Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy

NASA Astrophysics Data System (ADS)

Shubitidze, Fridon; Kekalo, Katsiaryna; Stigliano, Robert; Baker, Ian

2015-03-01

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2-5 nm) single crystals of gamma-Fe2O3 with saccharide chains implanted in their crystalline structure, forming 20-40 nm flower-like aggregates with a hydrodynamic diameter of 110-120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99-164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue.

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy.

PubMed

Shubitidze, Fridon; Kekalo, Katsiaryna; Stigliano, Robert; Baker, Ian

2015-03-07

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2-5 nm) single crystals of gamma-Fe 2 O 3 with saccharide chains implanted in their crystalline structure, forming 20-40 nm flower-like aggregates with a hydrodynamic diameter of 110-120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99-164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue.

Isokinetic exercise: A review of the literature

NASA Technical Reports Server (NTRS)

Olree, H. D.; Corbin, B.; Smith, C.

1978-01-01

Isokinetic muscle training has all the advantages of isometrics and isotonics while minimizing their deficiencies. By holding the speed of movement constant throughout the full range of motion, isokinetic training devices respond with increased resistance rather than acceleration when the power output of the muscle is increased. Isokinetic training is superior to isometric and isotonic training with respect to increases in strength, specificity of training, desirable changes in motor performance tasks, lack of muscle soreness, and decreases in relative body fat.

Damage-Tolerant Polymer Composite Systems

NASA Astrophysics Data System (ADS)

Reifsnider, Kenneth L.

1988-11-01

One of the reasons for the rapid growth in the application of polymer composites is the opportunity they provide for the design and construction of composite structures that are especially resistant to losses of strength or reduced life resulting from damage during service. The usefulness of such materials is enhanced by the variety of reinforcement schemes that can be chosen to reflect specific service conditions. Under cyclic loading and demanding mechanical situations (e.g., helicopter parts, vehicle springs and high-speed rotors), polymer composites are considerably superior to competing materials.

Regional homogeneity of the resting-state brain activity correlates with individual intelligence.

PubMed

Wang, Leiqiong; Song, Ming; Jiang, Tianzi; Zhang, Yunting; Yu, Chunshui

2011-01-25

Resting-state functional magnetic resonance imaging has confirmed that the strengths of the long distance functional connectivity between different brain areas are correlated with individual differences in intelligence. However, the association between the local connectivity within a specific brain region and intelligence during rest remains largely unknown. The aim of this study is to investigate the relationship between local connectivity and intelligence. Fifty-nine right-handed healthy adults participated in the study. The regional homogeneity (ReHo) was used to assess the strength of local connectivity. The associations between ReHo and full-scale intelligence quotient (FSIQ) scores were studied in a voxel-wise manner using partial correlation analysis controlling for age and sex. We found that the FSIQ scores were positively correlated with the ReHo values of the bilateral inferior parietal lobules, middle frontal, parahippocampal and inferior temporal gyri, the right thalamus, superior frontal and fusiform gyri, and the left superior parietal lobule. The main findings are consistent with the parieto-frontal integration theory (P-FIT) of intelligence, supporting the view that general intelligence involves multiple brain regions throughout the brain. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Multimodal assessment of sensorimotor shoulder function in patients with untreated anterior shoulder instability and asymptomatic handball players.

PubMed

Mornieux, Guillaume; Hirschmüller, Anja; Gollhofer, Albert; Südkamp, Norbert P; Maier, Dirk

2018-04-01

Functional evaluation of sensorimotor function of the shoulder joint is important for guidance of sports-specific training, prevention and rehabilitation of shoulder instability. Such assessment should be multimodal and comprise all qualities of sensorimotor shoulder function. This study evaluates feasibility of such multimodal assessment of glenohumeral sensorimotor function in patients with shoulder instability and handball players. Nine patients with untreated anterior instability of their dominant shoulder and 15 asymptomatic recreational handball players performed proprioceptive joint position sense and dynamic stabilization evaluations on an isokinetic device, as well as a functional throwing performance task. Outcome measures were analysed individually and equally weighted in a Shoulder-Specific Sensorimotor Index (S-SMI). Finally, isokinetic strength evaluations were conducted. We observed comparable sensorimotor functions of unstable dominant shoulders compared to healthy, contralateral shoulders (e.g. P=0.59 for S-SMI). Handball players demonstrated superior sensorimotor function of their dominant shoulders exhibiting a significantly higher throwing performance and S-SMI (P<0.001 and P=0.002, respectively), but comparable internal rotator peak torques for both shoulders (P>0.22). The present study proves feasibility of multimodal assessment of shoulder sensorimotor function in overhead athletes and patients with symptomatic anterior shoulder instability. Untreated shoulder instability led to a loss of dominance-related sensorimotor superiority indicating functional internal rotation deficiency. Dominant shoulders of handball players showed a superior overall sensorimotor function but weakness of dominant internal rotation constituting a risk factor for occurrence of posterior superior impingement syndrome. The S-SMI could serve as a diagnostic tool for guidance of sports-specific training, prevention and rehabilitation of shoulder instability.

Effects of Different Types of Exercise on Body Composition, Muscle Strength, and IGF-1 in the Elderly with Sarcopenic Obesity.

PubMed

Chen, Hung-Ting; Chung, Yu-Chun; Chen, Yu-Jen; Ho, Sung-Yen; Wu, Huey-June

2017-04-01

To investigate the influence of resistance training (RT), aerobic training (AT), or combination training (CT) interventions on the body composition, muscle strength performance, and insulin-like growth factor 1 (IGF-1) of patients with sarcopenic obesity. Randomized controlled trial. Community center and research center. Sixty men and women aged 65-75 with sarcopenic obesity. Participants were randomly assigned to RT, AT, CT, and control (CON) groups. After training twice a week for 8 weeks, the participants in each group ceased training for 4 weeks before being examined for the retention effects of the training interventions. The body composition, grip strength, maximum back extensor strength, maximum knee extensor muscle strength, and blood IGF-1 concentration were measured. The skeletal muscle mass (SMM), body fat mass, appendicular SMM/weight %, and visceral fat area (VFA) of the RT, AT, and CT groups were significantly superior to those of the CON group at both week 8 and week 12. Regarding muscle strength performance, the RT group exhibited greater grip strength at weeks 8 and 12 as well as higher knee extensor performance at week 8 than that of the other groups. At week 8, the serum IGF-1 concentration of the RT group was higher than the CON group, whereas the CT group was superior to the AT and CON groups. Older adults with sarcopenic obesity who engaged in the RT, AT, and CT interventions demonstrated increased muscle mass and reduced total fat mass and VFA compared with those without training. The muscle strength performance and serum IGF-1 level in trained groups, especially in the RT group, were superior to the control group. © 2017, Copyright the Authors Journal compilation © 2017, The American Geriatrics Society.

Strong, ductile, and thermally stable Cu-based metal-intermetallic nanostructured composites.

PubMed

Dusoe, Keith J; Vijayan, Sriram; Bissell, Thomas R; Chen, Jie; Morley, Jack E; Valencia, Leopolodo; Dongare, Avinash M; Aindow, Mark; Lee, Seok-Woo

2017-01-09

Bulk metallic glasses (BMGs) and nanocrystalline metals (NMs) have been extensively investigated due to their superior strengths and elastic limits. Despite these excellent mechanical properties, low ductility at room temperature and poor microstructural stability at elevated temperatures often limit their practical applications. Thus, there is a need for a metallic material system that can overcome these performance limits of BMGs and NMs. Here, we present novel Cu-based metal-intermetallic nanostructured composites (MINCs), which exhibit high ultimate compressive strengths (over 2 GPa), high compressive failure strain (over 20%), and superior microstructural stability even at temperatures above the glass transition temperature of Cu-based BMGs. Rapid solidification produces a unique ultra-fine microstructure that contains a large volume fraction of Cu 5 Zr superlattice intermetallic compound; this contributes to the high strength and superior thermal stability. Mechanical and microstructural characterizations reveal that substantial accumulation of phase boundary sliding at metal/intermetallic interfaces accounts for the extensive ductility observed.

Strength Development: Using Functional Isometrics in an Isotonic Strength Training Program.

ERIC Educational Resources Information Center

Jackson, Allen; And Others

1985-01-01

A study was made to determine if a combination of functional isometrics and standard isotonic training would be superior to a standard isotonic program in an instructional setting. The results provide support for functional isometrics as an enhancement where achievement of maximum strength is the goal. (Author/MT)

Morphological, motor and situation-motor characteristics of elite female handball players according to playing performance and position.

PubMed

Cavala, Marijana; Katić, Ratko

2010-12-01

The aim of the study was to define biomotor characteristics that determine playing performance and position in female handball. A battery of 13 variables consisting of somatotype components (3 variables), basic motor abilities (5 variables) and specific motor abilities (5 variables) were applied in a sample of 52 elite female handball players. Differences in biomotor characteristics according to playing performance and position of female handball players were determined by use of the analysis of variance (ANOVA) and discriminative analysis. Study results showed the high-quality female handball players to predominantly differ from the less successful ones in the specific factor of throw strength and basic dash factor, followed by the specific abilities of movement without and with ball, basic coordination/agility and specific ability of ball manipulation, and a more pronounced mesomorphic component. Results also revealed the wing players to be superior in the speed of movement frequency (psychomotor speed), run (explosive strength) and speed of movement with ball as compared with players at other playing positions. Also, endomorphic component was less pronounced in players at the wing and back player positions as compared with goalkeeper and pivot positions, where endomorphic component was considerably more pronounced.

Environment-friendly wood fibre composite with high bonding strength and water resistance

PubMed Central

Ji, Xiaodi; Dong, Yue; Nguyen, Tat Thang; Chen, Xueqi

2018-01-01

With the growing depletion of wood-based materials and concerns over emissions of formaldehyde from traditional wood fibre composites, there is a desire for environment-friendly binders. Herein, we report a green wood fibre composite with specific bonding strength and water resistance that is superior to a commercial system by using wood fibres and chitosan-based adhesives. When the mass ratio of solid content in the adhesive and absolute dry wood fibres was 3%, the bonding strength and water resistance of the wood fibre composite reached the optimal level, which was significantly improved over that of wood fibre composites without adhesive and completely met the requirements of the Chinese national standard GB/T 11718-2009. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations revealed that the excellent performance of the binder might partly be due to the amide linkages and hydrogen bonding between wood fibres and the chitosan-based adhesive. We believe that this strategy could open new insights into the design of environment-friendly wood fibre composites with high bonding strength and water resistance for multifunctional applications. PMID:29765653

Environment-friendly wood fibre composite with high bonding strength and water resistance

NASA Astrophysics Data System (ADS)

Ji, Xiaodi; Dong, Yue; Nguyen, Tat Thang; Chen, Xueqi; Guo, Minghui

2018-04-01

With the growing depletion of wood-based materials and concerns over emissions of formaldehyde from traditional wood fibre composites, there is a desire for environment-friendly binders. Herein, we report a green wood fibre composite with specific bonding strength and water resistance that is superior to a commercial system by using wood fibres and chitosan-based adhesives. When the mass ratio of solid content in the adhesive and absolute dry wood fibres was 3%, the bonding strength and water resistance of the wood fibre composite reached the optimal level, which was significantly improved over that of wood fibre composites without adhesive and completely met the requirements of the Chinese national standard GB/T 11718-2009. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations revealed that the excellent performance of the binder might partly be due to the amide linkages and hydrogen bonding between wood fibres and the chitosan-based adhesive. We believe that this strategy could open new insights into the design of environment-friendly wood fibre composites with high bonding strength and water resistance for multifunctional applications.

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy

PubMed Central

Stigliano, Robert; Baker, Ian

2015-01-01

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2–5 nm) single crystals of gamma-Fe2O3 with saccharide chains implanted in their crystalline structure, forming 20–40 nm flower-like aggregates with a hydrodynamic diameter of 110–120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99–164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue. PMID:25825545

Is inertial flywheel resistance training superior to gravity-dependent resistance training in improving muscle strength? A systematic review with meta-analyses.

PubMed

Vicens-Bordas, J; Esteve, E; Fort-Vanmeerhaeghe, A; Bandholm, T; Thorborg, K

2018-01-01

The primary aim of this systematic review was to determine if inertial flywheel resistance training is superior to gravity-dependent resistance training in improving muscle strength. The secondary aim was to determine whether inertial flywheel resistance training is superior to gravity-dependent resistance training in improving other muscular adaptations. A systematic review with meta-analyses of randomised and non-randomised controlled trials. We searched MEDLINE, Scopus, SPORTDiscus, Web of Science and Cochrane Central Register of Controlled Trials with no publication date restrictions until November 2016. We performed meta-analyses on randomised and non-randomised controlled trials to determine the standardized mean difference between the effects of inertial flywheel and gravity-dependent resistance training on muscle strength. A total of 76 and 71 participants were included in the primary and secondary analyses, respectively. After systematic review, we included three randomised and four non-randomised controlled trials. In the primary analysis for the primary outcome muscle strength, the pooled results from randomised controlled trials showed no difference (SMD=-0.05; 95%CI -0.51 to 0.40; p=0.82; I 2 =0%). In the secondary analyses of the primary outcome, the pooled results from non-randomised controlled trials showed no difference (SMD=0.02; 95%CI -0.45 to 0.49; p=0.93; I 2 =0%; and SMD=0.03; 95%CI -0.43 to 0.50; p=0.88; I 2 =0%). Meta-analysis on secondary outcomes could not be performed. Based on the available data, inertial flywheel resistance training was not superior to gravity-dependent resistance training in enhancing muscle strength. Data for other strength variables and other muscular adaptations was insufficient to draw firm conclusions from. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Development of hydrogen resistant structural alloy NASA-23

NASA Technical Reports Server (NTRS)

Bhat, B. N.; Mcpherson, W. B.; Kuruvilla, A. K.; Chen, P. S.; Panda, B.

1993-01-01

Hydrogen-resistant alloy NASA-23 was developed specifically as a structural alloy for application in liquid propulsion systems that use hydrogen fuel. NASA-23 was designed to be similar to Alloy 718 in strength, ductility, and corrosion resistance, but with superior resistance to hydrogen environment embrittlement. The alloy is readily processed; it can be both hot and cold worked and is castable and weldable. A material property data base is being generated for both cast and wrought NASA-23. This paper will present the status of alloy development and discuss potential applications in propulsion systems.

Design and implementation of observational studies to measure disease burden with a focus on stroke.

PubMed

Howard, George; Howard, Virginia J

2018-02-01

Observational epidemiological studies have the dual goals of measuring disease burden and assessing the association between exposures and outcomes. This report focuses on the first of these goals and provides an overview of design considerations of commonly used approaches, specifically community surveillance studies, cross-sectional studies, and longitudinal cohort studies. Each of these designs has strengths and weaknesses, with no study design being superior in all cases. Rather, these designs are complementary to achieve a better understanding of the burden of stroke.

Withdrawal Strength and Bending Yield Strength of Stainless Steel Nails

Treesearch

Douglas R. Rammer; Samuel L. Zelinka

2015-01-01

It has been well established that stainless steel nails have superior corrosion performance compared to carbon steel or galvanized nails in treated wood; however, their mechanical fastening behavior is unknown. In this paper, the performance of stainless steel nails is examined with respect to two important properties used in wood connection design: withdrawal strength...

Research on graphite reinforced glass matrix composites

NASA Technical Reports Server (NTRS)

Bacon, J. F.; Prewo, K. M.; Thompson, E. R.

1978-01-01

A composite that can be used at temperatures up to 875 K with mechanical properties equal or superior to graphite fiber reinforced epoxy composites is presented. The composite system consist of graphite fiber, uniaxially or biaxially, reinforced borosilicate glass. The mechanical and thermal properties of such a graphite fiber reinforced glass composite are described, and the system is shown to offer promise as a high performance structural material. Specific properties that were measured were: a modified borosilicate glass uniaxially reinforced by Hercules HMS graphite fiber has a three-point flexural strength of 1030 MPa, a four-point flexural strength of 964 MPa, an elastic modulus of 199 GPa and a failure strain of 0.0052. The preparation and properties of similar composites with Hercules HTS, Celanese DG-102, Thornel 300 and Thornel Pitch graphite fibers are also described.

The Motive for Support and the Identification of Responsive Partners

PubMed Central

Turan, Bulent; Horowitz, Leonard M.

2010-01-01

To obtain support from others, a person must first identify responsive partners. One strategy for doing so is to use indicators of responsive partners. We argue that a person with a strong motive for support should rate all indicators highly useful—the “Elevated Motives Effect.” Study 1 confirmed this hypothesis by correlating participants’ total ratings with existing measures of motive-strength. Study 2 applied the Elevated Motives Effect to demonstrate that motive-strength (in interaction with knowledge of indicators) predicts performance on a laboratory task in which participants evaluated a person: Superior knowledge led to superior performance only when motive-strength was high. Study 3, an experience-sampling study, showed that in everyday life, motivated people more often seek support from others when distressed. PMID:20544011

Effects of Elastic Resistance Exercise on Muscle Strength and Functional Performance in Healthy Adults: A Systematic Review and Meta-Analysis.

PubMed

de Oliveira, Poliana Alves; Blasczyk, Juscelino Castro; Souza Junior, Gerson; Lagoa, Karina Ferreira; Soares, Milene; de Oliveira, Ricardo Jacó; Filho, Paulo José Barbosa Gutierres; Carregaro, Rodrigo Luiz; Martins, Wagner Rodrigues

2017-04-01

Elastic Resistance Exercise (ERE) has already demonstrated its effectiveness in older adults and, when combined with the resistance generated by fixed loads, in adults. This review summarizes the effectiveness of ERE performed as isolated method on muscle strength and functional performance in healthy adults. A database search was performed (MEDLine, Cochrane Library, PEDro and Web of Knowledge) to identify controlled clinical trials in English language. The mean difference (MD) with 95% confidence intervals (CIs) and overall effect size were calculated for all comparisons. The PEDro scale was used assess the methodological quality. From the 93 articles identified by the search strategy, 5 met the inclusion criteria, in which 3 presented high quality (PEDro > 6). Meta-analyses demonstrated that the effects of ERE were superior when compared with passive control on functional performance and muscle strength. When compared with active controls, the effect of ERE was inferior on function performance and with similar effect on muscle strength. ERE are effective to improve functional performance and muscle strength when compared with no intervention, in healthy adults. ERE are not superior to other methods of resistance training to improve functional performance and muscle strength in health adults.

High-strength tungsten alloy with improved ductility

NASA Technical Reports Server (NTRS)

Klopp, W. D.; Raffo, P. L.; Rubenstein, L. S.; Witzke, W. R.

1967-01-01

Alloy combines superior strength at elevated temperatures with improved ductility at lower temperatures relative to unalloyed tungsten. Composed of tungsten, rhenium, hafnium, and carbon, the alloy is prepared by consumable electrode vacuum arc-melting and can be fabricated into rod, plate, and sheet.

Static Strength of Adhesively-bonded Woven Fabric Kenaf Composite Plates

NASA Astrophysics Data System (ADS)

Hilton, Ahmad; Lee, Sim Yee; Supar, Khairi

2017-06-01

Natural fibers are potentially used as reinforcing materials and combined with epoxy resin as matrix system to form a superior specific strength (or stiffness) materials known as composite materials. The advantages of implementing natural fibers such as kenaf fibers are renewable, less hazardous during fabrication and handling process; and relatively cheap compared to synthetic fibers. The aim of current work is to conduct a parametric study on static strength of adhesively bonded woven fabric kenaf composite plates. Fabrication of composite panels were conducted using hand lay-up techniques, with variation of stacking sequence, over-lap length, joint types and lay-up types as identified in testing series. Quasi-static testing was carried out using mechanical testing following code of practice. Load-displacement profiles were analyzed to study its structural response prior to ultimate failures. It was found that cross-ply lay-up demonstrates better static strength compared to quasi-isotropic lay-up counterparts due to larger volume of 0° plies exhibited in cross-ply lay-up. Consequently, larger overlap length gives better joining strength, as expected, however this promotes to weight penalty in the joining structure. Most samples showed failures within adhesive region known as cohesive failure modes, however, few sample demonstrated interface failure. Good correlations of parametric study were found and discussed in the respective section.

Investigation into the energy-absorbing properties of multilayered circular thin-walled tube

NASA Astrophysics Data System (ADS)

Qi, Aidong; Liu, Chuanhua; Hu, Gongli; Gu, Hongjun

2002-05-01

With the rise in collision accident and the increase in requirement for resistance of blastproof structures in recent years, people attach much importance to the research and application of energy-absorbing device. In this paper the author calculates the specific strength, the specific hardness and ultimate internal force of a circular thin-walled tube by theoretic calculations, discusses the feasibility of using circular thin-walled tube as an energy-absorbing element, analyzes the energy-absorbing properties and the energy-absorbing mechanism through the energy-absorbing experiments using various materials and forms of arrangement, reaches the conclusion that the load-bearing capacity and energy-absorbing properties of multilayered tubes are superior to that of single tube, and puts forward the concept of 'grading tube'.

The effects of high resistance-few repetitions and low resistance-high repetitions resistance training on climbing performance.

PubMed

Hermans, Espen; Andersen, Vidar; Saeterbakken, Atle Hole

2017-05-01

The aim of the study was to compare the effects of different strength training intensities on climbing performance, climbing-specific tests and a general strength test. Thirty lower grade and intermediate-level climbers participated in a 10-week training programme. The participants were randomized into three groups: high resistance-few repetitions training groups (HR-FR), low resistance-high repetitions training groups (LR-HR) and a control group (CON) which continued climbing/training as usual. Post-testing results demonstrated statistical tendencies for climbing performance improvements in the HR-FR and LR-HR (p = 0.088-0.090, effect size = 0.55-0.73), but no differences were observed between the groups (p = 0.950). For the climbing-specific tests, no differences were observed between the groups (p = 0.507-1.000), but the HR-FR and LR-HR improved their time in both Dead-hang (p = 0.004-0.026) and Bent-arm hang (p < 0.001-0.002). The HR-FR and LR-HR improved their 12RM strength in pull-down (p ≤ 0.001), but not the CON group (p = 0.250). No differences were observed in the CON group in any of the tests (p = 0.190-0.596) with the exception of improvement in Bent-arm Hang (p = 0.018). The training groups reduced their climbing sessions during the intervention compared to the CON group (p = 0.057-0.074). In conclusion, HR-FR and LR-HR training programmes demonstrated an 11% and 12% non-significant improvement in climbing performance despite a 50% reduction in climbing sessions, but improved the results in strength and climbing-specific tests. None of the training intensities was superior compared to the others.

Time perspective and weight management behaviors in newly diagnosed Type 2 diabetes: a mediational analysis.

PubMed

Hall, Peter A; Fong, Geoffrey T; Cheng, Alice Y

2012-12-01

The primary objective of the current study was to examine the extent to which domain-specific time perspective predicts weight management behaviors (dietary behavior and physical activity) among those newly diagnosed with Type 2 diabetes. A secondary objective was to test potential mediators of the hypothesized effect (behavioral intention, self-efficacy and control beliefs). A total of 204 adults newly diagnosed (≤6 months) with Type 2 diabetes participated in the study, which included a baseline assessment of domain-general and domain-specific time perspective, as well as strength of intention to perform two weight-management behaviors (dietary choice and physical activity); both weight-management behaviors were assessed again at 6 month follow-up. Hierarchical multiple regression analyses revealed a prospective association between domain-specific time perspective and uptake of weight management behaviors. Individuals with newly diagnosed T2DM possessing a future-oriented time perspective reported making less frequent fatty food choices and greater increases in physical activity over the 6-month follow-up interval. These effects were selectively mediated by intention strength, and not competing social cognitive variables. For both behaviors, the total effects and meditational models were robust to adjustments for demographics, body composition and disease variables. A future-oriented time perspective is prospectively associated with superior uptake of weight management behaviors among those with newly diagnosed Type 2 diabetes. The facilitating effect of future-oriented thinking appears to occur via enhanced strength of intentions to perform weight management behaviors.

An oxide dispersion strengthened Ni-W-Al alloy with superior high temperature strength

NASA Technical Reports Server (NTRS)

Glasgow, T. K.

1976-01-01

An experimental oxide dispersion strengthened (ODS) alloy, WAZ-D, derived from the WAZ-20 composition was produced by the mechanical alloying process. Cast WAZ-20 is strengthened by both a high refractory metal content, and 70 volume percent of gamma prime. The ODS alloy WAZ-D was responsive to variables of alloy content, of attritor processing, of consolidation by extrusion, and of heat treatment. The best material produced had large highly elongated grains. It exhibited tensile strengths generally superior to a comparable cast alloy. The ODS alloy exhibited high temperature stress rupture life considerably superior to any known cast superalloy. Tensile and rupture ductility were low, as was intermediate temperature rupture life. Very low creep rates were noted and some specimens failed with essentially no third stage creep. Also the benefit derived from the oxide dispersion, far out-weighed that from the elongated microstructure alone.

Development of a comprehensive performance-testing protocol for competitive surfers.

PubMed

Sheppard, Jeremy M; Nimphius, Sophia; Haff, Greg G; Tran, Tai T; Spiteri, Tania; Brooks, Hedda; Slater, Gary; Newton, Robert U

2013-09-01

Appropriate and valid testing protocols for evaluating the physical performances of surfing athletes are not well refined. The purpose of this project was to develop, refine, and evaluate a testing protocol for use with elite surfers, including measures of anthropometry, strength and power, and endurance. After pilot testing and consultation with athletes, coaches, and sport scientists, a specific suite of tests was developed. Forty-four competitive junior surfers (16.2 ± 1.3 y, 166.3 ± 7.3 cm, 57.9 ± 8.5 kg) participated in this study involving a within-day repeated-measures analysis, using an elite junior group of 22 international competitors (EJG), to establish reliability of the measures. To reflect validity of the testing measures, a comparison of performance results was then undertaken between the EJG and an age-matched competitive junior group of 22 nationally competitive surfers (CJG). Percent typical error of measurement (%TEM) for primary variables gained from the assessments ranged from 1.1% to 3.0%, with intraclass correlation coefficients ranging from .96 to .99. One-way analysis of variance revealed that the EJG had lower skinfolds (P = .005, d = 0.9) than the CJG, despite no difference in stature (P = .102) or body mass (P = .827). The EJG were faster in 15-m sprint-paddle velocity (P < .001, d = 1.3) and had higher lower-body isometric peak force (P = .04, d = 0.7) and superior endurance-paddling velocity (P = .008, d = 0.9). The relatively low %TEM of these tests in this population allows for high sensitivity to detect change. The results of this study suggest that competitively superior junior surfers are leaner and possess superior strength, paddling power, and paddling endurance.

Axial collapse characteristics of CFRP composites with stacking conditions under the hygrothermal

NASA Astrophysics Data System (ADS)

Yang, Yongjun; Choi, Juho; Hwang, Woochae; Son, Jaekyung; Kook, Hyun; Im, Kwanghee; Sim, Jaeki; Yang, Inyoung

2012-04-01

CFRP composite material has superior specific strength and rigidity compared to metallic material, and is widely adopted in the various fields. Exceptional corrosion resistance enables the acceptance in maritime structural members such as ship and oildrilling machineries. However, CFRP composite material has the weakness in hygrothermal environment and crash environment. Especially, moisture ingress into composite material under hygrothermal environment can change molecule arrangement and chemical properties. In addition, interface characteristics and component material properties can be degraded. An experimental investigation was carried out to study the crash evaluations of CFRP composites to dynamic crushing by impact loading. We have made a collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed specimen. As a result, the effect of moisture absorption and impact loads of approximately 30~50% reduction in strength are shown.

Axial collapse characteristics of CFRP composites with stacking conditions under the hygrothermal

NASA Astrophysics Data System (ADS)

Yang, Yongjun; Choi, Juho; Hwang, Woochae; Son, Jaekyung; Kook, Hyun; Im, Kwanghee; Sim, Jaeki; Yang, Inyoung

2011-11-01

CFRP composite material has superior specific strength and rigidity compared to metallic material, and is widely adopted in the various fields. Exceptional corrosion resistance enables the acceptance in maritime structural members such as ship and oildrilling machineries. However, CFRP composite material has the weakness in hygrothermal environment and crash environment. Especially, moisture ingress into composite material under hygrothermal environment can change molecule arrangement and chemical properties. In addition, interface characteristics and component material properties can be degraded. An experimental investigation was carried out to study the crash evaluations of CFRP composites to dynamic crushing by impact loading. We have made a collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed specimen. As a result, the effect of moisture absorption and impact loads of approximately 30~50% reduction in strength are shown.

Preparation and mechanical properties of rubber composites reinforced with carbon nanohorns.

PubMed

Isshiki, Tetsuya; Hashimoto, Mikiko; Morii, Masato; Ota, Yuki; Kaneda, Kazuo; Takahashi, Hidetaka; Yudasaka, Masako; Iijima, Sumio; Okino, Fujio

2010-06-01

Nitrile butadiene rubber (NBR) composites with single-wall carbon nanohorns (SWNHs, or simply NHs), hole-opened NHs (h-NHs), and carbon black (CB), the most commonly used nanocarbon rubber filler, were prepared, and their mechanical properties were compared. The NBR composites with h-NHs (NBR/h-NH) showed higher tensile strength than those with NHs (NBR/NH), and the tensile strength of NBR/h-NH or NBR/NH was much greater than those of the NBR composites with CB (NBR/CB). At 5 parts per hundred of rubber (phr), the tensile stresses at break of NBR/h-NH was about 1.8 times larger than those of NBR/CB, and the strain at the break, 1.2 times larger. Similarly, at 20 phr, both the tensile strength and strain at the break of NBR/h-NH were 1.4 times larger than those of NBR/CB. NBR/NH showed the highest hardness while having the smallest specific gravity. The present results indicate that NHs and h-NHs have much superior reinforcement effects to CB for NBR rubber matrix.

Effects on Subtalar Joint Stress Distribution After Cannulated Screw Insertion at Different Positions and Directions.

PubMed

Yuan, Cheng-song; Chen, Wan; Chen, Chen; Yang, Guang-hua; Hu, Chao; Tang, Kang-lai

2015-01-01

We investigated the effects on subtalar joint stress distribution after cannulated screw insertion at different positions and directions. After establishing a 3-dimensional geometric model of a normal subtalar joint, we analyzed the most ideal cannulated screw insertion position and approach for subtalar joint stress distribution and compared the differences in loading stress, antirotary strength, and anti-inversion/eversion strength among lateral-medial antiparallel screw insertion, traditional screw insertion, and ideal cannulated screw insertion. The screw insertion approach allowing the most uniform subtalar joint loading stress distribution was lateral screw insertion near the border of the talar neck plus medial screw insertion close to the ankle joint. For stress distribution uniformity, antirotary strength, and anti-inversion/eversion strength, lateral-medial antiparallel screw insertion was superior to traditional double-screw insertion. Compared with ideal cannulated screw insertion, slightly poorer stress distribution uniformity and better antirotary strength and anti-inversion/eversion strength were observed for lateral-medial antiparallel screw insertion. Traditional single-screw insertion was better than double-screw insertion for stress distribution uniformity but worse for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion was slightly worse for stress distribution uniformity than was ideal cannulated screw insertion but superior to traditional screw insertion. It was better than both ideal cannulated screw insertion and traditional screw insertion for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion is an approach with simple localization, convenient operation, and good safety. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barham, R.E.; Butz, G.W.; Ansell, J.S.

Wound strength in the rectus muscle of rabbits is greater at any measured time interval when sutured with polyglycolic acid than when sutured with chromic catgut. This is true for both irradiated and nonirradiated tissues. No significant advantage is seen for either suture in nonirradiated bladder, although the trend favors polyglycolic acid. In irradiated bladders, a significant advantage is seen for polyglycolic acid at 15 days. In measuring repaired ureteral orifice size, only chromic catgut suture in nonirradiated rabbits caused marked edema and ureteral obstruction. Postoperative ureteral dilation with both materials resolved over a 90 day period. In the irradiatedmore » ureter, however, resolution of this obstruction appears to occur earlier and more dependably when polyglycolic acid suture has been used. Polyglycolic acid showed a trend for superior strength in urothelial wounds tested. The healing of bladder epithelium is usually completed in ten to 14 days. The entire bladder wound gains strength rapidly until day 21 and gains little strength thereafter. A suture material that does not increase the inflammatory response but lasts long enough for complete bladder healing is advisable. Using the criterion of wound breaking strength in our experimental work, polyglycolic acid was shown to be superior to chromic catgut suture material.« less

Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men.

PubMed

Schoenfeld, Brad J; Ratamess, Nicholas A; Peterson, Mark D; Contreras, Bret; Sonmez, G T; Alvar, Brent A

2014-10-01

Regimented resistance training has been shown to promote marked increases in skeletal muscle mass. Although muscle hypertrophy can be attained through a wide range of resistance training programs, the principle of specificity, which states that adaptations are specific to the nature of the applied stimulus, dictates that some programs will promote greater hypertrophy than others. Research is lacking, however, as to the best combination of variables required to maximize hypertophic gains. The purpose of this study was to investigate muscular adaptations to a volume-equated bodybuilding-type training program vs. a powerlifting-type routine in well-trained subjects. Seventeen young men were randomly assigned to either a hypertrophy-type resistance training group that performed 3 sets of 10 repetition maximum (RM) with 90 seconds rest or a strength-type resistance training (ST) group that performed 7 sets of 3RM with a 3-minute rest interval. After 8 weeks, no significant differences were noted in muscle thickness of the biceps brachii. Significant strength differences were found in favor of ST for the 1RM bench press, and a trend was found for greater increases in the 1RM squat. In conclusion, this study showed that both bodybuilding- and powerlifting-type training promote similar increases in muscular size, but powerlifting-type training is superior for enhancing maximal strength.

Bayesian characterization of uncertainty in species interaction strengths.

PubMed

Wolf, Christopher; Novak, Mark; Gitelman, Alix I

2017-06-01

Considerable effort has been devoted to the estimation of species interaction strengths. This effort has focused primarily on statistical significance testing and obtaining point estimates of parameters that contribute to interaction strength magnitudes, leaving the characterization of uncertainty associated with those estimates unconsidered. We consider a means of characterizing the uncertainty of a generalist predator's interaction strengths by formulating an observational method for estimating a predator's prey-specific per capita attack rates as a Bayesian statistical model. This formulation permits the explicit incorporation of multiple sources of uncertainty. A key insight is the informative nature of several so-called non-informative priors that have been used in modeling the sparse data typical of predator feeding surveys. We introduce to ecology a new neutral prior and provide evidence for its superior performance. We use a case study to consider the attack rates in a New Zealand intertidal whelk predator, and we illustrate not only that Bayesian point estimates can be made to correspond with those obtained by frequentist approaches, but also that estimation uncertainty as described by 95% intervals is more useful and biologically realistic using the Bayesian method. In particular, unlike in bootstrap confidence intervals, the lower bounds of the Bayesian posterior intervals for attack rates do not include zero when a predator-prey interaction is in fact observed. We conclude that the Bayesian framework provides a straightforward, probabilistic characterization of interaction strength uncertainty, enabling future considerations of both the deterministic and stochastic drivers of interaction strength and their impact on food webs.

Nial and Nial-Based Composites Directionally Solidified by a Containerless Zone Process. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Joslin, Steven M.

1995-01-01

A containerless electromagnetically levitated zone (CELZ) process has been used to directionally solidify NiAl and NiAl-based composites. The CELZ processing results in single crystal NiAl (HP-NiAl) having higher purity than commercially pure NiAl grown by a modified Bridgman process (CP-NiAl). The mechanical properties, specifically fracture toughness and creep strength, of the HP-NiAl are superior to binary CP-NiAl and are used as a base-line for comparison with the composite materials subsequently studied. Two-phase composite materials (NiAl-based eutectic alloys) show improvement in room temperature fracture toughness and 1200 to 1400 K creep strength over that of binary HP-NiAl. Metallic phase reinforcements produce the greatest improvement in fracture toughness, while intermetallic reinforcement produces the largest improvement in high temperature strength. Three-phase eutectic alloys and composite materials were identified and directionally solidified with the intent to combine the improvements observed in the two-phase alloys into one alloy. The room temperature fracture toughness and high temperature strength (in air) serve as the basis for comparison between all of the alloys. Finally, the composite materials are discussed in terms of dominant fracture mechanism observed by fractography.

Effect of screw position on load transfer in lumbar pedicle screws: A non-idealized finite element analysis

PubMed Central

Newcomb, Anna G. U. S.; Baek, Seungwon; Kelly, Brian P.; Crawford, Neil R.

2016-01-01

Angled screw insertion has been advocated to enhance fixation strength during posterior spine fixation. Stresses on a pedicle screw and surrounding vertebral bone with different screw angles were studied by finite element analysis during simulated multidirectional loading. Correlations between screw-specific vertebral geometric parameters and stresses were studied. Angulations in both the sagittal and axial planes affected stresses on the cortical and cancellous bones and the screw. Pedicle screws pointing laterally (vs. straight or medially) in the axial plane during superior screw angulation may be advantageous in terms of reducing the risk of both screw loosening and screw breakage. PMID:27454197

Drying time of tray adhesive for adequate tensile bond strength between polyvinylsiloxane impression and tray resin material.

PubMed

Yi, Myong-Hee; Shim, Joon-Sung; Lee, Keun-Woo; Chung, Moon-Kyu

2009-07-01

Use of custom tray and tray adhesive is clinically recommended for elastomeric impression material. However there is not clear mention of drying time of tray adhesive in achieving appropriate bonding strength of tray material and impression material. This study is to investigate an appropriate drying time of tray adhesives by evaluating tensile bonding strength between two types of polyvinylsiloxane impression materials and resin tray, according to various drying time intervals of tray adhesives, and with different manufacturing company combination of impression material and tray adhesive. Adhesives used in this study were Silfix (Dentsply Caulk, Milford, Del, USA) and VPS Tray Adhesive (3M ESPE, Seefeld, Germany) and impression materials were Aquasil Ultra (monophase regular set, Dentsply Caulk, Milford, Del, USA) and Imprint II Garant (regular body, 3M ESPE, Seefeld, Germany). They were used combinations from the same manufacture and exchanged combinations of the two. The drying time was designed to air dry, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes. Total 240 of test specimens were prepared by auto-polymerizing tray material (Instant Tray Mix, Lang, Wheeling, Il, USA) with 10 specimens in each group. The specimens were placed in the Universal Testing machine (Instron, model 3366, Instron Corp, University avenue, Nowood, MA, USA) to perform the tensile test (cross head speed 5 mm/min). The statistically efficient drying time was evaluated through ANOVA and Scheffe test. All the tests were performed at 95% confidence level. The results revealed that at least 10 minutes is needed for Silfix-Aquasil, and 15 minutes for VPS Tray Adhesive-Imprint II, to attain an appropriate tensile bonding strength. VPS Tray Adhesive-Imprint II had a superior tensile bonding strength when compared to Silfix-Aquasil over 15 minutes. Silfix-Aquasil had a superior bonding strength to VPS Tray Adhesive-Aquasil, and VPS Tray Adhesive-Imprint II had a superior tensile bonding strength to Silfix-Imprint II at all drying periods. Significant increase in tensile bonding strength with Silfix-Aquasil and VPS Tray adhesive-Imprint II combination until 10 and 15 minutes respectively. Tray adhesive-impression material combination from the same company presented higher tensile bonding strength at all drying time intervals than when using tray adhesive-impression material of different manufactures.

The impact of top-down spatial attention on laterality and hemispheric asymmetry in the human parietal cortex

PubMed Central

Jeong, Su Keun; Xu, Yaoda

2016-01-01

The human parietal cortex exhibits a preference to contralaterally presented visual stimuli (i.e., laterality) as well as an asymmetry between the two hemispheres with the left parietal cortex showing greater laterality than the right. Using visual short-term memory and perceptual tasks and varying target location predictability, this study examined whether hemispheric laterality and asymmetry are fixed characteristics of the human parietal cortex or whether they are dynamic and modulated by the deployment of top-down attention to the target present hemifield. Two parietal regions were examined here that have previously been shown to be involved in visual object individuation and identification and are located in the inferior and superior intraparietal sulcus (IPS), respectively. Across three experiments, significant laterality was found in both parietal regions regardless of attentional modulation with laterality being greater in the inferior than superior IPS, consistent with their roles in object individuation and identification, respectively. Although the deployment of top-down attention had no effect on the superior IPS, it significantly increased laterality in the inferior IPS. The deployment of top-down spatial attention can thus amplify the strength of laterality in the inferior IPS. Hemispheric asymmetry, on the other hand, was absent in both brain regions and only emerged in the inferior but not the superior IPS with the deployment of top-down attention. Interestingly, the strength of hemispheric asymmetry significantly correlated with the strength of laterality in the inferior IPS. Hemispheric asymmetry thus seems to only emerge when there is a sufficient amount of laterality present in a brain region. PMID:27494544

The impact of top-down spatial attention on laterality and hemispheric asymmetry in the human parietal cortex.

PubMed

Jeong, Su Keun; Xu, Yaoda

2016-08-01

The human parietal cortex exhibits a preference to contralaterally presented visual stimuli (i.e., laterality) as well as an asymmetry between the two hemispheres with the left parietal cortex showing greater laterality than the right. Using visual short-term memory and perceptual tasks and varying target location predictability, this study examined whether hemispheric laterality and asymmetry are fixed characteristics of the human parietal cortex or whether they are dynamic and modulated by the deployment of top-down attention to the target present hemifield. Two parietal regions were examined here that have previously been shown to be involved in visual object individuation and identification and are located in the inferior and superior intraparietal sulcus (IPS), respectively. Across three experiments, significant laterality was found in both parietal regions regardless of attentional modulation with laterality being greater in the inferior than superior IPS, consistent with their roles in object individuation and identification, respectively. Although the deployment of top-down attention had no effect on the superior IPS, it significantly increased laterality in the inferior IPS. The deployment of top-down spatial attention can thus amplify the strength of laterality in the inferior IPS. Hemispheric asymmetry, on the other hand, was absent in both brain regions and only emerged in the inferior but not the superior IPS with the deployment of top-down attention. Interestingly, the strength of hemispheric asymmetry significantly correlated with the strength of laterality in the inferior IPS. Hemispheric asymmetry thus seems to only emerge when there is a sufficient amount of laterality present in a brain region.

Properties of styrene-maleic anhydride copolymers containing wood-based fillers

Treesearch

John Simonsen; Rodney Jacobson; Roger Rowell

1998-01-01

Recycled newsprint (ONP) and dry process aspen fiber were combined with styrene maleic anhydride (SMA) copolymers containing either 7 or 14 percent maleic anhydride. The fiber-filled SMA composites were equivalent or superior to unfilled SMA in strength, stiffness, and notched Izod impact strength. ONP performed surprisingly well as a filler. Unnotched Izod impact...

Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

DOEpatents

Liu, Chain T.

2000-01-01

Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.

Grain-Refined AZ92 Alloy with Superior Strength and Ductility

NASA Astrophysics Data System (ADS)

Lee, Jong Un; Kim, Sang-Hoon; Jo, Wan-Kuen; Hong, Won-Hwa; Kim, Woong; Bae, Jun Ho; Park, Sung Hyuk

2018-03-01

Grain-refined AZ92 (GR-AZ92) alloy with superior tensile properties is developed by adding 1 wt% Zn and a very small amount of SiC (0.17 wt%) to commercial AZ91 alloy for enhancing the solid-solution strengthening effect and refining the crystal grains, respectively. The homogenized GR-AZ92 alloy with an average grain size of 91 μm exhibits a tensile yield strength (TYS) of 125 MPa, ultimate tensile strength (UTS) of 281 MPa, and elongation of 12.1%, which are significantly higher than those of AZ91 alloy with a grain size of 420 μm (TYS of 94 MPa, UTS of 192 MPa, and elongation of 7.0%). The peak-aging time of GR-AZ92 alloy (8 h) is significantly shorter than that of AZ91 alloy (32 h) owing to a larger amount of grain boundaries in the former, which serve as nucleation sites of Mg17Al12 precipitates. A short-aging treatment for less than 1 h of the GR-AZ92 alloy causes an effective improvement in its strength without a significant reduction in its ductility. The 30-min-aged GR-AZ92 alloy has an excellent combination of strength and ductility, with a TYS of 142 MPa, UTS of 304 MPa, and elongation of 8.0%.

Individual differences in chess expertise: a psychometric investigation.

PubMed

Grabner, Roland H; Stern, Elsbeth; Neubauer, Aljoscha C

2007-03-01

Starting from controversies over the role of general individual characteristics (especially intelligence) for the attainment of expert performance levels, a comprehensive psychometric investigation of individual differences in chess expertise is presented. A sample of 90 adult tournament chess players of varying playing strengths (1311-2387 ELO) was screened with tests on intelligence and personality variables; in addition, experience in chess play, tournament participation, and practice activities were assessed. Correlation and regression analyses revealed a clear-cut moderate relationship between general (and in particular numerical) intelligence and the participants' playing strengths, suggesting that expert chess play does not stand in isolation from superior mental abilities. The strongest predictor of the attained expertise level, however, was the participants' chess experience which highlights the relevance of long-term engagement for the development of expertise. Among all analysed personality dimensions, only domain-specific performance motivation and emotion expression control incrementally contributed to the prediction of playing strength. In total, measures of chess experience, current tournament activity, intelligence, and personality accounted for about 55% of variance in chess expertise. The present results suggest that individual differences in chess expertise are multifaceted and cannot be reduced to differences in domain experience.

A new model of selection in women's handball.

PubMed

Srhoj, Vatromir; Rogulj, Nenad; Zagorac, Nebojsa; Katić, Ratko

2006-09-01

The aim of the study was to assess the basic motor abilities that determine top performance in women's handball, and to identify test panel for primary selection at handball school. The study included 155 female attendants of the Split Handball School, mean age 12.5 years. Differences in the basic motor abilities between the subjects that developed into elite handball players after 7-year training process and those that abandoned handball for being unable to meet the competition criteria were evaluated by use of discriminative analysis. The former were found to have also been superior initially in all variables analyzed, and in arm coordination, overall body coordination, throw and jump explosive strength, arm movement frequency and repetitive trunk strength in particular. Motor superiority based on the abilities of coordination, explosive strength and speed determines performance in women's handball, qualifying these abilities as reliable selection criteria. Based on this study results, a new model of selection in women's handball, with fine arm coordination as the major limiting factor of performance, has been proposed.

Low molecular weight glutenin subunit gene Glu-B3h confers superior dough strength and breadmaking quality in wheat (Triticum aestivum L.)

PubMed Central

Wang, Yaping; Zhen, Shoumin; Luo, Nana; Han, Caixia; Lu, Xiaobing; Li, Xiaohui; Xia, Xianchun; He, Zhonghu; Yan, Yueming

2016-01-01

Low molecular weight glutenin subunit is one of the important quality elements in wheat (Triticum aestivum L.). Although considerable allelic variation has been identified, the functional properties of individual alleles at Glu-3 loci are less studied. In this work, we performed the first comprehensive study on the molecular characteristics and functional properties of the Glu-B3h gene using the wheat cultivar CB037B and its Glu-B3 deletion line CB037C. The results showed that the Glu-B3h deletion had no significant effects on plant morphological or yield traits, but resulted in a clear reduction in protein body number and size and main quality parameters, including inferior mixing property, dough strength, loaf volume, and score. Molecular characterization showed that the Glu-B3h gene consists of 1179 bp, and its encoded B-subunit has a longer repetitive domain and an increased number of α-helices, as well as higher expression, which could contribute to superior flour quality. The SNP-based allele-specific PCR markers designed for the Glu-B3h gene were developed and validated with bread wheat holding various alleles at Glu-B3 locus, which could effectively distinguish the Glu-B3h gene from others at the Glu-B3 locus, and have potential applications for wheat quality improvement through marker-assisted selection. PMID:27273251

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xiaoming; Ke, Changhong, E-mail: xqwang@uga.edu, E-mail: cke@binghamton.edu; Zhang, Liuyang

We investigate the mechanical strength of boron nitride nanotube (BNNT) polymer interfaces by using in situ electron microscopy nanomechanical single-tube pull-out techniques. The nanomechanical measurements show that the shear strengths of BNNT-epoxy and BNNT-poly(methyl methacrylate) interfaces reach 323 and 219 MPa, respectively. Molecular dynamics simulations reveal that the superior load transfer capacity of BNNT-polymer interfaces is ascribed to both the strong van der Waals interactions and Coulomb interactions on BNNT-polymer interfaces. The findings of the extraordinary mechanical strength of BNNT-polymer interfaces suggest that BNNTs are excellent reinforcing nanofiller materials for light-weight and high-strength polymer nanocomposites.

Production of Bulk and Fiber Glass in Space

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

The production of bulk glass and fiber glass in space and on the moon and Mars should lead to superior products. Specifically glass plates for windows and optical elements could be produced with theoretical strengths by production in vacuum. Water vapor is known to decrease glass strength by up to two orders of magnitude from theoretical. A low gravity glass plate apparatus prototype has been designed and built which uses centrifugal force to shape the glass and solar energy to melt the glass. Glass fiber could be produced on the moon or Mars from in-situ materials using standard technologies. This material could then be used as reinforcement in composite materials in construction of bases. Also, it has been shown that processing in reduced gravity suppresses crystallization in certain heavy metal fluoride glasses. It is proposed to reprocess optical fiber preforms on the space station and then pull these into optical fiber. It is estimated that the attenuation coefficient should be reduced by two orders of magnitude.

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants

PubMed Central

Dimitriou, G; Greenough, A; Pink, L; McGhee, A; Hickey, A; Rafferty, G

2002-01-01

Objective: To determine if differences in respiratory muscle strength could explain any posture related effects on oxygenation in convalescent neonates. Methods: Infants were examined in three postures: supine, supine with head up tilt of 45°, and prone. A subsequent study was performed to determine the influence of head position in the supine posture. In each posture/head position, oxygen saturation (SaO2) was determined and respiratory muscle strength assessed by measurement of the maximum inspiratory pressure (PIMAX). Patients: Twenty infants, median gestational age 34.5 weeks (range 25–43), and 10 infants, median gestational age 33 weeks (range 30–36), were entered into the first and second study respectively. Results: Oxygenation was higher in the prone and supine with 45° head up tilt postures than in the supine posture (p<0.001), whereas PIMAX was higher in the supine and supine with head up tilt of 45° postures than in the prone posture (p<0.001). Head position did not influence the effect of posture on PIMAX or oxygenation. Conclusion: Superior oxygenation in the prone posture in convalescent infants was not explained by greater respiratory muscle strength, as this was superior in the supine posture. PMID:11978742

Bioinspired Hierarchical Alumina-Graphene Oxide-Poly(vinyl alcohol) Artificial Nacre with Optimized Strength and Toughness.

PubMed

Wang, Jinrong; Qiao, Jinliang; Wang, Jianfeng; Zhu, Ying; Jiang, Lei

2015-05-06

Due to hierarchical organization of micro- and nanostructures, natural nacre exhibits extraordinary strength and toughness, and thus provides a superior model for the design and fabrication of high-performance artificial composite materials. Although great progress has been made in constructing layered composites by alternately stacking hard inorganic platelets and soft polymers, the real issue is that the excellent strength of these composites was obtained at the sacrifice of toughness. In this work, inspired by the layered aragonite microplatelets/chitin nanofibers-protein structure of natural nacre, alumina microplatelets-graphene oxide nanosheets-poly(vinyl alcohol) (Al2O3/GO-PVA) artificial nacre is successfully constructed through layer-by-layer bottom-up assembly, in which Al2O3 and GO-PVA act as "bricks" and "mortar", respectively. The artificial nacre has hierarchical "brick-and-mortar" structure and exhibits excellent strength (143 ± 13 MPa) and toughness (9.2 ± 2.7 MJ/m(3)), which are superior to those of natural nacre (80-135 MPa, 1.8 MJ/m(3)). It was demonstrated that the multiscale hierarchical structure of ultrathin GO nanosheets and submicrometer-thick Al2O3 platelets can deal with the conflict between strength and toughness, thus leading to the excellent mechanical properties that cannot be obtained using only one size of platelet. We strongly believe that the work presented here provides a creative strategy for designing and developing new composites with excellent strength and toughness.

Comparing the use of sewage sludge ash and glass powder in cement mortars.

PubMed

Chen, Zhen; Poon, Chi Sun

2017-06-01

This study explored the suitability of using sewage sludge ash (SSA) and mixed-colored glass powder (MGP) as construction materials in cement mortars. Positive findings from this study may help promote the recycling of waste SSA and MGP in construction works. The results indicated that the SSA decreased while MGP improved the mortar workability. The SSA exhibited very low pozzolanic activity, but the cement mortar prepared with 20% SSA yielded strength values slightly superior to those of the glass mortars due to its water absorption ability. MGP can serve as a pozzolan and when 20% of cement was replaced by MGP, apparent compressive strength gains were found at later curing ages. The SSA could be used to mitigate ASR expansion while the MGP was superior in resisting drying shrinkage.

Biomechanical Comparison of Superior Versus Anterior Plate Position for Fixation of Distal Clavicular Fractures: A New Model.

PubMed

Wilkerson, James; Paryavi, Ebrahim; Kim, Hyunchul; Murthi, Anand; Pensy, Raymond A

2017-01-01

Although most clavicular fractures are amenable to nonoperative management, metadiaphyseal fractures are considerably more complex, with rates of suboptimal healing as high as 75% when treated nonoperatively. The poor results are ascribed to the deforming forces on the distal clavicle from the surrounding muscles and the weight of the arm. It recently has been noted that some operative fixations of these fractures are also failing when a standard superiorly placed plate is used. We hypothesized that anterior plating, when compared with superior plating, improves the strength and durability of the construct by redirecting the axis of the major deforming force across rather than in line with the screws of the construct. Six pairs of fresh-frozen human cadaveric clavicles with the scapula attached by the coracoclavicular ligaments were osteotomized just medial to the ligaments and plated with a standard 3.5-mm limited-contact dynamic compression plate. Specimens were potted and mounted on a materials testing system machine, preserving the anatomic relationship of the clavicle and scapula. They were then loaded through the coracoclavicular ligaments to mimic the weight of the arm pulling inferiorly. Each specimen was loaded with 375 N at 1 Hz for 2000 cycles. Sequential loading was then applied at 25-N intervals until failure. Statistical analysis was performed using a Wilcoxon signed-rank test. The superiorly plated specimens failed after fewer cycles and with lower force than the anteriorly plated specimens. The median number of cycles to failure was 2082 for anterior plated specimens and 50 for superiorly plated (P = 0.028). The median load to failure was 587.5 N in the anterior group and 375 N in the superior group (P = 0.035). The median stiffness was 46.13 N/mm for anterior and 40.45 N/mm for superior (P = 0.375) plates. Anteriorly plated distal third clavicular fractures have superior strength and durability compared with fractures plated superiorly when using a physician-contoured, 3.5-mm, limited-contact, dynamic compression plate in this cadaver model.

Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

NASA Technical Reports Server (NTRS)

Yun, Hee Mann; Titran, Robert H.

1993-01-01

The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

A mathematical model of hiking positions in a sailing dinghy.

PubMed

Putnam, C A

1979-01-01

A mathematical model of the human body designed to calculate the resultant muscle torques required at the hip and knee joints for specific hiking techniques is presented. Data for the model were obtained from ten male subjects who adopted three basic positions: Position 1 with the knees located at the inside edge of the sidedeck, Position 2 with the knees at the middle of the sidedeck, and Position 3 with the knees at the outside edge of the sidedeck. Each resultant muscle torque was expressed as a percentage of each subject's maximum voluntary hip flexion or knee extension torque. It was found that where Positions 1 and 2 were equally effective in keeping the boat upright, Position 2 was superior to Position 1 in regard to the per cent of maximum muscle torque required. The superiority of Position 2 over Position 3 depended on the individual's relative muscle strength at the hip and knee joints. The stronger the hip flexors with respect to the knee estensors, the more desirable was Position 2 and vice versa.

Structural and physico-mechanical characterization of bio-cellulose produced by a cell-free system.

PubMed

Ullah, Muhammad Wajid; Ul-Islam, Mazhar; Khan, Shaukat; Kim, Yeji; Park, Joong Kon

2016-01-20

This study was aimed to characterize the structural and physico-mechanical properties of bio-cellulose produced through cell-free system. Fourier transform-infrared spectrum illustrated exact matching of structural peaks with microbial cellulose, used as reference. Field-emission scanning electron microscopy revealed that fibrils of bio-cellulose were thicker and more compact than microbial cellulose. The specific positions of peaks in the X-ray diffraction and nuclear magnetic resonance spectra indicated that bio-cellulose possessed cellulose II polymorphic structure. Bio-cellulose presented superior physico-mechanical properties than microbial cellulose. The water holding capacity of bio-cellulose and microbial cellulose were found to be 188.6 ± 5.41 and 167.4 ± 4.32 times their dry-weights, respectively. Tensile strengths and degradation temperature of bio-cellulose were 17.63 MPa and 352 °C, respectively compared to 14.71 MPa and 327 °C of microbial cellulose. Overall, the results indicated successful synthesis and superior properties of bio-cellulose that advocate its effectiveness for various applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

A comparison of mechanical properties of some foams and honeycombs

NASA Technical Reports Server (NTRS)

Bhat, Balakrishna T.; Wang, T. G.

1990-01-01

A comparative study is conducted of the mechanical properties of foam-core and honeycomb-core sandwich panels, using a normalizing procedure based on common properties of cellular solids and related properties of dense solids. Seven different honeycombs and closed-foam cells are discussed; of these, three are commercial Al alloy honeycombs, one is an Al-alloy foam, and two are polymeric foams. It is concluded that ideal, closed-cell foams may furnish compressive strengths which while isotropic can be fully comparable to the compressive strengths of honeycombs in the thickness direction. The shear strength of ideal closed-cell foams may be superior to the shear strength of honeycombs.

Evaluation of spiral acquisition variants for functional imaging of human superior colliculus at 3T field strength.

PubMed

Singh, Vimal; Pfeuffer, Josef; Zhao, Tiejun; Ress, David

2018-04-01

High-resolution functional magnetic resonance imaging of human subcortical brain structures is challenging because of their deep location in the cranium, and their comparatively weak blood oxygen level dependent responses to strong stimuli. Magnetic resonance imaging data for subcortical brain regions exhibit both low signal-to-noise ratio and low functional contrast-to-noise ratio. To overcome these challenges, this work evaluates the use of dual-echo spiral variants that combine outward and inward trajectories. Specifically, in-in, in-out, and out-out combinations are evaluated. For completeness, single-echo spiral-in and parallel-receive-accelerated echo-planar-imaging sequences are also evaluated. Sequence evaluation was based on comparison of functional contrast-to-noise ratio within retinotopically predefined regions of interest. Superior colliculus was chosen as sample subcortical brain region because it exhibits a strong visual response. All sequences were compared relative to a single-echo spiral-out trajectory to establish a within-session reference. In superior colliculus, the dual-echo out-out outperformed the reference trajectory by 55% in contrast-to-noise ratio, while all other trajectories had performance similar to the reference. The sequences were also compared in early visual cortex. Here, both dual-echo spiral out-out and in-out outperformed the reference by ∼25%. Dual-echo spiral variants offer improved contrast-to-noise ratio performance for high-resolution imaging for both superior colliculus and cortex. Magn Reson Med 79:1931-1940, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Lightweight orthotic appliances

NASA Technical Reports Server (NTRS)

Baucom, R. M.; St. Clair, T. L.

1976-01-01

Graphite-filament reinforced polymer materials are used in applications requiring high tensile strength and modulus. Superior properties of graphite composite materials permit fabrication of supports that are considerably lighter, thinner, and stiffer than conventional components.

Magnetic resonance imaging evaluation of adjacent segments after cervical disc arthroplasty: magnet strength and its effect on image quality. Clinical article.

PubMed

Antosh, Ivan J; DeVine, John G; Carpenter, Clyde T; Woebkenberg, Brian J; Yoest, Stephen M

2010-12-01

Disc arthroplasty is an alternative to fusion following anterior discectomy when treating either cervical radiculopathy or myelopathy. Its theoretical benefits include preservation of the motion segment and the potential prevention of adjacent-segment degeneration. There is a paucity of data regarding the ability to use MR imaging to evaluate the adjacent segments. The purpose of this study was for the authors to introduce open MR imaging as an alternative method in imaging adjacent segments following cervical disc arthroplasty using a Co-Cr implant and to report their preliminary results using this technique. Postoperative cervical MR images were obtained in the first 16 patients in whom the porous coated motion (PCM-V) cervical arthroplasty system was used to treat a single level between C-3 and C-7. Imaging was performed in all 16 patients with a closed 1.5-T unit, and in the final 6 patients it was also performed with an open 0.2-T unit. All images were evaluated by an independent radiologist observer for the ability to visualize the superior endplate, disc space, and inferior endplate at the superior and inferior adjacent levels. Utilizing the 1.5-T magnet to assess the superior adjacent level, the superior endplate, disc space, and inferior endplate could each be visualized less than 50% of the time on sagittal T1- and sagittal and axial T2-weighted images. Similarly, the inferior adjacent level structures were adequately visualized less than 50% of the time, with the exception of slightly improved visualization of the inferior endplate on T1-weighted images (56%). Axial images allowed worse visualization than sagittal images at both the superior and inferior adjacent levels. Utilizing the 0.2-T magnet to assess the superior and inferior adjacent levels, the superior endplate, disc space, and inferior endplate were adequately visualized in 100% of images. Based on the results of this case series, it appears that the strength of the magnet affects the artifact from the Co-Cr endplates. The open 0.2-T MR imaging unit reduces artifact at adjacent levels after cervical disc arthroplasty without a significant reduction in the image quality. Magnetic resonance imaging can be used to evaluate the adjacent segments after disc arthroplasty if magnet strength is addressed, providing another means to assess the long-term efficacy of this novel treatment.

Seismic Anisotropy Beneath Eastern North America: Results from Multi-Event Inversion

NASA Astrophysics Data System (ADS)

Li, Y.; Levin, V. L.; Chen, X.

2017-12-01

Seismic anisotropy observed from the split core-refracted shear phases reflects upper mantle deformation. To characterize anisotropic signatures beneath eastern North America, we collected observations along a 1300 km long array from James Bay to the Fundy Basin. The averaged splitting parameters of individual sites show uniform fast polarization orientation of 80° and delay times linearly decreasing from 1.0 s in the Appalachians to 0.5 s in the Superior Province. We also see directional variation of fast polarizations at most sites, which is a likely effect of vertical changes in anisotropic properties. For sites with 10 or more observations, we used a multi-event inversion technique to solve for the underlying anisotropic structure. The technique considers the NULL observations from single-event analysis that are excluded from the averaged splitting parameters. For models with a single 100 km thick anisotropic layer with a horizontal fast axis, we find up to 6% of anisotropy in the Appalachian Orogen, equivalent to a splitting delay time of 1.5 s. Anisotropy strength reduces to 1.8% in the Superior Province, equivalent to delay times under 0.5 s. The overall decrease in anisotropic strength is modified by local changes of up to 2%, suggesting small-scale local variations near the surface. Orientations of the fast axes change from 60° in the Appalachian Orogen to 90° in the Superior Province, and are also modulated by local deviations. In the Appalachian Orogen the fast axes are close to the absolute plate motion in a hot-spot reference frame, while those in the Superior Province differ from it by almost 30°. Average values of splitting delays agree well with results of inversions in the Superior Province, and diverge in the Appalachians. Conversely, averaged fast polarizations match inversion results in the Appalachians, and are systematically different in the Superior Province. For an set of sites with recording periods exceeding 5 years, we will test more complicated models of anisotropy, including dipping fast axes and multiple layers. Figure 1. The best fit anisotropic parameters, orientations of fast axes (top) and strength of anisotropy (bottom), assuming a single 100 km thick horizontal layer with a horizontal fast axis. The red line in top represents the absolute plate motion in a hot spot reference frame.

Strength-Power Performance of Visually Impaired Paralympic and Olympic Judo Athletes From the Brazilian National Team: A Comparative Study.

PubMed

Loturco, Irineu; Nakamura, Fábio Y; Winckler, Ciro; Bragança, Jaime R; da Fonseca, Roger A; Moraes-Filho, Josué; Zaccani, Wagner A; Kobal, Ronaldo; Cal Abad, Cesar C; Kitamura, Katia; Pereira, Lucas A; Franchini, Emerson

2017-03-01

Loturco, I, Nakamura, FY, Winckler, C, Bragança, JR, da Fonseca, RA, Filho, JM, Zaccani, WA, Kobal, R, Cal Abad, CC, Kitamura, K, Pereira, LA, and Franchini, E. Strength-power performance of visually impaired paralympic and olympic judo athletes from the brazilian national team: a comparative study. J Strength Cond Res 31(3): 743-749, 2017-The aim of this study was to compare the muscle power and maximal isometric strength capacities of Olympic and visually impaired Paralympic judo athletes. Twenty-eight elite judo athletes (7 men and 7 women per group) from the permanent Brazilian National Paralympic and Olympic teams took part in this study. After a specific warm-up, the athletes performed loaded jump squat (JS), bench press (BP), and standing barbell row (SBR) exercises to determine their values of maximum mean propulsive power (MPP) in these respective exercises. The maximal isometric strength (MIS) was also determined for both upper and lower limbs, through the use of BP and half-squat (HS) exercises. Finally, the jumping ability was assessed using unloaded squat jump (SJ). The magnitude-based inference was used to compare the groups. The Olympic judo athletes presented a likely higher SJ height than the Paralympic athletes. The Olympic group presented almost certainly higher MPP in the loaded JS and in the SBR exercises and likely higher MPP in the BP exercise. Importantly, in the MIS assessments the differences between groups in the HS and BP exercises were rated as unclear. In conclusion, our results showed that both Olympic and Paralympic judo athletes present similar levels of maximal isometric strength, but muscle power performance is superior in Olympic athletes.

The Influence of Multiple Nested Layer Waviness on the Compression Strength of Double Nested Wave Formations in a Carbon Fiber Composite Laminate

NASA Astrophysics Data System (ADS)

Khan, Z. M.; Adams, D. O.; Anas, S.

2016-01-01

As advanced composite materials having superior physical and mechanical properties are being developed, the optimization of their processing techniques is eagerly sought. One of the most common defects arising during processing of structural composites is layer waviness. The layer waviness is more pronounced in thick-section flat and cylindrical laminates, which are extensively used in large wind turbine blades, submersibles, and space platforms. The layer waviness undulates the entire layer of a multidirectional laminate in the throughthe-thickness direction, leading to a gross deterioration of its compressive strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wavy 0° layers were fabricated in an IM/8551-7 carbon-epoxy composite laminate on a steel mold by using a single-step fabrication procedure. The test laminates were cured on a heated press according to the specific curing cycle of epoxy. Their static compression testing was performed using a NASA short block compression fixture on an MTS servohydraulic machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of the composite laminate. The experimental and analytical results obtained revealed that the reduction in the compression strength of composite laminate was constant after the fraction of the wavy 0° layers exceeded 35%. This analysis indicated that the percentage of the 0° wavy layer may be used to estimate the reduction in the compression strength of a double nested wave formation in a composite laminate.

Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect

DOE PAGES

Hao, Shijie; Cui, Lishan; Guo, Fangmin; ...

2015-03-09

Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires-orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm 3 that is almost one order ofmore » larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This research provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components.« less

Improved Electroformed Structural Copper and Copper Alloys

NASA Technical Reports Server (NTRS)

Malone, G. A.; Hudson, W.; Babcock, B.; Edwards, R.

1998-01-01

Electroforming offers a superior means for fabricating internally cooled heat exchangers and structures subjected to thermal environments. Copper is deposited from many such applications because of the good thermal conductivity. It suffers from mediocre yield strength as a structural material and loses mechanical strength at intermediate temperatures. Mechanical properties similar to those of electroformed nickel are desired. Phase 1 examined innovative means to improve deposited copper structural performance. Yield strengths as high as 483 MPa (70 ksi) were obtained with useful ductility while retaining a high level of purity essential to good thermal conductivity. Phase 2 represents a program to explore new additive combinations in copper electrolytes to produce a more fine, equiaxed grain which can be thermally stabilized by other techniques such as alloying in modest degrees and dispersion strengthening. Evaluation of new technology - such as the codeposition of fullerness (diamond-like) particles were made to enhance thermal conductivity in low alloys. A test fire quality tube-bundle engine was fabricated using these copper property improvement concepts to show the superiority of the new coppers and fabrications methods over competitive technologies such as brazing and plasma deposition.

An evaluation of the benefits of utilizing rapid solidification for development of 2XXX (Al-Cu-Mg) alloys

NASA Technical Reports Server (NTRS)

Paris, H. G.; Chellman, D. J.

1986-01-01

The advantages of rapid solidification processing over ingot metallurgy processing in the development of 2XXX aluminum alloy compositions were evaluated using a similarly processed ingot metallurgy (IM) control alloy. The powder metallurgy (PM) alloy extrusions showed a reduced age-hardening response in comparison with similar IM compositions, with higher tensile properties for naturally aged extrusions but lower properties for artificially aged ones. However, the tensile properties of naturally and artificially aged PM alloy extrusions based on a version of IM 2034 alloy, but containing 0.6 weight percent zirconium, were comparable to those of the IM control extrusions and had significantly superior combinations of strength and toughness. The tensile properties of this PM alloy showed even greater advantage in 6.4-mm (0.25-in.) and 1.8-mm (0.070-in.) plate and sheet, the yield strength being about 68 MPa (10 ksi) greater than reported values for the IM 2034 alloy sheet. An artificially aged PM alloy based on 2219 alloy also showed a strength and strength-toughness combination comparable to those of the PM Al-Cu-Mg-Zr alloy, substantially outperforming the IM 2219 alloy. These results show that rapid solidification offers the flexibility needed to modify conventional IM compositions to produce new alloy compositions with superior mechanical properties.

Water vapor diffusion membrane development. [for water recovery purposes onboard manned spacecraft

NASA Technical Reports Server (NTRS)

Tan, M. K.

1974-01-01

The phase separator component used as a membrane in the vapor diffusion process (VRD) for the recovery of potable water from urine on manned space missions of extended duration was investigated, with particular emphasis on cation-selective membranes because of their noted mechanical strength, superior resistance to acids, oxidants, and germicides, and their potential resistance to organic foulants. Two of the membranes were tested for 700 hours continuously, and were selected on the basis of criteria deemed important to an effective water reclamation system onboard spacecraft. The samples of urine were successfully processed by removing 93 percent of their water content in 70 hours using the selected membranes. Pretreatment with an acid-oxidant formulation improved product quality. Cation exchange membranes were shown to possess superior mechanical strength and chemical resistance, as compared to cellulosic membranes.

Deletion of the low-molecular-weight glutenin subunit allele Glu-A3a of wheat (Triticum aestivum L.) significantly reduces dough strength and breadmaking quality.

PubMed

Zhen, Shoumin; Han, Caixia; Ma, Chaoying; Gu, Aiqin; Zhang, Ming; Shen, Xixi; Li, Xiaohui; Yan, Yueming

2014-12-19

Low-molecular-weight glutenin subunits (LMW-GS), encoded by Glu-3 complex loci in hexaploid wheat, play important roles in the processing quality of wheat flour. To date, the molecular characteristics and effects on dough quality of individual Glu-3 alleles and their encoding proteins have been poorly studied. We used a Glu-A3 deletion line of the Chinese Spring (CS-n) wheat variety to conduct the first comprehensive study on the molecular characteristics and functional properties of the LMW-GS allele Glu-A3a. The Glu-A3a allele at the Glu-A3 locus in CS and its deletion in CS-n were identified and characterized by proteome and molecular marker methods. The deletion of Glu-A3a had no significant influence on plant morphological and yield traits, but significantly reduced the dough strength and breadmaking quality compared to CS. The complete sequence of the Glu-A3a allele was cloned and characterized, which was found to encode a B-subunit with longer repetitive domains and an increased number of α-helices. The Glu-A3a-encoded B-subunit showed a higher expression level and accumulation rate during grain development. These characteristics of the Glu-A3a allele could contribute to achieving superior gluten quality and demonstrate its potential application to wheat quality improvement. Furthermore, an allele-specific polymerase chain reaction (AS-PCR) marker for the Glu-A3a allele was developed and validated using different bread wheat cultivars, including near-isogenic lines (NILs) and recombinant inbred lines (RILs), which could be used as an effective molecular marker for gluten quality improvement through marker-assisted selection. This work demonstrated that the LMW-GS allele Glu-A3a encodes a specific LMW-i type B-subunit that significantly affects wheat dough strength and breadmaking quality. The Glu-A3a-encoded B-subunit has a long repetitive domain and more α-helix structures as well as a higher expression level and accumulation rate during grain development, which could facilitate the formation of wheat with a stronger dough structure and superior breadmaking quality.

CpG island mapping by epigenome prediction.

PubMed

Bock, Christoph; Walter, Jörn; Paulsen, Martina; Lengauer, Thomas

2007-06-01

CpG islands were originally identified by epigenetic and functional properties, namely, absence of DNA methylation and frequent promoter association. However, this concept was quickly replaced by simple DNA sequence criteria, which allowed for genome-wide annotation of CpG islands in the absence of large-scale epigenetic datasets. Although widely used, the current CpG island criteria incur significant disadvantages: (1) reliance on arbitrary threshold parameters that bear little biological justification, (2) failure to account for widespread heterogeneity among CpG islands, and (3) apparent lack of specificity when applied to the human genome. This study is driven by the idea that a quantitative score of "CpG island strength" that incorporates epigenetic and functional aspects can help resolve these issues. We construct an epigenome prediction pipeline that links the DNA sequence of CpG islands to their epigenetic states, including DNA methylation, histone modifications, and chromatin accessibility. By training support vector machines on epigenetic data for CpG islands on human Chromosomes 21 and 22, we identify informative DNA attributes that correlate with open versus compact chromatin structures. These DNA attributes are used to predict the epigenetic states of all CpG islands genome-wide. Combining predictions for multiple epigenetic features, we estimate the inherent CpG island strength for each CpG island in the human genome, i.e., its inherent tendency to exhibit an open and transcriptionally competent chromatin structure. We extensively validate our results on independent datasets, showing that the CpG island strength predictions are applicable and informative across different tissues and cell types, and we derive improved maps of predicted "bona fide" CpG islands. The mapping of CpG islands by epigenome prediction is conceptually superior to identifying CpG islands by widely used sequence criteria since it links CpG island detection to their characteristic epigenetic and functional states. And it is superior to purely experimental epigenome mapping for CpG island detection since it abstracts from specific properties that are limited to a single cell type or tissue. In addition, using computational epigenetics methods we could identify high correlation between the epigenome and characteristics of the DNA sequence, a finding which emphasizes the need for a better understanding of the mechanistic links between genome and epigenome.

Thermal analysis on Al7075/Al2O3 metal matrix composites fabricated by stir casting process

NASA Astrophysics Data System (ADS)

Jacob, S.; Shajin, S.; Gnanavel, C.

2017-03-01

Metal matrix Composites (MMC’s) have evoked a keen interest in recent times for various applications in aerospace, renewable energy and automotive industries due to their superior strength, low cost, easy availability and high temperature resistance [1]. The crack and propagation occurs in conventional materials without any appreciable indication in a short span. Hence composite materials are preferred nowadays to overcome this problem [2]. The process of metal matrix composites (MMC’s) is to unite the enviable attributes of metals and ceramics. The Stir casting method is used for producing aluminium metal matrix composites (AMC’s). A key challenge of the process is to spread the ceramic particles to achieve a defect free microstructure [2]. By carefully selecting stir casting processing specification, such as stirring time, temperature of the melt and blade angle, the desired microstructure can be obtained. The focus of this work is to develop a high strength particulate strengthen aluminium metal matrix composites, and Al7075 was selected which can offer high strength without much disturbing ductility of metal matrix [4]. The composites will be examined using standard metallurgical and mechanical tests. The cast composites are analysed to Laser flash analysis (LFA) to determine Thermal conductivity [5]. Also changes in microstructure are determined by using SEM analysis.

Electron Beam Irradiated Intercalated CNT Yarns For Aerospace Applications

NASA Technical Reports Server (NTRS)

Waters, Deborah L.; Gaier, James R.; Williams, Tiffany S.; Lopez Calero, Johnny E.; Ramirez, Christopher; Meador, Michael A.

2015-01-01

Multi-walled CNT yarns have been experimentally and commercially created to yield lightweight, high conductivity fibers with good tensile properties for application as electrical wiring and multifunctional tendons. Multifunctional tendons are needed as the cable structures in tensegrity robots for use in planetary exploration. These lightweight robust tendons can provide mechanical strength for movement of the robot in addition to power distribution and data transmission. In aerospace vehicles, such as Orion, electrical wiring and harnessing mass can approach half of the avionics mass. Use of CNT yarns as electrical power and data cables could reduce mass of the wiring by thirty to seventy percent. These fibers have been intercalated with mixed halogens to increase their specific electrical conductivity to that near copper. This conductivity, combined with the superior strength and fatigue resistance makes it an attractive alternative to copper for wiring and multifunctional tendon applications. Electron beam irradiation has been shown to increase mechanical strength in pristine CNT fibers through increased cross-linking. Both pristine and intercalated CNT yarns have been irradiated using a 5-megavolt electron beam for various durations and the conductivities and tensile properties will be discussed. Structural information obtained using a field emission scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy will correlate microstructural details with bulk properties.

Manufacturing and Characterization of 18Ni Marage 300 Lattice Components by Selective Laser Melting.

PubMed

Contuzzi, Nicola; Campanelli, Sabina L; Casavola, Caterina; Lamberti, Luciano

2013-08-13

The spreading use of cellular structures brings the need to speed up manufacturing processes without deteriorating mechanical properties. By using Selective Laser Melting (SLM) to produce cellular structures, the designer has total freedom in defining part geometry and manufacturing is simplified. The paper investigates the suitability of Selective Laser Melting for manufacturing steel cellular lattice structures with characteristic dimensions in the micrometer range. Alternative lattice topologies including reinforcing bars in the vertical direction also are considered. The selected lattice structure topology is shown to be superior over other lattice structure designs considered in literature. Compression tests are carried out in order to evaluate mechanical strength of lattice strut specimens made via SLM. Compressive behavior of samples also is simulated by finite element analysis and numerical results are compared with experimental data in order to assess the constitutive behavior of the lattice structure designs considered in this study. Experimental data show that it is possible to build samples of relative density in the 0.2456-0.4367 range. Compressive strength changes almost linearly with respect to relative density, which in turns depends linearly on the number of vertical reinforces. Specific strength increases with cell and strut edge size. Numerical simulations confirm the plastic nature of the instability phenomena that leads the cellular structures to collapse under compression loading.

CHITOSAN-CELLULOSE COMPOSITE MATERIALS: PREPARATION, CHARACTERIZATION AND APPLICATION FOR REMOVAL OF MICROCYSTIN

PubMed Central

Tran, Chieu D.; Duri, Simon; Delneri, Ambra; Franko, Mladen

2013-01-01

We developed a simple and one-step method to prepare biocompatible composites from cellulose (CEL) and chitosan (CS). [BMIm+Cl−], an ionic liquid (IL), was used as a green solvent to dissolve and prepare the [CEL+CS] composites. Since majority (>88%) of IL used was recovered for reuse by distilling the aqueous washings of [CEL+CS], the method is recyclable. XRD, FTIR, NIR, 13C CP-MAS-NMR and SEM were used to monitor the dissolution and to characterize the composites. The composite was found to have combined advantages of their components: superior mechanical strength (from CEL) and excellent adsorption capability for microcystin-LR, a deadly toxin produced by cyanobacteria (from CS). Specifically, the mechanical strength of the composites increased with CEL loading; e.g., up to 5X increase in tensile strength was achieved by adding 80% of CEL into CS. Kinetic results of adsorption confirm that unique properties of CS remain intact in the composite, i.e., it is not only a very good adsorbent for microcystin but also is better than all other available adsorbents. For example, it can adsorb 4X times more microcystin than the best reported adsorbent. Importantly, the microcystin adsorbed can be quantitatively desorbed to enable the composite to be reused with similar adsorption efficiency. PMID:23542326

Thermoplastic composites for veneering posterior teeth-a feasibility study.

PubMed

Gegauff, Anthony G; Garcia, Jose L; Koelling, Kurt W; Seghi, Robert R

2002-09-01

This pilot study was conducted to explore selected commercially-available thermoplastic composites that potentially had physical properties superior to currently available dental systems for restoring esthetic posterior crowns. Polyurethane, polycarbonate, and poly(ethylene/tetrafluoroethylene) (ETFE) composites and unfilled polyurethane specimens were injection molded to produce shapes adaptive to five standardized mechanical tests. The mechanical testing included abrasive wear rate, yield strength, apparent fracture toughness (strength ratio), flexural strength, and compressive strength. Compared to commercially available dental composites, abrasion wear rates were lower for all materials tested, yield strength was greater for the filled polycarbonates and filled polyurethane resins, fracture toughness testing was invalid (strength ratios were calculated for comparison of the pilot test materials), flexural strength was roughly similar except for the filled ETFE which was significantly greater, and compressive strength was lower. Commercially available thermoplastic resin composites, such as polyurethane, demonstrate the potential for development of an artificial crown material which exceeds the mechanical properties of currently available esthetic systems, if compressive strength can be improved.

Which nanowire couples better electrically to a metal contact: Armchair or zigzag nanotube?

NASA Technical Reports Server (NTRS)

Anantram, M. P.; Biegel, Bryan (Technical Monitor)

2001-01-01

The fundamental question of how chirality affects tile electronic coupling of a nanotube to metal contacts is important for tile application of nanotubes as nanowires. We show that metallic-zigzag nanotubes are superior to armchair nanotubes as nanowires, by modeling the metal-nanotube interface. More specifically, we show that as a function of coupling strength, the total electron transmission of armchair nanotubes increases and tends to be pinned close to unity for a metal with Fermi wave vector close to that of gold. In contrast, the transmission probability of zigzag nanotubes increases to the maximum possible value of two. The origin of these effects lies in the details of the wave function, which is explained.

Retention Strength of Conical Welding Caps for Fixed Implant-Supported Prostheses.

PubMed

Nardi, Diego; Degidi, Marco; Sighinolfi, Gianluca; Tebbel, Florian; Marchetti, Claudio

This study evaluated the retention strength of welding caps for Ankylos standard abutments using a pull-out test. Each sample consisted of an implant abutment and its welding cap. The tests were performed with a Zwick Roell testing machine with a 1-kN load cell. The retention strength of the welding caps increased with higher abutment diameters and higher head heights and was comparable or superior to the values reported in the literature for the temporary cements used in implant dentistry. Welding caps provide a reliable connection between an abutment and a fixed prosthesis without the use of cement.

Precipitation Effect on Mechanical Properties and Phase Stability of High Manganese Steel

NASA Astrophysics Data System (ADS)

Bae, Cheoljun; Kim, Rosa; Lee, Un-Hae; Kim, Jongryoul

2017-09-01

High manganese (Mn) steels are attractive for automotive applications due to their excellent tensile strength and superior elongation. However, the relatively low yield strength of Mn steels compared to other advanced high-strength steels is a critical problem limiting their use in structural parts. In order to increase the yield strength, the precipitation hardening effect of Mn steels was investigated by the addition of carbide-forming elements. Changes in the austenite phase stability were also evaluated in terms of stacking fault energy (SFE). As a result, fine V(C,N) precipitates were found to increase the yield strength effectively but to lower the SFE by the consumption of matrix carbons. For achieving precipitation hardening without sacrificing austenite stability, the soluble carbon content was discussed.

Anaerobic power and muscle strength characteristics of 11 years old elite and non-elite boys and girls from gymnastics, team handball, tennis and swimming.

PubMed

Bencke, J; Damsgaard, R; Saekmose, A; Jørgensen, P; Jørgensen, K; Klausen, K

2002-06-01

The aim of the present investigation was to study the possible effects of specificity of training on muscle strength and anaerobic power in children from different sports and at different performance levels in relation to growth and maturation status. Hundred and eighty-four children of both gender participating either in swimming, tennis, team handball or gymnastics were recruited from the best clubs in Denmark. Within each sport, the coach had divided the children into an elite (E) and non-elite (NE) group according to performance level and talent. Tanner stage assessment and body weight and height measurements were performed by a physician. The anaerobic performances were assessed by Wingate tests and jumping performance in squat jump (SJ), countermovement jump (CMJ) and drop jump (DJ) from two heights. Most of the differences between groups in Wingate performance disappeared when the data were normalised to body mass. The gymnasts were the best jumpers and their superiority were increased in the more complex motor coordination tasks like DJ. The results may indicate some influence of training specificity, especially on the more complex motor tasks as DJ and there may be an effect of training before puberty. The performance in the less complex motor tasks like cycling and SJ and CMJ may also be influenced by specific training, but not to the same extent, and heritance may be an important factor for performance in these anaerobic tasks.

Chemically Crosslinked Hydrogel Film Leads to Integrated Flexible Supercapacitors with Superior Performance.

PubMed

Wang, Kai; Zhang, Xiong; Li, Chen; Sun, Xianzhong; Meng, Qinghai; Ma, Yanwei; Wei, Zhixiang

2015-12-02

A high-strength poly(vinyl alcohol) chemical hydrogel (PCH) film is prepared by coupling covalent crosslinking with a film-casting process. Conducting polyaniline (PANI) is then embedded in the PCH film by in situ growth to form a composite film with a PANI-hydrogel-PANI configuration, which leads to a new conceptual flexible supercapacitor with all-in-one configuration that exhibits superior electrochemical performance and mechanical flexibility. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comparison of the physiological profiles of elite Gaelic footballers, hurlers, and soccer players

PubMed Central

McIntyre, M

2005-01-01

Background: Gaelic football, soccer, and hurling are prominent field games in Ireland and involve participants undertaking a variety of playing tasks and skills which place various physiological demands on the participants. The aim of this study was to evaluate and compare the mid-season physiological profiles of elite players. Methods: Physiological assessment was carried out on 29 inter-county Gaelic footballers, 30 inter-county hurlers, and 21 League of Ireland soccer players. Results: Significant differences were reported for % body fat (p<0.05), aerobic capacity (p<0.05), flexibility (p<0.05), upper body strength (p<0.05), upper body strength endurance (p<0.05), abdominal endurance (p<0.05), and speed endurance (p<0.05), while there were no differences recorded for height, weight, or speed levels. A relatively heterogeneous body size is evident for all three sports. Soccer players had lower body fat levels, greater aerobic capacity, greater strength endurance, and greater flexibility compared to both Gaelic footballers and hurlers, possibly due to specific training and conditioning programmes or physical adaptation to match play The greater strength of both Gaelic footballers and hurlers and the superior speed endurance levels of Gaelic footballers also reflect the physical nature of the sports. Similar speed levels amongst all three sports reflect the importance of speed for performance. Conclusions: The various physiological attributes for Gaelic football, soccer, and hurling reflect the physical requirements for success and participation in each of these field games. PMID:15976166

Retrieval Search and Strength Evoke Dissociable Brain Activity during Episodic Memory Recall

PubMed Central

Reas, Emilie T.; Brewer, James B.

2014-01-01

Neuroimaging studies of episodic memory retrieval have revealed activations in the human frontal, parietal, and medial-temporal lobes that are associated with memory strength. However, it remains unclear whether these brain responses are veritable signals of memory strength or are instead regulated by concomitant subcomponents of retrieval such as retrieval effort or mental search. This study used event-related fMRI during cued recall of previously memorized word-pair associates to dissociate brain responses modulated by memory search from those modulated by the strength of a recalled memory. Search-related deactivations, dissociated from activity due to memory strength, were observed in regions of the default network, whereas distinctly strength-dependent activations were present in superior and inferior parietal and dorsolateral PFC. Both search and strength regulated activity in dorsal anterior cingulate and anterior insula. These findings suggest that, although highly correlated and partially subserved by overlapping cognitive control mechanisms, search and memory strength engage dissociable regions of frontoparietal attention and default networks. PMID:23190328

Chile Informed Question Paper - Military

DTIC Science & Technology

2003-01-01

superior military strength and regional economic integration. Internally, Chile also faces little threat; however, militants from the Mapuche ...considered a significant threat.11 The most significant internal security concern is the ongoing campaign by Mapuche indigenous community militants to

Application of ultra-high performance concrete to bridge girders.

DOT National Transportation Integrated Search

2009-02-01

"Ultra-High Performance Concrete (UHPC) is a new class of concrete that has superior performance characteristics : compared to conventional concrete. The enhanced strength and durability properties of UHPC are mainly due to optimized : particle grada...

Simultaneous structural and environmental loading of an ultra-high performance concrete component

DOT National Transportation Integrated Search

2010-07-01

Ultra-high performance concrete (UHPC) is an advanced cementitious composite material which tends to exhibit superior properties such as increased durability, strength, and long-term stability. This experimental investigation focused on the flexural ...

Finite Element Modelling Full Vehicle Side Impact with Ultrahigh Strength Hot Stamped Steels

NASA Astrophysics Data System (ADS)

Taylor, T.; Fourlaris, G.; Cafolla, J.

2016-10-01

"Hot stamped boron steel" 22MnB5 has been imperative in meeting the automotive industry's demand for materials exhibiting higher tensile strength in the final component. In this paper, the crash performance of three experimental grades developed for automotive hot stamping technologies, exhibiting wider tensile property ranges than 22MnB5, was validated by finite element modelling full vehicle side impact with the experimental material data applied to the B-pillar reinforcement. The superior anti-intrusive crash performance of grade 38MnB5 was demonstrated, with 11 mm less intrusion of the B-pillar reinforcement compared to 22MnB5. Moreover, the superior "impact-energy absorptive" crash performance of grade 15MnCr5 was demonstrated, with 0.15 kJ greater impact-energy absorption by the B-pillar reinforcement compared to 22MnB5.

Flexural properties of three kinds of experimental fiber-reinforced composite posts.

PubMed

Kim, Mi-Joo; Jung, Won-Chang; Oh, Seunghan; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka; Bae, Ji-Myung

2011-01-01

The aim of this study was to estimate the flexural properties of three kinds of experimental fiber-reinforced composite (FRC) posts and to evaluate their potential use as posts. Experimental FRC posts were fabricated with glass, aramid, and UHMWP fibers. Commercial FRC posts were used for comparison. A three-point bending test was performed at a crosshead speed of 1 mm/min. Experimental glass fiber posts showed significantly higher flexural strengths and moduli than aramid and UHMWP posts. Experimental UHMWP posts demonstrated superior toughness to the commercial posts. The glass fiber posts displayed stiff, strong and brittle features, while the UHMWP posts were flexible, weak and ductile. The flexural properties of the aramid posts fell between those of the glass and UHMWP posts. In conclusion, the glass fiber posts proved excellent in flexural strengths and moduli. However, the superior toughness of UHMWP fibers suggests the possibility of their use as posts in combination with glass fibers.

Hybrid flower pollination algorithm strategies for t-way test suite generation.

PubMed

Nasser, Abdullah B; Zamli, Kamal Z; Alsewari, AbdulRahman A; Ahmed, Bestoun S

2018-01-01

The application of meta-heuristic algorithms for t-way testing has recently become prevalent. Consequently, many useful meta-heuristic algorithms have been developed on the basis of the implementation of t-way strategies (where t indicates the interaction strength). Mixed results have been reported in the literature to highlight the fact that no single strategy appears to be superior compared with other configurations. The hybridization of two or more algorithms can enhance the overall search capabilities, that is, by compensating the limitation of one algorithm with the strength of others. Thus, hybrid variants of the flower pollination algorithm (FPA) are proposed in the current work. Four hybrid variants of FPA are considered by combining FPA with other algorithmic components. The experimental results demonstrate that FPA hybrids overcome the problems of slow convergence in the original FPA and offers statistically superior performance compared with existing t-way strategies in terms of test suite size.

On flaw tolerance of nacre: a theoretical study

PubMed Central

Shao, Yue; Zhao, Hong-Ping; Feng, Xi-Qiao

2014-01-01

As a natural composite, nacre has an elegant staggered ‘brick-and-mortar’ microstructure consisting of mineral platelets glued by organic macromolecules, which endows the material with superior mechanical properties to achieve its biological functions. In this paper, a microstructure-based crack-bridging model is employed to investigate how the strength of nacre is affected by pre-existing structural defects. Our analysis demonstrates that owing to its special microstructure and the toughening effect of platelets, nacre has a superior flaw-tolerance feature. The maximal crack size that does not evidently reduce the tensile strength of nacre is up to tens of micrometres, about three orders higher than that of pure aragonite. Through dimensional analysis, a non-dimensional parameter is proposed to quantify the flaw-tolerance ability of nacreous materials in a wide range of structural parameters. This study provides us some inspirations for optimal design of advanced biomimetic composites. PMID:24402917

Hybrid flower pollination algorithm strategies for t-way test suite generation

PubMed Central

Zamli, Kamal Z.; Alsewari, AbdulRahman A.

2018-01-01

The application of meta-heuristic algorithms for t-way testing has recently become prevalent. Consequently, many useful meta-heuristic algorithms have been developed on the basis of the implementation of t-way strategies (where t indicates the interaction strength). Mixed results have been reported in the literature to highlight the fact that no single strategy appears to be superior compared with other configurations. The hybridization of two or more algorithms can enhance the overall search capabilities, that is, by compensating the limitation of one algorithm with the strength of others. Thus, hybrid variants of the flower pollination algorithm (FPA) are proposed in the current work. Four hybrid variants of FPA are considered by combining FPA with other algorithmic components. The experimental results demonstrate that FPA hybrids overcome the problems of slow convergence in the original FPA and offers statistically superior performance compared with existing t-way strategies in terms of test suite size. PMID:29718918

Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

NASA Astrophysics Data System (ADS)

Zhu, J.; Zheng, W. Z.; Qin, C. Z.; Xu, Z. Z.; Wu, Y. Q.

2018-01-01

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

Microstructures and Mechanical Properties of Friction Stir Spot Welded Aluminum Alloy AA2014

NASA Astrophysics Data System (ADS)

Babu, S.; Sankar, V. S.; Janaki Ram, G. D.; Venkitakrishnan, P. V.; Madhusudhan Reddy, G.; Prasad Rao, K.

2013-01-01

Friction stir spot welding (FSSW) is a relatively recent development, which can provide a superior alternative to resistance spot welding and riveting for fabrication of aluminum sheet metal structures. In the current work, FSSW experiments were conducted in 3-mm thick sheets of aluminum alloy 2014 in T4 and T6 conditions, with and without Alclad layers. The effects of tool geometry and welding process parameters on joint formation were investigated. A good correlation between process parameters, bond width, hook height, joint strength, and fracture mode was observed. The presence of Alclad layers and the base metal temper condition were found to have no major effect on joint formation and joint strength. Friction stir spot welds produced under optimum conditions were found to be superior to riveted joints in lap-shear and cross-tension tests. The prospects of FSSW in aluminum sheet metal fabrication are discussed.

Stuck between a rock and a hard place: the work situation for nurses as leaders in municipal health care

PubMed Central

Nilsen, Etty R; Olafsen, Anja H; Steinsvåg, Anne Grethe; Halvari, Hallgeir; Grov, Ellen K

2016-01-01

Background The paper aims to present how nursing leaders in the municipal health care perceive the interaction with and support from their superiors and peers. The paper further aims to identify the leaders’ vulnerability and strength at work in the current situation of shortage of manpower and other resources in the health care sector. This is seen through the lens of self-determination theory. Methods Qualitative interviews were conducted with nine nursing leaders in nursing homes and home-care services, which, in part, capture the municipal health care service in a time of reform. Results The nursing leaders are highly independent regarding their role as leaders. They act with strength and power in their position as superiors for their own staff, but they lack support and feel left alone by their leader, the municipal health director. The relation between the nursing leaders and their superiors is characterized by controlling structures and lack of autonomy support. As a consequence, the nursing leaders’ relations with subordinates and particularly peers, contribute to satisfy their needs for competence and relatedness, and, to some extent, autonomy. However, this cannot substitute for the lack of support from the superior level. Conclusion The paper maintains a need to increase the consciousness of the value of horizontal support and interaction with peers and subordinates for the municipal nursing leader. Also, the need for increased focus on “the missing link” upward between the municipal health director and the nursing leader is revealed. The impact of extensive controlling structures and lack of autonomy support from superiors might lead to reduced motivation and well-being. PMID:27103816

Mechanical properties of low-nickel stainless steel

NASA Technical Reports Server (NTRS)

Montano, J. W.

1978-01-01

Demand for improved corrosion-resistant steels, coupled with increased emphasis on conserving strategic metals, has led to development of family of stainless steels in which manganese and nitrogen are substituted for portion of usual nickel content. Advantages are approximately-doubled yield strength in annealed condition, better resistance to stress-corrosion cracking, retention of low magnetic permeability even after severe cold working, excellent strength and ductility at cryogenic temperatures, superior resistance to wear and galling, and excellent high-temperature properties.

A Comparison of Isometric Midthigh-Pull Strength, Vertical Jump, Sprint Speed, and Change-of-Direction Speed in Academy Netball Players.

PubMed

Thomas, Christopher; Comfort, Paul; Jones, Paul A; Dos'Santos, Thomas

2017-08-01

To investigate the relationships between maximal isometric strength, vertical jump (VJ), sprint speed, and change-of-direction speed (CoDS) in academy netball players and determine whether players who have high performance in isometric strength testing would demonstrate superior performance in VJ, sprint speed, and CoDS measures. Twenty-six young female netball players (age 16.1 ± 1.2 y, height 173.9 ± 5.7 cm, body mass 66.0 ± 7.2 kg) from a regional netball academy performed isometric midthigh pull (IMTP), squat jumps (SJs), countermovement jumps (CMJs), 10-m sprints, and CoDS (505). IMTP measures displayed moderate to strong correlations with sprint and CoDS performance (r = -.41 to -.66). The VJs, which included SJs and CMJs, demonstrated strong correlations with 10-m sprint times (r = -.60 to -.65; P < .01) and CoDS (r = -.60 to -.71; P = .01). Stronger players displayed significantly faster sprint (ES = 1.1-1.2) and CoDS times (ES = 1.2-1.7) and greater VJ height (ES = 0.9-1.0) than weaker players. The results of this study illustrate the importance of developing high levels of lower-body strength to enhance VJ, sprint, and CoDS performance in youth netball players, with stronger athletes demonstrating superior VJ, sprint, and CoDS performances.

Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses.

PubMed

Jang, Dongchan; Greer, Julia R

2010-03-01

Amorphous metallic alloys, or metallic glasses, are lucrative engineering materials owing to their superior mechanical properties such as high strength and large elastic strain. However, their main drawback is their propensity for highly catastrophic failure through rapid shear banding, significantly undercutting their structural applications. Here, we show that when reduced to 100 nm, Zr-based metallic glass nanopillars attain ceramic-like strengths (2.25 GPa) and metal-like ductility (25%) simultaneously. We report separate and distinct critical sizes for maximum strength and for the brittle-to-ductile transition, thereby demonstrating that strength and ability to carry plasticity are decoupled at the nanoscale. A phenomenological model for size dependence and brittle-to-homogeneous deformation is provided.

Separator material for electrochemical cells

DOEpatents

Cieslak, Wendy R.; Storz, Leonard J.

1991-01-01

An electrochemical cell characterized as utilizing an aramid fiber as a separator material. The aramid fibers are especially suited for lithium/thionyl chloride battery systems. The battery separator made of aramid fibers possesses superior mechanical strength, chemical resistance, and is flame retardant.

Development of a Family of Ultra-High Performance Concrete Pi-Girders

DOT National Transportation Integrated Search

2014-01-01

Ultra-high performance concrete (UHPC) is an advanced cementitious composite material, which tends to exhibit superior properties such as exceptional durability, increased strength, and long-term stability. (See references 1-4.) The use of existing s...

Elevated-Temperature Mechanical Properties of Lead-Free Sn-0.7Cu- xSiC Nanocomposite Solders

NASA Astrophysics Data System (ADS)

Mohammadi, A.; Mahmudi, R.

2018-02-01

Mechanical properties of Sn-0.7 wt.%Cu lead-free solder alloy reinforced with 0 vol.%, 1 vol.%, 2 vol.%, and 3 vol.% 100-nm SiC particles have been assessed using the shear punch testing technique in the temperature range from 25°C to 125°C. The composite materials were fabricated by the powder metallurgy route by blending, compacting, sintering, and finally extrusion. The 2 vol.% SiC-containing composite showed superior mechanical properties. In all conditions, the shear strength was adversely affected by increasing test temperature, and the 2 vol.% SiC-containing composite showed superior mechanical properties. Depending on the test temperature, the shear yield stress and ultimate shear strength increased, respectively, by 3 MPa to 4 MPa and 4 MPa to 5.5 MPa, in the composite materials. The strength enhancement was mostly attributed to the Orowan particle strengthening mechanism due to the SiC nanoparticles, and to a lesser extent to the coefficient of thermal expansion mismatch between the particles and matrix in the composite solder. A modified shear lag model was used to predict the total strengthening achieved by particle addition, based on the contribution of each of the above mechanisms.

Composite strengthening. [of nonferrous, fiber reinforced alloys

NASA Technical Reports Server (NTRS)

Stoloff, N. S.

1976-01-01

The mechanical behavior of unidirectionally reinforced metals is examined, with particular attention to fabrication techniques for artificial composites and eutectic alloys and to principles of fiber reinforcement. The properties of artificial composites are discussed in terms of strength of fiber composites, strength of ribbon-reinforced composites, crack initiation, crack propagation, and creep behavior. The properties of eutectic composites are examined relative to tensile strength, compressive strength, fracture, high-temperature strength, and fatigue. In the case of artificial composites, parallelism of fibers, good bonding between fibers and matrix, and freedom of fibers from damage are all necessary to ensure superior performance. For many eutectic systems there are stringent boundary conditions relative to melt purity and superheat, atmosphere control, temperature gradient, and growth rate in order to provide near-perfect alignment of the reinforcements with a minimum of growth defects.

Feasibility of using an acoustic velocity meter to measure flow in the Chipps Island channel, Suisun Bay, California

USGS Publications Warehouse

Hoffard, Stuart H.

1980-01-01

Tests were conducted in 1978 to determine the feasibility of using an acoustic velocity meter to measure the Sacramento-San Joaquin Delta outflow in the Chipps Island Channel, Suisun Bay, Calif. Three parts of transducers with frequencies of 100, 40, and 24 kilohertz were installed on a cross-channel test path and operated at three elevations, 15.5, 8.0, and 4.0 feet below mean lower low water, to test signal transmission at varying depths. Transmission was most reliable at the lowest depth, and the 24-kilohertz transducers at the 7-millivolt threshold of signal strength met the study 's criterion of no persistent signal loss of more than one hour 's duration in any phase of the tidal cycle. Signal strength was statistically correlated with the environmental factors of wind velocity, wind direction, solar insolation, electrical conductivity, water temperature, water velocity, stage, rate of change in stage, and the acceleration of the rate of change in stage. All correlations were weak. Signal strength is apparently a function of the interaction of several environmental factors. A 32-day test to observe if aquatic growth on the transducers would affect signal transmission showed no reduction in signal strength. Suspended-sediment samples indicated that both the size and concentration of particles are greater than presumed in earlier studies. According to the results of this study, chances are good for reliable transmission of acoustic velocity meter signals. Usually some signals were much stronger than the average 20-second signal strength at 15-minute intervals used for correlation and the frequency analysis. Superior equipment is now being developed specifically for the Chipps Island site to transmit signals several times stronger than the signals analyzed in these tests. (USGS)

Comparison of electric field strength and spatial distribution of electroconvulsive therapy and magnetic seizure therapy in a realistic human head model

PubMed Central

Lee, Won Hee; Lisanby, Sarah H.; Laine, Andrew F.; Peterchev, Angel V.

2017-01-01

Background This study examines the strength and spatial distribution of the electric field induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). Methods The electric field induced by standard (bilateral, right unilateral, and bifrontal) and experimental (focal electrically administered seizure therapy and frontomedial) ECT electrode configurations as well as a circular MST coil configuration was simulated in an anatomically realistic finite element model of the human head. Maps of the electric field strength relative to an estimated neural activation threshold were used to evaluate the stimulation strength and focality in specific brain regions of interest for these ECT and MST paradigms and various stimulus current amplitudes. Results The standard ECT configurations and current amplitude of 800–900 mA produced the strongest overall stimulation with median of 1.8–2.9 times neural activation threshold and more than 94% of the brain volume stimulated at suprathreshold level. All standard ECT electrode placements exposed the hippocampi to suprathreshold electric field, although there were differences across modalities with bilateral and right unilateral producing respectively the strongest and weakest hippocampal stimulation. MST stimulation is up to 9 times weaker compared to conventional ECT, resulting in direct activation of only 21% of the brain. Reducing the stimulus current amplitude can make ECT as focal as MST. Conclusions The relative differences in electric field strength may be a contributing factor for the cognitive sparing observed with right unilateral compared to bilateral ECT, and MST compared to right unilateral ECT. These simulations could help understand the mechanisms of seizure therapies and develop interventions with superior risk/benefit ratio. PMID:27318858

Comparison of the compressive strength of 3 different implant design systems.

PubMed

Pedroza, Jose E; Torrealba, Ysidora; Elias, Augusto; Psoter, Walter

2007-01-01

The aims of this study were twofold: to compare the static compressive strength at the implant-abutment interface of 3 design systems and to describe the implant abutment connection failure mode. A stainless steel holding device was designed to align the implants at 30 degrees with respect to the y-axis. Sixty-nine specimens were used, 23 for each system. A computer-controlled universal testing machine (MTS 810) applied static compression loading by a unidirectional vertical piston until failure. Specimens were evaluated macroscopically for longitudinal displacement, abutment looseness, and screw and implant fracture. Data were analyzed by analysis of variance (ANOVA). The mean compressive strength for the Unipost system was 392.5 psi (SD +/-40.9), for the Spline system 342.8 psi (SD+/-25.8), and for the Screw-Vent system 269.1 psi (SD+/-30.7). The Unipost implant-abutment connection demonstrated a statistically significant superior mechanical stability (P < or = .009) compared with the Spline implant system. The Spline implant system showed a statistically significant higher compressive strength than the Screw-Vent implant system (P < or =.009). Regarding failure mode, the Unipost system consistently broke at the same site, while the other systems failed at different points of the connection. The Unipost system demonstrated excellent fracture resistance to compressive forces; this resistance may be attributed primarily to the diameter of the abutment screw and the 2.5 mm counter bore, representing the same and a unique piece of the implant. The Unipost implant system demonstrated a statistically significant superior compressive strength value compared with the Spline and Screw-Vent systems, at a 30 degrees angulation.

Fatigue limits of titanium-bar joints made with the laser and the electric resistance welding techniques: microstructural characterization and hardness properties.

PubMed

Degidi, Marco; Nardi, Diego; Morri, Alessandro; Sighinolfi, Gianluca; Tebbel, Florian; Marchetti, Claudio

2017-09-01

Fatigue behavior of the titanium bars is of utmost importance for the safe and reliable operation of dental implants and prosthetic constructions based on these implants. To date, however, only few data are available on the fatigue strength of dental prostheses made with electric resistance welding and laser welding techniques. This in-vitro study highlighted that although the joints made with the laser welding approach are credited of a superior tensile strength, joints made with electric resistance welding exhibited double the minimum fatigue strength with respect to the joints made with laser welding (120 vs 60 N).

Improved sensitivity and specificity for resting state and task fMRI with multiband multi-echo EPI compared to multi-echo EPI at 7 T.

PubMed

Boyacioğlu, Rasim; Schulz, Jenni; Koopmans, Peter J; Barth, Markus; Norris, David G

2015-10-01

A multiband multi-echo (MBME) sequence is implemented and compared to a matched standard multi-echo (ME) protocol to investigate the potential improvement in sensitivity and spatial specificity at 7 T for resting state and task fMRI. ME acquisition is attractive because BOLD sensitivity is less affected by variation in T2*, and because of the potential for separating BOLD and non-BOLD signal components. MBME further reduces TR thus increasing the potential reduction in physiological noise. In this study we used FSL-FIX to clean ME and MBME resting state and task fMRI data (both 3.5mm isotropic). After noise correction, the detection of resting state networks improves with more non-artifactual independent components being observed. Additional activation clusters for task data are discovered for MBME data (increased sensitivity) whereas existing clusters become more localized for resting state (improved spatial specificity). The results obtained indicate that MBME is superior to ME at high field strengths. Copyright © 2015 Elsevier Inc. All rights reserved.

Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.

PubMed

Donius, Amalie E; Liu, Andong; Berglund, Lars A; Wegst, Ulrike G K

2014-09-01

Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C. Copyright © 2014 Elsevier Ltd. All rights reserved.

Physiologic profile of professional cricketers.

PubMed

Johnstone, James A; Ford, Paul A

2010-11-01

This study aims to provide a physiologic profile of professional cricketers and note positional differences at the start of the 2007/08 competitive season. Fifteen participants (9 bowlers, 6 batsmen) aged 25.0 ± 5.0 years (mean ± SD) took part in this study. Participants (bowlers and batsmen) completed a series of field-based fitness assessments: body composition (sum of 7 skinfolds, 72.5 ± 16.5 and 65.5 ± 19.3 mm, respectively), flexibility (sit and reach 8.1 ± 10.3 and 6.0 ± 6.2 cm, respectively), predicted maximal oxygen uptake (multistage shuttle run, 54.1 ± 2.8 and 56.1 ± 4.5 ml-1·kg-1·min-1, respectively), upper- (medicine ball throw, 7.7 ± 0.6 and 7.0 ± 0.1 m, respectively) and lower-body strength (countermovement jump, 45.7 ± 5.8 and 43.9 ± 4.1 cm, respectively), speed (sprint 17.7 m, 2.76 ± 0.6 and 2.77 ± 0.1 s, respectively), and explosive power (repeated jump, 31.0 ± 2.0 and 34.1 ± 4.8 cm, respectively). The data provided the physical fitness profile for each player, which, compared with normative data, identified that this cohort of professional cricketers had some superior fitness parameters compared with the general population, and where applicable, were comparable with other professional athletes. In addition, after effect size calculations, the results showed that some physical fitness differences existed between playing positions. Cricket professionals possess a superior level of physical fitness and strength, and conditioning coaches should seek to progress these physical parameters and further identify position-specific physical requirements to progress the modern game.

Evaluation of SF6-alternative gas C5-PFK based on arc extinguishing performance and electric strength

NASA Astrophysics Data System (ADS)

Wu, Yi; Wang, Chunlin; Sun, Hao; Rong, Mingzhe; Murphy, Anthony Bruce; Li, Tianwei; Zhong, Jianying; Chen, Zhexin; Yang, Fei; Niu, Chunpin

2017-09-01

C5-PFK (C5-perfluoroketone, C5F10O) is under wide consideration as an environmentally-friendly alternative gas to SF6 in high-voltage applications, because of its superior insulation performance. The aim of this work is to study theoretically the arc extinguishing performance and electric strength of C5-PFK. The arc extinguishing performance of C5-PFK was evaluated by analyzing and comparing the thermophysical properties of C5-PFK, SF6, CF4, CO2 and N2 plasmas. It was difficult to obtain the species formed in C5-PFK plasmas because of the complex C5-PFK molecular decomposition process. In this work, the decomposition process of C5-PFK and the related species were analyzed by the bond energy analysis method. For the species for which parameters such as the partition function and the enthalpy of formation were not available, computational chemistry methods were used to obtain the required data. The collision integrals were calculated using the phenomenological potential model. Using these results, the local thermodynamic equilibrium composition at temperatures from 300 to 30 000 K at 1-10 atm of pure C5-PFK was calculated by the method of minimization of the Gibbs free energy, and the corresponding transport coefficients were calculated by Chapman-Enskog method. Through the comparison of the thermophysical properties, it was found that C5-PFK had similar characteristics to SF6, with large peaks in specific heat below 4500 K, indicating potentially good thermal interruption capability. However, the specific heat peak at 7000 K corresponding to CO decomposition may detract from the thermal interruption capability. Specific heat peaks at higher temperatures are associated with the breaking of double or triple bonds, and should be avoided if possible in the new alternative gases. The electric strength of C5-PFK was assessed using the molecular electrostatic potential, which can be accurately calculated or measured, and gives strong insights into important characteristics of the molecule. Based on the analysis of the molecular surface electrostatic potential and electric strength of C5-PFK, SF6, CF4, CO2, and N2, it is found that the positive potential area of the molecular surface has a strong correlation with the electric strength and is expected to be one of the predictors of electric strength. To verify this phenomenon, 36 kinds of particles were used for the correlation analysis. The correlation coefficient between the positive potential area and electric strength is up to 0.9 which means strong correlation.

Separator material for electrochemical cells

DOEpatents

Cieslak, W.R.; Storz, L.J.

1991-03-26

An electrochemical cell is characterized as utilizing an aramid fiber as a separator material. The aramid fibers are especially suited for lithium/thionyl chloride battery systems. The battery separator made of aramid fibers possesses superior mechanical strength, chemical resistance, and is flame retardant.

The Structure and Properties of Parachute Cloths

NASA Technical Reports Server (NTRS)

Mcnicholas, H J; Hedrick, F

1930-01-01

The requisite properties of a parachute cloth are discussed and the methods for measuring these properties described. In addition to the structural analysis of the cloths, the properties measured were weight, breaking strength, tear resistance, elasticity, and air permeability. Thirty-six silk cloths of domestic manufacture, not previously used in parachute construction are compared with some silk cloths of foreign manufacture. These foreign cloths were ones proven by trial and extended use to be suitable materials for parachute construction. Contrary to the belief that domestic woven cloths were not suitable materials for parachute construction, it is shown that many domestic silk cloths are satisfactory and in some respects superior to the foreign products. Based on a comparative study of all the cloths, specifications are drawn for the manufacture of silk parachute cloth.

Investigation on the Activity Activation and Cementitious Property of Coal Gangue with High Iron and Silica Contents

NASA Astrophysics Data System (ADS)

Wu, Hong; Li, Yu; Teng, Min; Yang, Yu

2017-11-01

The activity of coal gangue by thermal activation and composite activation technologies was investigated. The crystal composition, framework structure and morphology change were analyzed by XRD, FT-IR and SEM, respectively. The cementitious property of coal gangue was measured by strength test. The results showed that thermal activation decomposed kaolinite in coal gangue, and formed the metastable structure with a porous state, multiple internal broken bonds and large specific surface areas. Based on thermal activation, the added lime provided the alkaline environment, then this reduced the bond energy of reactant particles and the degree of crystallinity of quartz in coal gangue. The two activation methods could effectively improve the cementitious property of coal gangue based unburned bricks, and that the composite activation technology was superior performance.

Compressive and swelling behavior of cuttlebone derived hydroxyapatite loaded PVA hydrogel implants for articular cartilage

NASA Astrophysics Data System (ADS)

Kumar, B. Y. Santosh; Kumar, G. C. Mohan; Isloor, Arun M.

2018-04-01

Developing a novel antibacterial, nontoxic and biocompatible hydrogel with superior physio mechanical properties is still becoming a challenge. Herein, we synthesize hydroxyapatite (HA) powder from cuttlefish bone and prepare a series of stiff, tough, high strength, biocompatible hydrogel reinforced with HA by integrating glutaraldehyde into PVA/HA. Powder was characterized by SEM and XRD. Compressive strength and swelling properties are studied and compare the results with the properties of healthy natural articular cartilage.

Manufacturing and Characterization of 18Ni Marage 300 Lattice Components by Selective Laser Melting

PubMed Central

Contuzzi, Nicola; Campanelli, Sabina L.; Casavola, Caterina; Lamberti, Luciano

2013-01-01

The spreading use of cellular structures brings the need to speed up manufacturing processes without deteriorating mechanical properties. By using Selective Laser Melting (SLM) to produce cellular structures, the designer has total freedom in defining part geometry and manufacturing is simplified. The paper investigates the suitability of Selective Laser Melting for manufacturing steel cellular lattice structures with characteristic dimensions in the micrometer range. Alternative lattice topologies including reinforcing bars in the vertical direction also are considered. The selected lattice structure topology is shown to be superior over other lattice structure designs considered in literature. Compression tests are carried out in order to evaluate mechanical strength of lattice strut specimens made via SLM. Compressive behavior of samples also is simulated by finite element analysis and numerical results are compared with experimental data in order to assess the constitutive behavior of the lattice structure designs considered in this study. Experimental data show that it is possible to build samples of relative density in the 0.2456–0.4367 range. Compressive strength changes almost linearly with respect to relative density, which in turns depends linearly on the number of vertical reinforces. Specific strength increases with cell and strut edge size. Numerical simulations confirm the plastic nature of the instability phenomena that leads the cellular structures to collapse under compression loading. PMID:28811445

Comparative effectiveness of lumbar stabilization, dynamic strengthening, and Pilates on chronic low back pain: randomized clinical trial.

PubMed

Bhadauria, Esha A; Gurudut, Peeyoosha

2017-08-01

The aim of the present study was to compare three different forms of exercises namely lumbar stabilization, dynamic strengthening, and Pilates on chronic low back pain (LBP) in terms of pain, range of motion, core strength and function. In this study, 44 subjects suffering from non-specific LBP for more than 3 months were randomly allocated into the lumbar stabilization group, the dynamic strengthening group, and the Pilates group. Ten sessions of exercises for 3 weeks were prescribed along with interferential current and hot moist pack. Pain was assessed by visual analog scale, functional affection by modified Oswestry Disability Questionnaire, range of motion by assessing lumbar flexion and extension by modified Schober test and core strength was assessed by pressure biofeedback on day 1 and day 10 of the treatment. There was reduction of pain, improvement in range of motion, functional ability and core strength in all the 3 exercise groups. The improvement was significantly greater in the lumbar stabilization group for all the outcome measures, when compared the posttreatment after 10th session. Pairwise comparison showed that there was greater reduction of disability in the Pilates group than the dynamic strengthening group. It was concluded that the lumbar stabilization is more superior compared to the dynamic strengthening and Pilates in chronic nonspecific LBP. However, long-term benefits need to be assessed and compared with prospective follow-up studies.

Comparison of retention models for polymers 1. Poly(ethylene glycol)s.

PubMed

Bashir, Mubasher A; Radke, Wolfgang

2006-10-27

The suitability of three different retention models to predict the retention times of poly(ethylene glycol)s (PEGs) in gradient and isocratic chromatography was investigated. The models investigated were the linear (LSSM) and the quadratic solvent strength model (QSSM). In addition, a model describing the retention behaviour of polymers was extended to account for gradient elution (PM). It was found that all models are suited to properly predict gradient retention volumes provided the extraction of the analyte specific parameters is performed from gradient experiments as well. The LSSM and QSSM on principle cannot describe retention behaviour under critical or SEC conditions. Since the PM is designed to cover all three modes of polymer chromatography, it is therefore superior to the other models. However, the determination of the analyte specific parameters, which are needed to calibrate the retention behaviour, strongly depend on the suitable selection of initial experiments. A useful strategy for a purposeful selection of these calibration experiments is proposed.

Carbon fiber composites for cryogenic filament-wound vessels

NASA Technical Reports Server (NTRS)

Larsen, J. V.; Simon, R. A.

1972-01-01

Advanced unidirectional and bidirectional carbon fiber/epoxy resin composites were evaluated for physical and mechanical properties over a cryogenic to room temperature range for potential application to cryogenic vessels. The results showed that Courtaulds HTS carbon fiber was the superior fiber in terms of cryogenic strength properties in epoxy composites. Of the resin systems tested in ring composites, CTBN/ERLB 4617 exhibited the highest composite strengths at cryogenic temperatures, but very low interlaminar shear strengths at room temperature. Tests of unidirectional and bidirectional composite bars showed that the Epon 828/Empol 1040 resin was better at all test temperatures. Neither fatigue cycling nor thermal shock had a significant effect on composite strengths or moduli. Thermal expansion measurements gave negative values in the fiber direction and positive values in the transverse direction of the composites.

A New Maraging Stainless Steel with Excellent Strength-Toughness-Corrosion Synergy.

PubMed

Tian, Jialong; Wang, Wei; Babar Shahzad, M; Yan, Wei; Shan, Yiyin; Jiang, Zhouhua; Yang, Ke

2017-11-10

A new maraging stainless steel with superior strength-toughness-corrosion synergy has been developed based on an innovative concept of alloy design. The high strength-toughness combination is achieved by forming dispersive nano-sized intermetallic compounds in the soft lath martensitic matrix with a slight amount of residual austenite. The good corrosion resistance is guaranteed by exactly controlling the Co content based on understanding the synergistic effect between Co and Cr. The fine structure characteristics of two dominant strengthening precipitations including Ni₃Ti and Mo-rich phases were finely characterized associated with transmission electron microscope (TEM) and atom probe tomography (APT) analyses. The relationship among microstructure, strength and toughness is discussed. The precipitation mechanism of different precipitates in the new maraging stainless steel is revealed based on the APT analysis.

Experimental investigation of the effect of surface markings on the mechanical integrity of weathering bridge steels : [summary].

DOT National Transportation Integrated Search

2014-11-01

High-strength low-alloy steel (HSLA) weathering : steels are the conventional choice for fracture-critical members in bridge construction. HSLA : weathering steels offer superior corrosion : resistance, important in Floridas humid and : coastal en...

Accuracy of magnetic resonance imaging, magnetic resonance arthrography and computed tomography for the detection of chondral lesions of the knee.

PubMed

Smith, Toby O; Drew, Benjamin T; Toms, Andoni P; Donell, Simon T; Hing, Caroline B

2012-12-01

To assess the diagnostic test accuracy of magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA) and computed tomography arthrography (CTA) for the detection of chondral lesions of the patellofemoral and tibiofemoral joints. A review of published and unpublished literature sources was conducted on 22nd September 2011. All studies assessing the diagnostic test accuracy (sensitivity/specificity) of MRI or MRA or CTA for the assessment of adults with chondral (cartilage) lesions of the knee (tibiofemoral/patellofemoral joints) with surgical comparison (arthroscopic or open) as the reference test were included. Data were analysed through meta-analysis. Twenty-seven studies assessing 2,592 knees from 2,509 patients were included. The findings indicated that whilst presenting a high specificity (0.95-0.99), the sensitivity of MRA, MRI and CTA ranged from 0.70 to 0.80. MRA was superior to MRI and CTA for the detection of patellofemoral joint chondral lesions and that higher field-strength MRI scanner and grade four lesions were more accurately detected compared with lower field-strength and grade one lesions. There appeared no substantial difference in diagnostic accuracy between the interpretation from musculoskeletal and general radiologists when undertaking an MRI review of tibiofemoral and patellofemoral chondral lesions. Specialist radiological imaging is specific for cartilage disease in the knee but has poorer sensitivity to determine the therapeutic options in this population. Due to this limitation, there remains little indication to replace the 'gold-standard' arthroscopic investigation with MRI, MRA or CTA for the assessment of adults with chondral lesions of the knee. II.

A virtual reality test identifies the visuospatial strengths of adolescents with dyslexia.

PubMed

Attree, Elizabeth A; Turner, Mark J; Cowell, Naina

2009-04-01

Research suggests that the deficits characterizing dyslexia may also be associated with superior visuospatial abilities. Other research suggests that superior visuospatial abilities of people with dyslexia may not have been so far identified because of the lack of appropriate tests of real-life spatial ability. A recent small-scale study found that visuospatial superiority was evident in men with dyslexia. This study assessed the visuospatial ability of adolescents with dyslexia in order to determine whether these adolescents performed better on a pseudo real-life visuospatial test than did their nondyslexic peers. Forty-two adolescents took part in the study. There was an equal numerical split between the experimental and control groups. The experimental group all had a diagnosis of dyslexia by an educational psychologist or specialist teacher. Visuospatial ability was assessed using the Recall of Designs and the Pattern Construction subtests from the British Ability Scales (2nd edition; BAS-11) together with a computer-generated virtual environment test. The assessments were administered in a counterbalanced order. Adolescents with dyslexia tended to perform less well than their nondyslexic peers on the BAS-11 tests; however, this difference was not statistically significant. For the computer-generated virtual environment test (pseudo real-life measure), statistically significant higher scores were achieved by the dyslexic group. These findings suggest that adolescents with dyslexia may exhibit superior visuospatial strengths on certain pseudo real-life tests of spatial ability. The usefulness of these findings is discussed in relation to possible implications for assessment and educational intervention programs for adolescents with dyslexia.

Mechanical properties of acacia and eucalyptus wood chars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, M.; Verma, B.B.; Gupta, R.C.

1999-10-01

In the present investigation the effects of carbonization conditions (temperature and heating rate) on the mechanical properties (such as crushing and impact strengths and shatter index) of acacia and eucalyptus wood chars have been determined. The crushing and impact strengths of both the acacia and eucalyptus wood chars (made by slow carbonization) decreased with increase of preparation temperature up to 600 C, followed by an increase thereafter. These wood chars showed a continuous increase in shatter index values with carbonization temperature. In contrast to slow carbonization (heating rate 4 C min{sup {minus}1}), rapid carbonization (heating rate 30 C min{sup {minus}1})more » yielded chars of lower crushing strengths. Slowly carbonized eucalyptus wood gave chars of superior crushing and impact strengths than those produced from acacia wood under the same carbonization conditions. The crushing and impact strengths of these wood chars, in general, have shown an increase with increase in their apparent density. The crushing strength of cubic-shaped wood char decreased with increase in size.« less

A comparison of obsidian and surgical steel scalpel wound healing in rats.

PubMed

Disa, J J; Vossoughi, J; Goldberg, N H

1993-10-01

There are several anecdotal clinical articles claiming wound healing and scar superiority using obsidian (volcanic glass) scalpels. In order to determine if skin incisions made with obsidian were superior to those made with standard surgical steel, wound tensile strength, scar width, and histology were assessed in 40 adult male Sprague-Dawley rats. Each rat received two parallel 8-cm dorsal skin incisions, one with an obsidian scalpel and the other with a surgical steel scalpel (no. 15 blade). Data were analyzed by ANOVA. Tensile strength of the two wound types was not different at 7, 14, 21, and 42 days. Scar width, however, was significantly less in the obsidian wounds at 7, 10, and 14 days (p < 0.005). At 21 days, scar width was not different in the two groups. At 42 days, all wounds were barely detectable, thus precluding scar width analysis. A blinded histologic review suggested that obsidian wounds contained fewer inflammatory cells and less granulation tissue at 7 days.

An oxide dispersion strengthened Ni-W-Al alloy with superior high temperature strength

NASA Technical Reports Server (NTRS)

Glasgow, T. K.

1976-01-01

Oxide dispersion strengthened alloys based on the WAZ-20 nickel-base alloy were prepared by the mechanical alloying process described by Benjamin (1973), and evaluated. The results of microstructural examinations and mechanical property determinations are discussed. It is shown that WAZ-20, a high gamma-prime fraction alloy having a high gamma-prime solvus temperature, can be effectively dispersion strengthened. The strengths obtained were outstanding, especially at 1150 and 1205 C. The strength is attributed to a combination of highly alloyed matrix, elongated grain structure, and hard phase dispersion. Tensile ductility can be improved by post-recrystallization heat treatment. The new alloy shows some potential for low stress post-extrusion forming.

Less-invasive stabilization of rib fractures by intramedullary fixation: a biomechanical evaluation.

PubMed

Bottlang, Michael; Helzel, Inga; Long, William; Fitzpatrick, Daniel; Madey, Steven

2010-05-01

This study evaluated intramedullary fixation of rib fractures with Kirschner wires and novel ribs splints. We hypothesized that rib splints can provide equivalent fixation strength while avoiding complications associated with Kirschner wires, namely wire migration and cutout. The durability, strength, and failure modes of rib fracture fixation with Kirschner wires and rib splints were evaluated in 22 paired human ribs. First, intact ribs were loaded to failure to determine their strength. After fracture fixation with Kirschner wires and rib splints, fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load to determine their durability. Finally, constructs were loaded to failure to determine residual strength and failure modes. All constructs sustained dynamic loading without failure. Dynamic loading caused three times more subsidence in Kirschner wire constructs (1.2 mm +/- 1.4 mm) than in rib splint constructs (0.4 mm +/- 0.2 mm, p = 0.09). After dynamic loading, rib splint constructs remained 48% stronger than Kirschner wire constructs (p = 0.001). Five of 11 Kirschner wire constructs failed catastrophically by cutting through the medial cortex, leading to complete loss of stability and wire migration through the lateral cortex. The remaining six constructs failed by wire bending. Rib splint constructs failed by development of fracture lines along the superior and interior cortices. No splint construct failed catastrophically, and all splint constructs retained functional reduction and fixation. Because of their superior strength and absence of catastrophic failure mode, rib splints can serve as an attractive alternative to Kirschner wires for intramedullary stabilization of rib fractures, especially in the case of posterior rib fractures where access for plating is limited.

Ion release and mechanical properties of calcium silicate and calcium hydroxide materials used for pulp capping.

PubMed

Natale, L C; Rodrigues, M C; Xavier, T A; Simões, A; de Souza, D N; Braga, R R

2015-01-01

To compare the ion release and mechanical properties of a calcium hydroxide (Dycal) and two calcium silicate (MTA Angelus and Biodentine) cements. Calcium and hydroxyl ion release in water from 24-h set cements were calculated from titration with HCl (n = 3). Calcium release after 7, 14, 21 and 28 days at pH 5.5 and 7.0 was measured using ICP-OES (n = 6). Flexural strength (FS) and modulus (E) were tested after 48-h storage, and compressive strength (CS) was tested after 48 h and 7 days (n = 10). Ion release and mechanical data were subjected to anova/Tukey and Kruskal-Wallis/Mann-Whitney tests, respectively (α = 0.05). Titration curves revealed that Dycal released significantly fewer ions in solution than calcium silicates (P < 0.001). Calcium release remained constant at pH 7.0, whilst at pH 5.5, it dropped significantly by 24% after 21 days (P < 0.05). At pH 5.5, MTA Angelus released significantly more calcium than Dycal (P < 0.01), whilst Biodentine had superior ion release than Dycal at pH 7.0 (P < 0.01). Biodentine had superior flexural strength, flexural modulus and compressive strength than the other cements, whilst MTA Angelus had higher modulus than Dycal (P < 0.001). Immediate calcium and hydroxyl ion release in solution was significantly lower for Dycal. In general, all materials released constant calcium levels over 28 days, but release from Dycal was significantly lower than Biodentine and MTA Angelus depending on pH conditions. Biodentine had substantially higher strength and modulus than MTA Angelus and Dycal, both of which demonstrated low stress-bearing capabilities. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

A Comparative Study of the Retentive Strengths of Commercial and Indigenously Developed Luting Cements using Both Lathe-cut and Clinically Simulated Specimens.

PubMed

Mathew, Joe; Kurian, Byju P; Philip, Biju; Mohammed, Sunil; Menon, Preetha; Raj, Rajan S

2016-08-01

Superior adhesive strength in luting agents is of paramount significance in fixed partial denture success. In this in vitro study five cements were tested for retentive qualities, using both lathe-cut and hand-prepared specimens. A total of 104 freshly extracted tooth specimens were prepared. Seventy of them were lathe-cut and 30 specimens were hand-prepared to simulate clinical conditions. Five different cements were tested, which included a compomer, a composite, a zinc phosphate, and 2 glass-ionomer luting cements. Of the 5, 2 trial cements were indigenously developed by Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, India - a glass-ionomer cement (Chitra GIC) and a chemical-cure composite (Chitra CCC). All cements were compared within each group and between groups (lathe-prepared and hand-prepared). GC Fuji 1 (GC America) exhibited superior retentive strengths in both lathe-cut and hand-prepared specimens, whereas the compomer cement displayed the lowest values when tested. In lathe-cut specimens, statistical analysis showed no significant difference between GC Fuji 1 and indigenously developed Chitra CCC. Both Chitra CCC and GC Fuji 1 have comparable strengths in lathe-cut samples, making Chitra CCC a potential luting agent. Statistical analysis reveals that all cements, except GC Fuji 1, exhibited a significant decrease in strength due to the change in design uniformity. The chemical bonding of GC Fuji 1 proves to be quite strong irrespective of shape and precision of the tooth crown. The indigenously developed Chitra GIC and Chitra CCC showed promising results to be used as a potential luting agent.

Structural connectivity of right frontal hyperactive areas scales with stuttering severity

PubMed Central

Neef, Nicole E; Bütfering, Christoph; Schmidt-Samoa, Carsten; Friederici, Angela D; Paulus, Walter; Sommer, Martin

2018-01-01

Abstract A neuronal sign of persistent developmental stuttering is the magnified coactivation of right frontal brain regions during speech production. Whether and how stuttering severity relates to the connection strength of these hyperactive right frontal areas to other brain areas is an open question. Scrutinizing such brain–behaviour and structure–function relationships aims at disentangling suspected underlying neuronal mechanisms of stuttering. Here, we acquired diffusion-weighted and functional images from 31 adults who stutter and 34 matched control participants. Using a newly developed structural connectivity measure, we calculated voxel-wise correlations between connection strength and stuttering severity within tract volumes that originated from functionally hyperactive right frontal regions. Correlation analyses revealed that with increasing speech motor deficits the connection strength increased in the right frontal aslant tract, the right anterior thalamic radiation, and in U-shaped projections underneath the right precentral sulcus. In contrast, with decreasing speech motor deficits connection strength increased in the right uncinate fasciculus. Additional group comparisons of whole-brain white matter skeletons replicated the previously reported reduction of fractional anisotropy in the left and right superior longitudinal fasciculus as well as at the junction of right frontal aslant tract and right superior longitudinal fasciculus in adults who stutter compared to control participants. Overall, our investigation suggests that right fronto-temporal networks play a compensatory role as a fluency enhancing mechanism. In contrast, the increased connection strength within subcortical-cortical pathways may be implied in an overly active global response suppression mechanism in stuttering. Altogether, this combined functional MRI–diffusion tensor imaging study disentangles different networks involved in the neuronal underpinnings of the speech motor deficit in persistent developmental stuttering. PMID:29228195

Structural connectivity of right frontal hyperactive areas scales with stuttering severity.

PubMed

Neef, Nicole E; Anwander, Alfred; Bütfering, Christoph; Schmidt-Samoa, Carsten; Friederici, Angela D; Paulus, Walter; Sommer, Martin

2018-01-01

A neuronal sign of persistent developmental stuttering is the magnified coactivation of right frontal brain regions during speech production. Whether and how stuttering severity relates to the connection strength of these hyperactive right frontal areas to other brain areas is an open question. Scrutinizing such brain-behaviour and structure-function relationships aims at disentangling suspected underlying neuronal mechanisms of stuttering. Here, we acquired diffusion-weighted and functional images from 31 adults who stutter and 34 matched control participants. Using a newly developed structural connectivity measure, we calculated voxel-wise correlations between connection strength and stuttering severity within tract volumes that originated from functionally hyperactive right frontal regions. Correlation analyses revealed that with increasing speech motor deficits the connection strength increased in the right frontal aslant tract, the right anterior thalamic radiation, and in U-shaped projections underneath the right precentral sulcus. In contrast, with decreasing speech motor deficits connection strength increased in the right uncinate fasciculus. Additional group comparisons of whole-brain white matter skeletons replicated the previously reported reduction of fractional anisotropy in the left and right superior longitudinal fasciculus as well as at the junction of right frontal aslant tract and right superior longitudinal fasciculus in adults who stutter compared to control participants. Overall, our investigation suggests that right fronto-temporal networks play a compensatory role as a fluency enhancing mechanism. In contrast, the increased connection strength within subcortical-cortical pathways may be implied in an overly active global response suppression mechanism in stuttering. Altogether, this combined functional MRI-diffusion tensor imaging study disentangles different networks involved in the neuronal underpinnings of the speech motor deficit in persistent developmental stuttering. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency.

PubMed

Yang, Xuan; Berthold, Fredrik; Berglund, Lars A

2018-05-23

To expand the use of renewable materials, paper products with superior mechanical and optical properties are needed. Although beating, bleaching, and additives are known to improve industrially produced Kraft pulp papers, properties are limited by the quality of the fibers. While the use of nanocellulose has been shown to significantly increase paper properties, the current cost associated with their production has limited their industrial relevance. Here, using a simple mild peracetic acid (PAA) delignification process on spruce, we produce hemicellulose-rich holocellulose fibers (28.8 wt %) with high intrinsic strength (1200 MPa for fibers with microfibrillar angle smaller than 10°). We show that PAA treatment causes less cellulose/hemicellulose degradation and better preserves cellulose nanostructure in comparison to conventional Kraft pulping. High-density holocellulose papers with superior mechanical properties (Young's modulus of 18 GPa and ultimate strength of 195 MPa) are manufactured using a water-based hot-pressing process, without the use of beating or additives. We propose that the preserved hemicelluloses act as "glue" in the interfiber region, improving both mechanical and optical properties of papers. Holocellulose fibers may be affordable and applicable candidates for making special paper/composites where high mechanical performance and/or optical transmittance are of interest.

A comparative clinical evaluation of arthroscopic single-row versus double-row supraspinatus tendon repair.

PubMed

Buess, Eduard; Waibl, Bernhard; Vogel, Roger; Seidner, Robert

2009-10-01

Cadaveric studies and commercial pressure have initiated a strong trend towards double-row repair in arthroscopic cuff surgery. The objective of this study was to evaluate if the biomechanical advantages of a double-row supraspinatus tendon repair would result in superior clinical outcome and higher abduction strength. A retrospective study of two groups of 32 single-row and 33 double-row repairs of small to medium cuff tears was performed. The Simple Shoulder Test (SST) and a visual analog scale for pain were used to evaluate the outcome. The participation rate was 100%. A subset of patients was further investigated with the Constant Score (CS) including electronic strength measurement. The double-row repair patients had significantly more (p = 0.01) yes answers in the SST than the single-row group, and pain reduction was slightly better (p = 0.03). No difference was found for the relative CS (p = 0.86) and abduction strength (p = 0.74). Patient satisfaction was 100% for double-row and 97% for single-row repair. Single- and double-row repairs both achieved excellent clinical results. Evidence of superiority of double-row repair is still scarce and has to be balanced against the added complexity of the procedure and higher costs.

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

2016-04-01

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

Interacting Watershed Size and Landcover Influences on Habitat and Biota of Lake Superior Coastal Wetlands

EPA Science Inventory

Coastal wetlands are important contributors to the productivity and biodiversity of large lakes and important mediators of the lake - watershed connection. This study explores how strength of connection to the watershed (represented by watershed size and wetland morphological ty...

Investigation of a Training Shoe as a Supplemental Conditioning Device

ERIC Educational Resources Information Center

McKinney, Donald; And Others

1975-01-01

This study investigated the use of the "LEGG" Shoe as a supplemental conditioner for leg strength, flexibility, and sprint speed of college varisity football players. The investigation concluded that a program using the "LEGG" Shoe was significantly superior to the regular conditioning program. (RC)

Microstructure and Mechanical Properties of Reaction-Formed Silicon Carbide (RFSC) Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.; Behrendt, D. R.

1994-01-01

The microstructure and mechanical properties of reaction-formed silicon carbide (RFSC) ceramics fabricated by silicon infiltration of porous carbon preforms are discussed. The morphological characterization of the carbon preforms indicates a very narrow pore size distribution. Measurements of the preform density by physical methods and by mercury porosimetry agree very well and indicate that virtually all of the porosity in the preforms is open to infiltrating liquids. The average room temperature flexural strength of the RFSC material with approximately 8 at.% free silicon is 369 +/- 28 MPa (53.5 +/- 4 ksi). The Weibull strength distribution data give a characteristic strength value of 381 MPa (55 ksi) and a Weibull modulus of 14.3. The residual silicon content is lower and the strengths are superior to those of most commercially available reaction-bonded silicon carbide materials.

Solidification/stabilization of dredged marine sediments for road construction.

PubMed

Wang, Dong Xing; Abriak, Nor Edine; Zentar, Rachid; Xu, WeiYa

2012-01-01

Cement/lime-based solidification is an environmentally sound solution for the management of dredged marine sediments, instead of traditional solutions such as immersion. Based on the mineralogical composition and physical characteristics of Dunkirk sediments, the effects of cement and lime are assessed through Atterberg limits, modified Proctor compaction, unconfined compressive strength and indirect tensile strength tests. The variation of Atterberg limits and the improvement in strength are discussed at different binder contents. The potential of sediments solidified with cement or lime for road construction is evaluated through a proposed methodology from two aspects: I-CBR value and material classification. The test results show the feasibility of solidified dredged sediments for beneficial use as a material in road construction. Cement is superior to lime in terms of strength improvement, and adding 6% cement is an economic and reasonable method to stabilize fine sediments.

Thermomechanical processing of HAYNES alloy No. 188 sheet to improve creep strength

NASA Technical Reports Server (NTRS)

Klarstrom, D. L.

1978-01-01

Improvements in the low strain creep strength of HAYNES alloy No. 188 thin gauge sheet by means of thermomechanical processing were developed. Processing methods designed to develop a sheet with strong crystallographic texture after recrystallization and to optimize grain size were principally studied. The effects of thickness-to-grain diameter ratio and prestrain on low strain creep strength were also briefly examined. Results indicate that the most significant improvements were obtained in the sheets having a strong crystallographic texture. The low strain creep strength of the textured sheets was observed to be superior to that of standard production sheets in the 922 K to 1255 K temperature range. Tensile, stress rupture, fabricability, and surface stability properties of the experimental sheets were also measured and compared to property values reported for the baseline production sheets.

Hybrid PET/MR imaging in two sarcoma patients - clinical benefits and implications for future trials.

PubMed

Partovi, Sasan; Kohan, Andres A; Zipp, Lisa; Faulhaber, Peter; Kosmas, Christos; Ros, Pablo R; Robbin, Mark R

2014-01-01

PET/MRI is an evolving hybrid imaging modality which combines the inherent strengths of MRIs soft-tissue and contrast resolution and PETs functional metabolic capabilities. Bone and soft-tissue sarcoma are a relatively rare tumor entity, relying on MRI for local staging and often on PET/CT for lymph node involvement and metastatic spread evaluation. The purpose of this article is to demonstrate the successful use of PET/MRI in two sarcoma patients. We also use these patients as a starting point to discuss how PET/MRI might be of value in sarcoma. Among its potential benefits are: superior TNM staging than either modality alone, decreased radiation dose, more sensitive and specific follow-up and better assessment of treatment response. These potentials need to be investigated in future PET/MRI soft-tissue sarcoma trials.

Theoretical studies on 2-diazo-4,6-dinitrophenol derivatives aimed at finding superior propellants.

PubMed

Liu, Yan; Wang, Lianjun; Wang, Guixiang; Du, Hongchen; Gong, Xuedong

2012-04-01

In an attempt to find superior propellants, 2-diazo-4,6-dinitrophenol (DDNP) and its -NO(2), -NH(2), -CN, -NC, -ONO(2), and -NF(2) derivatives were studied at the B3LYP/6-311++G level of density functional theory (DFT). Sensitivity was evaluated using bond dissociation enthalpies (BDEs) and molecular surface electrostatic potentials. The C-NO(2) bond appears to be the trigger bond during the thermolysis process for these compounds, except for the -ONO(2) and -NF(2) derivatives. Electrostatic potential results show that electron-withdrawing substituents make the charge imbalance more anomalous, which may change the strength of the bond, especially the weakest trigger bond. Most of the DDNP derivatives have the impact sensitivities that are higher than that of DDNP, making them favorable for use as solid propellants in micro-rockets. The theoretical densities (ρ), heats of formation (HOFs), detonation energies (Q), detonation pressures (P), and detonation velocities (D) of the compounds were estimated. The effects of various substituent groups on ρ, HOF, Q, D, and P were investigated. Some derivatives exhibit perfect detonation properties. The calculated relative specific impulses (I (r,sp)) of all compounds except for -NH(2) derivatives were higher than that of DDNP, and also meet the requirements of propellants.

How music alters a kiss: superior temporal gyrus controls fusiform-amygdalar effective connectivity.

PubMed

Pehrs, Corinna; Deserno, Lorenz; Bakels, Jan-Hendrik; Schlochtermeier, Lorna H; Kappelhoff, Hermann; Jacobs, Arthur M; Fritz, Thomas Hans; Koelsch, Stefan; Kuchinke, Lars

2014-11-01

While watching movies, the brain integrates the visual information and the musical soundtrack into a coherent percept. Multisensory integration can lead to emotion elicitation on which soundtrack valences may have a modulatory impact. Here, dynamic kissing scenes from romantic comedies were presented to 22 participants (13 females) during functional magnetic resonance imaging scanning. The kissing scenes were either accompanied by happy music, sad music or no music. Evidence from cross-modal studies motivated a predefined three-region network for multisensory integration of emotion, consisting of fusiform gyrus (FG), amygdala (AMY) and anterior superior temporal gyrus (aSTG). The interactions in this network were investigated using dynamic causal models of effective connectivity. This revealed bilinear modulations by happy and sad music with suppression effects on the connectivity from FG and AMY to aSTG. Non-linear dynamic causal modeling showed a suppressive gating effect of aSTG on fusiform-amygdalar connectivity. In conclusion, fusiform to amygdala coupling strength is modulated via feedback through aSTG as region for multisensory integration of emotional material. This mechanism was emotion-specific and more pronounced for sad music. Therefore, soundtrack valences may modulate emotion elicitation in movies by differentially changing preprocessed visual information to the amygdala. © The Author (2013). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

How music alters a kiss: superior temporal gyrus controls fusiform–amygdalar effective connectivity

PubMed Central

Deserno, Lorenz; Bakels, Jan-Hendrik; Schlochtermeier, Lorna H.; Kappelhoff, Hermann; Jacobs, Arthur M.; Fritz, Thomas Hans; Koelsch, Stefan; Kuchinke, Lars

2014-01-01

While watching movies, the brain integrates the visual information and the musical soundtrack into a coherent percept. Multisensory integration can lead to emotion elicitation on which soundtrack valences may have a modulatory impact. Here, dynamic kissing scenes from romantic comedies were presented to 22 participants (13 females) during functional magnetic resonance imaging scanning. The kissing scenes were either accompanied by happy music, sad music or no music. Evidence from cross-modal studies motivated a predefined three-region network for multisensory integration of emotion, consisting of fusiform gyrus (FG), amygdala (AMY) and anterior superior temporal gyrus (aSTG). The interactions in this network were investigated using dynamic causal models of effective connectivity. This revealed bilinear modulations by happy and sad music with suppression effects on the connectivity from FG and AMY to aSTG. Non-linear dynamic causal modeling showed a suppressive gating effect of aSTG on fusiform–amygdalar connectivity. In conclusion, fusiform to amygdala coupling strength is modulated via feedback through aSTG as region for multisensory integration of emotional material. This mechanism was emotion-specific and more pronounced for sad music. Therefore, soundtrack valences may modulate emotion elicitation in movies by differentially changing preprocessed visual information to the amygdala. PMID:24298171

Application of C/C composites to the combustion chamber of rocket engines. Part 1: Heating tests of C/C composites with high temperature combustion gases

NASA Astrophysics Data System (ADS)

Tadano, Makoto; Sato, Masahiro; Kuroda, Yukio; Kusaka, Kazuo; Ueda, Shuichi; Suemitsu, Takeshi; Hasegawa, Satoshi; Kude, Yukinori

1995-04-01

Carbon fiber reinforced carbon composite (C/C composite) has various superior properties, such as high specific strength, specific modulus, and fracture strength at high temperatures of more than 1800 K. Therefore, C/C composite is expected to be useful for many structural applications, such as combustion chambers of rocket engines and nose-cones of space-planes, but C/C composite lacks oxidation resistivity in high temperature environments. To meet the lifespan requirement for thermal barrier coatings, a ceramic coating has been employed in the hot-gas side wall. However, the main drawback to the use of C/C composite is the tendency for delamination to occur between the coating layer on the hot-gas side and the base materials on the cooling side during repeated thermal heating loads. To improve the thermal properties of the thermal barrier coating, five different types of 30-mm diameter C/C composite specimens constructed with functionally gradient materials (FGM's) and a modified matrix coating layer were fabricated. In this test, these specimens were exposed to the combustion gases of the rocket engine using nitrogen tetroxide (NTO) / monomethyl hydrazine (MMH) to evaluate the properties of thermal and erosive resistance on the thermal barrier coating after the heating test. It was observed that modified matrix and coating with FGM's are effective in improving the thermal properties of C/C composite.

Systematic review on strength training in Parkinson’s disease: an unsolved question

PubMed Central

Ramazzina, Ileana; Bernazzoli, Benedetta; Costantino, Cosimo

2017-01-01

The purpose of this study was to investigate the effectiveness of strength training, performed against a different resistance from body weight, in improving motor and nonmotor symptoms in patients with Parkinson’s disease (PD). The following electronic databases were searched: PubMed, Physiotherapy Evidence Database, Cochrane Central Register of Controlled Trials, Scopus, and Web of Science. The review was conducted and reported in accordance with the PRISMA statement. Thirteen high-quality randomized controlled trials were included. Strength training performed against external resistance is well tolerated and appears to be a suitable physical activity to improve both physical parameters and quality of life parameters of PD subjects. However, although the study intervention included strength training, only a few selected studies assessed the improvement of muscle strength. Despite the encouraging results, it is difficult to establish a correlation between strength training and the improvements made. Our review highlights the lack of common intent in terms of study design and the presence of different primary and secondary outcomes. Accordingly, further studies are needed to support the beneficial effects of different types of strength training in PD subjects and to underline the superiority of strength training in PD patients with respect to other training. PMID:28408811

New QCT analysis approach shows the importance of fall orientation on femoral neck strength.

PubMed

Carpenter, R Dana; Beaupré, Gary S; Lang, Thomas F; Orwoll, Eric S; Carter, Dennis R

2005-09-01

The influence of fall orientation on femur strength has important implications for understanding hip fracture risk. A new image analysis technique showed that the strength of the femoral neck in 37 males varied significantly along the neck axis and that bending strength varied by a factor of up to 2.8 for different loading directions. Osteoporosis is associated with decreased BMD and increased hip fracture risk, but it is unclear whether specific osteoporotic changes in the proximal femur lead to a more vulnerable overall structure. Nonhomogeneous beam theory, which is used to determine the mechanical response of composite structures to applied loads, can be used along with QCT to estimate the resistance of the femoral neck to axial forces and bending moments. The bending moment [My(theta)] sufficient to induce yielding within femoral neck sections was estimated for a range of bending orientations (theta) using in vivo QCT images of 37 male (mean age, 73 years; range, 65-87 years) femora. Volumetric BMD, axial stiffness, average moment at yield (M(y,avg)), maximum and minimum moment at yield (M(y,max) and M(y,min)), bone strength index (BSI), stress-strain index (SSI), and density-weighted moments of resistance (Rx and Ry) were also computed. Differences among the proximal, mid-, and distal neck regions were detected using ANOVA. My(theta) was found to vary by as much as a factor of 2.8 for different bending directions. Axial stiffness, M(y,avg), M(y,max), M(y,min), BSI, and Rx differed significantly between all femoral neck regions, with an overall trend of increasing axial stiffness and bending strength when moving from the proximal neck to the distal neck. Mean axial stiffness increased 62% between the proximal and distal neck, and mean M(y,avg) increased 53% between the proximal and distal neck. The results of this study show that femoral neck strength strongly depends on both fall orientation and location along the neck axis. Compressive yielding in the superior portion of the femoral neck is expected to initiate fracture in a fall to the side.

Treatment of Phobic Disorders Using Cognitive and Exposure Methods: A Self-Efficacy Analysis.

ERIC Educational Resources Information Center

Biran, Mia; Wilson, G. Terence

1981-01-01

Examined predictions derived from self-efficacy theory in comparing the effects of exposure and cognitive interventions with simple phobics. Guided exposure (GE) was significantly superior to cognitive restructuring (CR) in enhancing approach behavior, increasing level and strength of self-efficacy, reducing subjective fear, and decreasing…

Gender Differences in Physical Performance Characteristics of Elite Surfers.

PubMed

Parsonage, Joanna R; Secomb, Josh L; Tran, Tai T; Farley, Oliver R L; Nimphius, Sophia; Lundgren, Lina; Sheppard, Jeremy M

2017-09-01

Parsonage, JR, Secomb, JL, Tran, TT, Farley, ORL, Nimphius, S, Lundgren, L, and Sheppard, JM. Gender differences in physical performance characteristics of elite surfers. J Strength Cond Res 31(9): 2417-2422, 2017-The purpose of this study was to describe and compare the gender differences in physical performance characteristics of elite surfers. Twenty competitive female surfers (CFS) and 20 competitive male surfers (CMS) performed a battery of physical performance tests: squat jump (SJ), isometric midthigh pull (IMTP), 15-m sprint paddle, and 400-m endurance paddle during a single testing session. All performance measures were significantly different between CFS and CMS (p < 0.01). Specifically, CMS produced greater peak force production (28.5%) and jumped higher (27.7%) in the SJ and produced greater normalized peak force during the IMTP (18.9%) compared with CFS. For paddling performance, CMS were faster over 5, 10, and 15 m (12.4%, 9.7%, and 10.9%), possessed a higher peak paddling velocity (11.3%), and recorded faster paddle times over 400 m (11.8%). The results of this study suggest that CMS exhibit superior physical performance characteristics than CFS, in relation to both the lower and upper body. Strength and conditioning practitioners should therefore implement a structured and periodized program to facilitate strength qualities that underpin surfing performance for all participants, but as highlighted in the current investigation, female surfers may have a greater window for adaptation and therefore vast benefit of targeting their underdeveloped physical qualities.

Comparative effectiveness of lumbar stabilization, dynamic strengthening, and Pilates on chronic low back pain: randomized clinical trial

PubMed Central

Bhadauria, Esha A.; Gurudut, Peeyoosha

2017-01-01

The aim of the present study was to compare three different forms of exercises namely lumbar stabilization, dynamic strengthening, and Pilates on chronic low back pain (LBP) in terms of pain, range of motion, core strength and function. In this study, 44 subjects suffering from non-specific LBP for more than 3 months were randomly allocated into the lumbar stabilization group, the dynamic strengthening group, and the Pilates group. Ten sessions of exercises for 3 weeks were prescribed along with interferential current and hot moist pack. Pain was assessed by visual analog scale, functional affection by modified Oswestry Disability Questionnaire, range of motion by assessing lumbar flexion and extension by modified Schober test and core strength was assessed by pressure biofeedback on day 1 and day 10 of the treatment. There was reduction of pain, improvement in range of motion, functional ability and core strength in all the 3 exercise groups. The improvement was significantly greater in the lumbar stabilization group for all the outcome measures, when compared the posttreatment after 10th session. Pairwise comparison showed that there was greater reduction of disability in the Pilates group than the dynamic strengthening group. It was concluded that the lumbar stabilization is more superior compared to the dynamic strengthening and Pilates in chronic nonspecific LBP. However, long-term benefits need to be assessed and compared with prospective follow-up studies. PMID:29114516

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kervick, R.; Blue, C. A.; Kadolkar, P. B.

Forging is a manufacturing process in which metal is pressed, pounded or squeezed under great pressure and, often, under high strain rates into high-strength parts known as forgings. The process is typically performed hot by preheating the metal to a desired temperature before it is worked. The forging process can create parts that are stronger than those manufactured by any other metal working process. Forgings are almost always used where reliability and human safety are critical. Forgings are normally component parts contained inside assembled items such airplanes, automobiles, tractors, ships, oil drilling equipment, engines missiles, and all kinds of capitalmore » equipment Forgings are stronger than castings and surpass them in predictable strength properties, producing superior strength that is assured, part to part.« less

Mucosal prior to systemic application of recombinant adenovirus boosting is more immunogenic than systemic application twice but confers similar protection against SIV-challenge in DNA vaccine-primed macaques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulte, Reiner; Suh, You-Suk; Sauermann, Ulrike

2009-01-20

We investigated the immunogenicity and efficacy of a bimodal prime/boost vaccine regimen given by various routes in the Simian immunodeficiency virus (SIV) rhesus monkey model for AIDS. Twelve animals were immunized with SIV DNA-vectors followed by the application of a recombinant adenovirus (rAd5) expressing the same genes either intramuscularly (i.m.) or by oropharyngeal spray. The second rAd5-application was given i.m. All vaccinees plus six controls were challenged orally with SIVmac239 12 weeks post-final immunization. Both immunization strategies induced strong SIV Gag-specific IFN-{gamma} and T-cell proliferation responses and mediated a conservation of CD4{sup +} memory T-cells and a reduction of viralmore » load during peak viremia following infection. Interestingly, the mucosal group was superior to the systemic group regarding breadth and strength of SIV-specific T-cell responses and exhibited lower vector specific immune responses. Therefore, our data warrant the inclusion of mucosal vector application in a vaccination regimen which makes it less invasive and easier to apply.« less

New scale-down methodology from commercial to lab scale to optimize plant-derived soft gel capsule formulations on a commercial scale.

PubMed

Oishi, Sana; Kimura, Shin-Ichiro; Noguchi, Shuji; Kondo, Mio; Kondo, Yosuke; Shimokawa, Yoshiyuki; Iwao, Yasunori; Itai, Shigeru

2018-01-15

A new scale-down methodology from commercial rotary die scale to laboratory scale was developed to optimize a plant-derived soft gel capsule formulation and eventually manufacture superior soft gel capsules on a commercial scale, in order to reduce the time and cost for formulation development. Animal-derived and plant-derived soft gel film sheets were prepared using an applicator on a laboratory scale and their physicochemical properties, such as tensile strength, Young's modulus, and adhesive strength, were evaluated. The tensile strength of the animal-derived and plant-derived soft gel film sheets was 11.7 MPa and 4.41 MPa, respectively. The Young's modulus of the animal-derived and plant-derived soft gel film sheets was 169 MPa and 17.8 MPa, respectively, and both sheets showed a similar adhesion strength of approximately 4.5-10 MPa. Using a D-optimal mixture design, plant-derived soft gel film sheets were prepared and optimized by varying their composition, including variations in the mass of κ-carrageenan, ι-carrageenan, oxidized starch and heat-treated starch. The physicochemical properties of the sheets were evaluated to determine the optimal formulation. Finally, plant-derived soft gel capsules were manufactured using the rotary die method and the prepared soft gel capsules showed equivalent or superior physical properties compared with pre-existing soft gel capsules. Therefore, we successfully developed a new scale-down methodology to optimize the formulation of plant-derived soft gel capsules on a commercial scale. Copyright © 2017 Elsevier B.V. All rights reserved.

Cortical thickness and prosocial behavior in school-age children: A population-based MRI study.

PubMed

Thijssen, Sandra; Wildeboer, Andrea; Muetzel, Ryan L; Bakermans-Kranenburg, Marian J; El Marroun, Hanan; Hofman, Albert; Jaddoe, Vincent W V; van der Lugt, Aad; Verhulst, Frank C; Tiemeier, Henning; van IJzendoorn, Marinus H; White, Tonya

2015-01-01

Prosocial behavior plays an important role in establishing and maintaining relationships with others and thus may have important developmental implications. This study examines the association between cortical thickness and prosocial behavior in a population-based sample of 6- to 9-year-old children. The present study was embedded within the Generation R Study. Magnetic resonance scans were acquired from 464 children whose parents had completed the prosocial scale of the Strengths and Difficulties Questionnaire. To study the association between cortical thickness and prosocial behavior, we performed whole-brain surface-based analyses. Prosocial behavior was related to a thicker cortex in a cluster that covers part of the left superior frontal and rostral middle frontal cortex (p < .001). Gender moderated the association between prosocial behavior and cortical thickness in a cluster including the right rostral middle frontal and superior frontal cortex (p < .001) as well as in a cluster covering the right superior parietal cortex, cuneus, and precuneus (p < .001). Our results suggest that prosocial behavior is associated with cortical thickness in regions related to theory of mind (superior frontal cortex, rostral middle frontal cortex cuneus, and precuneus) and inhibitory control (superior frontal and rostral middle frontal cortex).

Physical and mechanical properties of carbon fiber reinforced smart porous concrete for planting

NASA Astrophysics Data System (ADS)

Park, Seung-Bum; Kim, Jung-Hwan; Seo, Dae-Seuk

2005-05-01

The reinforcement strength of porous concrete and its applicability as a recycled aggregate was measured. Changes in physical and mechanical properties, subsequent to the mixing of carbon fiber and silica fume, were examined, and the effect of recycled aggregate depending on their mixing rate was evaluated. The applicability of planting to concrete material was also assessed. The results showed that there were not any remarkable change in the porosity and strength characteristics although its proportion of recycled aggregate increased. Also, the mixture of 10% of silica was found to be most effective for strength enforcement. In case of carbon fiber, the highest flexural strength was obtained with its mixing rate being 3%. It was also noticed that PAN-derived carbon fiber was superior to Pitch-derived ones in view of strength. The evaluation of its use for vegetation proved that the growth of plants was directly affected by the existence of covering soil, in case of having the similar size of aggregate and void.

Super-strengthening and stabilizing with carbon nanotube harnessed high density nanotwins in metals by shock loading

PubMed Central

Lin, Dong; Saei, Mojib; Suslov, Sergey; Jin, Shengyu; Cheng, Gary J.

2015-01-01

CNTs reinforced metal composites has great potential due to their superior properties, such as light weight, high strength, low thermal expansion and high thermal conductivity. The current strengthening mechanisms of CNT/metal composite mainly rely on CNTs’ interaction with dislocations and CNT’s intrinsic high strength. Here we demonstrated that laser shock loading the CNT/metal composite results in high density nanotwins, stacking fault, dislocation around the CNT/metal interface. The composites exhibit enhanced strength with excellent stability. The results are interpreted by both molecular dynamics simulation and experiments. It is found the shock wave interaction with CNTs induces a stress field, much higher than the applied shock pressure, surrounding the CNT/metal interface. As a result, nanotwins were nucleated under a shock pressure much lower than the critical values to generate twins in metals. This hybrid unique nanostructure not only enhances the strength, but also stabilize the strength, as the nanotwin boundaries around the CNTs help pin the dislocation movement. PMID:26493533

Aggressive-antisocial boys develop into physically strong young men.

PubMed

Isen, Joshua D; McGue, Matthew K; Iacono, William G

2015-04-01

Young men with superior upper-body strength typically show a greater proclivity for physical aggression than their weaker male counterparts. The traditional interpretation of this phenomenon is that young men calibrate their attitudes and behaviors to their physical formidability. Physical strength is thus viewed as a causal antecedent of aggressive behavior. The present study is the first to examine this phenomenon within a developmental framework. We capitalized on the fact that physical strength is a male secondary sex characteristic. In two longitudinal cohorts of children, we estimated adolescent change in upper-body strength using the slope parameter from a latent growth model. We found that males' antisocial tendencies temporally precede their physical formidability. Boys, but not girls, with greater antisocial tendencies in childhood attained larger increases in physical strength between the ages of 11 and 17. These results support sexual selection theory, indicating an adaptive congruence between male-typical behavioral dispositions and subsequent physical masculinization during puberty. © The Author(s) 2015.

Use of electromyography to optimize Lokomat® settings for subject-specific gait rehabilitation in post-stroke hemiparetic patients: A proof-of-concept study.

PubMed

Cherni, Yosra; Begon, Mickael; Chababe, Hicham; Moissenet, Florent

2017-09-01

While generic protocols exist for gait rehabilitation using robotic orthotics such as the Lokomat ® , several settings - guidance, body-weight support (BWS) and velocity - may be adjusted to individualize patient training. However, no systematic approach has yet emerged. Our objective was to assess the feasibility and effects of a systematic approach based on electromyography to determine subject-specific settings with application to the strengthening of the gluteus maximus muscle in post-stroke hemiparetic patients. Two male patients (61 and 65 years) with post-stroke hemiparesis performed up to 9 Lokomat ® trials by changing guidance and BWS while electromyography of the gluteus maximus was measured. For each subject, the settings that maximized gluteus maximus activity were used in 20 sessions of Lokomat ® training. Modified Functional Ambulation Classification (mFAC), 6-minutes walking test (6-MWT), and extensor strength were measured before and after training. The greatest gluteus maximus activity was observed at (Guidance: 70% -BWS: 20%) for Patient 1 and (Guidance: 80% - BWS: 30%) for Patient 2. In both patients, mFAC score increased from 4 to 7. The additional distance in 6-MWT increased beyond minimal clinically important difference (MCID=34.4m) reported for post-stroke patients. The isometric strength of hip extensors increased by 43 and 114%. Defining subject-specific settings for a Lokomat ® training was feasible and simple to implement. These two case reports suggest a benefit of this approach for muscle strengthening. It remains to demonstrate the superiority of such an approach for a wider population, compared to the use of a generic protocol. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Controlling the mechanical properties of carbon steel by thermomechanical treatment

NASA Astrophysics Data System (ADS)

Balavar, Mohsen; Mirzadeh, Hamed

2018-01-01

The effect of thermomechanical processing and heat treatment on the microstructure and mechanical properties of low carbon steel was studied. It was revealed that the dual phase ferritic-martensitic microstructure shows a good combination of tensile strength and ductility along with superior work hardening response. On the other hand, the bimodal-sized structure containing ultrafine grained (UFG) and micron-sized ferrite phase can be easily produced by cold rolling and annealing of the dual phase starting microstructure. This steel showed high yield stress, tensile strength, and ductility, but poor work hardening ability. The full annealed ferritic-pearlitic sheet with banded morphology exhibited low strength and high total elongation with the appearance of the yield point phenomenon. The martensitic steels, however, had high tensile strength and low ductility. By comparing the tensile properties of these steels, it was shown that it is possible to control the mechanical properties of low carbon steel by simple processing routes.

Shear bond strength in zirconia veneered ceramics using two different surface treatments prior veneering.

PubMed

Gasparić, Lana Bergman; Schauperl, Zdravko; Mehulić, Ketij

2013-03-01

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference = -190.67; df = 10, t = -6.386, p < 0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material.

A promising structure for fabricating high strength and high electrical conductivity copper alloys

PubMed Central

Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

2016-01-01

To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

Association between anthropometry and upper-body strength qualities with sprint paddling performance in competitive wave surfers.

PubMed

Sheppard, Jeremy M; McNamara, Phil; Osborne, Mark; Andrews, Mark; Oliveira Borges, Thiago; Walshe, Phil; Chapman, Dale W

2012-12-01

This study aimed to evaluate the potential association with anthropometry and upper-body pulling strength with sprint kinematics of competitive surfers. Ten competitive male surfers (23.9 ± 6.8 years, 177.0 ± 6.5 cm, 72.2 ± 2.4 kg) were assessed for stature, mass, arm span, ∑ 7 site skinfold thickness, pronated pull-up strength, and sprint paddling performance from a stationary start to 15 m. Pearson correlation analysis, and independent t-tests were used to compare potential differences between the slower and faster group of sprint paddlers. Strong associations were found between relative (total kilograms lifted per athlete mass) upper-body pulling strength and sprint paddling time to 5, 10, and 15 m, and peak sprint paddling velocity (r = 0.94, 0.93, 0.88, 0.66, respectively, p < 0.05) and relative upper-body pulling strength was found to be superior (p < 0.05) in the faster group, with large effect (d = 1.88). The results of this study demonstrate a strong association between relative upper-body pulling strength and sprint paddling ability in surfers. Strength and conditioning coaches working with competitive surfers should implement strength training with surfers, including an emphasis on developing relative strength, because this may have a strong influence on sprint paddling performance.

Microstructure control for high strength 9Cr ferritic-martensitic steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Lizhen; Hoelzer, David T; Busby, Jeremy T

2012-01-01

Ferritic-martensitic (F-M) steels with 9 wt.%Cr are important structural materials for use in advanced nuclear reactors. Alloying composition adjustment, guided by computational thermodynamics, and thermomechanical treatment (TMT) were employed to develop high strength 9Cr F-M steels. Samples of four heats with controlled compositions were subjected to normalization and tempering (N&T) and TMT, respectively. Their mechanical properties were assessed by Vickers hardness and tensile testing. Ta-alloying showed significant strengthening effect. The TMT samples showed strength superior to the N&T samples with similar ductility. All the samples showed greater strength than NF616, which was either comparable to or greater than the literaturemore » data of the PM2000 oxide-dispersion-strengthened (ODS) steel at temperatures up to 650 C without noticeable reduction in ductility. A variety of microstructural analyses together with computational thermodynamics provided rational interpretations on the strength enhancement. Creep tests are being initiated because the increased yield strength of the TMT samples is not able to deduce their long-term creep behavior.« less

Investigation of deformation mechanisms of staggered nanocomposites using molecular dynamics

NASA Astrophysics Data System (ADS)

Mathiazhagan, S.; Anup, S.

2016-08-01

Biological materials with nanostructure of regularly or stair-wise staggered arrangements of hard platelets reinforced in a soft protein matrix have superior mechanical properties. Applications of these nanostructures to ceramic matrix composites could enhance their toughness. Using molecular dynamics simulations, mechanical behaviour of the bio-inspired nanocomposites is studied. Regularly staggered model shows better flow behaviour compared to stair-wise staggered model due to the symmetrical crack propagation along the interface. Though higher stiffness and strength are obtained for stair-wise staggered models, rapid crack propagation reduces the toughness. Arresting this crack propagation could lead to superior mechanical properties in stair-wise staggered models.

Lightweight Open-Cell Scaffolds from Sea Urchin Spines with Superior Material Properties for Bone Defect Repair.

PubMed

Cao, Lei; Li, Xiaokang; Zhou, Xiaoshu; Li, Yong; Vecchio, Kenneth S; Yang, Lina; Cui, Wei; Yang, Rui; Zhu, Yue; Guo, Zheng; Zhang, Xing

2017-03-22

Sea urchin spines (Heterocentrotus mammillatus), with a hierarchical open-cell structure similar to that of human trabecular bone and superior mechanical property (compressive strength ∼43.4 MPa) suitable for machining to shape, were explored for potential applications of bone defect repair. Finite element analyses reveal that the compressive stress concentrates along the dense growth rings and dissipates through strut structures of the stereoms, indicating that the exquisite mesostructures play an important role in high strength-to-weight ratios. The fracture strength of magnesium-substituted tricalcium phosphate (β-TCMP) scaffolds produced by hydrothermal conversion of urchin spines is about 9.3 MPa, comparable to that of human trabecular bone. New bone forms along outer surfaces of β-TCMP scaffolds after implantation in rabbit femoral defects for one month and grows into the majority of the inner open-cell spaces postoperation in three months, showing tight interface between the scaffold and regenerative bone tissue. Fusion of beagle lumbar facet joints using a Ti-6Al-4V cage and β-TCMP scaffold can be completed within seven months with obvious biodegradation of the β-TCMP scaffold, which is nearly completely degraded and replaced by newly formed bone ten months after implantation. Thus, sea urchin spines suitable for machining to shape have advantages for production of biodegradable artificial grafts for bone defect repair.

Effect of Sandblasting and Type of Cement on the Bond Strength of Molar Bands on Stainless Steel Crowns.

PubMed

Bawazir, Omar A; Elaraby, Alaa; Alshamrani, Hamed; Salama, Fouad S

2015-01-01

The purposes of this study were to: (1) compare the bond strength of molar bands cemented to stainless steel crowns (SSCs) using glass ionomer cement (GIC), resin-modified glass ionomer cement (RMGIC), or polycarboxylate cement (PXC); and (2) assess the influence of sandblasting molar bands on the mean bond strength between the band and the SSC. Sixty SSCs and 60 molar bands were used. The inner surfaces of 30 molar bands were roughened by sandblasting prior to cementation. The bond strength was measured after dislodging the SSC using a push-out test. In the nonsandblasted group, a significant difference was observed between PXC and RMGIC (P >.04). In the sandblasted group, a significant difference was observed between PXC and RMGIC (P >.02), while there was only a marginal difference between GIC and RMGIC (P >.05). The sandblasted group exhibited superior bond strength overall. However, the only significant improvement was observed for GIC (P >.03). PXC showed the highest bond strength of molar bands to SSCs, while RMGIC showed the lowest. Sandblasting the inner surface of bands enhanced the bond strength of different cements.

Evaluation and prediction of long-term environmental effects of nonmetallic materials

NASA Technical Reports Server (NTRS)

Papazian, H.

1985-01-01

The properties of a number of nonmetallic materials were evaluated experimentally in simulated space environments in order to develop models for accelerated test methods useful for predicting such behavioral changes. Graphite-epoxy composites were exposed to thermal cycling. Adhesive foam tapes were subjected to a vacuum environment. Metal-matrix composites were tested for baseline data. Predictive modeling designed to include strength and aging effects on composites, polymeric films, and metals under such space conditions (including the atomic oxygen environment) is discussed. The Korel 8031-00 high strength adhesive foam tape was shown to be superior to the other two tested.

Functional ankle control of rock climbers

PubMed Central

Schweizer, A; Bircher, H; Kaelin, X; Ochsner, P

2005-01-01

Objective: To evaluate whether rock climbing type exercise would be of value in rehabilitating ankle injuries to improve ankle stability and coordination. Results: The rock climbers showed significantly better results in the stabilometry and greater absolute and relative maximum strength of flexion in the ankle. The soccer players showed greater absolute but not relative strength in extension. Conclusion: Rock climbing, because of its slow and controlled near static movements, may be of value in the treatment of functional ankle instability. However, it has still to be confirmed whether it is superior to the usual rehabilitation exercises such as use of the wobble board. PMID:15976164

Spatial Cognition in Autism Spectrum Disorders: Superior, Impaired, or Just Intact?

ERIC Educational Resources Information Center

Edgin, Jamie O.; Pennington, Bruce F.

2005-01-01

The profile of spatial ability is of interest across autism spectrum disorders (ASD) because of reported spatial strengths in ASD and due to the recent association of Asperger's syndrome with Nonverbal Learning Disability. Spatial functions were examined in relation to two cognitive theories in autism: the central coherence and executive function…

Thin silicon-solar cell fabrication

NASA Technical Reports Server (NTRS)

Lindmayer, J.

1979-01-01

Flexible silicon slices of uniform thicknesses are fabricated by etching in sodium hydroxide solution. Maintaining uniform thickness across slices during process(fabrication) is important for cell strength and resistance to damage in handling. Slices formed by procedure have reproducible surface with fine orange peel texture, and are far superior to slices prepared by other methods.

Ceramic fiber-reinforced monoclinic celsian phase glass-ceramic matrix composite material

NASA Technical Reports Server (NTRS)

Bansal, Narottam P. (Inventor); Dicarlo, James A. (Inventor)

1994-01-01

A hyridopolysilazane-derived ceramic fiber reinforced monoclinic celsian phase barium aluminum silicate glass-ceramic matrix composite material is prepared by ball-milling an aqueous slurry of BAS glass powder and fine monoclinic celsian seeds. The fibers improve the mechanical strength and fracture toughness and with the matrix provide superior dielectric properties.

Superior Nonverbal Intelligence in Children with High-Functioning Autism or Asperger's Syndrome

ERIC Educational Resources Information Center

Chen, Fei; Planche, Pascale; Lemonnier, Eric

2010-01-01

Some early studies showed discordance in cognitive strengths and weaknesses in individuals with high-functioning autism (HFA) or Asperger's syndrome (AS). The present study administered the French version of Colored Raven's Progressive Matrices in 14 children with HFA/AS and in 26 chronological age matched peers with typical development. We found…

46 CFR 160.135-7 - Design, construction, and performance of lifeboats.

Code of Federal Regulations, 2013 CFR

2013-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on.... (8) Starting system batteries. Any battery fitted in a totally enclosed lifeboat must be stored in a... starting battery is required per engine. (9) Exhaust. Engine exhaust must be routed away from bilge and...

46 CFR 160.135-7 - Design, construction, and performance of lifeboats.

Code of Federal Regulations, 2012 CFR

2012-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on.... (8) Starting system batteries. Any battery fitted in a totally enclosed lifeboat must be stored in a... starting battery is required per engine. (9) Exhaust. Engine exhaust must be routed away from bilge and...

46 CFR 160.135-7 - Design, construction, and performance of lifeboats.

Code of Federal Regulations, 2014 CFR

2014-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on.... (8) Starting system batteries. Any battery fitted in a totally enclosed lifeboat must be stored in a... starting battery is required per engine. (9) Exhaust. Engine exhaust must be routed away from bilge and...

Trophic omnivory across a productivity gradient: intraguild predation theory and the structure and strength of species interactions.

PubMed

Novak, Mark

2013-09-07

Intraguild predation theory centres on two predictions: (i) for an omnivore and an intermediate predator (IG-prey) to coexist on shared resources, the IG-prey must be the superior resource competitor, and (ii) increasing resource productivity causes the IG-prey's equilibrium abundance to decline. I tested these predictions with a series of species-rich food webs along New Zealand's rocky shores, focusing on two predatory whelks, Haustrum haustorium, a trophic omnivore, and Haustrum scobina, the IG-prey. In contrast to theory, the IG-prey's abundance increased with productivity. Furthermore, feeding rates and allometric considerations indicate a competitive advantage for the omnivore when non-shared prey are considered, despite the IG-prey's superiority for shared prey. Nevertheless, clear and regular cross-gradient changes in network structure and interaction strengths were observed that challenge the assumptions of current theory. These insights suggest that the consideration of consumer-dependent functional responses, non-equilibrium dynamics, the dynamic nature of prey choice and non-trophic interactions among basal prey will be fruitful avenues for theoretical development.

Trophic omnivory across a productivity gradient: intraguild predation theory and the structure and strength of species interactions

PubMed Central

Novak, Mark

2013-01-01

Intraguild predation theory centres on two predictions: (i) for an omnivore and an intermediate predator (IG-prey) to coexist on shared resources, the IG-prey must be the superior resource competitor, and (ii) increasing resource productivity causes the IG-prey's equilibrium abundance to decline. I tested these predictions with a series of species-rich food webs along New Zealand's rocky shores, focusing on two predatory whelks, Haustrum haustorium, a trophic omnivore, and Haustrum scobina, the IG-prey. In contrast to theory, the IG-prey's abundance increased with productivity. Furthermore, feeding rates and allometric considerations indicate a competitive advantage for the omnivore when non-shared prey are considered, despite the IG-prey's superiority for shared prey. Nevertheless, clear and regular cross-gradient changes in network structure and interaction strengths were observed that challenge the assumptions of current theory. These insights suggest that the consideration of consumer-dependent functional responses, non-equilibrium dynamics, the dynamic nature of prey choice and non-trophic interactions among basal prey will be fruitful avenues for theoretical development. PMID:23864601

An Experimental Evaluation of Mechanical Properties of Hybrid Reinforcements

NASA Astrophysics Data System (ADS)

Sai Kumar, A.; Ganesan, G.; Karthikeyan, K.

2017-07-01

This paper presents the mechanical properties of unidirectional hybrid reinforcements formed from continuous fibres impregnated with a fibre binding material which are used for reinforcing the concrete. Recently FRP (Fibre Reinforced Polymer) manufacturers and suppliers have been increased all over the world because of the superior performance of FRP products in the construction industry. Its non-corrosive nature has turned the attention of many researchers to make several studies on different type of FRP products. Through a vast research, several standards also have been formulated. In this regard a new combination of FRP materials is tried in this paper and its properties have been derived. Carbon fibre and glass fibres fuse in this study to form a new hybrid rebar. The design properties such as tensile strength, tensile modulus, and compressive strength have been studied as per ASTM standards and it has been identified that the Hybrid rebar show a superior performance in comparison with GFRP (Glass FRP) and Steel rebars. This extraordinary performance of hybrid composite material increases the extensive engineering applications such as transport industry, aeronautics, naval, automotive industries.

Sulfate and acid resistant concrete and mortar

DOEpatents

Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

1998-01-01

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction and other applications, which hardenable mixtures demonstrate significant levels of acid and sulfate resistance while maintaining acceptable compressive strength properties. The acid and sulfate hardenable mixtures of the invention containing fly ash comprise cementitious materials and a fine aggregate. The cementitous materials may comprise fly ash as well as cement. The fine aggregate may comprise fly ash as well as sand. The total amount of fly ash in the hardenable mixture ranges from about 60% to about 120% of the total amount of cement, by weight, whether the fly ash is included as a cementious material, fine aggregate, or an additive, or any combination of the foregoing. In specific examples, mortar containing 50% fly ash and 50% cement in cementitious materials demonstrated superior properties of corrosion resistance.

Sulfate and acid resistant concrete and mortar

DOEpatents

Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

1998-06-30

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction and other applications, which hardenable mixtures demonstrate significant levels of acid and sulfate resistance while maintaining acceptable compressive strength properties. The acid and sulfate hardenable mixtures of the invention containing fly ash comprise cementitious materials and a fine aggregate. The cementitous materials may comprise fly ash as well as cement. The fine aggregate may comprise fly ash as well as sand. The total amount of fly ash in the hardenable mixture ranges from about 60% to about 120% of the total amount of cement, by weight, whether the fly ash is included as a cementious material, fine aggregate, or an additive, or any combination of the foregoing. In specific examples, mortar containing 50% fly ash and 50% cement in cementitious materials demonstrated superior properties of corrosion resistance. 6 figs.

Rice straw-wood particle composite for sound absorbing wooden construction materials.

PubMed

Yang, Han-Seung; Kim, Dae-Jun; Kim, Hyun-Joong

2003-01-01

In this study, rice straw-wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10/90, 20/80, and 30/70 weight of rice straw/wood particle) of 10, 20, and 30 wt.%. A commercial urea-formaldehyde adhesive was used as the composite binder, to achieve 140-290 psi of bending modulus of rupture (MOR) with 0.4 specific gravity, 700-900 psi of bending MOR with 0.6 specific gravity, and 1400-2900 psi of bending MOR with a 0.8 specific gravity. All of the composite boards were superior to insulation board in strength. Width and length of the rice straw particle did not affect the bending MOR. The composite boards made from a random cutting of rice straw and wood particles were the best and recommended for manufacturing processes. Sound absorption coefficients of the 0.4 and 0.6 specific gravity boards were higher than the other wood-based materials. The recommended properties of the rice straw-wood particle composite boards are described, to absorb noises, preserve the temperature of indoor living spaces, and to be able to partially or completely substitute for wood particleboard and insulation board in wooden constructions.

A comparison of the mechanical properties of fiberglass cast materials and their clinical relevance.

PubMed

Berman, A T; Parks, B G

1990-01-01

The mechanical properties of five synthetic fiberglass casting materials were evaluated and compared with the properties of plaster of Paris. Two of the tests were designed to bear clinical relevance and the third to determine intrinsic material properties. The effect of water on strength degradation was also evaluated. It was found that the synthetics as a group are far superior to plaster of Paris in all methods of testing and that, among the synthetics, KCast Tack Free, Deltalite "S", and KCast Improved were the stronger materials. Clinically, the most important results are that the synthetics attain their relatively high strength in a much shorter time frame than does plaster of Paris, and retain 70-90% of their strength after being immersed in water and allowed to dry.

Metal-Phenolic Carbon Nanocomposites for Robust and Flexible Energy-Storage Devices.

PubMed

Oh, Jun Young; Jung, Yeonsu; Cho, Young Shik; Choi, Jaeyoo; Youk, Ji Ho; Fechler, Nina; Yang, Seung Jae; Park, Chong Rae

2017-04-22

Future electronics applications such as wearable electronics depend on the successful construction of energy-storage devices with superior flexibility and high electrochemical performance. However, these prerequisites are challenging to combine: External forces often cause performance degradation, whereas the trade-off between the required nanostructures for strength and electrochemical performance only results in diminished energy storage. Herein, a flexible supercapacitor based on tannic acid (TA) and carbon nanotubes (CNTs) with a unique nanostructure is presented. TA was self-assembled on the surface of the CNTs by metal-phenolic coordination bonds, which provides the hybrid film with both high strength and high pseudocapacitance. Besides 17-fold increased mechanical strength of the final composite, the hybrid film simultaneously exhibits excellent flexibility and volumetric capacitance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural and biomechanical characteristics after early mobilization in an Achilles tendon rupture model: operative versus nonoperative treatment.

PubMed

Krapf, Daniel; Kaipel, Martin; Majewski, Martin

2012-09-01

Acute Achilles tendon ruptures are common sports injuries; however, treatment remains a clinical challenge. Studies show a superior effect of early mobilization and full weight bearing on tendon healing and clinical outcome; however, few data exist on structural and biomechanical characteristics in the early healing phase. This study investigated the histological and biomechanical characteristics of early mobilization and full weight bearing in an Achilles tendon rupture model. Eighty rats underwent dissection of a hindpaw Achilles tendon; 40 rats were treated conservatively and 40 underwent open repair of the transected Achilles tendon by suturing. Early mobilization and full weight bearing were allowed in both groups. At 1, 2, 4, and 8 weeks after tenotomy, tensile strength, stiffness, thickness, tissue characteristics (histological analysis), and length were determined. Dissected Achilles tendons healed in all animals during full weight-bearing early mobilization. One and 2 weeks after tenotomy, rats in the operative group showed increased tensile strength and stiffness compared with the nonoperative group. Repair-site diameters were increased at 1, 2, and 8 weeks after tenotomy. Tendon length was decreased in the operative group throughout observation, whereas the nonoperative group showed increased structural characteristics on the cellular level and a more homogeneous collagen distribution. Surgical treatment of dissected rat Achilles tendons showed superior biomechanical characteristics within the first 2 weeks. Conservative treatment resulted in superior histological findings but significant lengthening of the tendon in the early healing phase (weeks 1-8). Copyright 2012, SLACK Incorporated.

33 CFR 117.495 - Superior Oil Canal.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Superior Oil Canal. 117.495 Section 117.495 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Louisiana § 117.495 Superior Oil Canal. The draw of...

33 CFR 117.495 - Superior Oil Canal.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Superior Oil Canal. 117.495 Section 117.495 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Louisiana § 117.495 Superior Oil Canal. The draw of...

33 CFR 117.495 - Superior Oil Canal.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Superior Oil Canal. 117.495 Section 117.495 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Louisiana § 117.495 Superior Oil Canal. The draw of...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Kang; Wu, Sujun; Guan, Juan

Strong and tough epoxy composites are developed using a less-studied fibre reinforcement, that of natural silk. Two common but structurally distinct silks from the domestic B. mori/Bm and the wild A. pernyi/Ap silkworms are selected in fabric forms. We show that the toughening effects on silk-epoxy composites or SFRPs are dependent on the silk species and the volume fraction of silk. Both silks enhance the room-temperature tensile and flexural mechanical properties of the composite, whereas the more resilient Ap silk shows a more pronounced toughening effect and a lower critical reinforcement volume for the brittle-ductile transition. Specifically, our 60 vol.%more » Ap-SFRP displays a three-fold elevation in tensile and flexural strength, as compared to pure epoxy resin, with an order of magnitude higher breaking energy via a distinct, ductile failure mode. Importantly, the 60 vol.% Ap-SFRP remains ductile with 7% flexural elongation at lower temperatures (-50 °C). Under impact, these SFRPs show significantly improved energy absorption, and the 60 vol.% Ap-SFRP has an impact strength some eight times that of pure epoxy resin. Lastly, the findings demonstrate both marked toughening and strengthening effects for epoxy composites from natural silk reinforcements, which presents opportunities for mechanically superior and "green" structural composites.« less

Enhancing the Mechanical Toughness of Epoxy-Resin Composites Using Natural Silk Reinforcements

DOE PAGES

Yang, Kang; Wu, Sujun; Guan, Juan; ...

2017-09-20

Strong and tough epoxy composites are developed using a less-studied fibre reinforcement, that of natural silk. Two common but structurally distinct silks from the domestic B. mori/Bm and the wild A. pernyi/Ap silkworms are selected in fabric forms. We show that the toughening effects on silk-epoxy composites or SFRPs are dependent on the silk species and the volume fraction of silk. Both silks enhance the room-temperature tensile and flexural mechanical properties of the composite, whereas the more resilient Ap silk shows a more pronounced toughening effect and a lower critical reinforcement volume for the brittle-ductile transition. Specifically, our 60 vol.%more » Ap-SFRP displays a three-fold elevation in tensile and flexural strength, as compared to pure epoxy resin, with an order of magnitude higher breaking energy via a distinct, ductile failure mode. Importantly, the 60 vol.% Ap-SFRP remains ductile with 7% flexural elongation at lower temperatures (-50 °C). Under impact, these SFRPs show significantly improved energy absorption, and the 60 vol.% Ap-SFRP has an impact strength some eight times that of pure epoxy resin. Lastly, the findings demonstrate both marked toughening and strengthening effects for epoxy composites from natural silk reinforcements, which presents opportunities for mechanically superior and "green" structural composites.« less

Effect of Low-Dose MDCT and Iterative Reconstruction on Trabecular Bone Microstructure Assessment.

PubMed

Kopp, Felix K; Holzapfel, Konstantin; Baum, Thomas; Nasirudin, Radin A; Mei, Kai; Garcia, Eduardo G; Burgkart, Rainer; Rummeny, Ernst J; Kirschke, Jan S; Noël, Peter B

2016-01-01

We investigated the effects of low-dose multi detector computed tomography (MDCT) in combination with statistical iterative reconstruction algorithms on trabecular bone microstructure parameters. Twelve donated vertebrae were scanned with the routine radiation exposure used in our department (standard-dose) and a low-dose protocol. Reconstructions were performed with filtered backprojection (FBP) and maximum-likelihood based statistical iterative reconstruction (SIR). Trabecular bone microstructure parameters were assessed and statistically compared for each reconstruction. Moreover, fracture loads of the vertebrae were biomechanically determined and correlated to the assessed microstructure parameters. Trabecular bone microstructure parameters based on low-dose MDCT and SIR significantly correlated with vertebral bone strength. There was no significant difference between microstructure parameters calculated on low-dose SIR and standard-dose FBP images. However, the results revealed a strong dependency on the regularization strength applied during SIR. It was observed that stronger regularization might corrupt the microstructure analysis, because the trabecular structure is a very small detail that might get lost during the regularization process. As a consequence, the introduction of SIR for trabecular bone microstructure analysis requires a specific optimization of the regularization parameters. Moreover, in comparison to other approaches, superior noise-resolution trade-offs can be found with the proposed methods.

A laboratory means to produce tough aluminum sheet from powder

NASA Technical Reports Server (NTRS)

Singleton, O. R.; Royster, D. M.; Thomas, J. R.

1990-01-01

The rapid solidification of aluminum alloys as powder and the subsequent fabrication processes can be used to develop and tailor alloys to satisfy specific aerospace design requirements, including high strength and toughness. Laboratory procedures to produce aluminum powder-metallurgy (PM) materials are efficient but require evidence that the laboratory methods used can produce a product with superior properties. This paper describes laboratory equipment and procedures which can be used to produce tough aluminum PM sheet. The processing of a 2124 + 0.9 percent Zr aluminum alloy powder is used as an example. The fully hardened sheet product is evaluated in terms of properties and microstructure. The key features of the vacuum hot press pressing operation used to consolidate the powder are described. The 2124 + 0.9 percent Zr - T8 temper aluminum sheet produced was both strong (460-490 MPa yield strength) and tough (Kahn Tear unit-propagation- energy values over three times those typical for ingot metallurgy 2024-T81). Both the longitudinal and longitudinal-transverse directions of the sheet were tested. The microstructure was well refined with subgrains of one or two micrometers. Fine dispersoids of Al3Zr in the precipitate free regions adjacent to boundaries are believed to contribute to the improved toughness.

FEM assisted evaluation of PMMA and Ti6Al4V as materials for cranioplasty resulting mechanical behaviour and the neurocranial protection.

PubMed

Tsouknidas, Alexander; Maropoulos, Stergios; Savvakis, Savvas; Michailidis, Nikolaos

2011-01-01

Recent advances in Computer Aided Design and Manufacturing techniques (CAD/CAM) have facilitated the rapid and precise construction of customized implants used for craniofacial reconstruction. Data of the patients' trauma, acquired through Computer Topographies (CT), provide sufficient information with regard to the defect contour profile, thus allowing a thorough preoperative evaluation whilst ensuring excellent implant precision. During the selection, however, of a suitable implant material for the specific trauma, the mechanical aspects of the implant have to be considered. This investigation aims to assess the mechanical strength, the shock resistance and the critical deflection of cranial implants manufactured with two commonly used materials, Polymethylmethacrylate (PMMA) and Ti6Al4V. Even though the strength properties of Ti-alloys are far superior to those of PMMA, there are several aspects that may act in advantage of PMMA, e.g., it is known that discontinuities in the elastic modulus of adjoined parts (bone-implant) lead to bone resorption thus loosening the fixation of the implant over time.The implant design and fixation was the same in both cases allowing a direct comparison of the implant behavior for various loads. Finite Element Methods (FEM) assisted procedures were employed, providing a valuable insight to the neurocranial protection granted by these implants.

Property Criteria for Automotive Al-Mg-Si Sheet Alloys

PubMed Central

Prillhofer, Ramona; Rank, Gunther; Berneder, Josef; Antrekowitsch, Helmut; Uggowitzer, Peter J.; Pogatscher, Stefan

2014-01-01

In this study, property criteria for automotive Al-Mg-Si sheet alloys are outlined and investigated in the context of commercial alloys AA6016, AA6005A, AA6063 and AA6013. The parameters crucial to predicting forming behavior were determined by tensile tests, bending tests, cross-die tests, hole-expansion tests and forming limit curve analysis in the pre-aged temper after various storage periods following sheet production. Roping tests were performed to evaluate surface quality, for the deployment of these alloys as an outer panel material. Strength in service was also tested after a simulated paint bake cycle of 20 min at 185 °C, and the corrosion behavior was analyzed. The study showed that forming behavior is strongly dependent on the type of alloy and that it is influenced by the storage period after sheet production. Alloy AA6016 achieves the highest surface quality, and pre-ageing of alloy AA6013 facilitates superior strength in service. Corrosion behavior is good in AA6005A, AA6063 and AA6016, and only AA6013 shows a strong susceptibility to intergranular corrosion. The results are discussed below with respect to the chemical composition, microstructure and texture of the Al-Mg-Si alloys studied, and decision-making criteria for appropriate automotive sheet alloys for specific applications are presented. PMID:28788119

Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis.

PubMed

Williams, Tyler D; Tolusso, Danilo V; Fedewa, Michael V; Esco, Michael R

2017-10-01

Periodization is a logical method of organizing training into sequential phases and cyclical time periods in order to increase the potential for achieving specific performance goals while minimizing the potential for overtraining. Periodized resistance training plans are proposed to be superior to non-periodized training plans for enhancing maximal strength. The primary aim of this study was to examine the previous literature comparing periodized resistance training plans to non-periodized resistance training plans and determine a quantitative estimate of effect on maximal strength. All studies included in the meta-analysis met the following inclusion criteria: (1) peer-reviewed publication; (2) published in English; (3) comparison of a periodized resistance training group to a non-periodized resistance training group; (4) maximal strength measured by 1-repetition maximum (1RM) squat, bench press, or leg press. Data were extracted and independently coded by two authors. Random-effects models were used to aggregate a mean effect size (ES), 95% confidence intervals (CIs) and potential moderators. The cumulative results of 81 effects gathered from 18 studies published between 1988 and 2015 indicated that the magnitude of improvement in 1RM following periodized resistance training was greater than non-periodized resistance training (ES = 0.43, 95% CI 0.27-0.58; P < 0.001). Periodization model (β = 0.51; P = 0.0010), training status (β = -0.59; P = 0.0305), study length (β = 0.03; P = 0.0067), and training frequency (β = 0.46; P = 0.0123) were associated with a change in 1RM. These results indicate that undulating programs were more favorable for strength gains. Improvements in 1RM were greater among untrained participants. Additionally, higher training frequency and longer study length were associated with larger improvements in 1RM. These results suggest that periodized resistance training plans have a moderate effect on 1RM compared to non-periodized training plans. Variation in training stimuli appears to be vital for increasing maximal strength, and longer periods of higher training frequency may be preferred.

Resin cements formulated with thio-urethanes can strengthen porcelain and increase bond strength to ceramics.

PubMed

Bacchi, Atais; Spazzin, Aloisio Oro; de Oliveira, Gabriel Rodrigues; Pfeifer, Carmem; Cesar, Paulo Francisco

2018-06-01

The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20 wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60 wt%. The microshear bond strength (μSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σ bf ) and m were calculated in the tensile surfaces of porcelain and RC structures (Z = 0 and Z = -t 2 , respectively). The μSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σ bf had superior values at Z = 0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σ bf increased with all RCs composed by thio-urethanes at Z = -t 2 . Fractographic analysis revealed all fracture origins at Z = 0. The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the μSBS to LD and ZR. The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers. Copyright © 2018 Elsevier Ltd. All rights reserved.

Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations.

PubMed

Zhao, M; Sun, Y; Zhang, J; Zhang, Y

2018-03-01

An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T IT ) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T IT values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T IT , TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size <1 µm coupled with a porosity level <0.7% could yield translucency values ( T IT , TP, CR) similar to those of the commercial high-translucency porcelains. These values are far superior to the high-translucency lithium disilicate glass-ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.

The Neuromuscular Qualities of Higher- and Lower-Level Mixed-Martial-Arts Competitors.

PubMed

James, Lachlan P; Beckman, Emma M; Kelly, Vincent G; Haff, G Gregory

2017-05-01

To determine whether the maximal strength, impulse, and power characteristics of competitive mixed-martial-arts (MMA) athletes differ according to competition level. Twenty-nine male semiprofessional and amateur MMA competitors were stratified into either higher-level (HL) or lower-level (LL) performers on the basis of competition grade and success. The 1-repetition-maximum (1RM) squat was used to assess lower-body dynamic strength, and a spectrum of impulse, power, force, and velocity variables were evaluated during an incremental-load jump squat. In addition, participants performed an isometric midthigh pull (IMTP) and 1RM bench press to determine whole-body isometric force and upper-body dynamic strength capabilities, respectively. All force and power variables were expressed relative to body mass (BM). The HL competitors produced significantly superior values across a multitude of measures. These included 1RM squat strength (1.84 ± 0.23 vs 1.56 ± 0.24 kg BM; P = .003), in addition to performance in the incremental-load jump squat that revealed greater peak power (P = .005-.002), force (P = .002-.004), and velocity (P = .002-.03) at each load. Higher measures of impulse (P = .01-.04) were noted in a number of conditions. Average power (P = .002-.02) and velocity (P = .01-.04) at all loads in addition to a series of rate-dependent measures were also superior in the HL group (P = .005-.02). The HL competitors' 1RM bench-press values approached significantly greater levels (P = .056) than the LL group's, but IMTP performance did not differ between groups. Maximal lower-body neuromuscular capabilities are key attributes distinguishing HL from LL MMA competitors. This information can be used to inform evidenced-based training and performance-monitoring practices.

Improvement of Ice Hockey Players' On-Ice Sprint With Combined Plyometric and Strength Training.

PubMed

Dæhlin, Torstein E; Haugen, Ole C; Haugerud, Simen; Hollan, Ivana; Raastad, Truls; Rønnestad, Bent R

2017-08-01

Combined plyometric and strength training has previously been suggested as a strategy to improve skating performance in ice hockey players. However, the effects of combined plyometric and strength training have not previously been compared with the effects of strength training only. To compare the effects of combined plyometric and strength training on ice hockey players' skating sprint performance with those of strength training only. Eighteen participants were randomly assigned to 2 groups that completed 5 strength-training sessions/wk for 8 wk. One group included plyometric exercises at the start of 3 sessions/wk (PLY+ST), and the other group included core exercises in the same sessions (ST). Tests of 10- and 35-m skating sprints, horizontal jumping, 1-repetition-maximum (1 RM) squat, skating multistage aerobic test (SMAT), maximal oxygen consumption, repeated cycle sprints, and body composition were performed before and after the intervention. The participants increased their 1RM squat, lean mass, and body mass (P < .05), with no difference between the groups. Furthermore, they improved their 3×broad jump, repeated cycle sprint, and SMAT performance (P < .05), with no difference between the groups. PLY+ST gained a larger improvement in 10-m on-ice sprint performance than ST (P < .025). Combining plyometric and strength training for 8 wk was superior to strength training alone at improving 10-m on-ice sprint performance in high-level ice hockey players.

Mapping by sequencing in cotton (Gossypium hirsutum) line MD52ne identified candidate genes for fiber strength and its related quality attributes.

PubMed

Islam, Md S; Zeng, Linghe; Thyssen, Gregory N; Delhom, Christopher D; Kim, Hee Jin; Li, Ping; Fang, David D

2016-06-01

Three QTL regions controlling three fiber quality traits were validated and further fine-mapped with 27 new single nucleotide polymorphism (SNP) markers. Transcriptome analysis suggests that receptor-like kinases found within the validated QTLs are potential candidate genes responsible for superior fiber strength in cotton line MD52ne. Fiber strength, length, maturity and fineness determine the market value of cotton fibers and the quality of spun yarn. Cotton fiber strength has been recognized as a critical quality attribute in the modern textile industry. Fine mapping along with quantitative trait loci (QTL) validation and candidate gene prediction can uncover the genetic and molecular basis of fiber quality traits. Four previously-identified QTLs (qFBS-c3, qSFI-c14, qUHML-c14 and qUHML-c24) related to fiber bundle strength, short fiber index and fiber length, respectively, were validated using an F3 population that originated from a cross of MD90ne × MD52ne. A group of 27 new SNP markers generated from mapping-by-sequencing (MBS) were placed in QTL regions to improve and validate earlier maps. Our refined QTL regions spanned 4.4, 1.8 and 3.7 Mb of physical distance in the Gossypium raimondii reference genome. We performed RNA sequencing (RNA-seq) of 15 and 20 days post-anthesis fiber cells from MD52ne and MD90ne and aligned reads to the G. raimondii genome. The QTL regions contained 21 significantly differentially expressed genes (DEGs) between the two near-isogenic parental lines. SNPs that result in non-synonymous substitutions to amino acid sequences of annotated genes were identified within these DEGs, and mapped. Taken together, transcriptome and amino acid mutation analysis indicate that receptor-like kinase pathway genes are likely candidates for superior fiber strength and length in MD52ne. MBS along with RNA-seq demonstrated a powerful strategy to elucidate candidate genes for the QTLs that control complex traits in a complex genome like tetraploid upland cotton.

Development of the weldbond process for joining titanium

NASA Technical Reports Server (NTRS)

Fields, D.

1972-01-01

High quality resistance spot welds were produced by welding through epoxy adhesive on titanium alloys. Weldbond joints were consistently stronger than those of either mechanical fasteners, structural adhesive bonds, or mechanical fasteners with adhesive at the joint interface. Weldbond joints and/or spot weld joints showed superior strength at all temperature ranges as compared to other joints tested.

46 CFR 160.156-7 - Design, construction and performance of rescue boats and fast rescue boats.

Code of Federal Regulations, 2014 CFR

2014-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on... this subpart) meets these requirements for fuel tanks. (9) Starting system batteries. Each battery... the rescue boat has more than one engine, then only one starting battery is required per engine. (10...

46 CFR 160.156-7 - Design, construction and performance of rescue boats and fast rescue boats.

Code of Federal Regulations, 2012 CFR

2012-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on... this subpart) meets these requirements for fuel tanks. (9) Starting system batteries. Each battery... the rescue boat has more than one engine, then only one starting battery is required per engine. (10...

46 CFR 160.156-7 - Design, construction and performance of rescue boats and fast rescue boats.

Code of Federal Regulations, 2013 CFR

2013-10-01

... materials equivalent or superior in strength, design, wet out, and efficiency will be given consideration on... this subpart) meets these requirements for fuel tanks. (9) Starting system batteries. Each battery... the rescue boat has more than one engine, then only one starting battery is required per engine. (10...

Mouth and Voice: A Relationship between Visual and Auditory Preference in the Human Superior Temporal Sulcus

PubMed Central

2017-01-01

Cortex in and around the human posterior superior temporal sulcus (pSTS) is known to be critical for speech perception. The pSTS responds to both the visual modality (especially biological motion) and the auditory modality (especially human voices). Using fMRI in single subjects with no spatial smoothing, we show that visual and auditory selectivity are linked. Regions of the pSTS were identified that preferred visually presented moving mouths (presented in isolation or as part of a whole face) or moving eyes. Mouth-preferring regions responded strongly to voices and showed a significant preference for vocal compared with nonvocal sounds. In contrast, eye-preferring regions did not respond to either vocal or nonvocal sounds. The converse was also true: regions of the pSTS that showed a significant response to speech or preferred vocal to nonvocal sounds responded more strongly to visually presented mouths than eyes. These findings can be explained by environmental statistics. In natural environments, humans see visual mouth movements at the same time as they hear voices, while there is no auditory accompaniment to visual eye movements. The strength of a voxel's preference for visual mouth movements was strongly correlated with the magnitude of its auditory speech response and its preference for vocal sounds, suggesting that visual and auditory speech features are coded together in small populations of neurons within the pSTS. SIGNIFICANCE STATEMENT Humans interacting face to face make use of auditory cues from the talker's voice and visual cues from the talker's mouth to understand speech. The human posterior superior temporal sulcus (pSTS), a brain region known to be important for speech perception, is complex, with some regions responding to specific visual stimuli and others to specific auditory stimuli. Using BOLD fMRI, we show that the natural statistics of human speech, in which voices co-occur with mouth movements, are reflected in the neural architecture of the pSTS. Different pSTS regions prefer visually presented faces containing either a moving mouth or moving eyes, but only mouth-preferring regions respond strongly to voices. PMID:28179553

Mouth and Voice: A Relationship between Visual and Auditory Preference in the Human Superior Temporal Sulcus.

PubMed

Zhu, Lin L; Beauchamp, Michael S

2017-03-08

Cortex in and around the human posterior superior temporal sulcus (pSTS) is known to be critical for speech perception. The pSTS responds to both the visual modality (especially biological motion) and the auditory modality (especially human voices). Using fMRI in single subjects with no spatial smoothing, we show that visual and auditory selectivity are linked. Regions of the pSTS were identified that preferred visually presented moving mouths (presented in isolation or as part of a whole face) or moving eyes. Mouth-preferring regions responded strongly to voices and showed a significant preference for vocal compared with nonvocal sounds. In contrast, eye-preferring regions did not respond to either vocal or nonvocal sounds. The converse was also true: regions of the pSTS that showed a significant response to speech or preferred vocal to nonvocal sounds responded more strongly to visually presented mouths than eyes. These findings can be explained by environmental statistics. In natural environments, humans see visual mouth movements at the same time as they hear voices, while there is no auditory accompaniment to visual eye movements. The strength of a voxel's preference for visual mouth movements was strongly correlated with the magnitude of its auditory speech response and its preference for vocal sounds, suggesting that visual and auditory speech features are coded together in small populations of neurons within the pSTS. SIGNIFICANCE STATEMENT Humans interacting face to face make use of auditory cues from the talker's voice and visual cues from the talker's mouth to understand speech. The human posterior superior temporal sulcus (pSTS), a brain region known to be important for speech perception, is complex, with some regions responding to specific visual stimuli and others to specific auditory stimuli. Using BOLD fMRI, we show that the natural statistics of human speech, in which voices co-occur with mouth movements, are reflected in the neural architecture of the pSTS. Different pSTS regions prefer visually presented faces containing either a moving mouth or moving eyes, but only mouth-preferring regions respond strongly to voices. Copyright © 2017 the authors 0270-6474/17/372697-12$15.00/0.

JiTTree: A Just-in-Time Compiled Sparse GPU Volume Data Structure.

PubMed

Labschütz, Matthias; Bruckner, Stefan; Gröller, M Eduard; Hadwiger, Markus; Rautek, Peter

2016-01-01

Sparse volume data structures enable the efficient representation of large but sparse volumes in GPU memory for computation and visualization. However, the choice of a specific data structure for a given data set depends on several factors, such as the memory budget, the sparsity of the data, and data access patterns. In general, there is no single optimal sparse data structure, but a set of several candidates with individual strengths and drawbacks. One solution to this problem are hybrid data structures which locally adapt themselves to the sparsity. However, they typically suffer from increased traversal overhead which limits their utility in many applications. This paper presents JiTTree, a novel sparse hybrid volume data structure that uses just-in-time compilation to overcome these problems. By combining multiple sparse data structures and reducing traversal overhead we leverage their individual advantages. We demonstrate that hybrid data structures adapt well to a large range of data sets. They are especially superior to other sparse data structures for data sets that locally vary in sparsity. Possible optimization criteria are memory, performance and a combination thereof. Through just-in-time (JIT) compilation, JiTTree reduces the traversal overhead of the resulting optimal data structure. As a result, our hybrid volume data structure enables efficient computations on the GPU, while being superior in terms of memory usage when compared to non-hybrid data structures.

Nitrogen-Doped Hollow Carbon Nanospheres for High-Performance Li-Ion Batteries.

PubMed

Yang, Yufen; Jin, Song; Zhang, Zhen; Du, Zhenzhen; Liu, Huarong; Yang, Jia; Xu, Hangxun; Ji, Hengxing

2017-04-26

N-doped carbon materials is of particular attraction for anodes of lithium-ion batteries (LIBs) because of their high surface areas, superior electrical conductivity, and excellent mechanical strength, which can store energy by adsorption/desorption of Li + at the interfaces between the electrolyte and electrode. By directly carbonization of zeolitic imidazolate framework-8 nanospheres synthesized by an emulsion-based interfacial reaction, we obtained N-doped hollow carbon nanospheres with tunable shell thickness (20 nm to solid sphere) and different N dopant concentrations (3.9 to 21.7 at %). The optimized anode material possessed a shell thickness of 20 nm and contained 16.6 at % N dopants that were predominately pyridinic and pyrrolic. The anode delivered a specific capacity of 2053 mA h g -1 at 100 mA g -1 and 879 mA h g -1 at 5 A g -1 for 1000 cycles, implying a superior cycling stability. The improved electrochemical performance can be ascribed to (1) the Li + adsorption dominated energy storage mechanism prevents the volume change of the electrode materials, (2) the hollow nanostructure assembled by the nanometer-sized primary particles prevents the agglomeration of the nanoparticles and favors for Li + diffusion, (3) the optimized N dopant concentration and configuration facilitate the adsorption of Li + ; and (4) the graphitic carbon nanostructure ensures a good electrical conductivity.

Occupational-Specific Strength Predicts Astronaut-Related Task Performance in a Weighted Suit.

PubMed

Taylor, Andrew; Kotarsky, Christopher J; Bond, Colin W; Hackney, Kyle J

2018-01-01

Future space missions beyond low Earth orbit will require deconditioned astronauts to perform occupationally relevant tasks within a planetary spacesuit. The prediction of time-to-completion (TTC) of astronaut tasks will be critical for crew safety, autonomous operations, and mission success. This exploratory study determined if the addition of task-specific strength testing to current standard lower body testing would enhance the prediction of TTC in a 1-G test battery. Eight healthy participants completed NASA lower body strength tests, occupationally specific strength tests, and performed six task simulations (hand drilling, construction wrenching, incline walking, collecting weighted samples, and dragging an unresponsive crewmember to safety) in a 48-kg weighted suit. The TTC for each task was recorded and summed to obtain a total TTC for the test battery. Linear regression was used to predict total TTC with two models: 1) NASA lower body strength tests; and 2) NASA lower body strength tests + occupationally specific strength tests. Total TTC of the test battery ranged from 20.2-44.5 min. The lower body strength test alone accounted for 61% of the variability in total TTC. The addition of hand drilling and wrenching strength tests accounted for 99% of the variability in total TTC. Adding occupationally specific strength tests (hand drilling and wrenching) to standard lower body strength tests successfully predicted total TTC in a performance test battery within a weighted suit. Future research should couple these strength tests with higher fidelity task simulations to determine the utility and efficacy of task performance prediction.Taylor A, Kotarsky CJ, Bond CW, Hackney KJ. Occupational-specific strength predicts astronaut-related task performance in a weighted suit. Aerosp Med Hum Perform. 2018; 89(1):58-62.

Superior spatial resolution in confocal X-ray techniques using collimating channel array optics: elemental mapping and speciation in archaeological human bone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhury, S.; Agyeman-Budu, D. N.; Woll, A. R.

Confocal X-ray fluorescence imaging (CXFI) and confocal X-ray absorption spectroscopy (CXAS) respectively enable the study of three dimensionally resolved localization and speciation of elements. Applied to a thick sample, essentially any volume element of interest within the X-ray fluorescence escape depth can be examined without the need for physical thin sectioning. To date, X-ray confocal detection generally has employed a polycapillary optic in front of the detector to collect fluorescence from the probe volume formed at the intersection of its focus with the incident microfocus beam. This work demonstrates the capability of a novel Collimating Channel Array (CCA) optic inmore » providing an improved and essentially energy independent depth resolution approaching 2 μm. By presenting a comparison of elemental maps of archaeological bone collected without confocal detection, and with polycapillary- and CCA-based confocal detection, this study highlights the strengths and limitations of each mode. Unlike the polycapillary, the CCA shows similar spatial resolution in maps for both low (Ca) and high (Pb and Sr) energy X-ray fluorescence, thus illustrating the energy independent nature of the CCA optic resolution. While superior spatial resolution is demonstrated for all of these elements, the most significant improvement is observed for Ca, demonstrating the advantage of employing the CCA optic in examining light elements. In addition to CXFI, this configuration also enables the collection of Pb L3 CXAS data from micro-volumes with dimensions comparable to bone microstructures of interest. Our CXAS result, which represents the first CCA-based biological CXAS, demonstrates the ability of CCA optics to collect site specific spectroscopic information. The demonstrated combination of site-specific elemental localization and speciation data will be useful in diverse fields.« less

Plain radiography or magnetic resonance imaging (MRI): Which is better in assessing outcome in clinical trials of disease-modifying osteoarthritis drugs? Summary of a debate held at the World Congress of Osteoarthritis 2014.

PubMed

Eckstein, Felix; Le Graverand, Marie-Pierre Hellio

2015-12-01

Osteoarthritis (OA) is the most common disease of synovial joints and currently lacks treatment options that modify structural pathology. Imaging is ideally suited for directly evaluating efficacy of disease-modifying OA drugs (DMOADs) in clinical trials, with plain radiography and MRI being most often applied. The current article is based on a debate held on April 26, 2014, at the World Congress of Osteoarthritis: The authors were invited to contrast strengths and limitations of both methods, highlighting scientific evidence on reliability, construct-validity, and correlations with clinical outcome, and comparing their sensitivity to change in knee OA and sensitivity to DMOAD treatment. The authors concluded that MRI provides more comprehensive information on articular tissues pathology, and that implementation of radiography in clinical trials remains a challenge. However, neither technique has thus far been demonstrated to be strongly superior over the other; for the time being it therefore appears advisable to use both in parallel in clinical trials, to provide more evidence on their relative performance. Radiographic JSW strongly depends on adequate positioning; it is not specific to cartilage loss but also to the meniscus. MRI provides somewhat superior sensitivity to change compared with the commonly used non-fluoroscopic radiographic acquisition protocols, and has recently provided non-location-dependent measures of cartilage thickness loss and gain, which are potentially more sensitive in detecting DMOAD effects than radiographic JSW or region-specific MRI. Non-location-dependent measures of cartilage thickness change should thus be explored further in context of anabolic and anti-catabolic DMOADs. Copyright © 2015 Elsevier Inc. All rights reserved.

PET/MRI in Oncological Imaging: State of the Art

PubMed Central

Bashir, Usman; Mallia, Andrew; Stirling, James; Joemon, John; MacKewn, Jane; Charles-Edwards, Geoff; Goh, Vicky; Cook, Gary J.

2015-01-01

Positron emission tomography (PET) combined with magnetic resonance imaging (MRI) is a hybrid technology which has recently gained interest as a potential cancer imaging tool. Compared with CT, MRI is advantageous due to its lack of ionizing radiation, superior soft-tissue contrast resolution, and wider range of acquisition sequences. Several studies have shown PET/MRI to be equivalent to PET/CT in most oncological applications, possibly superior in certain body parts, e.g., head and neck, pelvis, and in certain situations, e.g., cancer recurrence. This review will update the readers on recent advances in PET/MRI technology and review key literature, while highlighting the strengths and weaknesses of PET/MRI in cancer imaging. PMID:26854157

Effect of respiratory muscle training on exercise performance in healthy individuals: a systematic review and meta-analysis.

PubMed

Illi, Sabine K; Held, Ulrike; Frank, Irène; Spengler, Christina M

2012-08-01

Two distinct types of specific respiratory muscle training (RMT), i.e. respiratory muscle strength (resistive/threshold) and endurance (hyperpnoea) training, have been established to improve the endurance performance of healthy individuals. We performed a systematic review and meta-analysis in order to determine the factors that affect the change in endurance performance after RMT in healthy subjects. A computerized search was performed without language restriction in MEDLINE, EMBASE and CINAHL and references of original studies and reviews were searched for further relevant studies. RMT studies with healthy individuals assessing changes in endurance exercise performance by maximal tests (constant load, time trial, intermittent incremental, conventional [non-intermittent] incremental) were screened and abstracted by two independent investigators. A multiple linear regression model was used to identify effects of subjects' fitness, type of RMT (inspiratory or combined inspiratory/expiratory muscle strength training, respiratory muscle endurance training), type of exercise test, test duration and type of sport (rowing, running, swimming, cycling) on changes in performance after RMT. In addition, a meta-analysis was performed to determine the effect of RMT on endurance performance in those studies providing the necessary data. The multiple linear regression analysis including 46 original studies revealed that less fit subjects benefit more from RMT than highly trained athletes (6.0% per 10 mL · kg⁻¹ · min⁻¹ decrease in maximal oxygen uptake, 95% confidence interval [CI] 1.8, 10.2%; p = 0.005) and that improvements do not differ significantly between inspiratory muscle strength and respiratory muscle endurance training (p = 0.208), while combined inspiratory and expiratory muscle strength training seems to be superior in improving performance, although based on only 6 studies (+12.8% compared with inspiratory muscle strength training, 95% CI 3.6, 22.0%; p = 0.006). Furthermore, constant load tests (+16%, 95% CI 10.2, 22.9%) and intermittent incremental tests (+18.5%, 95% CI 10.8, 26.3%) detect changes in endurance performance better than conventional incremental tests (both p < 0.001) with no difference between time trials and conventional incremental tests (p = 0.286). With increasing test duration, improvements in performance are greater (+0.4% per minute test duration, 95% CI 0.1, 0.6%; p = 0.011) and the type of sport does not influence the magnitude of improvements (all p > 0.05). The meta-analysis, performed on eight controlled trials revealed a significant improvement in performance after RMT, which was detected by constant load tests, time trials and intermittent incremental tests, but not by conventional incremental tests. RMT improves endurance exercise performance in healthy individuals with greater improvements in less fit individuals and in sports of longer durations. The two most common types of RMT (inspiratory muscle strength and respiratory muscle endurance training) do not differ significantly in their effect, while combined inspiratory/expiratory strength training might be superior. Improvements are similar between different types of sports. Changes in performance can be detected by constant load tests, time trials and intermittent incremental tests only. Thus, all types of RMT can be used to improve exercise performance in healthy subjects but care must be taken regarding the test used to investigate the improvements.

Friction Stir Welding of Low-Carbon AISI 1006 Steel: Room and High-Temperature Mechanical Properties

NASA Astrophysics Data System (ADS)

Shunmugasamy, Vasanth C.; Mansoor, Bilal; Ayoub, Georges; Hamade, Ramsey

2018-03-01

Friction stir welding (FSW) is an ecologically benign solid-state joining process. In this work, FSW of low-carbon AISI 1006 steel was carried out to study the microstructure and mechanical properties of the resulting joints at both room temperature (RT) and 200 °C. In the parameter space investigated here, a rotational tool speed and translation feed combination of 1200 rpm and 60 mm/min produced a defect-free weld with balanced mechanical properties and a superior Vickers microhardness profile compared to all other conditions and to base metal (BM). At faster translation feeds (100 and 150 mm/min), wormhole defects were observed in the weld microstructure and were attributed to higher strain rate experienced by the weld zone. Under tensile loading, welded material exhibited yield strength that was up to 86 and 91% of the BM at RT and 200 °C, respectively. On the other hand, tensile strength of welded material was nearly similar to that of the base metal at both RT and 200 °C. However, at both temperatures the tensile ductility of the welded joints was observed to be significantly lower than the BM. Annealing of the 1200 rpm and 60 mm/min FSW specimen resulted in tensile strength of 102% compared to base material and 47% increase in the strain at failure compared to the as-welded specimen. The Charpy impact values revealed up to 62 and 53% increase in the specific impact energy for the 1200 rpm and 60 mm/min welded joints as compared with the BM.

The effect of re-ageing on a novel thermomechanical treatment for improving the mechanical properties of AA2139 aerospace aluminium alloys

NASA Astrophysics Data System (ADS)

Ragkousis, A.; Bakare, F.; Babalola, M. I.

2017-11-01

This study presents the effects of a novel thermomechanical treatment on the mechanical properties of the AA2139 aerospace aluminium alloys. The novel treatment, which is comprised of a combination of under-aging, cold-rolling, and re-aging, was successfully employed by Wang et al (2014 Mater. Sci. Eng. A 607 313-7) to enhance the mechanical and microstructure properties of 6000 series aluminium alloys. The influence of under-ageing and re-aging parameters of the treatment on the AA2139 properties has been examined by tensile and hardness testing, differential scanning calorimetry, and thermoelectric power measurements. It was determined that a higher temperature under-ageing, combined with lower temperature and long duration re-ageing resulted in the most attractive mechanical properties, which significantly exceeded those of other traditional treatments. More specifically, a 175 °C/1.5 h under-ageing treatment, followed by a cold rolling reduction of 75% and a 110 °C/96 h re-ageing resulted in a yield strength of 554 MPa, an ultimate tensile strength of 618 MPa, and an elongation of 7.5%, far exceeding the strength requirements and 5% acceptable elongation for applications in the aerospace industry. These results, in conjunction with the results of the parallel study focusing on the effects of the cold-rolling component of the treatment (Bakare et al 2017 Mater. Res. Express 4) further reinforce the position that the treatment employed is superior to conventional ones for the 2139 alloy.

Antimicrobial activity and properties of irreversible hydrocolloid impression materials incorporated with silver nanoparticles.

PubMed

Ginjupalli, Kishore; Alla, Rama Krishna; Tellapragada, Chaitanya; Gupta, Lokendra; Upadhya Perampalli, Nagaraja

2016-06-01

Conventional spray and the immersion disinfection of irreversible hydrocolloid impression materials may lead to dimensional changes. The purpose of this in vitro study was to investigate the antimicrobial activity and properties of irreversible hydrocolloid impression materials incorporated with silver nanoparticles. The antimicrobial activity and properties of 2 commercially available irreversible hydrocolloid impression materials were evaluated after incorporating varying concentrations of silver nanoparticles. Antimicrobial activity was determined using the disk diffusion method. The gel strength, permanent deformation, flow, and gelation time were measured according to American Dental Association specification #18. Analysis of variance was used to identify the significant differences within and across the groups (α=.05). Adding silver nanoparticles to irreversible hydrocolloid impression materials resulted in superior antimicrobial activity without adversely affecting their properties. Adding silver nanoparticles to Zelgan significantly increased the gel strength compared with the control group, except at 5 wt%. However, the gel strength of Tropicalgin was unaffected except at 5 wt%. An increase in the permanent deformation was found with the incorporation of silver nanoparticles in both Zelgan and Tropicalgin. The flow of Zelgan increased with the incorporation of silver nanoparticles, whereas a decrease in the flow of Tropicalgin was observed at 1 wt% and 2 wt%. An increase in the gelation time of both Zelgan and Tropicalgin was observed with the incorporation of silver nanoparticles. Based on this in vitro study, silver nanoparticles can be incorporated into irreversible hydrocolloid impression materials as antimicrobial agents without adversely affecting their properties. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Responsiveness, Sensitivity, and Minimally Detectable Difference of the Graded and Redefined Assessment of Strength, Sensibility, and Prehension, Version 1.0.

PubMed

Kalsi-Ryan, Sukhvinder; Beaton, Dorcas; Ahn, Henry; Askes, Heather; Drew, Brian; Curt, Armin; Popovic, Milos R; Wang, Justin; Verrier, Mary C; Fehlings, Michael G

2016-02-01

As spinal cord injury (SCI) trials begin to involve subjects with acute cervical SCI, establishing the property of an upper limb outcome measure to detect change over time is critical for its usefulness in clinical trials. The objectives of this study were to define responsiveness, sensitivity, and minimally detectable difference (MDD) of the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP). An observational, longitudinal study was conducted. International Standards of Neurological Classification of SCI (ISNCSCI), GRASSP, Capabilities of Upper Extremity Questionnaire (CUE-Q), and Spinal Cord Independence Measure (SCIM) were administered 0-10 days, 1, 3, 6, and 12 months post-injury. Standardized Response Means (SRM) for GRASSP and ISNCSCI measures were calculated. Longitudinal construct validity was calculated using Pearson correlation coefficients. Smallest real difference for all subtests was calculated to define the MDD values for all GRASSP subtests. Longitudinal construct validity demonstrated GRASSP and all external measures to be responsive to neurological change for 1 year post-injury. SRM values for the GRASSP subtests ranged from 0.25 to 0.85 units greater than that for ISNCSCI strength and sensation, SCIM-SS, and CUE-Q. MDD values for GRASSP subtests ranged from 2-5 points. GRASSP demonstrates good responsiveness and excellent sensitivity that is superior to ISNCSCI and SCIM III. MDD values are useful in the evaluation of interventions in both clinical and research settings. The responsiveness and sensitivity of GRASSP make it a valuable condition-specific measure in tetraplegia, where changes in upper limb neurological and functional outcomes are essential for evaluating the efficacy of interventions.

High strength nanostructured Al-based alloys through optimized processing of rapidly quenched amorphous precursors.

PubMed

Kim, Song-Yi; Lee, Gwang-Yeob; Park, Gyu-Hyeon; Kim, Hyeon-Ah; Lee, A-Young; Scudino, Sergio; Prashanth, Konda Gokuldoss; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

2018-01-18

We report the methods increasing both strength and ductility of aluminum alloys transformed from amorphous precursor. The mechanical properties of bulk samples produced by spark-plasma sintering (SPS) of amorphous Al-Ni-Co-Dy powders at temperatures above 673 K are significantly enhanced by in-situ crystallization of nano-scale intermetallic compounds during the SPS process. The spark plasma sintered Al 84 Ni 7 Co 3 Dy 6 bulk specimens exhibit 1433 MPa compressive yield strength and 1773 MPa maximum strength together with 5.6% plastic strain, respectively. The addition of Dy enhances the thermal stability of primary fcc Al in the amorphous Al-TM -RE alloy. The precipitation of intermetallic phases by crystallization of the remaining amorphous matrix plays important role to restrict the growth of the fcc Al phase and contributes to the improvement of the mechanical properties. Such fully crystalline nano- or ultrafine-scale Al-Ni-Co-Dy systems are considered promising for industrial application because their superior mechanical properties in terms of a combination of very high room temperature strength combined with good ductility.

[Methodological aspects of functional neuroimaging at high field strength: a critical review].

PubMed

Scheef, L; Landsberg, M W; Boecker, H

2007-09-01

The last few years have proven that high field magnetic resonance imaging (MRI) is superior in nearly every way to conventional equipment up to 1.5 tesla (T). Following the global success of 3T-scanners in research institutes and medical practices, a new generation of MRI devices with field strengths of 7T and higher is now on the horizon. The introduction of ultra high fields has brought MRI technology closer to the physical limitations and increasingly greater costs are required to achieve this goal. This article provides a critical overview of the advantages and problems of functional neuroimaging using ultra high field strengths. This review is principally limited to T2*-based functional imaging techniques not dependent on contrast agents. The main issues include the significance of high field technology with respect to SNR, CNR, resolution, and sequences, as well as artifacts, noise exposure, and SAR. Of great relevance is the discussion of parallel imaging, which will presumably determine the further development of high and ultra high field strengths. Finally, the importance of high field strengths for functional neuroimaging is explained by selected publications.

Decreased long- and short-range functional connectivity at rest in drug-naive major depressive disorder.

PubMed

Guo, Wenbin; Liu, Feng; Chen, Jindong; Wu, Renrong; Zhang, Zhikun; Yu, Miaoyu; Xue, Zhimin; Zhao, Jingping

2016-08-01

Abnormal functional connectivity has been observed in major depressive disorder. Anatomical distance may affect functional connectivity in patients with major depressive disorder. However, whether and how anatomical distance affects functional connectivity at rest remains unclear in drug-naive patients with major depressive disorder. Forty-four patients with major depressive disorder, as well as 44 age-, sex- and education-matched healthy controls, underwent resting-state functional magnetic resonance imaging scanning. Regional functional connectivity strength was calculated for each voxel in the whole brain, which was further divided into short- and long-range functional connectivity strength. The patients showed decreased long-range positive functional connectivity strength in the right inferior parietal lobule, as well as decreased short-range positive functional connectivity strength in the right insula and right superior temporal gyrus relative to those of the controls. No significant correlations existed between abnormal functional connectivity strength and the clinical variables of the patients. The findings revealed that anatomical distance decreases long- and short-range functional connectivity strength in patients with major depressive disorder, which may underlie the neurobiology of major depressive disorder. © The Royal Australian and New Zealand College of Psychiatrists 2015.

Influence of brazing conditions on the strength of brazed joints of alumina dispersion-strengthened copper to 316 stainless steel

NASA Astrophysics Data System (ADS)

Nishi, H.; Kikuchi, K.

1998-10-01

Brazing of alumina dispersion-strengthened copper (DS Cu) to 316 stainless steel were conducted in order to investigate the influence of filler metals and brazing conditions on the joint strength. The brazing were performed with a silver-base (BAg-8) and three kinds of gold-base (BAu-2,4,11) filler metals with varying brazing joint clearance and brazing time. The filler metal had a greater effect on the joint strength than the brazing joint clearance and brazing time. The joint with BAu-2 was superior to the joint with other filler metals. The tensile strength of the joint with BAu-2 was as large as that of DS Cu, however, the Charpy and low cycle fatigue strength were lower than those of DS Cu. The DS Cu melted near the brazed zone, consequently recrystallization and agglomeration of alumina occurred in the diffusion layer for all filler metals. The grain size after the recrystallization was small in order of BAu-2, BAu-4 and BAu-11, that was in accordance with the order of the brazing temperature. The excellent fracture strength for the joint with BAu-2 was attributed to the smallest grain size.

The Importance of Muscular Strength: Training Considerations.

PubMed

Suchomel, Timothy J; Nimphius, Sophia; Bellon, Christopher R; Stone, Michael H

2018-04-01

This review covers underlying physiological characteristics and training considerations that may affect muscular strength including improving maximal force expression and time-limited force expression. Strength is underpinned by a combination of morphological and neural factors including muscle cross-sectional area and architecture, musculotendinous stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition. Although single- and multi-targeted block periodization models may produce the greatest strength-power benefits, concepts within each model must be considered within the limitations of the sport, athletes, and schedules. Bilateral training, eccentric training and accentuated eccentric loading, and variable resistance training may produce the greatest comprehensive strength adaptations. Bodyweight exercise, isolation exercises, plyometric exercise, unilateral exercise, and kettlebell training may be limited in their potential to improve maximal strength but are still relevant to strength development by challenging time-limited force expression and differentially challenging motor demands. Training to failure may not be necessary to improve maximum muscular strength and is likely not necessary for maximum gains in strength. Indeed, programming that combines heavy and light loads may improve strength and underpin other strength-power characteristics. Multiple sets appear to produce superior training benefits compared to single sets; however, an athlete's training status and the dose-response relationship must be considered. While 2- to 5-min interset rest intervals may produce the greatest strength-power benefits, rest interval length may vary based an athlete's training age, fiber type, and genetics. Weaker athletes should focus on developing strength before emphasizing power-type training. Stronger athletes may begin to emphasize power-type training while maintaining/improving their strength. Future research should investigate how best to implement accentuated eccentric loading and variable resistance training and examine how initial strength affects an athlete's ability to improve their performance following various training methods.

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

NASA Technical Reports Server (NTRS)

Hundley, N. H.; Patterson, W. J.

1985-01-01

Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

NASA-427: A New Aluminum Alloy

NASA Technical Reports Server (NTRS)

Nabors, Sammy A.

2015-01-01

NASA's Marshall Space Flight Center researchers have developed a new, stronger aluminum alloy, ideal for cast aluminum products that have powder or paint-baked thermal coatings. With advanced mechanical properties, the NASA-427 alloy shows greater tensile strength and increased ductility, providing substantial improvement in impact toughness. In addition, this alloy improves the thermal coating process by decreasing the time required for heat treatment. With improvements in both strength and processing time, use of the alloy provides reduced materials and production costs, lower product weight, and better product performance. The superior properties of NASA-427 can benefit many industries, including automotive, where it is particularly well-suited for use in aluminum wheels.

Quantitative and qualitative optimization of allergen extraction from peanut and selected tree nuts. Part 2. Optimization of buffer and ionic strength using a full factorial experimental design.

PubMed

L'Hocine, Lamia; Pitre, Mélanie

2016-03-01

A full factorial design was used to assess the single and interactive effects of three non-denaturing aqueous (phosphate, borate, and carbonate) buffers at various ionic strengths (I) on allergen extractability from and immunoglobulin E (IgE) immunoreactivity of peanut, almond, hazelnut, and pistachio. The results indicated that the type and ionic strength of the buffer had different effects on protein recovery from the nuts under study. Substantial differences in protein profiles, abundance, and IgE-binding intensity with different combinations of pH and ionic strength were found. A significant interaction between pH and ionic strength was observed for pistachio and almond. The optimal buffer system conditions, which maximized the IgE-binding efficiency of allergens and provided satisfactory to superior protein recovery yield and profiles, were carbonate buffer at an ionic strength of I=0.075 for peanut, carbonate buffer at I=0.15 for almond, phosphate buffer at I=0.5 for hazelnut, and borate at I=0.15 for pistachio. The buffer type and its ionic strength could be manipulated to achieve the selective solubility of desired allergens. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Fracture behaviors of ceramic tissue scaffolds for load bearing applications

NASA Astrophysics Data System (ADS)

Entezari, Ali; Roohani-Esfahani, Seyed-Iman; Zhang, Zhongpu; Zreiqat, Hala; Dunstan, Colin R.; Li, Qing

2016-07-01

Healing large bone defects, especially in weight-bearing locations, remains a challenge using available synthetic ceramic scaffolds. Manufactured as a scaffold using 3D printing technology, Sr-HT-Gahnite at high porosity (66%) had demonstrated significantly improved compressive strength (53 ± 9 MPa) and toughness. Nevertheless, the main concern of ceramic scaffolds in general remains to be their inherent brittleness and low fracture strength in load bearing applications. Therefore, it is crucial to establish a robust numerical framework for predicting fracture strengths of such scaffolds. Since crack initiation and propagation plays a critical role on the fracture strength of ceramic structures, we employed extended finite element method (XFEM) to predict fracture behaviors of Sr-HT-Gahnite scaffolds. The correlation between experimental and numerical results proved the superiority of XFEM for quantifying fracture strength of scaffolds over conventional FEM. In addition to computer aided design (CAD) based modeling analyses, XFEM was conducted on micro-computed tomography (μCT) based models for fabricated scaffolds, which took into account the geometric variations induced by the fabrication process. Fracture strengths and crack paths predicted by the μCT-based XFEM analyses correlated well with relevant experimental results. The study provided an effective means for the prediction of fracture strength of porous ceramic structures, thereby facilitating design optimization of scaffolds.

Carpal height and postoperative strength after proximal row carpectomy or four-corner arthrodesis: Clinical, anatomical and biomechanical study.

PubMed

Laronde, Pascale; Christiaens, Nicolas; Aumar, Aurélien; Chantelot, Christophe; Fontaine, Christian

2016-04-01

Proximal row carpectomy (PRC) and four-corner arthrodesis (4CA) are the two most commonly performed surgical procedures to treat wrist arthritis. Postoperative strength is one of the criteria for choosing between the two techniques. Some authors believe that strength is correlated with residual carpal height. The goal of this study was to determine if postoperative carpal height was predictive of postoperative strength. This study consisted of two parts: a clinical evaluation of grip strength after 4CA or PRC; anatomical and radiological measurements of carpal height before and after 4CA or PRC. Grip strength was better preserved after PRC (87.5%) than after 4CA (76.1%), when expressed relative to the opposite hand (P=0.053). There was a significant decrease in carpal height for the PRC group with a Youm's index of 0.37 versus 0.50 for the 4CA group (P<0.0001). Our clinical results and analysis of the literature indicate that 4CA is not superior to PRC when it comes to grip strength, whereas carpal height is significantly decreased after PRC. The decreased tendon excursion after PRC is balanced by an increase in joint stresses after 4CA. Copyright © 2016 SFCM. Published by Elsevier Masson SAS. All rights reserved.

Remembering 1500 Pictures: The Right Hemisphere Remembers Better than the Left

ERIC Educational Resources Information Center

Laeng, Bruno; Overvoll, Morten; Ole Steinsvik, Oddmar

2007-01-01

We hypothesized that the right hemisphere would be superior to the left hemisphere in remembering having seen a specific picture before, given its superiority in perceptually encoding specific aspects of visual form. A large set of pictures (N=1500) of animals, human faces, artifacts, landscapes, and art paintings were shown for 2 s in central…

33 CFR 117.661 - Duluth Ship Canal (Duluth-Superior Harbor).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Duluth Ship Canal (Duluth-Superior Harbor). 117.661 Section 117.661 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Minnesota § 117.661 Duluth Ship Canal (Duluth-Superior Harbor). The draw o...

A study on fatigue strength reduction factor for small diameter socket welded pipe joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higuchi, Makoto; Nakagawa, Akira; Hayashi, Makoto

1996-12-01

Factors that may exert influence on the fatigue strength of small diameter socket welded joints of nominal diameter in the 20--50 mm range have been investigated by the fully reversed four-point bending fatigue test with the material, diameter, pipe schedule, throat depth, bead shape, slip-on gap, and root defect as the testing parameters. The fatigue strength of socket joints depended acutely on the diameter. When the diameter is large, the fatigue strength tended to be low and the fracture is of the root-failure mode; when it is small, on the other hand, the fatigue strength is high and the fracturemore » is of the toe-failure mode. Stainless steel proved to be superior to carbon steel; it gave rise to 1.37 times the fatigue strength of the latter for socket joints of nominal diameter 50 mm; the fatigue strength reduction factor determined at 10{sup 7} cycles with respect to the fatigue strength of smooth base metal in the fully reversed fatigue was about 4 for stainless steel and about 5 for carbon steel. The fatigue strength was higher, the larger the Sche number (i.e., the thicker the pipe wall); it was improved markedly by placing one final refinement pass on the toe or by eliminating the slip-on gap. An empirical formula relating the size of the root defect to the fatigue strength reduction has been proposed.« less

Hip Abductor Strengthening Improves Physical Function Following Total Knee Replacement: One-Year Follow-Up of a Randomized Pilot Study.

PubMed

Harikesavan, Karvannan; Chakravarty, Raj D; Maiya, Arun G; Hegde, Sanjay P; Y Shivanna, Shivakumar

2017-01-01

Total knee replacement (TKR) is the commonest surgical procedure for patients with severe pain and impaired physical function following end stage knee osteoarthritis. The hip abductors are well renowned in stabilization of the trunk and hip during walking, maintaining the lower limb position, and transferring the forces from the lower limbs to the pelvis. To assess the efficacy of hip abductor strengthening exercise on functional outcome using performance based outcome measures following total knee replacement. An observer blinded randomized pilot trial design was conducted at Manipal hospital, Bangalore, India. Participants designated for elective TKR were randomized to experimental group hip abductor strengthening along with standard rehabilitation (n=10) or control group standard rehabilitation alone (n=10). Participants followed for one year to assess physical function using performance based outcomes, such as timed up and go test, single leg stance test, six minute walk test, knee extensor strength and hip abductor strength. Eighteen participants with a mean age of 63.1 ± 5.5 years (8 Males and 10 Females) completed the study. Improvement in hip abduction strength, single leg stand test was superior in hip abductor strengthening group at 3 months and 1 year when compared to standard rehabilitation alone. Hip abductor strengthening showed superior improvements in single leg stance test and six minute walk test. Hip abductor strengthening exercises has the potential to improve physical function following total knee replacement.

Design of novel dual-port tapered waveguide plasma apparatus by numerical analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, D.; Zhou, R.; Yang, X. Q., E-mail: yyxxqq-mail@163.com

Microwave plasma apparatus is often of particular interest due to their superiority of low cost, electrode contamination free, and suitability for industrial production. However, there exist problems of unstable plasma and low electron density in conventional waveguide apparatus based on single port, due to low strength and non-uniformity of microwave field. This study proposes a novel dual-port tapered waveguide plasma apparatus based on power-combining technique, to improve the strength and uniformity of microwave field for the applications of plasma. A 3D model of microwave-induced plasma (field frequency 2.45 GHz) in argon at atmospheric pressure is presented. On the condition thatmore » the total input power is 500 W, simulations indicate that coherent power-combining will maximize the electric-field strength to 3.32 × 10{sup 5 }V/m and improve the uniformity of distributed microwave field, which raised 36.7% and 47.2%, respectively, compared to conventional waveguide apparatus of single port. To study the optimum conditions for industrial application, a 2D argon fluid model based on above structure is presented. It demonstrates that relatively uniform and high-density plasma is obtained at an argon flow rate of 200 ml/min. The contrastive result of electric-field distribution, electron density, and gas temperature is also valid and clearly proves the superiority of coherent power-combining to conventional technique in flow field.« less

Hip Abductor Strengthening Improves Physical Function Following Total Knee Replacement: One-Year Follow-Up of a Randomized Pilot Study

PubMed Central

Harikesavan, Karvannan; Chakravarty, Raj D.; Maiya, Arun G; Hegde, Sanjay P.; Y. Shivanna, Shivakumar

2017-01-01

Background: Total knee replacement (TKR) is the commonest surgical procedure for patients with severe pain and impaired physical function following end stage knee osteoarthritis. The hip abductors are well renowned in stabilization of the trunk and hip during walking, maintaining the lower limb position, and transferring the forces from the lower limbs to the pelvis. Objective: To assess the efficacy of hip abductor strengthening exercise on functional outcome using performance based outcome measures following total knee replacement. Methods: An observer blinded randomized pilot trial design was conducted at Manipal hospital, Bangalore, India. Participants designated for elective TKR were randomized to experimental group hip abductor strengthening along with standard rehabilitation (n=10) or control group standard rehabilitation alone (n=10). Participants followed for one year to assess physical function using performance based outcomes, such as timed up and go test, single leg stance test, six minute walk test, knee extensor strength and hip abductor strength. Result: Eighteen participants with a mean age of 63.1 ± 5.5 years (8 Males and 10 Females) completed the study. Improvement in hip abduction strength, single leg stand test was superior in hip abductor strengthening group at 3 months and 1 year when compared to standard rehabilitation alone. Conclusion: Hip abductor strengthening showed superior improvements in single leg stance test and six minute walk test. Hip abductor strengthening exercises has the potential to improve physical function following total knee replacement. PMID:28567148

Modeling of High-Strain-Rate Deformation, Fracture, and Impact Behavior of Advanced Gas Turbine Engine Materials at Low and Elevated Temperatures

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Nathenson, David; Prakash, Vikas

2003-01-01

Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention, and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, Gamma-met PX has been developed by GKSS, Germany. These alloys have been observed to have superior strengths at elevated temperatures and quasi-static deformation rates and good oxidation resistance at elevated temperatures when compared with other gamma titanium aluminides. The present paper discusses results of a study to understand dynamic response of gamma-met PX in uniaxial compression. The experiments were conducted by using a modified split Hopkinson pressure bar between room temperature and 900 C and strain rates of up to 3500 per second. The Gamma met PX alloy showed superior strength when compared to nickel based superalloys and other gamma titanium aluminides at all test temperatures. It also showed strain and strain-rate hardening at all levels of strain rates and temperatures and without yield anomaly up to 900 C. After approximately 600 C, thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 and 900 C. However, these flow stress levels are comparatively higher in Gamma met PX than those observed for other TiAl alloys.

Development of new generation reduced activation ferritic-martenstic steels for advanced fusion reactors

DOE PAGES

Tan, Lizhen; Snead, Lance Lewis; Katoh, Yutai

2016-05-26

International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M 23C 6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ~500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods.more » Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. Furthermore, the strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9–20Cr oxide dispersion-strengthened ferritic alloys.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Lizhen; Snead, Lance Lewis; Katoh, Yutai

International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M 23C 6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ~500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods.more » Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. Furthermore, the strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9–20Cr oxide dispersion-strengthened ferritic alloys.« less

The right hemisphere supports but does not replace left hemisphere auditory function in patients with persisting aphasia.

PubMed

Teki, Sundeep; Barnes, Gareth R; Penny, William D; Iverson, Paul; Woodhead, Zoe V J; Griffiths, Timothy D; Leff, Alexander P

2013-06-01

In this study, we used magnetoencephalography and a mismatch paradigm to investigate speech processing in stroke patients with auditory comprehension deficits and age-matched control subjects. We probed connectivity within and between the two temporal lobes in response to phonemic (different word) and acoustic (same word) oddballs using dynamic causal modelling. We found stronger modulation of self-connections as a function of phonemic differences for control subjects versus aphasics in left primary auditory cortex and bilateral superior temporal gyrus. The patients showed stronger modulation of connections from right primary auditory cortex to right superior temporal gyrus (feed-forward) and from left primary auditory cortex to right primary auditory cortex (interhemispheric). This differential connectivity can be explained on the basis of a predictive coding theory which suggests increased prediction error and decreased sensitivity to phonemic boundaries in the aphasics' speech network in both hemispheres. Within the aphasics, we also found behavioural correlates with connection strengths: a negative correlation between phonemic perception and an inter-hemispheric connection (left superior temporal gyrus to right superior temporal gyrus), and positive correlation between semantic performance and a feedback connection (right superior temporal gyrus to right primary auditory cortex). Our results suggest that aphasics with impaired speech comprehension have less veridical speech representations in both temporal lobes, and rely more on the right hemisphere auditory regions, particularly right superior temporal gyrus, for processing speech. Despite this presumed compensatory shift in network connectivity, the patients remain significantly impaired.

The right hemisphere supports but does not replace left hemisphere auditory function in patients with persisting aphasia

PubMed Central

Barnes, Gareth R.; Penny, William D.; Iverson, Paul; Woodhead, Zoe V. J.; Griffiths, Timothy D.; Leff, Alexander P.

2013-01-01

In this study, we used magnetoencephalography and a mismatch paradigm to investigate speech processing in stroke patients with auditory comprehension deficits and age-matched control subjects. We probed connectivity within and between the two temporal lobes in response to phonemic (different word) and acoustic (same word) oddballs using dynamic causal modelling. We found stronger modulation of self-connections as a function of phonemic differences for control subjects versus aphasics in left primary auditory cortex and bilateral superior temporal gyrus. The patients showed stronger modulation of connections from right primary auditory cortex to right superior temporal gyrus (feed-forward) and from left primary auditory cortex to right primary auditory cortex (interhemispheric). This differential connectivity can be explained on the basis of a predictive coding theory which suggests increased prediction error and decreased sensitivity to phonemic boundaries in the aphasics’ speech network in both hemispheres. Within the aphasics, we also found behavioural correlates with connection strengths: a negative correlation between phonemic perception and an inter-hemispheric connection (left superior temporal gyrus to right superior temporal gyrus), and positive correlation between semantic performance and a feedback connection (right superior temporal gyrus to right primary auditory cortex). Our results suggest that aphasics with impaired speech comprehension have less veridical speech representations in both temporal lobes, and rely more on the right hemisphere auditory regions, particularly right superior temporal gyrus, for processing speech. Despite this presumed compensatory shift in network connectivity, the patients remain significantly impaired. PMID:23715097

Effect of hypoxia on the retina and superior colliculus of neonatal pigs

PubMed Central

Ruzafa, Noelia; Rey-Santano, Carmen; Mielgo, Victoria; Pereiro, Xandra; Vecino, Elena

2017-01-01

Purpose To evaluate the effect of hypoxia on the neonatal pig retina and brain, we analysed the retinal ganglion cells (RGCs) and neurons in the superior colliculus, as well as the response of astrocytes in both these central nervous system (CNS) structures. Methods Newborn pigs were exposed to 120 minutes of hypoxia, induced by decreasing the inspiratory oxygen fraction (FiO2: 10–15%), followed by a reoxygenation period of 240 minutes (FiO2: 21–35%). RGCs were quantified using Brn3a, a specific nuclear marker for these cells, and apoptosis was assessed through the appearance of active caspase-3. A morphometric analysis of the cytoskeleton of astrocytes (identified with GFAP) was performed in both the retina and superior colliculus. Results Hypoxia produced no significant change in the RGCs, although, it did induce a 37.63% increase in the number of active caspase-3 positive cells in the superior colliculus. This increase was particularly evident in the superficial layers of the superior colliculus, where 56.93% of the cells were positive for active caspase-3. In addition, hypoxia induced changes in the morphology of the astrocytes in the superior colliculus but not in the retina. Conclusions Hypoxia in the neonatal pig does not affect the retina but it does affect more central structures in the brain, increasing the number of apoptotic cells in the superior colliculus and inducing changes in astrocyte morphology. This distinct sensibility to hypoxia may pave the way to design specific approaches to combat the effects of hypoxia in specific areas of the CNS. PMID:28407001

Fracture strength of the particulate-reinforced ultra-high temperature ceramics based on a temperature dependent fracture toughness model

NASA Astrophysics Data System (ADS)

Wang, Ruzhuan; Li, Weiguo; Ji, Baohua; Fang, Daining

2017-10-01

The particulate-reinforced ultra-high temperature ceramics (pUHTCs) have been particularly developed for fabricating the leading edge and nose cap of hypersonic vehicles. They have drawn intensive attention of scientific community for their superior fracture strength at high temperatures. However, there is no proper model for predicting the fracture strength of the ceramic composites and its dependency on temperature. In order to account for the effect of temperature on the fracture strength, we proposed a concept called energy storage capacity, by which we derived a new model for depicting the temperature dependent fracture toughness of the composites. This model gives a quantitative relationship between the fracture toughness and temperature. Based on this temperature dependent fracture toughness model and Griffith criterion, we developed a new fracture strength model for predicting the temperature dependent fracture strength of pUHTCs at different temperatures. The model takes into account the effects of temperature, flaw size and residual stress without any fitting parameters. The predictions of the fracture strength of pUHTCs in argon or air agreed well with the experimental measurements. Additionally, our model offers a mechanism of monitoring the strength of materials at different temperatures by testing the change of flaw size. This study provides a quantitative tool for design, evaluation and monitoring of the fracture properties of pUHTCs at high temperatures.

Examination of factors affecting gait properties in healthy older adults: focusing on knee extension strength, visual acuity, and knee joint pain.

PubMed

Demura, Tomohiro; Demura, Shin-ichi; Uchiyama, Masanobu; Sugiura, Hiroki

2014-01-01

Gait properties change with age because of a decrease in lower limb strength and visual acuity or knee joint disorders. Gait changes commonly result from these combined factors. This study aimed to examine the effects of knee extension strength, visual acuity, and knee joint pain on gait properties of for 181 healthy female older adults (age: 76.1 (5.7) years). Walking speed, cadence, stance time, swing time, double support time, step length, step width, walking angle, and toe angle were selected as gait parameters. Knee extension strength was measured by isometric dynamometry; and decreased visual acuity and knee joint pain were evaluated by subjective judgment whether or not such factors created a hindrance during walking. Among older adults without vision problems and knee joint pain that affected walking, those with superior knee extension strength had significantly greater walking speed and step length than those with inferior knee extension strength (P < .05). Persons with visual acuity problems had higher cadence and shorter stance time. In addition, persons with pain in both knees showed slower walking speed and longer stance time and double support time. A decrease of knee extension strength and visual acuity and knee joint pain are factors affecting gait in the female older adults. Decreased knee extension strength and knee joint pain mainly affect respective distance and time parameters of the gait.

Withdrawal strength of ring-shank nails embedded in southern pine lumber

Treesearch

M. J. Skulteti; D. A. Bender; S. G. Winistorfer; D. G. Pollock

1997-01-01

Ring-shank nails are used extensively in post-frame construction due to their superior performance, yet surprisingly little testing has been done on nail sizes above 12d Experience in the post-frame industry suggests that published allowable design values for ring-shank nails may be overly conservative and need revision. The goal of the research reported herein was to...

Soviet Military Power

DTIC Science & Technology

1981-09-01

land-based KIROV, the USSR’s first nucler - powered surface warship, symbolizes the increasing strength of the Soviet Armed Forces and the Increasing...53 VI QUEST FOR TECHNOLOGICAL SUPERIORITY ............ 7 VII SOVIET GLOBAL POWER PROJECTION...................83 VIII THE CHALLENGE...military power at a pace that shows no signs of slackening in the future. All elements of the Soviet Armed Forces -the Strategic Rocket Forces, the

The development of high strength corrosion resistant precipitation hardening cast steels

NASA Astrophysics Data System (ADS)

Abrahams, Rachel A.

Precipitation Hardened Cast Stainless Steels (PHCSS) are a corrosion resistant class of materials which derive their properties from secondary aging after a normalizing heat treatment step. While PHCSS materials are available in austenitic and semi-austenitic forms, the martensitic PHCSS are most widely used due to a combination of high strength, good toughness, and corrosion resistance. If higher strength levels can be achieved in these alloys, these materials can be used as a lower-cost alternative to titanium for high specific strength applications where corrosion resistance is a factor. Although wrought precipitation hardened materials have been in use and specified for more than half a century, the specification and use of PHCSS has only been recent. The effects of composition and processing on performance have received little attention in the cast steel literature. The work presented in these investigations is concerned with the experimental study and modeling of microstructural development in cast martensitic precipitation hardened steels at high strength levels. Particular attention is focused on improving the performance of the high strength CB7Cu alloy by control of detrimental secondary phases, notably delta ferrite and retained austenite, which is detrimental to strength, but potentially beneficial in terms of fracture and impact toughness. The relationship between age processing and mechanical properties is also investigated, and a new age hardening model based on simultaneous precipitation hardening and tempering has been modified for use with these steels. Because the CB7Cu system has limited strength even with improved processing, a higher strength prototype Fe-Ni-Cr-Mo-Ti system has been designed and adapted for use in casting. This prototype is expected to develop high strengths matching or exceed that of cast Ti-6Al-4V alloys. Traditional multicomponent constitution phase diagrams widely used for phase estimation in conventional stainless steels, give poor estimates of secondary phases in PHCSS. No measureable retained austenite was observed in any of the CB7Cu-1 steels studied, in spite of the fact that austenite is predicted by the constitution diagrams. A designed experiment using computationally derived phase equilibrium diagrams and actual experimental tests on CB7Cu of different compositions suggests that the ferrite phase is less stable than the constitution diagrams for austenitic stainless steels suggest. Delta ferrite was also more stable in slower-cooled sand cast material as compared to thin, fast-cooled investment cast material. High temperature solutionizing treatments were effective in dissolving delta ferrite at temperatures above 1900°F (˜1040°C). Delta ferrite dissolution was found to proceed at high rates during initial dissolution, and then was found to slow after 1 hour. Diffusion during the later stages is well-predicted by classical diffusion models. Repeated solution treatments were found to modestly increase both ductility and strength, likely due to subgrain refinement through austenite regrowth. Multistaged aging provided superior strength and toughness increases over similarly peak-aged and near peak-aged material aged at a single temperature. Peak-aged material fractography suggested that low energy quasi-cleavage fracture was likely due to age precipitate embrittlement along with some nucleation of MnS particulates at prior austenite grain boundaries. Yield strengths approaching 190 ksi (1310MPa) can be achieved in CB7Cu-1 if appropriate best-practices "+" processing techniques are used. This includes hot isostatic processing to reduce solidification segregation and heal microporosity, high temperature homogenization for effective age hardening and ferrite reduction, double-cycle solutionizing for structure refinement, and multistaged age strengthening for finer precipitate control. The experimental prototype 11-11PH (Fe-Ni-Cr-Ti-Mo) casting alloys was cast and was found to be delta-ferrite free in the as-cast condition. In this material, proper quench processing to eliminate excessive retained austenite was found to be most influential in terms of high strengths. It was also found that cooling below 0°C provided the best combination of strength and toughness, with the specific strength of the material exceeding that of cast Ti-6Al-4V material. Fractography studies suggest that titanium carbonitride and titanium carbon-nitride-sulfide inclusions limit the toughness of cast materials due to long exposures to ideal growth conditions during initial cooling. OIM studies also suggest that the retained austenite in properly processed 11-11PH alloy takes on an interlath structure, which likely contributes to toughness of the alloy, even at high-strength, peak aged conditions. Yield strengths approaching 235 ksi (1620 MPa) were achieved during initial heat treatment trials. It is expected that further improvements in properties can be achieved with continued improvement of processing for this new cast alloy system.

Ti-6Al-4V Additively Manufactured by Selective Laser Melting with Superior Mechanical Properties

NASA Astrophysics Data System (ADS)

Xu, W.; Sun, S.; Elambasseril, J.; Liu, Q.; Brandt, M.; Qian, M.

2015-03-01

The Achilles' heel of additively manufactured Ti-6Al-4V by selective laser melting (SLM) is its inferior mechanical properties compared with its wrought (forged) counterparts. Acicular α' martensite resulted from rapid cooling by SLM is primarily responsible for high strength but inadequate tensile ductility achieved in the as-fabricated state. This study presents a solution to eliminating the adverse effect of the nonequilibrium α' martensite. This is achieved by enabling in situ martensite decomposition into a novel ultrafine (200-300 nm) lamellar ( α + β) microstructure via the selection of an array of processing variables including the layer thickness, energy density, and focal offset distance. The resulting tensile elongation reached 11.4% while the yield strength was kept above 1100 MPa. These properties compare favorably with those of mill-annealed Ti-6Al-4V consisting of globular α and β. The fatigue life of SLM-fabricated Ti-6Al-4V with an ultrafine lamellar ( α + β) structure has approached that of the mill-annealed counterparts and is much superior to that of SLM-fabricated Ti-6Al-4V with α' martensite.

Age, year‐class strength variability, and partial age validation of Kiyis from Lake Superior

USGS Publications Warehouse

Lepak, Taylor A.; Ogle, Derek H.; Vinson, Mark

2017-01-01

ge estimates of Lake Superior Kiyis Coregonus kiyi from scales and otoliths were compared and 12 years (2003–2014) of length frequency data were examined to assess year‐class strength and validate age estimates. Ages estimated from otoliths were precise and were consistently older than ages estimated from scales. Maximum otolith‐derived ages were 20 years for females and 12 years for males. Age estimates showed high numbers of fish of ages 5, 6, and 11 in 2014, corresponding to the 2009, 2008, and 2003 year‐classes, respectively. Strong 2003 and 2009 year‐classes, along with the 2005 year‐class, were also evident based on distinct modes of age‐1 fish (<110 mm) in the length frequency distributions from 2004, 2010, and 2006, respectively. Modes from these year‐classes were present as progressively larger fish in subsequent years. Few to no age‐1 fish (<110 mm) were present in all other years. Ages estimated from otoliths were generally within 1 year of the ages corresponding to strong year‐classes, at least for age‐5 and older fish, suggesting that Kiyi age may be reliably estimated to within 1 year by careful examination of thin‐sectioned otoliths.

Novel Nanofiber-based Membrane Separators for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Yanilmaz, Meltem

Lithium-ion batteries have been widely used in electronic devices including mobile phones, laptop computers, and cameras due to their high specific energy, high energy density, long cycling lifetime, and low self-discharge rate. Nowadays, lithium-ion batteries are finding new applications in electric/hybrid vehicles and energy storage for smart grids. To be used in these new applications, novel battery components are needed so that lithiumion batteries with higher cell performance, better safety, and lower cost can be developed. A separator is an important component to obtain safe batteries and its primary function is to prevent electronic contact between electrodes while regulating cell kinetics and ionic flow. Currently, microporous membranes are the most commonly used separator type and they have good mechanical properties and chemical stability. However, their wettability and thermal stabilities are not sufficient for applications that require high operating temperature and high performance. Due to the superior properties such as large specific surface area, small pore size and high porosity, electrospun nanofiber membranes can be good separator candidate for highperformance lithium-ion batteries. In this work, we focus our research on fabricating nanofiber-based membranes to design new high-performance separators with good thermal stability, as well as superior electrochemical performance compared to microporous polyolefin membranes. To combine the good mechanical strength of PP nonwovens with the excellent electrochemical properties of SiO2/polyvinylidene fluoride (PVDF) composite nanofibers, SiO 2/PVDF composite nanofiber-coated PP nonwoven membranes were prepared. It was found that the addition of SiO2 nanoparticles played an important role in improving the overall performance of these nanofiber-coated nonwoven membranes. Although ceramic/polymer composites can be prepared by encapsulating ceramic particles directly into polymer nanofibers, the performance of the resultant composite membranes is restricted because these nanoparticles are not exposed to liquid electrolytes and have limited effect on improving the cell performance. Hence, we introduced new nanoparticle-on-nanofiber hybrid membrane separators by combining electrospraying with electrospinning techniques. Electrochemical properties were enhanced due to the increased surface area caused by the unique hybrid structure of SiO2 nanoparticles and PVDF nanofibers. To design a high-performance separator with enhanced mechanical properties and good thermal stability, electrospun SiO2/nylon 6,6 nanofiber membranes were fabricated. It was found that SiO2/nylon 6,6 nanofiber membranes had superior thermal stability and mechanical strength. Electrospinning has serious drawbacks such as low spinning rate and high production cost. Centrifugal spinning is a fast, cost-effective and safe alternative to the electrospinning. SiO2/polyacrylonitrile (PAN) membranes were produced by using centrifugal spinning. Compared with commercial microporous polyolefin membranes, SiO2/PAN membranes had larger liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO2/PAN membrane separators were assembled into lithium/lithium iron phosphate cells and these cells exhibited good cycling and C-rate performance.

[Value of using polyethylene glycol in the indirect antiglobulin test with erythrocytes].

PubMed

Michalewska, B; Walewska, I; Seyfriedowa, H; Kuśnierz-Alejska, G

1991-01-01

A series of comparative investigations was carried out for establishing the value of the indirect antiglobulin test (IAT) in its first phase. The results showed that PEG, in relation to NaCl solution of low ionic strength, increased the reactivity of various antibodies of different specificity present in 72 studied sera. A significant superiority of IAT-PEG to IAT-BISS was noted in 45.8% of these sera. In search for antibodies in sera of 1160 patients IAT-PEG detected 7 antibodies not reacting in the IAT-LISS, and 5 of them had Rh system specificity, one was anti-K and one anti-Jka. Although the IAT-PEG was more sensitive than IAT-LISS in the detection of anti-Rh antibodies, it was less sensitive in this range than the enzymatic LEN test with which not only 5 of these antibodies were demonstrated but which detected also 8 antibodies not demonstrated in IAT-PEG or IAT-LISS. All 5 antibodies not detected by the IAT-PEG but demonstrated in the IAT-LISS were specific for the Lewis system. The per cent of reactions regarded as non-specific in the IAT-PEG was 1.3%. The IAT-PEG modification may be recommended as a sensitive, simple and specific method extending the possibilities of immunohematological diagnosis, especially in cases of post-transfusion reactions and in difficulties of interpretation connected with the occurrence of weakly positive reactions in the IAT-LISS.

Experimental and theoretical investigation of a mesoporous KxWO3 material having superior mechanical strength

NASA Astrophysics Data System (ADS)

Dey, Sonal; Anderson, Sean T.; Mayanovic, Robert A.; Sakidja, Ridwan; Landskron, Kai; Kokoszka, Berenika; Mandal, Manik; Wang, Zhongwu

2016-01-01

Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K0.07WO3.Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K0.07WO3. Electronic supplementary information (ESI) available: Experimental details of SEM and TEM measurements, SAXS data analysis, the procedure for Rietveld refinement, peak fitting for the Raman results, the modelling approach, UV-Vis and N2 sorption measurements. See DOI: 10.1039/c5nr07941a

Spatial cognition in autism spectrum disorders: superior, impaired, or just intact?

PubMed

Edgin, Jamie O; Pennington, Bruce F

2005-12-01

The profile of spatial ability is of interest across autism spectrum disorders (ASD) because of reported spatial strengths in ASD and due to the recent association of Asperger's syndrome with Nonverbal Learning Disability. Spatial functions were examined in relation to two cognitive theories in autism: the central coherence and executive function (EF) theories. Performance on spatial tasks, EFs, and global/local processing was compared in children with ASD and controls. While the ASD group had faster reaction times on the Embedded Figures task, spatial performance was intact, but not superior, on other tasks. There was no evidence for impairments in EF or in processing global/local information, therefore contradicting these two theories. The implications of these results for these two theories are discussed.

Mechanical stretching for tissue engineering: two-dimensional and three-dimensional constructs.

PubMed

Riehl, Brandon D; Park, Jae-Hong; Kwon, Il Keun; Lim, Jung Yul

2012-08-01

Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols.

Mechanical Stretching for Tissue Engineering: Two-Dimensional and Three-Dimensional Constructs

PubMed Central

Riehl, Brandon D.; Park, Jae-Hong; Kwon, Il Keun

2012-01-01

Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols. PMID:22335794

Functional relevance of interindividual differences in temporal lobe callosal pathways: a DTI tractography study.

PubMed

Westerhausen, René; Grüner, Renate; Specht, Karsten; Hugdahl, Kenneth

2009-06-01

The midsagittal corpus callosum is topographically organized, that is, with regard to their cortical origin several subtracts can be distinguished within the corpus callosum that belong to specific functional brain networks. Recent diffusion tensor tractography studies have also revealed remarkable interindividual differences in the size and exact localization of these tracts. To examine the functional relevance of interindividual variability in callosal tracts, 17 right-handed male participants underwent structural and diffusion tensor magnetic resonance imaging. Probabilistic tractography was carried out to identify the callosal subregions that interconnect left and right temporal lobe auditory processing areas, and the midsagittal size of this tract was seen as indicator of the (anatomical) strength of this connection. Auditory information transfer was assessed applying an auditory speech perception task with dichotic presentations of consonant-vowel syllables (e.g., /ba-ga/). The frequency of correct left ear reports in this task served as a functional measure of interhemispheric transfer. Statistical analysis showed that a stronger anatomical connection between the superior temporal lobe areas supports a better information transfer. This specific structure-function association in the auditory modality supports the general notion that interindividual differences in callosal topography possess functional relevance.

Adolescents' ability to read different emotional faces relates to their history of maltreatment and type of psychopathology.

PubMed

Leist, Tatyana; Dadds, Mark R

2009-04-01

Emotional processing styles appear to characterize various forms of psychopathology and environmental adversity in children. For example, autistic, anxious, high- and low-emotion conduct problem children, and children who have been maltreated, all appear to show specific deficits and strengths in recognizing the facial expressions of emotions. Until now, the relationships between emotion recognition, antisocial behaviour, emotional problems, callous-unemotional (CU) traits and early maltreatment have never been assessed simultaneously in one study, and the specific associations of emotion recognition to maltreatment and child characteristics are therefore unknown. We examined facial-emotion processing in a sample of 23 adolescents selected for high-risk status on the variables of interest. As expected, maltreatment and child characteristics showed unique associations. CU traits were uniquely related to impairments in fear recognition. Antisocial behaviour was uniquely associated with better fear recognition, but impaired anger recognition. Emotional problems were associated with better recognition of anger and sadness, but lower recognition of neutral faces. Maltreatment was predictive of superior recognition of fear and sadness. The findings are considered in terms of social information-processing theories of psychopathology. Implications for clinical interventions are discussed.

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys

NASA Technical Reports Server (NTRS)

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.

1986-01-01

A study was conducted: (1) to develop rapid solidification processed (RSP) dispersoid-containing Al-3Cu-2Li-1Mg-0.2Zr alloys as substitutes for titanium alloys and commercial 2XXX aluminum alloys for service to at least 150 C; and (2) to develop RSP Al-4Li-Cu-Mg-Zr alloys as substitutes for high-strength commercial 7XXX alloys in ambient-temperature applications. RSP Al-3Cu-2Li-1Mg-0.2Zr alloys have density-normalized yield stresses at 150 C up to 52% larger than that of 2124-T851 and up to 30% larger than that of Ti-6Al-4V. Strength at 150 C in these alloys is provided by thermally stable delta' (Al3Li), T1 (Al2LiCu), and S' (Al2CuMg) precipitates. Density-normalized yield stresses of RSP Al-3Cu-2Li-1Mg-0.2Zr alloys are up to 100% larger than that of 2124-T851 and equivalent to that of Al-8Fe-4Ce at 260 C. Strength in the RSP alloys at 260 C is provided by incoherent dispersoids and subboundary constituent particles such as T1 and S. The RSP alloys are attractive substitutes in less than or = 100-h exposures for 2xxx and Al-4Fe-Ce alloys up to 260 C and for titanium alloys up to 150 C. RSP Al-4Li-Cu-Mg-Zr alloys have ambient-temperature yield and ultimate tensile stresses similar to that of 7050-T7651, and are 14% less dense. RSP Al-4Li-0.5Cu-1.5Mg-0.2Zr has a 20% higher specific yield stress, 40% higher specific elastic modulus, and superior corrosion resistance compared to the properties of 7050-T7651. Strength in the Al-4Li-Cu-Mg-Zr alloy class is primarily provided by the substructure and delta' precipitates and is independent of Cu:Mg ratio. Improvements in fracture toughness and transverse-orientation properties in both alloy classes depend on improved melt practices to eliminate oxide inclusions which are incorporated into the consolidated forms.

Semi-2-interpenetrating polymer networks of high temperature systems

NASA Technical Reports Server (NTRS)

Hanky, A. O.; St. Clair, T. L.

1985-01-01

A semi-interpenetrating (semi-IPN) polymer system of the semi-2-IPN type is described in which a polymer of acetylene-terminated imidesulfone (ATPISO2) is cross linked in the presence of polyimidesulfone (PISO2). Six different formulations obtained by mixing of either ATPISO2-1n or ATPISO2-3n with PISO2 in three different proportions were characterized in terms of glass transition temperature, thermooxidative stability, inherent viscosity, and dynamic mechanical properties. Adhesive (lap shear) strength was tested at elevated temperatures on aged samples of adhesive scrim cloth prepared from each resin. Woven graphite (Celion 1000)/polyimide composites were tested for flexural strength, flexural modulus, and shear strength. The network polymers have properties intermediate between those of the component polymers alone, have greatly improved processability over either polyimide, and are able to form good adhesive bonds and composites, making the semi-2-IPN systems superior materials for aerospace structures.

Research on mechanical properties of silver-bearing antibacterial duplex stainless steel

NASA Astrophysics Data System (ADS)

Liu, Dong; Xiang, Hongliang

2017-04-01

In this paper, silver-bearing antibacterial duplex stainless steels were prepared by adding Ag or Cu-Ag alloy particles. The microstructure, mechanical properties and fracture morphology were investigated in detail by OM, ESEM and tensile testing machine. Tensile tests indicate that the tensile fractures of Ag-bearing antibacterial duplex stainless steel and CD4MCu have the typical ductile character and toughening nests are isometric. After the solution treatment at 1050 ℃, for the material prepared by adding 150-300 µm Cu-Ag master alloy after the solution treatment at 1050 ℃, its plasticity is superior to that of CD4MCu, the strength and hardness are equivalent. But for the material prepared by adding pure Ag alloy particles, its plasticity, strength and hardness are less than that of CD4MCu. When the solution temperature rises, the plastic, strength and hardness of the material prepared by adding 150-300 µm Cu-Ag decrease.

Examining Mechanical Strength Characteristics of Selective Inhibition Sintered HDPE Specimens Using RSM and Desirability Approach

NASA Astrophysics Data System (ADS)

Rajamani, D.; Esakki, Balasubramanian

2017-09-01

Selective inhibition sintering (SIS) is a powder based additive manufacturing (AM) technique to produce functional parts with an inexpensive system compared with other AM processes. Mechanical properties of SIS fabricated parts are of high dependence on various process parameters importantly layer thickness, heat energy, heater feedrate, and printer feedrate. In this paper, examining the influence of these process parameters on evaluating mechanical properties such as tensile and flexural strength using Response Surface Methodology (RSM) is carried out. The test specimens are fabricated using high density polyethylene (HDPE) and mathematical models are developed to correlate the control factors to the respective experimental design response. Further, optimal SIS process parameters are determined using desirability approach to enhance the mechanical properties of HDPE specimens. Optimization studies reveal that, combination of high heat energy, low layer thickness, medium heater feedrate and printer feedrate yielded superior mechanical strength characteristics.

Improved TIG weld joint strength in aluminum alloy 2219-T87 by filler metal substitution

NASA Technical Reports Server (NTRS)

Poorman, R. M.; Lovoy, C. V.

1972-01-01

The results of an investigation on weld joint characteristics of aluminum alloy 2219-T87 are given. Five different alloys were utilized as filler material. The mechanical properties of the joints were determined at ambient and cryogenic temperatures for weldments in the as-welded condition and also, for weldments after elevated temperature exposures. Other evaluations included hardness surveys, stress corrosion susceptibility, and to a limited extent, the internal metallurgical weld structures. The overall results indicate that M-943 filler weldments are superior in strength to weldments containing either the standard 2319 filler or fillers 2014, 2020, and a dual wire feed consisting of three parts 2319 and one part 5652. In addition, no deficiencies were evident in M-934 filler weldments with regard to ductility, joint strength after elevated temperature exposure, weld hardness, metallographic structures, or stress corrosion susceptibility.

Ambient Cured Alkali Activated Flyash Masonry Units

NASA Astrophysics Data System (ADS)

Venugopal, K.; Radhakrishna; Sasalatti, Vinod M.

2016-09-01

Geopolymers belong to a category of non-conventional and non-Portland cement based cementitious binders which are produced using industrial by products like fly ash and ground granulated blast furnace slag (GGBFS). This paper reports on the development of geopolymer mortars for production of masonry units. The geopolymer mortars were prepared by mixing various by products with manufactured sand and a liquid mixture of sodium silicate and sodium hydroxide solutions. After curing at ambient conditions, the masonry units were tested for strength properties such as water absorption, initial rate of absorption, compression, shear- bond, and stress-strain behaviour etc. It was observed that the flexural strength of the blocks is more than 2 MPa and shear bond strength is more than 0.4MPa. It was found that the properties of geopolymer blocks were superior to the traditional masonry units. Hence they can be recommended for structural masonry.

Mechanical properties of nanostructure of biological materials

NASA Astrophysics Data System (ADS)

Ji, Baohua; Gao, Huajian

2004-09-01

Natural biological materials such as bone, teeth and nacre are nanocomposites of protein and mineral with superior strength. It is quite a marvel that nature produces hard and tough materials out of protein as soft as human skin and mineral as brittle as classroom chalk. What are the secrets of nature? Can we learn from this to produce bio-inspired materials in the laboratory? These questions have motivated us to investigate the mechanics of protein-mineral nanocomposite structure. Large aspect ratios and a staggered alignment of mineral platelets are found to be the key factors contributing to the large stiffness of biomaterials. A tension-shear chain (TSC) model of biological nanostructure reveals that the strength of biomaterials hinges upon optimizing the tensile strength of the mineral crystals. As the size of the mineral crystals is reduced to nanoscale, they become insensitive to flaws with strength approaching the theoretical strength of atomic bonds. The optimized tensile strength of mineral crystals thus allows a large amount of fracture energy to be dissipated in protein via shear deformation and consequently enhances the fracture toughness of biocomposites. We derive viscoelastic properties of the protein-mineral nanostructure and show that the toughness of biocomposite can be further enhanced by the viscoelastic properties of protein.

Creep rupture behavior of Stirling engine materials

NASA Technical Reports Server (NTRS)

Titran, R. H.; Scheuerman, C. M.; Stephens, J. R.

1985-01-01

The automotive Stirling engine, being investigated jointly by the Department of Energy and NASA Lewis as an alternate to the internal combustion engine, uses high-pressure hydrogen as the working fluid. The long-term effects of hydrogen on the high temperature strength properties of materials is relatively unknown. This is especially true for the newly developed low-cost iron base alloy NASAUT 4G-A1. This iron-base alloy when tested in air has creep-rupture strengths in the directionally solidified condition comparable to the cobalt base alloy HS-31. The equiaxed (investment cast) NASAUT 4G-A1 has superior creep-rupture to the equiaxed iron-base alloy XF-818 both in air and 15 MPa hydrogen.

Zirconia based dental ceramics: structure, mechanical properties, biocompatibility and applications.

PubMed

Gautam, Chandkiram; Joyner, Jarin; Gautam, Amarendra; Rao, Jitendra; Vajtai, Robert

2016-12-06

Zirconia (ZrO 2 ) based dental ceramics have been considered to be advantageous materials with adequate mechanical properties for the manufacturing of medical devices. Due to its very high compression strength of 2000 MPa, ZrO 2 can resist differing mechanical environments. During the crack propagation on the application of stress on the surface of ZrO 2 , a crystalline modification diminishes the propagation of cracks. In addition, zirconia's biocompatibility has been studied in vivo, leading to the observation of no adverse response upon the insertion of ZrO 2 samples into the bone or muscle. In vitro experimentation has exhibited the absence of mutations and good viability of cells cultured on this material leading to the use of ZrO 2 in the manufacturing of hip head prostheses. The mechanical properties of zirconia fixed partial dentures (FPDs) have proven to be superior to other ceramic/composite restorations and hence leading to their significant applications in implant supported rehabilitations. Recent developments were focused on the synthesis of zirconia based dental materials. More recently, zirconia has been introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures in combination with computer aided design/computer aided manufacturing (CAD/CAM) techniques. This systematic review covers the results of past as well as recent scientific studies on the properties of zirconia based ceramics such as their specific compositions, microstructures, mechanical strength, biocompatibility and other applications in dentistry.

Fabrication and Characteristics of Sintered Cutting Stainless Steel Fiber Felt with Internal Channels and an Al₂O₃ Coating.

PubMed

Huang, Shufeng; Wan, Zhenping; Zou, Shuiping

2018-03-20

A novel sintered cutting stainless steel fiber felt with internal channels (SCSSFFC) composed of a stainless-steel fiber skeleton, three-dimensional interconnected porous structure and multiple circular microchannels is developed. SCSSFFC has a jagged and rough surface morphology and possesses a high specific surface area, which is approximately 2.4 times larger than that of the sintered bundle-drawing stainless steel fiber felt with internal channels (SBDSSFFC) and is expected to enhance adhesive strength. The sol-gel and wet impregnation methods are adopted to prepare SCSSFFC with an Al₂O₃ coating (SCSSFFC/Al₂O₃). The adhesive strength of SCSSFFC/Al₂O₃ is investigated using ultrasonic vibration and thermal shock tests. The experimental results indicate that the weight loss rate of the Al₂O₃ coating has a 4.2% and 8.42% reduction compared with those of SBDSSFFCs based on ultrasonic vibration and thermal shock tests. In addition, the permeability of SCSSFFC/Al₂O₃ is investigated based on forced liquid flow tests. The experimental results show that the permeability and inertial coefficients of SCSSFFC/Al₂O₃ are mainly affected by the coating rate, porosity and open ratio; however, the internal microchannel diameter has little influence. It is also found that SCSSFFC/Al₂O₃ yields superior permeability, as well as inertial coefficients compared with those of other porous materials reported in the literature.

Probabilistic fatigue methodology for six nines reliability

NASA Technical Reports Server (NTRS)

Everett, R. A., Jr.; Bartlett, F. D., Jr.; Elber, Wolf

1990-01-01

Fleet readiness and flight safety strongly depend on the degree of reliability that can be designed into rotorcraft flight critical components. The current U.S. Army fatigue life specification for new rotorcraft is the so-called six nines reliability, or a probability of failure of one in a million. The progress of a round robin which was established by the American Helicopter Society (AHS) Subcommittee for Fatigue and Damage Tolerance is reviewed to investigate reliability-based fatigue methodology. The participants in this cooperative effort are in the U.S. Army Aviation Systems Command (AVSCOM) and the rotorcraft industry. One phase of the joint activity examined fatigue reliability under uniquely defined conditions for which only one answer was correct. The other phases were set up to learn how the different industry methods in defining fatigue strength affected the mean fatigue life and reliability calculations. Hence, constant amplitude and spectrum fatigue test data were provided so that each participant could perform their standard fatigue life analysis. As a result of this round robin, the probabilistic logic which includes both fatigue strength and spectrum loading variability in developing a consistant reliability analysis was established. In this first study, the reliability analysis was limited to the linear cumulative damage approach. However, it is expected that superior fatigue life prediction methods will ultimately be developed through this open AHS forum. To that end, these preliminary results were useful in identifying some topics for additional study.

Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study.

PubMed

Philip, Jacob M; Ganapathy, Dhanraj M; Ariga, Padma

2012-07-01

This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin. A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05). This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base. Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

Comparative evaluation of tensile bond strength and microleakage of conventional glass ionomer cement, resin modified glass ionomer cement and compomer: An in vitro study.

PubMed

Rekha, C Vishnu; Varma, Balagopal; Jayanthi

2012-07-01

The purpose of this study was to evaluate and compare the tensile bond strength and microleakage of Fuji IX GP, Fuji II LC, and compoglass and to compare bond strength with degree of microleakage exhibited by the same materials. Occlusal surfaces of 96 noncarious primary teeth were ground perpendicular to long axis of the tooth. Preparations were distributed into three groups consisting of Fuji IX GP, Fuji II LC and Compoglass. Specimens were tested for tensile bond strength by mounting them on Instron Universal Testing Machine. Ninety-six primary molars were treated with Fuji IX GP, Fuji II LC, and compoglass on box-only prepared proximal surface. Samples were thermocycled, stained with dye, sectioned, and scored for microleakage under stereomicroscope. ANOVA and Bonferrani correction test were done for comparisons. Pearson Chi-square test and regression analysis were done to assess the association between the parameters. Compoglass showed highest tensile strength and Fuji II LC showed least microleakage. There was a significant difference between the three groups in tensile strength and microleakage levels. The correlation between tensile strength and microleakage level in each group showed that there was a significant negative correlation only in Group 3. Fuji II LC and compoglass can be advocated in primary teeth because of their superior physical properties when compared with Fuji IX GP.

Skeletal assessment with finite element analysis: relevance, pitfalls and interpretation.

PubMed

Campbell, Graeme Michael; Glüer, Claus-C

2017-07-01

Finite element models simulate the mechanical response of bone under load, enabling noninvasive assessment of strength. Models generated from quantitative computed tomography (QCT) incorporate the geometry and spatial distribution of bone mineral density (BMD) to simulate physiological and traumatic loads as well as orthopaedic implant behaviour. The present review discusses the current strengths and weakness of finite element models for application to skeletal biomechanics. In cadaver studies, finite element models provide better estimations of strength compared to BMD. Data from clinical studies are encouraging; however, the superiority of finite element models over BMD measures for fracture prediction has not been shown conclusively, and may be sex and site dependent. Therapeutic effects on bone strength are larger than for BMD; however, model validation has only been performed on untreated bone. High-resolution modalities and novel image processing methods may enhance the structural representation and predictive ability. Despite extensive use of finite element models to study orthopaedic implant stability, accurate simulation of the bone-implant interface and fracture progression remains a significant challenge. Skeletal finite element models provide noninvasive assessments of strength and implant stability. Improved structural representation and implant surface interaction may enable more accurate models of fragility in the future.

Effects of silviculture and genetics on branch/knot attributes of coastal Pacific Northwest Douglas-fir and implications for wood quality--a synthesis

Treesearch

Eini C. Lowell; Douglas A. Maguire; David G. Briggs; Eric C. Turnblom; Keith J.S. Jayawickrama; Jed Bryce

2014-01-01

Douglas-fir is the most commercially important timber species in the US Pacific Northwest due to its ecological prevalence and its superior wood attributes, especially strength and stiffness properties that make it highly prized for structural applications. Its economic significance has led to extensive establishment and management of plantations over the last few...

A Pilot Study on the Gross Motor Proficiency of Hong Kong Preschoolers Aged 5 to 6 Years.

ERIC Educational Resources Information Center

Lam, Hazel Mei Yung; Schiller, Wendy

2001-01-01

Used the Bruininks-Oseretsky Test of Motor Proficiency to examine the gross motor proficiency of Hong Kong 5- to 6-year-old preschoolers. Found that both age groups scored well below norms in running speed and agility and well above norms on balance, bilateral coordination, strength, and upper-limb coordination. Boys were superior to girls on…

Comparison of physical performance among Brazilian elite soccer players of different age-categories.

PubMed

Kobal, Ronaldo; Loturco, Irineu; Gil, Saulo; Cal Abad, Cesar C; Cuniyochi, Rogério; Barroso, Renato; Tricoli, Valmor

2016-04-01

The purpose of this study was to compare the physical performance (i.e., strength, power, speed and endurance) between Brazilian elite soccer players from different categories of the same club: professionals (PRO), under-20 (U-20), and under-17 (U-17). Seventy-one soccer players from three categories (PRO=24; U-20=21 and U-17=26) were assessed at the beginning of pre-season. Before the tests, they were familiarized with all experimental procedures. Squat jump (SJ), countermovement jump (CMJ), sprint (10 m/20 m), maximum dynamic strength (1RM), and Yo-Yo intermittent recovery tests level 1 were performed in three non-consecutive sessions. No significant differences were found between the categories for sprint times. The PRO players presented higher outcomes in the 1RM, SJ, CMJ, and Yo-Yo tests than the U-20 and U-17 players (P≤0.05). No significant differences were found between the U-20 and U-17 players in 1RM, and SJ/CMJ heights. The U-20 presented superior performance than the U-17 in the Yo-Yo test (P≤0.05). The findings indicated that PRO performed better than younger players in all assessments, except for the sprint tests. This may have been possible due to the differences in training experience, technical expertise and individual levels of strength/power. However, the absence of differences between the U-20 and U-17 groups highlighted the necessity of developing specific training strategies in order to improve the physical capacities of younger players, throughout the maturation process. Moreover, due to the importance of sprinting in soccer, it is strongly recommended that fitness coaches develop more effective strategies to improve speed ability in professional players.

Aquatic exercise training and stable heart failure: A systematic review and meta-analysis.

PubMed

Adsett, Julie A; Mudge, Alison M; Morris, Norman; Kuys, Suzanne; Paratz, Jennifer D

2015-01-01

A meta-analysis and review of the evidence was conducted to determine the efficacy of aquatic exercise training for individuals with heart failure compared to traditional land-based programmes. A systematic search was conducted for studies published prior to March 2014, using MEDLINE, PUBMED, Cochrane Library, CINAHL and PEDro databases. Key words and synonyms relating to aquatic exercise and heart failure comprised the search strategy. Interventions included aquatic exercise or a combination of aquatic plus land-based training, whilst comparator protocols included usual care, no exercise or land-based training alone. The primary outcome of interest was exercise performance. Studies reporting on muscle strength, quality of life and a range of haemodynamic and physiological parameters were also reviewed. Eight studies met criteria, accounting for 156 participants. Meta-analysis identified studies including aquatic exercise to be superior to comparator protocols for 6 minute walk test (p < 0.004) and peak power (p < 0.044). Compared to land-based training programmes, aquatic exercise training provided similar benefits for VO(2peak), muscle strength and quality of life, though was not superior. Cardiac dimensions, left ventricular ejection fraction, cardiac output and BNP were not influenced by aquatic exercise training. For those with stable heart failure, aquatic exercise training can improve exercise capacity, muscle strength and quality of life similar to land-based training programmes. This form of exercise may provide a safe and effective alternative for those unable to participate in traditional exercise programmes. Crown Copyright © 2015. Published by Elsevier Ireland Ltd. All rights reserved.

Neuromuscular electrical stimulation via the peroneal nerve is superior to graduated compression socks in reducing perceived muscle soreness following intense intermittent endurance exercise.

PubMed

Ferguson, Richard A; Dodd, Matthew J; Paley, Victoria R

2014-10-01

A novel technique of neuromuscular electrical stimulation (NMES) via the peroneal nerve has been shown to augment limb blood flow which could enhance recovery following exercise. The present study examined the effects of NMES, compared to graduated compression socks on muscle soreness, strength, and markers of muscle damage and inflammation following intense intermittent exercise. Twenty-one (age 21 ± 1 years, height 179 ± 7 cm, body mass 76 ± 9 kg,) healthy males performed a 90-min intermittent shuttle running test on three occasions. Following exercise, the following interventions were applied: passive recovery (CON), graduated compression socks (GCS) or NMES. Perceived muscle soreness (PMS) and muscle strength (isometric maximal voluntary contraction of knee extensors and flexors) were measured and a venous blood sample taken pre-exercise and 0, 1, 24, 48 and 72 h following exercise for measurement of creatine kinase (CK) and Lactate dehydrogenase (LDH) activity and IL-6 and CRP concentrations. PMS increased in all conditions immediately, 1 and 24 h post-exercise. At 24 h PMS was lower in NMES compared to GCS and CON (2.0 ± 1.6, 3.2 ± 2.1, 4.6 ± 2.0, respectively). At 48 h PMS was lower in NMES compared to CON (1.3 ± 1.5 and 3.1 ± 1.8, respectively). There were no differences between treatments for muscle strength, CK and LDH activity, IL-6 and CRP concentrations. The novel NMES technique is superior to GCS in reducing PMS following intense intermittent endurance exercise.

Comparative Effectiveness Review of Cooled Versus Pulsed Radiofrequency Ablation for the Treatment of Knee Osteoarthritis: A Systematic Review.

PubMed

Gupta, Anita; Huettner, Daniel P; Dukewich, Matthew

2017-03-01

Patients suffering from osteoarthritis of the knee and patients post total knee arthroplasty often develop refractory, disabling chronic knee pain. Radiofrequency ablation, including conventional, pulsed, and cooled, has recently become more accepted as an interventional technique to manage chronic knee pain in patients who have failed conservative treatment or who are not suitable candidates for surgical treatment. This systematic review aimed to analyze published studies on radiofrequency ablation to provide an overview of the current knowledge regarding variations in procedures, nerve targets, adverse events, and temporal extent of clinical benefit. A systematic review of published studies investigating conventional, pulsed, or cooled radiofrequency ablation in the setting of chronic knee pain. Medline, Google Scholar, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases were reviewed for studies on radiofrequency ablation for patients with chronic knee pain through July 29, 2016. From the studies, the procedural details, outcomes after treatment, follow-up points, and complications were compiled and analyzed in this literature review. Included studies were analyzed for clinical relevance and strength of evidence was graded using either the NHLBI Quality assessment of controlled intervention studies or the NHLBI quality assessment for before-after (pre-post) studies with no control group. Seventeen total publications were identified in the search, including articles investigating conventional, pulsed, or cooled radiofrequency ablation. These studies primarily targeted either the genicular nerves or used an intraarticular approach. Of the studies, 5 were small-sized randomized controlled trials, although one involved diathermy radiofrequency ablation. There were 8 retrospective or prospective case series and 4 case reports. Utilizing the strength of evidence grading, there is a low level of certainty to suggest a superior benefit between targeting the genicular nerve, an intraarticular approach, or targeting the larger nerves such as femoral and tibial nerves. Utilizing the strength of evidence grading, there is a low level of certainty in supporting the superiority of any specific RFA procedure modality. The majority of the studies report positive patient outcomes, but the inconsistent procedural methodology, inconsistent patient assessment measures, and small study sizes limit the applicability of any specific study to clinical practice. While the wide search strategy included a variety of articles, broad conclusions and pooled data could not be obtained based on the studies analyzed. Overall, the studies showed promising results for the treatment of severe chronic knee pain by radiofrequency ablation at up to one year with minimal complications. Numerous studies, however, yielded concerns about procedural protocols, study quality, and patient follow-up. Radiofrequency ablation can offer substantial clinical and functional benefit to patients with chronic knee pain due to osteoarthritis or post total knee arthroplasty.Key words: Radiofrequency ablation, knee osteoarthritis, knee pain, genicular nerve, total knee arthroplasty (TKA), cooled radiofrequency ablation, pulsed radiofrequency ablation.

The stress-strain relationships in wood and fiber-reinforced plastic laminae of reinforced glued-laminated wood beams

NASA Astrophysics Data System (ADS)

Tingley, Daniel Arthur

The reinforcement of wood and wood composite structural products to improve their mechanical properties has been in practice for many years. Recently, the use of high-strength fiber-reinforced plastic (FRP) as a reinforcement in such applications has been commercialized. The reinforcement is manufactured using a standard pultrusion process or alternatively a sheet-forming process commonly referred to as "pulforming". The high-modulus fibers are predominately unidirectional, although off-axis fibers are often used to enhance off-axis properties. The fibers used are either of a single type or multiple types, which are called "hybrids". Unidirectional, single, and hybrid fiber FRP physical properties and characteristics were compared to wood. Full-scale reinforced glulams were tested. Aramid-reinforced plastics (ARP) used as tensile reinforcements were found to be superior in strength applications to other types of FRP made with fiber, such as carbon and fiberglass. Carbon/aramid-reinforced plastic (CARP) was shown to be superior in both modulus and strength design situations. Fiberglass was shown to be suitable only in hybrid situations with another fiber such as aramid or carbon and only in limited use situations where modulus was a design criteria. The testing and analysis showed that the global response of reinforced glulam beams is controlled by localized strength variations in the wood such as slope of grain, knots, finger joints, etc. in the tensile zone. The elemental tensile strains in the extreme wood tensile laminae, due to global applied loads, were found to be well below the strain at failure in clear wood samples recovered from the failure area. Two areas affecting the relationship between the wood and the FRP were investigated: compatibility of the wood and FRP materials and interface characteristics between the wood and FRP. The optimum strain value at yield point for an FRP was assessed to be slightly higher than the clear wood value in tension for a species/grade to be reinforced. The effects of localized strength variations in the tensile wood laminae adjacent to the FRP were found to be the predominate cause of failure in full-scale reinforced glulams with less than 1.5% by cross section reinforcement.

A fundamental study on the structural integrity of magnesium alloys joined by friction stir welding

NASA Astrophysics Data System (ADS)

Rao, Harish Mangebettu

The goal of this research is to study the factors that influence the physical and mechanical properties of lap-shear joints produced using friction stir welding. This study focuses on understanding the effect of tool geometry and weld process parameters including the tool rotation rate, tool plunge depth and dwell time on the mechanical performance of similar magnesium alloy and dissimilar magnesium to aluminum alloy weld joints. A variety of experimental activities were conducted including tensile and fatigue testing, fracture surface and failure analysis, microstructure characterization, hardness measurements and chemical composition analysis. An investigation on the effect of weld process conditions in friction stir spot welding of magnesium to magnesium produced in a manner that had a large effective sheet thickness and smaller interfacial hook height exhibited superior weld strength. Furthermore, in fatigue testing of friction stir spot welded of magnesium to magnesium alloy, lap-shear welds produced using a triangular tool pin profile exhibited better fatigue life properties compared to lap-shear welds produced using a cylindrical tool pin profile. In friction stir spot welding of dissimilar magnesium to aluminum, formation of intermetallic compounds in the stir zone of the weld had a dominant effect on the weld strength. Lap-shear dissimilar welds with good material mixture and discontinues intermetallic compounds in the stir zone exhibited superior weld strength compared to lap-shear dissimilar welds with continuous formation of intermetallic compounds in the stir zone. The weld structural geometry like the interfacial hook, hook orientation and bond width also played a major role in influencing the weld strength of the dissimilar lap-shear friction stir spot welds. A wide scatter in fatigue test results was observed in friction stir linear welds of aluminum to magnesium alloys. Different modes of failure were observed under fatigue loading including crack propagation into the top sheet, into the bottom sheet, and interfacial separation. Investigation of the tested welds revealed that the voids in the weld nugget reduced the weld strength, resulting in lower fatigue life. A thin layer of IMCs formed along the faying surface which accelerated the fatigue failure.

Root hairs improve root penetration, root-soil contact, and phosphorus acquisition in soils of different strength.

PubMed

Haling, Rebecca E; Brown, Lawrie K; Bengough, A Glyn; Young, Iain M; Hallett, Paul D; White, Philip J; George, Timothy S

2013-09-01

Root hairs are a key trait for improving the acquisition of phosphorus (P) by plants. However, it is not known whether root hairs provide significant advantage for plant growth under combined soil stresses, particularly under conditions that are known to restrict root hair initiation or elongation (e.g. compacted or high-strength soils). To investigate this, the root growth and P uptake of root hair genotypes of barley, Hordeum vulgare L. (i.e. genotypes with and without root hairs), were assessed under combinations of P deficiency and high soil strength. Genotypes with root hairs were found to have an advantage for root penetration into high-strength layers relative to root hairless genotypes. In P-deficient soils, despite a 20% reduction in root hair length under high-strength conditions, genotypes with root hairs were also found to have an advantage for P uptake. However, in fertilized soils, root hairs conferred an advantage for P uptake in low-strength soil but not in high-strength soil. Improved root-soil contact, coupled with an increased supply of P to the root, may decrease the value of root hairs for P acquisition in high-strength, high-P soils. Nevertheless, this work demonstrates that root hairs are a valuable trait for plant growth and nutrient acquisition under combined soil stresses. Selecting plants with superior root hair traits is important for improving P uptake efficiency and hence the sustainability of agricultural systems.

Synergistic effects from graphene and carbon nanotubes enable flexible and robust electrodes for high-performance supercapacitors.

PubMed

Cheng, Yingwen; Lu, Songtao; Zhang, Hongbo; Varanasi, Chakrapani V; Liu, Jie

2012-08-08

Flexible and lightweight energy storage systems have received tremendous interest recently due to their potential applications in wearable electronics, roll-up displays, and other devices. To manufacture such systems, flexible electrodes with desired mechanical and electrochemical properties are critical. Herein we present a novel method to fabricate conductive, highly flexible, and robust film supercapacitor electrodes based on graphene/MnO(2)/CNTs nanocomposites. The synergistic effects from graphene, CNTs, and MnO(2) deliver outstanding mechanical properties (tensile strength of 48 MPa) and superior electrochemical activity that were not achieved by any of these components alone. These flexible electrodes allow highly active material loading (71 wt % MnO(2)), areal density (8.80 mg/cm(2)), and high specific capacitance (372 F/g) with excellent rate capability for supercapacitors without the need of current collectors and binders. The film can also be wound around 0.5 mm diameter rods for fabricating full cells with high performance, showing significant potential in flexible energy storage devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Guoqiang; Wu, Feng; Zhan, Chun

The development of safe, stable, and long-life Li-ion batteries is being intensively pursued to enable the electrification of transportation and intelligent grid applications. Here, we report a new solid-state Li-ion battery technology, using a solid nanocomposite electrolyte composed of porous silica matrices with in situ immobilizing Li+ conducting ionic liquid, anode material of MCMB, and cathode material of LiCoO 2, LiNi 1/3Co 1/3Mn 1/3O 2, or LiFePO 4. An injection printing method is used for the electrode/electrolyte preparation. Solid nanocomposite electrolytes exhibit superior performance to the conventional organic electrolytes with regard to safety and cycle-life. They also have a transparentmore » glassy structure with high ionic conductivity and good mechanical strength. Solid-state full cells tested with the various cathodes exhibited high specific capacities, long cycling stability, and excellent high temperature performance. This solid-state battery technology will provide new avenues for the rational engineering of advanced Li-ion batteries and other electrochemical devices.« less

Carbon composite bipolar plate for high-temperature proton exchange membrane fuel cells (HT-PEMFCs)

NASA Astrophysics Data System (ADS)

Lee, Dongyoung; Lee, Dai Gil

2016-09-01

A carbon/epoxy composite bipolar plate is an ideal substitute for the brittle graphite bipolar plate for lightweight proton exchange membrane fuel cells (PEMFCs) because of its high specific strength and stiffness. However, conventional carbon/epoxy composite bipolar plates are not applicable for high-temperature PEMFCs (HT-PEMFCs) because these systems are operated at higher temperatures than the glass transition temperatures of conventional epoxies. Therefore, in this study, a cyanate ester-modified epoxy is adopted for the development of a carbon composite bipolar plate for HT-PEMFCs. The composite bipolar plate with exposed surface carbon fibers is produced without any surface treatments or coatings to increase the productivity and is integrated with a silicone gasket to reduce the assembly cost. The developed carbon composite bipolar plate exhibits not only superior electrical properties but also high thermo-mechanical properties. In addition, a unit cell test is performed, and the results are compared with those of the conventional graphite bipolar plate.

Evaluation of potential for reuse of industrial wastewater using metal-immobilized catalysts and reverse osmosis.

PubMed

Choi, Jeongyun; Chung, Jinwook

2015-04-01

This report describes a novel technology of reusing the wastewater discharged from the display manufacturing industry through an advanced oxidation process (AOP) with a metal-immobilized catalyst and reverse osmosis (RO) in the pilot scale. The reclaimed water generated from the etching and cleaning processes in display manufacturing facilities was low-strength organic wastewater and was required to be recycled to secure a water source. For the reuse of reclaimed water to ultrapure water (UPW), a combination of solid-phase AOP and RO was implemented. The removal efficiency of TOC by solid-phase AOP and RO was 92%. Specifically, the optimal acid, pH, and H2O2 concentrations in the solid-phase AOP were determined. With regard to water quality and operating costs, the combination of solid-phase AOP and RO was superior to activated carbon/RO and ultraviolet AOP/anion polisher/coal carbon. Copyright © 2014 Elsevier Ltd. All rights reserved.

A hybrid approach EMD-HW for short-term forecasting of daily stock market time series data

NASA Astrophysics Data System (ADS)

Awajan, Ahmad Mohd; Ismail, Mohd Tahir

2017-08-01

Recently, forecasting time series has attracted considerable attention in the field of analyzing financial time series data, specifically within the stock market index. Moreover, stock market forecasting is a challenging area of financial time-series forecasting. In this study, a hybrid methodology between Empirical Mode Decomposition with the Holt-Winter method (EMD-HW) is used to improve forecasting performances in financial time series. The strength of this EMD-HW lies in its ability to forecast non-stationary and non-linear time series without a need to use any transformation method. Moreover, EMD-HW has a relatively high accuracy and offers a new forecasting method in time series. The daily stock market time series data of 11 countries is applied to show the forecasting performance of the proposed EMD-HW. Based on the three forecast accuracy measures, the results indicate that EMD-HW forecasting performance is superior to traditional Holt-Winter forecasting method.

Influence of irradiation by a novel CO2 9.3-μm short-pulsed laser on sealant bond strength.

PubMed

Rechmann, P; Sherathiya, K; Kinsel, R; Vaderhobli, R; Rechmann, B M T

2017-04-01

The objective of this in vitro study was to evaluate whether irradiation of enamel with a novel CO 2 9.3-μm short-pulsed laser using energies that enhance caries resistance influences the shear bond strength of composite resin sealants to the irradiated enamel. Seventy bovine and 240 human enamel samples were irradiated with a 9.3-μm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with four different laser energies known to enhance caries resistance or ablate enamel (pulse duration from 3 μs at 1.6 mJ/pulse to 43 μs at 14.9 mJ/pulse with fluences between 3.3 and 30.4 J/cm 2 , pulse repetition rate between 4.1 and 41.3 Hz, beam diameter of 0.25 mm and 1-mm spiral pattern, and focus distance of 4-15 mm). Irradiation was performed "freehand" or using a computerized, motor-driven stage. Enamel etching was achieved with 37% phosphoric acid (Scotchbond Universal etchant, 3M ESPE, St. Paul, MN). As bonding agent, Adper Single Bond Plus was used followed by placing Z250 Filtek Supreme flowable composite resin (both 3M ESPE). After 24 h water storage, a single-plane shear bond test was performed (UltraTester, Ultradent Products, Inc., South Jordan, UT). All laser-irradiated samples showed equal or higher bond strength than non-laser-treated controls. The highest shear bond strength values were observed with the 3-μs pulse duration/0.25-mm laser pattern (mean ± SD = 31.90 ± 2.50 MPa), representing a significant 27.4% bond strength increase over the controls (25.04 ± 2.80 MPa, P ≤ 0.0001). Two other caries-preventive irradiation (3 μs/1 mm and 7 μs/0.25 mm) and one ablative pattern (23 μs/0.25 mm) achieved significantly increased bond strength compared to the controls. Bovine enamel also showed in all test groups increased shear bond strength over the controls. Computerized motor-driven stage irradiation did not show superior bond strength values over the clinically more relevant freehand irradiation. Enamel that is made caries-resistant with CO 2 9.3-μm short-pulsed laser irradiation showed at least equal or significantly higher shear bond strength to pit and fissure sealants than non-laser-irradiated enamel. The risk of a sealant failure due to CO 2 9.3-μm short-pulsed laser irradiation appears reduced. If additional laser ablation is required before placing a sealant, the CO 2 9.3-μm enamel laser-cut showed equivalent or superior bond strength to a flowable sealant.

Formulating appropriate statistical hypotheses for treatment comparison in clinical trial design and analysis.

PubMed

Huang, Peng; Ou, Ai-hua; Piantadosi, Steven; Tan, Ming

2014-11-01

We discuss the problem of properly defining treatment superiority through the specification of hypotheses in clinical trials. The need to precisely define the notion of superiority in a one-sided hypothesis test problem has been well recognized by many authors. Ideally designed null and alternative hypotheses should correspond to a partition of all possible scenarios of underlying true probability models P={P(ω):ω∈Ω} such that the alternative hypothesis Ha={P(ω):ω∈Ωa} can be inferred upon the rejection of null hypothesis Ho={P(ω):ω∈Ω(o)} However, in many cases, tests are carried out and recommendations are made without a precise definition of superiority or a specification of alternative hypothesis. Moreover, in some applications, the union of probability models specified by the chosen null and alternative hypothesis does not constitute a completed model collection P (i.e., H(o)∪H(a) is smaller than P). This not only imposes a strong non-validated assumption of the underlying true models, but also leads to different superiority claims depending on which test is used instead of scientific plausibility. Different ways to partition P fro testing treatment superiority often have different implications on sample size, power, and significance in both efficacy and comparative effectiveness trial design. Such differences are often overlooked. We provide a theoretical framework for evaluating the statistical properties of different specification of superiority in typical hypothesis testing. This can help investigators to select proper hypotheses for treatment comparison inclinical trial design. Copyright © 2014 Elsevier Inc. All rights reserved.

Influence of nanoclay on interlaminar shear strength and fracture toughness of glass fiber reinforced nanocomposites

NASA Astrophysics Data System (ADS)

Senthil Kumar, M. S.; Chithirai Pon Selvan, M.; Sampath, P. S.; Raja, K.; Balasundaram, K.

2018-04-01

Multilayer glass fiber reinforced polymer (GFRP) laminates filled with nanoclay was manufactured with compression moulding machine. In the present work, five kinds of nanoclay (Cloisite 25A) loadings viz. 2, 4, 6, 8 and 10% on weight basis of epoxy resin were employed to modify the interlaminar shear strength (ILSS), critical energy release rate (GIc) and impact energy properties of GFRP laminates. Experimental results obtained from ILSS test on clay filled GFRP confirm that the superior strength was attained at low clay content of 155.10 MPa. Furthermore, the mode I interlaminar fracture toughness test conducted on DCB specimens revealed that the commanding improvement of GIc was obtained at 2 wt.% clay content level. On the other hand, both ILSS and fracture toughness was getting reduced at higher clay loadings. At last, the impact strength of the test samples was investigated by using Izod impact test apparatus and observed that the impact energy was increased by 44.39% for 2 wt.% and followed by 24.87% for 4 wt.% clay loadings.

Ultra-tough and strong, hybrid thin films based on ionically crosslinked polymers and 2D inorganic platelets

NASA Astrophysics Data System (ADS)

Ji, Dong Hwan; Choi, Suji; Kim, Jaeyun; nanobiomaterials lab Team

Integration of high strength and toughness tend to be mutually exclusive and synthesized hybrid films with superior mechanical properties have been difficult to fabricate controllable shapes and various scales. Although diverse synthesized hybrid films consisting of organic matrix and inorganic materials with brick-and-mortar structure, show improved mechanical properties, these films are still limited in toughness and fabrication methods. Herein, we report ultra-tough and strong hybrid thin films with self-assembled uniform microstructures with controllable shapes and various scale based on hydrogel-mediated process. Ca2+-crosslinking in alginate chains and well-aligned alumina platelets in alginate matrix lead to a synergistic enhancement of strength and toughness in the resulting film. Consequentially, Ca2+-crosslinked Alg/Alu films showed outstanding toughness of 29 MJ m-3 and tensile strength of 160 MPa. Furthermore, modifying Alu surface with polyvinylpyrrolidone (PVP), tensile strength was further improved up to 200 MPa. Our results suggest an alternative approach to design and processing of self-assembled hydrogel-mediated hybrid films with outstanding mechanical properties.

Flat growth of 7075, 7475, 7050 and 7049 aluminum alloy plate in stress corrosion environments: 2-year marine atmosphere results

NASA Technical Reports Server (NTRS)

Dorward, R. C.; Hasse, K. R.

1978-01-01

Marine atmospheric exposure of smooth and precracked specimens from 7075, 7475, 7050 and 7049 plates support the conclusion that for a given strength level, the short transverse stress corrosion resistance of 7050-T7X and 7049-T7X is superior to that of 7075-T7X. The threshold stress intensity (K sub Iscc) for these alloys is about 25 MPa square root m at a yield strength of about 460 MPa; the corresponding yield strength level for 7075-T7X at this SCR level is about 425 MPa. Additional tests on two lots of high-toughness 7475 plate indicate that this alloy is capable of achieving K sub Iscc values of about 35 MPa square root m at yield strengths of 400-450 MPa. Precracked specimens from all these 7XXX-series alloys are subject to self loading from corrosion product wedging. This effect causes stress corrosion cracks to continue growing at very low apparent stress intensities, and should therefore be considered a potential driving force for stress corrosion in design and materials selection.

Exercise as a remedy for sarcopenia.

PubMed

Landi, Francesco; Marzetti, Emanuele; Martone, Anna M; Bernabei, Roberto; Onder, Graziano

2014-01-01

Although prolongation of life is a significant public health aim, at the same time the extended life should involve preservation of the capacity to live independently. Consequently, the identification of cost-effectiveness interventions to prevent frailty is one of the most important public health challenges. In the present review, we present the available evidence regarding the impact of physical exercise on the components of frailty syndrome and, in particular, as a remedy for sarcopenia. Resistance exercise training is more effective in increasing muscle mass and strength, whereas endurance exercises training is superior for maintaining and improving maximum aerobic power. Based on these evidences, recommendations for adult and frail older people should include a balanced program of both endurance and strength exercises, performed on a regular schedule (at least 3 days a week). Regular exercise is the only strategy found to consistently prevent frailty and improve sarcopenia and physical function in older adults. Physical exercises increase aerobic capacity, muscle strength and endurance, by ameliorating aerobic conditioning and/or strength. In older patients, exercise and physical activity produce at least the same beneficial effects observed in younger individuals.

Development of Alkali Activated Geopolymer Masonry Blocks

NASA Astrophysics Data System (ADS)

Venugopal, K.; Radhakrishna; Sasalatti, Vinod

2016-09-01

Cement masonry units are not considered as sustainable since their production involves consumption of fuel, cement and natural resources and therefore it is essential to find alternatives. This paper reports on making of geopolymer solid & hollow blocks and masonry prisms using non conventional materials like fly ash, ground granulated blast furnace slag (GGBFS) and manufactured sand and curing at ambient temperature. They were tested for water absorption, initial rate of water absorption, dry density, dimensionality, compressive, flexural and bond-strength which were tested for bond strength with and without lateral confinement, modulus of elasticity, alternative drying & wetting and masonry efficiency. The properties of geopolymer blocks were found superior to traditional masonry blocks and the masonry efficiency was found to increase with decrease in thickness of cement mortar joints. There was marginal difference in strength between rendered and unrendered geopolymer masonry blocks. The percentage weight gain after 7 cycles was less than 6% and the percentage reduction in strength of geopolymer solid blocks and hollow blocks were 26% and 28% respectively. Since the properties of geopolymer blocks are comparatively better than the traditional masonry they can be strongly recommended for structural masonry.

Comparison Between Elite and Subelite Swimmers on Dry Land and Tumble Turn Leg Extensor Force-Time Characteristics.

PubMed

Jones, Julian V; Pyne, David B; Haff, G Greg; Newton, Robert U

2018-06-01

Jones, JV, Pyne, DB, Haff, GG, and Newton, RU. Comparison between elite and subelite swimmers on dry land and tumble turn leg extensor force-time characteristics. J Strength Cond Res 32(6): 1762-1769, 2018-Elite swimmers demonstrate faster swimming turn times that are potentially a result of having better strength-power characteristics than subelite swimmers. We quantified differences between dry-land and swimming turn force-time characteristics in elite swimmers and subelite swimmers. Subelite (11 males: 17.4 ± 0.6 years; 10 females: 17.1 ± 0.6 years) and elite swimmers (15 male: 23.2 ± 2.3 years; 7 female: 21.6 ± 2.5 years) were tested in a cross-sectional design. All swimmers performed a body weight and loaded (20 kg females, 30 kg males) squat jump (SJ) on a portable force platform. On the same day, all swimmers completed swimming turn analyses using a force platform fixed within the pool wall. The magnitude of difference between groups was estimated using a standardized mean difference (effect size statistic). Elite male and female swimmers had superior swimming turn and dry-land force-time characteristics to subelite swimmers in all tests. The standardized mean differences between groups ranged from small to very large. The largest differences were SJ peak velocity unloaded (3.07 ± 1.0 m·s males, 3.49 ± 2.29 m·s females; standardized mean difference ± 90% confidence limits) and SJ peak power unloaded (2.59 ± 0.79 w male, 2.80 ± 1.64 w female) with elite male and female swimmers having a ∼25-50% higher performance than the subelites in both characteristics. Elite swimmers exhibit superior strength and power characteristics for the swimming turn compared with younger and less experienced swimmers. A well-planned and executed strength and conditioning program is needed for emerging swimmers to develop these qualities, as they transition to senior levels.

Hip and Knee Strengthening Is More Effective Than Knee Strengthening Alone for Reducing Pain and Improving Activity in Individuals With Patellofemoral Pain: A Systematic Review With Meta-analysis.

PubMed

Nascimento, Lucas R; Teixeira-Salmela, Luci F; Souza, Ricardo B; Resende, Renan A

2018-01-01

Study Design Systematic review with meta-analysis. Background The addition of hip strengthening to knee strengthening for persons with patellofemoral pain has the potential to optimize treatment effects. There is a need to systematically review and pool the current evidence in this area. Objective To examine the efficacy of hip strengthening, associated or not with knee strengthening, to increase strength, reduce pain, and improve activity in individuals with patellofemoral pain. Methods A systematic review of randomized and/or controlled trials was performed. Participants in the reviewed studies were individuals with patellofemoral pain, and the experimental intervention was hip and knee strengthening. Outcome data related to muscle strength, pain, and activity were extracted from the eligible trials and combined in a meta-analysis. Results The review included 14 trials involving 673 participants. Random-effects meta-analyses revealed that hip and knee strengthening decreased pain (mean difference, -3.3; 95% confidence interval [CI]: -5.6, -1.1) and improved activity (standardized mean difference, 1.4; 95% CI: 0.03, 2.8) compared to no training/placebo. In addition, hip and knee strengthening was superior to knee strengthening alone for decreasing pain (mean difference, -1.5; 95% CI: -2.3, -0.8) and improving activity (standardized mean difference, 0.7; 95% CI: 0.2, 1.3). Results were maintained beyond the intervention period. Meta-analyses showed no significant changes in strength for any of the interventions. Conclusion Hip and knee strengthening is effective and superior to knee strengthening alone for decreasing pain and improving activity in persons with patellofemoral pain; however, these outcomes were achieved without a concurrent change in strength. Level of Evidence Therapy, level 1a-. J Orthop Sports Phys Ther 2018;48(1):19-31. Epub 15 Oct 2017. doi:10.2519/jospt.2018.7365.

Central and peripheral components of writing critically depend on a defined area of the dominant superior parietal gyrus.

PubMed

Magrassi, Lorenzo; Bongetta, Daniele; Bianchini, Simonetta; Berardesca, Marta; Arienta, Cesare

2010-07-30

Classical neuropsychological models of writing separate central (linguistic) processes common to oral spelling, writing and typing from peripheral (motor) processes that are modality specific. Damage to the left superior parietal gyrus, an area of the cortex involved in peripheral processes specific to handwriting, should generate distorted graphemes but not misspelled words, while damage to other areas of the cortex like the frontal lobe should produce alterations in written and oral spelling without distorted graphemes. We describe the clinical and neuropsychological features of a patient with combined agraphia for handwriting and typewriting bearing a small glioblastoma in the left parietal lobe. His agraphia resolved after antiedema therapy and we tested by bipolar cortical stimulation his handwriting abilities during an awake neurosurgical procedure. We found that we could reversibly re-induce the same defects of writing by stimulating during surgery a limited area of the superior parietal gyrus in the same patient and in an independent patient that was never agraphic before the operation. In those patients stimulation caused spelling errors, poorly formed letters and in some cases a complete cessation of writing with minimal or no effects on oral spelling. Our results suggest that stimulating a specific area in the superior parietal gyrus we can generate different patterns of agraphia. Moreover, our findings also suggest that some of the central processes specific for typing and handwriting converge with motor processes at least in the limited portion of the superior parietal gyrus we mapped in our patients. Copyright 2010 Elsevier B.V. All rights reserved.

Auditory Perceptual Abilities Are Associated with Specific Auditory Experience

PubMed Central

Zaltz, Yael; Globerson, Eitan; Amir, Noam

2017-01-01

The extent to which auditory experience can shape general auditory perceptual abilities is still under constant debate. Some studies show that specific auditory expertise may have a general effect on auditory perceptual abilities, while others show a more limited influence, exhibited only in a relatively narrow range associated with the area of expertise. The current study addresses this issue by examining experience-dependent enhancement in perceptual abilities in the auditory domain. Three experiments were performed. In the first experiment, 12 pop and rock musicians and 15 non-musicians were tested in frequency discrimination (DLF), intensity discrimination, spectrum discrimination (DLS), and time discrimination (DLT). Results showed significant superiority of the musician group only for the DLF and DLT tasks, illuminating enhanced perceptual skills in the key features of pop music, in which miniscule changes in amplitude and spectrum are not critical to performance. The next two experiments attempted to differentiate between generalization and specificity in the influence of auditory experience, by comparing subgroups of specialists. First, seven guitar players and eight percussionists were tested in the DLF and DLT tasks that were found superior for musicians. Results showed superior abilities on the DLF task for guitar players, though no difference between the groups in DLT, demonstrating some dependency of auditory learning on the specific area of expertise. Subsequently, a third experiment was conducted, testing a possible influence of vowel density in native language on auditory perceptual abilities. Ten native speakers of German (a language characterized by a dense vowel system of 14 vowels), and 10 native speakers of Hebrew (characterized by a sparse vowel system of five vowels), were tested in a formant discrimination task. This is the linguistic equivalent of a DLS task. Results showed that German speakers had superior formant discrimination, demonstrating highly specific effects for auditory linguistic experience as well. Overall, results suggest that auditory superiority is associated with the specific auditory exposure. PMID:29238318

Enhancing the specificity of polymerase chain reaction by graphene oxide through surface modification: zwitterionic polymer is superior to other polymers with different charges.

PubMed

Zhong, Yong; Huang, Lihong; Zhang, Zhisen; Xiong, Yunjing; Sun, Liping; Weng, Jian

Graphene oxides (GOs) with different surface characteristics, such as size, reduction degree and charge, are prepared, and their effects on the specificity of polymerase chain reaction (PCR) are investigated. In this study, we demonstrate that GO with a large size and high reduction degree is superior to small and nonreduced GO in enhancing the specificity of PCR. Negatively charged polyacrylic acid (PAA), positively charged polyacrylamide (PAM), neutral polyethylene glycol (PEG) and zwitterionic polymer poly(sulfobetaine) (pSB) are used to modify GO. The PCR specificity-enhancing ability increases in the following order: GO-PAA < GO-PAM < GO-PEG < GO-pSB. Thus, zwitterionic polymer-modified GO is superior to other GO derivatives with different charges in enhancing the specificity of PCR. GO derivatives are also successfully used to enhance the specificity of PCR for the amplification of human mitochondrial DNA using blood genomic DNA as template. Molecular dynamics simulations and molecular docking are performed to elucidate the interaction between the polymers and Pfu DNA polymerase. Our data demonstrate that the size, reduction degree and surface charge of GO affect the specificity of PCR. Based on our results, zwitterionic polymer-modified GO may be used as an efficient additive for enhancing the specificity of PCR.

Three-dimensional dosimetric considerations from different point A definitions in cervical cancer low-dose-rate brachytherapy

PubMed Central

Chen, Ting; Kim, Leonard H.; Nelson, Carl; Gabel, Molly; Narra, Venkat; Haffty, Bruce; Yue, Ning J.

2013-01-01

Purpose To investigate the dosimetric difference due to the different point A definitions in cervical cancer low-dose-rate (LDR) intracavitary brachytherapy. Material and methods Twenty CT-based LDR brachytherapy plans of 11 cervical patients were retrospectively reviewed. Two plans with point As following the modified Manchester system which defines point A being 2 cm superior to the cervical os along the tandem and 2 cm lateral (Aos), and the American Brachytherapy Society (ABS) guideline definition in which the point A is 2 cm superior to the vaginal fornices instead of os (Aovoid) were generated. Using the same source strength, two plans prescribed the same dose to Aos and Aovoid. Dosimetric differences between plans including point A dose rate, treatment volume encompassed by the prescription isodose line (TV), and dose rate of 2 cc of the rectum and bladder to the prescription dose were measured. Results On average Aovoid was 8.9 mm superior to Aos along the tandem direction with a standard deviation of 5.4 mm. With the same source strength and arrangement, Aos dose rate was 19% higher than Aovoid dose rate. The average TV(Aovoid) was 118.0 cc, which was 30% more than the average TV(Aos) of 93.0 cc. D2cc/D(Aprescribe) increased from 51% to 60% for rectum, and increased from 89% and 106% for bladder, if the prescription point changed from Aos to Aovoid. Conclusions Different point A definitions lead to significant dose differences. Careful consideration should be given when changing practice from one point A definition to another, to ensure dosimetric and clinical equivalency from the previous clinical experiences. PMID:24474971

Management of acromioclavicular joint injuries.

PubMed

Li, Xinning; Ma, Richard; Bedi, Asheesh; Dines, David M; Altchek, David W; Dines, Joshua S

2014-01-01

Acromioclavicular joint injuries are among the most common shoulder girdle injuries in athletes and most commonly result from a direct force to the acromion with the arm in an adducted position. Acromioclavicular joint injuries often present with associated injuries to the glenohumeral joint, including an increased incidence of superior labrum anterior posterior (SLAP) tears that may warrant further evaluation and treatment. Anteroposterior stability of the acromioclavicular joint is conferred by the capsule and acromioclavicular ligaments, of which the posterior and superior ligaments are the strongest. Superior-inferior stability is maintained by the coracoclavicular (conoid and trapezoid) ligaments. Type-I or type-II acromioclavicular joint injuries have been treated with sling immobilization, early shoulder motion, and physical therapy, with favorable outcomes. Return to activity can occur when normal shoulder motion and strength are obtained and the shoulder is asymptomatic as compared with the contralateral normal extremity. The management of type-III injuries remains controversial and is individualized. While a return to the previous level of functional activity with nonsurgical treatment has been documented in a number of case series, surgical reduction and coracoclavicular ligament reconstruction has been associated with a favorable outcome and can be considered in patients who place high functional demands on their shoulders or in athletes who participate in overhead sports. Surgical management is indicated for high-grade (≥type IV) acromioclavicular joint injuries to achieve anatomic reduction of the acromioclavicular joint, reconstruction of the coracoclavicular ligaments, and repair of the deltotrapezial fascia. Outcomes after surgical reconstruction of the coracoclavicular ligaments have been satisfactory with regard to achieving pain relief and return to functional activities, but further improvements in the biomechanical strength of these constructs are necessary to avoid loss of reduction and creep with cyclic loading.

The futility study—progress over the last decade

PubMed Central

Levin, Bruce

2015-01-01

We review the futility clinical trial design (also known as the non-superiority design) with respect to its emergence and methodologic developments over the last decade, especially in regard to its application to clinical trials for neurological disorders. We discuss the design’s strengths as a programmatic screening device to weed out unpromising new treatments, its limitations and pitfalls, and a recent critique of the logic of the method. PMID:26123873

Registration of five upland cotton mutant germplasm lines with superior fiber length, strength, and uniformity

USDA-ARS?s Scientific Manuscript database

Mutant germplasm lines MD 15-Mut 13 (Reg. No. GP-1025, PI 681706), MD 15-Mut 31 (Reg. No. GP-1026, PI 681707), MD 15-Mut 61 (Reg. No. GP-1027, PI 681708), MD 15-Mut 89 (Reg. No. GP-1028, PI 681709), and MD 15-Mut 138 (Reg. No. GP-1029, PI 681710) are unique genotypes of upland cotton (Gossypium hirs...

RF Bearing Estimation in Wireless Sensor Networks

DTIC Science & Technology

2010-01-01

are the main design drivers. Techniques based on ultrasonic and infrared signal modalities have short range and require line-of-sight. Clearly, RF...generating a Doppler shifted RF signal . The small frequency change can be measured even on low cost resource constrained nodes using a radio...is already included in the power budget and RF range is superior to most other signals . Radio signal strength (RSS) based approaches are the most

Export Controls and the U.S. Defense Industrial Base. Volume 1. Summary Report, and Volume 2. Appendices

DTIC Science & Technology

2007-01-01

producers still have a reservoir of intellectual property , product capabilities and process know-how built over several decades. These historical...remarkable properties superior to conventional materials (ultra lightweight, high strength and stiffness). Characteristics of these materials important to...with enforcement of trade agreements and intellectual property (IP) rights. Accordingly, the report recommends more federal support for S&T and

Export Control and the U.S. Defense Industrial Base - Revised. Volume 1: Summary Report and Volume 2: Appendices

DTIC Science & Technology

2008-10-01

advanced materials, US producers still have a reservoir of intellectual property , product capabilities and process know-how built over several...while providing remarkable properties superior to conventional materials (ultra lightweight, high strength and stiffness). Characteristics of these...investor and tax environment; and • A level playing field, with enforcement of trade agreements and intellectual property (IP) rights. Accordingly, the

The development of Nb-based advanced intermetallic alloys for structural applications

NASA Astrophysics Data System (ADS)

Subramanian, P. R.; Mendiratta, M. G.; Dimiduk, D. M.

1996-01-01

A new generation of refractory material systems with significant increases in temperature capability is required to meet the demands of future aerospace applications. Such materials require a balance of properties such as low-temperature damage tolerance, high-temperature strength, creep resistance, and superior environmental stability for implementation in advanced aerospace systems. Systems incorporating niobium-based beta alloys and intermetallic compounds have the potential for meeting these requirements.

Effect of Movement Velocity During Resistance Training on Dynamic Muscular Strength: A Systematic Review and Meta-Analysis.

PubMed

Davies, Timothy B; Kuang, Kenny; Orr, Rhonda; Halaki, Mark; Hackett, Daniel

2017-08-01

Movement velocity is an acute resistance-training variable that can be manipulated to potentially optimize dynamic muscular strength development. However, it is unclear whether performing faster or slower repetitions actually influences dynamic muscular strength gains. We conducted a systematic review and meta-analysis to examine the effect of movement velocity during resistance training on dynamic muscular strength. Five electronic databases were searched using terms related to movement velocity and resistance training. Studies were deemed eligible for inclusion if they met the following criteria: randomized and non-randomized comparative studies; published in English; included healthy adults; used isotonic resistance-exercise interventions directly comparing fast or explosive training to slower movement velocity training; matched in prescribed intensity and volume; duration ≥4 weeks; and measured dynamic muscular strength changes. A total of 15 studies were identified that investigated movement velocity in accordance with the criteria outlined. Fast and moderate-slow resistance training were found to produce similar increases in dynamic muscular strength when all studies were included. However, when intensity was accounted for, there was a trend for a small effect favoring fast compared with moderate-slow training when moderate intensities, defined as 60-79% one repetition maximum, were used (effect size 0.31; p = 0.06). Strength gains between conditions were not influenced by training status and age. Overall, the results suggest that fast and moderate-slow resistance training improve dynamic muscular strength similarly in individuals within a wide range of training statuses and ages. Resistance training performed at fast movement velocities using moderate intensities showed a trend for superior muscular strength gains as compared to moderate-slow resistance training. Both training practices should be considered for novice to advanced, young and older resistance trainers targeting dynamic muscular strength.

Comparative Evaluation of Tensile Strength in Die Stone Incorporated with Sodium and Calcium Hypochlorite as Disinfectants: An in vitro Study.

PubMed

Pramodh, N R; Kumar, C N Vijay; Pradeep, M R; Naik, Ravi; Mahesh, C S; Kumari, Manju R

2017-12-01

The aim of this study was to evaluate the tensile strength of die stone incorporated with sodium and calcium hypochlorite as disinfectants. Two commercially available type IV die stone (Kalrock: Kalabhai Karson Pvt., Ltd and Pearlstone: Asian Chemicals) and two commercially available disinfectant solutions (sodium hypochlorite and calcium hypochlorite: Beachem Laboratory Chemical Private Limited, Chennai and Leo Chem Private Limited, Bengaluru) were used in this study, and the tensile strength was measured using Lloyd's Universal Testing Machine. The results show that incorporating the disinfecting solutions decreases the tensile strength of both products. The effect of decreasing tensile strength on type IV gypsum product is seen more in calcium hypochlorite when compared with sodium hypochlorite disinfecting solution, and the tensile strength of Kalrock specimens is higher than Pearlstone specimens after disinfecting with sodium hypochlorite and calcium hypochlorite solution. The statistical results also show significant results in all the groups when compared with the control group. The incorporation of sodium and calcium hypochlorite disinfecting solutions is not an encouraging method for both die materials as it reduces the tensile strength of type IV gypsum product. Tensile strength of Kalstone® die material is superior than Pearlstone® die material after mixing with sodium hypochlorite and calcium hypochlorite. According to the recommendations of Americans with Disability Act (ADA) and the Centers for Disease Control and Prevention, disinfecting the whole cast without or minimal changes in physical and mechanical properties was the motto of the study. The tensile strength in type IV gypsum product plays a most important role in retrieval of cast from impression, especially in narrow tooth preparation. This study reveals that incorporating method of disinfecting solutions is not recommended as it reduces the tensile strength.

Comparison of Fatigue Properties and Fatigue Crack Growth Rates of Various Implantable Metals

PubMed Central

Okazaki, Yoshimitsu

2012-01-01

The fatigue strength, effects of a notch on the fatigue strength, and fatigue crack growth rate of Ti-15Zr-4Nb-4Ta alloy were compared with those of other implantable metals. Zr, Nb, and Ta are important alloying elements for Ti alloys for attaining superior long-term corrosion resistance and biocompatibility. The highly biocompatible Ti-15Zr-4Nb-4Ta alloy exhibited an excellent balance between strength and ductility. Its notched tensile strength was much higher than that of a smooth specimen. The strength of 20% cold-worked commercially pure (C.P.) grade 4 Ti was close to that of Ti alloy. The tension-to-tension fatigue strength of an annealed Ti-15Zr-4Nb-4Ta rod at 107 cycles was approximately 740 MPa. The fatigue strength of this alloy was much improved by aging treatment after solution treatment. The fatigue strengths of C.P. grade 4 Ti and stainless steel were markedly improved by 20% cold working. The fatigue strength of Co-Cr-Mo alloy was markedly increased by hot forging. The notch fatigue strengths of 20% cold-worked C.P. grade 4 Ti, and annealed and aged Ti-15Zr-4Nb-4Ta, and annealed Ti-6Al-4V alloys were less than those of the smooth specimens. The fatigue crack growth rate of Ti-15Zr-4Nb-4Ta was the same as that of Ti-6Al-4V. The fatigue crack growth rate in 0.9% NaCl was the same as that in air. Stainless steel and Co-Cr-Mo-Ni-Fe alloy had a larger stress-intensity factor range (ΔK) than Ti alloy.

Cross-correlated and oscillatory visual responses of superficial-layer and tecto-reticular neurones in cat superior colliculus.

PubMed

Chabli, A; Guitton, D; Fortin, S; Molotchnikoff, S

2000-03-01

The present study examined, in the superior colliculus (SC) of anaesthetised cats, the functional connectivity between superficial-layer neurones (SLNs) and tectoreticular neurones (TRNs: collicular output cells). TRNs were antidromically identified by electrical stimulation of the predorsal bundle. The auto- and cross-correlation histograms of visual responses of both types of neurones were recorded and analysed. A delayed, sharp peak in cross-correlograms allowed us to verify whether SLN and TRN cells were coupled; in addition, oscillatory activities were compared to verify if rhythmic responses of SLN sites were transmitted to TRN sites. We found that oscillatory activity was rarely observed in spontaneous activity of superficial (1/74) and TRN sites (1/48). Moving light bars induced oscillation in 31% (23/74) of the superficial-layer and in 23% (11/48) of the TRN sites. The strength of the rhythmic responses was determined by specific ranges of stimulus velocity in 83% (19/23) and 64% (7/11) of oscillating SLN and TRN sites, respectively. Frequencies of oscillations ranged between 5 and 125 Hz and were confined, for 53% of the cells, to the 5-20 Hz band. Thus, the band-width of frequencies of the stimulus-related oscillations in the superior colliculus was broader than the gamma range. Analysis of cross-correlation histograms revealed a significant predominant peak with a mean delay of 2.7+/-0.9 ms in 46% (17/37) of SLN-TRN pairs. Most correlated SLN-TRN pairs (88%: 15/17) had superimposed receptive fields, suggesting they were functionally interconnected. However, individual oscillatory frequencies of correlated and oscillatory SLN and TRN cells were never the same (0/8). Together, these results suggest that the neurones in collicular superficial layer contact TRNs and, consequently, support the idea that the superficial layers contribute to collicular outputs producing eye- and head-orienting movements.

Mechanically strong nanocrystalline Fe-Si-B-P-Cu soft magnetic powder cores utilizing magnetic metallic glass as a binder

NASA Astrophysics Data System (ADS)

Luan, Jian; Sharma, Parmanand; Yodoshi, Noriharu; Zhang, Yan; Makino, Akihiro

2016-05-01

We report on the fabrication and properties of soft magnetic powder cores with superior mechanical strength as well as low core loss (W). Development of such cores is important for applications in automobiles/devices operating in motion. High saturation magnetic flux density (Bs) Fe-Si-B-P-Cu powder was sintered with Fe55C10B5P10Ni15Mo5 metallic glass (MG) powder in its supercooled liquid state by spark plasma sintering. The sintered cores are made from the nanocrystalline powder particles of Fe-Si-B-P-Cu alloy, which are separated through a magnetic Fe55C10B5P10Ni15Mo5 MG alloy. Low W of ˜ 2.2 W/kg (at 1T and 50 Hz), and high fracture strength (yielding stress ˜500 MPa), which is an order of magnitude higher than the conventional powder cores, were obtained. Stronger metal-metal bonding and magnetic nature of MG binder (which is very different than the conventional polymer based binders) are responsible for the superior mechanical and magnetic properties. The MG binder not only helps in improving the mechanical properties but it also enhances the overall Bs of the core.

Mechanical properties, electrochemical corrosion and in-vitro bioactivity of yttria stabilized zirconia reinforced hydroxyapatite coatings prepared by gas tunnel type plasma spraying.

PubMed

Yugeswaran, S; Yoganand, C P; Kobayashi, A; Paraskevopoulos, K M; Subramanian, B

2012-05-01

Yttria stabilized zirconia reinforced hydroxyapatite coatings were deposited by a gas tunnel type plasma spray torch under optimum spraying conditions. For this purpose, 10, 20 and 30 wt% of yttria stabilized zirconia (YSZ) powders were premixed individually with hydroxyapatite (HA) powder and were used as the feedstocks for the coatings. The effect of YSZ reinforcement on the phase formation and mechanical properties of the coatings such as hardness, adhesive strength and sliding wear rates was examined. The results showed that the reinforcement of YSZ in HA could significantly enhance the hardness and adhesive strength of the coatings. The potentiodynamic polarization and impedance measurements showed that the reinforced coatings exhibited superior corrosion resistance compared to the HA coating in SBF solution. Further the results of the bioactivity test conducted by immersion of coatings in SBF showed that after 10 days of immersion of the obtained coatings with all the above compositions commonly exhibited the onset of bioactive apatite formation except for HA+10%YSZ coating. The cytocompatibility was investigated by culturing the green fluorescent protein (GFP)-labeled marrow stromal cells (MSCs) on the coating surface. The cell culture results revealed that the reinforced coatings have superior cell growth than the pure HA coatings. Copyright © 2012. Published by Elsevier Ltd.

Resorbable bone fixation alloys, forming, and post-fabrication treatments.

PubMed

Ibrahim, Hamdy; Esfahani, Sajedeh Nasr; Poorganji, Behrang; Dean, David; Elahinia, Mohammad

2017-01-01

Metallic alloys have been introduced as biodegradable metals for various biomedical applications over the last decade owing to their gradual corrosion in the body, biocompatibility and superior strength compared to biodegradable polymers. Mg alloys possess advantageous properties that make them the most extensively studied biodegradable metallic material for orthopedic applications such as their low density, modulus of elasticity, close to that of the bone, and resorbability. Early resorption (i.e., <3months) and relatively inadequate strength are the main challenges that hinder the use of Mg alloys for bone fixation applications. The development of resorbable Mg-based bone fixation hardware with superior mechanical and corrosion performance requires a thorough understanding of the physical and mechanical properties of Mg alloys. This paper discusses the characteristics of successful Mg-based skeletal fixation hardware and the possible ways to improve its properties using different methods such as mechanical and heat treatment processes. We also review the most recent work pertaining to Mg alloys and surface coatings. To this end, this paper covers (i) the properties and development of Mg alloys and coatings with an emphasis on the Mg-Zn-Ca-based alloys; (ii) Mg alloys fabrication techniques; and (iii) strategies towards achieving Mg-based, resorbable, skeletal fixation devices. Copyright © 2016 Elsevier B.V. All rights reserved.

Functional characterization of a serine-threonine protein kinase from Bambusa balcooa that implicates in cellulose overproduction and superior quality fiber formation

PubMed Central

2013-01-01

Background Molecular markers allow rapid identification of biologically important germplasm/s having desired character. Previously we have reported a genotype specific molecular marker, Balco1128 [GenBank ID EU258678] of Bambusa balcooa containing an ORF (375 bp) having high similarity with receptor like cytoplasmic kinase of Arabidopsis and Oryza. Balco1128 was found to be associated only with bamboo genotypes endowed with high cellulose and low lignin contents of fibers. Under the above backdrop, it was necessitated to characterize this genetic marker for better understanding of its biological significance in context of superior quality fiber development. Results The full length cDNA (3342 bp) of BbKst, a serine-threonine protein kinase was isolated from B. balcooa comprising of six LRR domains at the N-terminal end and a kinase domain at the C-terminal end. Bacteria-expressed BbKst-kinase domain (3339 bp long) showed Mg2+ dependent kinase activity at pH 7.0, 28°C. Bioinformatics study followed by phospho-amino analysis further confirmed that BbKst-kinase belongs to the serine/threonine protein kinase family. Transcript analysis of the BbKst gene following RNA slot blot hybridization and qPCR revealed higher expression of BbKst during initiation and elongation stages of fiber development. Tissue specific expression studies showed much higher expression of BbKst transcript in stems and internodes of B. balcooa than in leaves and rhizomes. Southern analysis revealed single copy insertion of BbKst in most of the Agrobacterium mediated transgenic tobacco plants. Real-time PCR detected 150-200 fold enhanced expression of BbKst in different T1 tobacco lines than that of the vector transformed plants. Heterologous expression of BbKst under control of 35S promoter in transgenic tobacco showed high cellulose deposition in the xylem fibers. Number of xylary fibers was higher in transgenic T0 and T1 plants than that of empty-vector transformed tobacco plants offering enhanced mechanical strength to the transgenic plants, which was also substantiated by their strong upright phenotypes, significantly higher cellulose contents, flexibility coefficient, slenderness ratio, and lower Runkel ratio of the fibers. Conclusions This finding clearly demonstrated that BbKst gene (GenBank ID JQ432560) encodes a serine/threonine protein kinase. BbKst induced higher cellulose deposition/synthesis in transgenic tobacco plants, an important attribute of fiber quality bestowing additional strength to the plant. PMID:24015925

Anisotropic Responses of Mechanical and Thermal Processed Cast Al-Si-Mg-Cu Alloy

NASA Astrophysics Data System (ADS)

Adeosun, S. O.; Akpan, E. I.; Balogun, S. A.; Onoyemi, O. K.

2015-05-01

The effects of ambient directional rolling and heat treatments on ultimate tensile strength (UTS), hardness (HD), percent elongation (PE), and impact energy (IE) on Al-Si-Mg-Cu alloy casting with reference to inclination to rolling direction are discussed in this article. The results show that rolled and quenched (CQ) sample possess superior UTS and HD to as-cast and those of rolled and aged samples (CA). Improved IE resistance with ductility is shown by both CQ and CA samples. However, these mechanical properties are enhanced as changes in the test sample direction moved away from rolling direction for all heat-treated samples. The CQ samples displayed highest tensile strength (108 MPa) and PE (19.8%) in the 90° direction.

Evaluation the pozzolanic reactivity of sonochemically fabricated nano natural pozzolan.

PubMed

Askarinejad, Azadeh; Pourkhorshidi, Ali Reza; Parhizkar, Tayebeh

2012-01-01

Natural pozzolans are appropriate supplementary cementitious materials in cement and concrete industry. A simple sonochemical method was developed to synthesize nanostructures of natural pozzolan. Chemical composition, crystallinity, morphology and reactivity of the natural pozzolan samples were compared before and after the sonochemical process, by using powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetry and Differential Thermal Analysis (TG/DTA). Compressive strength tests were performed to evaluate the properties of blended cements incorporating nano natural pozzolan. Under optimized conditions, the nano natural pozzolans showed a superior reactivity as compared with the bulk natural pozzolan. Also higher compressive strength was obtained for the cement specimen incorporating nano natural pozzolan. Copyright © 2011 Elsevier Ltd. All rights reserved.

In-Situ Characterization of Deformation and Fracture Behavior of Hot-Rolled Medium Manganese Lightweight Steel

NASA Astrophysics Data System (ADS)

Zhao, Zheng-zhi; Cao, Rong-hua; Liang, Ju-hua; Li, Feng; Li, Cheng; Yang, Shu-feng

2018-02-01

The deformation and fracture behavior of hot-rolled medium manganese lightweight (0.32C-3.85Mn-4.18Al-1.53Si) steel was revealed by an in situ tensile test. Deformed δ-ferrite with plenty of cross-parallel deformation bands during in situ tensile tests provides δ-ferrite of good plasticity and ductility, although it is finally featured by the cleavage fracture. The soft and ductile δ-ferrite and high-volume fraction of austenite contribute to the superior mechanical properties of medium manganese lightweight steel heated at 800°C, with a tensile strength of 924 MPa, total elongation of 35.2% and product of the strength and elongation of 32.5 GPa %.

Use of the Empress all-ceramic restoration system.

PubMed

Goulet, M K

1997-01-01

New dental materials and techniques have been introduced in the past few years to fabricate aesthetic ceramic restorations with improved strength, biocompatibility, resistance to wear, and better fit. Aesthetic concerns and increasing demand for tooth-colored posterior restorations have led to a number of all-ceramic restorations such as IPS Empress (Ivoclar-Williams, Amherst, NY). The Empress system offers superior aesthetics and physical properties. New generation ceramics along with the current adhesive techniques have resulted in the ability to provide higher strength, therefore indicating crowns for posterior restorations as well. These materials are being used more frequently and in more extensive oral prosthetic rehabilitations such as the case that will be presented. We discuss the different properties and advantages of IPS Empress.

Application of the shifted excitation Raman difference spectroscopy (SERDS) to the analysis of trace amounts of methanol in red wines

NASA Astrophysics Data System (ADS)

Volodin, Boris; Dolgy, Sergei; Ban, Vladimir S.; Gracin, Davor; Juraić, Krunoslav; Gracin, Leo

2014-03-01

Shifted Excitation Raman Difference Spectroscopy (SERDS) has proven an effective method for performing Raman analysis of fluorescent samples. This technique allows achieving excellent signal to noise performance with shorter excitation wavelengths, thus taking full advantage of the superior signal strength afforded by shorter excitation wavelengths and the superior performance, also combined with lower cost, delivered by silicon CCDs. The technique is enabled by use of two closely space fixed-wavelength laser diode sources stabilized with the Volume Bragg gratings (VBGs). A side by side comparison reveals that SERDS technique delivers superior signal to noise ratio and better detection limits in most situations, even when a longer excitation wavelength is employed for the purpose of elimination of the fluorescence. We have applied the SERDS technique to the quantitative analysis of the presence of trace amounts of methanol in red wines, which is an important task in quality control operations within wine industry and is currently difficult to perform in the field. So far conventional Raman spectroscopy analysis of red wines has been impractical due to the high degree of fluorescence.

Depth-specific Analyses of the Lake Superior Food Web

EPA Science Inventory

Characteristics of large, deep aquatic systems include depth gradients in community composition, in the quality and distribution of food resources, and in the strategies that organisms use to obtain their nutrition. In Lake Superior, nearshore communities that rely upon a combina...

[Slipped superior rectus in Grave's orbitopathy. A case report].

PubMed

Spielmann, A C

2007-02-01

Superior rectus slippage after its surgical recession is characterized by short-term progressive overcorrection. Similarities with inferior rectus slippage are pronounced, especially a history of Grave's orbitopathy and the use of an adjustable suture. In the present clinical case, upper eyelid retraction and a history of upper eyelid elevator muscle surgery might be specific risk factors, due to the close anatomical links between the superior rectus and the upper eyelid elevator.

Design and development of advanced castable refractory materials

NASA Astrophysics Data System (ADS)

Davis, Robert Bruce

New formulations of castable refractory composite materials were studied. This technology is used to produce low cost composite concrete structures designed for high temperature stability, superior wear resistance and improved strength. An in situ fired, castable cement installation is a heterogeneous structure divided into three zones according to the temperature history and microstructure. The properties of each zone depend on the predominant bonding mode between constituents. Each zone has a characteristic microstructure that influences the integrity of the monolith. The hot side may have a highly dense and developed network of ceramic bonds between constituent particles while the cold side may never reach temperatures sufficient to drive off free water. The thermal, structural and tribological properties depend on the microstructure and the type of bonding that holds the monolith together. The phase distributions are defined by sets of metastable phase conditions driven by the local hydrated chemistry, nearest neighbor oxide compounds, impurities and sintering temperature. Equilibrium phase diagrams were used to select optimum compositions based on higher melting point phases. The phase diagrams were also used to target high temperature phase fields that are stable over wide temperature and stoichiometric ranges. Materials selection of candidate hydraulic clinkers, high temperature oxides, and reinforcement phases were based on requirements for high temperature stability. The calcium aluminate (CaO-Al2O3) and calcium dialuminate (CaO-(Al2O3)2) are common refractory clinkers used in castable refractory cements. The thermodynamics and kinetics of cement hydrate formation are well studied and suited to become the building block of a design for a superior refractory castable cement. The inert oxides mixed with the calcium aluminate clinkers are magnesia (MgO), alumina (Al 2O3), spinel (MgAl2O4) and chromic (Cr2O3). The bulk of the experiments concentrated in the Al2O3--MgO--CaO ternary system. Materials selection criteria for reinforcement materials was based on improved high temperature stability, increased strength, reduced thermal expansion mismatch, low thermal conductivity and increasing wear resistance. The reinforcement phases selected for this investigation are zircon (ZrSiO4), zirconia (ZrO2), spinel (MgAl2O4) and dead burnt magnesia (MgO). Batches of the formulations were tested for thermal conductivity, wear resistance and mechanical strength. Relative rankings of the formulations against commercial products indicate improved or similar performance with increased maximum temperature limits and improved thermal insulating power. The new cement formulations proved to exhibit superior high temperature stability with an increasing volume fraction of high temperature oxides. The addition of reinforcement aggregates and powder sizing to offset the loss of strength. The room temperature compression strength and wear resistance of the optimized formulations exceeded the properties of conventional refractory, brick and castable cement tested concurrently.

Assessment of the Resistance of Several Suture Techniques in Human Cadaver Achilles Tendons.

PubMed

Manent, Andrea; Lopez, Laia; Vilanova, Joan; Mota, Tiago; Alvarez, Jordi; Santamaría, Alejandro; Oliva, Xavier Martí

Many treatments are available for acute Achilles tendon ruptures, conservative and surgical, with none superior to another. For surgical treatment, one can use various techniques. Recent studies have shown that double stitches are superior to simple sutures. Therefore, in the present study, we sought to determine the suture technique that is the most resistant to rupture. We performed an experimental anatomic study with 27 fresh-frozen human cadaveric Achilles tendons obtained through the body donation program of the University of Barcelona, testing the maximum strength. We simulated a rupture by performing resection in the middle portion of the tendon, 4 cm proximal to the calcaneus insertion. We then evaluated the double Kessler, double Bunnell, Krackow, and percutaneous Ma and Griffith technique. We used absorbable suture (polydioxanone no. 1) with all the techniques. Traction was performed using a machine that pulls the tendon at 10 to 100 N in 1000 repetitive cycles. Statistical analysis was performed using the χ 2 test and analysis of variance, with the 95% confidence intervals (p < .05). All repairs failed at the site of the suture knots, with none pulling out through the substance of the tendon. We found no significant differences among the different open suture techniques (p > .05). The Krackow suture presented with superior resistance, with a rupture rate 16.70% but with a mean elongation of 7.11 mm. The double Bunnell suture had the same rupture rate as the Krakow suture (16.70%) but with an inferior mean elongation of 4.53 mm. The Krackow and Bunnell suture were superior in endurance, strength of failure, and primary stability compared with the other suture types. However, the former presented with greater tendon elongation, although the difference was not statistically significant. Therefore, according to our findings and the published data, we recommend double Bunnell sutures for the surgical treatment of acute Achilles tendon rupture. Copyright © 2017 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers.

PubMed

Raut, Anjana; Rao, Polsani Laxman; Vikas, B V J; Ravindranath, T; Paradkar, Archana; Malakondaiah, G

2013-01-01

Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.

Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer

The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted formore » by the glass transition temperature, T g, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, T ref, by the same amount as the T g depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive T g depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.« less

Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

DOE PAGES

Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer; ...

2015-08-06

The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted formore » by the glass transition temperature, T g, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, T ref, by the same amount as the T g depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive T g depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.« less

Simultaneously enhanced strength and ductility for 3D-printed stainless steel 316L by selective laser melting

NASA Astrophysics Data System (ADS)

Sun, Zhongji; Tan, Xipeng; Tor, Shu Beng; Chua, Chee Kai

2018-04-01

Laser-based powder-bed fusion additive manufacturing or three-dimensional printing technology has gained tremendous attention due to its controllable, digital, and automated manufacturing process, which can afford a refined microstructure and superior strength. However, it is a major challenge to additively manufacture metal parts with satisfactory ductility and toughness. Here we report a novel selective laser melting process to simultaneously enhance the strength and ductility of stainless steel 316L by in-process engineering its microstructure into a <011> crystallographic texture. We find that the tensile strength and ductility of SLM-built stainless steel 316L samples could be enhanced by 16% and 40% respectively, with the engineered <011> textured microstructure compared to the common <001> textured microstructure. This is because the favorable nano-twinning mechanism was significantly more activated in the <011> textured stainless steel 316L samples during plastic deformation. In addition, kinetic simulations were performed to unveil the relationship between the melt pool geometry and crystallographic texture. The new additive manufacturing strategy of engineering the crystallographic texture can be applied to other metals and alloys with twinning-induced plasticity. This work paves the way to additively manufacture metal parts with high strength and high ductility.

Differential Effects of Heavy Versus Moderate Loads on Measures of Strength and Hypertrophy in Resistance-Trained Men.

PubMed

Schoenfeld, Brad J; Contreras, Bret; Vigotsky, Andrew D; Peterson, Mark

2016-12-01

The purpose of the present study was to evaluate muscular adaptations between heavy- and moderate-load resistance training (RT) with all other variables controlled between conditions. Nineteen resistance-trained men were randomly assigned to either a strength-type RT routine (HEAVY) that trained in a loading range of 2-4 repetitions per set (n = 10) or a hypertrophy-type RT routine (MODERATE) that trained in a loading range of 8-12 repetitions per set (n = 9). Training was carried out 3 days a week for 8 weeks. Both groups performed 3 sets of 7 exercises for the major muscle groups of the upper and lower body. Subjects were tested pre- and post-study for: 1 repetition maximum (RM) strength in the bench press and squat, upper body muscle endurance, and muscle thickness of the elbow flexors, elbow extensors, and lateral thigh. Results showed statistically greater increases in 1RM squat strength favoring HEAVY compared to MODERATE. Alternatively, statistically greater increases in lateral thigh muscle thickness were noted for MODERATE versus HEAVY. These findings indicate that heavy load training is superior for maximal strength goals while moderate load training is more suited to hypertrophy-related goals when an equal number of sets are performed between conditions.

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel

PubMed Central

Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-01

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint. PMID:29361743

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel.

PubMed

Shi, Yonghua; Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-22

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint.

Strength advantages of chemically polished boron fibers before and after reaction with aluminum

NASA Technical Reports Server (NTRS)

Dicarlo, J. A.; Smith, R. J.

1982-01-01

In order to determine their strength potential, the fracture properties of different types of commercial boron fibers were measured before and after application of secondary strengthening treatments. The principal treatments employed were a slight chemical polish, which removed low strength surface flaws, and a heat treatment in oxygen, which contracted the fibers and thereby compressed intrinsic bulk flaws. Those fiber types most significantly strengthened were 200 to 400 micrometers (8 to 16 mil) diameter boron on tungsten fibers produced in a single chemical vapor deposition reactor. The slight polish increased average tensile strenghts from 3.4 to 4.4 CN/m2 (500 to 640 ksi) and reduced coefficients of variation from about 15 to 3 percent. The oxygen heat treatment plus slight polish further improved average strengths to 5.5 GN/m2 (800 ksi) with coefficients near 3 percent. To ascertain whether these excellent properties could be retained after fabrication of B/Al composites, as produced and polished 203 micrometers (8 mil) fibers were thinly coated with aluminum, heat treated at B/Al fabrication temperatures, and then tested in tension and flexure at room temperature. The pre-polished fibers were observed to retain their superior strengths to higher temperatures than the as-produced fibers even though both were subjected to the same detrimental reaction with aluminum.

Elastic and Plastic Behavior of an Ultrafine-Grained Mg Reinforced with BN Nanoparticles

NASA Astrophysics Data System (ADS)

Trojanová, Zuzanka; Dash, Khushbu; Máthis, Kristián; Lukáč, Pavel; Kasakewitsch, Alla

2018-04-01

Pure microcrystalline magnesium (µMg) was reinforced with hexagonal boron nitride (hBN) nanoparticles and was fabricated by powder metallurgy process followed by hot extrusion. For comparison pure magnesium powder was consolidated by hot extrusion too. Both materials exhibited a significant fiber texture. Mg-hBN nanocomposites (nc) and pure Mg specimens were deformed between room temperature and 300 °C under tension and compression mode. The yield strength and ultimate tensile and compression strength as well as characteristic stresses were evaluated and reported. The tensile and compressive strengths of Mg-hBN nc are quiet superior in values compared to monolithic counterpart as well as Mg alloys. The compressive yield strength of µMg was recorded as 90 MPa, whereas the Mg-hBN nancomposite shows 125 MPa at 200 °C. The tensile yield strength of µMg was computed as 67 MPa which is quite lower as compared to Mg-hBN nanocomposite's value which was recorded as 157 MPa at 200 °C. Under tensile stress the true stress-strain curves are flat in nature, whereas the stress-strain curves observed in compression at temperatures up to 100 °C exhibited small local maxima at the onset of deformation followed by a significant work hardening.

Magnesia tuned multi-walled carbon nanotubes–reinforced alumina nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Iftikhar, E-mail: ifahmad@ksu.edu.sa; Islam, Mohammad; Dar, Mushtaq Ahmad

2015-01-15

Magnesia tuned alumina ceramic nanocomposites, reinforced with multi-walled carbon nanotubes, were condensed using pressureless and hot-press sintering processes. Densification, microstructure and mechanical properties of the produced nanocomposites were meticulously investigated. Electron microscopy studies revealed the homogenous carbon nanotube dispersion within the alumina matrix and confirmed the retention of carbon nanotubes' distinctive tubular morphology and nanoscale features during the extreme mixing/sintering processes. Pressureless sintered nanocomposites showed meagre mechanical responses due to the poorly-integrated microstructures with a slight improvement upon magnesia addition. Conversely, both the magnesia addition and application of hot-press sintering technique resulted in the nanocomposite formation with near-theoretical densities (~more » 99%), well-integrated microstructures and superior mechanical properties. Hot-press sintered nanocomposites incorporating 300 and 600 ppm magnesia exhibited an increase in hardness (10 and 11%), flexural strength (5 and 10%) and fracture toughness (15 and 20%) with respect to similar magnesia-free samples. Compared to monolithic alumina, a decent rise in fracture toughness (37%), flexural strength (22%) and hardness (20%) was observed in the hot-press sintered nanocomposites tuned with merely 600 ppm magnesia. Mechanically superior hot-press sintered magnesia tailored nanocomposites are attractive for several load-bearing structural applications. - Highlights: • MgO tailored Al{sub 2}O{sub 3}–2 wt.% CNT nanocomposites are presented. • The role of MgO and sintering on nanocomposite structures and properties was studied. • Well-dispersed CNTs maintained their morphology/structure after harsh sintering. • Hot-pressing and MgO led nanocomposites to higher properties/unified structures. • MgO tuned composites showed higher toughness (37%) and strength (22%) than Al{sub 2}O{sub 3}.« less

Implementing resistance training in the rehabilitation of coronary heart disease: A systematic review and meta-analysis.

PubMed

Xanthos, Paul D; Gordon, Brett A; Kingsley, Michael I C

2017-03-01

Resistance training has demonstrated efficacy in cardiac rehabilitation programs, but the optimal prescription of resistance training is unknown. This systematic review with meta-analysis compared the effectiveness of cardiac rehabilitation consisting of resistance training either alone (RT) or in combination with aerobic training (CT) with aerobic training only (AT) on outcomes of physical function. Further, resistance training intensity and intervention duration were examined to identify if these factors moderate efficacy. Six electronic databases were searched to identify studies investigating RT, coronary heart disease and physical function. The overall quality of evidence was assessed using the GRADE approach. Meta-analyses were performed when possible and qualitative analysis was performed for the remaining data. Improvements in peak oxygen uptake (WMD: 0.61, 95% CI: 0.20-1.10), peak work capacity (SMD: 0.38, 95% CI: 0.11-0.64) and muscular strength (SMD: 0.65, 95% CI: 0.43-0.87) significantly favoured CT over AT with moderate quality evidence. There was no evidence of a difference in effect when comparing RT and AT. Shorter duration CT was superior to shorter duration AT for improving peak oxygen uptake and muscular strength (low quality evidence) while longer duration CT was only superior to longer duration AT in improving muscular strength (moderate quality evidence). CT is more beneficial than AT alone for improving physical function. Although preliminary findings are promising, more high-quality evidence is required to determine the efficacy of high intensity resistance training. Shorter duration interventions that include resistance training might allow patients to return to their normal activities of daily living earlier. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Depth-specific Analyses of the Lake Superior Food Web, oral presentation

EPA Science Inventory

Characteristics of large, deep aquatic systems include depth gradients in community composition, in the quality and distribution of food resources, and in the strategies that organisms use to obtain their nutrition. In Lake Superior, nearshore communities that rely upon a combina...

Cross-sectional echocardiographic diagnosis of systemic venous return.

PubMed Central

Huhta, J C; Smallhorn, J F; Macartney, F J; Anderson, R H; de Leval, M

1982-01-01

To determine the sensitivity and specificity of cross-sectional echocardiography in diagnosing anomalous systemic venous return we used the technique in 800 consecutive children with congenital heart disease and whom the diagnosis was ultimately confirmed by angiography. Cross-sectional echocardiography was performed without prior knowledge of the diagnosis in all but 11 patients, who were recalled because of a known abnormality of atrial situs. The sensitivity of cross-sectional echocardiographic detection of various structures was as follows: right superior vena cava 792/792 (100%); left superior vena cava 46/48 (96%); bilateral superior vena cava 38/40 (95%); bridging innominate vein with bilateral superior vena cava 13/18 (72%); connection of superior caval segment to heart (coronary sinus or either atrium) (100%); absence of suprarenal inferior vena cava 23/23 (100%); azygos continuation of the inferior vena cava 31/33 (91%); downstream connection of azygos continuation, once seen, 21/21 (100%); partial anomalous hepatic venous connection (one hepatic vein not connected to the inferior vena cava) 1/1 (100%); total anomalous hepatic venous connection (invariably associated with left isomerism) 23/23 (100%). The specificity of each above diagnoses was 100% except in one infant with exomphalos in whom absence of the suprarenal inferior vena cava was incorrectly diagnosed. Thus cross-sectional echocardiography is an extremely specific and highly sensitive method of recognizing anomalous systemic venous return. It is therefore of great value of planning both cardiac catheterisation and cannulation for open heart surgery. Images PMID:6751361

Association with isokinetic ankle strength measurements and normal clinical muscle testing in sciatica patients.

PubMed

Ustun, N; Erol, O; Ozcakar, L; Ceceli, E; Ciner, O Akar; Yorgancioglu, Z R

2013-01-01

Sensitive muscle strength tests are needed to measure muscle strength in the diagnosis and management of sciatica patients. The aim of this study was to assess the isokinetic muscle strength in sciatica patients' and control subjects' ankles that exhibited normal ankle muscle strength when measured clinically. Forty-six patients with L5 and/or S1 nerve compression, and whose age, sex, weight, and height matched 36 healthy volunteers, were recruited to the study. Heel-walking, toe-walking, and manual muscle testing were used to perform ankle dorsiflexion and plantar flexion strengths in clinical examination. Patients with normal ankle dorsiflexion and plantar flexion strengths assessed by manual muscle testing and heel-and toe-walking tests were included in the study. Bilateral isokinetic (concentric/concentric) ankle plantar-flexion-dorsiflexion measurements of the patients and controls were performed within the protocol of 30°/sec (5 repetitions). Peak torque and peak torque/body weight were obtained for each ankle motion of the involved limb at 30°/s speed. L5 and/or S1 nerve compression was evident in 46 patients (76 injured limbs). Mean disease duration was two years. The plantar flexion muscle strength of the patients was found to be lower than that of the controls (p=0.036). The dorsiflexion muscle strength of the patients was found to be the same as that of the controls (p=0.211). Isokinetic testing is superior to clinical muscle testing when evaluating ankle plantar flexion torque in sciatica patients. Therefore, isokinetic muscle testing may be helpful when deciding whether to place a patient into a focused rehabilitation program.

The role of muscle strengthening in exercise therapy for knee osteoarthritis: A systematic review and meta-regression analysis of randomized trials.

PubMed

Bartholdy, Cecilie; Juhl, Carsten; Christensen, Robin; Lund, Hans; Zhang, Weiya; Henriksen, Marius

2017-08-01

To analyze if exercise interventions for patients with knee osteoarthritis (OA) following the American College of Sports Medicine (ACSM) definition of muscle strength training differs from other types of exercise, and to analyze associations between changes in muscle strength, pain, and disability. A systematic search in 5 electronic databases was performed to identify randomized controlled trials comparing exercise interventions with no intervention in knee OA, and reporting changes in muscle strength and in pain or disability assessed as standardized mean differences (SMD) with 95% confidence intervals (95% CI). Interventions were categorized as ACSM interventions or not-ACSM interventions and compared using stratified random effects meta-analysis models. Associations between knee extensor strength gain and changes in pain/disability were assessed using meta-regression analyses. The 45 eligible trials with 4699 participants and 56 comparisons (22 ACSM interventions) were included in this analysis. A statistically significant difference favoring the ACSM interventions with respect to knee extensor strength was found [SMD difference: 0.448 (95% CI: 0.091-0.805)]. No differences were observed regarding effects on pain and disability. The meta-regressions indicated that increases in knee extensor strength of 30-40% would be necessary for a likely concomitant beneficial effect on pain and disability, respectively. Exercise interventions following the ACSM criteria for strength training provide superior outcomes in knee extensor strength but not in pain or disability. An increase of less than 30% in knee extensor strength is not likely to be clinically beneficial in terms of changes in pain and disability (PROSPERO: CRD42014015344). Copyright © 2017 Elsevier Inc. All rights reserved.

An overview of strength training injuries: acute and chronic.

PubMed

Lavallee, Mark E; Balam, Tucker

2010-01-01

This article introduces the history of strength training, explains the many different styles of strength training, and discusses common injuries specific to each style. Strength training is broken down into five disciplines: basic strength or resistance training, bodybuilding, power lifting, style-dependant strength sports (e.g., strongman competitions, Highland games, field events such as shot put, discus, hammer throw, and javelin), and Olympic-style weightlifting. Each style has its own principal injuries, both acute and chronic, related to the individual technique. Acute injuries should be further categorized as emergent or nonemergent. Specific age-related populations (i.e., the very young and the aging athlete) carry additional considerations.

Effects of dry-land vs. in-water specific strength training on professional male water polo players' performance.

PubMed

de Villarreal, Eduardo Sáez; Suarez-Arrones, Luis; Requena, Bernardo; Haff, G Gregory; Ramos-Veliz, Rafael

2014-11-01

We compared the effects of 6-week dry-land and in-water specific strength training combined with a water polo (WP) program on 7 sport-specific performance parameters. Nineteen professional players were randomly assigned to 2 groups: in-water strength group (WSG) (in-water training only) and dry-land strength group (LSG). The program included 3 weekly strength training sessions and 5 days of WP training per week for 6 weeks during the preseason. Ten-meter T-agility test, 20-m maximal sprint swim, maximal dynamic strength (1 repetition maximum), bench press (BP) and full squat (FS), in-water boost, countermovement jump (CMJ), and WP throwing speed were measured. Significant improvements (p ≤ 0.05) were found in the experimental groups in some variables: CMJ in the LSG and WSG (2.35 cm, 9.07%, effect size [ES] = 0.89; and 2.6 cm, 7.6%, ES = 0.83, respectively), in-water boost increased in the WSG group (4.1 cm; 11.48%; ES = 0.70), and FS and BP increased (p ≤ 0.05) only in the LSG group (12.1 kg; 11.27%; ES = 1.15 and 8.3 kg; 9.55%; ES = 1.30, respectively). There was a decrease of performance in agility test (-0.55 seconds; 5.60%; ES = 0.74). Both dry-land and in-water specific strength training and high-intensity training in these male WP players produced medial to large effects on most WP-specific performance parameters. Therefore, we propose modifications to current training methodology for WP players in preseason to include both the training programs (dry-land and in-water specific strength training and high-intensity training) for athlete preparation in this sport.

An alternative respiratory sounds classification system utilizing artificial neural networks.

PubMed

Oweis, Rami J; Abdulhay, Enas W; Khayal, Amer; Awad, Areen

2015-01-01

Computerized lung sound analysis involves recording lung sound via an electronic device, followed by computer analysis and classification based on specific signal characteristics as non-linearity and nonstationarity caused by air turbulence. An automatic analysis is necessary to avoid dependence on expert skills. This work revolves around exploiting autocorrelation in the feature extraction stage. All process stages were implemented in MATLAB. The classification process was performed comparatively using both artificial neural networks (ANNs) and adaptive neuro-fuzzy inference systems (ANFIS) toolboxes. The methods have been applied to 10 different respiratory sounds for classification. The ANN was superior to the ANFIS system and returned superior performance parameters. Its accuracy, specificity, and sensitivity were 98.6%, 100%, and 97.8%, respectively. The obtained parameters showed superiority to many recent approaches. The promising proposed method is an efficient fast tool for the intended purpose as manifested in the performance parameters, specifically, accuracy, specificity, and sensitivity. Furthermore, it may be added that utilizing the autocorrelation function in the feature extraction in such applications results in enhanced performance and avoids undesired computation complexities compared to other techniques.

Fatigue and Fracture of Polycrystalline Silicon and Diamond MEMS at Room and Elevated Temperatures

DTIC Science & Technology

2006-12-01

amorphous diamond-like carbon (ta-C) and polycrystalline silicon ( polysilicon ) for microelectromechanical systems (MEMS). Polysilicon and ta-C test...toughness were obtained, many of them for the first time. Compared to polysilicon , ta-C was found to have superior mechanical properties: Its fracture...toughness and strength were 3.5 times and two times that of polysilicon , respectively. Its elastic modulus was 4.5 times that of polysilicon and its

Global UAS Proliferation Challenges USAF Air Superiority

DTIC Science & Technology

2016-01-18

wingspan or rotor -blade diameter less than six feet, can be concealed within the confines of a vehicle, suitcase or backpack, costs less than $25K... helicopters at designated locations governed by the rules and requirements of the local club’s airfield. With the arrival of electric, quiet, easy to...the strength and reliability of plastics and composites as a weight saver has allowed for tremendous capability in endless applications. A leader in

Bioinspired, Graphene/Al2O3 Doubly Reinforced Aluminum Composites with High Strength and Toughness.

PubMed

Zhang, Yunya; Li, Xiaodong

2017-11-08

Nacre, commonly referred to as nature's armor, has served as a blueprint for engineering stronger and tougher bioinspired materials. Nature organizes a brick-and-mortar-like architecture in nacre, with hard bricks of aragonite sandwiched with soft biopolymer layers. However, cloning nacre's entire reinforcing mechanisms in engineered materials remains a challenge. In this study, we employed hybrid graphene/Al 2 O 3 platelets with surface nanointerlocks as hard bricks for primary load bearer and mechanical interlocking, along with aluminum laminates as soft mortar for load distribution and energy dissipation, to replicate nacre's architecture and reinforcing effects in aluminum composites. Compared with aluminum, the bioinspired, graphene/Al 2 O 3 doubly reinforced aluminum composite demonstrated an exceptional, joint improvement in hardness (210%), strength (223%), stiffness (78%), and toughness (30%), which are even superior over nacre. This design strategy and model material system should guide the synthesis of bioinspired materials to achieve exceptionally high strength and toughness.

Reuse of industrial sludge as construction aggregates.

PubMed

Tay, J H; Show, K Y; Hong, S Y

2001-01-01

Industrial wastewater sludge and dredged marine clay are high volume wastes that needed enormous space at landfill disposal sites. Due to the limitation of land space, there is an urgent need for alternative disposal methods for these two wastes. This study investigates the possibility of using the industrial sludge in combination with marine clay as construction aggregates. Different proportions of sludge and clay were made into round and angular aggregates. It was found that certain mix proportions could provide aggregates of adequate strength, comparable to that of conventional aggregates. Concrete samples cast from the sludge-clay aggregates yield compressive strengths in the range of 31.0 to 39.0 N/mm2. The results showed that the round aggregates of 100% sludge and the crush aggregates of sludge with up to 20% clay produced concrete of compressive strengths which are superior to that of 38.0 N/mm2 for conventional aggregate. The study indicates that the conversion of high volume wastes into construction materials is a potential option for waste management.

What Are Strength Training Activities?

Cancer.gov

Strength training is any practice or exercise specifically designed to increase muscle tone, strength, and fitness. Concerned that strength training will make you bulky and too muscle-y? You are not alone.

Effects of exercise on brain activity during walking in older adults: a randomized controlled trial.

PubMed

Shimada, Hiroyuki; Ishii, Kenji; Makizako, Hyuma; Ishiwata, Kiichi; Oda, Keiichi; Suzukawa, Megumi

2017-05-30

Physical activity may preserve neuronal plasticity, increase synapse formation, and cause the release of hormonal factors that promote neurogenesis and neuronal function. Previous studies have reported enhanced neurocognitive function following exercise training. However, the specific cortical regions activated during exercise training remain largely undefined. In this study, we quantitatively and objectively evaluated the effects of exercise on brain activity during walking in healthy older adults. A total of 24 elderly women (75-83 years old) were randomly allocated to either an intervention group or a control group. Those in the intervention group attended 3 months of biweekly 90-min sessions focused on aerobic exercise, strength training, and physical therapy. We monitored changes in regional cerebral glucose metabolism during walking in both groups using positron emission tomography (PET) and [ 18 F]fluorodeoxyglucose (FDG). All subjects completed the 3-month experiment and the adherence to the exercise program was 100%. Compared with the control group, the intervention group showed a significantly greater step length in the right foot after 3 months of physical activity. The FDG-PET assessment revealed a significant post-intervention increase in regional glucose metabolism in the left posterior entorhinal cortex, left superior temporal gyrus, and right superior temporopolar area in the intervention group. Interestingly, the control group showed a relative increase in regional glucose metabolism in the left premotor and supplemental motor areas, left and right somatosensory association cortex, and right primary visual cortex after the 3-month period. We found no significant differences in FDG uptake between the intervention and control groups before vs. after the intervention. Exercise training increased activity in specific brain regions, such as the precuneus and entorhinal cortices, which play an important role in episodic and spatial memory. Further investigation is required to confirm whether alterations in glucose metabolism within these regions during walking directly promote physical and cognitive performance. UMIN-CTR ( UMIN000021829 ). Retrospectively registered 10 April 2016.

Reliability and Validity of Finger Strength and Endurance Measurements in Rock Climbing

ERIC Educational Resources Information Center

Michailov, Michail Lubomirov; Baláš, Jirí; Tanev, Stoyan Kolev; Andonov, Hristo Stoyanov; Kodejška, Jan; Brown, Lee

2018-01-01

Purpose: An advanced system for the assessment of climbing-specific performance was developed and used to: (a) investigate the effect of arm fixation (AF) on construct validity evidence and reliability of climbing-specific finger-strength measurement; (b) assess reliability of finger-strength and endurance measurements; and (c) evaluate the…

Cancer-Specific Mortality Relative to Engagement in Muscle-Strengthening Activities and Lower Extremity Strength.

PubMed

Dankel, Scott J; Loenneke, Jeremy P; Loprinzi, Paul D

2018-02-01

Skeletal muscle strength and engagement in muscle-strengthening activities are each inversely associated with all-cause mortality; however, less is known on their relationship with cancer-specific mortality. Data from the 1999-2002 National Health and Nutrition Examination Survey were used assessing 2773 individuals aged 50 years or older. Individuals being dichotomized at the 75th percentile for knee extensor strength, and engagement in muscle-strengthening activities was acquired through self-report with ≥2 sessions per week were classified as meeting guidelines. With respect to cancer-specific mortality, individuals in the upper quartile for muscle strength were at a 50% reduced risk (hazard ratio = 0.50; 95% confidence interval, 0.29-0.85; P = .01) and those meeting muscle-strengthening activities were at a nonsignificant 8% reduced risk (hazard ratio = 0.92; 95% confidence interval, 0.45-1.86, P = .81) of cancer-specific mortality after adjusting for covariates. Clinicians should routinely assess lower extremity strength and promote engagement in muscle-strengthening activities aimed at increasing muscle strength.

Corrigendum to 'On the influence of microstructure on the fracture behaviour of hot extruded ferritic ODS steels' [J. Nucl. Mater. 497 (2017) 60-75

NASA Astrophysics Data System (ADS)

Das, A.; Viehrig, H. W.; Altstadt, E.; Heintze, C.; Hoffmann, J.

2018-02-01

ODS steels are known to show inferior fracture properties as compared to ferritic martensitic non-ODS steels. Hot extruded 13Cr ODS steel however, showed excellent fracture toughness at a temperature range from room temperature to 400 °C. In this work, the factors which resulted in superior and anisotropic fracture behaviour were investigated by comparing different orientations of two hot extruded materials using scanning electron, electron backscatter and transmission electron microscopy. Fracture behaviour of the two materials was compared using unloading compliance fracture toughness tests. Anisotropic fracture toughness was predominantly influenced by grain morphology. Superior fracture toughness in 13Cr ODS-KIT was predominantly influenced by factors such as smaller void inducing particle size and higher sub-micron particle-matrix interfacial strength.

Effect of SiC particle size on the microstructure and properties of cold-sprayed Al/SiCp composite coating

NASA Astrophysics Data System (ADS)

Yu, Min; Hua, Junwei

2017-07-01

The Al5056/SiC composite coatings were prepared by cold spraying. Experimental results show that the SiC content in the composite coating deposited with the SiC powder having an average size of 67 μm (Al5056/SiC-67) is similar to that deposited with the SiC powder having an average size of 27 μm (Al5056/SiC-27). The microhardness and cohesion strength of Al5056/SiC-67 coating are higher than those of the Al5056/SiC-27 coating. In addition, the Al5056/SiC-67 coating having a superior wear resistance because of the coarse SiC powder with a superior kinetic energy contributes to the deformation resistance of the matrix Al5056 particles.

33 CFR 117.661 - Duluth Ship Canal (Duluth-Superior Harbor).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Duluth Ship Canal (Duluth-Superior Harbor). 117.661 Section 117.661 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Minnesota § 117.661 Duluth...

33 CFR 117.661 - Duluth Ship Canal (Duluth-Superior Harbor).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Duluth Ship Canal (Duluth-Superior Harbor). 117.661 Section 117.661 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Minnesota § 117.661 Duluth...

33 CFR 117.661 - Duluth Ship Canal (Duluth-Superior Harbor).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Duluth Ship Canal (Duluth-Superior Harbor). 117.661 Section 117.661 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Minnesota § 117.661 Duluth...

Imaging of congenital heart disease in adults: choice of modalities.

PubMed

Orwat, Stefan; Diller, Gerhard-Paul; Baumgartner, Helmut

2014-01-01

Major advances in noninvasive imaging of adult congenital heart disease have been accomplished. These tools play now a key role in comprehensive diagnostic work-up, decision for intervention, evaluation for the suitability of specific therapeutic options, monitoring of interventions and regular follow-up. Besides echocardiography, magnetic resonance (CMR) and computed tomography (CT) have gained particular importance. The choice of imaging modality has thus become a critical issue. This review summarizes strengths and limitations of the different imaging modalities and how they may be used in a complementary fashion. Echocardiography obviously remains the workhorse of imaging routinely used in all patients. However, in complex disease and after surgery echocardiography alone frequently remains insufficient. CMR is particularly useful in this setting and allows reproducible and accurate quantification of ventricular function and comprehensive assessment of cardiac anatomy, aorta, pulmonary arteries and venous return including complex flow measurements. CT is preferred when CMR is contraindicated, when superior spatial resolution is required or when "metallic" artefacts limit CMR imaging. In conclusion, the use of currently available imaging modalities in adult congenital heart disease needs to be complementary. Echocardiography remains the basis tool, CMR and CT should be added considering specific open questions and the ability to answer them, availability and economic issues.

The specificity of neural responses to music and their relation to voice processing: an fMRI-adaptation study.

PubMed

Armony, Jorge L; Aubé, William; Angulo-Perkins, Arafat; Peretz, Isabelle; Concha, Luis

2015-04-23

Several studies have identified, using functional magnetic resonance imaging (fMRI), a region within the superior temporal gyrus that preferentially responds to musical stimuli. However, in most cases, significant responses to other complex stimuli, particularly human voice, were also observed. Thus, it remains unknown if the same neurons respond to both stimulus types, albeit with different strengths, or whether the responses observed with fMRI are generated by distinct, overlapping neural populations. To address this question, we conducted an fMRI experiment in which short music excerpts and human vocalizations were presented in a pseudo-random order. Critically, we performed an adaptation-based analysis in which responses to the stimuli were analyzed taking into account the category of the preceding stimulus. Our results confirm the presence of a region in the anterior STG that responds more strongly to music than voice. Moreover, we found a music-specific adaptation effect in this area, consistent with the existence of music-preferred neurons. Lack of differences between musicians and non-musicians argues against an expertise effect. These findings provide further support for neural separability between music and speech within the temporal lobe. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Spatial heterogeneity of plant-soil feedback affects root interactions and interspecific competition.

PubMed

Hendriks, Marloes; Ravenek, Janneke M; Smit-Tiekstra, Annemiek E; van der Paauw, Jan Willem; de Caluwe, Hannie; van der Putten, Wim H; de Kroon, Hans; Mommer, Liesje

2015-08-01

Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Highly compressible three-dimensional graphene hydrogel for foldable all-solid-state supercapacitor

NASA Astrophysics Data System (ADS)

Liu, Xianbin; Zou, Shuai; Liu, Kaixi; Lv, Chao; Wu, Ziping; Yin, Yanhong; Liang, Tongxiang; Xie, Zailai

2018-04-01

The fabrication of three-dimensional (3D) graphene-based macroscopic materials with superior mechanical and electrical properties for flexible energy storage devices is still extremely challenging. Here, we report a novel 3D graphene hydrogel decorated by the biomass phytic acid (PAGH) with developed porosity and strengthen mechanical property via hydrothermal and freeze-drying methods. The phytic acid molecules are intercalated into the graphene sheets, enabling robust network structure. This induces the formation of materials with larger specific surface area, lower density and enhanced compressive strength compared with pure GH. When directly employed as an electrode, the PAGH exhibits a high specific capacitance of 248.8 F g-1 at 1 A g-1 and excellent rate performance of 67.9% as current density increasing to 20 A g-1. Furthermore, the all-solid-state supercapacitor based PAGH can deliver outstanding cycle life (86.2% after cycling 10,000 times), glorious energy density (26.5 Wh kg-1) and power density (5135.1 W kg-1). The prepared device shows stable electrochemical behaviors at random bending angles. Therefore, the present work will open a new avenue to design and fabricate new flexible and portable graphene-based electrodes for future applications in energy storage devices.

Artificial Intelligence: Bayesian versus Heuristic Method for Diagnostic Decision Support.

PubMed

Elkin, Peter L; Schlegel, Daniel R; Anderson, Michael; Komm, Jordan; Ficheur, Gregoire; Bisson, Leslie

2018-04-01

Evoking strength is one of the important contributions of the field of Biomedical Informatics to the discipline of Artificial Intelligence. The University at Buffalo's Orthopedics Department wanted to create an expert system to assist patients with self-diagnosis of knee problems and to thereby facilitate referral to the right orthopedic subspecialist. They had two independent sports medicine physicians review 469 cases. A board-certified orthopedic sports medicine practitioner, L.B., reviewed any disagreements until a gold standard diagnosis was reached. For each case, the patients entered 126 potential answers to 26 questions into a Web interface. These were modeled by an expert sports medicine physician and the answers were reviewed by L.B. For each finding, the clinician specified the sensitivity (term frequency) and both specificity (Sp) and the heuristic evoking strength (ES). Heuristics are methods of reasoning with only partial evidence. An expert system was constructed that reflected the posttest odds of disease-ranked list for each case. We compare the accuracy of using Sp to that of using ES (original model, p  < 0.0008; term importance * disease importance [DItimesTI] model, p  < 0.0001: Wilcoxon ranked sum test). For patient referral assignment, Sp in the DItimesTI model was superior to the use of ES. By the fifth diagnosis, the advantage was lost and so there is no difference between the techniques when serving as a reminder system. Schattauer GmbH Stuttgart.

How culture gets embrained: Cultural differences in event-related potentials of social norm violations.

PubMed

Mu, Yan; Kitayama, Shinobu; Han, Shihui; Gelfand, Michele J

2015-12-15

Humans are unique among all species in their ability to develop and enforce social norms, but there is wide variation in the strength of social norms across human societies. Despite this fundamental aspect of human nature, there has been surprisingly little research on how social norm violations are detected at the neurobiological level. Building on the emerging field of cultural neuroscience, we combine noninvasive electroencephalography (EEG) with a new social norm violation paradigm to examine the neural mechanisms underlying the detection of norm violations and how they vary across cultures. EEG recordings from Chinese and US participants (n = 50) showed consistent negative deflection of event-related potential around 400 ms (N400) over the central and parietal regions that served as a culture-general neural marker of detecting norm violations. The N400 at the frontal and temporal regions, however, was only observed among Chinese but not US participants, illustrating culture-specific neural substrates of the detection of norm violations. Further, the frontal N400 predicted a variety of behavioral and attitudinal measurements related to the strength of social norms that have been found at the national and state levels, including higher culture superiority and self-control but lower creativity. There were no cultural differences in the N400 induced by semantic violation, suggesting a unique cultural influence on social norm violation detection. In all, these findings provided the first evidence, to our knowledge, for the neurobiological foundations of social norm violation detection and its variation across cultures.

Using short-range and long-range functional connectivity to identify schizophrenia with a family-based case-control design.

PubMed

Guo, Wenbin; Liu, Feng; Chen, Jindong; Wu, Renrong; Li, Lehua; Zhang, Zhikun; Chen, Huafu; Zhao, Jingping

2017-06-30

Abnormal short-range and long-range functional connectivities (FCs) have been implicated in the neurophysiology of schizophrenia. This study was conducted to examine the potential of short-range and long-range FCs for differentiating the patients from the controls with a family-based case-control design. Twenty-eight first-episode, drug-naive patients with schizophrenia, 28 unaffected siblings of the patients (family-based controls, FBCs), and 40 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging (fMRI) scans. The data were analyzed by short-range and long-range FC analyses, receiver operating characteristic curve (ROC) and support vector machine (SVM). Compared with the FBCs/HCs, the patients exhibit increased short-range positive FC strength (spFCS) and/or long-range positive FC strength (lpFCS) in the default-mode network (DMN) and decreased spFCS and lpFCS in the sensorimotor circuits. Furthermore, a combination of the spFCS values in the right superior parietal lobule and the lpFCS values in the left fusiform gyrus/cerebellum VI can differentiate the patients from the FBCs with high sensitivity and specificity. The findings highlight the importance of the DMN and sensorimotor circuits in the pathogenesis of schizophrenia. Combining with family-based case-control design may be a viable option to limit the confounding effects of environmental risk factors in neuroimaging studies of schizophrenia. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Fabrication and Characteristics of Sintered Cutting Stainless Steel Fiber Felt with Internal Channels and an Al2O3 Coating

PubMed Central

Huang, Shufeng; Wan, Zhenping; Zou, Shuiping

2018-01-01

A novel sintered cutting stainless steel fiber felt with internal channels (SCSSFFC) composed of a stainless-steel fiber skeleton, three-dimensional interconnected porous structure and multiple circular microchannels is developed. SCSSFFC has a jagged and rough surface morphology and possesses a high specific surface area, which is approximately 2.4 times larger than that of the sintered bundle-drawing stainless steel fiber felt with internal channels (SBDSSFFC) and is expected to enhance adhesive strength. The sol-gel and wet impregnation methods are adopted to prepare SCSSFFC with an Al2O3 coating (SCSSFFC/Al2O3). The adhesive strength of SCSSFFC/Al2O3 is investigated using ultrasonic vibration and thermal shock tests. The experimental results indicate that the weight loss rate of the Al2O3 coating has a 4.2% and 8.42% reduction compared with those of SBDSSFFCs based on ultrasonic vibration and thermal shock tests. In addition, the permeability of SCSSFFC/Al2O3 is investigated based on forced liquid flow tests. The experimental results show that the permeability and inertial coefficients of SCSSFFC/Al2O3 are mainly affected by the coating rate, porosity and open ratio; however, the internal microchannel diameter has little influence. It is also found that SCSSFFC/Al2O3 yields superior permeability, as well as inertial coefficients compared with those of other porous materials reported in the literature. PMID:29558438

Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries.

PubMed

Gaikwad, Abhinav M; Arias, Ana Claudia

2017-02-22

Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm 2 ) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

A novel ultrafine-grained Fe−22Mn−0.6C TWIP steel with superior strength and ductility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Y.Z., E-mail: yztian@imr.ac.cn

A fully recrystallized ultrafine-grained (UFG) Fe−22wt.%Mn−0.6wt.%C twinning-induced plasticity (TWIP) steel with mean grain size of 576 nm was fabricated by cold rolling and annealing process. Tensile test showed that this UFG steel possessed high yield strength of 785 MPa, and unprecedented uniform elongation of 48%. The Hall-Petch relationship was verified from the coarse-grained (CG) regime to the ultrafine-grained (UFG) regime. The microstructures at specified tensile strains were characterized by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The microstructures and strain hardening behavior of the UFG TWIP steel were compared with the CG counterpart. The strong strain hardening capabilitymore » of the UFG steel is supposed to be responsible for the high strength and good ductility. - Highlights: • A fully recrystallized Fe−22Mn−0.6C TWIP steel with mean grain size of 576 nm was fabricated. • The ultrafine-grained (UFG) steel exhibits strong strain-hardening capability, excellent strength and ductility. • The Hall-Petch relationship is fitted well from the CG regime to the UFG regime.« less

Four-point-bend fatigue of AA 2026 aluminum alloys

NASA Astrophysics Data System (ADS)

Li, J. X.; Zhai, T.; Garratt, M. D.; Bray, G. H.

2005-09-01

High-cycle fatigue tests were carried out on a newly developed high-strength AA 2026 Al alloy, which was in the form of extrusion bars with square and rectangular cross sections, using a self-aligning four-point-bend rig at room temperature, 15 Hz, and R = 0.1, in lab air. The fatigue strength of the square and rectangular bars was measured to be 85 and 90 pct of their yield strength, respectively, more than twice that of the predecessor to the 2026 alloy (the AA 2024 Al alloy). Fatigue cracks were found to be always initiated at large Θ' (Al7Cu2(Fe,Mn)) particles and to propagate predominantly in a crystallographic mode in the AA 2026 alloy. The fatigue fractographies of the square and rectangular extrusion bars were found to be markedly different, due to their different grain structures (fibril and layered, respectively). Fracture steps on the crack face were found in both of these extrusion bars. Since the 2026 alloy was purer in terms of Fe and Si content, it contained much less coarse particles than in a 2024 alloy. This partially accounted for the superior fatigue strength of the 2026 alloy.

Effect of grit-blasting on substrate roughness and coating adhesion

NASA Astrophysics Data System (ADS)

Varacalle, Dominic J.; Guillen, Donna Post; Deason, Douglas M.; Rhodaberger, William; Sampson, Elliott

2006-09-01

Statistically designed experiments were performed to compare the surface roughness produced by grit blasting A36/1020 steel using different abrasives. Grit blast media, blast pressure, and working distance were varied using a Box-type statistical design of experiment (SDE) approach. The surface textures produced by four metal grits (HG16, HG18, HG25, and HG40) and three conventional grits (copper slag, coal slag, and chilled iron) were compared. Substrate roughness was measured using surface profilometry and correlated with operating parameters. The HG16 grit produced the highest surface roughness of all the grits tested. Aluminum and zinc-aluminum coatings were deposited on the grit-blasted substrates using the twin-wire electric are (TWEA) process. Bond strength of the coatings was measured with a portable adhesion tester in accordance with ASTM standard D 4541. The coatings on substrates roughened with steel grit exhibit superior bond strength to those prepared with conventional grit. For aluminum coatings sprayed onto surfaces prepared with the HG16 grit, the bond strength was most influenced by current, spray distance, and spray gun pressure (in that order). The highest bond strength for the zinc-aluminum coatings was attained on surfaces prepared using the metal grits.

33 CFR 117.669 - St. Louis River (Duluth Superior Harbor).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false St. Louis River (Duluth Superior Harbor). 117.669 Section 117.669 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Minnesota § 117.669 St. Louis River...

Treatment of methicillin-resistant Staphylococcus aureus: vancomycin and beyond.

PubMed

Holmes, Natasha E; Tong, Steven Y C; Davis, Joshua S; van Hal, Sebastiaan J

2015-02-01

There has been a welcome increase in the number of agents available for the treatment of methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin remains an acceptable treatment option, with moves toward individualized dosing to a pharmacokinetic/pharmacodynamic (PK/PD) target. Numerous practicalities, however, would need to be resolved before implementation. Lipoglycopeptides as a class show excellent in vitro potency. Their long half-lives and complex PKs may preclude these agents being used in critically ill patients. Anti-MRSA cephalosporins provide great promise in the treatment of MRSA. These agents, despite broad-spectrum activity, should be reserved for patients with MRSA infections as it is likely that usage will be associated with increased rates of resistance. Daptomycin is currently the only antibiotic to have shown noninferiority to vancomycin in the treatment of MRSA bacteremia. The results of an open-labeled trial to address the superiority of daptomycin compared with vancomycin in reduced vancomycin susceptibility infections are eagerly anticipated. No drug to date has shown superiority to vancomycin in the treatment of MRSA infections with the possible exception of linezolid in hospital-acquired pneumonia (HAP), making linezolid an important option in the treatment of MRSA-proven HAP. Whether these strengths and features are agent or class specific are unclear but will likely be answered with the marketing of tedizolid. There are insufficient data to recommend either quinupristin/dalfopristin or tigecycline, as first line in the treatment of severe MRSA infections. These agents however remain options in patients with no other alternatives. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Triphasic Composite And Method Of Making Same

DOEpatents

Kear, Bernard H.; Sadangi, Rajendra K.; McCandlish, Larry E.; Voronov, Oleg

2000-07-18

A method for fabricating a triphasic composite such as a WC/Co/diamond composite with a high volume fraction of diamond in a WC/Co matrix. The method involves sintering of a WC/Co powder compact to develop a porous preform, which displays some rigidity and strength, infiltrating the porous preform with a controlled distribution of carbon, and high pressure/high temperature treatment of the carbon-containing WC/Co preform to transform the carbon to diamond. The distribution of diamond in the composite can be functionally graded to provide a WC/Co core and a diamond-enriched surface, wherein all three phases form an interconnected structure in three dimensions. Such a tricontinuous structure combines high strength and toughness with superior wear resistance, making it attractive for applications in machine tools and drill bits.

Highly thermally conductive and mechanically strong graphene fibers.

PubMed

Xin, Guoqing; Yao, Tiankai; Sun, Hongtao; Scott, Spencer Michael; Shao, Dali; Wang, Gongkai; Lian, Jie

2015-09-04

Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is the thinnest, strongest, and stiffest known material and an excellent conductor of heat and electricity. However, these superior properties have yet to be realized for graphene-derived macroscopic structures such as graphene fibers. We report the fabrication of graphene fibers with high thermal and electrical conductivity and enhanced mechanical strength. The inner fiber structure consists of large-sized graphene sheets forming a highly ordered arrangement intercalated with small-sized graphene sheets filling the space and microvoids. The graphene fibers exhibit a submicrometer crystallite domain size through high-temperature treatment, achieving an enhanced thermal conductivity up to 1290 watts per meter per kelvin. The tensile strength of the graphene fiber reaches 1080 megapascals. Copyright © 2015, American Association for the Advancement of Science.

Evaluation of hot forming effects mapping for CAE analyses

NASA Astrophysics Data System (ADS)

Knoerr, L.; Faath, T.; Dykeman, J.; Malcolm, S.

2016-08-01

Hot forming has grown significantly in the manufacturing of structural components within the vehicle Body-In-White construction. The superior strength of press hardened steels not only guarantee high resistance to deformation, it also brings a significant weight saving compared to conventional cold formed products. However, the benefit of achieving ultrahigh strength with hot stamping, comes with a reduction in ductility of the press hardened part. This will require advanced material modeling to capture the predicted performances accurately. A technique to optically measure and map the thinning distribution after hot stamping has shown to improve numerical analysis for fracture prediction. The proposed method to determine the forming effects and mapping to CAE models can be integrated into the Vehicle Development Process to shorten the time to production.

ILLUMINATING THE ROLE OF AGGLOMERATES ON CRITICAL PHYSICOCHEMICAL PROPERTIES OF AMORPHOUS CALCIUM PHOSPHATE COMPOSITES

PubMed Central

O’Donnell, J.N.R.; Antonucci, J.M.; Skrtic, D.

2009-01-01

Water sorption (WS), mechanical strength, and ion release of polymeric composites formulated with 40 % as-made or milled amorphous calcium phosphate (ACP) are compared after 1, 2 and 3 months of aqueous exposure. Ethoxylated bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and methacryloxyethyl phthalate comprised the resin. The WS (mass %) peaked at 3 months. WS of as-made ACP composites was significantly higher than WS of milled ACP composites and copolymers. Both composite groups experienced decreases in biaxial flexural strength (BFS) with water aging, with milled ACP composites retaining a significantly higher BFS throughout immersion. Ion release was moderately reduced in milled ACP composites, though they remained superior to as-made ACP composites due to significantly lower WS and higher BFS after prolonged aqueous exposure. PMID:19774100

Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration.

PubMed

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

2011-10-01

The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires the development of porous, high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inks were optimized for the printing of features as fine as 30 μm and of three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds showed a compressive strength (136 ± 22 MPa) comparable with that of human cortical bone (100-150 MPa), while the porosity (60%) was in the range of that of trabecular bone (50-90%). The strength is ~100-times that of polymer scaffolds and 4-5-times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in SBF, the value (77 MPa) is still far above that of trabecular bone after 3 weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration. Published by Elsevier Ltd.

Direct Ink Writing of Highly Porous and Strong Glass Scaffolds for Load-bearing Bone Defects Repair and Regeneration

PubMed Central

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

2011-01-01

The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires development of porous and high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work, bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inkswere optimized for the printing of features as fine as 30 μm and of the three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds show a compressive strength (136 ± 22 MPa) comparable to that of human cortical bone (100-150 MPa), while the porosity (60%) is in the range of that of trabecular bone (50-90%).The strength is ~100 times that of polymer scaffolds and 4–5 times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in an SBF, the value (77 MPa) is still far above that of trabecular bone after three weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration. PMID:21745606

Transcriptome Analysis Suggests That Chromosome Introgression Fragments from Sea Island Cotton (Gossypium barbadense) Increase Fiber Strength in Upland Cotton (Gossypium hirsutum).

PubMed

Lu, Quanwei; Shi, Yuzhen; Xiao, Xianghui; Li, Pengtao; Gong, Juwu; Gong, Wankui; Liu, Aiying; Shang, Haihong; Li, Junwen; Ge, Qun; Song, Weiwu; Li, Shaoqi; Zhang, Zhen; Rashid, Md Harun Or; Peng, Renhai; Yuan, Youlu; Huang, Jinling

2017-10-05

As high-strength cotton fibers are critical components of high quality cotton, developing cotton cultivars with high-strength fibers as well as high yield is a top priority for cotton development. Recently, chromosome segment substitution lines (CSSLs) have been developed from high-yield Upland cotton ( Gossypium hirsutum ) crossed with high-quality Sea Island cotton ( G. barbadense ). Here, we constructed a CSSL population by crossing CCRI45, a high-yield Upland cotton cultivar, with Hai1, a Sea Island cotton cultivar with superior fiber quality. We then selected two CSSLs with significantly higher fiber strength than CCRI45 (MBI7747 and MBI7561), and one CSSL with lower fiber strength than CCRI45 (MBI7285), for further analysis. We sequenced all four transcriptomes at four different time points postanthesis, and clustered the 44,678 identified genes by function. We identified 2200 common differentially-expressed genes (DEGs): those that were found in both high quality CSSLs (MBI7747 and MBI7561), but not in the low quality CSSL (MBI7285). Many of these genes were associated with various metabolic pathways that affect fiber strength. Upregulated DEGs were associated with polysaccharide metabolic regulation, single-organism localization, cell wall organization, and biogenesis, while the downregulated DEGs were associated with microtubule regulation, the cellular response to stress, and the cell cycle. Further analyses indicated that three genes, XLOC_036333 [mannosyl-oligosaccharide-α-mannosidase ( MNS1 )], XLOC_029945 ( FLA8 ), and XLOC_075372 ( snakin-1 ), were potentially important for the regulation of cotton fiber strength. Our results suggest that these genes may be good candidates for future investigation of the molecular mechanisms of fiber strength formation and for the improvement of cotton fiber quality through molecular breeding. Copyright © 2017 Lu et al.

Profiling Isokinetic Strength by Leg Preference and Position in Rugby Union Athletes.

PubMed

Brown, Scott R; Brughelli, Matt; Bridgeman, Lee A

2016-05-01

Muscle imbalances aid in the identification of athletes at risk for lower-extremity injury. Little is known regarding the influence that leg preference or playing position may have on lower-extremity muscle strength and asymmetry. To investigate lower-extremity strength profiles in rugby union athletes and compare isokinetic knee- and hip-strength variables between legs and positions. Thirty male academy rugby union athletes, separated into forwards (n = 15) and backs (n = 15), participated in this cross-sectional analysis. Isokinetic dynamometry was used to evaluate peak torque, angle of peak torque, and strength ratios of the preferred and nonpreferred legs during seated knee extension/flexion and supine hip extension/flexion at 60°/s. Backs were older (ES = 1.6) but smaller in stature (ES = -0.47) and body mass (ES = -1.3) than the forwards. The nonpreferred leg was weaker than the preferred leg for forwards during extension (ES = -0.37) and flexion (ES = -0.21) actions and for backs during extension (ES = -0.28) actions. Backs were weaker at the knee than forwards in the preferred leg during extension (ES = -0.50) and flexion (ES = -0.66) actions. No differences were observed in strength ratios between legs or positions. Backs produced peak torque at longer muscle lengths in both legs at the knee (ES = -0.93 to -0.94) and hip (ES = -0.84 to -1.17) than the forwards. In this sample of male academy rugby union athletes, the preferred leg and forwards displayed superior strength compared with the nonpreferred leg and backs. These findings highlight the importance of individualized athletic assessments to detect crucial strength differences in male rugby union athletes.

Functional and cosmetic outcome of single-digit ray amputation in hand.

PubMed

Bhat, A K; Acharya, A M; Narayanakurup, J K; Kumar, B; Nagpal, P S; Kamath, A

2017-12-01

To assess patient satisfaction, functional and cosmetic outcomes of single-digit ray amputation in hand and identify factors that might affect the outcome. Forty-five patients who underwent ray amputation were evaluated, 37 males and eight females whose mean age was 36.6 years ranging between 15 and 67 years. Twenty-eight patients had dominant hand involvement. Twenty-one patients underwent primary ray amputation, and 24 patients had secondary ray amputation. Eight out of the 23 patients with central digit injuries underwent transposition. Grip strength, pinch strength, tactile sensibility and functional evaluation using Result Assessment Scale (RAS) and DASH score were analysed. Cosmetic assessment was performed using visual analogue scale (VAS) for cosmesis. Median time of assessment after surgery was 20 months. Average loss of grip strength and pinch strength was found to be 43.3 and 33.6%, respectively. Average RAS score was 3.75. Median DASH score was 23.4. Eighty-three percentage of patients had excellent or good cosmesis on the VAS. Transposition causes significant increase in DASH scores for central digit ray amputations but was cosmetically superior. Middle finger ray amputation had the maximum loss of grip strength, and index finger ray amputation had greater loss of pinch strength. Affection of neighbouring digits caused greater grip and pinch loss, and a higher DASH score. Primary ray resection decreased the total disability and eliminated the costs of a second procedure. Following ray amputation, one can predict an approximate 43.3% loss of grip strength and 33.6% loss of pinch strength. The patients can be counselled regarding the expected time off from work, amount of disability and complications after a single-digit ray amputation. Majority of the patients can return to the same occupation after a period of dedicated hand therapy. Therapeutic, Level III.

Preparation Of Strong, Dense Potassium Beta''-Alumina Ceramic

NASA Technical Reports Server (NTRS)

Williams, Roger M.; Jeffries-Nakamura, Barbara; Ryan, Margaret A.; O'Connor, Dennis E.; Kisor, Adam; Kikkert, Stanley J.; Losey, Robert; Suitor, Jerry W.

1995-01-01

Improved process for making mechanically strong, dense, phase-pure potassium beta''-alumina solid electrolyte (K-BASE) results in material superior to all previous K-BASE preparations and similar to commercial Na-BASE in strength, phase purity and high-temperature ionic conductivity. Potassium-based alkali-metal thermal-to-electric conversion (AMTEC) cells expected to operate efficiently at lower heat-input temperatures and lower rejection temperatures than sodium-based AMTEC cells, making them appropriate for somewhat different applications.

Effects of rolling temperature and subsequent annealing on mechanical properties of ultrafine-grained Cu–Zn–Si alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiangkai; Yang, Xuyue, E-mail: yangxuyue@csu.edu.cn; Institute for Materials Microstructure, Central South University, Changsha 410083

2015-08-15

The effects of rolling temperature and subsequent annealing on mechanical properties of Cu–Zn–Si alloy were investigated by using X-ray diffraction, transmission electron microscope, electron back scattered diffraction and tensile tests. The Cu–Zn–Si alloy has been processed at cryogenic temperature (approximately 77 K) and room temperature up to different rolling strains. It has been identified that the cryorolled Cu–Zn–Si alloy samples show a higher strength compared with those room temperature rolled samples. The improved strength of cryorolled samples is resulted from grain size effect and higher densities of dislocations and deformation twins. And subsequent annealing, as a post-heat treatment, enhanced themore » ductility. An obvious increase in uniform elongation appears when the volume fraction of static recrystallization grains exceeds 25%. The strength–ductility combination of the annealed cryorolled samples is superior to that of annealed room temperature rolled samples, owing to the finer grains, high fractions of high angle grain boundaries and twins. - Highlights: • An increase in hardness of Cu–Zn–Si alloy is noticed during annealing process. • Thermal stability is reduced in Cu–Zn–Si alloy by cryorolling. • An obvious enhancement in UE is noticed when fraction of SRX grains exceeds 25%. • A superior strength–ductility combination is achieved in the cryorolling samples.« less

Core neuropsychological characteristics of children and adolescents with 22q11.2 deletion.

PubMed

Jacobson, C; Shearer, J; Habel, A; Kane, F; Tsakanikos, E; Kravariti, E

2010-08-01

The 22q11.2 deletion syndrome (22qDS) confers high risk for intellectual disability and neuropsychological/academic impairment, although a minority of patients show average intelligence. Intellectual heterogeneity and the high prevalence of psychiatric diagnoses in earlier studies may have obscured the prototypical neuropsychological profile in 22qDS. We examined intelligence, memory, reading and mathematical processes in 31 children/adolescents with 22qDS, selected for educational underachievement and an absence of psychiatric diagnoses, using standardised, psychometrically matched instruments that specify how typical a score is for a given intelligence quotient (IQ). Corroborating earlier findings, verbal IQ was significantly superior to performance IQ; verbal memory and basic reading were relative strengths; and visual/spatial memory was a relative weakness. All four findings transcended performance characteristics that are typical of low-IQ individuals. Rote learning yielded the highest score; reading comprehension, numerical operations and mathematical reasoning were among the lowest-performed academic domains. Albeit in the expected direction, performance in the respective components could not be clearly differentiated from what is IQ-appropriate. A superiority of verbal intelligence over non-verbal intelligence, relative strengths in verbal memory and basic reading, and a relative weakness in visual/spatial memory are likely to be core characteristics of children/adolescents with 22qDS, transcending performance features that are typical of individuals with low IQ.

Robot-assisted practice of gait and stair climbing in nonambulatory stroke patients.

PubMed

Hesse, Stefan; Tomelleri, Christopher; Bardeleben, Anita; Werner, Cordula; Waldner, Andreas

2012-01-01

A novel gait robot enabled nonambulatory patients the repetitive practice of gait and stair climbing. Thirty nonambulatory patients with subacute stroke were allocated to two groups. During 60 min sessions every workday for 4 weeks, the experimental group received 30 min of robot training and 30 min of physiotherapy and the control group received 60 min of physiotherapy. The primary variable was gait and stair climbing ability (Functional Ambulation Categories [FAC] score 0-5); secondary variables were gait velocity, Rivermead Mobility Index (RMI), and leg strength and tone blindly assessed at onset, intervention end, and follow-up. Both groups were comparable at onset and functionally improved over time. The improvements were significantly larger in the experimental group with respect to the FAC, RMI, velocity, and leg strength during the intervention. The FAC gains (mean +/- standard deviation) were 2.4 +/- 1.2 (experimental group) and 1.2 +/- 1.5 (control group), p = 0.01. At the end of the intervention, seven experimental group patients and one control group patient had reached an FAC score of 5, indicating an ability to climb up and down one flight of stairs. At follow-up, this superior gait ability persisted. In conclusion, the therapy on the novel gait robot resulted in a superior gait and stair climbing ability in nonambulatory patients with subacute stroke; a higher training intensity was the most likely explanation. A large randomized controlled trial should follow.

Double-row vs single-row rotator cuff repair: a review of the biomechanical evidence.

PubMed

Wall, Lindley B; Keener, Jay D; Brophy, Robert H

2009-01-01

A review of the current literature will show a difference between the biomechanical properties of double-row and single-row rotator cuff repairs. Rotator cuff tears commonly necessitate surgical repair; however, the optimal technique for repair continues to be investigated. Recently, double-row repairs have been considered an alternative to single-row repair, allowing a greater coverage area for healing and a possibly stronger repair. We reviewed the literature of all biomechanical studies comparing double-row vs single-row repair techniques. Inclusion criteria included studies using cadaveric, animal, or human models that directly compared double-row vs single-row repair techniques, written in the English language, and published in peer reviewed journals. Identified articles were reviewed to provide a comprehensive conclusion of the biomechanical strength and integrity of the repair techniques. Fifteen studies were identified and reviewed. Nine studies showed a statistically significant advantage to a double-row repair with regards to biomechanical strength, failure, and gap formation. Three studies produced results that did not show any statistical advantage. Five studies that directly compared footprint reconstruction all demonstrated that the double-row repair was superior to a single-row repair in restoring anatomy. The current literature reveals that the biomechanical properties of a double-row rotator cuff repair are superior to a single-row repair. Basic Science Study, SRH = Single vs. Double Row RCR.

Effect of topically applied sildenafil citrate on wound healing: experimental study.

PubMed

Gürsoy, Koray; Oruç, Melike; Kankaya, Yüksel; Ulusoy, Mustafa Gürhan; Koçer, Uğur; Kankaya, Duygu; Gürsoy, Reyhan Neslihan; Çevik, Özge; Öğüş, Elmas; Fidanci, Vildan

2014-08-16

Wound healing is a complex process that necessitates organization of different cell types and several signalling molecules. The aim of this study is to evaluate the effect of different concentrations of sildenafil citrate, which decreases cGMP degradation, on wound healing by secondary intention.This study was performed using 25 Sprague Dawley rats weighing 200-250 grams. 4 dorsal defects were created. Four different treatment modalities which were 1% and 5% sildenafil citrate gel prepared with carbopol, pure carbopol gel without any drug in it and 0,9% NaCl solution; were applied to each lesion of the same rat. Randomly selected five rats (25 rats in total) were sacrificed on 3rd, 5th, 7th, 10th, and 14th days; and the effect of each modality was evaluated by means of defect area measurement, histopathological examination and measurement of tissue hydroxyproline levels.Sildenafil citrate gel application decreased the defect areas in a dose independent manner starting from 3rd day and dose dependent manner after 7th day. By means of vascularization, sildenafil citrate increased vascularity starting from 3rd day. The strength of acute inflammation was superior in sildenafil groups starting from 5th day; and the amount and maturation of granulation in the wound bed, as well as the strength of chronic inflammation were superior in defects treated with sildenafil citrate as early as 7th day.

Effect of topically applied sildenafil citrate on wound healing: experimental study

PubMed Central

Gürsoy, Koray; Oruç, Melike; Kankaya, Yüksel; Ulusoy, M. Gürhan; Koçer, Uğur; Kankaya, Duygu; Gürsoy, R. Neslihan; Çevik, Özge; Öğüş, Elmas; Fidanci, Vildan

2014-01-01

Wound healing is a complex process that necessitates organization of different cell types and several signalling molecules. The aim of this study is to evaluate the effect of different concentrations of sildenafil citrate, which decreases cGMP degradation, on wound healing by secondary intention. This study was performed using 25 Sprague Dawley rats weighing 200-250 grams. 4 dorsal defects were created. Four different treatment modalities which were 1% and 5% sildenafil citrate gel prepared with carbopol, pure carbopol gel without any drug in it and 0,9% NaCl solution; were applied to each lesion of the same rat. Randomly selected five rats (25 rats in total) were sacrificed on 3rd, 5th, 7th, 10th, and 14th days; and the effect of each modality was evaluated by means of defect area measurement, histopathological examination and measurement of tissue hydroxyproline levels. Sildenafil citrate gel application decreased the defect areas in a dose independent manner starting from 3rd day and dose dependent manner after 7th day. By means of vascularization, sildenafil citrate increased vascularity starting from 3rd day. The strength of acute inflammation was superior in sildenafil groups starting from 5th day; and the amount and maturation of granulation in the wound bed, as well as the strength of chronic inflammation were superior in defects treated with sildenafil citrate as early as 7th day. PMID:25172969

The effect of antimicrobial agents on bond strength of orthodontic adhesives: a meta-analysis of in vitro studies.

PubMed

Altmann, A S P; Collares, F M; Leitune, V C B; Samuel, S M W

2016-02-01

Antimicrobial orthodontic adhesives aim to reduce white spot lesions' incidence in orthodontic patients, but they should not jeopardizing its properties. Systematic review and meta-analysis were performed to answer the question whether the association of antimicrobial agents with orthodontic adhesives compromises its mechanical properties and whether there is a superior antimicrobial agent. PubMed and Scopus databases. In vitro studies comparing shear bond strength of conventional photo-activated orthodontic adhesives to antimicrobial photo-activated orthodontic adhesives were considered eligible. Search terms included the following: orthodontics, orthodontic, antimicrobial, antibacterial, bactericidal, adhesive, resin, resin composite, bonding agent, bonding system, and bond strength. The searches yielded 494 citations, which turned into 467 after duplicates were discarded. Titles and abstracts were read and 13 publications were selected for full-text reading. Twelve studies were included in the meta-analysis. The global analysis showed no statistically significant difference between control and experimental groups. In the subgroup analysis, only the chlorhexidine subgroup showed a statistically significant difference, where the control groups had higher bond strength than the experimental groups. Many studies on in vitro orthodontic bond strength fail to report test conditions that could affect their outcomes. The pooled in vitro data suggest that adding an antimicrobial agent to an orthodontic adhesive system does not influence bond strength to enamel. It is not possible to state which antimicrobial agent is better to be associated. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Executive Functions Are Employed to Process Episodic and Relational Memories in Children With Autism Spectrum Disorders

PubMed Central

2013-01-01

Objective: Long-term memory functioning in autism spectrum disorders (ASDs) is marked by a characteristic pattern of impairments and strengths. Individuals with ASD show impairment in memory tasks that require the processing of relational and contextual information, but spared performance on tasks requiring more item-based, acontextual processing. Two experiments investigated the cognitive mechanisms underlying this memory profile. Method: A sample of 14 children with a diagnosis of high-functioning ASD (age: M = 12.2 years), and a matched control group of 14 typically developing (TD) children (age: M = 12.1 years), participated in a range of behavioral memory tasks in which we measured both relational and item-based memory abilities. They also completed a battery of executive function measures. Results: The ASD group showed specific deficits in relational memory, but spared or superior performance in item-based memory, across all tasks. Importantly, for ASD children, executive ability was significantly correlated with relational memory but not with item-based memory. No such relationship was present in the control group. This suggests that children with ASD atypically employed effortful, executive strategies to retrieve relational (but not item-specific) information, whereas TD children appeared to use more automatic processes. Conclusions: The relational memory impairment in ASD may result from a specific impairment in automatic associative retrieval processes with an increased reliance on effortful and strategic retrieval processes. Our findings allow specific neural predictions to be made regarding the interactive functioning of the hippocampus, prefrontal cortex, and posterior parietal cortex in ASD as a neural network supporting relational memory processing. PMID:24245930

Effectiveness of Traditional Strength vs. Power Training on Muscle Strength, Power and Speed with Youth: A Systematic Review and Meta-Analysis

PubMed Central

Behm, David G.; Young, James D.; Whitten, Joseph H. D.; Reid, Jonathan C.; Quigley, Patrick J.; Low, Jonathan; Li, Yimeng; Lima, Camila D.; Hodgson, Daniel D.; Chaouachi, Anis; Prieske, Olaf; Granacher, Urs

2017-01-01

Numerous national associations and multiple reviews have documented the safety and efficacy of strength training for children and adolescents. The literature highlights the significant training-induced increases in strength associated with youth strength training. However, the effectiveness of youth strength training programs to improve power measures is not as clear. This discrepancy may be related to training and testing specificity. Most prior youth strength training programs emphasized lower intensity resistance with relatively slow movements. Since power activities typically involve higher intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics), there is a conflict between the training medium and testing measures. This meta-analysis compared strength (e.g., training with resistance or body mass) and power training programs (e.g., plyometric training) on proxies of muscle strength, power, and speed. A systematic literature search using a Boolean Search Strategy was conducted in the electronic databases PubMed, SPORT Discus, Web of Science, and Google Scholar and revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for inclusion in this systematic review and meta-analysis. The meta-analysis showed small to moderate magnitude changes for training specificity with jump measures. In other words, power training was more effective than strength training for improving youth jump height. For sprint measures, strength training was more effective than power training with youth. Furthermore, strength training exhibited consistently large magnitude changes to lower body strength measures, which contrasted with the generally trivial, small and moderate magnitude training improvements of power training upon lower body strength, sprint and jump measures, respectively. Maturity related inadequacies in eccentric strength and balance might influence the lack of training specificity with the unilateral landings and propulsions associated with sprinting. Based on this meta-analysis, strength training should be incorporated prior to power training in order to establish an adequate foundation of strength for power training activities. PMID:28713281

Effectiveness of Traditional Strength vs. Power Training on Muscle Strength, Power and Speed with Youth: A Systematic Review and Meta-Analysis.

PubMed

Behm, David G; Young, James D; Whitten, Joseph H D; Reid, Jonathan C; Quigley, Patrick J; Low, Jonathan; Li, Yimeng; Lima, Camila D; Hodgson, Daniel D; Chaouachi, Anis; Prieske, Olaf; Granacher, Urs

2017-01-01

Numerous national associations and multiple reviews have documented the safety and efficacy of strength training for children and adolescents. The literature highlights the significant training-induced increases in strength associated with youth strength training. However, the effectiveness of youth strength training programs to improve power measures is not as clear. This discrepancy may be related to training and testing specificity. Most prior youth strength training programs emphasized lower intensity resistance with relatively slow movements. Since power activities typically involve higher intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics), there is a conflict between the training medium and testing measures. This meta-analysis compared strength (e.g., training with resistance or body mass) and power training programs (e.g., plyometric training) on proxies of muscle strength, power, and speed. A systematic literature search using a Boolean Search Strategy was conducted in the electronic databases PubMed, SPORT Discus, Web of Science, and Google Scholar and revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for inclusion in this systematic review and meta-analysis. The meta-analysis showed small to moderate magnitude changes for training specificity with jump measures. In other words, power training was more effective than strength training for improving youth jump height. For sprint measures, strength training was more effective than power training with youth. Furthermore, strength training exhibited consistently large magnitude changes to lower body strength measures, which contrasted with the generally trivial, small and moderate magnitude training improvements of power training upon lower body strength, sprint and jump measures, respectively. Maturity related inadequacies in eccentric strength and balance might influence the lack of training specificity with the unilateral landings and propulsions associated with sprinting. Based on this meta-analysis, strength training should be incorporated prior to power training in order to establish an adequate foundation of strength for power training activities.

Effect of moisture content on dowel-bearing strength

Treesearch

Douglas R. Rammer; Steve G. Winistorfer

2001-01-01

Dowel bearing strength (embedment strength) is a critical component of wood connection design. Previous tests have concentrated on defining the relationship between dowel-bearing strength, specific gravity, and fastener characteristics such as diameter. However, because adoption of yield theory in defining connection strength is relatively new in the United States, few...

REGIONAL, WATERSHED, AND SITE-SPECIFIC ENVIRONMENTAL INFLUENCES ON FISH ASSEMBLAGE STRUCTURE AND FUNCTION IN WESTERN LAKE SUPERIOR TRIBUTARIES

EPA Science Inventory

The relative importance of regional, watershed, and in-stream environmental factors on stream fish assemblage structure and function was investigated as part of a comparative watershed project in the western Lake Superior basin. We selected 48 second and third order watersheds fr...

An in-depth cognitive examination of individuals with superior face recognition skills.

PubMed

Bobak, Anna K; Bennetts, Rachel J; Parris, Benjamin A; Jansari, Ashok; Bate, Sarah

2016-09-01

Previous work has reported the existence of "super-recognisers" (SRs), or individuals with extraordinary face recognition skills. However, the precise underpinnings of this ability have not yet been investigated. In this paper we examine (a) the face-specificity of super recognition, (b) perception of facial identity in SRs, (c) whether SRs present with enhancements in holistic processing and (d) the consistency of these findings across different SRs. A detailed neuropsychological investigation into six SRs indicated domain-specificity in three participants, with some evidence of enhanced generalised visuo-cognitive or socio-emotional processes in the remaining individuals. While superior face-processing skills were restricted to face memory in three of the SRs, enhancements to facial identity perception were observed in the others. Notably, five of the six participants showed at least some evidence of enhanced holistic processing. These findings indicate cognitive heterogeneity in the presentation of superior face recognition, and have implications for our theoretical understanding of the typical face-processing system and the identification of superior face-processing skills in applied settings. Copyright © 2016 Elsevier Ltd. All rights reserved.

Central Memory CD4+ T Cells Are Responsible for the Recombinant Bacillus Calmette-Guérin ΔureC::hly Vaccine's Superior Protection Against Tuberculosis

PubMed Central

Vogelzang, Alexis; Perdomo, Carolina; Zedler, Ulrike; Kuhlmann, Stefanie; Hurwitz, Robert; Gengenbacher, Martin; Kaufmann, Stefan H. E.

2014-01-01

Bacillus Calmette-Guérin (BCG) has been used for vaccination against tuberculosis for nearly a century. Here, we analyze immunity induced by a live tuberculosis vaccine candidate, recombinant BCG ΔureC::hly vaccine (rBCG), with proven preclinical and clinical safety and immunogenicity. We pursue in-depth analysis of the endogenous mycobacteria-specific CD4+ T-cell population, comparing the more efficacious rBCG with canonical BCG to determine which T-cell memory responses are prerequisites for superior protection against tuberculosis. rBCG induced higher numbers and proportions of antigen-specific memory CD4+ T cells than BCG, with a CXCR5+CCR7+ phenotype and low expression of the effector transcription factors T-bet and Bcl-6. We found that the superior protection of rBCG, compared with BCG, correlated with higher proportions and numbers of these central memory T cells and of T follicular helper cells associated with specific antibody responses. Adoptive transfer of mycobacteria-specific central memory T cells validated their critical role in protection against pulmonary tuberculosis. PMID:24943726

Development of advanced antimicrobial and sterilized plasma polypropylene grafted muga (Antheraea assama) silk as suture biomaterial.

PubMed

Gogoi, Dolly; Choudhury, Arup Jyoti; Chutia, Joyanti; Pal, Arup Ratan; Khan, Mojibur; Choudhury, Manash; Pathak, Pallabi; Das, Gouranga; Patil, Dinkar S

2014-04-01

Surface modification of silk fibroin (SF) materials using environmentally friendly and non-hazardous process to tailor them for specific application as biomaterials has drawn a great deal of interest in the field of biomedical research. To further explore this area of research, in this report, polypropylene (PP) grafted muga (Antheraea assama) SF (PP-AASF) suture is developed using plasma treatment and plasma graft polymerization process. For this purpose, AASF is first sterilized in argon (Ar) plasma treatment followed by grafting PP onto its surface. AASF is a non-mulberry variety having superior qualities to mulberry SF and is still unexplored in the context of suture biomaterial. AASF, Ar plasma treated AASF (AASFAr) and PP-AASF are subjected to various characterization techniques for better comparison and the results are attempted to correlate with their observed properties. Excellent mechanical strength, hydrophobicity, antibacterial behavior, and remarkable wound healing activity of PP-AASF over AASF and AASFAr make it a promising candidate for application as sterilized suture biomaterial. Copyright © 2013 Wiley Periodicals, Inc.

Compressive failure modes and parameter optimization of the trabecular structure of biomimetic fully integrated honeycomb plates.

PubMed

Chen, Jinxiang; Tuo, Wanyong; Zhang, Xiaoming; He, Chenglin; Xie, Juan; Liu, Chang

2016-12-01

To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Dislocation loop formation by swift heavy ion irradiation of metals.

PubMed

Khara, Galvin S; Murphy, Samuel T; Duffy, Dorothy M

2017-07-19

A coupled two-temperature, molecular dynamics methodology is used to simulate the structural evolution of bcc metals (Fe and W) and fcc metals (Cu and Ni) following irradiation by swift heavy ions. Electronic temperature dependent electronic specific heat capacities and electron-phonon coupling strengths are used to capture the full effects of the variation in the electronic density of states. Tungsten is found to be significantly more resistant to damage than iron, due both to the higher melting temperature and the higher thermal conductivity. Very interesting defect structures, quite different from defects formed in cascades, are found to be created by swift heavy ion irradiation in the bcc metals. Isolated vacancies form a halo around elongated interstitial dislocation loops that are oriented along the ion path. Such configurations are formed by rapid recrystallization of the molten cylindrical region that is created by the energetic ion. Vacancies are created at the recrystallization front, resulting in excess atoms at the core which form interstitial dislocation loops on completion of crystallization. These unique defect structures could, potentially, be used to create metal films with superior mechanical properties and interesting nanostructures.

Dislocation loop formation by swift heavy ion irradiation of metals

NASA Astrophysics Data System (ADS)

Khara, Galvin S.; Murphy, Samuel T.; Duffy, Dorothy M.

2017-07-01

A coupled two-temperature, molecular dynamics methodology is used to simulate the structural evolution of bcc metals (Fe and W) and fcc metals (Cu and Ni) following irradiation by swift heavy ions. Electronic temperature dependent electronic specific heat capacities and electron-phonon coupling strengths are used to capture the full effects of the variation in the electronic density of states. Tungsten is found to be significantly more resistant to damage than iron, due both to the higher melting temperature and the higher thermal conductivity. Very interesting defect structures, quite different from defects formed in cascades, are found to be created by swift heavy ion irradiation in the bcc metals. Isolated vacancies form a halo around elongated interstitial dislocation loops that are oriented along the ion path. Such configurations are formed by rapid recrystallization of the molten cylindrical region that is created by the energetic ion. Vacancies are created at the recrystallization front, resulting in excess atoms at the core which form interstitial dislocation loops on completion of crystallization. These unique defect structures could, potentially, be used to create metal films with superior mechanical properties and interesting nanostructures.

Dye Wastewater Cleanup by Graphene Composite Paper for Tailorable Supercapacitors.

PubMed

Yu, Dandan; Wang, Hua; Yang, Jie; Niu, Zhiqiang; Lu, Huiting; Yang, Yun; Cheng, Liwei; Guo, Lin

2017-06-28

Currently, the energy crisis and environmental pollution are two critical challenges confronted by humans. The development of smart strategies to address the above-mentioned issues simultaneously is significant. As the main accomplices for water pollution, several kinds of organic dyes with intrinsic redox functional groups such as phenothiazines derivatives, anthraquinone, and indigoid dyes are potential candidates for the replacement of the conventional pseudocapacitive materials. In this work, three typical organic dyes can be efficiently removed by a facile adsorption procedure using reduced graphene oxide coated cellulose fiber (rGO@CF) paper. Flexible supercapacitors based on dye/rGO@CF electrodes exhibit excellent electrochemical performances that are superior to or comparable with those of conventional pseudocapacitive materials based devices, presenting a new type of promising electrode materials. Moreover, benefiting from the high flexibility and considerable mechanical strength of the graphene composite paper, the operating potential and capacitance of the devices can be easily adjusted by tailoring the hybrid electrodes into different specific shapes followed by rational integrating. The smart design of these dye/rGO@CF paper based electrodes shows that energy storage and environmental remediation can be achieved simultaneously.

A quest for 2D lattice materials for actuation

NASA Astrophysics Data System (ADS)

Pronk, T. N.; Ayas, C.; Tekõglu, C.

2017-08-01

In the last two decades, most of the studies in shape morphing technology have focused on the Kagome lattice materials, which have superior properties such as in-plane isotropy, high specific stiffness and strength, and low energy requirement for actuation of its members. The Kagome lattice is a member of the family of semi-regular tessellations of the plane. Two fundamental questions naturally arise: i-) What makes a lattice material suitable for actuation? ii-) Are there other tessellations more effective than the Kagome lattice for actuation? The present paper tackles both questions, and provides a clear answer to the first one by comparing an alternative lattice material, the hexagonal cupola, with the Kagome lattice in terms of mechanical/actuation properties. The second question remains open, but, hopefully easier to challenge owing to a newly-discovered criterion: for an n-dimensional (n = 2 , 3) in-plane isotropic lattice material to be suitable for actuation, its pin-jointed equivalent must obey the generalised Maxwell's rule, and must possess M = 3(n - 1) non strain-producing finite kinematic mechanisms.

Supervised Versus Home Exercise Training Programs on Functional Balance in Older Subjects.

PubMed

Youssef, Enas Fawzy; Shanb, Alsayed Abd Elhameed

2016-11-01

Aging is associated with a progressive decline in physical capabilities and a disturbance of both postural control and daily living activities. The aim of this study was to evaluate the effects of supervised versus home exercise programs on muscle strength, balance and functional activities in older participants. Forty older participants were equally assigned to a supervised exercise program (group-I) or a home exercise program (group-II). Each participant performed the exercise program for 35-45 minutes, two times per week for four months. Balance indices and isometric muscle strength were measured with the Biodex Balance System and Hand-Held Dynamometer. Functional activities were evaluated by the Berg Balance Scale (BBS) and the timed get-up-and-go test (TUG). The mean values of the Biodex balance indices and the BBS improved significantly after both the supervised and home exercise programs ( P < 0.05). However, the mean values of the TUG and muscle strength at the ankle, knee and hip improved significantly only after the supervised program. A comparison between the supervised and home exercise programs revealed there were only significant differences in the BBS, TUG and muscle strength. Both the supervised and home exercise training programs significantly increased balance performance. The supervised program was superior to the home program in restoring functional activities and isometric muscle strength in older participants.

Infiltrated W–Cu composites with combined architecture of hierarchical particulate tungsten and tungsten fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Shuhua, E-mail: liangsh@xaut.edu.cn; Shaanxi Province Key Laboratory for Electrical Materials and Infiltration Technology, Xi'an 710048; Chen, Long

In this article, novel W–Cu composites reinforced with topologically-inserted tungsten fibers (W{sub f}) have been fabricated by hot-press sintering and infiltration method. By pre-sputtering of ~ 100 nm thick chromium layer onto the surface of W{sub f}, the contiguity or connectivity between W{sub f} and neighboring tungsten particles (W{sub p}) or Cu after sintering and infiltration was enhanced. Combined SEM, TEM and STEM techniques confirmed that the intact interfaces of W{sub f}/W{sub p} and W{sub f}/Cu free from precipitates, impurities and porosities would provide desirable strength and ductility. Further mechanical tests also validated its superior compressive strength and plasticity atmore » various temperatures, together with significantly improved tensile strength (by 23.6%) and hardness (by 9.3%) for the W–Cu composite after reinforcement with Cr-coated W{sub f}, which promotes the engineering application of the composite greatly. - Highlights: • W-fibers reinforced W–Cu composites were fabricated by sintering and infiltration. • The sputtered Cr onto W{sub f} has dissolved into adjacent W{sub f} and W{sub p} during fabrication. • The intact interfaces of W{sub f}/W{sub p} and W{sub f}/Cu confer enhanced strength and ductility. • Tensile strength and hardness improve by 23.6% and 9.3% after interface tuning.« less

Loading capacity of zirconia implant supported hybrid ceramic crowns.

PubMed

Rohr, Nadja; Coldea, Andrea; Zitzmann, Nicola U; Fischer, Jens

2015-12-01

Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05). The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load. Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Improvements of reinforced silica aerogel nanocomposites thermal properties for architecture applications.

PubMed

Saboktakin, Amin; Saboktakin, Mohammad Reza

2015-01-01

An 1,4-cis polybutadiene rubber/carboxymethyl starch (CMS)-based silica aerogel nanocomposites as a insulation material was developed that will provide superior thermal insulation properties, flexibility, toughness, durability of the parent polymer, yet with the low density and superior insulation properties associated with the aerogels. In this study, reinforced 1,4-cis polybutadiene-CMS-silica aerogel nanocomposites were prepared from a silica aerogel with a surface area 710 m(2) g(-1), a pore size of 25.3 nm and a pore volume of 4.7 cm(3) g(-1). The tensile properties and dynamic mechanical properties of 1,4-cis polybutadiene/CMS nanocomposites were systematically enhanced at low silica loading. Similar improvements in tensile modulus and strength have been observed for 1,4-cis polybutadiene/CMS mesoporous silica aerogel nanocomposites. Copyright © 2014 Elsevier B.V. All rights reserved.

A case study of a multiply talented savant with an autism spectrum disorder: neuropsychological functioning and brain morphometry.

PubMed

Wallace, Gregory L; Happé, Francesca; Giedd, Jay N

2009-05-27

Neuropsychological functioning and brain morphometry in a savant (case GW) with an autism spectrum disorder (ASD) and both calendar calculation and artistic skills are quantified and compared with small groups of neurotypical controls. Good memory, mental calculation and visuospatial processing, as well as (implicit) knowledge of calendar structure and 'weak' central coherence characterized the cognitive profile of case GW. Possibly reflecting his savant skills, the superior parietal region of GW's cortex was the only area thicker (while areas such as the superior and medial prefrontal, middle temporal and motor cortices were thinner) than that of a neurotypical control group. Taken from the perspective of learning/practice-based models, skills in domains (e.g. calendars, art, music) that capitalize upon strengths often associated with ASD, such as detail-focused processing, are probably further enhanced through over-learning and massive exposure, and reflected in atypical brain structure.

A case study of a multiply talented savant with an autism spectrum disorder: neuropsychological functioning and brain morphometry

PubMed Central

Wallace, Gregory L.; Happé, Francesca; Giedd, Jay N.

2009-01-01

Neuropsychological functioning and brain morphometry in a savant (case GW) with an autism spectrum disorder (ASD) and both calendar calculation and artistic skills are quantified and compared with small groups of neurotypical controls. Good memory, mental calculation and visuospatial processing, as well as (implicit) knowledge of calendar structure and ‘weak’ central coherence characterized the cognitive profile of case GW. Possibly reflecting his savant skills, the superior parietal region of GW's cortex was the only area thicker (while areas such as the superior and medial prefrontal, middle temporal and motor cortices were thinner) than that of a neurotypical control group. Taken from the perspective of learning/practice-based models, skills in domains (e.g. calendars, art, music) that capitalize upon strengths often associated with ASD, such as detail-focused processing, are probably further enhanced through over-learning and massive exposure, and reflected in atypical brain structure. PMID:19528026

Superior Tensile Ductility in Bulk Metallic Glass with Gradient Amorphous Structure

PubMed Central

Wang, Q.; Yang, Y.; Jiang, H.; Liu, C. T.; Ruan, H. H.; Lu, J.

2014-01-01

Over centuries, structural glasses have been deemed as a strong yet inherently ‘brittle’ material due to their lack of tensile ductility. However, here we report bulk metallic glasses exhibiting both a high strength of ~2 GPa and an unprecedented tensile elongation of 2–4% at room temperature. Our experiments have demonstrated that intense structural evolution can be triggered in theses glasses by the carefully controlled surface mechanical attrition treatment, leading to the formation of gradient amorphous microstructures across the sample thickness. As a result, the engineered amorphous microstructures effectively promote multiple shear banding while delay cavitation in the bulk metallic glass, thus resulting in superior tensile ductility. The outcome of our research uncovers an unusual work-hardening mechanism in monolithic bulk metallic glasses and demonstrates a promising yet low-cost strategy suitable for producing large-sized, ultra-strong and stretchable structural glasses. PMID:24755683

Discrimination among spawning concentrations of Lake Superior lake herring based on trace element profiles in sagittae

USGS Publications Warehouse

Bronte, Charles R.; Hesselberg, Robert J.; Shoesmith, John A.; Hoff, Michael H.

1996-01-01

Little is known about the stock structure of lake herring Coregonus artedi in Lake Superior, and recent increases in harvestable stock sizes has led to expanded exploitation in some areas. Research on marine teleosts has demonstrated that chemical differences in sagittal otoliths can be used for identification of fish stocks. We used plasma emission spectrophotometry to measure the concentrations of 10 trace elements in the sagittal otoliths from lake herring captured at eight spawning sites in Lake Superior and from Little Star Lake, an inland lake outside the Lake Superior basin. Discriminant function analysis indicated that elemental concentrations provided site-specific information but that considerable overlap existed among some locations, especially those in western Lake Superior. Correct classification rates varied from 12.0% to 86.1% and were generally higher for spawning locations from embayments in eastern Lake Superior and for the outgroup population from Little Star Lake. The results presented here demonstrate the potential usefulness of this technique for strictly freshwater species, especially those that live in highly oligotrophic waters such as Lake Superior.

Beneficial use of off-specification fly ashes to increase the shear strength and stiffness of expansive soil-rubber (ESR) mixtures.

DOT National Transportation Integrated Search

2011-07-01

The use of off-specification fly ashes to increase the shear strength and stiffness of an expansive soil-rubber (ESR) mixture is investigated systematically in this study. The off-specification fly ashes used include a high-sulfur content and a high-...

Comparing Three Patterns of Strengths and Weaknesses Models for the Identification of Specific Learning Disabilities

ERIC Educational Resources Information Center

Miller, Daniel C.; Maricle, Denise E.; Jones, Alicia M.

2016-01-01

Processing Strengths and Weaknesses (PSW) models have been proposed as a method for identifying specific learning disabilities. Three PSW models were examined for their ability to predict expert identified specific learning disabilities cases. The Dual Discrepancy/Consistency Model (DD/C; Flanagan, Ortiz, & Alfonso, 2013) as operationalized by…

Rapid Repairs: Surface Preparation of Ti-3 Al-2.5V Alloy Tubes by Fiber Laser and Welding

DTIC Science & Technology

2008-11-01

processing of titanium 6Al - 4V alloy for potential aerospace component cleaning application, Appl Surf Sci 2005;247:623-630. [11] Turner MW, Crouse...Debroy T, Heat transfer and fluid flow during keyhole mode laser welding of tantalum, Ti- 6Al - 4V , 304 Stainless Steel and Vanadium, J Phy D : Appl Phy...14Titanium alloys are used extensively in aerospace applications mainly due to their superior strength to weight ratio. Different grades of titanium

Color surface-flow visualization of fin-generated shock wave boundary-layer interactions

NASA Technical Reports Server (NTRS)

Lu, F. K.; Settles, G. S.

1990-01-01

Kerosene-lampblack mixtures with addition of a ground colored chalk were used in an experiment on visualizing surface flows of swept shock boundary-layer interactions. The results show that contrasting colors intensify the visualization of different regions of the interaction surface, and help the eye in following the fine streaks to locate the upstream influence. The study confirms observations of the separation occurring at shock strength below accepted values. The superiority of the reported technique over the previous monochrome technique is demonstrated.

An overview of contemporary nuclear cardiology.

PubMed

Lewin, Howard C; Sciammarella, Maria G; Watters, Thomas A; Alexander, Herbert G

2004-01-01

Myocardial perfusion single photon emission computed tomography (SPECT) is a widely utilized noninvasive imaging modality for the diagnosis, prognosis, and risk stratification of coronary artery disease. It is clearly superior to the traditional planar technique in terms of imaging contrast and consequent diagnostic and prognostic yield. The strength of SPECT images is largely derived from the three-dimensional, volumetric nature of its image. Thus, this modality permits three-dimensional assessment and quantitation of the perfused myocardium and functional assessment through electrocardiographic gating of the perfusion images.

Fiber grating system used to measure strain in a 22-ft composite utility pole

NASA Astrophysics Data System (ADS)

Udd, Eric; Corona, Kelli; Slattery, Kerry T.; Dorr, Donald J.

1996-05-01

Composite utility poles have significant advantages with respect to wooden utility poles that include superior strength and uniformity, light weight for ease of deployment, the ability to be recycled reducing hazardous waste associated with chemically treated wooden poles, and compatibility with embedded fiber optic sensors allowing structural loads to be monitored. This paper reports tests conducted of fiber optic grating sensors in combination with an overcoupled coupler demodulation system to support structural testing of a 22 foot composite pole.

Tension and compression measurements in composite utility poles using fiber optic grating sensors

NASA Astrophysics Data System (ADS)

Udd, Eric; Corona-Bittick, Kelli; Slattery, Kerry T.; Dorr, Donald J.

1995-04-01

Composite utility poles have the potential to overcome many of the limitations of wooden poles that are currently widely used. Significant advantages include superior strength and uniformity, light weight for ease of deployment, the ability to be recycled reducing hazardous waste associated with chemically treated wooden poles, and compatibility with embedded fiber optic sensors allowing structural loads to be monitored. This paper describes the usage of fiber optic grating sensors to support structural testing of a 22 foot composite pole.

Cloning Nacre's 3D Interlocking Skeleton in Engineering Composites to Achieve Exceptional Mechanical Properties.

PubMed

Zhao, Hewei; Yue, Yonghai; Guo, Lin; Wu, Juntao; Zhang, Youwei; Li, Xiaodong; Mao, Shengcheng; Han, Xiaodong

2016-07-01

Ceramic/polymer composite equipped with 3D interlocking skeleton (3D IL) is developed through a simple freeze-casting method, exhibiting exceptionally light weight, high strength, toughness, and shock resistance. Long-range crack energy dissipation enabled by 3D interlocking structure is considered as the primary reinforcing mechanism for such superior properties. The smart composite design strategy should hold a place in developing future structural engineering materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Color surface-flow visualization of fin-generated shock wave boundary-layer interactions

NASA Astrophysics Data System (ADS)

Lu, F. K.; Settles, G. S.

1990-03-01

Kerosene-lampblack mixtures with addition of a ground colored chalk were used in an experiment on visualizing surface flows of swept shock boundary-layer interactions. The results show that contrasting colors intensify the visualization of different regions of the interaction surface, and help the eye in following the fine streaks to locate the upstream influence. The study confirms observations of the separation occurring at shock strength below accepted values. The superiority of the reported technique over the previous monochrome technique is demonstrated.

30 CFR 75.335 - Seal strengths, design applications, and installation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... properties, construction specifications, quality control, design references, and other information related to... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Seal strengths, design applications, and... Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or...

30 CFR 75.335 - Seal strengths, design applications, and installation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... properties, construction specifications, quality control, design references, and other information related to... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Seal strengths, design applications, and... Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or...

30 CFR 75.335 - Seal strengths, design applications, and installation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... properties, construction specifications, quality control, design references, and other information related to... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Seal strengths, design applications, and... Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or...

30 CFR 75.335 - Seal strengths, design applications, and installation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... properties, construction specifications, quality control, design references, and other information related to... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Seal strengths, design applications, and... Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or...

30 CFR 75.335 - Seal strengths, design applications, and installation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... properties, construction specifications, quality control, design references, and other information related to... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Seal strengths, design applications, and... Seal strengths, design applications, and installation. (a) Seal strengths. Seals constructed on or...

Modified Daily Undulating Periodization Model Produces Greater Performance Than a Traditional Configuration in Powerlifters.

PubMed

Zourdos, Michael C; Jo, Edward; Khamoui, Andy V; Lee, Sang-Rok; Park, Bong-Sup; Ormsbee, Michael J; Panton, Lynn B; Contreras, Robert J; Kim, Jeong-Su

2016-03-01

The primary aim of this study was to compare 2 daily undulating periodization (DUP) models on one-repetition maximum (1RM) strength in the squat, bench press, deadlift, total volume (TV) lifted, and temporal hormone response. Eighteen male, college-aged (21.1 ± 1.9 years) powerlifters participated in this study and were assigned to one of 2 groups: (a) traditional DUP training with a weekly training order: hypertrophy-specific, strength-specific, and power-specific training (HSP, n = 9) or (b) modified DUP training with a weekly training order: hypertrophy-specific, power-specific, and strength-specific training (HPS, n = 9). Both groups trained 3 nonconsecutive days per week for 6 weeks and performed the squat, bench press, and deadlift exercises. During hypertrophy and power sessions, subjects performed a fixed number of sets and repetitions but performed repetitions until failure at a given percentage during strength sessions to compare TV. Testosterone and cortisol were measured at pretesting and posttesting and before each strength-specific day. Hypertrophy, power, and strength produced greater TV in squat and bench press (p ≤ 0.05) than HSP, but not for deadlift (p > 0.05). For squat and deadlift, there was no difference between groups for 1RM (p > 0.05); however, HPS exhibited greater increases in 1RM bench press than HSP (p ≤ 0.05). Effect sizes (ES) showed meaningful differences (ES > 0.50) in favor of HPS for squat and bench press 1RM. Testosterone decreased (p ≤ 0.05) at weeks 5 and 6 and cortisol decline at weeks 3 and 4. However, neither hormone was different at posttesting compared with pretesting (p > 0.05). Our findings suggest that an HPS configuration of DUP has enhanced performance benefits compared with HSP.

CNR considerations for rapid real-time MRI tumor tracking in radiotherapy hybrid devices: Effects of B{sub 0} field strength

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wachowicz, K., E-mail: keith.wachowicz@albertaheal

2016-08-15

Purpose: This work examines the subject of contrast-to-noise ratio (CNR), specifically between tumor and tissue background, and its dependence on the MRI field strength, B{sub 0}. This examination is motivated by the recent interest and developments in MRI/radiotherapy hybrids where real-time imaging can be used to guide treatment beams. The ability to distinguish a tumor from background tissue is of primary importance in this field, and this work seeks to elucidate the complex relationship between the CNR and B{sub 0} that is too often assumed to be purely linear. Methods: Experimentally based models of B{sub 0}-dependant relaxation for various tumormore » and normal tissues from the literature were used in conjunction with signal equations for MR sequences suitable for rapid real-time imaging to develop field-dependent predictions for CNR. These CNR models were developed for liver, lung, breast, glioma, and kidney tumors for spoiled gradient-echo, balanced steady-state free precession (bSSFP), and single-shot half-Fourier fast spin echo sequences. Results: Due to the pattern in which the relaxation properties of tissues are found to vary over B{sub 0} field (specifically the T{sub 1} time), there was always an improved CNR at lower fields compared to linear dependency. Further, in some tumor sites, the CNR at lower fields was found to be comparable to, or sometimes higher than those at higher fields (i.e., bSSFP CNR for glioma, kidney, and liver tumors). Conclusions: In terms of CNR, lower B{sub 0} fields have been shown to perform as well or better than higher fields for some tumor sites due to superior T{sub 1} contrast. In other sites this effect was less pronounced, reversing the CNR advantage. This complex relationship between CNR and B{sub 0} reveals both low and high magnetic fields as viable options for tumor tracking in MRI/radiotherapy hybrids.« less

Spawning Cisco investigations in Canada waters of Lake Superior during 2007

USGS Publications Warehouse

Yule, Daniel L.; Evrard, Lori M.; Cholwek, Gary A.; Addison, Peter A.; Cullis, Ken I.

2008-01-01

Cisco Coregonus artedi form pre-spawning aggregations in Lake Superior during November with the bulk of spawning occurring during late November through early December (Dryer and Beil 1964). Eggs are broadcast into open water (Smith 1956) with fertilized eggs settling to the lakebed (Dryer and Beil 1964). Peak hatching occurs the following May (United States Geological Survey – Great Lakes Science Center, GLSC, unpublished data). Interannual variability in year class strength is high, but tends to be synchronous across different regions of Lake Superior (Bronte et al. 2003). November 2005 sampling of Thunder Bay showed 14 year-classes were present with the oldest fish being from the 1984 year-class (Yule et al. 2008). The ciscoes sampled were predominantly from five year classes that hatched during 1988, 1989, 1990, 1998, and 2003. These same strong year-classes were found in the western arm of Lake Superior during November 2006 (GLSC, unpublished data). Growth is rapid in the first few years of life with minimal growth after age-8 (Yule et al. 2008). Ciscoes exceeding 250 mm total length (TL) are typically sexually mature (Yule et al. 2006b, 2008). Thunder Bay ciscoes have high annual survival with rates for females and males averaging 0.80 and 0.75, respectively; females have higher rates of fishing-induced mortality compared to males but lower rates of natural mortality (Yule et al. 2008). Some Lake Superior stocks are currently commercially fished with the bulk of harvest occurring during November when fishers target females for their roe. The bulk of fish are harvested from Thunder Bay using suspended gillnets with mesh sizes ranging from 79-89 mm stretch measure. Ciscoes younger then age-5 make up a very small proportion (<0.1%) of the harvest (Yule, et al. 2008).

Torque Limit for Bolted Joint for Composites. Part A; TTTC Properties of Laminated Composites

NASA Technical Reports Server (NTRS)

Zhao, Yi

2003-01-01

The existing design code for torque limit of bolted joints for composites at Marshall Space Flight Center is MSFC-STD-486B, which was originally developed in 1960s for metallic materials. The theoretical basis for this code was a simplified mechanics analysis, which takes into account only the bolt, nut and washers, but not the structural members to be connected. The assumption was that metallic materials would not fail due to the bearing stress at the contact area between washer and the mechanical member. This is true for metallic materials; but for composite materials the results could be completely different. Unlike most metallic materials, laminated composite materials have superior mechanical properties (such as modulus and strength) in the in-plane direction, but not in the out-of-plane, or through-the-thickness (TTT) direction. During the torquing, TTT properties (particularly compressive modulus and compressive strength) play a dominant role in composite failure. Because of this concern, structural design engineers at Marshall are currently using a compromised empirical approach: using 50% of the torque value for composite members. Companies like Boeing is using a similar approach. An initial study was conducted last summer on this topic to develop theoretical model(s) that takes into consideration of composite members. Two simplified models were developed based on stress failure criterion and strain failure criterion, respective. However, these models could not be used to predict the torque limit because of the unavailability of material data, specifically, through-the-thickness compression (TTTC) modulus and strength. Therefore, the task for this summer is to experimentally determine the TTTC properties. Due to the time limitation, only one material has been tested: IM7/8552 with [0 degrees,plus or minus 45 degrees, 90 degree ] configuration. This report focuses the test results and their significance, while the experimentation will be described in a separate report by Mr. Kris Kostreva.

Genetic effect of interleukin-1 beta (C-511T) polymorphism on the structural covariance network and white matter integrity in Alzheimer's disease.

PubMed

Huang, Chi-Wei; Hsu, Shih-Wei; Tsai, Shih-Jen; Chen, Nai-Ching; Liu, Mu-En; Lee, Chen-Chang; Huang, Shu-Hua; Chang, Weng-Neng; Chang, Ya-Ting; Tsai, Wan-Chen; Chang, Chiung-Chih

2017-01-18

Inflammatory processes play a pivotal role in the degenerative process of Alzheimer's disease. In humans, a biallelic (C/T) polymorphism in the promoter region (position-511) (rs16944) of the interleukin-1 beta gene has been significantly associated with differences in the secretory capacity of interleukin-1 beta. In this study, we investigated whether this functional polymorphism mediates the brain networks in patients with Alzheimer's disease. We enrolled a total of 135 patients with Alzheimer's disease (65 males, 70 females), and investigated their gray matter structural covariance networks using 3D T1 magnetic resonance imaging and their white matter macro-structural integrities using fractional anisotropy. The patients were classified into two genotype groups: C-carriers (n = 108) and TT-carriers (n = 27), and the structural covariance networks were constructed using seed-based analysis focusing on the default mode network medial temporal or dorsal medial subsystem, salience network and executive control network. Neurobehavioral scores were used as the major outcome factors for clinical correlations. There were no differences between the two genotype groups in the cognitive test scores, seed, or peak cluster volumes and white matter fractional anisotropy. The covariance strength showing C-carriers > TT-carriers was the entorhinal-cingulum axis. There were two peak clusters (Brodmann 6 and 10) in the salience network and four peak clusters (superior prefrontal, precentral, fusiform, and temporal) in the executive control network that showed C-carriers < TT-carriers in covariance strength. The salience network and executive control network peak clusters in the TT group and the default mode network peak clusters in the C-carriers strongly predicted the cognitive test scores. Interleukin-1 beta C-511 T polymorphism modulates the structural covariance strength on the anterior brain network and entorhinal-interconnected network which were independent of the white matter tract integrity. Depending on the specific C-511 T genotype, different network clusters could predict the cognitive tests.

Association between dietary fiber intake and physical performance in older adults: a nationwide study in Taiwan.

PubMed

Wu, I-Chien; Chang, Hsing-Yi; Hsu, Chih-Cheng; Chiu, Yen-Feng; Yu, Shu-Han; Tsai, Yi-Fen; Shen, Shi-Chen; Kuo, Ken N; Chen, Ching-Yu; Liu, Kiang; Lee, Marion M; Hsiung, Chao A

2013-01-01

Physical performance is a major determinant of health in older adults, and is related to lifestyle factors. Dietary fiber has multiple health benefits. It remains unclear whether fiber intake is independently linked to superior physical performance. We aimed to assess the association between dietary fiber and physical performance in older adults. This was a cross-sectional study conducted with community-dwelling adults aged 55 years and older (n=2680) from the ongoing Healthy Aging Longitudinal Study (HALST) in Taiwan 2008-2010. Daily dietary fiber intake was assessed using a validated food frequency questionnaire. Physical performance was determined objectively by measuring gait speed, 6-minute walk distance, timed "up and go" (TUG), summary performance score, hand grip strength. Adjusting for all potential confounders, participants with higher fiber intake had significantly faster gait speed, longer 6-minute walk distance, faster TUG, higher summary performance score, and higher hand grip strength (all P <.05). Comparing with the highest quartile of fiber intake, the lowest quartile of fiber intake was significantly associated with the lowest sex-specific quartile of gait speed (adjusted OR, 2.18 in men [95% CI, 1.33-3.55] and 3.65 in women [95% CI, 2.20-6.05]), 6-minute walk distance (OR, 2.40 in men [95% CI, 1.38-4.17] and 4.32 in women [95% CI, 2.37-7.89]), TUG (OR, 2.42 in men [95% CI, 1.43-4.12] and 3.27 in women [95% CI, 1.94-5.52]), summary performance score (OR, 2.12 in men [95% CI, 1.19-3.78] and 5.47 in women [95% CI, 3.20-9.35]), and hand grip strength (OR, 2.64 in men [95% CI, 1.61-4.32] and 4.43 in women [95% CI, 2.62-7.50]). Dietary fiber intake was independently associated with better physical performance.

Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

NASA Technical Reports Server (NTRS)

Petter, George E.; Figert, John D.; Rybicki, Daniel J.; Burns, Timothy

2006-01-01

A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility. This method of heat treatment is a superior alternative to a specification-required heat treatment that caused the formation of large columnar grains, which are undesired. Workpieces subjected to the prior heat treatment exhibited elongations <2 percent, and standard three-point bend specimens shattered. The development of the present heat treatment method was guided partly by the principles that (1) by minimizing grain sizes and relieving deformation stresses, one can minimize or eliminate stress corrosion cracking and (2) the key to maximizing strength and eliminating residual stresses is to perform post-weld solution heating for as long a time as possible while incurring little or no development of large columnar grains in friction stir weld nuggets. It is necessary to perform some of the solution heat treatment (to soften the alloy and improve machine welding parameters) before welding. The following is an example of thickness- dependent pre- and post-weld heat treatments according to the present method: For plates 0.270 in. (approx.6.86 mm) thick milled from plates 4.5 in. (114.3 mm) thick, perform pre-weld solution heating at 890 F (477 C) for 1 hour, then cool in air. After friction stir welding, perform solution heating for 10 minutes, quench, hold at room temperature for 96 hours, then age at 250 F (121 C) for 5 hours followed by 325 F (163 C) for 27 hours.

Easy-Going On-Spectrometer Optimisation of Phase Modulated Homonuclear Decoupling Sequences in Solid-State NMR

NASA Astrophysics Data System (ADS)

Grimminck, Dennis L. A. G.; Vasa, Suresh K.; Meerts, W. Leo; Kentgens, P. M.

2011-06-01

A global optimisation scheme for phase modulated proton homonuclear decoupling sequences in solid-state NMR is presented. Phase modulations, parameterised by DUMBO Fourier coefficients, were optimized using a Covariance Matrix Adaptation Evolution Strategies algorithm. Our method, denoted EASY-GOING homonuclear decoupling, starts with featureless spectra and optimises proton-proton decoupling, during either proton or carbon signal detection. On the one hand, our solutions closely resemble (e)DUMBO for moderate sample spinning frequencies and medium radio-frequency (rf) field strengths. On the other hand, the EASY-GOING approach resulted in a superior solution, achieving significantly better resolved proton spectra at very high 680 kHz rf field strength. N. Hansen, and A. Ostermeier. Evol. Comput. 9 (2001) 159-195 B. Elena, G. de Paepe, L. Emsley. Chem. Phys. Lett. 398 (2004) 532-538

NASA research on refractory compounds.

NASA Technical Reports Server (NTRS)

Gangler, J. J.

1971-01-01

The behavior and properties of the refractory carbides, nitrides, and borides are being investigated by NASA as part of its research aimed at developing superior heat resistant materials for aerospace applications. Fundamental studies on the electronic and defect structures of the carbides indicate that there is promise for improving the strength and ductility of these materials. Studies of the zirconium-carbon-oxygen system show that zirconium oxycarbides of different compositions and lattice parameters can be formed between 1500 and 1900 C and are stable below 1500 C. More applied studies show that hot working generally improves the microstructure and therefore the strength of TiC and NbC. Sintering studies on UN indicate that very high densities can be achieved. Hot pressing of cermets of HfN and HfC produces good mechanical properties for high temperature bearing applications.

Antibacterial Titanium Produced Using Selective Laser Melting

NASA Astrophysics Data System (ADS)

Macpherson, Andrew; Li, Xiaopeng; McCormick, Paul; Ren, Ling; Yang, Ke; Sercombe, Timothy B.

2017-12-01

Titanium and titanium alloys used in current medical and dental applications do not possess antibacterial properties, and therefore, postoperative infection remains a significant risk. Recently, the addition of silver and copper to conventional biomaterials has been shown to produce a material with good antibacterial properties. In this article, we investigate selective laser melting as a method of producing antibacterial Ti-6Al-4V containing elemental additions of Cu or Ag. The addition of Ag had no effect on the microstructure or strength, but it did result in a 300% increase in the ductility of the alloy. In contrast, the addition of Cu resulted in an increase in strength but in a decrease in ductility, along with a change in the structure of the material. The Cu-containing alloy also showed moderate antibacterial properties and was superior to the Ag-containing alloy.

"A L C L A D" A New Corrosion Resistant Aluminum Product

NASA Technical Reports Server (NTRS)

Dix, E H , Jr

1927-01-01

Described here is a new corrosion resistant aluminum product which is markedly superior to the present strong alloys. Its use should result in greatly increased life of a structural part. Alclad is a heat-treated aluminum, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath. Of particular importance is the thorough character of the union between the alloy and the pure aluminum. Preliminary results of salt spray tests (24 weeks of exposure) show changes in tensile strength and elongation of Alclad 17ST, when any occurred, to be so small as to be well within the limits of experimental error. Some surface corrosion of the pure metal had taken place, but not enough to cause the specimens to break through those areas.

Effect of rolling on the high temperature tensile and stress-rupture properties of tungsten fiber-superalloy composites

NASA Technical Reports Server (NTRS)

Petrasek, D. W.

1974-01-01

An investigation was conducted to determine the effects of mechanical working on the 1093 C (2000 F) tensile and stress-rupture strength of tungsten alloy/superalloy composites. Hot pressed composites containing either conventional tungsten lamp filament wire or tungsten-1% ThO2 wire and a nickel base alloy matrix were hot rolled at 1093 C (2000 F). The hot pressed and rolled composite specimens were then tested in tension and stress-rupture at 1093 C (2000 F). Rolling decreased the degree of fiber-matrix reaction as a function of time of exposure at 1093 C (2000 F). The stress-rupture properties of the rolled composites were superior to hot pressed composites containing equivalent diameter fibers. Rolling did not appreciably affect the 1093 C (2000 F) ultimate tensile strength of the composites.

Tube manufacturing and characterization of oxide dispersion strengthened ferritic steels

NASA Astrophysics Data System (ADS)

Ukai, Shigeharu; Mizuta, Shunji; Yoshitake, Tunemitsu; Okuda, Takanari; Fujiwara, Masayuki; Hagi, Shigeki; Kobayashi, Toshimi

2000-12-01

Oxide dispersion strengthened (ODS) ferritic steels have an advantage in radiation resistance and superior creep rupture strength at elevated temperature due to finely distributed Y2O3 particles in the ferritic matrix. Using a basic composition of low activation ferritic steel (Fe-12Cr-2W-0.05C), cladding tube manufacturing by means of pilger mill rolling and subsequent recrystallization heat-treatment was conducted while varying titanium and yttria contents. The recrystallization heat-treatment, to soften the tubes hardened due to cold-rolling and to subsequently improve the degraded mechanical properties, was demonstrated to be effective in the course of tube manufacturing. For a titanium content of 0.3 wt% and yttria of 0.25 wt%, improvement of the creep rupture strength can be attained for the manufactured cladding tubes. The ductility is also adequately maintained.

Nonfaradaic nanoporous electrochemistry for conductometry at high electrolyte concentration.

PubMed

Bae, Je Hyun; Kang, Chung Mu; Choi, Hyoungseon; Kim, Beom Jin; Jang, Woohyuk; Lim, Sung Yul; Kim, Hee Chan; Chung, Taek Dong

2015-02-17

Nanoporous electrified surfaces create a unique nonfaradaic electrochemical behavior that is sensitively influenced by pore size, morphology, ionic strength, and electric field modulation. Here, we report the contributions of ion concentration and applied ac frequency to the electrode impedance through an electrical double layer overlap and ion transport along the nanopores. Nanoporous Pt with uniform pore size and geometry (L2-ePt) responded more sensitively to conductivity changes in aqueous solutions than Pt black with poor uniformity despite similar real surface areas and enabled the previously difficult quantitative conductometry measurements at high electrolyte concentrations. The nanopores of L2-ePt were more effective in reducing the electrode impedance and exhibited superior linear responses to not only flat Pt but also Pt black, leading to successful conductometric detection in ion chromatography without ion suppressors and at high ionic strengths.

Performance of promising clones from Atlantic x Superior and Superior x Snowden populations evaluated in several locations

USDA-ARS?s Scientific Manuscript database

Atlantic is the standard variety for chipping from the field or very short-term cold storage. It has traits desired by the chip industry such as uniformity, high specific gravity and high yield. However, Atlantic tubers are susceptible to common scab and internal defects such as internal brown spot,...

The angle-torque-relationship of the subtalar pronators and supinators in male athletes: A comparative study of soccer and handball players.

PubMed

Hagen, Marco; Asholt, Johannes; Lemke, Martin; Lahner, Matthias

2016-05-18

It is currently unclear how participation in different sports affects the angle-specific subtalar pronator and supinator muscle strength and pronator-to-supinator strength ratio (PSR). Based on the hypothesis that both differences sport-related patterns of play and foot-ground interaction may lead to sport-specific muscle adaptations, this study compared the angle specific pronator and supinator strength capacity of handball and soccer players. Eighteen healthy male handball and 19 soccer players performed maximum isometric voluntary isometric contractions using a custom-made testing apparatus. Peak pronator (PPT) and supinator torques (PST), pronator and supinator strength curves (normalised to the peak torque across all joint angles) and PSR were measured in five anatomical joint angles across the active subtalar range of motion (ROM). All analysed parameters were dependent on the subtalar joint angle. The ANOVA revealed significant `joint angle' × `group' interactions on PPT, pronator strength curves and PSR. No group differences were found for active subtalar ROM. In previously uninjured handball and soccer athletes, there were intrinsic differences in angle-specific subtalar pronator muscle strength. The lower PSR, which was found in the most supinated angle, can be seen as a risk factor for sustaining an ankle sprain.

A comparative study of the influence of alpha-lactose monohydrate particle morphology on granule and tablet properties after roll compaction/dry granulation.

PubMed

Grote, Simon; Kleinebudde, Peter

2018-05-29

The influence of particle morphology and size of alpha-lactose monohydrate on dry granules and tablets was studied. Four different morphologies were investigated: Two grades of primary crystals, which differed in their particle size and structure (compact crystals vs. agglomerates). The materials were roll compacted at different specific compaction forces and changes in the particle size distribution and the specific surface area were measured. Afterwards, two fractions of granules were pressed to tablets and the tensile strength was compared to that from tablets compressed from the raw materials. The specific surface area was increased induced by roll compaction/dry granulation for all materials. At increased specific compaction forces, the materials showed sufficient size enlargement. The morphology of lactose determined the strength of direct compressed tablets. In contrast, the strength of granule tablets was leveled by the previous compression step during roll compaction/dry granulation. Thus, the tensile strength of tablets compressed directly from the powder mixtures determined whether materials exhibited a loss in tabletability after roll compaction/dry granulation or not. The granule size had only a slight influence on the strength of produced tablets. In some cases, the fraction of smaller granules showed a higher tensile strength compared to the larger fraction.

The Role of Perceived In-group Moral Superiority in Reparative Intentions and Approach Motivation.

PubMed

Szabó, Zsolt P; Mészáros, Noémi Z; Csertő, István

2017-01-01

Three studies examined how members of a national group react to in-group wrongdoings. We expected that perceived in-group moral superiority would lead to unwillingness to repair the aggression. We also expected that internal-focused emotions such as group-based guilt and group-based shame would predict specific, misdeed-related reparative intentions but not general approach motivation toward the victim groups. In Study 1, facing the in-group's recent aggression, participants who believed that the Hungarians have been more moral throughout their history than members of other nations, used more exonerating cognitions, experienced less in-group critical emotions and showed less willingness to provide reparations for the members of the victim group. Study 2 and Study 3 confirmed most findings of Study 1. Perceived in-group moral superiority directly or indirectly reduced willingness to provide either general or specific reparations, while internally focused in-group critical emotions predicted specific misdeed-related reparative intentions but not general approach motivation. The role of emotional attachment to the in-group is considered.

The Role of Perceived In-group Moral Superiority in Reparative Intentions and Approach Motivation

PubMed Central

Szabó, Zsolt P.; Mészáros, Noémi Z.; Csertő, István

2017-01-01

Three studies examined how members of a national group react to in-group wrongdoings. We expected that perceived in-group moral superiority would lead to unwillingness to repair the aggression. We also expected that internal-focused emotions such as group-based guilt and group-based shame would predict specific, misdeed-related reparative intentions but not general approach motivation toward the victim groups. In Study 1, facing the in-group’s recent aggression, participants who believed that the Hungarians have been more moral throughout their history than members of other nations, used more exonerating cognitions, experienced less in-group critical emotions and showed less willingness to provide reparations for the members of the victim group. Study 2 and Study 3 confirmed most findings of Study 1. Perceived in-group moral superiority directly or indirectly reduced willingness to provide either general or specific reparations, while internally focused in-group critical emotions predicted specific misdeed-related reparative intentions but not general approach motivation. The role of emotional attachment to the in-group is considered. PMID:28620333

Strength and Performance Enhancement of Bonded Joints by Spatial Tailoring of Adhesive Compliance via 3D Printing.

PubMed

Kumar, S; Wardle, Brian L; Arif, Muhamad F

2017-01-11

Adhesive bonding continues to emerge as a preferred route for joining materials with broad applications including advanced structures, microelectronics, biomedical systems, and consumer goods. Here, we study the mechanics of deformation and failure of tensile-loaded single-lap joints with a compliance-tailored adhesive. Tailoring of the adhesive compliance redistributes stresses and strains to reduce both shear and peel concentrations at the ends of the adhesive that determine failure of the joint. Utilizing 3D printing, the modulus of the adhesive is spatially varied along the bondlength. Experimental strength testing, including optical strain mapping, reveals that the strain redistribution results in a greater than 100% increase in strength and toughness concomitant with a 50% increase in strain-to-break while maintaining joint stiffness. The tailoring demonstrated here is immediately realizable in a broad array of 3D printing applications, and the level of performance enhancement suggests that compliance tailoring of the adhesive is a generalizable route for achieving superior performance of joints in other applications, such as advanced structural composites.

Mechanical Properties and Wear Behavior of AA5182/WC Nanocomposite Fabricated by Friction Stir Welding at Different Tool Traverse Speeds

NASA Astrophysics Data System (ADS)

Paidar, Moslem; Asgari, Ali; Ojo, Olatunji Oladimeji; Saberi, Abbas

2018-03-01

Grain growth inhibition at the heat-affected zone, improved weld strength and superior tribological properties of welds are desirable attributes of modern manufacturing. With the focused on these attributes, tungsten carbide (WC) nanoparticles were employed as reinforcements for the friction stir welding of 5-mm-thick AA5182 aluminum alloy by varying tool traverse speeds. The microstructure, microhardness, ultimate tensile strength, fracture and wear behavior of the resultant WC-reinforced welds were investigated, while unreinforced AA5182 welds were employed as controls for the study. The result shows that the addition of WC nanoparticles causes substantial grain refinement within the weld nugget. A decrease in traverse speed caused additional particle fragmentation, improved hardness value and enhanced weld strength in the reinforced welds. Improved wear rate and friction coefficient of welds were attained at a reduced traverse speed of 100 mm/min in the WC-reinforced welds. This improvement is attributed to the effects of reduced grain size/grain fragmentation and homogeneous dispersion of WC nanoparticles within the WC-reinforced weld nugget.

A new EEG synchronization strength analysis method: S-estimator based normalized weighted-permutation mutual information.

PubMed

Cui, Dong; Pu, Weiting; Liu, Jing; Bian, Zhijie; Li, Qiuli; Wang, Lei; Gu, Guanghua

2016-10-01

Synchronization is an important mechanism for understanding information processing in normal or abnormal brains. In this paper, we propose a new method called normalized weighted-permutation mutual information (NWPMI) for double variable signal synchronization analysis and combine NWPMI with S-estimator measure to generate a new method named S-estimator based normalized weighted-permutation mutual information (SNWPMI) for analyzing multi-channel electroencephalographic (EEG) synchronization strength. The performances including the effects of time delay, embedding dimension, coupling coefficients, signal to noise ratios (SNRs) and data length of the NWPMI are evaluated by using Coupled Henon mapping model. The results show that the NWPMI is superior in describing the synchronization compared with the normalized permutation mutual information (NPMI). Furthermore, the proposed SNWPMI method is applied to analyze scalp EEG data from 26 amnestic mild cognitive impairment (aMCI) subjects and 20 age-matched controls with normal cognitive function, who both suffer from type 2 diabetes mellitus (T2DM). The proposed methods NWPMI and SNWPMI are suggested to be an effective index to estimate the synchronization strength. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of machinability of manganese alloyed austempered ductile iron produced using conventional and two step austempering processes

NASA Astrophysics Data System (ADS)

Hegde, Ananda; Sharma, Sathyashankara

2018-05-01

Austempered Ductile Iron (ADI) is a revolutionary material with high strength and hardness combined with optimum ductility and toughness. The discovery of two step austempering process has lead to the superior combination of all the mechanical properties. However, because of the high strength and hardness of ADI, there is a concern regarding its machinability. In the present study, machinability of ADI produced using conventional and two step heat treatment processes is assessed using tool life and the surface roughness. Speed, feed and depth of cut are considered as the machining parameters in the dry turning operation. The machinability results along with the mechanical properties are compared for ADI produced using both conventional and two step austempering processes. The results have shown that two step austempering process has produced better toughness with good hardness and strength without sacrificing ductility. Addition of 0.64 wt% manganese did not cause any detrimental effect on the machinability of ADI, both in conventional and two step processes. Marginal improvement in tool life and surface roughness were observed in two step process compared to that with conventional process.

Integrative Examination of Motor Abilities in Dialysis Patients and Selection of Tests for a Standardized Physical Function Assessment.

PubMed

Bučar Pajek, Maja; Leskošek, Bojan; Vivoda, Tjaša; Svilan, Katarina; Čuk, Ivan; Pajek, Jernej

2016-06-01

To reduce the need for a large number of executed physical function tests we examined inter-relations and determined predictive power for daily physical activity of the following tests: 6-min walk, 10 repetition sit-to-stand, time up-and-go, Storke balance, handgrip strength, upper limb tapping and sitting forward bend tests. In 90 dialysis and 140 healthy control subjects we found high correlations between all tests, especially those engaging lower extremities. Sit-to-stand, forward bend and handgrip strength were selected for the test battery and composite motor performance score. Sit-to-stand test was superior in terms of sensitivity to uremia effects and association with daily physical function in adjusted analyses. There was no incremental value in calculating the composite performance score. We propose to standardize the physical function assessment of dialysis patients for cross-sectional and longitudinal observations with three simple, cheap, well-accessible and easily performed test tools: sit-to-stand test, handgrip strength and Human Activity Profile questionnaire. © 2016 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy.

Processing and Properties of a Phenolic Composite System

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Bai, J. M.; Baughman, James M.

2006-01-01

Phenolic resin systems generate water as a reaction by-product via condensation reactions during curing at elevated temperatures. In the fabrication of fiber reinforced phenolic resin matrix composites, volatile management is crucial in producing void-free quality laminates. A commercial vacuum-bag moldable phenolic prepreg system was selected for this study. The traditional single-vacuum-bag (SVB) process was unable to manage the volatiles effectively, resulting in inferior voidy laminates. However, a double vacuum bag (DVB) process was shown to afford superior volatile management and consistently yielded void-free quality parts. The DVB process cure cycle (temperature /pressure profiles) for the selected composite system was designed, with the vacuum pressure application point carefully selected, to avoid excessive resin squeeze-outs and achieve the net shape and target resin content in the final consolidated laminate parts. Laminate consolidation quality was characterized by optical photomicrography for the cross sections and measurements of mechanical properties. A 40% increase in short beam shear strength, 30% greater flexural strength, 10% higher tensile and 18% higher compression strengths were obtained in composite laminates fabricated by the DVB process.

Tilted hexagonal post arrays: DNA electrophoresis in anisotropic media

PubMed Central

Chen, Zhen; Dorfman, Kevin D.

2013-01-01

Using Brownian dynamics simulations, we show that DNA electrophoresis in a hexagonal array of micron-sized posts changes qualitatively when the applied electric field vector is not coincident with the lattice vectors of the array. DNA electrophoresis in such “tilted” post arrays is superior to the standard “un-tilted” approach; while the time required to achieve a resolution of unity in a tilted post array is similar to an un-tilted array at a low electric field strengths, this time (i) decreases exponentially with electric field strength in a tilted array and (ii) increases exponentially with electric field strength in an un-tilted array. Although the DNA dynamics in a post array are complicated, the electrophoretic mobility results indicate that the “free path”, i.e., the average distance of ballistic trajectories of point sized particles launched from random positions in the unit cell until they intersect the next post, is a useful proxy for the detailed DNA trajectories. The analysis of the free path reveals a fundamental connection between anisotropy of the medium and DNA transport therein that goes beyond simply improving the separation device. PMID:23868490

White Paper: Recommendations on the Conduct of Superiority and Organism-Specific Clinical Trials of Antibacterial Agents for the Treatment of Infections Caused by Drug-Resistant Bacterial Pathogens

PubMed Central

2012-01-01

There is a critical need for new pathways to develop antibacterial agents to treat life-threatening infections caused by highly resistant bacteria. Traditionally, antibacterial agents have been studied in noninferiority clinical trials that focus on one site of infection (eg, pneumonia, intra-abdominal infection). Conduct of superiority trials for infections caused by highly antibiotic-resistant bacteria represents a new, and as yet, untested paradigm for antibacterial drug development. We sought to define feasible trial designs of antibacterial agents that could enable conduct of superiority and organism-specific clinical trials. These recommendations are the results of several years of active dialogue among the white paper's drafters as well as external collaborators and regulatory officials. Our goal is to facilitate conduct of new types of antibacterial clinical trials to enable development and ultimately approval of critically needed new antibacterial agents. PMID:22891041

Subcutaneous immunoglobulin preserves muscle strength in chronic inflammatory demyelinating polyneuropathy.

PubMed

Markvardsen, L H; Harbo, T; Sindrup, S H; Christiansen, I; Andersen, H; Jakobsen, J

2014-12-01

Subcutaneous immunoglobulin (SCIG) is superior to placebo treatment for maintenance of muscle strength during 12 weeks in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). The present study evaluated whether SCIG preserves muscle strength for 1 year in an open-label follow-up study. Seventeen responders to intravenous immunoglobulin (IVIG) who had participated in the previous study of SCIG versus placebo in CIDP were included. After one IVIG infusion 2 weeks prior to baseline, all continued on SCIG treatment at weekly equal dosage and were evaluated after 3, 6 and 12 months. Primary end-points were changes in muscle strength evaluated by isokinetic dynamometry in four affected muscle groups and a composite score of muscle performance and function tests, including Medical Research Council (MRC) score, grip strength, 40-m walking test (40-MWT) and nine-hole peg test (9-HPT). Secondary end-points were changes of each of the listed parameters at each time point as well as an overall disability sum score (ODSS). The dose of SCIG was significantly unaltered during the follow-up period. Overall the isokinetic dynamometry value increased by 7.2% (P = 0.033) and after 3, 6 and 12 months by 5.7%, 8.2% and 6.8% (ns). The overall composite score at all time intervals and for each interval remained unchanged. Amongst the secondary parameters the MRC score increased significantly by 1.7% (P = 0.007), whereas grip strength, 40-MWT, 9-HPT and ODSS remained unchanged. SCIG preserves muscle strength and functional ability in patients with CIDP who previously responded to IVIG. SCIG should be considered as an alternative in long-term treatment of CIDP patients. © 2014 The Author(s) European Journal of Neurology © 2014 EAN.

Effect of organic solvents compared to sandblasting on the repair bond strength of nanohybrid and nanofilled composite resins.

PubMed

Brum, Rafael Torres; Vieira, Sergio; Freire, Andrea; Mazur, Rui Fernando; De Souza, Evelise Machado; Rached, Rodrigo Nunes

2017-01-01

This study evaluated the effect of different surface treatments on the repair bond strength of nanohybrid (Empress Direct) and nanofilled (Filtek Z350 XT) composite resins. A total of 120 specimens of each material (7.5 x 4.5 x 3 mm) were prepared and polished with SiC paper. Half of the specimens were kept in water for seven days and the other half for six months; they were then divided into six groups according to the type of surface treatment: negative control (no treatment), Al2O3sandblasted, liquid acetone, acetone gel, liquid alcohol and alcohol gel. Following application of the silane coupling agent and the adhesive system, composite resin cylinders were fabricated on the specimens and light cured (20 seconds). The same composite resins were used for the repair. Additionally, ten intact specimens of each composite resin (without repair) were prepared (positive control). The specimens were then loaded to failure in the microshear mode. Three additional specimens were fabricated in each group, and the surface treatments were analyzed by atomic force microscopy, energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The nanofilled composite resin showed higher cohesive strength and repair bond strength than the nanohybrid composite resin. The aging process affected the repair bond strength of the nanofilled composite resin. Al2O3sandblasting was more efficient for the nanofilled composite resin and promoted greater surface roughness in both materials. The solvents demonstrated higher efficacy for the nanohybrid composite resin. The strengths resulting from the solvents were material dependent, and Al2O3sandblasting resulted in superior repair bond strength in both materials.

Effects of 8 Weeks’ Specific Physical Training on the Rotator Cuff Muscle Strength and Technique of Javelin Throwers

PubMed Central

Kim, Hyeyoung; Lee, Youngsun; Shin, Insik; Kim, Kitae; Moon, Jeheon

2014-01-01

[Purpose] For maximum efficiency and to prevent injury during javelin throwing, it is critical to maintain muscle balance and coordination of the rotator cuff and the glenohumeral joint. In this study, we investigated the change in the rotator cuff muscle strength, throw distance and technique of javelin throwers after they had performed a specific physical training that combined elements of weight training, function movement screen training, and core training. [Subjects] Ten javelin throwers participated in this study: six university athletes in the experimental group and four national-level athletes in the control group. [Methods] The experimental group performed 8 weeks of the specific physical training. To evaluate the effects of the training, measurements were performed before and after the training for the experimental group. Measurements comprised anthropometry, isokinetic muscle strength measurements, the function movement screen test, and movement analysis. [Results] After the specific physical training, the function movement screen score and external and internal rotator muscle strength showed statistically significant increases. Among kinematic factors, only pull distance showed improvement after training. [Conclusion] Eight weeks of specific physical training for dynamic stabilizer muscles enhanced the rotator cuff muscle strength, core stability, throw distance, and flexibility of javelin throwers. These results suggest that specific physical training can be useful for preventing shoulder injuries and improving the performance for javelin throwers. PMID:25364111

Effects of 8 weeks' specific physical training on the rotator cuff muscle strength and technique of javelin throwers.

PubMed

Kim, Hyeyoung; Lee, Youngsun; Shin, Insik; Kim, Kitae; Moon, Jeheon

2014-10-01

[Purpose] For maximum efficiency and to prevent injury during javelin throwing, it is critical to maintain muscle balance and coordination of the rotator cuff and the glenohumeral joint. In this study, we investigated the change in the rotator cuff muscle strength, throw distance and technique of javelin throwers after they had performed a specific physical training that combined elements of weight training, function movement screen training, and core training. [Subjects] Ten javelin throwers participated in this study: six university athletes in the experimental group and four national-level athletes in the control group. [Methods] The experimental group performed 8 weeks of the specific physical training. To evaluate the effects of the training, measurements were performed before and after the training for the experimental group. Measurements comprised anthropometry, isokinetic muscle strength measurements, the function movement screen test, and movement analysis. [Results] After the specific physical training, the function movement screen score and external and internal rotator muscle strength showed statistically significant increases. Among kinematic factors, only pull distance showed improvement after training. [Conclusion] Eight weeks of specific physical training for dynamic stabilizer muscles enhanced the rotator cuff muscle strength, core stability, throw distance, and flexibility of javelin throwers. These results suggest that specific physical training can be useful for preventing shoulder injuries and improving the performance for javelin throwers.

Do sporting activities convey benefits to bone mass throughout the skeleton?

PubMed

Nevill, Alan; Holder, Roger; Stewart, Arthur

2004-07-01

It is well known that sport and exercise play an important role in stimulating site-specific bone mineral density (BMD). However, what is less well understood is how these benefits dissipate throughout the body. Hence, the aim of the present study was to compare the BMD (recorded at nine sites throughout the skeleton) of 106 male athletes (from nine sports) with that of 15 male non-exercising age-matched controls. Given that BMD is known to increase with body mass and peak with age, multivariate and univariate analyses of covariance were performed to compare the BMD of the nine sports groups with controls (at all sites) using body mass and age as covariates. Our results confirmed a greater adjusted BMD in the arms of the upper-body athletes, the right arm of racket players and the legs of runners (compared with controls), supporting the site-specific nature (i.e. specific to the externally loaded site) of the bone remodelling response (all P <0.01). However, evidence that bone mass acquisition is not just site-specific comes from the results of the rugby players, strength athletes, triathletes and racket players. The rugby players' adjusted BMD was the greatest of all sports groups and greater than controls at all nine sites (all P <0.01), with differences ranging from 8% greater in the left arm to 21% in the lumbar spine. Similarly, the strength athletes' adjusted BMD was superior to that of controls at all sites (P <0.05) except the legs. The adjusted BMD of the triathletes was significantly greater than that of the controls in both the arms and the legs as well as the thoracic and lumbar spine. The racket players not only had significantly greater right arm BMD compared with the controls but also a greater BMD of the lumbar spine, the pelvis and legs. In contrast, the low-strain, low-impact activities of keep-fit, cycling and rowing failed to benefit BMD compared with the age-matched controls. These results suggest that sporting activities involving high impact, physical contact and/or rotational forces or strains are likely to convey significant benefits not only to the loaded sites, but also to other unloaded peripheral and axial sites throughout the skeleton.

[Examination of the hypothesis 'the factors and mechanisms of superiority'].

PubMed

Sierra-Fitzgerald, O; Quevedo-Caicedo, J; López-Calderón, M G

INTRODUCTION. The hypothesis of Geschwind and Galaburda suggests that specific cognitive superiority arises as a result of an alteration in development of the nervous system. In this article we review the co existence of superiority and inferiority . PATIENTS AND METHODS. A study was made of six children aged between 6 and 8 years old at the Instituto de Belles Artes Antonio Maria Valencia in Cali,Columbia with an educational level between second and third grade at a primary school and of medium low socio economic status. The children were considered to have superior musical ability by music experts, which is the way in which the concept of superiority was to be tested. The concept of inferiority was tested by neuropsychological tests = 1.5 DE below normal for the same age. We estimated the perinatal neurological risk in each case. Subsequently the children s general intelligence and specific cognitive abilities were evaluated. In the first case the WISC R and MSCA were used. The neuropsychological profiles were obtained by broad evaluation using a verbal fluency test, a test using counters, Boston vocabulary test, the Wechster memory scale, sequential verbal memory test, super imposed figures test, Piaget Head battery, Rey Osterrieth complex figure and the Wisconsin card classification test. The RESULTS showed slight/moderate deficits in practical construction ability and mild defects of memory and concept abilities. In general the results supported the hypothesis tested. The mechanisms of superiority proposed in the classical hypothesis mainly involve the contralateral hemisphere: in this study the ipsilateral mechanism was more important.

Incomplete segregation of endorgan-specific vestibular ganglion cells in mice and rats

NASA Technical Reports Server (NTRS)

Maklad, A.; Fritzsch, B.

1999-01-01

The endorgan-specific distribution of vestibular ganglion cells was studied in neonatal and postnatal rats and mice using indocarbocyanine dye (DiI) and dextran amines for retrograde and anterograde labeling. Retrograde DiI tracing from the anterior vertical canal labeled neurons scattered throughout the whole superior vestibular ganglion, with denser labeling at the dorsal and central regions. Horizontal canal neurons were scattered along the dorsoventral axis with more clustering toward the dorsal and ventral poles of this axis. Utricular ganglion cells occupied predominantly the central region of the superior vestibular ganglion. This utricular population overlapped with both the anterior vertical and horizontal canals' ganglion cells. Posterior vertical canal neurons were clustered in the posterior part of the inferior vestibular ganglion. The saccular neurons were distributed in the two parts of the vestibular ganglion, the superior and inferior ganglia. Within the inferior ganglion, the saccular neurons were clustered in the anterior part. In the superior ganglion, the saccular neurons were widely scattered throughout the whole ganglion with more numerous neurons at the posterior half. Small and large neurons were labeled from all endorgans. Examination of the fiber trajectory within the superior division of the vestibular nerve showed no clear lamination of the fibers innervating the different endorgans. These results demonstrate an overlapping pattern between the different populations within the superior ganglion, while in the inferior ganglion, the posterior canal and saccular neurons show tighter clustering but incomplete segregation. This distribution implies that the ganglion cells are assigned for their target during development in a stochastic rather than topographical fashion.

Morphological variation of siscowet lake trout in Lake Superior

USGS Publications Warehouse

Bronte, C.R.; Moore, S.A.

2007-01-01

Historically, Lake Superior has contained many morphologically distinct forms of the lake trout Salvelinus namaycush that have occupied specific depths and locations and spawned at specific times of the year. Today, as was probably the case historically, the siscowet morphotype is the most abundant. Recent interest in harvesting siscowets to extract oil containing omega-3 fatty acids will require additional knowledge of the biology and stock structure of these lightly exploited populations. The objective of this study was to determine whether shape differences exist among siscowet populations across Lake Superior and whether these shape differences can be used to infer stock structure. Morphometric analysis (truss protocol) was used to differentiate among siscowets sampled from 23 locations in Lake Superior. We analyzed 31 distance measurements among 14 anatomical landmarks taken from digital images of fish recorded in the field. Cluster analysis of size-corrected data separated fish into three geographic groups: The Isle Royale, eastern (Michigan), and western regions (Michigan). Finer scales of stock structure were also suggested. Discriminant function analysis demonstrated that head measurements contributed to most of the observed variation. Cross-validation classification rates indicated that 67–71% of individual fish were correctly classified to their region of capture. This is the first study to present shape differences associated with location within a lake trout morphotype in Lake Superior.

500-Gray γ-Irradiation May Increase Adhesion Strength of Lyophilized Cadaveric Split-Thickness Skin Graft to Wound Bed.

PubMed

Wei, Lin-Gwei; Chen, Chieh-Feng; Wang, Chi-Hsien; Cheng, Ya-Chen; Li, Chun-Chang; Chiu, Wen-Kuan; Wang, Hsian-Jenn

2017-03-01

Human cadaveric skin grafts are considered as the "gold standard" for temporary wound coverage because they provide a more conductive environment for natural wound healing. Lyophilization, packing, and terminal sterilization with gamma-ray can facilitate the application of cadaveric split-thickness skin grafts, but may alter the adhesion properties of the grafts. In a pilot study, we found that 500 Gy γ-irradiation seemed not to reduce the adherence between the grafts and wound beds. We conducted this experiment to compare the adherences of lyophilized, 500-Gy γ-irradiated skin grafts to that of lyophilized, nonirradiated grafts. Pairs of wounds were created over the backs of Sprague- Dawley rats. Pairs of "lyophilized, 500-Gy γ-irradiated" and "lyophilized, nonirradiated" cadaveric split-thickness skin grafts were fixed to the wound beds. Adhesion strength between the grafts and the wound beds was measured and compared. On post-skin-graft day 7 and day 10, the adhesion strength of γ-irradiated grafts was greater than that of the nonirradiated grafts. Because lyophilized cadaveric skin grafts can be vascularized and the collagen of its dermal component can be remodeled after grafting, the superior adhesion strength of 500-Gy γ-irradiated grafts can be explained by the collagen changes from irradiation.

Improvement of toughness and water resistance of bioplastic based on wheat gluten using epoxidized natural rubber

NASA Astrophysics Data System (ADS)

Hemsri, S.; Thongpin, C.; Somkid, P.; Sae-arma, S.; Paiykaew, A.

2015-07-01

Novel blends based on wheat gluten (WG) and epoxidized natural rubber (ENR) were fabricated with different ENR contents of 10, 20 and 30 wt% in an internal mixer. Sulfur vulcanization was used to crosslink the ENR phase in the blends. Comparatively, blends of WG and natural rubber (WG/NR) were prepared in the same condition as the WG/ENR blends. Tensile mechanical properties and impact strength of the WG/ENR blends were investigated and compared with the WG/NR blends as well as pure WG. Moreover, water absorption of pure WG and the WG/ENR blends was also tested. As investigated by scanning electron microscopy (SEM), the results revealed more compatibility between WG and ENR compared with NR. The elongation at break, impact strength and water resistance of the WG/ENR blends were found to remarkably increase with respect to the pure WG. Thus, incorporation of ENR into WG could improve toughness and water resistance of WG. Furthermore, the effect of adding glycerol acting as a plasticizer on the mechanical properties and impact strength of the WG/ENR blends was also studied. The blends with glycerol-plasticized WG (WG-Gly/ENR) showed more homogeneous morphologies and superior results in the mechanical properties and impact strength compared with the WG/ENR blends.

Effects of solvent drying time on micro-shear bond strength and mechanical properties of two self-etching adhesive systems.

PubMed

Sadr, Alireza; Shimada, Yasushi; Tagami, Junji

2007-09-01

The all-in-one adhesives are simplified forms of two-step self-etching adhesive systems that must be air dried to remove solvent and water before curing. It was investigated whether those two systems perform equally well and if their performance is affected by air-drying of the solvent containing agent. Two adhesive systems (both by Kuraray Medical) were evaluated; Clearfil Tri-S bond (TS) and Clearfil SE bond (SE). Micro-shear bond strengths to human dentin after solvent air-drying times of 2, 5 or 10 s for each group were measured (n=10). The indentation creep and hardness of the bonding layer were also determined for each group. The lowest micro-shear bond strength, nano-indentation hardness and creep stress exponents were obtained for 2 s air dried specimens of each material. After 10 s air blowing, SE showed superior properties compared to TS groups (p<0.05). When properly handled, two step self-etching material performs better than the all-in-one adhesive. Air-drying is a crucial step in the application of solvent containing adhesives and may affect the overall clinical performance of them, through changes in the bond strength and altering nano-scale mechanical properties.

Intermediate Temperature Strength Degradation in SiC/SiC Composites

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Cawley, James D.; Levine, Stanley (Technical Monitor)

2001-01-01

Woven silicon carbide fiber-reinforced, silicon carbide matrix composites are leading candidate materials for an advanced jet engine combustor liner application. Although the use temperature in the hot region for this application is expected to exceed 1200 C, a potential life-limiting concern for this composite system exists at intermediate temperatures (800 +/- 200 C), where significant time-dependent strength degradation has been observed under stress-rupture loading. A number of factors control the degree of stress-rupture strength degradation, the major factor being the nature of the interphase separating the fiber and the matrix. BN interphases are superior to carbon interphases due to the slower oxidation kinetics of BN. A model for the intermediate temperature stress-rupture of SiC/BN/SiC composites is presented based on the observed mechanistic process that leads to strength degradation for the simple case of through-thickness matrix cracks. The approach taken has much in common with that used by Curtin and coworkers, for two different composite systems. The predictions of the model are in good agreement with the rupture data for stress-rupture of both precracked and as-produced composites. Also, three approaches that dramatically improve the intermediate temperature stress-rupture properties are described: Si-doped BN, fiber spreading, and 'outside debonding'.

Applicability of recycled aggregates in concrete piles for soft soil improvement.

PubMed

Medeiros-Junior, Ronaldo A; Balestra, Carlos Et; Lima, Maryangela G

2017-01-01

The expressive generation of construction and demolition waste is stimulating several studies for reusing this material. The improvement of soft soils by concrete compaction piles has been widely applied for 40 years in some Brazilian cities. This technique is used to improve the bearing capacity of soft soils, allowing executing shallow foundations instead of deep foundations. The compaction piles use a high volume of material. This article explored the possibility of using recycled aggregates from construction waste to replace the natural aggregates in order to improve the bearing capacity of the soft soil, regarding its compressive strength. Construction wastes from different stages of a construction were used in order to make samples of concrete with recycled aggregates. The strength of concretes with natural aggregates was compared with the strength of concretes with recycled (fine and coarse) aggregates. Results show that all samples met the minimum compressive strength specified for compaction piles used to improve the bearing capacity of soft soils. The concrete with recycled aggregate from the structural stage had even higher resistances than the concrete with natural aggregates. This behaviour was attributed to the large amount of cementitious materials in the composition of this type of concrete. It was also observed that concrete with recycled fine aggregate has a superior resistance to concrete with recycled coarse aggregate.

Laser tissue melding: use of 1.32-μm computerized Nd:YAG laser, results of leak/burst strength studies in microsurgical procedures

NASA Astrophysics Data System (ADS)

Anderson, Dallas W.; Hsu, Tung M.; Halpern, Steven J.; Honaker, Arnold

1993-07-01

The ProClosureTM System (PCS) consists of a low power 1.32micrometers Nd:YAG laser coupled to a handheld disposable fiber optic device. The system has been designed to perform a wide range of tissue welding applications such as cosmetic skin closure,vascular surgery, and minimally invasive surgical procedures normally performed with sutures and staples. Utilizing a wavelength for tissue fusion that is least distracted by medium in the surgical field coupled with a computerized delivery system allows for a more precise application (+/- 5%) of laser energy to the tissue. The study design involved the micro-surgical anastomosis of twenty Sprague-Dawley rats (vas deferens) and twenty-one Sprague-Dawley rats (femoral arteries). Each rat is its own contralateral control. Laser repair time is approximately one-third that of conventional suturing. Postoperative dissection and burst strength testing was conducted at day 0, 1, 7, and 14. At each postoperative interval, the mean leak/burst strength for laser-assisted closure v. control, was markedly higher. The precise application of energy fluence resulting from ProClosure's computerized system yields an initial strength and a fluid static seal that is superior to conventional suture closure.

Development of sugar palm yarn/glass fibre reinforced unsaturated polyester hybrid composites

NASA Astrophysics Data System (ADS)

Nurazzi, N. Mohd; Khalina, A.; Sapuan, S. Mohd; Rahmah, M.

2018-04-01

This study investigates the effect of fibre hybridization for sugar palm yarn fibre with glass fibre reinforced with unsaturated polyester composites. In this work, unsaturated polyester resin are reinforced with fibre at a ratio of 70:30 wt% and 60:40 wt%. The hybrid composites were characterized in terms of physical (density and water absorption), mechanical (tensile, flexural and compression) and thermal properties through thermal gravimetry analysis (TGA). Density determination showed that density increased with higher wt% of glass fibre. The inherently higher density of glass fibre increased the density of hybrid composite. Resistance to water absorption is improved upon the incorporation of glass fibre and the hybrid composites were found to reach equilibrium absorption at days 4 and 5. As for mechanical performance, the highest tensile strength, tensile modulus, flexural strength, flexural modulus and compression strength were obtained from 40 wt% of fibres reinforcement with ratio of 50:50 wt% of sugar palm yarn fibre and glass fibre reinforced unsaturated polyester composites. The increase of glass fibre loading had a synergistic effect on the mechanical properties to the composites structure due to its superior strength and modulus. The thermal stability of hybrid composites was improved by the increase of onset temperature and the reduction of residues upon increase in temperature.

Modeling of Stiffness and Strength of Bone at Nanoscale.

PubMed

Abueidda, Diab W; Sabet, Fereshteh A; Jasiuk, Iwona M

2017-05-01

Two distinct geometrical models of bone at the nanoscale (collagen fibril and mineral platelets) are analyzed computationally. In the first model (model I), minerals are periodically distributed in a staggered manner in a collagen matrix while in the second model (model II), minerals form continuous layers outside the collagen fibril. Elastic modulus and strength of bone at the nanoscale, represented by these two models under longitudinal tensile loading, are studied using a finite element (FE) software abaqus. The analysis employs a traction-separation law (cohesive surface modeling) at various interfaces in the models to account for interfacial delaminations. Plane stress, plane strain, and axisymmetric versions of the two models are considered. Model II is found to have a higher stiffness than model I for all cases. For strength, the two models alternate the superiority of performance depending on the inputs and assumptions used. For model II, the axisymmetric case gives higher results than the plane stress and plane strain cases while an opposite trend is observed for model I. For axisymmetric case, model II shows greater strength and stiffness compared to model I. The collagen-mineral arrangement of bone at nanoscale forms a basic building block of bone. Thus, knowledge of its mechanical properties is of high scientific and clinical interests.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia].

PubMed

Placzek, R; Deuretzbacher, G; Meiss, A L

2002-12-01

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

Age Dependent Differences in Collagen Alignment of Glutaraldehyde Fixed Bovine Pericardium

PubMed Central

Sizeland, Katie H.; Wells, Hannah C.; Higgins, John; Cunanan, Crystal M.; Kirby, Nigel; Hawley, Adrian; Mudie, Stephen T.; Haverkamp, Richard G.

2014-01-01

Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4–7 days old) is advantageously thinner and is considered as an alternative to that from adult animals. Here, the structures of adult and neonatal bovine pericardium tissues fixed with glutaraldehyde are characterized by synchrotron-based small angle X-ray scattering (SAXS) and compared with the mechanical properties of these materials. Significant differences are observed between adult and neonatal tissue. The glutaraldehyde fixed neonatal tissue has a higher modulus of elasticity (83.7 MPa) than adult pericardium (33.5 MPa) and a higher normalised ultimate tensile strength (32.9 MPa) than adult pericardium (19.1 MPa). Measured edge on to the tissue, the collagen in neonatal pericardium is significantly more aligned (orientation index (OI) 0.78) than that in adult pericardium (OI 0.62). There is no difference in the fibril diameter between neonatal and adult pericardium. It is shown that high alignment in the plane of the tissue provides the mechanism for the increased strength of the neonatal material. The superior strength of neonatal compared with adult tissue supports the use of neonatal bovine pericardium in heterografts. PMID:25295250

Towards understanding the effects of van der Waals strengths on the electric double-layer structures and capacitive behaviors

NASA Astrophysics Data System (ADS)

Yang, Huachao; Bo, Zheng; Yang, Jinyuan; Yan, Jianhua; Cen, Kefa

2017-10-01

Solid-liquid interactions are considered to play a crucial role in charge storage capability of electric double-layer capacitors (EDLCs). In this work, effects of van der Waals (VDW) strengths on the EDL structures and capacitive performances within two representative electrolytes of solvated aqueous solutions and solvent-free ionic liquids are illuminated by molecular dynamics simulations. Single crystalline metals with similar lattice constant but diverse VDW potentials are employed as electrodes. Upon enhancing VDW strengths, capacitance of aqueous electrolytes first increases conspicuously by ∼34.0% and then descends, manifesting a non-monotonic trend, which goes beyond traditional perspectives. Such unusual observation is interpreted by the excluded-volume effects stemmed from ion-solvent competitions. Stimulated by predominant coulombic interactions, more ions are aggregated at the interface despite of the increasing VDW potentials, facilitating superior screening efficiency and capacitance. However, further enhancing strengths preferentially attracts more solvents instead of ions to the electrified surface, which in turn strikingly repels ions from Helmholtz layers, deteriorating electrode capacitance. An essentially similar feather is also recognized for ionic liquids, while the corresponding mechanisms are prominently ascribed to the suppressed ionic separations issued from cation-anion competitions. We highlight that constructing electrode materials with a moderate-hydrophilicity could further advance the performances of EDLCs.

Correlates of meeting the combined and independent aerobic and strength exercise guidelines in hematologic cancer survivors.

PubMed

Vallerand, James R; Rhodes, Ryan E; Walker, Gordon J; Courneya, Kerry S

2017-03-28

Most previous research on the correlates of physical activity has examined the aerobic or strength exercise guidelines separately. Such an approach does not allow an examination of the correlates of meeting the combined guidelines versus a single guideline, or one guideline versus the other. Here, we report the prevalence and correlates of meeting the combined and independent exercise guidelines in hematologic cancer survivors (HCS). In a population-based, cross-sectional survey of 606 HCS from Alberta, Canada using a mailed questionnaire, we obtained separate assessments of aerobic and strength exercise behaviors, as well as separate assessments for motivations, regulations, and reflective processes using the multi-process action control framework (M-PAC). Overall, 22% of HCS met the combined exercise guideline, 22% met aerobic-only, 10% met strength-only, and 46% met neither exercise guideline. HCS were more likely to meet the combined guideline over the aerobic-only guideline if they had no children living at home, and over both the aerobic and strength-only guidelines if they had completed university. As hypothesized, those meeting the combined guideline also had a more favorable strength-specific M-PAC profile (i.e., motivations, regulations, and reflective processes) than those meeting the aerobic-only guideline, and a more favorable aerobic-specific M-PAC profile than those meeting the strength-only guideline. Interestingly and unexpectedly, HCS meeting the combined guidelines also reported significantly greater aerobic-specific perceived control, planning, and obligation/regret than those meeting the aerobic-only guideline, and greater strength-specific perceived control, planning, and obligation/regret than those meeting the strength-only guideline. Few HCS are meeting the combined exercise guidelines. M-PAC based variables are strong correlates of meeting the combined guidelines compared to aerobic or strength only guidelines. Strategies to help HCS meet the combined guidelines may need to promote more favorable behavioral regulations and reflective processes for both types of exercise rather than just the type of exercise in which HCS are deficient.

Specific physiological and biomechanical performance in elite, sub-elite and in non-elite male team handball players.

PubMed

Wagner, Herbert; Fuchs, Philip X; von Duvillard, Serge P

2018-01-01

Team handball is a dynamic sport game that is played professionally in numerous countries. However, knowledge about training and competition is based mostly on practical experience due to limited scientific studies. Consequently, the aims of our study were to compare specific physiological and biomechanical performance in elite, sub-elite and in non-elite male team handball players. Thirty-six elite, sub-elite and non-elite male team handball players performed a game based performance test, upper-body and lower-body strength tests, 30-m sprint test, counter movement jump test and an incremental treadmill running test. Significant differences (P<0.05) were found for the peak oxygen uptake, heart rate, offense and defense time, jump height and ball velocity during the jump throw in the game based performance test, maximal oxygen uptake in the incremental treadmill running test as well as in maximal leg strength and leg explosive strength in the isometric strength test. Elite male players have an enhanced specific agility, a better throwing performance, a higher team handball specific oxygen uptake and higher leg strength compared to sub-elite and non-elite players. Based on these results we recommend that training in team handball should focus on game based training methods to improve performance in specific agility, endurance and technique.

Strength Training. Rationale for Current Guidelines for Adult Fitness Programs.

ERIC Educational Resources Information Center

Feigenbaum, Matthew S.; Pollock, Michael L.

1997-01-01

Strength training is an effective method of developing musculoskeletal strength and is often prescribed for fitness, health, and for prevention and rehabilitation of orthopedic injuries. This paper describes and presents a rationale for the population-specific strength training guidelines established by major health organizations. (SM)

Three-dimensional high-entropy alloy-polymer composite nanolattices that overcome the strength-recoverability trade-off.

PubMed

Zhang, Xuan; Yao, Jiahao; Liu, Bin; Yan, Jun; Lu, Lei; Li, Yi; Gao, Huajian; Li, Xiaoyan

2018-06-14

Mechanical metamaterials with three-dimensional micro- and nano-architectures exhibit unique mechanical properties, such as high specific modulus, specific strength and energy absorption. However, a conflict exists between strength and recoverability in nearly all the mechanical metamaterials reported recently, in particular the architected micro-/nanolattices, which restricts the applications of these materials in energy storage/absorption and mechanical actuation. Here, we demonstrated the fabrication of three-dimensional architected composite nanolattices that overcome the strength-recoverability trade-off. The nanolattices under study are made up of a high entropy alloy coated (14.2-126.1 nm in thickness) polymer strut (approximately 260 nm in the characteristic size) fabricated via two-photon lithography and magnetron sputtering deposition. In situ uniaxial compression inside a scanning electron microscope showed that these composite nanolattices exhibit a high specific strength of 0.027 MPa/kg m3, an ultra-high energy absorption per unit volume of 4.0 MJ/m3, and nearly complete recovery after compression under strains exceeding 50%, thus overcoming the traditional strength-recoverability trade-off. During multiple compression cycles, the composite nanolattices exhibit a high energy loss coefficient (converged value after multiple cycles) of 0.5-0.6 at a compressive strain beyond 50%, surpassing the coefficients of all the micro-/nanolattices fabricated recently. Our experiments also revealed that for a given unit cell size, the composite nanolattices coated with a high entropy alloy with thickness in the range of 14-50 nm have the optimal specific modulus, specific strength and energy absorption per unit volume, which is related to a transition of the dominant deformation mechanism from local buckling to brittle fracture of the struts.

[Biomechanical performance of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability].

PubMed

Liu, Tie-long; Yan, Wang-jun; Han, Yu; Ye, Xiao-jian; Jia, Lian-shun; Li, Jia-shun; Yuan, Wen

2010-05-01

To compare the biomechanical performances of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability, and test the effect of different fixation strengths and fixation approaches on the surgical outcomes. Six specimens of the atlantoaxial complex (C0-C3) were used to establish models of the normal complex, unstable complex (type II odontoid fracture) and fixed complex. On the wd-5 mechanical testing machine, the parameters including the strength and rigidity of anti-rotation, change and strength of stress, and stability were measured for the normal complex, atlantoaxial instability complex, the new type titanium cable fixation system, Atlas titanium cable, Songer titanium cable, and stainless wire. The strength and rigidity of anti-rotation, change and strength of stress, stability of flexion, extension and lateral bending of the unstable atlantoaxial complex fixed by the new double locking titanium cable fixation system were superior to those of the Songer or Atlas titanium cable (P<0.05) and medical stainless wire (P<0.05). Simultaneous cable fastening on both sides resulted in better fixation effect than successive cable fastening (P<0.05). Better fixation effect was achieved by fastening the specimen following a rest (P<0.05). The fixation effects can be enhanced by increased fastening strengths. The new type double locking titanium cable fixation system has better biomechanical performance than the conventional Songer and Atlas titanium cables. Fastening the unstable specimens after a rest following simultaneous fastening of the specimen on both sides produces better fixation effect.

Comparison of the Microtensile Bond Strength of a Polyetherketoneketone (PEKK) Tooth Post Cemented with Various Surface Treatments and Various Resin Cements.

PubMed

Song, Chan-Hong; Choi, Jae-Won; Jeon, Young-Chan; Jeong, Chang-Mo; Lee, So-Hyoun; Kang, Eun-Sook; Yun, Mi-Jung; Huh, Jung-Bo

2018-05-29

The aim of this in-vitro research was to evaluate the microtensile bond strength in the newly introduced PEKK tooth post with various surface treatments and resin cements. A fiberglass tooth post was included in order to compare it with PEKK as a possible post material. The microtensile bond strengths of the fiberglass post (FRC Postec Plus) and the PEKK post (Pekkton ® ) were tested using three kinds of self-adhesive resin cements (G-CEM LinkAce, Multilink Speed, and RelyX U200) and one self-etching resin cement (PANAVIA F2.0). The surface treatments of the fiberglass posts were processed according to the manufacturer's recommendations (F1, application of 37% phosphoric acid etching gel and silanization). For the PEKK post groups, various surface treatments were performed like no surface treatment (P1), sandblasting (P2), silica-coating and silanization (P3), and sandblasting with a composite primer (P4). In the surface treatment, PEKK posts with silica coating and silane treatment (P3) showed a significantly higher microtensile bond strength (mean MPa: 18.09, p < 0.05). The highest microtensile bond strength was shown when the PEKK posts were treated with a silica coating and silane treatment and cemented with RelyX U200 (mean MPa: 22.22). The PEKK posts with surface treatments of silica-coating and silanization or sandblasting displayed superior microtensile bond strengths (mean MPa: 18.09 and 16.25, respectively) compared to the conventional fiberglass posts (mean MPa: 14.93, p < 0.05).

In Vitro Tensile Strength Study on Suturing Technique and Material.

PubMed

González-Barnadas, Albert; Camps-Font, Octavi; Espanya-Grifoll, Dunia; España-Tost, Antoni; Figueiredo, Rui; Valmaseda-Castellón, Eduard

2017-06-01

Suture technique and materials are important in preventing complications such as wound dehiscences. The purpose of this study was to determine the tensile strength of different suturing techniques, comparing several materials with different diameters. One hundred sixty sutures were performed using silk, e-PTFE, and 2 types of polyamide (monofilament and Supramid). Ten simple, 10 horizontal mattress, and 10 combinations of the two stitches were performed with 4-0 gauge of each material. Additionally, 10 simple sutures were performed with the 5-0 gauge of each material. The maximum tensile force resisted by each suture was recorded. When 5 mm of traction was applied, the polyamide monofilament resisted significantly better without untying or breaking compared with Supramid or silk, while the e-PTFE was superior to all the others. However, the force when e-PTFE 4-0 sutures untied or broke was lower than for either type of polyamide. The combined technique withstood a significantly higher tensile force before unknotting or breaking than did the simple and mattress stitches. The 5-0 gauges of silk and both types of polyamide showed lower tensile strengths than the 4-0 materials. Among the 5-0 sutures, Supramid showed a higher tensile strength than silk. The combined suture technique possessed greater tensile strength than did a simple or a horizontal mattress suture, and e-PTFE 4-0 withstood more traction without untying or breaking than did all the other materials, although at a lower tensile force. With the exception of e-PTFE, 4-0 sutures had greater tensile strength than did 5-0 sutures.

Bioactive glass-reinforced bioceramic ink writing scaffolds: sintering, microstructure and mechanical behavior.

PubMed

Shao, Huifeng; Yang, Xianyan; He, Yong; Fu, Jianzhong; Liu, Limin; Ma, Liang; Zhang, Lei; Yang, Guojing; Gao, Changyou; Gou, Zhongru

2015-09-10

The densification of pore struts in bioceramic scaffolds is important for structure stability and strength reliability. An advantage of ceramic ink writing is the precise control over the microstructure and macroarchitecture. However, the use of organic binder in such ink writing process would heavily affect the densification of ceramic struts and sacrifice the mechanical strength of porous scaffolds after sintering. This study presents a low-melt-point bioactive glass (BG)-assisted sintering strategy to overcome the main limitations of direct ink writing (extrusion-based three-dimensional printing) and to produce high-strength calcium silicate (CSi) bioceramic scaffolds. The 1% BG-added CSi (CSi-BG1) scaffolds with rectangular pore morphology sintered at 1080 °C have a very small BG content, readily induce apatite formation, and show appreciable linear shrinkage (∼21%), which is consistent with the composite scaffolds with less or more BG contents sintered at either the same or a higher temperature. These CSi-BG1 scaffolds also possess a high elastic modulus (∼350 MPa) and appreciable compressive strength (∼48 MPa), and show significant strength enhancement after exposure to simulated body fluid-a performance markedly superior to those of pure CSi scaffolds. Particularly, the honeycomb-pore CSi-BG1 scaffolds show markedly higher compressive strength (∼88 MPa) than the scaffolds with rectangular, parallelogram, and Archimedean chord pore structures. It is suggested that this approach can potentially facilitate the translation of ceramic ink writing and BG-assisted sintering of bioceramic scaffold technologies to the in situ bone repair.

How culture gets embrained: Cultural differences in event-related potentials of social norm violations

PubMed Central

Mu, Yan; Kitayama, Shinobu; Han, Shihui; Gelfand, Michele J.

2015-01-01

Humans are unique among all species in their ability to develop and enforce social norms, but there is wide variation in the strength of social norms across human societies. Despite this fundamental aspect of human nature, there has been surprisingly little research on how social norm violations are detected at the neurobiological level. Building on the emerging field of cultural neuroscience, we combine noninvasive electroencephalography (EEG) with a new social norm violation paradigm to examine the neural mechanisms underlying the detection of norm violations and how they vary across cultures. EEG recordings from Chinese and US participants (n = 50) showed consistent negative deflection of event-related potential around 400 ms (N400) over the central and parietal regions that served as a culture-general neural marker of detecting norm violations. The N400 at the frontal and temporal regions, however, was only observed among Chinese but not US participants, illustrating culture-specific neural substrates of the detection of norm violations. Further, the frontal N400 predicted a variety of behavioral and attitudinal measurements related to the strength of social norms that have been found at the national and state levels, including higher culture superiority and self-control but lower creativity. There were no cultural differences in the N400 induced by semantic violation, suggesting a unique cultural influence on social norm violation detection. In all, these findings provided the first evidence, to our knowledge, for the neurobiological foundations of social norm violation detection and its variation across cultures. PMID:26621713

"Superior cleft sign" as a marker of rectus abdominus/adductor longus tear in patients with suspected sportsman's hernia.

PubMed

Murphy, Grainne; Foran, Paul; Murphy, Darra; Tobin, Oliver; Moynagh, Michael; Eustace, Stephen

2013-06-01

We describe a new imaging sign, the "superior cleft sign", identified at both symphysography and MRI, which should be used as a marker of rectus abdominis/adductor longus attachment tearing. A study population of 25 patients presenting with clinically suspected sportsman's hernia, who had undergone both symphysography and MRI of the groin were included for study. In each case, images were reviewed to determine the presence of a superior cleft, secondary cleft, and or both abnormalities. Images of all patients complaining of groin crease discomfort similar to sportsman's hernia revealed the presence of a superior cleft at the rectus abdominis/adductor longus attachment. This "superior cleft sign" correlated with the side of symptoms in each case, and, in contrast to the previously described secondary cleft along the inferior margin of the inferior pubic ramus, occurred parallel to the inferior margin of the superior pubic ramus. The presence of the "superior cleft sign" should be sought in addition to the previously described secondary cleft sign in sportspeople presenting with exercise-related groin pain or pubalgia. It should specifically be sought in patients referred with suspected sportsman's hernia.

DETERMINING THE INFLUENCE OF LANDSCAPE AND RESEARCH-SPECIFIC HABITAT VARIABLES ON VARIATION OF THERMAL CHARACTERISTICS OF STREAMS WITHIN WESTERN LAKE SUPERIOR WATERSHEDS

EPA Science Inventory

As part of a study to develop and test a framework for predicting sensitivity of watersheds to land-use activities, temperatures were monitored in 48 second- and third- order streams on the north and south shores of western Lake Superior. Maximun 21-day average temperatures, whic...

Topographical gradients of semantics and phonology revealed by temporal lobe stimulation.

PubMed

Miozzo, Michele; Williams, Alicia C; McKhann, Guy M; Hamberger, Marla J

2017-02-01

Word retrieval is a fundamental component of oral communication, and it is well established that this function is supported by left temporal cortex. Nevertheless, the specific temporal areas mediating word retrieval and the particular linguistic processes these regions support have not been well delineated. Toward this end, we analyzed over 1000 naming errors induced by left temporal cortical stimulation in epilepsy surgery patients. Errors were primarily semantic (lemon → "pear"), phonological (horn → "corn"), non-responses, and delayed responses (correct responses after a delay), and each error type appeared predominantly in a specific region: semantic errors in mid-middle temporal gyrus (TG), phonological errors and delayed responses in middle and posterior superior TG, and non-responses in anterior inferior TG. To the extent that semantic errors, phonological errors and delayed responses reflect disruptions in different processes, our results imply topographical specialization of semantic and phonological processing. Specifically, results revealed an inferior-to-superior gradient, with more superior regions associated with phonological processing. Further, errors were increasingly semantically related to targets toward posterior temporal cortex. We speculate that detailed semantic input is needed to support phonological retrieval, and thus, the specificity of semantic input increases progressively toward posterior temporal regions implicated in phonological processing. Hum Brain Mapp 38:688-703, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Generation of a neurodegenerative disease mouse model using lentiviral vectors carrying an enhanced synapsin I promoter.

PubMed

Matsuzaki, Yasunori; Oue, Miho; Hirai, Hirokazu

2014-02-15

Certain inherited progressive neurodegenerative disorders, such as spinocerebellar ataxia (SCA), affect neurons in large areas of the central nervous system (CNS). The selective expression of disease-causing and therapeutic genes in susceptible regions and cell types is critical for the generation of animal models and development of gene therapies for these diseases. Previous studies have demonstrated the advantages of the short synapsin I (SynI) promoter (0.5 kb) as a neuron-specific promoter for robust transgene expression. However, the short SynI promoter has also shown some promoter activity in glia and a lack of transgene expression in significant areas of the CNS. New methods: To improve the SynI promoter, we used a SynI promoter that is twice as long (1.0 kb) as the short SynI promoter and incorporated a minimal CMV (minCMV) sequence. We observed that the 1.0 kb rat SynI promoter with minCMV [rSynI(1.0)-minCMV] exhibited robust promoter strength, excellent neuronal specificity and wide-ranging transgene expression throughout the CNS. Comparison with existing methods: Compared with the two previously reported short (0.5 kb) promoters, the new promoter was superior with respect to neuronal specificity and more efficiently transduced neurons. Moreover, transgenic mice expressing the mutant protein ATXN1[Q98], which causes SCA type 1 (SCA1), under the control of the rSynI(1.0)-minCMV promoter showed robust transgene expression specifically in neurons throughout the CNS and exhibited progressive ataxia. rSynI(1.0)-minCMV drives robust and neuron-specific transgene expression throughout the CNS and is therefore useful for viral vector-mediated neuron-specific gene delivery and generation of neuron-specific transgenic animals. Copyright © 2013 Elsevier B.V. All rights reserved.

A Systematic Review of the Effect of Cognitive Strategies on Strength Performance.

PubMed

Tod, David; Edwards, Christian; McGuigan, Mike; Lovell, Geoff

2015-11-01

Researchers have tested the beliefs of sportspeople and sports medicine specialists that cognitive strategies influence strength performance. Few investigators have synthesised the literature. The specific objectives were to review evidence regarding (a) the cognitive strategy-strength performance relationship; (b) participant skill level as a moderator; and (c) cognitive, motivational, biomechanical/physiological, and emotional mediators. Studies were sourced via electronic databases, reference lists of retrieved articles, and manual searches of relevant journals. Studies had to be randomised or counterbalanced experiments with a control group or condition, repeated measures, and a quality control score above 0.5 (out of 1). Cognitive strategies included goal setting, imagery, self-talk, preparatory arousal, and free choice. Dependent variables included maximal strength, local muscular endurance, or muscular power. Globally, cognitive strategies were reliability associated with increased strength performance (results ranged from 61 to 65 %). Results were mixed when examining the effects of specific strategies on particular dependent variables, although no intervention had an overall negative influence. Indeterminate relationships emerged regarding hypothesised mediators (except cognitive variables) and participant skill level as a moderator. Although cognitive strategies influence strength performance, there are knowledge gaps regarding specific types of strength, especially muscular power. Cognitive variables, such as concentration, show promise as possible mediators.

Bovine versus Porcine Acellular Dermal Matrix: A Comparison of Mechanical Properties.

PubMed

Adelman, David M; Selber, Jesse C; Butler, Charles E

2014-05-01

Porcine and bovine acellular dermal matrices (PADM and BADM, respectively) are the most commonly used biologic meshes for ventral hernia repair. A previous study suggests a higher rate of intraoperative device failures using PADM than BADM. We hypothesize that this difference is, in part, related to intrinsic mechanical properties of the matrix substrate and source material. The following study directly compares these 2 matrices to identify any potential differences in mechanical properties that may relate to clinical outcomes. Sections of PADM (Strattice; Lifecell, Branchburg, N.J.) and BADM (SurgiMend; TEI Biosciences, Boston, Mass.) were subjected to a series of biomechanical tests, including suture retention, tear strength, and uniaxial tensile strength. Results were collected and compared statistically. In all parameters, BADM exhibited a superior mechanical strength profile compared with PADM of similar thickness. Increased BADM thickness correlated with increased mechanical strength. In suture tear-through testing with steel wire, failure of the steel wire occurred in the 4-mm-thick BADM, whereas the matrix material failed in all other thicknesses of BADM and PADM. Before implantation, BADM is inherently stronger than PADM at equivalent thicknesses and considerably stronger at increased thicknesses. These results corroborate clinical data from a previous study in which PADM was associated with a higher intraoperative device failure rate. Although numerous properties of acellular dermal matrix contribute to clinical outcomes, surgeons should consider initial mechanical strength properties when choosing acellular dermal matrices for load-bearing applications such as hernia repair.

Strength of fixation constructs for basilar osteotomies of the first metatarsal.

PubMed

Lian, G J; Markolf, K; Cracchiolo, A

1992-01-01

Twenty-four pairs of fresh-frozen human feet had a proximal osteotomy of the first metatarsal that was fixed using either screws, staples, or K wires. Each metatarsal was excised and the specimen was loaded to failure in a cantilever beam configuration by applying a superiorly directed force to the metatarsal head using an MTS servohydraulic test machine. Specimens with a crescentic osteotomy that were fixed using a single screw demonstrated higher mean failure moments than pairs that were fixed with four staples or two K wires; staples were the weakest construct. All specimens fixed with staples failed by bending of the staples without bony fracture; all K wire constructs but one failed by wire bending. Chevron and crescentic osteotomies fixed with a single screw demonstrated equal bending strengths; the bending strength of an oblique osteotomy fixed with two screws was 82% greater than for a crescentic osteotomy fixed with a single screw. Basilar osteotomies of the first metatarsal are useful in correcting metatarsus primus varus often associated with hallux valgus pathology. Fixation strength is an important consideration since weightbearing forces on the head of the first metatarsal acting at a distance from the osteotomy site subject the construct to a dorsiflexion bending moment, as simulated in our tests. Our results show that screw fixation is the strongest method for stabilizing a basilar osteotomy. Based upon the relatively low bending strengths of the staple and K wire constructs, we would not recommend these forms of fixation.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological and anthropometric characteristics of starters and non-starters and playing positions in elite Australian Rules Football: a case study.

PubMed

Young, W B; Newton, R U; Doyle, T L A; Chapman, D; Cormack, S; Stewart, G; Dawson, B

2005-09-01

A purpose of this study was to determine if pre-season anthropometric and physiological measures were significantly different for the players from one Australian Football League (AFL) club selected to play in the first game of the season compared to the players not selected. Another purpose was to compare fitness test results for defenders, forwards and mid-fielders in the same AFL club. Thirty-four players were tested for isolated quadriceps and hamstrings strength, leg extensor muscle strength and power, upper body strength, sprinting speed, vertical jump (VJ), endurance, skinfolds and hamstring flexibility. The starters who were selected to play the first game were a significantly older and more experienced playing group, and were significantly better (p < 0.05) in measures of leg power, sprinting speed and the distance covered in the Yo Yo intermittent recovery test compared to the non-starters. Although there were trends for the superiority of the starters, the differences in lower and upper body strength, VJ and predicted VO2max were non-significant. The forwards generally produced the worst fitness scores of the playing positions with the midfielders having significantly lower skinfolds and the defenders possessing better hamstring strength and VJ compared to the forwards. It was concluded that some fitness qualities can differentiate between starters and non-starters, at least in one AFL club. Comparisons of playing positions and the development of fitness norms for AFL players require further research.

Effects of thermomechanical processing on the microstructure and mechanical properties of Nb-1Zr-C alloys

NASA Technical Reports Server (NTRS)

Titran, Robert H.; Uz, Mehmet

1996-01-01

A systematic study to evaluate the effects of thermomechanical processing on the microstructure and mechanical properties of Nb-1Zr alloy sheet containing 0.06 and 0.1 wt.%C (PWC-11) was conducted and compared to the results of Nb-1Zr. Coarse orthorhombic Nb2C precipitates were present in all the cast, extruded and cold rolled Nb-Zr samples containing C. After high temperature (greater than 0.5 T(sub m)) exposure (with or without applied stress), the Nb2C transforms to very fine and extremely stable FCC (Zr, Nb)C dispersoid, resulting in a highly creep resistant material. Only ZrO2 precipitates were found in Nb-1Zr. The creep strength of the 0.06C and the 0.1C carbide strengthened alloys were much superior to Nb-1Zr. At 1350 K the strength of the 0.06C alloy was about three times that of Nb-1Zr, while the 0.1C alloy had about five times the creep stress capability of Nb-1Zr. The tensile strength, long term creep strength, and stability of the microstructure of the PWC-11 sheet appear to be independent of the number of 1900 K extrusions performed prior to cold rolling. The microhardness of these single, double and triple extnided PWC-11 sheets also were comparable. The tensile strength of PWC-11 and Nb-1Zr at room temperature and 1350 K were comparable.

Pullout strength of standard vs. cement-augmented rotator cuff repair anchors in cadaveric bone.

PubMed

Aziz, Keith T; Shi, Brendan Y; Okafor, Louis C; Smalley, Jeremy; Belkoff, Stephen M; Srikumaran, Uma

2018-05-01

We evaluate a novel method of rotator cuff repair that uses arthroscopic equipment to inject bone cement into placed suture anchors. A cadaver model was used to assess the pullout strength of this technique versus anchors without augmentation. Six fresh-frozen matched pairs of upper extremities were screened to exclude those with prior operative procedures, fractures, or neoplasms. One side from each pair was randomized to undergo standard anchor fixation with the contralateral side to undergo anchor fixation augmented with bone cement. After anchor fixation, specimens were mounted on a servohydraulic testing system and suture anchors were pulled at 90° to the insertion to simulate the anatomic pull of the rotator cuff. Sutures were pulled at 1 mm/s until failure. The mean pullout strength was 540 N (95% confidence interval, 389 to 690 N) for augmented anchors and 202 N (95% confidence interval, 100 to 305 N) for standard anchors. The difference in pullout strength was statistically significant (P < 0.05). This study shows superior pullout strength of a novel augmented rotator cuff anchor technique. The described technique, which is achieved by extruding polymethylmethacrylate cement through a cannulated in situ suture anchor with fenestrations, significantly increased the ultimate failure load in cadaveric human humeri. This novel augmented fixation technique was simple and can be implemented with existing instrumentation. In osteoporotic bone, it may substantially reduce the rate of anchor failure. Copyright © 2018 Elsevier Ltd. All rights reserved.

Efficacy of different irrigation regimes on the push-out bond strength of various resin-based sealers at different root levels: An in vitro study.

PubMed

Verma, Diksha; Taneja, Sonali; Kumari, Manju

2018-01-01

This study aims to evaluate and compare the efficacy of various irrigation regimens on push-out bond strength of AH Plus/gutta-percha, Real Seal/Resilon, and MetaSeal/gutta-percha at three different root levels. Single-rooted mandibular premolars ( n = 120) were prepared and divided into four groups ( n = 30) based on irrigation regimen used: I: 5.25% sodium hypochlorite (NaOCl)-17% ethylenediaminetetraacetic acid (EDTA); II: 5.25% NaOCl-2.25% Peracetic acid (PAA); III: 5.25% NaOCl-18% 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) (Etidronic Acid); and IV: Distilled Water. Each group was further divided into three subgroups ( n = 10); A: AH Plus/gutta-percha; B: MetaSEAL/gutta-percha; C: RealSeal/Resilon. After obturation, roots were sectioned at 3 levels and push-out tests were performed. One-way ANOVA with post hoc Tukey-honestly significant difference tests were applied to assess the significance among various groups. Among irrigants, 2.25% PAA showed significantly lower values when compared with rest of the irrigants. There was no significant difference found among EDTA and HEBP. The push-out bond strength of AH Plus was significantly higher among all sealers. The bond strength values were significantly decreased in apico-coronal direction. There was superior efficacy of EDTA and HEBP on the bond strength of AH Plus at apical root level when compared with other irrigants and sealers at various root levels.

Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue.

PubMed

Matthews, Martyn J; Heron, Kate; Todd, Stefanie; Tomlinson, Andrew; Jones, Paul; Delextrat, Anne; Cohen, Daniel D

2017-05-01

To investigate the effect of two hamstring training protocols on eccentric peak torque before and after soccer specific fatigue. Twenty-two university male soccer players. Isokinetic strength tests were performed at 60°/s pre and post fatigue, before and after 2 different training interventions. A 45-min soccer specific fatigue modified BEAST protocol (M-BEAST) was used to induce fatigue. Players were randomly assigned to a 4 week hamstrings conditioning intervention with either a maximum strength (STR) or a muscle endurance (END) emphasis. The following parameters were evaluated: Eccentric peak torque (EccPT), angle of peak torque (APT), and angle specific torques at knee joint angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. There was a significant effect of the M-BEAST on the Eccentric torque angle profile before training as well as significant improvements in post-fatigue torque angle profile following the effects of both strength and muscle endurance interventions. Forty-five minutes of simulated soccer activity leads to reduced eccentric hamstring torque at longer muscle lengths. Short-term conditioning programs (4-weeks) with either a maximum strength or a muscular endurance emphasis can equally reduce fatigue induced loss of strength over this time period. Copyright © 2017 Elsevier Ltd. All rights reserved.

High Strength Reinforcing Steel Bars : Concrete Shear Friction Interface : final report : Part A.

DOT National Transportation Integrated Search

2017-03-01

High-strength steel (HSS) reinforcement, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) steel reinf...

High strength reinforcing steel bars : concrete shear friction interface : final report : Part A.

DOT National Transportation Integrated Search

2017-03-01

High-strength steel (HSS) reinforcement, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) steel reinf...

High strength reinforcing steel bars : low cycle fatigue behavior : final report - part B.

DOT National Transportation Integrated Search

2017-03-01

High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

High strength reinforcing steel bars : low-cycle fatigue behavior : final report - part B.

DOT National Transportation Integrated Search

2017-03-01

High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study

PubMed Central

Kommi, Pradeep Babu; Kumar, M Senthil; Hanumanth; Venkatesan; Aniruddh; Arvinth; Kumar, Arani Nanda

2016-01-01

Introduction Most of the patients seek orthodontic treatment to improve the smile, which improves the facial profile by means of fixed appliances i.e., brackets and wires. The brackets are of different types like stainless steel and ceramic. Ceramic brackets were considered as aesthetic appliance which was divided into mono-crystalline, polycrystalline and sapphire brackets. The light transmittance might influence the degree of curing adhesive material in mono crystalline, polycrystalline and sapphire brackets. Aim The aim of the present study was to evaluate the translucency and intensity of three different aesthetic brackets (mono crystalline, poly crystalline and sapphire ceramic brackets) and to determine their influence on shear bond strength of the brackets. The adhesive remnant index was also measured after debonding of the brackets from the tooth surface. Materials and Methods Twenty six samples each of monocrystalline, polycrystalline and sapphire brackets (total 78 ceramic brackets) were used for the study. The bracket samples were subjected to optical fluorescence test using spectrofluorometer to measure the intensity of the brackets. Seventy eight extracted premolar teeth were procured and divided into 3 groups. The brackets were then bonded to the tooth using Transbond XT (3M Unitek) light cure composite material and cured with new light cure unit (Light Emitting Diode) of wood pecker company (400-450nm) for 30 seconds, and these samples were subjected to shear bond strength test with Instron Universal Testing Machine (UNITEK-94100) with a load range between 0 to 100 KN with a maximum cross head speed of 0.5mm/min. ARI (Adhesive Remnant Index) scores were evaluated according to Artun and Bergland scoring system using stereomicroscope at 20x magnification. Results The light absorption values obtained from spectrofluorometeric study were 3300000–3500000 cps for group 1 (monocrystalline ceramic brackets), 6000000–6500000 cps for Group 2 (polycrystalline ceramic brackets) and 2700000 –3000000 cps for Group 3 (sapphire ceramic brackets) i.e., Group 2 showed the highest light absorption and the least translucency followed by groups 1 and 3. Shear bond strength results were 2.4 mpa, 1.9 mpa and 3.6 mpa for groups 1,2 and 3 respectively. Superior shear bond strength was recorded in group 3 (sapphire ceramic brackets). ARI results showed that group 3 had increased bond between bracket adhesive interfaces when compared to the other 2 groups. Conclusion From this study, it has been concluded that sapphire ceramic brackets (Group 3) was superior in translucency and shear bond strength followed by monocrystalline and polycrystalline ceramic brackets. PMID:27656556