Noncontact Manner Using a Circumferential Lamb Wave Generated and Detected by a Pair of Air-Coupled Transducers

    NASA Astrophysics Data System (ADS)

    Nishino, Hideo; Asano, Tadashi; Taniguchi, Yuta; Yoshida, Kenichi; Ogawa, Hitoshi; Takahashi, Masakazu; Ogura, Yukio

    2011-07-01

    In this paper, we present a novel method of accurately estimating pipe wall thickness by detecting the minute difference in the angular wave number of a circumferential (C-) Lamb wave. A C-Lamb wave circling along a circumference of a pipe is transmitted and received by a pair of noncontact air-coupled ultrasonic transducers. For the accurate detection of the angular wave number, a large number of tone-burst cycles are used so as to superpose the C-Lamb wave on itself along its circumferential orbit. In this setting, the amplitude of the superposed region changes considerably with the angular wave number, from which the wall thickness can be estimated. This method is very useful to monitor the integrity of piping in high-temperature environments because of its noncontact nature. The principle of the method and experimental verification are shown.

  3. Lamb-wave (X, Y) giant tap screen panel with built-in microphone and loudspeaker.

    PubMed

    Nikolovski, Jean-Pierre

    2013-06-01

    This paper presents a passive (X, Y) giant tap screen panel (GTP). Based on the time difference of arrival principle (TDOA), the device localizes low-energy impacts of around 1 mJ generated by fingernail taps. Selective detection of A0 Lamb waves generated in the upper frequency spectrum, around 100 kHz, makes it possible to detect light to strong impacts with equal resolution or precision, close to 1 cm and 2 mm, respectively, for a 10-mm-thick and 1-m(2) glass plate. Additionally, with glass, symmetrical beveling of the edges is used to create a tsunami effect that reduces the minimum impacting speed for light taps by a factor of three. Response time is less than 1 ms. Maximum panel size is of the order of 10 m(2). A rugged integrated flat design with embedded transducers in an electrically shielding frame features waterproof and sticker/ tag proof operation. Sophisticated electronics with floating amplification maintains the panel at its maximum possible sensitivity according to the surrounding noise. Amplification and filtering turns the panel into a microphone and loudspeaker featuring 50 mV/Pa as a microphone and up to 80 dBlin between 500 Hz and 8 kHz as a loudspeaker.

  4. Lamb waves propagation in a novel metal-matrix phononic crystals plate

    NASA Astrophysics Data System (ADS)

    Li, Suobin; Chen, Tianning; Wang, Xiaopeng; Xi, Yanhui

    2016-09-01

    In this paper, the propagation properties of Lamb waves in a novel phononic crystals (PCs) plate composed of a square array of double-sided composite taper stubs, which are deposited on a 2D locally resonant PC plate that composes of an array of rubber fillers embedded in the steel plate is studied. It is shown that the spring-mass system of the resonator will be decoupled by introducing the rubber filler, and then the out-of-plane band gap (BG) and the in-plane BG can be adjusted into the same lowest frequency range, respectively (the out-of-plane BG is adjusted by the rubber filler and the in-plane BG is adjusted by the taper stub). As a result, the frequency range of the generated complete BG is between 59-93 Hz due to the overlap between the in-plane and out-of-plane BG. Compared with the classic double-sided stubbed PC plate, the relative bandwidth of the BG is enlargement by a factor of 5.5 and the location of the BG is reduced by a factor of 5.5 in the proposed structure. It provides an effective way for metal-matrix PCs to obtain complete BGs in low-frequency range (below 100 Hz), which has potential for the reduction of the vibration at low frequency in practical case.

  5. Design and characterization of an ultrasonic lamb-wave power delivery system.

    PubMed

    Kural, Aleksander; Pullin, Rhys; Holford, Karen; Lees, Jonathan; Naylon, Jack; Paget, Christophe; Featherston, Carol

    2013-06-01

    In this paper, a novel design for an ultrasonic power transmission system designed for use in aircraft structural monitoring systems is described. The prototype system uses ultrasonic Lamb waves to carry energy along plates, such as those used in aircraft structures, and commercially available piezoelectric patch transducers as the transmitter and receiver. This sets it apart from other acoustic power transmission systems reported to date. The optimum configuration transmitted 12.7 mW of power across a distance of 54 cm in a 1.5-mm-thick aluminum plate, while being driven by a 20-Vpp, 35-kHz sinusoidal electric signal. This is in the same order of magnitude as the power required by the wireless sensors nodes of a structural health monitoring system currently being developed by Cardiff University and its partners. Thus, the power transmission system can be considered a viable component of the power source combination considered for the sensor nodes, which will also include vibration and thermal energy harvesting. The paper describes the design and optimization of the transmission and reception circuits with the use of inductive compensation. The use of laser vibrometry to characterize the transducers and to understand the signal propagation between them is also reported. PMID:25004476

  6. Lamb wave ultrasonic evaluation of welded AA2024 specimens at tensile static and fatigue testing

    NASA Astrophysics Data System (ADS)

    Burkov, M. V.; Byakov, A. V.; Shah, R. T.; Lyubutin, P. S.; Panin, S. V.

    2015-10-01

    The paper deals with the investigation of Lamb waves ultrasonic testing technique applied for evaluation of different stress-strain and damaged state of aluminum specimens at static and fatigue loading in order to develop a Structural Health Monitoring (SHM) approach. The experimental results of tensile testing of AA2024T3 specimens with welded joints are presented. Piezoelectric transducers used as actuators and sensors were adhesively bonded to the specimen's surface using two component epoxy. The set of static and cyclic tensile tests with two frequencies of acoustic testing (50 kHz and 335 kHz) were performed. The recorded signals were processed to calculate the maximum envelope in order to evaluate the changes of the stress-strain state of the specimen and its microstructure during static tension. The registered data are analyzed and discussed in terms of signal attenuation due to the formation of fatigue defects during cyclic loading. Understanding the relations between acoustic signal features and fatigue damages will provide us the ability to determine the damage state of the structure and its residual lifetime in order to design a robust SHM system.

  7. Design and characterization of an ultrasonic lamb-wave power delivery system.

    PubMed

    Kural, Aleksander; Pullin, Rhys; Holford, Karen; Lees, Jonathan; Naylon, Jack; Paget, Christophe; Featherston, Carol

    2013-06-01

    In this paper, a novel design for an ultrasonic power transmission system designed for use in aircraft structural monitoring systems is described. The prototype system uses ultrasonic Lamb waves to carry energy along plates, such as those used in aircraft structures, and commercially available piezoelectric patch transducers as the transmitter and receiver. This sets it apart from other acoustic power transmission systems reported to date. The optimum configuration transmitted 12.7 mW of power across a distance of 54 cm in a 1.5-mm-thick aluminum plate, while being driven by a 20-Vpp, 35-kHz sinusoidal electric signal. This is in the same order of magnitude as the power required by the wireless sensors nodes of a structural health monitoring system currently being developed by Cardiff University and its partners. Thus, the power transmission system can be considered a viable component of the power source combination considered for the sensor nodes, which will also include vibration and thermal energy harvesting. The paper describes the design and optimization of the transmission and reception circuits with the use of inductive compensation. The use of laser vibrometry to characterize the transducers and to understand the signal propagation between them is also reported.

  8. Lamb-wave (X, Y) giant tap screen panel with built-in microphone and loudspeaker.

    PubMed

    Nikolovski, Jean-Pierre

    2013-06-01

    This paper presents a passive (X, Y) giant tap screen panel (GTP). Based on the time difference of arrival principle (TDOA), the device localizes low-energy impacts of around 1 mJ generated by fingernail taps. Selective detection of A0 Lamb waves generated in the upper frequency spectrum, around 100 kHz, makes it possible to detect light to strong impacts with equal resolution or precision, close to 1 cm and 2 mm, respectively, for a 10-mm-thick and 1-m(2) glass plate. Additionally, with glass, symmetrical beveling of the edges is used to create a tsunami effect that reduces the minimum impacting speed for light taps by a factor of three. Response time is less than 1 ms. Maximum panel size is of the order of 10 m(2). A rugged integrated flat design with embedded transducers in an electrically shielding frame features waterproof and sticker/ tag proof operation. Sophisticated electronics with floating amplification maintains the panel at its maximum possible sensitivity according to the surrounding noise. Amplification and filtering turns the panel into a microphone and loudspeaker featuring 50 mV/Pa as a microphone and up to 80 dBlin between 500 Hz and 8 kHz as a loudspeaker. PMID:25004480

  9. Effects of slits in a patch of omnidirectional Lamb-wave MPT on the transducer output

    NASA Astrophysics Data System (ADS)

    Kim, Kiyean; Lee, Hyung Jin; Lee, Joo Kyung; Kim, Yoon Young

    2016-03-01

    An omnidirectional Lamb-wave magnetostrictive patch transducer (MPT) uses a thin circular magnetostrictive patch excited by the axisymmetric turns of a plane coil placed over it. Since the dynamic magnetic field applied by the coil induces an eddy current only on the top surface due to the skin effect, the mechanical deformation in the patch is confined only near the surface, considerably limiting the transducer output power. This study shows that if a radial slit is introduced in the patch, the circular flow of the eddy current on the top surface only becomes broken, and thus the eddy current flows on both the top and bottom surfaces. As a consequence, there is a substantial increase in the dynamic magnetic field in the patch and, in turn, an increased transducer output power. Interestingly, the material type, either metallic or nonmetallic, of the test waveguide plate affects the magnitude of the eddy current near the bottom surface and the overall magnetic field. If the number of slits is over a certain number, say, 8, and the slits are symmetrically made in the patch, the omni-directivity of the resulting MPT is virtually ensured. Finally, the present findings are verified both numerically and experimentally.

  10. A quantitative method for evaluating numerical simulation accuracy of time-transient Lamb wave propagation with its applications to selecting appropriate element size and time step.

    PubMed

    Wan, Xiang; Xu, Guanghua; Zhang, Qing; Tse, Peter W; Tan, Haihui

    2016-01-01

    Lamb wave technique has been widely used in non-destructive evaluation (NDE) and structural health monitoring (SHM). However, due to the multi-mode characteristics and dispersive nature, Lamb wave propagation behavior is much more complex than that of bulk waves. Numerous numerical simulations on Lamb wave propagation have been conducted to study its physical principles. However, few quantitative studies on evaluating the accuracy of these numerical simulations were reported. In this paper, a method based on cross correlation analysis for quantitatively evaluating the simulation accuracy of time-transient Lamb waves propagation is proposed. Two kinds of error, affecting the position and shape accuracies are firstly identified. Consequently, two quantitative indices, i.e., the GVE (group velocity error) and MACCC (maximum absolute value of cross correlation coefficient) derived from cross correlation analysis between a simulated signal and a reference waveform, are proposed to assess the position and shape errors of the simulated signal. In this way, the simulation accuracy on the position and shape is quantitatively evaluated. In order to apply this proposed method to select appropriate element size and time step, a specialized 2D-FEM program combined with the proposed method is developed. Then, the proper element size considering different element types and time step considering different time integration schemes are selected. These results proved that the proposed method is feasible and effective, and can be used as an efficient tool for quantitatively evaluating and verifying the simulation accuracy of time-transient Lamb wave propagation. PMID:26315506

  11. Lamb wave dispersion and anisotropy profiling of composite plates via non-contact air-coupled and laser ultrasound

    NASA Astrophysics Data System (ADS)

    Harb, M. S.; Yuan, F. G.

    2015-03-01

    Conventional ultrasound inspection has been a standard non-destructive testing method for providing an in-service evaluation and noninvasive means of probing the interior of a structure. In particular, measurement of the propagation characteristics of Lamb waves allows inspection of plates that are typical components in aerospace industry. A rapid, complete non-contact hybrid approach for excitation and detection of Lamb waves is presented and applied for non-destructive evaluation of composites. An air-coupled transducer (ACT) excites ultrasonic waves on the surface of a composite plate, generating different propagating Lamb wave modes and a laser Doppler vibrometer (LDV) is used to measure the out-of-plane velocity of the plate. This technology, based on direct waveform imaging, focuses on measuring dispersive curves for A0 mode in a composite laminate and its anisotropy. A two-dimensional fast Fourier transform (2D-FFT) is applied to out-of-plane velocity data captured experimentally using LDV to go from the time-spatial domain to frequency-wavenumber domain. The result is a 2D array of amplitudes at discrete frequencies and wavenumbers for A0 mode in a given propagation direction along the composite. The peak values of the curve are then used to construct frequency wavenumber and phase velocity dispersion curves, which are also obtained directly using Snell's law and the incident angle of the excited ultrasonic waves. A high resolution and strong correlation between numerical and experimental results are observed for dispersive curves with Snell's law method in comparison to 2D-FFT method. Dispersion curves as well as velocity curves for the composite plate along different directions of wave propagation are measured. The visual read-out of the dispersion curves at different propagation directions as well as the phase velocity curves provide profiling and measurements of the composite anisotropy. The results proved a high sensitivity of the air-coupled and laser

  12. A New Omni-Directional EMAT for Ultrasonic Lamb Wave Tomography Imaging of Metallic Plate Defects

    PubMed Central

    Huang, Songling; Wei, Zheng; Zhao, Wei; Wang, Shen

    2014-01-01

    This paper proposes a new omni-directional electromagnetic acoustic transducer (EMAT) for the ultrasonic Lamb wave (ULW) tomography imaging (TI) of defects in metallic plates. The proposed EMAT is composed of a permanent magnet and a coil with a contra-flexure structure. This new EMAT coil structure is used for omni-directional ULW transmission and reception and ULW TI for the first time. The theoretical background and the working principles of this EMAT are presented and analyzed. The experimental results of its use on a 3 mm thick aluminum plate indicate that the EMAT with a contra-flexure coil (CFC) can transmit and receive a pure single A0 mode ULW with a high signal-to-noise ratio (SNR). Thus, the extraction of the projection data used for ULW TI may be performed accurately. The circumferential consistency of the projection data is only slightly influenced by the distortion of the eddy current field that is induced by the new CFC with an irregular shape. When the new EMAT array is used for ULW TI using the cross-hole method and SIRT arithmetic, a desirable imaging quality can be achieved, and the estimated size of an artificial corrosion defect agreed well with its actual value. The relation between the reconstruction resolution and the number of the new EMATs used is analyzed. More TI experiments are carried out when the aluminum plate defect is in two different locations relative to the EMAT array, for the further investigation of the performances of the new EMATs. PMID:24561398

  13. Determination of the in-plane components of motion in a Lamb wave from single-axis laser vibrometry.

    PubMed

    Rajic, Nik; Rosalie, Cedric; Norman, Patrick; Davis, Claire

    2014-06-01

    A method is proposed for determining in-plane components of motion in a Lamb wave from laser vibrometer measurements of surface motion out of plane. The approach relies on a frequency domain transformation that assumes knowledge only of the plate thickness and the bulk wave speeds. An outline of the relevant theory is followed by several validation case studies that generally affirm a useful level of accuracy and robust performance across a relatively wide frequency-thickness product range. In a comparison to the two-angle vibrometry approach, the proposed method is shown to be simpler to implement and to yield estimates with a consistently higher signal to noise ratio. The approach is then used to furnish estimates of the in-plane strains in Lamb waves propagating in an aluminum plate at frequencies below the first cut-off. These estimates are compared to strain measurements obtained from an adhesively bonded fiber Bragg grating. The agreement is shown to be excellent overall with an average discrepancy of less than 6%; however, systematic errors of twice that amount were recorded in the low-frequency-thickness product regime. These low-frequency discrepancies are not consistent with known sources of experimental error and cannot be explained by shear-lag theory. PMID:24907808

  14. Fast characterization of aluminum plates with TV-holography measurements of the frequency spectrum of multimode, quasi- monochromatic Lamb waves.

    PubMed

    Deán-Ben, X Luís; Trillo, Cristina; Doval, Angel F; Fernández, José L

    2011-06-01

    We introduce a novel approach for measuring the frequency spectrum of Lamb waves and, subsequently, for obtaining the thickness and the bulk wave velocities of isotropic, homogeneous plates. It is based on Fourier transforming a set of spatial and temporal samples of the acoustic displacement but, in contrast to the traditional approach that employs dense temporal sampling and a reduced set of spatial sampling locations, our data set is a sequence of 2-D high-resolution maps of the instantaneous out-of-plane displacement obtained with TV holography. We have devised three variants to obtain a set of points of the wavenumber-frequency space, based, respectively, on the spatial (1-D or 2-D) and on the spatio-temporal (3-D) Fourier transforms. The whole process to obtain these points can be easily automated and substantial time savings can be achieved, compared with other full-field techniques that require human intervention or with pointwise scanned probes. Experimental demonstration of the three variants with quasimonochromatic multimode Lamb waves in aluminum plates is presented. The characteristic parameters of the plates are calculated by fitting the theoretical model to the experimental points of the frequency spectrum. The analysis of the uncertainties shows that the accuracy of the method is only slightly lower than the accuracy of a previously reported method based on measuring the wavelength of single-modes, for which the data acquisition procedure is much slower.

  15. Effects of adhesive thickness on the Lamb wave pitch-catch signal using bonded piezoelectric wafer transducers

    NASA Astrophysics Data System (ADS)

    Islam, M. M.; Huang, H.

    2016-08-01

    This paper investigates the effects of adhesive layer on Lamb wave ultrasound pitch-catch signals that are excited and sensed by piezoelectric wafer transducers bonded on a slender structure. Analytical models were established to simulate the longitudinal and flexural vibrations of the structures separately and parametric studies of the bonding layer properties, i.e. the shear transfer parameter, adhesive thickness, and shear modulus, were performed. The parametric studies indicate that there exists an optimal adhesive layer thickness that generates maximum ultrasound pitch-catch signal for both wave modes. This prediction was subsequently validated by measurements. In addition, an improved match between the measured and simulated pitch-catch signals was achieved by adjusting the adhesive layer parameters.

  16. Note: Modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonator with precise two-port Y-parameter characterizations

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Hong, Yan; Goh, Wang Ling; Mu, Xiaojing

    2016-10-01

    Dual-mode Lamb-wave resonator has become a powerful component for clock reference and sensing applications, enabling efficient compensations of temperature effects, concurrent measurements of multiple environmental parameters, etc. An equivalent circuit model for the dual-mode Lamb-wave resonator is indispensable as it provides a means as well as being an effective tool for evaluating device characteristics and to aid the designing of circuitry for the resonators. This could be the first time ever that an efficient equivalent-circuit model, i.e., modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonators is reported. Evaluated by experiments, this model attains noteworthy agreements on both the magnitudes and phases of Y11 and Y21 of the measurement results. Compared to literature, the proposed model is capable of modeling the dual resonances efficiently. Moreover, this work also proves more accurate when viewing the Y-parameters across a wide frequency range. The gained features of this model are most beneficial for the analysis of the dual-mode Lamb-wave resonator and also for the designing of circuits.

  17. Beam paths of flexural Lamb waves at high frequency in the first band within phononic crystal-based acoustic lenses

    SciTech Connect

    Zhao, J.; Boyko, O.; Bonello, B.

    2014-12-15

    This work deals with an analytical and numerical study of the focusing of the lowest order anti-symmetric Lamb wave in gradient index phononic crystals. Computing the ray trajectories of the elastic beam allowed us to analyze the lateral dimensions and shape of the focus, either in the inner or behind the phononic crystal-based acoustic lenses, for frequencies within a broad range in the first band. We analyzed and discussed the focusing behaviors inside the acoustic lenses where the focalization at sub-wavelength scale was achieved. The focalization behind the gradient index phononic crystal is shown to be efficient as well: we report on FMHM = 0.63λ at 11MHz.

  18. A New Inverse Method of Elastic Constants for a Fibre-Reinforced Composite Plate from Laser-Based Ultrasonic Lamb Waves

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Cheng, Jian-Chun

    2001-12-01

    A new inverse method based on the wavelet transform and artificial neural networks (ANN) is presented to recover elastic constants of a fibre-reinforced composite plate from laser-based ultrasonic Lamb waves. The transient waveforms obtained by numerical simulations under different elastic constants are taken as the input of the ANN for training and learning. The wavelet transform is employed for extracting the eigenvectors from the raw Lamb wave signals so as to simplify the structure of the ANN. Then these eigenvectors are input to a multi-layer internally recurrent neural network with a back-propagation algorithm. Finally, the experimental waveforms are used as the input in the whole system to inverse elastic constants of the experimental material.

  19. Lamb Waves Propagation along 3C-SiC/AlN Membranes for Application in Temperature-Compensated, High-Sensitivity Gravimetric Sensors

    PubMed Central

    Caliendo, Cinzia; D'Amico, Arnaldo; Castro, Fabio Lo

    2013-01-01

    The propagation of the fundamental quasi-symmetric Lamb mode S0 travelling along 3C-SiC/c-AlN composite plates is theoretically studied with respect to the AlN and SiC film thickness, the acoustic wave propagation direction and the electrical boundary conditions. The temperature effects on the phase velocity have been considered for four AlN/SiC-based electroacoustic coupling configurations, specifically addressing the design of temperature-compensated, enhanced-coupling, GHz-range electroacoustic devices. The gravimetric sensitivity and resolution of the four temperature-stable SiC/AlN composite structures are theoretically investigated with respect to both the AlN and SiC sensing surface. The SiC/AlN-based sensor performances are compared to those of surface acoustic waves and Lamb S0 mode mass sensors implemented on bulk conventional piezoelectric materials and on thin suspended membranes. PMID:23282585

  20. Excitation of ultrasonic Lamb waves using a phased array system with two array probes: phantom and in vitro bone studies.

    PubMed

    Nguyen, Kim-Cuong T; Le, Lawrence H; Tran, Tho N H T; Sacchi, Mauricio D; Lou, Edmond H M

    2014-07-01

    Long bones are good waveguides to support the propagation of ultrasonic guided waves. The low-order guided waves have been consistently observed in quantitative ultrasound bone studies. Selective excitation of these low-order guided modes requires oblique incidence of the ultrasound beam using a transducer-wedge system. It is generally assumed that an angle of incidence, θi, generates a specific phase velocity of interest, co, via Snell's law, θi=sin(-1)(vw/co) where vw is the velocity of the coupling medium. In this study, we investigated the excitation of guided waves within a 6.3-mm thick brass plate and a 6.5-mm thick bovine bone plate using an ultrasound phased array system with two 0.75-mm-pitch array probes. Arranging five elements as a group, the first group of a 16-element probe was used as a transmitter and a 64-element probe was a receiver array. The beam was steered for six angles (0°, 20°, 30°, 40°, 50°, and 60°) with a 1.6-MHz source signal. An adjoint Radon transform algorithm mapped the time-offset matrix into the frequency-phase velocity dispersion panels. The imaged Lamb plate modes were identified by the theoretical dispersion curves. The results show that the 0° excitation generated many modes with no modal discrimination and the oblique beam excited a spectrum of phase velocities spread asymmetrically about co. The width of the excitation region decreased as the steering angle increased, rendering modal selectivity at large angles. The phenomena were well predicted by the excitation function of the source influence theory. The low-order modes were better imaged at steering angle ⩾30° for both plates. The study has also demonstrated the feasibility of using the two-probe phased array system for future in vivo study.

  1. A new multichannel time reversal focusing method for circumferential Lamb waves and its applications for defect detection in thick-walled pipe with large-diameter.

    PubMed

    Liu, Zenghua; Xu, Qinglong; Gong, Yu; He, Cunfu; Wu, Bin

    2014-09-01

    This paper proposes a new multichannel time reversal focusing (MTRF) method for circumferential Lamb waves which is based on modified time reversal algorithm and applies this method for detecting different kinds of defects in thick-walled pipe with large-diameter. The principle of time reversal of circumferential Lamb waves in pipe is presented along with the influence from multiple guided wave modes and propagation paths. Experimental study is carried out in a thick-walled and large-diameter pipe with three artificial defects, namely two axial notches on its inner and outer surface respectively, and a corrosion-like defect on its outer surface. By using the proposed MTRF method, the multichannel signals focus at the defects, leading to the amplitude improvement of the defect scattered signal. Besides, another energy focus arises in the direct signal due to the partial compensation of dispersion and multimode of circumferential Lamb waves, alongside the multichannel focusing, during MTRF process. By taking the direct focus as a time base, accurate defect localization is implemented. Secondly, a new phenomenon is exhibited in this paper that defect scattered wave packet appears just before the right boundary of truncation window after time reversal, and to which two feasible explanations are given. Moreover, this phenomenon can be used as the theoretical basis in the determination of defect scattered waves in time reversal response signal. At last, in order to detect defects without prior knowing their exact position, a large-range truncation window is used in the proposed method. As a result, the experimental operation of MTRF method is simplified and defect detection and localization are well accomplished. PMID:24877582

  2. Multi-Mode Electromagnetic Ultrasonic Lamb Wave Tomography Imaging for Variable-Depth Defects in Metal Plates.

    PubMed

    Huang, Songling; Zhang, Yu; Wang, Shen; Zhao, Wei

    2016-05-02

    This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this work, the sensitivities to thickness variation of A0- and S0-mode LWs are theoretically studied. The principles and procedures for the cooperation of A0- and S0-mode LW CTI are proposed. Moreover, the experimental LW imaging system on an aluminum plate with a variable-depth defect is set up, based on A0- and S0-mode EMAT (electromagnetic acoustic transducer) arrays. For comparison, the traditional single-mode LW CTI method is used in the same experimental platform. The imaging results show that the computed thickness distribution by the proposed multi-mode method more accurately reflects the actual thickness variation of the defect, while neither the S0 nor the A0 single-mode method was able to distinguish thickness variation in the defect region. Moreover, the quantification of the defect's thickness variation is more accurate with the multi-mode method. Therefore, theoretical and practical results prove that the variable-depth defect in metal plates can be successfully quantified and visualized by the proposed multi-mode electromagnetic ultrasonic LW CTI method.

  3. Multi-Mode Electromagnetic Ultrasonic Lamb Wave Tomography Imaging for Variable-Depth Defects in Metal Plates.

    PubMed

    Huang, Songling; Zhang, Yu; Wang, Shen; Zhao, Wei

    2016-01-01

    This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this work, the sensitivities to thickness variation of A0- and S0-mode LWs are theoretically studied. The principles and procedures for the cooperation of A0- and S0-mode LW CTI are proposed. Moreover, the experimental LW imaging system on an aluminum plate with a variable-depth defect is set up, based on A0- and S0-mode EMAT (electromagnetic acoustic transducer) arrays. For comparison, the traditional single-mode LW CTI method is used in the same experimental platform. The imaging results show that the computed thickness distribution by the proposed multi-mode method more accurately reflects the actual thickness variation of the defect, while neither the S0 nor the A0 single-mode method was able to distinguish thickness variation in the defect region. Moreover, the quantification of the defect's thickness variation is more accurate with the multi-mode method. Therefore, theoretical and practical results prove that the variable-depth defect in metal plates can be successfully quantified and visualized by the proposed multi-mode electromagnetic ultrasonic LW CTI method. PMID:27144571

  4. Multi-Mode Electromagnetic Ultrasonic Lamb Wave Tomography Imaging for Variable-Depth Defects in Metal Plates

    PubMed Central

    Huang, Songling; Zhang, Yu; Wang, Shen; Zhao, Wei

    2016-01-01

    This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this work, the sensitivities to thickness variation of A0- and S0-mode LWs are theoretically studied. The principles and procedures for the cooperation of A0- and S0-mode LW CTI are proposed. Moreover, the experimental LW imaging system on an aluminum plate with a variable-depth defect is set up, based on A0- and S0-mode EMAT (electromagnetic acoustic transducer) arrays. For comparison, the traditional single-mode LW CTI method is used in the same experimental platform. The imaging results show that the computed thickness distribution by the proposed multi-mode method more accurately reflects the actual thickness variation of the defect, while neither the S0 nor the A0 single-mode method was able to distinguish thickness variation in the defect region. Moreover, the quantification of the defect’s thickness variation is more accurate with the multi-mode method. Therefore, theoretical and practical results prove that the variable-depth defect in metal plates can be successfully quantified and visualized by the proposed multi-mode electromagnetic ultrasonic LW CTI method. PMID:27144571

  5. Detection of Underwater Limpet Mines on Ship Hulls with Rayleigh-Lamb Waves

    NASA Astrophysics Data System (ADS)

    Bingham, J. P.; Hinders, M. K.

    2010-02-01

    We describe the use of ultrasonic guided waves for identifying the mass loading due to underwater limpet mines on ship hulls. The Dynamic Wavelet Fingerprint (DFWP) technique is used to render the guided wave mode information in two-dimensional binary images because the waveform features of interest are too subtle to identify in time domain. The use of wavelets allows both time and scale features from the original signals to be retained, and image processing can be used to automatically extract features that correspond to the arrival times of the guided wave modes. For further understanding of how the guided wave modes propagate through the real structures, a parallel processing, 3D elastic wave simulation is developed using the finite integration technique. This full field technique models situations that are too complex for analytical solutions, such as built-up 3D structures. The simulations have produced informative visualizations of the guided wave modes in the structures as well as mimicking directly the output from sensors placed in the simulation space for direct comparison to experiments. Results from both drydock and in-water experiments with dummy mines are also shown.

  6. Numerical study and topology optimization of 1D periodic bimaterial phononic crystal plates for bandgaps of low order Lamb waves.

    PubMed

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, Mohammad

    2015-03-01

    The optimum topology of bimaterial phononic crystal (PhCr) plates with one-dimensional (1D) periodicity to attain maximum relative bandgap width of low order Lamb waves is computationally investigated. The evolution of optimized topology with respect to filling fraction of constituents, alternatively stiff scattering inclusion, is explored. The underlying idea is to develop PhCr plate structures with high specific bandgap efficiency at particular filling fraction, or further with multiscale functionality through gradient of optimized PhCr unitcell all over the lattice array. Multiobjective genetic algorithm (GA) is employed in this research in conjunction with finite element method (FEM) for topology optimization of silicon-tungsten PhCr plate unitcells. A specialized FEM model is developed and verified for dispersion analysis of plate waves and calculation of modal response. Modal band structure of regular PhCr plate unitcells with centric scattering layer is studied as a function of aspect ratio and filling fraction. Topology optimization is then carried out for a few aspect ratios, with and without prescribed symmetry, over various filling fractions. The efficiency of obtained solutions is verified as compared to corresponding regular centric PhCr plate unitcells. Moreover, being inspired by the obtained optimum topologies, definite and easy to produce topologies are proposed with enhanced bandgap efficiency as compared to centric unitcells. Finally a few cases are introduced to evaluate the frequency response of finite PhCr plate structures produced by achieved topologies and also to confirm the reliability of calculated modal band structures. Cases made by consecutive unitcells of different filling fraction are examined in order to attest the bandgap efficiency and multiscale functionality of such graded PhCr plate structures.

  7. Damage localization in metallic plate structures using edge-reflected lamb waves

    NASA Astrophysics Data System (ADS)

    Ebrahimkhanlou, A.; Dubuc, B.; Salamone, S.

    2016-08-01

    This paper presents a model-based guided ultrasonic waves imaging algorithm, in which multiple ultrasonic echoes caused by reflections from the plate’s boundaries are leveraged to enhance imaging performance. An analytical model is proposed to estimate the envelope of scattered waves. Correlation between the estimated and experimental data is used to generate images. The proposed method is validated through experimental tests on an aluminum plate instrumented with three low profile piezoelectric transducers. Different damage conditions are simulated including through-thickness holes. Results are compared with two other imaging localization methods, that is, delay and sum and minimum variance.

  8. Attenuation of a Stoneley wave and higher Lamb modes due to the scattering by two-dimensional irregularities of the walls of a fluid-filled borehole

    NASA Astrophysics Data System (ADS)

    Maximov, G. A.; Ortega, E.; Pod”Yachev, E. V.

    2007-02-01

    Attenuation of Stoneley waves and higher Lamb modes propagating along an irregular surface of a fluid-filled borehole is investigated. This problem generalizes the problem on the attenuation of Rayleigh waves by an irregular surface of an empty borehole [10]. The technique used to evaluate the attenuation coefficient is based on the perturbation method (surface irregularity heights are considered to be small in comparison with the wavelength) and the mean field method. As a result, an expression is obtained for the partial coefficients of the eigenmode attenuation due to the scattering of eigenmodes by the irregularities of the borehole walls into the same or other eigenmodes, as well as into the bulk longitudinal and transverse waves. The frequency-dependent behavior of the partial attenuation coefficients of both Stoneley waves and higher modes is analyzed against the ratio between the irregularity correlation length and the borehole radius for different correlation functions of irregularities.

  9. Ultrasonic detection of embedded and surface defects in thin plates using Lamb waves

    NASA Astrophysics Data System (ADS)

    Conry, M. J.; Crane, L. J.; Gilchrist, Michael

    2003-03-01

    Non-destructive Testing and Evaluation (NDT&E) is critical in the safety assurance of modern engineering structures, particularly when using high performance materials. Frequently, such materials are subject to mechanisms of damage uncommon in conventional structures. Additionally, many high performance alloys such as advanced aerospace aluminiums are more susceptible to fatigue failure than more traditional metals. In all such cases, it is essential to have good knowledge of the defects present in a component in order to assess its soundness. One of the most common and verstaile techniques used in NDT&E is ultrasonic testing, where the integrity of a component is characterized using acoustic waves.

  10. Analysis of transient Lamb waves generated by dynamic surface sources in thin composite plates

    NASA Astrophysics Data System (ADS)

    Banerjee, Sauvik; Mal, Ajit K.; Prosser, William H.

    2004-05-01

    A theoretical analysis is carried out in an effort to understand certain unusual properties of transient guided waves produced in a thin unidirectional graphite/epoxy composite plate by a localized dynamic surface load. The surface motion is calculated using an approximate plate theory, called the shear deformation plate theory (SDPT), as well as a recently developed finite element analysis (FEA), for their mutual verification. The results obtained by the two methods are shown to have excellent agreement. An interesting, nearly periodic ``phase reversal'' of the signal with propagation distance is observed for each propagation direction relative to the fiber direction. For clarification, a closed form analytical expression for the vertical surface displacement in an aluminum plate to an impulsive point force is obtained using the steepest descent method. It is found that the strong dispersion of the first antisymmetric waves at low frequencies is the main reason behind the phase reversal. This is verified further by measuring the surface response of a relatively thick aluminum plate to a pencil lead break source. The understanding developed in the paper is expected to be helpful in detecting and characterizing the occurrence of damage in composite structures.

  11. Relationships of serum thyroid hormones and follicle-stimulating hormone concentrations to Sertoli cell differentiation during the first wave of spermatogenesis in euthyroid ram lambs.

    PubMed

    Oluwole, Olutobi A; Bartlewski, Pawel M; Hahnel, Ann

    2013-06-01

    The main purpose of this study was to determine if temporal relationships exist between serum concentrations of free fractions of thyroxin (fT4) and triiodothyronine (fT3), follicle-stimulating hormone (FSH) levels, and Sertoli cell differentiation in euthyroid ram lamb testes. Additionally, testicular thyroid hormone (TH) receptors (TRs) were identified using immunohistochemistry and Western blot analysis. Weekly testicular biopsies and jugular blood samples were collected from 12 ram lambs over the 9 weeks of study. Hormone concentrations and the numbers of dividing Sertoli cells per seminiferous tubule (ST) area were analyzed relative to chronological age of animals and the two distinctive stages of Sertoli cell differentiation: (a) tight junction/ST lumen formation and (b) the onset of support mechanisms for the development of multiple germ cell types (presence of primary spermatocytes in >95% STs). Circulating FSH concentrations increased (p<0.05) immediately after first detection of ST lumen and reached a nadir (p<0.05) just prior to the end of the first wave of spermatogenesis. A decline in both fT4 and fT3 levels (p<0.05) occurred after Sertoli cells had formed the ST lumen and began supporting germ cell differentiation. There was a positive correlation between the numbers of proliferating Sertoli cells and serum fT4 (r=0.51, p<0.001) and fT3 (r=0.52, p<0.001) concentrations. TRs were expressed throughout the study period; however, prior to the formation of ST lumen, two isoforms were detected while only one TR isoform was present by the end of the first wave of spermatogenesis. Overall, the exit of Sertoli cells from the cell cycle that presages their final differentiation begins when THs and FSH levels are high, suggesting a permissive role of these hormones in the maturation of STs in prepubertal ram lambs.

  12. Guided Lamb wave based 2-D spiral phased array for structural health monitoring of thin panel structures

    NASA Astrophysics Data System (ADS)

    Yoo, Byungseok

    2011-12-01

    In almost all industries of mechanical, aerospace, and civil engineering fields, structural health monitoring (SHM) technology is essentially required for providing the reliable information of structural integrity of safety-critical structures, which can help reduce the risk of unexpected and sometimes catastrophic failures, and also offer cost-effective inspection and maintenance of the structures. State of the art SHM research on structural damage diagnosis is focused on developing global and real-time technologies to identify the existence, location, extent, and type of damage. In order to detect and monitor the structural damage in plate-like structures, SHM technology based on guided Lamb wave (GLW) interrogation is becoming more attractive due to its potential benefits such as large inspection area coverage in short time, simple inspection mechanism, and sensitivity to small damage. However, the GLW method has a few critical issues such as dispersion nature, mode conversion and separation, and multiple-mode existence. Phased array technique widely used in all aspects of civil, military, science, and medical industry fields may be employed to resolve the drawbacks of the GLW method. The GLW-based phased array approach is able to effectively examine and analyze complicated structural vibration responses in thin plate structures. Because the phased sensor array operates as a spatial filter for the GLW signals, the array signal processing method can enhance a desired signal component at a specific direction while eliminating other signal components from other directions. This dissertation presents the development, the experimental validation, and the damage detection applications of an innovative signal processing algorithm based on two-dimensional (2-D) spiral phased array in conjunction with the GLW interrogation technique. It starts with general backgrounds of SHM and the associated technology including the GLW interrogation method. Then, it is focused on the

  13. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T.-C.; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.

  14. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations.

    PubMed

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T-C; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators. PMID:27131699

  15. Stress dependent dispersion relations of acoustic waves travelling on a chain of point masses connected by anharmonic linear and torsional springs

    NASA Astrophysics Data System (ADS)

    Pluta, Mieczysław; Amjad, Umar; Klinghammer, Hermann; Jha, Diwaker; Tarar, Khurram; Grill, Wolfgang

    2012-05-01

    The propagation of a deformation along a flexural beam or plate depends on material properties, geometrical conditions like the beam cross-section, effects of stiffening or softening due to external stress, and last but not least the mode of the wave including its polarization. The time-of-flight (TOF) of acoustic waves is influenced by any of the above listed parameters. This effect is utilized in ultrasonic NDE and structural health monitoring applications. It was shown in earlier publications that the solutions of wave equations for a linear chain model consisting of identical mass points, subject to a direction and distance dependent potential, show the dispersion properties and dependencies on externally applied stress of the lowest longitudinal and transversal plate modes. In the model presented here anharmonic potentials are introduced. The potentials are represented by torsional springs at each mass point and linear springs between them. Dynamic equations are derived, based on interactions with next and second next neighbors. The results obtained with the developed model are compared with experimental observations concerning the reaction of the TOF for the lowest Lamb modes in an aluminum plate under variable in plane stress. The developed models are capable to demonstrate general aspects of the mode and frequency dependence of the acousto-elastic coefficients for the lowest symmetric and antisymmetric Lamb waves. The introduced anharmonicities allow furthermore for a close approximation of the experimental findings.

  16. Acoustoelastic effect of textured (Ba,Sr)TiO{sub 3} thin films under an initial mechanical stress

    SciTech Connect

    Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi; Donner, Wolfgang

    2015-12-14

    Acoustoelastic (AE) analysis of initial stresses plays an important role as a nondestructive tool in current engineering. Two textured BST (Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3}) thin films, with different substrate to target distance, were grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrate by rf-magnetron sputtering deposition techniques. A conventional “sin{sup 2} ψ” method to determine residual stress and strain in BST films by X-ray diffraction is applied. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples. Young's modulus E and Poisson ratio ν of BST films in different propagation directions are derived from the measured dispersion curves. Estimation of effective second-order elastic constants of BST thin films in stressed states is served in SAW study. This paper presents an original investigation of AE effect in prestressed Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3} films, where the effective elastic constants and the effect of texture on second and third order elastic tensor are considered and used. The propagation behavior of Rayleigh and Love waves in BST thin films under residual stress is explored and discussed. The guiding velocities affected by residual stresses, reveal some shifts which do not exceed four percent mainly in the low frequency range.

  17. Acoustoelastic effect of textured (Ba,Sr)TiO3 thin films under an initial mechanical stress

    NASA Astrophysics Data System (ADS)

    Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar; Donner, Wolfgang; Ben Ghozlen, Mohamed Hédi

    2015-12-01

    Acoustoelastic (AE) analysis of initial stresses plays an important role as a nondestructive tool in current engineering. Two textured BST (Ba0.65Sr0.35TiO3) thin films, with different substrate to target distance, were grown on Pt(111)/TiO2/SiO2/Si(001) substrate by rf-magnetron sputtering deposition techniques. A conventional "sin2 ψ" method to determine residual stress and strain in BST films by X-ray diffraction is applied. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples. Young's modulus E and Poisson ratio ν of BST films in different propagation directions are derived from the measured dispersion curves. Estimation of effective second-order elastic constants of BST thin films in stressed states is served in SAW study. This paper presents an original investigation of AE effect in prestressed Ba0.65Sr0.35TiO3 films, where the effective elastic constants and the effect of texture on second and third order elastic tensor are considered and used. The propagation behavior of Rayleigh and Love waves in BST thin films under residual stress is explored and discussed. The guiding velocities affected by residual stresses, reveal some shifts which do not exceed four percent mainly in the low frequency range.

  18. GHz spurious mode free AlN lamb wave resonator with high figure of merit using one dimensional phononic crystal tethers

    NASA Astrophysics Data System (ADS)

    Wu, Guoqiang; Zhu, Yao; Merugu, Srinivas; Wang, Nan; Sun, Chengliang; Gu, Yuandong

    2016-07-01

    This letter reports a spurious mode free GHz aluminum nitride (AlN) lamb wave resonator (LWR) towards high figure of merit (FOM). One dimensional gourd-shape phononic crystal (PnC) tether with large phononic bandgaps is employed to reduce the acoustic energy dissipation into the substrate. The periodic PnC tethers are based on a 1 μm-thick AlN layer with 0.26 μm-thick Mo layer on top. A clean spectrum over a wide frequency range is obtained from the measurement, which indicates a wide-band suppression of spurious modes. Experimental results demonstrate that the fabricated AlN LWR has an insertion loss of 5.2 dB and a loaded quality factor (Q) of 1893 at 1.02 GHz measured in air. An impressive ratio of the resistance at parallel resonance (Rp) to the resistance at series resonance (Rs) of 49.8 dB is obtained, which is an indication of high FOM for LWR. The high Rp to Rs ratio is one of the most important parameters to design a radio frequency filter with steep roll-off.

  19. Acoustoelastic Effects on the Natural Frequencies of Pre-Stressed Concrete Beams

    NASA Astrophysics Data System (ADS)

    Ryden, N.; Lundqvist, L.; Thelandersson, S.

    2011-06-01

    Pre-stressed concrete is used to increase the load capacity in many civil engineering structures. There is a need for non-destructive methods to estimate the potential loss of pre-stress in these structures. In this study we investigate the acoustoelastic effect on the natural resonance frequencies of a pre-stressed concrete beam. Measured resonant frequencies increase with increasing compressive stress. Results agree with predicted frequency shifts obtained from a non-linear finite element model based on Murnaghan's third order elastic theory.

  20. Dynamic Acousto-Elasticity: Pressure and Frequency Dependences in Berea Sandstone.

    NASA Astrophysics Data System (ADS)

    Riviere, J. V.; Pimienta, L.; Latour, S.; Fortin, J.; Schubnel, A.; Johnson, P. A.

    2014-12-01

    Nonlinear elasticity is studied at the laboratory scale with the goal of understanding observations at earth scales, for instance during strong ground motion, tidal forcing and earthquake slip processes. Here we report frequency and pressure dependences on elasticity when applying dynamic acousto-elasticity (DAE) of rock samples, analogous to quasi-static acousto-elasticity. DAE allows one to obtain the elastic behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. We perform DAE on a sample of Berea sandstone subject to 0.5MPa uniaxial load, with sinusoidal oscillating strain amplitudes ranging from 10-6 to 10-5 and at frequencies from 0.1 to 260Hz. In addition, the confining pressure is increased stepwise from 0 to 30MPa. We compare results to previous measurements made at lower (mHz) and higher (kHz) frequencies. Nonlinear elastic parameters corresponding to conditioning effects, third order elastic constants and fourth order elastic constants are quantitatively compared over the pressure and frequency ranges. We observe that the decrease in modulus due to conditioning increases with frequency, suggesting a frequency and/or strain-rate dependence that should be included in nonlinear elastic models of rocks. In agreement with previous measurements, nonlinear elastic effects also decrease with confining pressure, suggesting that nonlinear elastic sources such as micro-cracks, soft bonds and dislocations are turned off as the pressure increases.

  1. On the influence of strain rate in acousto-elasticity : experimental results for Berea sandstone

    NASA Astrophysics Data System (ADS)

    Riviere, J. V.; Candela, T.; Scuderi, M.; Marone, C.; Guyer, R. A.; Johnson, P. A.

    2013-12-01

    Elastic nonlinear effects are pervasive in the Earth, including during strong ground motion, tidal forcing and earthquake slip processes. We study elastic nonlinear effects in the laboratory with the goal of developing new methods to probe elastic changes in the Earth, and to characterize and understand their origins. Here we report on nonlinear, frequency dispersion effects by applying a method termed dynamic acousto-elasticity (DAE), analogous to quasi-static acousto-elasticity. DAE allows one to obtain the elastic behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. We perform DAE on samples of Berea sandstone subject to 0.5 MPa uniaxial and biaxial loading conditions with oscillating loads at frequencies from 0.001 to 10 Hz and amplitudes of a few 100 kPa. We compare results to DAE measurements made in the kHz range. We observe that the average decrease in modulus due to nonlinear material softening increases with frequency, suggesting a frequency and/or a strain rate dependence. Previous quasi-static measurements (Claytor et al., GRL 2009) show that stress-strain nonlinear hysteretic behavior disappears when the experiment is performed at a very low strain-rate, implying that a rate dependent nonlinear elastic model would be useful (Gusev et al., PRB 2004). Our results also suggest that when elastic nonlinear Earth processes are studied, stress forcing frequency is an important consideration, and may lead to unexpected behaviors.

  2. 7 CFR 65.190 - Lamb.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., PORK, LAMB, CHICKEN, GOAT MEAT, PERISHABLE AGRICULTURAL COMMODITIES, MACADAMIA NUTS, PECANS, PEANUTS, AND GINSENG General Provisions Definitions § 65.190 Lamb. Lamb means meat produced from sheep....

  3. Willis E. Lamb

    NASA Astrophysics Data System (ADS)

    Berman, Paul

    2009-03-01

    The atomic and optical physics community lost one of its pioneers with the death of Willis E. Lamb, Jr. on May 15, 2008. Lamb was born on July 12, 1913, received the BS degree in Chemistry at Berkeley in 1934, and obtained his PhD under the tutelage of J. Robert Oppenheimer at Berkeley in 1938. He served on the faculties of Columbia University, Stanford University, Oxford University, Yale University, and the University of Arizona. Lamb received the Nobel prize in 1955 for his work on the fine structure of hydrogen and was awarded the President's National Medal for Science in 2000...

  4. 7 CFR 1280.111 - Lamb.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE LAMB PROMOTION, RESEARCH, AND INFORMATION ORDER Lamb Promotion, Research, and Information Order Definitions § 1280.111 Lamb. Lamb means ovine animals of any age, including ewes and rams....

  5. 7 CFR 1280.111 - Lamb.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE LAMB PROMOTION, RESEARCH, AND INFORMATION ORDER Lamb Promotion, Research, and Information Order Definitions § 1280.111 Lamb. Lamb means ovine animals of any age, including ewes and rams....

  6. NDT process using Lamb waves generated/detected by ultrasonic phased array probes for the defect detection in metallic and composite plates

    NASA Astrophysics Data System (ADS)

    Leleux, A.; Micheau, P.; Castaings, M.

    2013-01-01

    One gel-coupled multi-element matrix ultrasonic probe is driven using the phased array principle, for launching/detecting pure Lamb modes in/from different directions along various types of plates, and taking into account the modes frequency and angular dispersive effects. It allows rapid inspection of large structures, from one remote fixed position of the probe. The set-up and principle of the process are presented, as well as its measured performances in terms of modal selectivity and directivity. Finally examples of defect detection are shown.

  7. 7 CFR 1280.217 - Lamb purchases.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... required by regulations recommended by the Board and prescribed by the Secretary, that the requirements of... products of that person's own production and marketing such lambs or lamb products, shall pay an assessment on such lambs or lamb products on the live weight of the lamb at the time of slaughter at the...

  8. Unraveling complex nonlinear elastic behaviors in rocks using dynamic acousto-elasticity

    NASA Astrophysics Data System (ADS)

    Riviere, J.; Guyer, R.; Renaud, G.; TenCate, J. A.; Johnson, P. A.

    2012-12-01

    In comparison with standard nonlinear ultrasonic methods like frequency mixing or resonance based measurements that allow one to extract average, bulk variations of modulus and attenuation versus strain level, dynamic acousto-elasticity (DAE) allows to obtain the elastic behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. This method consists of exciting a sample in Bulk-mode resonance at strains of 10-7 to 10-5 and simultaneously probing with a sequence of high frequency, low amplitude pulses. Time of flight and amplitudes of these pulses, respectively related to nonlinear elastic and dissipative parameters, can be plotted versus vibration strain level. Despite complex nonlinear signatures obtained for most rocks, it can be shown that for low strain amplitude (< 10-6), the nonlinear classical theory issued from a Taylor decomposition can explain the harmonic content. For higher strain, harmonic content becomes richer and the material exhibits more hysteretic behaviors, i.e. strain rate dependencies. Such observations have been made in the past (e.g., Pasqualini et al., JGR 2007), but not with the extreme detail of elasticity provided by DAE. Previous quasi-static measurements made in Berea sandstone (Claytor et al, GRL 2009), show that the hysteretic behavior disappears when the protocol is performed at a very low strain-rate (static limit). Therefore, future work will aim at linking quasi-static and dynamic observations, i.e. the frequency or strain-rate dependence, in order to understand underlying physical phenomena.

  9. 7 CFR 1280.111 - Lamb.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Lamb. 1280.111 Section 1280.111 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... INFORMATION ORDER Lamb Promotion, Research, and Information Order Definitions § 1280.111 Lamb. Lamb...

  10. 7 CFR 1280.217 - Lamb purchases.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Lamb purchases. 1280.217 Section 1280.217 Agriculture... INFORMATION ORDER Lamb Promotion, Research, and Information Order Assessments § 1280.217 Lamb purchases. (a... payment to a producer, seedstock producer, or feeder for lambs purchased from such producer,...

  11. 7 CFR 65.190 - Lamb.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... MARKETING ACT OF 1946 AND THE EGG PRODUCTS INSPECTION ACT (CONTINUED) COUNTRY OF ORIGIN LABELING OF BEEF, PORK, LAMB, CHICKEN, GOAT MEAT, PERISHABLE AGRICULTURAL COMMODITIES, MACADAMIA NUTS, PECANS, PEANUTS, AND GINSENG General Provisions Definitions § 65.190 Lamb. Lamb means meat produced from sheep....

  12. Sarcocystosis in a stillborn lamb

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Confirmed congenital sarcocystosis has not been reported in sheep and extremely rarely in other domestic ruminants. Sarcocystosis was diagnosed in a stillborn lamb with microscopic lesions predominantly in the central nervous system and placenta. Encephalitis was characterized by multiple foci of gl...

  13. Purcell effect and Lamb shift as interference phenomena.

    PubMed

    Rybin, Mikhail V; Mingaleev, Sergei F; Limonov, Mikhail F; Kivshar, Yuri S

    2016-01-01

    The Purcell effect and Lamb shift are two well-known physical phenomena which are usually discussed in the context of quantum electrodynamics, with the zero-point vibrations as a driving force of those effects in the quantum approach. Here we discuss the classical counterparts of these quantum effects in photonics, and explain their physics trough interference wave phenomena. As an example, we consider a waveguide in a planar photonic crystal with a side-coupled defect, and demonstrate a perfect agreement between the results obtained on the basis of quantum and classic approaches and reveal their link to the Fano resonance. We find that in such a waveguide-cavity geometry the Purcell effect can modify the lifetime by at least 25 times, and the Lamb shift can exceed 3 half-widths of the cavity spectral line. PMID:26860195

  14. Purcell effect and Lamb shift as interference phenomena.

    PubMed

    Rybin, Mikhail V; Mingaleev, Sergei F; Limonov, Mikhail F; Kivshar, Yuri S

    2016-01-01

    The Purcell effect and Lamb shift are two well-known physical phenomena which are usually discussed in the context of quantum electrodynamics, with the zero-point vibrations as a driving force of those effects in the quantum approach. Here we discuss the classical counterparts of these quantum effects in photonics, and explain their physics trough interference wave phenomena. As an example, we consider a waveguide in a planar photonic crystal with a side-coupled defect, and demonstrate a perfect agreement between the results obtained on the basis of quantum and classic approaches and reveal their link to the Fano resonance. We find that in such a waveguide-cavity geometry the Purcell effect can modify the lifetime by at least 25 times, and the Lamb shift can exceed 3 half-widths of the cavity spectral line.

  15. Purcell effect and Lamb shift as interference phenomena

    PubMed Central

    Rybin, Mikhail V.; Mingaleev, Sergei F.; Limonov, Mikhail F.; Kivshar, Yuri S.

    2016-01-01

    The Purcell effect and Lamb shift are two well-known physical phenomena which are usually discussed in the context of quantum electrodynamics, with the zero-point vibrations as a driving force of those effects in the quantum approach. Here we discuss the classical counterparts of these quantum effects in photonics, and explain their physics trough interference wave phenomena. As an example, we consider a waveguide in a planar photonic crystal with a side-coupled defect, and demonstrate a perfect agreement between the results obtained on the basis of quantum and classic approaches and reveal their link to the Fano resonance. We find that in such a waveguide-cavity geometry the Purcell effect can modify the lifetime by at least 25 times, and the Lamb shift can exceed 3 half-widths of the cavity spectral line. PMID:26860195

  16. Nondestructive Testing Residual Stress Using Ultrasonic Critical Refracted Longitudinal Wave

    NASA Astrophysics Data System (ADS)

    Xu, Chunguang; Song, Wentao; Pan, Qinxue; Li, Huanxin; Liu, Shuai

    Residual stress has significant impacts on the performance of the mechanical components, especially on its strength, fatigue life and corrosion resistance and dimensional stability. Based on theory of acoustoelasticity, the testing principle of ultrasonic LCR wave method is analyzed. The testing system of residual stress is build. The method of calibration of stress coefficient is proposed in order to improve the detection precision. At last, through experiments and applications on residual stress testing of oil pipeline weld joint, vehicle's torsion shaft, glass and ceramics, gear tooth root, and so on, the result show that it deserved to be studied deeply on application and popularization of ultrasonic LCR wave method.

  17. Guided ultrasonic waves for non-destructive monitoring of the stress levels in prestressed steel strands.

    PubMed

    Chaki, S; Bourse, G

    2009-02-01

    The safety of prestressed civil structures such as bridges, dams, nuclear power plants, etc. directly involves the security of both environment and users. Health monitoring of the tensioning components, such as strands, tendons, bars, anchorage bolts, etc. is an important research topic and a challenging task bringing together the non-destructive evaluation (NDE) and civil engineering communities. This paper deals with a guided ultrasonic wave procedure for monitoring the stress levels in seven-wire steel strands (15.7 mm in diameter). The mechanical and geometrical characteristics of the prestressed strands were taken into account for optimizing the measurement configuration and then the choice of the guided ultrasonic mode at a suitable frequency. Simplified acoustoelastic formulations were derived from the acoustoelasticity theory according to either calibration test or in situ measurement. The results from acoustoelastic measurements on the seven-wire steel strands are presented and discussed in the case of calibration tests and industrially prestressed strands. They show the potential and the suitability of the proposed guided wave method for evaluating the stress levels in the tested seven-wire steel strands. PMID:18804832

  18. Slow Dynamics in Berea Sandstone: a Non-logarithmic Relaxation at Early Times Revealed by Dynamic Acousto-Elasticity.

    NASA Astrophysics Data System (ADS)

    Riviere, J. V.; Shokouhi, P.; Marone, C.; Elsworth, D.; Guyer, R. A.; Johnson, P. A.

    2015-12-01

    We study nonlinear elastic/acoustic phenomena in rocks at the laboratory scale, with the goal of understanding observations at crustal scales, for instance during strong ground motion and earthquake slip processes. In particular, a long-term goal is to relate microstructure of rocks/gouge to nonlinear acoustic properties. A dynamic perturbation with modest (i.e. acoustic) strain amplitude (10-6 < ɛ < 10-5) in rocks typically leads to a transient elastic softening (elastic modulus decrease) followed by a log(t)-relaxation back to the initial elastic modulus as soon as the excitation is turned off. The relaxation typically lasts from minutes to hours depending on rock type and amplitude/duration/frequency of perturbation. This log(t)-recovery implies that no characteristic time or rate can be extracted, i.e., the relaxation spectrum is flat. In this study, we use Dynamic Acousto-Elasticity (DAE) to probe the relaxation characteristics of a sample of Berea sandstone to explore short-term relaxation, down to 10-4s (DAE is the dynamic equivalent of measuring acoustic velocity as a function of applied pressure). We find that early recovery does not follow a logarithmic law, while some earlier studies based on resonance techniques and at times larger than 1s do exhibit log(t)-recovery. From this non-log(t) dataset, we extract a spectrum of relaxation rates and discuss the potential relation between characteristic rates and rock microstructure. We also discuss the possible links between transient elastic softening and transient increase in permeability due to dynamic perturbation.

  19. Techniques for capturing bighorn sheep lambs

    USGS Publications Warehouse

    Smith, Joshua B.; Walsh, Daniel P.; Goldstein, Elise J.; Parsons, Zachary D.; Karsch, Rebekah C.; Stiver, Julie R.; Cain, James W.; Raedeke, Kenneth J.; Jenks, Jonathan A.

    2014-01-01

    Low lamb recruitment is a major challenge facing managers attempting to mitigate the decline of bighorn sheep (Ovis canadensis), and investigations into the underlying mechanisms are limited because of the inability to readily capture and monitor bighorn sheep lambs. We evaluated 4 capture techniques for bighorn sheep lambs: 1) hand-capture of lambs from radiocollared adult females fitted with vaginal implant transmitters (VITs), 2) hand-capture of lambs of intensively monitored radiocollared adult females, 3) helicopter net-gunning, and 4) hand-capture of lambs from helicopters. During 2010–2012, we successfully captured 90% of lambs from females that retained VITs to ≤1 day of parturition, although we noted differences in capture rates between an area of high road density in the Black Hills (92–100%) of South Dakota, USA, and less accessible areas of New Mexico (71%), USA. Retention of VITs was 78% with pre-partum expulsion the main cause of failure. We were less likely to capture lambs from females that expelled VITs ≥1 day of parturition (range = 80–83%) or females that were collared without VITs (range = 60–78%). We used helicopter net-gunning at several sites in 1999, 2001–2002, and 2011, and it proved a useful technique; however, at one site, attempts to capture lambs led to lamb predation by golden eagles (Aquila chrysaetos). We attempted helicopter hand-captures at one site in 1999, and they also were successful in certain circumstances and avoided risk of physical trauma from net-gunning; however, application was limited. In areas of low accessibility or if personnel lack the ability to monitor females and/or VITs for extended periods, helicopter capture may provide a viable option for lamb capture.

  20. Lamb Shift in Nonrelativistic Quantum Electrodynamics.

    ERIC Educational Resources Information Center

    Grotch, Howard

    1981-01-01

    The bound electron self-energy or Lamb shift is calculated in nonrelativistic quantum electrodynamics. Retardation is retained and also an interaction previously dropped in other nonrelativistic approaches is kept. Results are finite without introducing a cutoff and lead to a Lamb shift in hydrogen of 1030.9 MHz. (Author/JN)

  1. Mixed variational formulation of finite element analysis of acoustoelastic/slosh fluid-structure interaction

    NASA Technical Reports Server (NTRS)

    Felippa, C. A.; Ohayon, R.

    1990-01-01

    A general three-field variational principle is obtained for the motion of an acoustic fluid enclosed in a rigid or flexible container by the method of canonical decomposition applied to a modified form of the wave equation in the displacement potential. The general principle is specialized to a mixed two-field principle that contains the fluid displacement potential and pressure as independent fields. This principle contains a free parameter alpha. Semidiscrete finite-element equations of motion based on this principle are displayed and applied to the transient response and free-vibrations of the coupled fluid-structure problem. It is shown that a particular setting of alpha yields a rich set of formulations that can be customized to fit physical and computational requirements. The variational principle is then extended to handle slosh motions in a uniform gravity field, and used to derived semidiscrete equations of motion that account for such effects.

  2. Unilateral mandibular condylectomy in lambs.

    PubMed

    Miyamoto, H; Matsuura, H; Jones, R H; Kurita, K; Goss, A N

    2001-08-01

    The purpose of this experimental study was to investigate the degree of regeneration of the mandibular condyle after unilateral condylectomy in 10-week-old lambs. The lambs were killed three months after the operation, and the joints examined radiologically and histologically. Scoring systems were used to assess the radiological changes and histological regeneration of the condyle. All joints showed regeneration of the condylar head postoperatively. The maximum degree of regeneration occurred on the medial side rather than the central or lateral areas. There was a significant correlation among the medial, central, and lateral planes (P<0.05). The reformed articular cartilage was irregular and thin (P<0.01), and the disc was thick in the central plane (P<0.01) compared with the control joints. The temporal bone was normal. This study shows that unilateral condylectomy in the growing period results in some condylar regeneration particularly on the medial side and reformation of some irregular and thin articular cartilage. PMID:11437430

  3. Feeding behaviour of artificially reared Romane lambs.

    PubMed

    David, I; Bouvier, F; Ricard, E; Ruesche, J; Weisbecker, J-L

    2014-06-01

    A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs. PMID:24666599

  4. Feeding behaviour of artificially reared Romane lambs.

    PubMed

    David, I; Bouvier, F; Ricard, E; Ruesche, J; Weisbecker, J-L

    2014-06-01

    A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.

  5. Measurement of velocity distribution for longitudinal acoustic waves in welds by a laser optoacoustic technique

    NASA Astrophysics Data System (ADS)

    Ivochkin, A. Yu.; Karabutov, A. A.; Lyamshev, M. L.; Pelivanov, I. M.; Rohatgi, U.; Subudhi, M.

    2007-07-01

    An optoacoustic technique for diagnostics of residual stress in metals is proposed. The theoretical part of the technique employs acoustoelastic relations establishing a linear relationship between the biaxial residual stress and the relative variation of the velocity of longitudinal ultrasonic waves. The experimental technique is based on laser excitation of nanosecond ultrasonic pulses at the surface of samples under investigation and their detection with a high time resolution. Distributions of the relative variation of longitudinal wave velocities due to the presence of residual stress in the samples are obtained.

  6. 7 CFR 65.170 - Ground lamb.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG PRODUCTS INSPECTION ACT (CONTINUED) COUNTRY OF ORIGIN LABELING... lamb of skeletal origin that is produced in conformance with all applicable Food Safety and...

  7. Determinants of heat production in newborn lambs

    NASA Astrophysics Data System (ADS)

    Eales, F. A.; Small, J.

    1980-06-01

    Measurement of summit metabolism (the maximum rate of heat production) in lambs aged 1 or 4h revealed considerable between animal variation. Summit metabolism per unit body weight decreased as body weight increased whereas summit metabolism per unit body surface area was independent of body weight. Severe pre-partum hypoxia was apparently associated with a low summit metabolism at 1 or 4h of age which made such lambs very susceptible to hypothermia. This deficiency in heat production capacity did not appear to be a permanent featuresince most lambs so affected recovered full thermoregulatory ability by 12h of age. Feeding of colostrum conferred an immediate 18% increase in summit metabolism. The significance of these findings to the prevention of hypothermia in the newborn lamb is discussed.

  8. Looping through the Lamb Shift

    SciTech Connect

    Hazi, A U

    2007-02-06

    Sometimes in science, a small measurement can have big ramifications. For a team of Livermore scientists, such was the case when they measured a small shift in the spectrum of extremely ionized atoms of uranium. The measurement involves the Lamb shift, a subtle change in the energy of an electron orbiting an atom's nucleus. The precision of the Livermore result was 10 times greater than that of existing measurements, making it the best measurement to date of a complicated correction to the simplest quantum description of how atoms behave. The measurement introduces a new realm in the search for deviations between the theory of quantum electrodynamics (QED), which is an extension of quantum mechanics, and the real world. Such deviations, if discovered, would have far-reaching consequences, indicating that QED is not a fundamental theory of nature.

  9. Food hypersensitivity to lamb in a cat.

    PubMed

    Reedy, L M

    1994-04-01

    Severe facial pruritus in a cat was caused by food hypersensitivity to lamb. The cat had been fed an exclusive diet of lamb for 2 years after it had been diagnosed to have food hypersensitivity to fish. Signs, including erythema, alopecia, and excoriations of the head and neck, were poorly responsive to corticosteroid administration, but resolved within a few weeks after removal of the suspected allergen.

  10. Propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il; Choi, Bok Kyoung

    2014-12-01

    The present study aims to investigate the propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom. The velocities of the guided waves in a 5-mm-thick acrylic plate were measured by using the axial transmission technique. A pure A0 Lamb mode could be successfully launched in the 5-mm-thick acrylic plate through a time reversal process of Lamb waves, consistent with the fact that the time reversal process can automatically compensate for the dispersive nature of Lamb waves. The experimental velocities of the slow guided wave (SGW) and the time-reversed Lamb wave were found to be in reasonable agreement with the theoretical group velocity of the A0 Lamb mode, suggesting that both the SGW and the time-reversed Lamb wave excited in the 5-mm-thick acrylic plate correspond to the A0 Lamb mode. These results suggest that the time reversal process of Lamb waves can be usefully applied to noninvasive characterization of long cortical bones.

  11. Live and carcass leg characteristics in terminally-sired lambs.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Live and carcass leg characteristics of F1 wether lambs were investigated to determine whether there were terminal-sire breed differences. Over a 3-yr period, Columbia, MARCIII, Suffolk, and Texel rams were mated with mature Rambouillet ewes to produce the lambs (n=521). Lambs were finished in a fee...

  12. 21 CFR 880.5640 - Lamb feeding nipple.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Lamb feeding nipple. 880.5640 Section 880.5640... Devices § 880.5640 Lamb feeding nipple. (a) Identification. A lamb feeding nipple is a device intended for use as a feeding nipple for infants with oral or facial abnormalities. (b) Classification. Class...

  13. 21 CFR 880.5640 - Lamb feeding nipple.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Lamb feeding nipple. 880.5640 Section 880.5640... Devices § 880.5640 Lamb feeding nipple. (a) Identification. A lamb feeding nipple is a device intended for use as a feeding nipple for infants with oral or facial abnormalities. (b) Classification. Class...

  14. 21 CFR 880.5640 - Lamb feeding nipple.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Lamb feeding nipple. 880.5640 Section 880.5640... Devices § 880.5640 Lamb feeding nipple. (a) Identification. A lamb feeding nipple is a device intended for use as a feeding nipple for infants with oral or facial abnormalities. (b) Classification. Class...

  15. 21 CFR 880.5640 - Lamb feeding nipple.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Lamb feeding nipple. 880.5640 Section 880.5640... Devices § 880.5640 Lamb feeding nipple. (a) Identification. A lamb feeding nipple is a device intended for use as a feeding nipple for infants with oral or facial abnormalities. (b) Classification. Class...

  16. 21 CFR 880.5640 - Lamb feeding nipple.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Lamb feeding nipple. 880.5640 Section 880.5640... Devices § 880.5640 Lamb feeding nipple. (a) Identification. A lamb feeding nipple is a device intended for use as a feeding nipple for infants with oral or facial abnormalities. (b) Classification. Class...

  17. 7 CFR 59.302 - Mandatory weekly reporting for lambs.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... slaughtered; (3) The quantity of lambs delivered under a formula marketing arrangement that were slaughtered... and discounts (including those associated with weight, quality grade, yield grade, or type of lamb... lambs purchased through a formula marketing arrangement and slaughtered during the prior slaughter...

  18. 7 CFR 59.302 - Mandatory weekly reporting for lambs.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... slaughtered; (3) The quantity of lambs delivered under a formula marketing arrangement that were slaughtered... and discounts (including those associated with weight, quality grade, yield grade, or type of lamb... lambs purchased through a formula marketing arrangement and slaughtered during the prior slaughter...

  19. Genetic evaluation of weaning weight and probability of lambing at 1 year of age in Targhee lambs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to investigate genetic control of 120-day weaning weight and the probability of lambing at 1 year of age in Targhee ewe lambs. Records of 5,967 ewe lambs born from 1989 to 2012 and first exposed to rams for breeding at approximately 7 months of age were analyzed. Reco...

  20. Lactation curves of commercial ewes rearing lambs.

    PubMed

    Cardellino, R A; Benson, M E

    2002-01-01

    Three-hour milk production measurements determined by machine milking at 3-d intervals throughout a 63-d lactation period were used to describe lactation curves for crossbred ewes lambing at 1 and 2 yr of age and rearing single and twin lambs. Age of ewe, type of rearing, and day of lactation affected (P < 0.05) milk production. Over the 63-d lactation, average daily milk production was 2.56 and 2.63 kg, respectively, for 1- and 2-yr-old ewes rearing single lambs and 2.73 and 3.47 kg, respectively, for 1- and 2-yr-old ewes rearing twins. Milk production of 2-yr-old ewes rearing twin lambs peaked at 21 d of lactation, and that of 1- and 2-yr-old ewes rearing singles peaked between 27 and 30 d of lactation. The largest differences in the lactation curves among age and rearing ewe classes were found in early lactation. These differences were reduced by midlactation, and by late lactation, milk production for all ewes was similar. Diurnal variation in milk production by ewes was evaluated in an 8 x 8 Latin square design. Diurnal variation in milk yield measurements of eight mature ewes, each bearing and rearing twin lambs, was similar between d 21 and 24 of lactation. Time of milk production measurements within a day did not affect yield determinations. Extrapolation from 3-h production estimates to daily milk production is valid in determining a ewe's milk contribution in support of lamb growth.

  1. Effect of weaning age on hair sheep lamb and ewe production traits in an accelerated lambing system in the tropics.

    PubMed

    Godfrey, R W; Weis, A J

    2016-03-01

    This study was designed to evaluate the impact of weaning age on lamb and ewe productivity in an accelerated lambing system. St. Croix White (STX) and Dorper × St. Croix White (DRPX) lambs were assigned at birth based on breed, gender, and litter size to be weaned at 63 (Early-1; 106 lambs and 68 ewes) or 90 d of age (Late-1; 99 lambs and 60 ewes) in Exp.1 or at 63 (Early-2; 77 lambs and 57 ewes) or 120 d of age (Late-2; 75 lambs and 56 ewes) in Exp. 2. After weaning, lambs were weighed weekly and fed a concentrate ration (2% BW·lamb·d) while grazing guinea grass pastures. In Exp. 1, weaning weight was greater ( < 0.0001) for Late-1 lambs than for Early-1 lambs (14.6 ± 0.3 vs. 11.0 ± 0.3 kg, respectively) and greater ( < 0.008) for DRPX lambs than for STX lambs (13.9 ± 0.4 vs. 11.5 ± 0.4 kg, respectively). Litter weaning weight was greater ( < 0.004) for Late-1 ewes than for Early-1 ewes (20.9 ± 0.8 vs. 17.4 ± 0.8 kg, respectively). Ewe efficiency ([ewe BW at weaning/litter weaning weight] × 100) was greater ( < 0.004) for Late-1 ewes than for Early-1 ewes (50.7 ± 1.9 vs. 42.3 ± 1.8%, respectively). Lamb weight gain between 63 and 90 d of age was lower ( < 0.03) for Early-1 lambs than for Late-1 lambs (2.7 ± 0.2 vs. 3.6 ± 0.3 kg, respectively). In Exp. 2, weaning weight was greater ( < 0.0001) for Late-2 lambs than for Early-2 lambs (18.7 ± 0.4 vs. 11.8 ± 0.4 kg, respectively) and greater ( < 0.008) for DRPX lambs than for STX lambs (16.9 ± 0.5 vs. 13.3 ± 0.5 kg, respectively). Litter weaning weight was greater ( < 0.0001) in Late-2 ewes than in Early-2 ewes (27.2 ± 1.0 vs. 17.5 ± 0.9 kg, respectively). Ewe efficiency was greater ( < 0.0001) for Late-2 ewes than for Early-2 ewes (68.1 ± 2.2 vs. 41.9 ± 2.0%, respectively). Lamb weight gain between 63 and 120 d of age was not different ( > 0.06) between Early-2 and Late-2 lambs (5.1 ± 0.2 vs. 5.6 ± 0.3 kg, respectively). In Exp. 1 and 2, ewe BW at breeding and lambing and weaning and lambing

  2. Quantitative imaging of nonlinear shear modulus by combining static elastography and shear wave elastography.

    PubMed

    Latorre-Ossa, Heldmuth; Gennisson, Jean-Luc; De Brosses, Emilie; Tanter, Mickaël

    2012-04-01

    The study of new tissue mechanical properties such as shear nonlinearity could lead to better tissue characterization and clinical diagnosis. This work proposes a method combining static elastography and shear wave elastography to derive the nonlinear shear modulus by applying the acoustoelasticity theory in quasi-incompressible soft solids. Results demonstrate that by applying a moderate static stress at the surface of the investigated medium, and by following the quantitative evolution of its shear modulus, it is possible to accurately and quantitatively recover the local Landau (A) coefficient characterizing the shear nonlinearity of soft tissues.

  3. Application of the Pseudo Wigner-Ville Distribution to the Measurement of the Dispersion of Lamb Modes in Graphite/Epoxy Plates

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Seale, M. D.; Smith, B. T.

    1997-01-01

    Acoustic waves propagate in thin plates as guided or Lamb modes. The velocities of these modes are dispersive in that they depend not only on the material elastic properties and density, but also on the frequency. Accurate characterization of Lamb wave dispersion is important in many acoustic based nondestructive evaluation techniques. It is necessary for ultrasonic measurements in thin plates to determine elastic properties and for flaw detection and localization. In acoustic emission (AE) testing, if not taken into account, highly dispersive Lamb mode propagation can lead to large errors in source location. In this study, the pseudo Wigner-Ville distribution (PWVD) was used for measurement of group velocity dispersion of Lamb waves in a unidirectional graphite/epoxy (AS4/3502) laminate. The PWVD is one of a number of transforms which provide a time-frequency representation of a digitized time series. Broad band acoustic waves were generated by a pencil lead fracture (Hsu-Neilsen source) and were detected with broad band ultrasonic transducers. The arrival times for the lowest order symmetric (S(sub 0)) and antisymmetric (A(sub 0)) Lamb modes were determined from measurements of the time at which the respective peak amplitudes occurred in the PWVD. Measurements were made at several source-to-detector distances and a least squares fit used to calculate the velocity. Results are presented for propagation along, and perpendicular to, the fiber direction. Theoretical dispersion curves were also calculated and a comparison between theory and experiment demonstrates good agreement.

  4. Effect of Stress on Energy Flux Deviation of Ultrasonic Waves in Ultrasonic Waves in GR/EP Composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1990-01-01

    Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis fiber axis) and the x1 axis for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers new nondestructive technique of evaluating stress in composites.

  5. 7 CFR 65.170 - Ground lamb.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Ground lamb. 65.170 Section 65.170 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE...

  6. 7 CFR 65.190 - Lamb.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Lamb. 65.190 Section 65.190 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG...

  7. 7 CFR 65.170 - Ground lamb.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Ground lamb. 65.170 Section 65.170 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE...

  8. 7 CFR 65.190 - Lamb.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Lamb. 65.190 Section 65.190 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG...

  9. 7 CFR 65.170 - Ground lamb.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Ground lamb. 65.170 Section 65.170 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE...

  10. 7 CFR 65.190 - Lamb.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Lamb. 65.190 Section 65.190 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG...

  11. 7 CFR 65.170 - Ground lamb.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Ground lamb. 65.170 Section 65.170 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946 AND THE...

  12. Cooperative Lamb shift and the cooperative decay rate for an initially detuned phased state

    SciTech Connect

    Friedberg, Richard; Manassah, Jamal T.

    2010-04-15

    The cooperative Lamb shift (CLS) is hard to measure because in samples much larger than a resonant wavelength it is much smaller, for an initially prepared resonantly phased state, than the cooperative decay rate (CDR). We show, however, that if the phasing of the initial state is detuned so that the spatial wave vector is k{sub 1} congruent with k{sub 0{+-}}O((1/R)) (where k{sub 0}={omega}{sub 0}/c is the resonant frequency), the CLS grows to 'giant' magnitudes making it comparable to the CDR. Moreover, for certain controlled values of detuning, the initial CDR becomes small so that the dynamical Lamb shift (DLS) can be measured over a considerable period of time.

  13. Quantitative assessment of corneal viscoelasticity using optical coherence elastography and a modified Rayleigh–Lamb equation

    PubMed Central

    Han, Zhaolong; Aglyamov, Salavat R.; Li, Jiasong; Singh, Manmohan; Wang, Shang; Vantipalli, Srilatha; Wu, Chen; Liu, Chih-hao; Twa, Michael D.; Larin, Kirill V.

    2015-01-01

    Abstract. We demonstrate the use of a modified Rayleigh–Lamb frequency equation in conjunction with noncontact optical coherence elastography to quantify the viscoelastic properties of the cornea. Phase velocities of air-pulse-induced elastic waves were extracted by spectral analysis and used for calculating the Young’s moduli of the samples using the Rayleigh–Lamb frequency equation (RLFE). Validation experiments were performed on 2% agar phantoms (n=3) and then applied to porcine corneas (n=3) in situ. The Young’s moduli of the porcine corneas were estimated to be ∼60  kPa with a shear viscosity ∼0.33  Pa·s. The results demonstrate that the RLFE is a promising method for noninvasive quantification of the corneal biomechanical properties and may potentially be useful for clinical ophthalmological applications. PMID:25649624

  14. Enteric viral infections in lambs or kids.

    PubMed

    Martella, V; Decaro, N; Buonavoglia, C

    2015-12-14

    Diarrhoea in lambs and kids is often a complex, multi-factorial syndrome. Common infectious causes of diarrhoea in lambs and kids during the first month of life are of bacterial or parasite nature. However, despite appreciable improvements in management practices and prevention and treatment strategies over the last decades, diarrhoea is still a common and costly syndrome affecting newborn small ruminants. Recent advances in the diagnostics and metagenomic investigations of the enteric environment have allowed discovering a number of novel viruses, although their pathobiological properties remain largely unknown. Assessing more in depth the impact of these viruses on the health and productions of these livestock animals is necessary and requires the development of accurate diagnostic tools and updating of the diagnostic algorithms of enteric pathological conditions.

  15. Sodium chlorate reduces presence of Escherichia coli in feces of lambs and ewes managed in shed-lambing systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our objective was to establish doses of orally-administered NaClO3 that reduced presence of generic Escherichia coli in intestines of ewes and neonatal lambs managed in a shed-lambing system. Neonatal lambs (n = 32; age = 7.1 ± 1.2 d; BW = 6.8 ± 1.0 kg) and yearling ewes (n = 44; BW = 74.8 ± 5.6 kg)...

  16. The effect of tilmicosin administered to ewes prior to lambing on incidence of clinical mastitis and subsequent lamb performance.

    PubMed

    Croft, A; Duffield, T; Menzies, P; Leslie, K; Bagg, R; Dick, P

    2000-04-01

    The effect of tilmicosin on the incidence of clinical mastitis and subsequent lamb performance was studied in 9 sheep flocks in Ontario. Ewes were treated randomly with either tilmicosin or placebo approximately one month prior to lambing. Outcome was assessed by comparing rates of clinical mastitis, palpable udder abnormalities, and preweaning (50-day) lamb weights between the 2 treatment groups, while controlling for other important variables. Lambs raised by multiparous ewes treated with tilmicosin were significantly heavier than lambs from placebo-treated multiparous ewes at 50 days. Lambs from tilmicosin-treated ewes were on average 0.52 kg heavier than lambs in the placebo group. There was no difference between treatment groups in the weight of lambs from first parity ewes. Tilmicosin treatment resulted in a 43% decrease in palpable udder abnormalities. Incidence of clinical mastitis did not differ between experimental groups. The administration of tilmicosin prelambing, at the time of routine clostridial disease vaccination, may be a beneficial and convenient way to reduce mastitis infection and improve the preweaning gain of lambs.

  17. Temperament and its heritability in Corriedale and Merino lambs.

    PubMed

    Zambra, N; Gimeno, D; Blache, D; van Lier, E

    2015-03-01

    Temperament can be defined as the fearfulness and reactivity of an animal in response to humans and strange, novel or threatening environments. The productive performance of an animal is affected by its temperament, and selection of calm animals might improve their adaptation to the farming environment and handling, as well as improve productivity. The temperament was measured in lambs of two breeds of sheep in Uruguay. The effects of dam's age, type of birth, age of the lamb and contemporary group (CG; lambs belonging to the same year, flock, sex and rearing group) on the temperament of the lambs and the heritability of temperament were estimated with a Bayesian analysis using Gibbs sampling. Overall, 4962 Corriedale lambs and 2952 Merino lambs from 13 farms were tested. Temperament was measured using the isolation box test, isolating a lamb inside the box for 30 s, and recording the vibrations produced by its movements. The average temperament score (±s.e.m.) of the Corriedale lambs was 24.7 (±0.23) and that of the Merino was 36.8 (±0.45). Temperament was not associated with dam's age, type of birth or lamb's age. There were no relevant differences in the agitation score between lambs born in 2010 and 2011. The mean of the distribution of possible values of heritability (±s.d.) was 0.18 (±0.05) for the Corriedale and 0.31 (±0.06) for the Merino. The likelihood of heritability values to be greater than 0.15 exceeded 70% in the Corriedale and 90% in the Merino. The temperament of Merino and Corriedale sheep in Uruguay is moderately heritable. It is not related to dam's age, type of birth or age of the lambs; however, it is affected by some aspect of the CG.

  18. Vitamin D-responsive rickets in neonatal lambs

    PubMed Central

    2004-01-01

    Abstract An unusual clinical presentation of rickets in nursing lambs is described. Two sets of twin nursing lambs were presented for enlarged joints and mild angular deformity. Rickets was suspected, based on radiographic evidence. Vitamin D deficiency was determined to be the cause, based on serum concentration and response to therapy. PMID:15532884

  19. Development of mother discrimination by single and multiple newborn lambs.

    PubMed

    Nowak, R; Poindron, P; Putu, I G

    1989-12-01

    Most research on recognition of the ewe by her lamb has focused on lambs several days or even several weeks old, whereas newly born lambs have received little attention. The aim of this work was therefore to study the attraction of Merino lambs to postparturient ewes and their ability to discriminate between their own and alien mothers in a two-choice situation 12, 18, 24, 48, and 72 hr after birth. A comparison between singles and multiples was also made in 18 and 24-hr-old lambs. When released in the testing pen, approximately 90% of the lambs in each group (older than 12 hr) spent more than 3 min with the two ewes during the 5-min test. It was only from 24 hr old, however, that a high proportion of lambs spent at least two-thirds of this time close to their own mothers (correct choice). The proportion of singles spending more than 3 min with the ewes or making a correct choice was higher than that of multiples. This effect was related to litter size but not to birth weight. It is concluded that a majority of Merino lambs are clearly attracted to ewes by the time they are 18 hr old and can discriminate their own dams from alien mothers at about 24 hr of age. At this stage singles perform better than multiples.

  20. 7 CFR 59.301 - Mandatory Daily Reporting for Lambs.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... prices for lambs (per hundredweight) established on that day as F.O.B. feedlot or delivered at the plant... were of a quality grade of Choice or better; (7) Any premiums or discounts associated with weight, quality grade, yield grade, or any type of purchase; (8) Lamb state of origin; (9) The pelt type; and...

  1. Lamb shift in heliumlike uranium (U/sup 90 +/)

    SciTech Connect

    Munger, C.; Gould, H.

    1986-05-01

    We report a preliminary value of the Lamb shift in two-electron heliumlike U/sup 90 +/ of 69.1 (8.0) eV which is in agreement with the theoretical value of 75 eV for the one-electron Lamb shift at Z = 92. 8 refs., 2 figs.

  2. Acoustic wave characterization of silicon phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Feng, Duan; Jiang, Wanli; Xu, Dehui; Xiong, Bin; Wang, Yuelin

    2015-08-01

    In this paper, characterization of megahertz Lamb waves in a silicon phononic crystal based asymmetry filter by laser Doppler vibrometer is demonstrated. The acoustic power from a piezoelectric substrate was transmitted into the silicon superstrate by fluid coupling method, and measured results show that the displacement amplitude of the acoustic wave in the superstrate was approximately one fifth of that in the piezoelectric substrate. Effect of the phononic bandgap on the propagation of Lamb wave in the silicon superstrate is also measured, and the result shows that the phononic crystal structure could reflect part of the acoustic waves back.

  3. 7 CFR 59.303 - Mandatory reporting of lamb carcasses and boxed lamb.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... officially designated representatives of each packer shall report to the Secretary each reporting day the... accordance with § 59.10(b): (1) The price for each lot of each lamb carcass transaction, quoted in dollars per hundredweight on an F.O.B. plant basis; (2) The quantity for each lot of each transaction,...

  4. Lamb Production Costs: Analyses of Composition and Elasticities Analysis of Lamb Production Costs

    PubMed Central

    Raineri, C.; Stivari, T. S. S.; Gameiro, A. H.

    2015-01-01

    Since lamb is a commodity, producers cannot control the price of the product they sell. Therefore, managing production costs is a necessity. We explored the study of elasticities as a tool for basing decision-making in sheep production, and aimed at investigating the composition and elasticities of lamb production costs, and their influence on the performance of the activity. A representative sheep production farm, designed in a panel meeting, was the base for calculation of lamb production cost. We then performed studies of: i) costs composition, and ii) cost elasticities for prices of inputs and for zootechnical indicators. Variable costs represented 64.15% of total cost, while 21.66% were represented by operational fixed costs, and 14.19% by the income of the factors. As for elasticities to input prices, the opportunity cost of land was the item to which production cost was more sensitive: a 1% increase in its price would cause a 0.2666% increase in lamb cost. Meanwhile, the impact of increasing any technical indicator was significantly higher than the impact of rising input prices. A 1% increase in weight at slaughter, for example, would reduce total cost in 0.91%. The greatest obstacle to economic viability of sheep production under the observed conditions is low technical efficiency. Increased production costs are more related to deficient zootechnical indexes than to high expenses. PMID:26104531

  5. A case presentation of spider lamb syndrome in a Kermanian breed lamb

    PubMed Central

    Nazem, Mohammad Naser; Shojaei, Bahador; Asadi, Akbar; Hasanzadeh, Mohammad

    2015-01-01

    Skeletal abnormalities are most often used to describe defects in the arms or legs that are associated with genes or chromosomes, or that occur due to an event that happens during pregnancy. Spider lamb syndrome (SLS) is a congenital disorder in sheep breeding that is recognized by some deformities in skeletal system especially in the limbs. A dead day-old cross-breed white lamb with deformed limbs was referred to the anatomy hall of the Veterinary Faculty of Shahid Bahonar University of Kerman. In the external examination, the lamb was very skinny and in the facial region, superior brachygnathia with a slight Roman nose were observed. Metacarpal and metatarsal regions were more elongated than that expected. Also Metacarpal and metatarsal bones were as long as the antebrachial and crural regions, respectively. This paper, the first report of this syndrome in Iran, described the anatomic and radiographic features of the skeletal deformities in a day-old dead Kermanian breed lamb. PMID:26973772

  6. A case presentation of spider lamb syndrome in a Kermanian breed lamb.

    PubMed

    Nazem, Mohammad Naser; Shojaei, Bahador; Asadi, Akbar; Hasanzadeh, Mohammad

    2015-01-01

    Skeletal abnormalities are most often used to describe defects in the arms or legs that are associated with genes or chromosomes, or that occur due to an event that happens during pregnancy. Spider lamb syndrome (SLS) is a congenital disorder in sheep breeding that is recognized by some deformities in skeletal system especially in the limbs. A dead day-old cross-breed white lamb with deformed limbs was referred to the anatomy hall of the Veterinary Faculty of Shahid Bahonar University of Kerman. In the external examination, the lamb was very skinny and in the facial region, superior brachygnathia with a slight Roman nose were observed. Metacarpal and metatarsal regions were more elongated than that expected. Also Metacarpal and metatarsal bones were as long as the antebrachial and crural regions, respectively. This paper, the first report of this syndrome in Iran, described the anatomic and radiographic features of the skeletal deformities in a day-old dead Kermanian breed lamb. PMID:26973772

  7. Effect of stress on energy flux deviation of ultrasonic waves in GR/EP composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1990-01-01

    Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis (fiber axis) and the x1 for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers a new nondestructive technique of evaluating stress in composites.

  8. Nonrelativistic Lamb shift for muonic molecules

    NASA Astrophysics Data System (ADS)

    Bukowski, Robert; Jeziorski, Bogumil

    1993-03-01

    A recently developed formula [R. Bukowski and B. Jeziorski, Phys. Rev. A46 (1992) 5437]. has been applied to estimate the soft-photon Lamb shift contribution to the energies of the muonic molecules ppμ, ddμ, ttμ, pdμ, ptμ and dtμ. The corresponding corrections to the dissociation energies for the excited P states of ddμ and dtμ have been found to be almost identical and equal to 0.048 meV. The magnitude of this stabilizing effect is too small to affect seriously the formation rates predictions.

  9. Second Harmonic Generation of Lamb Wave in Numerical Perspective

    NASA Astrophysics Data System (ADS)

    Zhu, Wu-Jun; Deng, Ming-Xi; Xiang, Yan-Xun; Xuan, Fu-Zhen; Liu, Chang-Jun

    2016-10-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 51325504, 11474093, 11622430 and 11474361, the National Key Research and Development Program of China (2016YFC0801903-02), and the Fundamental Research Funds for the Central Universities.

  10. Classification of flaw severity using pattern recognition for guided wave-based structural health monitoring.

    PubMed

    Miller, Corey A; Hinders, Mark K

    2014-01-01

    In this paper, the authors present a formal classification routine to characterize flaw severity in an aircraft-grade aluminum plate using Lamb waves. A rounded rectangle flat-bottom hole is incrementally introduced into the plate, and at each depth multi-mode Lamb wave signals are collected to study the changes in received signal due to mode conversion and scattering from the flaw. Lamb wave tomography reconstructions are used to locate and size the flaw at each depth, however information about the severity of the flaw is obscured when the flaw becomes severe enough that scattering effects dominate. The dynamic wavelet fingerprint is then used to extract features from the raw Lamb wave signals, and supervised pattern classification techniques are used to identify flaw severity with up to 80.7% accuracy for a training set and up to 51.7% accuracy on a series of validation data sets extracted from independent plate samples. PMID:23731948

  11. Detection and quantification of delamination in laminated plates from the phase of appropriate guided wave modes

    NASA Astrophysics Data System (ADS)

    Amjad, Umar; Yadav, Susheel Kumar; Kundu, Tribikram

    2016-01-01

    Applicability of specific Lamb wave modes for delamination detection and quantification in a laminated aluminum plate is investigated. The Lamb modes were generated in the plate using a broadband piezoelectric transducer structured with a rigid electrode. Appropriate excitation frequencies and modes for inspection were selected from theoretical dispersion curves. Sensitivity of antisymmetric and symmetric modes for delamination detection and quantification has been investigated using the Hilbert-Huang transform. The mode conversion phenomenon of Lamb waves during progressive delamination is observed. The antisymmetric mode is found to be more reliable for delamination detection and quantification. In this investigation, the changes in the phase of guided Lamb wave modes are related to the degree of delamination, unlike other studies, where mostly the attenuation of the propagating waves has been related to the extent of the internal damage, such as cracks and corrosions. Appropriate features for delamination detection and quantification are extracted from the experimental data.

  12. Classification of flaw severity using pattern recognition for guided wave-based structural health monitoring.

    PubMed

    Miller, Corey A; Hinders, Mark K

    2014-01-01

    In this paper, the authors present a formal classification routine to characterize flaw severity in an aircraft-grade aluminum plate using Lamb waves. A rounded rectangle flat-bottom hole is incrementally introduced into the plate, and at each depth multi-mode Lamb wave signals are collected to study the changes in received signal due to mode conversion and scattering from the flaw. Lamb wave tomography reconstructions are used to locate and size the flaw at each depth, however information about the severity of the flaw is obscured when the flaw becomes severe enough that scattering effects dominate. The dynamic wavelet fingerprint is then used to extract features from the raw Lamb wave signals, and supervised pattern classification techniques are used to identify flaw severity with up to 80.7% accuracy for a training set and up to 51.7% accuracy on a series of validation data sets extracted from independent plate samples.

  13. Nonlinear wave propagation in constrained solids subjected to thermal loads

    NASA Astrophysics Data System (ADS)

    Nucera, Claudio; Lanza di Scalea, Francesco

    2014-01-01

    The classical mathematical treatment governing nonlinear wave propagation in solids relies on finite strain theory. In this scenario, a system of nonlinear partial differential equations can be derived to mathematically describe nonlinear phenomena such as acoustoelasticity (wave speed dependency on quasi-static stress), wave interaction, wave distortion, and higher-harmonic generation. The present work expands the topic of nonlinear wave propagation to the case of a constrained solid subjected to thermal loads. The origin of nonlinear effects in this case is explained on the basis of the anharmonicity of interatomic potentials, and the absorption of the potential energy corresponding to the (prevented) thermal expansion. Such "residual" energy is, at least, cubic as a function of strain, hence leading to a nonlinear wave equation and higher-harmonic generation. Closed-form solutions are given for the longitudinal wave speed and the second-harmonic nonlinear parameter as a function of interatomic potential parameters and temperature increase. The model predicts a decrease in longitudinal wave speed and a corresponding increase in nonlinear parameter with increasing temperature, as a result of the thermal stresses caused by the prevented thermal expansion of the solid. Experimental measurements of the ultrasonic nonlinear parameter on a steel block under constrained thermal expansion confirm this trend. These results suggest the potential of a nonlinear ultrasonic measurement to quantify thermal stresses from prevented thermal expansion. This knowledge can be extremely useful to prevent thermal buckling of various structures, such as continuous-welded rails in hot weather.

  14. Comb-locked Lamb-dip spectrometer.

    PubMed

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-01-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm(2), which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10(-11) cm(-1) absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10(-23) cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed. PMID:27263858

  15. [Spina bifida aperta in a sheep lamb].

    PubMed

    Gutzwiller, N; Hilbe, M; Kircher, P; Bleull, U

    2015-01-01

    The case report describes the symptoms and diagnostic methods of a spina bifida aperta in a new born lamb. The most relevant clinical findings were recumbency immediately after birth with normal consciousness and suckling reflexes, alterations of the skin and coat in the lumbosacral region as well as dysuria. The biochemical and haematological screening of the blood indicated no abnormalities. While the radiological examination of the spine showed no clear evidence of the cause of the clinical sings the ultrasound and computed tomography examination revealed an incomplete closure of the vertebral arch between the 4th lumbar and the 3rd sacral vertebrae. Additionally, a hernia with similar density to the spinal cord was present in the same region of the spine. Based on the findings the lamb was euthanized. The pathological examination confirmed the incomplete closure of the vertebral arch and moreover a myelomeningocele has been diagnosed. In the histopathological examination the white and grey matter were separated in the area of the macroscopic visible lesions. Due to non-specific clinical symptoms imagining diagnostics can be crucial to confirm the diagnosis of this rare syndrome.

  16. Comb-locked Lamb-dip spectrometer.

    PubMed

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-06

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm(2), which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10(-11) cm(-1) absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10(-23) cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  17. Theory of Lamb Shift in Muonic Hydrogen

    SciTech Connect

    Karshenboim, Savely G.; Korzinin, Evgeny Yu.; Shelyuto, Valery A.; Ivanov, Vladimir G.

    2015-09-15

    There has been for a while a large discrepancy between the values of the proton charge radius measured by the Lamb shift in muonic hydrogen and by other methods. It has already been clear that theory of muonic hydrogen is reliable at the level of this discrepancy and an error there cannot be a reason for the contradiction. Still the status of theory at the level of the uncertainty of the muonic-hydrogen experiment (which is two orders of magnitude below the discrepancy level) requires an additional clarification. Here, we revisit theory of the 2p − 2s Lamb shift in muonic hydrogen. We summarize all the theoretical contributions in order α{sup 5}m, including pure quantum electrodynamics (QED) ones as well as those which involve the proton-structure effects. Certain enhanced higher-order effects are also discussed. We basically confirm former QED calculations of other authors, present a review of recent calculations of the proton-structure effects, and treat self-consistently higher-order proton-finite-size corrections. We also overview theory of the 2p states. Eventually, we derive a value of the root-mean-square proton charge radius. It is found to be 0.840 29(55) fm, which is slightly different from that previously published in the literature (0.840 87(39) fm [Antognini et al., Science 339, 417 (2013)])

  18. Comb-locked Lamb-dip spectrometer

    PubMed Central

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-01-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10−11 cm−1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10−23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed. PMID:27263858

  19. Comb-locked Lamb-dip spectrometer

    NASA Astrophysics Data System (ADS)

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10‑11 cm‑1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10‑23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  20. Development and validation of equations utilizing lamb vision system output to predict lamb carcass fabrication yields.

    PubMed

    Cunha, B C N; Belk, K E; Scanga, J A; LeValley, S B; Tatum, J D; Smith, G C

    2004-07-01

    This study was performed to validate previous equations and to develop and evaluate new regression equations for predicting lamb carcass fabrication yields using outputs from a lamb vision system-hot carcass component (LVS-HCC) and the lamb vision system-chilled carcass LM imaging component (LVS-CCC). Lamb carcasses (n = 149) were selected after slaughter, imaged hot using the LVS-HCC, and chilled for 24 to 48 h at -3 to 1 degrees C. Chilled carcasses yield grades (YG) were assigned on-line by USDA graders and by expert USDA grading supervisors with unlimited time and access to the carcasses. Before fabrication, carcasses were ribbed between the 12th and 13th ribs and imaged using the LVS-CCC. Carcasses were fabricated into bone-in subprimal/primal cuts. Yields calculated included 1) saleable meat yield (SMY); 2) subprimal yield (SPY); and 3) fat yield (FY). On-line (whole-number) USDA YG accounted for 59, 58, and 64%; expert (whole-number) USDA YG explained 59, 59, and 65%; and expert (nearest-tenth) USDA YG accounted for 60, 60, and 67% of the observed variation in SMY, SPY, and FY, respectively. The best prediction equation developed in this trial using LVS-HCC output and hot carcass weight as independent variables explained 68, 62, and 74% of the variation in SMY, SPY, and FY, respectively. Addition of output from LVS-CCC improved predictive accuracy of the equations; the combined output equations explained 72 and 66% of the variability in SMY and SPY, respectively. Accuracy and repeatability of measurement of LM area made with the LVS-CCC also was assessed, and results suggested that use of LVS-CCC provided reasonably accurate (R2 = 0.59) and highly repeatable (repeatability = 0.98) measurements of LM area. Compared with USDA YG, use of the dual-component lamb vision system to predict cut yields of lamb carcasses improved accuracy and precision, suggesting that this system could have an application as an objective means for pricing carcasses in a value

  1. Breathing in fetal lambs: the effect of brain stem section.

    PubMed

    Dawes, G S; Gardner, W N; Johnston, B M; Walker, D W

    1983-02-01

    The effects of section of the brain stem caudally (through the upper pons or mid-collicular) or rostrally (through the caudal hypothalamus or anterior commissure-suprachiasmatic nucleus) were studied in fetal lambs from 118 days gestation, after recovery in utero. In lambs sectioned caudally, breathing movements and electrocortical activity were dissociated. After some days recovery breathing tended to become continuous, with an abnormal prolongation of inspiratory time. Isocapnic hypoxia caused an increase in the rate and amplitude of breathing. After carotid denervation hypoxia still caused an increase in the amplitude of breathing. In lambs sectioned rostrally, there was also dissociation between breathing movements and electrocortical activity. Breathing remained episodic, with an incidence similar to that of intact fetal lambs. In two lambs after 10 days of recovery the breathing and electrocortical rhythms returned, from time to time, to their normal phasic relationship. Isocapnic hypoxia caused a diminution or arrest of breathing, as in intact lambs. The cardiovascular effects of transection were examined. Baroreflex sensitivity was normal in those lambs sectioned caudally and enhanced in those sectioned rostrally. It is concluded first that as a result of rostral section, independent episodic rhythms of fetal breathing and electrocortical activity can be dissociated. Secondly, moderate isocapnic hypoxia causes arrest of fetal breathing indirectly, requiring the integrity of a suprapontine mechanism. And thirdly, after caudal section of the brain stem, hypoxia causes enhancement of fetal breathing efforts, independently of the carotid chemoreceptors. Possible mechanisms are discussed. PMID:6875894

  2. Effect of vacuum ageing on quality changes of lamb steaks from early fattening lambs during aerobic display.

    PubMed

    Callejas-Cárdenas, Aída R; Caro, Irma; Blanco, Carolina; Villalobos-Delgado, Luz H; Prieto, Nuria; Bodas, Raúl; Giráldez, Francisco J; Mateo, Javier

    2014-12-01

    The effects of vacuum ageing on the quality changes of lamb steaks during retail display were assessed. Biceps femoris and Quadriceps femoris muscles from thirty early fattening lambs fed barley straw and concentrate or alfalfa and concentrate were used. Half of the muscles were vacuum aged for three weeks (VA), and the other half were not aged (control). Control and VA muscles were sliced and aerobically displayed. Weight loss, pH, aldehyde contents, instrumental color characteristics and color acceptance were measured at display days 1, 3, 7 and 14. At day 1 redness was higher in VA lamb. However, redness of VA lamb decreases more rapidly during further storage. Redness and color acceptance decreased in VA lamb from day 3, whereas in not-aged lamb the decrease was observed from day 7 onwards. From days 7 to 14 a drop of color acceptance accompanied by an increase in pH and a decrease in lightness was observed in control and VA lamb.

  3. Effect of vacuum ageing on quality changes of lamb steaks from early fattening lambs during aerobic display.

    PubMed

    Callejas-Cárdenas, Aída R; Caro, Irma; Blanco, Carolina; Villalobos-Delgado, Luz H; Prieto, Nuria; Bodas, Raúl; Giráldez, Francisco J; Mateo, Javier

    2014-12-01

    The effects of vacuum ageing on the quality changes of lamb steaks during retail display were assessed. Biceps femoris and Quadriceps femoris muscles from thirty early fattening lambs fed barley straw and concentrate or alfalfa and concentrate were used. Half of the muscles were vacuum aged for three weeks (VA), and the other half were not aged (control). Control and VA muscles were sliced and aerobically displayed. Weight loss, pH, aldehyde contents, instrumental color characteristics and color acceptance were measured at display days 1, 3, 7 and 14. At day 1 redness was higher in VA lamb. However, redness of VA lamb decreases more rapidly during further storage. Redness and color acceptance decreased in VA lamb from day 3, whereas in not-aged lamb the decrease was observed from day 7 onwards. From days 7 to 14 a drop of color acceptance accompanied by an increase in pH and a decrease in lightness was observed in control and VA lamb. PMID:25089789

  4. 16 CFR 301.8 - Use of terms “Persian Lamb,” “Broadtail Lamb,” and “Persian-broadtail Lamb” permitted.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...) The term Persian Lamb may be used to describe the skin of the young lamb of the Karakul breed of sheep or top-cross breed of such sheep, having hair formed in knuckled curls. (b) The term Broadtail Lamb... breed of sheep or top-cross breed of such sheep, having flat light-weight fur with a moire pattern....

  5. 16 CFR 301.8 - Use of terms “Persian Lamb,” “Broadtail Lamb,” and “Persian-broadtail Lamb” permitted.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...) The term Persian Lamb may be used to describe the skin of the young lamb of the Karakul breed of sheep or top-cross breed of such sheep, having hair formed in knuckled curls. (b) The term Broadtail Lamb... breed of sheep or top-cross breed of such sheep, having flat light-weight fur with a moire pattern....

  6. 16 CFR 301.8 - Use of terms “Persian Lamb,” “Broadtail Lamb,” and “Persian-broadtail Lamb” permitted.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) The term Persian Lamb may be used to describe the skin of the young lamb of the Karakul breed of sheep or top-cross breed of such sheep, having hair formed in knuckled curls. (b) The term Broadtail Lamb... breed of sheep or top-cross breed of such sheep, having flat light-weight fur with a moire pattern....

  7. 16 CFR 301.8 - Use of terms “Persian Lamb,” “Broadtail Lamb,” and “Persian-broadtail Lamb” permitted.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) The term Persian Lamb may be used to describe the skin of the young lamb of the Karakul breed of sheep or top-cross breed of such sheep, having hair formed in knuckled curls. (b) The term Broadtail Lamb... breed of sheep or top-cross breed of such sheep, having flat light-weight fur with a moire pattern....

  8. 16 CFR 301.8 - Use of terms “Persian Lamb,” “Broadtail Lamb,” and “Persian-broadtail Lamb” permitted.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) The term Persian Lamb may be used to describe the skin of the young lamb of the Karakul breed of sheep or top-cross breed of such sheep, having hair formed in knuckled curls. (b) The term Broadtail Lamb... breed of sheep or top-cross breed of such sheep, having flat light-weight fur with a moire pattern....

  9. Spontaneous mesangiocapillary glomerulonephritis in Finn cross lambs from Alberta.

    PubMed Central

    Frelier, P F; Pritchard, J; Armstrong, D L; Nagge, W T; Lewis, R M

    1984-01-01

    A spontaneous mesangiocapillary glomerulonephritis occurred in three, one to three month old Finnish Landrace cross lambs from a flock in northern Alberta. The ram was a purebred Finn sheep, and the ewes were Finn-Rambouillet and Finn-Suffolk-Rambouillet crosses. The lambs were found dead without previous clinical signs. Histologically there was marked thickening of glomerular capillary basement membranes, proliferation of mesangial cells, and peri-glomerular fibrosis. An interstitial infiltration of plasma cells and lymphocytes was present with occasional tubular degeneration and proteinaceous cast formation. Focal leukoencephalomalacia was present in one lamb. Electron microscopy demonstrated deposition of electron-dense deposits in a subendothelial location with occasional fusion of overlying foot processes in glomerular capillaries. Indirect immunofluorescence studies demonstrated positive staining material in glomerular capillary walls. These findings in Finnish Landrace cross lambs are characteristic of mesangiocapillary glomerulonephritis, a condition heretofore not reported in North America. Images Fig. 1. Fig. 2. PMID:6372972

  10. 7 CFR 59.301 - Mandatory Daily Reporting for Lambs.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... were of a quality grade of Choice or better; (7) Any premiums or discounts associated with weight, quality grade, yield grade, or any type of purchase; (8) Lamb state of origin; (9) The pelt type; and...

  11. Eyeblink classical conditioning in the preweanling lamb.

    PubMed

    Johnson, Timothy B; Stanton, Mark E; Goodlett, Charles R; Cudd, Timothy A

    2008-06-01

    Classical conditioning of eyeblink responses has been one of the most important models for studying the neurobiology of learning, with many comparative, ontogenetic, and clinical applications. The current study reports the development of procedures to conduct eyeblink conditioning in preweanling lambs and demonstrates successful conditioning using these procedures. These methods will permit application of eyeblink conditioning procedures in the analysis of functional correlates of cerebellar damage in a sheep model of fetal alcohol spectrum disorders, which has significant advantages over more common laboratory rodent models. Because sheep have been widely used for studies of pathogenesis and mechanisms of injury with many different prenatal or perinatal physiological insults, eyeblink conditioning can provide a well-studied method to assess postnatal behavioral outcomes, which heretofore have not typically been pursued with ovine models of developmental insults.

  12. Efficacy of moxidectin against multiple resistant Ostertagia spp. in lambs.

    PubMed

    Várady, M; Praslicka, J; Corba, J

    1995-06-01

    Moxidectin was demonstrated to have a high efficacy in lambs against Ostertagia spp. which were resistant to albendazole, levamisole and ivermectin in goats. Moxidectin reduced the number of eggs in faeces by 99.6% and the number of worms found at post-mortem dissection of the lambs by 99.9%. Of the adult worms found in abomasa, 91% were identified as Ostertagia circumcincta and 9% as Ostertagia trifurcata.

  13. Lung fluid balance in lambs before and after premature birth.

    PubMed Central

    Bland, R D; Carlton, D P; Scheerer, R G; Cummings, J J; Chapman, D L

    1989-01-01

    The purpose of this study was to see if lung vascular protein permeability is greater in preterm lambs with respiratory distress than it is in lambs without lung disease. We measured pulmonary vascular pressures, lung lymph flow, and concentrations of protein in lymph and plasma of 10 chronically catheterized preterm lambs (gestation 133 +/- 1 d) for 2-4 h before and for 4-8 h after delivery by cesarean section. All lambs were treated with mechanical ventilation after birth and received a constant intravenous infusion of glucose-saline solution at an hourly rate of 10 ml/kg. Respiratory failure developed in six lambs, in which there was a sustained threefold postnatal increase in lung lymph flow and lymph protein flow, with an even greater increase in pleural liquid drainage. Concentrations of protein in lymph and pleural liquid were almost identical, averaging approximately 75% of the plasma protein concentration. In the four preterm lambs without lung disease, lymph flow and lymph protein flow were either near or below fetal values by 6-8 h after birth, and there was little or no pleural liquid drainage. Extravascular lung water averaged 7.3 +/- .8 g/g dry lung in lambs with respiratory failure compared to 4.8 +/- .5 g/g dry lung in lambs without lung disease. Thus, pulmonary edema with abnormal leakage of protein-rich liquid from the lung microcirculation into the interstitium is an important pathological feature of the respiratory disease that often occurs after premature birth. Images PMID:2760201

  14. Calculation of the Lamb shift in neutral alkali metals

    NASA Astrophysics Data System (ADS)

    Sapirstein, J.; Cheng, K. T.

    2002-10-01

    The one-loop Lamb shift is calculated for the ground state of the neutral alkali metals lithium through francium. The method used is Furry representation QED, defined in terms of a variety of local potentials. The method is exact in binding corrections, but is potential dependent. Significant differences with known Lamb shift results for lithium are found, and it is shown that large corrections result from a partial set of screening corrections. Comparison with other calculations is made.

  15. Acoustic-Gravity Waves from Bolide Sources

    NASA Astrophysics Data System (ADS)

    Revelle, Douglas O.

    2008-06-01

    We have developed a new approach to modeling the acoustic-gravity wave (AGW) radiation from bolide sources. This first effort involves entry modeling of bolide sources that have available satellite data through procedures developed in ReVelle (Earth Moon Planets 95, 441-476, 2004a; in: A. Milani, G. Valsecchi, D. Vokrouhlicky (eds) NEO Fireball Diversity: Energetics-based Entry Modeling and Analysis Techniques, Near-earth Objects: Our Celestial Neighbors (IAU S236), 2007b). Results from the entry modeling are directly coupled to AGW production through line source blast wave theory for the initial wave amplitude and period at x=10 (at 10 blast wave radii and perpendicular to the trajectory). The second effort involves the prediction of the formation and or dominance of the propagation of the atmospheric Lamb, edge-wave composite mode in a viscous fluid (Pierce, J. Acoust. Soc. Amer. 35, 1798-1807, 1963) as a function of the source energy, horizontal range and source altitude using the Lamb wave frequency that was deduced directly during the entry modeling and that is used as a surrogate for the source energy. We have also determined that Lamb wave production by bolides at close range decreases dramatically as either the source energy decreases or the source altitude increases. Finally using procedures in Gill ( Atmospheric-Ocean Dynamics, 1982) and in Tolstoy ( Wave Propagation, 1973), we have analyzed two simple dispersion relationships and have calculated the expected dispersion for the Lamb edge-wave mode and for the excited, propagating internal acoustic waves. Finally, we have used the above formalism to fully evaluate these techniques for four large bolides, namely: the Tunguska bolide of June 30, 1908; the Revelstoke bolide of March 31, 1965; the Crete bolide of June 6, 2002 and the Antarctic bolide of September 3, 2004. Due to page limitations, we will only present results in detail for the Revelstoke bolide.

  16. Development of rumen metabolism and ruminal epithelium in lambs.

    PubMed

    Zitnan, R; Bomba, A; Sommer, A; Kolodzieyski, L

    1993-01-01

    The concentrations of volatile fatty acids and the development of rumen epithelium and microflora adhered to rumen wall in suckling lambs were observed. Total VFA concentration increased with age. The differences between the 1st (28.5 mmol.l-1) and 4th week of age (78.7 mmol.l-1) and between 6th (82.1 mmol.l-1 and 10th week of age (117.4 mmol.l-1) were significant (p < 0.01). The highest molar proportion of acetic acid (71.2 mol%) was observed in 1 week-old lambs and the highest molar proportion of propionic acid in 6 week-old lambs (20.8 mol%). Length and surface characteristics of papillae changed dramatically over the 10-week period. In samples from 1-week and 4-week-old lambs, the papilla surface was relatively smooth and epithelial cells were relatively thin and flat. In samples from 6-week and 10-week-old lambs the tissue topography was typically rough. In the 1-week-old lambs the cocci, single rods and short rods in pairs were present at very low population levels. At 4 weeks the epimural community became notably more complex and bacteria were present at a higher population level. The dominant morphotype at 6 weeks was a rod-shaped end-on attached bacterium. The epimural microflora became the most complex at 10 weeks.

  17. Isolation of adenovirus from lambs with upper respiratory syndrome.

    PubMed

    Pommer, J; Schamber, G

    1991-07-01

    The role of viruses in the etiology of recurrent upper respiratory disease in newly weaned lambs was studied during 1984-1985 at the North Dakota Sheep Experiment Station. Serum samples collected from lambs at weaning, from lambs with signs of respiratory disease, and 3 weeks following the onset of clinical signs were tested for antibodies to ovine adenovirus (OAV), respiratory syncytial virus (RSV), and parainfluenza type-3 virus (PI-3). Virus isolation studies were performed on nasal secretions samples taken at the same time. Parainfluenza type-3 was isolated from 1 of 275 lambs tested, and there was 2.5% overall 4-fold increase in antibody titer to PI-3 during the 2-year study. An adenovirus with a different restriction endonuclease digestion pattern from that previously reported adenovirus strains in the United States was isolated from 13 of 275 nasal secretions collected from lambs at the time of weaning. There was a 17.6% overall 4-fold increase in seroconversion to the adenovirus isolated from the lambs with clinical disease.

  18. Acoustoelasticity. [sound-structure interaction

    NASA Technical Reports Server (NTRS)

    Dowell, E. H.

    1977-01-01

    Sound or pressure variations inside bounded enclosures are investigated. Mathematical models are given for determining: (1) the interaction between the sound pressure field and the flexible wall of a Helmholtz resonator; (2) coupled fluid-structural motion of an acoustic cavity with a flexible and/or absorbing wall; (3) acoustic natural modes in multiple connected cavities; and (4) the forced response of a cavity with a flexible and/or absorbing wall. Numerical results are discussed.

  19. Behavioural development in the neonatal lamb: effect of maternal and birth-related factors.

    PubMed

    Dwyer, C M

    2003-02-01

    The survival of the neonate relies on the integrated expression of appropriate behaviours from both the mother and young. In precocious species, like the sheep, the speed with which the lamb stands and seeks the udder is related to lamb survival. In this study the effects of birth difficulty, lamb birth weight, ewe loss or gain in backfat from conception to delivery, ewe parity, litter size, and lamb sex on neonatal lamb behavioural development were investigated in over 500 lambs of two breeds (Scottish Blackface and Suffolk). Lambs that required assistance to be delivered were significantly slower to perform all neonatal behaviours than unassisted lambs (P<0.001), and were less active over the first 3 days after delivery (P<0.05). There were no effects of lamb birthweight that were not accounted for by the increased likelihood of requiring assistance in heavier birth weight lambs. Ewes that mobilised less body fat during their pregnancy produced lambs that stood and sucked quickly (P<0.001), and were more active over the first 3 days of life. Lambs born to first parity ewes were slower to stand and suck than lambs born to experienced ewes (P<0.001). There was an improvement in time taken by lambs to stand, seek the udder and to suck with each increase in ewe parity. Litter size had an additional retarding influence on the behaviour of multiple-born lambs that could not be accounted for by birthweight. In the Suffolk breed male lambs were slower to stand and suck than female lambs, this effect was not seen in Blackface lambs. These data demonstrate that lambs that require assistance at birth, even if they survive the birth process, lambs born to ewes that lose a lot of condition over pregnancy or first parity ewes, triplet lambs and, at least in some breeds, male lambs are slower to progress through the sequence of neonatal behaviours. These lambs are, therefore, at greater risk of not surviving to weaning.

  20. Bond lengths of diatomic molecules periodically driven by light: the p-LAMB scheme.

    PubMed

    Sola, Ignacio R; Shin, Seokmin; Chang, Bo Y

    2011-03-14

    A laser scheme using a periodically changing frequency is used to induce oscillations of the internuclear motion, which are quantum analogs of classical vibrations in diatomic molecules. This is what we call the periodic laser adiabatic manipulation of the bond, or p-LAMB scheme. In p-LAMB, the carrier frequency of the laser must vary periodically from the blue to the red of a photodissociation band and backwards, following for instance a cosine-dependent frequency of period τ(c). In the adiabatic regime the dynamics is fully time-reversible. The amplitude of the internuclear oscillation is controlled by the pulse frequency ω(t), while τ(c) determines the duration (or period) of the bond oscillation. In the presence of efficient dipole coupling, the bandwidth of the pulse is the main constraint to the maximum bond stretch that can be obtained. Before the onset of the adiabatic regime the dynamics are more complex, showing dispersion of the vibrational wave packet and anharmonic deformation of the bond. However, the nonadiabatic effects are mostly canceled and full revivals are observed at certain multiples of τ(c).

  1. Knife and impact cutting of lamb bone.

    PubMed

    King, M J

    1999-05-01

    The forces and hence fracture energies required to cut bone are presented in this paper and the merits of cutting with a high speed blade are considered. A plain knife blade was used to cut cancellous and compact lamb bone using three different methods. A microtome was used to produce a range of cut thicknesses which enabled the fracture energy to be separated into friction, surface fracture and plastic deformation energies. A tensile test machine was used to produce thicker off-cuts so that the energy required to cut through full sections of bone could be determined. A high speed rail gun was used to cut at speeds up to 130 m/s. The energy required to cut bone did not change with blade speed. However, the energies measured during the cutting varied over a wide range. In situations in which the surface of the cut bone exhibited a very uneven surface high energy was required, whereas when the resulting cut surface was planar the cutting energy was low. A light weight blade which impacts the bone at high speed will transmit a small impulse to the carcass which may be absorbed without transmitting strain to the muscle/connective tissue. This may allow the development of a high speed knife which will cut bone without excessively damaging the meat surrounding the cut. PMID:22062140

  2. Hepatic Cobalt and Copper Levels in Lambs in Norway

    PubMed Central

    Sivertsen, T; Plassen, C

    2004-01-01

    Cobalt and copper concentrations were measured in 599 lamb livers collected at slaughter from 58 sheep flocks in 6 different parts of Norway in 1993. Information about pasture, additional feeding and mineral supplements in the flocks was obtained through a questionnaire. Average hepatic levels of cobalt in the lamb flocks varied from <0.003 to 0.22 μg/g ww, and of copper from 5 to 240 μg/g ww. Flocks with deficient or marginal cobalt status were found in all parts of southern Norway, but primarily in the west and south-west. Some flocks with marginal copper status were found in the south-west, while flocks with signs of excessive hepatic copper concentrations were found mainly in inner parts of central and northern Norway. Hepatic copper concentrations were significantly higher in lambs that had grazed mountain pastures than in those that had grazed lowland pastures in the summer. PMID:15535087

  3. [Care of pregnancy and prevention of lamb diseases in goats].

    PubMed

    Elze, K; Krische, G

    1995-12-01

    The breeding of dairy goats has spread in Saxony for over 200 years. Recently the keeping of bigger flocks (30-300 animals) for milk and cheese production has become more common. Within the care of the pregnant she goats the feeding recommendation is a main point of the veterinary herd management. The special performances done by the pregnant animals are discussed. The daily need of energy intake is given with about 11 Megajoule Nettoenergy-lactation as well as the daily need of protein with 230 g. Additionally the minimal daily intake of minerals and vitamins is mentioned. Supervising she goats during lambing and avoiding temperatures lower than 18 degrees C in the stables is considered as necessary to prevent hypoglycemia of the newborn lambs. The enzootic process of Clostridium-perfringens-type-B-infection is discussed in connection with the intake of colostrum and the increasing density of pathogen microorganism during the lambing period.

  4. Fatty acid metabolism in lambs fed citrus pulp.

    PubMed

    Lanza, M; Scerra, M; Bognanno, M; Buccioni, A; Cilione, C; Biondi, L; Priolo, A; Luciano, G

    2015-06-01

    In the present study, we have hypothesized that replacing barley with high proportions of dried citrus pulp in a concentrate-based diet for lambs could increase the intake of unsaturated fatty acids and could reduce the rate of the ruminal biohydrogenation of PUFA, with a consequent improvement of the intramuscular fatty acid composition. To test this hypothesis, 26 Comisana lambs were divided into 3 groups and for 56 d were fed a barley-based concentrate diet (CON; 8 lambs) or 2 diets in which barley was replaced with 24% (CIT24; 9 lambs) or 35% (CIT35; 9 lambs) dried citrus pulp. An overall improvement of the fatty acid composition of LM from lambs fed citrus pulp-containing diets was found. The PUFA/SFA ratio was lower (P < 0.05) in the LM from lambs in the CON group compared with both the CIT24 and CIT35 groups. The thrombogenic index was lower (P < 0.05) in meat from lambs fed the CIT35 diet compared with those fed the CON diet. The CIT35 diet increased the proportion of C20:5 n-3 in the LM (P < 0.05), whereas the CIT24 diet enhanced that of C22:6 -3 (P < 0.05) compared with the CON diet. Some of these results might be explained considering that feeding the CIT24 and CIT35 diets increased the intake of total fatty acids (P < 0.05) and of C18:3 n-3 (P < 0.01) compared with feeding the CON treatment. On the other hand, phenolic compounds present in citrus pulp could have inhibited the ruminal biohydrogenation of PUFA. This is supported by the fact that regardless of the level of inclusion in the diet, citrus pulp increased the proportion of rumenic acid (P < 0.001) in LM compared with the CON diet. The plasma from lambs fed both CIT24 and CIT35 diets had a greater percentage of vaccenic acid (VA; < 0.001) compared with that from lambs fed the CON diet, and the CIT35 diet increased the proportion of rumenic acid in plasma compared with the CON treatment (P < 0.05). In the ruminal fluid, stearic acid (SA) tended to decrease, and the sum of CLA tended to increase

  5. Parasitic gastro-enteritis in lambs — A model for estimating the timing of the larval emergence peak

    NASA Astrophysics Data System (ADS)

    Starr, J. R.; Thomas, R. J.

    1980-09-01

    The life history of the nematode parasites of domestic ruminants usually involves the development and survival of free-living stages on pasture. The pasture is, therefore, the site of deposition, development and transmission of nematode infection and meteorological factors affecting the pasture will affect the parasites. Recently Thomas and Starr (1978) discussed an empirical technique for forecasting the timing of the summer wave of gastro-intestinal parasitism in North-East England in the lamb crop using meteorological data and in particular estimates of the duration of “surface wetness”. This paper presents an attempt to model “surface wetness” and the temperature limitation to nematode development.

  6. Broad-angle negative reflection and focusing of elastic waves from a plate edge

    NASA Astrophysics Data System (ADS)

    Veres, Istvan A.; Grünsteidl, Clemens; Stobbe, David M.; Murray, Todd W.

    2016-05-01

    Guided elastic waves in plates, or Lamb waves, generally undergo reflection and mode conversion upon encountering a free edge. In the case where a backward-propagating Lamb wave is mode-converted to a forward-propagating wave or vice versa, the mode-converted wave is reflected on the same side of the surface normal as the incident wave. In this paper, we study such negative reflection and show that this effect can be achieved over a broad angular range at a simple plate edge. We demonstrate, through both numerical and experimental approaches, that a plate edge can act as a lens and focus a mode-converted Lamb wave field. Furthermore, we show that as the wave vectors of the incident and mode-converted Lamb waves approach each other, the mode-converted field nearly retraces the incident field. We propose that broad-angle negative reflection may find application in the nondestructive testing of structures supporting guided waves and in the development of new acoustic devices including resonators, lenses, and filters.

  7. Time-Frequency Analysis of the Dispersion of Lamb Modes

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Seale, Michael D.; Smith, Barry T.

    1999-01-01

    Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A(sub 0), A(sub 1), S(sub 0), and S(sub 2)Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along, and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results.

  8. Study of concrete's behavior under 4-point bending load using Coda Wave Interferometry (CWI) analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Abraham, O.; Chapeleau, X.; Cottineau, L.-M.; Tournat, V.; Le Duff, A.; Lascoup, B.; Durand, O.

    2013-01-01

    Coda Wave Interferometry (CWI) is an ultrasonic NDT method suitable for complex material such as concrete that can precisely measure small propagation velocity variation (10-2%). By measuring variation of propagation velocity in concrete caused by acoustoelasticity phenomena, CWI analysis can be used to monitor concrete's internal stress level. For the first time, CWI is used to measure propagation velocity variations due to a stress field in a concrete beam under four-points bending test, which contains simultaneously compressive and tensile stress. Embedded optical-fiber sensors, strain gauges are used in the experiment, in order to confirm and validate the CWI analysis result. Thermocouples are also embedded into concrete beams for monitoring internal temperature fluctuations.

  9. Higher-order binding corrections to the Lamb shift

    SciTech Connect

    Pachucki, K. )

    1993-08-15

    In this work a new analytical method for calculating the one-loop self-energy correction to the Lamb shift is presented in detail. The technique relies on division into the low and the high energy parts. The low energy part is calculated using the multipole expansion and the high energy part is calculated by expanding the Dirac-Coulomb propagator in powers of the Coulomb field. The obtained results are in agreement with those previously known, but are more accurate. A new theoretical value of the Lamb shift is also given. 47 refs., 2 figs., 1 tab.

  10. The Lamb shift in heliumlike uranium (U/sup 90 +/)

    SciTech Connect

    Munger, C.T. Jr.

    1987-01-01

    An experimental value of 70.4 (8.3) eV for the one-electron Lamb shift in uranium is reported, in agreement with the theoretical value of 75.3 (0.4) eV. The Lamb shift is extracted from a beam-foil time-of-flight measurement of the 54.4 (3.4) ps lifetime of the 1s 2p/sub 1/2/ /sup 3/P/sub 0/ state of heliumlike (two-electron) uranium. 18 figs.

  11. Atomic many-body effects and Lamb shifts in alkali metals

    NASA Astrophysics Data System (ADS)

    Ginges, J. S. M.; Berengut, J. C.

    2016-05-01

    We present a detailed study of the radiative potential method [V. V. Flambaum and J. S. M. Ginges, Phys. Rev. A 72, 052115 (2005), 10.1103/PhysRevA.72.052115], which enables the accurate inclusion of quantum electrodynamics (QED) radiative corrections in a simple manner in atoms and ions over the range 10 ≤Z ≤120 , where Z is the nuclear charge. Calculations are performed for binding energy shifts to the lowest valence s , p , and d waves over the series of alkali-metal atoms Na to E119. The high accuracy of the radiative potential method is demonstrated by comparison with rigorous QED calculations in frozen atomic potentials, with deviations on the level of 1%. The many-body effects of core relaxation and second- and higher-order perturbation theory on the interaction of the valence electron with the core are calculated. The inclusion of many-body effects tends to increase the size of the shifts, with the enhancement particularly significant for d waves; for K to E119, the self-energy shifts for d waves are only an order of magnitude smaller than the s -wave shifts. It is shown that taking into account many-body effects is essential for an accurate description of the Lamb shift.

  12. Establishment and development of ruminal hydrogenotrophs in methanogen-free lambs.

    PubMed

    Fonty, Gérard; Joblin, Keith; Chavarot, Michel; Roux, Remy; Naylor, Graham; Michallon, Fabien

    2007-10-01

    The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (10(7) to 10(8) cells g(-1)) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H(2) utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H(2) utilization was similar to that in conventional lambs. H(2) utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H(2) utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H(2) in the rumen.

  13. Lamb Receives 2012 Luna B. Leopold Young Scientist Award: Citation

    NASA Astrophysics Data System (ADS)

    Myrow, Paul

    2013-09-01

    Michael Lamb received the 2012 Luna B. Leopold Young Scientist Award at the 2012 AGU Fall Meeting, held 3-7 December in San Francisco, Calif. The award recognizes "a young scientist for making a significant and outstanding contribution that advances the field of Earth and planetary surface processes."

  14. Preferences for lamb meat: a choice experiment for Spanish consumers.

    PubMed

    Gracia, Azucena; de-Magistris, Tiziana

    2013-10-01

    This paper analyzes consumers' preferences for different lamb meat attributes using a choice experiment. In particular, preferences for the type of commercial lamb meat ("Ternasco" and "Suckling") and the origin of production (locally produced "Ojinegra from Teruel") were evaluated. Moreover, we endogenously identify consumers' segments based on consumers' preferences for the analyzed attributes. Data come from a survey administrated in Spain during 2009. A latent class model was used to estimate the effect of the attributes on consumer utility, derive the willingness to pay and determine consumers' segments. Results suggest that consumers' preferences for both attributes are heterogeneous and two homogenous consumers' segments were detected. The largest segment (79%) did not value any of the analyzed attributes while the smaller one (21%) valued both of them positively. In particular, consumers in this second segment are willing to pay an extra premium for the "Ternasco" lamb meat, around double the premium they are willing to pay for the locally produced lamb meat "Ojinegra from Teruel".

  15. Cultivar Preference of Lambs Grazing Forage Chicory in Ohio

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This project compared grazing preferences of lambs between seven cultivars of forage chicory (Cichorium intybus L.). This on-farm trial was conducted in central Ohio (40.53 degrees N, 82.46 degrees W, 1089 ft above sea level). The chicory was established by using conventional tillage in Bogart Silt...

  16. Nutritive value of a vegetable amaranth cultivar for growing lambs.

    PubMed

    Pond, W G; Lehmann, J W

    1989-11-01

    Current interest in amaranth as a food resource for humans and animals has been stimulated by activities in germplasm collection and testing in the U.S. Fifteen growing, intact male lambs weighing 18.7 kg were assigned randomly to three diets (five lambs/diet) for a 14-d growth trial followed immediately by an 8-d (4-d adjustment, 4-d collection) digestion and N balance trial to determine the utilization of the forage component (leaves and stems) of an African cultivar (Zimbabwe cultivar PI 482049, Amaranthus cruentus L.) All diets contained 40.95% ground corn, 8.0% soybean meal and 1.05% mineral-vitamin supplement plus either 50% ground alfalfa hay, 25% ground alfalfa hay plus 25% ground amaranth forage or 50% ground amaranth forage. Lambs had ad libitum access to feed during the growth trial and at 4% of BW daily during the digestion and N balance period. Replacement of half or all the alfalfa in the diet with amaranth had no effect on weight gain or feed utilization. Apparent digestibility of cell contents, NDF, ADF, cellulose, ADL, N and GE and percentage of absorbed N retained did not differ among the three diets. The amaranth vegetable cultivar Zimbabwe PI 482049 promoted weight gain and feed utilization equal to that obtained with alfalfa as the sole forage for growing lambs. Additional research is needed to evaluate further the potential role of forage/vegetable amaranth as an animal feed resource.

  17. Dynamical Lamb effect versus dissipation in superconducting quantum circuits

    NASA Astrophysics Data System (ADS)

    Zhukov, A. A.; Shapiro, D. S.; Pogosov, W. V.; Lozovik, Yu. E.

    2016-06-01

    Superconducting circuits provide a new platform for study of nonstationary cavity QED phenomena. An example of such a phenomenon is the dynamical Lamb effect, which is the parametric excitation of an atom due to nonadiabatic modulation of its Lamb shift. This effect was initially introduced for a natural atom in a varying cavity, while we suggest its realization in a superconducting qubit-cavity system with dynamically tunable coupling. In the present paper, we study the interplay between the dynamical Lamb effect and the energy dissipation, which is unavoidable in realistic systems. We find that despite naive expectations, this interplay can lead to unexpected dynamical regimes. One of the most striking results is that photon generation from vacuum can be strongly enhanced due to qubit relaxation, which opens another channel for such a process. We also show that dissipation in the cavity can increase the qubit excited-state population. Our results can be used for experimental observation and investigation of the dynamical Lamb effect and accompanying quantum effects.

  18. A Review of the Latent and Manifest Benefits (LAMB) Scale

    ERIC Educational Resources Information Center

    Muller, Juanita; Waters, Lea

    2012-01-01

    The latent and manifest benefits (LAMB) scale (Muller, Creed, Waters & Machin, 2005) was designed to measure the latent and manifest benefits of employment and provide a single scale to test Jahoda's (1981) and Fryer's (1986) theories of unemployment. Since its publication in 2005 there have been 13 studies that have used the scale with 5692…

  19. Using the Mystery of the Cyclopic Lamb to Teach Biotechnology

    ERIC Educational Resources Information Center

    Jensen, Jamie L.

    2010-01-01

    I present a learning cycle that explores different biotechnologies using the process of in situ hybridization as a platform. Students are presented with a cyclopic lamb and must use biotechnology to discover the mechanism behind the deformity. Through this activity, students learn about signal transduction and discover the processes of polymerase…

  20. Copper toxicity in confinement-housed ram lambs.

    PubMed Central

    Lewis, N J; Fallah-Rad, A H; Connor, M L

    1997-01-01

    Fourteen Suffolk rams (6 mo) were diagnosed with chronic copper poisoning. Preliminary results indicated that a combination of serum aspartate aminotransferase, gamma glutamyltransferase, and copper could be used as a test so that high risk lambs could be treated more aggressively. PMID:9262859

  1. Effects of ozone on lamb tracheal mucosa. Quantitative glycoconjugate histochemistry

    SciTech Connect

    Mariassy, A.T.; Sielczak, M.W.; McCray, M.N.; Abraham, W.M.; Wanner, A. )

    1989-11-01

    Whether or not the previously reported O3-induced abnormality in the postnatal development of tracheal secretory function in lambs is accompanied by changes in epithelial cell populations and their glycoconjugate composition was determined. Six lambs were killed at birth and 12 lambs at age 2 weeks. Of the latter 12, six were exposed to O3 (1 ppm, 4 hours daily for 5 days during the 1st week of life) and five had air-sham exposures (controls). Tracheal glycoconjugates were localized in situ with lectins to detect N-acetyl-galactosamine (galNAc), alpha-D-galactose (alpha-gal), beta-D-gal(1----3)-galNAc (beta-gal), and fucose (fuc). Mean (+/- SD) epithelial cell density (cells/mm basal lamina) was 418 +/- 57 in the newborns, 385 +/- 63 in controls (P was not significant), and 342 +/- 47 in O3-exposed lambs (P less than 0.05). Mucous cell density was 87 +/- 12 in newborns, 63 +/- 10 in controls (P less than 0.05), and 76 +/- 10 in O3 exposed lambs (P was not significant). Ciliated cells remained unchanged from birth to 2 weeks (P was not significant), but decreased (P less than 0.05) in O3-exposed lambs. All counted mucous cells contained fuc and galNAc at birth and retained these residues after sham and O3 exposure. The alpha-gal-containing mucous cells declined from 97 +/- 13 to 7 +/- 1 (P less than 0.05) and beta-gal containing cells from 39 +/- 5 to 25 +/- 4 in controls. In contrast, cells containing alpha-gal 71 +/- 10 remained at newborn levels (97 +/- 13) and beta-gal-containing cells increased from 40 +/- 5 at birth to 58 +/- 8 in O3-exposed animals (P less than 0.05). It was concluded that early postnatal exposure of lambs to O3 causes a decrease in epithelial cell density, but retards the developmental decrease in the number of tracheal mucous cells and alters the lectin detectable carbohydrate composition of mucus in these cells.

  2. Lamb survival, glutathione redox state and immune function of neonates and lambs from periparturient Merino ewes supplemented with rumen-protected methionine.

    PubMed

    Liu, Shimin; Lei, Jason; Hancock, Serina; Scanlan, Victoria; Broomfield, Steve; Currie, Andrew; Thompson, Andrew

    2016-10-01

    Wool growth in Merino sheep demands a high level of sulphur amino acids, competing with body growth and the immune system, which may play a role in increasing the risk of lamb mortality. The hypothesis that dietary supplementation of methionine (Met) to Merino ewes during the late stages of pregnancy will improve foetal growth and alter immune competency of ewes and lambs was tested in a total of 120 grazing, pregnant Merino ewes. Sixty ewes were group-supplemented with 6.3 g/d rumen-protected Met (Met-Plus) per sheep from day 111 of pregnancy until day 7 after lambing, and the other 60 animals were used as a non-supplemented Control. Lambs from Met-supplemented ewes tended to be 10% heavier than Control lambs (p = 0.10), which did not affected the survival rate at weaning significantly. The supplemented ewes had slightly higher concentrations of total glutathione (GSH) in plasma at lambing (p < 0.06), but there were no differences between 1 and 3 months post-lambing in GSH, glutathione disulphide (GSSG) and the GSSG:GSH ratio. The GSSG:GSH ratio in the blood of ewes was elevated at lambing (p < 0.05), hinting that ewes were undergoing increased oxidative stress. The Met supplementation elevated the total IgG concentration (p < 0.05) in lambs aged 4 and 6 weeks, but did not change the IgG concentrations in colostrum and in plasma of 1-week-old lambs, and white blood cell counts and leukocyte types. The trend towards higher lamb birth weights in the Met-supplemented group requires further investigation as this may influence survival at birth and weaning. PMID:27462932

  3. A model explaining and predicting lamb flavour from the aroma-active chemical compounds released upon grilling light lamb loins.

    PubMed

    Bueno, Mónica; Campo, M Mar; Cacho, Juan; Ferreira, Vicente; Escudero, Ana

    2014-12-01

    The objective of the work is to understand the role of the different aroma compounds in the perception of the local "lamb flavour" concept. For this, a set of 70 loins (Longissimus dorsi) from approximately seventy day-old Rasa Aragonesa male lambs were grilled and the aroma-active chemicals released during the grilling process were trapped and analyzed. Carbonyl compounds were derivatizated and determined by GC-NCI-MS, whereas other aromatic compounds were directly analyzed by GC-GC-MS. Odour activity values (OAVs) were calculated using their odour threshold values in air. Lamb flavour could be satisfactory explained by a partial least-squares model (74% explained variance in cross-validation) built by the OAVs of 32 aroma-active chemical compounds. The model demonstrates that the lamb flavour concept is the result of a complex balance. Its intensity critically and positively depends to the levels of volatile fatty acids and several dimethylpyrazines while is negatively influenced by the different alkenals and alkadienals. (E,E)-2,4-decadienal and (E)-2-nonenal showed top OAVs. PMID:25089786

  4. A model explaining and predicting lamb flavour from the aroma-active chemical compounds released upon grilling light lamb loins.

    PubMed

    Bueno, Mónica; Campo, M Mar; Cacho, Juan; Ferreira, Vicente; Escudero, Ana

    2014-12-01

    The objective of the work is to understand the role of the different aroma compounds in the perception of the local "lamb flavour" concept. For this, a set of 70 loins (Longissimus dorsi) from approximately seventy day-old Rasa Aragonesa male lambs were grilled and the aroma-active chemicals released during the grilling process were trapped and analyzed. Carbonyl compounds were derivatizated and determined by GC-NCI-MS, whereas other aromatic compounds were directly analyzed by GC-GC-MS. Odour activity values (OAVs) were calculated using their odour threshold values in air. Lamb flavour could be satisfactory explained by a partial least-squares model (74% explained variance in cross-validation) built by the OAVs of 32 aroma-active chemical compounds. The model demonstrates that the lamb flavour concept is the result of a complex balance. Its intensity critically and positively depends to the levels of volatile fatty acids and several dimethylpyrazines while is negatively influenced by the different alkenals and alkadienals. (E,E)-2,4-decadienal and (E)-2-nonenal showed top OAVs.

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

    PubMed

    Ratassepp, M; Klauson, A; Chati, F; Léon, F; Décultot, D; Maze, G; Fritzsche, M

    2015-03-01

    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.

  6. Responses of ram lambs to active immunization against testosterone and luteinizing hormone-releasing hormone.

    PubMed

    Schanbacher, B D

    1982-03-01

    Active immunization of young ram lambs against testosterone and luteinizing hormone-releasing hormone (LHRH) was shown to block the growth attributes characteristic of intact ram lambs. Testosterone and LHRH-immunized lambs grew at a slower rate and converted feed to live weight gain less efficiently than albumin-immunized controls. Lambs immunized against testosterone and LHRH had high antibody titers for their respective antigens. Moreover, testosterone-immunized lambs had high serum concentrations of luteinizing hormone (LH) and testosterone, whereas LHRH-immunized lambs had low to nondetectable serum concentrations of these hormones. Release of LH and testosterone following the intravenous administration of LHRH (250 ng) was absent in LHRH-immunized lambs, but quantitatively similar for intact and albumin-immunized control lambs. Testosterone-immunized lambs responded as did conventional castrates with a large LH release, but testosterone concentrations were unchanged. These findings are discussed relative to the integrity of the hypothalamic-pituitary-testicular endocrine axis and the importance of gonadotropin support for normal testicular development. These data show that LHRH immunoneutralization effectively retards testicular development and produces a castration effect in young ram lambs.

  7. Environmental effects on thermoregulation and breathing patterns during early postnatal development in hand-reared lambs.

    PubMed

    Symonds, M E; Andrews, D C; Buss, D S; Clarke, L; Darby, C J; Johnson, P; Lomax, M A

    1995-09-01

    This study examines the effect of hand-rearing developing lambs in a warm (WR; 25 degrees C) or cool (CR; 10-15 degrees C) ambient temperature on the control of thermoregulation and breathing patterns, when maintained at a fixed level of nutrition over the first month of postnatal life. Measurements were made during non-rapid eye movement sleep whilst lambs were maintained for at least 1 h at warm (28-19 degrees C) and cold (14-5 degrees C) ambient temperatures at 1, 7, 14 and 30 days of age. All lambs were able to maintain normal body temperature, but oxygen consumption was higher in CR lambs at 14 and 30 days of age. At 1 day of age shivering was rarely observed in any lambs, but at 7 and 14 days of age more WR than CR lambs responded to cold exposure via shivering. Plasma concentrations of triiodothyronine were higher at 7 and 14 days of age in CR lambs. Breathing frequencies were similar in WR and CR lambs, and from 7 days of age the incidence of expiratory laryngeal braking was higher in warm compared with cold study temperatures. By 30 days of age the recruitment of this mechanism was greater in CR lambs. Mean growth rate was slower over the first week of postnatal life in CR compared with WR lambs. This difference decreased over the first month of life, as growth rate increased from 83 to 130 g day-1 in the CR group but remained constant at approximately 150 g day-1 in the WR lambs. Total weight of the lungs and heart, but not the liver, were lower at 1 month but not at 1 week of postnatal life in CR lambs. It is concluded that a modest decrease in the ambient temperature in which postnatal lambs are reared, when on a fixed feed intake, alters lung size, the recruitment of laryngeal braking and the control of body temperature.

  8. Necessary condition for solitary wave induced in a water wave field

    NASA Astrophysics Data System (ADS)

    Nakamura, Shigehisa

    2014-05-01

    This work concerns to a problem on monitoring of nonlinear waves on water surface where a water surface wave field is existing. As for solitary wave as a nonlinear wave, there has been developed after formulation and reduction under some given specific condition of a uniform bathymetry. It is well known that this solitary wave can be reduced after a formulation as layleigh noted (which is found in "Hydrodynamics" written by Lamb inn 1879). This can be found in the Lamb's version of 1932. Lamb noted about height of solitary wave is expresssed by a hyperbolic function of water depth with a uniform bathymetry on a horizontal flat. The author has had to work for reproducing this kind of solitary wave in a water basin where a periodical water surface wave field can be generated even the water in the basin is a viscous fluid. What is the point in this work, is that a solitary wave can be reproduced even in a viscous water of an existing water wave field when several conditions are exactly established. That is, the interested water basin has a very gentle sloping of the bed. The water surface wave field is formed to crossing a couple of boundary with slit. The first slit acts to induce a Fresnel-like diffraction of the wave train. The second slit acts to relese wave energy behind the second barrier parallel to the first first barrier. A coupleof solid boundary arranged normal to the second boundary to locateing a symmetric position on both sidess of the slit. At each of the corners formed in front of the second barrier, the incident wave acts to grow its wave height as if it is following to Green's law for a linear simple harmonic wave. These waves on both sides of the corners are established by the incident wave and the refracted wave and start to form a coupled translational motion along the second boundary between the two corners to form a couple of solitary wave train just in front of the second boundary. The couple of solitary wave train has been identified them to

  9. Maternal behaviour and lamb survival: from neuroendocrinology to practical application.

    PubMed

    Dwyer, C M

    2014-01-01

    Parental care promotes offspring survival and, for livestock species, this care is provided solely by the mother. Maternal behaviour in the sheep has been exceptionally well-studied compared with other species and many of the underpinning biological processes leading to the expression of maternal care are known. In this review the current state of play with regard to the biology of maternal care will be reviewed, and its application to provide practical solutions to reduce lamb mortality considered. For maternal care to be elicited at birth the ewe requires elevated circulating oestradiol in late gestation, which stimulates the expression of oxytocin receptors in both peripheral and central areas (particularly the hypothalamic and limbic areas of the brain). At birth stretching of the vaginocervical canal elicits a spinal reflex which triggers the release of oxytocin primarily from neurones within the paraventricular nucleus of the hypothalamus. Oxytocin release causes an increase in the neurotransmitters noradrenaline, acetylcholine, glutamate and γ-aminobutyric acid (GABA) in the olfactory bulb, and other brain regions important for maternal behaviour. Finally, sensory cues provided by the lamb, in particular the amniotic fluids surrounding it, lead to the expression of maternal behaviours (licking, low-pitched bleats, acceptance of the lamb at the udder and suckling). This allows the expression of the two facets of maternal behaviour in the ewe: nurturance of the young and maternal selectivity, whereby a specific olfactory memory for the ewes own lamb is formed and the expression of maternal care is restricted to this lamb. Variation in the expression of maternal care has been demonstrated in primiparous ewes compared with multiparous, in different sheep genotypes, with undernutrition, stress in pregnancy, following a difficult delivery, and may occur with variation in ewe temperament. An understanding of the importance of the timing of various events in late

  10. The development of the pupillary light reflex and menace response in neonatal lambs and kids.

    PubMed

    Raoofi, Afshin; Mirfakhraie, Pejman; Yourdkhani, Sorush

    2011-03-01

    The aim of this study was to investigate the development of the pupillary light reflex and menace response in neonatal lambs and goat kids. Thirty lambs and 33 kids were assessed daily from birth until the pupillary light reflex and menace response had become established. All animals had a controlled pupillary light reflex within 20 h of birth. Lambs and kids had developed menace responses by 8 ± 3 and 14 ± 2 days, respectively. The Mann-Whitney test revealed a significant difference (P < 0.001) in the ages at which lambs and kids developed a menace response. Male kids developed this response significantly (P = 0.006) later than females. There was no sex difference in the menace response in the lambs. Overall, the findings indicated that lambs develop a menace response earlier than kids, and female kids develop this response more rapidly than their male counterparts.

  11. A supplement containing multiple types of gluconeogenic substrates alters intake but not productivity of heat-stressed Afshari lambs.

    PubMed

    Mahjoubi, E; Amanlou, H; Hossein Yazdi, M; Aghaziarati, N; Noori, G R; Vahl, C I; Bradford, B J; Baumgard, L H

    2016-06-01

    Thirty-two Afshari lambs were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments to evaluate a nutritional supplement designed to provide multiple gluconeogenic precursors during heat stress (HS). Lambs were housed in thermal neutral (TN) conditions and fed ad libitum for 8 d to obtain covariate data (period 1 [P1]) for the subsequent experimental period (period 2 [P2]). During P2, which lasted 9 d, half of the lambs were subjected to HS and the other 16 lambs were maintained in TN conditions but pair fed (PFTN) to the HS lambs. Half of the lambs in each thermal regime were fed (top-dressed) 100 g/d of a feed supplement designed to provide gluconeogenic precursors (8 lambs in HS [heat stress with Glukosa {HSG}] and 8 lambs in PFTN [pair-fed thermal neutral with Glukosa]) and the other lambs in both thermal regimes were fed only the basal control diet (HS without Glukosa [HSC] and pair-fed thermal neutral without Glukosa). Heat stress decreased DMI (14%) and by design there were no differences between the thermal treatments, but HSG lambs had increased DMI (7.5%; < 0.05) compared with the HSC lambs. Compared with PFTN lambs, rectal temperature and skin temperature at the rump, shoulder, and legs of HS lambs were increased ( < 0.05) at 0700 and 1400 h. Rectal temperature at 1400 h decreased for HSG lambs (0.15 ± 0.03°C; < 0.05) compared with HSC lambs. Despite similar DMI between thermal treatments, ADG for HS and PFTN lambs in P2 was decreased 55 and 85%, respectively, compared with lambs in P1 ( < 0.01). Although the prefeeding glucose concentration was not affected by thermal treatment or diet, HSG lambs had increased postfeeding glucose concentration compared with HSC lambs ( < 0.05). In contrast to the glucose responses, circulating insulin was influenced only by thermal treatment; HS lambs had increased insulin concentration ( < 0.01) before feeding and decreased concentration ( < 0.05) after feeding compared with PFTN

  12. Damage detection in reusable launch vehicle components using guided ultrasonic waves and 3D laser vibrometry

    NASA Astrophysics Data System (ADS)

    Barnoncel, David; Staszewski, Wieslaw J.; Schell, Jochen; Peres, Patrick

    2013-04-01

    Reusable Launch Vehicles are often used in space applications to guarantee space exploration with reduced costs. These structures often use components from newly developed materials. It is inevitable that reliable inspection methods will be required for quality control and maintenance of such structures to avoid potential damage. This paper describes some initial results from evaluation tests based on Lamb waves for damage detection of Reusable Launch Vehicle composite components. Low-profile, surface-bonded piezoceramic transducers were used for Lamb wave generation. Non-contact measurements of Lamb wave responses were taken by a laser vibrometer. The results presented in this paper demonstrate the great potential of the method for quality inspection and structural damage detection of space composite structures.

  13. An evaluation of the lamb vision system as a predictor of lamb carcass red meat yield percentage.

    PubMed

    Brady, A S; Belk, K E; LeValley, S B; Dalsted, N L; Scanga, J A; Tatum, J D; Smith, G C

    2003-06-01

    An objective method for predicting red meat yield in lamb carcasses is needed to accurately assess true carcass value. This study was performed to evaluate the ability of the lamb vision system (LVS; Research Management Systems USA, Fort Collins, CO) to predict fabrication yields of lamb carcasses. Lamb carcasses (n = 246) were evaluated using LVS and hot carcass weight (HCW), as well as by USDA expert and on-line graders, before fabrication of carcass sides to either bone-in or boneless cuts. On-line whole number, expert whole-number, and expert nearest-tenth USDA yield grades and LVS + HCW estimates accounted for 53, 52, 58, and 60%, respectively, of the observed variability in boneless, saleable meat yields, and accounted for 56, 57, 62, and 62%, respectively, of the variation in bone-in, saleable meat yields. The LVS + HCW system predicted 77, 65, 70, and 87% of the variation in weights of boneless shoulders, racks, loins, and legs, respectively, and 85, 72, 75, and 86% of the variation in weights of bone-in shoulders, racks, loins, and legs, respectively. Addition of longissimus muscle area (REA), adjusted fat thickness (AFT), or both REA and AFT to LVS + HCW models resulted in improved prediction of boneless saleable meat yields by 5, 3, and 5 percentage points, respectively. Bone-in, saleable meat yield estimations were improved in predictive accuracy by 7.7, 6.6, and 10.1 percentage points, and in precision, when REA alone, AFT alone, or both REA and AFT, respectively, were added to the LVS + HCW output models. Use of LVS + HCW to predict boneless red meat yields of lamb carcasses was more accurate than use of current on-line whole-number, expert whole-number, or expert nearest-tenth USDA yield grades. Thus, LVS + HCW output, when used alone or in combination with AFT and/or REA, improved on-line estimation of boneless cut yields from lamb carcasses. The ability of LVS + HCW to predict yields of wholesale cuts suggests that LVS could be used as an objective

  14. Cardiovascular effects of isoproterenol in the preterm newborn lamb

    SciTech Connect

    Crone, R.K.

    1984-01-01

    A study was made of the effects of an isoproterenol infusion on cardiac output and the distribution of blood flow in 5 preterm newborn lambs. Cardiac output and regional organ blood flow were measured by injecting radionuclide-labeled microspheres into the superior vena cava and left ventricle. We found that an average infusion of 0.5 microgram/kg X min of isoproterenol increased cardiac output 73% which correlated closely with an increase in stroke volume, but not with HR. The increase in systemic blood flow was distributed exclusively to the myocardium and skeletal muscle, bone, and skin. We conclude that isoproterenol increases cardiac output in preterm newborn lambs similarly to adults and that the stroke volume of the immature heart is more changeable than previously thought.

  15. Cardiorespiratory response to cyanide of arterial chemoreceptors in fetal lambs

    SciTech Connect

    Itskovitz, J.; Rudolph, A.M.

    1987-05-01

    Cardiorespiratory response to the stimulation of the carotid and aortic receptors by sodium cyanide was examined in fetal lambs in utero at 0.8 (120 days) gestation. Injections of 50-400 ..mu..g cyanide into the inferior vena cava or the carotid artery of intact fetuses elicited bradycardia and respiratory responses that varied from a single gasp to rhythmic respiratory movements but no significant change in arterial blood pressure. Carotid sinus denervation eliminated the cardiorespiratory response to intracarotid injection of cyanide and sinoaortic denervation abolished the response to inferior vena caval injection. It is concluded that in fetal lamb in utero the aortic and carotid bodies are active, and hypoxic stimulation of these chemoreceptors results in cardiorespiratory response characterized by slowing of fetal heart rate, respiratory effort, and no consistent change in arterial blood pressure.

  16. Lamb Shift Measurement in Hydrogen by the Anisotropy Method

    NASA Astrophysics Data System (ADS)

    Drake, G. W. F.; van Wijngaarden, A.; Holuj, F.

    1998-05-01

    The Lamb shift in hydrogen and hydrogenic ions continues to provide one of the most important tests of quantum electrodynamics. A previous measurement in He^+ by the anisotropy method( A. van Wijngaarden, J. Kwela and G. W. F. Drake, Phys. Rev. A 43), 3325 (1991). yields a value that is 70(12) parts per million higher than theory when two-loop binding corrections are included (K. Pachucki et al.), J. Phys. B 29, 117 (1996).. A new high-precision measurement of the Lamb shift in hydrogen by the same method will be reported( Can. J. Phys. 76), February (1998).. The result of 1057.852(15) MHz is consistent with theory and other measurements, thereby confirming that the anisotropy method and its interpretation are valid at the 15 parts per million level of accuracy. The remaining discrepancy for He^+ could be explained by an additional contribution to theory that scales as Z^6.

  17. Measuring the antihydrogen Lamb shift with a relativistic antihydrogen beam

    SciTech Connect

    Blanford, G.; Gollwitzer, K.; Mandelkern, M.; Schultz, J.; Takei, G.; Zioulas, G.; Christian, D.C.; Munger, C.T.

    1998-06-01

    We propose an experiment to measure the Lamb shift and fine structure (the intervals 2s{sub 1/2}{minus}2p{sub 1/2} and 2p{sub 1/2}{minus}2p{sub 3/2}) in antihydrogen. A sample of 10000 antihydrogen atoms at a momentum of 8.85GeV/c suffices to measure the Lamb shift to 5{percent} and the fine structure to 1{percent}. Atomic collisions excite antihydrogen atoms to states with n=2; field ionization in a Lorentz-transformed laboratory magnetic field then prepares a particular n=2 state, and is used again to analyze that state after it is allowed to oscillate in a region of zero field. This experiment is feasible at Fermilab. {copyright} {ital 1998} {ital The American Physical Society}

  18. Lamb-shift polarized ion sources-after 15 years

    NASA Astrophysics Data System (ADS)

    Clegg, Thomas B.

    1982-03-01

    The technique of producing spin-polarized beams of H- and D- ions by the Lamb-shift method is reviewed. Maximum useable beam intensities are shown to depend on the flux of metastable H0 (2S) or D0(2S) atoms which can be obtained with a useable beam emittance. Factors limiting this flux are discussed. Two methods of spin-state selection, the spin-filter, and the diabatic field-reversal process, are discussed. The former selects atoms in a single nuclear hyperfine state and is the best method for D↘- ions; the latter yields larger beam intensities and is often the best choice for H↘- ion beams. Best sources of the Lamb-shift type produce currents ≥1μA with proton beam polarizations ≥0.7. Intensity increases of up to a factor of 3 may be possible by improving the present technology, but progress will be difficult to achieve.

  19. [Mycoplasma carrier state in the respiratory apparatus of sheep and lambs].

    PubMed

    Todorov, D

    1985-01-01

    Mycoplasma and acholeplasma organisms (M. ovipneumoniae, M. arginini, etc.) were isolated from clinically normal lambs and sheep as well as from lambs with a respiratory disease. M. ovipneumoniae was more frequently isolated than M. arginini, and was found in higher percent during the winter. Both sheep and lambs of the Romanovska breed proved more susceptible, however, lambs of local breeds, aged 30-40 days also contracted the disease in conditions of overpopulation and higher humidity. The respiratory diseases were complicated with P. haemolytica infections.

  20. Growth and slaughter characteristics of ram and wether lambs implanted with zeranol.

    PubMed

    Field, R A; Snowder, G D; Maiorano, G; McCormick, R J; Riley, M L

    1993-03-01

    Forty-nine Columbia ram and wether lambs born in April 1990 and 46 born in April 1991 were studied to determine the effects of zeranol implants on growth, difficulty of pelt removal, and carcass characteristics. Implanting ram and wether lambs once (1990) or twice (1991) with 12 mg of zeranol did not change live weight or ADG but gain/feed decreased (P < .05) in ram lambs slaughtered at approximately 50 kg. Testes weight was reduced approximately 50% by implanting. Two implants reduced (P < .05) the force needed to pull the pelt from the hind legs of ram lambs, but implanting tended to increase the force required to pull the pelt from wether lambs. Data for pelt weight, force required to pull the pelt, percentage of the carcass in the shoulder or splenius muscle, and Warner-Bratzler shear values showed that zeranol implants resulted in ram lambs becoming more like wethers and wether lambs becoming more like rams. Implanting with zeranol did not affect closure of the metacarpal growth plate in ram or in wether lambs. Difficulty of pelt removal can be reduced by implanting ram lambs with 12 mg of zeranol at approximately 114 d of age and reimplanting zeranol 28 d later.

  1. Origin assignment by multi-element stable isotopes of lamb tissues.

    PubMed

    Sun, Shumin; Guo, Boli; Wei, Yimin

    2016-12-15

    The carbon, nitrogen and hydrogen isotopic compositions in lamb meat and wool samples under two feeding regimes from five different regions of China were determined by IRMS, which is to investigate their potential for assigning the lamb meat according to geographical origins. The δ(13)C, δ(15)N and δ(2)H values in lamb tissues had significant differences among different regions, with the δ(13)C value is highly related to that of the lamb feeds (p<0.01) and the δ(2)H value is significantly correlated with lamb drinking water (p<0.05). Moreover, δ(13)C, δ(15)N and δ(2)H values of lamb muscle are all highly correlated with the wool samples. A total correct classification of 88.9% and 83.8% were obtained from the combination of C, N and H isotopes of lamb muscle and wool, respectively. These results demonstrate that multi-element isotopes are effective in identifying the geographical origin of lamb meat. Moreover, both muscle and hair tissue can be used for lamb traceability.

  2. Origin assignment by multi-element stable isotopes of lamb tissues.

    PubMed

    Sun, Shumin; Guo, Boli; Wei, Yimin

    2016-12-15

    The carbon, nitrogen and hydrogen isotopic compositions in lamb meat and wool samples under two feeding regimes from five different regions of China were determined by IRMS, which is to investigate their potential for assigning the lamb meat according to geographical origins. The δ(13)C, δ(15)N and δ(2)H values in lamb tissues had significant differences among different regions, with the δ(13)C value is highly related to that of the lamb feeds (p<0.01) and the δ(2)H value is significantly correlated with lamb drinking water (p<0.05). Moreover, δ(13)C, δ(15)N and δ(2)H values of lamb muscle are all highly correlated with the wool samples. A total correct classification of 88.9% and 83.8% were obtained from the combination of C, N and H isotopes of lamb muscle and wool, respectively. These results demonstrate that multi-element isotopes are effective in identifying the geographical origin of lamb meat. Moreover, both muscle and hair tissue can be used for lamb traceability. PMID:27451234

  3. Lamb shift in the hydrogen atom: Leading logarithmic corrections

    SciTech Connect

    Karshenboim, S.G.

    1995-04-01

    The leading logarithmic correction to the difference of the Lamb shifts of the 1s{sub 1/2} and 2s{sub 1/2} levels is found. The difference {Delta}E{sub L}(1s{sub 1/2}) {minus} 8{Delta}E{sub L}(2s{sub 1/2}) for the hydrogen atom is found to be {minus}187.236(11) MHz. 13 refs., 2 figs.

  4. Polarization operator contributions to the Lamb shift and hyperfine splitting

    SciTech Connect

    Eides, Michael I.; Shelyuto, Valery A.

    2003-10-01

    We calculate radiative corrections to the Lamb shift of order {alpha}{sup 3}(Z{alpha}){sup 5}m and radiative corrections to hyperfine splitting of order {alpha}{sup 3}(Z{alpha})E{sub F} generated by the diagrams with insertions of radiative photons and electron polarization loops in the graphs with two external photons. We also obtain the radiative-recoil correction to hyperfine splitting in muonium generated by the diagrams with the {tau} polarization loop.

  5. Alopecia in lambs associated with micronutrient-deficient milk replacer.

    PubMed

    2016-09-24

    ▪ Alopecia associated with micronutrient deficiency in lambs fed milk replacer▪ Idiopathic necrotising enteritis in suckler calves▪ Mannheimia haemolytica abomasitis in a five-week-old calf▪ Increased diagnoses of nematodirosis in lambs▪ Enteric and spinal listeriosis in sheepThese are among matters discussed in the disease surveillance report for June 2016 from SAC Consulting: Veterinary Services (SAC C VS). PMID:27660354

  6. Acute respiratory distress syndrome (ARDS) in lambs. Hematology.

    PubMed

    Ulvund, M J; Grønstøl, H

    1984-01-01

    Lambs suffering from Acute Respiratory Distress Syndrome (ARDS) showed elevated PCV, neutrophilia, a tendency towards lymphopenia, eosinopenia, hyperphosphatemia, hypoglycemia and extremely low serum Ca values during the first couple of days after the outbreak of symptoms. During the very early phase, plasma potassium values were mostly lowered (Figs. 1-3, Table I). The possible involvement of histamine is shortly discussed: either 1) through an atopic reaction, 2) because of acute ruminal acidosis and sudden histamine formation, or 3) involvement of endotoxins.

  7. Mode-selective excitation and detection of ultrasonic guided waves for delamination detection in laminated aluminum plates.

    PubMed

    Shelke, Amit; Kundu, Tribikram; Amjad, Umar; Hahn, Katrin; Grill, Wolfgang

    2011-03-01

    Selective modes of guided Lamb waves are generated in a laminated aluminum plate for damage detection using a broadband piezoelectric transducer structured with a rigid electrode. Appropriate excitation frequencies and modes for inspection are selected from theoretical and experimental dispersion curves. Dispersion curves are obtained experimentally by short time Fourier transform of the transient signals. Sensitivity of antisymmetric and symmetric modes for delamination detection are investigated. The antisymmetric mode is found to be more reliable for delamination detection. Unlike other studies, in which the attenuation of the propagating waves is related to the extent of the internal damage, in this investigation, the changes in the time-of-flight (TOF) of guided Lamb waves are related to the damage progression. The mode conversion phenomenon of Lamb waves during progressive delamination is investigated. Close matching between the theoretical and experimentally derived dispersion curves and TOF assures the reliability of the results presented here.

  8. Cricothyroid muscle electrical activity during respiration and apneas in lambs.

    PubMed

    Samson, Nathalie; Lafond, Joëlle Rouillard; Moreau-Bussière, François; Reix, Philippe; Praud, Jean-Paul

    2007-02-15

    Respiratory function of the cricothyroid muscle (CT) is virtually unknown in the neonatal period. This study was aimed at assessing CT electrical activity (EMG) during respiration and central apneas in non-sedated lambs. Seven full-term and four preterm lambs were instrumented for polysomnographic recording, including EMG of the diaphragm, thyroarytenoid (TA, a glottal constrictor), posterior cricoarytenoid (PCA, the primary glottal dilator) and CT. Phasic CT EMG was usually observed during inspiration and late expiration, whereas phasic TA EMG was observed during early expiration. While TA EMG virtually disappeared in REM sleep, both inspiratory and expiratory CT EMG increased. Overall, while CT EMG was not frequently observed during central apneas in either full-term (10% of apneas, but never simultaneously with TA EMG) or preterm lambs (30% of apneas), it was associated with decreased lung volume and subglottal pressure when present alone or with PCA EMG. Our results concur with the assumption that CT behaves as a laryngeal dilator in the neonatal period.

  9. Latency and persistence of diet volatile biomarkers in lamb fats.

    PubMed

    Sivadier, Guilhem; Ratel, Jérémy; Engel, Erwan

    2009-01-28

    Several studies have shown that volatile compounds are particularly well-suited for the authentication lamb diet by gas chromatography-mass spectrometry (GC-MS) analysis of adipose tissue. The aim of the present work was to use dynamic headspace-GC-MS to study the variations in the amounts of volatile diet tracers in perirenal fat (PRF) and caudal subcutaneous fat (CSCF) in lambs (n = 24) that were fed with concentrate and then allowed to graze for 0, 17, 51, or 85 days. Twenty-six volatile compounds were found to distinguish between the four diets (p < 0.05) in both PRF and CSCF. Of these diet tracers, 16 were found to be related to the pasture diet and increased at different rates according to the time spent at pasture (latency), while 10 were found in higher amounts in tissues of lambs fed with exclusive concentrate and exhibited different rates of clearance (persistence). Twenty-four of these discriminant compounds, including alkanes, ketones, terpenes, and 2,3-octanedione, were previously stated as pasture diet tracers in several earlier studies, suggesting their potential universality. All degrees of latency or persistence were exhibited by the pasture and concentrate diet tracers, respectively. A principal component analysis performed on ratios of selected diet tracers from both adipose tissues evidenced successful differentiation of the four feeding situations. PMID:19154165

  10. Pre-rigor infusion with kiwifruit juice improves lamb tenderness.

    PubMed

    Han, J; Morton, J D; Bekhit, A E D; Sedcole, J R

    2009-07-01

    The ability of pre-rigor infusion of kiwifruit juice to improve the tenderness of lamb was investigated. Lamb carcasses were infused (10% body weight) with fresh kiwifruit juice (Ac), water (W) and a non-infusion control (C) treatment. Infusion treatment had no effect on lamb hot carcass weight, cold carcass weight and chilling evaporative losses. The infused treatment carcasses of Ac and W had lower (P<0.05) pH values than C carcasses during the initial 12h post-mortem. The LD muscles from Ac carcasses were more tender with significantly lower shear force (P<0.001) compared with C and W carcasses during the six days following infusion with the kiwifruit juice. The enhanced proteolytic activity (P=0.002) resulting from the infused kiwifruit juice in Ac carcasses was associated with significant degradation of the myofibrillar proteins, appearance of new peptides and activation of m-calpain during post-mortem ageing. Thus, kiwifruit juice is powerful and easily prepared meat tenderizer, which could contribute efficiently and effectively to the meat tenderization process. PMID:20416722

  11. Perinatal activity of the hypothalamic-pituitary-gonadal axis in the lamb. III. LH, testosterone and prolactin secretory pattern in newborn lambs.

    PubMed

    Savoie, S; Polychronakos, C; Forest, M G; Haour, F; Collu, R; Ducharme, J R

    1981-01-01

    Crossbred male and female lambs from Suffolk rams and Dorset-Finnish ewes born in January and February were studied at 1, 3, 7, 21 and 28 days of age and female lambs at 14 days. Ultradian variations in plasma luteinizing hormone (LH), prolactin (PRL) and testosterone were studied at 30-min intervals during a 4-hour period. In female lambs LH secretory peaks were observed at 7 days of age the amplitude of LH peaks increasing 8-fold between 7 and 14 days and 2-fold between 21 and 28 days. The number of secretory peaks also increased with age. Ultradian variations in PRL were observed from 1 day of age, the amplitude of the PRL peaks increasing also with age. In male lambs, LH and testosterone peaks were observed at 3 days of age, the testosterone peak being preceded by or concomitant with LH peaks. The amplitude of LH peaks increased with age together with basal testosterone levels although the amplitude of testosterone peaks was unchanged. This study demonstrates pulsatile secretion of LH and PRL in lambs of both sexes and of testosterone in male lambs in the first week of postnatal life. In addition, since the ovine testis is responsive to endogenous gonadotropic stimulation at this period, it is suggested that the hypothalamic-pituitary-gonadal axis is already operative at this age. It can be concluded that the hypothalamic activity concerned with pulsatile LH and prolactin secretion is present very early in the lamb neonate.

  12. Cerebral Autoregulation Is Minimally Influenced by the Superior Cervical Ganglion in Two- Week-Old Lambs, and Absent in Preterm Lambs Immediately Following Delivery

    PubMed Central

    Czynski, Adam J.; Terry, Michael H.; Deming, Douglas D.; Power, Gordon G.; Buchholz, John N.; Blood, Arlin B.

    2013-01-01

    Cerebral vessels in the premature newborn brain are well supplied with adrenergic nerves, stemming from the superior cervical ganglia (SCG), but their role in regulation of blood flow remains uncertain. To test this function twelve premature or two-week-old lambs were instrumented with laser Doppler flow probes in the parietal cortices to measure changes in blood flow during changes in systemic blood pressure and electrical stimulation of the SCG. In lambs delivered prematurely at ∼129 days gestation cerebral perfusion and driving pressure demonstrated a direct linear relationship throughout the physiologic range, indicating lack of autoregulation. In contrast, in lambs two-weeks of age, surgical removal of one SCG resulted in ipsilateral loss of autoregulation during pronounced hypertension. Electrical stimulation of one SCG elicited unilateral increases in cerebral resistance to blood flow in both pre-term and two-week-old lambs, indicating functioning neural pathways in the instrumented, anesthetized lambs. We conclude cerebral autoregulation is non-functional in preterm lambs following cesarean delivery. Adrenergic control of cerebral vascular resistance becomes effective in newborn lambs within two-weeks after birth but SCG-dependent autoregulation is essential only during pronounced hypertension, well above the normal range of blood pressure. PMID:24349256

  13. Hereditary lissencephaly and cerebellar hypoplasia in Churra lambs

    PubMed Central

    2013-01-01

    Background Lissencephaly is a rare developmental brain disorder in veterinary and human medicine associated with defects in neuronal migration leading to a characteristic marked reduction or absence of the convolutional pattern of the cerebral hemispheres. In many human cases the disease has a genetic basis. In sheep, brain malformations, mainly cerebellar hypoplasia and forms of hydrocephalus, are frequently due to in utero viral infections. Although breed-related malformations of the brain have been described in sheep, breed-related lissencephaly has not been previously recorded in a peer reviewed publication. Results Here we report neuropathological findings in 42 newborn lambs from a pure Churra breed flock, with clinical signs of weakness, inability to walk, difficulty in sucking and muscular rigidity observed immediately after birth. All the lambs showed near-total agyria with only a rudimentary formation of few sulci and gyri, and a severe cerebellar hypoplasia. On coronal section, the cerebral grey matter was markedly thicker than that of age-matched unaffected lambs and the ventricular system was moderately dilated. Histologically, the normal layers of the cerebral cortex were disorganized and, using an immunohistochemical technique against neurofilaments, three layers were identified instead of the six present in normal brains. The hippocampus was also markedly disorganised and the number and size of lobules were reduced in the cerebellum. Heterotopic neurons were present in different areas of the white matter. The remainder of the brain structures appeared normal. The pathological features reported are consistent with the type LCH-b (lissencephaly with cerebellar hypoplasia group b) defined in human medicine. No involvement of pestivirus or bluetongue virus was detected by immunohistochemistry. An analysis of pedigree data was consistent with a monogenic autosomal recessive pattern inheritance. Conclusions The study describes the clinical and

  14. Influence of rearing temperature on lung development following methimazole treatment of postnatal lambs.

    PubMed

    Symonds, M E; Andrews, D C; Buss, D S; Clarke, L; Lomax, M A

    1996-07-01

    This study examines the effect of ambient temperature on lung development over the first month of postnatal life in lambs treated with a drug which inhibits thyroid hormone synthesis (methimazole, 50 mg day-1 (kg body wt-1)). Twin lambs were hand-reared at a fixed level of nutrition in either a warm (WR, 25 degrees C) or cool (CR, 10-15 degrees C) ambient temperature. Plasma thyroid hormone concentrations were significantly (P < 0.05) lower in WR lambs, but there were no differences between WR and CR groups in thyroid gland weight or hepatic iodothyronine 5'-deiodinase activity at 8 or 29 days of age. Lung weights and the ratio of lung weight to O2 consumption were similar in WR and CR groups at 8 days but both were significantly lower (P < 0.01) in CR lambs at 29 days. Lung weight at 29 days was significantly (P = 0.002) correlated with plasma triiodothyronine concentration in CR but not WR lambs, and laryngeal braking of expiratory airflow was observed in three of seven CR lambs but not in WR lambs. Four WR, but no CR, lambs exhibited a rapid deterioration in health or died unexpectedly between 14 and 21 days of age. These WR lambs were characterized by having small lungs and slower growth rates. It is concluded that in WR lambs chronically treated with methimazole, both lung development and the ability of an individual to adapt effectively to methimazole treatment are compromised. In CR lambs, although lung growth may be reduced this does not appear to compromise O2 consumption or health.

  15. Finite element simulation of core inspection in helicopter rotor blades using guided waves.

    PubMed

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2015-09-01

    This paper extends the work presented earlier on inspection of helicopter rotor blades using guided Lamb modes by focusing on inspecting the spar-core bond. In particular, this research focuses on structures which employ high stiffness, high density core materials. Wave propagation in such structures deviate from the generic Lamb wave propagation in sandwich panels. To understand the various mode conversions, finite element models of a generalized helicopter rotor blade were created and subjected to transient analysis using a commercial finite element code; ANSYS. Numerical simulations showed that a Lamb wave excited in the spar section of the blade gets converted into Rayleigh wave which travels across the spar-core section and mode converts back into Lamb wave. Dispersion of Rayleigh waves in multi-layered half-space was also explored. Damage was modeled in the form of a notch in the core section to simulate a cracked core, and delamination was modeled between the spar and core material to simulate spar-core disbond. Mode conversions under these damaged conditions were examined numerically. The numerical models help in assessing the difficulty of using nondestructive evaluation for complex structures and also highlight the physics behind the mode conversions which occur at various discontinuities.

  16. Stiochiometry of maltodextrin-binding sites in LamB, an outer membrane protein from Escherichia coli

    SciTech Connect

    Gehring, K.; Cheng, Chaohsiung; Jap, B.K. ); Nikaido, H. )

    1991-03-01

    The authors have directly measured the stoichiometry of maltodextrin-binding sites in LamB. Scatchard plots and computer fitting of flow dialysis (rate-of-dialysis) experiments clearly establish three independent binding sites per LamB trimer, with a dissociation constant of approximately 60 {mu}M for maltoheptaose. The current model for LamB's function as a specific pore is discussed with respect to the symmetry in LamB's kinetic properties and the implications of their results.

  17. Preference for flavored wheat straw by lambs conditioned with intraruminal administrations of sodium propionate.

    PubMed

    Villalba, J J; Provenza, F D

    1996-10-01

    We hypothesized that volatile fatty acids are feedback signals that condition food preferences in ruminants, and we tested two predictions based on this hypothesis: 1) low doses of propionate condition preferences for low-quality foods (Exp. 1 and 2) preferences are not caused by osmotic load (Exp. 2). In Exp. 1, lambs were offered chopped wheat straw flavored with either oregano or onion on odd days, whereas on even days flavors were switched and lambs received capsules containing sodium propionate. During four 8-d conditioning periods, the amounts of propionate delivered ranged from .7 to 1.4% of the daily DE intake (Period 1) or were fixed at .7% (Period 2) and 1% of the daily DE intake (Periods 3 and 4). After each 8-d conditioning period, lambs were offered oregano- and onion-flavored straw. Conditioning was then suspended and lambs were offered onion- and oregano-flavored straw at weekly intervals for 1 mo (extinction). Lambs preferred the flavor paired with propionate during conditioning (P < .001) and extinction (P < .07). During Exp. 2, a different group of lambs was conditioned as in Exp. 1, but sodium chloride was delivered at osmotic loads equivalent to those when propionate supplied .7% and 1% of the daily DE intake. Lambs strongly avoided the flavor paired with sodium chloride (P < .001). Thus, lambs acquired preferences for straw conditioned with doses of propionate typically considered ineffective in the regulation of food intake, and osmolalities generated by propionate did not cause, but probably attenuated, food preferences.

  18. Genetic evaluation of the probability of lambing in yearling Targhee ewes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the additive genetic control of lambing percentage in yearling Targhee ewes. The records of 3,103 ewe lambs born from 1989 to 2011 and mated at approximately 7.5 mo of age were analyzed. Records included sire, dam, weaning weight, breeding pen, age of dam...

  19. Behavioural expression of positive anticipation for food or opportunity to play in lambs.

    PubMed

    Anderson, Claes; Yngvesson, Jenny; Boissy, Alain; Uvnäs-Moberg, Kerstin; Lidfors, Lena

    2015-04-01

    Anticipatory behaviours may serve a useful tool in studying positive emotional states in animals. This study aimed to investigate if lambs express anticipatory behaviours for opportunities to play or a food reward and if these behaviours would differ depending on the anticipated event. Forty-two male lambs were allocated into three treatment groups (control, play, food). Play and food lambs were conditioned to anticipate play or food in a holding pen for three minutes prior to accessing a reward arena containing toy objects or concentrate, respectively. Control lambs returned to their home pen following three minutes in the holding pen. Compared to the control lambs, both play and food lambs differed in several behaviours frequencies and durations, e.g. by an increased frequency of behavioural transitions and duration of walking. Following these observations, food lambs received the toy objects when entering the reward arena. The subsequent session in the holding pen resulted in a decrease in number of behavioural transitions, time spent walking and an increase in time standing still. In conclusion, anticipating a positive event resulted in differences in behaviour compared to a control group, and these behaviours are affected when the anticipated event does not fit with the lambs' expectations.

  20. The Lamb shift in the hydrogen atom: Shift of s states

    SciTech Connect

    Karshenboim, S.G.

    1995-02-01

    A theoretical expression for the difference of the Lamb shifts of the 1s{sub 1/2} and 2s{sub 1/2} levels is obtained. The Lamb shift of the ground state in the hydrogen atom is recalculated and found to be 8172.898(26) MHz. 22 refs.

  1. Sericea lespdeza as an aid in the control of Emeria spp. in lambs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to examine the effects of feeding sericea lespedeza leaf meal [SL, Lespedeza cuneata (Dum.-Cours. G. Don)] on control of coccidiosis in lambs. In Exp. 1, naturally infected lambs (n = 76) were weaned (102.7 ± 1.4 d of age) in May (spring) and randomly assigned to ...

  2. 9 CFR 311.28 - Carcasses of young calves, pigs, kids, lambs, and foals.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 2 2013-01-01 2013-01-01 false Carcasses of young calves, pigs, kids... PARTS § 311.28 Carcasses of young calves, pigs, kids, lambs, and foals. Carcasses of young calves, pigs, kids, lambs, and foals are unwholesome and shall be condemned if (a) the meat has the appearance...

  3. 9 CFR 311.28 - Carcasses of young calves, pigs, kids, lambs, and foals.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Carcasses of young calves, pigs, kids... PARTS § 311.28 Carcasses of young calves, pigs, kids, lambs, and foals. Carcasses of young calves, pigs, kids, lambs, and foals are unwholesome and shall be condemned if (a) the meat has the appearance...

  4. 9 CFR 311.28 - Carcasses of young calves, pigs, kids, lambs, and foals.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 2 2014-01-01 2014-01-01 false Carcasses of young calves, pigs, kids... PARTS § 311.28 Carcasses of young calves, pigs, kids, lambs, and foals. Carcasses of young calves, pigs, kids, lambs, and foals are unwholesome and shall be condemned if (a) the meat has the appearance...

  5. 9 CFR 311.28 - Carcasses of young calves, pigs, kids, lambs, and foals.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 2 2011-01-01 2011-01-01 false Carcasses of young calves, pigs, kids... PARTS § 311.28 Carcasses of young calves, pigs, kids, lambs, and foals. Carcasses of young calves, pigs, kids, lambs, and foals are unwholesome and shall be condemned if (a) the meat has the appearance...

  6. The experimental infection of specific pathogen free lambs with Mycoplasma ovipneumoniae.

    PubMed

    Foggie, A; Jones, G E; Buxton, D

    1976-07-01

    Six colostrum-deprived SPF lambs inoculated endobronchially with a second passage broth culture of a Scottish strain of Mycoplasma ovipneumoniae, were killed in batches of two at seven, 14 and 28 days post-inoculation. One lamb from each batch showed macroscopic and microscopic lung lesions similar to but milder than those described for respiratory mycoplasmoses in other species of animals and exhibited minor clinical symptoms. Mycoplasma were recovered from all infected but from no control animals: five infected lambs yielded mycoplasma from lung tissue. Two lambs infected with M ovipneumoniae by endobronchial intubation were placed in contact with six other SPF lambs. M ovipneumoniae was recovered from the upper respiratory tract only of all six contact lambs, but no pathological changes were noted in their lungs. Both donor lambs yielded mycoplasma from lung tissue, but microscopic lesions were detected in only one of them, and these were minimal. No seroconversion due to the infection could be demonstrated in any of the lambs by either the indirect haemagglutination or metabolic inhibition tests.

  7. Adverse outcome of using tilmicosin in a lamb with multiple ventricular septal defects.

    PubMed

    Christodoulopoulos, Georgios

    2009-01-01

    A 15-day-old, 6.08 kg, lamb was injected subcutaneously with tilmicosin 15 mg/kg body weight. Approximately 15 min later, the lamb died. During necropsy, the heart was found to have multiple ventricular septal defects. Death was attributed to sudden heart failure due to the cardiac effects of tilmicosin in a heart having congenital defects.

  8. Fattening performance and carcass traits of Chios male lambs fed under traditional and intensive feeding conditions.

    PubMed

    Soycan Önenç, Sibel; Ozdoğan, Mürsel; Erdoğan Ataç, Funda; Taşkın, Turgay

    2012-06-01

    This study was carried out to compare the fattening performance and carcass traits of Chios male lambs fed under traditional and intensive feeding conditions. In the study, a total of 34 lambs were randomly separated into traditional (T) and intensive (I) groups in equal numbers. Lambs in group T were fed on ration prepared in local style and grazed in olive grove for 8 h/day. On the other hand, lambs in group I were fed on 255 g alfalfa hay animal(-1) day(-1) and ad libitum mixed feed. After a period of 8 weeks, lambs were transported to the slaughterhouse. The results showed that Chios lambs fed under intensive conditions has better performance and produced heavier carcass compared to those fed under traditional conditions. However, consumption of concentrate feed mixture was about twice as much in group I as in group T. Total feed consumption and feed conversion ratio was similar in each group. The values of carcass traits of lambs in group I were found to be significantly higher than those of group T. On the other hand, carcass fat thickness was slightly lower in group T. Traditional condition is considered to respond to better to consumer demands for lean lamb carcass.

  9. Sheep Stockmanship (Lambing). Youth Training Scheme. Core Exemplar Work Based Project.

    ERIC Educational Resources Information Center

    Further Education Staff Coll., Blagdon (England).

    This trainer's guide is intended to assist supervisors of work-based career training projects in helping students gather and record information about sheep breeding, learn about treatment of diseases, prepare the lambing area, and assist with the aftercare of lambs and ewes. The guide is one in a series of core curriculum modules that is intended…

  10. 7 CFR 4279.279 - Domestic lamb industry adjustment assistance program.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Domestic lamb industry adjustment assistance program. 4279.279 Section 4279.279 Agriculture Regulations of the Department of Agriculture (Continued) RURAL... Biorefinery Assistance Loans § 4279.279 Domestic lamb industry adjustment assistance program. The...

  11. 7 CFR 4279.175 - Domestic lamb industry adjustment assistance program set aside.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Domestic lamb industry adjustment assistance program set aside. 4279.175 Section 4279.175 Agriculture Regulations of the Department of Agriculture... GUARANTEED LOANMAKING Business and Industry Loans § 4279.175 Domestic lamb industry adjustment...

  12. 7 CFR 4279.175 - Domestic lamb industry adjustment assistance program set aside.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 15 2011-01-01 2011-01-01 false Domestic lamb industry adjustment assistance program set aside. 4279.175 Section 4279.175 Agriculture Regulations of the Department of Agriculture... GUARANTEED LOANMAKING Business and Industry Loans § 4279.175 Domestic lamb industry adjustment...

  13. 7 CFR 4279.279 - Domestic lamb industry adjustment assistance program.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Domestic lamb industry adjustment assistance program. 4279.279 Section 4279.279 Agriculture Regulations of the Department of Agriculture (Continued) RURAL... Biorefinery Assistance Loans § 4279.279 Domestic lamb industry adjustment assistance program. The...

  14. 7 CFR 4279.175 - Domestic lamb industry adjustment assistance program set aside.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Domestic lamb industry adjustment assistance program set aside. 4279.175 Section 4279.175 Agriculture Regulations of the Department of Agriculture... GUARANTEED LOANMAKING Business and Industry Loans § 4279.175 Domestic lamb industry adjustment...

  15. 7 CFR 4279.175 - Domestic lamb industry adjustment assistance program set aside.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Domestic lamb industry adjustment assistance program set aside. 4279.175 Section 4279.175 Agriculture Regulations of the Department of Agriculture... GUARANTEED LOANMAKING Business and Industry Loans § 4279.175 Domestic lamb industry adjustment...

  16. 7 CFR 4279.279 - Domestic lamb industry adjustment assistance program.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Domestic lamb industry adjustment assistance program. 4279.279 Section 4279.279 Agriculture Regulations of the Department of Agriculture (Continued) RURAL... Biorefinery Assistance Loans § 4279.279 Domestic lamb industry adjustment assistance program. The...

  17. 7 CFR 4279.175 - Domestic lamb industry adjustment assistance program set aside.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Domestic lamb industry adjustment assistance program set aside. 4279.175 Section 4279.175 Agriculture Regulations of the Department of Agriculture... GUARANTEED LOANMAKING Business and Industry Loans § 4279.175 Domestic lamb industry adjustment...

  18. Changes in concentrations of trace minerals in lambs fed sericea lespedeza leaf meal pellets with or without dietary sodium molybdate.

    PubMed

    Acharya, M; Burke, J M; Coffey, K P; Kegley, E B; Miller, J E; Smyth, E; Welborn, M G; Terrill, T H; Mosjidis, J A; Rosenkrans, C

    2016-04-01

    Prolonged feeding of sericea lespedeza (SL) previously led to reduced serum concentrations of Mo, a cofactor in an enzyme complex that may be involved in weight gain. The current objective was to determine the effect of Mo supplementation on changes in serum, fecal, urine, and liver concentrations of trace minerals in lambs fed SL leaf meal pellets. Thirty ram lambs weaned in May (84 ± 1.5 d of age and 27 ± 1.1 kg; D 0) were blocked by BW, breed type (full or three-fourths Katahdin), and EBV of parasite resistance and randomly assigned to be fed 900 g/d of an alfalfa-based supplement (CON; = 10) or a SL-based supplement ( = 20) for 103 d. Supplements were formulated to be isonitrogenous and isocaloric and to meet trace mineral requirements. Within the SL group, individual lambs were administered either 5 mL water or 5 mL of water with 163.3 mg of sodium molybdate (SLMO). Serum was collected on d 28, 56, and 104; a liver sample was collected by biopsy on d 104 to determine concentrations of trace minerals. Data were analyzed using a mixed model and orthogonal contrasts. Serum concentrations of Mo increased in response to the drench and were greatest in SLMO lambs and then CON lambs and lowest in SL lambs ( < 0.001). Concentrations of Mo in the liver ( < 0.001) were similar between CON and SLMO lambs and were lower in SL lambs than other groups. Serum ( < 0.001) and liver ( = 0.013) concentrations of zinc (Zn) were reduced in both SL and SLMO lambs compared with CON lambs. Serum concentrations of cobalt (Co) increased in CON lambs compared with SL and SLMO lambs between d 0 and 56 but were similar on d 104 (diet × day, < 0.005) as with concentrations in the liver. Serum and liver concentrations of copper (Cu) were greatest ( < 0.001 and < 0.001, respectively) in CON lambs followed by SL lambs and then SLMO lambs. Serum concentrations of selenium (Se) tended ( = 0.10) to be reduced in SL lambs compared with CON and SLMO lambs, but concentrations in the liver were

  19. Changes in concentrations of trace minerals in lambs fed sericea lespedeza leaf meal pellets with or without dietary sodium molybdate.

    PubMed

    Acharya, M; Burke, J M; Coffey, K P; Kegley, E B; Miller, J E; Smyth, E; Welborn, M G; Terrill, T H; Mosjidis, J A; Rosenkrans, C

    2016-04-01

    Prolonged feeding of sericea lespedeza (SL) previously led to reduced serum concentrations of Mo, a cofactor in an enzyme complex that may be involved in weight gain. The current objective was to determine the effect of Mo supplementation on changes in serum, fecal, urine, and liver concentrations of trace minerals in lambs fed SL leaf meal pellets. Thirty ram lambs weaned in May (84 ± 1.5 d of age and 27 ± 1.1 kg; D 0) were blocked by BW, breed type (full or three-fourths Katahdin), and EBV of parasite resistance and randomly assigned to be fed 900 g/d of an alfalfa-based supplement (CON; = 10) or a SL-based supplement ( = 20) for 103 d. Supplements were formulated to be isonitrogenous and isocaloric and to meet trace mineral requirements. Within the SL group, individual lambs were administered either 5 mL water or 5 mL of water with 163.3 mg of sodium molybdate (SLMO). Serum was collected on d 28, 56, and 104; a liver sample was collected by biopsy on d 104 to determine concentrations of trace minerals. Data were analyzed using a mixed model and orthogonal contrasts. Serum concentrations of Mo increased in response to the drench and were greatest in SLMO lambs and then CON lambs and lowest in SL lambs ( < 0.001). Concentrations of Mo in the liver ( < 0.001) were similar between CON and SLMO lambs and were lower in SL lambs than other groups. Serum ( < 0.001) and liver ( = 0.013) concentrations of zinc (Zn) were reduced in both SL and SLMO lambs compared with CON lambs. Serum concentrations of cobalt (Co) increased in CON lambs compared with SL and SLMO lambs between d 0 and 56 but were similar on d 104 (diet × day, < 0.005) as with concentrations in the liver. Serum and liver concentrations of copper (Cu) were greatest ( < 0.001 and < 0.001, respectively) in CON lambs followed by SL lambs and then SLMO lambs. Serum concentrations of selenium (Se) tended ( = 0.10) to be reduced in SL lambs compared with CON and SLMO lambs, but concentrations in the liver were

  20. General solutions of the Stokes flow --- Lamb's solution and multipole expansion

    NASA Astrophysics Data System (ADS)

    Ichiki, Kengo

    2004-11-01

    The objective of this talk is to relate the two major representations of the Stokes flow; Lamb's general solution (Lamb 1932, and Happel and Brenner 1973) and the multipole expansion of the Oseen tensor (Ichiki 2002). For low Reynolds number hydrodynamics, the governing equation is the Stokes equation, which is a linear partial differential equation. The general solution can be obtained by the conventional potential theory and we have a lot of equivalent representations. It is obvious that these various formulations are mathematically equivalent. However, to the author's knowledge, the relations among them are limited (Weinbaum and Ganatos 1990, and Kim and Karrila 1991). Here we write Lamb's solution by Cartesian tensors and express the force moments on particles by the Lamb's solution. Using this relation, we compare the suspension stress expressed by Lamb's solution (Tanksley and Prosperetti 2001) with that by force moments.

  1. Active Wave Propagation and Sensing in Plates

    NASA Technical Reports Server (NTRS)

    Ghoshal, Anindya; Martin, William N.; Sundaresan, Mannur J.; Schulz, Mark J.; Ferguson, Frederick

    2001-01-01

    Health monitoring of aerospace structures can be done using an active interrogation approach with diagnostic Lamb waves. Piezoelectric patches are often used to generate the waves, and it is helpful to understand how these waves propagate through a structure. To give a basic understanding of the actual physical process of wave propagation, a model is developed to simulate asymmetric wave propagation in a panel and to produce a movie of the wave motion. The waves can be generated using piezoceramic patches of any size or shape. The propagation, reflection, and interference of the waves are represented in the model. Measuring the wave propagation is the second important aspect of damage detection. Continuous sensors are useful for measuring waves because of the distributed nature of the sensor and the wave. Two sensor designs are modeled, and their effectiveness in measuring acoustic waves is studied. The simulation model developed is useful to understand wave propagation and to optimize the type of sensors that might be used for health monitoring of plate-like structures.

  2. Laminin gene LAMB4 is somatically mutated and expressionally altered in gastric and colorectal cancers.

    PubMed

    Choi, Mi Ryoung; An, Chang Hyeok; Yoo, Nam Jin; Lee, Sug Hyung

    2015-01-01

    Laminins are important in tumor invasion and metastasis as well as in maintenance of normal epithelial cell structures. However, mutation status of laminin chain-encoding genes remains unknown in cancers. Aim of this study was to explore whether laminin chain genes are mutated and expressionally altered in gastric (GC) and colorectal cancers (CRC). In a public database, we found that laminin chain genes LAMA1, LAMA3, LAMB1 and LAMB4 had mononucleotide repeats in the coding sequences that might be mutation targets in the cancers with microsatellite instability (MSI). We analyzed the genes in 88 GC and 139 CRC [high MSI (MSI-H) or stable MSI/low MSI (MSS/MSI-L)] by single strand conformation polymorphism analysis and DNA sequencing. In the present study, we found LAMB4 (11.8% of GC and 7.6% of CRC with MSI-H), LAMA3 (2.9% of GC and 2.5 of CRC with MSI-H), LAMA1 (5.9% of GC with MSI-H) and LAMB1 frameshift mutations (1.3% of CRC with MSI-H). These mutations were not found in MSS/MSI-L (0/114). We also analyzed LAMB4 expression in GC and CRC by immunohistochemistry. Loss of LAMB4 expression was identified in 17-32% of the GC and CRC. Of note, the loss expression was more common in the cancers with LAMB4 mutation or those with MSI-H. Our data show that frameshift mutations of LAMA1, LAMA3, LAMB1 and LAMB4, and loss of LAMB4 may be features of GC and CRC with MSI-H. PMID:25257191

  3. Lymphocyte Depletion in Ileal Peyer’s Patch Follicles in Lambs Infected with Eimeria ovinoidalis

    PubMed Central

    Aleksandersen, Mona; Lie, Kai-Inge; Gjerde, Bjørn; Landsverk, Thor

    2002-01-01

    A total of 14 lambs were experimentally infected with Eimeria ovinoidalis in two separate experiments in two consecutive years. Nine lambs served as uninoculated controls. Material was collected from the ileum 2 weeks after infection in eight lambs and 3 weeks after infection in six lambs. Lambs examined 2 weeks after infection had normal follicles. After three weeks, the follicle-associated epithelium covering the lymphoid follicles of the ileal Peyer’s patches showed fusions with adjacent absorptive epithelium, focal hyperplasia, and occasionally necrosis. Macrogametes, microgamonts, and oocysts were often found in the follicle-associated epithelium and the dome region. Various degrees of lymphocyte depletion were present in the ileal lymphoid follicles in all six infected lambs 3 weeks after infection, and four lambs had decreased follicle size. Reduced staining for leukocyte common antigen (CD45), B-cell markers, and the proliferation marker Ki-67 was present in these lambs. Application of the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling method for apoptotic cells revealed decreased staining in the ileal lymphoid follicles 3 weeks after infection. A marker of follicular dendritic cells, 5′- nucleotidase, showed increased reactivity, probably due to condensation of reticular cells following loss of follicle lymphocytes. Reduced staining for carbonic anhydrase in the follicle-associated epithelium and the domes was present in all six lambs examined 3 weeks after infection, indicating decreased production of carbonic anhydrase-reactive 50-nm particles and a decreased lymphoproliferative stimulus. In conclusion, the present study shows that severe E. ovinoidalis infection in lambs causes lesions of the follicle-associated epithelium and may result in lymphocyte depletion and atrophy of the ileal Peyer’s patch follicles. PMID:11777834

  4. Effect of milk replacer and rumen inert fat on growth and reproduction of Malpura ram lambs.

    PubMed

    Kumar, D; Bhatt, R S; Karim, S A; Naqvi, S M K

    2014-04-01

    The objective of this study was to assess the effects of milk replacer and rumen inert fat on growth, testicular development, puberty, semen production and sperm motion characteristics of ram lambs reared under intensive management in semi-arid climatic conditions. Seven-day-old male lambs of Malpura breed (n=20) were divided equally into two groups. Up to weaning, the lambs in G1 group (control) were fed concentrate, green khejri (Prosopis cineraria) leaves and cowpea (Vigna unguiculata) hay along with suckling of dams, whereas lambs in G2 group were fed reconstituted milk at 17 g/lamb per day for the 1st week and at 34 g/lamb per day from 2nd week in addition to the feed inputs given in G1. During post weaning, lambs in the G1 group were given control concentrate, whereas in G2 the control concentrate supplemented with 40 g rumen inert fat per kg of feed was offered along with dry pala (Zizyphus nummularia) and ardu (Ailanthus excelsa) leaves. BWs of lambs were recorded weekly up to 6 months of age. Ram lambs of both the groups were trained for semen collection at a weekly interval from the age of 5 months and simultaneously testicular measurements were recorded fortnightly. The feeding of milk replacer and rumen inert fat had positive (P<0.05) effects on BW, testicular length, testicular volume, semen volume, sperm concentration, mass motility, % motility, % rapid, medium or slow motile spermatozoa. However, no significant effect was observed on testicular breadth, scrotal circumference, age of puberty, sperm velocities and other CASA-derived parameters. The results of this study indicate that higher plane of nutrition in the form of milk-replacer feeding during preweaning and rumen inert fat-supplemented feed during the postweaning period to growing ram lambs enhances their growth, testicular development and semen quality.

  5. Do Lambs Perceive Regular Human Stroking as Pleasant? Behavior and Heart Rate Variability Analyses

    PubMed Central

    Coulon, Marjorie; Nowak, Raymond; Peyrat, Julie; Chandèze, Hervé; Boissy, Alain; Boivin, Xavier

    2015-01-01

    Stroking by humans is beneficial to the human-animal relationship and improves welfare in many species that express intraspecific allogrooming, but very few studies have looked at species like sheep that do not express such contact except around parturition. This study investigated the way lambs perceive regular human tactile contact using behavioral and physiological responses. Twenty-four lambs were reared and bucket-fed in groups of four. All were stroked daily by their familiar caregiver. At 8 weeks of age, the lambs were individually tested in their home pen but in a 1×1m open-barred pen after a 15h period of habituation to physical separation from peers while remaining in visual and auditory contact. Half of the lambs received stroking by their caregiver for 8min and half were exposed to their caregiver’s immobile presence. Heart rate and heart rate variability were recorded and analyzed by 2-min slots over the same interval based on three measures: mean heart rate value (HR), root mean square of successive differences (RMSSD) and standard deviation of all intervals measured between consecutive sinus beats (SDNN). Behavioral responses (ear postures of the lamb and time spent in contact with the familiar caregiver, on the knees of the familiar caregiver, and moving) were recorded throughout the test. Lamb HR decreased continuously while in the presence of their caregiver. Lambs being stroked showed slower HR and higher RMSSD which reflected positive emotional states compared to lambs left unstroked. All behavioral variables were highly correlated with the main component axis of the PCA analyses: the more the animals stayed in contact with their caregiver, the less they moved and the more their ears were hanging. This first component clearly differentiates lambs being stroked or not. Behavioral and physiological observations support the hypothesis that gentle physical contact with the caregiver is perceived positively by lambs. PMID:25714604

  6. Numerical modeling of wave propagation in functionally graded materials using time-domain spectral Chebyshev elements

    NASA Astrophysics Data System (ADS)

    Hedayatrasa, Saeid; Bui, Tinh Quoc; Zhang, Chuanzeng; Lim, Chee Wah

    2014-02-01

    Numerical modeling of the Lamb wave propagation in functionally graded materials (FGMs) by a two-dimensional time-domain spectral finite element method (SpFEM) is presented. The high-order Chebyshev polynomials as approximation functions are used in the present formulation, which provides the capability to take into account the through thickness variation of the material properties. The efficiency and accuracy of the present model with one and two layers of 5th order spectral elements in modeling wave propagation in FGM plates are analyzed. Different excitation frequencies in a wide range of 28-350 kHz are investigated, and the dispersion properties obtained by the present model are verified by reference results. The through thickness wave structure of two principal Lamb modes are extracted and analyzed by the symmetry and relative amplitude of the vertical and horizontal oscillations. The differences with respect to Lamb modes generated in homogeneous plates are explained. Zero-crossing and wavelet signal processing-spectrum decomposition procedures are implemented to obtain phase and group velocities and their dispersion properties. So it is attested how this approach can be practically employed for simulation, calibration and optimization of Lamb wave based nondestructive evaluation techniques for the FGMs. The capability of modeling stress wave propagation through the thickness of an FGM specimen subjected to impact load is also investigated, which shows that the present method is highly accurate as compared with other existing reference data.

  7. [IgE-induced anaphylactic reaction after eating lamb meat].

    PubMed

    Johansen, Kasper Lorenz; Rasmussen, Kirsten

    2014-08-25

    This article presents the case of a 54-year-old male, who was admitted to hospital after suffering a severe anaphylactic reaction after tasting a spoonful of chili con carne and four months later after eating lamb meat. Galactose-alpha-1,3-galactose allergy was suspected and the subsequent blood test showed highly elevated specific IgE levels. Delayed allergy to meat is a relatively new type of allergy and the delayed onset of allergic symptoms poses a diagnostic challenge to the physician. This type of allergy should be considered when there has been no obvious allergen exposition prior to the allergic reaction. PMID:25293709

  8. [Natural and experimental infections of lambs with Mycoplasma ovipneumoniae].

    PubMed

    Bocklisch, H; Pfützner, H; Zepezauer, V

    1989-01-01

    Mycoplasma (M.) ovipneumoniae was isolated pure or mixed with bacteria from 47 lungs of lambs of 14 in 22 tested flocks. M. ovipneumoniae was obtained as pure culture in cases of mild bronchopneumonia. Experimental intratracheal or intranasal infection caused several days of rising body temperature above 39.7 degrees C. Nasal discharge, coughing, and dyspnea did not occur. M. ovipneumoniae was successfully re-isolated from nasal swabs, beginning 2 d from infection. Lobular catarrhal bronchopneumonia was established by postmortem examinations, 10-14 d from infection, and M. ovipneumoniae was re-isolated from the lungs. Histological patterns of lungs were characterised by interstitial cell reactions.

  9. Congenital biliary atresia and jaundice in lambs and calves.

    PubMed

    Harper, P; Plant, J W; Unger, D B

    1990-01-01

    An outbreak of congenital biliary atresia and jaundice is described, in which approximately 300 crossbred lambs and 9 crossbred calves died. The affected animals failed to thrive, developed jaundice and white scours and died within 4 weeks of birth. A common feature of this outbreak and a similar occurrence 24 years previously was the grazing of plants growing on the exposed silt foreshores of Burrinjuck Dam by ewes and cows in the early stages of pregnancy. Epidemiological and pathological findings suggested that a toxic insult to the foetus in early gestation caused choledysgenesis and biliary atresia, leading to diffuse, subacute to chronic cholangiohepatopathy and cirrhosis.

  10. Patent ductus arteriosus in a lamb: A case report

    PubMed Central

    Jafari Dehkordi, Afshin; Hoseini, Farzaneh

    2016-01-01

    Patent ductus arteriosus (PDA) is a persistent patency of a vessel normally present in the fetus that connects the pulmonary arterial system to the aorta. The ductus arteriosus fails to close at birth when breathing commences and placental blood circulation is removed. Closure of the ductus arteriosus arises in response to decline pulmonary vascular resistance and increased systemic vascular resistance. This report describes a case of PDA in a two-month-old male lamb with clinical signs of machinery murmur, tachycardia, increase respiratory rate, weakness and ill thrift. Echocardiographic examination and necropsy finding confirmed PDA. PMID:27226893

  11. Focusing of the lowest-order antisymmetric Lamb mode behind a gradient-index acoustic metalens with local resonators

    NASA Astrophysics Data System (ADS)

    Zhao, Jinfeng; Bonello, Bernard; Boyko, Olga

    2016-05-01

    We have investigated the focusing of the lowest-order antisymmetric Lamb mode (A0) behind a positive gradient-index (GRIN) acoustic metalens consisting of air holes drilled in a silicon plate with silicon pillars erected on one face of the lens. We have analyzed the focusing in the near field as the result of the coupling between the flexural resonant mode of the pillars and the vibration mode of the air/silicon phononic crystal. We highlight the role played by the polarization coherence between the resonant mode and the vibration of the plate. We demonstrate both numerically and experimentally the focusing behind the lens over a spot less than half a wavelength, paving a way for performance of acoustic lenses beyond the diffraction limit. Our findings can be easily extended to other types of elastic wave.

  12. Carcass composition and meat quality of equally mature kids and lambs.

    PubMed

    Santos, V A C; Silva, S R; Azevedo, J M T

    2008-08-01

    Carcass composition and meat quality attributes of 55 suckling kids (27 males and 28 females) and 57 suckling lambs (28 males and 29 females) of Portuguese native breeds were investigated. These suckling kid and lamb meats are European meat quality labels produced according to "Cabrito de Barroso- PGI" and "Borrego Terrincho-PDO" specifications, respectively. Female kids were slaughtered at 9.1 +/- 0.36 kg of BW, and male kids were slaughtered at 10.4 +/- 0.37 kg of BW, corresponding to 20.1 and 17.7% of maturity, respectively. Female lambs were slaughtered at 8.6 +/- 0.53 kg of BW, and male lambs were slaughtered at 9.9 +/- 0.23 kg of BW, corresponding to 19.9 and 17.1% of maturity, respectively. At 24 h postmortem, various yield and quality measurements were collected. The left sides of the carcasses were dissected into muscle, subcutaneous fat, intermuscular fat, and bone. Final pH, instrumental color (L*, a*, b*), carcass measurements, and kidney knob and pelvic fat were also determined. Samples of LM were taken from the lumbar and thoracic cuts for intramuscular and meat quality determinations. At 72 h postmortem, a sample of LM was used for cooking losses and Warner-Bratzler shear force determination. Suckling lambs had greater dressing proportion than suckling kids (P < 0.01). Carcass fatness was not affected by species (P > 0.05), but females had greater kidney knob and pelvic fat proportion than males (P < 0.01). Lambs had greater proportions of the highly valued leg cut and lower proportions of shoulder, anterior rib, and neck cuts than kids. Dissection results indicated that kid carcasses had greater muscle content and lower dissected fat and bone than lambs. Kids had greater (P < 0.001) muscle ultimate pH value than lambs (5.8 +/- 0.02 vs. 5.6 +/- 0.02). Males had greater (P < 0.05) muscle ultimate pH value than females (5.7 +/- 0.02 vs. 5.6 +/- 0.02). The kid meat was significantly lighter (P < 0.05) and less yellow (P < 0.001) than the lamb meat. Kids

  13. The effect of vitamin E supplementation on an experimental Haemonchus contortus infection in lambs.

    PubMed

    De Wolf, B M; Zajac, A M; Hoffer, K A; Sartini, B L; Bowdridge, S; LaRoith, T; Petersson, K H

    2014-09-15

    The objective of this study was to investigate the effect of vitamin E supplementation on an experimental Haemonchus contortus infection in lambs. Twenty lambs were stratified into two treatment groups based on fecal egg count. Worm-free lambs, 28-32 weeks of age, were supplemented with vitamin E (d-α-tocopherol) for 12 weeks following the recommendations of the National Research Council for the minimum daily requirement (control; 5.3 IU/kg body weight (BW)/day (d), n=10) or the requirement for optimal immune function (VE10; 10 IU/kg BW/d, n=10). Five weeks following initiation of vitamin E supplementation, lambs were infected with 10,000 H. contortus third stage larvae. Samples were taken weekly to quantify serum α-tocopherol, serum total non-specific immunoglobulin (Ig)G, whole worm antigen specific IgG, packed cell volume (PCV), and fecal egg count (FEC). Expression of cytokine genes IFN-λ and IL-4 were measured in peripheral blood collected prior to slaughter. Lambs were necropsied six weeks after infection and the α-tocopherol concentration of liver, muscle and lymph node were measured as well as abomasal worm burden and histologic evaluation of the abomasum for inflammation and enumeration of eosinophils and globule leukocytes. The livers of VE10 lambs contained slightly more α-tocopherol than control lambs. No differences were observed in serum, muscle or lymph node α-tocopherol concentration, serum IgG or peripheral mRNA expression of IL-4 or IFN-λ between control and VE10 lambs. However, lambs supplemented at 10IU/kg BW/d had a lower PCV reduction, FEC and worm burden 49% less than control lambs. Worm burden was negatively correlated with eosinophil (-0.720, P<0.05) and globule leukocyte count (-0.867, P<0.05). Strong positive correlations were observed within the inflammatory cell response in VE10 lambs that was absent in control lambs. These data indicate that additional vitamin E supplementation resulted in lower worm burden and greater

  14. Dietary zinc affects concentrations of insulin, insulin-like growth factor-I and growth hormone in lambs

    SciTech Connect

    Droke, E.A.; Spears, J.W.; Armstrong, J.D. )

    1991-03-15

    Glucose tolerance and concentrations of insulin, growth hormone (GH) and insulin-like growth factor-I (IGF-I) were evaluated in lambs deficient, marginal or adequate in zinc (Zn). Lambs were fed a semipurified diet that contained either 3.7, 8.7, or 43.7 mg Zn/kg. Zinc deficiency resulted in lower serum insulin levels 1 h after feeding while levels in marginal lambs were not different from that of adequate lambs. Dietary Zn did not affect plasma glucose post feeding. One h after IV glucose administration plasma glucose concentrations were lower in deficient lambs compared to adequate lambs; marginal lambs had intermediate glucose levels. Concentration of GH before and after feeding or glucose challenge were not affected by Zn status; however, serum IGF-I was lower in deficient than in marginal or adequate lambs. A GH releasing factor (GRF) analog was given to evaluate the release of GH. Serum GH in response to GRF challenge was higher in deficient lambs and tended to be higher in marginal lambs when compared to adequate lambs. Impaired growth observed with Zn deficiency may be mediated in part by its effect on insulin, GH and IGF-I concentrations.

  15. Wave-equation migration velocity inversion using passive seismic sources

    NASA Astrophysics Data System (ADS)

    Witten, B.; Shragge, J. C.

    2015-12-01

    Seismic monitoring at injection sites (e.g., CO2 sequestration, waste water disposal, hydraulic fracturing) has become an increasingly important tool for hazard identification and avoidance. The information obtained from this data is often limited to seismic event properties (e.g., location, approximate time, moment tensor), the accuracy of which greatly depends on the estimated elastic velocity models. However, creating accurate velocity models from passive array data remains a challenging problem. Common techniques rely on picking arrivals or matching waveforms requiring high signal-to-noise data that is often not available for the magnitude earthquakes observed over injection sites. We present a new method for obtaining elastic velocity information from earthquakes though full-wavefield wave-equation imaging and adjoint-state tomography. The technique exploits the fact that the P- and S-wave arrivals originate at the same time and location in the subsurface. We generate image volumes by back-propagating P- and S-wave data through initial Earth models and then applying a correlation-based extended-imaging condition. Energy focusing away from zero lag in the extended image volume is used as a (penalized) residual in an adjoint-state tomography scheme to update the P- and S-wave velocity models. We use an acousto-elastic approximation to greatly reduce the computational cost. Because the method requires neither an initial source location or origin time estimate nor picking of arrivals, it is suitable for low signal-to-noise datasets, such as microseismic data. Synthetic results show that with a realistic distribution of microseismic sources, P- and S-velocity perturbations can be recovered. Although demonstrated at an oil and gas reservoir scale, the technique can be applied to problems of all scales from geologic core samples to global seismology.

  16. Surfactant phosphatidylcholine metabolism and surfactant function in preterm, ventilated lambs

    SciTech Connect

    Jobe, A.H.; Ikegami, M.; Seidner, S.R.; Pettenazzo, A.; Ruffini, L.

    1989-02-01

    Preterm lambs were delivered at 138 days gestational age and ventilated for periods up to 24 h in order to study surfactant metabolism and surfactant function. The surfactant-saturated phosphatidylcholine pool in the alveolar wash was 13 +/- 4 mumol/kg and did not change from 10 min to 24 h after birth. Trace amounts of labeled natural sheep surfactant were mixed with fetal lung fluid at birth. By 24 h, 80% of the label had become lung-tissue-associated, yet there was no loss of label from phosphatidylcholine in the lungs when calculated as the sum of the lung tissue plus alveolar wash. De novo synthesized phosphatidylcholine was labeled with choline given by intravascular injection at 1 h of age. Labeled phosphatidylcholine accumulated in the lung tissue linearly to 24 h, and the labeled phosphatidylcholine moved through lamellar body to alveolar pools. The turnover time for alveolar phosphatidylcholine was estimated to be about 13 h, indicating an active metabolic pool. A less surface-active surfactant fraction recovered as a supernatant after centrifugation of the alveolar washes at 40,000 x g increased from birth to 10 min of ventilation, but no subsequent changes in the distribution of surfactant phosphatidylcholine in surfactant fractions occurred. The results were consistent with recycling pathway(s) that maintained surface-active surfactant pools in preterm ventilated lambs.

  17. LAMB3 mutations causing autosomal-dominant amelogenesis imperfecta.

    PubMed

    Kim, J W; Seymen, F; Lee, K E; Ko, J; Yildirim, M; Tuna, E B; Gencay, K; Shin, T J; Kyun, H K; Simmer, J P; Hu, J C-C

    2013-10-01

    Amelogenesis imperfecta (AI) can be either isolated or part of a larger syndrome. Junctional epidermolysis bullosa (JEB) is a collection of autosomal-recessive disorders featuring AI associated with skin fragility and other symptoms. JEB is a recessive syndrome usually caused by mutations in both alleles of COL17A1, LAMA3, LAMB3, or LAMC2. In rare cases, heterozygous carriers in JEB kindreds display enamel malformations in the absence of skin fragility (isolated AI). We recruited two kindreds with autosomal-dominant amelogenesis imperfecta (ADAI) characterized by generalized severe enamel hypoplasia with deep linear grooves and pits. Whole-exome sequencing of both probands identified novel heterozygous mutations in the last exon of LAMB3 that likely truncated the protein. The mutations perfectly segregated with the enamel defects in both families. In Family 1, an 8-bp deletion (c.3446_3453del GACTGGAG) shifted the reading frame (p.Gly 1149Glufs*8). In Family 2, a single nucleotide substitution (c.C3431A) generated an in-frame translation termination codon (p.Ser1144*). We conclude that enamel formation is particularly sensitive to defects in hemidesmosome/basement-membrane complexes and that syndromic and non-syndromic forms of AI can be etiologically related. PMID:23958762

  18. Relative bioavailability of soil-bound chlordecone in growing lambs.

    PubMed

    Jurjanz, S; Jondreville, C; Mahieu, M; Fournier, A; Archimède, H; Rychen, G; Feidt, C

    2014-10-01

    The pollution of soil with the pesticide chlordecone (CLD) is a problem for the use of agricultural surfaces even years after its use has been forbidden. Therefore, the exposure of free-ranged animals such as ruminants needs to be investigated in order to assess the risk of contamination of the food chain. Indeed, measured concentrations could be integrated in a lowered extent if the soil binding would reduce the bioavailability of the pesticide. This bioavailability of soil-bound CLD in a heavily polluted andosol has been investigated relatively of CLD given via spiked oil. Twenty-four weaned lambs were exposed to graded doses of 2, 4 or 6 μg CLD/kg body weight during 15 days via the contaminated soil in comparison to spiked oil. The concentration of this pesticide has been determined in two target tissues: blood serum and kidney fat. The relative bioavailability (RBA) corresponds to the slope ratio between the test matrix-contaminated soil- in comparison to the reference matrix oil. The RBA of the soil-bound CLD was not found to significantly differ from the reference matrix oil in lambs meaning that the pesticide ingested by grazing ruminants would not be sequestered by soil binding. Therefore, CLD from soil gets bioavailable within the intestinal level and exposure to contaminated soil has to be integrated in risk assessments.

  19. Meat quality of lambs fed diets with peanut cake.

    PubMed

    Bezerra, L S; Barbosa, A M; Carvalho, G G P; Simionato, J I; Freitas, J E; Araújo, M L G M L; Pereira, L; Silva, R R; Lacerda, E C Q; Carvalho, B M A

    2016-11-01

    Replacement of soybean meal by peanut cake was evaluated on the meat quality of 45 Dorper × Santa Inês crossbred lambs. Animals were distributed in a completely randomized design, with five treatments and nine repetitions, and fed Tifton-85 hay and a concentrate mixed with 0.0%, 25.0%, 50.0%, 75.0% or 100.0% peanut cake based on the dry mass of the complete diet. The longissimus lumborum muscle was used to determine the proximate composition, physical-chemical characteristics and fatty acid profile. Significant differences (P<0.05) were found for the crude protein and ether extract levels, with average values of 23.38% and 2.15% in the sheep meat, respectively. The physical-chemical characteristics of the loin were not affected (P>0.05) by the diets. The fatty acid profile was affected by peanut cake supplementation for myristic, myristoleic, palmitoleic, linolenic and arachidonic fatty acids. Peanut cake can be added in the diet of lambs no effect on physical-chemical characteristics. However, the total replacement of the soybean meal altered the proximate composition and fatty acid profile of the meat. PMID:27288901

  20. Ingestive behavior of lambs fed diets containing castor seed meal.

    PubMed

    Nicory, Isis Miranda Carvalho; de Carvalho, Gleidson Giordano Pinto; Ribeiro, Ossival Lolato; Silva, Robério Rodrigues; Tosto, Manuela Silva Libanio; Costa-Lopes, Lívia Santos; Souza, Fábio Nicory Costa; de Oliveira Nascimento, Camila

    2015-06-01

    The objective of this study was to evaluate the substitution of soybean meal for castor seed meal (CSM) in diets for feedlot lambs and the effects of these diets on their ingestive behavior. Fifty male Santa Inês lambs were used. The diets were composed of Tifton 85 hay and a concentrate containing detoxified CSM substituting 0, 25, 50, 75, or 100 % of the soybean meal. There was no effect (P > 0.05) of the CSM levels on the feeding, rumination, idle times, chews and time spent chewing per bolus, total chewing time, number of boli chewed, and number of chews per day. The dry matter (DM) intake decreased linearly (P < 0.05), but did not affect the neutral detergent fiber (NDF) intake. The feeding and rumination efficiencies had a quadratic response (P < 0.05). The experimental diets did not affect (P > 0.05) the numbers of feeding, rumination, and idle periods, but had a quadratic effect (P < 0.05) on the time per feeding activity and on the chewing periods. Substitution of soybean meal for detoxified CSM reduces the DM intake but does not change the ingestive behavior.

  1. Meat quality of lambs fed diets with peanut cake.

    PubMed

    Bezerra, L S; Barbosa, A M; Carvalho, G G P; Simionato, J I; Freitas, J E; Araújo, M L G M L; Pereira, L; Silva, R R; Lacerda, E C Q; Carvalho, B M A

    2016-11-01

    Replacement of soybean meal by peanut cake was evaluated on the meat quality of 45 Dorper × Santa Inês crossbred lambs. Animals were distributed in a completely randomized design, with five treatments and nine repetitions, and fed Tifton-85 hay and a concentrate mixed with 0.0%, 25.0%, 50.0%, 75.0% or 100.0% peanut cake based on the dry mass of the complete diet. The longissimus lumborum muscle was used to determine the proximate composition, physical-chemical characteristics and fatty acid profile. Significant differences (P<0.05) were found for the crude protein and ether extract levels, with average values of 23.38% and 2.15% in the sheep meat, respectively. The physical-chemical characteristics of the loin were not affected (P>0.05) by the diets. The fatty acid profile was affected by peanut cake supplementation for myristic, myristoleic, palmitoleic, linolenic and arachidonic fatty acids. Peanut cake can be added in the diet of lambs no effect on physical-chemical characteristics. However, the total replacement of the soybean meal altered the proximate composition and fatty acid profile of the meat.

  2. Dietary citrus pulp reduces lipid oxidation in lamb meat.

    PubMed

    Inserra, L; Priolo, A; Biondi, L; Lanza, M; Bognanno, M; Gravador, R; Luciano, G

    2014-04-01

    This study investigated the effect of replacing cereal concentrates with high levels of dried citrus pulp in the diet on lamb meat oxidative stability. Over 56 days, lambs were fed a barley-based concentrate (Control) or concentrates in which 24% and 35% dried citrus pulp were included to partially replace barley (Citrus 24% and Citrus 35%, respectively). Meat was aged under vacuum for 4 days and subsequently stored aerobically at 4 °C. The Control diet increased the redness, yellowness and saturation of meat after blooming (P<0.01). Regardless of the level of supplementation, dietary dried citrus pulp strongly reduced meat lipid oxidation over 6 days of aerobic storage (P<0.001), while colour parameters did not change noticeably over storage and their variation rate was not affected by the diet. In conclusion, replacing cereals with dried citrus pulp in concentrate-based diets might represent a feasible strategy to naturally improve meat oxidative stability and to promote the exploitation of this by-product.

  3. Metabolic maturity at birth and neonate lamb survival and growth: the effects of maternal low-dose dexamethasone treatment.

    PubMed

    Miller, D R; Jackson, R B; Blache, D; Roche, J R

    2009-10-01

    Perinatal mortality is a major contributing factor to reproductive wastage in grazing sheep industries. Enhanced metabolic and endocrine maturity at birth may improve the behavioral competency and thermoregulatory ability of neonates, potentially improving lamb survival over the first 72 h of life. Maternal glucocorticoid treatment in late gestation was investigated as a mechanism for manipulating metabolic and endocrine maturity in the ovine neonate. Multiparous, fine-wool Merino ewes (n = 150) were divided into 3 groups to lamb on pasture. Within each group, 5 single-lamb and 5 twin-lamb bearing ewes were randomly allocated to 1 of 5 treatments. Treatments included a saline control (1 mL), or dexamethasone (2 mg/mL as the sodium phosphate) injected intramuscularly at 1 of 2 dose rates (1.5 or 3.0 mg) at d 130 or 141 of gestation. One-half of the control ewes were injected at d 130 and the remainder at d 141. Dexamethasone treatment had no effect on lamb survival to 72 h after birth, although there tended (P = 0.09) to be a smaller proportion of lambs dying due to dystocia than for control lambs. Heart girth at birth in singleton and twin lambs was reduced (P < 0.01) at the greater dose rate. Further, treatment also reduced birth weight (by about 5%) and presuckling rectal temperatures in twin lambs, but not in singleton lambs. These reductions were also dependent on the sex of the lamb. Dexamethasone treatment did not alter gestation length or lamb presuckling plasma glucose, NEFA, urea, or leptin concentrations, but treatment at d 141 increased (P < 0.05) ghrelin concentrations in singleton and male lambs. Behavioral interactions between ewes and neonatal lambs were generally unaffected, although treatment at d 130 produced lambs that took longer to bleat than lambs of untreated ewes (P < 0.05). Treatment did not affect the concentration of measured blood metabolites or hormones at weaning. Although there were interactions between litter size, lamb sex, and the

  4. Effect of pre-slaughter handling, exercise and the presence of a dog on lamb welfare and meat quality.

    PubMed

    Sutherland, M A; Worth, G M; Stuart, A D; Dobbie, P M; Clerens, S

    2016-08-01

    Before slaughter, lambs may experience several stressors such as feed and water deprivation, handling and transport that have the potential to negatively impact welfare and meat quality. The objective of this study was to evaluate the effect of pre-slaughter handling, exercise and the presence of a dog on the behaviour and physiology of lambs and meat quality at slaughter. At 6 months of age, 60 lambs (n=20 lambs/replicate; three replicates) were allocated to one of the two treatment groups (n=30 lambs/treatment): low (LOW) intensive handling or high (HIGH) intensive handling. LOW lambs were moved short distances, quietly and without the use of a dog before transport. HIGH lambs were moved quickly, long distances and with a dog present before transport. Lamb behaviour (standing, lying, rumination and panting) was recorded for 1 h before (post-treatment) and after transport (post-transport), and for 30 min before slaughter (pre-slaughter). Blood samples were collected before (baseline), after transport (post-transport) and at exsanguination (at slaughter) to assess cortisol, lactate and non-esterified fatty acid (NEFA) concentrations. At slaughter, lamb carcases (M. longissimus lumborum) were evaluated for pH levels, drip and cook loss, and tenderness. HIGH lambs spent more time standing (P<0.001) and panting (P<0.001) and less time lying (P<0.001) and ruminating (P<0.001) post-treatment than LOW lambs, but more (P<0.001) time ruminating post-transport. All lambs spent more time standing (P<0.001) and less time lying (P<0.001) and panting (P<0.001) post-transport and pre-slaughter than post-treatment. Cortisol concentrations were greater (P<0.001) in lambs post-transport and at slaughter compared with baseline values. Lactate concentrations were lower (P=0.002) in HIGH than LOW lambs. In addition, NEFA concentrations were higher (P<0.001) post-transport and at slaughter in HIGH compared with LOW lambs. Ultimate pH was higher (P<0.001) in HIGH than LOW lambs and p

  5. Effects of road type during transport on lamb welfare and meat quality in dry hot climates.

    PubMed

    Miranda-de la Lama, Genaro C; Monge, Paula; Villarroel, Morris; Olleta, Jose Luis; García-Belenguer, Sylvia; María, Gustavo A

    2011-06-01

    This study determined whether transporting lambs on paved (PR) or unpaved roads (UR) for 3 h had an effect on plasma stress indicators (cortisol, lactate, glucose, creatine kinase [CK], red blood cells, white blood cells, hematocrit, and neutrophil/lymphocyte [N/L] ratio) and instrumental meat quality (pH24, bruising score, water holding capacity [WHC], color, and texture). A total of 48 Rasa Aragonesa male lambs were used that were approximately 100 days old (12.5 kg ± 1.64, carcass weight). The results suggest that transport on unpaved roads had a significant influence on physiological and hematological stress parameters. Road type had a significant effect on all variables, except for white and red blood cells, and hematocrit levels. The UR lambs had significantly higher (at least p ≤ 0.01) cortisol, lactate, glucose, and CK levels and a higher N/L ratio than PR lambs. Meat from UR lambs had some dark-cutting characteristics, with a darker color, higher ultimate pH, and higher tenderness values than PR. In conclusion, lambs transported on unpaved roads had a more intense stress response and poorer meat quality than lambs transported on paved roads. An effort to improve the logistics associated with route planning is necessary to prevent welfare problems during transport to slaughter. PMID:21240654

  6. Surfactant and pulmonary blood flow distributions following treatment of premature lambs with natural surfactant.

    PubMed Central

    Jobe, A; Ikegami, M; Jacobs, H; Jones, S

    1984-01-01

    Prematurely delivered lambs were treated with radiolabeled natural surfactant by either tracheal instillation at birth and before the onset of mechanical ventilation, or after 23 +/- 1 (+/- SE) min of mechanical ventilation. Right ventricular blood flow distributions, left ventricular outputs, and left-to-right ductal shunts were measured with radiolabeled microspheres. After sacrifice, the lungs of lambs receiving surfactant at birth inflated uniformly with constant distending pressure while the lungs of lambs treated after a period of ventilation had aerated, partially aerated, and atelectatic areas. All lungs were divided into pieces which were weighed and catalogued as to location. The amount of radiolabeled surfactant and microsphere-associated radioactivity in each piece of lung was quantified. Surfactant was relatively homogenously distributed to pieces of lung from lambs that were treated with surfactant at birth; 48% of lung pieces received amounts of surfactant within +/- 25% of the mean value. Surfactant was preferentially recovered from the aerated pieces of lungs of lambs treated after a period of mechanical ventilation, and the distribution of surfactant to these lungs was very nonhomogeneous. Right ventricular blood flow distributions to the lungs were quite homogeneous in both groups of lambs. However, in 8 of 12 lambs, pulmonary blood flow was preferentially directed away from those pieces of lung that received relatively large amounts of surfactant and toward pieces of lung that received less surfactant. This acute redirection of pulmonary blood flow distribution may result from the local changes in compliances within the lung following surfactant instillation. PMID:6546766

  7. Factors associated with the purchase of designation of origin lamb meat.

    PubMed

    Sepúlveda, Wilmer S; Maza, María T; Mantecón, Angel R

    2010-05-01

    As in other products, quality labels that designate the origin of lamb meat are increasingly used by consumers as a cue for inferring the quality of the meat. The aim of the present paper is to identify those factors that most affect the purchase of lamb with an origin quality label. For this purpose a total of 371 questionnaires were carried out in the region of Aragón located in the north east of Spain. This region produces 48.5% of the total amount of lamb meat with a Spanish protected geographical indication, whilst it also has the country's greatest per capita consumption (6.8 kg/person/year). To identify the most determining factors a logistic regression analysis was performed between three groups of buyers, characterised by their degree of loyalty towards purchasing origin quality-labelled lamb. The results show that those buyers who are less loyal to the label pay less attention to the origin of the meat when forming quality expectations at the time of purchase, whilst these are the buyers that place greatest importance on animal feeding as an aspect affecting the final quality of lamb meat. The buyers that are very loyal to the quality label associate this label with a product that offers greater guarantees and is healthier. Lamb meat buyers with medium loyalty to quality labels, consider quality-labelled lamb meat has better intrinsic attributes. PMID:20374881

  8. The impact of genetics on retail meat value in Australian lamb.

    PubMed

    Anderson, F; Pethick, D W; Gardner, G E

    2016-07-01

    Lean (muscle), fat, and bone composition of 1554 lamb carcasses from Maternal, Merino and Terminal sired lambs was measured using computed tomography scanning. Lamb sires were diverse in their range of Australian Sheep Breeding Values for post weaning c-site eye muscle depth (PEMD) and fat depth (PFAT), and post weaning weight (PWWT). Lean value, representing predicted lean weight multiplied by retail value, was determined for lambs at the same carcass weight or the same age. At the same carcass weight, lean value was increased the most by reducing sire PFAT, followed by increasing PEMD and PWWT. However for lambs of the same age, increasing sire PWWT increased lean value the most. Terminal sired lambs, on average, had greater lean value irrespective of whether comparisons were made at the same age or weight. Lean value was greater in Merino compared to Maternal sired lambs at equal carcass weight, however the reverse was true when comparisons were made at the same age. PMID:26974594

  9. Environmental impacts on offspring survival during the lambing period in central Patagonia

    NASA Astrophysics Data System (ADS)

    Coronato, F.

    Weather conditions are the main factors affecting the survival rate of newborn lambs. In the windy climate of Patagonia, the influence of weather conditions is exacerbated as the wind speed increases noticeably in spring. If the wind increases faster than the temperature rises, wind chill conditions worsen temporarily. This departure from the predictable improvement in bioclimatic conditions as the season moves towards summer may coincide with lambing, if this is not adequately regulated. This paper explores bioclimatic conditions during the 2-month period in which lambing may take place (i.e. mid-September to mid-November), and identifies the unfavourable period that occurs in the second fortnight of October. Starting from the Mount and Brown (Agric Meteorol 27:241-255, 1982) model to assess thermal stress in sheep by means of common meteorological records, a simpler model was developed employing in long-term records. For 2-week averages of temperature (Tf), wind speed (Vf) and total precipitation (Pf), the average heat loss in sheep (HLf) was 40.40-2.07Tf+5.64Vf+0.04Pf. (r2=0.95). A 24-year series of Tf, Vf and Pf data was employed in the calculation of HLf, and results showed this parameter was significantly higher in the second fortnight in October. HLf values were classified into four groups (from ''very good'' to ''very bad'' conditions); once again, significant differences appeared in the second fortnight in October. Finally, HLf during the lambing period was correlated to the percentage of lambs surviving 2 months later. Significant differences between the survival of lambs born under ''very bad'' and ''very good'' conditions were found, but intermediate HLf conditions did not show a clear pattern. The survival rate was best correlated to HLf in the fortnight preceding lambing (P<0.05). This suggests that bioclimatic conditions during late pregnancy are at least as important as conditions during lambing in determining the survival lambs.

  10. Anthelmintic effects of Salix babylonica L. and Leucaena leucocephala Lam. extracts in growing lambs.

    PubMed

    Hernandez, Pablo Mejia; Salem, Abdelfattah Z M; Elghandour, Mona M M Y; Cipriano-Salazar, Moisés; Cruz-Lagunas, Blas; Camacho, Luis Miguel

    2014-01-01

    Twenty Katahdin × Pelibuey crossbreed male lambs, 3 to 4 months of age and 24 ± 0.3 kg of body weight, were used to study the anthelmintic effects of administering extracts of Salix babylonica L. (SB) and Leucaena leucocephala Lam. (LL). Lambs had not been treated with anthelmintics previously and were randomly allocated into four groups of five lambs each in a completely randomized design. Treatments were as follows: control (lambs fed on total mixed ration without extracts), SB (as control plus S. babylonica L. extract at 30 ml/day), LL (as control plus L. leucocephala Lam. extract at 30 ml/day), and SBLL (as control plus 30 ml/day of S. babylonica L. and L. leucocephala Lam. extracts in a 1:1 (v/v) mixture) for 63 days. Extracts were orally administered before the 8:00 a.m. feeding to each lamb. Rectal fecal samples were collected from each lamb at day 22 (P1), day 43 (P2), and day 63 (P3) of the experiment. Adult worm and egg counts were determined in each fecal sample immediately after collection. Plant secondary metabolites of total phenolics, saponins, and the aqueous fraction were 50 % lower in the SB versus LL extracts. Overall, the oral administration of extracts has improved the egg and worm count reductions in lamb feces by 54, 47, and 40 % for LL, SB, and SBLL, respectively, versus the control lambs. Reductions of worm egg counts in lamb feces were higher (P < 0.05) in P2 and P3 versus P1. Extracts of SB and LL or possibly isolated bioactive compounds could be a promising alternative to conventional anthelmintics to treat gastrointestinal parasites of small ruminants. Such treatments could be used in control strategies against gastrointestinal nematodes in organic and conventional production systems. PMID:24077919

  11. Reproductive and sexual behaviour development of dam or artificially reared male lambs.

    PubMed

    Damián, Juan Pablo; Beracochea, Florencia; Hötzel, Maria José; Banchero, Georgget; Ungerfeld, Rodolfo

    2015-08-01

    The objective of this study was to determine if artificially reared male lambs differ from those reared by their mothers in their reproductive development and sexual behaviour during the first breeding season and in their serum testosterone to a GnRH challenge at the end of the first breeding season. Lambs were assigned to two experimental groups: 1) artificially reared lambs, separated from their dams 24-36h after birth (Week 0) and fed sheep milk until 10weeks of age (group AR, n=14); and 2) lambs reared by their dams until 10weeks of age (group DR, n=13). Reproductive parameters and sexual behaviour were recorded from Weeks 9 to 39. The GnRH challenge was performed on Week 40. Body weight, scrotal circumference, gonado-somatic index, testosterone concentration and sperm parameters were unaffected by group, but increased with age (P<0.0001). Lambs reared by their mothers had greater values of gonado-somatic index on Weeks 9, 16 and 19 (P<0.05), and tended to reach puberty earlier than AR (22.9±0.7 vs. 25.1±1.1weeks, respectively, P=0.087). Lambs reared by their mothers presented more lateral approaches and mount attempts than AR (P<0.05), and DR lambs presented more mounts on Weeks 32 and 39 than AR (P<0.05). Blood testosterone concentrations 3.5 and 4h after the GnRH challenge were higher in AR than in DR lambs (P<0.05). In conclusion mother rearing promoted sexual behaviour and reproductive performance of male lambs. PMID:25846838

  12. Anthelmintic effects of Salix babylonica L. and Leucaena leucocephala Lam. extracts in growing lambs.

    PubMed

    Hernandez, Pablo Mejia; Salem, Abdelfattah Z M; Elghandour, Mona M M Y; Cipriano-Salazar, Moisés; Cruz-Lagunas, Blas; Camacho, Luis Miguel

    2014-01-01

    Twenty Katahdin × Pelibuey crossbreed male lambs, 3 to 4 months of age and 24 ± 0.3 kg of body weight, were used to study the anthelmintic effects of administering extracts of Salix babylonica L. (SB) and Leucaena leucocephala Lam. (LL). Lambs had not been treated with anthelmintics previously and were randomly allocated into four groups of five lambs each in a completely randomized design. Treatments were as follows: control (lambs fed on total mixed ration without extracts), SB (as control plus S. babylonica L. extract at 30 ml/day), LL (as control plus L. leucocephala Lam. extract at 30 ml/day), and SBLL (as control plus 30 ml/day of S. babylonica L. and L. leucocephala Lam. extracts in a 1:1 (v/v) mixture) for 63 days. Extracts were orally administered before the 8:00 a.m. feeding to each lamb. Rectal fecal samples were collected from each lamb at day 22 (P1), day 43 (P2), and day 63 (P3) of the experiment. Adult worm and egg counts were determined in each fecal sample immediately after collection. Plant secondary metabolites of total phenolics, saponins, and the aqueous fraction were 50 % lower in the SB versus LL extracts. Overall, the oral administration of extracts has improved the egg and worm count reductions in lamb feces by 54, 47, and 40 % for LL, SB, and SBLL, respectively, versus the control lambs. Reductions of worm egg counts in lamb feces were higher (P < 0.05) in P2 and P3 versus P1. Extracts of SB and LL or possibly isolated bioactive compounds could be a promising alternative to conventional anthelmintics to treat gastrointestinal parasites of small ruminants. Such treatments could be used in control strategies against gastrointestinal nematodes in organic and conventional production systems.

  13. Embryo development, fetal growth and postnatal phenotype of eGFP lambs generated by lentiviral transgenesis.

    PubMed

    Crispo, M; Vilariño, M; dos Santos-Neto, P C; Núñez-Olivera, R; Cuadro, F; Barrera, N; Mulet, A P; Nguyen, T H; Anegón, I; Menchaca, A

    2015-02-01

    Lentiviral technology has been recently proposed to generate transgenic farm animals more efficiently and easier than traditional techniques. The objective was to evaluate several parameters of lambs obtained by lentiviral transgenesis in comparison with non-transgenic counterparts. In vitro produced embryos were microinjected (TG group) at two-cell stage with a lentiviral construct containing enhanced green fluorescent protein (eGFP) gene, while embryos produced by in vitro fertilization (IVF group) or intrauterine insemination (IUI group) were not microinjected. Microinjection technique efficiently generated eight-cell transgenic embryos (97.4%; 114/117). Development rate on day 5 after fertilization was similar for TG (39.3%, 46/117) and IVF embryos (39.6%, 44/111). Pregnancy rate was detected in 50.0% (6/12) of recipient ewes with TG embryos, in 46.7% (7/15) with IVF embryos, and in 65.0% (13/20) of IUI ewes (P = NS). Nine lambs were born in TG group, six lambs in IVF group, and 16 lambs in IUI group. All TG lambs (9/9) were GFP positive to real-time PCR and eight (88.9%) showed a strong and evident GFP expression in mucosae, eyes and keratin tissues. Fetal growth monitored every 15 day by ultrasonography did not show significant differences. Transgenic lambs neither differ in morphometric variables in comparison with non transgenic IVF lambs within 3 months after birth. Transmission of the transgene to the progeny was observed in green fluorescent embryos produced by IVF using semen from the TG founder lambs. In conclusion, this study demonstrates the high efficiency of lentiviral technology to produce transgenic sheep, with no clinic differences in comparison with non transgenic lambs.

  14. Isolation of Streptococcus suis from 2 lambs with a history of lameness

    PubMed Central

    Muckle, Anne; López, Alfonso; Gottschalk, Marcelo; López-Méndez, Carlos; Giles, Jan; Lund, Lorraine; Saab, Matthew

    2014-01-01

    Streptococcus suis was isolated postmortem from 2 lambs with a history of lameness. Identity of S. suis was confirmed by species-specific polymerase chain reaction (PCR) and by 16S rRNA gene sequencing. One isolate was untypable by serotyping and non-encapsulated, while the other isolate was serotype 33. The lambs had come from the same farm, and there was no evidence of contact between the lambs and pigs. Although the natural niche for S. suis is considered to be the pig, a wide range of host species may be affected by this pathogen. PMID:25320381

  15. Michael E. Lamb: Award for Distinguished Senior Career Contributions to Psychology in the Public Interest.

    PubMed

    2015-11-01

    The APA Awards for Distinguished Contributions to Psychology in the Public Interest recognize persons who have advanced psychology as a science and/or profession by a single extraordinary achievement or a lifetime of outstanding contributions in the public interest. The 2015 co-recipient of the Award for Distinguished Senior Career Contributions to Psychology in the Public Interest is Michael E. Lamb. Lamb was selected because his "work profoundly shaped the fields of developmental psychology, social welfare, child and family policy, and law." Lamb's award citation, biography, and a selected bibliography are presented here.

  16. The effect of cyclical and severe heat stress on growth performance and metabolism in Afshari lambs.

    PubMed

    Mahjoubi, E; Yazdi, M Hossein; Aghaziarati, N; Noori, G R; Afsarian, O; Baumgard, L H

    2015-04-01

    The extent to which reduced feed intake contributes to decreased growth during heat stress (HS) in the ovine model is not clear. To evaluate the impact of decreased DMI on performance, we conducted an experiment on growing lambs experiencing a cyclical but extensive heat load. Sixteen intact male Afshari lambs (40.1 ± 1.9 kg) were used in a completely randomized design in 2 periods. In period 1, all 16 lambs were housed in thermal neutral (TN) conditions (22.2 ± 3.1°C and a temperature-humidity index [THI] of 67.9 ± 3.2) and fed at libitum for 8 d. In period 2 (P2), which lasted 9 d, 8 lambs were subjected to a cyclical HS condition (33.0 to 45.0°C and a THI of more than 80 at least for 24 h/d and more than 90 for 8 h/d). The other 8 lambs were maintained in TN conditions but pair-fed (pair-fed thermal neutral [PFTN]) to the HS lambs. During each period, DMI and water intake were measured daily. Respiration rate, rectal temperature, and skin temperature at the shoulder, rump, and front and rear leg were recorded at 0700 and 1400 h daily. Dry matte intake declined (17.5%; P < 0.01) in HS lambs and, by design, the temporal pattern and magnitude of reduced feed intake was similar in the PFTN controls. Water intake increased (19%; P < 0.05) during P2 in HS but not in the PFTN controls. Heat stress increased the 0700 and 1400 h skin temperature at the shoulder (5 and 9.2%), rump (6.2 and 10.3%), rear (6 and 9.2%), and front leg (6.5 and 9.8%) and respiratory rates (84 and 163% [P < 0.01]at 0700 and 1400 h, respectfully), but only the 1400 h rectal temperature was increased (P < 0.01; 0.65°C) in HS lambs. Neither environment nor period affected blood urea nitrogen and glucose concentrations. However, circulating NEFA and insulin were increased and declined (P < 0.01) in PFTN lambs, respectively, but neither variable was altered in the HS lambs. Growth was reduced in P2 for lambs in both treatments, but despite being on a similar reduced plane of nutrition, the HS

  17. Effect of maternal cold exposure on brown adipose tissue and thermogenesis in the neonatal lamb.

    PubMed

    Symonds, M E; Bryant, M J; Clarke, L; Darby, C J; Lomax, M A

    1992-09-01

    1. This study examines the effect of chronic cold exposure during pregnancy, induced by winter shearing twin-bearing ewes 4 weeks before predicted lambing date, on O2 consumption and CO2 production during non-rapid-eye-movement (REM) sleep in lambs maintained for at least 1 h at warm (28-18 degrees C) and cold (14-5 degrees C) ambient temperatures at 1, 4, 14 and 30 days of age. This was combined with measurement of the thermogenic activity (GDP binding to uncoupling protein in mitochondrial preparations) of perirenal adipose tissue from lambs immediately after birth and at 33 days of age. 2. Lambs born from shorn (cold-exposed) ewes were 15% heavier (P < 0.01) and possessed 21% (P < 0.01) more perirenal adipose tissue that contained 40% more protein and mitochondrial protein than unshorn (P < 0.05) controls. Total GDP binding in perirenal adipose tissue was 40% greater (P < 0.05) in lambs born from shorn ewes but there was no difference in lipid content of this tissue between the two groups. 3. At 1 day of age, lambs born from shorn ewes exhibited a 16% higher (P < 0.05) rate of O2 consumption (per kilogram bodyweight) at the warm temperature and a 40% greater metabolic response to the cold ambient temperature. All lambs born from shorn ewes responded to cold exposure without shivering (i.e. via non-shivering thermogenesis) whilst shivering was measured in four out of seven lambs in the unshorn group. These differences had disappeared by 4 days of age as a result of a 25% increased (P < 0.01) rate of O2 consumption in the warm in lambs born from unshorn ewes and a 20% decrease (P < 0.05) in the response to the cold in lambs from shorn ewes. Shivering during cold exposure was measured in six out of nine lambs born from shorn ewes indicating a rapid alteration in thermoregulatory responses to cold during the first few days of life. 4. The levels of GDP binding and mitochondrial protein in perirenal adipose tissue fell by one-third in both groups of lambs during the

  18. The effect of cyclical and severe heat stress on growth performance and metabolism in Afshari lambs.

    PubMed

    Mahjoubi, E; Yazdi, M Hossein; Aghaziarati, N; Noori, G R; Afsarian, O; Baumgard, L H

    2015-04-01

    The extent to which reduced feed intake contributes to decreased growth during heat stress (HS) in the ovine model is not clear. To evaluate the impact of decreased DMI on performance, we conducted an experiment on growing lambs experiencing a cyclical but extensive heat load. Sixteen intact male Afshari lambs (40.1 ± 1.9 kg) were used in a completely randomized design in 2 periods. In period 1, all 16 lambs were housed in thermal neutral (TN) conditions (22.2 ± 3.1°C and a temperature-humidity index [THI] of 67.9 ± 3.2) and fed at libitum for 8 d. In period 2 (P2), which lasted 9 d, 8 lambs were subjected to a cyclical HS condition (33.0 to 45.0°C and a THI of more than 80 at least for 24 h/d and more than 90 for 8 h/d). The other 8 lambs were maintained in TN conditions but pair-fed (pair-fed thermal neutral [PFTN]) to the HS lambs. During each period, DMI and water intake were measured daily. Respiration rate, rectal temperature, and skin temperature at the shoulder, rump, and front and rear leg were recorded at 0700 and 1400 h daily. Dry matte intake declined (17.5%; P < 0.01) in HS lambs and, by design, the temporal pattern and magnitude of reduced feed intake was similar in the PFTN controls. Water intake increased (19%; P < 0.05) during P2 in HS but not in the PFTN controls. Heat stress increased the 0700 and 1400 h skin temperature at the shoulder (5 and 9.2%), rump (6.2 and 10.3%), rear (6 and 9.2%), and front leg (6.5 and 9.8%) and respiratory rates (84 and 163% [P < 0.01]at 0700 and 1400 h, respectfully), but only the 1400 h rectal temperature was increased (P < 0.01; 0.65°C) in HS lambs. Neither environment nor period affected blood urea nitrogen and glucose concentrations. However, circulating NEFA and insulin were increased and declined (P < 0.01) in PFTN lambs, respectively, but neither variable was altered in the HS lambs. Growth was reduced in P2 for lambs in both treatments, but despite being on a similar reduced plane of nutrition, the HS

  19. Cardiovascular and endocrine response to hemorrhage after. cap alpha. /sub 1/-blockade in lambs and ewes

    SciTech Connect

    Block, S.M.; Rose, J.C.; Ernest, J.M.; Flowe, K.; South, S.; Zimmerman, C.

    1987-02-01

    To evaluate the role of the ..cap alpha../sub 1/-adrenergic system in the response to hemorrhage during development, lambs and adult sheep were chronically catheterized and hemorrhaged after pretreatment with prazosin or vehicle. The adults became markedly more hypotensive after ..cap alpha../sub 1/-blockade and hemorrhage than after vehicle and hemorrhage, whereas the lambs were no more hypotensive when hemorrhaged after prazosin. In the adults and the lambs hemorrhage produced elevations in plasma renin activity and arginine vasopressin measured by radioimmunoassay. However, after prazosin, the adults had a far greater increase in arginine vasopressin levels than after vehicle treatment.

  20. Periconceptional growth hormone treatment alters fetal growth and development in lambs.

    PubMed

    Koch, J M; Wilmoth, T A; Wilson, M E

    2010-05-01

    Research in the area of fetal programming has focused on intrauterine growth restriction. Few studies have attempted to examine programming mechanisms that ultimately lead to lambs with a greater potential for postnatal growth. We previously demonstrated that treatment of ewes with GH at the time of breeding led to an increase in birth weight. Therefore, the objective of this study was to determine the effects of a single injection of sustained-release GH given during the periconceptional period on fetal growth and development and to determine if the GH axis would be altered in these offspring. Estrus was synchronized using 2 injections of PGF(2alpha); at the time of the second injection, ewes assigned to treatment were also given an injection of sustained-release GH. A maternal jugular vein sample was taken weekly to analyze IGF-I as a proxy for GH to estimate the duration of the treatment effect. In ewes treated with GH, IGF-I increased (P < 0.05) by wk 1 and remained elevated until wk 4 postinjection. Lambs were weighed, crown-rump length and abdominal girth were determined, and a plasma sample was collected. In a subset of male lambs, liver, heart, and brain weights were obtained, as well as left and right ventricular wall thicknesses. On postnatal d 100, a subset of ewe lambs were weighed and challenged with an intravenous injection of GHRH. Lambs from treated ewes had increased (P < 0.05) birth weight and abdominal girth compared with control lambs; however, there was no difference in crown-rump length. Expression of GH receptor and IGF-I were increased (P < 0.05) in lambs gestated by GH-treated ewes compared with control ewes. The left ventricular wall was thinner (P < 0.05) from lambs in the GH-treated group compared with control lambs. On postnatal d 100, those ewe lambs born to ewes treated with GH continued to be heavier (P < 0.05) and had no IGF-I response to GHRH challenge. In conclusion, treating ewes with a single injection of GH appeared to alter

  1. A case of omphalo-ischiopagus (dicephalic dithoracic abdominopagus tetrascelus tetrabrachius) in lambs.

    PubMed

    Samuel, M O; Wachida, N; Abenga, J H; Kisani, A I; Adamu, S S; Hambesha, P; Gyang, E; Oyedipe, E O

    2014-08-01

    This case report describes a rare occurrence of asymmetrical conjoined twinning in lambs in Makurdi (Benue state), Middle Belt region of Nigeria. The conjoined twins were delivered normally by a multiparous ewe of about three and a half years old; the female twins had two complete set of limbs. Barium meal and X-ray revealed abnormalities of the skeletal, digestive, urinary and reproductive systems. This condition is rare in sheep and is to the best of our knowledge the first report of omphalo-ishiopagus (dicephalic dithoracic tetrabrachius) twinned lambs. The condition always leads to death of the twin lambs due to various physical abnormalities. PMID:23738777

  2. Maternal influence on feeding site selection of male and female lambs.

    PubMed

    Wesley, R L; Cibils, A F; Black-Rubio, C M; Pollak, E R; Utsumi, S A

    2014-06-01

    We conducted an experiment to determine whether early-life social learning of feeding site selection in lambs was sex-specific. Sixteen ewes and their new born lambs were used in a controlled experiment. Eight ewe-lamb pairs included a male lamb and the remaining eight a female lamb. All pairs were individually exposed to an experimental arena containing a safe and unsafe artificial feeding site (SFS, UFS) each consisting of nine bowls which contained either ground Bermuda grass hay (SFS) or ground alfalfa hay (UFS). The bowls in UFS were surrounded by bright orange traffic cones (visual cues). Half the ewes were trained with controlled electric shock to avoid UFS. Thus, pairs were randomly assigned to: (1) shock aversion training (SAT) to mothers of male lambs (MS); (2) SAT to mothers of female lambs (FS); (3) no aversion training (NAT, control) to mothers of male lambs (MC); and (4) NAT (control) to mothers of female lambs (FC). None of the lambs were subjected to SAT. During training, testing, extinction, and retraining ewe-lamb pairs were exposed to the arena together. Ewes were then removed from the experiment and two additional extinction phases were conducted with weaned lambs alone. Fear conditioning elicited UFS avoidance of both the trained ewes (means±s.e.m. % times observed in UFS during testing phase: FC=95.3±1.70; MC=94.4±4.87; FS=1.6±1.63; MS=0 ±0; P<0.01) and their naïve lambs (FC=83.8±6.07%; MC=76.6±6.56%; FS=30.4±7.90%; MS=33.9±9.23%; P<0.01). UFS avoidance in lambs occurred regardless of sex and tended to persist after weaning (% times observed in UFS during 1st post-weaning extinction phase: FC=92.6±4.50%; MC=89.8±6.09%; FS=45.1±10.57%; MS=43.5±10.42%; P=0.06). Fear conditioning in mothers appeared to alter sex-related differences in mother-infant behavioral synchrony by increasing and decreasing feeding synchrony of male and female lambs, respectively (FC: r=0.52, P<0.01; MC: r=-0.02, P=0.86; FS: r=0.14, P=0.26; MS: r=0.46, P<0

  3. The impact of lambing stress on post-parturient behaviour of sheep with consequences on neonatal homeothermy and survival.

    PubMed

    Darwish, R A; Ashmawy, T A M

    2011-10-01

    During lambing the expression of an appropriate behavioural response from both the ewe and the lamb are extremely important to lamb survival. The aim of this study was to show the effect of length and difficulty of the birth process on the expression of maternal and neonatal behaviour with consequences on homeothermy and survival of the neonate lamb. Data were collected from 61 Finnish Landrace × Rahmani crossbred (second generation) primiparous ewes and their single born lambs. Based on the average length of parturition, the ewes were grouped into short birth (less than 32.5 min) and long birth (equal to or higher than 32.5 min) classes. The data recorded include maternal and neonatal behaviour, lamb body temperature over the first 3 days of life and survival rate of the neonate lamb during the first week after birth. Blood samples were also collected from the lamb, pre-suckling and at 24 and 72 h after birth. The obtained sera were assayed for thyroid hormones (T(3) and T(4)) that are associated with heat production. Ewes that had prolonged and difficult births did not show competent maternal behaviour compared to mothers with short and un-complicated deliveries, as they were slower to begin grooming their lambs after birth, spent less time licking their lambs, made less low-pitched vocalizations and nosing, were more likely to show rejection behaviour (10.34 % vs 5.4 %, P < 0.05), and were more likely to move away when the lamb sought the udder in an attempt to suck (acceptance rate, 55.5 % vs 64.79 %, P < 0.05). Similarly, lambs from a prolonged and difficult birth were significantly less vigorous after birth, as they had taken more time to stand, reach the udder and to suck successfully. These lambs had lower serum concentrations of T(3) and T(4), and they also had a reduced ability to maintain body temperature after birth. This effect persisted over the first 3 days of life and was associated with higher neonatal mortality in the first week after birth (11

  4. Enhancement technology improves palatability of normal and callipyge lambs.

    PubMed

    Everts, A K R; Wulf, D M; Wheeler, T L; Everts, A J; Weaver, A D; Daniel, J A

    2010-12-01

    The objective of this research was to determine if BPI Processing Technology (BPT) improved palatability of normal (NN) and callipyge (CN) lamb meat and to determine the mechanism by which palatability was improved. Ten ewe and 10 wether lambs of each phenotype were slaughtered, and carcass traits were assessed by a trained evaluator. The LM was removed at 2 d postmortem. Alternating sides served as controls (CON) or were treated with BPT. Muscles designated BPT were injected to a target 120% by weight with a patented solution containing water, ammonium hydroxide, carbon monoxide, and salt. Muscle pH, cooking loss, Warner-Bratzler shear force (WBS), sarcomere length, cooked moisture retention, and desmin degradation were measured. A trained sensory panel and a take-home consumer panel evaluated LM chops. Callipyge had a heavier BW and HCW, less adjusted fat thickness, reduced yield grades, and greater conformation scores than NN (P < 0.05). For LM, NN had shorter sarcomeres, smaller WBS values, greater juiciness ratings, more off-flavors, reduced consumer ratings for raw characteristics (like of portion size, like of color, like of leanness, overall like of appearance) and greater consumer ratings for eating characteristics (like of juiciness, like of flavor) than CN (P < 0.05). For LM, BPT had greater cooked moisture retention, smaller WBS values, greater juiciness ratings, less off-flavors, and greater consumer ratings for raw characteristics (like of portion size, like of color, overall like of appearance) and eating characteristics (like of juiciness, like of flavor) than CON (P < 0.05). Significant phenotype × treatment interactions occurred for LM muscle pH, desmin degradation, tenderness, consumer like of texture/tenderness, and consumer overall like of eating quality (P < 0.05). For LM, BPT increased muscle pH more for NN than CN (P < 0.01) and increased desmin degradation for NN but decreased desmin degradation for CN (P < 0.01). The BPT enhancement

  5. Dietary protein and chromium tripicolinate in Suffolk wether lambs: effects on production characteristics, metabolic and hormonal responses, and immune status.

    PubMed

    Gentry, L R; Fernandez, J M; Ward, T L; White, T W; Southern, L L; Bidner, T D; Thompson, D L; Horohov, D W; Chapa, A M; Sahlu, T

    1999-05-01

    Thirty-two Suffolk wether lambs were fed for 84 d in a 2 x 2 factorial experiment using two levels of dietary protein (9.0 to 12.1% CP, low protein, LP; or 12.8 to 14.4% CP, high protein, HP) and supplemental Cr (none, C; or 400 ppb Cr as chromium tripicolinate, Cr). At 14- to 21-d intervals, lambs were weighed, and jugular blood samples were collected. Mean ADG and carcass weight (P > .10) did not differ. In lambs fed HP, Cr reduced liver weight and increased kidney weight (P < .01). Lambs fed HP had elevated plasma urea N (PUN; P < .01) and albumin (P < .04). During an i.v. epinephrine challenge on d 43, plasma cortisol declined in lambs fed Cr (Cr x time, P < .03) and in lambs fed LP (CP x time, P < .001). An i.v. glucose tolerance test conducted 3 h later showed that supplemental Cr decreased glucose clearance rate in lambs fed HP (CP x Cr, P < .10) but not in lambs fed LP. On d 62, PUN was increased in lambs fed HP (P < .001) between 0 and 3 h postprandial, and there was a Cr x CP interaction (P < .04). Postprandial plasma NEFA declined with Cr vs C (Cr x time, P < .07) and with HP vs LP (CP x time, P < .10). By d 66, lambs fed Cr had an elevated (P < .03) blood platelet and fibrinogen content. Chromium increased erythrocyte count in lambs fed HP (Cr x CP, P < .08), and isolated peripheral lymphocytes had greater blastogenic response to 4 microg/mL of phytohemagglutinin (Cr x CP, P < .001). The lymphocyte response to pokeweed mitogen (.2 microg/mL) was reduced in lambs fed Cr (P < .10). In the present experiment, Cr supplementation had minimal and inconsistent effects on production and metabolic criteria of lambs.

  6. JOINT RIGIDITY ASSESSMENT WITH PIEZOELECTRIC WAFERS AND ACOUSTIC WAVES

    SciTech Connect

    Montoya, Angela C.; Maji, Arup K.

    2010-02-22

    There has been an interest in the development of rapid deployment satellites. In a modular satellite design, different panels of specific functions can be pre-manufactured. The satellite can then be assembled and tested just prior to deployment. Traditional vibration testing is time-consuming and expensive. An alternative test method to evaluate the connection between two plates will be proposed. The method investigated and described employs piezoelectric wafers to induce and sense lamb waves in two aluminum plates, which were joined by steel brackets to form an 'L-Style' joint. Lamb wave behavior and piezoelectric material properties will be discussed; the experimental setup and results will be presented. A set of 4 piezoelectric ceramic wafers were used alternately as source and sensor. The energy transmitted was shown to correlate with a mechanical assessment of the joint, demonstrating that this method of testing is a feasible and reliable way to inspect the rigidity of joints.

  7. Fatty acids and oxidative stability of meat from lambs fed carob-containing diets.

    PubMed

    Gravador, Rufielyn S; Luciano, Giuseppe; Jongberg, Sisse; Bognanno, Matteo; Scerra, Manuel; Andersen, Mogens L; Lund, Marianne N; Priolo, Alessandro

    2015-09-01

    Male Comisana lambs were individually stalled and, for 56 days, were fed concentrates with 60% barley (n = 8 lambs), or concentrates in which barley was partially replaced by 24% or 35% carob pulp (n = 9 lambs in each group). The intramuscular fatty acids were analyzed and the color stability, lipid and protein oxidation were measured in fresh meat overwrapped with polyvinyl chloride film at 0, 3 or 6 days of storage at 4 °C in the dark. Carob pulp increased the concentration of polyunsaturated fatty acids (PUFA) in muscle, including the rumenic acid (P < 0.01), and reduced the saturated fatty acids (P < 0.01) and the n-6/n-3 PUFA ratio (P = 0.01). The meat did not undergo extensive oxidative deterioration and the diet did not affect the oxidative stability parameters. Therefore, carob in lamb diet could increase PUFA in muscle without compromising meat oxidative stability.

  8. Cell-mediated immune responses of lambs to challenge with bovine respiratory syncytial virus.

    PubMed Central

    Sharma, A K; Woldehiwet, Z

    1995-01-01

    The lamb is a good model to study the pathogenesis and immune responses to infections with respiratory syncytial virus (RSV) as lambs experimentally infected with bovine or human RSV may develop overt clinical disease. In the present study the development of cellular cytotoxic responses was studied in splenic, pulmonary and peripheral blood mononuclear cells obtained from lambs after primary and secondary infection with bovine RSV. Infection with bovine RSV was followed by the appearance of cytotoxic cells in the peripheral blood, the spleen and lung lavage fluids. These effector cells lysed virus-infected targets in a self-restricted manner. Depletion techniques revealed that cytotoxic activity was largely due to OvCD8+ cells. When effector cells obtained from primed lambs were stimulated with inactivated bovine RSV or with virus-infected cells in vitro, virus-specific cytotoxicity was significantly increased. PMID:7544251

  9. Fatty acids and oxidative stability of meat from lambs fed carob-containing diets.

    PubMed

    Gravador, Rufielyn S; Luciano, Giuseppe; Jongberg, Sisse; Bognanno, Matteo; Scerra, Manuel; Andersen, Mogens L; Lund, Marianne N; Priolo, Alessandro

    2015-09-01

    Male Comisana lambs were individually stalled and, for 56 days, were fed concentrates with 60% barley (n = 8 lambs), or concentrates in which barley was partially replaced by 24% or 35% carob pulp (n = 9 lambs in each group). The intramuscular fatty acids were analyzed and the color stability, lipid and protein oxidation were measured in fresh meat overwrapped with polyvinyl chloride film at 0, 3 or 6 days of storage at 4 °C in the dark. Carob pulp increased the concentration of polyunsaturated fatty acids (PUFA) in muscle, including the rumenic acid (P < 0.01), and reduced the saturated fatty acids (P < 0.01) and the n-6/n-3 PUFA ratio (P = 0.01). The meat did not undergo extensive oxidative deterioration and the diet did not affect the oxidative stability parameters. Therefore, carob in lamb diet could increase PUFA in muscle without compromising meat oxidative stability. PMID:25842304

  10. Nondestructive evaluation of helicopter rotor blades using guided Lamb modes.

    PubMed

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2014-03-01

    This paper presents an application for turning and direct modes in a complex composite laminate structure. The propagation and interaction of turning modes and fundamental Lamb modes are investigated in the skin, spar and web sections of a helicopter rotor blade. Finite element models were used to understand the various mode conversions at geometric discontinuities such as web-spar joints. Experimental investigation was carried out with the help of air coupled ultrasonic transducers. The turning and direct modes were confirmed with the help of particle displacements and velocities. Experimental B-Scans were performed on damaged and undamaged samples for qualitative and quantitative assessment of the structure. A strong correlation between the numerical and experimental results was observed and reported. PMID:24210414

  11. Theory of the Lamb shift in muonic helium ions

    SciTech Connect

    Krutov, A. A.; Martynenko, A. P. Martynenko, G. A.; Faustov, R. N.

    2015-01-15

    The Lamb shift (2P{sub 1/2}-2S{sub 1/2}) in muonic helium ions (μ{sub 2}{sup 3}){sup +}, (μ{sup 2/4}He){sup +} is calculated taking into account the contributions of the order of α{sup 3}, α{sup 4}, α{sup 5}, and α{sup 6}. Special attention is paid to corrections for the polarization of the vacuum, as well as the structure and recoil of the nucleus. Numerical values 1259.8583 meV ((μ{sub 2}{sup 3}He){sup +}) and 1379.1107 meV ((μ{sub 2}{sup 4}He){sup +}) obtained for the shifts can be considered reliable estimates when compared to the experimental data of the CREMA collaboration.

  12. Nondestructive evaluation of helicopter rotor blades using guided Lamb modes.

    PubMed

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2014-03-01

    This paper presents an application for turning and direct modes in a complex composite laminate structure. The propagation and interaction of turning modes and fundamental Lamb modes are investigated in the skin, spar and web sections of a helicopter rotor blade. Finite element models were used to understand the various mode conversions at geometric discontinuities such as web-spar joints. Experimental investigation was carried out with the help of air coupled ultrasonic transducers. The turning and direct modes were confirmed with the help of particle displacements and velocities. Experimental B-Scans were performed on damaged and undamaged samples for qualitative and quantitative assessment of the structure. A strong correlation between the numerical and experimental results was observed and reported.

  13. Nuclear polarization corrections to the μ4He+ Lamb shift.

    PubMed

    Ji, C; Nevo Dinur, N; Bacca, S; Barnea, N

    2013-10-01

    Stimulated by the proton radius conundrum, measurements of the Lamb shift in various light muonic atoms are planned at PSI. The aim is to extract the rms charge radius with high precision, limited by the uncertainty in the nuclear polarization corrections. We present an ab initio calculation of the nuclear polarization for μ(4)He(+) leading to an energy correction in the 2S-2P transitions of δ(pol)(A)=-2.47 meV ±6%. We use two different state-of-the-art nuclear Hamiltonians and utilize the Lorentz integral transform with hyperspherical harmonics expansion as few-body methods. We take into account the leading multipole contributions, plus Coulomb, relativistic, and finite-nucleon-size corrections. Our main source of uncertainty is the nuclear Hamiltonian, which currently limits the attainable accuracy. Our predictions considerably reduce the uncertainty with respect to previous estimates and should be instrumental to the μ(4)He(+) experiment planned for 2013.

  14. Morphological studies of front limb deformities in lambs.

    PubMed

    Uhthoff, H K; Liskova-Kiar, M; Hidiroglou, M

    1980-05-01

    Long bones of 16 3- to 6-month-old lambs with bowed forelimbs underwent radiologic, microradiographic and histologic examinations. The distal ends of the radii showed a combination of valgus, flexion and internal rotation. There were thin cortical bone and large marrow cavity adjacent to the growth plate in the radii and metacarpi. Histological studies showed increased numbers of osteoclasts adjacent to the zone of calcified cartilage of the growth plate. The trabeculae of primary and secondary spongiosa were fewer and thinner than those of controls. The length of secondary spongiosa were greatly reduced and the lateral compaction of the metaphysis was defective. The growth plate was normal. The predominant finding was osteoporosis resulting from increased osteoclastic resorption of bone trabeculae.

  15. The key components of resistance to Ostertagia circumcincta in lambs.

    PubMed

    Stear, M J; Park, M; Bishop, S C

    1996-11-01

    One of the most remarkable features of parasitic infections in general, and Ostertagia circumcincta infection of sheep in particular, is the extensive variation among hosts in resistance to infection, as assessed by parasite burdens and production of eggs or infective larvae. Here Mike Stear, Michael Park and Stephen Bishop describe the factors that account for the variation among animals within a flock, including dam, sire, sex, date of birth and history of exposure to infection. There are no detectable genetic effects in lambs less than three months old. Genetic control of an acquired response develops in two stages: first, a reduction in the average egg production per worm, which is associated with the development of a parasite-specific local IgA response; and second, control of worm burden, which is associated with the production of globule leukocytes in the abomasal mucosa.

  16. Rumen microbial communities influence metabolic phenotypes in lambs

    PubMed Central

    Morgavi, Diego P.; Rathahao-Paris, Estelle; Popova, Milka; Boccard, Julien; Nielsen, Kristian F.; Boudra, Hamid

    2015-01-01

    The rumen microbiota is an essential part of ruminants shaping their nutrition and health. Despite its importance, it is not fully understood how various groups of rumen microbes affect host-microbe relationships and functions. The aim of the study was to simultaneously explore the rumen microbiota and the metabolic phenotype of lambs for identifying host-microbe associations and potential biomarkers of digestive functions. Twin lambs, separated in two groups after birth were exposed to practices (isolation and gavage with rumen fluid with protozoa or protozoa-depleted) that differentially restricted the acquisition of microbes. Rumen microbiota, fermentation parameters, digestibility and growth were monitored for up to 31 weeks of age. Microbiota assembled in isolation from other ruminants lacked protozoa and had low bacterial and archaeal diversity whereas digestibility was not affected. Exposure to adult sheep microbiota increased bacterial and archaeal diversity independently of protozoa presence. For archaea, Methanomassiliicoccales displaced Methanosphaera. Notwithstanding, protozoa induced differences in functional traits such as digestibility and significantly shaped bacterial community structure, notably Ruminococcaceae and Lachnospiraceae lower up to 6 folds, Prevotellaceae lower by ~40%, and Clostridiaceae and Veillonellaceae higher up to 10 folds compared to microbiota without protozoa. An orthogonal partial least squares-discriminant analysis of urinary metabolome matched differences in microbiota structure. Discriminant metabolites were mainly involved in amino acids and protein metabolic pathways while a negative interaction was observed between methylotrophic methanogens Methanomassiliicoccales and trimethylamine N-oxide. These results stress the influence of gut microbes on animal phenotype and show the potential of metabolomics for monitoring rumen microbial functions. PMID:26528248

  17. Rumen microbial communities influence metabolic phenotypes in lambs.

    PubMed

    Morgavi, Diego P; Rathahao-Paris, Estelle; Popova, Milka; Boccard, Julien; Nielsen, Kristian F; Boudra, Hamid

    2015-01-01

    The rumen microbiota is an essential part of ruminants shaping their nutrition and health. Despite its importance, it is not fully understood how various groups of rumen microbes affect host-microbe relationships and functions. The aim of the study was to simultaneously explore the rumen microbiota and the metabolic phenotype of lambs for identifying host-microbe associations and potential biomarkers of digestive functions. Twin lambs, separated in two groups after birth were exposed to practices (isolation and gavage with rumen fluid with protozoa or protozoa-depleted) that differentially restricted the acquisition of microbes. Rumen microbiota, fermentation parameters, digestibility and growth were monitored for up to 31 weeks of age. Microbiota assembled in isolation from other ruminants lacked protozoa and had low bacterial and archaeal diversity whereas digestibility was not affected. Exposure to adult sheep microbiota increased bacterial and archaeal diversity independently of protozoa presence. For archaea, Methanomassiliicoccales displaced Methanosphaera. Notwithstanding, protozoa induced differences in functional traits such as digestibility and significantly shaped bacterial community structure, notably Ruminococcaceae and Lachnospiraceae lower up to 6 folds, Prevotellaceae lower by ~40%, and Clostridiaceae and Veillonellaceae higher up to 10 folds compared to microbiota without protozoa. An orthogonal partial least squares-discriminant analysis of urinary metabolome matched differences in microbiota structure. Discriminant metabolites were mainly involved in amino acids and protein metabolic pathways while a negative interaction was observed between methylotrophic methanogens Methanomassiliicoccales and trimethylamine N-oxide. These results stress the influence of gut microbes on animal phenotype and show the potential of metabolomics for monitoring rumen microbial functions. PMID:26528248

  18. [Castration in the bull calf and ram lamb].

    PubMed

    Steiner, A; Janett, F

    2013-11-01

    This paper aims to provide an overview of the accepted techniques of pain relief and castration and guidelines of how to best perform these painful interventions in an animal-friendly way under Swiss conditions. Calves should be castrated at the age of 14 days or less, at least 10 minutes after local anesthesia with lidocaine, applying a single rubber ring. Concurrently, a NSAID should be administered intravenously (ketoprofen, 3 mg/kg of bodyweight) and Tetanus-serum subcutaneously (off label use). If possible, ketoprofen(4.5 mg/kg BW) should be orally administered for 3 - 5 days postoperatively. At 10 days after applying the rubber ring, the dried-off scrotum including the rubber ring should be removed with a clean knife or a scalpel. Local anesthesia is not necessary for this procedure. Ram lambs should be castrated at the age of 14 days or less, at least 10 minutes after local anesthesia with lidocaine, applying a rubber ring. The toxic dose of 4 mg lidocaine/kg BW (corresponds to 1 ml lidocaine 2 % per lamb of 5 kg BW) should not be exceeded. Concurrently, a NSAID (off label use) and Tetanus-serum should be administered systemically. Immunization against GnRH represents an animal-friendly and economically feasible alternative to rubber ring castration. With two immunizations at an interval of 3 - 4 weeks testicular development can be inhibited for at least 3 months and the onset of puberty clearly delayed. However, a specific vaccine for use in ruminants is currently registered neither in Switzerland nor in Europe.

  19. Unpredictable feeding impairs glucose tolerance in growing lambs.

    PubMed

    Jaquiery, Anne L; Oliver, Mark H; Landon-Lane, Nina; Matthews, Samuel J; Harding, Jane E; Bloomfield, Frank H

    2013-01-01

    Irregular eating is associated with insulin resistance and metabolic disease in adults but may affect young, growing children differently. We investigated the metabolic effects of unpredictable feeding in female juvenile lambs randomly assigned to receive, for six weeks, maintenance feed given twice daily in equal portions (Control Group, C; n = 24) or the same weekly feed amount in aliquots of variable size at unpredictable times (Unpredictable Group, U; n = 21). Intravenous glucose tolerance tests (IVGTT), insulin tolerance tests (ITT), and measurement of diurnal plasma cortisol concentrations were performed pre and post the dietary intervention. Groups were compared using t test and RM ANOVA. Weight gain was similar in both groups (C 18 ± 2%; U 16 ± 2% of initial body weight). Glucose area under the curve (AUC) was unchanged in C (AUC pre 818 ± 34, post 801 ± 33 mmol.min.l(-1)), but increased by 20% in U (pre 830 ± 25, post 1010 ± 19 mmol.min.l(-1); p<0.0001), with an inadequate insulin response to glucose load (log(AUC insulin first 40 minutes) post intervention C 1.49 ± 0.04 vs U 1.36 ± 0.04 ng.min.ml(-1); p = 0.03). Insulin tolerance and diurnal variation of plasma cortisol concentrations were not different between groups. Unpredictable feeding impairs insulin response to glucose in growing lambs despite high quality food and normal weight gain. Irregular eating warrants investigation as a potentially remediable risk factor for disordered glucose metabolism.

  20. Reduced postnatal cerebral glucose metabolism measured by PET after asphyxia in near term fetal lambs.

    PubMed

    Thorngren-Jerneck, K; Ley, D; Hellström-Westas, L; Hernandez-Andrade, E; Lingman, G; Ohlsson, T; Oskarsson, G; Pesonen, E; Sandell, A; Strand, S E; Werner, O; Marsal, K

    2001-12-01

    The effects of fetal asphyxia on cerebral function and development, involve the transition from fetal to neonatal life. Changes in cerebral glucose metabolism may be an early postnatal indicator of fetal asphyxia. The objective is to develop an experimental lamb model involving the transition from fetal to neonatal life and to examine the effect of fetal asphyxia with cerebral hypoxic ischemia on early postnatal cerebral glucose metabolism. Fetal asphyxia was induced by total umbilical cord occlusion in eight near-term fetal lambs (134-138 days) with the ewe under isoflurane-opiate anesthesia. The mean occlusion time until cardiac arrest was 14.5 (4.2) min (SD). Lambs were immediately delivered and standardized resuscitation was instituted after 2 min asystole. At 4 hr postnatal age, [18-F]Fluoro-2-deoxy-glucose (18-FDG) was injected intravenously in eight asphyxiated lambs and in eight controls. Cerebral glucose metabolism was examined by positron emission tomography (PET). As a result the mean arterial blood pressure, acid-base values, blood glucose and serum lactate at 4 hr postnatal age did not differ significantly between lambs subjected to umbilical cord occlusion and controls. EEG was abnormal in all lambs subjected to cord occlusion and normal in the controls at 4 hr postnatal age. Global cerebral metabolic rate (CMRgl) as determined by PET was significantly lower in lambs subjected to cord occlusion mean/median (SD) 22.2/19.6 (8.4) micromol/min/100 g) than in controls mean/median (SD) 37.8/35.9 (6.1); P < 0.01). Global CMRgl is significantly reduced in newborn lambs 4 hr after fetal asphyxia induced by umbilical cord occlusion. A reduction in CMRgl is an early indicator of global hypoxic cerebral ischemia.

  1. Food flavor and nutritional characteristics alter dynamics of food preference in lambs.

    PubMed

    Early, D M; Provenza, F D

    1998-03-01

    We addressed two questions involving food preference. First, we determined how a food's flavor and nutritional characteristics affected preference. In three trials, we offered lambs isonitrogenous foods differing in energy (trial 1, 90% TDN; trial 2, 100% TDN; trial 3, 110% TDN); each food was offered in apple and maple flavors. We hypothesized that preference for apple- or maple-flavored food would decrease with increasing duration of exposure (1, 2, or 4 d), and we speculated that the change in preference would intensify when food contained inadequate or excessive levels of energy. After eating food in one flavor, lambs preferred the alternative flavor, even after only a 1-d exposure, and preference for the alternative flavor was greater when the food had inadequate or excessive energy (P < .05). The second experiment determined whether eating a food with rapidly or slowly digestible sources of energy in the morning affected lambs' food preferences in the evening. We speculated that lambs fed rapidly digestible food in the morning may prefer a slowly digestible food in the afternoon because slowly digestible food better maintains nutrient status throughout the night or because preference for the rapidly digestible food decreases after exposure in the morning. We offered lambs isonitrogenous and isocaloric foods, that differed in rates of digestion, in apple and maple flavors. Lambs fed rapidly digestible food in the morning preferred slowly digestible food in the alternative flavor in the evening. However, lambs fed slowly digestible food in either flavor in the morning preferred slowly digestible food in both flavors in the evening (P < .05). These results show that lambs' preferences change as a result of food ingestion, and the degree of change in preference depends on the nutritional characteristics of the food. These findings further suggest food intake might be increased by providing a variety of foods to livestock on rangelands, pastures, or in confinement.

  2. Effect of periconceptional nutrition on the growth, behaviour and survival of the neonatal lamb.

    PubMed

    Kleemann, D O; Kelly, J M; Rudiger, S R; McMillen, I C; Morrison, J L; Zhang, S; MacLaughlin, S M; Smith, D H; Grimson, R J; Jaensch, K S; Brien, F D; Plush, K J; Hiendleder, S; Walker, S K

    2015-09-01

    Periconceptional nutrition (PCN) can influence foetal hypothalamo-pituitary adrenal (HPA) axis function and alter cortisol secretion with possible consequences for maturation and growth of major organs, gestation length and behaviour. We examined effects of PCN on phenotype and survival of the neonatal lamb in 466 Merino ewes allocated to treatments providing 70%, 100% and 150% respectively, of maintenance requirements for 17 days prior and 6 days after insemination. Gestation length and birth weight for lambs in PCN treatment groups was similar (P > 0.05) but low PCN decreased the size of the neonate (crown-rump-length and metacarpal length P < 0.05). A subset of lambs euthanased at 5 days of age further showed that low PCN decreased the amount of peri-renal fat (P < 0.05) and increased liver mass (P < 0.05) while high PCN increased neck thymus and ovary mass (P < 0.05). Neonatal lambs from low PCN ewes returned faster to their mothers after release (P < 0.05) and contacted the udder in the shortest time (P < 0.05). Significant interactions between PCN treatment and sex (P < 0.05) and between PCN treatment and ewe age (P < 0.05) were also observed for time lambs took to follow the ewe. Survival of lambs was similar but potential differences may have been masked by favourable weather conditions. In conclusion, this study provides evidence of significant changes in lamb growth and development dependent on PCN and, for the first time, links these changes with significant changes in behaviour of the neonate. The impact of these effects on lamb survival and potential reproductive capacity of female offspring remains to be determined.

  3. Occurrence of autoantibodies to cilia in lambs with a 'coughing syndrome'.

    PubMed

    Niang, M; Rosenbusch, R F; Andrews, J J; Lopez-Virella, J; Kaeberle, M L

    1998-07-31

    A respiratory disease of lambs that has been termed the 'coughing syndrome' has been observed in the mid-western region of the United States of America. Mycoplasma ovipneumoniae (M. ovipneumoniae) and Mycoplasma arginini (M. arginini) were routinely isolated from the respiratory tract of lambs with this disease. A high level of antibodies reactive with ovine cilia of the upper respiratory tract was detected in the sera from many of the lambs in affected flocks but not in sera of lambs from unaffected flocks. The reactivity of these antibodies with cilia was demonstrated by ELISA and confirmed by indirect immunofluorescent staining and western immunoblotting. These antibodies were predominantly of the IgG isotype. They were distinct from cold or warm agglutinins and could be absorbed from the sera with cilia but not with antigens of common bacterial pathogens of the sheep respiratory tract including M. ovipneumoniae, M. arginini, Pasteurella haemolytica, Pasteurella multocida or Neisseria ovis. In addition, their occurrence appeared to be independent of the specific antibodies to M. ovipneumoniae and M. arginini. Western immunoblotting indicated that the antibodies were directed primarily against an antigen with apparent molecular weight of 50 kDa. In one flock from which serial serum samples were collected from the same lambs over a 10-month period, antibodies to ovine cilia developed before the onset of the clinical disease and persisted for a period of several months until most of the lambs had apparently recovered. However, colonization of the respiratory tract of the lambs by M. ovipneumoniae preceded the production of these antibodies. Sequential serum samples taken from another flock, with no known history of this coughing, showed no such antibodies throughout the sampling period. It is suggested that an immunopathologic mechanism involving production of autoantibodies directed against a ciliary antigen of the lambs could be a contributing factor to the

  4. The role of the environment in transmission of Dichelobacter nodosus between ewes and their lambs

    PubMed Central

    Muzafar, Mohd; Calvo-Bado, Leo A.; Green, Laura E.; Smith, Edward M.; Russell, Claire L.; Grogono-Thomas, Rose; Wellington, Elizabeth M.H.

    2015-01-01

    Dichelobacter nodosus (D. nodosus) is the essential causative agent of footrot in sheep. The current study investigated when D. nodosus was detectable on newborn lambs and possible routes of transmission. Specific qPCR was used to detect and quantify the load of D. nodosus in foot swabs of lambs at birth and 5–13 h post-partum, and their mothers 5–13 h post-partum; and in samples of bedding, pasture, soil and faeces. D. nodosus was not detected on the feet of newborn lambs swabbed at birth, but was detected 5–13 h after birth, once they had stood on bedding containing naturally occurring D. nodosus. Multiple genotypes identified by cloning and sequencing a marker gene, pgrA, and by multi locus variable number tandem repeat analysis (MLVA) of community DNA from swabs on individual feet indicated a mixed population of D. nodosus was present on the feet of both ewes and lambs. There was high variation in pgrA tandem repeat number (between 3 and 21 repeats), and multiple MLVA types. The overall similarity index between the populations on ewes and lambs was 0.45, indicating moderate overlap. Mother offspring pairs shared some alleles but not all, suggesting lambs were infected from sources(s) other than just their mother's feet. We hypothesise that D. nodosus is transferred to the feet of lambs via bedding containing naturally occurring populations of D. nodosus, probably as a result of transfer from the feet of the group of housed ewes. The results support the hypothesis that the environment plays a key role in the transmission of D. nodosus between ewes and lambs. PMID:25953734

  5. Intake of honey mesquite (Prosopis glandulosa) leaves by lambs using different levels of activated charcoal

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 24-day feeding trial was conducted to assess the effect of feeding four levels of activated charcoal (0.0, 0.33, 0.67 and 1.00 g/kg of body weight) on intake of honey mesquite leaves (Prosopis glandulosa Torr.) by 20 wether lambs (36.6 ± 0.6 kg) that were randomly assigned to treatments. Lambs wer...

  6. Failure of maternal colostral antibody transfer in lambs linked to excess dietary iodine.

    PubMed

    2016-07-01

    Failure of maternal colostral antibody transfer in lambsHypomagnesaemia in calvesHyperplastic goitre in a stillborn calfAbortion storm in a beef herd due to Salmonella MontevideoRickets in hogg lambsStaphylococcus hyicus isolated from piglets with joint ill These are among matters discussed in the disease surveillance report for March 2016 from SAC Consulting: Veterinary Services (SAC C VS). PMID:27389751

  7. Serological serum protein fraction and responses to Brucella melitensis in lambs fed aflatoxins.

    PubMed

    Fernandez, A; Hernandez, M; Sanz, M C; Verde, M T; Ramos, J J

    1997-06-01

    Twenty-four lambs were given 2 ppm aflatoxins (AF) in their diet for 37 d and 12 were kept as a control group. After this time, toxic feed was removed for a further 35 days (clearance period). On day 17 all lambs were vaccinated with B melitensis strain Rev-1, and blood samples were taken regularly to determine the levels of antibodies and serum proteins. Aflatoxins decreased titers of Rose Bengal test and optical densities of ELISA, both in the intoxicated and clearance periods. Complement fixation titers were lower in intoxicated lambs, except on the 23rd day of intoxication, but not statistically different (P > 0.05). No effect of AF was noted on total serum proteins, but albumin and alfa-globulin levels were lower for intoxicated lambs than for the control group. Beta-globulin concentration did not change, and increases in gamma-globulins levels in dosed lambs were observed throughout the experiment. These results suggest that AF causes a failure in the acquired immunity system of lambs by decreasing antibody production and altering serum profile proteins.

  8. Neuropathological changes in a lamb model of non-accidental head injury (the shaken baby syndrome).

    PubMed

    Finnie, J W; Blumbergs, P C; Manavis, J; Turner, R J; Helps, S; Vink, R; Byard, R W; Chidlow, G; Sandoz, B; Dutschke, J; Anderson, R W G

    2012-08-01

    Non-accidental head injury (NAHI), also termed the "shaken baby syndrome", is a major cause of death and severe neurological dysfunction in children under three years of age, but it is debated whether shaking alone is sufficient to produce brain injury and mortality or whether an additional head impact is required. In an attempt to resolve this question, we used a lamb model of NAHI since these animals have a relatively large gyrencephalic brain and weak neck muscles resembling those of a human infant. Three anaesthetised lambs of lower body weight than others in the experimental group died unexpectedly after being shaken, proving that shaking alone can be lethal. In these lambs, axonal injury, neuronal reaction and albumin extravasation were widely distributed in the hemispheric white matter, brainstem and at the craniocervical junction, and of much greater magnitude than in higher body weight lambs which did not die. Moreover, in the eyes of these shaken lambs, there was damage to retinal inner nuclear layer neurons, mild, patchy ganglion cell axonal injury, widespread Muller glial reaction, and uveal albumin extravasation. This study proved that shaking of a subset of lambs can result in death, without an additional head impact being required.

  9. Effects of early feeding on the host rumen transcriptome and bacterial diversity in lambs

    PubMed Central

    Wang, Weimin; Li, Chong; Li, Fadi; Wang, Xiaojuan; Zhang, Xiaoxue; Liu, Ting; Nian, Fang; Yue, Xiangpeng; Li, Fei; Pan, Xiangyu; La, Yongfu; Mo, Futao; Wang, Fangbin; Li, Baosheng

    2016-01-01

    Early consumption of starter feed promotes rumen development in lambs. We examined rumen development in lambs fed starter feed for 5 weeks using histological and biochemical analyses and by performing high-throughput sequencing in rumen tissues. Additionally, rumen contents of starter feed-fed lambs were compared to those of breast milk-fed controls. Our physiological and biochemical findings revealed that early starter consumption facilitated rumen development, changed the pattern of ruminal fermentation, and increased the amylase and carboxymethylcellulase activities of rumen micro-organisms. RNA-seq analysis revealed 225 differentially expressed genes between the rumens of breast milk- and starter feed-fed lambs. These DEGs were involved in many metabolic pathways, particularly lipid and carbohydrate metabolism, and included HMGCL and HMGCS2. Sequencing analysis of 16S rRNA genes revealed that ruminal bacterial communities were more diverse in breast milk-than in starter feed-fed lambs, and each group had a distinct microbiota. We conclude that early starter feeding is beneficial to rumen development and physiological function in lambs. The underlying mechanism may involve the stimulation of ruminal ketogenesis and butanoate metabolism via HMGCL and HMGCS2 combined with changes in the fermentation type induced by ruminal microbiota. Overall, this study provides insights into the molecular mechanisms of rumen development in sheep. PMID:27576848

  10. Comparison of hepatic drug metabolizing enzymes in three-month-old lambs and kids.

    PubMed

    Kaddouri, M; Larrieu, G; Eeckhoutte, C; Galtier, P

    1990-01-01

    1. The comparative activity of hepatic cytochrome P-450 monooxygenase system, glucuronyl-transferase, glutathione S-transferase and N-acetyltransferase was studied in three-month-old male and female Lacaune lambs and male Saanen kids. 2. The study of mixed-function oxidase components showed that total cytochrome P-450 ranged from 0.54 in kids to 0.85-0.88 nmol/mg-1 in lambs. Male lambs had higher levels than kids (122-165%) for aminopyrine, benzphetamine, ethylmorphine and erythromycin demethylases or benzo(a)pyrene hydroxylase whereas NADPH-cytochrome c reductase was 1.19-fold lower in lambs. 3. Sex-related changes were observed in lambs in case of microsomal benzo(a)pyrene hydroxylase activity which appeared 1.31-fold more potent in male liver. Cytosolic N-acetyltransferase accepting sulfamethazine as substrate was about 8-fold higher in female than in male lambs. 4. The analysis of samples from various liver lobes, indicated the heterogenous distribution of microsomal proteins which is related to higher concentrations of both cytochrome b5, NADPH-cytochrome c reductase and p-nitrophenol glucuronyltransferase in left lobes.

  11. Colonisation of the respiratory tract of lambs by strains of Mycoplasma ovipneumoniae.

    PubMed

    Ionas, G; Mew, A J; Alley, M R; Clarke, J K; Robinson, A J; Marshall, R B

    1985-12-01

    The age and time of year when colonisation of the nasal cavity of lambs by Mycoplasma ovipneumoniae occurs; the persistence of the organism, and its prevalence in the lungs at slaughter were examined in 2 flocks of sheep in New Zealand. No colonisation had occurred at the time of weaning at 6-7 weeks, but M. ovipneumoniae was recovered from most lambs on at least one occasion before they were slaughtered when about 8 months old. In most cases, colonisation of the nasal cavity by M. ovipneumoniae was a transient phenomenon. At slaughter M. ovipneumoniae was recovered from the lungs of 89% of the lambs of one flock and 80% of the other flock. Bacterial restriction endonuclease DNA analysis (BRENDA) of 34 nasal isolates from one flock showed that it was possible to identify 7 "groups" each with markedly different BRENDA patterns. Lambs initially colonised by one strain, often lost that strain, and if recolonisation occurred it was with a different strain. M. ovipneumoniae was recovered at slaughter from the lungs of most lambs, both normal and pneumonic. The isolates from one flock were examined by BRENDA, and approximately 90% of them gave similar or identical patterns. The predominant strain isolated from the lungs had been recovered from the nasal cavity of many of the lambs about 3 weeks earlier. This suggests that the nasal and lung isolates do not represent independent populations. However, nasal strains may differ in their ability to colonise the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. A calibration of the lamb airflow classification model to predict past precipitation in Wales

    NASA Astrophysics Data System (ADS)

    Beaumont, Peter; Hawksworth, Kevin

    1997-11-01

    Daily precipitation data from 146 sites for the period 1982 to 1991 inclusive have been analysed in conjunction with the 27 Lamb airflow types. An areal mean precipitation (AMP) series for Wales is constructed for the period 1861 to 1995 by summing the mean daily AMP values associated with each Lamb airflow type. The results reveal that the use of coherent precipitation regions together with seasonal AMP values are more likely to provide a better estimate of mean annual precipitation than those combining a simple unweighted summation with non-seasonal values. The mean annual series for Wales compares favourably with that provided by Wigley et al. and Woodley for England and Wales. Finally, the importance of the major Lamb airflow types are considered in relation to periods of the record when dry and wet phases occur. Anticyclonic and cyclonic Lamb types are shown to be better predictors of mean annual precipitation than Lamb westerlies. In part, this reflects the fact that at the regional scale non-westerly Lamb airflow types can be embedded within a mobile westerly circulation. These non-westerly airflow types often produce high precipitation totals over Wales.

  13. Effects of early feeding on the host rumen transcriptome and bacterial diversity in lambs.

    PubMed

    Wang, Weimin; Li, Chong; Li, Fadi; Wang, Xiaojuan; Zhang, Xiaoxue; Liu, Ting; Nian, Fang; Yue, Xiangpeng; Li, Fei; Pan, Xiangyu; La, Yongfu; Mo, Futao; Wang, Fangbin; Li, Baosheng

    2016-01-01

    Early consumption of starter feed promotes rumen development in lambs. We examined rumen development in lambs fed starter feed for 5 weeks using histological and biochemical analyses and by performing high-throughput sequencing in rumen tissues. Additionally, rumen contents of starter feed-fed lambs were compared to those of breast milk-fed controls. Our physiological and biochemical findings revealed that early starter consumption facilitated rumen development, changed the pattern of ruminal fermentation, and increased the amylase and carboxymethylcellulase activities of rumen micro-organisms. RNA-seq analysis revealed 225 differentially expressed genes between the rumens of breast milk- and starter feed-fed lambs. These DEGs were involved in many metabolic pathways, particularly lipid and carbohydrate metabolism, and included HMGCL and HMGCS2. Sequencing analysis of 16S rRNA genes revealed that ruminal bacterial communities were more diverse in breast milk-than in starter feed-fed lambs, and each group had a distinct microbiota. We conclude that early starter feeding is beneficial to rumen development and physiological function in lambs. The underlying mechanism may involve the stimulation of ruminal ketogenesis and butanoate metabolism via HMGCL and HMGCS2 combined with changes in the fermentation type induced by ruminal microbiota. Overall, this study provides insights into the molecular mechanisms of rumen development in sheep. PMID:27576848

  14. Effects of early feeding on the host rumen transcriptome and bacterial diversity in lambs.

    PubMed

    Wang, Weimin; Li, Chong; Li, Fadi; Wang, Xiaojuan; Zhang, Xiaoxue; Liu, Ting; Nian, Fang; Yue, Xiangpeng; Li, Fei; Pan, Xiangyu; La, Yongfu; Mo, Futao; Wang, Fangbin; Li, Baosheng

    2016-01-01

    Early consumption of starter feed promotes rumen development in lambs. We examined rumen development in lambs fed starter feed for 5 weeks using histological and biochemical analyses and by performing high-throughput sequencing in rumen tissues. Additionally, rumen contents of starter feed-fed lambs were compared to those of breast milk-fed controls. Our physiological and biochemical findings revealed that early starter consumption facilitated rumen development, changed the pattern of ruminal fermentation, and increased the amylase and carboxymethylcellulase activities of rumen micro-organisms. RNA-seq analysis revealed 225 differentially expressed genes between the rumens of breast milk- and starter feed-fed lambs. These DEGs were involved in many metabolic pathways, particularly lipid and carbohydrate metabolism, and included HMGCL and HMGCS2. Sequencing analysis of 16S rRNA genes revealed that ruminal bacterial communities were more diverse in breast milk-than in starter feed-fed lambs, and each group had a distinct microbiota. We conclude that early starter feeding is beneficial to rumen development and physiological function in lambs. The underlying mechanism may involve the stimulation of ruminal ketogenesis and butanoate metabolism via HMGCL and HMGCS2 combined with changes in the fermentation type induced by ruminal microbiota. Overall, this study provides insights into the molecular mechanisms of rumen development in sheep.

  15. The impact of supplementing lambs with algae on growth, meat traits and oxidative status.

    PubMed

    Hopkins, D L; Clayton, E H; Lamb, T A; van de Ven, R J; Refshauge, G; Kerr, M J; Bailes, K; Lewandowski, P; Ponnampalam, E N

    2014-10-01

    The current study examined the effect of supplementing lambs with algae. Forty, three month old lambs were allocated to receive a control ration based on oats and lupins (n=20) or the control ration with DHA-Gold™ algae (~2% of the ration, n=20). These lambs came from dams previously fed a ration based on either silage (high in omega-3) or oats and cottonseed meal (OCSM: high in omega-6) at joining (dam nutrition, DN). Lamb performance, carcase weight and GR fat content were not affected by treatment diet (control vs algae) or DN (silage vs OSCM). Health claimable omega-3 fatty acids (EPA+DHA) were significantly greater in the LL of lambs fed algae (125±6mg/100g meat) compared to those not fed algae (43±6mg/100g meat) and this effect was mediated by DN. Supplementing with algae high in DHA provides a means of improving an aspect of the health status of lamb meat.

  16. Net Phosphorus Requirements of Dorper×Thin-tailed Han Crossbred Ram Lambs.

    PubMed

    Ji, Shoukun; Xu, Guishan; Jiang, Chenggang; Deng, Kaidong; Tu, Yan; Zhang, Naifeng; Ma, Tao; Lou, Can; Diao, Qiyu

    2013-09-01

    A comparative slaughter trial was conducted to estimate the phosphorus (P) requirement for maintenance and growth of crossbred lambs of Dorper with a Chinese indigenous sheep breed, thin-tailed Han sheep. Thirty-five Dorper×thin-tailed Han crossbred, noncastrated ram lambs (20.3±0.22 kg of shrunk body weight (SBW)) were used. Seven lambs were randomly chosen and slaughtered at 20 kg SBW as the baseline group for measuring initial body composition. Another seven lambs were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 28 kg SBW. The remaining 21 sheep were randomly divided into 3 groups with 7 sheep each and subject to the same diet of either 70 or 40% of ad libitum intake. The 3 groups were slaughtered when the sheep fed ad libitum reached 35 kg of SBW. Body P contents were determined after slaughter. The results showed that the net P requirement for maintenance was 30.0 mg/kg of empty body weight (EBW) or 23.4 mg/kg body weight (BW), and the P requirement for growth decreased from 5.3 to 5.0 g/kg of EBW gain as the lamb grew from 20 to 35 kg. The net P requirement for growth of Dorper×thin-tailed Han crossbred ram lambs was lower than that of sheep adopted by the American nutritional system.

  17. Net Phosphorus Requirements of Dorper×Thin-tailed Han Crossbred Ram Lambs

    PubMed Central

    Ji, Shoukun; Xu, Guishan; Jiang, Chenggang; Deng, Kaidong; Tu, Yan; Zhang, Naifeng; Ma, Tao; Lou, Can; Diao, Qiyu

    2013-01-01

    A comparative slaughter trial was conducted to estimate the phosphorus (P) requirement for maintenance and growth of crossbred lambs of Dorper with a Chinese indigenous sheep breed, thin-tailed Han sheep. Thirty-five Dorper×thin-tailed Han crossbred, noncastrated ram lambs (20.3±0.22 kg of shrunk body weight (SBW)) were used. Seven lambs were randomly chosen and slaughtered at 20 kg SBW as the baseline group for measuring initial body composition. Another seven lambs were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 28 kg SBW. The remaining 21 sheep were randomly divided into 3 groups with 7 sheep each and subject to the same diet of either 70 or 40% of ad libitum intake. The 3 groups were slaughtered when the sheep fed ad libitum reached 35 kg of SBW. Body P contents were determined after slaughter. The results showed that the net P requirement for maintenance was 30.0 mg/kg of empty body weight (EBW) or 23.4 mg/kg body weight (BW), and the P requirement for growth decreased from 5.3 to 5.0 g/kg of EBW gain as the lamb grew from 20 to 35 kg. The net P requirement for growth of Dorper×thin-tailed Han crossbred ram lambs was lower than that of sheep adopted by the American nutritional system. PMID:25049910

  18. Effect of beta 3-adrenergic agonist (Zeneca D7114) on thermoregulation in near-term lambs delivered by cesarean section.

    PubMed

    Clarke, L; Bird, J A; Lomax, M A; Symonds, M E

    1996-08-01

    We investigated the effect of a beta 3-adrenergic agonist, Zeneca D7114, on thermoregulation in near-term lambs delivered by cesarean section. Lambs were delivered into a cool ambient temperature of 15 degrees C, and between 60 and 80 min of life were given an oral dose of Zeneca D7114 (10 mg.kg body weight-1) dissolved in 20 mL of milk, or milk alone. During the first 0.5 h of life colonic temperature decreased in all lambs, and then increased to plateau levels (39.6-40.4 degrees C) after 120-150 min of life, in 19 out of 23 lambs studied. In the remaining lambs, colonic temperature failed to return to normothermic values, plateauing at 34.3 degrees C. All control lambs were observed to shiver throughout the study, but after Zeneca D7114 treatment 7 out of 10 normothermic lambs stopped shivering, and plateau colonic temperature was 0.8 degree C higher. Hypothermic beta 3-agonist-treated lambs had significantly lower rates of heat production, breathing frequency, and plasma triiodothyronine and cortisol concentrations than normothermic lambs. the level of GDP binding and norepinephrine content of brown adipose tissue (BAT) sampled from hypothermic beta 3-agonist-treated lambs was significantly lower than in normothermic lambs. There was no difference in GDP binding in BAT between control and Zeneca D7114-treated groups, but the Hb content was higher in the latter group. It is concluded that administration of Zeneca D7114 to euthyroid lambs enhances their ability to thermoregulate and restore colonic temperature without altering the thermogenic activity of BAT. This response may be mediated by increasing blood flow to BAT and/or an improvement in the animal's thermal efficiency (i.e. decreased heat loss) due to a reduced reliance on shivering thermogenesis. PMID:8827786

  19. Thermogenesis, blood metabolites and hormones, and growth of lambs born to ewes supplemented with algae-derived docosahexaenoic acid.

    PubMed

    Keithly, J I; Kott, R W; Berardinelli, J G; Moreaux, S; Hatfield, P G

    2011-12-01

    Neonatal lamb mortality is a major factor affecting profitability in the sheep industry, and lamb thermogenesis is a key element in neonatal lamb survival. Increased lamb vigor has been reported when ewes were supplemented during late gestation with algae-derived docosahexaenoic acid (DHA); however, the effects of DHA on lamb thermogenesis and immunocompetence have not been investigated. Eighty twin-bearing Targhee ewes (ages 2 to 5 yr; 68.5 ± 3 kg) were assigned randomly to 1 of 2 supplement treatments to determine the effects of feeding DHA to ewes during late gestation and early lactation on lamb thermogenesis, serum metabolites and hormones, and lamb growth. Supplement treatments were 12 g·ewe(-1)·d(-1) of algae-derived DHA (DHA Gold Advanced Bionutrition Corp., Columbia, MD; algae-derived DHA); and no algae-derived DHA (control). Supplements were individually fed daily during the last 30 d (±7 d) of gestation and pen fed (6 pens/treatment with 6 or 7 ewes/pen) during the first 38 d (±7 d) of lactation. One hour after lambing and before nursing, twin-born lambs were weighed, blood sampled via jugular puncture, and placed in a dry cold chamber for 30 min (0°C), and rectal temperatures were recorded every minute for 30 min. Lambs were removed from the cold chamber, blood sampled, warmed for 15 min, and returned to their dam. Ewes were blood sampled, and colostrum samples were collected 1 h postpartum. Ewe and lamb sera were assayed for glucose, NEFA, cortisol, and leptin. Lamb rectal temperature, glucose, NEFA, cortisol, leptin, and birth weights did not differ between treatments. The BW at 38 d was greater (P = 0.03) for lambs born to control ewes than for lambs born to algae-derived DHA-supplemented ewes; however, the colostrum of algae-derived DHA-supplemented ewes had a greater specific gravity (P = 0.05) than for control ewes. Overall, despite a potentially positive effect on ewe colostral IgG concentrations, supplementation of algae-derived DHA during

  20. Stoichiometry of maltodextrin-binding sites in LamB, an outer membrane protein from Escherichia coli.

    PubMed Central

    Gehring, K; Cheng, C H; Nikaido, H; Jap, B K

    1991-01-01

    We have directly measured the stoichiometry of maltodextrin-binding sites in LamB. Scatchard plots and computer fitting of flow dialysis (rate-of-dialysis) experiments clearly establish three independent binding sites per LamB trimer, with a dissociation constant of approximately 60 microM for maltoheptaose. The current model for LamB's function as a specific pore is discussed with respect to the symmetry in LamB's kinetic properties and the implications of our results. Images PMID:2001992

  1. Interaction between a tannin-containing legume and endophyte-infected tall fescue seed on lambs' feeding behavior and physiology.

    PubMed

    Villalba, J J; Spackman, C; Goff, B M; Klotz, J L; Griggs, T; MacAdam, J W

    2016-02-01

    It was hypothesized that a tannin-rich legume such as sainfoin attenuates the negative postingestive effects of ergot alkaloids in tall fescue. Thirty-two 4-mo-old lambs were individually penned and randomly assigned to a 2 × 2 factorial arrangement with 2 legume species, sainfoin (SAN; 2.9% condensed tannins) or cicer milkvetch (CIC; without tannins) and a mixed ration containing tall fescue seed (50:30:20 seed:beet pulp:alfalfa) with 2 levels of endophyte infection (endophyte-infected tall fescue seed [E+; 3,150 ug/L ergovaline] or endophyte-free tall fescue seed [E-]). For a 10-d baseline period, half of the lambs were fed SAN and half were fed CIC and all lambs had ad libitum amounts of E-. In an ensuing 10-d experimental period, the protocol was the same except half of the lambs fed SAN or CIC received E+ instead of E-. Subsequently, all lambs could choose between their respective legume and seed-containing ration and between E+ and E-. Finally, an in vitro radial diffusion assay was conducted to determine whether tannins isolated from SAN would bind to alkaloids isolated from E+. All groups consumed similar amounts of E- during baseline period ( > 0.10), but lambs ate more E- than E+ during the experimental period ( < 0.05) and lambs offered SAN ate more E+ than lambs offered CIC ( < 0.05). Groups fed E- during the baseline and experimental periods had similar rectal temperatures ( > 0.10), but lambs fed E+ had lower rectal temperatures per gram of feed ingested when supplemented with SAN than with CIC ( < 0.05). Lambs fed E+ had greater concentrations of hemoglobin and more red blood cells than lambs fed E- ( < 0.05), but plasmatic concentrations of cortisol and prolactin did not differ among treatments ( > 0.10). All lambs preferred their treatment ration over their treatment legume, but lambs in the SAN and E+ treatment ate more legume + ration than lambs in the CIC and E+ (CIC-E+; < 0.05) treatment. All lambs preferred E- over E+, but lambs in the CIC

  2. Development of affinity to the stockperson in lambs from two breeds.

    PubMed

    Caroprese, M; Napolitano, F; Boivin, X; Albenzio, M; Annicchiarico, G; Sevi, A

    2012-01-18

    The interactions between genetic and environmental factors on the development of lamb affinity to humans was assessed on 48 animals from two breeds (Gentile di Puglia and Comisana) and two treatments (Gentled and Not Gentled) producing 4 groups (GPg, GPng, Cg, Cng, respectively). The Gentile di Puglia and Comisana gentled animals were subjected to a period of training consisting of gently handling each lamb for 5 min three times a day for the first week and then twice a week for three additional weeks. The gentling procedure included both tactile and visual/auditory interactions. At 30-32 days of age lambs were subjected to three arena tests conducted in a novel environment: i) isolation test (each animal was exposed to a novel environment, and isolated from tactile and visual contact with conspecifics for 5 min), ii) stationary human test (as previously but a human sitting in a corner of the pen), and iii) pen-mates' test (each animal was tested in the presence of 2 pen-mates whose behaviour was not recorded). During the 13 training sessions lambs exhibited an increasing number of contacts with the human and a decreasing number of bleats (P<0.001), although Gentile di Puglia lambs interacted more with the human (P<0.001) and tended to bleat less (P<0.10) than Comisana lambs. Lambs vocalised more and climbed more when tested in isolation as compared with lambs tested either with the human or with the pen-mates (P<0.01) and they vocalised more in the presence of the human than with the pen-mates (P<0.001). A higher number of contacts with the human stimulus was observed in gentled animals (P<0.05). However, differences between gentled and not gentled animals were only significant in Gentile di Puglia subjects (P<0.01). GPng lambs displayed the longest ambulatory activity during the isolation test (P<0.05) and exhibited more climbing attempts during the isolation test as compared with the human or the pen-mates' tests (P<0.001). A higher cortisol level was shown by

  3. Photothermal ablation of liver tissue with 1940-nm thulium fiber laser: an ex vivo study on lamb liver

    NASA Astrophysics Data System (ADS)

    Alagha, Heba Z.; Gülsoy, Murat

    2016-01-01

    The purpose of this study was to investigate the ablation efficiency of 1940-nm thulium fiber laser on liver tissue, while utilizing a real-time measurement system to monitor the temperature rise in adjacent tissues. Thulium fiber laser was delivered to lamb liver tissue samples via 400-μm bare tip fiber in contact mode. Eight different laser parameter combinations [power, continuous-wave (cw)/pulsed-modulated (pm) mode, and exposure time] were used. Exposure times were chosen to give the same total applied energy of 4 J for comparative purposes. Following laser irradiations, tissues were processed and stained with hematoxylin and eosin for macroscopic evaluation of ablation areas and total altered areas, and ablation efficiencies were calculated. Temperature of the nearby tissue at a distance of 1 mm from the fiber was measured, and rate of temperature change was calculated. A strong correlation between the rate of temperature change and ablation area was noted. Thermal effects increased with increasing power for both modes. The continuous-wave mode yielded higher ablation efficiencies than the pulse-modulated mode. Histological evaluation revealed a narrow vacuolization zone and negligible carbonization for higher-power values.

  4. Lamb Model of Respiratory Syncytial Virus–Associated Lung Disease: Insights to Pathogenesis and Novel Treatments

    PubMed Central

    Ackermann, Mark R.

    2014-01-01

    Preterm birth is a risk factor for respiratory syncytial virus (RSV) bronchiolitis and hospitalization. The pathogenesis underlying this is not fully understood, and in vivo studies are needed to better clarify essential cellular features and molecular mechanisms. Such studies include analysis of lung tissue from affected human infants and various animal models. The preterm and newborn lamb lung has developmental, structural, cellular, physiologic, and immunologic features similar to that of human infants. Also, the lamb lung is susceptible to various strains of RSV that infect infants and cause similar bronchiolar lesions. Studies in lambs suggest that viral replication in airways (especially bronchioles) is extensive by 4 days after infection, along with bronchiolitis characterized by degeneration and necrosis of epithelial cells, syncytial cell formation, neutrophil infiltration, epithelial cell hypertrophy and hyperplasia, and innate and adaptive immune responses. RSV bronchiolitis greatly affects airflow and gaseous exchange. RSV disease severity is increased in preterm lambs compared with full-term lambs; similar to human infants. The lamb is conducive to experimental assessment of novel, mechanistic therapeutic interventions such as delivery of vascular endothelial growth factor and enhancement of airway epithelial oxidative responses, Club (Clara) cell protein 10, and synthesized compounds such as nanobodies. In contrast, exposure of the fetal ovine lung in vivo to ethanol, a risk factor for preterm birth, reduces pulmonary alveolar development and surfactant protein A expression. Because the formalin-inactivated RSV vaccination enhances some inflammatory responses to RSV infection in lambs, this model has the potential to assess mechanisms of formalin-inactivated RSV enhanced disease as well as newly developed vaccines. PMID:24936027

  5. Thyroid gland in vitro activity and reactivity to TRH in newborn lambs.

    PubMed

    Wronska, D

    2015-10-01

    The aim of the study was to determine the thyroid gland tissue concentration and activity on T4 and T3 in vitro release to the medium without (control) or with TRH (10 μg/ml) for 90 min of incubation in lambs just after birth and after the first 6h of postnatal life. The results obtained show that T4 concentration in the blood plasma in newborn lambs as well after 6h of life is higher than in thyroid gland tissue. In the case of T3 the concentration in blood plasma of lambs just after birth is lower than after 6h of postnatal life. Inversely, the higher level of that hormone concentration in blood plasma just after birth is higher than in the thyroid gland tissue. The results clearly indicate the inhibitory TRH effect on in vitro T4 especially, and in lesser degree T3 release from the thyroid gland tissue of lambs just after birth. Stimulation of the TRH thyroid gland tissue from lambs after 6h of life caused an increase in T4 release, especially after 60 min of the experiment. Similarly, a significant increase of T3 release was found only after 60 min of incubation. The transient promoting TRH effect on the amount of iodothyronine release from the thyroid gland in older lambs is probably connected with this gland's function not occurring before the designated time of postnatal adaptation. The described in vitro experiment visibly shows that changing thyroid gland activity in newborn lambs is not only conditioned by the entire HPT activity, but by the immanent thyroid gland attributes as well.

  6. The effect of shearing in a hot environment on some welfare indicators in Awassi lambs.

    PubMed

    Dikmen, Serdal; Orman, Abdulkadir; Ustuner, Hakan

    2011-10-01

    The aim of this study was to analyze the effects of shearing on the individual behaviors and rectal temperature profile during the day at hot environment in Awassi lambs. Twenty Awassi male lambs were randomly allocated into shorn (n = 10) and unshorn (n = 10) groups (28.8 ± 0.7 and 29.9 ± 0.7 kg, respectively) and were kept indoor during the experiment. The physiological and behavioral response variables measured were rectal temperature, standing, lying, feeding, ruminating, drinking, locomotor activity, and elimination. The effect of day, time of day, and all interactions on rectal temperature were found significant (P < 0.001). The effect of shearing on the rectal temperatures of lambs was tend to be significant (P = 0.06). Overall, unshorn lambs showed more frequencies of locomotor activity (P < 0.05) and there was a tendency of less standing behavior (P = 0.08) when compared to the lambs in shorn group. The difference of the other behaviors was not significant (P > 0.05). Within the observation hours, there was a tendency of difference for behavioral frequencies between groups especially early in the day and late at night (P = 0.07). But during the day, the difference of behavior type between groups was highly significant at 1300 and 1600 hours (P < 0.01 and P < 0.001, respectively). The findings of the current study showed that the behavior of shorn lambs changed with the changing of environmental heat and showed more behavioral differences at 1300 hours but they tend to cope with heat stress better than unshorn lambs in a hot environment when their rectal temperatures were compared.

  7. Selective pulmonary vasodilation by low-dose infusion of adenosine triphosphate in newborn lambs.

    PubMed

    Konduri, G G; Woodard, L L

    1991-07-01

    The systemic and pulmonary vascular effects of adenosine 5'-triphosphate (ATP) were investigated in 12 newborn lambs during normoxia and during alveolar hypoxia (10% oxygen, 5% carbon dioxide, and 85% nitrogen). Lambs had catheters in the descending aorta, main pulmonary artery, and were studied after a 3-day recovery. We infused ATP or an equal volume of saline solution (control) into the right atrial line in doses ranging from 0.01 to 2.5 mumol/kg per minute. In normoxic lambs, ATP caused a significant decrease in pulmonary vascular resistance in doses of 0.08 to 2.5 mumol/kg per minute, and in systemic vascular resistance in doses of 0.3 to 2.5 mumol/kg per minute. Infusion of ATP in hypoxic lambs caused decreases in pulmonary artery pressure and pulmonary vascular resistance in all the doses tested. Systemic vascular resistance decreased, and cardiac output and heart rate increased in doses greater than 0.3 mumol/kg per minute in hypoxic lambs during ATP infusion. The effects of ATP in hypoxic lambs were not blocked by propranolol, indomethacin, or theophylline. Plasma ATP levels in left atrial blood samples did not change significantly during the infusion of ATP. We conclude that ATP is a vasodilator in lambs, and its effects are specific for pulmonary circulation at doses of less than or equal to 0.15 mumol/kg per minute. The vasodilator effects of ATP appear to be independent of P1 purinergic and beta-adrenergic mechanisms, and of prostacyclin synthesis. PMID:1906103

  8. Impact evaluation of an energy savings plan project at Lamb-Weston, Inc

    SciTech Connect

    Spanner, G.E.; Wilfert, G.L.

    1990-06-01

    This impact evaluation of an energy conservation measure (ECM) that was recently installed at Lamb-Weston, Inc. (Lamb-Weston) was conducted for the Bonneville Power Administration (Bonneville) as part of an evaluation of its Energy $avings Plan (E$P) Program. The Program awards cash incentives to firms that install energy conservation measures in their industrial processes. The objective of this impact evaluation was to assess how much electrical energy is being saved at Lamb-Weston as a result of the E$P and to determine how much the savings cost Bonneville and the region. The impact of the ECM was evaluated with a combination of engineering analysis, financial analysis, interviews, submittal reviews (Lamb-Weston's Completion Report, Proposal, and Abstract), and process evaluation reviews. The ECM itself consists of a heat recovery heat exchanger added to the hot drain of a potato blancher to reclaim heat that would otherwise be discarded at Lamb-Weston's Plant 1 in Quincy, Washington. At this facility, Lamb-Weston makes frozen French fried potatoes for institutional and consumer markets. Energy savings resulting from this ECM are expected to be 4,037,101 kWh per year. The ECM cost $67, 020 to install and Lamb-Weston received an incentive from Bonneville of $40, 212. The levelized cost of these energy savings to Bonneville will be 0.83 mills/kWh over the ECM's expected 15-year life, and the levelized cost to the region will be 1.50 mills/kWh.

  9. Guided wave helical ultrasonic tomography of pipes.

    PubMed

    Leonard, Kevin R; Hinders, Mark K

    2003-08-01

    Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT) that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel the various helical criss-cross paths between two parallel circumferential transducer arrays instead of the planar criss-cross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. In this paper we demonstrate HUT via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.

  10. Effect of rearing temperature on perirenal adipose tissue development and thermoregulation following methimazole treatment of postnatal lambs.

    PubMed

    Symonds, M E; Andrews, D C; Buss, D S; Clarke, L; Darby, C J; Lomax, M A

    1996-11-01

    This study examined the effect of ambient temperature on perirenal adipose tissue development and thermoregulation over the first month of postnatal life in lambs treated with a drug that reduces thyroid hormone synthesis (methimazole; at a dose of 50 mg day-1 (kg body weight)-1). Twin lambs were hand-reared at a fixed level of nutrition in either a warm (WR; 25 degrees C) or cool (CR; 10-15 degrees C) ambient temperature. Oxygen consumption, heart rate and colonic temperature were measured during non-rapid eye movement sleep in different ambient temperatures (6, 15, 25 and 34-36 degrees C) at 7, 14 and 28 days of age. Plasma thyroid hormone concentrations decreased with postnatal age and were higher in CR than in WR lambs. All lambs increased plasma thyroid hormone concentrations and O2 consumption during cold exposure but this was associated with a mean increase in colonic temperature in WR lambs at 7 or 28 days. Colonic temperature increased with the onset of panting at all ages when lambs were exposed to 34-36 degrees C, a response that was greatest at 28 days in CR lambs. An increase in colonic temperature with age was observed in CR but not WR lambs. Heart rate declined with age only in the WR group. At 8 and 29 days there were no significant differences between WR and CR groups in the occurrence of shivering or in the thermogenic activity (i.e. GDP binding to mitochondria) of perirenal adipose tissue. At 29 days WR lambs possessed more adipose tissue with a higher lipid and DNA content. It is concluded that modest changes in rearing temperature can have a large influence on the control of body temperature and thyroid hormone response to methimazole treatment. CR lambs are able to maintain higher plasma thyroid hormone concentrations and exhibit improved thermoregulation compared with WR lambs without any detectable differences in brown adipose tissue function.

  11. Retinal image recognition for verifying the identity of fattening and replacement lambs.

    PubMed

    Rojas-Olivares, M A; Caja, G; Carné, S; Salama, A A K; Adell, N; Puig, P

    2011-08-01

    With the objective of verifying the presumed identity of sheep in a traceability study based on visual ear tags and electronic boluses, retinal image recognition was used as an auditing biomarker on 152 lambs of 2 dairy breeds (Manchega, n=82; Lacaune, n=70). Lambs were identified with temporary ear tags (birth to weaning), and with official ear tags and electronic mini-boluses (weaning to yearling). At 3 mo of age, 58 lambs were recruited for flock replacement, and the rest were transported to a slaughterhouse. Retinal images (RI) and capturing times (CT) were recorded from the left and right eyes of each lamb in duplicate and by the same operator using an OptiReader device (Optibrand, Fort Collins, CO) at 3, 6, and 12 mo of age in 152, 58, and 58 lambs, respectively. The 3-mo RI were used as reference images and to assess operator training and accuracy of the technique. Intra- and inter-age comparisons were made to obtain the matching score (MS; 0 to 100) of pairs of RI from the same eye, using Optibrand's software. Operator skill improved with training sessions, but MS reached a plateau after the sixth session (264 images; MS=93.2 ± 1.5). Values of CT also decreased in trained compared with untrained operators (63 ± 5 vs. 144 ± 15 s, respectively; P < 0.001). Training data were eliminated from further analysis. Matching exclusion criteria were estimated from trained operator images at random (804 images) using a nonparametric receiver operating characteristic curve analysis for MS=70. No breed, eye, or age effects were detected in the MS intra-age comparisons at 3-, 6-, and 12-mo periods, which averaged 96.3 ± 0.3. Capturing time was longer in Lacaune than in Manchega lambs (P < 0.01) and decreased by age (34 ± 4 and 21 ± 2 s, for 6- and 12-mo periods, respectively; P < 0.001). Regarding lamb traceability, 2.8% temporary ear tags were lost from birth to weaning (traceability, 97.2%), but no official ear tag or mini-bolus losses were reported from weaning

  12. Progesterone administration reduces the behavioural and physiological responses of ewes to abrupt weaning of lambs.

    PubMed

    Freitas-de-Melo, A; Banchero, G; Hötzel, M J; Damián, J P; Ungerfeld, R

    2013-08-01

    Abrupt weaning, a usual management in sheep productive systems, may provoke behavioural and physiological responses indicative of stress in ewes and lambs. Progesterone (P4) has anxiolytic and sedative effects through the union of its metabolites that contain 3α-hydroxyl group to the γ-aminobutyricacidA receptor. Our first aim was to determine whether P4 administration reduces the behavioural and physiological responses of ewes to abrupt weaning of lambs. A complementary aim was to determine whether P4 treatment affects the milk yield and composition of ewes, and the BW of their lambs. In experiment 1, seven ewes received P4 treatment for 32 days (group E1-P4), and eight ewes remained as an untreated control group (group E1-C). BW of the lambs was recorded during P4 treatment. Lambs were weaned at 59 days (Day 0 = weaning). The main behaviours of the ewes before and after weaning were recorded using 10 min scan sampling. The ewes' serum total protein, albumin and globulin concentrations were measured before and after weaning of the lambs. In experiment 2, milk yield and composition were determined in two different groups of six ewes treated with P4 (group E2-P4) for 16 days and in five untreated controls (group E2-C). The BW of lambs increased with time (P = 0.001) in both groups and did not differ. The percentage of observations in which the ewes were seen pacing on Day 0 was greater in the E1-C group than in the E1-P4 group (P = 0.0007). Similarly, the percentage of observations in which the ewes were recorded vocalizing on Day 0 was greater in the E1-C group than in the E1-P4 group (P = 0.04). The percentage of observations in which E1-C ewes were recorded lying did not change from Days 0 to 1; however, it increased in E1-P4 ewes. Total serum protein concentration did not change in E1-P4 ewes from Days 0 to 3, although a decrease was seen in E1-C ewes (P = 0.04). Serum globulin concentration was greater in E1-P4 ewes on Day 3 than in E1-C ewes (P = 0.0008). In

  13. Comparison of meat and carcass quality in organically reared and conventionally reared pasture-fed lambs.

    PubMed

    Prache, S; Gatellier, P; Thomas, A; Picard, B; Bauchart, D

    2011-12-01

    The 'Organic' product label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises recourse to pharmaceuticals or veterinary drugs; however, the product's quality remains an issue that needs to be addressed in response to consumer demand. Consequently, this study was conducted to compare the sensory and nutritional qualities of meat and carcasses from pasture-fed lambs reared organically (O) or conventionally (C). Mean lamb growth profile was kept similar between the two treatments to avoid confounding effects with lamb age or weight at slaughter. The experiment was conducted over 3 years (2005 to 2007) with 12 O and 12 C lambs each year. The O and C treatments differed in the level of on-pasture mineral N fertilisation inducing a higher proportion of white clover in the organic pasture than the conventional pasture. Lambs were slaughtered when they attained a fat class of 2 to 3, and carcass and meat quality were evaluated. Lambs were slaughtered at an average weight and age of 35.3 kg and 156 days in the O treatment, respectively, and 35.2 kg and 155 days in the C treatment, respectively. Sensory evaluation indicated that loin chops from the O treatment had a higher level of abnormal fat odour compared with the C treatment. Carcasses from the O treatment had a softer subcutaneous fat one among 3 years (2007) compared to the C treatment. These results are probably due to a higher proportion of white clover in the diet. Organically reared lambs did offer the slight advantage of muscle fatty acid containing a higher level of stearic acid, which may have positive effects in the prevention of cardiovascular disease in humans. This may be the result of a higher rumen bio-hydrogenation of C18:3n-3 due to differences in the botanical composition between the O and the C pasture. Production system had no effect on the colour characteristics of the meat and subcutaneous fat, except lightness of subcutaneous dorsal

  14. Intake, digestibility, nitrogen balance, performance, and carcass yield of lambs fed licuri cake.

    PubMed

    Costa, J B; Oliveira, R L; Silva, T M; Ribeiro, R D X; Silva, A M; Leão, A G; Bezerra, L R; Rocha, T C

    2016-07-01

    This study aimed to determine the impact of the inclusion of licuri cake in the diets of crossbred Santa Inês lambs, based on intake, digestibility, N balance, urea N, and performance. We used 44 male lambs that were vaccinated and wormed, with an average age of 6 mo and an average BW of 21.2 kg ± 2.7 kg. The lambs were fed a mixture of Tifton-85 hay (40%) and a concentrated mixture (60%) composed of ground corn, soybean meal, and mineral premix. For the treatments, licuri cake was added at levels of 0, 8, 16, and 24% of DM, with the licuri cake replacing soybean meal and ground corn. We used 11 lambs per treatment in a randomized design. The lambs were confined for 70 d, and the digestibility trial occurred between Day 40 and Day 55. The increased level of licuri cake inclusion promoted a linear reduction in DM intake ( = 0.00) with a 39% reduction between treatments with the 0 and 24% cakes. On the other hand, ether extract () consumption showed an initial quadratic increase ( = 0.00). The total weight gain and ADG showed a linear decrease ( = 0.00) with the addition of licuri cake. The inclusion of licuri cake linearly enhanced ( = 0.02) the digestibility of CP and EE, whereas the digestibility of other nutrients in lambs remained unchanged ( > 0.05). The licuri cake increase led to a linear decrease ( < 0.05) in the N intake, fecal N, and retained N in lambs. Urinary N was not changed. The slaughter carcass weight, HCW, cold carcass weight, hot carcass yield, and cold carcass yield showed linear decreases ( < 0.05) with the addition of licuri cake. Carcass morphometric measurements were influenced by experimental diets, showing linear decreases ( < 0.05) with the addition of licuri cake to diets. The fat thickness, conformation, external length, internal length, leg length, rump width, and chest circumference showed linear decreases ( < 0.05) with the inclusion of licuri cake in diets. The inclusion of licuri cake decreased DMI and digestibility, reflecting

  15. Intake, digestibility, nitrogen balance, performance, and carcass yield of lambs fed licuri cake.

    PubMed

    Costa, J B; Oliveira, R L; Silva, T M; Ribeiro, R D X; Silva, A M; Leão, A G; Bezerra, L R; Rocha, T C

    2016-07-01

    This study aimed to determine the impact of the inclusion of licuri cake in the diets of crossbred Santa Inês lambs, based on intake, digestibility, N balance, urea N, and performance. We used 44 male lambs that were vaccinated and wormed, with an average age of 6 mo and an average BW of 21.2 kg ± 2.7 kg. The lambs were fed a mixture of Tifton-85 hay (40%) and a concentrated mixture (60%) composed of ground corn, soybean meal, and mineral premix. For the treatments, licuri cake was added at levels of 0, 8, 16, and 24% of DM, with the licuri cake replacing soybean meal and ground corn. We used 11 lambs per treatment in a randomized design. The lambs were confined for 70 d, and the digestibility trial occurred between Day 40 and Day 55. The increased level of licuri cake inclusion promoted a linear reduction in DM intake ( = 0.00) with a 39% reduction between treatments with the 0 and 24% cakes. On the other hand, ether extract () consumption showed an initial quadratic increase ( = 0.00). The total weight gain and ADG showed a linear decrease ( = 0.00) with the addition of licuri cake. The inclusion of licuri cake linearly enhanced ( = 0.02) the digestibility of CP and EE, whereas the digestibility of other nutrients in lambs remained unchanged ( > 0.05). The licuri cake increase led to a linear decrease ( < 0.05) in the N intake, fecal N, and retained N in lambs. Urinary N was not changed. The slaughter carcass weight, HCW, cold carcass weight, hot carcass yield, and cold carcass yield showed linear decreases ( < 0.05) with the addition of licuri cake. Carcass morphometric measurements were influenced by experimental diets, showing linear decreases ( < 0.05) with the addition of licuri cake to diets. The fat thickness, conformation, external length, internal length, leg length, rump width, and chest circumference showed linear decreases ( < 0.05) with the inclusion of licuri cake in diets. The inclusion of licuri cake decreased DMI and digestibility, reflecting

  16. Antioxidant diet supplementation and lamb quality throughout preservation time.

    PubMed

    Muela, E; Alonso, V; Campo, M M; Sañudo, C; Beltrán, J A

    2014-10-01

    Diet supplementation (DS) (100, 200, 300ppm vitamin E -VE; 150ppm product rich in flavonoids-PRF; 100+100ppm VE-PRF; no supplementation) effect was evaluated on lamb quality throughout 10days after sampling (preservation time: PT). pH, colour, myoglobin forms and lipid oxidation were analyzed on Longissimus muscle. Trained panellists evaluated colour intensity of chops packaged in modified atmosphere under display up to 12days. PT had a larger effect on quality than DS. DS showed a clear antioxidant effect on lipids, especially at long PT and at high doses of VE. Visual test showed statistical differences among DS from day 4 of display where 200 and 300ppm VE improved visual colour score. In general, supplementation with antioxidants showed better meat quality and diets higher than 100ppm VE showed higher antioxidant capacity than the rest. The PRF diet was similar for a short PT but lower at a long PT. More research on flavonoids is necessary.

  17. Crude glycerin combined with sugar cane silage in lamb diets.

    PubMed

    de Oliveira Filho, Carlos Alberto Alves; Azevêdo, José Augusto Gomes; de Carvalho, Gleidson Giordano Pinto; da Silva, Camilla Flávia Portela Gomes; Cabral, Ícaro dos Santos; Pereira, Luiz Gustavo Ribeiro; dos Reis, Larissa Gomes; de Almeida, Flávio Moreira; Souza, Lígia Lins

    2016-02-01

    This study aimed to evaluate the effect of the level of crude glycerin (CG) on in vitro fermentation kinetics (0, 20, 40, 60, and 80 g/kg DM of sugar cane silage), on in vitro neutral detergent fiber (NDF) degradation (0, 30, 60, and 90 g/kg DM of sugar cane silage), and intake and digestibility of nutrients and nitrogen balance (0, 20, 55, 82, and 108 g/kg DM of sugar cane silage) in lambs. The in vitro trials were conducted in a completely randomized design with three repetitions. The in vivo trial was conducted in a Latin square design with five repetitions (5 × 5). For variables in which the F test was considered significant, the statistical interpretation of the effect of CG substitution levels was carried out through regression analyses. Kinetic parameters were not affected by CG inclusion. On in vitro NDF degradation, a significant effect of CG levels was observed on the potentially degradable fraction of NDF, the insoluble potentially degradable fraction of NDF, and the undegradable NDF fraction. The intake and digestibility of nutrients and nitrogen balance were not affected by CG inclusion. The CG levels change in vitro NDF degradability parameters; however, there were no changes in animal intake, digestibility, and nitrogen balance with the inclusion levels used.

  18. Crude glycerin combined with sugar cane silage in lamb diets.

    PubMed

    de Oliveira Filho, Carlos Alberto Alves; Azevêdo, José Augusto Gomes; de Carvalho, Gleidson Giordano Pinto; da Silva, Camilla Flávia Portela Gomes; Cabral, Ícaro dos Santos; Pereira, Luiz Gustavo Ribeiro; dos Reis, Larissa Gomes; de Almeida, Flávio Moreira; Souza, Lígia Lins

    2016-02-01

    This study aimed to evaluate the effect of the level of crude glycerin (CG) on in vitro fermentation kinetics (0, 20, 40, 60, and 80 g/kg DM of sugar cane silage), on in vitro neutral detergent fiber (NDF) degradation (0, 30, 60, and 90 g/kg DM of sugar cane silage), and intake and digestibility of nutrients and nitrogen balance (0, 20, 55, 82, and 108 g/kg DM of sugar cane silage) in lambs. The in vitro trials were conducted in a completely randomized design with three repetitions. The in vivo trial was conducted in a Latin square design with five repetitions (5 × 5). For variables in which the F test was considered significant, the statistical interpretation of the effect of CG substitution levels was carried out through regression analyses. Kinetic parameters were not affected by CG inclusion. On in vitro NDF degradation, a significant effect of CG levels was observed on the potentially degradable fraction of NDF, the insoluble potentially degradable fraction of NDF, and the undegradable NDF fraction. The intake and digestibility of nutrients and nitrogen balance were not affected by CG inclusion. The CG levels change in vitro NDF degradability parameters; however, there were no changes in animal intake, digestibility, and nitrogen balance with the inclusion levels used. PMID:26530907

  19. Availability of phosphorus contained in poultry litter for lambs.

    PubMed

    Tagari, H; Silanikove, N; Hurwitz, S

    1981-03-01

    Percentage net phosphorus availability (NPHA) and set phosphorus utilization (NPHU) of the phosphorus contained in a heat-sterilized poultry litter (PL) as compared to feed grade dicalcium phosphate (DCP) for lambs was assessed by the "slope" method. The method was based on the evaluation of the function of apparent phosphorus absorption (NPHA), or retention (NPHU), on phosphorus intake. Nitrogen retention was also evaluated. Plasma inorganic phosphorus concentration as a function of phosphorus intake was evaluated and compared to NPHA and NPHU. The percentage of NPHA was found to be 63.7 and 39, and that of NPHU was 63 and 38 for the phosphorus supplied by DCP and PL, respectively. Thus, the NPHA or NPHU for the phosphorus contained in PL is 60.9 and 60.3% of that of DCP, respectively. The slope ratio between the two phosphate supplements as observed for plasma inorganic phosphorus concentrations was similar to those found for NPHA and NPHU but the coefficient of variation was 5 times higher. Nitrogen digestibility was not affected by the level of phosphorus in the diets. Correlation between nitrogen retention and NPHA or NPHU was, however, significant (P less than 0.05). The slopes of dependence of N retention upon phosphorus intake were 2.81 and 1.6 (P less than 0.05) for DCP and PL treatments, respectively, and the ratio between the slopes was 0.57, close to the ratio of NPHU in PL to DCP-supplemented diets.

  20. Antioxidant diet supplementation and lamb quality throughout preservation time.

    PubMed

    Muela, E; Alonso, V; Campo, M M; Sañudo, C; Beltrán, J A

    2014-10-01

    Diet supplementation (DS) (100, 200, 300ppm vitamin E -VE; 150ppm product rich in flavonoids-PRF; 100+100ppm VE-PRF; no supplementation) effect was evaluated on lamb quality throughout 10days after sampling (preservation time: PT). pH, colour, myoglobin forms and lipid oxidation were analyzed on Longissimus muscle. Trained panellists evaluated colour intensity of chops packaged in modified atmosphere under display up to 12days. PT had a larger effect on quality than DS. DS showed a clear antioxidant effect on lipids, especially at long PT and at high doses of VE. Visual test showed statistical differences among DS from day 4 of display where 200 and 300ppm VE improved visual colour score. In general, supplementation with antioxidants showed better meat quality and diets higher than 100ppm VE showed higher antioxidant capacity than the rest. The PRF diet was similar for a short PT but lower at a long PT. More research on flavonoids is necessary. PMID:24976562