Development of laboratory testing facility for evaluation of base-soil behavior under repeated loading : phase-1 : feasibility study.

DOT National Transportation Integrated Search

2008-03-01

The main objective of this study was to determine the most beneficial and cost-effective accelerated load facility that can be used in conjunction with LTRCs Accelerated Load Facility (ALF). The facility will be used primarily for conducting preli...

Spatial context learning survives interference from working memory load

PubMed Central

Vickery, Timothy J.; Sussman, Rachel S.; Jiang, Yuhong V.

2010-01-01

The human visual system is constantly confronted with an overwhelming amount of information, only a subset of which can be processed in complete detail. Attention and implicit learning are two important mechanisms that optimize vision. This study addresses the relationship between these two mechanisms. Specifically we ask: Is implicit learning of spatial context affected by the amount of working memory load devoted to an irrelevant task? We tested observers in visual search tasks where search displays occasionally repeated. Observers became faster searching repeated displays than unrepeated ones, showing contextual cueing. We found that the size of contextual cueing was unaffected by whether observers learned repeated displays under unitary attention or when their attention was divided using working memory manipulations. These results held when working memory was loaded by colors, dot patterns, individual dot locations, or multiple potential targets. We conclude that spatial context learning is robust to interference from manipulations that limit the availability of attention and working memory. PMID:20853996

A Repeated Power Training Enhances Fatigue Resistance While Reducing Intraset Fluctuations.

PubMed

Gonzalo-Skok, Oliver; Tous-Fajardo, Julio; Moras, Gerard; Arjol-Serrano, José Luis; Mendez-Villanueva, Alberto

2018-04-04

Oliver, GS, Julio, TF, Moras, G, José Luis, AS, and Alberto, MV. A repeated power training enhances fatigue resistance while reducing intraset fluctuations. J Strength Cond Res XX(X): 000-000, 2018-The present study analyzed the effects of adding an upper-body repeated power ability (RPA) training to habitual strength training sessions. Twenty young elite male basketball players were randomly allocated into a control group (CON, n = 10) or repeated power group (RPG, n = 10) and evaluated by 1 repetition maximum (1RM), incremental load, and RPA tests in the bench press exercise before and after a 7-week period and a 4-week cessation period. Repeated power group performed 1-3 blocks of 5 sets of 5 repetitions using the load that maximized power output with 30 seconds and 3 minute of passive recovery between sets and blocks, respectively. Between-group analysis showed substantial greater improvements in RPG compared with CON in: best set (APB), last set (APL), mean power over 5 sets (APM), percentage of decrement, fluctuation decrease during APL and RPA index (APLpost/APBpre) during the RPA test (effect size [ES] = 0.64-1.86), and 1RM (ES = 0.48) and average power at 80% of 1RM (ES = 1.11) in the incremental load test. The improvements of APB and APM were almost perfectly correlated. In conclusion, RPA training represents an effective method to mainly improve fatigue resistance together with the novel finding of a better consistency in performance (measured as reduced intraset power fluctuations) at the end of a dynamic repeated effort.

Protection of Buried Pipe under Repeated Loading by Geocell Reinforcement

NASA Astrophysics Data System (ADS)

Khalaj, Omid; Joz Darabi, N.; Moghaddas Tafreshi, S. N.; Mašek, Bohuslav

2017-12-01

With increase in cities’ population and development of urbane life, passing buried pipelines near ground’s surface is inevitable in urban areas, roads, subways and highways. This paper presents the results of three-dimensional full scale model tests on high-density polyethylene (HDPE) pipe with diameter of 250 mm in geocell reinforced soil, subjected to repeated loading to simulate the vehicle loads. The effect of geocell’s pocket size (55*55 mm and 110*110 mm) and embedment depth of buried pipe (1.5 and 2 times pipe diameter) in improving the behaviour of buried pipes was investigated. The geocell’s height of 100 mm was used in all tests. The repeated load of 800 kPa was applied on circular loading plate with diameter of 250 mm. The results show that the pipe displacement, soil surface settlement and transferred pressure on the pipe’s crown has been influenced significantly upon the use of geocells. For example, the vertical diametric strain (VDS) and soil surface settlement (SSS), in a way that using a geocell with pocket size of 110*110 mm reduces by 27% and 43%, respectively, compared with the unreinforced one. Meanwhile, by increasing buried depth of pipe from 1.5D to 2D, the use of geocell of 110*110 mm delivers about 50% reduction in SSS and VDS, compared with the unreinforced soil.

Subjective evaluation of experimental dyspnoea – Effects of isocapnia and repeated exposure

PubMed Central

Hayen, Anja; Herigstad, Mari; Wiech, Katja; Pattinson, Kyle T.S.

2015-01-01

Resistive respiratory loading is an established stimulus for the induction of experimental dyspnoea. In comparison to unloaded breathing, resistive loaded breathing alters end-tidal CO2 (PETCO2), which has independent physiological effects (e.g. upon cerebral blood flow). We investigated the subjective effects of resistive loaded breathing with stabilized PETCO2 (isocapnia) during manual control of inspired gases on varying baseline levels of mild hypercapnia (increased PETCO2). Furthermore, to investigate whether perceptual habituation to dyspnoea stimuli occurs, the study was repeated over four experimental sessions. Isocapnic hypercapnia did not affect dyspnoea unpleasantness during resistive loading. A post hoc analysis revealed a small increase of respiratory unpleasantness during unloaded breathing at +0.6 kPa, the level that reliably induced isocapnia. We did not observe perceptual habituation over the four sessions. We conclude that isocapnic respiratory loading allows stable induction of respiratory unpleasantness, making it a good stimulus for multi-session studies of dyspnoea. PMID:25578628

Development of laboratory testing facility for evaluation of base-soil behavior under repeated loading : phase 1 : feasibility study.

DOT National Transportation Integrated Search

2005-02-01

Accelerated load testing of paved and unpaved roads is the application of a large number of load repetitions in a short period of time. This type of testing is an economic way to determine the behavior of roads and compare different materials, struct...

Incremental Dynamic Analysis of Koyna Dam under Repeated Ground Motions

NASA Astrophysics Data System (ADS)

Zainab Nik Azizan, Nik; Majid, Taksiah A.; Nazri, Fadzli Mohamed; Maity, Damodar; Abdullah, Junaidah

2018-03-01

This paper discovers the incremental dynamic analysis (IDA) of concrete gravity dam under single and repeated earthquake loadings to identify the limit state of the dam. Seven ground motions with horizontal and vertical direction as seismic input considered in the nonlinear dynamic analysis based on the real repeated earthquake in the worldwide. All the ground motions convert to respond spectrum and scaled according to the developed elastic respond spectrum in order to match the characteristic of the ground motion to the soil type. The scaled was depends on the fundamental period, T1 of the dam. The Koyna dam has been selected as a case study for the purpose of the analysis by assuming that no sliding and rigid foundation, has been estimated. IDA curves for Koyna dam developed for single and repeated ground motions and the performance level of the dam identifies. The IDA curve of repeated ground motion shown stiffer rather than single ground motion. The ultimate state displacement for a single event is 45.59mm and decreased to 39.33mm under repeated events which are decreased about 14%. This showed that the performance level of the dam based on seismic loadings depend on ground motion pattern.

Influence of Axial Load on Electromechanical Impedance (EMI) of Embedded Piezoceramic Transducers in Steel Fiber Concrete.

PubMed

Wang, Zhijie; Chen, Dongdong; Zheng, Liqiong; Huo, Linsheng; Song, Gangbing

2018-06-01

With the advantages of high tensile, bending, and shear strength, steel fiber concrete structures have been widely used in civil engineering. The health monitoring of concrete structures, including steel fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly used. Structures are often subject to changing axial load and ignoring the effect of axial forces may introduce error to Structural Health Monitoring (SHM), including the EMI-based method. However, many of the concrete structure monitoring algorithms do not consider the effects of axial loading. To investigate the influence of axial load on the EMI of a steel fiber concrete structure, concrete specimens with different steel fiber content (0, 30, 60, 90, 120) (kg/m³) were casted and the Lead Zirconate Titanate (PZT)-based Smart Aggregate (SA) was used as the EMI sensor. During tests, the step-by-step loading procedure was applied on different steel fiber content specimens, and the electromechanical impedance values were measured. The Normalized root-mean-square deviation Index (NI) was developed to analyze the EMI information and evaluate the test results. The results show that the normalized root-mean-square deviation index increases with the increase of the axial load, which clearly demonstrates the influence of axial load on the EMI values for steel fiber concrete and this influence should be considered during a monitoring or damage detection procedure if the axial load changes. In addition, testing results clearly reveal that the steel fiber content, often at low mass and volume percentage, has no obvious influence on the PZT's EMI values. Furthermore, experiments to test the repeatability of the proposed method were conducted. The repeating test results show that the EMI-based indices are repeatable and there is a great linearity between the NI and the applied loading.

Strength Investigations in Aircraft Construction Under Repeated Application of the Load

NASA Technical Reports Server (NTRS)

Gassner, E.

1946-01-01

In the calculation of the dimensions of modern machines and building constructions, account is taken of the frequency of the occurrence of the anticipated loads. It is generally assumed that these loads will be repeated an infinite number, or at any rate some millions, of times during the total working life of the construction, When calculating the dimensions of the structural parts of aircraft, on the contrary, a consideration only of those frequencies in the appearance of the loads which actually come into play in the various states of stress is allowable. This is because in aircraft construction it is absolutely essential not only to ensure adequate structural strength but also to keep down the structural weight to the lowest possible limit, Strength tests in which this requirement is directly taken into account have recently been carried out by the DVL Material Strength Department.

Importance of Muscle Power Variables in Repeated and Single Sprint Performance in Soccer Players

PubMed Central

López-Segovia, Manuel; Dellal, Alexandre; Chamari, Karim; González-Badillo, Juan José

2014-01-01

This study examined the relationship between lower body power and repeated as well as single sprint performance in soccer players. The performance of nineteen male soccer players was examined. The first testing session included the countermovement jump (CMJL) and the progressive full squat (FSL), both with external loads. Power in the CMJL and FSL was measured with each load that was lifted. The second session included a protocol of 40-m repeated sprints with a long recovery period (2 min). The number of sprints executed until there was a 3% decrease in performance for the best 40-m sprint time was recorded as a repeated sprint index (RSI). The RSI was moderately associated with power output relative to body mass in the CMJL and FSL (r = 0.53/0.54, p ≤ 0.05). The most and least powerful players (determined by FSL) showed significant differences in the RSI (9.1 ± 4.2 vs. 6.5 ± 1.6) and 10 m sprint time (p ± 0.01). Repeated and single sprints are associated with relatively lower body power in soccer players. PMID:25031688

Effects of repeated Valsalva maneuver straining on cardiac and vasoconstrictive baroreflex responses

NASA Technical Reports Server (NTRS)

Convertino, Victor A.; Ratliff, Duane A.; Doerr, Donald F.; Ludwig, David A.; Muniz, Gary W.; Benedetti, Erik; Chavarria, Jose; Koreen, Susan; Nguyen, Claude; Wang, Jeff

2003-01-01

INTRODUCTION: We hypothesized that repeated respiratory straining maneuvers (repeated SM) designed to elevate arterial BPs (arterial baroreceptor loading) would acutely increase baroreflex responses. METHODS: We tested this hypothesis by measuring cardiac baroreflex responses to carotid baroreceptor stimulation (neck pressures), and changes in heart rate and diastolic BP after reductions in BP induced by a 15-s Valsalva maneuver in 10 female and 10 male subjects at 1, 3, 6, and 24 h after performing repeated SM. Baroreflex responses were also measured in each subject at 1, 3, 6, and 24 h at the same time on a separate day without repeated SM (control) in a randomized, counter-balanced cross-over experimental design. RESULTS: There was no statistical difference in carotid-cardiac and peripheral vascular baroreflex responses measured across time following repeated SM compared with the control condition. Integrated cardiac baroreflex response (deltaHR/ deltaSBP) measured during performance of a Valsalva maneuver was increased by approximately 50% to 1.1 +/- 0.2 bpm x mm Hg(-1) at 1 h and 1.0 +/- 0.1 bpm x mm Hg(-1) at 3 h following repeated SM compared with the control condition (0.7 +/- 0.1 bpm x mm Hg(-1) at both 1 and 3 h, respectively). However, integrated cardiac baroreflex response after repeated SM returned to control levels at 6 and 24 h after training. These responses did not differ between men and women. CONCLUSIONS: Our results are consistent with the notion that arterial baroreceptor loading induced by repeated SM increased aortic, but not carotid, cardiac baroreflex responses for as long as 3 h after repeated SM. We conclude that repeated SM increases cardiac baroreflex responsiveness which may provide patients, astronauts, and high-performance aircraft pilots with protection from development of orthostatic hypotension.

Upper and Lower Neck Loads in Belted Human Surrogates in Frontal Impacts

PubMed Central

Yoganandan, Narayan; Pintar, Frank A.; Moore, Jason; Rinaldi, James; Schlick, Michael; Maiman, Dennis J.

2012-01-01

The upper and lower neck loads in the restrained Hybrid III dummy and Test Device for Human Occupant Restraint (THOR) were computed in simulated frontal impact sled tests at low, medium, and high velocities; repeatability performance of the two dummies were evaluated at all energy inputs; peak forces and moments were compared with computed loads at the occipital condyles and cervical-thoracic junctions from tests using post mortem human surrogates (PMHS). A custom sled buck was used to position the surrogates. Repeated tests were conducted at each velocity for each dummy and sufficient time was allowed to elapse between the two experiments. The upper and lower neck forces and moments were determined from load cell measures and its locations with respect to the ends of the neck. Both dummies showed good repeatability for axial and shear forces and bending moments at all changes in velocity inputs. Morphological characteristics in the neck loading responses were similar in all surrogates, although the peak magnitudes of the variables differed. In general, the THOR better mimicked the PMHS response than the Hybrid III dummy, and factors such as neck design and chest compliance were attributed to the observed variations. While both dummies were not designed for use at the two extremes of the tested velocities, results from the present study indicate that, currently the THOR may be the preferred anthropomorphic testing device in crashworthiness research studies and full-scale vehicle tests at all velocities. PMID:23169123

Constitutive acoustic-emission elastic-stress behavior of magnesium alloy

NASA Technical Reports Server (NTRS)

Williams, J. H., Jr.; Emerson, G. P.

1977-01-01

Repeated laoding and unloading of a magnesium alloy below the macroscopic yield stress result in continuous acoustic emissions which are generally repeatable for a given specimen and which are reproducible between different specimens having the same load history. An acoustic emission Bauschinger strain model is proposed to describe the unloading emission behavior. For the limited range of stress examined, loading and unloading stress delays of the order of 50 MN/sq m are observed, and they appear to be dependent upon the direction of loading, the stress rate, and the stress history. The stress delay is hypothesized to be the manifestation of an effective friction stress. The existence of acoustic emission elastic stress constitutive relations is concluded, which provides support for a previously proposed concept for the monitoring of elastic stresses by acoustic emission.

Roughness evolution of metallic implant surfaces under contact loading and nanometer-scale chemical etching.

PubMed

Ryu, J J; Letchuman, S; Shrotriya, P

2012-10-01

Surface damage of metallic implant surface at taper lock and clamped interfaces may take place through synergistic interactions between repeated contact loading and corrosion. In the present research, we investigated the influence of surface roughness and contact loading on the mechanical and chemical damage phenomena. Cobalt-chromium (CoCrMo) specimens with two different roughness configurations created by milling and grinding process were subjected to normal and inclined contact loading. During repeated contact loading, amplitude of surface roughness reached a steady value after decreasing during the first few cycles. During the second phase, the alternating experiment of rough surface contact and micro-etching was conducted to characterize surface evolution behavior. As a result, surface roughness amplitude continuously evolved-decreasing during contact loading due to plastic deformation of contacting asperities and increasing on exposure to corrosive environment by the preferential corrosion attack on stressed area. Two different instabilities could be identified in the surface roughness evolution during etching of contact loaded surfaces: increase in the amplitude of dominant wavenumber and increase in amplitude of a small group of roughness modes. A damage mechanism that incorporates contact-induced residual stress development and stress-assisted dissolution is proposed to elucidate the measured instabilities in surface roughness evolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

The more often you see an object, the easier it becomes to track it

PubMed Central

Pinto, Yaïr; Howe, Piers D. L.; Cohen, Michael A.; Horowitz, Todd S.

2010-01-01

Is it easier to track objects that you have seen repeatedly? We compared repeated blocks, where identities were the same from trial to trial, to unrepeated blocks, where identities varied. People were better in tracking objects that they saw repeatedly. We tested four hypotheses to explain this repetition benefit. First, perhaps the repeated condition benefits from consistent mapping of identities to target and distractor roles. However, the repetition benefit persisted even when both the repeated and the unrepeated conditions used consistent mapping. Second, repetition might improve the ability to recover targets that have been lost, or swapped with distractors. However, we observed a larger repetition benefit for color-color conjunctions, which do not benefit from such error recovery processes, than for unique features, which do. Furthermore, a repetition benefit was observed even in the absence of distractors. Third, perhaps repetition frees up resources by reducing memory load. However, increasing memory load by masking identities during the motion phase reduced the repetition benefit. The fourth hypothesis is that repetition facilitates identity tracking, which in turn improves location tracking. This hypothesis is consistent with all our results. Thus, our data suggest that identity and location tracking share a common resource. PMID:20884469

Lateral capacity of rock sockets in limestone under cyclic and repeated loading.

DOT National Transportation Integrated Search

2010-08-01

This report contains the results from full scale lateral load testing of two short rock socketed shafts in : limestone, and the development of recommendations for p-y analysis using those results. Two short shafts 42 : inches in diameter were constru...

Effects of repeated bending load at room temperature for composite Nb3Sn wires

NASA Astrophysics Data System (ADS)

Awaji, Satoshi; Watanabe, Kazuo; Katagiri, Kazumune

2003-09-01

In order to realize a react and wind (R&W) method for Nb3Sn wires, the influences of a bending load at room temperature are investigated. Usually, the superconducting wires undergo bending loads at room temperature repeatedly during winding and insulation processes. We define these bending loads as 'pre-bending' treatments. We applied the pre-bending strain of 0 and 0.5% to the highly strengthened CuNb/(Nb, Ti)3Sn wires, and measured the stress/strain properties and critical currents. The improvements of stress dependence of normalized critical current and the increase of the maximum critical current by the pre-bending treatments were found. The model based on the distribution of the local tensile strain as a bending strain describes the experimental results well without the increase of the maximum critical current. When the pre-bending strain was applied, the calculated results indicate that the mechanical properties are improved due to the local work hardening, and hence the stress dependence of Ic increases.

Bone healing response in cyclically loaded implants: Comparing zero, one, and two loading sessions per day.

PubMed

de Barros E Lima Bueno, Renan; Dias, Ana Paula; Ponce, Katia J; Wazen, Rima; Brunski, John B; Nanci, Antonio

2018-05-31

When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days. Finite element analysis was used to characterize the mechanobiological conditions produced by the loading sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological, histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase in bone-implant distance, as compared to unloaded implants and those subjected to only one loading session. Gene expression profiles differed during osseointegration between all groups mainly with respect to inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue damage and associated inflammatory reaction at the bone-implant interface. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Laboratory investigation of a novel method to accelerate healing in asphalt mixtures using thermal treatment.

DOT National Transportation Integrated Search

2009-08-01

Asphalt binders have an inherent ability to reverse damage in the form of micro-cracks that is caused : due to the repeated action of external loads. This reversal occurs during rest periods between load : cycles. The phenomenon of crack reversal is ...

Lateral capacity of rock sockets in limestone under cyclic and repeated loading : technical summary.

DOT National Transportation Integrated Search

2010-08-01

Drilled shafts are a type of deep foundation that is capable of supporting very large vertical and lateral loads. Drilled shafts are constructed by drilling a hole from the ground surface to the target depth or formation and filling the hole with rei...

Evaluation of the base/subgrade soil under repeated loading : phase II, in-box and ALF cyclic plate load tests [tech summary].

DOT National Transportation Integrated Search

2012-03-01

The inadequacy of many existing roads due to rapid growth in traffic volume provides a motivation for exploring alternatives to : existing methods of constructing and rehabilitating roads. The use of geosynthetics to stabilize and reinforce paved and...

Effects of varying material properties on the load deformation characteristics of heel cushions.

PubMed

Sun, Pi-Chang; Wei, Hung-Wen; Chen, Chien-Hua; Wu, Chun-Hao; Kao, Hung-Chan; Cheng, Cheng-Kung

2008-07-01

Various insole materials were used in attenuation of heel-strike impact. This study presented a compression test to investigate the deformation characteristics of common heel cushions. There were two materials (thermoplastic elastomer "TPE" and silicone) with three hardness and six thickness being analyzed. They underwent consecutive loading-unloading cycles with a load control mode. The displacement of material thickness was recorded during cyclic compression being applied and released from 0 to 1050 N. The energy input, return and dissipation were evaluated based on the load deformation curves when new and after repeated compression. The TPE recovered more deformed energy and thickness than the silicone after the first loading cycle. The silicone would preserve more strain energy with increasing its hardness for the elastic recovery in the unloading process. The deformed energy was decreased as the original thickness did not completely recover under cyclic tests. The reduction in hysteresis area was gradually converged within 20 cycles. The silicone attenuated more impact energy in the initial cycles, but its energy dissipation was reduced after repeated loading. To increase hardness or thickness should be considered to improve resilience or accommodate persistent compression without flattening. The careful selection of cushion materials is imperative to meet individual functional demands.

Reducing random measurement error in assessing postural load on the back in epidemiologic surveys.

PubMed

Burdorf, A

1995-02-01

The goal of this study was to design strategies to assess postural load on the back in occupational epidemiology by taking into account the reliability of measurement methods and the variability of exposure among the workers under study. Intermethod reliability studies were evaluated to estimate the systematic bias (accuracy) and random measurement error (precision) of various methods to assess postural load on the back. Intramethod reliability studies were reviewed to estimate random variability of back load over time. Intermethod surveys have shown that questionnaires have a moderate reliability for gross activities such as sitting, whereas duration of trunk flexion and rotation should be assessed by observation methods or inclinometers. Intramethod surveys indicate that exposure variability can markedly affect the reliability of estimates of back load if the estimates are based upon a single measurement over a certain time period. Equations have been presented to evaluate various study designs according to the reliability of the measurement method, the optimum allocation of the number of repeated measurements per subject, and the number of subjects in the study. Prior to a large epidemiologic study, an exposure-oriented survey should be conducted to evaluate the performance of measurement instruments and to estimate sources of variability for back load. The strategy for assessing back load can be optimized by balancing the number of workers under study and the number of repeated measurements per worker.

Taking the easy way out? Increasing implementation effort reduces probability maximizing under cognitive load.

PubMed

Schulze, Christin; Newell, Ben R

2016-07-01

Cognitive load has previously been found to have a positive effect on strategy selection in repeated risky choice. Specifically, whereas inferior probability matching often prevails under single-task conditions, optimal probability maximizing sometimes dominates when a concurrent task competes for cognitive resources. We examined the extent to which this seemingly beneficial effect of increased task demands hinges on the effort required to implement each of the choice strategies. Probability maximizing typically involves a simple repeated response to a single option, whereas probability matching requires choice proportions to be tracked carefully throughout a sequential choice task. Here, we flipped this pattern by introducing a manipulation that made the implementation of maximizing more taxing and, at the same time, allowed decision makers to probability match via a simple repeated response to a single option. The results from two experiments showed that increasing the implementation effort of probability maximizing resulted in decreased adoption rates of this strategy. This was the case both when decision makers simultaneously learned about the outcome probabilities and responded to a dual task (Exp. 1) and when these two aspects were procedurally separated in two distinct stages (Exp. 2). We conclude that the effort involved in implementing a choice strategy is a key factor in shaping repeated choice under uncertainty. Moreover, highlighting the importance of implementation effort casts new light on the sometimes surprising and inconsistent effects of cognitive load that have previously been reported in the literature.

Transient Reactivation of a Deep-Seated Landslide by Undrained Loading Captured With Repeat Airborne and Terrestrial Lidar

NASA Astrophysics Data System (ADS)

Booth, Adam M.; McCarley, Justin; Hinkle, Jason; Shaw, Susan; Ampuero, Jean-Paul; Lamb, Michael P.

2018-05-01

Landslides reactivate due to external environmental forcing or internal mass redistribution, but the process is rarely documented quantitatively. We capture the three-dimensional, 1-m resolution surface deformation field of a transiently reactivated landslide with image correlation of repeat airborne lidar. Undrained loading by two debris flows in the landslide's head, rather than external forcing, triggered reactivation. After that loading, the lower 2 km of the landslide advanced by up to 14 m in 2 years before completely stopping. The displacement field over those 2 years implies that the slip surface gained 1 kPa of shear strength, which was likely accomplished by a negative dilatancy-pore pressure feedback as material deformed around basal roughness elements. Thus, landslide motion can be decoupled from external environmental forcing in cases, motivating the need to better understand internal perturbations to the stress field to predict hazards and sediment fluxes as landscapes evolve.

Assessment of Experimental Uncertainty for a Floating Wind Semisubmersible under Hydrodynamic Loading: Preprint

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

Robertson, Amy N; Wendt, Fabian F; Jonkman, Jason

The objective of this paper is to assess the sources of experimental uncertainty in an offshore wind validation campaign focused on better understanding the nonlinear hydrodynamic response behavior of a floating semisubmersible. The test specimen and conditions were simplified compared to other floating wind test campaigns to reduce potential sources of uncertainties and better focus on the hydrodynamic load attributes. Repeat tests were used to understand the repeatability of the test conditions and to assess the level of random uncertainty in the measurements. Attention was also given to understanding bias in all components of the test. The end goal ofmore » this work is to set uncertainty bounds on the response metrics of interest, which will be used in future work to evaluate the success of modeling tools in accurately calculating hydrodynamic loads and the associated motion responses of the system.« less

Repeatability of knee impulsive loading measurements with skin-mounted accelerometers and lower limb surface electromyographic recordings during gait in knee osteoarthritic and asymptomatic individuals

PubMed Central

Lyytinen, T.; Bragge, T.; Hakkarainen, M.; Liikavainio, T.; Karjalainen, P.A.; Arokoski, J.P.

2016-01-01

Objectives: To determine the repeatability of knee joint impulsive loading measurements with skin-mounted accelerometers (SMAs) and lower limb surface electromyography (EMG) recordings during gait. Methods: Triaxial SMA and EMG from 4 muscles during level and stair walking in nine healthy and nine knee osteoarthritis (OA) subjects were used. The initial peak acceleration (IPA), root mean square (RMS), maximal acceleration transient rate (ATRmax) and mean EMG activity (EMGact) were calculated. The coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated to measure repeatability. Results: The CV and ICC of RMS accelerations ranged from 4.9% to 10.9% and from 0.69 to 0.96 in both study groups during level walking. The CV and ICC of IPA and ATRmax varied from 7.7% to 14.2% and from 0.85 to 0.99 during level and stairs up walking in healthy subjects. The CV and ICC of EMGact ranged from 8.3% to 31.7% and from 0.16 to 0.97 in both study groups. Conclusions: RMS accelerations exhibited good repeatability during walking in healthy and knee OA subjects. The repeatability of EMG measurements was acceptable in healthy subjects depending on the measured muscles. PMID:26944825

Continental hydrology loading observed by VLBI measurements

NASA Astrophysics Data System (ADS)

Eriksson, David; MacMillan, D. S.

2014-07-01

Variations in continental water storage lead to loading deformation of the crust with typical peak-to-peak variations at very long baseline interferometry (VLBI) sites of 3-15 mm in the vertical component and 1-2 mm in the horizontal component. The hydrology signal at VLBI sites has annual and semi-annual components and clear interannual variations. We have calculated the hydrology loading series using mass loading distributions derived from the global land data assimilation system (GLDAS) hydrology model and alternatively from a global grid of equal-area gravity recovery and climate experiment (GRACE) mascons. In the analysis of the two weekly VLBI 24-h R1 and R4 network sessions from 2003 to 2010 the baseline length repeatabilities are reduced in 79 % (80 %) of baselines when GLDAS (GRACE) loading corrections are applied. Site vertical coordinate repeatabilities are reduced in about 80 % of the sites when either GLDAS or GRACE loading is used. In the horizontal components, reduction occurs in 70-80 % of the sites. Estimates of the annual site vertical amplitudes were reduced for 16 out of 18 sites if either loading series was applied. We estimated loading admittance factors for each site and found that the average admittances were 1.01 0.05 for GRACE and 1.39 0.07 for GLDAS. The standard deviations of the GRACE admittances and GLDAS admittances were 0.31 and 0.68, respectively. For sites that have been observed in a set of sufficiently temporally dense daily sessions, the average correlation between VLBI vertical monthly averaged series and GLDAS or GRACE loading series was 0.47 and 0.43, respectively.

Mental Load in Listening, Speech Shadowing and Simultaneous Interpreting: A Pupillometric Study.

ERIC Educational Resources Information Center

Tommola, Jorma; Hyona, Jukka

This study investigated the sensitivity of the pupillary response as an indicator of average mental load during three language processing tasks of varying complexity. The tasks included: (1) listening (without any subsequent comprehension testing); (2) speech shadowing (repeating a message in the same language while listening to it); and (3)…

Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Lake Depth and Volume

EPA Science Inventory

Global nutrient cycles have been altered by use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutr...

A pulsed load model and its impact on a synchronous-rectifier system

NASA Astrophysics Data System (ADS)

Hou, Pengfei; Xu, Ye; Li, Jianke; Wang, Jinquan; Zhang, Haitao; Yan, Jun; Wang, Chunming; Chen, Jingjing

2017-02-01

The pulsed load has become a developing trend of power loading. Unlike traditional loads, pulsed loads with current abrupt and repeated charges will result in unstable Microgrid operations because of their small capacity and inertia. In this paper, an Average Magnitude Sum Function (AMSF) is proposed to calculate the frequency of the grid, and based on AMSF, the Relative Deviation Rate (RDR) that characterises the impact of pulsed load on the AC side of the grid is defined and its calculation process is described in detail. In addition, the system dynamic characteristics under a pulsed load are analysed using an Insulated Gate Bipolar Transistor (IGBT) to control the on/off state of the resistive load for simulating a pulsed load. Finally, the transient characteristics of a synchronous-rectifier system with a pulsed load are studied and validated experimentally.

Effect of Repeated Screw Joint Closing and Opening Cycles and Cyclic Loading on Abutment Screw Removal Torque and Screw Thread Morphology: Scanning Electron Microscopy Evaluation.

PubMed

Arshad, Mahnaz; Mahgoli, Hosseinali; Payaminia, Leila

To evaluate the effect of repeated screw joint closing and opening cycles and cyclic loading on abutment screw removal torque and screw thread morphology using scanning electron microscopy (SEM). Three groups (n = 10 in each group) of implant-abutment-abutment screw assemblies were created. There were also 10 extra abutment screws as new screws in group 3. The abutment screws were tightened to 12 Ncm with an electronic torque meter; then they were removed and removal torque values were recorded. This sequence was repeated 5 times for group 1 and 15 times for groups 2 and 3. The same screws in groups 1 and 2 and the new screws in group 3 were then tightened to 12 Ncm; this was also followed by screw tightening to 30 Ncm and retightening to 30 Ncm 15 minutes later. Removal torque measurements were performed after screws were subjected to cyclic loading (0.5 × 10⁶ cycles; 1 Hz; 75 N). Moreover, the surface topography of one screw from each group before and after cyclic loading was evaluated with SEM and compared with an unused screw. All groups exhibited reduced removal torque values in comparison to insertion torque in each cycle. However, there was a steady trend of torque loss in each group. A comparison of the last cycle of the groups before loading showed significantly greater torque loss value in the 15th cycle of groups 2 and 3 compared with the fifth cycle of group 1 (P < .05). Nonetheless, torque loss values after loading were not shown to be significantly different from each other. Using a new screw could not significantly increase the value of removal torque. It was concluded that restricting the amount of screw tightening is more important than replacing the screw with a new one when an abutment is definitively placed.

Toward an MRI-based method to measure non-uniform cartilage deformation: an MRI-cyclic loading apparatus system and steady-state cyclic displacement of articular cartilage under compressive loading.

PubMed

Neu, C P; Hull, M L

2003-04-01

Recent magnetic resonance imaging (MRI) techniques have shown potential for measuring non-uniform deformations throughout the volume (i.e. three-dimensional (3D) deformations) in small orthopedic tissues such as articular cartilage. However, to analyze cartilage deformation using MRI techniques, a system is required which can construct images from multiple acquisitions of MRI signals from the cartilage in both the underformed and deformed states. The objectives of the work reported in this article were to 1) design an apparatus that could apply highly repeatable cyclic compressive loads of 400 N and operate in the bore of an MRI scanner, 2) demonstrate that the apparatus and MRI scanner can be successfully integrated to observe 3D deformations in a phantom material, 3) use the apparatus to determine the load cycle necessary to achieve a steady-state deformation response in normal bovine articular cartilage samples using a flat-surfaced and nonporous indentor in unconfined compression. Composed of electronic and pneumatic components, the apparatus regulated pressure to a double-acting pneumatic cylinder so that (1) load-controlled compression cycles were applied to cartilage samples immersed in a saline bath, (2) loading and recovery periods within a cycle varied in time duration, and (3) load magnitude varied so that the stress applied to cartilage samples was within typical physiological ranges. In addition the apparatus allowed gating for MR image acquisition, and operation within the bore of an MRI scanner without creating image artifacts. The apparatus demonstrated high repeatability in load application with a standard deviation of 1.8% of the mean 400 N load applied. When the apparatus was integrated with an MRI scanner programmed with appropriate pulse sequences, images of a phantom material in both the underformed and deformed states were constructed by assembling data acquired through multiple signal acquisitions. Additionally, the number of cycles to reach a steady-state response in normal bovine articular cartilage was 49 for a total cycle duration of 5 seconds, but decreased to 33 and 27 for increasing total cycle durations of 10 and 15 seconds, respectively. Once the steady-state response was achieved, 95% of all displacements were within +/- 7.42 microns of the mean displacement, indicating that the displacement response to the cyclic loads was highly repeatable. With this performance, the MRI-loading apparatus system meets the requirements to create images of articular cartilage from which 3D deformation can be determined.

Working memory dependence of spatial contextual cueing for visual search.

PubMed

Pollmann, Stefan

2018-05-10

When spatial stimulus configurations repeat in visual search, a search facilitation, resulting in shorter search times, can be observed that is due to incidental learning. This contextual cueing effect appears to be rather implicit, uncorrelated with observers' explicit memory of display configurations. Nevertheless, as I review here, this search facilitation due to contextual cueing depends on visuospatial working memory resources, and it disappears when visuospatial working memory is loaded by a concurrent delayed match to sample task. However, the search facilitation immediately recovers for displays learnt under visuospatial working memory load when this load is removed in a subsequent test phase. Thus, latent learning of visuospatial configurations does not depend on visuospatial working memory, but the expression of learning, as memory-guided search in repeated displays, does. This working memory dependence has also consequences for visual search with foveal vision loss, where top-down controlled visual exploration strategies pose high demands on visuospatial working memory, in this way interfering with memory-guided search in repeated displays. Converging evidence for the contribution of working memory to contextual cueing comes from neuroimaging data demonstrating that distinct cortical areas along the intraparietal sulcus as well as more ventral parieto-occipital cortex are jointly activated by visual working memory and contextual cueing. © 2018 The British Psychological Society.

In vitro mechanical fatigue behavior of poly-ɛ-caprolactone macroporous scaffolds for cartilage tissue engineering: Influence of pore filling by a poly(vinyl alcohol) gel.

PubMed

Panadero, J A; Vikingsson, L; Gomez Ribelles, J L; Lanceros-Mendez, S; Sencadas, V

2015-07-01

Polymeric scaffolds used in regenerative therapies are implanted in the damaged tissue and submitted to repeated loading cycles. In the case of articular cartilage engineering, an implanted scaffold is typically subjected to long-term dynamic compression. The evolution of the mechanical properties of the scaffold during bioresorption has been deeply studied in the past, but the possibility of failure due to mechanical fatigue has not been properly addressed. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. In this work fatigue studies of polycaprolactone scaffolds were carried by subjecting the scaffold to repeated compression cycles in conditions simulating the scaffold implanted in the articular cartilage. The behavior of the polycaprolactone sponge with the pores filled with a poly(vinyl alcohol) gel simulating the new formed tissue within the pores was compared with that of the material immersed in water. Results were analyzed with Morrow's criteria for failure and accurate fittings are obtained just up to 200 loading cycles. It is also shown that the presence of poly(vinyl alcohol) increases the elastic modulus of the scaffolds, the effect being more pronounced with increasing the number of freeze/thawing cycles. © 2014 Wiley Periodicals, Inc.

A device for characterising the mechanical properties of the plantar soft tissue of the foot.

PubMed

Parker, D; Cooper, G; Pearson, S; Crofts, G; Howard, D; Busby, P; Nester, C

2015-11-01

The plantar soft tissue is a highly functional viscoelastic structure involved in transferring load to the human body during walking. A Soft Tissue Response Imaging Device was developed to apply a vertical compression to the plantar soft tissue whilst measuring the mechanical response via a combined load cell and ultrasound imaging arrangement. Accuracy of motion compared to input profiles; validation of the response measured for standard materials in compression; variability of force and displacement measures for consecutive compressive cycles; and implementation in vivo with five healthy participants. Static displacement displayed average error of 0.04 mm (range of 15 mm), and static load displayed average error of 0.15 N (range of 250 N). Validation tests showed acceptable agreement compared to a Houndsfield tensometer for both displacement (CMC > 0.99 RMSE > 0.18 mm) and load (CMC > 0.95 RMSE < 4.86 N). Device motion was highly repeatable for bench-top tests (ICC = 0.99) and participant trials (CMC = 1.00). Soft tissue response was found repeatable for intra (CMC > 0.98) and inter trials (CMC > 0.70). The device has been shown to be capable of implementing complex loading patterns similar to gait, and of capturing the compressive response of the plantar soft tissue for a range of loading conditions in vivo. Copyright © 2015. Published by Elsevier Ltd.

Potential regenerative rehabilitation technology: implications of mechanical stimuli to tissue health

PubMed Central

2014-01-01

Background Mechanical loads induced through muscle contraction, vibration, or compressive forces are thought to modulate tissue plasticity. With the emergence of regenerative medicine, there is a need to understand the optimal mechanical environment (vibration, load, or muscle force) that promotes cellular health. To our knowledge no mechanical system has been proposed to deliver these isolated mechanical stimuli in human tissue. We present the design, performance, and utilization of a new technology that may be used to study localized mechanical stimuli on human tissues. A servo-controlled vibration and limb loading system were developed and integrated into a single instrument to deliver vibration, compression, or muscle contractile loads to a single limb (tibia) in humans. The accuracy, repeatability, transmissibility, and safety of the mechanical delivery system were evaluated on eight individuals with spinal cord injury (SCI). Findings The limb loading system was linear, repeatable, and accurate to less than 5, 1, and 1 percent of full scale, respectively, and transmissibility was excellent. The between session tests on individuals with spinal cord injury (SCI) showed high intra-class correlations (>0.9). Conclusions All tests supported that therapeutic loads can be delivered to a lower limb (tibia) in a safe, accurate, and measureable manner. Future collaborations between engineers and cellular physiologists will be important as research programs strive to determine the optimal mechanical environment for developing cells and tissues in humans. PMID:24894666

The effect of ligation on the load deflection characteristics of nickel titanium orthodontic wire.

PubMed

Kasuya, Shugo; Nagasaka, Satoshi; Hanyuda, Ai; Ishimura, Sadao; Hirashita, Ayao

2007-12-01

This study examined the effect of ligation on the load-deflection characteristics of nickel-titanium (NiTi) orthodontic wire. A modified three-point bending system was used for bending the NiTi round wire, which was inserted and ligated in the slots of three brackets, one of which was bonded to each of the three bender rods. Three different ligation methods, stainless steel ligature (SSL), slot lid (SL), and elastomeric ligature (EL), were employed, as well as a control with neither bracket nor ligation (NBL). The tests were repeated five times under each condition. Comparisons were made of load-deflection curve, load at maximum deflection of 2,000 microm, and load at a deflection of 1,500 microm during unloading. Analysis of Variance (ANOVA) and Dunnett's test were conducted to determine method difference (alpha = 0.05). The interaction between deflection and ligation was tested, using repeated-measures ANOVA (alpha = 0.05). The load values of the ligation groups were two to three times greater than the NBL group at a deflection of 1,500 microm during unloading: 4.37 N for EL, 3.90 N for SSL, 3.02 N for SL, and 1.49 N for NBL (P < 0.01). For the EL, a plateau region disappeared in the unloading curve. SL showed the smallest load. The ligation of the bracket wire may make NiTi wire exhibit a significantly heavier load than that traditionally expected. NiTi wire exhibited the majority of its true superelasticity with SL, whereas EL may act as a restraint on its superelasticity.

Activation of Wnt Signaling by Mechanical Loading Is Impaired in the Bone of Old Mice

PubMed Central

Holguin, Nilsson; Brodt, Michael D; Silva, Matthew J

2017-01-01

Aging diminishes bone formation engendered by mechanical loads, but the mechanism for this impairment remains unclear. Because Wnt signaling is required for optimal loading-induced bone formation, we hypothesized that aging impairs the load-induced activation of Wnt signaling. We analyzed dynamic histomorphometry of 5-month-old, 12-month-old, and 22-month-old C57Bl/6JN mice subjected to multiple days of tibial compression and corroborated an age-related decline in the periosteal loading response on day 5. Similarly, 1 day of loading increased periosteal and endocortical bone formation in young-adult (5-month-old) mice, but old (22-month-old) mice were unresponsive. These findings corroborated mRNA expression of genes related to bone formation and the Wnt pathway in tibias after loading. Multiple bouts (3 to 5 days) of loading upregulated bone formation–related genes, e.g., Osx and Col1a1, but older mice were significantly less responsive. Expression of Wnt negative regulators, Sost and Dkk1, was suppressed with a single day of loading in all mice, but suppression was sustained only in young-adult mice. Moreover, multiple days of loading repeatedly suppressed Sost and Dkk1 in young-adult, but not in old tibias. The age-dependent response to loading was further assessed by osteocyte staining for Sclerostin and LacZ in tibia of TOPGAL mice. After 1 day of loading, fewer osteocytes were Sclerostin-positive and, corroboratively, more osteocytes were LacZ-positive (Wnt active) in both 5-month-old and 12-month-old mice. However, although these changes were sustained after multiple days of loading in 5-month-old mice, they were not sustained in 12-month-old mice. Last, Wnt1 and Wnt7b were the most load-responsive of the 19 Wnt ligands. However, 4 hours after a single bout of loading, although their expression was upregulated threefold to 10-fold in young-adult mice, it was not altered in old mice. In conclusion, the reduced bone formation response of aged mice to loading may be due to failure to sustain Wnt activity with repeated loading. PMID:27357062

Distributed Decision Making in a Dynamic Network Environment

DTIC Science & Technology

1990-01-01

protocols, particularly when traffic arrival statistics are varying or unknown, and loads are high. Both nonpreemptive and preemptive repeat disciplines are...The simulation model allows general value functions, continuous time operation, and preemptive or nonpreemptive service. For reasons of tractability... nonpreemptive LIFO, (4) nonpreemptive LIFO with discarding, (5) nonpreemptive HOL, (6) nonpreemp- tive HOL with discarding, (7) preemptive repeat HOL, (8

Law of damage accumulation and fracture criteria in highly filled polymer materials

NASA Astrophysics Data System (ADS)

Bykov, D. L.; Kazakov, A. V.; Konovalov, D. N.; Mel'nikov, V. P.; Milyokhin, Yu. M.; Peleshko, V. A.; Sadovnichii, D. N.

2014-09-01

We present the results of a large series of experiments aimed at the study of laws of damage accumulation and fracture in highly filled polymer materials under loading conditions of various types: monotone, repeated, low- and high-cycle, with varying type of stress state, dynamic (in general, more than 50 programs implemented on specimens from one lot of material). The data obtained in these test allow one to make conclusions about the constitutive role of the attained maximum of strain intensity when estimating the accumulated damage in the process of uniaxial tension by various programs (in particular, an additional cyclic deformation below the preliminary attained strain maximum does not affect the limit values of strain and stress in the subsequent active extension), about the strong influence of the stress state on the deformation and fracture, about the specific features of the nonlinear behavior of the material under the shock loading conditions and its influence on the repeated deformation. All tests are described (with an accuracy acceptable in practical calculations, both with respect to stresses and strains in the process of loading and at the moment of fracture) in the framework of the same model of nonlinear viscoelasticity with the same set of constants. The constants of the proposed model are calculated according to a relatively simple algorithm by using the results of standard uniaxial tension tests with constant values of the strain rate and hydrostatic pressure (each test for 2-3 levels of these parameters chosen from the ranges proposed in applications, each loading lasts until the fracture occurs, and one of the tests contains an intermediate interval of total loading and repeated loading) and one axial shock compression test if there are dynamic problems in the applications. The model is based on the use of the criterion fracture parameter which, in the class of proportional loading processes, is the sum of partial increments of the strain intensity on active segments of the process (where the strain intensity is at its historical maximum) with the form of the stress state and the intensity of strain rates taken into account.

Swarms of repeating stick-slip icequakes triggered by snow loading at Mount Rainier volcano

NASA Astrophysics Data System (ADS)

Allstadt, Kate; Malone, Stephen D.

2014-05-01

We have detected over 150,000 small (M < 1) low-frequency ( 1-5 Hz) repeating earthquakes over the past decade at Mount Rainier volcano, most of which were previously undetected. They are located high (>3000 m) on the glacier-covered edifice and occur primarily in weeklong to monthlong swarms composed of simultaneous distinct families of events. Each family contains up to thousands of earthquakes repeating at regular intervals as often as every few minutes. Mixed polarity first motions, a linear relationship between recurrence interval and event size, and strong correlation between swarm activity and snowfall suggest the source is stick-slip basal sliding of glaciers. The sudden added weight of snow during winter storms triggers a temporary change from smooth aseismic sliding to seismic stick-slip sliding in locations where basal conditions are favorable to frictional instability. Coda wave interferometry shows that source locations migrate over time at glacial speeds, starting out fast and slowing down over time, indicating a sudden increase in sliding velocity triggers the transition to stick-slip sliding. We propose a hypothesis that this increase is caused by the redistribution of basal fluids rather than direct loading because of a 1-2 day lag between snow loading and earthquake activity. This behavior is specific to winter months because it requires the inefficient drainage of a distributed subglacial drainage system. Identification of the source of these frequent signals offers a view of basal glacier processes, discriminates against alarming volcanic noises, documents short-term effects of weather on the cryosphere, and has implications for repeating earthquakes, in general.

Immediate responses to backpack carriage on postural angles in young adults: A crossover randomized self-controlled study with repeated measures.

PubMed

Abaraogu, Ukachukwu O; Ezenwankwo, Elochukwu F; Nwadilibe, Ijeoma B; Nwafor, Geoffrey C; Ugwuele, Bianca O; Uzoh, Pascal C; Ani, Ifunanya; Amarachineke, Kinsley; Atuma, Collins; Ewelunta, Obed

2017-01-01

Heavy backpacks have been associated with various postural changes and consequently musculoskeletal disorders. We evaluated the immediate responses of varying backpack loads on cranio-vertebral angle (CVA), sagittal shoulder angle (SSA) and trunk forward lean (TFL) of young adults between the ages of 18-25 years. This was a 3×3 cross over randomized controlled study with repeated measures among a convenience sample of young adults (n = 30; 50% male, 50% female). Each participant in a standing posture was assessed at four different loads: no backpack, carrying backpack of 5%, 10%, and 15% of body weight (BW). A sagittal photograph was taken of the area of the body corresponding to spinal angle during each of these test conditions to allow for later analysis of postural deviations. Comparisons of the mean deviations of the different postural angles from baseline and between test conditions were made using ANOVA at p≤0.05. Generally, there was a trend toward a decrease in the CVA and TFL with increasing backpack loads. Specifically, a significant decrease was seen for TFL at10% and 15% BW loads when compared with no load condition. In contrast, the decrease in CVA was only significant between no load condition and 15% body weight load. The SSA remained unchanged with backpack weight within 15% BW. Whereas the SSA of young adults may not be upset by an acute loading with a backpack within 15% of body weight, a 15% BW backpack led to more forward posture of the head on the neck. In addition, backpack load as low as 10% BW is enough to cause an immediate forward lean of the trunk.

Summary of Results of Tests Made by Aluminum Research Laboratories of Spot-welded Joints and Structural Elements

NASA Technical Reports Server (NTRS)

HARTMANN E C; Stickley, G W

1942-01-01

Available information concerning spot welding as a means of joining aluminum-alloy parts has been summarized and comparisons have been made of the relative merits of spot-welded and riveted aluminum-alloy structural elements. The results indicated that spot welding was as satisfactory as riveting insofar as resistance to static loads is concerned. Spot welds showed slightly lower resistance to impact loads but definitely lower resistance to repeated loads than rivets.

Voluntary task switching under load: contribution of top-down and bottom-up factors in goal-directed behavior.

PubMed

Demanet, Jelle; Verbruggen, Frederick; Liefooghe, Baptist; Vandierendonck, André

2010-06-01

The present study investigated the relative contribution of bottom-up and top-down control to task selection in the voluntary task-switching (VTS) procedure. In order to manipulate the efficiency of top-down control, a concurrent working memory load was imposed during VTS. In three experiments, bottom-up factors, such as stimulus repetitions, repetition of irrelevant information, and stimulus-task associations, were introduced in order to investigate their influence on task selection. We observed that the tendency to repeat tasks was stronger under load, suggesting that top-down control counteracts the automatic tendency to repeat tasks. The results also indicated that task selection can be guided by several elements in the environment, but that only the influence of stimulus repetitions depends on the efficiency of top-down control. The theoretical implications of these findings are discussed within the interplay between top-down and bottom-up control that underlies the voluntary selection of tasks.

Contact Electrification of Individual Dielectric Microparticles Measured by Optical Tweezers in Air.

PubMed

Park, Haesung; LeBrun, Thomas W

2016-12-21

We measure charging of single dielectric microparticles after interaction with a glass substrate using optical tweezers to control the particle, measure its charge with a sensitivity of a few electrons, and precisely contact the particle with the substrate. Polystyrene (PS) microparticles adhered to the substrate can be selected based on size, shape, or optical properties and repeatedly loaded into the optical trap using a piezoelectric (PZT) transducer. Separation from the substrate leads to charge transfer through contact electrification. The charge on the trapped microparticles is measured from the response of the particle motion to a step excitation of a uniform electric field. The particle is then placed onto a target location of the substrate in a controlled manner. Thus, the triboelectric charging profile of the selected PS microparticle can be measured and controlled through repeated cycles of trap loading followed by charge measurement. Reversible optical trap loading and manipulation of the selected particle leads to new capabilities to study and control successive and small changes in surface interactions.

Blast Load Simulator Experiments for Computational Model Validation: Report 2

DTIC Science & Technology

2017-02-01

repeatability. The uncertainty in the experimental pressures and impulses was evaluated by computing 95% confidence intervals on the results. DISCLAIMER: The...Experiment uncertainty The uncertainty in the experimental pressure and impulse was evaluated for the five replicate experiments for which, as closely as...comparisons were made among the replicated experiments to evaluate repeatability. The uncertainty in the experimental pressures and impulses was

Passive Orbital Disconnect Strut (PODS 3) structural test program

NASA Technical Reports Server (NTRS)

Parmley, R. T.

1985-01-01

A passive orbital disconnect strut (PODS-3) was analyzed structurally and thermally. Development tests on a graphite/epoxy orbit tube and S glass epoxy launch tube provided the needed data to finalize the design. A detailed assembly procedure was prepared. One strut was fabricated. Shorting loads in both the axial and lateral direction (vs. load angle and location) were measured. The strut was taken to design limit loads at both ambient and 78 K (cold end only). One million fatigue cycles were performed at predicted STS loads (half in tension, half in compression) with the cold end at 78 K. The fatigue test was repeated at design limit loads. Six struts were then fabricated and tested as a system. Axial loads, side loads, and simulated asymmetric loads due to temperature gradients around the vacuum shell were applied. Shorting loads were measured for all tests.

Repeat-Associated Fission Yeast-Like Regional Centromeres in the Ascomycetous Budding Yeast Candida tropicalis

PubMed Central

Chatterjee, Gautam; Sankaranarayanan, Sundar Ram; Guin, Krishnendu; Thattikota, Yogitha; Padmanabhan, Sreedevi; Siddharthan, Rahul; Sanyal, Kaustuv

2016-01-01

The centromere, on which kinetochore proteins assemble, ensures precise chromosome segregation. Centromeres are largely specified by the histone H3 variant CENP-A (also known as Cse4 in yeasts). Structurally, centromere DNA sequences are highly diverse in nature. However, the evolutionary consequence of these structural diversities on de novo CENP-A chromatin formation remains elusive. Here, we report the identification of centromeres, as the binding sites of four evolutionarily conserved kinetochore proteins, in the human pathogenic budding yeast Candida tropicalis. Each of the seven centromeres comprises a 2 to 5 kb non-repetitive mid core flanked by 2 to 5 kb inverted repeats. The repeat-associated centromeres of C. tropicalis all share a high degree of sequence conservation with each other and are strikingly diverged from the unique and mostly non-repetitive centromeres of related Candida species—Candida albicans, Candida dubliniensis, and Candida lusitaniae. Using a plasmid-based assay, we further demonstrate that pericentric inverted repeats and the underlying DNA sequence provide a structural determinant in CENP-A recruitment in C. tropicalis, as opposed to epigenetically regulated CENP-A loading at centromeres in C. albicans. Thus, the centromere structure and its influence on de novo CENP-A recruitment has been significantly rewired in closely related Candida species. Strikingly, the centromere structural properties along with role of pericentric repeats in de novo CENP-A loading in C. tropicalis are more reminiscent to those of the distantly related fission yeast Schizosaccharomyces pombe. Taken together, we demonstrate, for the first time, fission yeast-like repeat-associated centromeres in an ascomycetous budding yeast. PMID:26845548

Properties of axially loaded implant-abutment assemblies using digital holographic interferometry analysis.

PubMed

Brozović, Juraj; Demoli, Nazif; Farkaš, Nina; Sušić, Mato; Alar, Zeljko; Gabrić Pandurić, Dragana

2014-03-01

The aim of this study was to (i) obtain the force-related interferometric patterns of loaded dental implant-abutment assemblies differing in diameter and brand using digital holographic interferometry (DHI) and (ii) determine the influence of implant diameter on the extent of load-induced implant deformation by quantifying and comparing the obtained interferometric data. Experiments included five implant brands (Ankylos, Astra Tech, blueSKY, MIS and Straumann), each represented by a narrow and a wide diameter implant connected to a corresponding abutment. A quasi-Fourier setup with a 25mW helium-neon laser was used for interferometric measurements in the cervical 5mm of the implants. Holograms were recorded in two conditions per measurement: a 10N preloaded and a measuring-force loaded assembly, resulting with an interferogram. This procedure was repeated throughout the whole process of incremental axial loading, from 20N to 120N. Each measurement series was repeated three times for each assembly, with complete dismantling of the implant-loading device in between. Additional software analyses calculated deformation data. Deformations were presented as mean values±standard deviations. Statistical analysis was performed using linear mixed effects modeling in R's lme4 package. Implants exhibited linear deformation patterns. The wide diameter group had lower mean deformation values than the narrow diameter group. The diameter significantly affected the deformation throughout loading sessions. This study gained in vitro implant performance data, compared the deformations in implant bodies and numerically stated the biomechanical benefits of wider diameter implants. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Simulation of Crack Propagation in Engine Rotating Components under Variable Amplitude Loading

NASA Technical Reports Server (NTRS)

Bonacuse, P. J.; Ghosn, L. J.; Telesman, J.; Calomino, A. M.; Kantzos, P.

1998-01-01

The crack propagation life of tested specimens has been repeatedly shown to strongly depend on the loading history. Overloads and extended stress holds at temperature can either retard or accelerate the crack growth rate. Therefore, to accurately predict the crack propagation life of an actual component, it is essential to approximate the true loading history. In military rotorcraft engine applications, the loading profile (stress amplitudes, temperature, and number of excursions) can vary significantly depending on the type of mission flown. To accurately assess the durability of a fleet of engines, the crack propagation life distribution of a specific component should account for the variability in the missions performed (proportion of missions flown and sequence). In this report, analytical and experimental studies are described that calibrate/validate the crack propagation prediction capability ]or a disk alloy under variable amplitude loading. A crack closure based model was adopted to analytically predict the load interaction effects. Furthermore, a methodology has been developed to realistically simulate the actual mission mix loading on a fleet of engines over their lifetime. A sequence of missions is randomly selected and the number of repeats of each mission in the sequence is determined assuming a Poisson distributed random variable with a given mean occurrence rate. Multiple realizations of random mission histories are generated in this manner and are used to produce stress, temperature, and time points for fracture mechanics calculations. The result is a cumulative distribution of crack propagation lives for a given, life limiting, component location. This information can be used to determine a safe retirement life or inspection interval for the given location.

Goal equivalent manifold analysis of task performance in non-specific LBP and healthy subjects during repetitive trunk movement: Effect of load, velocity, symmetry.

PubMed

Chehrehrazi, Mahshid; Sanjari, Mohammad Ali; Mokhtarinia, Hamid Reza; Jamshidi, Ali Ashraf; Maroufi, Nader; Parnianpour, Mohamad

2017-01-01

Motor abundance allows reliability of motor performance despite its variability. The nature of this variability provides important information on the flexibility of control strategies. This feature of control may be affected by low back pain (LPB) and trunk flexion/extension conditions. Goal equivalent manifold (GEM) analysis was used to quantify the ability to exploit motor abundance during repeated trunk flexion/extension in healthy individuals and people with chronic non-specific LBP (CNSLBP). Kinematic data were collected from 22 healthy volunteers and 22 CNSLBP patients during metronomically timed, repeated trunk flexion/extension in three conditions of symmetry, velocity, and loading; each at two levels. A goal function for the task was defined as maintaining a constant movement time at each cycle. Given the GEM, flexibility index and performance index were calculated respectively as amounts of goal-equivalent variability and the ratio of goal-equivalent to non-goal-equivalent variability. CNSLBP group was as similar as healthy individuals in both flexibility index (p=0.41) and performance index (p=0.24). Performance index was higher in asymmetric (p<0.001), high velocity (p<0.001), and loaded (p=0.006) conditions. Performance and flexibility in using motor abundance were influenced by repeated trunk flexion/extension conditions. However, these measures were not significantly affected by CNSLBP. Copyright © 2016 Elsevier B.V. All rights reserved.

Multi-planar bending properties of lumbar intervertebral joints following cyclic bending.

PubMed

Chow, Daniel H K; Luk, Keith D K; Holmes, Andrew D; Li, Xing-Fei; Tam, Steven C W

2004-02-01

To assess the changes in the multi-planar bending properties of intervertebral joints following cyclic bending along different directions. An in vitro biomechanical study using porcine lumbar motion segments. Repeated bending has been suggested as part of the etiology of gradual prolapse of the intervertebral disc, but the multi-planar changes in bending properties following cyclic loading have not been examined in detail. Porcine lumbar motion segments were subject to 1500 cycles of bending along directions of 0 degrees (flexion), 30 degrees, 60 degrees, or 90 degrees (right lateral bending). The multi-planar bending moments and hysteresis energies were recorded before loading and after various cycle numbers. Repeated bending at 30 degrees and 60 degrees resulted in greater decreases in mean bending moment and hysteresis energy than bending at 0 degrees or 90 degrees. No significant differences were seen between loading groups for the change in bending moment along the anterior testing directions, but significant differences were observed in the posterior and lateral testing directions, with bending at 30 degrees causing a significantly greater decrease in bending moment in the postero-lateral directions. The change in mechanical properties of porcine intervertebral joints due to cyclic bending depend on the direction of loading and the direction in which the properties are measured. Loading at 30 degrees provokes the most marked changes in bending moment and hysteresis energy.

Remotely Adjustable Hydraulic Pump

NASA Technical Reports Server (NTRS)

Kouns, H. H.; Gardner, L. D.

1987-01-01

Outlet pressure adjusted to match varying loads. Electrohydraulic servo has positioned sleeve in leftmost position, adjusting outlet pressure to maximum value. Sleeve in equilibrium position, with control land covering control port. For lowest pressure setting, sleeve shifted toward right by increased pressure on sleeve shoulder from servovalve. Pump used in aircraft and robots, where hydraulic actuators repeatedly turned on and off, changing pump load frequently and over wide range.

Ultra Lightweight Mirror Fabrication Technology

DTIC Science & Technology

1983-12-01

supported on-back at three points, 120 degrees apart at the 0.7 radial zone. The surface deformation, produced by a one-g gravity load applied to a...reliable and repeatable simulation of zero- gravity . 16 * ....- • • ~~~~~~. ,. ........ ...... ....... o....... .. -.. . ...... " . - tively... gravity loading. The stability of this mirru, over these environmental conditions is considered to be excellent. The interferometrically measured surface

Homemade battery-operated multi-barreled muzzle-loading gun.

PubMed

Ramiah, R; Thirunavukkarasu, G

2003-11-01

In a recent shootout by a terrorist group against a law enforcement agency, some unusual firearms were seized. On examination, these firearms were found to be homemade, battery-operated, multi-barreled muzzle-loading guns, analogous to a repeater. Reference to battery-operated firearms is rather scanty in the literature. Hence, the unique design features, electrical circuit, and the operation system of these unusual guns are described.

The dopamine receptor D4 gene and familial loading interact with perceived parenting in predicting externalizing behavior problems in early adolescence: the TRacking Adolescents' Individual Lives Survey (TRAILS).

PubMed

Marsman, Rianne; Oldehinkel, Albertine J; Ormel, Johan; Buitelaar, Jan K

2013-08-30

Although externalizing behavior problems show in general a high stability over time, the course of externalizing behavior problems may vary from individual to individual. Our main goal was to investigate the predictive role of parenting on externalizing behavior problems. In addition, we investigated the potential moderating role of gender and genetic risk (operationalized as familial loading of externalizing behavior problems (FLE), and presence or absence of the dopamine receptor D4 (DRD4) 7-repeat and 4-repeat allele, respectively). Perceived parenting (rejection, emotional warmth, and overprotection) and FLE were assessed in a population-based sample of 1768 10- to 12-year-old adolescents. Externalizing behavior problems were assessed at the same age and 212 years later by parent report (CBCL) and self-report (YSR). DNA was extracted from blood samples. Parental emotional warmth predicted lower, and parental overprotection and rejection predicted higher levels of externalizing behavior problems. Whereas none of the parenting factors interacted with gender and the DRD4 7-repeat allele, we did find interaction effects with FLE and the DRD4 4-repeat allele. That is, the predictive effect of parental rejection was only observed in adolescents from low FLE families and the predictive effect of parental overprotection was stronger in adolescents not carrying the DRD4 4-repeat allele. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Performance of Asphalt Concrete Wearing Course (AC-WC) Utilizing Reclaimed Asphalt Pavement from Cold Milling Bound with 80/100 Pen Asphalt

NASA Astrophysics Data System (ADS)

Thanya, I. N. A.; Suweda, I. W.; Putra, G. K.

2018-03-01

Demands on natural aggregate materials for road pavement can be reduced by utilizing reclaimed asphalt pavement (RAP). This research was aimed at evaluating the performance of AC-WC mixture using RAP materials from cold milling, bound with 80/100 pen asphalt. The RAP aggregate gradation was adjusted by adding the required amount of natural aggregates to meet the specification in Indonesia. The RAP and added aggregates were hotmixed and compacted with Marshall hummer at 2×75 blows. The asphalt content were varied. It was found that the optimum asphalt content was 6.05 % with the following Marshall characteristics: stability 1237.08 kg; flow 3.36 mm; Marshall quotient 324,73kg/mm; void in mix (VIM) 3,360%; void in mineral aggregate (VMA) 15.103; and void filled with bitumen (VFB) 77.759% and residual stability 91.04; all met the Indonesian specification. The cantabro abration loss (CAL) at 30°C was 9,02%. The indirect tensile stiffness modulus (ITSM) at 20 °C was 7961.4 MPa; dynamic creep with 100 kPa pressure at 40°C gave slope 0.0112 microsstrain/pulse which is suitable for heavy load traffic. The fatigue test results was obtained at increased stress level, i.e. at 900, 1100, and 1300 kPa. Based on the equation derived from the fatigue strain and repeated loading relationship, at 100 microstrain (με) the repeated load was 434,661.58 times, and at one million (106) repeated loading, the samples could withstand strain of 92,38 microstrain. The performance of the samples were overall better than AC-WC mixture using virgin aggregates bound with 60/70 pen asphalt.

Implementation of a Smeared Crack Band Model in a Micromechanics Framework

NASA Technical Reports Server (NTRS)

Pineda, Evan J.; Bednarcyk, Brett A.; Waas, Anthony M.; Arnold, Steven M.

2012-01-01

The smeared crack band theory is implemented within the generalized method of cells and high-fidelity generalized method of cells micromechanics models to capture progressive failure within the constituents of a composite material while retaining objectivity with respect to the size of the discretization elements used in the model. An repeating unit cell containing 13 randomly arranged fibers is modeled and subjected to a combination of transverse tension/compression and transverse shear loading. The implementation is verified against experimental data (where available), and an equivalent finite element model utilizing the same implementation of the crack band theory. To evaluate the performance of the crack band theory within a repeating unit cell that is more amenable to a multiscale implementation, a single fiber is modeled with generalized method of cells and high-fidelity generalized method of cells using a relatively coarse subcell mesh which is subjected to the same loading scenarios as the multiple fiber repeating unit cell. The generalized method of cells and high-fidelity generalized method of cells models are validated against a very refined finite element model.

Progressive Failure of a Unidirectional Fiber-Reinforced Composite Using the Method of Cells: Discretization Objective Computational Results

NASA Technical Reports Server (NTRS)

Pineda, Evan J.; Bednarcyk, Brett A.; Waas, Anthony M.; Arnold, Steven M.

2012-01-01

The smeared crack band theory is implemented within the generalized method of cells and high-fidelity generalized method of cells micromechanics models to capture progressive failure within the constituents of a composite material while retaining objectivity with respect to the size of the discretization elements used in the model. An repeating unit cell containing 13 randomly arranged fibers is modeled and subjected to a combination of transverse tension/compression and transverse shear loading. The implementation is verified against experimental data (where available), and an equivalent finite element model utilizing the same implementation of the crack band theory. To evaluate the performance of the crack band theory within a repeating unit cell that is more amenable to a multiscale implementation, a single fiber is modeled with generalized method of cells and high-fidelity generalized method of cells using a relatively coarse subcell mesh which is subjected to the same loading scenarios as the multiple fiber repeating unit cell. The generalized method of cells and high-fidelity generalized method of cells models are validated against a very refined finite element model.

Dynamic strength of cylindrical fiber-glass shells and basalt plastic shells under multiple explosive loading

NASA Astrophysics Data System (ADS)

Syrunin, M. A.; Fedorenko, A. G.

2006-08-01

We have shown experimentally that, for cylindrical shells made of oriented fiberglass platic and basalt plastic there exists a critical level of deformations, at which a structure sustains a given number of explosions from the inside. The magnitude of critical deformation for cylindrical fiberglass shells depends linearly on the logarithm of the number of loads that cause failure. For a given type of fiberglass, there is a limiting level of explosive action, at which the number of loads that do not lead to failure can be sufficiently large (more than ˜ 102). This level is attained under loads, which are an order of magnitude lower than the limiting loads under a single explosive action. Basalt plastic shells can be repeatedly used even at the loads, which cause deformation by ˜ 30-50% lower than the safe value ˜ 3.3.5% at single loading.

Role of Information Anxiety and Information Load on Processing of Prescription Drug Information Leaflets.

PubMed

Bapat, Shweta S; Patel, Harshali K; Sansgiry, Sujit S

2017-10-16

In this study, we evaluate the role of information anxiety and information load on the intention to read information from prescription drug information leaflets (PILs). These PILs were developed based on the principals of information load and consumer information processing. This was an experimental prospective repeated measures study conducted in the United States where 360 (62% response rate) university students (>18 years old) participated. Participants were presented with a scenario followed by exposure to the three drug product information sources used to operationalize information load. The three sources were: (i) current practice; (ii) pre-existing one-page text only; and (iii) interventional one-page prototype PILs designed for the study. Information anxiety was measured as anxiety experienced by the individual when encountering information. The outcome variable of intention to read PILs was defined as the likelihood that the patient will read the information provided in the leaflets. A survey questionnaire was used to capture the data and the objectives were analyzed by performing a repeated measures MANOVA using SAS version 9.3. When compared to current practice and one-page text only leaflets, one-page PILs had significantly lower scores on information anxiety ( p < 0.001) and information load ( p < 0.001). The intention to read was highest and significantly different ( p < 0.001) for PILs as compared to current practice or text only leaflets. Information anxiety and information load significantly impacted intention to read ( p < 0.001). Newly developed PILs increased patient's intention to read and can help in improving the counseling services provided by pharmacists.

Role of Information Anxiety and Information Load on Processing of Prescription Drug Information Leaflets

PubMed Central

Bapat, Shweta S.; Patel, Harshali K.; Sansgiry, Sujit S.

2017-01-01

In this study, we evaluate the role of information anxiety and information load on the intention to read information from prescription drug information leaflets (PILs). These PILs were developed based on the principals of information load and consumer information processing. This was an experimental prospective repeated measures study conducted in the United States where 360 (62% response rate) university students (>18 years old) participated. Participants were presented with a scenario followed by exposure to the three drug product information sources used to operationalize information load. The three sources were: (i) current practice; (ii) pre-existing one-page text only; and (iii) interventional one-page prototype PILs designed for the study. Information anxiety was measured as anxiety experienced by the individual when encountering information. The outcome variable of intention to read PILs was defined as the likelihood that the patient will read the information provided in the leaflets. A survey questionnaire was used to capture the data and the objectives were analyzed by performing a repeated measures MANOVA using SAS version 9.3. When compared to current practice and one-page text only leaflets, one-page PILs had significantly lower scores on information anxiety (p < 0.001) and information load (p < 0.001). The intention to read was highest and significantly different (p < 0.001) for PILs as compared to current practice or text only leaflets. Information anxiety and information load significantly impacted intention to read (p < 0.001). Newly developed PILs increased patient’s intention to read and can help in improving the counseling services provided by pharmacists. PMID:29035337

Ascorbic acid prevents vascular dysfunction induced by oral glucose load in healthy subjects.

PubMed

De Marchi, Sergio; Prior, Manlio; Rigoni, Anna; Zecchetto, Sara; Rulfo, Fanny; Arosio, Enrico

2012-01-01

To examine the effects of oral glucose load on forearm circulatory regulation before and after ascorbic acid administration in healthy subjects. Microcirculation study with laser Doppler was performed at the hand in basal conditions, after ischemia and after acetylcholine and nitroprusside; strain gauge plethysmography was performed at basal and after ischemia. The tests were repeated in the same sequence 2 hour after oral administration of glucose (75 g). The subjects were randomised for administration of ascorbic acid (1 g bid) or placebo (sodium bicarbonate 1 g bid) for 10 days. After that, the tests were repeated before and after a new oral glucose load. Blood pressure and heart rate were monitored. Macrocirculatory flux, pressure values and heart rate were unvaried throughout the study. The glucose load caused a reduction in the hyperemic peak flow with laser Doppler and plethysmography; it reduced flux recovery time and hyperemic curve area after ischemia; acetylcholine elicited a minor increase in flux with laser Doppler. The response to nitroprusside was unvaried after glucose load as compared to basal conditions. Treatment with ascorbic acid prevented the decrease in hyperemia after glucose, detected with laser Doppler and plethysmography. Ascorbic acid prevented the decreased response to acetylcholine after glucose, the response to nitroprusside was unaffected by ascorbic acid. Results after placebo were unvaried. Oral glucose load impairs endothelium dependent dilation and hyperaemia at microcirculation, probably via oxidative stress; ascorbic acid can prevent it. Copyright © 2011 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.

Biaxial Mechanical Testing of Posterior Sclera using High-Resolution Ultrasound Speckle Tracking for Strain Measurements

PubMed Central

Cruz-Perez, Benjamin; Tang, Junhua; Morris, Hugh J.; Palko, Joel R.; Pan, Xueliang; Hart, Richard T.; Liu, Jun

2014-01-01

This study aimed to characterize the mechanical responses of the sclera, the white outer coat of the eye, under equal-biaxial loading with unrestricted shear. An ultrasound speckle tracking technique was used to measure tissue deformation through sample thickness, expanding the capabilities of surface strain techniques. Eight porcine scleral samples were tested within 72 hours postmortem. High resolution ultrasound scans of scleral cross-sections along the two loading axes were acquired at 25 consecutive biaxial load levels. An additional repeat of the biaxial loading cycle was performed to measure a third normal strain emulating a strain gauge rosette for calculating the in-plane shear. The repeatability of the strain measurements during identical biaxial ramps was evaluated. A correlation-based ultrasound speckle tracking algorithm was used to compute the displacement field and determine the distributive strains in the sample cross-sections. A Fung type constitutive model including a shear term was used to determine the material constants of each individual specimen by fitting the model parameters to the experimental stress-strain data. A non-linear stress-strain response was observed in all samples. The meridian direction had significantly larger strains than the circumferential direction during equal-biaxial loadings (P’s<0.05). The stiffness along the two directions were also significantly different (P=0.02) but highly correlated (R2=0.8). These results showed that the mechanical properties of the porcine sclera were nonlinear and anisotropic under biaxial loading. This work has also demonstrated the feasibility of using ultrasound speckle tracking for strain measurements during mechanical testing. PMID:24438767

46 CFR 169.683 - Overcurrent protection, general.

Code of Federal Regulations, 2013 CFR

2013-10-01

... time delay; (2) Instantaneous short circuit protection; and (3) Repeated opening of the circuit in... above the full-load rating for continuous rated machines or the overload rating for special rated machines. ...

46 CFR 169.683 - Overcurrent protection, general.

Code of Federal Regulations, 2014 CFR

2014-10-01

... time delay; (2) Instantaneous short circuit protection; and (3) Repeated opening of the circuit in... above the full-load rating for continuous rated machines or the overload rating for special rated machines. ...

46 CFR 169.683 - Overcurrent protection, general.

Code of Federal Regulations, 2012 CFR

2012-10-01

... time delay; (2) Instantaneous short circuit protection; and (3) Repeated opening of the circuit in... above the full-load rating for continuous rated machines or the overload rating for special rated machines. ...

Development of Human Posture Simulation Method for Assessing Posture Angles and Spinal Loads

PubMed Central

Lu, Ming-Lun; Waters, Thomas; Werren, Dwight

2015-01-01

Video-based posture analysis employing a biomechanical model is gaining a growing popularity for ergonomic assessments. A human posture simulation method of estimating multiple body postural angles and spinal loads from a video record was developed to expedite ergonomic assessments. The method was evaluated by a repeated measures study design with three trunk flexion levels, two lift asymmetry levels, three viewing angles and three trial repetitions as experimental factors. The study comprised two phases evaluating the accuracy of simulating self and other people’s lifting posture via a proxy of a computer-generated humanoid. The mean values of the accuracy of simulating self and humanoid postures were 12° and 15°, respectively. The repeatability of the method for the same lifting condition was excellent (~2°). The least simulation error was associated with side viewing angle. The estimated back compressive force and moment, calculated by a three dimensional biomechanical model, exhibited a range of 5% underestimation. The posture simulation method enables researchers to simultaneously quantify body posture angles and spinal loading variables with accuracy and precision comparable to on-screen posture matching methods. PMID:26361435

Effect of repeated earthquake on inelastic moment resisting concrete frame

NASA Astrophysics Data System (ADS)

Tahara, R. M. K.; Majid, T. A.; Zaini, S. S.; Faisal, A.

2017-10-01

This paper investigates the response of inelastic moment resisting concrete building under repeated earthquakes. 2D models consist of 3-storey, 6-storey and 9-storey representing low to medium rise building frame were designed using seismic load and ductility class medium (DCM) according to the requirements set by Euro Code 8. Behaviour factor and stiffness degradation were also taken into consideration. Seven sets of real repeated earthquakes as opposed to artificial earthquakes data were used. The response of the frame was measured in terms of the inter-storey drift and maximum displacement. By adopting repeated earthquake, the recorded mean IDR increased in the range of 3% - 21%. Similarly, in the case of maximum displacement, the values also increased from 20 mm to 40 mm. The findings concluded that the effect of using repeated earthquake in seismic analysis considerably influenced the inter-storey drift and the maximum displacement.

Repeatability Modeling for Wind-Tunnel Measurements: Results for Three Langley Facilities

NASA Technical Reports Server (NTRS)

Hemsch, Michael J.; Houlden, Heather P.

2014-01-01

Data from extensive check standard tests of seven measurement processes in three NASA Langley Research Center wind tunnels are statistically analyzed to test a simple model previously presented in 2000 for characterizing short-term, within-test and across-test repeatability. The analysis is intended to support process improvement and development of uncertainty models for the measurements. The analysis suggests that the repeatability can be estimated adequately as a function of only the test section dynamic pressure over a two-orders- of-magnitude dynamic pressure range. As expected for low instrument loading, short-term coefficient repeatability is determined by the resolution of the instrument alone (air off). However, as previously pointed out, for the highest dynamic pressure range the coefficient repeatability appears to be independent of dynamic pressure, thus presenting a lower floor for the standard deviation for all three time frames. The simple repeatability model is shown to be adequate for all of the cases presented and for all three time frames.

Analysis and Modeling of Process of Residual Deformations Accumulation in Soils and Granular Materials

NASA Astrophysics Data System (ADS)

Aleksandrov, A. S.; Dolgih, G. V.; Kalinin, A. L.

2017-11-01

It is established that under the influence of repeated loads the process of plastic deformation in soils and discrete materials is hereditary. To perform the mathematical modeling of plastic deformation, the authors applied the integral equation by solution of which they manage to obtain the power and logarithmic dependencies connecting plastic deformation with the number of repeated loads, the parameters of the material and components of the stress tensor in the principal axes. It is shown that these dependences generalize a number of models proposed earlier in Russia and abroad. Based on the analysis of the experimental data obtained during material testing in the dynamic devices of triaxial compression at different values of the stress deviator, the coefficients in the proposed models of deformation are determined. The authors determined the application domain for logarithmic and degree dependences.

Study on stress-strain response of multi-phase TRIP steel under cyclic loading

NASA Astrophysics Data System (ADS)

Dan, W. J.; Hu, Z. G.; Zhang, W. G.; Li, S. H.; Lin, Z. Q.

2013-12-01

The stress-strain response of multi-phase TRIP590 sheet steel is studied in cyclic loading condition at room temperature based on a cyclic phase transformation model and a multi-phase mixed kinematic hardening model. The cyclic martensite transformation model is proposed based on the shear-band intersection, where the repeat number, strain amplitude and cyclic frequency are used to control the phase transformation process. The multi-phase mixed kinematic hardening model is developed based on the non-linear kinematic hardening rule of per-phase. The parameters of transformation model are identified with the relationship between the austenite volume fraction and the repeat number. The parameters in Kinematic hardening model are confirmed by the experimental hysteresis loops in different strain amplitude conditions. The responses of hysteresis loop and stress amplitude are evaluated by tension-compression data.

Early changes in Achilles tendon behaviour in vivo following downhill backwards walking.

PubMed

Joseph, C W; Bradshaw, E J; Furness, T P; Kemp, J; Clark, R A

2016-01-01

Downhill backwards walking causes repeated, cyclical loading of the muscle-tendon unit. The effect this type of repeated loading has on the mechanical behaviour of the Achilles tendon is presently unknown. This study aimed to investigate the biomechanical response of the Achilles tendon aponeurosis complex following a downhill backwards walking protocol. Twenty active males (age: 22.3 ± 3.0 years; mass: 74.7 ± 5.6 kg; height: 1.8 ± 0.7 m) performed 60 min of downhill (8.5°), backwards walking on a treadmill at -0.67 m · s(-1). Data were collected before, immediately post, and 24-, 48- and 168-h post-downhill backwards walking. Achilles tendon aponeurosis elongation, strain and stiffness were measured using ultrasonography. Muscle force decreased immediately post-downhill backward walking (P = 0.019). There were increases in Achilles tendon aponeurosis stiffness at 24-h post-downhill backward walking (307 ± 179.6 N · mm(-1), P = 0.004), and decreases in Achilles tendon aponeurosis strain during maximum voluntary contraction at 24 (3.8 ± 1.7%, P = 0.008) and 48 h (3.9 ± 1.8%, P = 0.002) post. Repeated cyclical loading of downhill backwards walking affects the behaviour of the muscle-tendon unit, most likely by altering muscle compliance, and these changes result in tendon stiffness increases.

Effects of graded load of artificial gravity on cardiovascular functions in humans.

PubMed

Iwase, Satoshi; Fu, Qi; Narita, Kenichi; Morimoto, Eiichi; Takada, Hiroki; Mano, Tadaaki

2002-12-01

An artificial gravity and ergometric exercise loading device for human use was manufactured. It has the capacity of a max 2 G-load at the heart level, and a max 150 W of work-load. Eight subjects (six completed) were subjected to four repeated trials with or without 20 W ergometric exercise. Anti-G score, defined as the G-load x running time to the endpoint, was significantly higher in the exercise trials than standing trials. Heart rate (HR), mean arterial pressure (MAP), thoracic fluid index (TFI) were significantly superior during the exercise trials. Artificial gravity by centrifuge at 1.2 or 1.4 G with 40 or 60 W of ergometric workload may be an excellent countermeasure against cardiovascular deconditioning after long exposure to microgravity.

Strain accumulation in bituminous binders under repeated creep-recovery loading predicted from small-amplitude oscillatory shear (SAOS) experiments

NASA Astrophysics Data System (ADS)

Laukkanen, Olli-Ville; Winter, H. Henning

2017-11-01

The creep-recovery (CR) test starts out with a period of shearing at constant stress (creep) and is followed by a period of zero-shear stress where some of the accumulated shear strain gets reversed. Linear viscoelasticity (LVE) allows one to predict the strain response to repeated creep-recovery (RCR) loading from measured small-amplitude oscillatory shear (SAOS) data. Only the relaxation and retardation time spectra of a material need to be known and these can be determined from SAOS data. In an application of the Boltzmann superposition principle (BSP), the strain response to RCR loading can be obtained as a linear superposition of the strain response to many single creep-recovery tests. SAOS and RCR data were collected for several unmodified and modified bituminous binders, and the measured and predicted RCR responses were compared. Generally good agreement was found between the measured and predicted strain accumulation under RCR loading. However, in the case of modified binders, the strain accumulation was slightly overestimated (≤20% relative error) due to the insufficient SAOS information at long relaxation times. Our analysis also demonstrates that the evolution in the strain response under RCR loading, caused by incomplete recovery, can be reasonably well predicted by the presented methodology. It was also shown that the outlined modeling framework can be used, as a first approximation, to estimate the rutting resistance of bituminous binders by predicting the values of the Multiple Stress Creep Recovery (MSCR) test parameters.

Stress, Allostatic Load, Catecholamines, and Other Neurotransmitters in Neurodegenerative Diseases

PubMed Central

2016-01-01

As populations age, the prevalence of geriatric neurodegenerative diseases will increase. These diseases generally are multifactorial, arising from complex interactions among genes, environment, concurrent morbidities, treatments, and time. This essay provides a concept for the pathogenesis of Lewy body diseases such as Parkinson disease, by considering them in the context of allostasis and allostatic load. Allostasis reflects active, adaptive processes that maintain apparent steady states, via multiple, interacting effectors regulated by homeostatic comparators—“homeostats.” Stress can be defined as a condition or state in which a sensed discrepancy between afferent information and a setpoint for response leads to activation of effectors, reducing the discrepancy. “Allostatic load” refers to the consequences of sustained or repeated activation of mediators of allostasis. From the analogy of an idling car, the revolutions per minute of the engine can be maintained at any of a variety of levels (allostatic states). Just as allostatic load (cumulative wear and tear) reflects design and manufacturing variations, byproducts of combustion, and time, eventually leading to engine breakdown, allostatic load in catecholaminergic neurons might eventually lead to Lewy body diseases. Central to the argument is that catecholaminergic neurons leak vesicular contents into the cytoplasm continuously during life and that catecholamines in the neuronal cytoplasm are autotoxic. These neurons therefore depend on vesicular sequestration to limit autotoxicity of cytosolic transmitter. Parkinson disease might be a disease of the elderly because of allostatic load, which depends on genetic predispositions, environmental exposures, repeated stress-related catecholamine release, and time. PMID:22297542

Stress, Allostatic Load, Catecholamines, and Other Neurotransmitters in Neurodegenerative Diseases

PubMed Central

2017-01-01

As populations age, the prevalence of geriatric neurodegenerative diseases will increase. These diseases generally are multifactorial, arising from complex interactions among genes, environment, concurrent morbidities, treatments, and time. This essay provides a concept for the pathogenesis of Lewy body diseases such as Parkinson disease, by considering them in the context of allostasis and allostatic load. Allostasis reflects active, adaptive processes that maintain apparent steady states, via multiple, interacting effectors regulated by homeostatic comparators—“homeostats.” Stress can be defined as a condition or state in which a sensed discrepancy between afferent information and a setpoint for response leads to activation of effectors, reducing the discrepancy. “Allostatic load” refers to the consequences of sustained or repeated activation of mediators of allostasis. From the analogy of an idling car, the revolutions per minute of the engine can be maintained at any of a variety of levels (allostatic states). Just as allostatic load (cumulative wear and tear) reflects design and manufacturing variations, byproducts of combustion, and time, eventually leading to engine breakdown, allostatic load in catecholaminergic neurons might eventually lead to Lewy body diseases. Central to the argument is that catecholaminergic neurons leak vesicular contents into the cytoplasm continuously during life and that catecholamines in the neuronal cytoplasm are autotoxic. These neurons therefore depend on vesicular sequestration to limit autotoxicity of cytosolic transmitter. Parkinson disease might be a disease of the elderly because of allostatic load, which depends on genetic predispositions, environmental exposures, repeated stress-related catecholamine release, and time. PMID:21615193

An Observation of Repeating Events at local asperities during a Laboratory Stick-slip Experiment of a Saw-cut Cylindrical Lucite Sample

NASA Astrophysics Data System (ADS)

Gu, C.; Mighani, S.; Prieto, G. A.; Mok, U.; Evans, J. B.; Hager, B. H.; Toksoz, M. N.

2017-12-01

Repeating earthquakes have been found in subduction zones and interpreted as repeated ruptures of small local asperities. Repeating earthquakes have also been found in oil/gas fields, interpreted as the reactivation of pre-existing faults due to fluid injection/extraction. To mimic the fault rupture of a fault with local asperities, we designed a "stick-slip" experiment using a saw-cut cylindrical Lucite sample, which had sharp localized ridges parallel to the strike of the fault plane. The sample was subjected to conventional triaxial loading with a constant confining pressure of 10 MPa. The axial load was then increased to 6 MPa at a constant rate of 0.12 MPa/sec until the sliding occurred along the fault plane. Ultrasonic acoustic emissions (AEs) were monitored with eight PZT sensors. Two cycles of AEs were detected with the occurrence rate that decreased from the beginning to the end of each cycle, while the relative magnitudes increased. Correlation analysis indicated that these AEs were clustered into two groups - those with frequency content between 200-300kHz and a second group with frequency content between 10-50kHz. The locations of the high-frequency events, with almost identical waveforms, show that these events are from the sharp localized ridges on the saw-cut plane. The locations of the low-frequency events show an approaching process to the high-frequency events for each cycle. In this single experiment, there was a correlation of the proximity of the low-frequency events with the subsequent triggering of large high-frequency repeating events.

Detection of Unexpected High Correlations between Balance Calibration Loads and Load Residuals

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Volden, T.

2014-01-01

An algorithm was developed for the assessment of strain-gage balance calibration data that makes it possible to systematically investigate potential sources of unexpected high correlations between calibration load residuals and applied calibration loads. The algorithm investigates correlations on a load series by load series basis. The linear correlation coefficient is used to quantify the correlations. It is computed for all possible pairs of calibration load residuals and applied calibration loads that can be constructed for the given balance calibration data set. An unexpected high correlation between a load residual and a load is detected if three conditions are met: (i) the absolute value of the correlation coefficient of a residual/load pair exceeds 0.95; (ii) the maximum of the absolute values of the residuals of a load series exceeds 0.25 % of the load capacity; (iii) the load component of the load series is intentionally applied. Data from a baseline calibration of a six-component force balance is used to illustrate the application of the detection algorithm to a real-world data set. This analysis also showed that the detection algorithm can identify load alignment errors as long as repeat load series are contained in the balance calibration data set that do not suffer from load alignment problems.

A high-speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, D. E.

1990-01-01

The earlier study made by Jacobson and Hamrock on the cavitation of liquid lubricant films in a dynamically loaded journal bearing was repeated with a quartz sleeve, which was more rigid than the Polymethylmethacrylate (PMMA) sleeve used previously. Various improvements of the test rig were made concomitantly so that the experimental errors could be better controlled and assessed. The updated speed photography experiment and its results are described.

A high speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, D. E.

1991-01-01

The earlier study made by Jacobson and Hamrock on the cavitation of liquid lubricant films in a dynamically loaded journal bearing was repeated with a quartz sleeve, which was more rigid than the Polymethylmethacrylate (PMMA) sleeve used previously. Various improvements of the test rig were made concomitantly so that the experimental errors could be better controlled and assessed. The updated speed photography experiment and its results are described.

NCEL (Naval Civil Engineering Lab.) Ocean Platforms Seminar.

DTIC Science & Technology

1983-11-01

propagating and evanescent modes. The resulting pressure field from both the scattered and radiated waves are integrated over the submerged surface of...fully submerged value. At the same time, an impact load occurs due to water entry of the member. Repeated loading of this type can result in fatigue...pronounced on deeply submerged caissons than on surface-piercing caissons. In the case of surface piercing caissons where the nonlinear effects tend to

Prediction of resilient modulus from soil index properties.

DOT National Transportation Integrated Search

2004-11-01

Subgrade soil characterization in terms of Resilient Modulus (MR) has become crucial for pavement design. For a new : design, MR values are generally obtained by conducting repeated load triaxial tests on reconstituted/undisturbed cylindrical : speci...

Prediction of resilient modulus from soil index properties

DOT National Transportation Integrated Search

2004-11-01

Subgrade soil characterization in terms of Resilient Modulus (MR) has become crucial for pavement design. For a new design, MR values are generally obtained by conducting repeated load triaxial tests on reconstituted/undisturbed cylindrical specimens...

High Velocity Gas Gun

NASA Technical Reports Server (NTRS)

1988-01-01

A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

Falling weight deflectometer for estimating subgrade resilient moduli.

DOT National Transportation Integrated Search

2003-12-01

Subgrade soil characterization expressed in terms of resilient modulus, MR, has become crucial for pavement design. For : new pavement design, MR values are generally obtained by conducting repeated load triaxial tests on reconstituted/undisturbed : ...

Mechanical Characterization of the Human Lumbar Intervertebral Disc Subjected to Impact Loading Conditions

NASA Astrophysics Data System (ADS)

Jamison, David, IV

Low back pain is a large and costly problem in the United States. Several working populations, such as miners, construction workers, forklift operators, and military personnel, have an increased risk and prevalence of low back pain compared to the general population. This is due to exposure to repeated, transient impact shocks, particularly while operating vehicles or other machinery. These shocks typically do not cause acute injury, but rather lead to pain and injury over time. The major focus in low back pain is often the intervertebral disc, due to its role as the major primary load-bearing component along the spinal column. The formation of a reliable standard for human lumbar disc exposure to repeated transient shock could potentially reduce injury risk for these working populations. The objective of this project, therefore, is to characterize the mechanical response of the lumbar intervertebral disc subjected to sub-traumatic impact loading conditions using both cadaveric and computational models, and to investigate the possible implications of this type of loading environment for low back pain. Axial, compressive impact loading events on Naval high speed boats were simulated in the laboratory and applied to human cadaveric specimen. Disc stiffness was higher and hysteresis was lower than quasi-static loading conditions. This indicates a shift in mechanical response when the disc is under impact loads and this behavior could be contributing to long-term back pain. Interstitial fluid loss and disc height changes were shown to affect disc impact mechanics in a creep study. Neutral zone increased, while energy dissipation and low-strain region stiffness decreased. This suggests that the disc has greater clinical instability during impact loading with progressive creep and fluid loss, indicating that time of day should be considered for working populations subjected to impact loads. A finite element model was developed and validated against cadaver specimen subjected to impacts in the laboratory. Analysis showed greater total von Mises stress and pore pressure in the components of the disc under transient shocks compared to static or quasi-static loading. These findings support the idea that impact shocks cause a change in mechanical response and are potentially damaging to the disc in the long term.

Safety Identifying of Integral Abutment Bridges under Seismic and Thermal Loads

PubMed Central

Easazadeh Far, Narges; Barghian, Majid

2014-01-01

Integral abutment bridges (IABs) have many advantages over conventional bridges in terms of strength and maintenance cost. Due to the integrity of these structures uniform thermal and seismic loads are known important ones on the structure performance. Although all bridge design codes consider temperature and earthquake loads separately in their load combinations for conventional bridges, the thermal load is an “always on” load and, during the occurrence of an earthquake, these two important loads act on bridge simultaneously. Evaluating the safety level of IABs under combination of these loads becomes important. In this paper, the safety of IABs—designed by AASHTO LRFD bridge design code—under combination of thermal and seismic loads is studied. To fulfill this aim, first the target reliability indexes under seismic load have been calculated. Then, these analyses for the same bridge under combination of thermal and seismic loads have been repeated and the obtained reliability indexes are compared with target indexes. It is shown that, for an IAB designed by AASHTO LRFD, the indexes have been reduced under combined effects. So, the target level of safety during its design life is not provided and the code's load combination should be changed. PMID:25405232

Development of an optically-based tension-indicating implanted orthopedic screw with a luminescent spectral ruler

NASA Astrophysics Data System (ADS)

Ravikumar, Nakul; Rogalski, Melissa M.; Benza, Donny; Lake, Joshua; Urban, Matthew; Pelham, Hunter; Anker, Jeffrey N.; DesJardins, John D.

2017-03-01

An orthopaedic screw was designed with an optical tension-indicator to non-invasively quantify screw tension and monitor the load sharing between the bone and the implant. The screw both applies load to the bone, and measures this load by reporting the strain on the screw. The screw contains a colorimetric optical encoder that converts axial strain into colorimetric changes visible through the head of the screw, or luminescent spectral changes that are detected through tissue. Screws were tested under cyclic mechanical loading to mimic in-vivo conditions to verify the sensitivity, repeatability, and reproducibility of the sensor. In the absence to tissue, color was measured using a digital camera as a function of axial load on a stainless steel cannulated (hollow) orthopedic screw, modified by adding a passive colorimetric strain gauge through the central hole. The sensor was able to quantify clinically-relevant bone healing strains. The sensor exhibited good repeatability and reproducibility but also displayed hysteresis due to the internal mechanics of the screw. The strain indicator was also modified for measurement through tissue by replacing the reflective colorimetric sensor with a low-background X-ray excited optical luminescence signal. Luminescent spectra were acquired through 6 mm of chicken breast tissue. Overall, this research shows feasibility for a unique device which quantifies the strain on an orthopedic screw. Future research will involve reducing hysteresis by changing the mechanism of strain transduction in the screw, miniaturizing the luminescent strain gauge, monitoring bending as well as tension, using alternative luminescent spectral rulers based upon near infrared fluorescence or upconversion luminescence, and application to monitoring changes in pretension and load sharing during bone healing.

Reproducibility of the Internal Load and Performance-Based Responses to Simulated Amateur Boxing.

PubMed

Thomson, Edward D; Lamb, Kevin L

2017-12-01

Thomson, ED and Lamb, KL. Reproducibility of the internal load and performance-based responses to simulated amateur boxing. J Strength Cond Res 31(12): 3396-3402, 2017-The aim of this study was to examine the reproducibility of the internal load and performance-based responses to repeated bouts of a three-round amateur boxing simulation protocol (boxing conditioning and fitness test [BOXFIT]). Twenty-eight amateur boxers completed 2 familiarization trials before performing 2 complete trials of the BOXFIT, separated by 4-7 days. To characterize the internal load, mean (HRmean) and peak (HRpeak) heart rate, breath-by-breath oxygen uptake (V[Combining Dot Above]O2), aerobic energy expenditure, excess carbon dioxide production (CO2excess), and ratings of perceived exertion were recorded throughout each round, and blood lactate determined post-BOXFIT. Additionally, an indication of the performance-based demands of the BOXFIT was provided by a measure of acceleration of the punches thrown in each round. Analyses revealed there were no significant differences (p > 0.05) between repeated trials in any round for all dependent measures. The typical error (coefficient variation %) for all but 1 marker of internal load (CO2excess) was 1.2-16.5% and reflected a consistency that was sufficient for the detection of moderate changes in variables owing to an intervention. The reproducibility of the punch accelerations was high (coefficient of variance % range = 2.1-2.7%). In general, these findings suggest that the internal load and performance-based efforts recorded during the BOXFIT are reproducible and, thereby, offer practitioners a method by which meaningful changes impacting on performance could be identified.

Portable FWD (Prima 100) for in-situ subgrade evaluation.

DOT National Transportation Integrated Search

2006-06-01

Subgrade soil characterization measured in terms of resilient modulus, MR, has been a prerequisite for pavement design. For new pavement design, MR is obtained by conducting repeated load triaxial tests on reconstituted/undisturbed cylindrical specim...

On the role of working memory in spatial contextual cueing.

PubMed

Travis, Susan L; Mattingley, Jason B; Dux, Paul E

2013-01-01

The human visual system receives more information than can be consciously processed. To overcome this capacity limit, we employ attentional mechanisms to prioritize task-relevant (target) information over less relevant (distractor) information. Regularities in the environment can facilitate the allocation of attention, as demonstrated by the spatial contextual cueing paradigm. When observers are exposed repeatedly to a scene and invariant distractor information, learning from earlier exposures enhances the search for the target. Here, we investigated whether spatial contextual cueing draws on spatial working memory resources and, if so, at what level of processing working memory load has its effect. Participants performed 2 tasks concurrently: a visual search task, in which the spatial configuration of some search arrays occasionally repeated, and a spatial working memory task. Increases in working memory load significantly impaired contextual learning. These findings indicate that spatial contextual cueing utilizes working memory resources.

Latex improvement of recycled asphalt pavement

NASA Astrophysics Data System (ADS)

Drennon, C.

1982-08-01

The performance of a single unmodified milled recycled asphalt concrete was compared to milled asphalt concrete modified by addition of three types of rubber latex. Latex was added at 2, 3, 5, and 8 percent latex by weight of asphalt in the asphalt concrete. Lattices used were a styrene butadiene (SBR), a natural rubber (NR), an acrylonitrile butadiene (NBR), and four varieties of out of specification SBR lattices. Marshall tests, while indecisive, showed a modest improvement in properties of SBR and NR added material at 3 and 5 percent latex. Addition of NBR latex caused deterioration in Marshall stability and flow over that of control. Repeated load tests were run using the indirect tensile test, analyzed by the VESYS program, which computes life of pavements. Repeated load tests showed improvement in asphalt concrete life when 3 and 5 percent SBR was added. Improvement was also shown by the out of specification SBR.

Study on the repeatability of manufacturing nano-silica (SiO2) reinforced composite laminates

NASA Astrophysics Data System (ADS)

Prince Jeya Lal, L.; Ramesh, S.; Natarajan, Elango

2018-04-01

Repeatability to manufacture nano-silica reinforced composite laminates with consistent mechanical properties is studied. In this study, composite laminates are manufactured by hand layup and there after mechanical properties of the laminates are evaluated under tensile and flexural loading conditions. Composite laminates are fabricated and tested under equivalent conditions. Plain weave E-Glass fabric and epoxy LY556 are used as reinforcement and matrix. Nano-silica of size 17nm is used as filler. To enhance the reliability of composite characterization, utmost care is taken to avoid defects like voids, surface defects and under-saturations. Homogeneous distribution of nano silica in matrix is analyzed using TEM study. Inconsistencies in mechanical properties are quantified by coefficient of variation. In this study, the coefficient of variation is estimated in terms of break load for tensile test is 4.45 and for flexural test is 2.27 and is well within the limits.

Matrix multiplication operations using pair-wise load and splat operations

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

Eichenberger, Alexandre E.; Gschwind, Michael K.; Gunnels, John A.

Mechanisms for performing a matrix multiplication operation are provided. A vector load operation is performed to load a first vector operand of the matrix multiplication operation to a first target vector register. A pair-wise load and splat operation is performed to load a pair of scalar values of a second vector operand and replicate the pair of scalar values within a second target vector register. An operation is performed on elements of the first target vector register and elements of the second target vector register to generate a partial product of the matrix multiplication operation. The partial product is accumulatedmore » with other partial products and a resulting accumulated partial product is stored. This operation may be repeated for a second pair of scalar values of the second vector operand.« less

Preliminary results from fatigue tests with reference to operational statistics

NASA Technical Reports Server (NTRS)

Gassner, E

1950-01-01

Simple elements were subjected to repeated loads of variable ampliture, chosen in such a way that they may be regarded as approximations to the operational loads (gust and maneuver) experienced by an airplane. The effect of varying some parameters was investigated briefly. Some discussion is given of the question whether a design according to current (1938 German) requirements for static strength is adequate from the fatigue point of view, and existing requirements on fatigue strength are compared,

Development of load spectra for Airbus A330/A340 full scale fatigue tests

NASA Technical Reports Server (NTRS)

Schmidt, H.-J.; Nielsen, Thomas

1994-01-01

For substantiation of the recently certified medium range Airbus A330 and long range A340 the full scale fatigue tests are in progress. The airframe structures of both aircraft types are tested by one set of A340 specimens. The development of the fatigue test spectra for the two major test specimens which are the center fuselage and wing test and the rear fuselage test is described. The applied test load spectra allow a realistic simulation of flight, ground and pressurization loads and the finalization of the tests within the pre-defined test period. The paper contains details about the 1 g and incremental flight and ground loads and the establishment of the flight-by-flight test program, i.e., the definition of flight types, distribution of loads within the flights and randomization of flight types in repeated blocks. Special attention is given to procedures applied for acceleration of the tests, e.g. omission of lower spectrum loads and a general increase of all loads by ten percent.

The effect of distributed virtual reality simulation training on cognitive load during subsequent dissection training.

PubMed

Andersen, Steven Arild Wuyts; Konge, Lars; Sørensen, Mads Sølvsten

2018-05-07

Complex tasks such as surgical procedures can induce excessive cognitive load (CL), which can have a negative effect on learning, especially for novices. To investigate if repeated and distributed virtual reality (VR) simulation practice induces a lower CL and higher performance in subsequent cadaveric dissection training. In a prospective, controlled cohort study, 37 residents in otorhinolaryngology received VR simulation training either as additional distributed practice prior to course participation (intervention) (9 participants) or as standard practice during the course (control) (28 participants). Cognitive load was estimated as the relative change in secondary-task reaction time during VR simulation and cadaveric procedures. Structured distributed VR simulation practice resulted in lower mean reaction times (32% vs. 47% for the intervention and control group, respectively, p < 0.01) as well as a superior final-product performance during subsequent cadaveric dissection training. Repeated and distributed VR simulation causes a lower CL to be induced when the learning situation is increased in complexity. A suggested mechanism is the formation of mental schemas and reduction of the intrinsic CL. This has potential implications for surgical skills training and suggests that structured, distributed training be systematically implemented in surgical training curricula.

Dynamic permeability in fault damage zones induced by repeated coseismic fracturing events

NASA Astrophysics Data System (ADS)

Aben, F. M.; Doan, M. L.; Mitchell, T. M.

2017-12-01

Off-fault fracture damage in upper crustal fault zones change the fault zone properties and affect various co- and interseismic processes. One of these properties is the permeability of the fault damage zone rocks, which is generally higher than the surrounding host rock. This allows large-scale fluid flow through the fault zone that affects fault healing and promotes mineral transformation processes. Moreover, it might play an important role in thermal fluid pressurization during an earthquake rupture. The damage zone permeability is dynamic due to coseismic damaging. It is crucial for earthquake mechanics and for longer-term processes to understand how the dynamic permeability structure of a fault looks like and how it evolves with repeated earthquakes. To better detail coseismically induced permeability, we have performed uniaxial split Hopkinson pressure bar experiments on quartz-monzonite rock samples. Two sample sets were created and analyzed: single-loaded samples subjected to varying loading intensities - with damage varying from apparently intact to pulverized - and samples loaded at a constant intensity but with a varying number of repeated loadings. The first set resembles a dynamic permeability structure created by a single large earthquake. The second set resembles a permeability structure created by several earthquakes. After, the permeability and acoustic velocities were measured as a function of confining pressure. The permeability in both datasets shows a large and non-linear increase over several orders of magnitude (from 10-20 up to 10-14 m2) with an increasing amount of fracture damage. This, combined with microstructural analyses of the varying degrees of damage, suggests a percolation threshold. The percolation threshold does not coincide with the pulverization threshold. With increasing confining pressure, the permeability might drop up to two orders of magnitude, which supports the possibility of large coseismic fluid pulses over relatively large distances along a fault. Also, a relatively small threshold could potentially increase permeability in a large volume of rock, given that previous earthquakes already damaged these rocks.

Repeatability of a dynamic rollover test system.

PubMed

Seppi, Jeremy; Toczyski, Jacek; Crandall, Jeff R; Kerrigan, Jason

2016-08-17

The goal of this study was to characterize the rollover crash and to evaluate the repeatability of the Dynamic Rollover Test System (DRoTS) in terms of initial roof-to-ground contact conditions, vehicle kinematics, road reaction forces, and vehicle deformation. Four rollover crash tests were performed on 2 pairs of replicate vehicles (2 sedan tests and 2 compact multipurpose van [MPV] tests), instrumented with a custom inertial measurement unit to measure vehicle and global kinematics and string potentiometers to measure pillar deformation time histories. The road was instrumented with load cells to measure reaction loads and an optical encoder to measure road velocity. Laser scans of pre- and posttest vehicles were taken to provide detailed deformation maps. Initial conditions were found to be repeatable, with the largest difference seen in drop height of 20 mm; roll rate, roll angle, pitch angle, road velocity, drop velocity, mass, and moment of inertia were all 7% different or less. Vehicle kinematics (roll rate, road speed, roll and pitch angle, global Z' acceleration, and global Z' velocity) were similar throughout the impact; however, differences were seen in the sedan tests because of a vehicle fixation problem and differences were seen in the MPV tests due to an increase in reaction forces during leading side impact likely caused by disparities in roll angle (3° difference) and mass properties (2.2% in moment of inertia [MOI], 53.5 mm difference in center of gravity [CG] location). Despite those issues, kinetic and deformation measures showed a high degree of repeatability, which is necessary for assessing injury risk in rollover because roof strength positively correlates with injury risk (Brumbelow 2009). Improvements of the test equipment and matching mass properties will ensure highly repeatable initial conditions, vehicle kinematics, kinetics, and deformations.

Effects of forming history on crash simulation of a vehicle

NASA Astrophysics Data System (ADS)

Gökler, M. İ.; Doğan, U. Ç.; Darendeliler, H.

2016-08-01

The effects of forming on the crash simulation of a vehicle have been investigated by considering the load paths produced by sheet metal forming process. The frontal crash analysis has been performed by the finite element method, firstly without considering the forming history, to find out the load paths that absorb the highest energy. The sheet metal forming simulations have been realized for each structural component of the load paths and the frontal crash analysis has been repeated by including forming history. The results of the simulations with and without forming effects have been compared with the physical crash test results available in literature.

Culvert rating guide : August 2009.

DOT National Transportation Integrated Search

2009-08-01

The purpose of this Culvert Rating Guide is to present a clear, repeatable and valid procedure for Texas : Department of Transportation (TxDOT) engineers and their consultants to use for load rating culverts in the TxDOT : roadway system. : The Ameri...

Evaluation of HEPA vacuum cleaning and dry steam cleaning in reducing levels of polycyclic aromatic hydrocarbons and house dust mite allergens in carpets

PubMed Central

Yu, Chang Ho; Yiin, Lih-Ming; Fan, Zhi-Hua (Tina); Rhoads, George G.

2014-01-01

Dry steam cleaning, which has gained recent attention as an effective method to reduce house dust mite (HDM) allergen concentration and loading in carpets, was evaluated in this study for its efficacy in lowering levels of polycyclic aromatic hydrocarbons (PAHs) as well as HDM allergens. Fifty urban homes with wail-to-wall carpets, mostly low-income and with known lead contamination, were studied in 2003 and 2004. Two carpet-cleaning interventions were compared: Repeated HEPA (High Efficiency Particulate Air filtered) vacuuming alone and repeated HEPA vacuuming supplemented with dry steam cleaning. Vacuum samples were collected to measure carpet loading of dust and contaminants immediately before and after cleaning. Paired comparisons were conducted to evaluate the effectiveness of the cleaning protocols in reducing the levels of PAHs and HDM allergens in carpets. The results indicated that both cleaning methods substantially reduced the loading of PAHs and HDM allergens as well as dust in carpets (p < 0.0001). The reductions in loading of dust (64.4%), PAHs (69.1%), and HDM allergens (85.5%), by dry steam cleaning plus repetitive HEPA vacuuming were larger than the reductions by regular HEPA vacuuming alone: dust (55.5%), PAHs (58.6%), and HDM allergens (80.8%), although the difference was statistically significant only for dust and PAHs. We conclude that intensive HEPA vacuum cleaning substantially reduced the loading of PAHs and HDM allergens in carpets in these urban homes and that dry steam cleaning added modestly to cleaning effectiveness. PMID:19137159

Pneumatic Microvalve-Based Hydrodynamic Sample Injection for High-Throughput, Quantitative Zone Electrophoresis in Capillaries

PubMed Central

2015-01-01

A hybrid microchip/capillary electrophoresis (CE) system was developed to allow unbiased and lossless sample loading and high-throughput repeated injections. This new hybrid CE system consists of a poly(dimethylsiloxane) (PDMS) microchip sample injector featuring a pneumatic microvalve that separates a sample introduction channel from a short sample loading channel, and a fused-silica capillary separation column that connects seamlessly to the sample loading channel. The sample introduction channel is pressurized such that when the pneumatic microvalve opens briefly, a variable-volume sample plug is introduced into the loading channel. A high voltage for CE separation is continuously applied across the loading channel and the fused-silica capillary separation column. Analytes are rapidly separated in the fused-silica capillary, and following separation, high-sensitivity MS detection is accomplished via a sheathless CE/ESI-MS interface. The performance evaluation of the complete CE/ESI-MS platform demonstrated that reproducible sample injection with well controlled sample plug volumes could be achieved by using the PDMS microchip injector. The absence of band broadening from microchip to capillary indicated a minimum dead volume at the junction. The capabilities of the new CE/ESI-MS platform in performing high-throughput and quantitative sample analyses were demonstrated by the repeated sample injection without interrupting an ongoing separation and a linear dependence of the total analyte ion abundance on the sample plug volume using a mixture of peptide standards. The separation efficiency of the new platform was also evaluated systematically at different sample injection times, flow rates, and CE separation voltages. PMID:24865952

Pneumatic Microvalve-Based Hydrodynamic Sample Injection for High-Throughput, Quantitative Zone Electrophoresis in Capillaries

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

Kelly, Ryan T.; Wang, Chenchen; Rausch, Sarah J.

2014-07-01

A hybrid microchip/capillary CE system was developed to allow unbiased and lossless sample loading and high throughput repeated injections. This new hybrid CE system consists of a polydimethylsiloxane (PDMS) microchip sample injector featuring a pneumatic microvalve that separates a sample introduction channel from a short sample loading channel and a fused silica capillary separation column that connects seamlessly to the sample loading channel. The sample introduction channel is pressurized such that when the pneumatic microvalve opens briefly, a variable-volume sample plug is introduced into the loading channel. A high voltage for CE separation is continuously applied across the loading channelmore » and the fused silica capillary separation column. Analytes are rapidly separated in the fused silica capillary with high resolution. High sensitivity MS detection after CE separation is accomplished via a sheathless CE/ESI-MS interface. The performance evaluation of the complete CE/ESI-MS platform demonstrated that reproducible sample injection with well controlled sample plug volumes could be achieved by using the PDMS microchip injector. The absence of band broadening from microchip to capillary indicated a minimum dead volume at the junction. The capabilities of the new CE/ESI-MS platform in performing high throughput and quantitative sample analyses were demonstrated by the repeated sample injection without interrupting an ongoing separation and a good linear dependence of the total analyte ion abundance on the sample plug volume using a mixture of peptide standards. The separation efficiency of the new platform was also evaluated systematically at different sample injection times, flow rates and CE separation voltages.« less

Repeat testing of low-level HIV-1 RNA: assay performance and implementation in clinical trials.

PubMed

White, Kirsten; Garner, Will; Wei, Lilian; Eron, Joseph J; Zhong, Lijie; Miller, Michael D; Martin, Hal; Plummer, Andrew; Tran-Muchowski, Cecilia; Lindstrom, Kim; Porter, James; Piontkowsky, David; Light, Angela; Reiske, Heinz; Quirk, Erin

2018-05-15

Assess the performance of HIV-1 RNA repeat testing of stored samples in cases of low-level viremia during clinical trials. Prospective and retrospective analysis of randomized clinical trial samples and reference standards. To evaluate assay variability of the Cobas AmpliPrep/Cobas TaqMan HIV-1 Test, v2.0, three separate sources of samples were utilized: the World Health Organization (WHO) HIV reference standard (assayed using 50 independent measurements at six viral loads <200 copies/ml), retrospective analysis of four to six aliquots of plasma samples from four clinical trial participants, and prospective repeat testing of 120 samples from participants in randomized trials with low-level viremia. The TaqMan assay on the WHO HIV-1 RNA standards at viral loads <200 copies/ml performed within the expected variability according to assay specifications. However, standards with low viral loads of 36 and 18 copies/ml reported values of ≥ 50 copies/ml in 66 and 18% of tests, respectively. In participants treated with antiretrovirals who had unexpected viremia of 50-200 copies/ml after achieving <50 copies/ml, retesting of multiple aliquots of stored plasma found <50 copies/ml in nearly all cases upon retesting (14/15; 93%). Repeat testing was prospectively implemented in four clinical trials for all samples with virologic rebound of 50-200 copies/ml (n = 120 samples from 92 participants) from which 42% (50/120) had a retest result of less than 50 copies/ml and 58% (70/120) retested ≥ 50 copies/ml. The TaqMan HIV-1 RNA assay shows variability around 50 copies/ml that affects clinical trial results and may impact clinical practice. In participants with a history of viral load suppression, unexpected low-level viremia may be because of assay variability rather than low drug adherence or true virologic failure. Retesting a stored aliquot of the same sample may differentiate between assay variability and virologic failure as the source of viremia. This retesting strategy could save time, money, and anxiety for patients and their providers, as well as decrease follow-up clinic visits without increasing the risk of virologic failure and resistance development.

Micromechanics Fatigue Damage Analysis Modeling for Fabric Reinforced Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Min, J. B.; Xue, D.; Shi, Y.

2013-01-01

A micromechanics analysis modeling method was developed to analyze the damage progression and fatigue failure of fabric reinforced composite structures, especially for the brittle ceramic matrix material composites. A repeating unit cell concept of fabric reinforced composites was used to represent the global composite structure. The thermal and mechanical properties of the repeating unit cell were considered as the same as those of the global composite structure. The three-phase micromechanics, the shear-lag, and the continuum fracture mechanics models were integrated with a statistical model in the repeating unit cell to predict the progressive damages and fatigue life of the composite structures. The global structure failure was defined as the loss of loading capability of the repeating unit cell, which depends on the stiffness reduction due to material slice failures and nonlinear material properties in the repeating unit cell. The present methodology is demonstrated with the analysis results evaluated through the experimental test performed with carbon fiber reinforced silicon carbide matrix plain weave composite specimens.

Billions of basepairs of recently expanded, repetitive sequences are eliminated from the somatic genome during copepod development.

PubMed

Sun, Cheng; Wyngaard, Grace; Walton, D Brian; Wichman, Holly A; Mueller, Rachel Lockridge

2014-03-11

Chromatin diminution is the programmed deletion of DNA from presomatic cell or nuclear lineages during development, producing single organisms that contain two different nuclear genomes. Phylogenetically diverse taxa undergo chromatin diminution--some ciliates, nematodes, copepods, and vertebrates. In cyclopoid copepods, chromatin diminution occurs in taxa with massively expanded germline genomes; depending on species, germline genome sizes range from 15 - 75 Gb, 12-74 Gb of which are lost from pre-somatic cell lineages at germline--soma differentiation. This is more than an order of magnitude more sequence than is lost from other taxa. To date, the sequences excised from copepods have not been analyzed using large-scale genomic datasets, and the processes underlying germline genomic gigantism in this clade, as well as the functional significance of chromatin diminution, have remained unknown. Here, we used high-throughput genomic sequencing and qPCR to characterize the germline and somatic genomes of Mesocyclops edax, a freshwater cyclopoid copepod with a germline genome of ~15 Gb and a somatic genome of ~3 Gb. We show that most of the excised DNA consists of repetitive sequences that are either 1) verifiable transposable elements (TEs), or 2) non-simple repeats of likely TE origin. Repeat elements in both genomes are skewed towards younger (i.e. less divergent) elements. Excised DNA is a non-random sample of the germline repeat element landscape; younger elements, and high frequency DNA transposons and LINEs, are disproportionately eliminated from the somatic genome. Our results suggest that germline genome expansion in M. edax reflects explosive repeat element proliferation, and that billions of base pairs of such repeats are deleted from the somatic genome every generation. Thus, we hypothesize that chromatin diminution is a mechanism that controls repeat element load, and that this load can evolve to be divergent between tissue types within single organisms.

Billions of basepairs of recently expanded, repetitive sequences are eliminated from the somatic genome during copepod development

PubMed Central

2014-01-01

Background Chromatin diminution is the programmed deletion of DNA from presomatic cell or nuclear lineages during development, producing single organisms that contain two different nuclear genomes. Phylogenetically diverse taxa undergo chromatin diminution — some ciliates, nematodes, copepods, and vertebrates. In cyclopoid copepods, chromatin diminution occurs in taxa with massively expanded germline genomes; depending on species, germline genome sizes range from 15 – 75 Gb, 12–74 Gb of which are lost from pre-somatic cell lineages at germline – soma differentiation. This is more than an order of magnitude more sequence than is lost from other taxa. To date, the sequences excised from copepods have not been analyzed using large-scale genomic datasets, and the processes underlying germline genomic gigantism in this clade, as well as the functional significance of chromatin diminution, have remained unknown. Results Here, we used high-throughput genomic sequencing and qPCR to characterize the germline and somatic genomes of Mesocyclops edax, a freshwater cyclopoid copepod with a germline genome of ~15 Gb and a somatic genome of ~3 Gb. We show that most of the excised DNA consists of repetitive sequences that are either 1) verifiable transposable elements (TEs), or 2) non-simple repeats of likely TE origin. Repeat elements in both genomes are skewed towards younger (i.e. less divergent) elements. Excised DNA is a non-random sample of the germline repeat element landscape; younger elements, and high frequency DNA transposons and LINEs, are disproportionately eliminated from the somatic genome. Conclusions Our results suggest that germline genome expansion in M. edax reflects explosive repeat element proliferation, and that billions of base pairs of such repeats are deleted from the somatic genome every generation. Thus, we hypothesize that chromatin diminution is a mechanism that controls repeat element load, and that this load can evolve to be divergent between tissue types within single organisms. PMID:24618421

Effects of Wheel-Load Spatial Repeatability on Road Damage : A Literature Review

DOT National Transportation Integrated Search

1998-09-01

Concerns about growing governmental budgetary deficits and the awareness of the economic advantages associated with a safe and well-maintained road infrastructure are two of the main reasons for devoting attention to better understanding the problem ...

Human pelvis loading rig for static and dynamic stress analysis.

PubMed

Zanetti, Elisabetta M; Bignardi, Cristina; Audenino, Alberto L

2012-01-01

This work is aimed at designing and constructing a loading rig for the synthetic hemi-pelvis; this system has been conceived with the goal of applying differently oriented articular forces in order to experimentally test the stress distribution and the stability of surgical reconstructions like, for example, hip arthroplasty or pelvic fixation. This device can be interfaced with a usual loading machine; it preserves the anatomy of the hemi-pelvis; it is simply constrained and it allows the simulation of all physiologic activities. Moreover, the visual accessibility of the peri-acetabular area has been guaranteed and this is imperative in order to be able to perform full-field analyses like a thermoelastic or photoelastic stress analysis. First experimental trials have shown a good repeatability of loading-unloading cycles (<1.2%), a low hysteresis (<2.4%) and a good dynamic behaviour (up to 10 Hz loading frequencies).

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

NASA Technical Reports Server (NTRS)

Ko, W. L.; Fields, R. A.; Shideler, J. L.

1986-01-01

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panels. In spite of some data scattering resulting from large extrapolations of the data-fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

NASA Technical Reports Server (NTRS)

Ko, W. L.; Shideler, J. L.; Fields, R. A.

1986-01-01

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panel. In spite of some data scattering, resulting from large extrapolations of the data fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Simulation and Advanced Second Moment Reliability Analyses of Pile Groups Using CPGA-R: Formulation, User’s Guide, and Example Problems

DTIC Science & Technology

2013-09-01

that are going to be defined below. Card 3 – Variable data (repeated NUMVARS times): DATATYPE ERDC/ITL TR-13-2 120 DATAID DATACONSTITUENTID...DISTDATA1 DISTDATA2 DISTDATA3 DISTDATA4 DISTTYPE This card is repeated for as many variables specified in Card 2. DATATYPE is a string variable that...CPGA table that is being referenced. For instance, if LOAD is the DATATYPE , then px is the constituent force in the x direction for the specified

Failure of the human lumbar motion-segments resulting from anterior shear fatigue loading

PubMed Central

SKRZYPIEC, Daniel M.; NAGEL, Katrin; SELLENSCHLOH, Kay; KLEIN, Anke; PÜSCHEL, Klaus; MORLOCK, Michael M.; HUBER, Gerd

2016-01-01

An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32–42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the upper vertebra of the motion-segment, at a frequency of 5 Hz. During fatigue experiments, several failure events were observed in the dynamic creep curves. Post-test x-ray, CT and dissection revealed that all specimens had delamination of the intervertebral disc. Anterior shear fatigue predominantly resulted in fracture of the apophyseal processes of the upper vertebrae (n=4). Exposure to the anterior shear fatigue loading caused motion-segment instability and resulted in vertebral slip corresponding to grade I and ‘mild’ grade II spondylolisthesis, as observed clinically. PMID:26829975

Notes From the Field: Secondary Task Precision for Cognitive Load Estimation During Virtual Reality Surgical Simulation Training.

PubMed

Rasmussen, Sebastian R; Konge, Lars; Mikkelsen, Peter T; Sørensen, Mads S; Andersen, Steven A W

2016-03-01

Cognitive load (CL) theory suggests that working memory can be overloaded in complex learning tasks such as surgical technical skills training, which can impair learning. Valid and feasible methods for estimating the CL in specific learning contexts are necessary before the efficacy of CL-lowering instructional interventions can be established. This study aims to explore secondary task precision for the estimation of CL in virtual reality (VR) surgical simulation and also investigate the effects of CL-modifying factors such as simulator-integrated tutoring and repeated practice. Twenty-four participants were randomized for visual assistance by a simulator-integrated tutor function during the first 5 of 12 repeated mastoidectomy procedures on a VR temporal bone simulator. Secondary task precision was found to be significantly lower during simulation compared with nonsimulation baseline, p < .001. Contrary to expectations, simulator-integrated tutoring and repeated practice did not have an impact on secondary task precision. This finding suggests that even though considerable changes in CL are reflected in secondary task precision, it lacks sensitivity. In contrast, secondary task reaction time could be more sensitive, but requires substantial postprocessing of data. Therefore, future studies on the effect of CL modifying interventions should weigh the pros and cons of the various secondary task measurements. © The Author(s) 2015.

Real-time change and damage detection of landslides and other earth movements threatening public infrastructure.

DOT National Transportation Integrated Search

2012-03-01

Geologic hazards such as coastal erosion, landslides, seismic loading, etc. constantly threaten public highway construction and maintenance. Repeat surveys using terrestrial laser scanning (TLS, ground-based LiDAR) enable rapid 3D data acquisition to...

Real-Time Change and Damage Detection of Landslides and Other Earth Movements Threatening Public Infrastructure

DOT National Transportation Integrated Search

2012-03-01

Geologic hazards such as coastal erosion, landslides, seismic loading, etc. constantly threaten public highway construction and maintenance. Repeat surveys using terrestrial laser scanning (TLS, ground-based LiDAR) enable rapid 3D data acquisition to...

Properties of train load frequencies and their applications

NASA Astrophysics Data System (ADS)

Milne, D. R. M.; Le Pen, L. M.; Thompson, D. J.; Powrie, W.

2017-06-01

A train in motion applies moving steady loads to the railway track as well as dynamic excitation; this causes track deflections, vibration and noise. At low frequency, the spectrum of measured track vibration has been found to have a distinct pattern; with spectral peaks occurring at multiples of the vehicle passing frequency. This pattern can be analysed to quantify aspects of train and track performance as well as to design sensors and systems for trackside condition monitoring. To this end, analytical methods are developed to determine frequency spectra based on known vehicle geometry and track properties. It is shown that the quasi-static wheel loads from a moving train, which are the most significant cause of the track deflections at low frequency, can be understood by considering a loading function representing the train geometry in combination with the response of the track to a single unit load. The Fourier transform of the loading function describes how the passage of repeating vehicles within a train leads to spectral peaks at various multiples of the vehicle passing frequency. When a train consists of a single type of repeating vehicle, these peaks depend on the geometry of that vehicle type as the separation of axles on a bogie and spacing of those bogies on a vehicle cause certain frequencies to be suppressed. Introduction of different vehicle types within a train or coupling of trainsets with a different inter-car length changes the spectrum, although local peaks still occur at multiples of the passing frequency of the primary vehicle. Using data from track-mounted geophones, it is shown that the properties of the train load spectrum, together with a model for track behaviour, allows calculation of the track system support modulus without knowledge of the axle loads, and enables rapid determination of the train speed. For continuous remote condition monitoring, track-mounted transducers are ideally powered using energy harvesting devices. These need to be tuned to optimise energy abstraction; the appropriate energy harvesting frequencies for given vehicle types and line speeds can also be predicted using the models developed.

Effects of cryogenic thermal cycle and immersion on the mechanical characteristics of phenol-resin bonded plywood

NASA Astrophysics Data System (ADS)

Kim, Jeong-Hyeon; Park, Doo-Hwan; Lee, Chi-Seung; Park, Kwang-Jun; Lee, Jae-Myung

2015-12-01

The main objective of the present study is to investigate the performance degradation of the plywood used in a liquefied natural gas (LNG) cargo containment system (CCS). A plywood sheet features an odd number of thinly layered wooden plies bonded perpendicularly to the previous layer to give it a very strong and durable structure. Owing to this strong point, plywood is applied to a variety of interior and exterior applications. Above all, it is widely adopted as insulation panels in an LNG CCS owing to a high stiffness with low density and its superior mechanical capabilities. As an insulation material of an LNG CCS, plywood is constantly exposed to repeated wave-induced thermal variations caused by the loading (-163 °C) and unloading (20 °C) of LNG during general operating periods of 25 years on average. Therefore, the effects of cryogenic-level thermal loads on the material characteristics of plywood must be analyzed with respect to the design and safety aspects of LNG CCSs. In the present study, the influences of the estimated thermal load, testing temperature, and grain orientation on plywood adopted in an LNG CCS are investigated. In terms of safety and design, the repeated thermal loads in a LNG CCS must be considered because the modulus of elasticity (MOE), tensile strength (TS), and modulus of rupture (MOR) are degraded by thermal treatments, such as cyclic thermal-shock and cryogenic immersion.

Tips for longwall conveyor chain

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

Courtney, J.C.; Fortune, J.

1977-03-01

Mining chain must be capable of sustaining imposed loads of 80 or 90 percent of its minimum breaking strength, and still return to its original dimensions. This means that the chain should behave like an extremely sophisticated spring up to very high load levels, and return to its unloaded state without any plastic stretch or permanent dimensional deformation having taken place. This feature is absolutely essential, not only to enable repeat loadings to be made, but to ensure that constant, precise engagement of the drive and idler sprockets takes place. The mining chain production process, therefore, is carefully designed somore » that the last stage of manufacture introduces these necessary features.« less

A Revolute Joint With Linear Load-Displacement Response for Precision Deployable Structures

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Warren, Peter A.; Peterson, Lee D.

1996-01-01

NASA Langley Research center is developing key structures and mechanisms technologies for micron-accuracy, in-space deployment of future space instruments. Achieving micron-accuracy deployment requires significant advancements in deployment mechanism design such as the revolute joint presented herein. The joint presented herein exhibits a load-cycling response that is essentially linear with less than two percent hysteresis, and the joint rotates with less than one in.-oz. of resistance. A prototype reflector metering truss incorporating the joint exhibits only a few microns of kinematic error under repeated deployment and impulse loading. No other mechanically deployable structure found in literature has been demonstrated to be this kinematically accurate.

Elasticity of excised dog lung parenchyma

NASA Technical Reports Server (NTRS)

Vawter, D. L.; Fung, Y. C.; West, J. B.

1978-01-01

An optical-electromechanical system is used to measure the force-deformation behavior of biaxially loaded rectangular slabs of excised dog lung parenchyma. In the course of the study, the effects of time, the consistency of reference lengths and areas, the presence of hysteresis, the necessity of preconditioning, the repeatability of results, the effects of lateral load, the effect of strain rate, the effect of pH, the influence of temperature, and the variations among specimens are considered. A new finding is that there is a change in elastic behavior when the tissue undergoes a compressive strain. When the tissue is in tension, increasing the lateral load decreases the compliance, whereas the opposite is true when compressive strain is present.

Changes in psychosocial and physical working conditions and psychotropic medication in ageing public sector employees: a record-linkage follow-up study.

PubMed

Kouvonen, Anne; Mänty, Minna; Lallukka, Tea; Pietiläinen, Olli; Lahelma, Eero; Rahkonen, Ossi

2017-07-12

To investigate whether changes in psychosocial and physical working conditions are associated with subsequent psychotropic medication in ageing employees. Data were from the Helsinki Health Study, a cohort study of Finnish municipal employees, aged 40-60 years at phase 1 (2000-2002). Changes in psychosocial and physical working conditions were measured between phase 1 and phase 2 (2007). Survey data were longitudinally linked to data on prescribed, reimbursed psychotropic medication purchases (Anatomical Therapeutic Chemical) obtained from the registers of the Social Insurance Institution of Finland between the phase 2 survey and December 2013 (N=3587; 80% women). Outcomes were any psychotropic medication; antidepressants (N06A); anxiolytics (N05B); and sedatives and hypnotics (N05C). Cox regression analyses were performed. During the follow-up, 28% of the participants were prescribed psychotropic medication. Repeated exposures to low job control, high job demands and high physical work load were associated with an increased risk of subsequent antidepressant and anxiolytic medication. Increased and repeated exposure to high physical work load, increased job control and repeated high job demands were associated with subsequent sedative and hypnotic medication. Age and sex-adjusted HR varied from 1.18 to 1.66. Improvement in job control was associated with a lower risk of anxiolytic, but with a higher risk of sedatives and hypnotic medication. Decreased physical work load was associated with a lower risk of antidepressant and anxiolytic medications. Improvement in working conditions could lower the risk of mental ill-health indicated by psychotropic medication. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Repeatability of strain magnitude and strain rate measurements in the periodontal ligament using fibre Bragg gratings: An ex vivo study in a swine model.

PubMed

Romanyk, Dan L; Guan, Raymond; Major, Paul W; Dennison, Christopher R

2017-03-21

Measurement of periodontal ligament (PDL) strain in an ex vivo or in vivo setting of a complete tooth-PDL-bone complex (TPBC) has yet to be achieved in the literature. The objective of this study was to investigate inter- and intra-TPBC PDL strain measurement using fibre Bragg grating (FBG) strain sensors. Second and third premolars from the left and the right side of four swine mandibles were removed to yield sixteen TPBC samples. Samples were secured in a miniature load-frame equipped with a digital actuator used to apply apical-directed displacement to the tooth. The same tooth on left and right sides of the mouth were exposed to the same loading condition over ten trials allowing for comparisons in a split-mouth study. Displacements of 0.2 and 0.3mm were considered along with displacement rates of 0.025, 0.05, and 0.1mm/s, yielding six loading combinations. Hypothesis testing between left and right teeth revealed FBGs did not always measure the same strain between left and right TPBCs. For all strain measures, the average coefficient of variation (CV) (all data collected) was 2.16 (range: 0.274-10.71). For repeated measures in single TPBCs, the minimum CV ranged from 0.037 to 0.449, and generally coincided with the time of maximum strain measured over the test duration. Based on the findings of this study, it is suggested that FBGs can provide repeatable ex vivo strain measures in the PDL of complete TPBCs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal analysis of the intact mandibular premolar: a finite element analysis.

PubMed

Oskui, I Z; Ashtiani, M N; Hashemi, A; Jafarzadeh, H

2013-09-01

To obtain temperature distribution data through human teeth focusing on the pulp-dentine junction (PDJ). A three-dimensional tooth model was reconstructed using computer-aided design software from computed tomographic images. Subsequently, temperature distribution was numerically determined through the tooth for three different heat loads. Loading type I was equivalent to a 60° C mouth temperature for 1 s. Loading type II started with a 60° C mouth temperature, decreasing linearly to 37° C over 10 s. Loading type III repeated the pattern of type II in three consecutive cycles, with a 5 s resting time between cycles. The maximum temperatures of the pulp were 37.9° C, 39.0° C and 41.2° C for loading types I, II, and III, respectively. The largest temperature rise occurred with the cyclic loading, that is, type III. For the heat loads considered, the predicted peak temperatures at the PDJ were less than the reported temperature thresholds of irreversible pulpal damage. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Closed-form analysis of fiber-matrix interface stresses under thermo-mechanical loadings

NASA Technical Reports Server (NTRS)

Naik, Rajiv A.; Crews, John H., Jr.

1992-01-01

Closed form techniques for calculating fiber matrix (FM) interface stresses, using repeating square and diamond regular arrays, were presented for a unidirectional composite under thermo-mechanical loadings. An Airy's stress function micromechanics approach from the literature, developed for calculating overall composite moduli, was extended in the present study to compute FM interface stresses for a unidirectional graphite/epoxy (AS4/3501-6) composite under thermal, longitudinal, transverse, transverse shear, and longitudinal shear loadings. Comparison with finite element results indicate excellent agreement of the FM interface stresses for the square array. Under thermal and longitudinal loading, the square array has the same FM peak stresses as the diamond array. The square array predicted higher stress concentrations under transverse normal and longitudinal shear loadings than the diamond array. Under transverse shear loading, the square array had a higher stress concentration while the diamond array had a higher radial stress concentration. Stress concentration factors under transverse shear and longitudinal shear loadings were very sensitive to fiber volume fraction. The present analysis provides a simple way to calculate accurate FM interface stresses for both the square and diamond array configurations.

Assessment of Embedded Conjugated Polymer Sensor Arrays for Potential Load Transmission Measurement in Orthopaedic Implants

PubMed Central

Micolini, Carolina; Holness, Frederick Benjamin; Johnson, James A.

2017-01-01

Load transfer through orthopaedic joint implants is poorly understood. The longer-term outcomes of these implants are just starting to be studied, making it imperative to monitor contact loads across the entire joint implant interface to elucidate the force transmission and distribution mechanisms exhibited by these implants in service. This study proposes and demonstrates the design, implementation, and characterization of a 3D-printed smart polymer sensor array using conductive polyaniline (PANI) structures embedded within a polymeric parent phase. The piezoresistive characteristics of PANI were investigated to characterize the sensing behaviour inherent to these embedded pressure sensor arrays, including the experimental determination of the stable response of PANI to continuous loading, stability throughout the course of loading and unloading cycles, and finally sensor repeatability and linearity in response to incremental loading cycles. This specially developed multi-material additive manufacturing process for PANI is shown be an attractive approach for the fabrication of implant components having embedded smart-polymer sensors, which could ultimately be employed for the measurement and analysis of joint loads in orthopaedic implants for in vitro testing. PMID:29186079

Seismic performance of the typical RC beam-column joint subjected to repeated earthquakes

NASA Astrophysics Data System (ADS)

Hassanshahi, Omid; Majid, Taksiah A.; Lau, Tze Liang; Yousefi, Ali; Tahara, R. M. K.

2017-10-01

It is common that a building experience repeated earthquakes throughout its lifetime. Such earthquake is capable of creating severe damage in primary elements of the building due to accumulation of inelastic displacement from repetition. The present study focuses on the influence of repeated earthquakes on a typical Reinforced Concrete (RC) beam-column joint, especially on the maximum inelastic displacement demand and maximum residual displacement. For this purpose, the capability of nonlinear modelling in simulating the hysteretic behaviour of the prototype experimental specimen is first determined using RUAUMOKO. A nonlinear Incremental Dynamic Analysis (IDA) on the verified model is then carried out in order to estimate with maximum accuracy the ultimate load bearing capacity to progressive collapse of the RC joint under investigation. Twenty ground motions are selected, and single (C1), double (C2), and triple (C3) event of synthetic repeated earthquakes are then considered. The results show that the repeated earthquakes significantly increase the inelastic demand of the RC joint. On average, relative increment of maximum inelastic displacement demand is experienced about 28.9% and 39.4% when C2 and C3 events of repeated earthquakes are induced, respectively. Residual displacements for repeated earthquakes are also significantly higher than that for single earthquakes.

Condensin loaded onto the replication fork barrier site in the rRNA gene repeats during S phase in a FOB1-dependent fashion to prevent contraction of a long repetitive array in Saccharomyces cerevisiae.

PubMed

Johzuka, Katsuki; Terasawa, Masahiro; Ogawa, Hideyuki; Ogawa, Tomoko; Horiuchi, Takashi

2006-03-01

An average of 200 copies of the rRNA gene (rDNA) is clustered in a long tandem array in Saccharomyces cerevisiae. FOB1 is known to be required for expansion/contraction of the repeats by stimulating recombination, thereby contributing to the maintenance of the average copy number. In Deltafob1 cells, the repeats are still maintained without any fluctuation in the copy number, suggesting that another, unknown system acts to prevent repeat contraction. Here, we show that condensin acts together with FOB1 in a functionally complemented fashion to maintain the long tandem repeats. Six condensin mutants possessing severely contracted rDNA repeats were isolated in Deltafob1 cells but not in FOB1+ cells. We also found that the condensin complex associated with the nontranscribed spacer region of rDNA with a major peak coincided with the replication fork barrier (RFB) site in a FOB1-dependent fashion. Surprisingly, condensin association with the RFB site was established during S phase and was maintained until anaphase. These results indicate that FOB1 plays a novel role in preventing repeat contraction by regulating condensin association and suggest a link between replication termination and chromosome condensation and segregation.

14 CFR 23.571 - Metallic pressurized cabin structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure... the following: (a) A fatigue strength investigation in which the structure is shown by tests, or by analysis supported by test evidence, to be able to withstand the repeated loads of variable magnitude...

Plasma facing materials performance under ITER-relevant mitigated disruption photonic heat loads

NASA Astrophysics Data System (ADS)

Klimov, N. S.; Putrik, A. B.; Linke, J.; Pitts, R. A.; Zhitlukhin, A. M.; Kuprianov, I. B.; Spitsyn, A. V.; Ogorodnikova, O. V.; Podkovyrov, V. L.; Muzichenko, A. D.; Ivanov, B. V.; Sergeecheva, Ya. V.; Lesina, I. G.; Kovalenko, D. V.; Barsuk, V. A.; Danilina, N. A.; Bazylev, B. N.; Giniyatulin, R. N.

2015-08-01

PFMs (Plasma-facing materials: ITER grade stainless steel, beryllium, and ferritic-martensitic steels) as well as deposited erosion products of PFCs (Be-like, tungsten, and carbon based) were tested in QSPA under photonic heat loads relevant to those expected from photon radiation during disruptions mitigated by massive gas injection in ITER. Repeated pulses slightly above the melting threshold on the bulk materials eventually lead to a regular, "corrugated" surface, with hills and valleys spaced by 0.2-2 mm. The results indicate that hill growth (growth rate of ∼1 μm per pulse) and sample thinning in the valleys is a result of melt-layer redistribution. The measurements on the 316L(N)-IG indicate that the amount of tritium absorbed by the sample from the gas phase significantly increases with pulse number as well as the modified layer thickness. Repeated pulses significantly below the melting threshold on the deposited erosion products lead to a decrease of hydrogen isotopes trapped during the deposition of the eroded material.

Pre-strain effect on frequency-based impact energy dissipation through a silicone foam pad for shock mitigation [Pre-strain effect on the frequency response of shock mitigation through a silicone foam pad

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

Sanborn, Brett; Song, Bo; Smith, Scott

Silicone foams have been used in a variety of applications from gaskets to cushioning pads over a wide range of environments. Particularly, silicone foams are used as a shock mitigation material for shock and vibration applications. Understanding the shock mitigation response, particularly in the frequency domain, is critical for optimal designs to protect internal devices and components more effectively and efficiently. The silicone foams may be subjected to pre-strains during the assembly process which may consequently influence the frequency response with respect to shock mitigation performance. A Kolsky compression bar was modified with pre-compression capabilities to characterize the shock mitigationmore » response of silicone foam in the frequency domain to determine the effect of pre-strain. Lastly, a silicone sample was also intentionally subjected to repeated pre-strain and dynamic loadings to explore the effect of repeated loading on the frequency response of shock mitigation.« less

Pre-strain effect on frequency-based impact energy dissipation through a silicone foam pad for shock mitigation [Pre-strain effect on the frequency response of shock mitigation through a silicone foam pad

DOE PAGES

Sanborn, Brett; Song, Bo; Smith, Scott

2015-12-29

Silicone foams have been used in a variety of applications from gaskets to cushioning pads over a wide range of environments. Particularly, silicone foams are used as a shock mitigation material for shock and vibration applications. Understanding the shock mitigation response, particularly in the frequency domain, is critical for optimal designs to protect internal devices and components more effectively and efficiently. The silicone foams may be subjected to pre-strains during the assembly process which may consequently influence the frequency response with respect to shock mitigation performance. A Kolsky compression bar was modified with pre-compression capabilities to characterize the shock mitigationmore » response of silicone foam in the frequency domain to determine the effect of pre-strain. Lastly, a silicone sample was also intentionally subjected to repeated pre-strain and dynamic loadings to explore the effect of repeated loading on the frequency response of shock mitigation.« less

Development of implant loading device for animal study about various loading protocol: a pilot study

PubMed Central

Yoon, Joon-Ho; Park, Young-Bum; Cho, Yuna; Kim, Chang-Sung; Choi, Seong-Ho; Moon, Hong-Seok; Lee, Keun-Woo

2012-01-01

PURPOSE The aims of this pilot study were to introduce implant loading devices designed for animal study and to evaluate the validity of the load transmission ability of the loading devices. MATERIALS AND METHODS Implant loading devices were specially designed and fabricated with two implant abutments and cast metal bars, and orthodontic expansion screw. In six Beagles, all premolars were extracted and two implants were placed in each side of the mandibles. The loading device was inserted two weeks after the implant placement. According to the loading protocol, the load was applied to the implants with different time and method,simulating early, progressive, and delayed loading. The implants were clinically evaluated and the loading devices were removed and replaced to the master cast, followed by stress-strain analysis. Descriptive statistics of remained strain (µε) was evaluated after repeating three cycles of the loading device activation. Statistic analysis was performed using nonparametric, independent t-test with 5% significance level and Friedman's test was also used for verification. RESULTS The loading devices were in good action. However, four implants in three Beagles showed loss of osseointegration. In stress-strain analysis, loading devices showed similar amount of increase in the remained strain after applying 1-unit load for three times. CONCLUSION Specialized design of the implant loading device was introduced. The loading device applied similar amount of loads near the implant after each 1-unit loading. However, the direction of the loads was not parallel to the long axis of the implants as predicted before the study. PMID:23236575

Test method research on weakening interface strength of steel - concrete under cyclic loading

NASA Astrophysics Data System (ADS)

Liu, Ming-wei; Zhang, Fang-hua; Su, Guang-quan

2018-02-01

The mechanical properties of steel - concrete interface under cyclic loading are the key factors affecting the rule of horizontal load transfer, the calculation of bearing capacity and cumulative horizontal deformation. Cyclic shear test is an effective method to study the strength reduction of steel - concrete interface. A test system composed of large repeated direct shear test instrument, hydraulic servo system, data acquisition system, test control software system and so on is independently designed, and a set of test method, including the specimen preparation, the instrument preparation, the loading method and so on, is put forward. By listing a set of test results, the validity of the test method is verified. The test system and the test method based on it provide a reference for the experimental study on mechanical properties of steel - concrete interface.

Measuring Permeability of Composite Cryotank Laminants

NASA Technical Reports Server (NTRS)

Oliver, Stanley T.; Selvidge, Shawn; Watwood, Michael C.

2004-01-01

This paper describes a test method developed to identify whether certain materials and material systems are suitable candidates for large pressurized reusable cryogenic tanks intended for use in current and future manned launch systems. It provides a quick way to screen numerous candidate materials for permeability under anticipated loading environments consistent with flight conditions, as well as addressing reusability issues. cryogenic tank, where the major design issue was hydrogen permeability. It was successfully used to evaluate samples subjected to biaxial loading while maintaining test temperatures near liquid hydrogen. After each sample was thermally preconditioned, a cyclic pressure load was applied to simulate the in-plane strain. First permeability was measured while a sample was under load. Then the sample was unloaded and allowed to return to ambient temperature. The test was repeated to simulate reusability, in order to evaluate its effects on material permeability.

Coming out prevention by stopper for the shrink fitted sandwiched shaft from the ceramic sleeve

NASA Astrophysics Data System (ADS)

Zhang, Guowei; Noda, Nao-Aki; Sano, Yoshikazu; Sakai, Hiromasa; Oda, Kazuhiro

2017-05-01

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. The roller consists of sleeve and steel shaft connected only under a small shrink fitting ratio because of the brittleness. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated bending load. Therefore, how to prevent the coming out failure becomes an important issue. Based on the previous study, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Then, this research focuses on preventing the inner plate coming out from the outer plate by introducing a newly designed stopper on the outer plate. The simulation results shows that the coming out phenomenon can be prevented effectively due to the contact between the inter plate and the stopper installed on the outer plate. In order to evaluate the contact force between the inner plate and the stopper, the coming out mechanism is clarified. To prevent the coming out by stopper safely, the effects of the magnitude of repeated load and the friction coefficient upon the contact compressive force are investigated under large number of loading cycles by using 2D simulation.

Ground reaction forces and knee kinetics during single and repeated badminton lunges.

PubMed

Lam, Wing Kai; Ding, Rui; Qu, Yi

2017-03-01

Repeated movement (RM) lunge that frequently executed in badminton might be used for footwear evaluation. This study examined the influence of single movement (SM) and RM lunges on the ground reaction forces (GRFs) and knee kinetics during the braking phase of a badminton lunge step. Thirteen male university badminton players performed left-forward lunges in both SM and RM sessions. Force platform and motion capturing system were used to measure GRFs and knee kinetics variables. Paired t-test was performed to determine any significant differences between SM and RM lunges regarding mean and coefficient of variation (CV) in each variable. The kinetics results indicated that compared to SM lunges, the RM lunges had shorter contact time and generated smaller maximum loading rate of impact force, peak knee anterior-posterior force, and peak knee sagittal moment but generated larger peak horizontal resultant forces (Ps < 0.05). Additionally, the RM lunges had lower CV for peak knee medial-lateral and vertical forces (Ps < 0.05). These results suggested that the RM testing protocols had a distinct loading response and adaptation pattern during lunge and that the RM protocol showed higher within-trial reliability, which may be beneficial for the knee joint loading evaluation under different interventions.

Mechanical load plays little role in contraction-mediated glucose transport in mouse skeletal muscle

PubMed Central

Sandström, Marie E; Zhang, Shi-Jin; Westerblad, Håkan; Katz, Abram

2007-01-01

The factors responsible for control of glucose transport during exercise are not fully understood. We investigated the role of mechanical load in contraction-mediated glucose transport in an isolated muscle preparation. Mouse extensor digitorum longus muscles were stimulated with repeated contractions for 10 min with or without N-benzyl-p-toluene sulphonamide (BTS, an inhibitor of myosin II ATPase) to block crossbridge activity. BTS inhibited force production during repeated contraction to ∼5% of control. In contrast, BTS had little effect on glucose transport in the basal state (control = 0.55 ± 0.04; BTS = 0.47 ± 0.09 μmol (20 min)−1 ml−1) or after contraction (control = 2.27 ± 0.15; BTS = 2.10 ± 0.16 μmol (20 min)−1 ml−1). BTS did not significantly alter the contraction-mediated changes in high-energy phosphates, glutathione status (a measure of oxidant status) or AMP-activated protein kinase activity. In conclusion, these data show that mechanical load plays little role in contraction-mediated glucose transport. Instead, it is likely that the increased glucose transport during contraction is a consequence of the increase in myoplasmic Ca2+ and the subsequent alterations in metabolism, e.g. increased energy turnover and production of reactive oxygen species. PMID:17185338

Effect drug loading process on dissolution mechanism of encapsulated amoxicillin trihydrate in hydrogel semi-IPN chitosan methyl cellulose with pore forming agent KHCO3 as a floating drug delivery system

NASA Astrophysics Data System (ADS)

Fithawati, Garnis; Budianto, Emil

2018-04-01

Common treatment for Helicobacter pylori by repeated oral consumption of amoxicillin trihydrate is not effective. Amoxicillin trihydrate has a very short residence time in stomach which leads into its ineffectiveness. Residence time of amoxicillin trihydrate can be improved by encapsulating amoxicillin trihydrate into a floating drug delivery system. In this study, amoxicillin trihydrate is encapsulated into hydrogel semi-IPN chitosan methyl cellulose matrix as a floating drug delivery system and then treated with 20% KHCO3 as pore forming agent. Drug loading process used are in-situ loading and post loading. In-situ loading process has higher efficiency percentage and dissolution percentage than post loading process. In-situ loading process resulted 100% efficiency with 92,70% dissolution percentage. Post loading process resulted 98,7% efficiency with 90,42% dissolution percentage. Mechanism of drug dissolution study by kinetics approach showed both in-situ loading process and post loading process are diffusion and degradation process (n=0,4913) and (n=0,4602) respectively. These results are supported by characterization data from optical microscope and scanning electron microscopy (SEM). Data from optical microscope showed both loading process resulted in coarser hydrogel surface. Characterization using SEM showed elongated pores in both loading process after dissolution test.

Comparative evaluation of subgrade resilient modulus from non-destructive, in-situ, and laboratory methods : technical summary report.

DOT National Transportation Integrated Search

2008-09-01

The Resilient Modulus (Mr) of pavement materials and subgrades is an important input : parameter for the design of pavement structures. The Repeated Loading Triaxial (RLT) test : typically determines Mr. However, the RLT test requires well trained pe...

Microdamage healing in asphalt and asphalt concrete, volume 3 : a micromechanics fracture and healing model for asphalt concrete.

DOT National Transportation Integrated Search

2001-06-01

Volume 3 documents the development of a micromechanics fracture and healing model for asphalt : concrete. This model can be used to calculate the density and growth of microcracks during repeated direct : tensile controlled-strain loading. The model ...

Long-term consequences of pain in human neonates.

PubMed

Grunau, Ruth E; Holsti, Liisa; Peters, Jeroen W B

2006-08-01

The low tactile threshold in preterm infants when they are in the neonatal intensive care unit (NICU), while their physiological systems are unstable and immature, potentially renders them more vulnerable to the effects of repeated invasive procedures. There is a small but growing literature on pain and tactile responsivity following procedural pain in the NICU, or early surgery. Long-term effects of repeated pain in the neonatal period on neurodevelopment await further research. However, there are multiple sources of stress in the NICU, which contribute to inducing high overall 'allostatic load', therefore determining specific effects of neonatal pain in human infants is challenging.

A mechano-acoustic indentor system for in vivo measurement of nonlinear elastic properties of soft tissue.

PubMed

Koo, Terry K; Cohen, Jeffrey H; Zheng, Yongping

2011-11-01

Soft tissue exhibits nonlinear stress-strain behavior under compression. Characterizing its nonlinear elasticity may aid detection, diagnosis, and treatment of soft tissue abnormality. The purposes of this study were to develop a rate-controlled Mechano-Acoustic Indentor System and a corresponding finite element optimization method to extract nonlinear elastic parameters of soft tissue and evaluate its test-retest reliability. An indentor system using a linear actuator to drive a force-sensitive probe with a tip-mounted ultrasound transducer was developed. Twenty independent sites at the upper lateral quadrant of the buttock from 11 asymptomatic subjects (7 men and 4 women from a chiropractic college) were indented at 6% per second for 3 sessions, each consisting of 5 trials. Tissue thickness, force at 25% deformation, and area under the load-deformation curve from 0% to 25% deformation were calculated. Optimized hyperelastic parameters of the soft tissue were calculated with a finite element model using a first-order Ogden material model. Load-deformation response on a standardized block was then simulated, and the corresponding area and force parameters were calculated. Between-trials repeatability and test-retest reliability of each parameter were evaluated using coefficients of variation and intraclass correlation coefficients, respectively. Load-deformation responses were highly reproducible under repeated measurements. Coefficients of variation of tissue thickness, area under the load-deformation curve from 0% to 25% deformation, and force at 25% deformation averaged 0.51%, 2.31%, and 2.23%, respectively. Intraclass correlation coefficients ranged between 0.959 and 0.999, indicating excellent test-retest reliability. The automated Mechano-Acoustic Indentor System and its corresponding optimization technique offers a viable technology to make in vivo measurement of the nonlinear elastic properties of soft tissue. This technology showed excellent between-trials repeatability and test-retest reliability with potential to quantify the effects of a wide variety of manual therapy techniques on the soft tissue elastic properties. Copyright © 2011 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

Development of microbend sensors for pressure, load, and displacement measurements in civil engineering

NASA Astrophysics Data System (ADS)

Grossman, Barry G.; Cosentino, Paul J.; Doi, Shinobu; Kumar, Girish; Verghese, John

1994-05-01

We are developing low cost, rugged, and reliable fiberoptic sensors to meet current and future needs in civil engineering, including those of smart civil structures. Our work has concentrated on load, pressure, and displacement sensors, including pore water pressure sensors. We have built and demonstrated sensors in the laboratory with loads up to 50 lb., water pressures of 100 psi, and displacements up to 1 mm. Repeatability of sensor measurements are within 5% and are being improved with continued development. The range and sensitivity of the sensors can be easily changed without changing the basic sensor design. We also have multiplexed two water pressure sensors on a single fiber. We describe the sensor construction and experimental performance.

The Effect of Antiretroviral Combination Treatment on Epstein-Barr Virus (EBV) Genome Load in HIV-Infected Patients

PubMed Central

Friis, Anna M. C.; Gyllensten, Katarina; Aleman, Anna; Ernberg, Ingemar; Åkerlund, Börje

2010-01-01

We evaluated the effect of combination anti-retroviral treatment (cART) on the host control of EBV infection in moderately immunosuppressed HIV-1 patients. Twenty HIV-1 infected individuals were followed for five years with repeated measurements of EBV DNA load in peripheral blood lymphocytes in relation to HIV-RNA titers and CD4+ cell counts. Individuals with optimal response, i.e. durable non-detectable HIV-RNA, showed a decline of EBV load to the level of healthy controls. Individuals with non-optimal HIV-1 control did not restore their EBV control. Long-lasting suppression of HIV-replication after early initiation of cART is a prerequisite for re-establishing the immune control of EBV. PMID:21994658

The Development of a Conical Composite Energy Absorber for Use in the Attenuation of Crash/Impact Loads

NASA Technical Reports Server (NTRS)

Littell, Justin D.

2014-01-01

A design for a novel light-weight conical shaped energy absorbing (EA) composite subfloor structure is proposed. This composite EA is fabricated using repeated alternating patterns of a conical geometry to form long beam structures which can be implemented as aircraft subfloor keel beams or frame sections. The geometrical features of this conical design, along with the hybrid composite materials used in the manufacturing process give a strength tailored to achieve a constant 25-40 g sustained crush load, small peak crush loads and long stroke limits. This report will discuss the geometrical design and fabrication methods, along with results from static and dynamic crush testing of 12-in. long subcomponents.

Complementary Split-Ring Resonator-Loaded Microfluidic Ethanol Chemical Sensor.

PubMed

Salim, Ahmed; Lim, Sungjoon

2016-10-28

In this paper, a complementary split-ring resonator (CSRR)-loaded patch is proposed as a microfluidic ethanol chemical sensor. The primary objective of this chemical sensor is to detect ethanol's concentration. First, two tightly coupled concentric CSRRs loaded on a patch are realized on a Rogers RT/Duroid 5870 substrate, and then a microfluidic channel engraved on polydimethylsiloxane (PDMS) is integrated for ethanol chemical sensor applications. The resonant frequency of the structure before loading the microfluidic channel is 4.72 GHz. After loading the microfluidic channel, the 550 MHz shift in the resonant frequency is ascribed to the dielectric perturbation phenomenon when the ethanol concentration is varied from 0% to 100%. In order to assess the sensitivity range of our proposed sensor, various concentrations of ethanol are tested and analyzed. Our proposed sensor exhibits repeatability and successfully detects 10% ethanol as verified by the measurement set-up. It has created headway to a miniaturized, non-contact, low-cost, reliable, reusable, and easily fabricated design using extremely small liquid volumes.

Complementary Split-Ring Resonator-Loaded Microfluidic Ethanol Chemical Sensor

PubMed Central

Salim, Ahmed; Lim, Sungjoon

2016-01-01

In this paper, a complementary split-ring resonator (CSRR)-loaded patch is proposed as a microfluidic ethanol chemical sensor. The primary objective of this chemical sensor is to detect ethanol’s concentration. First, two tightly coupled concentric CSRRs loaded on a patch are realized on a Rogers RT/Duroid 5870 substrate, and then a microfluidic channel engraved on polydimethylsiloxane (PDMS) is integrated for ethanol chemical sensor applications. The resonant frequency of the structure before loading the microfluidic channel is 4.72 GHz. After loading the microfluidic channel, the 550 MHz shift in the resonant frequency is ascribed to the dielectric perturbation phenomenon when the ethanol concentration is varied from 0% to 100%. In order to assess the sensitivity range of our proposed sensor, various concentrations of ethanol are tested and analyzed. Our proposed sensor exhibits repeatability and successfully detects 10% ethanol as verified by the measurement set-up. It has created headway to a miniaturized, non-contact, low-cost, reliable, reusable, and easily fabricated design using extremely small liquid volumes. PMID:27801842

An electromyographic and kinematic comparison between an extendable conveyor system and an articulating belt conveyor used for truck loading and unloading tasks.

PubMed

Lavender, Steven A; Nagavarapu, Shasank; Allread, W Gary

2017-01-01

Many retail distribution centers (DCs) manually load and unload boxes into or out of trailers and shipping containers. This study investigated whether an articulating belt conveyor with a height adjustable platform, positioned at the end of an extendable conveyor, significantly reduces shoulder and back muscle loading and the spine kinematics associated with these tasks. Electromyographic and kinematic data were collected from eight volunteer employees as trailers at a shoe DC were unloaded and from nine volunteer employees as trailers at an apparel DC were loaded. Participants in this repeated measures study handled boxes with a conventional powered extendable conveyor system and with the articulating belt conveyor positioned at the end of the extendable conveyor. Bilaterally the normalized activation levels of the erector spinae and anterior deltoid muscles were reduced when loading and unloading boxes with the articulating belt conveyor. Spine movement speeds were also reduced with the articulating conveyor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Knowing how you are feeling depends on what's on my mind: Cognitive load and expression categorization.

PubMed

Ahmed, Lubna

2018-03-01

The ability to correctly interpret facial expressions is key to effective social interactions. People are well rehearsed and generally very efficient at correctly categorizing expressions. However, does their ability to do so depend on how cognitively loaded they are at the time? Using repeated-measures designs, we assessed the sensitivity of facial expression categorization to cognitive resources availability by measuring people's expression categorization performance during concurrent low and high cognitive load situations. In Experiment1, participants categorized the 6 basic upright facial expressions in a 6-automated-facial-coding response paradigm while maintaining low or high loading information in working memory (N = 40; 60 observations per load condition). In Experiment 2, they did so for both upright and inverted faces (N = 46; 60 observations per load and inversion condition). In both experiments, expression categorization for upright faces was worse during high versus low load. Categorization rates actually improved with increased load for the inverted faces. The opposing effects of cognitive load on upright and inverted expressions are explained in terms of a cognitive load-related dispersion in the attentional window. Overall, the findings support that expression categorization is sensitive to cognitive resources availability and moreover suggest that, in this paradigm, it is the perceptual processing stage of expression categorization that is affected by cognitive load. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The reliability of the Extra Load Index as a measure of relative load carriage economy.

PubMed

Hudson, Sean; Cooke, Carlton; Lloyd, Ray

2017-09-01

The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h -1 , 6 km·h -1 and a self-selected speed. Trial conditions were repeated 7 days later to assess test-retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy. Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.

Tensiomyographical responses to accelerometer loads in female collegiate basketball players.

PubMed

Peterson, Kyle D; Quiggle, Gabriela T

2017-12-01

The purpose of the present study was to characterise the relationship between relative versus absolute internal and external loads in collegiate basketball players throughout the course of a season. Five Division I basketball players wore triaxial accelerometers throughout the 2015-2016 season and were tensiomyographically assessed weekly. One-way repeated-measure analysis of variance (RM ANOVA) with least-significant-difference (LSD) pairwise comparisons was used to determine which absolute weekly loads were different across the season. Cohen's d was used to supplement the determination of meaningful relative load changes. Overall RM ANOVA models suggest absolute external load differences occurred (PlayerLoad™ F = 17.63; IMA™ F = 31.63). Two-way RM ANOVA models revealed main effect differences were revealed between muscle groups for Tc (F = 9.11) and Dm (F = 3.25). Meaningful relative load changes between weeks were observed for both external and internal. The present study observed that tensiomyography utilised as a tool to monitor internal load may be more suitable for detecting fatigue from relative external load changes versus absolute load attained. Limiting weekly training volume changes to ≤10% may maintain appropriate adaptation. Mediolateral plane IMA™ and adductor longus muscle group may be pertinent metrics when monitoring female collegiate basketball athletes.

Unknown loads affect force production capacity in early phases of bench press throws.

PubMed

Hernández Davó, J L; Sabido Solana, R; Sarabia Marínm, J M; Sánchez Martos, Á; Moya Ramón, M

2015-10-01

Explosive strength training aims to improve force generation in early phases of movement due to its importance in sport performance. The present study examined the influence of lack of knowledge about the load lifted in explosive parameters during bench press throws. Thirteen healthy young men (22.8±2.0 years) participated in the study. Participants performed bench press throws with three different loads (30, 50 and 70% of 1 repetition maximum) in two different conditions (known and unknown loads). In unknown condition, loads were changed within sets in each repetition and participants did not know the load, whereas in known condition the load did not change within sets and participants had knowledge about the load lifted. Results of repeated-measures ANOVA revealed that unknown conditions involves higher power in the first 30, 50, 100 and 150 ms with the three loads, higher values of ratio of force development in those first instants, and differences in time to reach maximal rate of force development with 50 and 70% of 1 repetition maximum. This study showed that unknown conditions elicit higher values of explosive parameters in early phases of bench press throws, thereby this kind of methodology could be considered in explosive strength training.

Cost Savings Associated with the Adoption of a Cloud Computing Data Transfer System for Trauma Patients.

PubMed

Feeney, James M; Montgomery, Stephanie C; Wolf, Laura; Jayaraman, Vijay; Twohig, Michael

2016-09-01

Among transferred trauma patients, challenges with the transfer of radiographic studies include problems loading or viewing the studies at the receiving hospitals, and problems manipulating, reconstructing, or evalu- ating the transferred images. Cloud-based image transfer systems may address some ofthese problems. We reviewed the charts of patients trans- ferred during one year surrounding the adoption of a cloud computing data transfer system. We compared the rates of repeat imaging before (precloud) and af- ter (postcloud) the adoption of the cloud-based data transfer system. During the precloud period, 28 out of 100 patients required 90 repeat studies. With the cloud computing transfer system in place, three out of 134 patients required seven repeat films. There was a statistically significant decrease in the proportion of patients requiring repeat films (28% to 2.2%, P < .0001). Based on an annualized volume of 200 trauma patient transfers, the cost savings estimated using three methods of cost analysis, is between $30,272 and $192,453.

A micro-mechanical model to determine changes of collagen fibrils under cyclic loading

NASA Astrophysics Data System (ADS)

Chen, Michelle L.; Susilo, Monica E.; Ruberti, Jeffrey A.; Nguyen, Thao D.

Dynamic mechanical loading induces growth and remodeling in biological tissues. It can alter the degradation rate and intrinsic mechanical properties of collagen through cellular activity. Experiments showed that repeated cyclic loading of a dense collagen fibril substrate increased collagen stiffness and strength, lengthened the substrate, but did not significantly change the fibril areal fraction or fibril anisotropy (Susilo, et al. ``Collagen Network Hardening Following Cyclic Tensile Loading'', Interface Focus, submitted). We developed a model for the collagen fibril substrate (Tonge, et al. ``A micromechanical modeling study of the mechanical stabilization of enzymatic degradation of collagen tissues'', Biophys J, in press.) to probe whether changes in the fibril morphology and mechanical properties can explain the tissue-level properties observed during cyclic loading. The fibrils were modeled as a continuous distribution of wavy elastica, based on experimental measurements of fibril density and collagen anisotropy, and can experience damage after a critical stress threshold. Other mechanical properties in the model were fit to the stress response measured before and after the extended cyclic loading to determine changes in the strength and stiffness of collagen fibrils.

Study on Roadheader Cutting Load at Different Properties of Coal and Rock

PubMed Central

2013-01-01

The mechanism of cutting process of roadheader with cutting head was researched, and the influences of properties of coal and rock on cutting load were deeply analyzed. Aimed at the defects of traditional calculation method of cutting load on fully expressing the complex cutting process of cutting head, the method of finite element simulation was proposed to simulate the dynamic cutting process. Aimed at the characteristics of coal and rock which affect the cutting load, several simulations with different firmness coefficient were taken repeatedly, and the relationship between three-axis force and firmness coefficient was derived. A comparative analysis of cutting pick load between simulation results and theoretical formula was carried out, and a consistency was achieved. Then cutting process with a total cutting head was carried out on this basis. The results show that the simulation analysis not only provides a reliable guarantee for the accurate calculation of the cutting head load and improves the efficiency of the cutting head cutting test but also offers a basis for selection of cutting head with different geological conditions of coal or rock. PMID:24302866

Torus elements used in effective shock absorber

NASA Technical Reports Server (NTRS)

Cunningham, P.; Platus, D. L.

1966-01-01

Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload.

Flow number as a discriminating HMA mixture property : [project brief].

DOT National Transportation Integrated Search

2013-02-01

T he flow number test is used to measure the rutting potential of asphalt concrete mixtures. It is a variation of the repeated load, permanent deformation test that has been used by researchers since the 1970s. The flow number is one of three tests t...

40 CFR 63.842 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... section as follows: Anode bake cycle means the period during which the regularly repeated sequence of loading, preheating, firing, cooling, and removing anodes from all sections within an anode bake furnace occurs one time. Anode bake furnace means an oven in which the formed green anodes are baked for use in a...

40 CFR 63.842 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... section as follows: Anode bake cycle means the period during which the regularly repeated sequence of loading, preheating, firing, cooling, and removing anodes from all sections within an anode bake furnace occurs one time. Anode bake furnace means an oven in which the formed green anodes are baked for use in a...

40 CFR 63.842 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... section as follows: Anode bake cycle means the period during which the regularly repeated sequence of loading, preheating, firing, cooling, and removing anodes from all sections within an anode bake furnace occurs one time. Anode bake furnace means an oven in which the formed green anodes are baked for use in a...

40 CFR 63.842 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... section as follows: Anode bake cycle means the period during which the regularly repeated sequence of loading, preheating, firing, cooling, and removing anodes from all sections within an anode bake furnace occurs one time. Anode bake furnace means an oven in which the formed green anodes are baked for use in a...

40 CFR 63.842 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... section as follows: Anode bake cycle means the period during which the regularly repeated sequence of loading, preheating, firing, cooling, and removing anodes from all sections within an anode bake furnace occurs one time. Anode bake furnace means an oven in which the formed green anodes are baked for use in a...

Evaluation of the base/subgrade soil under repeated loading : phase I--laboratory testing and numerical modeling of geogrid reinforced bases in flexible pavement.

DOT National Transportation Integrated Search

2009-10-01

This report documents the results of a study that was conducted to characterize the behavior of geogrid reinforced base : course materials. The research was conducted through an experimental testing and numerical modeling programs. The : experimental...

Microdamage healing in asphalt and asphalt concrete, Volume 3 : a micromechanics fracture and healing model for asphalt concrete

DOT National Transportation Integrated Search

2001-06-01

Volume 3 documents the development of a micromechanics fracture and healing model for asphalt concrete. This model can be used to calculate the density and growth of microcracks during repeated direct tensile controlled-strain loading. The model is b...

Using fiber-optic sensor technology to measure strains under the asphalt layer of a flexible pavement structure.

DOT National Transportation Integrated Search

2006-01-01

In this study, a flexible pavement system was instrumented using fiber-optic strain sensors (FOSS). The purpose of this study was to demonstrate the feasibility of a FOSS installation, monitor the long-term strains under repeated traffic loading, and...

Comparison of fatigue analysis approaches for hot-mix asphalt to ensure a state of good repair.

DOT National Transportation Integrated Search

2013-10-01

Fatigue cracking is a primary form of distress in hot-mix asphalt. The long-term nature of fatigue due to repeated : loading and aging and its required tie to pavement structure present challenges in terms of evaluating mixture : resistance. This pro...

Axial displacements in external and internal implant-abutment connection.

PubMed

Lee, Ji-Hye; Kim, Dae-Gon; Park, Chan-Jin; Cho, Lee-Ra

2014-02-01

The purpose of this study was to evaluate the axial displacement of the abutments during clinical procedures by the tightening torque and cyclic loading. Two different implant-abutment connection systems were used (external butt joint connection [EXT]; internal tapered conical connection [INT]). The master casts with two implant replicas, angulated 10° from each other, were fabricated for each implant connection system. Four types of impression copings were assembled and tightened with the corresponding implants (hex transfer impression coping, non-hex transfer impression coping, hex pick-up impression coping, non-hex pick-up impression coping). Resin splinted abutments and final prosthesis were assembled. The axial displacement was measured from the length of each assembly, which was evaluated repeatedly, after 30 Ncm torque tightening. After 250 N cyclic loading of final prosthesis for 1,000,000 cycles, additional axial displacement was recorded. The mean axial displacement was statistically analyzed (repeated measured ANOVA). There was more axial displacement in the INT group than that of the EXT group in impression copings, resin splinted abutments, and final prosthesis. Less axial displacement was found at 1-piece non-hex transfer type impression coping than other type of impression copings in the INT group. There was more axial displacement at the final prosthesis than resin splinted abutments in the INT and the EXT groups. After 250 N cyclic loading of final prosthesis, the INT group showed more axial displacement than that of the EXT group. Internal tapered conical connection demonstrated a varying amount of axial displacement with tightening torque and cyclic loading. © 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

A discrete element model for damage and fracture of geomaterials under fatigue loading

NASA Astrophysics Data System (ADS)

Gao, Xiaofeng; Koval, Georg; Chazallon, Cyrille

2017-06-01

Failure processes in geomaterials (concrete, asphalt concrete, masonry, etc.) under fatigue loading (repeated moving loads, cycles of temperature, etc.) are responsible for most of the dysfunctions in pavements, brick structures, etc. In the beginning of the lifetime of a structure, the material presents only inner defects (micro cracks, voids, etc.). Due to the effect of the cyclic loading, these small defects tend to grow in size and quantity which damage the material, reducing its stiffness. With a relatively high number of cycles, these growing micro cracks become large cracks, which characterizes the fracture behavior. From a theoretical point of view, both mechanisms are treated differently. Fracture is usually described locally, with the propagation of cracks defined by the energy release rate at the crack tip; damage is usually associated to non-local approaches. In the present work, damage and fracture mechanics are combined in a local discrete element approach.

Structural failure; International Symposium on Structural Crashworthiness, 2nd, Massachusetts Institute of Technology, Cambridge, June 6-8, 1988, Invited Lectures

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

Wierzbicki, T.; Jones, N.

1989-01-01

The book discusses the fragmentation of solids under dynamic loading, the debris-impact protection of space structures, the controlled fracturing of structures by shock-wave interaction and focusing, the tearing of thin metal sheets, and the dynamic inelastic failure of beams, and dynamic rupture of shells. Consideration is also given to investigations of the failure of brittle and composite materials by numerical methods, the energy absorption of polymer matrix composite structures (frictional effects), the mechanics of deep plastic collapse of thin-walled structures, the denting and bending of tubular beams under local loads, the dynamic bending collapse of strain-softening cantilever beams, and themore » failure of bar structures under repeated loading. Other topics discussed are on the behavior of composite and metallic superstructures under blast loading, the catastrophic failure modes of marine structures, and industrial experience with structural failure.« less

Aircraft stress sequence development: A complex engineering process made simple

NASA Technical Reports Server (NTRS)

Schrader, K. H.; Butts, D. G.; Sparks, W. A.

1994-01-01

Development of stress sequences for critical aircraft structure requires flight measured usage data, known aircraft loads, and established relationships between aircraft flight loads and structural stresses. Resulting cycle-by-cycle stress sequences can be directly usable for crack growth analysis and coupon spectra tests. Often, an expert in loads and spectra development manipulates the usage data into a typical sequence of representative flight conditions for which loads and stresses are calculated. For a fighter/trainer type aircraft, this effort is repeated many times for each of the fatigue critical locations (FCL) resulting in expenditure of numerous engineering hours. The Aircraft Stress Sequence Computer Program (ACSTRSEQ), developed by Southwest Research Institute under contract to San Antonio Air Logistics Center, presents a unique approach for making complex technical computations in a simple, easy to use method. The program is written in Microsoft Visual Basic for the Microsoft Windows environment.

System for controlling a hybrid energy system

DOEpatents

Hoff, Brian D.; Akasam, Sivaprasad

2013-01-29

A method includes identifying a first operating sequence of a repeated operation of at least one non-traction load. The method also includes determining first and second parameters respectively indicative of a requested energy and output energy of the at least one non-traction load and comparing the determined first and second parameters at a plurality of time increments of the first operating sequence. The method also includes determining a third parameter of the hybrid energy system indicative of energy regenerated from the at least one non-traction load and monitoring the third parameter at the plurality of time increments of the first operating sequence. The method also includes determining at least one of an energy deficiency or an energy surplus associated with the non-traction load of the hybrid energy system and selectively adjusting energy stored within the storage device during at least a portion of a second operating sequence.

Swarms of repeating stick-slip glacierquakes triggered by snow loading at Mount Rainier volcano

NASA Astrophysics Data System (ADS)

Allstadt, K.; Malone, S. D.; Shean, D. E.; Fahnestock, M. A.; Vidale, J. E.

2013-12-01

We have detected over 150,000 low-frequency (~1-5 Hz) repeating earthquakes over the past decade at Mount Rainier volcano by scanning continuous seismic data from the permanent seismic network. Most of these were previously undetected due to their small size (M<1), shallow locations, and emergent waveforms. The earthquakes are located high (>3000 m) on the glacier-covered part of the edifice. They occur primarily in week- to month-long swarms of activity that strongly correlate with precipitation, namely snowfall, with a lag of about 1-2 days. Furthermore, there is a linear relationship between inter-event repeat time and the size of the subsequent event - consistent with slip-predictable stick-slip behavior. This pattern suggests that the additional load imparted by the sudden added weight of snow during winter storms triggers a temporary change from smooth aseismic sliding to seismic stick-slip basal sliding in locations where basal conditions are close to frictional instability. This sensitivity is analogous to the triggering of repeating earthquakes due to tiny overall stress changes in more traditional tectonic environments (e.g., tremor modulated by tides, dynamic triggering of repeating earthquakes). Using codawave interferometry on stacks of the repeating waveforms of the families with the most events, we found that the sources move at speeds of ~1 m/day. Using a GAMMA ground based radar interferometer, we collected spatially continuous line-of-sight velocities of several glaciers at Mount Rainier in both summer and late fall. We found that the faster parts of the glaciers also move at ~1 m/day or faster, even in late fall. Movement of the sources of these repeating earthquakes at glacial speeds indicates that the asperities are dirty patches that move with the ice rather than stationary bedrock bumps. The reappearance of some event families up to several years apart suggests that certain areas at the base of certain glaciers are prodigious producers of conditions favorable to this behavior. Stick-slip basal sliding of glaciers is supported over other potential moving shallow source mechanisms such as crevassing, unsteady fluid flow, and calving because the source must be non-destructive, highly repeatable at regular intervals, large enough to be detected on multiple stations, lack strong spectral peaks, and have a potential physical tie to the effects of winter precipitation. Identification of the source of these frequent signals offers a view of basal glacier processes, discriminates against alarming volcanic noises, and documents effects of weather on the cryosphere.

Trends in detectable viral load by calendar year in the Australian HIV observational database.

PubMed

Law, Matthew G; Woolley, Ian; Templeton, David J; Roth, Norm; Chuah, John; Mulhall, Brian; Canavan, Peter; McManus, Hamish; Cooper, David A; Petoumenos, Kathy

2011-02-23

Recent papers have suggested that expanded combination antiretroviral treatment (cART) through lower viral load may be a strategy to reduce HIV transmission at a population level. We assessed calendar trends in detectable viral load in patients recruited to the Australian HIV Observational Database who were receiving cART. Patients were included in analyses if they had started cART (defined as three or more antiretrovirals) and had at least one viral load assessment after 1 January 1997. We analyzed detectable viral load (>400 copies/ml) in the first and second six months of each calendar year while receiving cART. Repeated measures logistic regression methods were used to account for within and between patient variability. Rates of detectable viral load were predicted allowing for patients lost to follow up. Analyses were based on 2439 patients and 31,339 viral load assessments between 1 January 1997 and 31 March 2009. Observed detectable viral load in patients receiving cART declined to 5.3% in the first half of 2009. Predicted detectable viral load based on multivariate models, allowing for patient loss to follow up, also declined over time, but at higher levels, to 13.8% in 2009. Predicted detectable viral load in Australian HIV Observational Database patients receiving cART declined over calendar time, albeit at higher levels than observed. However, over this period, HIV diagnoses and estimated HIV incidence increased in Australia.

Effect of same-sided and cross-body load carriage on 3D back shape in young adults.

PubMed

O'Shea, C; Bettany-Saltikov, J A; Warren, J G

2006-01-01

Regular carriage of heavy loads such as backpacks, satchels and mailbags results in a variety of acute medical problems and increased potential for back injury. There is a paucity of information about the specific changes in back posture that occur in response to asymmetrical loading. The purpose of this study was to examine the changes in back shape that occurred in response to asymmetrical load carriage, either on one shoulder (same-side) or across the body (cross-body), in healthy young adults. A convenience sample of 21 physiotherapy students randomly performed three trials (unloaded, same-side loaded, cross-body loaded) in standing with a 15% body load. The Microscribe 3DX digitiser (Immersion Group Ltd) recorded the three dimensional coordinates of 15 Key anatomical landmarks on the back in the three conditions. A one-way ANOVA with repeated measures and post-hoc tests was implemented to highlight statistical differences in the data collected (p<0.05). Significant differences were found in the x, y and z coordinates of the anatomical landmarks in the upper back between unloaded and loaded conditions. Results demonstrated significantly less impact on spinal posture from cross-body loading as compared to same-sided loading. This study confirms that there are significant three-dimensional changes in back shape in response to asymmetrical loading. Further work is needed to evaluate the optimal carriage type and maximal body load that results in the least spinal impact and injury potential in young adults.

Face and object encoding under perceptual load: ERP evidence.

PubMed

Neumann, Markus F; Mohamed, Tarik N; Schweinberger, Stefan R

2011-02-14

According to the perceptual load theory, processing of a task-irrelevant distractor is abolished when attentional resources are fully consumed by task-relevant material. As an exception, however, famous faces have been shown to elicit repetition modulations in event-related potentials - an N250r - despite high load at initial presentation, suggesting preserved face-encoding. Here, we recorded N250r repetition modulations by unfamiliar faces, hands, and houses, and tested face specificity of preserved encoding under high load. In an immediate (S1-S2) repetition priming paradigm, participants performed a letter identification task on S1 by indicating whether an "X" vs. "N" was among 6 different (high load condition) or 6 identical (low load condition) letters. Letter strings were superimposed on distractor faces, hands, or houses. Subsequent S2 probes were either identical repetitions of S1 distractors, non-repeated exemplars from the same category, or infrequent butterflies, to which participants responded. Independent of attentional load at S1, an occipito-temporal N250r was found for unfamiliar faces. In contrast, no repetition-related neural modulation emerged for houses or hands. This strongly suggests that a putative face-selective attention module supports encoding under high load, and that similar mechanisms are unavailable for other natural or artificial objects. Copyright © 2010 Elsevier Inc. All rights reserved.

Effects of static fingertip loading on carpal tunnel pressure

NASA Technical Reports Server (NTRS)

Rempel, D.; Keir, P. J.; Smutz, W. P.; Hargens, A.

1997-01-01

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20 degrees of ulnar deviation; 10 degrees of radial deviation; and 15, 30, and 45 degrees of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increase (p < 0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.

The effects of changes in object location on object identity detection: A simultaneous EEG-fMRI study.

PubMed

Yang, Ping; Fan, Chenggui; Wang, Min; Fogelson, Noa; Li, Ling

2017-08-15

Object identity and location are bound together to form a unique integration that is maintained and processed in visual working memory (VWM). Changes in task-irrelevant object location have been shown to impair the retrieval of memorial representations and the detection of object identity changes. However, the neural correlates of this cognitive process remain largely unknown. In the present study, we aim to investigate the underlying brain activation during object color change detection and the modulatory effects of changes in object location and VWM load. To this end we used simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) recordings, which can reveal the neural activity with both high temporal and high spatial resolution. Subjects responded faster and with greater accuracy in the repeated compared to the changed object location condition, when a higher VWM load was utilized. These results support the spatial congruency advantage theory and suggest that it is more pronounced with higher VWM load. Furthermore, the spatial congruency effect was associated with larger posterior N1 activity, greater activation of the right inferior frontal gyrus (IFG) and less suppression of the right supramarginal gyrus (SMG), when object location was repeated compared to when it was changed. The ERP-fMRI integrative analysis demonstrated that the object location discrimination-related N1 component is generated in the right SMG. Copyright © 2017 Elsevier Inc. All rights reserved.

77 FR 33106 - Energy Conservation Program: Test Procedure for Microwave Ovens

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-05

... due to the different masses and shapes of the potatoes. DOE observed, similar to the tests for... consumer use, (2) the repeatability of energy use measurements using different food loads, and (3) consumer... ``normal usage'' and the water temperature rise of 50 degrees Celsius ([deg]C) achieves eating temperature...

Establishment of design criteria for acceptable failure modes and fail safe considerations for the space shuttle structural system

NASA Technical Reports Server (NTRS)

Westrup, R. W.

1971-01-01

The application of general design approaches for preventing failures due to repeated load cycles is briefly discussed. Program objective, mission requirements, and structural design criteria are summarized. Discrete structural elements and associated sections were selected for detailed strength, fatigue, and fracture mechanics investigations.

Implementation of a system for controlling the lateral position of a moving vehicle : and field testing of ODOT sensor-assisted steering system

DOT National Transportation Integrated Search

2002-07-01

The overall objective was to design, implement, and test sensor-assisted driver control of an ODOT dump truck. Requirements included repeatably steering a loaded or unloaded truck over embedded sensors to a lateral accuracy of +/- one inch, time-shar...

The development of the friction coefficient inspection equipment for skin using a load cell.

PubMed

Song, Han Wook; Park, Yon Kyu; Lee, Sung Jun; Woo, Sam Yong; Kim, Sun Hyung; Kim, Dal Rae

2008-01-01

The skin is an indispensible organ for human because it contributes to the metabolism using its own biochemical functions as well as it protects the human body from the exterior stimuli. Recently, the friction coefficient have been used as the decision index of the progress for the bacterial aliments in the field of the skin physiology and the importance of friction coefficient have been increased in the skin care market because of the needs of the well being times. In addition, the usage of friction coefficient is known to have the big discrimination ability in classification of human constitutions, which is utilized in the alternative medicine. In this study, we designed a system which used the multi axes load cell and hemi-circular probe and tried to measure the friction coefficient of hand skins repeatedly. Using this system, the relative repeatability error for the measurement of the friction coefficient was below 4 %. The coefficient is not concerned in curvatures of tips. Using this system, we will try to establish the standard for classification of constitutions.

Basketball lay-up - foot loading characteristics and the number of trials necessary to obtain stable plantar pressure variables.

PubMed

Chua, YaoHui K; Quek, Raymond K K; Kong, Pui W

2017-03-01

This study aimed (1) to profile the plantar loading characteristics when performing the basketball lay-up in a realistic setting and (2) to determine the number of trials necessary to establish a stable mean for plantar loading variables during the lay-up. Thirteen university male basketball players [age: 23.0 (1.4) years, height: 1.75 (0.05) m, mass: 68.4 (8.6) kg] performed ten successful basketball lay-ups from a stationary position. Plantar loading variables were recorded using the Novel Pedar-X in-shoe system. Loading variables including peak force, peak pressure, and pressure-time integral were extracted from eight foot regions. Performance stability of plantar loading variables during the take-off and landing steps were assessed using the sequential averaging technique and intra-class correlation coefficient (ICC). High plantar loadings were experienced at the heel during the take-off steps, and both the heel and forefoot regions upon landing. The sequential estimation technique revealed a five-eight trial range to achieve a stable mean across all plantar loading variables, whereas ICC analysis was insensitive to inter-trial differences of repeated lay-up performances. Future studies and performance evaluation protocols on plantar loading during basketball lay-ups should include at least eight trials to ensure that the measurements obtained are sufficiently stable.

Control of impact loading during distracted running before and after gait retraining in runners.

PubMed

Cheung, Roy T H; An, Winko W; Au, Ivan P H; Zhang, Janet H; Chan, Zoe Y S; MacPhail, Aislinn J

2018-07-01

Gait retraining using visual biofeedback has been reported to reduce impact loading in runners. However, most of the previous studies did not adequately examine the level of motor learning after training, as the modified gait pattern was not tested in a dual-task condition. Hence, this study sought to compare the landing peak positive acceleration (PPA) and vertical loading rates during distracted running before and after gait retraining. Sixteen recreational runners underwent a two-week visual biofeedback gait retraining program for impact loading reduction, with feedback on the PPA measured at heel. In the evaluation of PPA and vertical loading rates before and after the retraining, the participants performed a cognitive and verbal counting task while running. Repeated measures ANOVA indicated a significant interaction between feedback and training on PPA (F = 4.642; P = 0.048) but not vertical loading rates (F > 1.953; P > 0.067). Pairwise comparisons indicated a significantly lower PPA and vertical loading rates after gait retraining (P < 0.007; Cohen's d > 0.68). Visual feedback after gait retraining reduced PPA and vertical loading rates during distracted running (P < 0.033; Cohen's d > 0.36). Gait retraining is effective in lowering impact loading even when the runners are distracted. In dual-task situation, visual biofeedback provided beneficial influence on kinetics control after gait retraining.

Establishing Immediate Reliability of Sonographic Measurements of the Transversus Abdominis in Asymptomatic Adults Performing Upright Loaded Functional Tasks in a Clinical Context Without Delayed Recorded Measurement.

PubMed

McPherson, Sue; Watson, Todd; Pate, Lindsey

2016-08-01

This study examined the reliability of sonographic measurements of the transversus abdominis of adults without low back pain during upright loaded functional tasks in real time, without relying on delayed recorded images. A single-group repeated-measures reliability study was conducted on 12 healthy participants without low back pain. Six of these adults reported a prior history of abdominal drawing-in maneuver training without sonographic measurement. The participants performed 3 trials of neutral standing, a loaded forward reach, and a loaded box lift under rest and with abdominal drawing-in maneuver instructions; task order was randomized. Transversus abdominis thickness measurements were obtained by an experienced rater using B-mode sonography in real-time via electronic calipers twice on the same static image during all trials by a rater. The rater was masked to group assignment and on-screen measurement output and required to respond to trivia questions between repeated measurements. The participants included 6 male and 6 female adults with a mean age ± SD of 26.3 ± 3.7 years. Intra-rater intraclass correlation coefficients (2,3) were high and precise for the rater's first and second measurements for all tasks and instruction conditions for mean transversus abdominis thickness and percent change in thickness measurements (eg, ranges were 0.968-0.997 for intraclass correlation coefficients, 0.01-0.21 mm for standard errors of the measurement, and 0.01-0.58 mm for minimal detectable changes). Calipers cleared by the rater or a research assistant produced similar findings of excellent reliability and precision. High intra-rater reliability and precision of transversus abdominis thickness measurements were obtained by a physical therapist in real time from asymptomatic adults performing upright loaded functional tasks under rest and with abdominal drawing-in maneuver instructions.

Comparison of strains produced by titanium and poly D, L-lactide Acid plating systems to in vitro forces.

PubMed

Chacon, Guillermo E; Dillard, Frederick Matt; Clelland, Nancy; Rashid, Robert

2005-07-01

To determine if a specific resorbable plating system provides similar fixation, in terms of strain distribution under load, to a titanium system when the Champy technique is applied for the treatment of a mandibular angle fracture. A formalin-fixed cadaver mandible was harvested just before the study. A bicortical osteotomy was then made using a diamond disc extending in an oblique direction in the area of the angle. It was then passively fixated with a 4-hole 2.0-mm miniplate. Two stacked rosette strain gauges were bonded to the mandible on either side of the fracture. Each rosette had 3 strain gauges arranged in specific degrees relative to each other. The mandible was then placed on a dynanometer and 30 lb loads were delivered on the ipsilateral molar. Static resistance was placed in the condylar neck region to simulate the glenoid fossa. Loading was repeated 10 times with a period of 3 minutes between loads. Measurements were recorded for each strain gauge after loads were in place for 30 seconds. The same process was repeated using a 4-hole 2.1-mm resorbable miniplate. The strains were then used to calculate the maximum and minimum strains for each rosette. Hooke's law was used to calculate the principal stresses. Differences were observed between the strain gauges for each individual plating system. There was variability within the resorbable plate measurements as shown by the standard deviation. Using the REML ANOVA test, a significant difference was found between the 2 materials. In this in vitro study, there were significant biomechanical differences observed between a 2.0-mm titanium miniplate and a 2.1-mm resorbable miniplate when used to treat a mandibular angle fracture following Champy's principles. Based on our finding, both systems cannot be used interchangeably for the treatment of mandibular angle fractures under the same clinical conditions.

Effect of hoof angle on joint contact area in the equine metacarpophalangeal joint following simulated impact loading ex vivo.

PubMed

McCarty, C A; Thomason, J J; Gordon, K; Hurtig, M; Bignell, W

2015-11-01

To add to the existing data on impact loading of the metacarpophalangeal (MCP) joint as a precursor to assessing the potential role of impact in joint disease. To examine the effect of impact loading on contact areas of the first phalanx (P1) and proximal sesamoids (PS) with the third metacarpal (McIII) under 3 hoof-strike conditions (toe-first, flat, heel-first). Randomised, repeated controlled experiment using cadaver material. Eight cadaver limbs were subjected to randomised, repeated controlled trials where the hoof was struck by a pendulum impact machine (impact velocity 3.55 m/s) under 3 strike conditions. Data from pressure sensitive film placed over medial and lateral McIII condyles and lateromedially across the dorsal aspect of McIII were quantified: total areas of P1 and PS contact (cm(2) ) at maximum recorded pressure; centroid locations of contact areas relative to the sagittal ridge (cm) and transverse ridge (cm) and dispersion of pixels (cm(4) ) for each McIII condyle (medial/lateral). The effect of the strike conditions on each variable were statistically tested using repeated-measures ANOVA (α = 0.05). Contact area between P1 and McIII condyles fell in well-defined areas bounded by the sagittal and transverse ridge, contact areas from PS were smaller and widely dispersed across McIII palmar border. Ratio of contact area of P1 to PS was 2.83 (P<0001). Hoof strike had no significant effect on contact area (P>0.54) CONCLUSIONS: Contact at impact (primarily from P1 and distally situated on McIII), contrasts with contact areas at midstance from both P1 and PS, symmetrically placed. Under impact, the greatest contact area was on the dorsal aspect of the medial condyle and coincides with the area subjected to the greatest increase in subchondral bone stiffening in joint disease. © 2014 EVJ Ltd.

Effects of Resistance Training and Combined Training Program on Repeated Sprint Ability in Futsal Players.

PubMed

Torres-Torrelo, Julio; Rodríguez-Rosell, David; Mora-Custodio, Ricardo; Pareja-Blanco, Fernando; Yañez-García, Juan Manuel; González-Badillo, Juan José

2018-05-16

The purpose of this study was to compare the effects of 6 weeks resistance training (RT) with combined RT and loaded change of direction (CD) exercise on muscle strength and repeated sprint ability (RSA) in futsal players. Thirty-four players (age: 23.7±4.1 years; height: 1.77±0.06 m; body mass: 74.1±8.2 kg) were randomly assigned into three groups: full squat group (SG, n=12), combined full squat and CD group (S+CDG, n=12), and control group (CG, n=10). The RT for SG consisted of full squat with low-load (~45-60% 1RM) and low-volume (2-3 sets and 4-6 repetitions), whereas the S+CDG performed the same RT program combined with loaded CD (2-5 sets of 10 s). Estimated one-repetition maximum (1RM est ) and variables derived from RSA test including mean sprint time (RSA mean ), best sprint time (RSA best ), percent sprint decrement (S dec ), mean ground contact time (GCT mean ) and mean step length (SL) were selected as testing variables. Changes in sprint time and GCT in each sprint were also analysed. Both experimental groups showed significant (P<0.05-0.001) improvements for 1RM est , RSA best and first and second sprint time. In addition, S+CDG achieved significant (P<0.05-0.001) improvements in RSA mean, sprint time (from fifth to ninth sprint) and GCT (from third to eighth sprint). These results indicate that only 6 weeks of low-load and low-volume RT combined with CD in addition to routine futsal training is enough to improve RSA and strength performance simultaneously in futsal players. © Georg Thieme Verlag KG Stuttgart · New York.

Laboratory simulation of the effects of overburden stress on the specific storage of shallow artesian aquifers

USGS Publications Warehouse

Sepúlveda, Nicasio; Zack, A.L.; Krishna, J.H.; Quinones-Aponte, Vicente; Gomez-Gomez, Fernando; Morris, G.L.

1990-01-01

A laboratory experiment to measure the specific storage of an aquifer material was conducted. A known dead load, simulating an overburden load, was applied to a sample of completely saturated aquifer material contained inside a cylinder. After the dead load was applied, water was withdrawn from the sample, causing the hydrostatic pressure to decrease and the effective stress to increase. The resulting compression of the sample and the amount of water withdrawn were measured after equilibrium was reached. The procedure was repeated by increasing the dead load and the hydrostatic pressure followed by withdrawing water to determine new values of effective stress and compaction. The simulated dead loads are typical of those experienced by shallow artesian aquifers. The void ratio and the effective stress of the aquifer sample, as simulated by different dead loads, determine the pore volume compressibility which, in turn, determines the values of specific storage. An analytical algorithm was used to independently determine the stress dependent profile of specific storage. These values are found to be in close agreement with laboratory results. Implications for shallow artesian aquifers, with relatively small overburden stress, are also addressed.

Modeling Load Dynamics to Support Resiliency-based Operations in Low-Inertia Microgrids

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

Tuffner, Francis K.; Schneider, Kevin P.; Hansen, Jacob

Microgrids have repeatedly demonstrated the ability to provide uninterrupted service to critical end-use loads during normal outages, severe weather events, and natural disasters. While their ability to provide critical services is well documented, microgrids present a more dynamic operational environment than grid-connected distribution systems. The electrodynamics of a microgrid are commonly driven by the high inertia of rotating generators, which are common in many microgrids. In such high-inertia systems, the impact of end-use load electromechanical dynamics are often not examined. However, with the increased penetration of inverter-based generation with little or no inertia, it is necessary to consider the impactmore » that the dynamics of the end-use loads have on the operations of microgrids, particularly for a resiliency-based operation. These operations include, but are not limited to, switching operations, loss of generating units, and the starting of induction motors. This paper examines the importance of including multi-state electromechanical dynamic models of the end-use load when evaluating the operations of low inertia microgrids, and shows that by properly representing their behavior, it is possible to cost effectively size equipment while supporting resilient operations of critical end-use loads.« less

Modeling Load Dynamics to Support Resiliency-based Operations in Low-Inertia Microgrids

DOE PAGES

Tuffner, Francis K.; Schneider, Kevin P.; Hansen, Jacob; ...

2018-03-07

Microgrids have repeatedly demonstrated the ability to provide uninterrupted service to critical end-use loads during normal outages, severe weather events, and natural disasters. While their ability to provide critical services is well documented, microgrids present a more dynamic operational environment than grid-connected distribution systems. The electrodynamics of a microgrid are commonly driven by the high inertia of rotating generators, which are common in many microgrids. In such high-inertia systems, the impact of end-use load electromechanical dynamics are often not examined. However, with the increased penetration of inverter-based generation with little or no inertia, it is necessary to consider the impactmore » that the dynamics of the end-use loads have on the operations of microgrids, particularly for a resiliency-based operation. These operations include, but are not limited to, switching operations, loss of generating units, and the starting of induction motors. This paper examines the importance of including multi-state electromechanical dynamic models of the end-use load when evaluating the operations of low inertia microgrids, and shows that by properly representing their behavior, it is possible to cost effectively size equipment while supporting resilient operations of critical end-use loads.« less

The development and reliability of a repeated anaerobic cycling test in female ice hockey players.

PubMed

Wilson, Kier; Snydmiller, Gary; Game, Alex; Quinney, Art; Bell, Gordon

2010-02-01

The purpose of this study was to develop and assess the reliability of a repeated anaerobic power cycling test designed to mimic the repeated sprinting nature of the sport of ice hockey. Nineteen female varsity ice hockey players (mean X +/- SD age, height and body mass = 21 +/- 2 yr, 166.6 +/- 6.3 cm and 62.3 +/- 7.3) completed 3 trials of a repeated anaerobic power test on a Monark cycle ergometer on different days. The test consisted of "all-out" cycling for 5 seconds separated by 10 seconds of low-intensity cycling, repeated 4 times. The relative load factor used for the resistance setting was equal to 0.095 kg per kilogram body mass. There was no significant difference between the peak 5-second power output (PO), mean PO, or the fatigue index (%) among the 3 different trials. The peak 5-second PO was 702.6 +/- 114.8 w and 11.3 +/- 1.1 w x kg, whereas the mean PO across the 4 repeats was 647.1 +/- 96.3 w and 10.4 +/- 1.0 w x kg averaged for the 3 different tests. The fatigue index averaged 17.8 +/- 6.5%. The intraclass correlation coefficient for peak 5-second, mean PO, and fatigue index was 0.82, 0.86, and 0.82, respectively. This study reports the methodology of a repeated anaerobic power cycling test that was reliable for the measurement of PO and calculated fatigue index in varsity women ice hockey players and can be used as a laboratory-based assessment of repeated anaerobic fitness.

Fabrication of wrist-like SMA-based actuator by double smart soft composite casting

NASA Astrophysics Data System (ADS)

Rodrigue, Hugo; Wei, Wang; Bhandari, Binayak; Ahn, Sung-Hoon

2015-12-01

A new manufacturing method for smart soft composite (SSC) actuators that consists of double casting a SSC actuator to produce an actuator with non-linear shape memory alloy (SMA) wire positioning is proposed. This method is used to manufacture a tube-shaped SSC actuator in which the SMA wires follow the curvature of the tube and is capable of pure-twisting deformations while sustaining a cantilever load. The concept is tested by measuring the maximum twisting angle and a simple control method is proposed to control the twisting angle of the actuator. Then, a soft robotic wrist with a length of 18 cm is built, its load-carrying capability is tested by measuring the cantilever force required for deforming the actuator, and its load-carrying capability during actuation is tested by loading one end with different objects and actuating the actuator. This wrist actuator shows good repeatability, is capable of twisting deformations up to 25° while holding objects weighing 100 g, and can sustain loads above 2 N without undergoing buckling.

Back muscle strength, lifting, and stooped working postures.

PubMed

Poulsen, E; Jørgensen, K

1971-09-01

When lifting loads and working in a forward stooped position, the muscles of the back rather than the ligaments and bony structures of the spine should overcome the gravitational forces. Formulae, based on measurements of back muscle strength, for prediction of maximal loads to be lifted, and for the ability to sustain work in a stooped position, have been worked out and tested in practical situations. From tests with 50 male and female subjects the simplest prediction formulae for maximum loads were: max. load = 1.10 x isometric back muscle strength for men; and max. load = 0.95 x isometric back muscle strength - 8 kg for women. Some standard values for maximum lifts and permissible single and repeated lifts have been calculated for men and women separately and are given in Table 1. From tests with 65 rehabilitees it was found that the maximum isometric strength of the back muscles measured at shoulder height should exceed 2/3 of the body weight, if fatigue and/or pain in the back muscles is to be avoided during work in a standing stooped position.

Texture evolution during isothermal, isostrain, and isobaric loading of polycrystalline shape memory NiTi

NASA Astrophysics Data System (ADS)

Nicholson, D. E.; Padula, S. A.; Benafan, O.; Vaidyanathan, R.

2017-06-01

In situ neutron diffraction was used to provide insights into martensite variant microstructures during isothermal, isobaric, and isostrain loading in shape memory NiTi. The results show that variant microstructures were equivalent for the corresponding strain, and more importantly, the reversibility and equivalency were immediately evident in variant microstructures that were first formed isobarically but then reoriented to near random self-accommodated microstructures following isothermal deformation. Variant microstructures formed isothermally were not significantly affected by a subsequent thermal cycle under constant strain. In all loading cases considered, the resulting variant microstructure correlated with strain and did not correlate with stress. Based on the ability to select a variant microstructure for a given strain despite thermomechanical loading history, the results demonstrated here can be obtained by following any sequence of thermomechanical loading paths over multiple cycles. Thus, for training shape memory alloys (repeating thermomechanical cycling to obtain the desired variant microstructure), optimal paths can be selected so as to minimize the number of training cycles required, thereby increasing the overall stability and fatigue life of these alloys in actuator or medical applications.

A Simple Test to Determine the Effectiveness of Different Braze Compositions for Joining Ti-Tubes to C/C Composite Plates

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Singh, Mrityunjay; Shpargel, Tarah; Asthana, Rajiv

2006-01-01

A simple tube-plate joint tensile test was implemented to compare the effectiveness of commercial brazes, namely, TiCuNi, TiCuSil, and Cu-ABA, used for bonding Ti-tubes joined to C-C composite plates. The different braze systems yielded different; yet, repeatable results. The Cu-ABA system proved to have about twice the load-carrying ability of the other two systems due to the fact that the bonded area between the braze material and the C-C plate was largest for this system. The orientation of the surface fiber tows also had a significant effect on load-carrying ability with tows oriented perpendicular to the tube axis displaying the highest failure loads. Increasing the process load and modifying the surface of the C-C plate by grooving out channels for the Ti-Tube to nest in resulted in increased load-carrying ability for the TiCuSil and Cu-ABA systems due to increased bonded area and better penetration of the braze material into the C-C composite.

Analysis of fatigue on surface course using dissipated energy approach

NASA Astrophysics Data System (ADS)

Michael; Setyawan, A.; Pramesti, F. P.

2018-03-01

As an important transportation infrastructure, pavement is subjected to repeated vehicle loads that may cause fatigue, which often leads to cracking. The point when this cracking initiates can be determined from the energy dissipated during the loading. This research investigates fatigue in Adi Soemarmo Airport mix-design using bitumen Pen 60/70 + EVA (Ethyl Vinyl Acetate) polymer. An Indirect Tensile Fatigue Test (ITFT) was conducted using stress-controlled loading mode to determine its fatigue life. The stress levels were 500, 600, and 700 kPa, while the loading frequency and the temperature were 10 Hz and 20°C, respectively. The test exhibits strain levels for each loading cycle, which were used to determine the dissipated energy (DE). The result indicates that the DE increases when the number of loading cycles increases, due to progress of the strain levels. The values of DE are 7122.8, 8614.3, and 2654.9 J/m3 for loading levels of 500, 600, and 700 kPa, respectively, whereas the failure points for stress levels of 500, 600, and 700 kPa are 8171, 5161, and 841 cycles, respectively. Thus, the longer the time until the pavement failure point is reached (fatigue life), the greater the amount of energy that is dissipated.

The Influence of Working Memory Load on Expectancy-Based Strategic Processes in the Stroop-Priming Task.

PubMed

Ortells, Juan J; Álvarez, Dolores; Noguera, Carmen; Carmona, Encarna; de Fockert, Jan W

2017-01-01

The present study investigated whether a differential availability of cognitive control resources as a result of varying working memory (WM) load could affect the capacity for expectancy-based strategic actions. Participants performed a Stroop-priming task in which a prime word (GREEN or RED) was followed by a colored target (red vs. green) that participants had to identify. The prime was incongruent or congruent with the target color on 80 and 20% of the trials, respectively, and participants were informed about the differential proportion of congruent vs. incongruent trials. This task was interleaved with a WM task, such that the prime word was preceded by a sequence of either a same digit repeated five times (low load) or five different random digits (high load), which should be retained by participants. After two, three, or four Stroop trials, they had to decide whether or not a probe digit was a part of the memory set. The key finding was a significant interaction between prime-target congruency and WM load: Whereas a strategy-dependent (reversed Stroop) effect was found under low WM load, a standard Stroop interference effect was observed under high WM load. These findings demonstrate that the availability of WM is crucial for implementing expectancy-based strategic actions.

In vitro evaluation of translating and rotating plates using a robot testing system under follower load.

PubMed

Yan, Y; Bell, K M; Hartman, R A; Hu, J; Wang, W; Kang, J D; Lee, J Y

2017-01-01

Various modifications to standard "rigid" anterior cervical plate designs (constrained plate) have been developed that allow for some degree of axial translation and/or rotation of the plate (semi-constrained plate)-theoretically promoting proper load sharing with the graft and improved fusion rates. However, previous studies about rigid and dynamic plates have not examined the influence of simulated muscle loading. The objective of this study was to compare rigid, translating, and rotating plates for single-level corpectomy procedures using a robot testing system with follower load. In-vitro biomechanical test. N = 15 fresh-frozen human (C3-7) cervical specimens were biomechanically tested. The follower load was applied to the specimens at the neutral position from 0 to 100 N. Specimens were randomized into a rigid plate group, a translating plate group and a rotating plate group and then tested in flexion, extension, lateral bending and axial rotation to a pure moment target of 2.0 Nm under 100N of follower load. Range of motion, load sharing, and adjacent level effects were analyzed using a repeated measures analysis of variance (ANOVA). No significant differences were observed between the translating plate and the rigid plate on load sharing at neutral position and C4-6 ROM, but the translating plate was able to maintain load through the graft at a desired level during flexion. The rotating plate shared less load than rigid and translating plates in the neutral position, but cannot maintain the graft load during flexion. This study demonstrated that, in the presence of simulated muscle loading (follower load), the translating plate demonstrated superior performance for load sharing compared to the rigid and rotating plates.

Impact of Intentional Overload on Joint Stability of Internal Implant-Abutment Connection System with Different Diameter.

PubMed

Lee, Ji-Hye; Lee, Won; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2017-09-05

To evaluate the axial displacement of the implant-abutment assembly of different implant diameter after static and cyclic loading of overload condition. An internal conical connection system with three diameters (Ø 4.0, 4.5, and 5.0) applying identical abutment dimension and the same abutment screw was evaluated. Axial displacement of abutment and reverse torque loss of abutment screw were evaluated under static and cyclic loading conditions. Static loading test groups were subjected to vertical static loading of 250, 400, 500, 600, 700, and 800 N consecutively. Cyclic loading test groups were subjected to 500 N cyclic loading to evaluate the effect of excessive masticatory loading. After abutment screw tightening for 30 Ncm, axial displacement was measured upon 1, 3, 10, and 1,000,000 cyclic loadings of 500 N. Repeated-measure ANOVA and 2-way ANOVA were used for statistical analysis (α = 0.05). The increasing magnitude of vertical load and thinner wall thickness of implant increased axial displacement of abutment and reverse torque loss of abutment screw (p < 0.05). Implants in the Ø 5.0 diameter group demonstrated significantly low axial displacement, and reverse torque loss after static loading than Ø 4.0 and Ø 4.5 diameter groups (p < 0.05). In the cyclic loading test, all diameter groups of implant showed significant axial displacement after 1 cycle of loading of 500 N (p < 0.05). There was no significant axial displacement after 3, 10, or 1,000,000 cycles of loading (p = 0.603). Implants with Ø 5.0 diameter demonstrated significantly low axial displacement and reverse torque loss after the cyclic and static loading of overload condition. © 2017 by the American College of Prosthodontists.

77 FR 24835 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-26

... inspections must be used for that wing for that visit and for all subsequent repeat inspections. Delta stated... Company Model 767 airplanes. This AD was prompted by reports of cracking in the upper wing skin at the... in the loss of the strut-to-wing upper link load path and possible separation of a strut and engine...

77 FR 53886 - February 2011 Southwest Cold Weather Event Follow-up Technical Conference; Notice of Technical...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-04

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD11-9-000] February 2011... repeat of the loss of approximately 700 megawatts of generation in WECC due to severe cold weather issues. This resulted in 1,000 megawatts of load shedding which affected over 250,000 customers in the WECC...

A High Power Solid State Circuit Breaker for Military Hybrid Electric Vehicle Applications

DTIC Science & Technology

2012-08-01

the SSCB to isolate a fault, breaker opening is latched and can be reset to reclose the breaker via remote logic input. SSCB state and health...rated load current (125 A). Figure 10 shows that after the SSCB detects a fault and opens, it can also be repeatedly reclosed remotely to attempt to

Fibrillatory conduction in branching atrial tissue--Insight from volumetric and monolayer computer models.

PubMed

Wieser, L; Fischer, G; Nowak, C N; Tilg, B

2007-05-01

Increased local load in branching atrial tissue (muscle fibers and bundle insertions) influences wave propagation during atrial fibrillation (AF). This computer model study reveals two principal phenomena: if the branching is distant from the driving rotor (>19 mm), the load causes local slowing of conduction or wavebreaks. If the driving rotor is close to the branching, the increased load causes first a slow drift of the rotor towards the branching. Finally, the rotor anchors, and a stable, repeatable pattern of activation can be observed. Variation of the bundle geometry from a cylindrical, volumetric structure to a flat strip of a comparable load in a monolayer model changed the local activation sequence in the proximity of the bundle. However, the global behavior and the basic effects are similar in all models. Wavebreaks in branching tissue contribute to the chaotic nature of AF (fibrillatory conduction). The stabilization (anchoring) of driving rotors by branching tissue might contribute to maintain sustained AF.

Change in Tongue Morphology in Response to Expiratory Resistance Loading Investigated by Magnetic Resonance Imaging

PubMed Central

Yanagisawa, Yukio; Matsuo, Yoshimi; Shuntoh, Hisato; Mitamura, Masaaki; Horiuchi, Noriaki

2013-01-01

[Purpose] The purpose of this study was to investigate the effect of expiratory resistance load on the tongue area encompassing the suprahyoid and genioglossus muscles. [Subjects] The subjects were 30 healthy individuals (15 males, 15 females, mean age: 28.9 years). [Methods] Magnetic resonance imaging was used to investigate morphological changes in response to resistive expiratory pressure loading in the area encompassing the suprahyoid and genioglossus muscles. Images were taken when water pressure was sustained at 0%, 10%, 30%, and 50% of maximum resistive expiratory pressure. We then measured tongue area using image analysis software, and the morphological changes were analyzed using repeated measures analysis of variance followed by post hoc comparisons. [Results] A significant change in the tongue area was detected in both sexes upon loading. Multiple comparison analysis revealed further significant differences in tongue area as well as changes in tongue area in response to the different expiratory pressures. [Conclusion] The findings demonstrate that higher expiratory pressure facilitates greater reduction in tongue area. PMID:24259824

Wearable woven supercapacitor fabrics with high energy density and load-bearing capability.

PubMed

Shen, Caiwei; Xie, Yingxi; Zhu, Bingquan; Sanghadasa, Mohan; Tang, Yong; Lin, Liwei

2017-10-30

Flexible power sources with load bearing capability are attractive for modern wearable electronics. Here, free-standing supercapacitor fabrics that can store high electrical energy and sustain large mechanical loads are directly woven to be compatible with flexible systems. The prototype with reduced package weight/volume provides an impressive energy density of 2.58 mWh g -1 or 3.6 mWh cm -3 , high tensile strength of over 1000 MPa, and bearable pressure of over 100 MPa. The nanoporous thread electrodes are prepared by the activation of commercial carbon fibers to have three-orders of magnitude increase in the specific surface area and 86% retention of the original strength. The novel device configuration woven by solid electrolyte-coated threads shows excellent flexibility and stability during repeated mechanical bending tests. A supercapacitor watchstrap is used to power a liquid crystal display as an example of load-bearing power sources with various form-factor designs for wearable electronics.

Creep Behavior of Passive Bovine Extraocular Muscle

PubMed Central

Yoo, Lawrence; Kim, Hansang; Shin, Andrew; Gupta, Vijay; Demer, Joseph L.

2011-01-01

This paper characterized bovine extraocular muscles (EOMs) using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV) relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed for each loading rate and was similar among all six anatomical EOMs. The mean creep coefficient after 1,500 seconds for a wide range of initial loading rates was at 1.37 ± 0.03 (standard deviation, SD). The creep function derived from the relaxation-based QLV model agreed with observed creep to within 2.7% following 16.67%/s ramp loading. Measured creep agrees closely with a derived QLV model of EOM relaxation, validating a previous QLV model for characterization of EOM biomechanics. PMID:22131809

Retention and wear behaviors of two implant overdenture stud-type attachments at different implant angulations.

PubMed

Choi, Jae-Won; Bae, Ji-Hyeon; Jeong, Chang-Mo; Huh, Jung-Bo

2017-05-01

Implant angulation should be considered when selecting an attachment. Some in vitro studies have investigated the relationship between implant angulation and changes in the retention force of the stud attachment, but few studies have evaluated the effect of cyclic loading and repeated cycles of insertion and removal on the stud attachment. The purpose of this in vitro study was to evaluate the effects of implant angulation on the retentive characteristics of overdentures with 2 different stud attachments, an experimental system and O-rings in red and orange, after cyclic loading and repeated insertion and removal cycles. The canine region of a mandibular experimental model was fitted with 2 implant fixtures with 2 different stud attachment systems at implant angulations of 0, 15, or 30 degrees. A mastication simulator was used to simulate cyclic loading, and a universal testing machine was used to evaluate retentive force changes after repeated insertion and removal cycles. To simulate the numbers of mastication and insertion and removal cycles per annum, 400000 cyclic loadings and 1080 insertion and removal cycles were performed. Wear patterns and attachment surface deformations were evaluated by scanning electron microscopy. Data were analyzed using the Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction (α=.05/3=.017), and the paired-sample Student t test (α=.05). When retentive forces before and after testing were compared, O-ring showed significant retention loss at all implant angulations (P<.001). In contrast, the experimental system showed little retention loss in the 0- and 15-degree models (P>.05), whereas the 30-degree model showed a significant increase in retentive force (P=.001). At all implant angulations, retention loss increased significantly for the orange O-ring, followed by the red O-ring, and the experimental system (P<.001). Scanning electron microscopy analysis showed more intense wear in the matrix than the patrix (abutment that matches to matrix) and more severe wear and deformation of the O-ring rubber matrix than of the experimental zirconia ball. Upon completion of the experiment, wear and deformation were found for all attachment systems. Even when implants are not installed in parallel, the experimental system can be used without involving great loss of retention. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Effect of the Coronal Wall Thickness of Dental Implants on the Screw Joint Stability in the Internal Implant-Abutment Connection.

PubMed

Lee, Ji-Hye; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2016-01-01

To evaluate the effect of implant coronal wall thickness on load-bearing capacity and screw joint stability. Experimental implants were customized after investigation of the thinnest coronal wall thickness of commercially available implant systems with a regular platform diameter. Implants with four coronal wall thicknesses (0.2, 0.3, 0.4, and 0.5 mm) were fabricated. Three sets of tests were performed. The first set was a failure test to evaluate load-bearing capacity and elastic limit. The second and third sets were cyclic and static loading tests. After abutment screw tightening of each implant, vertical cyclic loading of 250 N or static loading from 250 to 800 N was applied. Coronal diameter expansion, axial displacement, and removal torque values of the implants were compared. Repeated measures analysis of variance (ANOVA) was used for statistical analysis (α = .05). Implants with 0.2-mm coronal wall thickness demonstrated significantly low load-bearing capacity and elastic limit (both P < .05). These implants also showed significantly large coronal diameter expansion and axial displacement after screw tightening (both P < .05). Greater vertical load and thinner coronal wall thickness significantly increased coronal diameter expansion of the implant, axial displacement of the abutment, and removal torque loss of the abutment screw (all P < .05). Implant coronal wall thickness of 0.2 mm produces significantly inferior load-bearing capacity and screw joint stability.

Nonlinear response of unidirectional boron/aluminum

NASA Technical Reports Server (NTRS)

Pindera, M.-J.; Herakovich, C. T.; Becker, W.; Aboudi, J.

1990-01-01

Experimental results obtained for unidirectional boron/aluminum subjected to combined loading using off-axis tension, compression and Iosipescu shear specimens are correlated with a nonlinear micromechanics model. It is illustrated that the nonlinear response in the principal material directions is markedly influenced by the different loading modes and different ratios of the applied stress components. The observed nonlinear response under pure and combined loading is discussed in terms of initial yielding, subsequent hardening, stress-interaction effects and unloading-reloading characteristics. The micromechanics model is based on the concept of a repeating unit cell representative of the composite-at-large and employs the unified theory of Bodner and Partom to model the inelastic response of the matrix. It is shown that the employed micromechanics model is sufficiently general to predict the observed nonlinear response of unidirectional boron/aluminum with good accuracy.

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium redox flow cells

NASA Technical Reports Server (NTRS)

Reid, M. A.; Gahn, R. F.

1977-01-01

Performance of the iron-titanium redox flow cell was studied as a function of acid concentration. Anion permeable membranes separated the compartments. Electrodes were graphite cloth. Current densities ranged up to 25 mA/square centimeter. Open-circuit and load voltages decreased as the acidity was increased on the iron side as predicted. On the titanium side, open-circuit voltages decreased as the acidity was increased in agreement with theory, but load voltages increased due to decreased polarization with increasing acidity. High acidity on the titanium side coupled with low acidity on the iron side gives the best load voltage, but such cells show voltage losses as they are repeatedly cycled. Analyses show that the bulk of the voltage losses are due to diffusion of acid through the membrane.

An elastic analysis of stresses in a uniaxially loaded sheet containing an interference-fit bolt

NASA Technical Reports Server (NTRS)

Crews, J. H., Jr.

1972-01-01

The stresses in a sheet with an interference-fit bolt have been calculated for two sheet-bolt interface conditions: a frictionless interface and a fixed (no-slip) interface. The stress distributions were calculated for various combinations of sheet and bolt moduli. The results show that for repeated loading the local stress range is significantly smaller if an interference bolt is used instead of a loosely fitting one. This reduction in local stress range is more pronounced when the ratio of bolt modulus to sheet modulus is large. The analysis also indicates that currently used standard values of interference cause yielding in the sheet.

Development and test of a 100 kVA superconducting transformer operated at 77 K

NASA Astrophysics Data System (ADS)

Kummeth, P.; Schlosser, R.; Massek, P.; Schmidt, H.; Albrecht, C.; Breitfelder, D.; Neumüller, H.-W.

2000-05-01

High-temperature superconducting (HTS) transformers are very promising candidates for application in electrical power engineering. Their main advantages are reduced size, weight, better efficiency and reduced potential fire and environmental hazards. We have designed, constructed and tested a 100 kVA HTS power transformer operated at 77 K. The nominal primary and secondary currents (voltages) are 18 A (5.6 kV) and 92 A (1.1 kV), respectively. No-load tests, short-circuit tests and load tests proved repeatedly that the transformer has the rated capacity. HTS winding losses of 20.6 W and iron losses of 403 W were measured.

A Research on Low Modulus Distributed Fiber Optical Sensor for Pavement Material Strain Monitoring

PubMed Central

Meng, Lingjian; Wang, Linbing; Hou, Yue; Yan, Guannan

2017-01-01

The accumulated irreversible deformation in pavement under repeated vehicle loadings will cause fatigue failure of asphalt concrete. It is necessary to monitor the mechanical response of pavement under load by using sensors. Previous studies have limitations in modulus accommodation between the sensor and asphalt pavement, and it is difficult to achieve the distributed monitoring goal. To solve these problems, a new type of low modulus distributed optical fiber sensor (DOFS) for asphalt pavement strain monitoring is fabricated. Laboratory experiments have proved the applicability and accuracy of the newly-designed sensor. This paper presents the results of the development. PMID:29048393

Study on coming out of the shaft from ceramic sleeve in terms of the residual displacement

NASA Astrophysics Data System (ADS)

Zhang, G. W.; Noda, N.-A.; Sano, Y.; Sakai, H.

2018-06-01

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated load. In this paper, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Based on the model with stopper, the FEM simulation is performed under alternate loading with certain intervals newly added. The analysis results show that the coming out failure can be explained from the residual displacement accumulation during these intervals.

A Research on Low Modulus Distributed Fiber Optical Sensor for Pavement Material Strain Monitoring.

PubMed

Meng, Lingjian; Wang, Linbing; Hou, Yue; Yan, Guannan

2017-10-19

The accumulated irreversible deformation in pavement under repeated vehicle loadings will cause fatigue failure of asphalt concrete. It is necessary to monitor the mechanical response of pavement under load by using sensors. Previous studies have limitations in modulus accommodation between the sensor and asphalt pavement, and it is difficult to achieve the distributed monitoring goal. To solve these problems, a new type of low modulus distributed optical fiber sensor (DOFS) for asphalt pavement strain monitoring is fabricated. Laboratory experiments have proved the applicability and accuracy of the newly-designed sensor. This paper presents the results of the development.

Soldier-relevant body borne loads increase knee joint contact force during a run-to-stop maneuver.

PubMed

Ramsay, John W; Hancock, Clifford L; O'Donovan, Meghan P; Brown, Tyler N

2016-12-08

The purpose of this study was to understand the effects of load carriage on human performance, specifically during a run-to-stop (RTS) task. Using OpenSim analysis tools, knee joint contact force, grounds reaction force, leg stiffness and lower extremity joint angles and moments were determined for nine male military personnel performing a RTS under three load configurations (light, ~6kg, medium, ~20kg, and heavy, ~40kg). Subject-based means for each biomechanical variable were submitted to repeated measures ANOVA to test the effects of load. During the RTS, body borne load significantly increased peak knee joint contact force by 1.2 BW (p<0.001) and peak vertical (p<0.001) and anterior-posterior (p=0.002) ground reaction forces by 0.6 BW and 0.3 BW, respectively. Body borne load also had a significant effect on hip (p=0.026) posture with the medium load and knee (p=0.046) posture with the heavy load. With the heavy load, participants exhibited a substantial, albeit non-significant increase in leg stiffness (p=0.073 and d=0.615). Increases in joint contact force exhibited during the RTS were primarily due to greater GRFs that impact the soldier with each incremental addition of body borne load. The stiff leg, extended knee and large braking force the soldiers exhibited with the heavy load suggests their injury risk may be greatest with that specific load configuration. Further work is needed to determine if the biomechanical profile exhibited with the heavy load configuration translates to unsafe shear forces at the knee joint and consequently, a higher likelihood of injury. Published by Elsevier Ltd.

The Pneumatic Actuators As Vertical Dynamic Load Simulators On Medium Weighted Wheel Suspension Mechanism

NASA Astrophysics Data System (ADS)

Ka'ka, Simon; Himran, Syukri; Renreng, Ilyas; Sutresman, Onny

2018-02-01

Almost all of road damage can be caused by dynamic loads of vehicles that fluctuate according to the type of vehicle that passes through. This study aims to calculate the vertical dynamic load of the vehicle actually occurs on road construction by the mechanism of vehicle wheel suspension. Pneumatic cylinders driven by pressurized air directly load the spring and shock absorber installed on the wheels of the vehicle. The load fluctuations of the medium weight categorized vehicles are determined by the regulation of the amount of pressurized air that enters into the pneumatic cylinder chamber, pushing the piston and connecting rods. The displacement that occurs during compression on the spring and shock absorber, is substituted into the equation of vehicle dynamic load while taking into account the spring stiffness constant, and the fluid or damper gas coefficient. The results show that the magnitude of the displacement when the compression force works has significant influences to the amount of vertical dynamic load of the vehicle that overlies the road construction. The presence of dynamic load of vehicles that fluctuates and repeats, also affects on the reduction of road ability to receive the load. Experimental results using pneumatic actuators instead of real dynamic vehicle loads illustrate the characteristics of the relationship between work pressure and dynamic load. If the working pressure of P2 (bar) is greater, the vertical dynamic load Ft (N) that overloads the road structure is also greater. The associate graphs show that the shock absorber has a greater ability to reduce dynamic load vertically that burden the road structure when compared with the ability of screw spring.

Long-term monitoring FBG-based cable load sensor

NASA Astrophysics Data System (ADS)

Zhang, Zhichun; Zhou, Zhi; Wang, Chuan; Ou, Jinping

2006-03-01

Stay cables are the main load-bearing components of stayed-cable bridges. The cables stress status is an important factor to the stayed-cable bridge structure safety evaluation. So it's very important not only to the bridge construction, but also to the long-term safety evaluation for the bridge structure in-service. The accurate measurement for cable load depends on an effective sensor, especially to meet the long time durability and measurement demand. FBG, for its great advantage of corrosion resistance, absolute measurement, high accuracy, electro-magnetic resistance, quasi-distribution sensing, absolute measurement and so on, is the most promising sensor, which can cater for the cable force monitoring. In this paper, a load sensor has been developed, which is made up of a bushing elastic supporting body, 4 FBGs uniformly-spaced attached outside of the bushing supporting body, and a temperature compensation FBG for other four FBGs, moreover a cover for protection of FBGs. Firstly, the sensor measuring principle is analyzed, and relationship equation of FBG wavelength shifts and extrinsic load has also been gotten. And then the sensor calibration experiments of a steel cable stretching test with the FBG load sensor and a reference electric pressure sensor is finished, and the results shows excellent linearity of extrinsic load and FBG wavelength shifts, and good repeatability, which indicates that such kind of FBG-based load sensor is suitable for load measurement, especially for long-term, real time monitoring of stay-cables.

Improvement of Repeated-Sprint Ability and Horizontal-Jumping Performance in Elite Young Basketball Players With Low-Volume Repeated-Maximal-Power Training.

PubMed

Gonzalo-Skok, Oliver; Tous-Fajardo, Julio; Arjol-Serrano, José Luis; Suarez-Arrones, Luis; Casajús, José Antonio; Mendez-Villanueva, Alberto

2016-05-01

To examine the effects of a low-volume repeated-power-ability (RPA) training program on repeated-sprint and change-of- direction (COD) ability and functional jumping performance. Twenty-two male elite young basketball players (age 16.2 ± 1.2 y, height 190.0 ± 10.0 cm, body mass 82.9 ± 10.1 kg) were randomly assigned either to an RPA-training group (n = 11) or a control group (n = 11). RPA training consisted of leg-press exercise, twice a week for 6 wk, of 1 or 2 blocks of 5 sets × 5 repetitions with 20 s of passive recovery between sets and 3 min between blocks with the load that maximized power output. Before and after training, performance was assessed by a repeated-sprint-ability (RSA) test, a repeated-COD-ability test, a hop for distance, and a drop jump followed by tests of a double unilateral hop with the right and left legs. Within-group and between-groups differences showed substantial improvements in slowest (RSAs) and mean time (RSAm) on RSA; best, slowest and mean time on repeated-COD ability; and unilateral right and left hop in the RPA group in comparison with control. While best time on RSA showed no improvement in any group, there was a large relationship (r = .68, 90% CI .43;.84) between the relative decrement in RSAm and RSAs, suggesting better sprint maintenance with RPA training. The relative improvements in best and mean repeated-COD ability were very largely correlated (r = .89, 90% CI .77;.94). Six weeks of lowvolume (4-14 min/wk) RPA training improved several physical-fitness tests in basketball players.

Effects of riparian buffer width on wood loading in headwater streams after repeated forest thinning

Treesearch

Julia I. Burton; Deanna H. Olson; Klaus J. Puettmann

2016-01-01

Forested riparian buffer zones are used in conjunction with upland forest management, in part, to provide for the recruitment for large wood to streams. Small headwater streams account for the majority of stream networks in many forested regions. Yet, our understanding of how riparian buffer width influences wood dynamics in headwater streams is relatively less...

Post-fire surface fuel dynamics in California forests across three burn severity classes

Treesearch

Bianca N. I. Eskelson; Vicente J. Monleon

2018-01-01

Forest wildfires consume fuel and are followed by post-fire fuel accumulation. This study examines post-fire surface fuel dynamics over 9 years across a wide range of conditions characteristic of California fires in dry conifer and hardwood forests. We estimated post-fire surface fuel loadings (Mg ha _1) from 191 repeatedly measured United States...

Investigation of changes in the electrical properties of novel knitted conductive textiles during cyclic loading.

PubMed

Isaia, Cristina; McNally, Donal; McMaster, Simon A; Branson, David T

2016-08-01

Combining stainless steel with polyester fibres adds an attractive conductive behaviour to the yarn. Once knitted in such a manner, fabrics develop sensing properties that make the textiles, also known as e-textiles, suitable for smart/wearable applications. Structural deformations of the fibres (e.g. stretching) will cause changes in the conductivity of the fabric. This work investigates changes in the electrical properties exhibited by four knitted conductive textiles made of 20% stainless steel and 80% polyester fibres during cyclic loading. The samples were preconditioned first with 500 hundred cycles of unidirectional elongation and, after a rest interval, tested again for repeatability at the same conditions. In both cases the electrical behaviour stabilises after a few tens of cycles. In particular the repeatability test exhibited a considerably smaller settling time and a larger resistance due to the mechanical stabilisation and the loosening of the fabrics, respectively. It was found that the current provided to the fabrics affects the resistance measurements by decreasing the resistance value at which the samples become electrically stable. The reported findings present a valid method for the electrical characterisation of conductive textiles for use in further studies as a wearable technology.

Logarithmic contact time dependence of adhesion force and its dominant role among the effects of AFM experimental parameters under low humidity

NASA Astrophysics Data System (ADS)

Lai, Tianmao; Meng, Yonggang

2017-10-01

The influences of contact time, normal load, piezo velocity, and measurement number of times on the adhesion force between two silicon surfaces were studied with an atomic force microscope (AFM) at low humidity (17-15%). Results show that the adhesion force is time-dependent and increases logarithmically with contact time until saturation is reached, which is related with the growing size of a water bridge between them. The contact time plays a dominant role among these parameters. The adhesion forces with different normal loads and piezo velocities can be quantitatively obtained just by figuring out the length of contact time, provided that the contact time dependence is known. The time-dependent adhesion force with repeated contacts at one location usually increases first sharply and then slowly with measurement number of times until saturation is reached, which is in accordance with the contact time dependence. The behavior of the adhesion force with repeated contacts can be adjusted by the lengths of contact time and non-contact time. These results may help facilitate the anti-adhesion design of silicon-based microscale systems working under low humidity.

System and method for chromatography and electrophoresis using circular optical scanning

DOEpatents

Balch, Joseph W.; Brewer, Laurence R.; Davidson, James C.; Kimbrough, Joseph R.

2001-01-01

A system and method is disclosed for chromatography and electrophoresis using circular optical scanning. One or more rectangular microchannel plates or radial microchannel plates has a set of analysis channels for insertion of molecular samples. One or more scanning devices repeatedly pass over the analysis channels in one direction at a predetermined rotational velocity and with a predetermined rotational radius. The rotational radius may be dynamically varied so as to monitor the molecular sample at various positions along a analysis channel. Sample loading robots may also be used to input molecular samples into the analysis channels. Radial microchannel plates are built from a substrate whose analysis channels are disposed at a non-parallel angle with respect to each other. A first step in the method accesses either a rectangular or radial microchannel plate, having a set of analysis channels, and second step passes a scanning device repeatedly in one direction over the analysis channels. As a third step, the scanning device is passed over the analysis channels at dynamically varying distances from a centerpoint of the scanning device. As a fourth step, molecular samples are loaded into the analysis channels with a robot.

Extending substructure based iterative solvers to multiple load and repeated analyses

NASA Technical Reports Server (NTRS)

Farhat, Charbel

1993-01-01

Direct solvers currently dominate commercial finite element structural software, but do not scale well in the fine granularity regime targeted by emerging parallel processors. Substructure based iterative solvers--often called also domain decomposition algorithms--lend themselves better to parallel processing, but must overcome several obstacles before earning their place in general purpose structural analysis programs. One such obstacle is the solution of systems with many or repeated right hand sides. Such systems arise, for example, in multiple load static analyses and in implicit linear dynamics computations. Direct solvers are well-suited for these problems because after the system matrix has been factored, the multiple or repeated solutions can be obtained through relatively inexpensive forward and backward substitutions. On the other hand, iterative solvers in general are ill-suited for these problems because they often must restart from scratch for every different right hand side. In this paper, we present a methodology for extending the range of applications of domain decomposition methods to problems with multiple or repeated right hand sides. Basically, we formulate the overall problem as a series of minimization problems over K-orthogonal and supplementary subspaces, and tailor the preconditioned conjugate gradient algorithm to solve them efficiently. The resulting solution method is scalable, whereas direct factorization schemes and forward and backward substitution algorithms are not. We illustrate the proposed methodology with the solution of static and dynamic structural problems, and highlight its potential to outperform forward and backward substitutions on parallel computers. As an example, we show that for a linear structural dynamics problem with 11640 degrees of freedom, every time-step beyond time-step 15 is solved in a single iteration and consumes 1.0 second on a 32 processor iPSC-860 system; for the same problem and the same parallel processor, a pair of forward/backward substitutions at each step consumes 15.0 seconds.

A potential non-invasive glioblastoma treatment: Nose-to-brain delivery of farnesylthiosalicylic acid incorporated hybrid nanoparticles.

PubMed

Sekerdag, Emine; Lüle, Sevda; Bozdağ Pehlivan, Sibel; Öztürk, Naile; Kara, Aslı; Kaffashi, Abbas; Vural, Imran; Işıkay, Ilkay; Yavuz, Burҫin; Oguz, Kader Karlı; Söylemezoğlu, Figen; Gürsoy-Özdemir, Yasemin; Mut, Melike

2017-09-10

New drug delivery systems are highly needed in research and clinical area to effectively treat gliomas by reaching a high antineoplastic drug concentration at the target site without damaging healthy tissues. Intranasal (IN) administration, an alternative route for non-invasive drug delivery to the brain, bypasses the blood-brain-barrier (BBB) and eliminates systemic side effects. This study evaluated the antitumor efficacy of farnesylthiosalicylic acid (FTA) loaded (lipid-cationic) lipid-PEG-PLGA hybrid nanoparticles (HNPs) after IN application in rats. FTA loaded HNPs were prepared, characterized and evaluated for cytotoxicity. Rat glioma 2 (RG2) cells were implanted unilaterally into the right striatum of female Wistar rats. 10days later, glioma bearing rats received either no treatment, or 5 repeated doses of 500μM freshly prepared FTA loaded HNPs via IN or intravenous (IV) application. Pre-treatment and post-treatment tumor sizes were determined with MRI. After a treatment period of 5days, IN applied FTA loaded HNPs achieved a significant decrease of 55.7% in tumor area, equal to IV applied FTA loaded HNPs. Herewith, we showed the potential utility of IN application of FTA loaded HNPs as a non-invasive approach in glioblastoma treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Allostatic Load and Effort-Reward Imbalance: Associations over the Working-Career

PubMed Central

Coronado, José Ignacio Cuitún; Chandola, Tarani; Steptoe, Andrew

2018-01-01

Although associations between work stressors and stress-related biomarkers have been reported in cross-sectional studies, the use of single time measurements of work stressors could be one of the reasons for inconsistent associations. This study examines whether repeated reports of work stress towards the end of the working career predicts allostatic load, a measure of chronic stress related physiological processes. Data from waves 2 to 6 of the English Longitudinal Study of Ageing (ELSA) were analysed, with a main analytical sample of 2663 older adults (aged 50+) who had at least one measurement of effort-reward imbalance between waves 2–6 and a measurement of allostatic load at wave 6. Cumulative work stress over waves 2–6 were measured by the effort-reward imbalance model. ELSA respondents who had reported two or more occasions of imbalance had a higher (0.3) estimate of the allostatic load index than those who did not report any imbalance, controlling for a range of health and socio-demographic factors, as well as allostatic load at baseline. More recent reports of imbalance were significantly associated with a higher allostatic load index, whereas reports of imbalance from earlier waves of ELSA were not. The accumulation of work related stressors could have adverse effects on chronic stress biological processes. PMID:29364177

A Mechatronic Loading Device to Stimulate Bone Growth via a Human Knee.

PubMed

Prabhala, Sai Krishna; Chien, Stanley; Yokota, Hiroki; Anwar, Sohel

2016-09-29

This paper presents the design of an innovative device that applies dynamic mechanical load to human knee joints. Dynamic loading is employed by applying cyclic and periodic force on a target area. The repeated force loading was considered to be an effective modality for repair and rehabilitation of long bones that are subject to ailments like fractures, osteoporosis, osteoarthritis, etc. The proposed device design builds on the knowledge gained in previous animal and mechanical studies. It employs a modified slider-crank linkage mechanism actuated by a brushless Direct Current (DC) motor and provides uniform and cyclic force. The functionality of the device was simulated in a software environment and the structural integrity was analyzed using a finite element method for the prototype construction. The device is controlled by a microcontroller that is programmed to provide the desired loading force at a predetermined frequency and for a specific duration. The device was successfully tested in various experiments for its usability and full functionality. The results reveal that the device works according to the requirements of force magnitude and operational frequency. This device is considered ready to be used for a clinical study to examine whether controlled knee-loading could be an effective regimen for treating the stated bone-related ailments.

A Mechatronic Loading Device to Stimulate Bone Growth via a Human Knee

PubMed Central

Prabhala, Sai Krishna; Chien, Stanley; Yokota, Hiroki; Anwar, Sohel

2016-01-01

This paper presents the design of an innovative device that applies dynamic mechanical load to human knee joints. Dynamic loading is employed by applying cyclic and periodic force on a target area. The repeated force loading was considered to be an effective modality for repair and rehabilitation of long bones that are subject to ailments like fractures, osteoporosis, osteoarthritis, etc. The proposed device design builds on the knowledge gained in previous animal and mechanical studies. It employs a modified slider-crank linkage mechanism actuated by a brushless Direct Current (DC) motor and provides uniform and cyclic force. The functionality of the device was simulated in a software environment and the structural integrity was analyzed using a finite element method for the prototype construction. The device is controlled by a microcontroller that is programmed to provide the desired loading force at a predetermined frequency and for a specific duration. The device was successfully tested in various experiments for its usability and full functionality. The results reveal that the device works according to the requirements of force magnitude and operational frequency. This device is considered ready to be used for a clinical study to examine whether controlled knee-loading could be an effective regimen for treating the stated bone-related ailments. PMID:27690057

Real-time volume rendering of 4D image using 3D texture mapping

NASA Astrophysics Data System (ADS)

Hwang, Jinwoo; Kim, June-Sic; Kim, Jae Seok; Kim, In Young; Kim, Sun Il

2001-05-01

Four dimensional image is 3D volume data that varies with time. It is used to express deforming or moving object in virtual surgery of 4D ultrasound. It is difficult to render 4D image by conventional ray-casting or shear-warp factorization methods because of their time-consuming rendering time or pre-processing stage whenever the volume data are changed. Even 3D texture mapping is used, repeated volume loading is also time-consuming in 4D image rendering. In this study, we propose a method to reduce data loading time using coherence between currently loaded volume and previously loaded volume in order to achieve real time rendering based on 3D texture mapping. Volume data are divided into small bricks and each brick being loaded is tested for similarity to one which was already loaded in memory. If the brick passed the test, it is defined as 3D texture by OpenGL functions. Later, the texture slices of the brick are mapped into polygons and blended by OpenGL blending functions. All bricks undergo this test. Continuously deforming fifty volumes are rendered in interactive time with SGI ONYX. Real-time volume rendering based on 3D texture mapping is currently available on PC.

Allostatic Load and Effort-Reward Imbalance: Associations over the Working-Career.

PubMed

Coronado, José Ignacio Cuitún; Chandola, Tarani; Steptoe, Andrew

2018-01-24

Although associations between work stressors and stress-related biomarkers have been reported in cross-sectional studies, the use of single time measurements of work stressors could be one of the reasons for inconsistent associations. This study examines whether repeated reports of work stress towards the end of the working career predicts allostatic load, a measure of chronic stress related physiological processes. Data from waves 2 to 6 of the English Longitudinal Study of Ageing (ELSA) were analysed, with a main analytical sample of 2663 older adults (aged 50+) who had at least one measurement of effort-reward imbalance between waves 2-6 and a measurement of allostatic load at wave 6. Cumulative work stress over waves 2-6 were measured by the effort-reward imbalance model. ELSA respondents who had reported two or more occasions of imbalance had a higher (0.3) estimate of the allostatic load index than those who did not report any imbalance, controlling for a range of health and socio-demographic factors, as well as allostatic load at baseline. More recent reports of imbalance were significantly associated with a higher allostatic load index, whereas reports of imbalance from earlier waves of ELSA were not. The accumulation of work related stressors could have adverse effects on chronic stress biological processes.

A Universal Threshold for the Assessment of Load and Output Residuals of Strain-Gage Balance Data

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Volden, T.

2017-01-01

A new universal residual threshold for the detection of load and gage output residual outliers of wind tunnel strain{gage balance data was developed. The threshold works with both the Iterative and Non{Iterative Methods that are used in the aerospace testing community to analyze and process balance data. It also supports all known load and gage output formats that are traditionally used to describe balance data. The threshold's definition is based on an empirical electrical constant. First, the constant is used to construct a threshold for the assessment of gage output residuals. Then, the related threshold for the assessment of load residuals is obtained by multiplying the empirical electrical constant with the sum of the absolute values of all first partial derivatives of a given load component. The empirical constant equals 2.5 microV/V for the assessment of balance calibration or check load data residuals. A value of 0.5 microV/V is recommended for the evaluation of repeat point residuals because, by design, the calculation of these residuals removes errors that are associated with the regression analysis of the data itself. Data from a calibration of a six-component force balance is used to illustrate the application of the new threshold definitions to real{world balance calibration data.

The relation of cognitive load and pupillary unrest.

PubMed

Müller, Andreas; Petru, Raluca; Seitz, Lucia; Englmann, Ines; Angerer, Peter

2011-06-01

This study examines the relationship between pupillary unrest (PU) and cognitive load. PU represents a measure of reduced central nervous tonic arousal (sleepiness). A loss of tonic arousal can be associated with difficulties in maintaining the required level of performance. Thus, the measurement of tonic arousal in occupational contexts can help to prevent overload or errors. We compared a group with high cognitive load (30 apron controllers of an international airport) with a control group with low cognitive load (63 healthy people during their free time) in a non-randomized experimental design with pre- and post-test assessment of PU. PU was scanned by an infrared sensor with a frequency of 25 Hz and a resolution of .05 mm. To control for circadian effects, measurements for both groups were taken at the same time of the day. High PU at the start of the shift correlated with high perceived load during the shift. There were no indications of reverse effects. Analyses of group x time effects with generalized linear models (repeated measures) revealed that cognitive load did in no way affected PU. Initially low tonic arousal (indicated by high PU) may predict subsequent workload, but being exposed to high cognitive load does not influence tonic arousal after the end of the shift. With that, the study contributes to valid interpretations of pupillary unrest measurements in occupational contexts.

Dual fuel gradients in uranium silicide plates

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

Pace, B.W.

1997-08-01

Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final coremore » gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.« less

Global cerebral ischemia with subsequent respiratory arrest in a cat after repeated use of a spring-loaded mouth gag.

PubMed

Hartman, Emily A; McCarthy, Robert J; Labato, Mary A

2017-01-01

A 10-year-old neutered male domestic shorthair cat was evaluated because of signs of stertorous breathing and reverse sneezing of 8 months' duration. A CT scan performed 1 week before evaluation indicated nasopharyngeal stenosis or collapse. Increased respiratory effort, stertorous breathing, coughing, reverse sneezing, bilateral black ocular discharge and mucoid left nasal discharge were noted. Rhinoscopy suggested possible nasopharyngeal stenosis. Balloon dilation was attempted but unsuccessful. Ventral rhinotomy was performed the following day using a spring-loaded mouth gag to access the surgical site. After rhinotomy, the patient had neurologic signs attributed to global cerebral ischemia that progressed to respiratory arrest, subsequently resulting in euthanasia. While ischemic brain injury has been associated with the use of a spring-loaded mouth gag in cats, to our knowledge this is the first reported instance where use resulted in respiratory arrest culminating in euthanasia.

Precursory slow-slip loaded the 2009 L'Aquila earthquake sequence

NASA Astrophysics Data System (ADS)

Borghi, A.; Aoudia, A.; Javed, F.; Barzaghi, R.

2016-05-01

Slow-slip events (SSEs) are common at subduction zone faults where large mega earthquakes occur. We report here that one of the best-recorded moderate size continental earthquake, the 2009 April 6 moment magnitude (Mw) 6.3 L'Aquila (Italy) earthquake, was preceded by a 5.9 Mw SSE that originated from the decollement beneath the reactivated normal faulting system. The SSE is identified from a rigorous analysis of continuous GPS stations and occurred on the 12 February and lasted for almost two weeks. It coincided with a burst in the foreshock activity with small repeating earthquakes migrating towards the main-shock hypocentre as well as with a change in the elastic properties of rocks in the fault region. The SSE has caused substantial stress loading at seismogenic depths where the magnitude 4.0 foreshock and Mw 6.3 main shock nucleated. This stress loading is also spatially correlated with the lateral extent of the aftershock sequence.

Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills.

PubMed

Dutton, Christopher L; Subalusky, Amanda L; Hamilton, Stephen K; Rosi, Emma J; Post, David M

2018-05-16

Organic matter and nutrient loading into aquatic ecosystems affects ecosystem structure and function and can result in eutrophication and hypoxia. Hypoxia is often attributed to anthropogenic pollution and is not common in unpolluted rivers. Here we show that organic matter loading from hippopotami causes the repeated occurrence of hypoxia in the Mara River, East Africa. We documented 49 high flow events over 3 years that caused dissolved oxygen decreases, including 13 events resulting in hypoxia, and 9 fish kills over 5 years. Evidence from experiments and modeling demonstrates a strong mechanistic link between the flushing of hippo pools and decreased dissolved oxygen in the river. This phenomenon may have been more widespread throughout Africa before hippopotamus populations were severely reduced. Frequent hypoxia may be a natural part of tropical river ecosystem function, particularly in rivers impacted by large wildlife.

Photocatalytic degradation of diclofenac using TiO2-SnO2 mixed oxide catalysts.

PubMed

Mugunthan, E; Saidutta, M B; Jagadeeshbabu, P E

2017-12-26

The complex nature of diclofenac limits its biological degradation, posing a serious threat to aquatic organisms. Our present work aims to eliminate diclofenac from wastewater through photocatalytic degradation using TiO 2 -SnO 2 mixed-oxide catalysts under various operating conditions such as catalyst loading, initial diclofenac concentration and initial pH. Different molar ratios of Ti-Sn (1:1, 5:1, 10:1, 20:1 and 30:1) were prepared by the hydrothermal method and were characterized. The results indicated that addition of Sn in small quantity enhances the catalytic activity of TiO 2 . Energy Band gap of the TiO 2 -SnO 2 catalysts was found to increase with an increase in Tin content. TiO 2 -SnO 2 catalyst with a molar ratio of 20:1 was found to be the most effective when compared to other catalysts. The results suggested that initial drug concentration of 20 mg/L, catalyst loading of 0.8 g/L and pH 5 were the optimum operating conditions for complete degradation of diclofenac. Also, the TiO 2 -SnO 2 catalyst was effective in complete mineralization of diclofenac with a maximum total organic carbon removal of 90% achieved under ultraviolet irradiation. The repeatability and stability results showed that the TiO 2 -SnO 2 catalyst exhibited an excellent repeatability and better stability over the repeated reaction cycles. The photocatalytic degradation of diclofenac resulted in several photoproducts, which were identified through LC-MS.

A frictional population model of seismicity rate change

USGS Publications Warehouse

Gomberg, J.; Reasenberg, P.; Cocco, M.; Belardinelli, M.E.

2005-01-01

We study models of seismicity rate changes caused by the application of a static stress perturbation to a population of faults and discuss our results with respect to the model proposed by Dieterich (1994). These models assume distribution of nucleation sites (e.g., faults) obeying rate-state frictional relations that fail at constant rate under tectonic loading alone, and predicts a positive static stress step at time to will cause an immediate increased seismicity rate that decays according to Omori's law. We show one way in which the Dieterich model may be constructed from simple general idead, illustratted using numerically computed synthetic seismicity and mathematical formulation. We show that seismicity rate change predicted by these models (1) depend on the particular relationship between the clock-advanced failure and fault maturity, (2) are largest for the faults closest to failure at to, (3) depend strongly on which state evolution law faults obey, and (4) are insensitive to some types of population hetrogeneity. We also find that if individual faults fail repeatedly and populations are finite, at timescales much longer than typical aftershock durations, quiescence follows at seismicity rate increase regardless of the specific frictional relations. For the examined models the quiescence duration is comparable to the ratio of stress change to stressing rate ????/??,which occurs after a time comparable to the average recurrence interval of the individual faults in the population and repeats in the absence of any new load may pertubations; this simple model may partly explain observations of repeated clustering of earthquakes. Copyright 2005 by the American Geophysical Union.

A Novel Method for Quantifying Human In Situ Whole Brain Deformation under Rotational Loading Using Sonomicrometry.

PubMed

Alshareef, Ahmed; Giudice, J Sebastian; Forman, Jason; Salzar, Robert S; Panzer, Matthew B

2018-03-01

Traumatic brain injuries (TBI) are one of the least understood injuries to the body. Finite element (FE) models of the brain have been crucial for understanding concussion and for developing injury mitigation systems; however, the experimental brain deformation data currently used to validate these models are limited. The objective of this study was to develop a methodology for the investigation of in situ three-dimensional brain deformation during pure rotational loading of the head, using sonomicrometry. Sonomicrometry uses ultrasonic pulses to measure the dynamic distances between piezoelectric crystals implanted in any sound-transmitting media. A human cadaveric head-neck specimen was acquired 14 h postmortem and was instrumented with an array of 32 small sonomicrometry crystals embedded in the head: 24 crystals were implanted in the brain, and 8 were fixed to the inner skull. A dynamic rotation was then applied to the head using a closed-loop controlled test device. Four pulses with different severity levels were applied around three orthogonal anatomical axes of rotation. A repeated test of the highest severity rotation was conducted in each axis to assess repeatability. All tests were completed within 56 h postmortem. Overall, the combined experimental and sonomicrometry methods were demonstrated to reliably and repeatedly capture three-dimensional dynamic deformation of an intact human brain. These methods provide a framework for using sonomicrometry to acquire multidimensional experimental data required for FE model development and validation, and will lend insight into the deformations sustained by the brain during impact.

Recent developments on SMA actuators: predicting the actuation fatigue life for variable loading schemes

NASA Astrophysics Data System (ADS)

Wheeler, Robert W.; Lagoudas, Dimitris C.

2017-04-01

Shape memory alloys (SMAs), due to their ability to repeatably recover substantial deformations under applied mechanical loading, have the potential to impact the aerospace, automotive, biomedical, and energy industries as weight and volume saving replacements for conventional actuators. While numerous applications of SMA actuators have been flight tested and can be found in industrial applications, these actuators are generally limited to non-critical components, are not widely implemented and frequently one-off designs, and are generally overdesigned due to a lack of understanding of the effect of the loading path on the fatigue life and the lack of an accurate method for predicting actuator lifetimes. In recent years, multiple research efforts have increased our understanding of the actuation fatigue process of SMAs. These advances can be utilized to predict the fatigue lives and failure loads in SMA actuators. Additionally, these prediction methods can be implemented in order to intelligently design actuators in accordance with their fatigue and failure limits. In the following paper, both simple and complex thermomechanical loading paths have been considered. Experimental data was utilized from two material systems: equiatomic Nickel-Titanium and Nickelrich Nickel-Titanium.

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

PubMed

Kaigle, A; Ekström, L; Holm, S; Rostedt, M; Hansson, T

1998-02-01

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading.

PubMed

Firminger, Colin R; Edwards, W Brent

2016-12-01

To examine the effects of shoe type and stride length reduction on lower-extremity running mechanics and cumulative loading. Within-subject with four conditions: (1) control shoe at preferred stride length; (2) control shoe at 90% preferred stride length; (3) minimalist shoe at preferred stride length; (4) minimalist shoe at 90% preferred stride length. Fourteen young healthy males ran overground at their preferred speed while motion capture, force platform, and plantar pressure data were collected. Peak moments, impulse, mechanical work, and cumulative impulse were calculated at the metatarsophalangeal, ankle, and knee joint, and compared between conditions using a 2×2 factor repeated measures ANOVA. In general, running in minimalist footwear increased measures of loading at the metatarsophalangeal joint and ankle joint (mean increases of 7.3% and 5.9%, respectively), but decreased measures of loading at the knee (mean decrease of 7.3%). Conversely, running with reduced stride length decreased single-stance measures of loading at the ankle and knee joint (ranging from -0.9% to -20.5%), though cumulative impulse was higher at the ankle and lower at the knee. Running in minimalist shoes increased loads at the metatarsophalangeal and ankle joint, which may explain some of the incidence of overuse injuries observed in minimalist shoe users. Decreased ankle loads at 90% preferred stride length were not necessarily sufficient to reduce cumulative loads when impulse and loading cycles were weighted equally. Knee loads decreased more when running at 90% preferred stride length (16.2% mean reduction) versus running in a minimalist shoe (7.3% mean reduction), but both load reduction mechanisms appeared to have an additive effect (22.2% mean reduction). Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Dual stimuli-sensitive dendrimers: Photothermogenic gold nanoparticle-loaded thermo-responsive elastin-mimetic dendrimers.

PubMed

Fukushima, Daichi; Sk, Ugir Hossain; Sakamoto, Yasuhiro; Nakase, Ikuhiko; Kojima, Chie

2015-08-01

Dendrimers are synthetic macromolecules with unique structures that can work as nanoplatforms for both photothermogenic gold nanoparticles (AuNPs) and thermosensitive elastin-like peptides (ELPs) with valine-proline-glycine-valine-glycine (VPGVG) repeats. In this study, photothermogenic AuNPs were loaded into thermo-responsive elastin-mimetic dendrimers (dendrimers conjugating ELPs at their periphery) to produce dual stimuli-sensitive nanoparticles. Polyamidoamine G4 dendrimers were modified with acetylated VPGVG and (VPGVG)2, and the resulting materials were named ELP1-den and ELP2-den, respectively. The AuNPs were prepared by the reduction of Au ions using a dendrimer-nanotemplated method. The AuNP-loaded elastin-mimetic dendrimers exhibited photothermal properties. ELP1-den and ELP2-den showed similar temperature-dependent changes in their conformations. Phase transitions were observed at around 55°C and 35°C for the AuNP-loaded ELP1-den and AuNP-loaded ELP2-den, respectively, but not for the corresponding PEGylated dendrimer. In contrast to the AuNP-loaded PEGylated dendrimer, AuNP-loaded ELP2-den readily associated with cells and induced efficient photocytotoxicity at 37°C. The cell association and the photocytotoxicity properties of AuNP-loaded ELP2-den could be controlled by temperature. These results therefore suggest that dual stimuli-sensitive dendrimer nanoparticles of this type could be used for photothermal therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Opening Loads Analyses for Various Disk-Gap-Band Parachutes

NASA Technical Reports Server (NTRS)

Cruz, J. R.; Kandis, M.; Witkowski, A.

2003-01-01

Detailed opening loads data is presented for 18 tests of Disk-Gap-Band (DGB) parachutes of varying geometry with nominal diameters ranging from 43.2 to 50.1 ft. All of the test parachutes were deployed from a mortar. Six of these tests were conducted via drop testing with drop test vehicles weighing approximately 3,000 or 8,000 lb. Twelve tests were conducted in the National Full-Scale Aerodynamics Complex 80- by 120-foot wind tunnel at the NASA Ames Research Center. The purpose of these tests was to structurally qualify the parachute for the Mars Exploration Rover mission. A key requirement of all tests was that peak parachute load had to be reached at full inflation to more closely simulate the load profile encountered during operation at Mars. Peak loads measured during the tests were in the range from 12,889 to 30,027 lb. Of the two test methods, the wind tunnel tests yielded more accurate and repeatable data. Application of an apparent mass model to the opening loads data yielded insights into the nature of these loads. Although the apparent mass model could reconstruct specific tests with reasonable accuracy, the use of this model for predictive analyses was not accurate enough to set test conditions for either the drop or wind tunnel tests. A simpler empirical model was found to be suitable for predicting opening loads for the wind tunnel tests to a satisfactory level of accuracy. However, this simple empirical model is not applicable to the drop tests.

Changes in speckle patterns induced by load application onto an optical fiber and its possible application for sensing purpose

NASA Astrophysics Data System (ADS)

Hasegawa, Makoto; Okumura, Jyun-ya; Hyuga, Akio

2015-08-01

Speckle patterns to be observed in an output light spot from an optical fiber are known to be changed due to external disturbances applied onto the optical fiber. In order to investigate possibilities of utilizing such changes in speckle patterns for sensing application, a certain load was applied onto a jacket-covered communication-grade multi-mode glass optical fiber through which laser beams emitted from a laser diode were propagating, and observed changes in speckle patterns in the output light spot from the optical fiber were investigated both as image data via a CCD camera and as an output voltage from a photovoltaic panel irradiated with the output light spot. The load was applied via a load application mechanism in which several ridges were provided onto opposite flat plates and a certain number of weights were placed there so that corrugated bending of the optical fiber was intentionally induced via load application due to the ridges. The obtained results showed that the number of speckles in the observed pattern in the output light spot as well as the output voltage from the photovoltaic panel irradiated with the output light spot showed decreases upon load application with relatively satisfactory repeatability. When the load was reduced, i.e., the weights were removed, the number of speckles then showed recovery. These results indicate there is a certain possibility of utilizing changes in speckle patterns for sensing of load application onto the optical fiber.

Comparison of metabolic responses of United States Military Academy men and women in acute military load bearing.

PubMed

Stauffer, R W; McCarter, M; Campbell, J L; Wheeler, L F

1987-11-01

Twenty-four first year United States Military Academy (USMA) men and women were studied to compare metabolic response differences in seven horizontal walking velocities, under three military load bearing conditions. The treadmill protocol consisted of walking or jogging on a horizontal treadmill surface for 3-min intervals at velocities of 3, 3.5, 4, 4.5, 5, 5.5, and 6 mph. The three military load bearing conditions weighed 5, 12, and 20 kg. Metabolic measurements taken at each speed in each of the military load bearing conditions were: minute volume, tidal volume, respiratory rate, absolute and relative to body weight oxygen consumption, and respiratory quotient. Two three-way analyses of variance for repeated measures tests with main effects of gender, military load, and speed revealed that USMA men and women metabolically respond to different military load bearing conditions; they metabolically respond to different walking and jogging velocities under military load bearing conditions; and they have identifiable and quantifiable metabolic response differences to military load bearing. This study was designed to improve USMA physical and military training programs by providing information to equally and uniformly administer the USMA Doctrine of Comparable Training to men and women alike; and additionally to clarify the "...minimal essential adjustments...required because of physiological differences between male and female individuals ..." portion of Public Law 94-106 providing for the admission of women to America's Service Academies.

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium/redox flow cells

NASA Technical Reports Server (NTRS)

Reid, M. A.; Gahn, R. F.

1977-01-01

The effect of acid concentration on the performance of the iron-titanium redox flow cell was studied. When the acidity was increased, open-circuit voltages decreased on the titanium side but load voltages increased due to decreased polarization. The best load voltage occurs when there is high acidity on the titanium side coupled with low acidity on the iron side, but such cells show voltage losses with repeated cycling because of the diffusion of acid through the membrane. No membrane tested has been found capable of maintaining the differences in acidity. Chelating agents show some promise in reducing polarization at the Ti electrode and thus improving energy efficiency.

Strategic Interviewing to Detect Deception: Cues to Deception across Repeated Interviews

PubMed Central

Masip, Jaume; Blandón-Gitlin, Iris; Martínez, Carmen; Herrero, Carmen; Ibabe, Izaskun

2016-01-01

Previous deception research on repeated interviews found that liars are not less consistent than truth tellers, presumably because liars use a “repeat strategy” to be consistent across interviews. The goal of this study was to design an interview procedure to overcome this strategy. Innocent participants (truth tellers) and guilty participants (liars) had to convince an interviewer that they had performed several innocent activities rather than committing a mock crime. The interview focused on the innocent activities (alibi), contained specific central and peripheral questions, and was repeated after 1 week without forewarning. Cognitive load was increased by asking participants to reply quickly. The liars’ answers in replying to both central and peripheral questions were significantly less accurate, less consistent, and more evasive than the truth tellers’ answers. Logistic regression analyses yielded classification rates ranging from around 70% (with consistency as the predictor variable), 85% (with evasive answers as the predictor variable), to over 90% (with an improved measure of consistency that incorporated evasive answers as the predictor variable, as well as with response accuracy as the predictor variable). These classification rates were higher than the interviewers’ accuracy rate (54%). PMID:27847493

The Direct Insertion of the ACL Carries More Load than the Indirect Insertion

PubMed Central

Nawabi, Danyal H.; Tucker, Scott; Jones, Kristofer J.; Nguyen, Joseph; Wickiewicz, Thomas L.; Imhauser, Carl; Pearle, Andrew

2014-01-01

Objectives: Recent histological studies have shown that the ACL consists of two different structures: the direct and indirect insertions. The direct insertion is located along the lateral intercondylar ridge and the indirect insertion is ‘lower’ in the notch, adjacent to the posterior articular cartilage. The ‘lower’ position has become more popular for locating the femoral tunnel, as surgeons switch to the anteromedial (AM) portal drilling technique in order to place the graft in the region of the native footprint. However, a recent registry-based outcomes study has reported a 1.5 times higher graft failure rate for AM portal versus traditional transtibial techniques. The objective of this study was to investigate the load characteristics of the native ACL in the regions of the direct and indirect insertions. We hypothesized that the direct insertion would carry more load than the indirect insertion. Methods: Twelve cadaveric knees were mounted to a six degree of freedom robot equipped with a universal force-moment sensor. We simulated the Lachman and anterior drawer tests at 30oand 90o of flexion by applying a 134N anterior load, and the pivot shift test at 15o flexion by applying combined valgus (8Nm) and internal (4Nm) rotational moments. The kinematic pathway required to achieve these loading conditions was recorded for each intact knee. Using position control to repeat the loading paths, the robot recorded the loads for the ACL intact, ACL partially sectioned, and ACL completely sectioned states. Sectioning Protocol: The lateral intercondylar ridge and posterior articular margin was identified in each case. The 50% mark between this two areas was used to delineate the regions of the direct and indirect insertions (Fig. 1). Sectioning order was alternated between each cadaver. Footprint Digitization: The borders of the sectioned areas were digitized post-sectioning and mapped onto a computed tomography (CT) scan of each knee. The sectioning method was assessed under a blinded validation by experienced observers (TW, AP) who excluded two specimens that did not conform to the objective definitions of the sectioning method. Statistics: Loads were compared between direct and indirect locations at different flexion angles by conducting two-way repeated measures ANOVA models. Results: Under an anterior tibial load at 30o flexion, the direct insertion carried 83.9% (±7.2%) of the total ACL load compared to 16.1% (±7.2%) in the indirect insertion (p<0.001). The direct insertion also carried more load at 90o flexion (95.2% vs 4.8%; p<0.001). Under a combined rotatory load at 15o flexion, the direct insertion carried 84.2% (±4.2%)of the total ACL load compared to 15.8% (±4.2%) in the indirect insertion (p<0.001). Conclusion: The fibres in the direct insertion of the ACL carry more load than fibres in the indirect insertion. Previous studies have suggested that the direct insertion plays a major role in the mechanical link between the ACL and bone. With the current shift in emphasis towards anatomic ACL reconstruction, it may be beneficial to create the femoral tunnel within the direct insertion rather than ‘lower’ in the notch. Although further work is required in determining graft behaviour at the new insertions sites described in this study, our findings suggest that placing a graft in the region of the direct insertion may be an important consideration when adhering to the principles of anatomic ACL reconstruction.

Variability and repeatability analysis of plantar pressure during gait in older people.

PubMed

Franco, Pedro S; Silva, Caio Borella P da; Rocha, Emmanuel S da; Carpes, Felipe P

2015-01-01

Repeatability and variability of the plantar pressure during walking are important components in the clinical assessment of the elderly. However, there is a lack of information on the uniformity of plantar pressure patterns in the elderly. To analyze the repeatability and variability in plantar pressure considering mean, peak and asymmetries during aged gait. Plantar pressure was monitored in four different days for ten elderly subjects (5 female), with mean±standard-deviation age of 73±6 years, walking barefoot at preferred speed. Data were compared between steps for each day and between different days. Mean and peak plantar pressure values were similar between the different days of evaluation. Asymmetry indexes were similar between the different days evaluated. Plantar pressure presented a consistent pattern in the elderly. However, the asymmetry indexes observed suggest that the elderly are exposed to repetitive asymmetric loading during locomotion. Such result requires further investigation, especially concerning the role of these asymmetries for development of articular injuries. Copyright © 2015 Elsevier Editora Ltda. All rights reserved.

The Reusable Load Cell with Protection Applied for Online Monitoring of Overhead Transmission Lines Based on Fiber Bragg Grating

PubMed Central

Ma, Guoming; Mao, Naiqiang; Li, Yabo; Jiang, Jun; Zhou, Hongyang; Li, Chengrong

2016-01-01

Heavy ice coating of high–voltage overhead transmission lines may lead to conductor breakage and tower collapse causing the unexpected interrupt of power supply. The optical load cell applied in ice monitoring systems is immune to electromagnetic interference and has no need of a power supply on site. Therefore, it has become a hot research topic in China and other countries. In this paper, to solve the problem of eccentric load in measurement, we adopt the shearing structure with additional grooves to improve the strain distribution and acquire good repeatability. Then, the fiber Bragg grating (FBG) with a permanent weldable package are mounted onto the front/rear groove of the elastic element by spot welding, the direction deviation of FBGs is 90° from each other to achieve temperature compensation without an extra FBG. After that, protection parts are designed to guarantee high sensitivity for a light load condition and industrial safety under a heavy load up to 65 kN. The results of tension experiments indicate that the sensitivity and resolution of the load cell is 0.1285 pm/N and 7.782 N in the conventional measuring range (0–10 kN). Heavy load tension experiments prove that the protection structure works and the sensitivity and resolution are not changed after several high load (65 kN) cycles. In addition, the experiment shows that the resolution of the sensor is 87.79 N in the large load range, allowing the parameter to be used in heavy icing monitoring. PMID:27338403

Dual-task and anticipation impact lower limb biomechanics during a single-leg cut with body borne load.

PubMed

Seymore, Kayla D; Cameron, Sarah E; Kaplan, Jonathan T; Ramsay, John W; Brown, Tyler N

2017-12-08

This study quantified how a dual cognitive task impacts lower limb biomechanics during anticipated and unanticipated single-leg cuts with body borne load. Twenty-four males performed anticipated and unanticipated cuts with and without a dual cognitive task with three load conditions: no load (∼6 kg), medium load (15% of BW), and heavy load (30% of BW). Lower limb biomechanics were submitted to a repeated measures linear mixed model to test the main and interaction effects of load, anticipation, and dual task. With body borne load, participants increased peak stance (PS) hip flexion (p = .004) and hip internal rotation (p = .001) angle, and PS hip flexion (p = .001) and internal rotation (p = .018), and knee flexion (p = .016) and abduction (p = .001) moments. With the dual task, participants decreased PS knee flexion angle (p < .001) and hip flexion moment (p = .027), and increased PS knee external rotation angle (p = .034). During the unanticipated cut, participants increased PS hip (p = .040) and knee flexion angle (p < .001), and decreased PS hip adduction (p = .001), and knee abduction (p = .005) and external rotation (p = .026) moments. Adding body borne load produces lower limb biomechanical adaptations thought to increase risk of musculoskeletal injury, but neither anticipation nor dual task exaggerated those biomechanical adaptations. With a dual task, participants adopted biomechanics known to increase injury risk; whereas, participants used lower limb biomechanics thought to decrease injury risk during unanticipated cuts. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Mechanism for the Loading-Unloading Substorm Cycle Missing in MHD Global Magnetospheric Simulation Models

NASA Technical Reports Server (NTRS)

Klimas, A. J.; Uritsky, V.; Vassiliadis, D.; Baker, D. N.

2005-01-01

Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading- unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current- driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading- unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval, the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.

Laboratory constraints on models of earthquake recurrence

NASA Astrophysics Data System (ADS)

Beeler, N. M.; Tullis, Terry; Junger, Jenni; Kilgore, Brian; Goldsby, David

2014-12-01

In this study, rock friction "stick-slip" experiments are used to develop constraints on models of earthquake recurrence. Constant rate loading of bare rock surfaces in high-quality experiments produces stick-slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip-rate-dependent process that also determines the size of the stress drop and, as a consequence, stress drop varies weakly but systematically with loading rate. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low-frequency earthquakes loaded by episodic slip. The experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a nonlinear slip predictable model. The fault's rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence covary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability, and successive stress drops are strongly correlated indicating a "memory" of prior slip history that extends over at least one recurrence cycle.

Performance of single-use and multiuse diamond rotary cutting instruments with turbine and electric handpieces.

PubMed

Rotella, Mario; Ercoli, Carlo; Funkenbusch, Paul D; Russell, Scott; Feng, Changyong

2014-01-01

As single-use rotary cutting instruments and electric handpieces become more available, the performance of these instruments with electric as compared to turbine handpieces requires evaluation. In addition, if rotary cutting instruments marketed as single-use instruments are used for multiple patients, the effects on their performance of cleaning, sterilization, and repeated use are of interest to the clinician. The purpose of the study was to evaluate how the cleaning, autoclaving, and repeated use of single-use and multiuse rotary cutting instruments, with either a turbine or electric handpiece, affected their performance. The effects on cutting performance of 2 handpieces (turbine and electric), 2 cleaning and sterilization conditions (cleaned and autoclaved versus noncleaned and nonautoclaved), and 6 different diamond rotary cutting instruments (4 single-use and 2 multiuse) during simulated tooth preparations were evaluated by using a 24-treatment condition full-factorial experimental design. A computer-controlled dedicated testing apparatus was used to simulate the cutting procedures, and machinable glass ceramic blocks were used as the cutting substrate for tangential cuts. In addition, for each treatment condition, 8 consecutive cuts, for a total of 192 cuts, were measured to assess the durability of the rotary cutting instruments. A linear mixed model was used to study the effect of instrument type, handpiece, cleaning, and sterilization, as well as the status and number of cuts on the outcome variables. The Tukey honestly significant difference test was used for the post hoc pairwise comparisons (α=.05). Performance, as measured by the rate of advancement, decreased with the repeated use of rotary cutting instruments (P<.001), while cleaning and sterilization procedures improved the average performance of the 8 cuts (P=.002). The electric handpiece showed a greater load than the turbine (P<.001) and a lower rate/load metric, but no differences in the rate of advancement. Significant differences were also detected among the different rotary cutting instruments tested with the Two Striper, which showed the highest cumulative performance of all groups. The repeated use of both single-use and multiuse rotary cutting instruments decreased cutting performance. The use of a cleaning and sterilization procedure between cuts improved the average cutting performance. During a tangential cutting process, although the ease of advancement (rate/load) was greater for the turbine, the electric handpiece did not produce a statistically different cutting rate. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

The potential benefits of Zumba Gold(®) in people with mild-to-moderate Parkinson's: Feasibility and effects of dance styles and number of sessions.

PubMed

Delextrat, A; Bateman, J; Esser, P; Targen, N; Dawes, H

2016-08-01

To assess the feasibility of Zumba Gold(®) in people with PD, and to investigate the effects of dance styles and number of sessions on activity levels and physiological load. Repeated measure uncontrolled (single group) feasibility study. Eleven participants (age: 64.0±8.1years) with mild-to-moderate idiopathic PD (Hoehn & Yahr stage<3.0) took part in a screening session, followed by six Zumba Gold(®) workouts each separated by one week, and a follow-up interview six months later. The main feasibility parameters measured were retention, compliance, and adverse events. Furthermore, during each Zumba Gold(®) session, physical activity levels were measured using tri-axial accelerometers, while physiological load was assessed by average heart rate (HRmean). A two-way ANOVA with repeated measures assessed the effects of dance styles and session number on activity level and HR. 73% retention and 81% compliance were achieved, and no adverse events were recorded. Participants' enjoyment was high and 38% started Zumba Gold(®) classes in the community after intervention. HR values were similar between dance styles and within the American College of Sports Medicine (ACSM)'s recommendations in 50% of participants. Backwards steps reduced physiological load but improvements in activity levels between the first and last sessions show that steps could be learnt with time. Zumba Gold(®) is safe and enjoyable for people with PD. The excellent compliance and positive participants' feedback suggest the need for a larger-scale trial. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sleep Quality but Not Quantity Altered With a Change in Training Environment in Elite Australian Rules Football Players.

PubMed

Pitchford, Nathan W; Robertson, Sam J; Sargent, Charli; Cordy, Justin; Bishop, David J; Bartlett, Jonathan D

2017-01-01

To assess the effects of a change in training environment on the sleep characteristics of elite Australian Rules football (AF) players. In an observational crossover trial, 19 elite AF players had time in bed (TIB), total sleep time (TST), sleep efficiency (SE), and wake after sleep onset (WASO) assessed using wristwatch activity devices and subjective sleep diaries across 8-d home and camp periods. Repeated-measures ANOVA determined mean differences in sleep, training load (session rating of perceived exertion [RPE]), and environment. Pearson product-moment correlations, controlling for repeated observations on individuals, were used to assess the relationship between changes in sleep characteristics at home and camp. Cohen effect sizes (d) were calculated using individual means. On camp TIB (+34 min) and WASO (+26 min) increased compared with home. However, TST was similar between home and camp, significantly reducing camp SE (-5.82%). Individually, there were strong negative correlations for TIB and WASO (r = -.75 and r = -.72, respectively) and a moderate negative correlation for SE (r = -.46) between home and relative changes on camp. Camp increased the relationship between individual s-RPE variation and TST variation compared with home (increased load r = -.367 vs .051, reduced load r = .319 vs -.033, camp vs home respectively). Camp compromised sleep quality due to significantly increased TIB without increased TST. Individually, AF players with higher home SE experienced greater reductions in SE on camp. Together, this emphasizes the importance of individualized interventions for elite team-sport athletes when traveling and/or changing environments.

Modelling endurance and resumption times for repetitive one-hand pushing.

PubMed

Rose, Linda M; Beauchemin, Catherine A A; Neumann, W Patrick

2018-07-01

This study's objective was to develop models of endurance time (ET), as a function of load level (LL), and of resumption time (RT) after loading as a function of both LL and loading time (LT) for repeated loadings. Ten male participants with experience in construction work each performed 15 different one-handed repetaed pushing tasks at shoulder height with varied exerted force and duration. These data were used to create regression models predicting ET and RT. It is concluded that power law relationships are most appropriate to use when modelling ET and RT. While the data the equations are based on are limited regarding number of participants, gender, postures, magnitude and type of exerted force, the paper suggests how this kind of modelling can be used in job design and in further research. Practitioner Summary: Adequate muscular recovery during work-shifts is important to create sustainable jobs. This paper describes mathematical modelling and presents models for endurance times and resumption times (an aspect of recovery need), based on data from an empirical study. The models can be used to help manage fatigue levels in job design.

Enhanced ionization efficiency in TIMS analyses of plutonium and americium using porous ion emitters

DOE PAGES

Baruzzini, Matthew L.; Hall, Howard L.; Watrous, Matthew G.; ...

2016-12-05

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10–100 pg for americium and 1–100 pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ~550% for plutonium and ~1100%more » for americium. A maximum average efficiency of 1.09% was observed at a 1 pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10 pg mass loadings of plutonium. As a result, platinum PIEs exhibited an additional ~134% boost in ion yield over standard PIEs and ~736% over traditional filaments at the same sample loading level.« less

What you say matters: exploring visual-verbal interactions in visual working memory.

PubMed

Mate, Judit; Allen, Richard J; Baqués, Josep

2012-01-01

The aim of this study was to explore whether the content of a simple concurrent verbal load task determines the extent of its interference on memory for coloured shapes. The task consisted of remembering four visual items while repeating aloud a pair of words that varied in terms of imageability and relatedness to the task set. At test, a cue appeared that was either the colour or the shape of one of the previously seen objects, with participants required to select the object's other feature from a visual array. During encoding and retention, there were four verbal load conditions: (a) a related, shape-colour pair (from outside the experimental set, i.e., "pink square"); (b) a pair of unrelated but visually imageable, concrete, words (i.e., "big elephant"); (c) a pair of unrelated and abstract words (i.e., "critical event"); and (d) no verbal load. Results showed differential effects of these verbal load conditions. In particular, imageable words (concrete and related conditions) interfered to a greater degree than abstract words. Possible implications for how visual working memory interacts with verbal memory and long-term memory are discussed.

A Peer-Led HIV Mediation Adherence Intervention Targeting Adults Linked to Medical Care but without a Suppressed Viral Load

PubMed Central

Enriquez, Maithe; Cheng, An-Lin; Banderas, Julie; Farnan, Rose; Chertoff, Keyna; Hayes, Deana; Ortego, Gerry; Moreno, Jose; Peterson, Jane; McKinsey, David

2017-01-01

Background Non-adherence to antiretroviral (ART) treatment remains a prevalent problem even among the segment of the U.S. HIV population that is ‘linked’ to medical care. Methods Controlled pilot feasibility study with ART experienced adult patients (n=20) linked to HIV medical care without suppressed viral load. Patients were randomized to a peer-led HIV medication adherence intervention named ‘Ready’ or a time equivalent ‘healthy eating’ control arm. Lay individuals living with HIV were trained to facilitate ‘Ready’. Results Patients had been prescribed a mean of three prior ART regimens. The group randomized to ‘Ready’ had significantly improved adherence. MEMS and pharmacy refill data correlated with viral load log drop. Higher readiness for healthful behavior change correlated with viral load drop and approached significance. Conclusion A peer-led medication adherence intervention had a positive impact among adults who had experienced repeated non-adherence to HIV treatment. A larger study is needed to examine intervention dissemination and efficacy. PMID:25412724

Atomic force microscope image contrast mechanisms on supported lipid bilayers.

PubMed

Schneider, J; Dufrêne, Y F; Barger, W R; Lee, G U

2000-08-01

This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures onto a monolayer of DSPE show an abrupt breakthrough event at a repeatable, material-dependent force. The breakthrough force for DSPE and MGDG is sizable, whereas the breakthrough force for DOPE is too small to measure accurately. Contact-mode AFM images on 1:1 mixed monolayers of DSPE/DOPE and MGDG/DOPE have a high topographic contrast at loads between the breakthrough force of each phase, and a low topographic contrast at loads above the breakthrough force of both phases. Frictional contrast is inverted and magnified at loads above the breakthrough force of both phases. These results emphasize the important role that surface forces and mechanics can play in imaging multicomponent biomembranes with AFM.

Inhibition of Non-ATG Translational Events in Cells via Covalent Small Molecules Targeting RNA.

PubMed

Yang, Wang-Yong; Wilson, Henry D; Velagapudi, Sai Pradeep; Disney, Matthew D

2015-04-29

One major class of disease-causing RNAs is expanded repeating transcripts. These RNAs cause diseases via multiple mechanisms, including: (i) gain-of-function, in which repeating RNAs bind and sequester proteins involved in RNA biogenesis and (ii) repeat associated non-ATG (RAN) translation, in which repeating transcripts are translated into toxic proteins without use of a canonical, AUG, start codon. Herein, we develop and study chemical probes that bind and react with an expanded r(CGG) repeat (r(CGG)(exp)) present in a 5' untranslated region that causes fragile X-associated tremor/ataxia syndrome (FXTAS). Reactive compounds bind to r(CGG)(exp) in cellulo as shown with Chem-CLIP-Map, an approach to map small molecule binding sites within RNAs in cells. Compounds also potently improve FXTAS-associated pre-mRNA splicing and RAN translational defects, while not affecting translation of the downstream open reading frame. In contrast, oligonucleotides affect both RAN and canonical translation when they bind to r(CGG)(exp), which is mechanistically traced to a decrease in polysome loading. Thus, designer small molecules that react with RNA targets can be used to profile the RNAs to which they bind in cells, including identification of binding sites, and can modulate several aspects of RNA-mediated disease pathology in a manner that may be more beneficial than oligonucleotides.

Effects of vest loading on sprint kinetics and kinematics.

PubMed

Cross, Matt R; Brughelli, Matt E; Cronin, John B

2014-07-01

The effects of vest loading on sprint kinetics and kinematics during the acceleration and maximum velocity phases of sprinting are relatively unknown. A repeated measures analysis of variance with post hoc contrasts was used to determine whether performing 6-second maximal exertion sprints on a nonmotorized force treadmill, under 2 weighted vest loading conditions (9 and 18 kg) and an unloaded baseline condition, affected the sprint mechanics of 13 males from varying sporting backgrounds. Neither vest load promoted significant change in peak vertical ground reaction force (GRF-z) outputs compared with baseline during acceleration, and only 18-kg loading increased GRF-z at the maximum velocity (8.8%; effect size [ES] = 0.70). The mean GRF-z significantly increased with 18-kg loading during acceleration and maximum velocity (11.8-12.4%; ES = 1.17-1.33). Horizontal force output was unaffected, although horizontal power was decreased with the 18-kg vest during maximum velocity (-14.3%; ES = -0.48). Kinematic analysis revealed decreasing velocity (-3.6 to -5.6%; ES = -0.38 to -0.61), decreasing step length (-4.2%; ES = -0.33 to -0.34), increasing contact time (5.9-10.0%; ES = 1.01-1.71), and decreasing flight time (-17.4 to -26.7%; ES = -0.89 to -1.50) with increased loading. As a vertical vector-training stimulus, it seems that vest loading decreases flight time, which in turn reduces GRF-z. Furthermore, it seems that heavier loads than that are traditionally recommended are needed to promote increases in the GRF-z output during maximum velocity sprinting. Finally, vest loading offers little as a horizontal vector-training stimulus and actually compromises horizontal power output.

Analyses of power output of piezoelectric energy-harvesting devices directly connected to a load resistor using a coupled piezoelectric-circuit finite element method.

PubMed

Zhu, Meiling; Worthington, Emma; Njuguna, James

2009-07-01

This paper presents, for the first time, a coupled piezoelectric-circuit finite element model (CPC-FEM) to analyze the power output of a vibration-based piezoelectric energy-harvesting device (EHD) when it is connected to a load resistor. Special focus is given to the effect of the load resistor value on the vibrational amplitude of the piezoelectric EHD, and thus on the current, voltage, and power generated by the device, which are normally assumed to be independent of the load resistor value to reduce the complexity of modeling and simulation. The presented CPC-FEM uses a cantilever with a sandwich structure and a seismic mass attached to the tip to study the following characteristics of the EHD as a result of changing the load resistor value: 1) the electric outputs: the current through and voltage across the load resistor; 2) the power dissipated by the load resistor; 3) the displacement amplitude of the tip of the cantilever; and 4) the shift in the resonant frequency of the device. It is found that these characteristics of the EHD have a significant dependence on the load resistor value, rather than being independent of it as is assumed in most literature. The CPC-FEM is capable of predicting the generated output power of the EHD with different load resistor values while simultaneously calculating the effect of the load resistor value on the displacement amplitude of the tip of the cantilever. This makes the CPC-FEM invaluable for validating the performance of a designed EHD before it is fabricated and tested, thereby reducing the recurring costs associated with repeat fabrication and trials. In addition, the proposed CPC-FEM can also be used for producing an optimized design for maximum power output.

Earthquake Prediction in Large-scale Faulting Experiments

NASA Astrophysics Data System (ADS)

Junger, J.; Kilgore, B.; Beeler, N.; Dieterich, J.

2004-12-01

We study repeated earthquake slip of a 2 m long laboratory granite fault surface with approximately homogenous frictional properties. In this apparatus earthquakes follow a period of controlled, constant rate shear stress increase, analogous to tectonic loading. Slip initiates and accumulates within a limited area of the fault surface while the surrounding fault remains locked. Dynamic rupture propagation and slip of the entire fault surface is induced when slip in the nucleating zone becomes sufficiently large. We report on the event to event reproducibility of loading time (recurrence interval), failure stress, stress drop, and precursory activity. We tentatively interpret these variations as indications of the intrinsic variability of small earthquake occurrence and source physics in this controlled setting. We use the results to produce measures of earthquake predictability based on the probability density of repeating occurrence and the reproducibility of near-field precursory strain. At 4 MPa normal stress and a loading rate of 0.0001 MPa/s, the loading time is ˜25 min, with a coefficient of variation of around 10%. Static stress drop has a similar variability which results almost entirely from variability of the final (rather than initial) stress. Thus, the initial stress has low variability and event times are slip-predictable. The variability of loading time to failure is comparable to the lowest variability of recurrence time of small repeating earthquakes at Parkfield (Nadeau et al., 1998) and our result may be a good estimate of the intrinsic variability of recurrence. Distributions of loading time can be adequately represented by a log-normal or Weibel distribution but long term prediction of the next event time based on probabilistic representation of previous occurrence is not dramatically better than for field-observed small- or large-magnitude earthquake datasets. The gradually accelerating precursory aseismic slip observed in the region of nucleation in these experiments is consistent with observations and theory of Dieterich and Kilgore (1996). Precursory strains can be detected typically after 50% of the total loading time. The Dieterich and Kilgore approach implies an alternative method of earthquake prediction based on comparing real-time strain monitoring with previous precursory strain records or with physically-based models of accelerating slip. Near failure, time to failure t is approximately inversely proportional to precursory slip rate V. Based on a least squares fit to accelerating slip velocity from ten or more events, the standard deviation of the residual between predicted and observed log t is typically 0.14. Scaling these results to natural recurrence suggests that a year prior to an earthquake, failure time can be predicted from measured fault slip rate with a typical error of 140 days, and a day prior to the earthquake with a typical error of 9 hours. However, such predictions require detecting aseismic nucleating strains, which have not yet been found in the field, and on distinguishing earthquake precursors from other strain transients. There is some field evidence of precursory seismic strain for large earthquakes (Bufe and Varnes, 1993) which may be related to our observations. In instances where precursory activity is spatially variable during the interseismic period, as in our experiments, distinguishing precursory activity might be best accomplished with deep arrays of near fault instruments and pattern recognition algorithms such as principle component analysis (Rundle et al., 2000).

[Analysis of the results of the SEIMC External Quality Control Program for HIV-1 and HCV viral loads. Year 2008].

PubMed

Mira, Nieves Orta; Serrano, María del Remedio Guna; Martínez, José Carlos Latorre; Ovies, María Rosario; Pérez, José L; Cardona, Concepción Gimeno

2010-01-01

Human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) viral load determinations are among the most relevant markers for the follow up of patients infected with these viruses. External quality control tools are crucial to ensure the accuracy of results obtained by microbiology laboratories. This article summarized the results obtained from the 2008 SEIMC External Quality Control Program for HIV-1 and HCV viral loads. In the HIV-1 program, a total of five standards were sent. One standard consisted in seronegative human plasma, while the remaining four contained plasma from 3 different viremic patients, in the range of 2-5 log(10) copies/mL; two of these standards were identical aiming to determine repeatability. The specificity was complete for all commercial methods, and no false positive results were reported by the participants. A significant proportion of the laboratories (24% on average) obtained values out of the accepted range (mean +/- 0.2 log(10) copies/mL), depending on the standard and on the method used for quantification. Repeatability was very good, with up to 95% of laboratories reporting results within the limits (D < 0.5 log(10) copias/mL). The HCV program consisted of two standards with different viral load contents. Most of the participants (88,7%) obtained results within the accepted range (mean +/- 1.96 SD log(10) UI/mL). Post-analytical errors due to mistranscription of the results were detected for HCV, but not for the HIV-1 program. Data from this analysis reinforce the utility of proficiency programmes to ensure the quality of the results obtained by a particular laboratory, as well as the importance of the post-analytical phase on the overall quality. Due to the remarkable interlaboratory variability, it is advisable to use the same method and the same laboratory for patient follow up. 2010 Elsevier España S.L. All rights reserved.

Effect of a lotion containing the heat-treated probiotic strain Lactobacillus johnsonii NCC 533 on Staphylococcus aureus colonization in atopic dermatitis.

PubMed

Blanchet-Réthoré, Sandrine; Bourdès, Valérie; Mercenier, Annick; Haddar, Cyrille H; Verhoeven, Paul O; Andres, Philippe

2017-01-01

Staphylococcus aureus dominates the skin microbiota in patients with atopic dermatitis (AD), with bacterial loads correlating with disease severity. The aim of this exploratory study was to investigate the effect of a cosmetic lotion containing heat-treated Lactobacillus johnsonii NCC 533 (HT La1) on S. aureus colonization in AD patients. This open-label, multicenter study was performed in AD patients in Germany. First, detection of S. aureus was performed in all patients using the swab or scrub-wash method of sampling, followed by quantitative culture or quantitative polymerase chain reaction. Repeatability and reproducibility of all method combinations were evaluated to select the best combination of sampling and quantification. Second, a lotion containing HT La1 was applied to lesional skin twice daily for 3 weeks. Scoring using local objective SCORing Atopic Dermatitis (SCORAD), measurement of S. aureus load, and lesional microbiome analysis were performed before and after the 3-week treatment period. Thirty-one patients with AD were included in the study. All sampling and quantification methods were found to be robust, reproducible, and repeatable for assessing S. aureus load. For simplicity, a combination of swab and quantitative polymerase chain reaction was chosen to assess the efficacy of HT La1. Following application of a lotion containing HT La1 to AD lesions for 3 weeks, a reduction in S. aureus load was observed in patients, which correlated with a decrease in local objective SCORAD. Interestingly, high baseline skin concentrations of S. aureus were associated with good responses to the lotion. This study demonstrated that the application of a lotion containing HT La1 to the lesional skin of patients with AD for 3 weeks controlled S. aureus colonization and was associated with local clinical improvement (SCORAD). These findings support further development of topical treatments containing heat-treated nonreplicating beneficial bacteria for patients with AD.

Effects of endurance training only versus same-session combined endurance and strength training on physical performance and serum hormone concentrations in recreational endurance runners.

PubMed

Schumann, Moritz; Mykkänen, Olli-Pekka; Doma, Kenji; Mazzolari, Raffaele; Nyman, Kai; Häkkinen, Keijo

2015-01-01

This study investigated the effects of endurance training only (E, n = 14) and same-session combined training, when strength training is repeatedly preceded by endurance loading (endurance and strength training (E+S), n = 13) on endurance (1000-m running time during incremental field test) and strength performance (1-repetition maximum (1RM) in dynamic leg press), basal serum hormone concentrations, and endurance loading-induced force and hormone responses in recreationally endurance-trained men. E was identical in the 2 groups and consisted of steady-state and interval running, 4-6 times per week for 24 weeks. E+S performed additional mixed-maximal and explosive-strength training (2 times per week) immediately following an incremental running session (35-45 min, 65%-85% maximal heart rate). E and E+S decreased running time at week 12 (-8% ± 5%, p = 0.001 and -7% ± 3%, p < 0.001) and 24 (-13% ± 5%, p < 0.001 and -9% ± 5%, p = 0.001). Strength performance decreased in E at week 24 (-5% ± 5%, p = 0.014) but was maintained in E+S (between-groups at week 12 and 24, p = 0.014 and 0.011, respectively). Basal serum testosterone and cortisol concentrations remained unaltered in E and E+S but testosterone/sex hormone binding globulin ratio decreased in E+S at week 12 (-19% ± 26%, p = 0.006). At week 0 and 24, endurance loading-induced acute force (-5% to -9%, p = 0.032 to 0.001) and testosterone and cortisol responses (18%-47%, p = 0.013 to p < 0.001) were similar between E and E+S. This study showed no endurance performance benefits when strength training was performed repeatedly after endurance training compared with endurance training only. This was supported by similar acute responses in force and hormonal measures immediately post-endurance loading after the training with sustained 1RM strength in E+S.

[Analysis of the results of the HIV-1, HCV and HBV viral load of SEIMC External Quality Control Program. Year 2013].

PubMed

Orta Mira, Nieves; Del Remedio Guna Serrano, María; Latorre Martínez, José-Carlos; Medina González, Rafael; Rosario Ovies, María; Poveda, Marta; Ruiz de Gopegui, Enrique; Gimeno Cardona, Concepción

2015-07-01

Human immunodeficiency virus type 1 (HIV-1) and hepatitis B (HBV) and C virus (HCV) viral load determinations are among the most relevant markers for the follow up of patients infected with these viruses. External quality control tools are crucial to ensure the accuracy of results obtained by microbiology laboratories. This article summarized the results obtained from the 2013 SEIMC External Quality Control Programme for HIV-1, HCV, and HBV viral loads. In the HIV-1 program, a total of five standards were sent. One standard consisted in seronegative human plasma, while the remaining four contained plasma from three different viremic patients, in the range of 2-5 log10 copies/mL; two of these standards were identical aiming to determine repeatability. A significant proportion of the laboratories (25% on average) obtained values out of the accepted range (mean ± 0.25 log10 copies/mL), depending on the standard and on the method used for quantification. Repeatability was excellent, with up to 98.9% of laboratories reporting results within the limits (D < 0.5 log10 copies/mL). The HBV and HCV program consisted of two standards with different viral load contents. Most of the participants, 82% in the case of HCV and 78% in the HBV, obtained all the results within the accepted range (mean ± 1.96 SD log10 UI/mL). Data from this analysis reinforce the utility of proficiency programmes to ensure the quality of the results obtained by a particular laboratory, as well as the importance of the post-analytical phase on the overall quality. Due to the remarkable interlaboratory variability, it is advisable to use the same method and the same laboratory for patient follow up. Copyright © 2015 Elsevier España, S.L.U. All rights reserved.

[Analysis of the results of the HIV-1, HCV and HBV viral load of SEIMC External Quality Control Program. Year 2014].

PubMed

Medina González, Rafael; Orta Mira, Nieves; Guna Serrano, María Del Remedio; Latorre Martínez, José-Carlos; Gopegui, Enrique Ruiz de; Rosario Ovies, María; Poveda, Marta; Gimeno Cardona, Concepción

2016-07-01

Human immunodeficiency virus type 1 (HIV-1), hepatitis B virus (HBV) and hepatitis C virus (HCV) viral load determinations are among the most relevant markers for the follow up of patients infected with these viruses. External quality control tools are crucial to ensure the accuracy of results obtained by microbiology laboratories. This article summarizes the results obtained from the 2014 SEIMC (Spanish Society of Infectious Diseases and Clinical Microbiology) External Quality Control Programme for HIV-1, HCV, and HBV viral loads. In the HIV-1 program, a total of 5 standards were sent. One standard consisted in seronegative human plasma, while the remaining 4 contained plasma from 3 different viremic patients, in the range of 2-5 log10 copies/mL; 2 of these standards were identical aiming to determine repeatability. A significant proportion of the laboratories (30.8% on average) obtained values out of the accepted range (mean ± 0.25 log10 copies/mL), depending on the standard and on the method used for quantification. Repeatability was excellent, with up to 95.8% of laboratories reporting results within the limits (Δ < 0.5 log10 copies/mL). The HBV and HCV program consisted of 2 standards with different viral load contents. Most of the participants, 83.7% in the case of HCV and 87.9% in the HBV, obtained all the results within the accepted range (mean ± 1.96 standard deviations log10 IU/mL). Data from this analysis reinforce the utility of proficiency programmes to ensure the quality of the results obtained by a particular laboratory, as well as the importance of the post-analytical phase on the overall quality. Due to the remarkable interlaboratory variability, it is advisable to use the same method and the same laboratory for patient follow up. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

Finite element analysis of residual stress field induced by laser shock peening

NASA Astrophysics Data System (ADS)

Nam, Taeksun

The finite element method is applied to analyze the laser shock peening process (LSP) for thick parts (considered as a semi-infinite half space) and thin parts (finite thickness domain). The technology of LSP is used to enhance mechanical properties such as fatigue life, fretting fatigue life, resistance to stress corrosion cracking and surface hardness. These enhanced material properties are directly related to the magnitude and distribution of the plastic strain and associated residual stresses due to shockwaves induced by LSP. To reduce the process development cost and time, the prediction of residual stress field is very useful to provide a base design guideline for selecting appropriate LSP conditions for evaluation. An axisymmetric Finite Element Analysis (FEA) code, named SHOCKWAVE, is developed in order to complement shortcomings of applying commercial FEA codes at extremely high strain rates (as high as 104 -106/sec). The rate dependent plasticity theory is applied along with the small strain assumption. The solution process consists of an explicit dynamic loading analysis for shock loading stage and a static unloading analysis (implicit) to determine the equilibrium state for the residual stress and plastic strain fields. Some of the highlights explored in this investigation entail: (i) overstress power law models for the rate dependence, (ii) various hardening models, (iii) a second-order accurate implicit algorithm for the plastic consistency condition, (iv) an adaptively expanding domain scheme to trace the stress-free boundary condition in a simple way, (v) a special uniform meshing scheme to avoid the usual assembly process and repeated calculations for the stiffness matrix, (vi) mesh sensitivity study, (vii) comparisons with measured data provided and supported by the LSP Technologies, Inc. The dynamic behavior of Ti-6Al-4V at high strain rates can be investigated by using the split torsional Hopkinson bar experiment and by a longitudinal shock loading simulation in uniaxial strain to obtain material parameters representing rate dependent plasticity. In case of the double-sided laser peening for a thin part, reversal in loading plays a significant role. The stress waves repeatedly recompose the pre-accumulated plastic strains because of the interaction of the primary and reflected stress waves. In an attempt to better represent the material behavior under repeated reversals and collapses in loading, a sequence of bend-reverse bend tests is performed to identify the material parameters of TI-6Al-4V needed for a nonlinear kinematic hardening model (Chaboche model). For a thick part (a semi-infinite domain), single shot as well as multiple shots (at the same location) cases are simulated and compared with measured data for two different loading magnitudes and three different hardening models. Some of the simulation results agree well with the measured data, depending on the choice of hardening model and the treatment of rate dependent material behavior at high strain rates. Only a single shot (on both sides) case is investigated for a thin part (a finite thickness domain) in terms of residual stress distribution. The disagreement between the computed results and the measured data is more pronounced in this case, needing further investigations on both sides of the fields.

Influence of central set on anticipatory and triggered grip-force adjustments

NASA Technical Reports Server (NTRS)

Winstein, C. J.; Horak, F. B.; Fisher, B. E.; Peterson, B. W. (Principal Investigator)

2000-01-01

The effects of predictability of load magnitude on anticipatory and triggered grip-force adjustments were studied as nine normal subjects used a precision grip to lift, hold, and replace an instrumented test object. Experience with a predictable stimulus has been shown to enhance magnitude scaling of triggered postural responses to different amplitudes of perturbations. However, this phenomenon, known as a central-set effect, has not been tested systematically for grip-force responses in the hand. In our study, predictability was manipulated by applying load perturbations of different magnitudes to the test object under conditions in which the upcoming load magnitude was presented repeatedly or under conditions in which the load magnitudes were presented randomly, each with two different pre-load grip conditions (unconstrained and constrained). In constrained conditions, initial grip forces were maintained near the minimum level necessary to prevent pre-loaded object slippage, while in unconstrained conditions, no initial grip force restrictions were imposed. The effect of predictable (blocked) and unpredictable (random) load presentations on scaling of anticipatory and triggered grip responses was tested by comparing the slopes of linear regressions between the imposed load and grip response magnitude. Anticipatory and triggered grip force responses were scaled to load magnitude in all conditions. However, regardless of pre-load grip force constraint, the gains (slopes) of grip responses relative to load magnitudes were greater when the magnitude of the upcoming load was predictable than when the load increase was unpredictable. In addition, a central-set effect was evidenced by the fewer number of drop trials in the predictable relative to unpredictable load conditions. Pre-load grip forces showed the greatest set effects. However, grip responses showed larger set effects, based on prediction, when pre-load grip force was constrained to lower levels. These results suggest that anticipatory processes pertaining to load magnitude permit the response gain of both voluntary and triggered rapid grip force adjustments to be set, at least partially, prior to perturbation onset. Comparison of anticipatory set effects for reactive torque and lower extremity EMG postural responses triggered by surface translation perturbations suggests a more general rule governing anticipatory processes.

Reduced knee flexion is a possible cause of increased loading rates in individuals with patellofemoral pain.

PubMed

Silva, Danilo de Oliveira; Briani, Ronaldo Valdir; Pazzinatto, Marcella Ferraz; Ferrari, Deisi; Aragão, Fernando Amâncio; Azevedo, Fábio Mícolis de

2015-11-01

Stair ascent is an activity that exacerbates symptoms of individuals with patellofemoral pain. The discomfort associated with this activity usually results in gait modification such as reduced knee flexion in an attempt to reduce pain. Although such compensatory strategy is a logical approach to decrease pain, it also reduces the normal active shock absorption increasing loading rates and may lead to deleterious and degenerative changes of the knee joint. Thus, the aims of this study were (i) to investigate whether there is reduced knee flexion in adults with PFP compared to healthy controls; and (ii) to analyze loading rates in these subjects, during stair climbing. Twenty-nine individuals with patellofemoral pain and twenty-five control individuals (18-30 years) participated in this study. Each subject underwent three-dimensional kinematic and kinetic analyses during stair climbing on two separate days. Between-groups analyses of variance were performed to identify differences in peak knee flexion and loading rates. Intraclass correlation coefficient was performed to verify the reliability of the variables. On both days, the patellofemoral pain group demonstrated significantly reduced peak knee flexion and increased loading rates. In addition, the two variables obtained high to very high reliability. Reduced knee flexion during stair climbing as a strategy to avoid anterior knee pain does not seem to be healthy for lower limb mechanical distributions. Repeated loading at higher loading rates may be damaging to lower limb joints. Copyright © 2015 Elsevier Ltd. All rights reserved.

Body armour: the effect of load, exercise and distraction on landing forces.

PubMed

Dempsey, Paddy C; Handcock, Phil J; Rehrer, Nancy J

2014-01-01

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 ± 9.2 years, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, maximal aerobic fitness (VO(₂max)) 50 ± 8.5 ml (.) kg(-1 .) min(-1), BMI 27.6 ± 3.1, mean ± s) completed a VO(₂max) test. Experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P < 0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P < 0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury.

Jump Shrug Height and Landing Forces Across Various Loads.

PubMed

Suchomel, Timothy J; Taber, Christopher B; Wright, Glenn A

2016-01-01

The purpose of this study was to examine the effect that load has on the mechanics of the jump shrug. Fifteen track and field and club/intramural athletes (age 21.7 ± 1.3 y, height 180.9 ± 6.6 cm, body mass 84.7 ± 13.2 kg, 1-repetition-maximum (1RM) hang power clean 109.1 ± 17.2 kg) performed repetitions of the jump shrug at 30%, 45%, 65%, and 80% of their 1RM hang power clean. Jump height, peak landing force, and potential energy of the system at jump-shrug apex were compared between loads using a series of 1-way repeated-measures ANOVAs. Statistical differences in jump height (P < .001), peak landing force (P = .012), and potential energy of the system (P < .001) existed; however, there were no statistically significant pairwise comparisons in peak landing force between loads (P > .05). The greatest magnitudes of jump height, peak landing force, and potential energy of the system at the apex of the jump shrug occurred at 30% 1RM hang power clean and decreased as the external load increased from 45% to 80% 1RM hang power clean. Relationships between peak landing force and potential energy of the system at jump-shrug apex indicate that the landing forces produced during the jump shrug may be due to the landing strategy used by the athletes, especially at lighter loads. Practitioners may prescribe heavier loads during the jump-shrug exercise without viewing landing force as a potential limitation.

Plantar loading changes with alterations in foot strike patterns during a single session in habitual rear foot strike female runners.

PubMed

Kernozek, Thomas W; Vannatta, Charles N; Gheidi, Naghmeh; Kraus, Sydnie; Aminaka, Naoko

2016-03-01

Characterize plantar loading parameters when habitually rear foot strike (RFS) runners change their pattern to a non-rear foot strike (NRFS). Experimental. University biomechanics laboratory. Twenty three healthy female runners (Age: 22.17 ± 1.64 yrs; Height: 168.91 ± 5.46 cm; Mass: 64.29 ± 7.11 kg). Plantar loading was measured using an in-sole pressure sensor while running down a 20-m runway restricted to a range of 3.52-3.89 m/s under two conditions, using the runner's typical RFS, and an adapted NRFS pattern. Repeated measures multivariate analysis of variance was performed to detect differences in loading between these two conditions. Force and pressure variables were greater in the forefoot and phalanx in NRFS and greater in the heel and mid foot in RFS pattern, but the total force imposed upon the whole foot and contact time remained similar between conditions. Total peak pressure was higher and contact area was lower during NRFS running. The primary finding of this investigation is that there are distinctly different plantar loads when changing from a RFS to NRFS during running. So, during a transition from RFS to a NRFS pattern; a period of acclimation should be considered to allow for adaptations to these novel loads incurred on plantar regions of the foot. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of hiking stick use on lateral stability while balancing with and without a load.

PubMed

Jacobson, B H; Caldwell, B; Kulling, F A

1997-08-01

To compare hiking stick use on lateral stability while balancing with or without a load (15-kg internal frame backpack) under conditions of no stick, 1 stick, and 2 sticks for six trials 15 volunteers ages 19 to 23 years (M = 21.7 yr.) were tested six separate times on a stability platform. During randomly ordered, 1-min. trials, the length of time (sec.) the subject maintained balance (+/-10 degrees of horizontal) and the number of deviations beyond 10 degrees were recorded simultaneously. Backpack and hiking sticks were individually adjusted for each subject. A 2 x 3 repeated factor analysis of variance indicated that subjects balanced significantly longer both with and without a load while using 2 hiking sticks than 1 or 0 sticks. Significantly fewer deviations beyond 10 degrees were found when subjects were without a load and using 1 or 2 sticks versus when they used none, and no significant difference in the number of deviations were found between 1 and 2 hiking sticks. When subjects were equipped with a load, significantly improved balance was found only between the 2 sticks and no sticks. Balance was significantly enhanced by using hiking sticks, and two sticks were more effective than one while carrying a load. An increase in maintenance of static balance may reduce the possibility of falling and injury while standing on loose alpine terrain.

Effects of a Prophylactic Knee Sleeve on Anterior Cruciate Ligament Loading During Sport Specific Movements.

PubMed

Sinclair, Jonathan; Taylor, Paul John

2017-07-17

Prophylactic knee bracing is extensively utilized in athletic populations, to reduce the high risk from knee injuries, but their role in the attenuation of anterior cruciate ligament (ACL) pathologies is not well understood. The aim of the current investigation was to investigate the effects of a prophylactic knee sleeve on ACL loading parameters linked to the aetiology of injury in recreational athletes. Laboratory. Repeated measures. Thirteen healthy male recreational athletes. Intervention Participants performed run, cut and single leg hop movements under two conditions; prophylactic knee sleeve and no-sleeve. Biomechanical data was captured using an eight-camera 3D motion capture system and a force platform. Peak ACL force, average ACL load rate and instantaneous ACL load rate were quantified using a musculoskeletal modelling approach. The results showed that both average and instantaneous ACL load rates were significantly reduced when wearing the knee sleeve in the hop (sleeve = 612.45/ 1286.39N/kg/s & no-sleeve = 743.91/ 1471.42 N/kg/s) and cut (sleeve = 222.55/ 1058.02 N/kg/s & no-sleeve = 377.38/ 1183.01 N/kg/s) movements. Given the biomechanical association between ACL loading and the aetiology of ACL injuries, it is proposed that athletes may be able to attenuate their risk from injury during cut and hop movements through utilization of a prophylactic knee sleeve.

Immediate effects of manipulation of the talocrural joint on stabilometry and baropodometry in patients with ankle sprain.

PubMed

López-Rodríguez, Sandra; Fernández de-Las-Peñas, César; Alburquerque-Sendín, Francisco; Rodríguez-Blanco, Cleofás; Palomeque-del-Cerro, Luis

2007-01-01

This study assessed the immediate effects of talocrural joint manipulation on stabilometric and baropodometric outcomes in patients with grade II ankle sprain. Fifty-two field hockey players (35 men and 17 women) between 18 and 40 years old (mean = 22.5 years, SD = 3.6 years) were included in this study. A simple blind, intrapatient, placebo-controlled, and repeated-measures study was carried out. All the patients underwent a baropodometric study performed with a Foot Work force platform (4 times; pre-post placebo group and pre-post intervention group). The sample was subjected to two techniques of manipulative treatment: (a) talocrural joint manipulation and (b) posterior gliding manipulation over the talus. In a second instance, placebo manipulation was applied. Unilateral analysis of variance and multivariate analysis of variance were used for statistical analysis. The results in the intervention group revealed significant differences in the percentage of posterior load on the foot (P = .015) and the percentage of bilateral anterior load (P = .02) before and after the manipulation. The placebo group did not show any change in any of the variables except for area (P = .045). Intergroup comparison revealed statistically significant differences in the increase in percentage of posterior load on the manipulated foot, percentage of bilateral posterior load, percentage of anterior load on the manipulated foot, and percentage of bilateral anterior load (with the exception of the total load on the foot). The application of caudal talocrural joint manipulation, as compared with placebo manipulation, in athletic patients with grade II ankle sprain redistributed the load supports at the level of the foot.

Kinematic evaluation of patients with total and reverse shoulder arthroplasty during rehabilitation exercises with different loads.

PubMed

de Toledo, Joelly Mahnic; Loss, Jefferson Fagundes; Janssen, Thomas W; van der Scheer, Jan W; Alta, Tjarco D; Willems, W Jaap; Veeger, DirkJan H E J

2012-10-01

Following shoulder arthroplasty, any well-planned rehabilitation program should include muscle strengthening. However, it is not always clear how different external loads influence shoulder kinematics in patients with shoulder prostheses. The objective of this study was to describe shoulder kinematics and determine the contribution of the scapulothoracic joint to total shoulder motion of patients with total and reverse shoulder arthroplasties and of healthy individuals during rehabilitation exercises (anteflexion and elevation in the scapular plane) using different loading conditions (without external load, 1 kg and elastic resistance). Shoulder motions were measured using an electromagnetic tracking device. A force transducer was used to record force signals during loaded conditions using elastic resistance. Statistical comparisons were made using a three-way repeated-measures analysis of variance with a Bonferroni post hoc testing. The scapula contributed more to movement of the arm in subjects with prostheses compared to healthy subjects. The same applies for loaded conditions (1 kg and elastic resistance) relative to unloaded tasks. For scapular internal rotation, upward rotation and posterior tilt no significant differences among groups were found during both exercises. Glenohumeral elevation angles during anteflexion were significantly higher in the total shoulder arthroplasty group compared to the reverse shoulder arthroplasty group. Differences in contribution of the scapula to total shoulder motion between patients with different types of arthroplasties were not significant. However, compared to healthy subjects, they were. Furthermore, scapular kinematics of patients with shoulder arthroplasty was influenced by implementation of external loads, but not by the type of load. Copyright © 2012 Elsevier Ltd. All rights reserved.

Adaptation to a cortex controlled robot attached at the pelvis and engaged during locomotion in rats

PubMed Central

Song, Weiguo; Giszter, Simon F.

2011-01-01

Brain Machine Interfaces (BMIs) should ideally show robust adaptation of the BMI across different tasks and daily activities. Most BMIs have used over-practiced tasks. Little is known about BMIs in dynamic environments. How are mechanically body-coupled BMIs integrated into ongoing rhythmic dynamics, e.g., in locomotion? To examine this we designed a novel BMI using neural discharge in the hindlimb/trunk motor cortex in rats during locomotion to control a robot attached at the pelvis. We tested neural adaptation when rats experienced (a) control locomotion, (b) ‘simple elastic load’ (a robot load on locomotion without any BMI neural control) and (c) ‘BMI with elastic load’ (in which the robot loaded locomotion and a BMI neural control could counter this load). Rats significantly offset applied loads with the BMI while preserving more normal pelvic height compared to load alone. Adaptation occurred over about 100–200 step cycles in a trial. Firing rates increased in both the loaded conditions compared to baseline. Mean phases of cells’ discharge in the step cycle shifted significantly between BMI and the simple load condition. Over time more BMI cells became positively correlated with the external force and modulated more deeply, and neurons’ network correlations on a 100ms timescale increased. Loading alone showed none of these effects. The BMI neural changes of rate and force correlations persisted or increased over repeated trials. Our results show that rats have the capacity to use motor adaptation and motor learning to fairly rapidly engage hindlimb/trunk coupled BMIs in their locomotion. PMID:21414932

Assessment of aortic valve calcium load by multidetector computed tomography. Anatomical validation, impact of scanner settings and incremental diagnostic value.

PubMed

Boulif, Jamila; Gerber, Bernhard; Slimani, Alisson; Lazam, Siham; de Meester, Christophe; Piérard, Sophie; Pasquet, Agnès; Pouleur, Anne-Catherine; Vancraeynest, David; El Khoury, Gébrine; de Kerchove, Laurent; Noirhomme, Philippe; Vanoverschelde, Jean-Louis

To validate aortic valve calcium (AVC) load measurements by multidetector row computed tomography (MDCT), to evaluate the impact of tube potential and slice thickness on AVC scores, to examine the accuracy of AVC load in distinguishing severe from nonsevere aortic stenosis (AS) and to investigate its effectiveness as an alternative diagnosis method when echocardiography remains inconclusive. We prospectively studied 266 consecutive patients with moderate to severe AS who underwent MDCT to measure AVC load and a comprehensive echocardiographic examination to assess AS severity. AVC load was validated against valve weight in 57 patients undergoing aortic valve replacement. The dependence of AVC scores on tube potential and slice thickness was also tested, as well as the relationship between AVC load and echocardiographic criteria of AS severity. MDCT Agatston score correlated well with valve weight (r = 0.82, p < 0.001) and hemodynamic indices of AS severity (all p < 0.001). Ex-vivo Agatston scores decreased significantly with increasing tube potential and slice thickness (repeated measures ANOVA p < 0.001). Multivariate analysis identified mean gradient, the indexed effective orifice area, male gender and left ventricular outflow tract cross-sectional area as independent correlates of the in-vivo AVC load. MDCT-derived AVC load correlated well with valve weight and hemodynamic indices of AS severity. It also depends on tube potential and slice thickness, thus suggesting that these parameters should be standardized to optimize reproducibility and accuracy. Copyright © 2017 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

Repeatability Measurements of Apparent Thermal Conductivity of Multilayer Insulation (MLI)

NASA Astrophysics Data System (ADS)

Vanderlaan, M.; Stubbs, D.; Ledeboer, K.; Ross, J.; Van Sciver, S.; Guo, W.

2017-12-01

This report presents and discusses the results of repeatability experiments gathered from the multi-layer insulation thermal conductivity experiment (MIKE) for the measurement of the apparent thermal conductivity of multi-layer insulation (MLI) at variable boundary temperatures. Our apparatus uses a calibrated thermal link between the lower temperature shield of a concentric cylinder insulation assembly and the cold head of a cryocooler to measure the heat leak. In addition, thermocouple readings are taken in-between the MLI layers. These measurements are part of a multi-phase NASA-Yetispace-FSU collaboration to better understand the repeatability of thermal conductivity measurements of MLI. NASA provided five 25 layer coupons and requested boundary temperatures of 20 K and 300 K. Yetispace provided ten 12-layer coupons and requested boundary temperatures of 77 K and 293 K. Test conditions must be met for a duration of four hours at a steady state variance of less than 0.1 K/hr on both cylinders. Temperatures from three Cernox® temperature sensors on each of the two cylinders are averaged to determine the boundary temperatures. A high vacuum, less than 10-5 torr, is maintained for the duration of testing. Layer density varied from 17.98 - 26.36 layers/cm for Yetispace coupons and 13.05 - 17.45 layers/cm for the NASA coupons. The average measured heat load for the Yetispace coupons was 2.40 W for phase-one and 2.92 W for phase-two. The average measured heat load for the NASA coupons was 1.10 W. This suggests there is still unknown variance of MLI performance. It has been concluded, variations in the insulation installation heavy effect the apparent thermal conductivity and are not solely dependent on layer density.

Glycemic index, glycemic load and invasive breast cancer incidence in postmenopausal women: The PREDIMED study.

PubMed

Castro-Quezada, Itandehui; Sánchez-Villegas, Almudena; Martínez-González, Miguel Á; Salas-Salvadó, Jordi; Corella, Dolores; Estruch, Ramón; Schröder, Helmut; Álvarez-Pérez, Jacqueline; Ruiz-López, María D; Artacho, Reyes; Ros, Emilio; Bulló, Mónica; Sorli, Jose V; Fitó, Montserrat; Ruiz-Gutiérrez, Valentina; Toledo, Estefanía; Buil-Cosiales, Pilar; García Rodríguez, Antonio; Lapetra, José; Pintó, Xavier; Salaverría, Itziar; Tur, Josep A; Romaguera, Dora; Tresserra-Rimbau, Anna; Serra-Majem, Lluís

2016-11-01

The objective of this study was to evaluate the prospective associations between dietary glycemic index (GI) and glycemic load (GL) and the risk for invasive breast cancer incidence in postmenopausal women at high cardiovascular disease (CVD) risk. This study was conducted within the framework of the PREvención con DIeta MEDiterránea (PREDIMED) study, a nutritional intervention trial for primary cardiovascular prevention. We included 4010 women aged between 60 and 80 years who were initially free from breast cancer but at high risk for CVD disease. Dietary information was collected using a validated 137-item food frequency questionnaire. We assigned GI values using the International Tables of GI and GL values. Cases were ascertained through yearly consultation of medical records and through consultation of the National Death Index. Only cases confirmed by results from cytology tests or histological evaluation were included. We estimated multivariable-adjusted hazard ratios for invasive breast cancer risk across tertiles of energy-adjusted dietary GI/GL using Cox regression models. We repeated our analyses using yearly repeated measures of GI/GL intakes. No associations were found between baseline dietary GI/GL and invasive breast cancer incidence. The multivariable hazard ratio and 95% confidence interval (CI) for the top tertile of dietary GI was 1.02 (95% CI: 0.42-2.46) and for dietary GL was 1.00 (95% CI: 0.44-2.30) when compared with the bottom tertile. Repeated-measures analyses yielded similar results. In sensitivity analyses, no significant associations were observed for women with obesity or diabetes. Dietary GI and GL did not appear to be associated with an increased risk for invasive breast cancer in postmenopausal women at high CVD risk.

Impact of spring or fall repeated prescribed fire on growth of ponderosa pine in eastern Oregon, USA

Treesearch

Walter G. Thies; Douglas J. Westlind; Mark. Loewen

2013-01-01

Prescribed burning is used to reduce fuel loads and to return fire to its historic disturbance role in western forests. Managers need to know the effects of prescribed fire on tree growth. Growth of residual ponderosa pine (Pinus ponderosa Dougl. ex Laws.) was measured in an existing long-term study of the effects of season-of-prescribed burn in...

A mesoporous nickel counter electrode for printable and reusable perovskite solar cells.

PubMed

Ku, Zhiliang; Xia, Xinhui; Shen, He; Tiep, Nguyen Huy; Fan, Hong Jin

2015-08-28

A mesoporous nickel layer is used as the counter electrode in printable perovskite solar cells. A unique reuse process is realized in such perovskite solar cell devices by repeated loading of the perovskite material. Under standard AM1.5 illumination, the fresh device shows a promising power conversion efficiency of 13.6%, and an efficiency of 12.1% is obtained in the reused devices.

Design and experiment of FBG-based icing monitoring on overhead transmission lines with an improvement trial for windy weather.

PubMed

Zhang, Min; Xing, Yimeng; Zhang, Zhiguo; Chen, Qiguan

2014-12-12

A scheme for monitoring icing on overhead transmission lines with fiber Bragg grating (FBG) strain sensors is designed and evaluated both theoretically and experimentally. The influences of temperature and wind are considered. The results of field experiments using simulated ice loading on windless days indicate that the scheme is capable of monitoring the icing thickness within 0-30 mm with an accuracy of ±1 mm, a load cell error of 0.0308v, a repeatability error of 0.3328v and a hysteresis error is 0.026%. To improve the measurement during windy weather, a correction factor is added to the effective gravity acceleration, and the absolute FBG strain is replaced by its statistical average.

Wing Torsional Stiffness Tests of the Active Aeroelastic Wing F/A-18 Airplane

NASA Technical Reports Server (NTRS)

Lokos, William A.; Olney, Candida D.; Crawford, Natalie D.; Stauf, Rick; Reichenbach, Eric Y.

2002-01-01

The left wing of the Active Aeroelastic Wing (AAW) F/A-18 airplane has been ground-load-tested to quantify its torsional stiffness. The test has been performed at the NASA Dryden Flight Research Center in November 1996, and again in April 2001 after a wing skin modification was performed. The primary objectives of these tests were to characterize the wing behavior before the first flight, and provide a before-and-after measurement of the torsional stiffness. Two streamwise load couples have been applied. The wing skin modification is shown to have more torsional flexibility than the original configuration has. Additionally, structural hysteresis is shown to be reduced by the skin modification. Data comparisons show good repeatability between the tests.

Fatigue of immature baboon cortical bone.

PubMed

Keller, T S; Lovin, J D; Spengler, D M; Carter, D R

1985-01-01

Strain-controlled uniaxial fatigue and monotonic tensile tests were conducted on turned femoral cortical bone specimens obtained from baboons at various ages of maturity. Fatigue loading produced a progressive loss in stiffness and an increase in hysteresis prior to failure, indicating that immature primate cortical bone responds to repeated loading in a fashion similar to that previously observed for adult human cortical bone. Bone fatigue resistance under this strain controlled testing decreased during maturation. Maturation was also associated with an increase in bone dry density, ash fraction and elastic modulus. The higher elastic modulus of more mature bone meant that these specimens were subjected to higher stress levels during testing than more immature bone specimens. Anatomical regions along the femoral shaft exhibited differences in strength and fatigue resistance.

A new class of high-G and long-duration shock testing machines

NASA Astrophysics Data System (ADS)

Rastegar, Jahangir

2018-03-01

Currently available methods and systems for testing components for survival and performance under shock loading suffer from several shortcomings for use to simulate high-G acceleration events with relatively long duration. Such events include most munitions firing and target impact, vehicular accidents, drops from relatively high heights, air drops, impact between machine components, and other similar events. In this paper, a new class of shock testing machines are presented that can be used to subject components to be tested to high-G acceleration pulses of prescribed amplitudes and relatively long durations. The machines provide for highly repeatable testing of components. The components are mounted on an open platform for ease of instrumentation and video recording of their dynamic behavior during shock loading tests.

Detonation charge size versus coda magnitude relations in California and Nevada

USGS Publications Warehouse

Brocher, T.M.

2003-01-01

Magnitude-charge size relations have important uses in forensic seismology and are used in Comprehensive Nuclear-Test-Ban Treaty monitoring. I derive empirical magnitude versus detonation-charge-size relationships for 322 detonations located by permanent seismic networks in California and Nevada. These detonations, used in 41 different seismic refraction or network calibration experiments, ranged in yield (charge size) between 25 and 106 kg; coda magnitudes reported for them ranged from 0.5 to 3.9. Almost all represent simultaneous (single-fired) detonations of one or more boreholes. Repeated detonations at the same shotpoint suggest that the reported coda magnitudes are repeatable, on average, to within 0.1 magnitude unit. An empirical linear regression for these 322 detonations yields M = 0.31 + 0.50 log10(weight [kg]). The detonations compiled here demonstrate that the Khalturin et al. (1998) relationship, developed mainly for data from large chemical explosions but which fits data from nuclear blasts, can be used to estimate the minimum charge size for coda magnitudes between 0.5 and 3.9. Drilling, loading, and shooting logs indicate that the explosive specification, loading method, and effectiveness of tamp are the primary factors determining the efficiency of a detonation. These records indicate that locating a detonation within the water table is neither a necessary nor sufficient condition for an efficient shot.

Novel cage stress alters remote contextual fear extinction and regional T2 magnetic resonance relaxation times in TASTPM mice overexpressing amyloid.

PubMed

Rattray, Ivan; Pitiot, Alain; Lowe, James; Auer, Dorothee P; Lima, Sarah-Jane; Schubert, Mirjam I; Prior, Malcolm J W; Marsden, Charles A; Diaz, Fernando Pérez; Kendall, David A; Pardon, Marie-Christine

2010-01-01

We have previously shown that repeated exposure to mild novel cage stress prevents the onset of recent contextual fear memory deficits and attenuated amyloid deposition in the TASTPM mouse model of Alzheimer's disease. Here, we extended this investigation to remote contextual fear memory and extinction. TASTPM and wild-type mice acquired contextual fear at 4 months of age. Retention and extinction of contextual fear were assessed at 5.5 months prior to in vivo MRI assessment of regional T2 relaxation times and brain volumes followed by immunostaining to determine amyloid plaque load. Remote contextual fear memory was preserved in TASTPM mice regardless of the stress condition. Stress impaired extinction in wild-type mice but facilitated this process in TASTPM mice. Genotype-dependent effects of stress were observed on regional T2 times which were prolonged in the subiculum and thalamus of stressed TASTPM, possibly reflecting reduced amyloid pathology. Amyloid plaque load was particularly decreased in the retrosplenial cortex of stressed TASTPM mice, which also showed an overall reduction in the number of diffuse plaques. These findings support the hypothesis that repeated mild levels of stress induced by novel activities can delay the progression of pathological changes relevant to Alzheimer's disease.

Laboratory constraints on models of earthquake recurrence

USGS Publications Warehouse

Beeler, Nicholas M.; Tullis, Terry; Junger, Jenni; Kilgore, Brian D.; Goldsby, David L.

2014-01-01

In this study, rock friction ‘stick-slip’ experiments are used to develop constraints on models of earthquake recurrence. Constant-rate loading of bare rock surfaces in high quality experiments produces stick-slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip rate-dependent process that also determines the size of the stress drop [Dieterich, 1979; Ruina, 1983] and as a consequence, stress drop varies weakly but systematically with loading rate [e.g., Gu and Wong, 1991; Karner and Marone, 2000; McLaskey et al., 2012]. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low-frequency earthquakes loaded by episodic slip. As follows from the previous studies referred to above, experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a non-linear slip-predictable model. The fault’s rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence co-vary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability and successive stress drops are strongly correlated indicating a ‘memory’ of prior slip history that extends over at least one recurrence cycle.

A Radiographic Comparison of Progressive and Conventional Loading on Crestal Bone Loss and Density in Single Dental Implants: A Randomized Controlled Trial Study

PubMed Central

Ghoveizi, Rahab; Alikhasi, Marzieh; Siadat, Mohammad-Reza; Siadat, Hakimeh; Sorouri, Majid

2013-01-01

Objective: Crestal bone loss is a biological complication in implant dentistry. The aim of this study was to compare the effect of progressive and conventional loading on crestal bone height and bone density around single osseointegrated implants in the posterior maxilla by a longitudinal radiographic assessment technique. Materials and Methods: Twenty micro thread implants were placed in 10 patients (two implants per patient). One of the two implants in each patient was assigned to progressive and the other to conventional loading groups. Eight weeks after surgery, conventional implants were restored with a metal ceramic crown and the progressive group underwent a progressive loading protocol. The progressive loading group took different temporary acrylic crowns at 2, 4 and 6 months. After eight months, acrylic crowns were replaced with a metal ceramic crown. Computer radiography of both progressive and conventional implants was taken at 2, 4, 6, and 12 months. Image analysis was performed to measure the height of crestal bone loss and bone density. Results: The mean values of crestal bone loss at month 12 were 0.11 (0.19) mm for progressively and 0.36 (0.36) mm for conventionally loaded implants, with a statistically significant difference (P < 0.05) using Wilcoxon sign rank. Progressively loaded group showed a trend for higher bone density gain compared to the conventionally loaded group, but when tested with repeated measure ANOVA, the differences were not statistically significant (P > 0.05). Conclusion: The progressive group showed less crestal bone loss in single osseointegrated implant than the conventional group. Bone density around progressively loaded implants showed increase in crestal, middle and apical areas. PMID:23724215

Effect of unilateral and bilateral use of laterally wedged insoles with arch supports on impact loading in medial knee osteoarthritis.

PubMed

Abd El Megeid Abdallah, Amira Abdallah

2016-04-01

Increased impact loading is implicated in knee osteoarthritis development and progression. This study examined the impact ground reaction force (GRF) peak, its loading rate, its relative timing to stance phase timing, and walking speed during unilateral and bilateral use of laterally wedged insoles with arch supports. Within-subject design. Thirty-three female patients with medial knee osteoarthritis were examined with (unilateral 6° and 11°, and bilateral 0°, 6°, and 11°) and without insole use. Repeated measures MANOVA revealed that the impact force increased significantly in bilateral 11° versus unilateral 6° and without-insole conditions. The loading rate decreased significantly in unilateral 11° versus bilateral 6° insoles. The relative timing increased significantly in each of bilateral 6°, bilateral 11°, and unilateral 11° versus bilateral 0° insoles and in each of bilateral 11° and unilateral 11° versus without-insole condition. There were significant positive correlations between the walking speed and each of the force and loading rate. The Chi-square test revealed insignificant association between the insole condition and the presence of impact forces. Unilateral 11° insoles are capable of reducing impact loading possibly through increasing foot pronation. Walking slowly is another possible strategy to reduce loading. Unilaterally applied 11° laterally wedged insoles are capable of reducing and delaying the initial impact ground reaction forces and reducing their loading rates during walking in patients with medial knee osteoarthritis, thus reducing osteoarthritis progression. Walking slowly could also be used as a strategy to reduce impact loading. © The International Society for Prosthetics and Orthotics 2015.

Changes in the flexion relaxation response induced by lumbar muscle fatigue.

PubMed

Descarreaux, Martin; Lafond, Danik; Jeffrey-Gauthier, Renaud; Centomo, Hugo; Cantin, Vincent

2008-01-24

The flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task. Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 x 2 repeated-measures ANOVA. Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition. The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.

Soldier-relevant loads impact lower limb biomechanics during anticipated and unanticipated single-leg cutting movements.

PubMed

Brown, Tyler N; O'Donovan, Meghan; Hasselquist, Leif; Corner, Brian; Schiffman, Jeffrey M

2014-11-07

This study quantified how body borne load impacts hip and knee biomechanics during anticipated and unanticipated single-leg cutting maneuvers. Fifteen male military personnel performed a series of single-leg cutting maneuvers with three different load configurations (light, ~6 kg, medium, ~20 kg, and heavy, ~40 kg). Subject-based means of the specific lower limb biomechanical variables were submitted to repeated measures ANOVA to test the main and interaction effects of body borne load and movement type. With body borne load, stance time (P<0.001) increased, while larger hip (P=0.027) and knee flexion (P=0.004), and hip adduction (P<0.001) moments, and decreased hip (P=0.002) and knee flexion (P<0.001), and hip adduction (P=0.003) postures were evident. Further, the hip (P<0.001) and ankle (P=0.024) increased energy absorption, while the knee (P=0.020) increased energy generation with body borne load. During the unanticipated maneuvers, the hip (P=0.009) and knee (P=0.032) increased energy generation, and peak hip flexion moment (P=0.002) increased relative to the anticipated movements. With the body borne load, participants adopted biomechanical patterns that decreased their locomotive ability including larger moments and reduced flexion postures of the lower limb. During the single-leg cut, participants used greater energy absorption from the large, proximal muscles of the hip and greater energy generation from the knee with the addition of load. Participant's performance when carrying a range of loads was not compromised by anticipation, as they did not exhibit the hip and knee kinetic and kinematic adaptations previously demonstrated when reacting to an unplanned stimulus. Published by Elsevier Ltd.

Frequency response of pig intervertebral disc cells subjected to dynamic hydrostatic pressure.

PubMed

Kasra, Mehran; Merryman, W David; Loveless, Kristen N; Goel, Vijay K; Martin, James D; Buckwalter, Joseph A

2006-10-01

The pathogenesis of vibration-induced disorders of intervertebral disc at the cellular level is largely unknown. Dynamic loads with frequencies close to that of the in vivo human spine resonant frequency (4-6 Hz) have a destructive effect, which may induce extracellular disc matrix (ECM) degradation. To investigate this issue, three-dimensional (3D) alginate cultures of normal pig intervertebral disc nucleus and inner annulus cells were tested under dynamic hydrostatic loading. Alginate cultures of each region were divided into six groups; five groups were exposed to cyclic hydrostatic pressures of frequencies 1, 3, 5, 8, and 10 Hz with the same amplitude (1 MPa), and group 6 was the control group (no loading). Cultures of different groups were loaded for 3 days (30 min daily) in a hydraulic chamber. Effects of loading frequency on disc collagen and protein metabolism were investigated by measuring 3H-proline-labeled proteins associated with the cells in the extracellular matrix and release of 3H-proline-labeled molecules into culture medium. The results indicated a poor synthesis rate and more degradation near the 5 Hz frequency. The repeatability of experiments was verified by performing two experiments with the same protocol. Both experiments indicated that a threshold frequency of around 5 Hz disrupted protein metabolism. Copyright (c) 2006 Orthopaedic Research Society.

Kinematic and Electromyographic Activity Changes during Back Squat with Submaximal and Maximal Loading

PubMed Central

Erdag, Deniz

2017-01-01

The aim of this study was to investigate the possible kinematic and muscular activity changes with maximal loading during squat maneuver. Fourteen healthy male individuals, who were experienced at performing squats, participated in this study. Each subject performed squats with 80%, 90%, and 100% of the previously established 1 repetition maximum (1RM). Electromyographic (EMG) activities were measured for the vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, gluteus maximus, and erector spinae by using an 8-channel dual-mode portable EMG and physiological signal data acquisition system (Myomonitor IV, Delsys Inc., Boston, MA, USA). Kinematical data were analyzed by using saSuite 2D kinematical analysis program. Data were analyzed with repeated measures analysis of variance (p < 0.05). Overall muscle activities increased with increasing loads, but significant increases were seen only for vastus medialis and gluteus maximus during 90% and 100% of 1RM compared to 80% while there was no significant difference between 90% and 100% for any muscle. The movement pattern in the hip joint changed with an increase in forward lean during maximal loading. Results may suggest that maximal loading during squat may not be necessary for focusing on knee extensor improvement and may increase the lumbar injury risk. PMID:28546738

Changes in tendon spatial frequency parameters with loading.

PubMed

Pearson, Stephen J; Engel, Aaron J; Bashford, Gregory R

2017-05-24

To examine and compare the loading related changes in micro-morphology of the patellar tendon. Fifteen healthy young males (age 19±3yrs, body mass 83±5kg) were utilised in a within subjects matched pairs design. B mode ultrasound images were taken in the sagittal plane of the patellar tendon at rest with the knee at 90° flexion. Repeat images were taken whilst the subjects were carrying out maximal voluntary isometric contractions. Spatial frequency parameters related to the tendon morphology were determined within regions of interest (ROI) from the B mode images at rest and during isometric contractions. A number of spatial parameters were observed to be significantly different between resting and contracted images (Peak spatial frequency radius (PSFR), axis ratio, spatial Q-factor, PSFR amplitude ratio, and the sum). These spatial frequency parameters were indicative of acute alterations in the tendon micro-morphology with loading. Acute loading modifies the micro-morphology of the tendon, as observed via spatial frequency analysis. Further research is warranted to explore its utility with regard to different loading induced micro-morphological alterations, as these could give valuable insight not only to aid strengthening of this tissue but also optimization of recovery from injury and treatment of conditions such as tendinopathies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptive cellular structures and devices with internal features for enhanced structural performance

NASA Astrophysics Data System (ADS)

Pontecorvo, Michael Eugene

This dissertation aims to develop a family of cellular and repeatable devices that exhibit a variety of force-displacement behaviors. It is envisioned that these cellular structures might be used either as stand-alone elements, or combined and repeated to create multiple types of structures (i.e. buildings, ship hulls, vehicle subfloors, etc.) with the ability to passively or actively perform multiple functions (harmonic energy dissipation, impact mitigation, modulus change) over a range of loading types, amplitudes, and frequencies. To accomplish this goal, this work combines repeatable structural frameworks, such as that provided by a hexagonal cellular structure, with internal structural elements such as springs, viscous dampers, buckling plates, bi-stable von Mises trusses (VMTs), and pneumatic artificial muscles (PAMs). The repeatable framework serves to position damping and load carrying elements throughout the structure, and the configuration of the internal elements allow each cell to be tuned to exhibit a desired force-displacement response. Therefore, gradient structures or structures with variable load paths can be created for an optimal global response to a range of loads. This dissertation focuses on the development of cellular structures for three functions: combined load-carrying capability with harmonic energy dissipation, impact mitigation, and cell modulus variation. One or more conceptual designs are presented for devices that can perform each of these functions, and both experimental measurements and simulations are used to gain a fundamental understanding of each device. Chapter 2 begins with a presentation of a VMT model that is the basis for many of the elements. The equations of motion for the VMT are derived and the static and dynamic behavior of the VMT are discussed in detail. Next, two metrics for the energy dissipation of the VMT - hysteresis loop area and loss factor - are presented. The responses of the VMT to harmonic displacement and force inputs are contrasted in relation to these metrics. The key innovation to the early structural elements presented here is the combination of the VMT with the pin-jointed hexagonal cell. Chapter 3 explores several prototypes of repeatable structural elements for simultaneous load-carrying capability and energy dissipation that are based on this innovation. The final demonstration prototype presented in this chapter is a column-like element that is based on a hexagonal cell containing two horizontal springs and one vertical damper. The unit is enclosed by a pair of buckling plates that serve to give the prototype a high initial stiffness and load carrying capability. The prototype is tested in both displacement and force input and its behavior is compared to simulation. Chapter 4 builds on the conceptual designs of Chapter 3 with the introduction of a plate-like element, that contains two compact VMTs connected by a horizontally oriented damper. Pre-loaded springs are used in the prototype to perform the same load carrying function as the buckling plates in the column-like prototype with increased predictability. The plate-like prototype is studied under impact to demonstrate its effectiveness as a protective layer. It is shown to reduce peak impact loads transmitted to the base of the device by over 60%. In most cases, the prototype compares well with a conventional protective rubber layer, and in cases of extreme impact loads, it exceeds the performance of the rubber layer. In addition to impact testing, the prototype is also experimentally tested under harmonic displacement input, and is simulated under both harmonic displacement and force input. The experiments illustrate that while the VMT parameters of a single layer can be optimized to a particular harmonic load amplitude, having two layers with softer and stiffer VMTs allows the system to show good energy dissipation characteristics at different harmonic load amplitude levels. Chapter 5 examines using PAM inclusions within planar hexagonal cells as variable stiffness springs to create a variable modulus cellular structure. The proposed concept is envisioned as a first step toward a structural unit cell whose in-plane modulus in a given direction can be tuned based on the orientation of PAMs within the cell and the pressure supplied to the individual muscles. To begin, a pin-jointed cell is considered, loaded in the horizontal direction, with three PAMs (one vertical PAM and two horizontal PAMs) oriented in an "H" configuration between the vertices of the cell. A method for calculation of the hexagonal cell modulus is introduced, as is an expression for the balance of tensile forces between the horizontal and vertical PAMs. An aluminum hexagonal unit cell is fabricated and simulation of the hexagonal cell with PAM inclusions is then compared to experimental measurement of the unit cell modulus in the horizontal direction over a pressure range up to 682 kPa. An increase in cell modulus of 200% and a corresponding change in cell angle of 1.53 degrees are demonstrated experimentally. A design study via simulation predicts that differential pressurization of the PAMs up to 1992 kPa can increase the cell modulus in the horizontal direction by a factor of 6.66 with a change in cell angle of only 2.75 degrees. Additionally, simulation predicts that variation of unpressurized cell equilibrium angle and vertical wall length coefficient can result in changes in cell modulus greater than 1000%. A drawback of the pin-jointed cell with PAM inclusions is that it is inherently underconstrained. To solve this problem, the pin-jointed cell walls are replaced with a continuous Delrin hexagon which gives the cell kinematic stability and allows for experimental measurement of modulus in both the horizontal and vertical directions. The Delrin cell is designed to have a modulus on the same order as that of the pin-jointed cell at zero pressure and is experimentally measured without the PAM inclusions. These measurements validate the use of a combined flexural/hinging analytical model that accurately simulates the cell modulus. This analysis is then combined with the PAM force equations to model the complete hexagonal cell with PAM inclusions. Simulation and experimental measurement of the cell modulus with the PAM inclusions are compared in both the horizontal and vertical directions over an expanded pressure range up to 1302 kPa. The interplay between the contraction ratio and pressure in orthogonal sets of PAMs is highlighted as the primary driver of overall cell modulus.

Free-Spinning Wind-Tunnel Tests of a Low-Wing Monoplane with Systematic Changes in Wings and Tails V : Effect of Airplane Relative Density

NASA Technical Reports Server (NTRS)

Seidman, Oscar; Neihouse, A I

1940-01-01

The reported tests are a continuation of an NACA investigation being made in the free-spinning wind tunnel to determine the effects of independent variations in load distribution, wing and tail arrangement, and control disposition on the spin characteristics of airplanes. The standard series of tests was repeated to determine the effect of airplane relative density. Tests were made at values of the relative-density parameter of 6.8, 8.4 (basic), and 12.0; and the results were analyzed. The tested variations in the relative-density parameter may be considered either as variations in the wing loading of an airplane spun at a given altitude, with the radii of gyration kept constant, or as a variation of the altitude at which the spin takes place for a given airplane. The lower values of the relative-density parameter correspond to the lower wing loadings or to the lower altitudes of the spin.

Melt layer formation in stainless steel under transient thermal loads

NASA Astrophysics Data System (ADS)

Steudel, I.; Klimov, N. S.; Linke, J.; Loewenhoff, Th.; Pintsuk, G.; Pitts, R. A.; Wirtz, M.

2015-08-01

To investigate the performance of stainless steel under transient thermal events, such as photon pulses caused by disruptions mitigated by massive gas injection (MGI), the material has been exposed to electron beam loads with ITER relevant power densities slightly above the melting threshold (245 MW/m2) and a pulse duration of 3 ms (Sugihara et al., 2012; Klimov et al., 2013; Pitts et al., 2013). The samples were manufactured from different steel grades with slightly modified chemical composition. To investigate the effect of repetitive surface heat loads on the melting process and the melt motion, identical heat pulses in the range of 100-3000 were applied. All tested materials showed intense melt-induced surface roughening, driven by repeated shallow surface melting up to several ten micrometre and fast re-solidification with epitaxial grain growth. During the liquid phase, melt motion induced by cohesive forces results in the formation of a wavy surface structure with apexes. Further experiments have been performed to study the effects of non-perpendicular surfaces or leading edges.

Glycaemic index, glycaemic load and dietary fibre characteristics of two commercially available fruit smoothies.

PubMed

Saltaouras, Georgios; Shaw, Patricia K; Fraser, Ann C; Hawes, Chris; Smith, Harry; Handley, Louisa; Whitby, Helen; Thondre, Sangeetha P; Lightowler, Helen J

2018-06-11

In light of the updated Eatwell Guide and the corresponding change in the consumption of fruit smoothies, the aim of this study was to measure the glycaemic index and load of two commercial fruit smoothies and to investigate the retention of dietary fibre following production. In vitro analysis was performed to identify fibre material (cellulose and pectins) using calcofluor staining and immunocytochemical labelling. A repeated measures cross-over study was conducted (n 10) to determine the glycaemic index (GI) and glycaemic load (GL) of the smoothies. Results showed that dietary fibre was still present in the smoothies after processing (16.9-17.5% cellular material by dry weight). The GI was low for both smoothies (39 and 36), whereas the GL was medium and borderline-low, respectively (11.4 and 9.7). The retention of fibre in these smoothies may have a potential positive effect on glycaemic response and may contribute to daily fibre requirements.

The relationship of training load to physical-capacity changes during international tours in high-performance junior tennis players.

PubMed

Murphy, Alistair P; Duffield, Rob; Kellett, Aaron; Reid, Machar

2015-03-01

Given the travel that punctuates junior tennis development, an understanding of the changes in fitness owing to touring and the association between training loads (TLs) and fitness on return is vital. The authors investigated physical-capacity changes from pretour to posttour, determining if those changes were related to the TL of athletes on tour. Thirty junior athletes completed fitness testing before and after 4-wk tours. Testing included double-leg countermovement jump (CMJ), dominant single-leg and nondominant single-leg CMJ, speed (5, 10, 20 m), modified 5-0-5 agility (left and right), 10 × 20-m repeated-sprint ability (RSA), and multistage fitness tests. Repeated-measures ANOVAs determined physical-capacity change, with effect-size analysis establishing the magnitude of change. To avoid regression toward the mean, a 1/3-split technique was implemented for comparative analysis (high to low TLs). Moderate effects (d=0.50-0.70) for reductions of up to 3.6% in 5-, 10-, and 20-m speeds were observed. However, all remaining changes were only of trivial to small magnitude (d<0.40). Closer analysis of the interaction between TL and physical capacities (1/3-split) revealed that subjects who completed the greatest amount of total and tennis TL returned with a greater decline in speed and aerobic capacities (d>0.80). Furthermore, it was observed that match load dictates on- and off-court TL, with an increase in matches won understandably stunting exposure to off-court TL. Specific training should be prescribed on tour to maintain speed characteristics over a 4-wk international tour. On-tour training schedules should be carefully monitored to maximize specific TL exposure after losses on tour.

Biomechanical responses to changes in friction on a clay court surface.

PubMed

Starbuck, Chelsea; Stiles, Victoria; Urà, Daniel; Carré, Matt; Dixon, Sharon

2017-05-01

To examine the influence of clay court frictional properties on tennis players' biomechanical response. Repeated measures. Lower limb kinematic and force data were collected on sixteen university tennis players during 10×180° turns (running approach speed 3.9±0.20ms -1 ) on a synthetic clay surface of varying friction levels. To adjust friction levels the volume of sand infill above the force plate was altered (kg per m 2 surface area; 12, 16 and 20kgm -2 ). Repeated measures ANOVA and Bonferroni's corrected alpha post-hoc analyses were conducted to identify significant differences in lower limb biomechanics between friction levels. Greater sliding distances (η p 2 =0.355, p=0.008) were observed for the lowest friction condition (20kgm -2 ) compared to the 12 and 16kgm -2 conditions. No differences in ankle joint kinematics and knee flexion angles were observed. Later peak knee flexion occurred on the 20kgm -2 condition compared to the 12kgm -2 (η p 2 =0.270, p=0.023). Lower vertical (η p 2 =0.345, p=0.027) and shear (η p 2 =0.396, p=0.016) loading rates occurred for the 20kgm 2 condition compared to the 16kgm 2 . Lower loading rates and greater sliding distances when clay surface friction was reduced suggests load was more evenly distributed over time reducing players' injury risks. The greater sliding distances reported were accompanied with later occurrence of peak knee flexion, suggesting longer time spent braking and a greater requirement for muscular control increasing the likelihood of fatigue. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Development of a standard gas generating vial comprised of a silicon oil-polystyrene/divinylbenzene composite sorbent.

PubMed

Grandy, Jonathan J; Gómez-Ríos, German A; Pawliszyn, Janusz

2015-09-04

In this work, a highly reproducible standard gas generating vial is proposed. The vial is comprised of a silicon diffusion pump oil spiked with an appropriate calibration compound, such as modified McReynolds probes (benzene, 2-pentanone, pyridine, 1-nitropropane, 1-pentanol, and n-octane), and then mixed with polystyrene/divinylbenzene (PS/DVB) particles. The concentrations of these compounds in gaseous headspace were found to substantially decrease in comparison to previously developed hydrocarbon pump oil based vials; hence, the amount of standard loaded onto SPME fibers was at most, half that of the previous vial design. Depletion for all compounds after 208 successive extractions was shown to be less than 3.5%. Smaller quantities of standards being used resulted in a vial that depleted slower while remaining statistically repeatable over a wider number of runs. Indeed, it was found that depletion could be largely predicted by using a mass balance theoretical model. This behavior allowed a further increase in the number of loadings that could be performed repeatedly. At a 95% level of confidence, the ANOVA test demonstrated that the prepared vials were statistically identical, with no significant intra- or inter-batch differences. In addition, it was found that vials stored under different conditions (e.g. under light exposure, room temperature, and within a refrigerator) were stable over 10 weeks. Silicon based vials proved to be ideal for performing instrument quality control and loading of internal standards onto fibers, both of which are of great importance when performing on-site analysis using portable GC-MS instrumentation and high throughput determinations in laboratory. Copyright © 2015 Elsevier B.V. All rights reserved.

Repeatability of in vitro measurements of the ultraviolet protection factor (UPF) by spectrophotometry with automatic sampling.

PubMed

Hoffmann, K; Kesners, P; Bader, A; Avermaete, A; Altmeyer, P; Gambichler, T

2001-11-01

Spectrophotometric assessment (in vitro) is the most established method for determining the ultraviolet protection factor (UPF) of textiles. Apart from stringent requirements for measurement precision, practical methods are required for the routine determination of the UPF. We report here spectrophotometric measurements of textiles using a newly developed autosampler. Measurement precision was evaluated under repeatable conditions. Fifteen different textiles were spectrophotometrically assessed for the determination of the UPF. Sample handling inside the spectrophotometer was performed with a computer-controlled sampling device, capable of loading and unloading a textile sample from a magazine as well as rotating the sample perpendicular to the spectrometer beam. In order to evaluate the repeatability of measurements, one sample of each textile was assessed eight times under the same conditions in the same laboratory. A mean percentage of the standard error of 1% [E(UPF)] was calculated for the UPF measurements. For UPFs >30, a significantly higher E(UPF) was found (r=0.78; P<0.001). E(UV) (3.9%) of ultraviolet A (UVA) transmission differed significantly from E(UV) (1.1 %) of ultraviolet B (UVB) transmission (P<0.05). Though a slight decrease of repeatability was observed for UVA transmission measurements and UPFs higher than 30, our data indicate a high measurement precision under repeatable conditions. In conclusion, spectrophotometric measurements of textiles with the aid of the autosampler presented have been shown to be highly practical, time saving and precise.

Effect of Impaction Sequence on Osteochondral Graft Damage: The Role of Repeated and Varying Loads

PubMed Central

Kang, Richard W.; Friel, Nicole A.; Williams, James M.; Cole, Brian J.; Wimmer, Markus A.

2013-01-01

Background Osteochondral autografts and allografts require mechanical force for proper graft placement into the defect site; however, impaction compromises the tissue. This study aimed to determine the effect of impaction force and number of hits to seat the graft on cartilage integrity. Hypothesis Under constant impulse conditions, higher impaction load magnitudes are more detrimental to cell viability, matrix integrity and collagen network organization and will result in proteoglycan loss and nitric oxide release. Study Design Controlled laboratory study Methods Osteochondral explants, harvested from fresh bovine trochleas, were exposed to a series of consistent impact loads delivered by a pneumatically driven device. Each plug received the same overall impulse of 7 Ns, reflecting the mean of 23 clinically inserted plugs. Impaction loads of 37.5N, 75N, 150N, and 300N were matched with 74, 37, 21, and 11 hits respectively. Following impaction, the plugs were harvested and cartilage was analyzed for cell viability, histology by safranin-o and picosirius red, and release of sulfated glycosaminoglycans and nitric oxide. Data were compared with non-impacted control. Results Impacted plugs had significantly lower cell viability than non-impacted plugs. A dose response relationship in loss of cell viability with respect to load magnitude was seen immediately and after 4 days but lost after 8 days. Histologic analysis revealed intact cartilage surface in all samples (loaded or control), with loaded samples showing alterations in birefringence. While the sulfated GAG release was similar across varying impaction loads, release of nitric oxide increased with increasing impaction magnitudes and time. Conclusions Impaction loading parameters have a direct effect on the time course of the viability of the cartilage in the graft tissue. Clinical Relevance Optimal loading parameters for surgical impaction of osteochondral grafts are those with lower load magnitudes and a greater number of hits to ensure proper fit. PMID:19915099

Short rest between cyclic flexion periods is a risk factor for a lumbar disorder.

PubMed

Hoops, Heather; Zhou, Bing-He; Lu, Yun; Solomonow, Moshe; Patel, Vikas

2007-08-01

The epidemiology identifies cyclic lumbar loading as a risk factor for cumulative trauma disorder. Experimental biomechanical and physiological confirmation is lacking. The objective of this study was to asses the impact of different rest durations applied between periods of cyclic loading on the development of an acute lumbar disorder which, if continued to be subjected to loading, may develop into a cumulative disorder. Three groups of in vivo feline preparations were subjected to six sequential 10 min loading periods of cyclic lumbar flexion at 40 N with a frequency of 0.25 Hz applied to the L-4/5 level. The rest durations varied from 5 min in the first group, to 10 min in the second and to 20 min in the third. Reflexive EMG from the multifidi and lumbar displacement were used to identify significant (P<0.001) effects of time and rest duration for post-load EMG and displacement. Single-cycle test were performed hourly for 7 h post-loading to assess recovery. A model developed earlier was applied to represent the experimental data. The groups allowed 5 and 10 min rest exhibited an acute neuromuscular disorder expressed by a significant (P<0.001) delayed hyperexcitability 2-3 h into the 7 h recovery period with the intensity of the hyperexcitability significantly higher (P<0.001) for the group allowed only 5 min rest. The group allowed 20 min rest had a slow, uneventful recovery, free of delayed hyperexcitability. Occupational and sports activities requiring repetitive (cyclic) loading of the lumbar spine may be a risk factor for the development of a cumulative lumbar disorder and may require sufficient rest, as much as twice as long as the loading period, for prevention. Comparison to similar data for static lumbar loading shows that cyclic loading is more deleterious than static loading, requiring more rest to offset the negative effect of the repeated acts of stretch.

Risk of Anterior Cruciate Ligament Fatigue Failure Is Increased by Limited Internal Femoral Rotation During In Vitro Repeated Pivot Landings

PubMed Central

Beaulieu, Mélanie L.; Wojtys, Edward M.; Ashton-Miller, James A.

2015-01-01

Background A reduced range of hip internal rotation is associated with increased peak anterior cruciate ligament (ACL) strain and risk for injury. It is unknown, however, whether limiting the available range of internal femoral rotation increases the susceptibility of the ACL to fatigue failure. Hypothesis Risk of ACL failure is significantly greater in female knee specimens with a limited range of internal femoral rotation, smaller femoral-ACL attachment angle, and smaller tibial eminence volume during repeated in vitro simulated single-leg pivot landings. Study Design Controlled laboratory study. Methods A custom-built testing apparatus was used to simulate repeated single-leg pivot landings with a 4×-body weight impulsive load that induces knee compression, knee flexion, and internal tibial torque in 32 paired human knee specimens from 8 male and 8 female donors. These test loads were applied to each pair of specimens, in one knee with limited internal femoral rotation and in the contralateral knee with femoral rotation resisted by 2 springs to simulate the active hip rotator muscles’ resistance to stretch. The landings were repeated until ACL failure occurred or until a minimum of 100 trials were executed. The angle at which the ACL originates from the femur and the tibial eminence volume were measured on magnetic resonance images. Results The final Cox regression model (P = .024) revealed that range of internal femoral rotation and sex of donor were significant factors in determining risk of ACL fatigue failure. The specimens with limited range of internal femoral rotation had a failure risk 17.1 times higher than did the specimens with free rotation (P = .016). The female knee specimens had a risk of ACL failure 26.9 times higher than the male specimens (P = .055). Conclusion Limiting the range of internal femoral rotation during repetitive pivot landings increases the risk of an ACL fatigue failure in comparison with free rotation in a cadaveric model. Clinical Relevance Screening for restricted internal rotation at the hip in ACL injury prevention programs as well as in individuals with ACL injuries and/or reconstructions is warranted. PMID:26122384

Risk of anterior cruciate ligament fatigue failure is increased by limited internal femoral rotation during in vitro repeated pivot landings.

PubMed

Beaulieu, Mélanie L; Wojtys, Edward M; Ashton-Miller, James A

2015-09-01

A reduced range of hip internal rotation is associated with increased peak anterior cruciate ligament (ACL) strain and risk for injury. It is unknown, however, whether limiting the available range of internal femoral rotation increases the susceptibility of the ACL to fatigue failure. Risk of ACL failure is significantly greater in female knee specimens with a limited range of internal femoral rotation, smaller femoral-ACL attachment angle, and smaller tibial eminence volume during repeated in vitro simulated single-leg pivot landings. Controlled laboratory study. A custom-built testing apparatus was used to simulate repeated single-leg pivot landings with a 4×-body weight impulsive load that induces knee compression, knee flexion, and internal tibial torque in 32 paired human knee specimens from 8 male and 8 female donors. These test loads were applied to each pair of specimens, in one knee with limited internal femoral rotation and in the contralateral knee with femoral rotation resisted by 2 springs to simulate the active hip rotator muscles' resistance to stretch. The landings were repeated until ACL failure occurred or until a minimum of 100 trials were executed. The angle at which the ACL originates from the femur and the tibial eminence volume were measured on magnetic resonance images. The final Cox regression model (P = .024) revealed that range of internal femoral rotation and sex of donor were significant factors in determining risk of ACL fatigue failure. The specimens with limited range of internal femoral rotation had a failure risk 17.1 times higher than did the specimens with free rotation (P = .016). The female knee specimens had a risk of ACL failure 26.9 times higher than the male specimens (P = .055). Limiting the range of internal femoral rotation during repetitive pivot landings increases the risk of an ACL fatigue failure in comparison with free rotation in a cadaveric model. Screening for restricted internal rotation at the hip in ACL injury prevention programs as well as in individuals with ACL injuries and/or reconstructions is warranted. © 2015 The Author(s).

Quantitative assessment of orthodontic mini-implant displacement: the effect of initial force application.

PubMed

Holst, Alexandra Ioana; Karl, Matthias; Karolczak, Marek; Goellner, Matthias; Holst, Stefan

2010-01-01

Primary stability and micromovement of orthodontic mini-implants depends on a number of factors and influences clinical success or failure. The purpose of this study was to assess the behavior of orthodontic mini-implants upon initial load application. Orthodontic mini-implants (n = 39) were inserted in the alveolar process of maxillary human cadaver specimens (n = 10). Increasing horizontal forces (up to 2.5 N) were applied, and triggered images were taken in 0.5-N load intervals. Additionally, peri-implant parameters based on micro-CT volume data were recorded. Data were subjected to a two-sided nonparametric Wilcoxon signed rank test, and between-group comparisons were assessed with a Mann-Whitney test (alpha = .05). Initial load application led to displacement beyond elastic recovery of the surrounding bone after force release (P < .001). Cortical thickness and insertion depth, despite numeric differences, did not reveal any statistical differences, while displacement of mini-implants was significantly affected by contact to neighboring teeth (P < .001). Insertion technique and initial load application on orthodontic mini-implants may be regarded as two crucial factors for success, while repeated application of orthodontic force does not seem to increase screw mobility.

Program Calculates Forces in Bolted Structural Joints

NASA Technical Reports Server (NTRS)

Buder, Daniel A.

2005-01-01

FORTRAN 77 computer program calculates forces in bolts in the joints of structures. This program is used in conjunction with the NASTRAN finite-element structural-analysis program. A mathematical model of a structure is first created by approximating its load-bearing members with representative finite elements, then NASTRAN calculates the forces and moments that each finite element contributes to grid points located throughout the structure. The user selects the finite elements that correspond to structural members that contribute loads to the joints of interest, and identifies the grid point nearest to each such joint. This program reads the pertinent NASTRAN output, combines the forces and moments from the contributing elements to determine the resultant force and moment acting at each proximate grid point, then transforms the forces and moments from these grid points to the centroids of the affected joints. Then the program uses these joint loads to obtain the axial and shear forces in the individual bolts. The program identifies which bolts bear the greatest axial and/or shear loads. The program also performs a fail-safe analysis in which the foregoing calculations are repeated for a sequence of cases in which each fastener, in turn, is assumed not to transmit an axial force.

Linkage analyses in Caribbean Hispanic families identify novel loci associated with familial late-onset Alzheimer's disease.

PubMed

Barral, Sandra; Cheng, Rong; Reitz, Christiane; Vardarajan, Badri; Lee, Joseph; Kunkle, Brian; Beecham, Gary; Cantwell, Laura S; Pericak-Vance, Margaret A; Farrer, Lindsay A; Haines, Jonathan L; Goate, Alison M; Foroud, Tatiana; Boerwinkle, Eric; Schellenberg, Gerard D; Mayeux, Richard

2015-12-01

We performed linkage analyses in Caribbean Hispanic families with multiple late-onset Alzheimer's disease (LOAD) cases to identify regions that may contain disease causative variants. We selected 67 LOAD families to perform genome-wide linkage scan. Analysis of the linked regions was repeated using the entire sample of 282 families. Validated chromosomal regions were analyzed using joint linkage and association. We identified 26 regions linked to LOAD (HLOD ≥3.6). We validated 13 of the regions (HLOD ≥2.5) using the entire family sample. The strongest signal was at 11q12.3 (rs2232932: HLODmax = 4.7, Pjoint = 6.6 × 10(-6)), a locus located ∼2 Mb upstream of the membrane-spanning 4A gene cluster. We additionally identified a locus at 7p14.3 (rs10255835: HLODmax = 4.9, Pjoint = 1.2 × 10(-5)), a region harboring genes associated with the nervous system (GARS, GHRHR, and NEUROD6). Future sequencing efforts should focus on these regions because they may harbor familial LOAD causative mutations. Copyright © 2015 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

NASA Technical Reports Server (NTRS)

Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

2009-01-01

Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of load on power output was: 30% > 40% > 50% = 60%. CONCLUSION: Loads of 40% and 30% of MIF elicit maximal power output during dynamic leg presses and bench presses, respectively. These findings are similar to those obtained when loading is based on 1-RM.

Cognition and Arousal as Predictors of Risk Taking: Effects of Load and Cognitive Style.

DTIC Science & Technology

1983-08-01

undesirable outcome may occur and the severity of that outcome may vary. People engage in risks with some frequency. Most of us would argue that our...risk taking but had little direct effect on changes in systolic or diastolic blood pressure . However, persons with greater diastolic arousal engaged in...blood pressure was repeatedly obtained. The following tasks were utilized in the present research: Baseline. Each participating subject rested alone

Solder Creep-Fatigue Interactions with Flexible Leaded Part

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.; Wen, L. C.

1994-01-01

In most electronic packaging applications it is not a single high stress event that breaks a component solder joint; rather it is repeated or prolonged load applications that result in fatigue or creep failure of the solder. The principal strain in solder joints is caused by differential expansion between the part and its mounting environment due to hanges in temperature (thermal cycles) and/or due to temperature gradients between the part and the board.

The national fire and fire surrogate study: vegetation changes over 11 years of fuel reduction treatments in the southern Appalachian Mountains

Treesearch

Thomas A. Waldrop; Helen H. Mohr; Ross J. Phillips; Dean M. Simon

2014-01-01

At the Appalachian site of the National Fire and Fire Surrogate Study, prescribed burning was repeated three times and chainsaw felling of shrubs was done twice between 2002 and 2012. Goals were to reduce fuel loading and to promote restoration of an open woodland community. Chainsaw felling created a vertical fuel break, but the effect was temporary, and no...

Permeability hysterisis of limestone during isotropic compression.

PubMed

Selvadurai, A P S; Głowacki, A

2008-01-01

The evolution of permeability hysterisis in Indiana Limestone during application of isotropic confining pressures up to 60 MPa was measured by conducting one-dimensional constant flow rate tests. These tests were carried out either during monotonic application of the confining pressure or during loading-partial unloading cycles. Irreversible permeability changes occurred during both monotonic and repeated incremental compression of the limestone. Mathematical relationships are developed for describing the evolution of path-dependent permeability during isotropic compression.

Plastics as structural materials for aircraft

NASA Technical Reports Server (NTRS)

Kline, G M

1937-01-01

The purpose here is to consider the mechanical characteristics of reinforced phenol-formaldehyde resin as related to its use as structural material for aircraft. Data and graphs that have appeared in the literature are reproduced to illustrate the comparative behavior of plastics and materials commonly used in aircraft construction. Materials are characterized as to density, static strength, modulus of elasticity, resistance to long-time loading, strength under repeated impact, energy absorption, corrosion resistance, and ease of fabrication.

Patient-Delivered Partner Treatment and Trichomonas vaginalis Repeat Infection Among Human Immunodeficiency Virus-Infected Women

PubMed Central

Gatski, Megan; Mena, Leandro; Levison, Judy; Clark, Rebecca A.; Henderson, Harold; Schmidt, Norine; Rosenthal, Susan L.; Martin, David H.; Kissinger, Patricia

2013-01-01

Background Repeat infections with Trichomonas vaginalis (TV) among human immunodeficiency virus (HIV)-infected women are common and may increase the risk of HIV transmission. Patient delivered partner treatment (PDPT) has been shown to reduce repeat infections of other sexually transmitted diseases. The purpose of this study was to evaluate adherence to PDPT and possible causes of repeat TV infection among HIV-infected women. Methods A multicentered cohort study was conducted in 3 US cities. Women coinfected with HIV and TV were treated with metro-nidazole and given treatment to deliver to all reported sex partners. A test-of-cure visit was conducted 6 to 12 days post index treatment completion and behavioral data were collected. Results Of 252 women (mean age = 40 years, s.d. 9.1) enrolled, 92.5% were black, 26.2% had CD4 cell counts <200/mm3, 34.1% had plasma viral loads >10,000 copies, 58.3% were taking antiretrovial therapy, and 15.1% had multiple partners. Of the 183 women with partners at baseline, 75.4% provided PDPT to all partners and 61.7% reported they were sure all of their partners took the medication. Factors associated with not giving medications to all partner(s) were multiple sex partners, being single, and having at least one partner unaware of the index woman’s HIV status. At test-of-cure, 10.3% were TV-positive and 16.7% reported having sex since baseline. Of the 24 repeat infections, 21 (87.5%) reported adherence to medication and no sexual exposure. Conclusion HIV-infected women with TV reported high adherence to PDPT, and treatment failure was the most common probable cause of repeat infection. PMID:20502393

Manipulation of Foot Strike and Footwear Increases Achilles Tendon Loading During Running.

PubMed

Rice, Hannah; Patel, Mubarak

2017-08-01

The Achilles tendon is the most common site of tendon overuse injury in humans. Running with a forefoot strike pattern and in minimal shoes is a topic of recent interest, yet evidence is currently limited regarding the combined influence of foot strike and footwear on Achilles tendon loading. To investigate the influence of both foot strike and footwear on Achilles tendon loading in habitual rearfoot strike runners. Controlled laboratory study. Synchronized kinematic and force data were collected from 22 habitual rearfoot strikers (11 male), who habitually ran in nonminimal running shoes, during overground running at 3.6 m·s -1 . Participants ran in 3 different footwear conditions (standard running shoe, minimal running shoe, and barefoot) with both a rearfoot strike (RFS) and an imposed forefoot strike (FFS) in each footwear condition. Achilles tendon loading was estimated by use of inverse dynamics, where the Achilles tendon moment arm was determined with a regression equation. A 2-way, repeated-measures analysis of variance was used to compare conditions. Achilles tendon impulse was greater when subjects ran with an FFS rather than an RFS in minimal shoes. Achilles tendon loading rates were higher when subjects ran either in minimal shoes or barefoot than in standard shoes, regardless of foot strike. In runners who habitually rearfoot strike in standard running shoes, running in minimal shoes or barefoot increased the rate of tendon loading, and running with a forefoot strike in minimal shoes increased the magnitude of tendon loading. Transitioning to these running conditions may increase the risk of tendinopathy.

Influence of learner knowledge and case complexity on handover accuracy and cognitive load: results from a simulation study.

PubMed

Young, John Q; van Dijk, Savannah M; O'Sullivan, Patricia S; Custers, Eugene J; Irby, David M; Ten Cate, Olle

2016-09-01

The handover represents a high-risk event in which errors are common and lead to patient harm. A better understanding of the cognitive mechanisms of handover errors is essential to improving handover education and practice. This paper reports on an experiment conducted to study the effects of learner knowledge, case complexity (i.e. cases with or without a clear diagnosis) and their interaction on handover accuracy and cognitive load. Participants were 52 Dutch medical students in Years 2 and 6. The experiment employed a repeated-measures design with two explanatory variables: case complexity (simple or complex) as the within-subject variable, and learner knowledge (as indicated by illness script maturity) as the between-subject covariate. The dependent variables were handover accuracy and cognitive load. Each participant performed a total of four simulated handovers involving two simple cases and two complex cases. Higher illness script maturity predicted increased handover accuracy (p < 0.001) and lower cognitive load (p = 0.007). Case complexity did not independently affect either outcome. For handover accuracy, there was no interaction between case complexity and illness script maturity. For cognitive load, there was an interaction effect between illness script maturity and case complexity, indicating that more mature illness scripts reduced cognitive load less in complex cases than in simple cases. Students with more mature illness scripts performed more accurate handovers and experienced lower cognitive load. For cognitive load, these effects were more pronounced in simple than complex cases. If replicated, these findings suggest that handover curricula and protocols should provide support that varies according to the knowledge of the trainee. © 2016 John Wiley & Sons Ltd and The Association for the Study of Medical Education.

Effect of dry heat and steam sterilization on load-deflection characteristics of β-titanium wires: An in vitro study

PubMed Central

Alavi, Shiva; Sinaee, Neda

2012-01-01

Background: Sterilization techniques could affect the characteristics of orthodontic wires. The aim of the present study was to evaluate the effect of steam and dry heat sterilization techniques on load-deflection behavior of five types of β-titanium alloy wires. Materials and Methods: The samples consisted of 30 straight lengths of five types of β-titanium alloy wires: Titanium Molybdenum Alloy (TMA) Low Friction (TMAL), TMA Low Friction Colored (HONE), Resolve (RES), BetaForce (BETA), and BETA CNA (CNA). Thirty wire segments were divided into three groups of 10. Group 1 was the control group and the group 2 samples were sterilized by dry heat in an oven (60 minutes at 160°C) and group 3 by steam in an autoclave (15 minutes at 121°C). Then all the wire samples underwent a three-point bending test in a testing machine to evaluate load-deflection properties. Data was analyzed by repeated measures ANOVA and Scheffé's test (α = 0.05). Results: The results showed that dry heat sterilization significantly increased force levels during both loading and unloading of CNA, BETA and RES and during loading of HONE (P < 0.05). Steam sterilization significantly increased force levels during both loading and unloading of BETA and during unloading of HONE (P < 0.05), with no effects on the load-deflection characteristics of TMAL, CNA and RES (P > 0.05). Conclusion: It appears dry heat sterilization increases stiffness of RES, BETA, CNA and HONE but autoclave sterilization did not have any effect on load-deflection characteristics of most of the β-titanium wires tested, indicating that clinicians who want to provide maximum safety for their patients can autoclave TMAL, RES and CNA before applying them. PMID:23559917

Voxel size dependency, reproducibility and sensitivity of an in vivo bone loading estimation algorithm

PubMed Central

Christen, Patrik; Schulte, Friederike A.; Zwahlen, Alexander; van Rietbergen, Bert; Boutroy, Stephanie; Melton, L. Joseph; Amin, Shreyasee; Khosla, Sundeep; Goldhahn, Jörg; Müller, Ralph

2016-01-01

A bone loading estimation algorithm was previously developed that provides in vivo loading conditions required for in vivo bone remodelling simulations. The algorithm derives a bone's loading history from its microstructure as assessed by high-resolution (HR) computed tomography (CT). This reverse engineering approach showed accurate and realistic results based on micro-CT and HR-peripheral quantitative CT images. However, its voxel size dependency, reproducibility and sensitivity still need to be investigated, which is the purpose of this study. Voxel size dependency was tested on cadaveric distal radii with micro-CT images scanned at 25 µm and downscaled to 50, 61, 75, 82, 100, 125 and 150 µm. Reproducibility was calculated with repeated in vitro as well as in vivo HR-pQCT measurements at 82 µm. Sensitivity was defined using HR-pQCT images from women with fracture versus non-fracture, and low versus high bone volume fraction, expecting similar and different loading histories, respectively. Our results indicate that the algorithm is voxel size independent within an average (maximum) error of 8.2% (32.9%) at 61 µm, but that the dependency increases considerably at voxel sizes bigger than 82 µm. In vitro and in vivo reproducibility are up to 4.5% and 10.2%, respectively, which is comparable to other in vitro studies and slightly higher than in other in vivo studies. Subjects with different bone volume fraction were clearly distinguished but not subjects with and without fracture. This is in agreement with bone adapting to customary loading but not to fall loads. We conclude that the in vivo bone loading estimation algorithm provides reproducible, sensitive and fairly voxel size independent results at up to 82 µm, but that smaller voxel sizes would be advantageous. PMID:26790999

PLAN2D - A PROGRAM FOR ELASTO-PLASTIC ANALYSIS OF PLANAR FRAMES

NASA Technical Reports Server (NTRS)

Lawrence, C.

1994-01-01

PLAN2D is a FORTRAN computer program for the plastic analysis of planar rigid frame structures. Given a structure and loading pattern as input, PLAN2D calculates the ultimate load that the structure can sustain before collapse. Element moments and plastic hinge rotations are calculated for the ultimate load. The location of hinges required for a collapse mechanism to form are also determined. The program proceeds in an iterative series of linear elastic analyses. After each iteration the resulting elastic moments in each member are compared to the reserve plastic moment capacity of that member. The member or members that have moments closest to their reserve capacity will determine the minimum load factor and the site where the next hinge is to be inserted. Next, hinges are inserted and the structural stiffness matrix is reformulated. This cycle is repeated until the structure becomes unstable. At this point the ultimate collapse load is calculated by accumulating the minimum load factor from each previous iteration and multiplying them by the original input loads. PLAN2D is based on the program STAN, originally written by Dr. E.L. Wilson at U.C. Berkeley. PLAN2D has several limitations: 1) Although PLAN2D will detect unloading of hinges it does not contain the capability to remove hinges; 2) PLAN2D does not allow the user to input different positive and negative moment capacities and 3) PLAN2D does not consider the interaction between axial and plastic moment capacity. Axial yielding and buckling is ignored as is the reduction in moment capacity due to axial load. PLAN2D is written in FORTRAN and is machine independent. It has been tested on an IBM PC and a DEC MicroVAX. The program was developed in 1988.

Can extra-articular strains be used to measure facet contact forces in the lumbar spine? An in-vitro biomechanical study.

PubMed

Zhu, Q A; Park, Y B; Sjovold, S G; Niosi, C A; Wilson, D C; Cripton, P A; Oxland, T R

2008-02-01

Experimental measurement of the load-bearing patterns of the facet joints in the lumbar spine remains a challenge, thereby limiting the assessment of facet joint function under various surgical conditions and the validation of computational models. The extra-articular strain (EAS) technique, a non-invasive measurement of the contact load, has been used for unilateral facet joints but does not incorporate strain coupling, i.e. ipsilateral EASs due to forces on the contralateral facet joint. The objectives of the present study were to establish a bilateral model for facet contact force measurement using the EAS technique and to determine its effectiveness in measuring these facet joint contact forces during three-dimensional flexibility tests in the lumbar spine. Specific goals were to assess the accuracy and repeatability of the technique and to assess the effect of soft-tissue artefacts. In the accuracy and repeatability tests, ten uniaxial strain gauges were bonded to the external surface of the inferior facets of L3 of ten fresh lumbar spine specimens. Two pressure-sensitive sensors (Tekscan) were inserted into the joints after the capsules were cut. Facet contact forces were measured with the EAS and Tekscan techniques for each specimen in flexion, extension, axial rotation, and lateral bending under a +/- 7.5 N m pure moment. Four of the ten specimens were tested five times in axial rotation and extension for repeatability. These same specimens were disarticulated and known forces were applied across the facet joint using a manual probe (direct accuracy) and a materials-testing system (disarticulated accuracy). In soft-tissue artefact tests, a separate set of six lumbar spine specimens was used to document the virtual facet joint contact forces during a flexibility test following removal of the superior facet processes. Linear strain coupling was observed in all specimens. The average peak facet joint contact forces during flexibility testing was greatest in axial rotation (71 +/- 25 N), followed by extension (27 +/- 35 N) and lateral bending (25 +/- 28 N), and they were most repeatable in axial rotation (coefficient of variation, 5 per cent). The EAS accuracy was about 20 per cent in the direct accuracy assessment and about 30 per cent in the disarticulated accuracy test. The latter was very similar to the Tekscan accuracy in the same test. Virtual facet loads (r.m.s.) were small in axial rotation (12 N) and lateral bending (20 N), but relatively large in flexion (34 N) and extension (35 N). The results suggested that the bilateral EAS model could be used to determine the facet joint contact forces in axial rotation but may result in considerable error in flexion, extension, and lateral bending.

Watershed-based sources of polycyclic aromatic hydrocarbons in urban storm water.

PubMed

Stein, Eric D; Tiefenthaler, Liesl L; Schiff, Kenneth

2006-02-01

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic compounds, ubiquitous in the air and water of urban environments, and have been shown to accumulate in coastal estuarine and marine sediments. Although previous studies have documented concentrations and loads of PAHs in urban runoff, little is known about the sources and temporal patterns of PAH loading from storm water. This study characterized the sources and temporal patterns of PAHs in urban storm water by analyzing PAH concentrations and loads from a range of homogeneous land use sites and in-river mass emission sites throughout the greater Los Angeles, California, USA, region. Samples were collected at 30- to 60-min intervals over the course of a storm during multiple storm events over a four-year period in order to investigate PAH sources and inter- and intrastorm patterns in loading. Polycyclic aromatic hydrocarbon storm fluxes ranged from 1.3 g/km2 for the largely undeveloped Arroyo Sequit watershed to 223.7 g/km2 for the highly urbanized Verdugo Wash watershed, with average storm fluxes being 46 times higher in developed versus undeveloped watersheds. Early-season storms repeatedly produced substantially higher loads than comparably sized late-season storms. Within individual storms, PAHs exhibited a moderate first flush with between 30 and 60% of the total PAH load being discharged in the first 20% of the storm volume. The relative distribution of individual PAHs demonstrated a consistent predominance of high-molecular-weight compounds indicative of pyrogenic sources.

Synthesized multi-station tribo-test system for bio-tribological evaluation in vitro

NASA Astrophysics Data System (ADS)

Wu, Tonghai; Du, Ying; Li, Yang; Wang, Shuo; Zhang, Zhinan

2016-07-01

Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication. Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities, which are far from the real friction behavior of human joints characterized with variable loads and multiple directions. In order to accurately obtain the bio-tribological performances of artificial joint materials, a tribological tester with a miniature four-station tribological system is proposed with four distinctive features. Firstly, comparability and repeatability of a test are ensured by four equal stations of the tester. Secondly, cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions. With this mechanism, the friction tracks can be designed by varying reciprocating and rotating speeds. Thirdly, variable loading system is realized by using a ball-screw mechanism driven by a stepper motor, by which loads under different gaits during walking are simulated. Fourthly, dynamic friction force and normal load can be measured simultaneously. The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks, and the accuracy of loading and friction force is within ±5%. Thus the high consistency among different stations can be obtained. Practically, the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.

Improving mechanical properties of maxillary complete dentures through a bioinspired engineering design.

PubMed

White, James A P; Bond, Ian P; Jagger, Daryll C

2011-01-01

This study investigated how ribbed design features, including palatal rugae, may be used to significantly improve the structural performance of a maxillary denture under load. A computer-aided design model of a generic maxillary denture, incorporating various rib features, was created and imported into a finite element analysis program. The denture and ribbed features were assigned the material properties of standard denture acrylic resin, and load was applied in two different ways: the first simulating a three-point flexural bend of the posterior section and the second simulating loading of the entire palatal region. To investigate the combined use of ribbing and reinforcement, the same simulations were repeated with the ribbed features having a Young modulus two orders of magnitude greater than denture acrylic resin. For a prescribed load, total displacements of tracking nodes were compared to those of a control denture (without ribbing) to assess relative denture rigidity. When subjected to flexural loading, an increase in rib depth was seen to result in a reduction of both the transverse displacement of the last molar and vertical displacement at the centerline. However, ribbed features assigned the material properties of denture acrylic resin require a depth that may impose on speech and bolus propulsion before significant improvements are observed. The use of ribbed features, when made from a significantly stiffer material (eg, fiber-reinforced polymer) and designed to mimic palatal rugae, offer an acceptable method of providing significant improvements in rigidity to a maxillary denture under flexural load.

Characterization and prediction of rate-dependent flexibility in lumbar spine biomechanics at room and body temperature.

PubMed

Stolworthy, Dean K; Zirbel, Shannon A; Howell, Larry L; Samuels, Marina; Bowden, Anton E

2014-05-01

The soft tissues of the spine exhibit sensitivity to strain-rate and temperature, yet current knowledge of spine biomechanics is derived from cadaveric testing conducted at room temperature at very slow, quasi-static rates. The primary objective of this study was to characterize the change in segmental flexibility of cadaveric lumbar spine segments with respect to multiple loading rates within the range of physiologic motion by using specimens at body or room temperature. The secondary objective was to develop a predictive model of spine flexibility across the voluntary range of loading rates. This in vitro study examines rate- and temperature-dependent viscoelasticity of the human lumbar cadaveric spine. Repeated flexibility tests were performed on 21 lumbar function spinal units (FSUs) in flexion-extension with the use of 11 distinct voluntary loading rates at body or room temperature. Furthermore, six lumbar FSUs were loaded in axial rotation, flexion-extension, and lateral bending at both body and room temperature via a stepwise, quasi-static loading protocol. All FSUs were also loaded using a control loading test with a continuous-speed loading-rate of 1-deg/sec. The viscoelastic torque-rotation response for each spinal segment was recorded. A predictive model was developed to accurately estimate spine segment flexibility at any voluntary loading rate based on measured flexibility at a single loading rate. Stepwise loading exhibited the greatest segmental range of motion (ROM) in all loading directions. As loading rate increased, segmental ROM decreased, whereas segmental stiffness and hysteresis both increased; however, the neutral zone remained constant. Continuous-speed tests showed that segmental stiffness and hysteresis are dependent variables to ROM at voluntary loading rates in flexion-extension. To predict the torque-rotation response at different loading rates, the model requires knowledge of the segmental flexibility at a single rate and specified temperature, and a scaling parameter. A Bland-Altman analysis showed high coefficients of determination for the predictive model. The present work demonstrates significant changes in spine segment flexibility as a result of loading rate and testing temperature. Loading rate effects can be accounted for using the predictive model, which accurately estimated ROM, neutral zone, stiffness, and hysteresis within the range of voluntary motion. Copyright © 2014 Elsevier Inc. All rights reserved.

Effects of Palladium Content, Quaternary Alloying, and Thermomechanical Processing on the Behavior of Ni-Ti-Pd Shape Memory Alloys for Actuator Applications

NASA Technical Reports Server (NTRS)

Bigelow, Glen

2008-01-01

The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently driving research in high-temperature shape memory alloys (HTSMA) having transformation temperatures above 100 C. One of the basic high temperature systems under investigation to fill this need is NiTiPd. Prior work on this alloy system has focused on phase transformations and respective temperatures, no-load shape memory behavior (strain recovery), and tensile behavior for selected alloys. In addition, a few tests have been done to determine the effect of boron additions and thermomechanical treatment on the aforementioned properties. The main properties that affect the performance of a solid state actuator, namely work output, transformation strain, and permanent deformation during thermal cycling under load have mainly been neglected. There is also no consistent data representing the mechanical behavior of this alloy system over a broad range of compositions. For this thesis, ternary NiTiPd alloys containing 15 to 46 at.% palladium were processed and the transformation temperatures, basic tensile properties, and work characteristics determined. However, testing reveals that at higher levels of alloying addition, the benefit of increased transformation temperature begins to be offset by lowered work output and permanent deformation or "walking" of the alloy during thermal cycling under load. In response to this dilemma, NiTiPd alloys have been further alloyed with gold, platinum, and hafnium additions to solid solution strengthen the martensite and parent austenite phases in order to improve the thermomechanical behavior of these materials. The tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared and discussed. In addition, the benefits of more advanced thermomechanical processing or training on the dimensional stability of these alloys during repeated actuation were investigated. Finally, the effect of quaternary alloying on the thermal stability of NiTiPdX alloys is determined via thermal cycling of the materials to increasing temperatures under load. It was found that solid solution additions of platinum and gold resulted in about a 30 C increase in upper use temperature compared to the baseline NiTiPd alloy, providing an added measure of over-temperature protection.

Design and Experiment of FBG-Based Icing Monitoring on Overhead Transmission Lines with an Improvement Trial for Windy Weather

PubMed Central

Zhang, Min; Xing, Yimeng; Zhang, Zhiguo; Chen, Qiguan

2014-01-01

A scheme for monitoring icing on overhead transmission lines with fiber Bragg grating (FBG) strain sensors is designed and evaluated both theoretically and experimentally. The influences of temperature and wind are considered. The results of field experiments using simulated ice loading on windless days indicate that the scheme is capable of monitoring the icing thickness within 0–30 mm with an accuracy of ±1 mm, a load cell error of 0.0308v, a repeatability error of 0.3328v and a hysteresis error is 0.026%. To improve the measurement during windy weather, a correction factor is added to the effective gravity acceleration, and the absolute FBG strain is replaced by its statistical average. PMID:25615733

Strand Plasticity Governs Fatigue in Colloidal Gels

NASA Astrophysics Data System (ADS)

van Doorn, Jan Maarten; Verweij, Joanne E.; Sprakel, Joris; van der Gucht, Jasper

2018-05-01

The repeated loading of a solid leads to microstructural damage that ultimately results in catastrophic material failure. While posing a major threat to the stability of virtually all materials, the microscopic origins of fatigue, especially for soft solids, remain elusive. Here we explore fatigue in colloidal gels as prototypical inhomogeneous soft solids by combining experiments and computer simulations. Our results reveal how mechanical loading leads to irreversible strand stretching, which builds slack into the network that softens the solid at small strains and causes strain hardening at larger deformations. We thus find that microscopic plasticity governs fatigue at much larger scales. This gives rise to a new picture of fatigue in soft thermal solids and calls for new theoretical descriptions of soft gel mechanics in which local plasticity is taken into account.

Method for making generally cylindrical underground openings

DOEpatents

Routh, J.W.

1983-05-26

A rapid, economical and safe method for making a generally cylindrical underground opening such as a shaft or a tunnel is described. A borehole is formed along the approximate center line of where it is desired to make the underground opening. The borehole is loaded with an explodable material and the explodable material is detonated. An enlarged cavity is formed by the explosive action of the detonated explodable material forcing outward and compacting the original walls of the borehole. The enlarged cavity may be increased in size by loading it with a second explodable material, and detonating the second explodable material. The process may be repeated as required until the desired underground opening is made. The explodable material used in the method may be free-flowing, and it may be contained in a pipe.

Gear fatigue crack prognosis using embedded model, gear dynamic model and fracture mechanics

NASA Astrophysics Data System (ADS)

Li, C. James; Lee, Hyungdae

2005-07-01

This paper presents a model-based method that predicts remaining useful life of a gear with a fatigue crack. The method consists of an embedded model to identify gear meshing stiffness from measured gear torsional vibration, an inverse method to estimate crack size from the estimated meshing stiffness; a gear dynamic model to simulate gear meshing dynamics and determine the dynamic load on the cracked tooth; and a fast crack propagation model to forecast the remaining useful life based on the estimated crack size and dynamic load. The fast crack propagation model was established to avoid repeated calculations of FEM and facilitate field deployment of the proposed method. Experimental studies were conducted to validate and demonstrate the feasibility of the proposed method for prognosis of a cracked gear.

Acoustic emission characteristics of copper alloys under low-cycle fatigue conditions

NASA Technical Reports Server (NTRS)

Krampfner, Y.; Kawamoto, A.; Ono, K.; Green, A.

1975-01-01

The acoustic emission (AE) characteristics of pure copper, zirconium-copper, and several copper alloys were determined to develop nondestructive evaluation schemes of thrust chambers through AE techniques. The AE counts rms voltages, frequency spectrum, and amplitude distribution analysis evaluated AE behavior under fatigue loading conditions. The results were interpreted with the evaluation of wave forms, crack propagation characteristics, as well as scanning electron fractographs of fatigue-tested samples. AE signals at the beginning of a fatigue test were produced by a sample of annealed alloys. A sample of zirconium-containing alloys annealed repeatedly after each fatigue loading cycle showed numerous surface cracks during the subsequent fatigue cycle, emitting strong-burst AE signals. Amplitude distribution analysis exhibits responses that are characteristic of certain types of AE signals.

Hydrogel Walkers with Electro-Driven Motility for Cargo Transport.

PubMed

Yang, Chao; Wang, Wei; Yao, Chen; Xie, Rui; Ju, Xiao-Jie; Liu, Zhuang; Chu, Liang-Yin

2015-08-28

In this study, soft hydrogel walkers with electro-driven motility for cargo transport have been developed via a facile mould-assisted strategy. The hydrogel walkers consisting of polyanionic poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylamide) exhibit an arc looper-like shape with two "legs" for walking. The hydrogel walkers can reversibly bend and stretch via repeated "on/off" electro-triggers in electrolyte solution. Based on such bending/stretching behaviors, the hydrogel walkers can move their two "legs" to achieve one-directional walking motion on a rough surface via repeated "on/off" electro-triggering cycles. Moreover, the hydrogel walkers loaded with very heavy cargo also exhibit excellent walking motion for cargo transport. Such hydrogel systems create new opportunities for developing electro-controlled soft systems with simple design/fabrication strategies in the soft robotic field for remote manipulation and transportation.

Evaluation of Quantitative Performance of Sequential Immobilized Metal Affinity Chromatographic Enrichment for Phosphopeptides

PubMed Central

Sun, Zeyu; Hamilton, Karyn L.; Reardon, Kenneth F.

2014-01-01

We evaluated a sequential elution protocol from immobilized metal affinity chromatography (SIMAC) employing gallium-based immobilized metal affinity chromatography (IMAC) in conjunction with titanium-dioxide-based metal oxide affinity chromatography (MOAC). The quantitative performance of this SIMAC enrichment approach, assessed in terms of repeatability, dynamic range, and linearity, was evaluated using a mixture composed of tryptic peptides from caseins, bovine serum albumin, and phosphopeptide standards. While our data demonstrate the overall consistent performance of the SIMAC approach under various loading conditions, the results also revealed that the method had limited repeatability and linearity for most phosphopeptides tested, and different phosphopeptides were found to have different linear ranges. These data suggest that, unless additional strategies are used, SIMAC should be regarded as a semi-quantitative method when used in large-scale phosphoproteomics studies in complex backgrounds. PMID:24096195

Improving the contact resistance at low force using gold coated carbon nanotube surfaces

NASA Astrophysics Data System (ADS)

McBride, J. W.; Yunus, E. M.; Spearing, S. M.

2010-04-01

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au-Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.

Stress fractures of the foot and ankle.

PubMed

Welck, M J; Hayes, T; Pastides, P; Khan, W; Rudge, B

2017-08-01

Stress fractures occur as a result of microscopic injuries sustained when bone is subjected to repeated submaximal stresses. Overtime, with repeated cycles of loading, accumulation of such injuries can lead to macro-structural failure and frank fracture. There are numerous stress fractures about the foot and ankle of which a trauma and orthopaedic surgeon should be aware. These include: metatarsal, tibia, calcaneus, navicular, fibula, talus, medial malleolus, sesamoid, cuneiform and cuboid. Awareness of these fractures is important as the diagnosis is frequently missed and appropriate treatment delayed. Late identification can be associated with protracted pain and disability, and may predispose to non-union and therefore necessitate operative intervention. This article outlines the epidemiology and risk factors, aetiology, presentation and management of the range of stress fractures in the foot and ankle. Copyright © 2015 Elsevier Ltd. All rights reserved.

Heavy-Load Lifting: Acute Response in Breast Cancer Survivors at Risk for Lymphedema

PubMed Central

BLOOMQUIST, KIRA; OTURAI, PETER; STEELE, MEGAN L.; ADAMSEN, LIS; MØLLER, TOM; CHRISTENSEN, KARL BANG; EJLERTSEN, BENT; HAYES, SANDRA C.

2018-01-01

ABSTRACT Purpose Despite a paucity of evidence, prevention guidelines typically advise avoidance of heavy lifting in an effort to protect against breast cancer–related lymphedema. This study compared acute responses in arm swelling and related symptoms after low- and heavy-load resistance exercise among women at risk for lymphedema while receiving adjuvant taxane-based chemotherapy. Methods This is a randomized, crossover equivalence trial. Women receiving adjuvant taxane-based chemotherapy for breast cancer who had undergone axillary lymph node dissection (n = 21) participated in low-load (60%–65% 1-repetition maximum, two sets of 15–20 repetitions) and heavy-load (85%–90% 1-repetition maximum, three sets of 5–8 repetitions) upper-extremity resistance exercise separated by a 1-wk wash-out period. Swelling was determined by bioimpedance spectroscopy and dual-energy x-ray absorptiometry, with breast cancer–related lymphedema symptoms (heaviness, swelling, pain, tightness) reported using a numeric rating scale (0–10). Order of low- versus heavy-load was randomized. All outcomes were assessed before, immediately after, and 24 and 72 h after exercise. Generalized estimating equations were used to evaluate changes over time between groups, with equivalence between resistance exercise loads determined using the principle of confidence interval inclusion. Results The acute response to resistance exercise was equivalent for all outcomes at all time points irrespective of loads lifted, with the exception of extracellular fluid at 72 h after exercise with less swelling after heavy loads (estimated mean difference, −1.00; 95% confidence interval, −3.17 to 1.17). Conclusions Low- and heavy-load resistance exercise elicited similar acute responses in arm swelling and breast cancer–related lymphedema symptoms in women at risk for lymphedema receiving adjuvant taxane-based chemotherapy. These represent important preliminary findings, which can be used to inform future prospective evaluation of the long-term effects of repeated exposure to heavy-load resistance exercise. PMID:28991039

Therapeutic efficacy of intra-articular hyaluronan derivative and platelet-rich plasma in mice following axial tibial loading

PubMed Central

Duan, Xin; Sandell, Linda J.; Chinzei, Nobuaki; Holguin, Nilsson; Silva, Matthew J.; Schiavinato, Antonella

2017-01-01

Objective To investigate the therapeutic potential of intra-articular hyaluronan-derivative HYADD® 4-G and/or platelet-rich plasma (PRP) in a mouse model of non-invasive joint injury. Methods Non-invasive axial tibial loading was used to induce joint injury in 10-week-old C57BL/6J mice (n = 86). Mice underwent a single loading of either 6 Newton (N) or 9N axial tibial compression. HYADD® 4-G was injected intra-articularly at 8 mg/mL or 15 mg/mL either before or after loading with or without PRP. Phosphate-buffered-saline was injected as control. Knee joints were harvested at 5 or 56 days post-loading and prepared for micro-computed tomography scanning and subsequently processed for histology. Immunostaining was performed for aggrecan to monitor its distribution, for CD44 to monitor chondrocyte reactive changes and for COMP (cartilage oligomeric matrix protein) as an index for cartilage matrix changes related to loading and cartilage injury. TUNEL assay was performed to identify chondrocyte apoptosis. Results Loading initiated cartilage proteoglycan loss and chondrocyte apoptosis within 5 days with slowly progressive post-traumatic osteoarthritis (no cartilage degeneration, but increased synovitis and ectopic calcification after 9N loading) at 56 days. Mice treated with repeated HYADD® 4-G (15 mg/mL) or HYADD® 4-G (8 mg/mL) ± PRP or PRP alone exhibited no significant improvement in the short-term (5 days) and long-term (56 days) consequences of joint loading except for a trend for improved bone changes compared to non-loaded joints. Conclusion While we failed to show an overall effect of intra-articular delivery of hyaluronan-derivative and/or PRP in reversing/protecting the pathological events in cartilage and synovium following joint injury, some bone alterations were relatively less severe with hyaluronan-derivative at higher concentration or in association with PRP. PMID:28406954

Omega 3 Chia seed loading as a means of carbohydrate loading.

PubMed

Illian, Travis G; Casey, Jason C; Bishop, Phillip A

2011-01-01

The purpose of this study was to determine if Omega 3 Chia seed loading is a viable option for enhancing sports performance in events lasting >90 minutes and allow athletes to decrease their dietary intake of sugar while increasing their intake of Omega 3 fatty acids. It has been well documented that a high dietary carbohydrate (CHO) intake for several days before competition is known to increase muscle glycogen stores resulting in performance improvements in events lasting >90 minutes. This study compared performance testing results between 2 different CHO-loading treatments. The traditional CHO-loading treatment served as the control (100% cals from Gatorade). The Omega 3 Chia drink (50% of calories from Greens Plus Omega 3 Chia seeds, 50% Gatorade) served as the Omega 3 Chia loading drink. Both CHO-loading treatments were based on the subject's body weight and were thus isocaloric. Six highly trained male subjects V(O2)max 47.8-84.2 ml · kg(-1); mean (SD) of V(O2)max 70.3 ml · kg(-1) (13.3) performed a 1-hour run at ∼65% of their V(O2)max on a treadmill, followed by a 10k time trial on a track. There were 2 trials in a crossover counterbalanced repeated-measures design with a 2-week washout between testing sessions to allow the participants to recover from the intense exercise and any effects of the treatment. There was no statistical difference (p = 0.83) between Omega 3 Chia loading (mean 10k time = 37 minutes 49 seconds) and CHO loading (mean = 37 minutes 43 seconds). Under our conditions, Omega 3 Chia loading appears a viable option for enhancing performance for endurance events lasting >90 minutes and allows athletes to decrease their dietary intake of sugar while increasing their intake of Omega 3 fatty acids but offered no performance advantages.

Effect of electrical spot welding on load deflection rate of orthodontic wires.

PubMed

Alavi, Shiva; Abrishami, Arezoo

2015-01-01

One of the methods used for joining metals together is welding, which can be carried out using different techniques such as electric spot welding. This study evaluated the effect of electric spot welding on the load deflection rate of stainless steel and chromium-cobalt orthodontic wires. In this experimental-laboratory study, load deflection rate of 0.016 × 0.022 inch stainless steel and chromium cobalt wires were evaluated in five groups (n =18): group one: Stainless steel wires, group two: chromium-cobalt wires, group three: stainless steel wires welded to stainless steel wires, group four: Stainless steel wires welded to chromium-cobalt wires, group five: chromium-cobalt wire welded to chromium-cobalt wires. Afterward, the forces induced by the samples in 0.5 mm, 1 mm, 1.5 mm deflection were measured using a universal testing machine. Then mean force measured for each group was compared with other groups. The data were analyzed using repeated measure analysis of variance (ANOVA), one-way ANOVA, and paired t-test by the SPSS software. The significance level was set as 0.05. The Tukey test showed that there were significant differences between the load deflection rates of welded groups compared to control ones (P < 0.001). Considering the limitation of this study, the electric spot welding process performed on stainless steel and chromium-cobalt wires increased their load deflection rates.

Influence of controlled immediate loading and implant design on peri-implant bone formation.

PubMed

Vandamme, Katleen; Naert, Ignace; Geris, Liesbet; Vander Sloten, Jozef; Puers, Robert; Duyck, Joke

2007-02-01

Tissue formation at the implant interface is known to be sensitive to mechanical stimuli. The aim of the study was to compare the bone formation around immediately loaded versus unloaded implants in two different implant macro-designs. A repeated sampling bone chamber with a central implant was installed in the tibia of 10 rabbits. Highly controlled loading experiments were designed for a cylindrical (CL) and screw-shaped (SL) implant, while the unloaded screw-shaped (SU) implant served as a control. An F-statistic model with alpha=5% determined statistical significance. A significantly higher bone area fraction was observed for SL compared with SU (p<0.0001). The mineralized bone fraction was the highest for SL and significantly different from SU (p<0.0001). The chance that osteoid- and bone-to-implant contact occurred was the highest for SL and significantly different from SU (p<0.0001), but not from CL. When bone-to-implant contact was observed, a loading (SL versus SU: p=0.0049) as well as an implant geometry effect (SL versus CL: p=0.01) was found, in favour of the SL condition. Well-controlled immediate implant loading accelerates tissue mineralization at the interface. Adequate bone stimulation via mechanical coupling may account for the larger bone response around the screw-type implant compared with the cylindrical implant.

Tailored magnetoelastic sensor geometry for advanced functionality in wireless biliary stent monitoring systems

NASA Astrophysics Data System (ADS)

Green, Scott R.; Gianchandani, Yogesh B.

2010-07-01

This paper presents three types of wireless magnetoelastic resonant sensors with specific functionalities for monitoring sludge accumulation within biliary stents. The first design uses a geometry with a repeated cell shape that provides two well-separated resonant mode shapes and associated frequencies to permit spatial localization of mass loading. The second design implements a pattern with specific variation in feature densities to improve sensitivity to mass loading. The third design uses narrow ribbons joined by flexible couplers; this design adopts the advantages in flexibility and expandability of the other designs while maintaining the robust longitudinal mode shapes of a ribbon-shaped sensor. The sensors are batch patterned using photochemical machining from 25 µm thick 2605SA1 Metglas™, an amorphous Fe-Si alloy. Accumulation of biliary sludge is simulated with paraffin or gelatin, and the effects of viscous bile are simulated with a range of silicone fluids. Results from the first design show that the location of mass loads can be resolved within ~5 mm along the length of the sensor. The second design offers twice the sensitivity to mass loads (3000-36 000 ppm mg-1) of other designs. The third design provides a wide range of loading (sensitive to at least 10× the mass of the sensor) and survives compression into a 2 mm diameter tube as would be required for catheter-based delivery.

Relationships between processing delay and microbial load of broiler neck skin samples.

PubMed

Lucianez, A; Holmes, M A; Tucker, A W

2010-01-01

The measurable microbial load on poultry carcasses during processing is determined by a number of factors including farm or origin, processing hygiene, and external temperature. This study investigated associations between carcass microbial load and progressive delays to processing. A total of 30 carcasses were delayed immediately after defeathering and before evisceration in a commercial abattoir in groups of five, and were held at ambient temperature for 1, 2, 3, 4, 6, and 8 h. Delayed carcasses were reintroduced to the processing line, and quantitative assessment of total viable count, coliforms, Staphylococcus aureus, and Pseudomonas spp. was undertaken on neck skin flap samples collected after carcass chilling and then pooled for each group. Sampling was repeated on 5 separate days, and the data were combined. Significant increases in total viable count (P = 0.001) and coliforms (P = 0.004), but not for S. aureus or Pseudomonas loads, were observed across the 8-h period of delay. In line with previous studies, there was significant variation in microbiological data according to sampling day. In conclusion, there is a significant and measurable decline in microbiological status of uneviscerated but defeathered poultry carcasses after an 8-h delay, but the variability of sampling results, reflecting the wide range of factors that impact microbial load, means that it is not possible to determine maximum or minimum acceptable periods of processing delay based on this criterion alone.

Predicting the Reliability of Brittle Material Structures Subjected to Transient Proof Test and Service Loading

NASA Astrophysics Data System (ADS)

Nemeth, Noel N.; Jadaan, Osama M.; Palfi, Tamas; Baker, Eric H.

Brittle materials today are being used, or considered, for a wide variety of high tech applications that operate in harsh environments, including static and rotating turbine parts, thermal protection systems, dental prosthetics, fuel cells, oxygen transport membranes, radomes, and MEMS. Designing brittle material components to sustain repeated load without fracturing while using the minimum amount of material requires the use of a probabilistic design methodology. The NASA CARES/Life 1 (Ceramic Analysis and Reliability Evaluation of Structure/Life) code provides a general-purpose analysis tool that predicts the probability of failure of a ceramic component as a function of its time in service. This capability includes predicting the time-dependent failure probability of ceramic components against catastrophic rupture when subjected to transient thermomechanical loads (including cyclic loads). The developed methodology allows for changes in material response that can occur with temperature or time (i.e. changing fatigue and Weibull parameters with temperature or time). For this article an overview of the transient reliability methodology and how this methodology is extended to account for proof testing is described. The CARES/Life code has been modified to have the ability to interface with commercially available finite element analysis (FEA) codes executed for transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.

Breast Cancer-Targeted Nuclear Drug Delivery Overcoming Drug Resistance for Breast Cancer Chemotherapy

DTIC Science & Technology

2010-09-01

compared with the reported results that the cur- cumin concentrations in tumor tissues were usu- ally very low when curcumin was administrated. The...prodrug and as a drug carrier. This cur- cumin prodrug has a fixed composition with a curcumin-loading content of 25.3 wt% and can release curcumin...200 or 400, Aldrich, 99%) was dried over calcium hydride. Cur- cumin (high purity, Axxora LLC) was further purified by repeated recrystallization in

Short-term repeated HRV-16 exposure results in an attenuated immune response in vivo in humans

PubMed Central

Koch, Rebecca M.; Kox, Matthijs; van den Kieboom, Corné; Ferwerda, Gerben; Gerretsen, Jelle; ten Bruggencate, Sandra; van der Hoeven, Johannes G.; de Jonge, Marien I.; Pickkers, Peter

2018-01-01

Introduction Naturally, development of adaptive immunity following HRV infection affects the immune response. However, it is currently unclear whether or not HRV re-exposure within a short time frame leads to an altered innate immune response. The “experimental cold model” is used to investigate the pathogenesis of HRV infection and allows us to investigate the effects of repeated exposure on both local and systemic innate immunity. Methods 40 healthy male and female (1:1) subjects were nasally inoculated with HRV-16 or placebo. One week later, all subjects received HRV-16. Baseline seronegative subjects (n = 18) were included for further analysis. Results Infection rate was 82%. Primary HRV infection induced a marked increase in viral load and IP-10 levels in nasal wash, while a similar trend was observed for IL-6 and IL-10. Apart from an increase in IP-10 plasma levels, HRV infection did not induce systemic immune effects nor lower respiratory tract inflammation. With similar viral load present during the second HRV challenge, IP-10 and IL-6 in nasal wash showed no increase, but gradually declined, with a similar trend for IL-10. Conclusion Upon a second HRV challenge one week after the first, a less pronounced response for several innate immune parameters is observed. This could be the result of immunological tolerance and possibly increases vulnerability towards secondary infections. PMID:29447199

Short-term repeated HRV-16 exposure results in an attenuated immune response in vivo in humans.

PubMed

Koch, Rebecca M; Kox, Matthijs; van den Kieboom, Corné; Ferwerda, Gerben; Gerretsen, Jelle; Ten Bruggencate, Sandra; van der Hoeven, Johannes G; de Jonge, Marien I; Pickkers, Peter

2018-01-01

Naturally, development of adaptive immunity following HRV infection affects the immune response. However, it is currently unclear whether or not HRV re-exposure within a short time frame leads to an altered innate immune response. The "experimental cold model" is used to investigate the pathogenesis of HRV infection and allows us to investigate the effects of repeated exposure on both local and systemic innate immunity. 40 healthy male and female (1:1) subjects were nasally inoculated with HRV-16 or placebo. One week later, all subjects received HRV-16. Baseline seronegative subjects (n = 18) were included for further analysis. Infection rate was 82%. Primary HRV infection induced a marked increase in viral load and IP-10 levels in nasal wash, while a similar trend was observed for IL-6 and IL-10. Apart from an increase in IP-10 plasma levels, HRV infection did not induce systemic immune effects nor lower respiratory tract inflammation. With similar viral load present during the second HRV challenge, IP-10 and IL-6 in nasal wash showed no increase, but gradually declined, with a similar trend for IL-10. Upon a second HRV challenge one week after the first, a less pronounced response for several innate immune parameters is observed. This could be the result of immunological tolerance and possibly increases vulnerability towards secondary infections.

Finite element analysis of the cyclic indentation of bilayer enamel

NASA Astrophysics Data System (ADS)

Jia, Yunfei; Xuan, Fu-zhen; Chen, Xiaoping; Yang, Fuqian

2014-04-01

Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel.

Research on fatigue cracking growth parameters in asphaltic mixtures using computed tomography

NASA Astrophysics Data System (ADS)

Braz, D.; Lopes, R. T.; Motta, L. M. G.

2004-01-01

Distress of asphalt concrete pavement due to repeated bending from traffic loads has been a well-recognized problem in Brazil. If it is assumed that fatigue cracking growth is governed by the conditions at the crack tip, and that the crack tip conditions can be characterized by the stress intensity factor, then fatigue cracking growth as a function of stress intensity range Δ K can be determined. Computed tomography technique is used to detect crack evolution in asphaltic mixtures which were submitted to fatigue tests. Fatigue tests under conditions of controlled stress were carried out using diametral compression equipment and repeat loading. The aim of this work is imaging several specimens at different stages of the fatigue tests. In preliminary studies it was noted that the trajectory of a crack was influenced by the existence of voids in the originally unloaded specimens. Cracks would first be observed in the central region of a specimen, propagating in the direction of the extremities. Analyzing the graphics, that represent the fatigue cracking growth (d c/d N) as a function of stress intensity factor (Δ K), it is noticed that the curve has practically shown the same behavior for all specimens at the same level of the static tension rupture stress. The experimental values obtained for the constants A and n (of the Paris-Erdogan Law) present good agreement with the results obtained by Liang and Zhou.

Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement

PubMed Central

Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

2017-01-01

Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ3 instead of the axial anisotropy coefficient γ1. The results from both approaches (γ1 and γ3) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ1 to γ3). The modelling results indicate that the modified Boyce model with γ3 is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed. PMID:29207504

Analysis of the mechanical behavior of a titanium scaffold with a repeating unit-cell substructure.

PubMed

Ryan, Garrett; McGarry, Patrick; Pandit, Abhay; Apatsidis, Dimitrios

2009-08-01

Titanium scaffolds with controlled microarchitecture have been developed for load bearing orthopedic applications. The controlled microarchitecture refers to a repeating array of unit-cells, composed of sintered titanium powder, which make up the scaffold structure. The objective of this current research was to characterize the mechanical performance of three scaffolds with increasing porosity, using finite element analysis (FEA) and to compare the results with experimental data. Scaffolds were scanned using microcomputed tomography and FEA models were generated from the resulting computer models. Macroscale and unit-cell models of the scaffolds were created. The material properties of the sintered titanium powders were first evaluated in mechanical tests and the data used in the FEA. The macroscale and unit-cell FEA models proved to be a good predictor of Young's modulus and yield strength. Although macroscale models showed similar failure patterns and an expected trend in UCS, strain at UCS did not compare well with experimental data. Since a rapid prototyping method was used to create the scaffolds, the original CAD geometries of the scaffold were also evaluated using FEA but they did not reflect the mechanical properties of the physical scaffolds. This indicates that at present, determining the actual geometry of the scaffold through computed tomography imaging is important. Finally, a fatigue analysis was performed on the scaffold to simulate the loading conditions it would experience as a spinal interbody fusion device.

Development of immobilized cellulase through functionalized gold nano-particles for glucose production by continuous hydrolysis of waste bamboo chopsticks.

PubMed

Cheng, Cheanyeh; Chang, Kuo-Chung

2013-12-10

Cellulase immobilized on silica through the assistance of l-cysteine functionalized gold nano-particle was applied for the continuous hydrolysis of waste bamboo chopsticks powder to produce glucose. The optimal conditions for the continuous hydrolysis were pH 8.0, 50°C. A 4-day reaction with an initial 0.3 gL⁻¹ waste bamboo chopsticks powder, a feed containing 0.2 gL⁻¹ waste bamboo chopsticks powder at a continuous feed and draw rate of 0.5 mLmin⁻¹, and an enzyme loading of 40 mgcellulase(gsilica)⁻¹, has 72.0-76.6% conversion rates of repeated hydrolyses that correspond to a total production of 630.5-671.2mg glucose and are much better than batch hydrolyses. At higher enzyme loading (117 mgcellulase(gsilica)⁻¹), higher initial concentration (0.5 gL⁻¹), and higher feed concentration (0.42 gL⁻¹) the conversion rate increases to 82.9% and a total amount of 1418 mgglucose. The immobilized cellulase can be recovered easily by filtration and used repeatedly at least 6 times over a period more than 90 days with a recovered activity approximately the same as or better than previous reactions. Thus the process is promising for scaling up. Copyright © 2013 Elsevier Inc. All rights reserved.

Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement.

PubMed

Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

2017-12-03

Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ ₃ instead of the axial anisotropy coefficient γ ₁. The results from both approaches ( γ ₁ and γ ₃) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ ₁ to γ ₃). The modelling results indicate that the modified Boyce model with γ ₃ is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed.

[Analysis of the results of the 2010 External Quality Control Program of the Spanish Society of Infectious Diseases and Clinical Microbiology for HIV-1, HCV, and HBV viral loads].

PubMed

Orta Mira, Nieves; Serrano, María del Remedio Guna; Martínez, José-Carlos Latorre; Ovies, María Rosario; Poveda, Marta; de Gopegui, Enrique Ruiz; Cardona, Concepción Gimeno

2011-12-01

Human immunodeficiency virus type 1 (HIV-1) and hepatitis B (HBV) and C virus (HCV) viral load determinations are among the most important markers for the follow-up of patients infected with these viruses. External quality control tools are crucial to ensure the accuracy of the results obtained by microbiology laboratories. This article summarized the results obtained in the 2010 External Quality Control Program of the Spanish Society of Infectious Diseases and Clinical Microbiology for HIV-1, HCV, and HBV viral loads and HCV genotyping. In the HIV-1 program, a total of five standards were sent. One standard consisted of seronegative human plasma, while the remaining four contained plasma from three different viremic patients, in the range of 3-5 log(10) copies/mL; two of these standards were identical, with the aim of determining repeatability. A significant proportion of the laboratories (22.6% on average) obtained values out of the accepted range (mean ± 0.2 log(10)copies/mL), depending on the standard and on the method used for quantification. Repeatability was very good, with up to 95% of laboratories reporting results within the limits (Δ<0.5 log(10)copies/mL). The HBV and HCV program consisted of two standards with different viral load contents. Most of the participants, 86.1% in the case of HCV and 87.1% in HBV, obtained all the results within the accepted range (mean ± 1.96 SD log(10)UI/mL). Post-analytical errors due to mistranscription of the results were detected in these controls. Data from this analysis reinforce the utility of proficiency programs to ensure the quality of the results obtained by a particular laboratory, as well as the importance of the post-analytical phase in overall quality. Due to interlaboratory variability, use of the same method and the same laboratory for patient follow-up is advisable. Copyright © 2011 Elsevier España S.L. All rights reserved.

Circulating, cell-free DNA as a marker for exercise load in intermittent sports.

PubMed

Haller, Nils; Helmig, Susanne; Taenny, Pascal; Petry, Julian; Schmidt, Sebastian; Simon, Perikles

2018-01-01

Attempts to establish a biomarker reflecting individual player load in intermittent sports such as football have failed so far. Increases in circulating DNA (cfDNA) have been demonstrated in various endurance sports settings. While it has been proposed that cfDNA could be a suitable marker for player load in intermittent sports, the effects on cfDNA of repeated sprinting as an essential feature in intermittent sports are unknown. For the first time, we assessed both alterations of cfDNA due to repeated maximal sprints and due to a professional football game. Nine participants were subjected to a standardised sprint training session with cross-over design of five maximal sprints of 40 meters with either "short" (1 minute) or "long" pauses (5 minutes). Capillary cfDNA and lactate were measured after every sprint and venous cfDNA before and after each series of sprints. Moreover, capillary cfDNA and lactate values were taken in 23 professional football players before and after incremental exercise testing, during the course of a training week at rest (baseline) and in all 17 enrolled players following a season game. Lactate and venous cfDNA increased more pronounced during "short" compared to "long" (1.4-fold, p = 0.032 and 1.7-fold, p = 0.016) and cfDNA correlated significantly with lactate (r = 0.69; p<0.001). Incremental exercise testing increased cfDNA 7.0-fold (p<0.001). The season game increased cfDNA 22.7-fold (p<0.0001), while lactate showed a 2.0-fold (p = 0.09) increase compared to baseline. Fold-changes in cfDNA correlated with distance covered during game (spearman's r = 0.87, p = 0.0012), while no correlation between lactate and the tracking data could be found. We show for the first time that cfDNA could be an objective marker for distance covered in elite intermittent sports. In contrast to the potential of more established blood-based markers like IL-6, CK, or CRP, cfDNA shows by far the strongest fold-change and a high correlation with a particular load related aspect in professional football.

Circulating, cell-free DNA as a marker for exercise load in intermittent sports

PubMed Central

Haller, Nils; Helmig, Susanne; Taenny, Pascal; Petry, Julian; Schmidt, Sebastian

2018-01-01

Background Attempts to establish a biomarker reflecting individual player load in intermittent sports such as football have failed so far. Increases in circulating DNA (cfDNA) have been demonstrated in various endurance sports settings. While it has been proposed that cfDNA could be a suitable marker for player load in intermittent sports, the effects on cfDNA of repeated sprinting as an essential feature in intermittent sports are unknown. For the first time, we assessed both alterations of cfDNA due to repeated maximal sprints and due to a professional football game. Methods Nine participants were subjected to a standardised sprint training session with cross-over design of five maximal sprints of 40 meters with either “short” (1 minute) or “long” pauses (5 minutes). Capillary cfDNA and lactate were measured after every sprint and venous cfDNA before and after each series of sprints. Moreover, capillary cfDNA and lactate values were taken in 23 professional football players before and after incremental exercise testing, during the course of a training week at rest (baseline) and in all 17 enrolled players following a season game. Results Lactate and venous cfDNA increased more pronounced during “short” compared to “long” (1.4-fold, p = 0.032 and 1.7-fold, p = 0.016) and cfDNA correlated significantly with lactate (r = 0.69; p<0.001). Incremental exercise testing increased cfDNA 7.0-fold (p<0.001). The season game increased cfDNA 22.7-fold (p<0.0001), while lactate showed a 2.0-fold (p = 0.09) increase compared to baseline. Fold-changes in cfDNA correlated with distance covered during game (spearman’s r = 0.87, p = 0.0012), while no correlation between lactate and the tracking data could be found. Discussion We show for the first time that cfDNA could be an objective marker for distance covered in elite intermittent sports. In contrast to the potential of more established blood-based markers like IL-6, CK, or CRP, cfDNA shows by far the strongest fold-change and a high correlation with a particular load related aspect in professional football. PMID:29370268

Development of a standardized testing system for orthodontic sliding mechanics.

PubMed

Fathimani, Maryam; Melenka, Garrett W; Romanyk, Dan L; Toogood, Roger W; Heo, Giseon; Carey, Jason P; Major, Paul W

2015-01-01

The primary objective of this study was to develop a computer-controlled three-dimensional friction measuring system, the orthodontic friction simulator (OFS). A clinically-based in vitro experiment considering wet and dry friction for conventionally and self-ligated brackets is presented to elucidate debate surrounding sliding mechanics and illustrate capabilities of the OFS. The OFS was designed and manufactured using sound engineering principles and with the primary concern of being able to measure all forces and moments generated during sliding mechanics. This required the implementation of a six-axis load cell. A variety of translation and rotation stages were also incorporated to allow for precise positioning of the bracket relative to the archwire. Once designed and built, the OFS was then used to compare conventional and self-ligation methods in both the wet and dry state. Damon Q brackets and 0.018″ × 0.025″ stainless steel wires were used for all tests with a sample size of n = 65 for each ligation method. Archwires were pulled at a speed of 0.1 mm/s in 11 increments of 0.1 mm. At each increment, the bracket would be rotated 0.5° resulting in a total archwire travel of 1.1 mm and a second-order bracket angle range of 0°-5°. A repeated measures ANOVA was conducted to determine if ligation method and/or addition of moisture effected resulting orthodontic loads. The developed equipment for studying orthodontic sliding mechanics was able to measure forces and moments in all three directions; a capability not previously realized in the literature. Additionally, it was found that passive ligation significantly reduced resistance to sliding, P ≤ 0.05, while the dry/wet state did not. The OFS certainly proved to be an adequate instrument for the scientific evaluation of orthodontic sliding mechanics. It is capable of measuring loads generated in all directions and is a fully automated apparatus allowing for simple and repeatable friction tests to be conducted. Furthermore, the addition of saliva was not found to significantly influence the loads generated during sliding mechanics regardless of ligation method.

Unravelling the relative contribution of bed and suspended sediment load on a large alluvial river

NASA Astrophysics Data System (ADS)

Darby, S. E.; Hackney, C. R.; Parsons, D. R.; Leyland, J.; Aalto, R. E.; Nicholas, A. P.; Best, J.

2017-12-01

The world's largest rivers transport 19 billion tonnes of sediment to the coastal zone annually, often supporting large deltas that rely on this sediment load to maintain their elevation in the face of rising sea level, and to sustain high levels of agricultural productivity and biodiversity. However, the majority of estimates of sediment delivery to coastal regions pertain solely to the suspended fraction of the sediment load, with the bedload fraction often being neglected due to the difficulty in estimating bedload flux and the assumption that bedload contributes a minor (<10%) fraction of the total sediment load. In large rivers, capturing accurate estimates of the suspended- and bed- load fractions is difficult given the large channel widths and depths and the intrusive nature of typical methodologies. Yet, for the successful implementation of sustainable river, and delta, management plans, improved estimates of all fractions of the sediment load are essential. Recent advances in non-intrusive, high-resolution, technology have begun to enable more accurate estimates of bedload transport rates. However, the characterisation of the holistic sediment transport regime of large alluvial rivers is still lacking. Here, we develop a sediment transport rating curve, combining both suspended- and bed- load sediment fractions, for the Lower Mekong River. We define suspended sediment rating curves using the inversion of acoustic return data from a series of acoustic Doppler current profiler surveys conducted through the Lower Mekong River in Cambodia, and into the bifurcating channels of the Mekong delta in Vietnam. Additionally, we detail estimates of bed-load sediment transport determined using repeat multibeam echo sounder surveys of the channel bed. By combining estimates of both fractions of the sediment load, we show the spatial and temporal contribution of bedload to the total sediment load of the Mekong and refine estimates of sediment transport to the Mekong delta. Our results indicate that the time-averaged suspended load transport rates for the Mekong River are 87 MT/yr, whilst bedload transport forms c. < 5% of the total sediment load within the Mekong River. Such estimates are integral to future channel management within this highly threatened river basin.

Assessing biofiltration repeatability: statistical comparison of two identical toluene removal systems.

PubMed

Jiménez, Lucero; Arriaga, Sonia; Aizpuru, Aitor

2016-01-01

Biofiltration of volatile organic compounds is still considered an emerging technology. Its reliability remains questionable as no data is available regarding process intrinsic repeatability. Herein, two identically operated toluene biofiltration systems are comprehensively compared, during long-term operation (129 days). Globally, reactors responded very similarly, even during transient conditions, with, for example, strong biological activities from the first days of operation, and comparable periods of lower removal efficiency (81.2%) after exposure to high inlet loads (140 g m(-3) h(-1)). Regarding steady states, very similar maximum elimination capacities up to 99 g m(-3) h(-1) were attained. Estimation of the process repeatability, with the paired samples Student's t-test, indicated no statistically significant difference between elimination capacities. Repeatability was also established for several descriptors of the process such as the carbon dioxide and biomass production, the pH and organic content of the leachates, and the moisture content of the packing material. While some parameters, such as the pH, presented a remarkably low divergence between biofilters (coefficient of variability of 1.4%), others, such as the organic content of the leachates, presented higher variability (30.6%) due to an uneven biomass lixiviation associated with stochastic hydrodynamics and biomass repartitions. Regarding process efficiency, it was established that less than 10% of fluctuation is to be expected between the elimination capacities of identical biofilter set-ups. A further statistical comparison between the first halves of the biofilter columns indicated very similar coefficients of variability, confirming the repeatability of the process, for different biofilter lengths.

Evaluation of wheelchair resistive forces during straight and turning trajectories across different wheelchair configurations using free-wheeling coast-down test.

PubMed

Lin, Jui-Te; Huang, Morris; Sprigle, Stephen

2015-01-01

The purpose of this study was to develop a simple approach to evaluate resistive frictional forces acting on manual wheelchairs (MWCs) during straight and turning maneuvers. Using a dummy-occupied MWC, decelerations were measured via axle-mounted encoders during a coast-down protocol that included straight trajectories and fixed-wheel turns. Eight coast-down trials were conducted to test repeatability and repeated on separate days to evaluate reliability. Without changing the inertia of the MWC system, three tire inflations were chosen to evaluate the sensitivity in discerning deceleration differences using effect sizes. The technique was also deployed to investigate the effect of different MWC masses and weight distributions on resistive forces. Results showed that the proposed coast-down technique had good repeatability and reliability in measuring decelerations and had good sensitivity in discerning differences in tire inflation, especially during turning. The results also indicated that increased loading on drive wheels reduced resistive losses in straight trajectories while increasing resistive losses during turning. During turning trajectories, the presence of tire scrub contributes significantly to the amount of resistive force. Overall, this new coast-down technique demonstrates satisfactory repeatability and sensitivity for detecting deceleration changes during straight and turning trajectories, indicating that it can be used to evaluate resistive loss of different MWC configurations and maneuvers.

Experimental Structural Dynamic Response of Plate Specimens Due to Sonic Loads in a Progressive Wave Tube

NASA Technical Reports Server (NTRS)

Betts, Juan F.

2001-01-01

The objective of the current study was to assess the repeatability of experiments at NASA Langley's Thermal Acoustic Fatigue Apparatus (TAFA) facility and to use these experiments to validate numerical models. Experiments show that power spectral density (PSD) curves were repeatable except at the resonant frequencies, which tended to vary between 5 Hz to 15 Hz. Results show that the thinner specimen had more variability in the resonant frequency location than the thicker sample, especially for modes higher than the first mode in the frequency range. Root Mean Square (RMS) tended to be more repeatable. The RMS behaved linearly through the SPL range of 135 to 153 dB. Standard Deviations (STDs) of the results tended to be relatively low constant up to about 147 dB. The RMS results were more repeatable than the PDS results. The STD results were less than 10% of the RMS results for both the 0.125 in (0.318 cm) and 0.062 in (0.1588 cm) thick plate. The STD of the PSD results were around 20% to 100% of the mean PSD results for non-resonant and resonant frequencies, respectively, for the 0.125 in (0.318 cm) thicker plate and between 25% to 125% of the mean PSD results, for nonresonant and resonant frequencies, respectively, for the thinner plate.

Immediate loading with fixed full-arch prostheses in the maxilla: Review of the literature

PubMed Central

Peñarrocha-Oltra, David; Covani, Ugo; Peñarrocha-Diago, Miguel

2014-01-01

Objectives: To critically review the evidence-based literature on immediate loading of implants with fixed full-arch prostheses in the maxilla to determine 1) currently recommended performance criteria and 2) the outcomes that can be expected with this procedure. Study Desing: Studies from 2001 to 2011 on immediate loading with fixed full-arch maxillary prostheses were reviewed. Clinical series with at least 5 patients and 12 months of follow-up were included. Case reports, studies with missing data and repeatedly published studies were excluded. In each study the following was assessed: type of study, implant type, number of patients, number of implants, number of implants per patient, use of post-extraction implants, minimum implant length and diameter, type of prosthesis, time until loading, implant survival rate, prosthesis survival rate, marginal bone loss, complications andmean follow-up time. Criteria for patient selection, implant primary stability and bone regeneration were also studied. Results: Thirteen studies were included, reporting a total of 2484 immediately loaded implants in 365 patients. Currently accepted performance criteria regarding patient and implant selection, and surgical and prosthetic procedures were deduced from the reviewed articles. Implant survival rates went from 87.5% to 100%, prosthesis survival rates from 93.8% to 100% and radiographic marginal bone loss from 0.8 mm to 1.6 mm.No intraoperative complications and only minor prosthetic complications were reported. Conclusions: The literature on immediate loading with fixed full-arch prostheses in the maxilla shows that a successful outcome can be expected if adequate criteria are used to evaluate the patient, choose the implant and perform the surgical and prosthetic treatment. Lack of homogeneity within studies limits the relevance of the conclusions that can be drawn, and more controlled randomized studies are necessary to enable comparison between the immediate and the conventional loading procedures. Key words:Immediate loading, full-arch, dental implants, loading protocols. PMID:24880445

Allostatic Load and Health in the Older Population of England: A Crossed-Lagged Analysis

PubMed Central

Read, Sanna; Grundy, Emily

2014-01-01

Objective Allostatic load, a composite measure of accumulated physical wear and tear, has been proposed as an early sign of physiological dysregulation predictive of health problems, functional limitation, and disability. However, much previous research has been cross sectional and few studies consider repeated measures. We investigate the directionality of associations between allostatic load, self-rated health, and a measure of physical function (walking speed). Methods The sample included men and women 60 and older who participated in Wave 2 (2004) and Wave 4 (2008) of the English Longitudinal Study of Ageing (n = 6132 in Wave 2). Allostatic load was measured with nine biomarkers using a multisystem summary approach. Self-rated health was measured using a global 5 point summary indicator. Time to walk 8 ft was used as a measure of function. We fitted and tested autoregressive cross-lagged models between the allostatic load measure, self-rated health, and walking speed in Waves 2 and 4. Models were adjusted for age, sex, educational level, and smoking status at Wave 2 and for time-varying indicators of marital status, wealth, physical activity, and social support. Results Allostatic load predicted slower walking speed (standardized estimate = −0.08, 95% confidence interval [CI] = −0.10 to −0.05). Better self-rated health predicted faster walking speed (standardized estimate = 0.11, 95% CI = 0.08-0.13) as well as lower allostatic load (standardized estimate = −0.15, 95% CI = −0.22 to −0.09), whereas paths from allostatic load and walking speed to self-rated health were weaker (standardized estimates = −0.05 [95% CI = −0.07 to −0.02] and 0.06 [95% CI = 0.04–0.08]). Conclusions Allostatic load can be a useful risk indicator of subsequent poor health or function. PMID:25153937

Knee Joint Kinetics in Relation to Commonly Prescribed Squat Loads and Depths

PubMed Central

Cotter, Joshua A.; Chaudhari, Ait M.; Jamison, Steve T.; Devor, Steven T.

2014-01-01

Controversy exists regarding the safety and performance benefits of performing the squat exercise to depths beyond 90° of knee flexion. Our aim was to compare the net peak external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. Sixteen recreationally trained males (n = 16; 22.7 ± 1.1 yrs; 85.4 ± 2.1 kg; 177.6 ± 0.96 cm; mean ± SEM) with no previous lower limb surgeries or other orthopedic issues and at least one year of consistent resistance training experience while utilizing the squat exercise performed single repetition squat trials in a random order at squat depths of above parallel, parallel, and below parallel. Less than one week before testing, one repetition maximum (1RM) values were found for each squat depth. Subsequent testing required subjects to perform squats at the three depths with three different loads: unloaded, 50% 1RM, and 85% 1RM (nine total trials). Force platform and kinematic data were collected to calculate pEKFM. To assess differences among loads and depths, a two-factor (load and depth) repeated-measures ANOVA with significance set at the P < 0.05 level was used. Squat 1RM significantly decreased 13.6% from the above parallel to parallel squat and another 3.6% from the parallel to the below parallel squat (P < 0.05). Net peak external knee flexion moments significantly increased as both squat depth and load were increased (P ≤ 0.02). Slopes of pEKFM were greater from unloaded to 50% 1RM than when progressing from 50% to 85% 1RM (P < 0.001). The results suggest that that typical decreases in squat loads used with increasing depths are not enough to offset increases in pEKFM. PMID:23085977

Effect of Bench Press Load Knowledge on Repetitions, Rating of Perceived Exertion, and Attentional Focus.

PubMed

Beaudoin, Christina M; Cox, Zachary; Dundore, Tyler; Thomas, Tayler; Kim, Johnathon; Pillivant, Daniel

2018-02-01

Beaudoin, CM, Cox, Z, Dundore, T, Thomas, T, Kim, J, and Pillivant, D. Effect of bench press load knowledge on repetitions, rating of perceived exertion, and attentional focus. J Strength Cond Res 32(2): 514-519, 2018-Few studies have examined the role of the teleoanticipation during resistance training. The purpose of this study was to examine the effect of bench press (BP) load knowledge on repetitions completed, ratings of perceived exertion (RPEs), and attentional focus (% associative). Thirty-six recreationally active resistance-trained men (n = 25) and women (n = 11) participated in this study (age = 20.97 ± 1.87 years; ht = 174.12 ± 9.41 cm; and mass = 80.14 ± 14.03 kg). All subjects completed 3 testing sessions: (a) 1 repetition maximum (1RM) BP determination; (b) submaximal BP repetitions to fatigue known load (KL); and (c) submaximal BP repetitions to fatigue unknown load (UL). Known load and UL sessions were randomized and counterbalanced and both completed at 70% 1RM. An estimated weight ratio was computed using the subject's estimate of the UL weight relative to the KL weight. An independent samples t-test revealed no significant testing order difference for the estimated weight ratio. Two-way repeated-measures analysis of variances revealed no significant differences in the number of repetitions (p = 0.63), RPE (p = 0.18), or attentional focus (% associative) (p = 0.93) between the KL and UL conditions. Pearson correlations found a moderate positive association between KL repetitions completed and % associative focus when the UL was completed before the KL. Load knowledge did not influence the number of repetitions, RPE, or attentional focus while completing the BP. Further research examining the use of pacing strategies, RPE, and attentional focus during KL and UL conditions are warranted.

Fatigue Life of Bovine Meniscus under Longitudinal and Transverse Tensile Loading

PubMed Central

Creechley, Jaremy J.; Krentz, Madison E.; Lujan, Trevor J.

2017-01-01

The knee meniscus is composed of a fibrous matrix that is subjected to large and repeated loads. Consequently, the meniscus is frequently torn, and a potential mechanism for failure is fatigue. The objective of this study was to measure the fatigue life of bovine meniscus when applying cyclic tensile loads either longitudinal or transverse to the principal fiber direction. Fatigue experiments consisted of cyclic loads to 60, 70, 80 or 90% of the predicted ultimate tensile strength until failure occurred or 20,000 cycles was reached. The fatigue data in each group was fit with a Weibull distribution to generate plots of stress level vs. cycles to failure (S-N curve). Results showed that loading transverse to the principal fiber direction gave a two-fold increase in failure strain, a three-fold increase in creep, and a nearly four-fold increase in cycles to failure (not significant), compared to loading longitudinal to the principal fiber direction. The S-N curves had strong negative correlations between the stress level and the mean cycles to failure for both loading directions, where the slope of the transverse S-N curve was 11% less than the longitudinal S-N curve (longitudinal: S=108–5.9ln(N); transverse: S=112–5.2ln(N)). Collectively, these results suggest that the non-fibrillar matrix is more resistant to fatigue failure than the collagen fibers. Results from this study are relevant to understanding the etiology of atraumatic radial and horizontal meniscal tears, and can be utilized by research groups that are working to develop meniscus implants with fatigue properties that mimic healthy tissue. PMID:28088070

Energy cost and mechanical work of walking during load carriage in soldiers.

PubMed

Grenier, Jordane G; Peyrot, Nicolas; Castells, Josiane; Oullion, Roger; Messonnier, Laurent; Morin, Jean-Benoit

2012-06-01

In the military context, soldiers carry equipments of total mass often exceeding 30%-40% of their body mass (BM) and complexly distributed around their body (backpack, weapons, electronics, protections, etc.), which represents severe load carrying conditions. This study aimed to better understand the effects of load carriage on walking energetics and mechanics during military-type walking. Ten male infantrymen recently retired from the French Foreign Legion performed 3-min walking trials at a constant speed of 4 km·h(-1) on an instrumented treadmill, during which walking pattern spatiotemporal parameters, energy cost (C(W)), external mechanical work (W(ext)), and the work done by one leg against the other during the double-contact period (W(int,dc)) were specifically assessed. Three conditions were tested: (i) light sportswear (SP, reference condition considered as unloaded), (ii) battle equipment (BT, ∼22 kg, ∼27% of subjects' BM, corresponding to a military intermediate load), and (iii) road march equipment (RM, ∼38 kg, ∼46% of subjects' BM, corresponding to a military high load). Repeated-measures ANOVA showed that military equipment carriage significantly (i) altered the spatiotemporal pattern of walking (all P < 0.01), (ii) increased absolute gross and net CW (P < 0.0001), and (iii) increased both absolute and mass-relative W(ext) (P < 0.01) and W(int,dc) (P < 0.0001) but did not alter the inverted pendulum recovery or locomotor efficiency. Military equipments carriage induced significant changes in walking mechanics and energetics, but these effects appeared not greater than those reported with loads carried around the waist and close to the center of mass. This result was not expected because the latter has been hypothesized to be the optimal method of load carriage from a metabolic standpoint.

Fracture behavior of human molars.

PubMed

Keown, Amanda J; Lee, James J-W; Bush, Mark B

2012-12-01

Despite the durability of human teeth, which are able to withstand repeated loading while maintaining form and function, they are still susceptible to fracture. We focus here on longitudinal fracture in molar teeth-channel-like cracks that run along the enamel sidewall of the tooth between the gum line (cemento-enamel junction-CEJ) and the occlusal surface. Such fractures can often be painful and necessitate costly restorative work. The following study describes fracture experiments made on molar teeth of humans in which the molars are placed under axial compressive load using a hard indenting plate in order to induce longitudinal cracks in the enamel. Observed damage modes include fractures originating in the occlusal region ('radial-median cracks') and fractures emanating from the margin of the enamel in the region of the CEJ ('margin cracks'), as well as 'spalling' of enamel (the linking of longitudinal cracks). The loading conditions that govern fracture behavior in enamel are reported and observations made of the evolution of fracture as the load is increased. Relatively low loads were required to induce observable crack initiation-approximately 100 N for radial-median cracks and 200 N for margin cracks-both of which are less than the reported maximum biting force on a single molar tooth of several hundred Newtons. Unstable crack growth was observed to take place soon after and occurred at loads lower than those calculated by the current fracture models. Multiple cracks were observed on a single cusp, their interactions influencing crack growth behavior. The majority of the teeth tested in this study were noted to exhibit margin cracks prior to compression testing, which were apparently formed during the functional lifetime of the tooth. Such teeth were still able to withstand additional loading prior to catastrophic fracture, highlighting the remarkable damage containment capabilities of the natural tooth structure.

Tekscan pressure sensor output changes in the presence of liquid exposure.

PubMed

Jansson, Kyle S; Michalski, Max P; Smith, Sean D; LaPrade, Robert F; Wijdicks, Coen A

2013-02-01

The purpose of the study was to evaluate the load output of a pressure sensor in the presence of liquid saturation in a controlled environment. We hypothesized that a calibrated pressure sensor would provide diminishing load outputs over time in controlled environments of both humidified air and while submerged in saline and the sensors would reach a steady state output once saturated. A consistent compressive load was repeatedly applied to pressure sensors over time (Model 4000, Tekscan, Inc., South Boston, MA) with a tensile testing machine (Instron ElectroPuls E10000, Norwood, MA). All sensors were initially calibrated in a dry environment and were tested in three groups: humid air, submerged in 0.9% saline solution, and dry. Linear regression of load output over time for the pressure sensors exposed to humidity and submerged showed a 4.6% and 4.7% decline in load output each hour for the initial 6h, respectively (β=-0.046, 95% CI: [-0.053 to -0.039]; p<0.001) (β=-0.047, 95% CI: [-0.053 to -0.042; p<0.001). Tests after 72 h of exposure had linear regression decline in load output over time of 0.40% and 0.47% per hour for humidified and submerged sensors, respectively (β=-0.004, 95% CI: [-0.006 to -0.003]; p<0.001) (β=-0.047, 95% CI: [-0.053 to -0.042]; p<0.001). Because outcomes in biomedical research can affect clinical practices and treatments, the diminishing load output of the sensor in the presence of liquids should be accounted for. We recommend soaking sensors for more than 48 h prior to testing in a moist environment. Copyright © 2012 Elsevier Ltd. All rights reserved.

Erosion and attrition of human enamel in vitro part II: influence of time and loading.

PubMed

Eisenburger, M; Addy, M

2002-01-01

To determine the influence of load and time on enamel wear by attrition under neutral and acid environments in vitro. Groups of 10 enamel cusp and smooth surface specimens obtained from unerupted third molars were opposed in a wear machine under loads of 200, 400 and 600 g in citric acid at pH 3.2 and in physiological saline at 35 degrees C for 30 min (2280 wear cycles). The experiment was repeated with a load of 600 g for 10 and 20 min accompanied by 10 taped specimens to measure erosion only. Erosion and attrition of smooth surface specimens was determined by profilometry. At a load of 600 g attrition in saline increased with time from 7.9 microm (SD 3.7 microm) at 10 min, 10.2 microm (SD 4.8 microm) at 20-25.5 microm (SD 9.1 microm) after 30 min and combined attrition/erosion in citric acid from 1.5 microm (SD 0.4 microm) to 2.5 microm (SD 0.9 microm) to 6.0 microm (SD 3.7 microm). At a fixed time of 30 min, attrition in saline was 5.2 microm (SD 3.6 microm) at 200 g and 8.1 microm (SD 1.5 microm) at 400 g and combined attrition/erosion in citric acid 2.8 microm (SD 1.2 microm) and 3.6 microm (SD 0.7 microm). Comparison between both environments revealed significant differences at fixed load at all time points (p < 0.01) and at fixed time between 400 and 600 g (p < 0.01). Load and time significantly influence enamel wear both in acid and neutral conditions but the effects were not linear. Copyright 2002 Elsevier Science Ltd.

The effect of temperature, gradient, and load carriage on oxygen consumption, posture, and gait characteristics.

PubMed

Hinde, Katrina; Lloyd, Ray; Low, Chris; Cooke, Carlton

2017-03-01

The purpose of this experiment was to evaluate the effect of load carriage in a range of temperatures to establish the interaction between cold exposure, the magnitude of change from unloaded to loaded walking and gradient. Eleven participants (19-27 years) provided written informed consent before performing six randomly ordered walking trials in six temperatures (20, 10, 5, 0, -5, and -10 °C). Trials involved two unloaded walking bouts before and after loaded walking (18.2 kg) at 4 km · h -1 , on 0 and 10% gradients in 4 min bouts. The change in absolute oxygen consumption (V̇O 2 ) from the first unloaded bout to loaded walking was similar across all six temperatures. When repeating the second unloaded bout, V̇O 2 at both -5 and -10 °C was greater compared to the first. At -10 °C, V̇O 2 was increased from 1.60 ± 0.30 to 1.89 ± 0.51 L · min -1 . Regardless of temperature, gradient had a greater effect on V̇O 2 and heart rate (HR) than backpack load. HR was unaffected by temperature. Stride length (SL) decreased with decreasing temperature, but trunk forward lean was greater during cold exposure. Decreased ambient temperature did not influence the magnitude of change in V̇O 2 from unloaded to loaded walking. However, in cold temperatures, V̇O 2 was significantly higher than in warm conditions. The increased V̇O 2 in colder temperatures at the same exercise intensity is predicted to ultimately lead to earlier onset of fatigue and cessation of exercise. These results highlight the need to consider both appropriate clothing and fitness during cold exposure.

Fracture load of complete-arch implant-supported prostheses reinforced with nylon-silica mesh: An in vitro study.

PubMed

Gonçalves, Fernanda de Cássia Papaiz; Amaral, Marina; Borges, Alexandre Luiz Souto; Gonçalves, Luiz Fernando Martins; Paes-Junior, Tarcisio José de Arruda

2018-04-01

Complete-arch implant-supported prostheses without a framework have a high risk of failure: a straightforward and inexpensive reinforcement material, such as nylon mesh, could improve their longevity. The purpose of this in vitro study was to evaluate a nylon-silica mesh compound on the fracture strength of acrylic resin and the fracture load of complete-arch implant-supported prostheses. Twenty-four complete mandibular arch implant-supported prostheses were divided into 2 groups according to cantilever length (molar and premolar) and subdivided into another 2 subgroups according to the presence or absence of reinforcing mesh. The specimens were submitted to a maximum load-to-fracture test in a universal testing machine, with a 100-N load cell, a 2 mm/min crosshead speed, and a spherical metal tip diameter of 4 mm at different points (molar and premolar). These were submitted to 1-way analysis of variance for repeated measurement and the post hoc Tukey multiple comparison test (α=.05). The mean maximum load ±standard deviation for the molar group was 393.4 ±95.0 N with reinforcement and 305.4 ±76.3 N without reinforcement (P=.02); and for the premolar group was 1083.3 ±283.7 N with reinforcement and 605.3 ±90.5 N without reinforcement (P=.001). Reinforcement with nylon mesh increased the mean maximum load of implant-supported complete-arch prostheses at both cantilever lengths. The cantilever to the premolar (5 mm) presented the highest maximum load values to fracture. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Quasi-Brittle Fracture of Compact Specimens with Sharp Notches and U-Shaped Cuts

NASA Astrophysics Data System (ADS)

Kornev, V. M.; Demeshkin, A. G.

2018-01-01

A two-parameter (coupled) discrete-integral criterion of fracture is proposed. It can be used to construct fracture diagrams for compact specimens with sharp cracks. Curves separating the stress-crack length plane into three domains are plotted. These domains correspond to the absence of fracture, damage accumulation in the pre-fracture region under repeated loading, and specimen fragmentation under monotonic loading. Constants used for the analytical description of fracture diagrams for quasi-brittle materials with cracks are selected with the use of approximation of the classical stress-strain diagrams for the initial material and the critical stress intensity factor. Predictions of the proposed theory are compared with experimental results on fracture of compact specimens with different radii made of polymethylmethacrylate (PMMA) and solid rubber with crack-type effects in the form of U-shaped cuts.

System performance predictions for Space Station Freedom's electric power system

NASA Technical Reports Server (NTRS)

Kerslake, Thomas W.; Hojnicki, Jeffrey S.; Green, Robert D.; Follo, Jeffrey C.

1993-01-01

Space Station Freedom Electric Power System (EPS) capability to effectively deliver power to housekeeping and user loads continues to strongly influence Freedom's design and planned approaches for assembly and operations. The EPS design consists of silicon photovoltaic (PV) arrays, nickel-hydrogen batteries, and direct current power management and distribution hardware and cabling. To properly characterize the inherent EPS design capability, detailed system performance analyses must be performed for early stages as well as for the fully assembled station up to 15 years after beginning of life. Such analyses were repeatedly performed using the FORTRAN code SPACE (Station Power Analysis for Capability Evaluation) developed at the NASA Lewis Research Center over a 10-year period. SPACE combines orbital mechanics routines, station orientation/pointing routines, PV array and battery performance models, and a distribution system load-flow analysis to predict EPS performance. Time-dependent, performance degradation, low earth orbit environmental interactions, and EPS architecture build-up are incorporated in SPACE. Results from two typical SPACE analytical cases are presented: (1) an electric load driven case and (2) a maximum EPS capability case.

Gas gun driven dynamic fracture and fragmentation of Ti-6Al-4V cylinders

NASA Astrophysics Data System (ADS)

Jones, D. R.; Chapman, D. J.; Eakins, D. E.

2014-05-01

The dynamic fracture and fragmentation of a material is a complex late stage phenomenon occurring in many shock loading scenarios. Improving our predictive capability depends upon exercising our current failure models against new loading schemes and data. We present axially-symmetric high strain rate (104 s-1) expansion of Ti-6Al-4V cylinders using a single stage light gas gun technique. A steel ogive insert was located inside the target cylinder, into which a polycarbonate rod was launched. Deformation of this rod around the insert drives the cylinder into rapid expansion. This technique we have developed facilitates repeatable loading, independent of the temperature of the sample cylinder, with straightforward adjustment of the radial strain rate. Expansion velocity was measured with multiple channels of photon Doppler velocimetry. High speed imaging was used to track the overall expansion process and record strain to failure and crack growth. Results from a cylinder at a temperature of 150 K are compared with work at room temperature, examining the deformation, failure mechanisms and differences in fragmentation.

Understanding behavioral effects of early life stress using the reactive scope and allostatic load models

PubMed Central

HOWELL, BRITTANY R.; SANCHEZ, MAR M.

2015-01-01

The mechanisms through which early life stress leads to psychopathology are thought to involve allostatic load, the “wear and tear” an organism is subjected to as a consequence of sustained elevated levels of glucocorticoids caused by repeated/prolonged stress activations. The allostatic load model described this phenomenon, but has been criticized as inadequate to explain alterations associated with early adverse experience in some systems, including behavior, which cannot be entirely explained from an energy balance perspective. The reactive scope model has been more recently proposed and focuses less on energy balance and more on dynamic ranges of physiological and behavioral mediators. In this review we examine the mechanisms underlying the behavioral consequences of early life stress in the context of both these models. We focus on adverse experiences that involve mother–infant relationship disruption, and dissect those mechanisms involving maternal care as a regulator of development of neural circuits that control emotional and social behaviors in the offspring. We also discuss the evolutionary purpose of the plasticity in behavioral development, which has a clear adaptive value in a changing environment. PMID:22018078

Noncontacting Laser Inspection System for Dimensional Profiling of Space Application Thermal Barriers

NASA Technical Reports Server (NTRS)

Taylor, Shawn C.

2011-01-01

A noncontacting, two-dimensional (2-D) laser inspection system has been designed and implemented to dimensionally profile thermal barriers being developed for space vehicle applications. In a vehicle as-installed state, thermal barriers are commonly compressed between load sensitive thermal protection system (TPS) panels to prevent hot gas ingestion through the panel interface during flight. Loads required to compress the thermal barriers are functions of their construction, as well as their dimensional characteristics relative to the gaps in which they are installed. Excessive loads during a mission could damage surrounding TPS panels and have catastrophic consequences. As such, accurate dimensional profiling of thermal barriers prior to use is important. Due to the compliant nature of the thermal barriers, traditional contact measurement techniques (e.g., calipers and micrometers) are subjective and introduce significant error and variability into collected dimensional data. Implementation of a laser inspection system significantly enhanced the method by which thermal barriers are dimensionally profiled, and improved the accuracy and repeatability of collected data. A statistical design of experiments study comparing laser inspection and manual caliper measurement techniques verified these findings.

Failure analysis of pinch-torsion tests as a thermal runaway risk evaluation method of Li-ion cells

NASA Astrophysics Data System (ADS)

Xia, Yuzhi; Li, Tianlei; Ren, Fei; Gao, Yanfei; Wang, Hsin

2014-11-01

Recently a pinch-torsion test is developed for safety testing of Li-ion batteries. It has been demonstrated that this test can generate small internal short-circuit spots in the separator in a controllable and repeatable manner. In the current research, the failure mechanism is examined by numerical simulations and comparisons to experimental observations. Finite element models are developed to evaluate the deformation of the separators under both pure pinch and pinch-torsion loading conditions. It is discovered that the addition of the torsion component significantly increased the maximum first principal strain, which is believed to induce the internal short circuit. In addition, the applied load in the pinch-torsion test is significantly less than in the pure pinch test, thus dramatically improving the applicability of this method to ultra-thick batteries which otherwise require heavy load in excess of machine capability. It is further found that the separator failure is achieved in the early stage of torsion (within a few degree of rotation). Effect of coefficient of friction on the maximum first principal strain is also examined.

Frequency-Switchable Microfluidic CSRR-Loaded QMSIW Band-Pass Filter Using a Liquid Metal Alloy

PubMed Central

Eom, Seunghyun; Memon, Muhammad Usman; Lim, Sungjoon

2017-01-01

In this paper, we have proposed a frequency-switchable complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) band-pass filter. For frequency switching, a microfluidic channel and liquid metal are used. The liquid metal used is eutectic gallium-indium (EGaIn), consisting of 24.5% indium and 75.5% gallium. The microfluidic channels are built using the elastomer polydimethylsiloxane (PDMS) and three-dimensional-printed microfluidic channel frames. The CSRR-loaded QMSIW band-pass filter is designed to have two states. Before the injection of the liquid metal, the measured center frequency and fractional bandwidths are 2.205 GHz and 6.80%, respectively. After injection, the center frequency shifts from 2.205 GHz to 2.56 GHz. Although the coupling coefficient is practically unchanged, the fractional bandwidth changes from 6.8% to 9.38%, as the CSRR shape changes and the external quality factor decreases. After the removal of the liquid metal, the measured values are similar to the values recorded before the liquid metal was injected. The repeatability of the frequency-switchable mechanism is, therefore, verified. PMID:28350355

Effect of high loading on substrate utilization kinetics and microbial community structure in super fast submerged membrane bioreactor.

PubMed

Sözen, S; Çokgör, E U; Başaran, S Teksoy; Aysel, M; Akarsubaşı, A; Ergal, I; Kurt, H; Pala-Ozkok, I; Orhon, D

2014-05-01

The study investigated the effect of high substrate loading on substrate utilization kinetics, and changes inflicted on the composition of the microbial community in a superfast submerged membrane bioreactor. Submerged MBR was sequentially fed with a substrate mixture and acetate; its performance was monitored at steady-state, at extremely low sludge age values of 2.0, 1.0 and 0.5d, all adjusted to a single hydraulic retention time of 8.0 h. Each MBR run was repeated when substrate feeding was increased from 200 mg COD/L to 1000 mg COD/L. Substrate utilization kinetics was altered to significantly lower levels when the MBR was adjusted to higher substrate loadings. Molecular analysis of the biomass revealed that variable process kinetics could be correlated with parallel changes in the composition of the microbial community, mainly by a replacement mechanism, where newer species, better adapted to the new growth conditions, substituted others that are washed out from the system. Copyright © 2014 Elsevier Ltd. All rights reserved.

Biodegradation of organics in landfill leachate by immobilized white rot fungi, Trametes versicolor BCC 8725.

PubMed

Saetang, Jenjira; Babel, Sandhya

2012-12-01

Immobilized Trametes versicolor BCC 8725 was evaluated for the biodegradation of the organic components of four different types of landfill leachate collected at different time periods and locations from the Nonthaburi landfill site of Thailand in batch treatment. The effects of carbon source, ammonia and organic loading on colour, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) removal, and the reuse of immobilized fungi were investigated. It was found that fungi can remove 78% of colour, reduce BOD by 68% and reduce COD by 57% in leachate within 15 days at optimum conditions. Organic loading and ammonia were the factors that affected the biodegradation. When immobilized T versicolor on polyurethane foam (PUF) was subjected to repeated use for treatment over the course of three cycles, the decolourization efficiency of the first and the second cycle was very similar, whereas the third cycle was about 20% lower than the first cycle under similar conditions. The obtained removal of colour, BOD and COD indicates the effectiveness of fungi for leachate treatment with high organic loading and varied leachate characteristics.

Use of intrathecal urokinase in repeated shunt and external ventricular drain blockage from high CSF protein due to an optic pathway glioma.

PubMed

Shooman, David; Vajramani, Girish V; Davidson, Jennifer; Sparrow, Owen C

2010-05-01

High cerebrospinal fluid (CSF) protein is a recognised association of optic pathway gliomas. This can occlude ventriculoperitoneal (VP) shunt catheters or external ventricular drains (EVD). We describe an 8-year-old boy with an optic pathway glioma, who had frequent episodes of a blocked VP shunt and EVD due to high CSF protein level. This responded favourably to repeated urokinase instillation into the catheter lumen. We present the course of treatment and the method of administration and review the literature behind thrombolytic therapy for occluded catheter devices. Intrathecal urokinase was effective in unblocking the EVD and lysing the protein clots within the ventricle. We found no previously published cases of intrathecal urokinase for this problem. This novel intervention seemed promising as a safe and effective means of maintaining EVD patency in cases complicated by excessive protein loads in CSF and hydrocephalus.

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

Harstad, E. N.; Harlow, Francis Harvey,; Schreyer, H. L.

Our goal is to develop constitutive relations for the behavior of a solid polymer during high-strain-rate deformations. In contrast to the classic thermodynamic techniques for deriving stress-strain response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDF. Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. Tomore » extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of nonuniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.« less

Posturedontics: How does dentistry fit you?

PubMed

Jodalli, Praveen S; Kurana, Suchi; Shameema; Ragher, Mallikarjuna; Khed, Jaishree; Prabhu, Vishnu

2015-08-01

Dentists are at high risk for musculoskeletal disorders (MSD's) due to their work. MSD's is an umbrella term for number of injuries affecting different parts of the body, including joints, muscles, tendons, nerves that can arise from sudden exertion or making the same motions repeatedly. These injuries can develop over time and can lead to long-term disability. Dental professional often develop musculoskeletal problems due to bad working habits, uncomfortable physical posture causing unnecessary musculoskeletal loading, discomfort and fatigue. Ergonomic principles when it is applied, it will help to reduce stress and eliminate many potential injuries and disorders associated with the overuse of muscles, bad posture, and repeated tasks. This can be accomplished by using a proper dental chair, lighting and the selection of ergonomically-friendly equipment to fit the dental professionals physical capabilities and limitations. This review addresses about the basics of ergonomics, positioning, viewing, handling, and prevention of MSD's.

Posturedontics: How does dentistry fit you?

PubMed Central

Jodalli, Praveen S.; Kurana, Suchi; Shameema; Ragher, Mallikarjuna; Khed, Jaishree; Prabhu, Vishnu

2015-01-01

Dentists are at high risk for musculoskeletal disorders (MSD's) due to their work. MSD's is an umbrella term for number of injuries affecting different parts of the body, including joints, muscles, tendons, nerves that can arise from sudden exertion or making the same motions repeatedly. These injuries can develop over time and can lead to long-term disability. Dental professional often develop musculoskeletal problems due to bad working habits, uncomfortable physical posture causing unnecessary musculoskeletal loading, discomfort and fatigue. Ergonomic principles when it is applied, it will help to reduce stress and eliminate many potential injuries and disorders associated with the overuse of muscles, bad posture, and repeated tasks. This can be accomplished by using a proper dental chair, lighting and the selection of ergonomically-friendly equipment to fit the dental professionals physical capabilities and limitations. This review addresses about the basics of ergonomics, positioning, viewing, handling, and prevention of MSD's. PMID:26538885

Investigation of Micro-Scale Architectural Effects on Damage of Composites

NASA Technical Reports Server (NTRS)

Stier, Bertram; Bednarcyk, Brett A.; Simon, Jaan W.; Reese, Stefanie

2015-01-01

This paper presents a three-dimensional, energy based, anisotropic, stiffness reduction, progressive damage model for composite materials and composite material constituents. The model has been implemented as a user-defined constitutive model within the Abaqus finite element software package and applied to simulate the nonlinear behavior of a damaging epoxy matrix within a unidirectional composite material. Three different composite microstructures were considered as finite element repeating unit cells, with appropriate periodicity conditions applied at the boundaries. Results representing predicted transverse tensile, longitudinal shear, and transverse shear stress-strain curves are presented, along with plots of the local fields indicating the damage progression within the microstructure. It is demonstrated that the damage model functions appropriately at the matrix scale, enabling localization of the damage to simulate failure of the composite material. The influence of the repeating unit cell geometry and the effect of the directionality of the applied loading are investigated and discussed.

Conducted noise analysis and protection of 45 kJ/s, ±50 kV capacitor charging power supply when interfaced with repetitive Marx based pulse power system.

PubMed

Naresh, P; Patel, Ankur; Sharma, Archana

2015-09-01

Pulse power systems with highly dynamic loads like klystron, backward wave oscillator (BWO), and magnetron generate highly dynamic noise. This noise leads to frequent failure of controlled switches in the inverter stage of charging power supply. Designing a reliable and compatible power supply for pulse power applications is always a tricky job when charging rate is in multiples of 10 kJ/s. A ±50 kV and 45 kJ/s capacitor charging power supply based on 4th order LCLC resonant topology has been developed for a 10 Hz repetitive Marx based system. Conditions for load independent constant current and zero current switching (ZCS) are derived mathematically. Noise generated at load end due to dynamic load is tackled effectively and reduction in magnitude noise voltage is achieved by providing shielding between primary and secondary of high voltage high frequency transformer and with LCLC low pass filter. Shielding scales down the ratio between coupling capacitance (Cc) and the collector-emitter capacitance of insulated gate bi-polar transistor switch, which in turn reduces the common mode noise voltage magnitude. The proposed 4th order LCLC resonant network acts as a low pass filter for differential mode noise in the reverse direction (from load to source). Power supply has been tested repeatedly with 5 Hz repetition rate with repetitive Marx based system connected with BWO load working fine without failure of single switch in the inverter stage.

Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair.

PubMed

Lee, Young-Joo; Kim, Robin E; Suh, Wonho; Park, Kiwon

2017-04-24

Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed.

Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair

PubMed Central

Lee, Young-Joo; Kim, Robin E.; Suh, Wonho; Park, Kiwon

2017-01-01

Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed. PMID:28441768

The VO(2)-on kinetics in constant load exercise sub-anaerobic threshold reflects endothelial function and dysfunction in muscle microcirculation.

PubMed

Maione, D; Cicero, A Fg; Bacchelli, S; Cosentino, E R; Degli Esposti, D; Manners, D N; Rinaldi, E R; Rosticci, M; Senaldi, R; Ambrosioni, E; Borghi, C

2015-01-01

To propose a test to evaluate endothelial function, based on VO(2) on-transition kinetics in sub-anaerobic threshold (AT) constant load exercise, we tested healthy subjects and patients with ischemic-hypertensive cardiopathy by two cardiopulmonary tests on a cycle ergometer endowed with an electric motor to overcome initial inertia: a pre-test and, after at least 24 h, one 6 min constant load exercise at 90 % AT. We measured net phase 3 VO(2)-on kinetics and, by phase 2 time constant (tau), valued endothelial dysfunction. We found shorter tau in repeated tests, shorter time between first and second test, by persisting endothelium-dependent arteriolar vasodilatation and/or several other mechanisms. Reducing load to 80 % and 90 % AT did not produce significant changes in tau of healthy volunteers, while in heart patients an AT load of 70 %, compared to 80 % AT, shortened tau (delta=4.38+/-1.65 s, p=0.013). In heart patients, no correlation was found between NYHA class, ejection fraction (EF), and the two variables derived from incremental cycle cardio-pulmonary exercise, as well as between EF and tau; while NYHA class groups were well correlated with tau duration (r=0.92, p=0.0001). Doxazosin and tadalafil also significantly reduced tau. In conclusion, the O(2) consumption kinetics during the on-transition of constant load exercise below the anaerobic threshold are highly sensitive to endothelial function in muscular microcirculation, and constitute a marker for the evaluation of endothelial dysfunction.

EFFECTIVENESS OF SELECTION IN REDUCING THE GENETIC LOAD IN POPULATIONS OF PEROMYSCUS POLIONOTUS DURING GENERATIONS OF INBREEDING.

PubMed

Lacy, Robert C; Ballou, Jonathan D

1998-06-01

It has been hypothesized that natural selection reduces the "genetic load" of deleterious alleles from populations that inbreed during bottlenecks, thereby ameliorating impacts of future inbreeding. We tested the efficiency with which natural selection purges deleterious alleles from three subspecies of Peromyscus polionotus during 10 generations of laboratory inbreeding by monitoring pairing success, litter size, viability, and growth in 3604 litters produced from 3058 pairs. In P. p. subgriseus, there was no reduction across generations in inbreeding depression in any of the fitness components. Strongly deleterious recessive alleles may have been removed previously during episodes of local inbreeding in the wild, and the residual genetic load in this population was not further reduced by selection in the lab. In P. p. rhoadsi, four of seven fitness components did show a reduction of the genetic load with continued inbreeding. The average reduction in the genetic load was as expected if inbreeding depression in this population is caused by highly deleterious recessive alleles that are efficiently removed by selection. For P. p. leucocephalus a population that experiences periodic bottlenecks in the wild, the effect of further inbreeding in the laboratory was to exacerbate rather than reduce the genetic load. Recessive deleterious alleles may have been removed from this population during repeated bottlenecks in the wild; the population may be close to a threshold level of heterozygosity below which fitness declines rapidly. Thus, the effects of selection on inbreeding depression varied substantially among populations, perhaps due to different histories of inbreeding and selection. © 1998 The Society for the Study of Evolution.

Conducted noise analysis and protection of 45 kJ/s, ±50 kV capacitor charging power supply when interfaced with repetitive Marx based pulse power system

NASA Astrophysics Data System (ADS)

Naresh, P.; Patel, Ankur; Sharma, Archana

2015-09-01

Pulse power systems with highly dynamic loads like klystron, backward wave oscillator (BWO), and magnetron generate highly dynamic noise. This noise leads to frequent failure of controlled switches in the inverter stage of charging power supply. Designing a reliable and compatible power supply for pulse power applications is always a tricky job when charging rate is in multiples of 10 kJ/s. A ±50 kV and 45 kJ/s capacitor charging power supply based on 4th order LCLC resonant topology has been developed for a 10 Hz repetitive Marx based system. Conditions for load independent constant current and zero current switching (ZCS) are derived mathematically. Noise generated at load end due to dynamic load is tackled effectively and reduction in magnitude noise voltage is achieved by providing shielding between primary and secondary of high voltage high frequency transformer and with LCLC low pass filter. Shielding scales down the ratio between coupling capacitance (Cc) and the collector-emitter capacitance of insulated gate bi-polar transistor switch, which in turn reduces the common mode noise voltage magnitude. The proposed 4th order LCLC resonant network acts as a low pass filter for differential mode noise in the reverse direction (from load to source). Power supply has been tested repeatedly with 5 Hz repetition rate with repetitive Marx based system connected with BWO load working fine without failure of single switch in the inverter stage.

Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

PubMed Central

Pitarresi, Giuseppe; Tumino, Davide; Mancuso, Antonio

2015-01-01

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously “yielded” samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material. PMID:28793643

Effect of different pushing speeds on bench press.

PubMed

Padulo, J; Mignogna, P; Mignardi, S; Tonni, F; D'Ottavio, S

2012-05-01

The purpose of this study was to investigate the effect on muscular strength after a 3-week training with the bench-press at a fixed pushing of 80-100% maximal speed (FPS) and self-selected pushing speed (SPS). 20 resistance-trained subjects were divided at random in 2 groups differing only regarding the pushing speed: in the FPS group (n=10) it was equal to 80-100% of the maximal speed while in the SPS group (n=10) the pushing speed was self-selected. Both groups were trained twice a week for 3 weeks with a load equal to 85% of 1RM and monitored with the encoder. Before and after the training we measured pushing speed and maximum load. Significant differences between and within the 2 groups were pointed out using a 2-way ANOVA for repeated measures. After 3 weeks a significant improvement was shown especially in the FPS group: the maximum load improved by 10.20% and the maximal speed by 2.22%, while in the SPS group the effect was <1%. This study shows that a high velocity training is required to increase the muscle strength further in subjects with a long training experience and this is possible by measuring the individual performance speed for each load. © Georg Thieme Verlag KG Stuttgart · New York.

Static and dynamic behaviours of railway prestressed concrete sleepers with longitudinal through hole

NASA Astrophysics Data System (ADS)

Ngamkhanong, C.; Kaewunruen, S.; Remennikov, A. M.

2017-10-01

As the crosstie beam in railway track systems, the prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground. Their design takes into account static and dynamic loading conditions. It is evident that prestressed concrete has played a significant role as to maintain the high endurance of the sleepers under low to moderate repeated impact loads. In spite of the most common use of the prestressed concrete sleepers in railway tracks, there have always been many demands from rail engineers to improve serviceability and functionality of concrete sleepers. For example, signalling, fibre optic, equipment cables are often damaged either by ballast corners or by tamping machine. There has been a need to re-design concrete sleeper to cater cables internally so that they would not experience detrimental or harsh environments. Accordingly, this study will investigate the effects of through hole or longitudinal hole on static and dynamic behaviours of concrete sleepers under rail shock loading. The modified compression field theory for ultimate strength design of concrete sleepers will be highlighted in this study. The outcome of this study will enable the new design and calculation methods for prestressed concrete sleepers with holes and web opening that practically benefits civil, track and structural engineers in railway industry.

Increased plantar force and impulse in American football players with high arch compared to normal arch

PubMed Central

Carson, Daniel W.; Myer, Gregory D.; Hewett, Timothy E.; Heidt, Robert S.; Ford, Kevin R.

2014-01-01

Background Risk of overuse injury among athletes is high due in part to repeated loading of the lower extremities. Compared to individuals with normal arch (NA) structure, those with high (HA) or low arch (LA) may be at increased risk of specific overuse injuries, including stress fractures. A high medial longitudinal arch may result in decreased shock absorbing properties due to increased rigidity in foot mechanics. While the effect of arch structure on dynamic function has been examined in straight line walking and running, the relationship between the two during multi-directional movements remains unstudied. Objective The purpose of this study was to determine if differences in plantar loading in football players occur during both walking and pivoting movements. Method Plantar loading was examined in 9 regions of the foot for 26 participants (16 NA, 10 HA). Results High arch athletes demonstrated increased maximum force in the lateral rear foot and medial forefoot, and force time integral in the medial forefoot while walking. HA athletes also demonstrated increased maximum force in the medial rear foot and medial and central forefoot during rapid pivoting. Conclusions The current findings demonstrate that loading patterns differ between football players with high and normal arch structure, which could possibly influence injury risk in this population. PMID:23141809

Delayed elasticity in Zerodur® at room temperature

NASA Astrophysics Data System (ADS)

Pepi, John W.; Golini, Donald

1991-12-01

Much has been written about structural relaxation, viscous flow, delayed elasticity, hysteresis, and other dimensional stability phenomena of glass and ceramics at elevated temperatures. Less has been documented about similar effects at room temperature. The time dependent phenomenon of delayed elasticity exhibited by Zerodur has been studied at room temperature and is presented here. Using a high-performance mechanical profilometer, a delayed strain on the order of 1 percent is realized over a period of a few weeks, under low stress levels. An independent test using optical interferometry validates the results. A comparison of Corning ULE silica glass is also made. The effect is believed to be related to the alkali oxide content of the glass ceramic and rearrangement of the ion groups within the structure during stress. The effect, apparent under externally applied load, is elastic and repeatable, that is, no hysteresis of permanent set, as measured at elevated temperature, is evidenced within measurement capabilities. Nonetheless, it must be accounted for in determining the magnitude of distortion under load (delayed elastic creep) and upon load removal (delayed elastic recovery). This is particularly important for large lightweight optics which might undergo large strain during fabrication and environmental loading, such as experienced in gravity release or in dynamic control of active optics.

PCNA function in the activation and strand direction of MutLα endonuclease in mismatch repair

PubMed Central

Pluciennik, Anna; Dzantiev, Leonid; Iyer, Ravi R.; Constantin, Nicoleta; Kadyrov, Farid A.; Modrich, Paul

2010-01-01

MutLα (MLH1–PMS2) is a latent endonuclease that is activated in a mismatch-, MutSα-, proliferating cell nuclear antigen (PCNA)-, replication factor C (RFC)-, and ATP-dependent manner, with nuclease action directed to the heteroduplex strand that contains a preexisting break. RFC depletion experiments and use of linear DNAs indicate that RFC function in endonuclease activation is limited to PCNA loading. Whereas nicked circular heteroduplex DNA is a good substrate for PCNA loading and for endonuclease activation on the incised strand, covalently closed, relaxed circular DNA is a poor substrate for both reactions. However, covalently closed supercoiled or bubble-containing relaxed heteroduplexes, which do support PCNA loading, also support MutLα activation, but in this case cleavage strand bias is largely abolished. Based on these findings we suggest that PCNA has two roles in MutLα function: The clamp is required for endonuclease activation, an effect that apparently involves interaction of the two proteins, and by virtue of its loading orientation, PCNA determines the strand direction of MutLα incision. These results also provide a potential mechanism for activation of mismatch repair on nonreplicating DNA, an effect that may have implications for the somatic phase of triplet repeat expansion. PMID:20713735

Does Ferrule Effect Affect Implant-Abutment Stability?

PubMed

Mohajerfar, Maryam; Beyabanaki, Elaheh; Geramy, Allahyar; Siadat, Hakimeh; Alikhasi, Marzieh

2016-12-01

This study investigated the influence of placing implant-supported crowns on the torque loss of the abutment screw before and after loading. Twenty implant-abutment assemblies were randomly assigned to two groups. The first group was consisted of abutments with abutment-level finishing line (abutment-level), and in the second group the crown margin was placed on the implant shoulder (implant-level). Initial torque loss was recorded for all specimens. After 500000 cyclic load of 75 N and frequency of 2 Hz, post loading torque loss was recorded. Finite element model of each group was also modeled and screw energy, and stress were analyzed and compared between two groups. ANOVA for repeated measurements showed that the torque loss did not change significantly after cyclic loading (P=0.73). Crown margin also had no significant effect on the torque loss (P=0.56). However, the energy and stress of screw in abutment-level model (4.49 mJ and 22.74 MPa) was higher than implant-level model (3.52 mJ and 20.81 MPa). Although embracing the implant with crown produced less stress and energy in the abutment-implant screw, it did not have any significant influence on the torque loss of the screw. Copyright© 2016 Dennis Barber Ltd

Analysis of Rail Vehicle Suspension Spring with Special Emphasis on Curving, Tracking and Tractive Efforts

NASA Astrophysics Data System (ADS)

Kumbhalkar, M. A.; Bhope, D. V.; Vanalkar, A. V.

2016-09-01

The dynamics of the rail vehicle represents a balance between the forces acting between wheel and rail, the inertia forces and the forces exerted by suspension and articulation. Axial loading on helical spring causes vertical deflection at straight track but failures calls to investigate for lateral and longitudinal loading at horizontal and vertical curves respectively. Goods carrying vehicle has the frequent failures of middle axle inner suspension spring calls for investigation. The springs are analyzed for effect of stress concentration due to centripetal force and due to tractive and breaking effort. This paper also discusses shear failure analysis of spring at curvature and at uphill at various speeds for different loading condition analytically and by finite element analysis. Two mass rail vehicle suspension systems have been analyzed for vibration responses analytically using mathematical tool Matlab Simulink and the same will be evaluated using FFT vibration analyzer to find peak resonance in vertical, lateral and longitudinal direction. The results prove that the suspension acquires high repeated load in vertical and lateral direction due to tracking and curving causes maximum stress concentration on middle axle suspension spring as height of this spring is larger than end axle spring in primary suspension system and responsible for failure of middle axle suspension spring due to high stress acquisition.

A New Load Residual Threshold Definition for the Evaluation of Wind Tunnel Strain-Gage Balance Data

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Volden, T.

2016-01-01

A new definition of a threshold for the detection of load residual outliers of wind tunnel strain-gage balance data was developed. The new threshold is defined as the product between the inverse of the absolute value of the primary gage sensitivity and an empirical limit of the electrical outputs of a strain{gage. The empirical limit of the outputs is either 2.5 microV/V for balance calibration or check load residuals. A reduced limit of 0.5 microV/V is recommended for the evaluation of differences between repeat load points because, by design, the calculation of these differences removes errors in the residuals that are associated with the regression analysis of the data itself. The definition of the new threshold and different methods for the determination of the primary gage sensitivity are discussed. In addition, calibration data of a six-component force balance and a five-component semi-span balance are used to illustrate the application of the proposed new threshold definition to different types of strain{gage balances. During the discussion of the force balance example it is also explained how the estimated maximum expected output of a balance gage can be used to better understand results of the application of the new threshold definition.

Changes in the state of heat-resistant steel induced by repeated hot deformation

NASA Astrophysics Data System (ADS)

Lyubimova, Lyudmila L.; Fisenko, Roman N.; Tashlykov, Alexander A.; Tabakaev, Roman B.

2018-01-01

This work deals with the problems of structural regeneration by thermal restoration treatment (TRT). These include the lack of a structural sign showing that TRT is possible, a consensus on TRT modes, the data on the necessary relaxation depth of residual stresses, or criteria of structural restoration. Performing a TRT without solving these problems may deteriorate the properties of steel or even accelerate its destruction. With this in view, the purpose of this work is to determine experimentally how the residual stress state changes under thermal and mechanical loads in order to specify the signs of the restoration of structure and structural stability. The object of this research is unused 12Cr1MoV steel that has been aged naturally for 13 years. Using X-ray dosimetry with X-ray spectral analysis, we study the distribution of internal residual stresses of the first kind during the repeated hot deformation. After repeated thermal deformation, the sample under study transforms from a viscoelastic Maxwell material into a Kelvin-Voigt material, which facilitates structural stabilization. A sign of this is the relaxation limit increase, prevention of continuous decay of an α-solid solution of iron and restoration of the lattice parameter.

Abrasion-Resistant Coating for Flexible Insulation

NASA Technical Reports Server (NTRS)

Mui, D.; Headding, R. E.

1986-01-01

Ceramic coating increases durability and heat resistance of flexible high-temperature insulation. Coating compatible with quartz-fabric insulation allowing it to remain flexible during and after repeated exposures to temperatures of 1,800 degree F (982 degree C). Prevents fabric from becoming brittle while increasing resistance to aerodynamic abrasion and loading. Coating consists of penetrating precoat and topcoat. Major ingredients high-purity colloidal silica binder and ground silica filler, which ensure stability and compatibility with fabric at high temperatures. Both precoat and topcoat cured at room temperature.

Mechanical properties of a nitrogen-bearing austenitic steel during static and cycle deformation

NASA Astrophysics Data System (ADS)

Blinov, E. V.; Terent'ev, V. F.; Prosvirnin, D. V.

2016-09-01

The mechanical properties of a nitrogen-bearing corrosion-resistant austenitic steel containing 0.311% nitrogen have been studied during static and cyclic deformation. It is found that the steel having an ultimate strength of 930 MPa exhibits a plasticity of 33%. The endurance limit under repeated tension at 106 loading cycles is 400 MPa. The propagation of a fatigue crack at low and high amplitudes of cyclic deformation follows a ductile fracture mechanism with the presence of fatigue grooves.

[Mantle dentin as biomodel of materials for structural teeth restoration].

PubMed

Starodubova, A V; Vinnichenko, Yu A; Pourovskaya, I Ya; Rusanov, F S

The article describes a structural element of natural teeth - mantle dentin. It has been shown that the presence of this element in the structure of a natural tooth largely ensures its strength under the influence of repeated loads in a functional oral environment and arrests crack growth at the enamel/dentine interface. This later effect is explained by the influence of a thin layer of mantle dentine, which has physical and mechanical characteristics different from that of the main dentin.

Rate-Dependent Homogenization Based Continuum Plasticity Damage Model for Dendritic Cast Aluminum Alloys

DTIC Science & Technology

2011-01-01

0.25 s−1 to 0.75 s−1 The return mapping algorithm consists of an initial elastic predictor step, where the elastic response is assumed and the stresses...18 different loadings are used. The parameters F, G, H are solved by an iterative algorithm with C = 3. The step is repeated for different values of...a. REPORT unclassified b. ABSTRACT unclassified c . THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 c⃝

Non-pulsed electrochemical impregnation of flexible metallic battery plaques

DOEpatents

Maskalick, Nicholas J.

1982-01-01

A method of loading active battery material into porous, flexible, metallic battery plaques, comprises the following steps: precipitating nickel hydroxide active material within the plaque, by making the plaque cathodic, at a high current density, in an electro-precipitation cell also containing a consumable nickel anode and a solution comprising nickel nitrate, having a pH of between 2.0 and 2.8; electrochemically oxidizing the precipitate in caustic formation solution; and repeating the electro-precipitation step at a low current density.

Fretting Fatigue Analysis of Additively Manufactured Blade Root Made of Intermetallic Ti-48Al-2Cr-2Nb Alloy at High Temperature.

PubMed

Lavella, Mario; Botto, Daniele

2018-06-21

Slots in the disk of aircraft turbines restrain the centrifugal load of blades. Contact surfaces between the blade root and the disk slot undergo high contact pressure and relative displacement that is the typical condition in which fretting occurs. The load level ranges from zero to the maximum during take-off. This cycle is repeated for each mission. In this paper, a fretting fatigue analysis of additively manufactured blades is presented. Blades are made of an intermetallic alloy γTiAl. Fretting fatigue experiments were performed at a frequency of 0.5 Hz and at a temperature of 640 °C to match the operating condition of real blades. The minimum load was fixed at 0.5 KN and three maximum loads were applied, namely 16, 18 and 20 kN. Both an analytical and a two-dimensional finite element model were used to evaluate the state of stress at the contact interfaces. The results of the analytical model showed good agreement with the numerical model. Experiments showed that cracks nucleate where the analytical model predicts the maximum contact pressure and the numerical model predicts the maximum equivalent stress. A parametric analysis performed with the analytical model indicates that there exists an optimum geometry to minimize the contact pressure. Tests showed that the component life changed dramatically with the maximum load variation. Optical topography and scanning electron microscopy (SEM) analysis reveals information about the damage mechanism.

In vitro method for assessing the biomechanics of the patellofemoral joint following total knee arthroplasty.

PubMed

Coles, L G; Gheduzzi, S; Miles, A W

2014-12-01

The patellofemoral joint is a common site of pain and failure following total knee arthroplasty. A contributory factor may be adverse patellofemoral biomechanics. Cadaveric investigations are commonly used to assess the biomechanics of the joint, but are associated with high inter-specimen variability and often cannot be carried out at physiological levels of loading. This study aimed to evaluate the suitability of a novel knee simulator for investigating patellofemoral joint biomechanics. This simulator specifically facilitated the extended assessment of patellofemoral joint biomechanics under physiological levels of loading. The simulator allowed the knee to move in 6 degrees of freedom under quadriceps actuation and included a simulation of the action of the hamstrings. Prostheses were implanted on synthetic bones and key soft tissues were modelled with a synthetic analogue. In order to evaluate the physiological relevance and repeatability of the simulator, measurements were made of the quadriceps force and the force, contact area and pressure within the patellofemoral joint using load cells, pressure-sensitive film, and a flexible pressure sensor. The results were in agreement with those previously reported in the literature, confirming that the simulator is able to provide a realistic physiological loading situation. Under physiological loading, average standard deviations of force and area measurements were substantially lower and comparable to those reported in previous cadaveric studies, respectively. The simulator replicates the physiological environment and has been demonstrated to allow the initial investigation of factors affecting patellofemoral biomechanics following total knee arthroplasty. © IMechE 2014.

Early stage fatigue damage occurs in bovine tendon fascicles in the absence of changes in mechanics at either the gross or micro-structural level

PubMed Central

Shepherd, Jennifer H.; Riley, Graham P.; Screen, Hazel R.C.

2014-01-01

Many tendon injuries are believed to result from repetitive motion or overuse, leading to the accumulation of micro-damage over time. In vitro fatigue loading can be used to characterise damage during repeated use and investigate how this may relate to the aetiology of tendinopathy. This study considered the effect of fatigue loading on fascicles from two functionally distinct bovine tendons: the digital extensor and deep digital flexor. Micro-scale extension mechanisms were investigated in fascicles before or after a period of cyclic creep loading, comparing two different measurement techniques – the displacement of a photo-bleached grid and the use of nuclei as fiducial markers. Whilst visual damage was clearly identified after only 300 cycles of creep loading, these visual changes did not affect either gross fascicle mechanics or fascicle microstructural extension mechanisms over the 900 fatigue cycles investigated. However, significantly greater fibre sliding was measured when observing grid deformation rather than the analysis of nuclei movement. Measurement of microstructural extension with both techniques was localised and this may explain the absence of change in microstructural deformation in response to fatigue loading. Alternatively, the data may demonstrate that fascicles can withstand a degree of matrix disruption with no impact on mechanics. Whilst use of a photo-bleached grid to directly measure the collagen is the best indicator of matrix deformation, nuclei tracking may provide a better measure of the strain perceived directly by the cells. PMID:25001495

Atmospheric pressure loading parameters from very long baseline interferometry observations

NASA Technical Reports Server (NTRS)

Macmillan, D. S.; Gipson, John M.

1994-01-01

Atmospheric mass loading produces a primarily vertical displacement of the Earth's crust. This displacement is correlated with surface pressure and is large enough to be detected by very long baseline interferometry (VLBI) measurements. Using the measured surface pressure at VLBI stations, we have estimated the atmospheric loading term for each station location directly from VLBI data acquired from 1979 to 1992. Our estimates of the vertical sensitivity to change in pressure range from 0 to -0.6 mm/mbar depending on the station. These estimates agree with inverted barometer model calculations (Manabe et al., 1991; vanDam and Herring, 1994) of the vertical displacement sensitivity computed by convolving actual pressure distributions with loading Green's functions. The pressure sensitivity tends to be smaller for stations near the coast, which is consistent with the inverted barometer hypothesis. Applying this estimated pressure loading correction in standard VLBI geodetic analysis improves the repeatability of estimated lengths of 25 out of 37 baselines that were measured at least 50 times. In a root-sum-square (rss) sense, the improvement generally increases with baseline length at a rate of about 0.3 to 0.6 ppb depending on whether the baseline stations are close to the coast. For the 5998-km baseline from Westford, Massachusetts, to Wettzell, Germany, the rss improvement is about 3.6 mm out of 11.0 mm. The average rss reduction of the vertical scatter for inland stations ranges from 2.7 to 5.4 mm.

Repeated wildfires alter forest recovery of mixed-conifer ecosystems.

PubMed

Stevens-Rumann, Camille; Morgan, Penelope

2016-09-01

Most models project warmer and drier climates that will contribute to larger and more frequent wildfires. However, it remains unknown how repeated wildfires alter post-fire successional patterns and forest structure. Here, we test the hypothesis that the number of wildfires, as well as the order and severity of wildfire events interact to alter forest structure and vegetation recovery and implications for vegetation management. In 2014, we examined forest structure, composition, and tree regeneration in stands that burned 1-18 yr before a subsequent 2007 wildfire. Three important findings emerged: (1) Repeatedly burned forests had 15% less woody surface fuels and 31% lower tree seedling densities compared with forests that only experienced one recent wildfire. These repeatedly burned areas are recovering differently than sites burned once, which may lead to alternative ecosystem structure. (2) Order of burn severity (high followed by low severity compared with low followed by high severity) did influence forest characteristics. When low burn severity followed high, forests had 60% lower canopy closure and total basal area with 92% fewer tree seedlings than when high burn severity followed low. (3) Time between fires had no effect on most variables measured following the second fire except large woody fuels, canopy closure and tree seedling density. We conclude that repeatedly burned areas meet many vegetation management objectives of reduced fuel loads and moderate tree seedling densities. These differences in forest structure, composition, and tree regeneration have implications not only for the trajectories of these forests, but may reduce fire intensity and burn severity of subsequent wildfires and may be used in conjunction with future fire suppression tactics. © 2016 by the Ecological Society of America.

Toward Standardization of Epstein-Barr Virus DNA Load Monitoring: Unfractionated Whole Blood as Preferred Clinical Specimen

PubMed Central

Stevens, Servi J. C.; Pronk, Inge; Middeldorp, Jaap M.

2001-01-01

Epstein-Barr virus (EBV) DNA load monitoring in peripheral blood has been shown to be a useful tool for the diagnosis of aberrant EBV infections. In the present study we compared the relative diagnostic values of EBV DNA load monitoring in unfractionated whole blood and simultaneously obtained serum or plasma samples from Burkitt's lymphoma (BL) patients, transplant recipients, human immunodeficiency virus (HIV)-infected individuals, and infectious mononucleosis (IM) patients by a quantitative competitive PCR (Q-PCR). The EBV DNA load in BL patients was mainly situated in the cellular blood compartment (up to 4.5 × 106 copies/ml). EBV DNA loads in unfractionated whole blood and parallel serum samples showed no correlation. In transplant recipients, IM patients, and HIV-infected patients, the EBV burden in the circulation was almost exclusively restricted to the cellular blood compartment, because serum or plasma samples from these patients yielded negative results by Q-PCR, despite high viral loads in corresponding whole-blood samples. A 10-fold more sensitive but qualitative BamHI-W-repeat PCR occasionally revealed the presence of EBV at <2,000 copies of EBV DNA per ml of serum. Spiking of 100 copies of EBV DNA in samples with negative Q-PCR results excluded the presence of inhibitory factors in serum or plasma that influenced the Q-PCR result. Serum samples from all populations were often positive for β-globin DNA, indicating cell damage in vivo or during serum preparation. We conclude that serum is an undesirable clinical specimen for EBV DNA load monitoring because it omits the presence of cell-associated virus and uncontrolled cell lysis may give irreproducible results or overestimation of the DNA load. Unfractionated whole blood is strongly preferred since it combines all blood compartments that may harbor EBV and it best reflects the absolute viral burden in the patient's circulation. PMID:11283029

Biomechanical Comparison of an Intramedullary and Extramedullary Free-Tissue Graft Reconstruction of the Acromioclavicular Joint Complex

PubMed Central

Garg, Rishi; Javidan, Pooya; Lee, Thay Q.

2013-01-01

Background Several different surgical techniques have been described to address the coracoclavicular (CC) ligaments in acromioclavicular (AC) joint injuries. However, very few techniques focus on reconstructing the AC ligaments, despite its importance in providing stability. The purpose of our study was to compare the biomechanical properties of two free-tissue graft techniques that reconstruct both the AC and CC ligaments in cadaveric shoulders, one with an extramedullary AC reconstruction and the other with an intramedullary AC reconstruction. We hypothesized intramedullary AC reconstruction will provide greater anteroposterior translational stability and improved load to failure characteristics than an extramedullary technique. Methods Six matched cadaveric shoulders underwent translational testing at 10 N and 15 N in the anteroposterior and superoinferior directions, under AC joint compression loads of 10 N, 20 N, and 30 N. After the AC and CC ligaments were transected, one of the specimens was randomly assigned the intramedullary free-tissue graft reconstruction while its matched pair received the extramedullary graft reconstruction. Both reconstructed specimens then underwent repeat translational testing, followed by load to failure testing, via superior clavicle distraction, at a rate of 50 mm/min. Results Intramedullary reconstruction provided significantly greater translational stability in the anteroposterior direction than the extramedullary technique for four of six loading conditions (p < 0.05). There were no significant differences in translational stability in the superoinferior direction for any loading condition. The intramedullary reconstructed specimens demonstrated improved load to failure characteristics with the intramedullary reconstruction having a lower deformation at yield and a higher ultimate load than the extramedullary reconstruction (p < 0.05). Conclusions Intramedullary reconstruction of the AC joint provides greater stability in the anteroposterior direction and improved load to failure characteristics than an extramedullary technique. Reconstruction of the injured AC joint with an intramedullary free tissue graft may provide greater strength and stability than other currently used techniques, allowing patients to have improved clinical outcomes. PMID:24340150

Effects of chronic low back pain, age and gender on vertical spinal creep.

PubMed

Kanlayanaphotporn, R; Trott, P; Williams, M; Fulton, I

2003-05-15

This study investigated the effect of chronic low back pain, age, gender, and time of measurement on the magnitude of vertical spinal creep (VSC) and its recovery. A mixed design, involving three independent variables (chronic low back pain, age, and gender) and one repeated variable (time), was used. One hundred and six subjects of both genders, with and without chronic low back pain, aged between 20 and 60 years, participated in the study. The measurement of VSC and its recovery was performed using a seated stadiometer that allowed continuous measurement of VSC without changing the subject's posture over 25 min. Unloaded VSC was measured during the initial 5 min, followed by 10 min with an additional load of 15% of the subject's body weight and then for a further 10 min after the removal of the load. Subjects were grouped into one of eight categories according to the presence of chronic low back pain, age (20-39 years or 40-60 years) and gender. Repeated measures analysis of variance was computed. A significant increase in VSC with time of measurement was observed (p<0.001). No significant main effects for chronic low back pain, age, or gender were found at any time during the 25-min VSC testing protocol. Significant interactions were found between age and gender during the loaded (p=0.02) and unloaded (p=0.02) phases. A significant interaction was found between chronic low back pain and gender at the end of the unloaded phase (p=0.04). These findings suggest a combined influence of chronic low back pain, age, and gender on VSC and its recovery and that the dominance of each variable changed with the time of the measurement. Thus, subjects who differ in the presence of chronic low back pain, age, and gender should not be combined for statistical analysis of VSC and its recovery.

Clonal origin of Epstein-Barr virus (EBV)-infected T/NK-cell subpopulations in EBV-positive T/NK-cell lymphoproliferative disorders of childhood.

PubMed

Ohga, Shouichi; Ishimura, Masataka; Yoshimoto, Goichi; Miyamoto, Toshihiro; Takada, Hidetoshi; Tanaka, Tamami; Ohshima, Koichi; Ogawa, Yoshiyasu; Imadome, Ken-Ichi; Abe, Yasunobu; Akashi, Koichi; Hara, Toshiro

2011-05-01

In Japan, chronic active Epstein-Barr virus infection (CAEBV) may manifest with infection of T-cells or NK-cells, clonal lymphoid proliferations, and overt lymphoid malignancy. These EBV-positive lymphoproliferative disorders (EBV(+)LPD) of childhood are related to, but distinct from the infectious mononucleosis-like CAEBV seen in Western populations. The clonal nature of viral infection within lymphoid subsets of patients with EBV(+)LPD of childhood is not well described. Viral distribution and clonotype were assessed within T-cell subsets, NK-cells, and CD34(+)stem cells following high purity cell sorting. Six Japanese patients with EBV(+)LPD of childhood (3 T-cell LPD and 3 NK-cell LPD) were recruited. Prior to immunochemotherapy, viral loads and clonal analyses of T-cell subsets, NK-cells, and CD34(+)stem cells were studied by high-accuracy cell sorting (>99.5%), Southern blotting and real-time polymerase chain reaction. Patient 1 had a monoclonal proliferation of EBV-infected γδT-cells and carried a lower copy number of EBV in αβT-cells. Patients 2 and 3 had clonal expansions of EBV-infected CD4(+)T-cells, and lower EBV load in NK-cells. Patients 4, 5 and 6 had EBV(+)NK-cell expansions with higher EBV load than T-cells. EBV-terminal repeats were determined as clonal bands in the minor targeted populations of 5 patients. The size of terminal repeats indicated the same clonotype in minor subsets as in the major subsets of four patients. EBV was not, however, detected in the bone marrow-derived CD34(+)stem cells of patients. A single EBV clonotype may infect multiple NK-cell and T-cell subsets of patients with EBV(+)LPD of childhood. CD34(+)stem cells are spared, suggesting infection of more differentiated elements. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of fatigue on bilateral ground reaction force asymmetries during the squat exercise.

PubMed

Hodges, Stephanie J; Patrick, Ryan J; Reiser, Raoul F

2011-11-01

Physical performance and injury risk have been related to functional asymmetries of the lower extremity. The effect of fatigue on asymmetries is not well understood. The goal of this investigation was to examine asymmetries during fatiguing repetitions and sets of the free-weight barbell back squat exercise. Seventeen healthy recreationally trained men and women (age = 22.3 ± 2.5 years; body mass = 73.4 ± 13.8 kg; squat 8 repetition maximum [8RM] = 113 ± 35% body mass [mean ± SD]) performed 5 sets of 8 repetitions with 90% 8RM while recording bilateral vertical ground reaction force (GRFv). The GRFv asymmetry during the first 2 (R1 and R2) and the last 2 (R7 and R8) repetitions of each set was calculated by subtracting the % load on the right foot from that of the left foot. Most subjects placed more load on their left foot (also their preferred non-kicking foot). Average absolute asymmetry level across all sets was 4.3 ± 2.5 and 3.6 ± 2.3% for R1 and R2 and R7 and R8, respectively. There were no effects of fatigue on GRFv asymmetries in whole-group analysis (n = 17). However, when initially highly symmetric subjects (±1.7% Left-Right) were removed, average absolute GRFv asymmetry dropped from the beginning to the end of a set (n = 12, p = 0.044) as did peak instantaneous GRFv asymmetry when exploring general shifts toward the left or right leg (n = 12, p = 0.042). The GRFv asymmetries were highly repeatable for 8 subjects that repeated the protocol (Cronbach's α ≥ 0.733, p ≤ 0.056). These results suggest that functional asymmetries, though low, are present in healthy people during the squat exercise and remain consistent. Asymmetries do not increase with fatigue, potentially even decreasing, suggesting that healthy subjects load limbs similarly as fatigue increases, exposing each to similar training stimuli.

Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Madaras, Eric I.

2004-01-01

The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for a duration of 10,000 hours are reported.

Safety and efficacy of ritonavir and saquinavir in combination with zidovudine and lamivudine.

PubMed

Michelet, C; Bellissant, E; Ruffault, A; Arvieux, C; Delfraissy, J F; Raffi, F; Bazin, C; Renard, I; Sébille, V; Chauvin, J P; Dohin, E; Cartier, F

1999-06-01

Ritonavir is a potent inhibitor of cytochrome P4503A4 that strongly increases saquinavir bioavailability. In this study we assessed the safety and antiretroviral efficacy of the combination of these two compounds in patients pretreated and receiving continued treatment with zidovudine and lamivudine who were protease inhibitor naive and who had a CD4 cell counts below 200/mm3. In this 48-week pilot study, all patients received 600 mg ritonavir and 400 mg saquinavir twice daily. Administration of zidovudine and lamivudine was continued without a change in previous doses. Viral load, CD4 cell count, and the emergence of resistance to the two protease inhibitors were evaluated repeatedly up to week 48. Sixteen patients were included in the study. Previous nucleoside analog treatment duration was 48+/-22 months (mean +/- SD). Two patients quit taking both protease inhibitors within 2 weeks. The ritonavir dose had to be reduced in 10 other patients because of side effects. Between inclusion and week 48, plasma viremia varied from 4.87+/-0.43 to 3.00+/-1.29 log10 copies/mL and CD4 cell counts ranged from 98+/-61 to 250+/-139/mm3. Ten patients (63%) had viral loads below 200 copies/mL and 7 (44%) had viral loads below 50 copies/mL. A single key mutation that conferred ritonavir resistance I84V and V82A/V developed in two patients. A mutation at codon 54 developed in another patient. These mutations were associated with repeated cessations of antiretroviral treatment. No lipodystrophy was observed. Ritonavir and saquinavir in combination are quite well tolerated and induce a high and sustained antiretroviral efficacy. A four-drug combination that includes these two protease inhibitors should be considered as a first line of treatment in patients with low CD4 cell counts.

Effects of Range of Stress and of Special Notches on Fatigue Properties of Aluminum Alloys Suitable for Airplane Propellers

NASA Technical Reports Server (NTRS)

Dolan, Thomas J

1942-01-01

Laboratory tests were made to obtain information on the load-resisting properties of X76S-T aluminum alloy when subjected to static, impact, and repeated loads. Results are presented from static-load test of unnotched specimens in tension and in torsion and of notched specimens in tension. Charpy impact values obtained from bend tests on notched specimens and tension impact values for both notched and unnotched specimens tested at several different temperatures are included. The endurance limits obtained from repeated bending fatigue tests made on three different types of testing machine are given for unnotched polished specimens, and the endurance limits of notched specimens subjected to six different ranges of bending stress are also reported. The results indicated that: (a) polished rectangular specimens had an endurance limit about 30 percent less than that obtained for round specimens; (b) a comparison of endurance limits obtained from tests on three different types of machine indicated that there was no apparent effect of speed of testing on the endurance limit for the range of speeds used (1,750 to 13,000 rpm). (c) the fatigue strength (endurance limit) of the X76S-T alloy was greatly decreased by the presence of a notch in the specimens; (d) no complete fractures of the entire specimens occurred in notched fatigue specimens when subjected to stress cycles for which the mean stress at the notch during the cycle was a compressive stress; for this test condition a microscopic cracking occurred near the root of the notch and was used as a criterion of failure of the specimen. (e) as the mean stress at the notch was decreased from a tensile (+) stress to a compressive (-) stress, it was found that the alternating stress that could be superimposed on the mean stress in the cycle without causing failure of the specimens was increased.

Dual photon excitation microscopy and image threshold segmentation in live cell imaging during compression testing.

PubMed

Moo, Eng Kuan; Abusara, Ziad; Abu Osman, Noor Azuan; Pingguan-Murphy, Belinda; Herzog, Walter

2013-08-09

Morphological studies of live connective tissue cells are imperative to helping understand cellular responses to mechanical stimuli. However, photobleaching is a constant problem to accurate and reliable live cell fluorescent imaging, and various image thresholding methods have been adopted to account for photobleaching effects. Previous studies showed that dual photon excitation (DPE) techniques are superior over conventional one photon excitation (OPE) confocal techniques in minimizing photobleaching. In this study, we investigated the effects of photobleaching resulting from OPE and DPE on morphology of in situ articular cartilage chondrocytes across repeat laser exposures. Additionally, we compared the effectiveness of three commonly-used image thresholding methods in accounting for photobleaching effects, with and without tissue loading through compression. In general, photobleaching leads to an apparent volume reduction for subsequent image scans. Performing seven consecutive scans of chondrocytes in unloaded cartilage, we found that the apparent cell volume loss caused by DPE microscopy is much smaller than that observed using OPE microscopy. Applying scan-specific image thresholds did not prevent the photobleaching-induced volume loss, and volume reductions were non-uniform over the seven repeat scans. During cartilage loading through compression, cell fluorescence increased and, depending on the thresholding method used, led to different volume changes. Therefore, different conclusions on cell volume changes may be drawn during tissue compression, depending on the image thresholding methods used. In conclusion, our findings confirm that photobleaching directly affects cell morphology measurements, and that DPE causes less photobleaching artifacts than OPE for uncompressed cells. When cells are compressed during tissue loading, a complicated interplay between photobleaching effects and compression-induced fluorescence increase may lead to interpretations in cell responses to mechanical stimuli that depend on the microscopic approach and the thresholding methods used and may result in contradictory interpretations. Copyright © 2013 Elsevier Ltd. All rights reserved.

Deviations of frequency and the mode of vibration of commercially available whole-body vibration training devices.

PubMed

Kaeding, T S

2015-06-01

Research in the field of whole body vibration (WBV) training and the use of it in practice might be hindered by the fact that WBV training devices generate and transmit frequencies and/or modes of vibration which are different to preset adjustments. This research project shall clarify how exact WBV devices apply the by manufacturer information promised preset frequency and mode of vibration. Nine professional devices for WBV training were tested by means of a tri-axial accelerometer. The accelerations of each device were recorded under different settings with a tri-axial accelerometer. Beneath the measurement of different combinations of preset frequency and amplitude the repeatability across 3 successive measurements with the same preset conditions and one measurement under loaded condition were carried out. With 3 exceptions (both Board 3000 & srt medical PRO) we did not find noteworthy divergences between preset and actual applied frequencies. In these 3 devices we found divergences near -25%. Loading the devices did not affect the applied frequency or mode of vibration. There were no important divergences measurable for the applied frequency and mode of vibration regarding repeatability. The results of our measurements cannot be generalized as we only measured one respectively at most two devices of one model in terms of a random sample. Based on these results we strongly recommend that user in practice and research should analyse their WBV training devices regarding applied frequency and mode of vibration.

Molecular dynamics simulation of thermomechanical properties of montmorillonite crystal. 3. montmorillonite crystals with PEO oligomer intercalates.

PubMed

Mazo, Mikhail A; Manevitch, Leonid I; Gusarova, Elena B; Shamaev, Mikhail Yu; Berlin, Alexander A; Balabaev, Nikolay K; Rutledge, Gregory C

2008-03-27

We present the results of molecular dynamics (MD) simulation of the structure and thermomechanical behavior of Wyoming-type Na+-montmorillonite (MMT) with poly(ethylene oxide) (PEO) oligomer intercalates. Periodic boundary conditions in all three directions and simulation cells containing two MMT lamellae [Si248Al8][Al112Mg16]O640[OH]128 oriented parallel to the XY-plane were used. The interlamellar space, or gallery, between neighboring MMT lamellae was populated by 24 Na+ counterions and PEO macromolecules of different lengths, ranging from 2 up to 240 repeat units. We considered three different loadings of PEO within the gallery: 80, 160, and 240 repeat units, corresponding to 13, 23, and 31 wt % PEO based on total mass of the nanocomposite, respectively. In the cases of 13 and 23 wt %, the polymer chains formed one or two well-defined amorphous layers with interlayer distances of 1.35 and 1.8 nm, respectively. We have observed also formation of a wider monolayer gallery with interlayer distances of 1.6 nm. Three-layer PEO films formed in the case of 31 wt % loading. The thermal properties were analyzed over the range 300-400 K, and the isothermal linear compressibility, transversal moduli, and shear moduli were calculated at 300 K. These properties are compared with the results of our simulation of thermal and mechanical properties of MMT crystal with galleries filled by one or two water layers as well as with those of an isolated clay nanoplate.

Probabilistic structural mechanics research for parallel processing computers

NASA Technical Reports Server (NTRS)

Sues, Robert H.; Chen, Heh-Chyun; Twisdale, Lawrence A.; Martin, William R.

1991-01-01

Aerospace structures and spacecraft are a complex assemblage of structural components that are subjected to a variety of complex, cyclic, and transient loading conditions. Significant modeling uncertainties are present in these structures, in addition to the inherent randomness of material properties and loads. To properly account for these uncertainties in evaluating and assessing the reliability of these components and structures, probabilistic structural mechanics (PSM) procedures must be used. Much research has focused on basic theory development and the development of approximate analytic solution methods in random vibrations and structural reliability. Practical application of PSM methods was hampered by their computationally intense nature. Solution of PSM problems requires repeated analyses of structures that are often large, and exhibit nonlinear and/or dynamic response behavior. These methods are all inherently parallel and ideally suited to implementation on parallel processing computers. New hardware architectures and innovative control software and solution methodologies are needed to make solution of large scale PSM problems practical.

An ergonomics approach model to prevention of occupational musculoskeletal injuries.

PubMed

Koltan, Altan

2009-01-01

The objective of this study was to prevent occupational musculoskeletal injuries. Our workers stacked boxes of ceramics weighing 10-27 kg, making low back pain common in our enterprise. In all the stacking stations, recommended weight limits (RWL) were separately calculated using the revised National Institute for Occupational Health lifting equation. Since the boxes weighed significantly more than the RWL, we developed a new ergonomic design that completely changed the stacking process. The load put on the workers' waist vertebrae in the new and the old stacking methods was compared to evaluate the success of the new ergonomic design, using Newton's third law of motion. Thanks to the new ergonomic design, the load on the workers' vertebrae decreased by 80%. Due to its simple technology and its very low cost compared to robots, the new ergonomic design can be commonly used in enterprises with repeated and constraining stacking.

Determination of stores pointing error due to wing flexibility under flight load

NASA Technical Reports Server (NTRS)

Lokos, William A.; Bahm, Catherine M.; Heinle, Robert A.

1995-01-01

The in-flight elastic wing twist of a fighter-type aircraft was studied to provide for an improved on-board real-time computed prediction of pointing variations of three wing store stations. This is an important capability to correct sensor pod alignment variation or to establish initial conditions of iron bombs or smart weapons prior to release. The original algorithm was based upon coarse measurements. The electro-optical Flight Deflection Measurement System measured the deformed wing shape in flight under maneuver loads to provide a higher resolution database from which an improved twist prediction algorithm could be developed. The FDMS produced excellent repeatable data. In addition, a NASTRAN finite-element analysis was performed to provide additional elastic deformation data. The FDMS data combined with the NASTRAN analysis indicated that an improved prediction algorithm could be derived by using a different set of aircraft parameters, namely normal acceleration, stores configuration, Mach number, and gross weight.

Myristicin and phenytoin toxicity in an infant

PubMed Central

Sivathanu, Shobhana; Sampath, Sowmya; David, Henry Suresh; Rajavelu, Kulandai Kasthuri

2014-01-01

A developmentally normal infant presented with repeated episodes of afebrile status epilepticus following nutmeg ingestion. He had developed two episodes of afebrile status epilepticus and had received different treatments earlier, but the details of treatment were not available. On admission, he redeveloped convulsions and loading doses of phenytoin, phenobarbitone and midazolam were administered. However, seizures persisted and extrapyramidal movements, nystagmus and visual dysfunction were noted. Iatrogenic phenytoin toxicity was considered and confirmed by drug levels. His symptoms completely disappeared after discontinuation of phenytoin therapy. The initial seizures were attributed to myristicin, an active component of nutmeg, because of the temporal association. However, the subsequent seizures were due to phenytoin toxicity caused by administration of multiple loading doses. This case highlights that nutmeg, a spice, can cause serious toxic effects like status epilepticus. Furthermore, treatment of status epilepticus with phenytoin can cause iatrogenic seizures due to its narrow therapeutic range. PMID:24903724

A new approach to assess movements and isometric postures of spine and trunk at the workplace.

PubMed

Wunderlich, Max; Rüther, Thomas; Essfeld, Dieter; Erren, Thomas C; Piekarski, Claus; Leyk, Dieter

2011-08-01

Low back pain is regarded as the primary cause of occupational disability in many countries worldwide. However, there is a lack of valid assessment of kinematic spine and trunk parameters to provide further insight into occupational spine loads. A new 3-dimensional mobile measurement system (3D-SpineMoveGuard) was developed and evaluated by means of repeated dynamic and isometric trunk positions by 10 male and 10 female volunteers. The interclass correlation coefficient indicates high test-retest reliability (r = 0.975-0.999) of the 3D-SpineMoveGuard. Moreover, analysis of validity revealed almost identical results for the new measurement system. The evaluation study indicates a good scientific quality for the use in occupational task analyses. The objective assessment of indirectly measured spine and trunk kinematics will give further insight to predict and prevent job-related spine loads.

Binaural Simulation Experiments in the NASA Langley Structural Acoustics Loads and Transmission Facility

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Silcox, Richard (Technical Monitor)

2001-01-01

A location and positioning system was developed and implemented in the anechoic chamber of the Structural Acoustics Loads and Transmission (SALT) facility to accurately determine the coordinates of points in three-dimensional space. Transfer functions were measured between a shaker source at two different panel locations and the vibrational response distributed over the panel surface using a scanning laser vibrometer. The binaural simulation test matrix included test runs for several locations of the measuring microphones, various attitudes of the mannequin, two locations of the shaker excitation and three different shaker inputs including pulse, broadband random, and pseudo-random. Transfer functions, auto spectra, and coherence functions were acquired for the pseudo-random excitation. Time histories were acquired for the pulse and broadband random input to the shaker. The tests were repeated with a reflective surface installed. Binary data files were converted to universal format and archived on compact disk.

Longitudinal study on potential neurotoxic effects of aluminium: II. Assessment of exposure and neurobehavioral performance of Al welders in the automobile industry over 4 years.

PubMed

Kiesswetter, Ernst; Schäper, M; Buchta, M; Schaller, K H; Rossbach, B; Kraus, T; Letzel, S

2009-11-01

This is the second of two parallel longitudinal studies investigating Al exposure and neurobehavioral health of Al welders over 4 years. While the first published study in the trail and truck construction industry examined the neurobehavioral development of Al welders from age 41-45 in the group mean (Kiesswetter et al. in Int Arch Occup Environ Health 81:41-67, 2007), the present study in the automobile industry followed the development from 35 to 39. Although no conspicuous neurobehavioral developments were detected in the first study, which furthermore exhibited the higher exposure, it cannot be excluded that exposure effects appear in earlier life and exposure stages. The longitudinal study is based on a repeated measurement design comprising 4 years with three measurements in 2 years intervals. 92 male Al welders in the automobile industry were compared with 50 non-exposed construction workers of the same industry and of similar age. The repeated measurements included total dust in air, and Al pre- and post-shift plasma and urine samples. Neurobehavioral methods comprised symptoms, verbal intelligence, logic thinking, psychomotor behavior, memory, and attention. The computer aided tests came from the Motor Performance Series and the European Neurobehavioral Evaluation System. The courses of neurobehavioral changes were analyzed with multivariate covariance-analytical methods considering the covariates age, indicators of 'a priori' intelligence differences (education or markers of 'premorbid' intelligence), and alcohol consumption (carbohydrate-deficient transferrin in plasma). Additionally, the interrelationship, reliability and validity of biomonitoring measures were examined. The mean environmental dust load during welding, 0.5-0.8 mg/m(3), and the mean internal load of the welders (pre-shift: 23-43 microg Al/g creatinine in urine; 5-9 microg Al/l plasma) were significantly lower than in the parallel study. Under low exposure, the stability of biomonitoring measures was reduced, but the Al load differed significantly between Al welders and referents. It could not be shown that the development of neurobehavioral performances over the 4-year period differed between both groups. Mainly, markers of premorbid intelligence and age were related to neurobehavioral performance differences but not Al exposure. The biomonitoring and neurobehavioral results are in line with the results of the first published study. The repeated measurement models of both studies showed no adverse neurobehavioral effects of Al welding. A modular lifetime-oriented research concept is outlined aiming at the investigation of sequential periods of exposure life with special focus on the biologically most sensitive phases like first exposure and old age.

Postprandial glucose and insulin levels in type 2 diabetes mellitus patients after consumption of ready-to-eat mixed meals.

PubMed

Manios, Yannis; Moschonis, George; Mavrogianni, Christina; Tsoutsoulopoulou, Konstantina; Kogkas, Stergios; Lambrinou, Christina-Paulina; Efstathopoulou, Eirini

2017-04-01

To compare the effects of three ready-to-eat mixed meals, with a high fiber content and low glycemic index, on postprandial glycemic and insulinemic response in patients with Type 2 diabetes mellitus (T2DM). The current study followed a prospective, three-way, cross-over design. Twenty-four patients with T2DM consumed three ready-to-eat mixed meals, i.e., "wild greens pie" (meal 1), "chicken burgers with boiled vegetables" (meal 2) and "vegetable moussaka" (meal 3) and an oral glucose load, all providing 50 g of carbohydrates. Venous blood was collected at 0, 30, 60, 90 and 120 min postprandial. Statistical analyses included repeated measures analysis of variance and calculations of the area under the glucose and insulin curves (AUC) for each one of the test meals and the oral glucose load. Patients consuming each one of the three mixed meals showed better postprandial glycemic responses compared to the oral glucose load (P < 0.001). Furthermore, patients consuming meal 3 showed a better insulinemic response compared to the oral glucose load and meal 1, after 60 and 120 min postprandial, respectively (P < 0.05). In addition, the increase observed in HOMA-IR values from T0 to T120 was significantly lower for meal 3, compared to the oral glucose load (P < 0.001). The three ready-to-eat mixed meals examined in the present study were found to elicit significantly lower glycemic responses compared to the oral glucose load in diabetic patients. The mixed meals examined in the present study could be proposed as effective, palatable and practical solutions for diabetics for glucose control.

Effects of turf and cleat footwear on plantar load distributions in adolescent American football players during resisted pushing.

PubMed

Taylor, Jeffrey B; Nguyen, Anh-Dung; Griffin, Janet R; Ford, Kevin R

2018-06-01

Metatarsal and midfoot injuries are common in American football. Footwear design may influence injury rates by altering plantar foot loading patterns in these regions. The purpose of this study was to determine the effect of cleat design on in-shoe plantar foot loading during a football-specific, resisted pushing task. Twenty competitive football players (age 14.7 ± 1.8 years, height 1.72 ± 0.10 m, and mass 71.8 ± 26.9 kg) completed three trials of pushing a weighted sled at maximal effort in a standard shoe (CLEAT) and artificial turf-specific shoe (TURF), with flexible in-shoe force measuring insoles. Repeated measures ANOVAs identified mean differences in maximum force and relative load under all regions of the foot. Results showed higher forces in the CLEAT under the medial (p < 0.001) and lateral (p = 0.004) midfoot, central (p = 0.007) and lateral (p < 0.001) forefoot, and lesser toes (p = 0.01), but lower forces in the hallux (p = 0.02) compared to the TURF shoe. Additionally, relative loading was higher in the CLEAT under the medial (p < 0.001) and lateral (p = 0.002) midfoot and lateral (p < 0.001) forefoot, but lower in the medial forefoot (p = 0.006) and hallux (p < 0.001) compared to the TURF shoe. The two shoes elicited distinct plantar loading profiles and may influence shoe selection decisions during injury prevention or rehabilitation practices.

Lifetime Reliability Prediction of Ceramic Structures Under Transient Thermomechanical Loads

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Jadaan, Osama J.; Gyekenyesi, John P.

2005-01-01

An analytical methodology is developed to predict the probability of survival (reliability) of ceramic components subjected to harsh thermomechanical loads that can vary with time (transient reliability analysis). This capability enables more accurate prediction of ceramic component integrity against fracture in situations such as turbine startup and shutdown, operational vibrations, atmospheric reentry, or other rapid heating or cooling situations (thermal shock). The transient reliability analysis methodology developed herein incorporates the following features: fast-fracture transient analysis (reliability analysis without slow crack growth, SCG); transient analysis with SCG (reliability analysis with time-dependent damage due to SCG); a computationally efficient algorithm to compute the reliability for components subjected to repeated transient loading (block loading); cyclic fatigue modeling using a combined SCG and Walker fatigue law; proof testing for transient loads; and Weibull and fatigue parameters that are allowed to vary with temperature or time. Component-to-component variation in strength (stochastic strength response) is accounted for with the Weibull distribution, and either the principle of independent action or the Batdorf theory is used to predict the effect of multiaxial stresses on reliability. The reliability analysis can be performed either as a function of the component surface (for surface-distributed flaws) or component volume (for volume-distributed flaws). The transient reliability analysis capability has been added to the NASA CARES/ Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code. CARES/Life was also updated to interface with commercially available finite element analysis software, such as ANSYS, when used to model the effects of transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.

Engineering behavior of small-scale foundation piers constructed from alternative materials

NASA Astrophysics Data System (ADS)

Prokudin, Maxim Mikhaylovich

Testing small-scale prototype pier foundations to evaluate engineering behavior is an alternative to full-scale testing that facilitates testing of several piers and pier groups at relatively low cost. In this study, various pier systems and pier groups at one tenth scale were subjected to static vertical loading under controlled conditions to evaluate stiffness, bearing capacity, and group efficiency. Pier length, material properties and methods of installation were evaluated. Pier length to diameter ratios varied between four and eight. A unique soil pit with dimensions of 2.1 m in width, 1.5 m in length and 2.0 m in depth was designed to carry out this research. The test pit was filled with moisture conditioned and compacted Western Iowa loess. A special load test frame was designed and fabricated to provide up to 25,000 kg vertical reaction force for load testing. A load cell and displacement instrumentation was setup to capture the load test data. Alternative materials to conventional cement concrete were studied. The pier materials evaluated in this study included compacted aggregate, cement stabilized silt, cementitious grouts, and fiber reinforced silt. Key findings from this study demonstrated that (1) the construction method influences the behavior of aggregate piers, (2) the composition of the pier has a significant impact on the stiffness, (3) group efficiencies were found to be a function of pier length and pier material, (4) in comparison to full-scale testing the scaled piers were found to produce a stiffer response with load-settlement and bearing capacities to be similar. Further, although full-scale test results were not available for all pier materials, the small-scale testing provided a means for comparing results between pier systems. Finally, duplicate pier tests for a given length and material were found to be repeatable.

The high frequency light load fatigue testing machine based on giant magnetostrictive material and stroke multiplier

NASA Astrophysics Data System (ADS)

Wang, M. D.; Li, D. S.; Huang, Y.; Zhang, C.; Zhong, K. M.; Sun, L. N.

2013-08-01

In the notebook and clamshell mobile phone, data communication wire often requires repeated bending. Generally, communication wire with the actual application conditions, the test data cannot assess bending resistance performance of data communication wire is tested conventionally using wires with weights of 90 degree to test bending number, this test method and device is not fully reflect the fatigue performance in high frequency and light load application condition, at the same time it has a large difference between the test data of the long-term reliability of high frequency and low load conditions. In this paper, high frequency light load fatigue testing machine based on the giant magnetostrictive material and stroke multiplier is put forward, in which internal reflux stroke multiplier is driven by giant magnetostrictive material to realize the rapid movement of light load. This fatigue testing device has the following advantages: (1) When the load is far less than the friction, reducing friction is very effective to improve the device performance. Because the body is symmetrical, the friction loss of radial does not exist in theory, so the stress situation of mechanism is good with high transmission efficiency and long service life. (2) The installation position of the output hydraulic cylinder, can be arranged conveniently as ordinary cylinder. (3) Reciprocating frequency, displacement and speed of high frequency movement can be programmed easily to change with higher position precision. (4)Hydraulic oil in this device is closed to transmit, which does not produce any environment pollution. The device has no hydraulic pump and tank, and less energy conversion processes, so it is with the trend of green manufacturing.

Manual handling: differences in perceived effort, success rate and kinematics between three different pushing techniques.

PubMed

Varcin, Lynn; Claus, Andrew; van den Hoorn, Wolbert; Hodges, Paul

2015-01-01

This study examined the perceived effort, success rates and kinematics for three push strategies in a simulated lateral patient transfer (horizontal slide). Thirteen healthy subjects (four males) completed three repetition pushing loads of 6, 10 and 14 kg in random order; with a spontaneous push strategy, then with a straight-back bent-knees (squat) strategy and the preparatory pelvic movement ('rockback') strategy in random order. Perceived effort and kinematic parameters measured at the onset of movement and at maximum push excursion were compared between strategies and between loads with repeated measures ANOVA. The spontaneous and 'rockback' strategies achieved the pushing task with less perceived effort across all loads than the squat push (P < 0.001). Only 3/13 participants were successful on all attempts at pushing the 14 kg load using a squat strategy, which contrasted with 12/13 participants when the spontaneous strategy or the 'rockback' strategy was used. Forward movement of the pelvis and forward trunk inclination may be positively associated with lower perceived effort in the push task. Practitioner Summary: In a manual-handling task that simulated a lateral patient transfer (horizontal slide), perceived effort and success rates of three push strategies were compared. A straight-back bent-knees push (squat) strategy demonstrated greater perceived effort and lower success rates than a spontaneous push strategy, or a push strategy with preparatory 'rockback' pelvic movement.

Early age at time of primary Epstein-Barr virus infection results in poorly controlled viral infection in infants from Western Kenya: clues to the etiology of endemic Burkitt lymphoma.

PubMed

Piriou, Erwan; Asito, Amolo S; Sumba, Peter O; Fiore, Nancy; Middeldorp, Jaap M; Moormann, Ann M; Ploutz-Snyder, Robert; Rochford, Rosemary

2012-03-15

Infection with Epstein-Barr virus (EBV) early in life and repeated malaria exposure have been proposed as risk factors for endemic Burkitt lymphoma (eBL). Infants were enrolled from 2 rural sites in Kenya: the Kisumu District, where malaria transmission is holoendemic and risk for eBL is high, and the Nandi District, where malaria transmission is limited and the risk for eBL is low. Blood samples were taken from infants through 2 years of age to measure EBV viral load, EBV antibodies, and malaria parasitemia. We observed a significantly younger age at time of primary EBV infection in children from Kisumu compared with children from Nandi (mean age, 7.28 months [±0.33 SEM] in Kisumu vs 8.39 months [±0.26 SEM] in Nandi), with 35.3% of children in Kisumu infected before 6 months of age. To analyze how different predictors affected EBV viral load over time, we performed multilevel mixed modeling. This modeling revealed that residence in Kisumu and younger age at first EBV infection were significant predictors for having a higher EBV viral load throughout the period of observation. Children from a region at high risk for eBL were infected very early in life with EBV, resulting in higher viral loads throughout infancy.

Structural Analysis Using Computer Based Methods

NASA Technical Reports Server (NTRS)

Dietz, Matthew R.

2013-01-01

The stiffness of a flex hose that will be used in the umbilical arms of the Space Launch Systems mobile launcher needed to be determined in order to properly qualify ground umbilical plate behavior during vehicle separation post T-0. This data is also necessary to properly size and design the motors used to retract the umbilical arms. Therefore an experiment was created to determine the stiffness of the hose. Before the test apparatus for the experiment could be built, the structure had to be analyzed to ensure it would not fail under given loading conditions. The design model was imported into the analysis software and optimized to decrease runtime while still providing accurate restlts and allow for seamless meshing. Areas exceeding the allowable stresses in the structure were located and modified before submitting the design for fabrication. In addition, a mock up of a deep space habitat and the support frame was designed and needed to be analyzed for structural integrity under different loading conditions. The load cases were provided by the customer and were applied to the structure after optimizing the geometry. Once again, weak points in the structure were located and recommended design changes were made to the customer and the process was repeated until the load conditions were met without exceeding the allowable stresses. After the stresses met the required factors of safety the designs were released for fabrication.

An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron–Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications

PubMed Central

Tu, Yun; Ye, Lin; Zhou, Shao-Ping; Tu, Shan-Tung

2017-01-01

Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG) fabricated in hydrogen (H2)-loaded boron–germanium (B–Ge) co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H2-loaded B–Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H2-loaded B–Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging. PMID:28241465

An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron-Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications.

PubMed

Tu, Yun; Ye, Lin; Zhou, Shao-Ping; Tu, Shan-Tung

2017-02-23

Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG) fabricated in hydrogen (H₂)-loaded boron-germanium (B-Ge) co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H₂-loaded B-Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H₂-loaded B-Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging.

Load redistribution in walking and trotting Beagles with induced forelimb lameness.

PubMed

Abdelhadi, Jalal; Wefstaedt, Patrick; Galindo-Zamora, Vladimir; Anders, Alexandra; Nolte, Ingo; Schilling, Nadja

2013-01-01

To evaluate the load redistribution mechanisms in walking and trotting dogs with induced forelimb lameness. 7 healthy adult Beagles. Dogs walked and trotted on an instrumented treadmill to determine control values for peak and mean vertical force as well as vertical impulse for all 4 limbs. A small sphere was attached to the ventral pad of the right forelimb paw to induce a reversible lameness, and recordings were repeated for both gaits. Additionally, footfall patterns were assessed to test for changes in temporal gait variables. During walking and trotting, peak and mean vertical force as well as vertical impulse were decreased in the ipsilateral forelimb, increased in the contralateral hind limb, and remained unchanged in the ipsilateral hind limb after lameness was induced. All 3 variables were increased in the contralateral forelimb during trotting, whereas only mean vertical force and vertical impulse were increased during walking. Stance phase duration increased in the contralateral forelimb and hind limb during walking but not during trotting. Analysis of the results suggested that compensatory load redistribution mechanisms in dogs depend on the gait. All 4 limbs should be evaluated in basic research and clinical studies to determine the effects of lameness on the entire body. Further studies are necessary to elucidate specific mechanisms for unloading of the affected limb and to determine the long-term effects of load changes in animals with chronic lameness.

Hydromechanical effects of continental glaciation on groundwater systems

USGS Publications Warehouse

Neuzil, C.E.

2012-01-01

Hydromechanical effects of continental ice sheets may involve considerably more than the widely recognized direct compression of overridden terrains by ice load. Lithospheric flexure, which lags ice advance and retreat, appears capable of causing comparable or greater stress changes. Together, direct and flexural loading may increase fluid pressures by tens of MPa in geologic units unable to drain. If so, fluid pressures in low-permeability formations subject to glaciation may have increased and decreased repeatedly during cycles of Pleistocene glaciation and can again in the future. Being asynchronous and normally oriented, direct and flexural loading presumably cause normal and shear stresses to evolve in a complex fashion through much or all of a glacial cycle. Simulations of fractured rock predict permeability might vary by two to three orders of magnitude under similar stress changes as fractures at different orientations are subjected to changing normal and shear stresses and some become critically stressed. Uncertainties surrounding these processes and their interactions, and the confounding influences of surface hydrologic changes, make it challenging to delineate their effects on groundwater flow and pressure regimes with any specificity. To date, evidence for hydromechanical changes caused by the last glaciation is sparse and inconclusive, comprising a few pressure anomalies attributed to the removal of direct ice load. This may change as more data are gathered, and understanding of relevant processes is refined.

Observation of tritium in gas/plasma loaded titanium samples

NASA Astrophysics Data System (ADS)

Srinivasan, M.; Shyam, A.; Kaushik, T. C.; Rout, R. K.; Kulkarni, L. V.; Krishnan, M. S.; Malhotra, S. K.; Nagvenkar, V. G.; Iyengar, P. K.

1991-05-01

The observation of significant neutron yield from gas loaded titanium samples at Frascati in April 1989 opened up an alternate pathway to the investigation of anomalous nuclear phenomena in deuterium/solid systems, complimenting the electrolytic approach. Since then at least six different groups have successfully measured burst neutron emission from deuterated titanium shavings following the Frascati methodology, the special feature of which was the use of liquid nitrogen to create repeated thermal cycles resulting in the production of non-equilibrium conditions in the deuterated samples. At Trombay several variations of the gas loading procedure have been investigated including induction heating of single machined titanium targets in a glass chamber as well as use of a plasma focus device for deuteriding its central titanium electrode. Stemming from earlier observations both at BARC and elsewhere that tritium yield is ≂108 times higher than neutron output in cold fusion experiments, we have channelised our efforts to the search for tritium rather than neutrons. The presence of tritium in a variety gas/plasma loaded titanium samples has been established successfully through a direct measurement of the radiations emitted as a result of tritium decay, in contradistinction to other groups who have looked for tritium in the extracted gases. In some samples we have thus observed tritium levels of over 10 MBq with a corresponding (t/d) ratio of ≳10-5.

The influence of hand positions on biomechanical injury risk factors at the wrist joint during the round-off skills in female gymnastics.

PubMed

Farana, Roman; Jandacka, Daniel; Uchytil, Jaroslav; Zahradnik, David; Irwin, Gareth

2017-01-01

The aim of this study was to examine the biomechanical injury risk factors at the wrist, including joint kinetics, kinematics and stiffness in the first and second contact limb for parallel and T-shape round-off (RO) techniques. Seven international-level female gymnasts performed 10 trials of the RO to back handspring with parallel and T-shape hand positions. Synchronised kinematic (3D motion analysis system; 247 Hz) and kinetic (two force plates; 1235 Hz) data were collected for each trial. A two-way repeated measure analysis of variance (ANOVA) assessed differences in the kinematic and kinetic parameters between the techniques for each contact limb. The main findings highlighted that in both the RO techniques, the second contact limb wrist joint is exposed to higher mechanical loads than the first contact limb demonstrated by increased axial compression force and loading rate. In the parallel technique, the second contact limb wrist joint is exposed to higher axial compression load. Differences between wrist joint kinetics highlight that the T-shape technique may potentially lead to reducing these bio-physical loads and consequently protect the second contact limb wrist joint from overload and biological failure. Highlighting the biomechanical risk factors facilitates the process of technique selection making more objective and safe.

The facilitative effects of glucose ingestion on memory retrieval in younger and older adults: is task difficulty or task domain critical?

PubMed

Riby, Leigh M; McMurtrie, Hazel; Smallwood, Jonathan; Ballantyne, Carrie; Meikle, Andrew; Smith, Emily

2006-02-01

The ingestion of a glucose-containing drink has been shown to improve cognitive performance, particularly memory functioning. However, it remains unclear as to the extent to which task domain and task difficulty moderate the glucose enhancement effect. The aim of this research was to determine whether boosts in performance are restricted to particular classes of memory (episodic v. semantic) or to tasks of considerable cognitive load. A repeated measures (25 g glucose v. saccharin), counterbalanced, double-blind design was used with younger and older adults. Participants performed a battery of episodic (e.g. paired associate learning) and semantic memory (e.g. category verification) tasks under low and high cognitive load. Electrophysiological measures (heart rate and galvanic skin response) of arousal and mental effort were also gathered. The results indicated that whilst glucose appeared to aid episodic remembering, cognitive load did not exaggerate the facilitative effect. For semantic memory, there was little evidence to suggest that glucose can boost semantic memory retrieval even when the load was manipulated. One exception was that glucose facilitated performance during the difficult category fluency task. Regardless, the present findings are consistent with the domain-specific account in which glucose acts primarily on the hippocampal region, which is known to support episodic memory. The possible contribution of the hippocampus in semantic memory processing is also discussed.

HIV Viral RNA Extraction in Wax Immiscible Filtration Assisted by Surface Tension (IFAST) Devices

PubMed Central

Berry, Scott M.; LaVanway, Alex J.; Pezzi, Hannah M.; Guckenberger, David J.; Anderson, Meghan A.; Loeb, Jennifer M.; Beebe, David J.

2015-01-01

The monitoring of viral load is critical for proper management of antiretroviral therapy for HIV-positive patients. Unfortunately, in the developing world, significant economic and geographical barriers exist, limiting access to this test. The complexity of current viral load assays makes them expensive and their access limited to advanced facilities. We attempted to address these limitations by replacing conventional RNA extraction, one of the essential processes in viral load quantitation, with a simplified technique known as immiscible filtration assisted by surface tension (IFAST). Furthermore, these devices were produced via the embossing of wax, enabling local populations to produce and dispose of their own devices with minimal training or infrastructure, potentially reducing the total assay cost. In addition, IFAST can be used to reduce cold chain dependence during transportation. Viral RNA extracted from raw samples stored at 37°C for 1 week exhibited nearly complete degradation. However, IFAST-purified RNA could be stored at 37°C for 1 week without significant loss. These data suggest that RNA isolated at the point of care (eg, in a rural clinic) via IFAST could be shipped to a central laboratory for quantitative RT-PCR without a cold chain. Using this technology, we have demonstrated accurate and repeatable measurements of viral load on samples with as low as 50 copies per milliliter of sample. PMID:24613822

Using in situ vertical displacements to characterize changes in moisture load

NASA Astrophysics Data System (ADS)

Murdoch, Lawrence C.; Freeman, Clay E.; Germanovich, Leonid N.; Thrash, Colby; DeWolf, Scott

2015-08-01

Changes in soil moisture content alter the load on underlying material, and we have developed a technique for characterizing this effect by using an extensometer to measure the displacement caused by the load change. The extensometer is pushed into soil at depths of 5 m or more, and displacement between two anchors separated by ˜1.5 m is measured with a resolution of better than 0.01 μm (10-8 m). The instrument is sensitive to load changes at the ground surface within a radial distance that is roughly twice its depth, potentially providing a method for averaging changes in water content over hundreds of m2 or more. During a field trial at a site in South Carolina, compressive displacements in unsaturated saprolite were strongly correlated to rainfall with a calibration factor of 0.16 μm displacement per mm of rainfall ±0.002 μm/mm (R2 = 0.95). Estimates of the net change in water volume per unit area made using the calibration factor from rainfall were similar to independent estimates of evapotranspiration. The technique was affected by barometric pressure variations, but the sensitivity was less than expected and does not hinder meaningful application. A companion instrument demonstrated the displacement signal was repeatable. This article was corrected on 11 SEP 2015. See the end of the full text for details.

Delivery of Flightless I Neutralizing Antibody from Porous Silicon Nanoparticles Improves Wound Healing in Diabetic Mice.

PubMed

Turner, Christopher T; McInnes, Steven J P; Melville, Elizabeth; Cowin, Allison J; Voelcker, Nicolas H

2017-01-01

Flightless I (Flii) is elevated in human chronic wounds and is a negative regulator of wound repair. Decreasing its activity improves healing responses. Flii neutralizing antibodies (FnAbs) decrease Flii activity in vivo and hold significant promise as healing agents. However, to avoid the need for repeated application in a clinical setting and to protect the therapeutic antibody from the hostile environment of the wound, suitable delivery vehicles are required. In this study, the use of porous silicon nanoparticles (pSi NPs) is demonstrated for the controlled release of FnAb to diabetic wounds. We achieve FnAb loading regimens exceeding 250 µg antibody per mg of vehicle. FnAb-loaded pSi NPs increase keratinocyte proliferation and enhance migration in scratch wound assays. Release studies confirm the functionality of the FnAb in terms of Flii binding. Using a streptozotocin-induced model of diabetic wound healing, a significant improvement in healing is observed for mice treated with FnAb-loaded pSi NPs compared to controls, including FnAb alone. FnAb-loaded pSi NPs treated with proteases show intact and functional antibody for up to 7 d post-treatment, suggesting protection of the antibodies from proteolytic degradation in wound fluid. pSi NPs may therefore enable new therapeutic approaches for the treatment of diabetic ulcers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tectonic state: its significance and characterization in the assessment of seismic effects associated with reservoir impounding

USGS Publications Warehouse

Castle, R.O.; Clark, M.M.; Grantz, A.; Savage, J.C.

1980-01-01

Any analysis of seismicity associated with the filling of large reservoirs requires an evaluation of the natural tectonic state in order to determine whether impoundment is the basic source, a mechanically unrelated companion feature, or a triggering stimulus of the observed seismicity. Several arguments indicate that the associated seismicity is usually a triggered effect. Among the elements of tectonic state considered here (existing fractures, accumulated elastic strain, and deformational style), deformational style is especially critical in forecasting the occurrence of impoundment-induced seismicity. The observational evidence indicates that seismicity associated with impounding generally occurs in areas that combine steeply dipping faults, relatively high strain rates, and either extensional or horizontal-shear strain. Simple physical arguments suggest: (1) that increased fluid pressures resulting from increased reservoir head should enhance the likelihood of seismic activity, whatever the tectonic environment; (2) that stress changes resulting from surface loading may increase the likelihood of crustal failure in areas of normal and transcurrent faulting, whereas they generally inhibit failure in areas of thrust faulting. Comparisons with other earthquake-producing artificial and natural processes (underground explosions, fluid injection, underground mining, fluid extraction, volcanic emissions) indicate that reservoir loading may similarly modify the natural tectonic state. Subsurface loading resulting from fluid extraction may be a particularly close analogue of reservoir loading; "seismotectonic" events associated with fluid extraction have been recognized in both seismically active and otherwise aseismic regions. Because the historic record of seismicity and surface faulting commonly is short in comparison with recurrence intervals of earthquake and fault-slip events, tectonic state is most reliably appraised through combined studies of historic seismicity and faulting, instrumentally measured strain, and the geological record, especially that of the Quaternary. Experience in California and elsewhere demonstrates that the character and activity of recognized faults can be assessed by means of: instrumental earthquake investigations, repeated geodetic measurements, written history, archeological studies, fault topography, and local stratigraphic relations. Where faults are less easily distinguished, appraisals of tectonic state may be based on both the regional seismicity and the regional history of vertical movement as shown by: repeated levelling and sea-level measurements, written history, archeologic investigations, terrace and shoreline deformation, and denudation and sedimentation studies. ?? 1980.

Wall-Friction Support of Vertical Loads in Submerged Sand and Gravel Columns

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

Walton, O. R.; Vollmer, H. J.; Hepa, V. S.

Laboratory studies of the ‘floor-loads’ under submerged vertical columns of sand and/or gravel indicate that such loads can be approximated by a buoyancy-corrected Janssen-silo-theory-like relationship. Similar to conditions in storage silos filled with dry granular solids, most of the weight of the sand or gravel is supported by wall friction forces. Laboratory measurements of the loads on the floor at the base of the water-filled columns (up to 25-diameters tall) indicate that the extra floor-load from the addition of the granular solid never exceeded the load that would exist under an unsupported (wide) bed of submerged sand or gravel thatmore » has a total depth corresponding to only two column-diameters. The measured floorloads reached an asymptotic maximum value when the depth of granular material in the columns was only three or four pipe-diameters, and never increased further as the columns were filled to the top (e.g. up to heights of 10 to 25 diameters). The floor-loads were stable and remained the same for days after filling. Aggressive tapping (e.g. hitting the containing pipe on the outside, manually with a wrench up and down the height and around the circumference) could increase (and occasionally decrease) the floor load substantially, but there was no sudden collapse or slumping to a state without significant wall friction effects. Considerable effort was required, repeatedly tapping over almost the entire column wall periphery, in order to produce floor-loads that corresponded to the total buoyancy-corrected weight of granular material added to the columns. Projecting the observed laboratory behavior to field conditions would imply that a stable floor-load condition, with only a slightly higher total floor pressure than the preexisting hydrostatic-head, would exist after a water-filled bore-hole is filled with sand or gravel. Significant seismic vibration (either a large nearby event or many micro-seismic events over an extended period) would likely be necessary before the full (buoyancy-corrected) weight of the sand and/or gravel would be ‘delivered’ to the bottom of the submerged column.« less

High-Precision Coupling Mechanism Operable By Robots

NASA Technical Reports Server (NTRS)

Voellmer, George

1992-01-01

Coupling mechanism has features making it easily operable by hand and suitable for operation by robots: tolerates some initial misalignment, imposes precise final alignment, and protects itself against overtightening. Typically used to mount equipment module on structure. Mechanism includes kinematic mounts, which tolerate small initial misalignment and enforce precise final alignment as two assemblies brought together. Clamping force applied to kinematic mounts via two flexible plates. Bolt and nut tightened on flexible plates to impose spring clamping load. Repeatability of interface tested and found to be better than forty-millionths of inch.

Compliant Electrode and Composite Material for Piezoelectric Wind and Mechanical Energy Conversions

NASA Technical Reports Server (NTRS)

Chen, Bin (Inventor)

2015-01-01

A thin film device for harvesting energy from wind. The thin film device includes one or more layers of a compliant piezoelectric material formed from a composite of a polymer and an inorganic material, such as a ceramic. Electrodes are disposed on a first side and a second side of the piezoelectric material. The electrodes are formed from a compliant material, such as carbon nanotubes or graphene. The thin film device exhibits improved resistance to structural fatigue upon application of large strains and repeated cyclic loadings.

Childhood poverty and adult psychological well-being

PubMed Central

Evans, Gary W.

2016-01-01

Childhood disadvantage has repeatedly been linked to adult physical morbidity and mortality. We show in a prospective, longitudinal design that childhood poverty predicts multimethodological indices of adult (24 y of age) psychological well-being while holding constant similar childhood outcomes assessed at age 9. Adults from low-income families manifest more allostatic load, an index of chronic physiological stress, higher levels of externalizing symptoms (e.g., aggression) but not internalizing symptoms (e.g., depression), and more helplessness behaviors. In addition, childhood poverty predicts deficits in adult short-term spatial memory. PMID:27956615

Sensitivity to emotional ill health

NASA Technical Reports Server (NTRS)

Felton, J. S.

1969-01-01

The services of mental specialists, such as psychologists, psychiatrists, or psychiatric social workers are required to assure maximum human performance in Government facilities. Contemporary mental health programming covers emotionally generated problems at operational sites to complete disclaiming of the existence of such difficulties among workers. Frequent taking of sick leave or annual leave when work seems demanding or when a promotion does not materialize, chronic or repeated tardiness, requests for frequent transfers, work over-loading, accidental injuries, and alcoholism are all forms of stress responses and indicate a need for emotional counselling.

Dynamically allocating sets of fine-grained processors to running computations

NASA Technical Reports Server (NTRS)

Middleton, David

1988-01-01

Researchers explore an approach to using general purpose parallel computers which involves mapping hardware resources onto computations instead of mapping computations onto hardware. Problems such as processor allocation, task scheduling and load balancing, which have traditionally proven to be challenging, change significantly under this approach and may become amenable to new attacks. Researchers describe the implementation of this approach used by the FFP Machine whose computation and communication resources are repeatedly partitioned into disjoint groups that match the needs of available tasks from moment to moment. Several consequences of this system are examined.

The Fatigue Characteristics of Bolted Lap Joints of 24S-T Alclad Sheet Materials

DTIC Science & Technology

1946-10-01

extremely close bolt fits are needed to o%tain maximum life of bolt ~oint~ under repeated etreseeci. -. Szvzral ty~+?+s of bolt patterns hava been tegted...Memorial Institute on spec~meris of 0.102-i.nch sheet. In particular, figure 4 shows, on a load- life diagram, . results of tests Qn single-bolt...results of tests at the Univer- sity of’ il~~nols on single—bolt specimens, Tables 10 and 11 give reeults of tests, made at the U“ uiversity of Illino~8 , on

Effects of plyometric training and creatine supplementation on maximal-intensity exercise and endurance in female soccer players.

PubMed

Ramírez-Campillo, Rodrigo; González-Jurado, José Antonio; Martínez, Cristian; Nakamura, Fábio Yuzo; Peñailillo, Luis; Meylan, Cesar M P; Caniuqueo, Alexis; Cañas-Jamet, Rodrigo; Moran, Jason; Alonso-Martínez, Alicia M; Izquierdo, Mikel

2016-08-01

To investigate the effects of a six-week plyometric training and creatine supplementation intervention on maximal-intensity and endurance performance in female soccer players during in-season training. Randomized, double-blind, placebo-controlled trial. Young (age 22.9±2.5y) female players with similar training load and competitive background were assigned to a plyometric training group receiving placebo (PLACEBO, n=10), a plyometric training group receiving creatine supplementation (CREATINE, n=10) or a control group receiving placebo without following a plyometric program (CONTROL, n=10). Athletes were evaluated for jumping, maximal and repeated sprinting, endurance and change-of-direction speed performance before and after six weeks of training. After intervention the CONTROL group did not change, whereas both plyometric training groups improved jumps (ES=0.25-0.49), sprint (ES=0.35-0.41), repeated sprinting (ES=0.48-0.55), endurance (ES=0.32-0.34) and change-of-direction speed performance (ES=0.46-0.55). However, the CREATINE group improved more in the jumps and repeated sprinting performance tests than the CONTROL and the PLACEBO groups. Adaptations to plyometric training may be enhanced with creatine supplementation. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Power output measurement during treadmill cycling.

PubMed

Coleman, D A; Wiles, J D; Davison, R C R; Smith, M F; Swaine, I L

2007-06-01

The study aim was to consider the use of a motorised treadmill as a cycling ergometry system by assessing predicted and recorded power output values during treadmill cycling. Fourteen male cyclists completed repeated cycling trials on a motorised treadmill whilst riding their own bicycle fitted with a mobile ergometer. The speed, gradient and loading via an external pulley system were recorded during 20-s constant speed trials and used to estimate power output with an assumption about the contribution of rolling resistance. These values were then compared with mobile ergometer measurements. To assess the reliability of measured power output values, four repeated trials were conducted on each cyclist. During level cycling, the recorded power output was 257.2 +/- 99.3 W compared to the predicted power output of 258.2 +/- 99.9 W (p > 0.05). For graded cycling, there was no significant difference between measured and predicted power output, 268.8 +/- 109.8 W vs. 270.1 +/- 111.7 W, p > 0.05, SEE 1.2 %. The coefficient of variation for mobile ergometer power output measurements during repeated trials ranged from 1.5 % (95 % CI 1.2 - 2.0 %) to 1.8 % (95 % CI 1.5 - 2.4 %). These results indicate that treadmill cycling can be used as an ergometry system to assess power output in cyclists with acceptable accuracy.

High pressure, energy, and impulse loading of the wall in a 1-GJ Laboratory Microfusion Facility

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

Harrach, R.J.

1989-07-24

A proposed Laboratory Microfusion Facility (LMF) must be able to withstand repeated, low-repetition-rate fusion explosions at the 1-GJ (one-quarter ton) yield level. The energy release will occur at the center of a chamber only a few meters in radius, subjecting the interior or first wall to severe levels of temperature, pressure, and impulse. We show by theory and computation that the wall loading can be ameliorated by interposing a spherical shell of low-Z material between the fuel and the wall. This sacrificial shield converts the source energy components that are most damaging to the wall (soft x-rays and fast ions)more » to more benign plasma kinetic energy from the vaporized shield, and stretches the time duration over which this energy is delivered to the wall from nanoseconds to microseconds. Numerical calculations emphasize thin, volleyball-sized plastic shields, and much thicker ones of frozen nitrogen. Wall shielding criteria of small (or no) amount of surface ablation, low impulse and pressure loading, minimal shrapnel danger, small expense, and convenience in handling all favor the thin plastic shields. 7 refs., 4 figs.« less

Regenerable cobalt oxide loaded magnetosphere catalyst from fly ash for mercury removal in coal combustion flue gas.

PubMed

Yang, Jianping; Zhao, Yongchun; Zhang, Junying; Zheng, Chuguang

2014-12-16

To remove Hg(0) in coal combustion flue gas and eliminate secondary mercury pollution of the spent catalyst, a new regenerable magnetic catalyst based on cobalt oxide loaded magnetospheres from fly ash (Co-MF) was developed. The catalyst, with an optimal loading of 5.8% cobalt species, attained approximately 95% Hg(0) removal efficiency at 150 °C under simulated flue gas atmosphere. O2 could enhance the Hg(0) removal activity of magnetospheres catalyst via the Mars-Maessen mechanism. SO2 displayed an inhibitive effect on Hg(0) removal capacity. NO with lower concentration could promote the Hg(0) removal efficiency. However, when increasing the NO concentration to 300 ppm, a slightly inhibitive effect of NO was observed. In the presence of 10 ppm of HCl, greater than 95.5% Hg(0) removal efficiency was attained, which was attributed to the formation of active chlorine species on the surface. H2O presented a seriously inhibitive effect on Hg(0) removal efficiency. Repeated oxidation-regeneration cycles demonstrated that the spent Co-MF catalyst could be regenerated effectively via thermally treated at 400 °C for 2 h.

Superelastic tension and bending characteristics of shape memory alloys

NASA Astrophysics Data System (ADS)

Bundara, B.; Tokuda, M.; Kuselj, B.; Ule, B.; Tuma, J. V.

2000-08-01

The objective of this study was to develop a numerical model of the superelastic behavior of shape memory alloys (SMA) on a macro-scale level. Results from a study on this behavior under tension and pure bending tests are presented and discussed. Two SMA samples were used in the experimental work and subjected to various loading paths in tension and pure bending: a single crystalline CuZnAl alloy and polycrystalline NiTi wire. Bending tests were performed under a pure bending loading condition on a new testing apparatus designed for the specific needs of this study. The experimental part of this study focused mainly on the response of the SMA to the loading paths in a quasi-plastic domain where the deformation mechanism is dominantly governed by the stress-induced martensitic transformation. Experimental results obtained from the NiTi polycrystals by tensile tests indicate that the superelastic SMA exhibits sufficient repeatability useful enough for a modeling task, while similar results obtained from the single crystalline CuZnAl indicate that the same modeling approach is not easily feasible. The facts have been qualitatively verified by the experimental data from pure bending tests, and a further area as study is suggested.

Ultrasound-enhanced nanotherapy of pancreatic cancer

NASA Astrophysics Data System (ADS)

Rapoport, N.; Nam, K.-H.; Christensen, D. A.; Kennedy, A. M.; Shea, J. E.; Scaife, C. L.

2010-03-01

The paper reports in vivo results of ultrasonic nanotherapy of orthotopically grown pancreatic cancer. Phase-shift paclitaxel (PTX) loaded perfluoropentane (PFP) nanoemusions combined with tumor-directed ultrasound have been used with a considerable success for tumor-targeted chemotherapy of gemcitabin (GEM)-refractory pancreatic cancer (PC). The GEM-resistant pancreatic cancer proved sensitive to treatment by a micellar PTX formulation Genexol PM (GEN) andor nanodroplet PTX formulation ndGEN. Due to increased permeability of tumor blood vessels, drug-loaded nanodroplets accumulated in the tumor via passive targeting, which was confirmed by ultrasound imaging. Nanodroplets converted into microbubbles in situ under the action of tumor-directed 1-MHz therapeutic ultrasound. The strongest therapeutic effect was observed for the combination therapy by PTX-loaded nanodroplets, GEM and ultrasound (ndGEN+GEM+ultrasound). This combination therapy resulted in a spectacular tumor regression and in some cases complete tumor resolution. Moreover, formation of metastases was dramatically decreased and ascitis generation was completely suppressed. However for all animal groups, local tumor recurrence was observed after the completion of the treatment indicating that some cancer cells survived the treatment. The recurrent tumors proved more resistant to the repeated therapy than initial tumors.

A Novel Sensor System for Measuring Wheel Loads of Vehicles on Highways

PubMed Central

Zhang, Wenbin; Suo, Chunguang; Wang, Qi

2008-01-01

With the development of the highway transportation and business trade, vehicle Weigh-In-Motion (WIM) technology has become a key technology for measuring traffic loads. In this paper a novel WIM system based on monitoring of pavement strain responses in rigid pavement was investigated. In this WIM system multiple low cost, light weight, small volume and high accuracy embedded concrete strain sensors were used as WIM sensors to measure rigid pavement strain responses. In order to verify the feasibility of the method, a system prototype based on multiple sensors was designed and deployed on a relatively busy freeway. Field calibration and tests were performed with known two-axle truck wheel loads and the measurement errors were calculated based on the static weights measured with a static weighbridge. This enables the weights of other vehicles to be calculated from the calibration constant. Calibration and test results for individual sensors or three-sensor fusions are both provided. Repeatability, sources of error, and weight accuracy are discussed. Successful results showed that the proposed method was feasible and proven to have a high accuracy. Furthermore, a sample mean approach using multiple fused individual sensors could provide better performance compared to individual sensors. PMID:27873952

Pretest predictions of the Fast Flux Test Facility Passive Safety Test Phase IIB transients using United States derived computer codes and methods

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

Heard, F.J.; Harris, R.A.; Padilla, A.

The SASSYS/SAS4A systems analysis code was used to simulate a series of unprotected loss of flow (ULOF) tests planned at the Fast Flux Test Facility (FFTF). The subject tests were designed to investigate the transient performance of the FFTF during various ULOF scenarios for two different loading patterns designed to produce extremes in the assembly load pad clearance and the direction of the initial assembly bows. The tests are part of an international program designed to extend the existing data base on the performance of liquid metal reactors (LMR). The analyses demonstrate that a wide range of power-to-flow ratios canmore » be reached during the transients and, therefore, will yield valuable data on the dynamic character of the structural feedbacks in LMRS. These analyses will be repeated once the actual FFTF core loadings for the tests are available. These predictions, similar ones obtained by other international participants in the FFTF program, and post-test analyses will be used to upgrade and further verify the computer codes used to predict the behavior of LMRS.« less

Angular-velocity control approach for stance-control orthoses.

PubMed

Lemaire, Edward D; Goudreau, Louis; Yakimovich, Terris; Kofman, Jonathan

2009-10-01

Currently, stance-control knee orthoses require external control mechanisms to control knee flexion during stance and allow free knee motion during the swing phase of gait. A new angular-velocity control approach that uses a rotary-hydraulic device to resist knee flexion when the knee angular velocity passes a preset threshold is presented. This angular-velocity approach for orthotic stance control is based on the premise that knee-flexion angular velocity during a knee-collapse event, such as a stumble or fall, is greater than that during walking. The new hydraulic knee-flexion control device does not require an external control mechanism to switch from free motion to stance control mode. Functional test results demonstrated that the hydraulic angular-velocity activated knee joint provided free knee motion during walking, engaged upon knee collapse, and supported body weight while the end-user recovered to a safe body position. The joint was tested to 51.6 Nm in single loading tests and passed 200,000 repeated loading cycles with a peak load of 88 Nm per cycle. The hydraulic, angular velocity activation approach has potential to improve safety and security for people with lower extremity weakness or when recovering from joint trauma.

Predilection sites for Toxoplasma gondii in sheep tissues revealed by magnetic capture and real-time PCR detection.

PubMed

Juránková, Jana; Basso, Walter; Neumayerová, Helena; Frencová, Anita; Baláž, Vojtech; Deplazes, Peter; Koudela, Břetislav

2015-12-01

Undercooked lamb and mutton are common sources of Toxoplasma gondii infection for humans. A sequence specific magnetic capture technique in combination with quantitative real-time PCR targeting the 529 bp repeat element of T. gondii was used for estimation of the parasite burdens in various sheep tissues (n = 6) three months after peroral experimental inoculation with 10,000 T. gondii oocysts. Brain was the most frequently affected organ (positive in all 6 sheep) and showed the highest estimated parasite loads (0.5-30,913 parasites/g tissue). Lung samples were positive in three sheep, with load estimates of 36.3 to <1 parasite/g tissue. Heart tissue was positive in three sheep and kidney only in one animal with low parasite loads (<1 parasite/g tissue). Only few skeletal muscle samples in 2 animals showed positive results, with very low parasite burdens, while samples from further internal organs (i.e. liver and spleen) were negative in all animals. This study identified the brain as the most important predilection site and therefore the most appropriate tissue for T. gondii detection. Copyright © 2015 Elsevier Ltd. All rights reserved.

Failure analysis of pinch-torsion tests as a thermal runaway risk evaluation method of Li-Ion Cells

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

Xia, Yuzhi; Li, Dr. Tianlei; Ren, Prof. Fei

2014-01-01

Recently a pinch-torsion test is developed for safety testing of Li-ion batteries (Ren et al., J. Power Source, 2013). It has been demonstrated that this test can generate small internal short-circuit spots in the separator in a controllable and repeatable manner. In the current research, the failure mechanism is examined by numerical simulations and comparisons to experimental observations. Finite element models are developed to evaluate the deformation of the separators under both pure pinch and pinch-torsion loading conditions. It is discovered that the addition of the torsion component significantly increased the maximum principal strain, which is believed to induce themore » internal short circuit. In addition, the applied load in the pinch-torsion test is significantly less than in the pure pinch test, thus dramatically improving the applicability of this method to ultra-thick batteries which otherwise require heavy load in excess of machine capability. It is further found that the separator failure is achieved in the early stage of torsion (within a few degree of rotation). Effect of coefficient of friction on the maximum principal strain is also examined.« less

Evaluation of shuttle solid rocket booster case materials. Corrosion and stress corrosion susceptibility of several high temperature materials

NASA Technical Reports Server (NTRS)

Pionke, L. J.; Garland, K. C.

1973-01-01

Candidate alloys for the Shuttle Solid Rocket Booster (SRB) case were tested under simulated service conditions to define subcritical flaw growth behavior under both sustained and cyclic loading conditions. The materials evaluated were D6AC and 18 Ni maraging steel, both heat treated to a nominal yield strength of 1380 MN/sq m (200 ksi). The sustained load tests were conducted by exposing precracked, stressed specimens of both alloys to alternate immersion in synthetic sea water. It was found that the corrosion and stress corrosion resistance of the 18 Ni maraging steel were superior to that of the D6AC steel under these test conditions. It was also found that austenitizing temperature had little influence on the threshold stress intensity of the D6AC. The cyclic tests were conducted by subjecting precracked surface-flawed specimens of both alloys to repeated load/thermal/environmental profiles which were selected to simulate the SRB missions. It was found that linear removal operations that involve heating to 589 K (600 F) cause a decrease in cyclic life of D6AC steel relative to those tests conducted with no thermal cycling.