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1.
Toxicol Sci ; 2024 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-38730555

RESUMEN

The zebrafish (Danio rerio) is becoming a critical component of New Approach Methods (NAMs) in chemical risk assessment. As a whole organism in vitro NAM, the zebrafish model offers significant advantages over individual cell-line testing, including toxicokinetic and toxicodynamic competencies. A transcriptomic approach not only allows for insight into mechanism of action for both apical endpoints and unobservable adverse outcomes, but also changes in gene expression induced by lower, environmentally relevant concentrations. In this study, we used a larval zebrafish model to assess the behavioral and transcriptomic alterations caused by sub-phenotypic concentrations of two chemicals with the same structural backbone, the endocrine disrupting chemicals: Bisphenol A and Tetrabromobisphenol A. Following assessment of behavioral toxicity, we used a transcriptomic approach to identify molecular pathways associated with previously described phenotypes. We also determined the transcriptomic Point of Departure (POD) for each chemical by modelling gene expression changes as continuous systems which allows for the identification of a single concentration at which toxic effects can be predicted. This can then be investigated with confirmatory cell-based testing in an integrated approach to testing and assessment (IATA) to determine risk to human health and the environment with greater confidence. This paper demonstrates the impact of using a multi-faceted approach for evaluating the physiological and neurotoxic effects of exposure to structurally related chemicals. By comparing phenotypic effects with transcriptomic outcomes, we were able to differentiate, characterize and rank the toxicities of related bisphenols, which demonstrates methodological advantages unique to the larval zebrafish NAM.

2.
Regul Toxicol Pharmacol ; 138: 105336, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36642323

RESUMEN

In Canada, the Canadian Environmental Protection Act (1999) requires human health and environmental risk assessments be conducted for new substances prior to their manufacture or import. While this toxicity data is historically obtained using rodents, in response to the international effort to eliminate animal testing, Health Canada is collaborating with the National Research Council (NRC) of Canada to develop a New Approach Method by refining existing NRC zebrafish models. The embryo/larval zebrafish model evaluates systemic (whole body) general toxicity which is currently unachievable with cell-based testing. The model is strengthened using behavioral, toxicokinetic and transcriptomic responses to assess non-visible indicators of toxicity following chemical exposure at sub-phenotypic concentrations. In this paper, the predictive power of zebrafish transcriptomics is demonstrated using two chemicals; Raloxifene and Resorcinol. Raloxifene exposure produced darkening of the liver and malformation of the nose/mandible, while Resorcinol exposure produced increased locomotor activity. Transcriptomic analysis correlated differentially expressed genes with the phenotypic effects and benchmark dose calculations determined that the transcriptomic Point of Departure (POD) occurred at subphenotypic concentrations. Correlating gene expression with apical (phenotypic) effects strengthens confidence in evaluation of chemical toxicity, thereby demonstrating the significant advancement that the larval zebrafish transcriptomics model represents in chemical risk assessment.


Asunto(s)
Contaminantes Químicos del Agua , Pez Cebra , Animales , Humanos , Pez Cebra/genética , Transcriptoma , Larva , Clorhidrato de Raloxifeno , Canadá , Medición de Riesgo , Contaminantes Químicos del Agua/toxicidad
3.
J Affect Disord ; 308: 466-472, 2022 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-35460735

RESUMEN

OBJECTIVE: Somatoform disorders and functional somatic syndromes (FSS) with symptoms that are not sufficiently explained by physical or technical examination are among the most challenging underlying causes. Many different somatoform disorders and FSS have overlapping symptoms, often with pain as the most prevalent one, leading to a high burden of disease. The concept of multisomatoform disorder (MSD) has been developed to acknowledge that fact. We analyzed a group of 151 patients and 149 matched controls to identify interactions of genetic and environmental factors with a possible influence on the development of MSD. DESIGN: In a retrospective case-control study, we performed a statistical analysis on 151 patients and 149 matched controls using logistic regression and a Classification and Regression Tree (CART) analysis. RESULTS: The logistic regression analysis of genes and environmental factors demonstrated significant differences in the results of the Trier Inventory of Chronic Stress (TICS) questionnaire, the single nucleotide polymorphism rs1800955 of the dopamine receptor D4 and the single nucleotide polymorphism rs4818 of the enzyme catechol-O-methyltransferase between patients with MSD and healthy controls. The resulting decision tree of the CART analysis determined that the TICS questionnaire was able to differentiate patients and controls most accurately, followed by certain genotypes of the 5-hydroxytryptamine receptor 2A and a single nucleotide polymorphism of the enzyme catechol-O-methyltransferase. CONCLUSIONS: The results of the statistical analysis identified a gene-environmental interaction possibly leading to MSD. The resulting identifiers could be used as a reference to inform diagnostic algorithms to easier identify patients suffering from MSD.


Asunto(s)
Catecol O-Metiltransferasa , Trastornos Somatomorfos , Estudios de Casos y Controles , Catecol O-Metiltransferasa/genética , Genotipo , Humanos , Dolor , Polimorfismo de Nucleótido Simple/genética , Estudios Retrospectivos , Trastornos Somatomorfos/diagnóstico , Trastornos Somatomorfos/genética
4.
Front Toxicol ; 4: 817999, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35387429

RESUMEN

Toxicological evaluation of chemicals using early-life stage zebrafish (Danio rerio) involves the observation and recording of altered phenotypes. Substantial variability has been observed among researchers in phenotypes reported from similar studies, as well as a lack of consistent data annotation, indicating a need for both terminological and data harmonization. When examined from a data science perspective, many of these apparent differences can be parsed into the same or similar endpoints whose measurements differ only in time, methodology, or nomenclature. Ontological knowledge structures can be leveraged to integrate diverse data sets across terminologies, scales, and modalities. Building on this premise, the National Toxicology Program's Systematic Evaluation of the Application of Zebrafish in Toxicology undertook a collaborative exercise to evaluate how the application of standardized phenotype terminology improved data consistency. To accomplish this, zebrafish researchers were asked to assess images of zebrafish larvae for morphological malformations in two surveys. In the first survey, researchers were asked to annotate observed malformations using their own terminology. In the second survey, researchers were asked to annotate the images from a list of terms and definitions from the Zebrafish Phenotype Ontology. Analysis of the results suggested that the use of ontology terms increased consistency and decreased ambiguity, but a larger study is needed to confirm. We conclude that utilizing a common data standard will not only reduce the heterogeneity of reported terms but increases agreement and repeatability between different laboratories. Thus, we advocate for the development of a zebrafish phenotype atlas to help laboratories create interoperable, computable data.

5.
Schmerz ; 35(2): 103-113, 2021 Apr.
Artículo en Alemán | MEDLINE | ID: mdl-32804299

RESUMEN

BACKGROUND: On 31 December 2016, a total of 1206 physicians participated in the outpatient care of chronic pain patients according to the criteria of a special pain management program (QSV). Because of the largely existing shortage of treatment resources for chronic pain patients, there is a lack of data regarding the evaluation of outpatient pain management by highly specialized pain therapists. METHODS: In a hybrid Delphi procedure, a questionnaire concerning the content, structural and personal assessment of outpatient pain management in Germany was developed. With the help of this instrument, an internet-based cross-sectional survey of 281 QSV pain therapists from four German states (Berlin, Lower Saxony, Saxony, Baden-Württemberg) and of all the heads of university outpatient pain services (n = 36) in Germany was conducted. RESULTS: The adjusted response rate of the survey was 35.9%. The response rate of the heads of university outpatient pain services was 66.7%. In 91% of the respondents the proportion of chronic pain patients in the medical practices was more than 70%. Whereas 67.3% were satisfied with the situation in their medical practice, 63.4% were dissatisfied with the current organizational structure of the pain management in Germany. They expressed their dissatisfaction especially in terms of budgeting regulations (69.3%), the cooperation with psychotherapists (69.3%) and interdisciplinary networking (50.5%). The 1­year specialist training in pain management (87.1%) and the completion of a psychosomatic basic care course (90.1%) were assessed as a good preparation for the later profession. A multitude of free comments indicated that the pain specialist training is too short and insufficient. Most of the respondents considered the establishment of a specialist board certification for pain management more suitable from the perspective of physicians (61.4%) and the patients (54.5%). Of the heads of university outpatient pain services 70.8% expressed the wish for autonomous structures with separate budgets and 75.0% indicated that under the current conditions their outpatient pain services are not working profitably. Only 39.7% of the QSV pain therapists provided fellowship training for physicians and 57.6% were planning to retire during the next 10 years. CONCLUSION: Highly specialized pain therapists are dissatisfied because of the lack of independence of the organizational structure of pain management care and the insufficient interdisciplinary network in outpatient pain management. A possible solution for a better pain management care and the recruitment problems may be the establishment of a board certification for pain management.


Asunto(s)
Pacientes Ambulatorios , Manejo del Dolor , Berlin , Estudios Transversales , Alemania , Humanos , Internet , Especialización
6.
J Cancer Res Clin Oncol ; 144(7): 1375-1383, 2018 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-29687154

RESUMEN

PURPOSE: The controlled phase III trial SATURN demonstrated that maintenance therapy with erlotinib after the first-line platinum-based chemotherapy prolonged progression-free survival (PFS) and overall survival (OS) of non-small cell lung cancer (NSCLC) patients with advanced, non-progressive disease. We conducted the non-interventional study SATURN NIS to investigate the effectiveness and tolerability of erlotinib maintenance in daily clinical practice. METHODS: This single-arm NIS screened 290 patients with locally advanced or metastatic NSCLC (stage IIIB or IV) and stable disease after standard platinum-based first-line chemotherapy in 95 institutions across Germany. Erlotinib was dosed and administered corresponding to the terms of the marketing authorization at the time of recruitment. The main effectiveness endpoint was subjects' OS at 1 year. Subgroup analyses of survival estimates of OS and PFS were performed. RESULTS: 272 patients were eligible for analysis (median age 66 years, 37.1% females, 99.6% Caucasian, median ECOG performance status 1, 61.8% adenocarcinoma, 96.3% of patients with stable disease). Maintenance therapy with erlotinib resulted in median OS comparable to that of the SATURN phase III trial 10.4 months [95% CI: (8.8; 12.5) vs. 11.9 months]. The 1-year survival rate was 45.6% [95% CI: (37.5%; 53.6%)]. No new safety signals were observed. As expected, patients with epidermal growth factor receptor (EGFR) mutations derived a greater benefit concerning OS and PFS than EGFR-wild-type patients. Moreover, a significant association of OS and PFS and the smoking status was observed. CONCLUSIONS: The results of this non-interventional study support the current clinical practice of erlotinib switch maintenance in EGFR-mutation-positive patients.


Asunto(s)
Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Clorhidrato de Erlotinib/administración & dosificación , Neoplasias Pulmonares/tratamiento farmacológico , Anciano , Anciano de 80 o más Años , Antineoplásicos/administración & dosificación , Antineoplásicos/efectos adversos , Carcinoma de Pulmón de Células no Pequeñas/enzimología , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Supervivencia sin Enfermedad , Receptores ErbB/genética , Clorhidrato de Erlotinib/efectos adversos , Femenino , Humanos , Neoplasias Pulmonares/enzimología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Quimioterapia de Mantención/métodos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/efectos adversos , Tasa de Supervivencia , Resultado del Tratamiento
7.
Behav Brain Res ; 337: 151-159, 2018 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-28935439

RESUMEN

It has been established that both adult and larval zebrafish are capable of showing nociceptive responses to noxious stimuli; however, the use of larvae to test novel analgesics has not been fully explored. Zebrafish larvae represent a low-cost, high-throughput alternative to traditional mammalian models for the assessment of product efficacy during the initial stages of drug development. In the current study, a novel model of nociception using zebrafish larvae is described. During the recovery from an acute exposure to low levels of acetic acid, larvae display innate changes in behaviour that may be indicative of nociception. To assess the usefulness of this model for testing potential analgesics, three known synthetic pain medications were assessed (ibuprofen, acetaminophen and tramadol) along with three naturally occurring products (honokiol, tetrahydrocannabinol and cannabidiol). When the effect of each compound on both the acetic acid recovery and control activity was compared there appeared to be both similarities and differences between the compounds. One of the most interesting effects was found for cannabidiol which appeared to oppose the activity change during the recovery period of AA exposed larvae while having a nominal effect on control activity. This would appear to be in line with current research that has demonstrated the nociceptive properties of cannabidiol. Here we have provided a novel model that will complement existing zebrafish models and will expand on the potential use of zebrafish larvae for studying both nociception and new analgesics.


Asunto(s)
Analgésicos/uso terapéutico , Cannabinoides/metabolismo , Cannabinoides/uso terapéutico , Nocicepción/fisiología , Dolor/tratamiento farmacológico , Acetaminofén , Ácido Acético/toxicidad , Animales , Agonistas de Receptores de Cannabinoides/uso terapéutico , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Dronabinol/uso terapéutico , Ibuprofeno , Larva , Locomoción/efectos de los fármacos , Nocicepción/efectos de los fármacos , Dolor/inducido químicamente , Análisis de Componente Principal , Factores de Tiempo , Tramadol , Pez Cebra
8.
Transbound Emerg Dis ; 64(5): 1393-1404, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-27211823

RESUMEN

African swine fever (ASF) is an important emerging transboundary animal disease (TAD), which currently has an impact on many countries in Africa, Eastern Europe, the Caucasus and the Russian Federation. The current situation in Europe shows the ability of the virus to rapidly spread, which stands to threaten the global swine industry. At present, there is no viable vaccine to minimize spread of the disease and stamping out is the main source of control. In February 2011, Ethiopia had reported its first suspected outbreaks of ASF. Genomic analyses of the collected ASF virus (ASFV) strains were undertaken using 23 tissue samples collected from domestic swine in Ethiopia from 2011 to 2014. The analysis of Ethiopian ASFVs partial p72 gene sequence showed the identification of a new genotype, genotype XXIII, that shares a common ancestor with genotypes IX and X, which comprise isolates circulating in Eastern African countries and the Republic of Congo. Analysis of the p54 gene also followed the p72 pattern and the deduced amino acid sequence of the central variable region (CVR) of the B602L gene showed novel tetramer repeats not previously characterized.


Asunto(s)
Virus de la Fiebre Porcina Africana/genética , Fiebre Porcina Africana/virología , Variación Genética , Fiebre Porcina Africana/diagnóstico , Fiebre Porcina Africana/epidemiología , Virus de la Fiebre Porcina Africana/clasificación , Virus de la Fiebre Porcina Africana/aislamiento & purificación , Secuencia de Aminoácidos , Animales , Brotes de Enfermedades/veterinaria , Etiopía/epidemiología , Genotipo , Filogenia , Análisis de Secuencia de ADN/veterinaria , Porcinos
9.
Transbound Emerg Dis ; 64(5): 1598-1609, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-27480888

RESUMEN

Sequencing and analysis of three discrete genome regions of African swine fever viruses (ASFV) from archival samples collected in 2007-2011 and active and passive surveillance between 2012 and 2015 in Nigeria were carried out. Analysis was conducted by genotyping of three single-copy African swine fever (ASF) genes. The E183L and B646L genes that encode structural proteins p54 and p72, respectively, were utilized to delineate genotypes before intragenotypic resolution by characterization of the tetrameric amino acid repeat region within the hypervariable central variable region of the B602L gene. The results showed no variation in the p72 and p54 gene regions sequenced. Phylogeny of p72 sequences revealed that all the Nigerian isolates belonged to genotype I, while that of the p54 recovered the Ia genotype. Analysis of B602L gene revealed the differences in the number of tetrameric repeats. Four new variants (Tet-15, Tet-17a, Tet-17b and Tet-48) were recovered, while a fifth variant (Tet-20) was the most widely distributed in the country displacing Tet-36 reported previously in 2003-2006. The viruses responsible for ASF outbreaks in Nigeria are from very closely related but mutated variants of the virus that have been circulating since 1997. A practical implication of the genetic variability of the Nigerian viral isolates in this study is the need for continuous sampling and analysis of circulating viruses, which will provide epidemiological information on the evolution of ASFV in the field versus new incursion for informed strategic control of the disease in the country.


Asunto(s)
Virus de la Fiebre Porcina Africana/genética , Fiebre Porcina Africana/epidemiología , Fiebre Porcina Africana/virología , Virus de la Fiebre Porcina Africana/aislamiento & purificación , Animales , Secuencia de Bases , Brotes de Enfermedades , Regulación Viral de la Expresión Génica , Variación Genética , Genotipo , Nigeria/epidemiología , Filogenia , Análisis de Secuencia de ADN , Porcinos , Proteínas Estructurales Virales/genética , Proteínas Estructurales Virales/metabolismo
10.
J Chem Phys ; 144(10): 104103, 2016 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-26979677

RESUMEN

We assess the concept of alchemical transformations for predicting how a further and not-tested change in composition would change materials properties. This might help to guide ab initio calculations through multidimensional property-composition spaces. Equilibrium volumes, bulk moduli, and relative lattice stability of fcc and bcc 4d transition metals Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag are calculated using density functional theory. Alchemical derivatives predict qualitative trends in lattice stability while equilibrium volumes and bulk moduli are predicted with less than 9% and 28% deviation, respectively. Predicted changes in equilibrium volume and bulk moduli for binary and ternary mixtures of Rh-Pd-Ag are in qualitative agreement even for predicted bulk modulus changes as large as +100% or -50%. Based on these results, it is suggested that alchemical transformations could be meaningful for enhanced sampling in the context of virtual high-throughput materials screening projects.

11.
Eur J Med Res ; 16(8): 367-74, 2011 Aug 08.
Artículo en Inglés | MEDLINE | ID: mdl-21813379

RESUMEN

OBJECTIVE: Atherosclerosis is a chronic inflammatory process. Poly(ADP-ribose) polymerase-1 (PARP), a nuclear enzyme linked to DNA repair, has been shown to be involved in atherogenesis; however, the effects on dendritic cells, T cells and serum auto-antibody levels are not fully understood. METHODS: Male Apoe-/- mice on a western diet were treated with the PARP inhibitor INO-1001 (n = 15), while the control group (n = 15) received 5% glucose solution for 10 weeks. RESULTS: Inhibition of PARP markedly reduced atherosclerotic lesion development (p = 0.001). Immunohistochemistry and mRNA analysis revealed a reduced inflammatory compound inside the lesion. Focusing on dendritic cells, INO-1001 reduced number of cells (p = 0.04), grade of activation, represented by Il12 (p = 0.04) and Cd83 (p = 0.03), and grade of attraction, represented by Mip3α (p = 0.02) in the plaque. Furthermore, INO-1001 decreased number of T lymphocyte (p = 0.003) in the lesion and grade of activation after stimulation with oxLDL in vitro. Moreover, serum IgM antibody levels to oxLDL were significantly lower in INO-1001 treated mice (p = 0.03). CONCLUSIONS: Functional blockade of PARP by INO-1001 reduces atherosclerotic lesion development. The anti-atherogenic effect is beside already known mechanisms also moderated due to modulation of DC and T cell invasion and activation, DC attraction as well as IgM antibody levels to oxLDL.


Asunto(s)
Aterosclerosis/enzimología , Autoanticuerpos/química , Células Dendríticas/enzimología , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Linfocitos T/enzimología , Animales , Apolipoproteínas E/genética , Aterosclerosis/genética , Aterosclerosis/metabolismo , Reparación del ADN , Células Dendríticas/citología , Inmunohistoquímica/métodos , Inflamación , Lipoproteínas LDL/metabolismo , Masculino , Ratones , Ratones Noqueados , Ratones Transgénicos , Poli(ADP-Ribosa) Polimerasas/genética , ARN/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Bazo/metabolismo , Linfocitos T/metabolismo
12.
Curr Pharm Biotechnol ; 5(4): 321-36, 2004 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-15320762

RESUMEN

DNAzymes, also known as deoxyribozymes or DNA enzymes, refer to single-stranded DNA molecules with catalytic capabilities. DNAzymes are generated de novo by in vitro selection--a powerful and yet simple technique that has been routinely used to isolate extremely rare DNA or RNA sequences with a function of interest (e.g. ligand-binding or catalysis) from an extraordinarily large population of single-stranded DNA or RNA molecules. Since the report of the first DNAzyme nearly ten years ago, hundreds of DNA sequences have been isolated in many research laboratories around the world to facilitate many chemical transformations of biological importance. In recent years, considerable efforts have been undertaken to assess a variety of DNAzymes for innovation-driven applications ranging from biosensing to gene regulation. This article provides a review on several key aspects of DNAzyme-related research. We will first review in vitro selection techniques used for DNAzyme creation as well as some DNAzymes created for a few representative chemical transformations. We will then discuss recent progresses in studying and developing DNAzymes as reporter molecules for detection-oriented applications, and as therapeutic agents to regulate gene expression at the RNA level. Future outlook on efforts aimed to bring the wonder of catalytic DNA from laboratory curiosity to real world application are also discussed.


Asunto(s)
Técnicas Biosensibles/métodos , ADN Catalítico/genética , ADN Catalítico/metabolismo , Marcación de Gen/métodos , Ingeniería Genética/métodos , Terapia Genética/métodos , Animales , Técnicas Biosensibles/instrumentación , ADN Catalítico/química , ADN Catalítico/uso terapéutico , Evolución Molecular , Regulación de la Expresión Génica/fisiología , Humanos
13.
Artículo en Inglés | MEDLINE | ID: mdl-18238585

RESUMEN

In this paper, we describe a fiber optic array sensor suitable for detection of bulk ultrasonic waves. This sensor is based on an intrinsic fiber optic Sagnac interferometer. The fiber array is formed by multiple folding of a continuous length of an optical fiber into flat coils. Depending on the orientation of the fiber array with respect to the ultrasonic wave, the proposed sensor can act as a conventional in-phase detector or as a narrowband detector. In the narrowband mode, the center frequency of detection can be tuned by adjusting the spacing of the fiber array elements to be equal to the ultrasonic wavelength of interest. This feature distinguishes this array sensor from conventional hydrophones in which a receiver is typically much smaller than the acoustical wavelength. It is shown that the array sensor provides an enhanced signal-to-noise ratio (SNR) compared with a single element detection scheme. Results are presented for detection of ultrasonic waves in water arising from both piezoelectric and laser ultrasonic sources. Potential areas of application of this sensor include process monitoring, smart structures, bio-medical ultrasound, and chemical sensing.

14.
Artículo en Inglés | MEDLINE | ID: mdl-18238429

RESUMEN

A linear array of surface wave transducers has been developed to generate focused surface wave motion. A novel theoretical approach, whereby time-harmonic surface wave motion is represented by a carrier wave that satisfies a reduced wave equation on the surface of the body and supports the subsurface motion, is used to model the beam generated by a single element of the array. Comparison of theoretical and experimental results show that, for a single element, the opening angle of the beam is about 20 degrees and its cross-section can be represented by a Gaussian distribution of the normal displacements. For an eight-element array, the focused beam is subsequently obtained by superposition considerations. For the focused beam comparisons of theoretical and experimental results, in which the latter have been obtained by the use of a laser interferometer, show excellent agreement both for the normal displacements along a radial line and across the width of the beam. The array can be used for self-focusing of surface waves on a surface defect.

15.
Artículo en Inglés | MEDLINE | ID: mdl-18263125

RESUMEN

The boundary element method is used to calculate the acoustic signature, produced by a line focus scanning acoustic microscope, of an elastic object containing a surface-breaking crack. The acoustic signature has a vertical (z) and horizontal (x) dependence. A model of the microscope developed earlier is used and extended to take account of the crack. The mathematical formulation of the scattering problem for the cracked object leads to hypersingular integral equations. A suitable technique is employed to solve such equations by the boundary element method. An electromechanical reciprocity identity is used to relate the received voltage to the acoustic wavefields collected by the lens. The acoustic wavefield scattered from the cracked object is investigated, and curves are presented that display the acoustic signature, as functions of (x ,z), for cracks of various depths and orientations. A method to measure the depth of a surface-breaking crack using the acoustic signature is suggested.

16.
Artículo en Inglés | MEDLINE | ID: mdl-18267599

RESUMEN

A model is presented for the computation of the acoustic material signature for a line focus scanning acoustic microscope, based on a boundary element calculation and an electromechanical reciprocity identity. This identity is used to relate the voltage at the terminals of the microscope's transducer to the acoustic wavefields at the interface between the specimen and the coupling fluid. A Gaussian beam, launched in the buffer rod, is tracked through the lens and its matching layer. A model for the matching layer that is convenient for use with the boundary element technique is presented. The wavefields scattered from the surface of the specimen, including the leaky Rayleigh wave, are then calculated. Knowing the wavefields incident on and scattered from the specimen, the acoustic signature is calculated using the reciprocity relation. Results are presented for a defect free halfspace, and are compared with those of an analytical model and an experimental measurement.

17.
Artículo en Inglés | MEDLINE | ID: mdl-18284979

RESUMEN

The authors present a rigorous proof of certain intuitively plausible reciprocal relations for time harmonic plane-wave transmission and reflection at the interface between a fluid and an anisotropic elastic solid. Precise forms of the reciprocity relations for the transmission coefficients and for the transmitted energy fluxes are derived, based on the reciprocity theorem of elastodynamics. It is shown that the reciprocity relations can be used in conjunction with measured values of peak amplitudes for transmission through a slab of the solid (water-solid-water) to obtain the water-solid coefficients. Experiments were performed for a slab of a unidirectional fiber-reinforced composite. Good agreement of the experimentally measured transmission coefficients with theoretical values was obtained.

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