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At least 1,477 records · Page 82Linked to original sources
PubMed1995

Mechanical evaluation of transosseous wire rope configurations in a large animal external fixator.

By use of wire ropes as the transosseous component, an external skeletal fixator for the repair of long bone fractures in horses and cattle has been designed and tested in axial compression. Theoretical methods were used in the design process to size fixator components; however, our results suggest that conventional methods of analyzing the displacement of the transosseous component may not apply to wire ropes. Large pretensions in the wire ropes are necessary to obtain functional stiffnesses for fracture fixation. Therefore, a method was sought for terminating the ropes so that an appropriate pretension could be introduced into the rope through its interface with the fixator rings. Ropes were terminated by use of 5 methods and were tested in axial tension to failure. These methods included 3 copper sleeve arrangements, welded ends, and drum sockets. The drum sockets (57.6% of rope breaking strength) far exceeded the strengths provided by the copper sleeves (8.5 to 26.6%) and the welded ends (44.3%). Using the drum sockets, 5 rope configurations were assembled to the fixator, using wood blocks to simulate bones with a gap defect. The fixator was loaded in axial compression for each of the rope configurations, and stiffnesses were determined from measured axial displacement and applied load. The 4-ring fixator configuration, with 2 ropes at 60 degrees angular separation/ring, was the stiffest. In a worst case (gap) model, a mean axial compression load of 1,730 N was observed at 2 mm of displacement for a 4-ring fixator configuration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Sutureless rabbit bladder mucosa patch graft urethroplasty using diode laser and solder.

Fistula and strictures at the site of sutured anastomoses are frequent complications of major urethroplasty. We harvested bladder mucosa in 26 rabbits to repair large defects in the proximal urethra using laser-activated solder in the hope that such a repair would be stronger, faster to create and avoid common complications seen with conventional repair. Large oval defects were created in the proximal urethra in all animals undergoing urethroplasty. Twelve animals underwent bladder mucosa graft closure via diode (808 nm.) laser activation of an albumin-based solder (50% were suture-free). Fourteen additional animals underwent closure with 7-zero polydiaxanone suture (controls). Leak pressure and time of repair were recorded for each graft. Additional sections of bladder mucosa were harvested, transected and repaired by laser welding to determine tensile strength. In both groups, radiography, urethroscopy and clinical course were evaluated for as much as 6 weeks postoperatively. Urethroplasty time was significantly (p < 0.01) shorter for the laser group (13.8 +/- 2.5 minutes) than for the sutured repair group (24.0 +/- 5.3 minutes). Initial leak pressures for the lasered grafts averaged at least 4 times those of sutured grafts (p < 0.01). The tensile strength for lasered bladder mucosa was 3.16 +/- 1.12 kg./cm.2 Early retrograde urethrograms (RUG) performed at 7 days (n = 5) revealed urinary extravasation and fistula formation in 2 control animals compared with a normal urethral appearance in 3 lasered repairs. Early retrograde urethrograms performed at 21 days (n = 21) demonstrated smooth-walled urethras with no evidence of fistula, stricture, or urinary extravasation in the lasered group; varying degrees of reactive mucosal proliferation were seen in the controls. Urethroscopy confirmed these observations. At 6 weeks, histologic examination confirmed the presence of viable graft in all animals. We conclude that bladder mucosa patch graft urethroplasty using diode laser welding and albumin-based solder is an attractive alternative to conventional methods.

Animals↗
PubMed1994

[A twining method for struts connection in Z-stents].

To compose Gianturco Z-stents without welding, a twining method was applied. The link portion of the struts of were spirally entwined by a thin stainless steel wire of 0.1 mm in diameter. The directional balance of spring force of the twined stents compared favorably with that of the conventionally welded stents. This twining method has theoretical benefit of less susceptible to corrosion than soldering. Then the twining method was thought to be beneficial in composing Z-stents.

Equipment Design↗
PubMedDate not supplied

In vitro laser nerve repair: protein solder strip irradiation or irradiation alone?

BACKGROUND: This study investigated the potential of sutureless nerve repair using two promising laser fusion methods: direct 2 microns irradiation of the epineurium, and protein solder assisted epineurial fusion using a 800 nm laser. MATERIALS AND METHODS: Laser anastomosis of the rat sciatic nerve was performed in vitro without stay sutures in two groups of six animals. In the first group, direct laser fusion used a pulsed Cr, Tm: YAG laser. In the second group an albumin-based fluid solder containing the dye indocyanine green was applied to the epineurium, then irradiated with a diode laser. These two techniques were compared with regards to coaptation success and axonal damage. RESULTS: Direct laser welding produced weak bonds despite microscopic investigation of the irradiated nerves showing fusion of the epineurium. The unsatisfactory bonding can be attributed to poor tissue overlap and insufficient protein in the thin epineurium denaturation of underlying axons was also observed. In contrast, the laser solder method produced successful welds with greatly reduced axonal damage, and significantly improved the tensile strength. CONCLUSIONS: This study confirmed the technical possibilities of sutureless nerve anastomosis. Laser activated solders enable stronger bonds, by the addition of protein to the anastomosis site, and less thermal damage to underlying tissue through selective absorption of laser energy by dye in the solder. Further in vivo studies are required before drawing final conclusions.

Anastomosis, Surgical↗
PubMedDate not supplied

Hydrogen-induced microelectronic capacitor failure in pacemakers.

Ceramic chip capacitors used in hybrid microelectronics for cardiac pacemakers are usually highly reliable. However, under certain conditions of capacitor construction, capacitor materials, mounting techniques, and environmental conditions, high failure rates may occur. A specific example is presented in which a ceramic capacitor used in an implanted pacemaker delaminated and failed approximately 30 days after being implanted. The failed capacitor caused a pulse rate rise, but due to circuit design techniques, the rate increase was limited to an acceptable value. The capacitor that failed was from an isolated lot of capacitors that was manufactured using pure palladium plates. The circuit containing this capacitor was hermetically sealed within a titanium case by welding. During the welding, a small amount of hydrogen was released from the titanium which, over a period of 2 to 4 weeks, was absorbed by the palladium plates in the capacitor. By absorbing the hydrogen, the palladium plates exhibit a volumetric expansion of sufficient magnitude to crack and delaminate the capacitor to the point of failure. Subsequently, the recurrence of this failure mode has been avoided by using capacitors containing special palladium alloys that cannot absorb hydrogen. This phenomenon is of interest to pacemaker designers since mercury batteries used in conventional pacemakers generate large amounts of hydrogen and potentially may be responsible for complications when used in conjunction with capacitors containing palladium.

Adult↗
PubMed1996

Cancer incidence among mild steel and stainless steel welders and other metal workers.

The cancer incidence in a historical cohort of 10,059 metal workers employed during the period 1964-1984 was investigated. Standardized incidence ratios (SIR) were calculated based on registry extracts from the Danish Cancer registry. Lifetime exposure data (occupational and other) were obtained by a postal questionnaire in living cohort members and interviews by proxy for deceased and emigrated subjects. The incidence of lung cancer was increased among workers ever "employed as welders" (SIR = 1.38, 95% C.I. 1.03-1.81). There was a significant excess risk of lung cancer among "mild steel (MS) only welders" (SIR = 1.61, 95% C.I. 1.07-2.33) and "nonwelders" (SIR = 1.69, 95% C.I. 1.23-2.26) (indicating carcinogenic exposures other than welding), a borderline significant lung cancer excess among "MS ever welders" (SIR = 1.32, 95% C.I. 0.97-1.76), and a nonsignificant excess risk of lung cancer among "stainless steel (SS) only welders" (SIR = 2.38, 95% C.I. 0.77-5.55). In spite of signs of inconsistency in the risk estimation by duration and latency, we find the results support the conclusions of other studies: employment as a welder is associated with an increased lung cancer risk.

Asbestos↗
PubMed2000

Neurobehavioral performance in aluminum welders.

METHODS: Twenty aluminum welders (mean age 33 years; range 21-52), who had been exposed to aluminum for an average of 8.1 years (range 2-21), were tested for tremor and reaction time and screened for neuropsychiatric symptoms in a cross-sectional study. The welders' median urinary aluminum concentration was 1.5 micromol/L (range 0. 7-4.8). Aluminum in air, measured inside the respiratory protection, was 0.9 mg/m(3) (range 0.6-3.8). The welders were compared with twenty construction workers matched for age. RESULTS: Welders reported more symptoms than referents did (median 2 vs. 1; P=0.047). Although the welders as a group performed better than the referents on a tremor test, years of exposure, but not age, was predictive of poorer performance. The welders' reaction times were rapid by clinical standards (mean simple reaction time (SRT): 221 milliseconds; mean continuous performance test (CPT): 364 milliseconds). Although, as a group, they performed better than the referents, there was a statistically significant relation between longer reaction times and aluminum in air (air-Al). CONCLUSIONS: The relations between hand steadiness and years exposed, and between reaction time and air-Al, could indicate slight effects from exposure to aluminum. The possibility of selection of workers with high manual skills into welding work and a possible job-related training effect, might partly serve to explain the good performance among the welders.

Adult↗
PubMed1983

Respiratory symptoms and pulmonary function in welders of mild steel: a cross-sectional study.

Pulmonary function measurements, respiratory symptoms, smoking history, and occupational history were obtained from 91 male welders of mild steel, with mean welding exposure of 108 months, and 80 male factory controls. Nonsmoking welders compared to nonsmoking controls reported higher frequencies of respiratory symptoms and the differences were statistically significant for two symptoms: phlegm, and episodes of cough and phlegm. In comparisons of smoking welders and smoking controls, no significant differences were found in the prevalence of respiratory symptoms. Nonsmoking welders and smoking welders, compared to respective controls, did not have significantly decreased mean values of forced vital capacity or forced expired volume in 1 sec. Mean mid-expiratory flow rates and forced expiratory flow rates at 75% of forced vital capacity were lower, but not significantly different, for welders, compared to controls. These decrements in peripheral flow rates could be trivial or they could represent the initial stages of chronic obstructive pulmonary disease. Long-term follow-up, provided by a large prospective study, is needed to make this distinction.

Alloys↗
PubMed1994

Mortality at an automotive stamping and assembly complex.

Mortality among workers with 2 or more years employment at an automotive stamping and assembly complex was analyzed using standardized mortality ratio (SMR), proportional mortality ratio (PMR), and mortality odds ratio (MOR) methods. The stamping plant all-cause SMR was considerably less than expected (for white men, SMR = 0.65, 95% confidence interval [CI] = 0.54, 0.79; for black men, SMR = 0.73, 95% CI = 0.45, 1.13), indicating a strong "healthy worker effect." However, six stomach cancer deaths produced an SMR of 4.4 (95% CI = 1.62, 9.6) and a PMR of 6.8 (95% CI = 2.5, 15). Based on small numbers of cases, stomach cancer risk increased with duration in stamping and tool and die departments where exposures included drawing compound and other metalworking fluids. Stamping plant lung cancer mortality was elevated among production welders (MOR = 2.7, 95% CI = 1.2, 6.3), and increased with duration. Welding was performed on sheet metal sometimes coated with drawing compound, primer, or epoxy resin adhesive. As was observed for the stamping plant, the all-cause SMR for the two assembly plants was unusually low (for white men, SMR = 0.64, 95% CI = 0.56, 0.73; for black men, SMR = 0.57, 95% CI = 0.43, 0.75). The lung cancer SMR was not elevated but the MOR was (MOR = 1.58, 95% CI = 1.1, 2.4) and increased with assembly plant duration (MOR = 1.78, 95% CI = 1.02, 3.1, at mean duration of cases). In the assembly plants, paint oven stack emissions had been reintroduced into the plant by the ventilation system.

Black or African American↗
PubMed1988

Occupation and lung cancer in two industrialized areas of northern Italy.

A population-based case-control study on lung cancer was conducted in 2 industrialized areas of northern Italy. Cases (126) were all males who died from lung cancer between 1976 and 1980. Controls (384) were a random sample of males dying from other causes during the same period. Jobs held during working life have been analyzed according to a list of occupations already known to be causally associated with lung cancer (list A) and a list of occupations suspected of being so (list B). Attributable risk percentages in the population for occupations included in either list A or B were about 36% and 12% in the 2 areas. Welders or workers in industries in which welding is common showed elevated odds ratios: 2.9 for welders (95% CI 0.9-9.8); 4.9 (1.1-22.9) for structural metal workers; 11.4 (2.6-49.9) for workers in structural metal production. Other job categories associated with lung cancer included: electricians and workers in electrical machine production, woodworkers (in furniture or cabinet making, but not in carpentry or joinery) and cleaning services. Smoking did not seem to exert a substantial confounding effect. Attributable risk percentages for tobacco smoking were about 78% and 76% in the population of the 2 areas.

Adult↗
PubMed1989

Argon laser vascular fusion: venous and arterial bursting pressures.

This study was designed to determine the optimal laser power (watts) for maximal strength of argon laser vascular fusions by measuring bursting pressures of repairs. Longitudinal incisions (n = 105) measuring either 2.5 or 5 mm in length were performed in canine femoral, carotid, and jugular veins and arteries and were fused with the argon laser at 0.3, 0.5, 0.7, or 0.9 W power. Total exposure time for each repair (50 to 80 sec/0.5 cm) was adjusted to yield identical energy fluences of 1,100 J/cm2. Bursting pressure of the fusions was determined by monitored infusion of anticoagulated blood into an isolated segment of the vessel that contained the fusion. Mean bursting pressures for venous and arterial repairs were significantly higher in the 2.5 mm incisions compared with the 5 mm incisions (P less than 0.05). Venous and arterial repairs of equal length performed at each power resulted in equivalent bursting strengths, except that 5 mm venous segments fused with 0.9 W withstood lower pressures than all other venous repairs (P less than 0.05), and 5 mm arterial segments were in turn significantly weaker at 0.3 W (P less than 0.02). We conclude that argon laser fusion is equally suitable for repair of medium-sized veins and arteries and that immediate strength decreases with increasing length of repair. To maximize strength of longer repairs, venotomies should be welded at power settings between 0.3 and 0.7 W while arteriotomies should be fused at power settings between 0.5 and 0.9 W. The differences in optimal power may be explained by variable wall composition and thickness between veins and arteries.

Animals↗
PubMed1993

Apolipoprotein D and alpha 1-microglobulin in human urine: effect of cadmium exposure.

Apolipoprotein D is a previously unrecognized urinary protein of unknown function which we have tested as a potential marker for kidney malfunction. This protein and alpha 1-microglobulin have been quantified by zone immunoelectrophoresis assay in urine samples from a group of eight men occupationally exposed to cadmium-containing welding fumes for many years. All these workers had highly elevated concentrations of urinary cadmium and indications of tubular proteinuria, as compared to a group of 50 apparently healthy normal men analyzed in parallel. The cadmium-exposed workers demonstrated three- and 15-fold average increases in apolipoprotein D and alpha 1-microglobulin, respectively, over normal values in urine, estimated both as excretion rates and as milligrams of protein per mmol of creatinine. All these increments were highly significantly different (P < 0.001) from the corresponding values of the reference group. Essentially the same results were obtained for each of the proteins from two independent consecutive samplings of the workers' urine. There were good linear (R = 0.70, 0.80) and logarithmic (R = 0.84, 0.81) correlations between the urinary concentrations of alpha 1-microglobulin and apolipoprotein D for both the reference and the study group. Although not as sensitive an indicator for tubular proteinuria as alpha 1-microglobulin, apolipoprotein D, being a storage-stable urinary protein, seems a valuable complement for the diagnosis of tubular malfunction.

Adult↗
PubMed1993

Biologic monitoring of chromium and nickel among stainless steel welders using the manual mental arc method.

Forty manual metal arc welders welding stainless steel (SS) were monitored for 1-7 workdays measuring total chromium (Cr), water-soluble hexavalent CrVI, and nickel (Ni) in the working atmosphere, and Cr and Ni in blood and urine. The mean daily increase was 1.0 microgram Cr/l in plasma and 5.6 micrograms Cr/g creatinine in urine. There were significant correlations between total Cr and CrVI in air and the total Cr in biologic fluids. This was not the case for the corresponding correlations for Ni. The observed correlations between urinary and plasma Cr levels may permit interchange of these body fluids for biologic monitoring at high exposures. The results indicate that urine sampled after work is a body fluid versatile for routine monitoring of Cr in SS welders. Smokers had higher levels of Cr in biologic fluids than did nonsmokers at equivalent levels of air CrVI. The results also indicate that filter masks provide better protection against uptake of Cr in the airways than air-stream helmets.

Adult↗
PubMed1993

Biomonitoring of nickel and chromium in human pulmonary tissue.

Nickel (Ni) and chromium (Cr) and some of its compounds may be able to induce cancer in the lungs as well as in the nose and paranasal sinuses after occupational exposure. Latency periods amount to 20 years and more. Therefore objective exposure data are not available in the most cases and expert evaluation of the causal connection is often difficult. Recent investigations have shown, that Ni and Cr can cumulate in human lung tissue after occupational exposure. For the evaluation of "normal" Ni- and Cr-values a total of 495 human lung tissue samples of 30 occupationally non-exposed persons were analysed by AAS including ZEEMAN-compensation after wet oxidative digestion. Additional samples of 10 deceased persons who have been occupationally exposed to nickel in previous times by nickel-refining and welding, especially flame spraying have been investigated. The median Ni- and Cr- concentrations in the lungs of the non-exposed persons ranged between 20-40 resp. 133-277 ng/g (wet weight). In nickel refinery workers Ni- concentrations were found which exceeded the normal range about 1,000. In welders, especially flame sprayers, also values more than 100 times higher could be analysed for Ni and Cr. Partially these concentrations were found years after the end of the inhalative exposure.

Chromium↗
PubMed1989

Arc welders' respiratory health evolution over five years.

The respiratory health of 138 arc welders and 106 control subjects in the same company was studied in 1981 and in 1986. Most of the subjects welded mild steel using the Metal Inert Gas (MIG) process. The controls were workers in the same company, not exposed to any known pulmonary risk. The welders and controls in the analysis had not changed their professional activity nor their smoking habits during these five years. The examinations consisted of a questionnaire on respiratory symptoms, a thoracic auscultation, a chest X-ray and lung function tests: flow-volume curve and steady state CO transfer test. The examinations in 1986 confirmed the risk of non specific radiological impairment (pulmonary reticulo-micronodulation) and of obstruction in the small bronchi, which had already been observed in 1981 in the arc welders in this company. These impairments did not seem to have evolved more than in the controls, but do however justify regular surveillance of the respiratory health of arc welders.

Adult↗
PubMed2000

[Sideroelastosis of pulmonary vessels after welder dust exposure].

Sideroelastosis pulmonum was first described by Ceelen (1931) and Gellerstedt (1939), mentioning an idiopathic type, but also vascular alterations in chronic pulmonary congestion. We analysed the question wether secondary sideroelastosis can be demonstrated also in lungs after previous welder dust exposure. Lung samples of 43 patients and deceased with various exposure periods to welder dust were investigated. On each sample, light microscopical, scan electron microscopical and energy dispersive x-ray micro analyses (EDX) were performed. In six samples (14%) vascular alterations in the area of denaturated elastic fibres with siderophilic "impregnation" were seen, corresponding to the features described by von Ceelen and Gellerstedt. Giant cell or granulomatous reactions, however, were present only in exceptional cases. This phenomenon was seen mostly in cases of marked local siderin deposits and reactive fibrosis. Using EDX, a number of metals characteristic for welder dust (Al, Ti, Cr, Ni) as well as iron were found in siderophages. No other metal than iron was detected in siderophilic elastic fibres using EDX. Causal pathogenetically, a correlation between increased iron uptake connected with welding particles and sideroelastosis of the vessel walls has to be established. However, in formal pathogenesis, other factors such as local perfusion disturbances due to fibrotic processes after exposure to harmful substances must be taken into consideration.

Dust↗
PubMed1994

The distribution of tachykinin binding sites in the brain of an electric fish (Apteronotus leptorhynchus).

We mapped the distribution of tachykinin binding sites utilizing quantitative autoradiography of iodinated substance P and eledoisin as prototypic ligands for neurokinin-1 (NK1) and neurokinin-3 (NK3) receptors, respectively. The two ligands produced highly heterogenous and quantitatively different patterns of specific binding, suggesting that they revealed different tachykinin receptor subtypes. Although [125I]substance P and [125I]eledoisin binding were correlated in most brain regions, the binding of substance P was usually denser. [125I]substance P binding and substance P-like immunoreactivity were reasonably correlated in most brain areas, although discrepancies were found in some nuclei. Dense [125I]substance P binding was found in most areas of the subpallium and in parts of the pallium related to the olfactory system, as well as in the glomerular layer of the olfactory bulb. Moderate to dense binding of both ligands was observed in preoptic area, hypothalamus, habenula, parts of the thalamus and preglomerular complex. Especially noteworthy was the presence of [125I] substance P binding in the diencephalic prepacemaker nucleus, a region involved in the control of electroncommuncatory behavior. Substance P-like immunoreactivity is sexually dimorphic in certain diencephalic nuclei, including the prepacemaker nucleus (Weld and Maler, 1992); no obvious difference was seen between [125I]substance P or [125I]eledoisin binding in the brains of male versus female fish. In the mesencephalon striking laminar patterns of binding were seen in the torus semicircularis dorsalis and the optic tectum. Dense binding was also noted in the raphé nuclei, the locus ceruleus and the sensory nucleus of the vagus. Although binding of substance P in the electrosensory lateral line lobe and nucleus preeminentialis was light, it was distributed in a discrete fashion, suggesting a role of substance P in electrosensory processing.

Amino Acid Sequence↗