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D Royer

Publications and source records attributed to D Royer.

At least 19 recordsLinked to original sources
PubMed2006

A combined finite element and modal decomposition method to study the interaction of Lamb modes with micro-defects.

This paper presents a combined finite element and modal decomposition method to study the interaction of Lamb waves with damaged area. The finite element mesh is used to describe the region around the defects. On the contrary to other hybrid models already developed, the interaction between Lamb waves and defects is computed in the temporal domain. Then, the modal decomposition method permits to determine the wave reflected and transmitted by the damaged area. Modal analysis allows also identifying the mode conversions induced by the defects. These numerical results agree with previous finite element results concerning the interaction of Lamb modes with a notch. Experiments, carried out with gauged defects on an aluminum plate, are also compared to numerical predictions to validate the simulation. Compared to classical techniques of simulation, this new method allows us to investigate the interaction of Lamb modes generated at high frequency-thickness product with micro-defects as corrosion pitting.

Computer Simulation↗
PubMed2004

Quantitative analysis of Fusarium mycotoxins in maize using accelerated solvent extraction before liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry.

A method for the simultaneous quantitative determination of deoxynivalenol (DON), fumonisin B1 (FB1) and zearalenone (ZEN) in maize by liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCIMS/MS), using stable isotopically labelled and structural analogues internal standards, is described. The procedure involves accelerated solvent extraction followed by two solid-phase clean-up steps on strong anion exchange resin and a Mycosep column. Typical recoveries were calculated by spiking blank maize at three different concentrations for deoxynivalenol (200, 400 and 1000 microg kg(-1)) at 70%, for fumonisin B1 (100, 200 and 1000 microg kg(-1)) at 90%, and for zearalenone (50, 100 and 200 microg kg(-1)) at 40%. LC-APCIMS/MS analyses were realized in collision-induced dissociation on an ion-trap instrument to provide a high degree of selectivity and sensitivity. Extraction of ions from two transition reactions, monitored by LC-APCIMS/MS for each analyte, enabled a limit of detection for DON, FB1 and ZEN at, respectively, 10, 20 and 3 microg kg(-1), and a limit of quantification at, respectively, 50, 50 and 10 microg kg(-1). The robustness of the method was also evaluated with the analysis of wheat samples.

Animals↗
PubMed2003

Analysis of chloramphenicol in honeys of different geographical origin by liquid chromatography coupled to electrospray ionization tandem mass spectrometry.

A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed to detect trace amounts of the antibiotic chloramphenicol (CAP) in honey. The methodology entailed a solid-phase extraction of aqueous honey solutions followed by liquid-liquid partitioning, filtration and direct injection onto the LC-MS/MS system. Honey extracts were spiked with an isotopically labelled internal standard (d(5)-CAP) to compensate for analyte loss and potential ion suppression during the MS stage. Detection of the analyte was achieved by negative ionization electrospray in the selected reaction monitoring (SAM) mode. For confirmation, four characteristic mass transitions were monitored each for the analyte and the surrogate standard. The method was validated according to the latest European Union criteria for the analyses of veterinary drug residues in food. At all three fortification levels studied (0.1, 0.2, 0.5 microg kg(-1)) the method was accurate to within 15%. The repeatability and within-laboratory reproducibilities were <12 and 18%, respectively. The decision limit (CC alpha) and detection capability (CC beta) were both <0.1 microg kg(-1). The procedure provides a sensitive and reliable method for the determination of residues of chloramphenicol in honey. Numerous raw honeys of various geographical origins were analysed, showing extensive contamination particularly those of Chinese origin.

Animals↗
PubMed2002

Detection of cracks in a thin air-filled hollow cylinder by application of the DORT method to elastic components of the echo.

The DORT method (Decomposition de l'Opérateur de Retournement Temporel in French) is a scattering analysis technique which uses arrays of transducers. This method is efficient for detection of selective focusing on point-like scatterers. It has been also applied to analyze the scattering by an air-filled cylindrical steel shell immersed in water. It was shown that the diagonalization of the time reversal operator allows us to separate the different elastic components of the scattered field. Here, we apply the method to detect flaws in hollow cylinders. In this case, the dominant components are the three circumferential waves (A0, A1 and S0 Lamb modes). Each Lamb mode corresponds to an invariant of the time reversal operator. The dispersion curves of these waves are calculated from these invariants. Resonance frequencies of the shell are deduced from the frequency dependence of the eigenvalues of the time reversal operator. It is shown that the presence of a crack (0.2 mm in depth) affects significantly the eigenvalue distribution of the time reversal operator. Thus, the DORT method offers a new means for detecting defects in a shell.

Journal Article↗
PubMed2002

Nondestructive evaluation of cylindrical parts using laser ultrasonics.

We applied the laser ultrasonic technique for detecting surface breaking slots in steel cylinders (25 mm in diameter). The observation of the detected signal over a long time (500 micros), shows that the interaction of the two contra-propagating incident Rayleigh waves reinforce the echoes coming from the defect. These echoes are slowly growing with time whereas the main signals decrease. This energy transfer occurring at each revolution of the waves around the cylinder allows the detection of cracks having a depth (h approximately 80 microm), very small compared to the Rayleigh wavelength (lambda approximately 2 mm). The evaluation of the material was performed by processing the detected signal in a sliding time window. A cross-correlation is made either between a reference signal and the signal from the tested sample or between two signals probed for two different positions of the sample. In both cases, the slope of the cross-correlation coefficient versus the number of turns is proportional to the depth of the slot.

Journal Article↗
PubMed2001

A study of the secular equation for rayleigh waves using the root locus method.

In a recent note Rahman and Barber [Trans. ASME 62 (1995) 250] proposed an exact expression for the roots of the secular equation for the Rayleigh waves in an isotropic half-space. Using the root locus method, we describe in a very simpler manner the evolution of the roots versus the Poisson's ratio and we derive easily the critical value for which the nature of the roots changes.

Journal Article↗
PubMed2001

Diffraction effects in the parametric interaction of acoustic waves: application to measurements of the nonlinearity parameter B/A in liquids.

This paper deals with diffraction effects related to the determination of nonlinearity parameters B/A in liquids using the parametric interaction. A diffraction model, based on plane wave expansions, is applied to weak nonlinear interactions between two ultrasonic waves propagating in an absorbing medium. A validation of the model has been carried out with an experiment performed using an optical interferometer. A method is proposed to measure nonlinearity parameters with the parametric interaction of two waves with a high frequency ratio. With respect to diffraction effects, the parametric interaction can then be identified with a phase modulation of the high frequency wave. A prototype, using the interaction of a 30-MHz frequency continuous wave with an acoustic pulse of central frequency 2.5 MHz, has been designed. The proposed method is validated by nonlinearity parameters measurements in well-known liquids (water and ethanol). The uncertainty on absolute measurements is discussed, and a relative method is proposed to increase the accuracy. This method enables measurements without any transducer calibration.

Journal Article↗
PubMed2000

Experimental and theoretical waveforms of Rayleigh waves generated by a thermoelastic laser line source.

An analytical model has been developed for the generation of surface acoustic (Rayleigh) waves in an isotropic solid by a thermoelastic laser line source. For a Gaussian light intensity profile, this model leads to an expression in closed form for the normal surface displacement of the Rayleigh wave either in the near field or in the far field domain. Quantitative agreement has been found for experiments carried out with an interferometric optical probe on a duraluminum plate.

Acoustics↗
PubMed2000

[The platelet/leukocyte ratio in red blood cell concentrates is an essential indicator of leukocyte removal filter efficiency which limits their use].

Performances of filter systems for leucocyte removal (Pall BPF4 and Sepacell RZ 200 B) have been studied following the preparation of red blood cell concentrates (RBCCs) obtained either by a soft-spin centrifugation at 2967xg (n = 438) or by a hard-spin centrifugation at 5275xg (n = 187). After deleucocytation, 43, i.e., 9.8% of RBCCs obtained following a soft-spin centrifugation contained a number of residual leucocytes higher than 1 x 10(6) leucocytes/RBCC which represents the legal upper limit in France, whereas RBCCs obtained following a hard-spin centrifugation always contained a number of residual leucocytes lower than this limit. Our results strongly suggest that the quality of deleucocytation depends on an adequate ratio of platelets to leucocytes, which favours the capture of leucocytes by filters. In fact, this ratio was higher in RBCCs obtained following a hard-spin centrifugation. Our results demonstrate that the use of these filters does not allow the removal of leucocytes complying with the legal limit of leucodepletion for all preparations of RBCCs.

Cell Separation↗
PubMed2000

A preliminary study of sonographic grading of fetal intracardiac echogenic foci: feasibility, reliability and association with aneuploidy.

OBJECTIVES: To prospectively and quantitatively grade intracardiac echogenic focus/foci (ICEF) using sonographic gain reduction and to determine the association of ICEF by grade with fetal aneuploidy. METHODS: Women referred for raised maternal age (> or = 35 years), or > 18 years of age and with a Down syndrome risk > or = 1/270, increased trisomy 18 risk by second trimester serum screen or a prior aneuploid offspring were included in this institutionally approved protocol. Only pregnancies of gestational age between 14 and 24 weeks were included. All women had a targeted ultrasound and were offered fetal chromosome analysis. The classification of ICEF was made from a four-chamber view of the fetal heart. The echo amplitude of the ICEF was compared to that of the thoracic spine and categorized according to the comparative gain setting at which the image of the relevant structure disappeared: Grade O = no ICEF present, Grade 1 = ICEF image lost before thoracic spine when gain was reduced, Grade 2 = ICEF image lost at same gain setting as thoracic spine, Grade 3 = thoracic spine image lost before ICEF. The primary outcome was a prenatally or post-natally detected chromosomal abnormality. RESULTS: A total of 885 eligible women were examined during the 21-month study period. ICEF were seen in 29 (3.3%) fetuses: 24(83%) in the left ventricle and five (17%) in the right ventricle. A chromosome abnormality was identified in 13/671 (1.9%) fetuses without ICEF (Grade 0) and 0/21 (0%) fetuses with Grade 1 ICEF. In contrast, two of five (40%) fetuses with Grade 2 ICEF were aneuploid (P = 0.005). No Grade 3 ICEF were observed. Additional sonographic abnormalities were seen in both aneuploid fetuses with Grade 2 ICEF. Interobserver agreement on ICEF grading was noted in 50/50 (100%) examinations (kappa = 1.0). CONCLUSIONS: Sonographic grading of ICEF is feasible and highly reliable. Grade 2 ICEF, especially when accompanied by additional sonographic markers of a chromosomal abnormality, are associated with aneuploidy significantly more frequently than Grade 1 ICEF.

Adult↗
PubMed2000

Efficacy of community-based second trimester genetic ultrasonography in detecting the chromosomally abnormal fetus.

We sought to assess prospectively the efficacy of community-based genetic ultrasonography in detecting chromosomally abnormal fetuses in a high-risk population and determine independent markers of aneuploidy. Patients 18 years old and older who were between 14 and 24 weeks' gestation were included if referred for maternal age greater than 35 years, increased risk of Down syndrome or trisomy 18 by second trimester serum screen, or prior affected offspring. All women had a targeted ultrasonographic examination between April 1997 and June 1999 and were offered fetal chromosomal analysis. Markers of aneuploidy and pregnancy outcomes were recorded prospectively. The primary outcome was prenatally or postnatally detected chromosomal abnormalities. Of the 1030 fetuses seen during the study, 789 had outcome data available and constituted the study group. In this group, 694 (87.9%) ultrasonograms were normal, 73 (9.2%) had one marker present, 17 (2.2%) had two markers present, and 5 (0.6%) had three or more markers present. Fourteen of 17 (82.3%) aneuploid fetuses had an abnormal ultrasonogram (one or more markers present), including 5 of 7 (71.4%) with Down syndrome. Logistic regression showed abnormal four-chamber view, structural anomaly, and intracardiac echogenic focus to be significant aneuploidy markers. The amniocentesis rate was 334 of 1030 (32.4%), and it increased with the number of sonographic markers noted (0 = 29.9%, 1 = 60.2%, 2 = 70.6%, 3 or more = 80%). Genetic ultrasonography is highly effective in identifying chromosomally abnormal fetuses in a community-based practice.

Adolescent↗
PubMed1999

Ultrasonographic diagnosis of thoracopagus conjoined twins in a monoamniotic triplet gestation.

Ultrasonographic examination at 16 weeks 5 days' gestation diagnosed a monoamniotic triplet gestation complicated by thoracopagus conjoined twins. After pregnancy termination, the ultrasonographic diagnoses were confirmed by pathologic examination. In reporting the first ultrasonographically diagnosed monamniotic triplets with conjoined twins, we demonstrate that a systematic evaluation by twin-derived ultrasonographic techniques may permit correct diagnosis of unusual triplet pregnancies.

Adolescent↗
PubMed1999

[Quality control of labile blood products. Why and howto properly take a specimen? Labile Blood Products Group of the French Blood Transfusion Society].

This article reviews the various techniques of sampling used for the quality control of blood cell products. The importance of this stage for the validity of quality control results is emphasized. Three sampling methods, i.e., stripping, the sterile connection of sampling bag and the destructive method, are described in the form of operating modes and analyzed according to their advantages and drawbacks. The results of a comparative study carried out by the working group 'Blood Cell Products' of the French Society of Blood Transfusion are presented, showing that each method is valid and permits one to obtain a representative sample of the product to be controlled. Thus the diversity of the sampling methods allows us to select the one most adapted to the product to be controlled and to the analyses to be carried out afterward.

Blood Specimen Collection↗
PubMed1992

Determination of yohimbine and its two hydroxylated metabolites in humans by high-performance liquid chromatography and mass spectral analysis.

The existence of at least two metabolites of yohimbine (YO) in humans is demonstrated. Combined high-performance liquid chromatographic (HPLC), NMR and mass spectral analyses permitted them to be identified as hydroxylated metabolites at the C-10 and C-11 positions. A normal-phase HPLC method allowing the simultaneous determination of YO and its main metabolite, 11-hydroxyyohimbine (11-OHYO), in biological samples is described. This assay was performed using a LiChrosorb Si 60 column and a mobile phase consisting of 0.02 M sodium acetate (pH 5)-methanol (5:95, v/v) at a flow-rate of 1 ml/min. Detection was achieved by a fluorimetric method (excitation at 280 nm and emission at 320 nm). The extraction yields of YO, 10-OHYO and 11-OHYO from plasma were 91.8, 45.3 and 17.8%, respectively, and their respective within-day reproducibilities were 3.8, 1.4 and 5.9%. The between-day reproducibility for YO at the concentrations of 1 and 10 ng/ml were 8.9 and 6.4%, respectively. The accuracy of the method for YO at concentrations of 1 and 10 ng/ml were 5.1 and 2.3%, respectively. The limits of determination of YO, 10-OHYO and 11-OHYO were 0.1, 0.5 and 1 ng/ml, respectively. The method was used in bioavailability study of YO following oral and intravenous administration in humans.

Biological Availability↗
PubMed1979

Skeletal muscle analysis of wheelchair athletes.

The present study reports the results of using the biopsy technique with members of the Canadian Wheelchair Internation Team. The results demonstrate that these athletes possess muscles with large fibre areas than seen in Olympic athletes.

Adult↗