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PubMedDate not supplied

Chlorine-36 data at Yucca Mountain: statistical tests of conceptual models for unsaturated-zone flow.

An extensive set of chlorine-36 (36Cl) data has been collected in the Exploratory Studies Facility (ESF), an 8-km-long tunnel at Yucca Mountain, Nevada, for the purpose of developing and testing conceptual models of flow and transport in the unsaturated zone (UZ) at this site. At several locations, the measured values of 36Cl/Cl ratios for salts leached from rock samples are high enough to provide strong evidence that at least a small component of bomb-pulse 36Cl, fallout from atmospheric testing of nuclear devices in the 1950s and 1960s, was measured, implying that some fraction of the water traveled from the ground surface through 200-300 m of unsaturated rock to the level of the ESF during the last 50 years. These data are analyzed here using a formal statistical approach based on log-linear models to evaluate alternative conceptual models for the distribution of such fast flow paths. The most significant determinant of the presence of bomb-pulse 36Cl in a sample from the welded Topopah Spring unit (TSw) is the structural setting from which the sample was collected. Our analysis generally supports the conceptual model that a fault that cuts through the nonwelded Paintbrush tuff unit (PTn) that overlies the TSw is required in order for bomb-pulse 36Cl to be transmitted to the sample depth in less than 50 years. Away from PTn-cutting faults, the ages of water samples at the ESF appear to be a strong function of the thickness of the nonwelded tuff between the ground surface and the ESF, due to slow matrix flow in that unit.

Chlorine↗
PubMed1989

Surgical repair of defects in the rabbit temporomandibular joint disc: a comparison of various techniques.

A study was designed to evaluate the effects of different types of repair (suture vs. graft), donor graft tissues (dermis vs. fascia), and methods of graft fixation (sutured vs. laser-assisted) on excisional defects of the rabbit TMJ disc made anterior to the retrodiscal tissue. Groups created to compare the different variables were assessed at 30 and 90 days postoperatively by macroscopic and histologic methods, microangiography, and mechanical strength testing. Without repair, all excisional defects of the disc failed to heal. Suturing of the reapproximated margins did not appear to promote healing or provide much strength beyond the properties of the suture material. Dermal grafts, fixed by suturing, induced healing by becoming incorporated into the disc, restoring discal continuity, and approximating normal disc strength. The use of laser-assisted tissue welding for dermal graft fixation was found to be inadequate and was subsequently abandoned. Fascial grafts could be fixed into position by both suture and laser-assistance, but consistently failed to exhibit successful transplantation and promote healing at the disc site.

Animals↗
PubMed2002

Cytotoxicity and oxidative mechanisms of different forms of chromium.

Chromium exists mostly in two valence states in nature: hexavalent chromium [chromium(VI)] and trivalent chromium [chromium(III)]. Chromium(VI) is commonly used in industrial chrome plating, welding, painting, metal finishes, steel manufacturing, alloy, cast iron and wood treatment, and is a proven toxin, mutagen and carcinogen. The mechanistic cytotoxicity of chromium(VI) is not completely understood, however, a large number of studies demonstrated that chromium(VI) induces oxidative stress, DNA damage, apoptotic cell death and altered gene expression. Conversely, chromium(III) is essential for proper insulin function and is required for normal protein, fat and carbohydrate metabolism, and is acknowledged as a dietary supplement. In this paper, comparative concentration- and time-dependent effects of chromium(VI) and chromium(III) were demonstrated on increased production of reactive oxygen species (ROS) and lipid peroxidation, enhanced excretion of urinary lipid metabolites, DNA fragmentation and apoptotic cell death in both in vitro and in vivo models. Chromium(VI) demonstrated significantly higher toxicity as compared with chromium(III). To evaluate the role of p53 gene, the dose-dependent effects of chromium(VI) were assessed in female C57BL/6Ntac and p53-deficient C57BL/6TSG p53 mice on enhanced production of ROS, lipid peroxidation and DNA fragmentation in hepatic and brain tissues. Chromium(VI) induced more pronounced oxidative damage in multiple target organs in p53 deficient mice. Comparative studies of chromium(III) picolinate and niacin-bound chromium(III), two popular dietary supplements, reveal that chromium(III) picolinate produces significantly more oxidative stress and DNA damage. Studies have implicated the toxicity of chromium picolinate in renal impairment, skin blisters and pustules, anemia, hemolysis, tissue edema, liver dysfunction; neuronal cell injury, impaired cognitive, perceptual and motor activity; enhanced production of hydroxyl radicals, chromosomal aberration, depletion of antioxidant enzymes, and DNA damage. Recently, chromium picolinate has been shown to be mutagenic and picolinic acid moiety appears to be responsible as studies show that picolinic acid alone is clastogenic. Niacin-bound chromium(III) has been demonstrated to be more bioavailable and efficacious and no toxicity has been reported. In summary, these studies demonstrate that a cascade of cellular events including oxidative stress, genomic DNA damage and modulation of apoptotic regulatory gene p53 are involved in chromium(VI)-induced toxicity and carcinogenesis. The safety of chromium(III) is largely dependent on the ligand, and adequate clinical studies are warranted to demonstrate the safety and efficacy of chromium(III) for human consumption.

Animals↗
PubMed1994

Management of orthopedic emergencies.

Initial management of injuries includes safely gaining control of the animal and assessing and treating systemic shock. If hemorrhage is life threatening, it must be controlled. If the limb is nonfunctional it should be stabilized. Any open orthopedic injury should be treated by cleaning the tissues, protecting the exposed tissues, and administering systemic antibiotics. A commercial splint is available (Equine Regular Leg Saver Splint, Kimzey Welding Works, Woodland, CA) that can immobilize and relieve weightbearing for cases of phalangeal fracture, flexor tendon rupture, fetlock breakdown, and lower joint luxations/subluxations. Hock and carpal luxation and radius fracture in foals can be stabilized by wooden or metal splint incorporation in a bandage. Tibial fractures can be stabilized with a modified Thomas splint. Injuries that expose a joint or infectious arthritis require emergency diagnosis of joint involvement, and subsequent joint lavage, intra-articular antibiotics, and systemic antibiotics. For further treatment of septic arthritis, the cases can be referred to a hospital for joint drainage. The appropriate emergency treatment of these injuries is often the determining factor in whether the injury remains in a condition that can be successfully repaired.

Animals↗
PubMed1994

The effects of the neodymium laser on meniscal repair in the avascular zone of the meniscus.

Thirty mature New Zealand white rabbits were divided into four surgical groups, and a 3- to 4-mm incision was made in the inner avascular zone of the central third of the medial meniscus. In group I, the tear was not treated by lasering or suturing. In group II, the tear was sutured. Group III was given four different doses of the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation with no suturing. Group IV underwent meniscal suturing followed by the same four different laser irradiation doses. The animals were killed at 2, 4, and 6 weeks, with gross and histologic evaluation of the healing responses by group and time. The overall results showed no healing of this meniscal tear in the avascular zone. Suturing generally showed increased cellular infiltration. The varying doses of the Nd:YAG lasing demonstrated no gradient effect, and no "welding" of menisci was noted. The maximum cellular inflammatory response was noted in the sutured and lased menisci, reinforcing the importance of a stable meniscal environment for healing meniscal tears.

Animals↗
PubMed1993

Bone ingrowth into a porous-coated total shoulder component retrieved postmortem.

An uncemented porous-coated humeral component, which functioned in vivo for over 2 1/2 years, was retrieved postmortem and examined histologically. Radiographs of the specimen revealed close approximation to the endosteal cortex medially and laterally. Apposition was limited or absent anteriorly and posteriorly. The overall extent of bone ingrowth was approximately 11% of the available pore volume with over 95% of ingrowth occurring in the medial and lateral quadrants. Bone ingrowth was limited anteriorly and posteriorly to regions in which spot welds were identified radiographically. There were no loose beads or coating failure observed.

Adult↗
PubMed1996

Early radiographic results comparing cemented and cementless total hip arthroplasty.

In a randomized clinical trial of cemented and cementless total hip arthroplasty, 147 patients (76 cemented, 71 cementless) have had a minimum 4-year clinical and radiographic follow-up evaluation. No revisions have been done in either group. Two cemented acetabular components were considered definitely loose and 18 were probably loose; 7 cemented stems were possibly loose at last follow-up examination. One cementless socket was considered unstable. Although cementless femoral component subsidence occurred in 10 cases, the sinkage always stabilized within 6 months, and no stem was considered unstable at last follow-up examination. Significant femoral bone resorption was rare, and so-called "spot welds" were uncommon using this titanium stem. Distal cortical hypertrophy was common, but the cause is uncertain. Osteolysis was seen around 10 cementless and 6 cemented sockets. A small area of lysis occurred in the proximal medial femoral neck in 15 cemented stems and 1 cementless stem. No cases of distal femoral lysis were seen in either group. Despite excellent clinical results with no difference between groups, the high rate of early radiographic failure of this metal-backed acetabulum should preclude its use. Osteolysis will continue to be a problem in both groups, and its prevention should remain the focus of future studies.

Acetabulum↗
PubMed1997

Integral porous femoral stem. 5-to 8-Year follow-up study.

The outcome of total hip arthroplasty without cement was prospectively followed in patients who received a titanium taper wedge femoral component with a circumferential titanium plasma spray coating on the proximal surface (Integral femoral stem, Biomet, Warsaw, IN). One hundred ninety femoral components were implanted in 179 patients. Nine patients (9 hips) died prior to their 5-year examination, leaving 170 patients available for follow-up evaluation. Thirty-one of the 170 patients (33 hips) were lost at an intermediate follow-up period of 5 years. (mean, 5.8 years, range; 5-8 years), giving a follow-up rate of 82% for patients and hips. The preoperative diagnoses included osteoarthritis (91 hips), avascular necrosis (38), post-traumatic arthritis (10), rheumatoid arthritis (4), congenital dislocation of the hip (3), and fractures (2). The 78 men and 61 women had a mean age of 55 years (range, 18-81 years) and a mean weight of 81 kg (range, 50-136 kg). Pre-operative Harris pain and function scores for the hip were 19.9 (range, 0-40) and 55.6 (range, 12-84), respectively. At the most recent follow-up visit, the mean pain score increased to 41.2 (range, 10-44) and the mean function score increased to 93.5 (range, 6-100). Thigh pain was present in 4% of the hips at the most recent follow-up visit. Radiographically, 99% of the femoral components demonstrated spot welds in the porous-coated zone. Two hips had demarcation of the femoral component in the porous-coated zone consistent with fibrous fixation. None of the femoral stems had been revised and there were no signs of aseptic loosening. Additionally, there were no cases of pain that could be directly attributed to the stem and there was no evidence of distal femoral osteolysis. It is concluded that the integral femoral stem provides excellent clinical and radiographic results at intermediate follow-up periods.

Adolescent↗
PubMed1991

Tunnelling instruments for vascular grafts: problems and solutions.

When autologous veins or vascular prostheses are implanted for bypass operations or haemodialysis, the use of an appropriate tunnelling device is extremely helpful. In order to avoid perigraft haemorrhage and allow undelayed graft incorporation, the tunneller should match the diameter of the implant. Interchangeable shafts of various lengths and blunt tips of various diameters are prerequisites for a versatile instrument. Most instruments on the market have an important drawback: the handle is welded to one end of the shaft thus preventing "bi-directional" use. We have therefore developed a modified tunneller that can be used equally well in either direction. The connection between shaft and handle affords torsional rigidity and thus allows precise guidance during insertion. The handle can be attached to both ends of the shaft. Thus, for example, in a femoro-popliteal bypass, the distal anastomosis can be constructed first, followed by the introduction of the tunneller from the knee to the groin. As a next step the tip and handle are interchanged and the graft is passed from the knee to the groin. When a haemodialysis shunt with a PTFE-loop is inserted, the bidirectional use of the tunneller makes it possible to insert the graft with a smooth curve into the smallest possible cavity. Thus, the new instrument set called the "Bi-directional Tunneller" is more versatile and easier to use than other tunnellers presently available.

Anastomosis, Surgical↗
PubMedDate not supplied

Determination of thorium in environmental and workplace materials by ICP-MS.

The paper outlines the advantages of the use of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) over radiometric techniques to measure natural thorium, 232Th. Experimental parameters that must be taken into account in the sample digestion, preparation and ICP-MS analysis of environmental (soils, rocks, sediments) or workplace (thorium oxide, reference solutions) materials are described. The methods presented are applied to various reference materials, with the aim of providing suitable procedures to be useful for other important thorium containing materials (such as monazite sands or welding electrodes). The participation in a European Commission intercomparison exercise is detailed and a comparison with alpha spectrometry is made.

Environmental Exposure↗
PubMedDate not supplied

Comparison of methods for preparation of 125I brachytherapy source cores for the treatment of eye cancer.

Two procedures for fixing the 125I activity on different matrices were explored. In the first method, anodic deposition of 125I on silver wire was used. In the second, 125I was adsorbed as iodate (IO3-) on alumina microspheres by using a solid-solution interface technique. While the 125I uptake was approximately 84% on the silver wires by electrodeposition method, the microspheres showed approximately 97% by the solid-solution interface technique. The low leachable (0.05%) wires, and comparatively high leachable (approximately 4%) spheres were trial encapsulated and laser welded. The encapsulated sources were measured for source strength and were found to be suitable for the treatment of eye cancer.

Adsorption↗
PubMed2000

Improved target system for production of high purity [18F]fluorine via the 18O(p,n)18F reaction.

An improved aluminium target system for production of elemental fluorine via the 18O(p,n)18F reaction using a two-step irradiation protocol is described. In the first step highly enriched gaseous oxygen-18 is irradiated with protons to form fluorine-18 which gets deposited on the inner target surface. In the second step, after cryogenic recovery of oxygen-18 target gas, a mixture of elemental 'cold' fluorine and krypton is introduced and a short proton irradiation is done, whereby an isotopic exchange between the gaseous fluorine and the deposited radiofluorine occurs. The second step leads to the recovery of the radiofluorine as [18F]fluorine. Optimisation studies were performed regarding the yield and specific radioactivity of [18F]fluorine. Furthermore, some irradiation parameters relevant to the recovery step were investigated. It was found that a 15 to 20 min irradiation with a beam current of 20 microA is sufficient for the isotopic exchange between the fluorine-carrier and the 18F-radioactivity deposited on the inner wall of the target. The distribution of the 18F-radioactivity deposited on the inner target surface is inhomogeneous, probably due to convection effects. Extensive radioanalytical techniques were applied to characterise the reactivity of [18F]fluorine and to identify undesired nonreactive 18F-compounds, mainly [18F]tetrafluoromethane and [18F]nitrogentrifluoride. The [18F]fluorine produced in the system used has the distinction of having a negligible contamination from those inert 18F-compounds. This is a combined effect of the use of highest purity gases and a welded target construction, which avoids any contact of the gases with organic material during irradiations. The target has proved to be very reliable for production of [18F]fluorine in high yields of up to 34 GBq and specific activities of 350-600 GBq/mmol, both at 30 min after end of activation bombardment.

Aluminum↗
PubMed1990

Thermal balloon angioplasty in a canine model: preliminary results.

Preliminary results suggest that thermal balloon angioplasty (BA) may produce plaque welding, decreased elastic recoil, and increased luminal caliber. The authors report results of a simple method of thermal BA in a canine model. Seven mongrel dogs (15-25 kg) underwent conventional BA of each iliac artery with balloons that were 1-2 mm larger than the vessel lumen. The balloons were then perfused with a mixture of saline and contrast material at either 25 degrees C (control) or 100 degrees C for 1 minute. Compared with baseline measurements, thermal BA produced greater lumen enlargement (+16.7%) than control BA (+3.4%) immediately after the procedure (P less than .05). This trend persisted in vessels studied after a delay of 2, 4, or 12 weeks. Histologic sections from specimens studied after a delay demonstrated intimal hyperplasia in both the thermally treated and control arteries. Medial sclerosis was consistently seen in the thermally treated arteries. The authors conclude that thermal BA results in immediate and delayed increases in arterial diameter compared with conventional BA due to decreased elastic recoil and medial sclerosis.

Angioplasty, Balloon↗
PubMed1998

[Staff certification for mobile blood collection units].

Training and official acknowledgment of the competence of each staff member are essential to the quality and safety of collected blood products prepared and delivered by a blood transfusion center. A procedure was created to indicate in detail the methods employed to implement such accreditation. Based on individual training according to activity, it defines for each type of activity (secretary, physician, collector, driver) the required theoretical and practical knowledge of his/her position. Accreditation, consisting of assessment of the degree of competence attained in these areas of responsibility, was applied to the members of mobile blood collection teams in 1995. No major deficiency was detected, and this certification was well accepted by the staff. In order to complete this initial accreditation, blood collection abnormalities (inadequate blood volumes, clots or defective welding of tubing) were assessed for each collector individually. Comparison of these abnormalities in qualified nurses and laboratory technicians with a blood collection diploma showed no differences. On the other hand, significantly higher numbers of abnormalities were found in intermittent as compared to regular collectors and in senior as compared to new collectors. The applied corrective measures led to obviation of differences and improvement in performance. In 1996, in the first individual evaluation of medical selection carried out by each physician, discrepancies of one to 20 donors (0.7-14.2%) were observed from one doctor to another in the frequency of elimination of candidates for blood donation after the medical interview. Regular meetings with physicians resulted in reducing these discrepancies to one to 3.1 donors (4.6-14.1%) in 1997. In conclusion, the association of an initial accreditation procedure with an individual follow-up of work quality allowed satisfactory assessment of the training and competence of staff members. This kind of method could be extended to those working in other fields of transfusion medicine.

Allied Health Personnel↗
PubMed2000

Large scale sonochemical processing: aspiration and actuality.

It has been recognised for many years that power ultrasound has great potential in a wide variety of processes in the chemical and allied industries. Some of these processes have been known for many years and continue to flourish as major commercial applications, e.g. plastic welding and cleaning. Others, like ultrasonic drilling, while showing great potential have not been widely exploited to date. The potential for the industrial use of power ultrasound is enormous, and yet industry seems somewhat reluctant to adopt it. In this article the existing uses of power ultrasound in processing are reviewed and the potentials are explored.

Journal Article↗
PubMed2001

Basic design and construction of the Vienna FES implants: existing solutions and prospects for new generations of implants.

We can distinguish 3 generations of FES implants for activation of neural structures: 1. RF-powered implants with antenna displacement dependent stimulation amplitude; 2. RF-powered implants with stabilised stimulation amplitude; and 3. battery powered implants. In Vienna an 8-channel version of the second generation type has been applied clinically to mobilisation of paraplegics and phrenic pacing. A 20-channel implant of the second generation type for mobilisation of paraplegics and an 8-channel implant of the third generation type for cardiac assist have been tested in animal studies. A device of completely new design for direct stimulation of denervated muscles is being tested in animal studies. There is a limited choice of technologically suitable biocompatible and bioresistant materials for implants. The physical design has to be anatomically shaped without corners or edges. Electrical conductors carrying direct current (D.C.) have to be placed inside a hermetic metal case. The established sealing materials, silicone rubber and epoxy resin, do not provide hermeticity and should only embed DC-free components. For electrical connections outside the hermetic metal case welding is preferable to soldering; conductive adhesives should be avoided. It is advisable to use a hydrophobic oxide ceramic core for telemetry antenna coils embedded in sealing polymer. Cleaning of all components before sealing in resin is of the utmost importance as well as avoidance of rapid temperature changes during the curing process.

Animals↗
PubMed2002

Detection, distribution, and quantification of carbon in steel microstructures by PEELS.

This work concerns the use of parallel electron energy loss spectroscopy (PEELS) to investigate the detection, distribution, and quantification of carbon in various steel microstructures generated by rapid cooling rates or by isothermal transformation. The feasibility of detecting C in steels containing very small amounts of carbon was first examined by calculating the minimum detectable mass fraction for a variety of binary Fe-C alloy specimen thicknesses and microscope conditions. These theoretical studies indicated that the detection of carbon in steel microconstituents containing about 0.01 wt.% (or even less) was easily possible with an analytical transmission electron microscope equipped with a LaB6 emitter and a PEEL spectrometer. These theoretical calculations seemed to be reasonable, as it proved possible to make a quantitative PEELS study of the partitioning between the microconstituents ferrite, retained austenite, and martensite found in an ultralow carbon (0.03 wt.%) steel weld metal provided care was taken to avoid hydrocarbon contamination. Studies of both carbon and molybdenum segregation to ferrite/martensite interfaces in an isothermally transformed Fe-C-Mo alloy were also carried out in order to investigate the nature of the "solute drag" effect in this alloy system.

Alloys↗
PubMed2005

Phase-changing sacrificial materials for solvent bonding of high-performance polymeric capillary electrophoresis microchips.

A new method for solvent bonding polymeric substrates to form microfluidic systems has been demonstrated. Prior to device sealing, channels in an embossed poly(methyl methacrylate) (PMMA) piece are filled with a heated liquid (paraffin wax) that forms a solid sacrificial layer at room temperature. The sacrificial material prevents the bonding solvent (acetonitrile) and softened PMMA from filling the channels. Once the sealing step is complete, the sacrificial layer is melted and removed, leaving enclosed microfluidic channels. We found that PMMA substrates welded together using this method could withstand internal pressures of >2250 psi, more than 1 order of magnitude higher than their thermally bonded counterparts. To demonstrate the usefulness of this method, microchip capillary electrophoresis (CE) devices in PMMA were created and tested. Amino acid and peptide mixtures were separated in <15 s, with >40,000 theoretical plates in a 2.5-cm separation distance. Electric fields as high as 1.5 kV/cm were applied in these microchips, and >300 CE runs were performed on a single device with no degradation of separation performance. The simplicity of the methods presented here and the improved robustness of the resulting devices should facilitate the broader implementation of polymer microchips in microfluidic analyses.

Acetonitriles↗