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The article contains a study of the cytotoxic properties of welding dusts (WD) and their capacity to activate lipoid peroxidation (LP) depending on the particles of chemical composition. A correlation was established between the WD cytotoxic properties, activation of LP in the lungs and the concentration of cremnium dioxide.
It was established that in welding of cast-iron wares with their preliminary heating, the thermal factor occupies the leading place in overstrain of the physiological reactions of the worker's body. The workers showed an increase of the average values of most indices of the thermal state and cardio-vascular system. Hygienic measures directed to prevent conveying heat to the working zone of the welder are described.
Composition and structure of metals in the meld zone connecting a dental burr handpiece made of hard alloy BK-6 with a shank made of steel 20X13 are examined by the X-ary microanalyzer MS-46 and the X-ray diffractometer "dPOH-2". Representative interdiffusion processes of alloy components into steel and, converserly, iron from steel into hard alloy are found. After melding, the transition layer has been shown to represent the cobalt-iron solid solution with variable concentration of the components through the layer, tungsten carbid particles being uniformly spread all over the metallic matrix. The phasic composition change is analysed in the course of material welding. The enrichment of stell melt with carbon of tungsten carbid results in the formation of gamma-Fe phase in the meld zone. The failure of burr blanks is noted to occur at the interface of the second (10-20 micrometer) and the first (130-140 micrometer) zones. The increase in the concentration of both iron and iron-containing phases--alpha-Fe, gamma-Fe, Fe3W3C--at the surface of steel fracture is responsible for the failures.
In a model experiment 8 test persons each were given 1 mg and 2 mg fluoride per os. In a subsequent period of urine collection of 4 hours on an average 10% of the adduced fluoride were eliminated. Taking into consideration extraprofessional intake of fluoride may be concluded that the estimation of fluoride in the urine of welders working with Kb-electrodes may give references to the individual load of the respiratory tract by weld fumes.
Alloys being investigated as possible direct-filling materials rely upon a cold-welded, deformable silver matrix phase for cohesion and strength. The silver matrix is formed by direct consolidation of comminuted silver under an oxide-removing acid. The object of this study was to determine the effect of conditions such as load, increment thickness, and concentration of oxide-removing acid on the properties of the silver matrix. Results indicate that the addition of higher impact loads significantly improved yield strength and specimens built up by using thinner increments were significantly stronger and denser.
BACKGROUND AND OBJECTIVE: Fifty percent human albumin solder significantly improves weld strength when compared to lower concentrations [Wright et al., ASLMS meeting, April, 1995]. We developed a method for preparing 50% human albumin that may be considered compatible for clinical applications. STUDY DESIGN/MATERIALS AND METHODS: Fifty percent human albumin solder was prepared from 25% commercially available human albumin using a lyophilization technique. Assessment of sterility, viscosity, pH, and peak absorption wavelength were performed. RESULTS: This report describes the methodology used to prepare a 50% human albumin solder that is compatible with clinical use. Maintenance of the structural integrity of the albumin was confirmed by polyacrylamide gel electrophoresis. CONCLUSION: This solder preparation can be used alone or with the addition of exogenous chromophores. The final product is sterile, incorporates viral free protocols, maintains high viscosity, and can be applied easily during open or laparoscopic procedures.
This study evaluates the use of sutureless laser welding for vasovasostomy. In 14 rodents, the left vas deferens underwent vasovasostomy using an albumin-based solder applied to the adventitia of the vas deferens. The solder contained the dye, indocyanine green, to allow selective absorption and denaturation by a fiber-coupled 800-nm diode laser. The right vas deferens served as a control, receiving conventional layered microsurgical repair. We used a removable 4/0 nylon stent and microclamps to appose the vas deferens during repair, with no need for stay sutures. The mean time to perform laser solder repair (23.5 min) and conventional repair (23.3 min) were not significantly different (P=0.91). However, examination after 8 weeks showed that granuloma formation (G) and patency (P) rates for the conventional suture technique (G, 14%; P, 93%) were significantly better than observed for the laser solder technique (G, 57%; P, 50%).
BACKGROUND AND OBJECTIVES: Concentrated protein solutions can be used as thermally polymerized solders in laser welding. Solders supplemented with biologically active chemicals may provide in situ drug delivery for localized therapeutics. These studies characterize a serum albumin (SA) solder containing heparin, designed to reduce microvascular thrombosis rates. STUDY DESIGN/MATERIALS AND METHODS: Samples of heparin added to 30% SA to obtain heparin-to-albumin molar ratios (HAMR) of 4:1 and 2:1 were thermally polymerized, and heparin release into saline was measured. Using a rat thrombosis model, patency was determined for suture, and 0 U/ml (control), 2.5 U/ml, 50 U/ml heparin solder repairs. RESULTS: Heparin release was five times higher for 4:1 than 2:1 HAMR solder acutely, but was equivalent after 2 days. Animal patency rates were: 50% suture, 0% control, 50% low heparin, 66% high heparin (P < 0.05 vs. control). CONCLUSIONS: Solders incorporating heparin should provide in situ anti-thrombotic therapy reducing the risk of microvascular thromboses.
Previous studies have demonstrated that the addition of a protein solder to augment the laser tissue weld significantly improves postoperative results. Herein we describe a method for the preparation of human albumin for use as a laser tissue solder. We also review the brief history of laser tissue solders and discuss recent advances using this technology.
We demonstrate that a high-intensity electron beam can be applied to create holes, gaps, and other patterns of atomic and nanometer dimensions on a single nanowire, to weld individual nanowires to form metal-metal or metal-semiconductor junctions, and to remove the oxide shell from a crystalline nanowire. In single-crystalline Si nanowires, the beam induces instant local vaporization and local amorphization. In metallic Au, Ag, Cu, and Sn nanowires, the beam induces rapid local surface melting and enhanced surface diffusion, in addition to local vaporization. These studies open up a novel approach for patterning and connecting nanomaterials in devices and circuits at the nanometer scale.
Using a milliwatt CO2 laser, a series of 160 arteries and 105 veins have been anastomosed in Wistar rats. Three stay sutures and a laser tissue welding technique were used. These were compared with a series of conventionally sutured vessels in terms of patency, speed and ease of procedure, and aneurysm formation. Patency rates of successful first time anastomoses are comparable with conventional suturing methods but the aneurysm rate is higher. Laser assisted anastomosis is faster to learn and perform than conventional suturing, but microsurgical skills are still needed. Despite the large number of variables the laser assisted technique has a high success rate, and work to minimise variables and optimise the laser parameters may improve these results.
This report presents a method of arthroscopic repair of the peripheral triangular fibrocartilage complex tears that replaces traditional suture knots with ultrasonic welding of sutures. This will help eliminate potential causes of ulnar-sided wrist discomfort during the postoperative period.
An important aim of implant-supported prostheses is to achieve a passive fit of the framework with the abutments to limit the amount of stress transfer to the bone-implant interface. An efficient and standardized technique is proposed. A definitive screw-retained, implant-supported complete denture was fabricated for an immediately loaded provisional screw-retained implant-supported complete denture. Precise fit was achieved by the use of industrial titanium components and the passivity, by an intraoral luting sequence and laser welding.
A technique to create an individually modified implant prosthetic abutment is described. An overcasting is waxed onto a machined titanium abutment, cast in titanium, and joined to it with laser welding. With the proposed technique, a custom-made titanium implant prosthetic abutment is created with adequate volume and contour of metal to support a screw-retained, metal-ceramic implant-supported crown.
We investigated the use of the KTP-532 laser to perform a patch graft urethroplasty in 24 adult male dogs using the inner preputial skin as the donor site. In group 1 (12 dogs) repairs were completed with conventional microsuturing techniques, while in group 2 (12 dogs) they were completed using the KTP-532 laser. In the laser welding group the addition of a protein solder (40% human albumin) doped with fluorescein was used. Assessment parameters included a preoperative and postoperative retrograde urethrogram, measurement of intraluminal bursting pressure in the first 6 animals in each group, operative time and histology. Operative time was 42% faster and acute intraluminal bursting pressures were significantly higher in the laser-solder group. No fistulas occurred in the laser-solder group compared to a 50% fistula rate in the suture group. Significant radiographic abnormalities were seen in the urethras of the suture repair group.
This clinical report describes repair of a fractured removable partial denture clasp using laser welding rather than a conventional torch soldering technique.
Electron Spectroscopy for Chemical Analysis (ESCA) was explored as a means of studying the oxidation state of chromium in SMAC (coated electrode) stainless steel welding fume collected on Nucleopore filters in the laboratory. Chromuim VI and III (as a percent of the total chromium) obtained from ESCA analysis was applied to results from Neutron Activation Analysis (NAA) to yield an average of 69 microgram chromium VI per sample. Diphenylcarbazide/atomic absorption (DPC/AA) results are reported for samples submitted to an industrial laboratory. Possible chemical species and solubility of chromium VI in stainless steel fumes is discussed in light of analogy between the SMAC process and the manufacturing process for chromates.
The bonding interface of explosively-welded aluminium and steel in three explosive conditions have been investigated by using scanning electron microscopy, transmission electron microscopy, electron diffraction and electron probe microanalysis methods. The results show that all the interfaces have the shape of waves with curled front formed by process of superplasticity and some discontinuous reacted zones. They consist of amorphous and nano sized crystals and quasi-crystals as well as the compounds such as AlFe, Al2Fe, Al3Fe and Al6Fe with various shapes. The basal steel crystal near the interface has structure of martensite and perlite crystals which are deformed by the process of superplasticity. The size of reacted zone becomes large with increasing amount of explosive charge powder and separation of the driver Al plate from the basal steel plate.