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PubMed2004

Lamb waves propagation in elastic plane layers with a joint strip.

The Lamb waves are used for the ultrasonic characterization of welds because of their relative long-range propagation. In this paper, a simplified model of a weld-strip between two identical semi-infinite elastic layers is investigated. The reflected and transmitted ultrasonic fields are expressed by modal series whose coefficients are obtained by application of orthogonality relation. Comparisons with solutions obtained by finite elements wave propagation simulations are made. The energy balance between the incident and the scattered waves is also used to verify the accuracy of the obtained modal amplitudes.

Journal Article↗
PubMed2006

Nonlinear ultrasonic imaging of imperfectly bonded interfaces.

A nonlinear ultrasonic imaging system is developed for detecting and imaging damages and defects with nm order gaps in industrial materials, which were undetectable by conventional ultrasonic imaging systems. A high power pulser generating large amplitude incident waves and high gain receiver with high-pass or band-pass filters extracting the second harmonic signals are combined with a conventional C-scan imaging system. The system is applied to visualize fiber/matrix debondings or matrix crackings in CFRP plates. It also visualizes anomalous substructures in amorphous diffusion-bonded interfaces, spot-welded nuggets, and projection-welded interfaces. This system would be also useful to detect semi-closed cracks whose opening is in nm order.

Journal Article↗
PubMed1997

Fit of implant frameworks fabricated by different techniques.

PURPOSE: This study evaluated the precision of fit between an implant framework and a patient simulation model that consisted of five implant abutments located in the mandibular symphysis area. One-piece cast frameworks were compared with Procera machined and laser-welded frameworks with laser videography. MATERIAL AND METHODS: Five frameworks of each type were measured with a laser digitizer and a graphics computer program to determine a single point represented as the "Centroid" for each framework component and each implant abutment. Differences between the paired centroids for each framework/abutment interface are reported as x- and y-axis displacements, and z-axis gaps. The direction of the x- and y-axis displacements was determined. RESULTS: There were significant differences (p < 0.05) in the precision of fit between both the one-piece cast frameworks and the Procera frameworks, when compared with the abutments in the patient simulation model. The laser-welded framework exhibited a more precise fit than the one-piece casting, with significant differences at four of the five prosthodontic interfaces, when evaluated by the mean z-axis gap at the centroid points.

Computer Graphics↗
PubMed1993

Laser-assisted enterocystoplasty in rats.

The employment of laser welds to anastomose bowel to bladder in urological surgery has never been described. Using rats, we compared laser-assisted enterocystoplasty (LAE) with conventional sutured enterocystoplasty (CSE). A "patch" ileocystoplasty was performed using distal ileum. Operative time, intraluminal bursting pressure and histologic changes were evaluated. Operative time was 38% less in the LAE (p < 0.001). No statistically significant differences in bursting pressure between LAE and CSE groups was demonstrated (p = 0.654) in rats sacrificed 2 weeks postoperatively. Histologic findings in the laser-assisted enterocystoplasties included early loose granulation tissue and later organization of the granulation tissue with significant collagen deposition. In our preliminary study, laser welding of bowel within the urinary stream was safe, efficacious and rapid and resulted in a mechanically comparable surgical outcome.

Anastomosis, Surgical↗
PubMed1992

Optimal parameters for CO2 laser reconstruction of urethral tissue using a protein solder.

This study was designed to determine the optimal laser parameters for welding urethral tissue and to develop further understanding of the welding process. A partial transection of the pendulous rat urethra was repaired using laser powers of 80, 120, and 160 milliwatts with shutter speeds of 50 milliseconds, 100 milliseconds, and in a continuous wave mode. Repairs were made using the laser alone and the laser plus a protein solder. Measurements of intraluminal bursting strength, percentage stricture and histology were performed. The highest bursting strength with the least amount of tissue damage was achieved using a power of 120 milliwatts with 100 milliseconds pulses and the addition of a protein solder. The average percentage stricture was lowest with the laser plus solder repair (4.2%) when compared to laser only repair (14%). Intraluminal bursting strength was similar in both types of repairs. Histology demonstrated marked changes in collagen organization after laser application in all models.

Analysis of Variance↗
PubMed2002

Recent observations with air-coupled NDE in the frequency range of 650 kHz to 1.2 mHz.

An air-coupled NDE-system has been used for the inspection and imaging of discontinuities and inhomogenities in different kinds of materials, such as coating variations on tissue, spot welds on steel, and air inclusions in metal plates and welds. The measurement system operates in either continuous or pulse mode at sound frequencies between 0.65 and 1.2 MHz. Air-coupled piezo-based transducers with matching layers are used to overcome the acoustic impedance gap with air.

Journal Article↗
PubMed2002

Control of the ultrasonic beam transmitted through an irregular profile using a smart flexible transducer: modelling and application.

In most of industries as aeronautics, aerospace and nuclear, the main part of the ultrasonic testing is carried out directly in touch with the inspected component. Among others, the cooling piping of French pressurized water reactor comprises many welding components with complex geometry: elbows, butt welds, nozzles. In service inspections of such components performed with conventional ultrasonic contact transducers present limited performances. Variations in sensitivity are produced by unmatched contact on irregular surface, which results in poor detection performances. In addition, the beam orientation transmitted through complex interfaces cannot be totally controlled, because of the disorientations suffered by the transducer during its displacement. As a result, a possible defect cannot be correctly detected, positioned and characterized. At last, the geometry of some components limits the displacement of the transducer, resulting in an uncovered scan area. To overcome these difficulties and to improve the performances of such inspections, the CEA, supported by the safety authorities (IPSN), has developed a new concept of phased array transducer. The phased array radiating surface is flexible to optimise the contact, and thus the sensitivity of the testing, while the characteristics of the transmitted beam (orientation and focal depth) are preserved during the scanning, thanks to a delay law optimising algorithm. This computation requires the actual position of the elements, so a specific instrumentation is coupled to the transducer to measure its radiating surface distortions. Thus, this smart flexible transducer becomes self-adaptive. Recent studies have been made to obtain further performances improvements of this system, including instrumentation development and a new phased array design. Both longitudinal and shear waves focused beams can therefore be generated and mastered with this smart transducer. Inspections have been performed on a specimen containing artificial defects under a realistic profile, with an adaptive mode to compensate the effect of the irregular profile. Experimental results, displayed using specific imaging, show the ability of this system to detect and characterize defects under irregular profiles, using longitudinal or shear waves in a fully mastered beam.

Journal Article↗
PubMed2000

Laser-assisted demucosalized gastrocystoplasty with autoaugmentation in a canine model.

OBJECTIVES: Laser-assisted autoaugmentation gastrocystoplasty has been performed successfully. Experiments were performed to determine the optimal laser for tissue welding during demucosalized autoaugmentation gastrocystoplasty using both a 1.9-microm diode and a 1.32-microm neodymium:yttrium-aluminum-garnet (Nd:YAG) laser with and without thermal control. METHODS: Autoaugmentation gastrocystoplasty was performed on 18 female mongrel dogs. Anastomoses were performed by either suture or laser welding with a 50% human albumin solution. A 1.9-microm diode laser was compared with a 1.32-microm Nd:YAG laser with and without thermal control. In vivo canine bladder capacity measurements were performed both before gastrocystoplasty and at euthanasia. The animals were studied on days 4 and 14. Samples of the anastomotic area from each group were taken to measure tensile strength. Histologic samples were assessed for tissue damage. RESULTS: There was a significant increase in bladder volume in the 4-day group compared with pregastrocystoplasty values. Both the 1.9-microm diode laser and suture control dogs with the 14-day repairs had significantly more tensile strength than their 4-day counterparts. In contrast, no statistical difference was found between the 4 and 14-day 1.32-microm Nd:YAG groups. The suture control group had evidence of minor tissue devitalization at the anastomosis at both 4 and 14 days. The 1.9 and 1.32-microm laser groups both had evidence of tissue devitalization at 4 and 14 days. The 1.32-microm laser group had primarily severe tissue injury. The laser groups at 14 days demonstrated an inflammatory reaction that was localized to the albumin. CONCLUSIONS: Demucosalized gastrocystoplasty with autoaugmentation can be safely and successfully performed with a 1.9-microm diode laser without significant differences in tensile strength when compared with suture controls. The 1.32-microm Nd:YAG laser can also be successfully used; however, the long-term results appear to be inferior to the 1.9-microm diode laser.

Anastomosis, Surgical↗
PubMedDate not supplied

On the physics of unstable infiltration, seepage, and gravity drainage in partially saturated tuffs.

To improve understanding of the physics of dynamic instabilities in unsaturated flow processes within the Paintbrush nonwelded unit (PTn) and the middle nonlithophysal portion of the Topopah Spring welded tuff unit (TSw) of Yucca Mountain, we analyzed data from a series of infiltration tests carried out at two sites (Alcove 4 and Alcove 6) in the Exploratory Studies Facility (ESF), using analytical and empirical functions. The analysis of infiltration rates measured at both sites showed three temporal scales of infiltration rate: (1) a macro-scale trend of overall decreasing flow, (2) a meso-scale trend of fast and slow motion exhibiting three-stage variations of the flow rate (decreasing, increasing, and [again] decreasing flow rate, as observed in soils in the presence of entrapped air), and (3) micro-scale (high frequency) fluctuations. Infiltration tests in the nonwelded unit at Alcove 4 indicate that this unit may effectively dampen episodic fast infiltration events; however, well-known Kostyakov, Horton, and Philip equations do not satisfactorily describe the observed trends of the infiltration rate. Instead, a Weibull distribution model can most accurately describe experimentally determined time trends of the infiltration rate. Infiltration tests in highly permeable, fractured, welded tuff at Alcove 6 indicate that the infiltration rate exhibits pulsation, which may have been caused by multiple threshold effects and water-air redistribution between fractures and matrix. The empirical relationships between the extrinsic seepage from fractures, matrix imbibition, and gravity drainage versus the infiltration rate, as well as scaling and self-similarity for the leading edge of the water front are the hallmark of the nonlinear dynamic processes in water flow under episodic infiltration through fractured tuff. Based on the analysis of experimental data, we propose a conceptual model of a dynamic fracture flow and fracture-matrix interaction in fractured tuff, incorporating the time-dependent processes of water redistribution in the fracture-matrix system.

Filtration↗
PubMed1985

The Monostrut Björk-Shiley heart valve.

To avoid the possibility of a fracture of the welded two-armed outflow strut of the Björk-Shiley heart valve, since 1982 it has been machined from one piece of Haynes 25 in the form of a monostrut valve without welds. Of the first 864 patients with a monostrut Björk-Shiley valve implanted, 268 have now been followed up to 3 years. The clinical findings, as well as absence of hemolysis, excellent hemodynamics even with a narrow aortic root as demonstrated by transseptal cardiac catheterization and excellent functional improvement are reported. No valve thrombosis in patients receiving anticoagulant therapy was observed with valves in either the aortic or the mitral position and there was no case of mechanical failure.

Adolescent↗
PubMed1995

Neodymium:yttrium-aluminum-garnet laser fusion of endarterectomy flaps.

PURPOSE: This study evaluated the efficacy of neodymium:yttrium-aluminum-garnet laser welding of flaps in canine arteries and in securing the distal flap during human carotid endarterectomy. METHODS: Endarterectomy flaps were created in both common carotid and both common femoral arteries in 12 dogs. The flaps were repaired with either the neodymium:yttrium-aluminum-garnet laser or with 6-0 polypropylene sutures. The arteries were removed after duplex scanning at either 7 or 28 days. Eighteen high carotid endarterectomy flaps in 16 patients have been subsequently secured with the laser welding technique. RESULTS: Laser repairs (125 +/- 19 joule) of the canine arteries were completed more quickly than suture repairs (mean 25 seconds vs 135 seconds, respectively; p < 0.04). Duplex ultrasonography revealed no discernable differences between the two groups of arteries. Arteries studied at 7 days revealed three microscopic flaps (two suture, one laser), more subintimal fibroblastic proliferation in suture than laser-repaired carotid arteries (3: 1, p = 0.0530), and similar amounts of inflammation in suture- and laser-repaired arteries. Arteries studied at 28 days revealed one microscopic intimal flap (suture-repaired); equal fibroblastic and inflammatory responses in suture- and laser-repaired vessels; and no evidence of laser thermal injury. Eighteen carotid endarterectomy flaps have been successfully fused with no immediate or long-term complications in 16 patients (follow-up of 0 to 24 months). CONCLUSION: Laser fusion appears to be a safe and effective method for securing distal carotid endarterectomy flaps.

Animals↗
PubMed2004

Spirituality, meaning, and transcendence.

End-of-life care provides an opportunity to help a patient find meaning in the experience of dying. This is a challenge because the experience of dying can rob a patient of meaning. The first step is to look at death as being a process of life rather than an event. This is brought about by welding the broken pieces of the mind-body connection. Medicine cannot always fix broken pieces, but spiritual welding always puts us back together again. Compassionate end-of-life care helps a patient connect spirituality with the search for meaning and transcendence.

Attitude to Death↗
PubMed1998

Dynamics of Polymer Interdiffusion: The Ripple Experiment.

We explore the interdiffusion of oppositely labeled triblock polystyrene chains, HDH/DHD, during welding in the melt using dynamic secondary ion mass spectroscopy (DSIMS) and specular neutron reflectivity (SNR). The HDH chains have the central portion of the chain deuterated (D) approximately 50% while the two ends (H) each have approximately 25% protonation; the DHD is oppositely labeled, but each set of chains contains about 50% deuteration. During welding, the deuterium depth profile exhibits "ripples" whose characteristic features, such as the time and molecular weight dependent shape, amplitude, and position, are very sensitive to the microscopic details of the polymer dynamics. The ripple experiment is especially sensitive to the presence, or absence, of topological constraints and anisotropic motion of chains. The current work significantly extends the molecular weight range up to 400 000. This allows greater separation of the six key ripple features used in deciphering the correct polymer dynamics model at the polymer-polymer interface. The DSIMS and SNR experimental results are compared to theoretical predictions and ripple simulations for Rouse, polymer mode-coupling, reptation (with and without tube broadening), and other phenomenological dynamics models. The six ripple characteristics were found to be perfectly correlated and convincingly consistent with the predictions of the reptation dynamics model. The ripple results are in significant disagreement with the polymer mode-coupling model proposed by Schweizer and other tubeless models. We conclude that the reptation model, proposed by DeGennes in 1971 with parallel developments by Edwards, is the correct model to describe the dynamics of polymer interdiffusion.

Journal Article↗
PubMed2002

A practical procedure to prevent electromagnetic interference with electronic medical equipment.

Problems involving electromagnetic interference (EMI) with electronic medical equipment are well-documented. However, no systematic investigation of EMI has been done. We have systematically investigated the causes of EMI. The factors involved in EMI were determined as follows: 1) Electric-field intensity induced by invasive radio waves from outside a hospital. 2) Residual magnetic-flux density at welding points in a building. 3) Electric-field intensity induced by conveyance systems with a linear motor. 4) The shielding capacity of hospital walls. 5) The shielding capacity of commercial shields against a wide range frequency radio waves. 6) The immunity of electronic medical equipment. 7) EMI by cellular telephone and personal handy-phone system handsets. From the results of our investigation, we developed a following practical procedure to prevent EMI. 1) Measurement of electric-field intensity induced by invasive radio waves from outside the hospital and industrial systems in the hospital. 2) Measurement of residual magnetic-flux density at electric welding points of hospital buildings with steel frame structures. 3) Control of the electromagnetic environment by utilizing the shielding capacity of walls. 4) Measurement of the immunity of electronic medical equipment. And 5) Installation of electronic gate equipment at the building entrance to screen for handsets.

Electric Power Supplies↗
PubMed2005

Airborne occupational exposure, ABO phenotype, and risk of obesity.

BACKGROUND: We have previously found a quite strong interplay between occupational airborne pollutants, ABO phenotypes, and risk of ischaemic heart disease (IHD), with long-term exposure being associated with a significantly increased risk among men with phenotype O, and not among men with other ABO phenotypes. We suggested that the biological pathway could be a stronger systemic inflammatory response in men with blood group O. Several inflammatory mediators likely to increase the risk of IHD have recently been linked also to obesity, suggesting that long-term exposure to airborne pollutants might play a role in the aetiology of obesity. Accordingly, we tested the hypothesis that long-term occupational exposure to airborne pollutants would be more strongly associated with obesity in men with phenotype O than in men with other ABO phenotypes. DESIGN: Cross-sectional exposure-response study taking into account potential confounders. SETTING: The Copenhagen Male Study. SUBJECTS: A total of 3290 men aged 53-74 y. MAIN OUTCOME MEASURE: Prevalence of obesity (BMI > or =30 (kg/m2)). RESULTS: Overall, no differences were found in the prevalence of obesity between men with the O phenotype (n=1399) and men with other phenotypes (n=1891), 8.6 and 9.0%. However, only among men with the O phenotype was long-term occupational exposure (at least 5 y of frequent exposure) to various respirable airborne pollutants: dust, asbestos, soldering fumes, welding fumes, organic solvents, fumes from lacquer, paint or varnish, toxic components, breath irritants, stench or strongly smelling products, and irritants (other than breath irritants or contagious components) associated with an increased prevalence of obesity. Statistically, the strongest univariate associations were found for asbestos exposure, welding fumes, and breath irritants. Odds ratios (95% confidence limits) for these factors were 3.7 (1.8-7.6), 2.7 (1.6-4.4), and 2.6 (1.5-4.4), respectively. This particular relationship of airborne exposures with obesity in men with phenotype O was supported in multivariate analysis including interaction terms and taking into account a number of potential confounders. In contrast, no gene-environment interactions with obesity were found with respect to ABO phenotypes and a number of nonrespirable exposures. CONCLUSION: The finding of a quite strong interplay between long-term exposure to airborne pollutants, ABO phenotypes, and risk of obesity may open up new possibilities for clarifying mechanisms underlying the global obesity epidemic.

ABO Blood-Group System↗
PubMed2000

Chemical composition of individual aerosol particles in workplace air during production of manganese alloys.

Aerosol particle samples were collected at ELKEM ASA ferromanganese (FeMn) and silicomanganese (SiMn) smelters at Porsgrunn, Norway, during different production steps: raw material mixing, welding of protective steel casings, tapping of FeMn and slag, crane operation moving the ladles with molten metal, operation of the Metal Oxygen Refinement (MOR) reactor and casting of SiMn. Aerosol fractions were assessed for the analysis of the bulk elemental composition as well as for individual particle analysis. The bulk elemental composition was determined by inductively coupled plasma atomic emission spectrometry. For individual particle analysis, an electron microprobe was used in combination with wavelength-dispersive techniques. Most particles show a complex composition and cannot be attributed to a single phase. Therefore, the particles were divided into six groups according to their chemical composition: Group I, particles containing mainly metallic Fe and/or Mn; Group II, slag particles containing mainly Fe and/or Mn oxides; Group III, slag particles consisting predominantly of oxidized flux components such as Si, Al, Mg, Ca, Na and K; Group IV, particles consisting mainly of carbon; Group V, mixtures of particles from Groups II, III and IV; Group VI, mixtures of particles from Groups II and III. In raw material mixing, particles originating from the Mn ores were mostly found. In the welding of steel casings, most particles were assigned to Group II, Mn and Fe oxides. During the tapping of slag and metal, mostly slag particles from Group III were found (oxides of the flux components). During movement of the ladles, most particles came from Group II. At the MOR reactor, most of the particles belonged to the slag phase consisting of the flux components (Group III). The particles collected during the casting of SiMn were mainly attributed to the slag phase (Groups III and V). Due to the compositional complexity of the particles, toxicological investigations on the kinetics of pure compounds may not be easily associated with the results of this study.

Aerosols↗
PubMed2002

Determination of isocyanates, aminoisocyanates and amines in air formed during the thermal degradation of polyurethane.

An air sampling method for the determination of isocyanates, aminoisocyanates and amines formed during the thermal degradation of polyurethane (PUR) is presented. The method is based on the collection of air samples using impinger flasks containing di-n-butylamine (DBA) in toluene with a glass fibre filter in series. Isocyanates are derivatized with DBA to urea derivatives, and amines are derivatized in a subsequent work-up procedure with ethyl chloroformate (ET) to carbamate esters. Amine, aminoisocyanate and isocyanate derivatives were characterized using liquid chromatography-time of flight mass spectrometry (LC-TOFMS) and liquid chromatography-chemiluminescent nitrogen detection (LC-CLND). Quantification was performed by LC-MS, monitoring molecular ions [MH]+ in the electrospray mode. The instrumental detection limits for amines, aminoisocyanates and isocyanates were in the ranges 30-40, 2-3 and 3-70 fmol, respectively. Thermal degradation products of PUR were observed in high concentrations during welding in district heating pipes and PUR-coated metal sheets. Eleven isocyanates, three amines and five aminoisocyanates were identified. The concentrations of isocyanates, aminoisocyanates and amines in samples collected in the smoke close to the welding spot were in the ranges 150-650, 4-290 and 1-70 ppb, respectively. In samples collected in the breathing zone, isocyanates and aminoisocyanates were observed in the ranges 9-120 and 4-19 ppb, respectively. The compounds were present in both gas and particle phases. Volatile compounds dominated in the gas phase, whereas less volatile compounds dominated in the particle phase. The method presented makes it possible to sample and determine amines and aminoisocyanates, in addition to isocyanates. The need to monitor these compounds is clearly illustrated by the high concentrations found during the thermal degradation of PUR.

Air Pollutants↗
PubMed1996

Assessment of alternative tissue approximation techniques for laparoscopy.

OBJECTIVE: To investigate the feasibility and results of applying alternative techniques of tissue approximation for experimental urothelial re-anastomosis in an open and laparoscopic setting. MATERIALS AND METHODS: The study was carried out in two phases; in phase 1, an open porcine ureteric re-anastomosis was performed using gelatin/resorcin/ formaldehyde (GRF) glue, fibrin glue or potassiumtitanyl-phosphate laser tissue-welding with a fluorescein-doped human albumin solder. The anastomoses were assessed both immediately, by leak pressure, and by the operating time, upper tract urodynamic studies and light and scanning electron microscopy, 6 weeks after surgery. In phase 2 the best technique from phase 1 was compared with sutured controls for porcine retroperitoneoscopic dismembered pyeloplasty, using the same assessment criteria. RESULTS: In phase 1, GRF glue produced adhesion which was insufficiently flexible to withstand rotation of the anastomosis and this technique was therefore abandoned. Fibrin-glued anastomoses withstood leak pressures equal to those from laser-welding (P = 0.91) and gave similar changes in maximum pressure with a Whitaker test at 6 weeks (P = 0.30), but were superior in requiring a shorter operating time (P = 0.02) and in their electron and light microscopic appearances. In phase 2, fibrin glue gave similar changes in maximum pressure with a Whitaker test to those from polyglactin 910 sutures (P = 0.51) but withstood higher leak pressures (P = 0.01), had a shorter operating time (P = 0.01) and had superior electron and light microscopic appearances. CONCLUSION: Fibrin glue produced effective experimental laparoscopic pelvi-ureteric anastomoses within less operating time than did sutured controls. Such anastomoses withstood supra-physiological pressures, with no evidence of functional obstruction and with a more favourable histological result after 6 weeks. Laparoscopic evaluation of this modality in a clinical setting is now justified.

Anastomosis, Surgical↗