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PubMed2000

Improved dialyzer reuse after use of a population pharmacodynamic model to determine heparin doses.

Anticoagulation with heparin is performed to prevent clotting during dialysis. However, heparin doses are usually determined empirically, and dialyzer clotting is a common reason for discarding reused dialyzers. We hypothesized that using a population pharmacodynamic model to determine individual heparin doses would improve dialyzer reuse rates. A previously published model was used to determine the loading dose and infusion rate of heparin needed to increase the intradialytic whole-blood clotting time to 150% of the predialysis value. The effectiveness of the model was assessed by comparing dialyzer reuse rates and delivered Kt/V(urea) before and after implementation of the model in 22 chronic hemodialysis patients. As an additional control, a similar group of 22 patients were followed up during the same period without adjustment of their heparin doses. Implementation of the model resulted in no change in the average loading dose (2,382 +/- 628 versus 2,425 +/- 908 IU; P = not significant) or average infusion rate (1,398 +/- 367 versus 1,393 +/- 532 IU/h; P = not significant) of heparin. However, individual patients required changes in loading dose or infusion rate. Dialyzer reuse rates increased significantly over time in the treatment group but remained unchanged in the control group (P < 0.003). Kt/V(urea) remained unchanged throughout the study period in both patient groups. From these data, we conclude that the use of a heparin model can improve dialyzer reuse rates without compromising the delivered dose of dialysis.

Aged↗
PubMed2006

Multi-center clinical experience with a lumenless, catheter-delivered, bipolar, permanent pacemaker lead: implant safety and electrical performance.

PURPOSE: Reduced lead diameter and reliability can be designed into transvenous permanent pacing leads through use of redundant insulation and removal of the stylet lumen. The model 3830 lead (Medtronic Inc., Minneapolis, MN, USA) is a bipolar, fixed-screw, steroid-eluting, lumenless, 4.1-Fr pacing lead. Implantation can be performed in a variety of right heart sites using a deflectable catheter (Model 10600, Medtronic). Lead performance and safety were studied. METHODS: Two prospective trials of 338 implanted subjects from 56 global sites were conducted. Electrical and safety data were obtained at implant, pre-discharge, and up to 18 months post-implant. Leads were implanted at traditional and alternate right heart sites. RESULTS: The study enrolled 338 subjects (204 males, 70.6 +/- 11.6 years) followed-up for a mean of 10.2 months (range, 0-21.6). Mean P-wave amplitudes ranged from 3.2 mV at 3 months to 2.9 mV at 18 months, while mean atrial pulse width thresholds at 2.5 V ranged from 0.07 ms at 3 months to 0.09 ms at 18 months. Mean R-wave amplitudes ranged from 11.3 mV to 11.1 mV and mean ventricular pulse width thresholds at 2.5 V ranged from 0.10 ms to 0.14 ms. There were 22 ventricular and 12 atrial lead complications within 3 months post-implant. Survival from lead-related complications improved to a clinically acceptable rate in the cohort of patients when revised implant techniques were employed. CONCLUSIONS: With the use of recommended implant techniques, the study results support the electrical efficacy and safety of a catheter-delivered, lumenless lead in traditional or alternate right atrium or right ventricle sites through 18 months post-implant.

Aged↗
PubMed2004

Reusing microarrays within closely related species: experimental validation through phylogenetic inference.

Microarrays are generally designed for a specific set of organisms, and this poses a limitation for researchers wanting to conduct investigations on gene expression in organisms that are, in some sense, not "popular" enough. In this article, we demonstrate that microarrays may in fact be reusable for aggregate expression analysis for species that are evolutionarily related. Our validation approach is based on this assumption and draws a phylogenetic conclusion that is deemed to be true only if the assumption of reusability is valid. This article demonstrates that microarrays developed using the human transcriptome are reusable for aggregate expression analysis of primates in general.

Animals↗
PubMed2005

Identification of the defective transmission devices using the wavelet transform.

In this paper, a system is described that uses the wavelet transform to automatically identify the particular failure mode of a known defective transmission device. The problem of identifying a particular failure mode within a costly failed assembly is of benefit in practical applications. In this system, external acoustic sensors, instead of intrusive vibrometers, are used to record the acoustic data of the operating transmission device. A skilled factory worker, who is unfamiliar with statistical classification, helps to determine the feature vector of the particular failure mode in the feature extraction process. In the automatic identification part, an improved learning vector quantization (LVQ) method with normalizing the inputting feature vectors is proposed to compensate for variations in practical data. Some acoustic data, which are collected from the manufacturing site, are utilized to test the effectiveness of the described identification system. The experimental results show that this system can identify the particular failure mode of a defective transmission device and find out the causes of failure successfully.

Acoustics↗
PubMed2005

Current concepts of metal-on-metal hip resurfacing.

The second-generation, metal-on-metal (MOM) bearing for total hip replacements was launched in the 1980s, and resurfacing followed in the mid-1990s. Remaining challenges include long-term bone remodeling of the femoral resurfacing and consideration of adverse MOM wear conditions. Precise understanding of manufacturing variables such as alloy types, bearing diameters, design tolerances, and surface finish is imperative in obtaining clinical consistency and safety in the patient. This review examines femoral fixation, bone remodeling, and wear studies of MOM implants and provides a brief overview of the latest outcome and retrieval data and how these data integrate with the in vitro wear studies.

Arthroplasty, Replacement, Hip↗
PubMed2003

Comparison of various safety guidelines for electronic article surveillance devices with pulsed magnetic fields.

The paper uses the two methods suggested in both the ICNIRP and proposed IEEE safety guidelines for compliance testing of security systems based on time-varying magnetic fields being introduced for electronic article surveillance (EAS), radiofrequency identification, and other applications. For nonsinusoidal pulses that are often used, the two procedures are to treat the exposure as a multifrequency exposure with various frequency components or to calculate the peak induced current densities or electric fields treating the highest of the pulses of duration t(p) as a single frequency, half sinusoid of the same duration and frequency 1/(2t(p)). Using either of the procedures, the induced current densities (J) or electric fields (E) are compared to the basic restrictions on J or E for compliance testing. Using a heterogeneous, tissue-classified anatomic model of the human body, we calculate the induced J and E for the various tissues for a realistic, EAS system for two typical nonsinusoidal pulses to show that the two methods give substantially different results. While the approximate but simpler method of treating the pulse as a half sinusoid results in peak induced J or E that may be compliant with safety guidelines, the rigorous method of treating such exposures as multifrequency exposures gives induced current densities or electric fields that may be up to twice as large, thus making such systems potentially noncompliant with the safety guidelines. Since it is more accurate, it is suggested that safety assessment based on the Fourier analysis leading to multifrequency components be used for compliance testing of such devices.

Computer Simulation↗
PubMed1999

Analysis of strength properties of light-cured resin composites.

OBJECTIVES: To determine and correlate the compressive and tensile strengths of resin composites, to scale their failure probability and to analyze their failure mode under combined state of stresses. METHODS: Ten brands of composites were tested for compressive and diametral tensile strengths. A recently introduced device for testing of pure shear stresses was modified to adapt to smaller specimens. Uniformity of pure shear stress distribution in the significant section was verified by a photoelastic model. Loading specimens in pure shear up to failure determined their mode of fracture under combined state of stresses. RESULTS: Diametral tensile strength yielded values that were 20% of their respective compressive strength. Multiple comparison test indicated that strength properties of the tensile strength test were much more sensitive in predicting differences between resin composites when compared to a compressive strength test. Pertac (Espe) had the highest compressive strength, Graft LC (GC) and Z-100 (3M) had the highest diametral tensile strength. No correlation was found between tensile and compressive strengths. The Weibull modulus disclosed differences in the liability of the materials to fracture. When combined state of stresses were applied through the pure shear test, failure of each specimen occurred at the principal tensile planes. SIGNIFICANCE: Compressive strength cannot predict the ability of the resin composite to withstand tensile stresses. The importance of compressive strength is limited as failure of a brittle material occurs in tension.

Analysis of Variance↗
PubMed2001

Suture closure of the femoral arteriotomy following invasive cardiac procedures: a detailed analysis of efficacy, complications, and the impact of early ambulation in 1,200 consecutive, unselected cases.

The purpose of this study was to assess the efficacy and safety of using a percutaneous suture device to close femoral arteriotomies following invasive cardiac procedures. All patients presenting for invasive cardiac procedures performed from the femoral artery were considered for suture closure. Patients were carefully assessed for access site complications, oozing, and the impact of suture closure on the safety of early ambulation. Clinical follow-up at 3-6 months was performed to assess for late complications. Femoral artery suture closures were performed in 1,200 consecutive cases in 1,097 patients. In 12.8% of cases, the patients ambulated within 1 hr. The success rate was 91.2% and the complication rate was 3.4%. Complications included the development of a hematoma (2.1%), the need for vascular surgery (0.6%), retroperitoneal hemorrhage (0.3%), blood transfusion (0.7%), local infection (0.5%), and pseudoaneurysm formation (0.1%). Factors found to be independently predictive of procedural failure were an age > 70 years, an ACT > 300 sec, left femoral artery access, and the performance of primary angioplasty. Follow-up at 3-6 months revealed no major hemorrhagic complications. We conclude that percutaneous suture closure effectively achieves femoral artery hemostasis in patients undergoing invasive cardiac procedures. The technique permits early ambulation and is associated with a relatively low incidence of complication.

Aged↗
PubMed2005

Detecting surface issues.

Surface analysis can be a significant aid in product development. Recent advances in these techniques allow the fine details of different coatings to be compared and optimised coating processes to be developed.

Biocompatible Materials↗
PubMed1996

A comparison of mandibular angle fracture plating techniques.

OBJECTIVE: The purpose of this investigation was to compare the conventional technique of mandibular angle fracture plating with two biomechanically dissimilar techniques in their abilities to resist vertical loads similar to masticatory forces. STUDY DESIGN: Three groups of five synthetic hemimandibles with simulated fracture repairs were compared for their capabilities to resist vertical deformation. The conventional group was stabilized with a thin tension band system at the superior border and thick stabilization plate system at the inferior border. The nontraditional group was stabilized with a thick tension band system at the superior border and thin stabilization plate system at the inferior border. The two miniplate group was stabilized with a thin tension band system at the superior border and thin stabilization plate at the inferior border. A cantilever beam design was used. Testing was performed with an instron 8511.20 (Instron Corp., Canton, Mass.) mechanical testing device. The three groups were compared with a two way analysis of variance. RESULTS: The forces resisted by the conventional group (167.6 +/- 18.2 N), the nontraditional group (156.3 +/- 33.9 N), and two miniplate group (154.0 +/- 18.4 N) were not statistically different (F = 0.44, p > 0.66). All failures occurred at the tension bands secured with monocortical screws. CONCLUSIONS: Under the conditions described in this in vitro investigation, plate thickness or pattern made no difference. All failures in this experiment occurred with monocortical screws in the superior border tension band system.

Analysis of Variance↗
PubMed2002

An association of silicone-gel breast implant rupture and fibromyalgia.

Silicone-gel breast implant rupture is common. Silicone-gel from ruptured implants may escape the scar capsule that forms around breast implants and become "extracapsular silicone." Our previously published study found that women with extracapsular silicone gel were at higher risk of reporting that they were diagnosed with fibromyalgia. There has been a limited number of studies addressing this association in the literature. Some studies addressing the issue of silicone breast implants and connective tissue disease specifically exclude patients with fibromyalgia from the sample or do not include the syndrome in the analysis. Case series describing fibromyalgia in patients with implants have been published, but many of these papers lack information on extracapsular silicone and are not representative because the patients are typically from referral populations. In addition, most studies do not have control groups of women without implants for comparison or do not distinguish between saline and silicone implants. Additional observational studies of women from nonreferral populations are necessary to validate an association. These studies should provide information on how the rupture is diagnosed, state whether the rupture extended beyond the capsule, and provide an appropriate control group for comparison. The findings from such studies may be important to physicians as they describe potential risks associated with implants to their patients. These findings should also be important for regulatory decision making on silicone-gel breast implants.

Breast Implants↗
PubMed2003

Derivation of an equation for quantitative SIL assignment.

Quantitative risk analysis for selection of safety integrity levels (SIL's) is becoming more prevalent due to the high equipment costs associated with qualitative methods. Procedures for applying quantitative methods to the SIL selection problem are in the early stages of development. Literature explaining quantitative methods is scarce and many engineers are forced to develop ad hoc procedures, some of which are mathematically flawed. One of the equations popularly used to assign a probability of failure on demand (PFD) to a safety instrumented function (SIF) based on tolerable risk and unmitigated event frequency is shown in the equation below. Variations of this equation are in use by various SIS practitioners: PFD(SIF) = f(Tolerable)_Risk/f(Unmitigated)_Event. This paper presents a rigorous derivation of this equation based on scientific laws of probability math and standardized definitions used in the field of SIS engineering. By publishing this derivation the author hopes to lend more credibility to this type of SIL selection process and increase its usage in the process industries.

Electronics↗
PubMed2006

Application of nondestructive testing in cyclic fatigue evaluation of endodontic Ni-Ti rotary instruments.

The purpose of this study was to investigate the application of nondestructive testing in cyclic fatigue evaluation of endodontic ProFile nickel-titanium (NiTi) rotary instruments. As-received ProFile instruments were made to rotate freely in sloped metal blocks by a contra-angle handpiece mounted on a testing machine. Rotation was interrupted periodically, and the instrument removed and engaged onto a device to monitor its stiffness by using two strain gauges in four different directions. This monitoring method has the potential to be developed into a convenient, nondestructive turnkey system that allows in situ assessment of the integrity of NiTi instruments in the clinic. Upon fracture, which was indicated by a change in instrument stiffness, the fractured surface would be examined under a scanning electron microscope. Microscopic evaluation indicated a small area of fatigue fracture with a large area of final ductile fracture, whereby the latter was the major cyclic failure mode. Based on the results of this study, we concluded that a potential nondestructive integrity assessment method for NiTi rotary instruments was developed.

Dental Alloys↗
PubMed1998

Evaluation of a new light-cured orthodontic bonding adhesive.

The purpose of this study was to compare a new light-cured bonding system that used a hybrid adhesive containing a resin reinforced glass ionomer (Fuji Ortho LC, GC America, Inc.) with a more traditional light-cured bonding system (Transbond, 3M Unitek) that contained resin material only. Seventy-five recently extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were randomly separated into five groups of 15 molars each: Group I--using Transbond adhesive system with the enamel etched and dried before bonding. Group II--using Fuji Ortho LC (FOLC) adhesive system with no etch and the enamel wet with water before bonding. Group III--using FOLC adhesive system with the enamel etched and wet with water before bonding. Group IV--using FOLC adhesive system with no etch and the enamel wet with saliva before bonding. Group V--using FOLC adhesive system with the enamel etched and wet with saliva before bonding. The shear bond strength was performed after thermal cycling between 5 degrees +/- 2 degrees C and 50 degrees +/- 2 degrees C for a total of 2000 cycles with the Zwick test machine (Zwick Gm bH & Co.). After debonding, the teeth and brackets were examined under x10 magnification to evaluate the site of bond failure and the presence of residual adhesive. The analysis of variance was used to determine whether significant differences existed between the various groups. The findings indicated that there were no statistically significant differences among the three experimental groups I, III, and V that had the enamel surface etched before bonding, regardless of the adhesive used or the enamel surface contamination with water or saliva. On the other hand, the two experimental groups that did not have the enamel etched before bonding (II and IV) had significantly lower bond strengths. In conclusion, etching the enamel surface is a critical variable that affects shear bond strength as well as bond failure location when using the new adhesive system.

Acid Etching, Dental↗
PubMed2007

Influence of a brushing working motion on the fatigue life of NiTi rotary instruments.

AIM: To evaluate the cyclic fatigue resistance of Mtwo NiTi rotary instruments when used with a brushing or no-brushing action in oval root canals. METHODOLOGY: Cyclic fatigue testing of instruments was performed in tapered artificial canals with a 5 mm radius of curvature and an angle of curvature of 60 degrees. Twenty Mtwo instruments for each size were selected and divided into two groups: group A = 10 instruments used with a no-brushing motion (control group); group B = 10 instruments used with a brushing-milling action. Each Mtwo instrument was used for cleaning and shaping 10 oval root canals. In all 80 instruments were rotated until fracture occurred and the number of cycles to failure (NCF) recorded. Data were analysed by one-way ANOVA, Tukey HSD test and independent sample t-test to determine any statistical difference; the significance was determined at the 95% confidence level. RESULTS: No statistically significant reduction of NCF between instruments used with a no-brushing motion (group A) and instruments used with a brushing motion (group B) were apparent except for size 25, 0.06 taper. Mtwo size 10, 0.04 taper, size 15, 0.05 taper, size 20, 0.06 taper, size 25, 0.06 taper instruments had a decrease in life span of 1%, 0.5%, 8% and 19%, respectively. CONCLUSIONS: Fatigue life of instruments of larger size could be reduced by using them with a lateral brushing or pressing movement. However, each file was successfully operated without intracanal failure, demonstrating that Mtwo rotary instruments can be used safely in a brushing action in simulated clinical conditions up to 10 times in oval canals.

Analysis of Variance↗