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Strength Data (strength + data)
Selected AbstractsIsokinetic and isometric muscle strength in a healthy population with special reference to age and genderACTA PHYSIOLOGICA, Issue 2009B. Danneskiold-Samsøe Abstract Aim:, Muscle strength is an excellent indicator of general health when based on reliable measurements. Muscle strength data for a healthy population are rare or non-existent. The aim of the present study was to measure a set of normal values for isometric and isokinetic muscle strength for all the major joint movements of the body and, from these data, to create a basis for comparison of the muscle strength of an individual with the expected value in a normal population. Methods:, A randomly selected group, aged 20,80 years, from the Copenhagen City Heart Study were studied. The group was subgrouped according to age and gender. Isometric and isokinetic muscle strength was measured in each subject across the main joints in the body. A statistical model was developed that encompassed the three main muscle groups: upper limbs, trunk and lower limbs. Results:, Muscle strength in healthy men decreases in a linear fashion from the age of 25 years down to between 54% and 89% at the age of 75 years, and seems not highly dependent on any other parameter than age. For women, the muscle strength is dependent on weight and is only related to age from around 40 years of age. The decrease in muscle strength from the age around 40 to 75 years is 48,92%. For most muscle groups, men are 1.5,2 times stronger than women, with the oldest men having strength similar to that observed among the youngest women. Conclusion:, We developed a model to compare the isometric and isokinetic muscle strength of all the major joint movements of an individual with values for a healthy man or woman at any age in the range of 20,80 years. In all age groups, women have lower muscle strength than men. Men's muscle strength declines with age, while women's muscle strength declines from the age of 41 years. [source] Assessment of test data for selection of 3-D failure criterion for sandINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2006Poul V. Lade Abstract Data from three-dimensional experiments performed on sand in true triaxial equipment have been reviewed to sort out apparent disarray resulting from their interpretation. This has been done based on analyses made possible by recent developments and understanding of factors influencing sand behaviour: occurrence of shear banding, boundary conditions and/or specimen slenderness ratio, cross-anisotropy, and stability of experimental technique. These factors are reviewed and test data from the literature are evaluated. Experimental data are divided into three groups in which: (a) homogeneous behaviour controls the sand strength; (b) shear banding affects the shape of the three-dimensional failure surface in the midrange of values of b=(,2,,3)/(,1,,3), and (c) the data has been misinterpreted. Appropriate interpretation of three-dimensional strength data for sand exhibiting isotropic, homogeneous behaviour is represented by a smoothly rounded triangular failure surface expressible in terms of the first and third stress invariants. Shear banding effects will cause the failure surface to be ,indented' in the midrange of b -values in all sectors of the octahedral plane. Effects of cross-anisotropy will result in lower strengths in sector III than in sector I of the octahedral plane, and the failure surface will appear as rotated around the stress origin in principal stress space. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of adhesive systems and luting agents on bonding of fiber posts to root canal dentinJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Francesca Monticelli Abstract The study evaluated the influence of different luting materials on the microtensile bond strength of glass fiber posts to root canal dentin. Thirty extracted maxillary premolars were endodontically treated, and the roots were prepared for post cementation using the FRC Postec system (Vivadent). Two luting materials (Multilink, Vivadent and Clearfil Photo Core, Kuraray) were used in combination with three adhesive: Multilink Primer (Vivadent), Clearfil Photo Bond, and Clearfil New Bond (Kuraray). A composite build-up was performed around the root to provide adequate gripping during testing. Specimens were cut to obtain beams with the post in the center and with the radicular dentin overlaid by the composite build-up on each side. Microtensile testing was performed with a universal testing machine at a cross-head speed of 0.5 mm/min. The failure mode was classified under a stereomicroscope and four representative beams of each group were selected for SEM analysis. Bond strength data that were analyzed with two-way ANOVA and Student-Newman-Keuls multiple comparisons tests revealed that adhesive systems, luting materials, and the interaction between these two factors significantly influenced the bond strength results (p < 0.01). Multilink applied with its own adhesive system obtained the best results, while the lowest bond strength was achieved with clearfil photo core in combination with multilink primer. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Direct Dentin Bonding Technique Sensitivity When Using Air/Suction Drying StepsJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 2 2008PASCAL MAGNE DMD ABSTRACT Statement of Problem:, Moisture control before and after application of the primer/adhesive components of etch-and-rinse dentin bonding agents is usually achieved using a stream of air delivered by an air syringe. Suction drying with a suction tip is a common alternative for moisture control, but data about the use of suction drying instead of the air syringe is scarce or nonexistent. Purpose:, The purpose of this study was to compare the dentin microtensile bond strength (MTBS) using either the air syringe or the suction tip to control the amount of moisture. Materials and Methods:, Fifteen freshly extracted human molars were divided randomly into three groups of five. A three-step etch-and-rinse dentin bonding agent (OptiBond FL) was used. Group 1 was the control group and utilized air drying alone (with an air syringe) during the placement of the dentin adhesive on the ground-flat occlusal dentin surface. Group 2 also used air drying alone, but teeth were prepared with a standardized MOD cavity. Group 3 utilized suction drying alone in the standardized MOD cavity. All teeth were restored with 1.5-mm-thick horizontal increments of composite resin (Filtek Z100). Specimens were stored in water for 24 hours, then prepared for a nontrimming MTBS test. Bond strength data were analyzed with a Kruskal,Wallis test at p < 0.05. Specimens were also evaluated for mode of fracture and interface characterization using scanning electron microscope (SEM) analysis. Results:, The mean MTBSs were not statistically different from one another (p = 0.54) at 54.0 MPa (air-drying, flat dentin), 53.4 MPa (air-drying, MOD), and 49.2 MPa (suction drying, MOD). Microscopic evaluation of failure modes indicated that most failures were interfacial. Failed interfaces, when analyzed under SEM, appeared typically mixed with areas of failed adhesive resin and areas of cohesively failed dentin. Conclusions:, There are no differences in MTBS to human dentin using either the air syringe or the suction tip to control the amount of moisture. The conventional three-step dentin bonding agent used in the present study not only proved insensitive to the moisture-control method but also to the effect of increased polymerization shrinkage stress (ground-flat versus MOD preparation). CLINICAL SIGNIFICANCE Although the effect of common errors on the performance of total-etch adhesives has been investigated, data about the use of suction drying instead of an air syringe is scarce or nonexistent. The present study demonstrated that both the air syringe and the suction tip can be used to control moisture when using etch-and-rinse dentin bonding agents. The conventional three-step dentin bonding agent tested, OptiBond FL, demonstrated low technique sensitivity. [source] Lost Mold Rapid Infiltration Forming of Mesoscale Ceramics: Part 1, FabricationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2009Nicholas E. Antolino Free-standing mesoscale (340 ,m × 30 ,m × 20 ,m) bend bars with an aspect ratio over 15:1 and an edge resolution as fine as a single grain diameter (,400 nm) have been fabricated in large numbers on refractory ceramic substrates by combining a novel powder processing approach with photoresist molds and an innovative lost-mold thermal process. The colloid and interfacial chemistry of the nanoscale zirconia particulates has been modeled and used to prepare highly concentrated suspensions. Engineering solutions to challenges in mold fabrication and casting have yielded free-standing, crack-free parts. Molds are fabricated using high-aspect-ratio photoresist on ceramic substrates. Green parts are formed using a rapid infiltration method that exploits the shear thinning behavior of the highly concentrated ceramic suspension in combination with gelcasting. The mold is thermally decomposed and the parts are sintered in place on the ceramic substrate. Chemically aided attrition milling disperses and concentrates the as-received 3Y-TZP powder to produce a dense, fine-grained sintered microstructure. Initial three-point bend strength data are comparable to that of conventional zirconia; however, geometric irregularities (e.g., trapezoidal cross sections) are present in this first generation and are discussed with respect to the distribution of bend strength. [source] Mechanical Properties of Monoclinic ZirconiaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Jens Eichler Fracture toughness and fracture strength data are presented for the first time for monoclinic zirconia. An undoped nanocrystalline zirconia powder was sintered at 1100°C and yielded a theoretical density of more than 90% with a grain size of about 150 nm. The surface crack in flexure (SCF) technique was deemed most suitable for nanocrystalline materials. Measurements of Young's modulus and the determination of the fracture origin are also provided. [source] Morphology and mechanical properties of impact modified polypropylene blendsPOLYMER ENGINEERING & SCIENCE, Issue 11 2008Nathan Tortorella Isotactic polypropylene (PP) has been reactively blended with various grades of an ethylene,octene copolymer (EOC) in a twin-screw extruder. Free radical polymerization of styrene and a multifunctional acrylate during melt extrusion has resulted in an enhancement of mechanical properties over the binary blend. The reactive blend exhibits a notched Izod impact strength over 12 times that of pure polypropylene and greater than double the performance of the binary blend. Electron microscopy shows that by grafting onto the polymers, elastomer particle size and interparticle distance decrease, while particle shape becomes less spherical. The acrylate is crucial to achieve superior performance, as infrared spectra correlate an increase in graft yield to improvements in stress,strain behavior and impact strength. In addition, melt flow index (MFI) and melt strength data indicate a reduction in unwanted side reactions of polypropylene and the presence of long-chain branching. Dynamic-mechanical analysis reveals that the reaction promotes miscibility between polypropylene and the EOC and reduces molecular mobility at their glass-transition temperatures. Mechanical properties, graft yield, and MFI are shown to be highly dependent upon the elastomer's concentration, density, and molecular weight, initiator and monomer concentration, as well as processing temperature. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Fracture prediction in tough polyethylene pipes using measured craze strengthPOLYMER ENGINEERING & SCIENCE, Issue 5 2008P. Davis In this study, an empirical model is developed that predicts the time to failure for PE pipes under combined pressure and deflection loads. The time-dependent craze strength of different PE materials is measured using the circumferentially deep-notched tensile (CDNT) test. In agreement with previous research, results indicate that bimodal materials with comonomer side-chain densities biased toward high-molecular-weight PE molecules exhibit significantly higher long-term craze strengths. A comparison of currently available PE materials with CDNT samples taken from a PE pipe that failed by slow crack growth in service clearly indicates the superior performance of new-generation materials. Using measured craze strength data from the CDNT test, a simplified model for predicting failure in buried PE pipes is developed. Extending previous research, the reference stress concept is used to calculate an equivalent craze stress for a pipe subjected to combined internal pressure and deflection loads. Good agreement is obtained between the model predictions and observed failure times in an experimental test-bed study of pipes under in-service loading conditions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Reliability of knee extension and flexion measurements using the Con-Trex isokinetic dynamometerCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2007Nicola A. Maffiuletti Summary The aim of this study was to evaluate the reliability of isokinetic and isometric assessments of the knee extensor and the flexor muscle function using the Con-Trex isokinetic dynamometer. Thirty healthy subjects (15 males, 15 females) were tested and retested 7 days later for maximal strength (isokinetic peak torque, work, power and angle of peak torque as well as isometric maximal voluntary contraction torque and rate of torque development) and fatigue (per cent loss and linear slope of torque and work across a series of 20 contractions). For both the knee extensor and the flexor muscle groups, all strength data , except angle of peak torque , demonstrated moderate-to-high reliability, with intraclass correlation coefficients (ICC) higher than 0·86. The highest reliability was observed for concentric peak torque of the knee extensor muscles (ICC = 0·99). Test,retest reliability of fatigue variables was moderate for the knee extensor (ICC range 0·84,0·89) and insufficient-to-moderate for the knee flexor muscles (ICC range 0·78,0·81). The more reliable index of muscle fatigue was the linear slope of the decline in work output. These findings establish the reliability of isokinetic and isometric measurements using the Con-Trex machine. [source] | |||||||||||||