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At least 487 records · Page 27Linked to original sources
PubMed1987

Large-artery welding with a milliwatt carbon dioxide laser.

Microvascular laser welding can be effectively used in large-diameter artery techniques. The carotid arteries of 12 anesthetized mongrel dogs were exposed. Following heparinization, the carotid arteries were transected, cleaned along their edges, and repaired on the right side by laser and on the left side by suture. The laser-assisted vascular anastomosis (LAVA) required four stay sutures and laser power for welding. Six-week patency for LAVA vs suture anastomosis was 100% vs 92%, respectively. Anastomotic time requirements were less with LAVA (seven vs 25 minutes). Intimal healing for both techniques immediately demonstrated an intraluminal thrombus, which resolved showing complete endothelial repair by four weeks. The laser seal demonstrated little inflammation compared with the giant cell reaction of suture anastomosis. Immediate wall tensions of 6 to 18 X 10(5) dynes/cm2 were tolerated after both techniques. Laser-assisted vascular anastomosis of large-diameter arteries is feasible, strong, and associated with minimal inflammation.

Animals↗
PubMed1987

Comparison between aqueous-phase and gas-phase exposure protocols for determining the mutagenic potential of nitrogen dioxide and the gas fraction of welding fumes.

Nitrogen dioxide and the gas fraction of welding fumes, a complex gas mixture which contains high concentrations of nitrogen dioxide, were tested for mutagenicity in Salmonella typhimurium tester strains, TA1535 and TA1538. A comparison between 2 exposure protocols, aqueous phase and gas phase, was made to evaluate the sensitivity of each in measuring the mutagenic potential of the gases. In the aqueous-phase exposure, a suspension of cells in an isotonic salt solution was exposed by bubbling the gas through the culture. In the gas-phase exposure, the plated cells were exposed to the gas in a chamber. For both gases tested, the gas-phase exposure resulted in a higher reversion frequency than the aqueous-phase exposure. Furthermore, we found that nitrogen dioxide accounted for only a fraction of the mutagenicity observed for the gas fraction of welding fumes.

Filtration↗
PubMed2006

The integrity of welded interfaces in ultra high molecular weight polyethylene: Part 1-Model.

The difficulty of eradicating memory of powder-particle interfaces in UHMWPE for bearing surfaces for hip and knee replacements is well-known, and 'fusion defects' have been implicated frequently in joint failures. During processing the polymer is formed into solid directly from the reactor powder, under pressure and at temperatures above the melting point, and two types of inter-particle defect occur: Type 1 (consolidation-deficient) and Type 2 (diffusion-deficient). To gain quantitative information on the extent of the problem, the formation of macroscopic butt welds in this material was studied, by (1) modelling the process and (2) measuring experimentally the resultant evolution of interface toughness. This paper reports on the model. A quantitative measure of interface structural integrity is defined, and related to the "maximum reptated molecular weight" introduced previously. The model assumes an idealised surface topography. It is used to calculate the evolution of interface integrity during welding, for given values of temperature, pressure, and parameters describing the surfaces, and a given molar mass distribution. Only four material properties are needed for the calculation; all of them available for polyethylene. The model shows that, for UHMWPE typically employed in knee transplants, the rate of eradication of Type 1 defects is highly sensitive to surface topography, process temperature and pressure. Also, even if Type 1 defects are prevented, Type 2 defects heal extremely slowly. They must be an intrinsic feature of UHMWPE for all reasonable forming conditions, and products and forming processes should be designed accordingly.

Adhesiveness↗
PubMed2006

Thermal welding versus bipolar tonsillectomy: a comparative study.

OBJECTIVE: To compare thermal welding tonsillectomy (TWT) with bipolar electrocautery tonsillectomy (BET) procedure. STUDY DESIGN AND SETTING: A prospective randomized study was conducted on 150 consecutive adult patients undergoing tonsillectomy. Indications included chronic tonsillitis and obstructive sleep apnea syndrome. Exclusion criteria included peritonsillar abscess history, bleeding disorders, and any other procedure together with tonsillectomy. Patients were randomly assigned to TWT or BET groups. Intraoperative bleeding, operative time, postoperative pain, complication rates, and return to normal diet were evaluated. RESULTS: In the TWT group there was no measurable intraoperative bleeding, while mean bleeding for BET group was 16 mL. No significant difference regarding mean operative time was noticed. Mean postoperative pain score and mean time for return to normal diet were significantly lower in the TWT group. Primary hemorrhage occurred in 1 subject of the BET group. Secondary postoperative hemorrhage was noticed in 1 subject of the TWT group and 3 subjects of the BET group. CONCLUSION: Thermal welding tonsillectomy procedure provides sufficient hemostasis, lower postoperative pain, and quick return to normal diet. EBM RATING: A-1b.

Adolescent↗
PubMed2006

Study on energy attenuation of ultrasonic guided waves going through girth welds.

Ultrasonic guided wave is introduced as a new non-destructive long range pipe inspection method. It can be used to inspect pipe which is inaccessible to other conventional NDT methods, and rapid, long distance inspection can be achieved. An investigation of the guided ultrasonic waves traveling along pipe with special geometry characteristics, such as elbow, several girth welds, and some artificial defects is described. In this paper, factors that may cause attenuation of ultrasonic guided waves are discussed and energy attenuation of longitudinal and torsional guided waves is studied on an experimental pipe having seven girth welds. Good agreement has been obtained between the experiments and the predictions. In the end, the detection sensitivity and locating precision of two guided waves, namely longitudinal and torsional, were compared on defects, such as notch, burr and branch.

Journal Article↗
PubMedDate not supplied

Artery weld strength after bipolar electrocoagulation is affected by electrolyte solutions around the artery.

We have recently shown that artery weld strength is significantly increased by increasing bipolar electrocoagulation time in fresh rabbit arteries, which had either 2 or 20 seconds of electrocoagulation under uniform conditions. In this study we investigated the effect of using either distilled water or physiologic saline around the artery during electrocoagulation in a total of 27 experiments, because it is the current practice to wash clot and liquid blood off bleeding ulcers with water. Fresh rabbit arteries were used, with a bipolar coagulation time of 2 seconds, with a constant weight of 500 gm applied to the head of the probe to standardize conditions. The bursting pressure of the coagulum was determined by cannulating the artery and increasing the pressure until the coagulum seal fractured. The artery weld strength was significantly lower when distilled water was used (median, 87.5 mm Hg; range, 10 to 225 mm Hg) compared with results when normal saline was used (median, 150 mm Hg; range, 100 to 850 mm Hg); by Mann-Whitney tests U = 42.5, Z = 2.36, and p = 0.018. These data suggest that more effective hemostasis of bleeding arteries may be achieved by not only more prolonged use of the diathermy probe, but also by using physiological saline as the washing solution instead of water, as is currently practiced.

Animals↗
PubMed1999

Assessment of cold welding properties of the internal conical interface of two commercially available implant systems.

STATEMENT OF PROBLEM: The cone-screw abutment has been shown to diminish micromovement by reducing the burden of component loosening and fracture. However, anecdotal concern for cold welding of cone-screw joints in implant design has been identified as a potential source for lack of retrievability. PURPOSE: This comparative study evaluated the loosening torque, as a percentage of tightening torque, for the ITI Straumann and Astra Tech (3.5 and 4.0 mm diameters) implant systems, which use an 8-degree and 11-degree internal cone, respectively. MATERIAL AND METHODS: Implants and abutments from each system were mounted in a torque device, and a range of tightening torques was applied. Loosening torques were then measured, and the influence of conus angle, interfacial surface area, saliva contamination, and time delay to loosening were all assessed. RESULTS: The loosening torque only exceeded tightening torque at the highest levels, just before component failure, when plastic deformation was expected. For all clinically relevant levels of torque, both in a dry environment and with components bathed in artificial saliva at 37 degrees C, loosening torque was always seen to be 80% to 90% of tightening torque, demonstrating that cold welding does not occur. There was a high correlation between loosening and tightening torque for all systems tested, but no statistical difference when comparing wet versus dry or comparing individual data for each system. CONCLUSIONS: It can be concluded that for clinically relevant levels of tightening torque, no problems are anticipated with respect to retrievability.

Cold Temperature↗
PubMed1989

Laser welding of pedicled flap skin tubes.

The efficacy of the carbon dioxide laser used at high power levels for tissue destruction is well established. This laser at lower power levels has been used to incise and anastomose blood vessels, tendons, nerves, dura, bowel, fallopian tube, vasa deferentia, ureters and skin. Laser welding is faster, reduces surgical manipulation and introduces less foreign material into the wound than conventional suturing techniques. We tested the feasibility of laser welding of pedicled flap skin tubes to determine if there is a potential application in reconstruction, particularly for hypospadias repair.

Animals↗
PubMed1998

Laser tissue welding.

Laser tissue welding is a technologic innovation that is beginning to move from the theoretical laboratory environment to the reality of clinical application. This article reviews the concepts, potential advantages, and techniques involved in laser tissue welding as they apply to urology.

Humans↗
PubMed1983

Wound healing of spleen ruptures by ultrasonic welding in animal experiments.

Violent ruptures of the spleen caused by accidents are regarded as an indication for necessary splenectomy. Experiences of modern ultrasonic surgery, e.g. in ultrasonic welding of bone fractures prompted us to experimentally investigate ultrasonic welding of spleen ruptures in dogs. We immediately obtained a safe closing of the ruptures with a durable scar and thus the method may give an alternative to splenectomy with saving of the organ.

Animals↗
PubMed1987

Laser vascular welding--how does it work?

This study evaluated the histology and electron microscopy of four samples of 2 cm long venotomies and artery-vein anastomoses formed in canine femoral arteries and veins using the argon laser (0.5 W power, 1 800 J/cm2, 4 min exposure/1 cm length of anastomosis). Welds were continuously irrigated with saline during the procedure to limit maximal temperatures to 44.2 +/- 1.6 degrees C (mean +/- SD), and the specimens were removed immediately following fusion and preserved for examination. Histologic and electron microscopic examination of different areas of the welds revealed various mechanisms of fusion including a) apposition of denatured collagen and elastin in the media and adventitia; b) bonding of vein medial collagen and elastin to the internal elastic membrane of the artery; and c) fusion consisting of a coagulum of platelets and fibrin depending on the alignment and apposition of the vessel edges. This study demonstrates that vascular tissue fusion by the argon laser occurs by various mechanisms. Future experiments should delineate which types of seal produce the optimal strength at the time of fusion, and enhance long-term healing.

Animals↗
PubMed2004

Validating the use of rectus muscle fragment welding to control presacral bleeding during rectal mobilization.

The incidence of presacral bleeding during rectal mobilization is low, but such bleeding may be massive and even fatal. Haemostasis can be difficult to achieve using conventional methods because of the complex interlacing of the venous network at the sacral periosteum. Historically, pelvic packing and metallic thumbtacks have been the more commonly used methods in our institution. However, the need for repeat surgery to remove the packs and the difficulties encountered in tack application have forced us to explore other methods. In 1994, the procedure termed muscle fragment welding, which uses electrocautery through a rectum muscle fragment, was introduced to control presacral bleeding. From January 1999 to February 2002, six of 416 patients undergoing pelvic surgery in our institution developed massive presacral haemorrhage and therefore, this technique was used. Haemostasis was immediate and permanent. No major untoward postoperative events such as re-bleeding or infection were noted. One cas developed a second-degree burn in the right elbow due to a misplaced ground conduction plate. Rectus muscle fragment welding is , in our experience, an effective and practical method of controlling presacral haemorrhage.

Adult↗
PubMed1991

Stented laser-welded vasovasostomy in the rat: comparison of Nd:YAG and CO2 lasers.

In 54 male Sprague-Dawley rats, 108 vasovasostomies were performed. Sutureless laser welding with the assistance of a removable stent was done using a CO2- and an Nd:YAG-laser system. Conventional two-layer microsurgical anastomoses served as controls. The Nd:YAG laser resulted in significantly lower patency rates, with a higher percentage of sperm granulomas; the CO2 laser produced results equivalent to conventional suturing. Sutureless laser welding utilizing a removable stent proved to be a time- and cost-saving procedure for vasovasostomies in the rat.

Animals↗
PubMedDate not supplied

Effects of electric arc welding on ventilatory lung function.

Respiratory symptoms, spirometry, forced expiratory flows, and the nitrogen closing volume test were studied in 119 welders and 90 controls, matched with respect to age, height, and smoking habits. Respiratory symptoms according to a questionnaire were more prevalent in the welders. No short-term changes of the measured variables during the day or week attributable to welding were found in twenty-one nonsmoking welders. Compared to the controls, closing volume and closing capacity (i. e., closing volume + residual volume) were significantly higher, and total lung capacity and the amplitude of the cardiogenic oscillations in the nitrogen curve were significantly lower in the welders who were nonsmokers or exsmokers, whereas there were no differences among smokers. These findings in welders may be attributable to deposition of welding fume particles in peripheral small airways or alveoli.

Aerosols↗
PubMed2003

Welded tracheal stent removal in a child under cardiopulmonary bypass.

Metallic tracheal stents have been used in the treatment of paediatric tracheomalacia for more than a decade. We describe a case in which critical airway obstruction occurred during removal of a welded tracheal stent using a rigid bronchoscope under general anaesthesia. Life-saving cardiopulmonary bypass was instituted urgently, and the welded stent was then removed successfully by directly opening the trachea.

Airway Obstruction↗
PubMed1990

Peri-epineurial tissue to supplement laser welding of nerve.

The principal difficulty with laser repair of nerves has been the inability to provide enough initial tensile strength to prevent separation of nerve ends. In previous experimental studies, dehiscence rates of laser-repaired nerves ranged between 12 to 25% whereas that for conventional epineurial suture repair was 0%. In our study, sciatic nerves of rats were transected bilaterally. Results of anastomosis by conventional epineurial suture on one side were compared with those of tissue welding by the CO2 laser using peri-epineurial sheath as a structural adjunct on the other side. At the time of reexploration at 7, 12, and 16 weeks, there was no dehiscence in nerves of either the laser with peri-epineurial sheath group or the suture repair groups. Electrophysiological and morphometric values after use of peri-epineurial tissue as an adjunct to tissue welding by the CO2 laser were comparable to those of conventional suture repair.

Action Potentials↗
PubMed2005

High-temperature creep rupture of low alloy ferritic steel butt-welded pipes subjected to combined internal pressure and end loadings.

Constitutive equations are reviewed and presented for low alloy ferritic steels which undergo creep deformation and damage at high temperatures; and, a thermodynamic framework is provided for the deformation rate potentials used in the equations. Finite element continuum damage mechanics studies have been carried out using these constitutive equations on butt-welded low alloy ferritic steel pipes subjected to combined internal pressure and axial loads at 590 and 620 degrees C. Two dominant modes of failure have been identified: firstly, fusion boundary failure at high stresses; and, secondly, Type IV failure at low stresses. The stress level at which the switch in failure mechanism takes place has been found to be associated with the relative creep resistance and lifetimes, over a wide range of uniaxial stresses, for parent, heat affected zone, Type IV and weld materials. The equi-biaxial stress loading condition (mean diameter stress equal to the axial stress) has been confirmed to be the worst loading condition. For this condition, simple design formulae are proposed for both 590 and 620 degrees C.

Journal Article↗
PubMed2005

A one-dimensional numerical model of acoustic wave propagation in a multilayered structure of a resistance spot weld.

A one-dimensional model of acoustic wave propagation in a multilayered structure of a spot weld is developed. The inhomogeneity of the material properties due to the thermal inhomogeneity is included in the equation of motion. The model enables us to deal with arbitrary spatial distributions of Lamé constants and density. The model allows analysis of travel time, multiple reflections, and interference in a given geometry. Use of this model could provide information to help predict behavior of the waves in the transmission (reflection) mode at different plate thicknesses and welding settings.

Journal Article↗