Insertion Of Plug Research Articles

Vibration studies of base-isolated liquid storage tanks

The effects of lead-rubber bearings on the seismic response of flexible liquid storage tanks are presented in this paper. The investigation of the seismic calamity of the storage tank shows that the yielding instability has a close relationship with the liquid sloshing. The design approach of the basic isolated liquid storage tanks can ensure that the structure has sufficient strength to sustain the forces induced by a moderate earthquake and has sufficient ductility under a strong earthquake. In this paper, the basic isolator is the lead-rubber bearing which is a steel-reinforced multilayer elastomeric bearing with a hole in its centre to facilitate the insertion of a lead plug. The coupling effects among liquid sloshing, shell vibration and isolator motion are included in this paper. The liquid is assumed to follow the velocity potential theory, and the shell is modelled by the finite element method. The hysterestic loop of the lead-rubber bearing is dealt with by the reduced hysteretic model. This theory can overcome the nonstandardization in determining the two stiffness in the bilinear model. The results show that the isolator can greatly reduce the hydrodynamic pressure, shell and liquid sloshing amplitudes.

Young Investigator Award: Percutaneous Facet Joint Fusion: Preliminary Experience

The synovium-lined apophysial joint is an important cause of back pain through facet arthrosis and nerve root pressure. The short-term results of two relatively noninvasive treatments--facet block and facet rhizotomy--have been better than their long-term results. The authors propose treatment with fusion of the posterior facet joints in the lumbar spine by means of a simple percutaneous procedure performed under local anesthetic with use of radiologic guidance. In the first phase of this study the technical feasibility of the concept was established in human cadaver spine. In the second phase a canine model was tested in which bone grafts were surgically inserted into lumbar facet joints. Five male and two female mongrel dogs, weighing 18-25 kg (mean, 20.3 kg), were operated on. Each procedure was done in three steps: First, preoperative computed tomographic (CT) scans were obtained to measure facet depth. Second, surgery was performed under fluoroscopic guidance with use of a threaded guide wire, a small cannulated coaxial drilling system, and hydroxyapatite cancellous bone plugs. Third, early postoperative CT scans were obtained to verify bone plug location. CT was repeated at 4 and 6 months after surgery to check for fusion. The dogs were killed at 6 months, and histologic examination was performed. Successful insertion of the bone plug was achieved in 12 of the 14 facets (86%). One dog died as a complication of the procedure. Fusion occurred in five of the 12 surgically treated facets (42%). Drilling and surgical insertion of bone plugs into facet joints of dogs were feasible. The fusion results are promising and may improve with future modifications of the technique.

Total Hip Arthroplasty in Patients With Avascular Necrosis of the Hip

Thirty-one patients with avascular necrosis of the hip were treated by 34 total hip arthroplasties (THAs). All patients were observed prospectively with a minimum two-year follow-up evaluation (average, 46 months; range, 24-84 months). Twenty had cemented arthroplasties using contemporary cementing techniques. This included insertion of a medullary plug, cleansing of the canal with a medullary brush, pulsatile lavage irrigation, and insertion of the cement with a cement gun. In 14 hips, a cementless prosthesis was used. Patients were rated using a modified Harris hip score. Sequential postoperative roentgenograms were analyzed in each patient. The overall Harris hip score ratings were 88 in the cemented and 84 in the noncemented groups. Mechanical failure with loosening of the femoral component occurred in one patient who developed deep sepsis. Significant thigh pain occurred in four patients in the noncemented group. Previous studies in the literature have generally reported unfavorable results in patients with avascular necrosis of the hip treated with THA. Using cementless and cemented fixation with contemporary cementing techniques, improved results can be expected. A high incidence of thigh pain (29%) in the cementless group remains a problem.

Femoral Arterial Hemostasis Using a Collagen Plug After Coronary Artery Stent Implantation

We have investigated the safety and efficacy of sealing the femoral arterial puncture site using purified bovine collagen in the catheter laboratory immediately after coronary stent implantation. Ten consecutive patients, mean age 64.6 years, pretreated with heparin, aspirin, and dextran underwent the insertion of a collagen plug immediately after coronary stent implantation. The mean activated clotting time was 512 seconds (range 320-999). Femoral arterial hemostasis was achieved before leaving the catheterization laboratory in nine of ten patients. Seven of these patients received additional mild groin compression with an air cushion compression device after hemostasis was successful. One of ten patients had persistent bleeding after delivery of the collagen plug and later required blood transfusion. The collagen plug may be a useful adjunct to obtaining hemostasis following coronary stent implantation, but further trials are required to test its reliability in fully anticoagulated patients.

The significance of skeletal magnetic resonance imaging after open bone biopsy

The performance of a bone biopsy results in a dramatically altered magnetic resonance image (MRI) signal in both the biopsied segment and the surrounding bone. An experimental canine model was used to determine the cause and imaging sensitivity of this postbiopsy signal change in the adjacent intraosseous contents. Six dogs were used in the study. Half of the dogs had the cortical window left open, and the other half had a polymethylmethacrylate plug inserted. After hemostatic closure, images were obtained immediately postbiopsy and 6 weeks thereafter. MRI defect length was examined on both T1 and T2 weighted sequences at both time periods. After the final image was taken at 6 weeks, the bone was harvested and examined grossly and histologically for the purpose of making pathoradiographic correlations. The results suggest that magnetic resonance imaging is a sensitive method that accurately reflects the defect caused by bone biopsy and the surrounding hemorrhage. The defect length increased in size over time. The image was slightly smaller than the corresponding histologic response. Insertion of a cortical plug had no predictable effect on defect length, which depended upon the amount of pressurization used during insertion. We conclude that MRI may be useful in the staging of intraosseous primary neoplasms of bone after bone biopsy, especially in the detection of an iatrogenically induced tumor/hemorrhage margin. This may be critical when planning an intraosseous surgical resection in which short, wide margins are anticipated.

Microdetermination of carbon and hydrogen in organoantimony compounds

Common methods for the microdetermination of carbon and hydrogen were found to be inadequate for the analysis of organoantimony compounds. Serious interferences from halogens in such compounds are discussed. Simple modifications are proposed for the accurate microdetermination of carbon and hydrogen in organoantimony compounds containing nitrogen and/or halogens using various combustion methods. The main modification involves the insertion of a short plug (2-cm long) of quartz-wool or polyurethane foam at the cooler end of the combustion tube to retain antimony tetraoxide and/or antimony halides formed during the ignition of organoantimony compounds.

Electro‐acoustical structure

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Finite element studies of some juxtarticular stress changes due to localized subchondral stiffening

A finite element analysis was undertaken in concert with an animal model of mechanically-induced osteoarthritis. The numerical model was used to explore stress transmission anomalies associated with localized subchondral stiffening due to implantation of small cylindrical plugs immediately below the subchondral plate of sheep. The quasi-static, plane strain computational formulation included solution of the non-linear intra-articular contact problem, and was validated by comparison with a corresponding analytical solution and with the in vivo experimental results. The numerical results showed that stress aberrations due to metal implant insertion were felt most greatly in the bone immediately surrounding the implant, but that nominal compressive stress elevations up to about 50% could also be induced in the overlying deep hyaline cartilage layer. This localized cartilage stress elevation following the insertion of a metal plug could be seriously affected by a number of factors, including the positioning of the implant, variation in the area of intra-articular contact, or the elastic modulus of the cancellous bone and/or subchondral plate. Experimentally-observed fibrous encapsulation also reduced the cartilage stress elevation effect, but later bony remodelling and the development of a corticalized shell around the implant encapsulation served to re-elevate the local cartilage stresses.

Effect of Uterine Litigation and Cervical Plugs on Retention of Frozen-Thawed Boar Sperm

Two experiments were conducted to determine whether the prevention of retrograde sperm expulsion from the uterus would enhance ovum fertilization by frozen-thawed boar sperm and whether insertion of a cervical plug would reduce the loss of frozen-thawed boar sperm from the uterus. In Exp. 1, 25 gilts were surgically inseminated and one uterine horn was ligated to prevent expulsion of sperm. Nine gilts were killed 4 h after insemination, and the sperm were recovered from the uterine horns and uterotubal sections. Significantly more sperm were recovered from the ligated than from the unligated uterine horns. Fertilized ova were recovered from nine of 16 gilts killed 48 to 90 h after insemination. More ova (P less than .005) were fertilized on the ligated than on the unligated sides of the reproductive tracts (87 vs 64%). In Exp. 2, 24 gilts were artificially inseminated with frozen-thawed boar sperm and then randomly selected to receive the intracervical insertion of a cotton tampon, a plastic plug or no treatment (control). Sperm were recovered from the uterine horns and uterotubal sections 4 h after insemination. The cervical plugs failed to significantly increase the retention of sperm in the uterotubal sections and uterine horns.

Effects of asymmetrical mucosal stimulation upon two-odor discrimination in the rat

Previous works have indicated that odor perception may, in part, depend upon the bilaterality and mucosal topography of the olfactory system. The present work attempted to verify such dependence by behaviorally testing the effects of asymmetrical stimulation of olfactory mucosae in rats. The effects upon performance of insertion of a nasal plug and/or an artificial septum before and after two-odor discrimination training were measured. Neither plug nor septum alone affected discriminative learning, whereas in combination they produced a decrement in learning rates. Post-criterion insertion or transfer of a plug produced a decrement in performance. Subsequent plug transfer had no effect upon performance. The deficit in initial learning rates was interpreted as resulting from the absence of mucosal stimulation on one side (asymmetrical input). Post-criterion deficits were attributed to the effects of changing the pattern of stimulation. These data support the view that odor discrimination employs information derived from topographic response patterns across the olfactory mucosal surface.