Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains.

PubMed

Sabater, Carlos; Untiedt, Carlos; van Ruitenbeek, Jan M

2015-01-01

This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a 'Berry force'. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose.

A narrative review of manual muscle testing and implications for muscle testing research

PubMed Central

Conable, Katharine M.; Rosner, Anthony L.

2011-01-01

Objective Manual muscle testing (MMT) is used for a variety of purposes in health care by medical, osteopathic, chiropractic, physical therapy, rehabilitation, and athletic training professionals. The purpose of this study is to provide a narrative review of variations in techniques, durations, and forces used in MMT putting applied kinesiology (AK) muscle testing in context and highlighting aspects of muscle testing important to report in MMT research. Method PubMed, the Collected Papers of the International College of Applied Kinesiology–USA, and related texts were searched on the subjects of MMT, maximum voluntary isometric contraction testing, and make/break testing. Force parameters (magnitude, duration, timing of application), testing variations of MMT, and normative data were collected and evaluated. Results “Break” tests aim to evaluate the muscle's ability to resist a gradually increasing pressure and may test different aspects of neuromuscular control than tests against fixed resistances. Applied kinesiologists use submaximal manual break tests and a binary grading scale to test short-term changes in muscle function in response to challenges. Many of the studies reviewed were not consistent in reporting parameters for testing. Conclusions To increase the chances for replication, studies using MMT should specify parameters of the tests used, such as exact procedures and instrumentation, duration of test, peak force, and timing of application of force. PMID:22014904

SPH Simulation of Impact of a Surge on a Wall

NASA Astrophysics Data System (ADS)

Diwakar, Manoj Kumar; Mohapatra, Pranab Kumar; Tripathi, Shivam

2014-05-01

Structures located on the downstream of a dam are prone to impact of the surge due to dam break flow. Ramsden (1996) experimentally studied the run-up height on a vertical wall due to propagation of bore and surge on dry bed and measured their impact on the wall. Mohapatra et al. (2000) applied Navier Stokes equations to numerically study the impact of bore on vertical and inclined walls. They also obtained the evolution of surge on dry bed. In the present work, the impact of a surge wave due to dam break flow against the wall is modeled with a two-dimensional smoothed particle hydrodynamics (SPH) model. SPH is a mesh-free method that relies on the particle view of the field problem and approximates the continuity and momentum equations on a set of particles. The method solves the strong form of Navier-Stokes equations. The governing equations are solved numerically in the vertical plane. The propagation of the surge wave, its impact and the maximum run-up on the wall located at the boundary are analyzed. Surface profile, velocity field and pressure distributions are simulated. Non-dimensional run-up height obtained from the present numerical model is 0.86 and is in good agreement with the available experimental data of Ramsden (1996) which is in the range of 0.75-0.9. Also, the simulated profile of the surge tip was comparable to the empirical equations refereed in Ramsden (1996). The model is applied to the study the maximum force and the run-up height on inclined walls with different inclinations. The results indicate that the maximum force and the run-up height on the wall increase with the increment of wall inclination. Comparison of numerical results with analytical solutions derived from shallow water equations clearly shows the breakdown of shallow water assumption during the impact. In addition to these results, the numerical simulation yields the complete velocity and pressure ?elds which may be used to design structures located in the path of a dam-break wave. The study shows that the smoothed particle hydrodynamics can effectively simulate fluid flow dynamics. References: Mohapatra, P. K., Bhallamudi, S. M., and Eswaran, V. (2000). 'Numerical simulation of impact of bores against inclined walls.' J. Hydraulic. Engg., ASCE, 126(12), 942-945. Ramsden, J. D. (1996). 'Forces on a vertical wall due to long waves, bores, and dry-bed surges.' J. Waterway, Port, Coastal, and Ocean Engg., ASCE, 122(3), 134-141.

76 FR 5341 - Notice of Federal Advisory Committee Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-31

... Medical Case Management 1:00 Break 1:15 Army Services for TBI and PTSD 2:15 Break 2:30 Army Programs for... Management 11:45 Break 1:00 Air Force Medical Services for TBI and PTSD 1:15 Air Force Programs for...

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains

PubMed Central

Sabater, Carlos; Untiedt, Carlos

2015-01-01

Summary This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a ‘Berry force’. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose. PMID:26734525

Non-uniform breaking of molecular bonds, peripheral morphology and releasable adhesion by elastic anisotropy in bio-adhesive contacts

PubMed Central

Liu, Yan; Gao, Yanfei

2015-01-01

Biological adhesive contacts are usually of hierarchical structures, such as the clustering of hundreds of sub-micrometre spatulae on keratinous hairs of gecko feet, or the clustering of molecular bonds into focal contacts in cell adhesion. When separating these interfaces, releasable adhesion can be accomplished by asymmetric alignment of the lowest scale discrete bonds (such as the inclined spatula that leads to different peeling force when loading in different directions) or by elastic anisotropy. However, only two-dimensional contact has been analysed for the latter method (Chen & Gao 2007 J. Mech. Phys. Solids 55, 1001–1015 (doi:10.1016/j.jmps.2006.10.008)). Important questions such as the three-dimensional contact morphology, the maximum to minimum pull-off force ratio and the tunability of releasable adhesion cannot be answered. In this work, we developed a three-dimensional cohesive interface model with fictitious viscosity that is capable of simulating the de-adhesion instability and the peripheral morphology before and after the onset of instability. The two-dimensional prediction is found to significantly overestimate the maximum to minimum pull-off force ratio. Based on an interface fracture mechanics analysis, we conclude that (i) the maximum and minimum pull-off forces correspond to the largest and smallest contact stiffness, i.e. ‘stiff-adhere and compliant-release’, (ii) the fracture toughness is sensitive to the crack morphology and the initial contact shape can be designed to attain a significantly higher maximum-to-minimum pull-off force ratio than a circular contact, and (iii) since the adhesion is accomplished by clustering of discrete bonds or called bridged crack in terms of fracture mechanics terminology, the above conclusions can only be achieved when the bridging zone is significantly smaller than the contact size. This adhesion-fracture analogy study leads to mechanistic predictions that can be readily used to design biomimetics and releasable adhesives. PMID:25392403

Attributing Historical Changes in Probabilities of Record-Breaking Daily Temperature and Precipitation Extreme Events

DOE PAGES

Shiogama, Hideo; Imada, Yukiko; Mori, Masato; ...

2016-08-07

Here, we describe two unprecedented large (100-member), longterm (61-year) ensembles based on MRI-AGCM3.2, which were driven by historical and non-warming climate forcing. These ensembles comprise the "Database for Policy Decision making for Future climate change (d4PDF)". We compare these ensembles to large ensembles based on another climate model, as well as to observed data, to investigate the influence of anthropogenic activities on historical changes in the numbers of record-breaking events, including: the annual coldest daily minimum temperature (TNn), the annual warmest daily maximum temperature (TXx) and the annual most intense daily precipitation event (Rx1day). These two climate model ensembles indicatemore » that human activity has already had statistically significant impacts on the number of record-breaking extreme events worldwide mainly in the Northern Hemisphere land. Specifically, human activities have altered the likelihood that a wider area globally would suffer record-breaking TNn, TXx and Rx1day events than that observed over the 2001- 2010 period by a factor of at least 0.6, 5.4 and 1.3, respectively. However, we also find that the estimated spatial patterns and amplitudes of anthropogenic impacts on the probabilities of record-breaking events are sensitive to the climate model and/or natural-world boundary conditions used in the attribution studies.« less

Remote Sensing Characterization of Two-dimensional Wave Forcing in the Surf Zone

NASA Astrophysics Data System (ADS)

Carini, R. J.; Chickadel, C. C.; Jessup, A. T.

2016-02-01

In the surf zone, breaking waves drive longshore currents, transport sediment, shape bathymetry, and enhance air-sea gas and particle exchange. Furthermore, wave group forcing influences the generation and duration of rip currents. Wave breaking exhibits large gradients in space and time, making it challenging to measure in situ. Remote sensing technologies, specifically thermal infrared (IR) imagery, can provide detailed spatial and temporal measurements of wave breaking at the water surface. We construct two-dimensional maps of active wave breaking from IR imagery collected during the Surf Zone Optics Experiment in September 2010 at the US Army Corps of Engineers' Field Research Facility in Duck, NC. For each breaker identified in the camera's field of view, the crest-perpendicular length of the aerated breaking region (roller length) and wave direction are estimated and used to compute the wave energy dissipation rate. The resultant dissipation rate maps are analyzed over different time scales: peak wave period, infragravity wave period, and tidal wave period. For each time scale, spatial maps of wave breaking are used to characterize wave forcing in the surf zone for a variety of wave conditions. The following phenomena are examined: (1) wave dissipation rates over the bar (location of most intense breaking) have increased variance in infragravity wave frequencies, which are different from the peak frequency of the incoming wave field and different from the wave forcing variability at the shoreline, and (2) wave forcing has a wider spatial distribution during low tide than during high tide due to depth-limited breaking over the barred bathymetry. Future work will investigate the response of the variability in wave setup, longshore currents and rip currents, to the variability in wave forcing in the surf zone.

Development of a unified oil droplet size distribution model with application to surface breaking waves and subsea blowout releases considering dispersant effects.

PubMed

Li, Zhengkai; Spaulding, Malcolm; French McCay, Deborah; Crowley, Deborah; Payne, James R

2017-01-15

An oil droplet size model was developed for a variety of turbulent conditions based on non-dimensional analysis of disruptive and restorative forces, which is applicable to oil droplet formation under both surface breaking-wave and subsurface-blowout conditions, with or without dispersant application. This new model was calibrated and successfully validated with droplet size data obtained from controlled laboratory studies of dispersant-treated and non-treated oil in subsea dispersant tank tests and field surveys, including the Deep Spill experimental release and the Deepwater Horizon blowout oil spill. This model is an advancement over prior models, as it explicitly addresses the effects of the dispersed phase viscosity, resulting from dispersant application and constrains the maximum stable droplet size based on Rayleigh-Taylor instability that is invoked for a release from a large aperture. Copyright © 2016 Elsevier Ltd. All rights reserved.

TYPE Ia SUPERNOVAE: CAN CORIOLIS FORCE BREAK THE SYMMETRY OF THE GRAVITATIONAL CONFINED DETONATION EXPLOSION MECHANISM?

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

García-Senz, D.; Cabezón, R. M.; Thielemann, F. K.

Currently the number of models aimed at explaining the phenomena of type Ia supernovae is high and distinguishing between them is a must. In this work we explore the influence of rotation on the evolution of the nuclear flame that drives the explosion in the so-called gravitational confined detonation models. Assuming that the flame starts in a pointlike region slightly above the center of the white dwarf (WD) and adding a moderate amount of angular velocity to the star we follow the evolution of the deflagration using a smoothed particle hydrodynamics code. We find that the results are very dependentmore » on the angle between the rotational axis and the line connecting the initial bubble of burned material with the center of the WD at the moment of ignition. The impact of rotation is larger for angles close to 90° because the Coriolis force on a floating element of fluid is maximum and its principal effect is to break the symmetry of the deflagration. Such symmetry breaking weakens the convergence of the nuclear flame at the antipodes of the initial ignition volume, changing the environmental conditions around the convergence region with respect to non-rotating models. These changes seem to disfavor the emergence of a detonation in the compressed volume at the antipodes and may compromise the viability of the so-called gravitational confined detonation mechanism.« less

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

Shiogama, Hideo; Imada, Yukiko; Mori, Masato

Here, we describe two unprecedented large (100-member), longterm (61-year) ensembles based on MRI-AGCM3.2, which were driven by historical and non-warming climate forcing. These ensembles comprise the "Database for Policy Decision making for Future climate change (d4PDF)". We compare these ensembles to large ensembles based on another climate model, as well as to observed data, to investigate the influence of anthropogenic activities on historical changes in the numbers of record-breaking events, including: the annual coldest daily minimum temperature (TNn), the annual warmest daily maximum temperature (TXx) and the annual most intense daily precipitation event (Rx1day). These two climate model ensembles indicatemore » that human activity has already had statistically significant impacts on the number of record-breaking extreme events worldwide mainly in the Northern Hemisphere land. Specifically, human activities have altered the likelihood that a wider area globally would suffer record-breaking TNn, TXx and Rx1day events than that observed over the 2001- 2010 period by a factor of at least 0.6, 5.4 and 1.3, respectively. However, we also find that the estimated spatial patterns and amplitudes of anthropogenic impacts on the probabilities of record-breaking events are sensitive to the climate model and/or natural-world boundary conditions used in the attribution studies.« less

Elastic properties of suspended black phosphorus nanosheets

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

Wang, Jia-Ying; Li, Yang; Zhen, Liang

2016-01-04

The mechanical properties of black phosphorus (BP) nanosheets suspended over circular holes were measured by an atomic force microscope nanoindentation method. The continuum mechanic model was introduced to calculate the elastic modulus and pretension of BP nanosheets with thicknesses ranging from 14.3 to 34 nm. Elastic modulus of BP nanosheets declines with thickness, and the maximum value is 276 ± 32.4 GPa. Besides, the effective strain of BP ranges from 8 to 17% with a breaking strength of 25 GPa. Our results show that BP nanosheets serve as a promising candidate for flexible electronic applications.

The ’In Lieu Of’ Myth. Airmen in Joint Ground Operations (Walker Paper, Number 13)

DTIC Science & Technology

2009-01-01

Romano, Dains , and Watts, “Air Force Breaks New Ground,” 14. 25. Air Force Print News, “Dangerous Road to Progress,” 42; and Air Force Print News...92 Romano, Lt Col Joseph L., III; Capt William M. Dains ; and Capt David T. Watts, “Air Force Breaks New Ground at Camp Bucca, Iraq.” Military

Axial strength test for round flat faced versus capsule shaped bilayer tablets.

PubMed

Franck, Jason; Abebe, Admassu; Keluskar, Rekha; Martin, Kyle; Majumdar, Antara; Kottala, Niranjan; Stamato, Howard

2015-03-01

There has been increasing interest in fixed dose combination (FDC) therapy. Multi-layer tablets are a popular choice among various technologies to deliver FDCs. In most cases, round flat faced tooling is used in testing tablets as they have the simplest geometry. However, shaped tooling is more common for commercial products and may have an effect on bilayer tablet strength. Capsule shaped bilayer tablets, similar to a commercial image, and holders conforming to the tablet topology, were compared with similar round flat faced bilayer tablets and their corresponding holders. Bilayer tablets were subjected to an axial test device, until fracture and the quantitative breaking force value was recorded. As the second layer compression force increases, regardless of holder design, an increase in breaking force occurs as expected. This consistent trend provides insight regarding the breaking force of capsule shaped bilayer tablets. The results of this study show that at lower second layer compression forces, tablet geometry does not significantly impact the results. However, at higher compression forces, a significant difference in breaking force between tablet geometries exists. Therefore, using a test geometry close to the final commercial tablet image is recommended to have the most accurate prediction for tablet breakage.

Ultrasonic friction power during Al wire wedge-wedge bonding

NASA Astrophysics Data System (ADS)

Shah, A.; Gaul, H.; Schneider-Ramelow, M.; Reichl, H.; Mayer, M.; Zhou, Y.

2009-07-01

Al wire bonding, also called ultrasonic wedge-wedge bonding, is a microwelding process used extensively in the microelectronics industry for interconnections to integrated circuits. The bonding wire used is a 25μm diameter AlSi1 wire. A friction power model is used to derive the ultrasonic friction power during Al wire bonding. Auxiliary measurements include the current delivered to the ultrasonic transducer, the vibration amplitude of the bonding tool tip in free air, and the ultrasonic force acting on the bonding pad during the bond process. The ultrasonic force measurement is like a signature of the bond as it allows for a detailed insight into mechanisms during various phases of the process. It is measured using piezoresistive force microsensors integrated close to the Al bonding pad (Al-Al process) on a custom made test chip. A clear break-off in the force signal is observed, which is followed by a relatively constant force for a short duration. A large second harmonic content is observed, describing a nonsymmetric deviation of the signal wave form from the sinusoidal shape. This deviation might be due to the reduced geometrical symmetry of the wedge tool. For bonds made with typical process parameters, several characteristic values used in the friction power model are determined. The ultrasonic compliance of the bonding system is 2.66μm/N. A typical maximum value of the relative interfacial amplitude of ultrasonic friction is at least 222nm. The maximum interfacial friction power is at least 11.5mW, which is only about 4.8% of the total electrical power delivered to the ultrasonic generator.

Steel Fibers Reinforced Concrete Pipes - Experimental Tests and Numerical Simulation

NASA Astrophysics Data System (ADS)

Doru, Zdrenghea

2017-10-01

The paper presents in the first part a state of the art review of reinforced concrete pipes used in micro tunnelling realised through pipes jacking method and design methods for steel fibres reinforced concrete. In part two experimental tests are presented on inner pipes with diameters of 1410mm and 2200mm, and specimens (100x100x500mm) of reinforced concrete with metal fibres (35 kg / m3). In part two experimental tests are presented on pipes with inner diameters of 1410mm and 2200mm, and specimens (100x100x500mm) of reinforced concrete with steel fibres (35 kg / m3). The results obtained are analysed and are calculated residual flexural tensile strengths which characterise the post-cracking behaviour of steel fibres reinforced concrete. In the third part are presented numerical simulations of the tests of pipes and specimens. The model adopted for the pipes test was a three-dimensional model and loads considered were those obtained in experimental tests at reaching breaking forces. Tensile stresses determined were compared with mean flexural tensile strength. To validate tensile parameters of steel fibres reinforced concrete, experimental tests of the specimens were modelled with MIDAS program to reproduce the flexural breaking behaviour. To simulate post - cracking behaviour was used the method σ — ε based on the relationship stress - strain, according to RILEM TC 162-TDF. For the specimens tested were plotted F — δ diagrams, which have been superimposed for comparison with the similar diagrams of experimental tests. The comparison of experimental results with those obtained from numerical simulation leads to the following conclusions: - the maximum forces obtained by numerical calculation have higher values than the experimental values for the same tensile stresses; - forces corresponding of residual strengths have very similar values between the experimental and numerical calculations; - generally the numerical model estimates a breaking force greater than that obtained in the experimental tests. Experimental and numerical studies are used to establish the residual characteristic flexural tensile strength minimum guaranteed and limits of applicability of concrete pipes reinforced with steel fibres used in various field and loading situations.

Torsional Rigidity of Single Actin Filaments and Actin-Actin Bond Breaking Force under Torsion Measured Directly by in vitro Micromanipulation

NASA Astrophysics Data System (ADS)

Tsuda, Yuri; Yasutake, Hironori; Ishijima, Akihiko; Yanagida, Toshio

1996-11-01

Knowledge of the elastic properties of actin filaments is crucial for considering its role in muscle contraction, cellular motile events, and formation of cell shape. The stiffness of actin filaments in the directions of stretching and bending has been determined. In this study, we have directly determined the torsional rigidity and breaking force of single actin filaments by measuring the rotational Brownian motion and tensile strength using optical tweezers and microneedles, respectively. Rotational angular fluctuations of filaments supplied the torsional rigidity as (8.0 ± 1.2) × 10-26 Nm2. This value is similar to that deduced from the longitudinal rigidity, assuming the actin filament to be a homogeneous rod. The breaking force of the actin-actin bond was measured while twisting a filament through various angles using microneedles. The breaking force decreased greatly under twist, e.g., from 600-320 pN when filaments were turned through 90 degrees, independent of the rotational direction. Our results indicate that an actin filament exhibits comparable flexibility in the rotational and longitudinal directions, but breaks more easily under torsional load.

a Study on Impact Analysis of Side Kick in Taekwondo

NASA Astrophysics Data System (ADS)

Lee, Jung-Hyun; Lee, Young-Shin; Han, Kyu-Hyun

Taekwondo is a martial art form and sport that uses the hands and feet for attack and defense. Taekwondo basic motion is composed of the breaking, competition and poomsea motions. The side kick is one of the most important breaking motions. The side kick with the front foot can be made in two steps. In the first step, the front foot is extended forward from the back stance free-fighting position. For the second step, the rear foot is followed simultaneously. Then, the side kick is executed while the entire body weight rests on the rear foot. In this paper, the impact analysis on a human model for kicking posture was carried out. The ADAMS/LifeMOD used numerical modeling and simulation for the side kick. The numerical human models for assailant and opponent in competition motion were developed. The maximum impact force on the human body was obtained by experiment and was applied to impact simulation. As a result, the impact displacement and velocity of the numerical human model were investigated.

Effect of Vacuum Frying on Changes in Quality Attributes of Jackfruit (Artocarpus heterophyllus) Bulb Slices.

PubMed

Maity, Tanushree; Bawa, A S; Raju, P S

2014-01-01

The effect of frying temperatures and durations on the quality of vacuum fried jackfruit (JF) chips was evaluated. Moisture content and breaking force of JF chips decreased with increase in frying temperature and time during vacuum frying whereas the oil content increased. The frying time for JF chips was found to be 30, 25, and 20 minutes at 80, 90, and 100°C, respectively. JF chips fried at higher temperature resulted in maximum shrinkage (48%). The lightness in terms of hunter L (*) value decreased significantly (P < 0.05) during frying. Sensory evaluation showed maximum acceptability for JF chips fried at 90°C for 25 min. Frying under vacuum at lower temperatures was found to retain bioactive compounds such as total phenolics, total flavonoids, and total carotenoids in JF chips. Almost 90% of carotenoids were lost from the samples after 30 min of frying at 100°C.

Avoiding early revision rhytidectomy: a biomechanical comparison of tissue plication suture techniques.

PubMed

White, Jeremy B; Barraja, Mathieu; Mengesha, Tewodros; Bose, Sumit; Ashktorab, Samaneh; Bahn, Ryan; Vallance, Ryan; Lindsey, William H

2008-12-01

Manipulation and suspension of the superficial musculoaponeurotic system (SMAS) is performed by 74% of rhytidectomy surgeons. Multiple variations in suture techniques are employed in this task, but they have never been evaluated for differences in their ability to withstand stress. To compare the biomechanical properties of two different suture techniques that are used in SMAS plications during rhytidectomy: a double-layered running locking (DRL) stitch and multiple horizontal mattress stitches. Fourteen horizontal mattress plications, in rows of six sutures, and comparable lengths of 16 DRL stitch plications of pig skin samples, were stressed using a tensometer with grip displacement increasing at a constant rate of 0.5 cm/Min. The required force to cause plication failure was recorded for each sample at three suture break points. There was no significant difference between the two groups in the force required to cause the initial suture failure. Unlike the horizontal mattress plication, an initial break seemed to cause minimal to no distortion of the DRL tissue plication. When results were normalized by the initial break forces to account for small variations in tissue properties, the force ratio required to cause a second suture break was significantly larger in the DRL group than in the horizontal mattress technique. This is evidenced by the average second to first break force ratios of 1.62 vs. 1.13 for the DRL and horizontal mattress stitches, respectively, with a P-value of .60. The mean ratios of third to first break forces for the DRL and horizontal mattress groups were 2.08 and 0.91, respectively, with a P-value of .08. The DRL stitch requires more force than the horizontal mattress stitch to cause significant failure of tissue plication. This technique may enable plastic surgeons to avoid early revision rhytidectomy due to suture failure, and to create a long-lasting, youthful cosmetic result.

Continental underplating after slab break-off

NASA Astrophysics Data System (ADS)

Magni, V.; Allen, M. B.; van Hunen, J.; Bouilhol, P.

2017-09-01

We present three-dimensional numerical models to investigate the dynamics of continental collision, and in particular what happens to the subducted continental lithosphere after oceanic slab break-off. We find that in some scenarios the subducting continental lithosphere underthrusts the overriding plate not immediately after it enters the trench, but after oceanic slab break-off. In this case, the continental plate first subducts with a steep angle and then, after the slab breaks off at depth, it rises back towards the surface and flattens below the overriding plate, forming a thick horizontal layer of continental crust that extends for about 200 km beyond the suture. This type of behaviour depends on the width of the oceanic plate marginal to the collision zone: wide oceanic margins promote continental underplating and marginal back-arc basins; narrow margins do not show such underplating unless a far field force is applied. Our models show that, as the subducted continental lithosphere rises, the mantle wedge progressively migrates away from the suture and the continental crust heats up, reaching temperatures >900 °C. This heating might lead to crustal melting, and resultant magmatism. We observe a sharp peak in the overriding plate rock uplift right after the occurrence of slab break-off. Afterwards, during underplating, the maximum rock uplift is smaller, but the affected area is much wider (up to 350 km). These results can be used to explain the dynamics that led to the present-day crustal configuration of the India-Eurasia collision zone and its consequences for the regional tectonic and magmatic evolution.

Seasonal Strength Performance and Its Relationship with Training Load on Elite Runners

PubMed Central

Balsalobre-Fernández, Carlos; Tejero-González, Carlos M.; del Campo-Vecino, Juan

2015-01-01

The aim of this study was to analyze the time-course of force production of elite middle and long-distance runners throughout an entire season and at the end of the off-season, as well as its relationships with training load and hormonal responses. Training load was recorded daily throughout an entire season by measuring and evaluating the session distance (km), training zone and session-RPE in a group of 15 elite middle and long-distance runners (12 men, 3 women; age = 26.3 ± 5.1yrs, BMI = 19.7 ± 1.1). Also, basal salivary-free cortisol levels were measured weekly, and 50-metre sprints, mean propulsive velocity (MPV), mean propulsive power (MPP), repetition maximum (RM) and peak rate of force development (RFD) of half-squats were measured 4 times during the season, and once more after the off-season break. There were no significant variations in force production during the season or after the off-season break, except for the RFD (-30.2%, p = 0.005) values, which changed significantly from the beginning to the end of the season. Significant correlations were found between session-RPE and MPV (r = -0.650, p = 0.004), MPP (r = -0.602, p = 0.009), RM (r = -0.650, p = 0.004), and the 50-metre sprint (r = 0.560, p = 0.015). Meanwhile, salivary-free cortisol correlated significantly with the 50-metre sprint (r = 0.737, p < 0.001) and the RM ( r = -0.514, p = 0.025). Finally, the training zone correlated with the 50-metre sprint (r = -0.463, p = 0.041). Session-RPE, training zone and salivary-free cortisol levels are related to force production in elite middle and long-distance runners. Monitoring these variables could be a useful tool in controlling the training programs of elite athletes. Key points Session-RPE, training zone and salivary free cortisol levels correlate significantly with strength-related variables in middle and long-distance elite runners. A month of active rest during the off-season break is enough to prevent decreases in force production of such athletes. Monitoring training loads through session-RPE is a suitable and simple method for controlling the training process in elite middle and long-distance runners. PMID:25729283

Method for Cleanly and Precisely Breaking Off a Rock Core Using a Radial Compressive Force

NASA Technical Reports Server (NTRS)

Richardson, Megan; Lin, Justin

2011-01-01

The Mars Sample Return mission has the goal to drill, break off, and retain rock core samples. After some results gained from rock core mechanics testing, the realization that scoring teeth would cleanly break off the core after only a few millimeters of penetration, and noting that rocks are weak in tension, the idea was developed to use symmetric wedging teeth in compression to weaken and then break the core at the contact plane. This concept was developed as a response to the break-off and retention requirements. The wedges wrap around the estimated average diameter of the core to get as many contact locations as possible, and are then pushed inward, radially, through the core towards one another. This starts a crack and begins to apply opposing forces inside the core to propagate the crack across the plane of contact. The advantage is in the simplicity. Only two teeth are needed to break five varieties of Mars-like rock cores with limited penetration and reasonable forces. Its major advantage is that it does not require any length of rock to be attached to the parent in order to break the core at the desired location. Test data shows that some rocks break off on their own into segments or break off into discs. This idea would grab and retain a disc, push some discs upward and others out, or grab a segment, break it at the contact plane, and retain the portion inside of the device. It also does this with few moving parts in a simple, space-efficient design. This discovery could be implemented into a coring drill bit to precisely break off and retain any size rock core.

Dynamics of Individual cilia to external loading- A simple one dimensional picture

NASA Astrophysics Data System (ADS)

Swaminathan, Vinay; Hill, David; Superfine, R.

2008-10-01

From being called the cellular janitors to swinging debauchers, cilia have captured the fascinations of researchers for over 200 years. In cystic fibrosis and chronic obstructive pulmonary disease where the cilia loses it's function, the protective mucus layer in the lung thickens and mucociliary clearance breaks down, leading to inflammation along the airways and an increased rate of infection. The mechanistic understanding of mucus clearance depends on a quantitative assessment of the axoneme dynamics and the maximum force the cilia are capable of generating and imparting to the mucus layer. Similar to the situation in molecular motors, detailed quantitative measurements of dynamics under applied load conditions are expected to be essential in developing predictive models. Based on our measurements of the dynamics of individual ciliary motion in the human bronchial epithelial cell under the application of an applied load, we present a simple one dimensional model for the axoneme dynamics and quantify the axoneme stiffness, the internal force generated by the axoneme, the stall force and show how the dynamics sheds insight on the time dependence of the internal force generation. The internal force generated by the axoneme is related to the ability of cilia to propel fluids and to their potential role in force sensing.

Numerical simulation of two-phase flow for sediment transport in the inner-surf and swash zones

NASA Astrophysics Data System (ADS)

Bakhtyar, R.; Barry, D. A.; Yeganeh-Bakhtiary, A.; Li, L.; Parlange, J.-Y.; Sander, G. C.

2010-03-01

A two-dimensional two-phase flow framework for fluid-sediment flow simulation in the surf and swash zones was described. Propagation, breaking, uprush and backwash of waves on sloping beaches were studied numerically with an emphasis on fluid hydrodynamics and sediment transport characteristics. The model includes interactive fluid-solid forces and intergranular stresses in the moving sediment layer. In the Euler-Euler approach adopted, two phases were defined using the Navier-Stokes equations with interphase coupling for momentum conservation. The k-ɛ closure model and volume of fluid approach were used to describe the turbulence and tracking of the free surface, respectively. Numerical simulations explored incident wave conditions, specifically spilling and plunging breakers, on both dissipative and intermediate beaches. It was found that the spatial variation of sediment concentration in the swash zone is asymmetric, while the temporal behavior is characterized by maximum sediment concentrations at the start and end of the swash cycle. The numerical results also indicated that the maximum turbulent kinetic energy and sediment flux occurs near the wave-breaking point. These predictions are in general agreement with previous observations, while the model describes the fluid and sediment phase characteristics in much more detail than existing measurements. With direct quantifications of velocity, turbulent kinetic energy, sediment concentration and flux, the model provides a useful approach to improve mechanistic understanding of hydrodynamic and sediment transport in the nearshore zone.

Analysis of brute-force break-ins of a palmprint authentication system.

PubMed

Kong, Adams W K; Zhang, David; Kamel, Mohamed

2006-10-01

Biometric authentication systems are widely applied because they offer inherent advantages over classical knowledge-based and token-based personal-identification approaches. This has led to the development of products using palmprints as biometric traits and their use in several real applications. However, as biometric systems are vulnerable to replay, database, and brute-force attacks, such potential attacks must be analyzed before biometric systems are massively deployed in security systems. This correspondence proposes a projected multinomial distribution for studying the probability of successfully using brute-force attacks to break into a palmprint system. To validate the proposed model, we have conducted a simulation. Its results demonstrate that the proposed model can accurately estimate the probability. The proposed model indicates that it is computationally infeasible to break into the palmprint system using brute-force attacks.

Mixing and Formation of Layers by Internal Wave Forcing

NASA Astrophysics Data System (ADS)

Dossmann, Yvan; Pollet, Florence; Odier, Philippe; Dauxois, Thierry

2017-12-01

The energy pathways from propagating internal waves to the scales of irreversible mixing in the ocean are not fully described. In the ocean interior, the triadic resonant instability is an intrinsic destabilization process that may enhance the energy cascade away from topographies. The present study focuses on the integrated impact of mixing processes induced by a propagative normal mode-1 over long-term experiments in an idealized setup. The internal wave dynamics and the evolution of the density profile are followed using the light attenuation technique. Diagnostics of the turbulent diffusivity KT and background potential energy BPE are provided. Mixing effects result in a partially mixed layer colocated with the region of maximum shear induced by the forcing normal mode. The maximum measured turbulent diffusivity is 250 times larger than the molecular value, showing that diapycnal mixing is largely enhanced by small-scale turbulent processes. Intermittency and reversible energy transfers are discussed to bridge the gap between the present diagnostic and the larger values measured in Dossmann et al. (). The mixing efficiency η is assessed by relating the BPE growth to the linearized KE input. One finds a value of Γ=12-19%, larger than the mixing efficiency in the case of breaking interfacial wave. After several hours of forcing, the development of staircases in the density profile is observed. This mechanism has been previously observed in experiments with weak homogeneous turbulence and explained by Phillips (1972) argument. The present experiments suggest that internal wave forcing could also induce the formation of density interfaces in the ocean.

Biomechanical properties of wheat grains: the implications on milling.

PubMed

Hourston, James E; Ignatz, Michael; Reith, Martin; Leubner-Metzger, Gerhard; Steinbrecher, Tina

2017-01-01

Millennia of continuous innovation have driven ever increasing efficiency in the milling process. Mechanically characterizing wheat grains and discerning the structure and function of the wheat bran layers can contribute to continuing innovation. We present novel shear force and puncture force testing regimes to characterize different wheat grain cultivars. The forces endured by wheat grains during the milling process can be quantified, enabling us to measure the impact of commonly applied grain pretreatments, such as microwave heating, extended tempering, enzyme and hormone treatments on grains of different 'hardness'. Using these methods, we demonstrate the importance of short tempering phases prior to milling and identify ways in which our methods can detect differences in the maximum force, energy and breaking behaviours of hard and soft grain types. We also demonstrate for the first time, endosperm weakening in wheat, through hormone stratification on single bran layers. The modern milling process is highly refined, meaning that small, cultivar specific, adjustments can result in large increases in downstream profits. We believe that methods such as these, which enable rapid testing of milling pretreatments and material properties can help to drive an innovation process that has been core to our industrial efforts since prehistory. © 2017 The Authors.

Biomechanical properties of wheat grains: the implications on milling

PubMed Central

Reith, Martin

2017-01-01

Millennia of continuous innovation have driven ever increasing efficiency in the milling process. Mechanically characterizing wheat grains and discerning the structure and function of the wheat bran layers can contribute to continuing innovation. We present novel shear force and puncture force testing regimes to characterize different wheat grain cultivars. The forces endured by wheat grains during the milling process can be quantified, enabling us to measure the impact of commonly applied grain pretreatments, such as microwave heating, extended tempering, enzyme and hormone treatments on grains of different ‘hardness’. Using these methods, we demonstrate the importance of short tempering phases prior to milling and identify ways in which our methods can detect differences in the maximum force, energy and breaking behaviours of hard and soft grain types. We also demonstrate for the first time, endosperm weakening in wheat, through hormone stratification on single bran layers. The modern milling process is highly refined, meaning that small, cultivar specific, adjustments can result in large increases in downstream profits. We believe that methods such as these, which enable rapid testing of milling pretreatments and material properties can help to drive an innovation process that has been core to our industrial efforts since prehistory. PMID:28100826

FAST TRACK COMMUNICATION: Criticality-induced universality in ratchets

NASA Astrophysics Data System (ADS)

Chacón, Ricardo

2010-08-01

Conclusive mathematical arguments are presented supporting the ratchet conjecture (Chacón 2007 J. Phys. A: Math. Theor. 40 F413), i.e. the existence of a universal force waveform which optimally enhances directed transport by symmetry breaking. Specifically, such a particular waveform is shown to be unique for both temporal and spatial biharmonic forces, and general (non-perturbative) laws providing the dependence of the strength of directed transport on the force parameters are deduced for these forces. The theory explains previous results for a great diversity of systems subjected to such biharmonic forces and provides a universal quantitative criterion to optimize any application of the ratchet effect induced by symmetry breaking of temporal and spatial biharmonic forces.

Simulation of the Greenland Ice Sheet over two glacial-interglacial cycles: investigating a sub-ice-shelf melt parameterization and relative sea level forcing in an ice-sheet-ice-shelf model

NASA Astrophysics Data System (ADS)

Bradley, Sarah L.; Reerink, Thomas J.; van de Wal, Roderik S. W.; Helsen, Michiel M.

2018-05-01

Observational evidence, including offshore moraines and sediment cores, confirm that at the Last Glacial Maximum (LGM) the Greenland ice sheet (GrIS) expanded to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and out onto the continental shelf break. Given this larger spatial extent and its close proximity to the neighbouring Laurentide Ice Sheet (LIS) and Innuitian Ice Sheet (IIS), it is likely these ice sheets will have had a strong non-local influence on the spatial and temporal behaviour of the GrIS. Most previous paleo ice-sheet modelling simulations recreated an ice sheet that either did not extend out onto the continental shelf or utilized a simplified marine ice parameterization which did not fully include the effect of ice shelves or neglected the sensitivity of the GrIS to this non-local bedrock signal from the surrounding ice sheets. In this paper, we investigated the evolution of the GrIS over the two most recent glacial-interglacial cycles (240 ka BP to the present day) using the ice-sheet-ice-shelf model IMAU-ICE. We investigated the solid earth influence of the LIS and IIS via an offline relative sea level (RSL) forcing generated by a glacial isostatic adjustment (GIA) model. The RSL forcing governed the spatial and temporal pattern of sub-ice-shelf melting via changes in the water depth below the ice shelves. In the ensemble of simulations, at the glacial maximums, the GrIS coalesced with the IIS to the north and expanded to the continental shelf break to the southwest but remained too restricted to the northeast. In terms of the global mean sea level contribution, at the Last Interglacial (LIG) and LGM the ice sheet added 1.46 and -2.59 m, respectively. This LGM contribution by the GrIS is considerably higher (˜ 1.26 m) than most previous studies whereas the contribution to the LIG highstand is lower (˜ 0.7 m). The spatial and temporal behaviour of the northern margin was highly variable in all simulations, controlled by the sub-ice-shelf melting which was dictated by the RSL forcing and the glacial history of the IIS and LIS. In contrast, the southwestern part of the ice sheet was insensitive to these forcings, with a uniform response in all simulations controlled by the surface air temperature, derived from ice cores.

Modelling wave-induced sea ice break-up in the marginal ice zone

NASA Astrophysics Data System (ADS)

Montiel, F.; Squire, V. A.

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

Modelling wave-induced sea ice break-up in the marginal ice zone

PubMed Central

Squire, V. A.

2017-01-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ. PMID:29118659

Modelling wave-induced sea ice break-up in the marginal ice zone.

PubMed

Montiel, F; Squire, V A

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

Nearshore Tsunami Inundation Model Validation: Toward Sediment Transport Applications

USGS Publications Warehouse

Apotsos, Alex; Buckley, Mark; Gelfenbaum, Guy; Jaffe, Bruce; Vatvani, Deepak

2011-01-01

Model predictions from a numerical model, Delft3D, based on the nonlinear shallow water equations are compared with analytical results and laboratory observations from seven tsunami-like benchmark experiments, and with field observations from the 26 December 2004 Indian Ocean tsunami. The model accurately predicts the magnitude and timing of the measured water levels and flow velocities, as well as the magnitude of the maximum inundation distance and run-up, for both breaking and non-breaking waves. The shock-capturing numerical scheme employed describes well the total decrease in wave height due to breaking, but does not reproduce the observed shoaling near the break point. The maximum water levels observed onshore near Kuala Meurisi, Sumatra, following the 26 December 2004 tsunami are well predicted given the uncertainty in the model setup. The good agreement between the model predictions and the analytical results and observations demonstrates that the numerical solution and wetting and drying methods employed are appropriate for modeling tsunami inundation for breaking and non-breaking long waves. Extension of the model to include sediment transport may be appropriate for long, non-breaking tsunami waves. Using available sediment transport formulations, the sediment deposit thickness at Kuala Meurisi is predicted generally within a factor of 2.

Why Chalk Breaks into Three Pieces When Dropped

NASA Astrophysics Data System (ADS)

Cross, Rod

2015-01-01

It has been the author's experience over many years, no doubt shared by others, that a stick of chalk usually breaks into three pieces when accidentally dropped onto the floor. I rarely gave it any thought, apart from noting that the fundamental mode of vibration of a freely supported, rigid rod has two nodes at an equal distance from each end. For example, a baseball bat has a node in the barrel (the sweet spot) about 15 cm from the end and another node in the handle. However, chalk is not expected to break at the node points, since maximum stress arises at the antinode in the middle of the chalk where bending is a maximum. Richard Feynman described a similar problem with long sticks of spaghetti.1 He found that they always break into three or more pieces when bent slowly beyond their breaking point, rather than simply breaking in half. He was unable to figure out why, although the problem was solved many years later2 and is nicely illustrated by Vollmer and Mollmann.3

Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the late Eocene of Egypt estimated by finite element analysis.

PubMed

Snively, Eric; Fahlke, Julia M; Welsh, Robert C

2015-01-01

Bite marks suggest that the late Eocence archaeocete whale Basilosaurus isis (Birket Qarun Formation, Egypt) fed upon juveniles of the contemporary basilosaurid Dorudon atrox. Finite element analysis (FEA) of a nearly complete adult cranium of B. isis enables estimates of its bite force and tests the animal's capabilities for crushing bone. Two loadcases reflect different biting scenarios: 1) an intitial closing phase, with all adductors active and a full condylar reaction force; and 2) a shearing phase, with the posterior temporalis active and minimized condylar force. The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion. Reaction forces with all muscles active indicate that B. isis maintained relatively greater bite force anteriorly than seen in large crocodilians, and exerted a maximum bite force of at least 16,400 N at its upper P3. Under the shearing scenario with minimized condylar forces, tooth reaction forces could exceed 20,000 N despite lower magnitudes of muscle force. These bite forces at the teeth are consistent with bone indentations on Dorudon crania, reatract-and-shear hypotheses of Basilosaurus bite function, and seizure of prey by anterior teeth as proposed for other archaeocetes. The whale's bite forces match those estimated for pliosaurus when skull lengths are equalized, suggesting similar tradeoffs of bite function and hydrodynamics. Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs. However, comparison of force estimates from FEA and regression data indicate that B. isis exerted the largest bite forces yet estimated for any mammal, and greater force than expected from its skull width. Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.

A depth-averaged 2-D shallow water model for breaking and non-breaking long waves affected by rigid vegetation

USDA-ARS?s Scientific Manuscript database

This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...

A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

PubMed Central

van Vörden, Dennis; Möller, Rolf

2012-01-01

Summary Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111) √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force–distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle. PMID:22496993

Mechanical circulator for elastic waves by using the nonreciprocity of flexible rotating rings

NASA Astrophysics Data System (ADS)

Beli, Danilo; Silva, Priscilla Brandão; Arruda, José Roberto de França

2018-01-01

Circulators have a wide range of applications in wave manipulation. They provide a nonreciprocal response by breaking the time-reversal symmetry. In the mechanical field, nonlinear isolators and ferromagnetic circulators can be used for this objective. However, they require high power and high volumes. Herein, a flexible rotating ring is used to break the time-reversal symmetry as a result of the combined effect of Coriolis acceleration and material damping. Complete asymmetry of oscillating and evanescent components of wavenumbers is achieved. The elastic ring produces a nonreciprocal response that is used to design a three port mechanical circulator. The rotational speed for maximum transmission in one port and isolation in the other one is determined using analytical equations. A spectral element formulation is used to compute the complex dispersion diagrams and the forced response. Waveguides that support longitudinal and flexural waves are investigated. In this case, the ring nonreciprocity is modulated by the waveguide reciprocal response and the transmission coefficients can be affected. The proposed device is compact, nonferromagnetic, and may open new directions for elastic wave manipulation.

A parametric symmetry breaking transducer

NASA Astrophysics Data System (ADS)

Eichler, Alexander; Heugel, Toni L.; Leuch, Anina; Degen, Christian L.; Chitra, R.; Zilberberg, Oded

2018-06-01

Force detectors rely on resonators to transduce forces into a readable signal. Usually, these resonators operate in the linear regime and their signal appears amidst a competing background comprising thermal or quantum fluctuations as well as readout noise. Here, we demonstrate a parametric symmetry breaking transduction method that leads to a robust nonlinear force detection in the presence of noise. The force signal is encoded in the frequency at which the system jumps between two phase states which are inherently protected against phase noise. Consequently, the transduction effectively decouples from readout noise channels. For a controlled demonstration of the method, we experiment with a macroscopic doubly clamped string. Our method provides a promising paradigm for high-precision force detection.

CHARACTERIZATION OF AORTIC TISSUE CUTTING PROCESS: EXPERIMENTAL INVESTIGATION USING PORCINE ASCENDING AORTA

PubMed Central

Hu, Zhongwei; Sun, Wei; Zhang, Bi

2012-01-01

Understanding biomechanical responses during soft tissue cutting is important for developing surgical simulators and robot-assisted surgery with haptic feedback. The biomechanics involved in the aortic tissue cutting process is largely unknown. In this study, porcine ascending aorta was selected as a representative aortic tissue, and tissue cutting experiments were performed using a novel tissue cutting apparatus. The tissue cutting responses under various cutting conditions were investigated, including differing initial tissue lateral holding force and distance, cutting speed, cutter inclination angle, tissue anatomical orientation and thickness. The results from this study suggest that a “break-in” cutting force of about 4 – 12 N, a cutter “break-in” distance of 5 – 15 mm, and a continuous cutting force of 2 – 4 N were needed to cut through the porcine ascending aorta tissue. For all testing conditions investigated in this study, the cutting force vs. the cutter displacement curves exhibited similar characteristics. More importantly, this study demonstrated that tissue cutting involving one or more of the following conditions: a larger lateral holding force, a smaller lateral hold distance, a higher cutting speed or a larger inclination angle, could result in a smaller “break in” cutting force and a smaller “break-in” distance. In addition, it was found that the cutting force in the vessel longitudinal direction was larger than that in the circumferential direction. There was a strong correlation between the tissue thickness and the cutting force. The experimental results reported in this study could provide a basis for understanding the characteristic response of aortic tissue to scalpel cutting, and offer insight into the development of surgical simulators. PMID:23262306

Effect of Vacuum Frying on Changes in Quality Attributes of Jackfruit (Artocarpus heterophyllus) Bulb Slices

PubMed Central

Bawa, A. S.; Raju, P. S.

2014-01-01

The effect of frying temperatures and durations on the quality of vacuum fried jackfruit (JF) chips was evaluated. Moisture content and breaking force of JF chips decreased with increase in frying temperature and time during vacuum frying whereas the oil content increased. The frying time for JF chips was found to be 30, 25, and 20 minutes at 80, 90, and 100°C, respectively. JF chips fried at higher temperature resulted in maximum shrinkage (48%). The lightness in terms of hunter L * value decreased significantly (P < 0.05) during frying. Sensory evaluation showed maximum acceptability for JF chips fried at 90°C for 25 min. Frying under vacuum at lower temperatures was found to retain bioactive compounds such as total phenolics, total flavonoids, and total carotenoids in JF chips. Almost 90% of carotenoids were lost from the samples after 30 min of frying at 100°C. PMID:26904648

The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

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

Visser, P. J. de, E-mail: p.j.devisser@tudelft.nl; Yates, S. J. C.; Guruswamy, T.

2015-06-22

We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creationmore » efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements.« less

Frictional behavior of atomically thin sheets: hexagonal-shaped graphene islands grown on copper by chemical vapor deposition.

PubMed

Egberts, Philip; Han, Gang Hee; Liu, Xin Z; Johnson, A T Charlie; Carpick, Robert W

2014-05-27

Single asperity friction experiments using atomic force microscopy (AFM) have been conducted on chemical vapor deposited (CVD) graphene grown on polycrystalline copper foils. Graphene substantially lowers the friction force experienced by the sliding asperity of a silicon AFM tip compared to the surrounding oxidized copper surface by a factor ranging from 1.5 to 7 over loads from the adhesive minimum up to 80 nN. No damage to the graphene was observed over this range, showing that friction force microscopy serves as a facile, high contrast probe for identifying the presence of graphene on Cu. Consistent with studies of epitaxially grown, thermally grown, and mechanically exfoliated graphene films, the friction force measured between the tip and these CVD-prepared films depends on the number of layers of graphene present on the surface and reduces friction in comparison to the substrate. Friction results on graphene indicate that the layer-dependent friction properties result from puckering of the graphene sheet around the sliding tip. Substantial hysteresis in the normal force dependence of friction is observed with repeated scanning without breaking contact with a graphene-covered region. Because of the hysteresis, friction measured on graphene changes with time and maximum applied force, unless the tip slides over the edge of the graphene island or contact with the surface is broken. These results also indicate that relatively weak binding forces exist between the copper foil and these CVD-grown graphene sheets.

Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

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

Oka, Yurie, E-mail: ok-yu@fuji.waseda.jp; Yanao, Tomohiro, E-mail: yanao@waseda.jp; Koon, Wang Sang, E-mail: koon@cds.caltech.edu

2015-04-07

This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internalmore » centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.« less

Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

NASA Astrophysics Data System (ADS)

Oka, Yurie; Yanao, Tomohiro; Koon, Wang Sang

2015-04-01

This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.

Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

NASA Technical Reports Server (NTRS)

Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

2003-01-01

The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In the tropics, only with the AD parameterization can the model produce realistic semiannual oscillations.

Coherent Structures and Evolution of Vorticity in Short-Crested Breaking Surface Waves

NASA Astrophysics Data System (ADS)

Kirby, James; Derakhti, Morteza

2017-11-01

We employ a multi-phase LES/VOF code to study turbulence and coherent structures generated during breaking of short-crested surface water waves. We examine the evolution of coherent vortex structures evolving at the scale of the width of the breaking event, and their long-time interaction with smaller vortex loops formed by the local instability of the breaking crest. Long-time results are often characterized by the detachment of the larger scale vortex loop from the surface and formation of a closed vortex ring. The evolution of circulation for the vortical flow field is examined. The initial concentration of forcing close to the free surface leads to spatial distributions of both span-wise and vertical vorticity distributions which are concentrated close to the surface. This result, which persists into shallow water, is at odds with the basic simplicity of the Peregrine mechanism, suggesting that even shallow flows such as the surf zone should be regarded as being forced (in dissipative situations) by a wave-induced surface stress rather than a uniform-over-depth body force. The localized forcing leads to the development of a complex pattern of stream-wise vorticity, comparable in strength to the vertical and span-wise components, and also persist into shallow water. NSF OCE-1435147.

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.

Jumping on water

NASA Astrophysics Data System (ADS)

Kim, Ho-Young

2016-11-01

Water striders can jump on water as high as they can jump on land. Quick jumps allow them to avoid sudden dangers such as predators' attacks, and therefore understanding how they make such a dramatic motion for survival can shed light on the ultimate level of semi-aquatic motility achievable through evolution. However, the mechanism of their vertical jumping from a water surface has eluded hydrodynamic explanations so far. By observing movements of water strider legs and theoretically analyzing their dynamic interactions with deforming liquid-air interface, we have recently found that different species of jumping striders always tune their leg rotation speed with a force just below that required to break the water surface to reach the maximum take-off velocity. Here, we start with discussing the fundamental theories of dynamics of floating and sinking of small objects. The theories then enable us to analyze forces acting on a water strider while it presses down the water surface to fully exploit the capillary force. We further introduce a 68-milligram at-scale robotic insect capable of jumping on water without splash, strikingly similar to the real strider, by utilizing the water surface just as a trampoline.

Interior view of entry hall in Communication Center (now Break ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior view of entry hall in Communication Center (now Break Room and Storage Area), facing north - MacDill Air Force Base, Fire & Guard House, 2709 Florida Keys Avenue, Tampa, Hillsborough County, FL

A Comparison of 2 Current-Issue Army Boots.

DTIC Science & Technology

2000-01-01

at 3.5 mph, mean (SD) 32 21 .Maximum heel- strike vertical force (N) while walking at 3.5 mph, mean (SD) 33 22 Maximum heel- strike braking force...while running at 6.5 mph, mean (SD) 38 34 Maximum force on the hip (N) while running at 6.5 mph, mean (SD) 38 35 Maximum vertical heel- strike force (N...during 6.5 mph running, mean (SD) 39 36. Maximum heel- strike braking force (N) while running at 6.5 mph, mean (SD) 39 37. Maximum vertical push

Rock deformation equations and application to the study on slantingly installed disc cutter

NASA Astrophysics Data System (ADS)

Zhang, Zhao-Huang; Meng, Liang; Sun, Fei

2014-08-01

At present the mechanical model of the interaction between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine (TBM) on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the functional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke's law and analyze the effect of the slanting installation angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.

A Practical Framework Toward Prediction of Breaking Force and Disintegration of Tablet Formulations Using Machine Learning Tools.

PubMed

Akseli, Ilgaz; Xie, Jingjin; Schultz, Leon; Ladyzhynsky, Nadia; Bramante, Tommasina; He, Xiaorong; Deanne, Rich; Horspool, Keith R; Schwabe, Robert

2017-01-01

Enabling the paradigm of quality by design requires the ability to quantitatively correlate material properties and process variables to measureable product performance attributes. Conventional, quality-by-test methods for determining tablet breaking force and disintegration time usually involve destructive tests, which consume significant amount of time and labor and provide limited information. Recent advances in material characterization, statistical analysis, and machine learning have provided multiple tools that have the potential to develop nondestructive, fast, and accurate approaches in drug product development. In this work, a methodology to predict the breaking force and disintegration time of tablet formulations using nondestructive ultrasonics and machine learning tools was developed. The input variables to the model include intrinsic properties of formulation and extrinsic process variables influencing the tablet during manufacturing. The model has been applied to predict breaking force and disintegration time using small quantities of active pharmaceutical ingredient and prototype formulation designs. The novel approach presented is a step forward toward rational design of a robust drug product based on insight into the performance of common materials during formulation and process development. It may also help expedite drug product development timeline and reduce active pharmaceutical ingredient usage while improving efficiency of the overall process. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Bone-Breaking Bite Force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt Estimated by Finite Element Analysis

PubMed Central

Snively, Eric; Fahlke, Julia M.; Welsh, Robert C.

2015-01-01

Bite marks suggest that the late Eocence archaeocete whale Basilosaurus isis (Birket Qarun Formation, Egypt) fed upon juveniles of the contemporary basilosaurid Dorudon atrox. Finite element analysis (FEA) of a nearly complete adult cranium of B. isis enables estimates of its bite force and tests the animal’s capabilities for crushing bone. Two loadcases reflect different biting scenarios: 1) an intitial closing phase, with all adductors active and a full condylar reaction force; and 2) a shearing phase, with the posterior temporalis active and minimized condylar force. The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion. Reaction forces with all muscles active indicate that B. isis maintained relatively greater bite force anteriorly than seen in large crocodilians, and exerted a maximum bite force of at least 16,400 N at its upper P3. Under the shearing scenario with minimized condylar forces, tooth reaction forces could exceed 20,000 N despite lower magnitudes of muscle force. These bite forces at the teeth are consistent with bone indentations on Dorudon crania, reatract-and-shear hypotheses of Basilosaurus bite function, and seizure of prey by anterior teeth as proposed for other archaeocetes. The whale’s bite forces match those estimated for pliosaurus when skull lengths are equalized, suggesting similar tradeoffs of bite function and hydrodynamics. Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs. However, comparison of force estimates from FEA and regression data indicate that B. isis exerted the largest bite forces yet estimated for any mammal, and greater force than expected from its skull width. Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation. PMID:25714832

Modelling bucket excavation by finite element

NASA Astrophysics Data System (ADS)

Pecingina, O. M.

2015-11-01

Changes in geological components of the layers from lignite pits have an impact on the sustainability of the cup path elements and under the action of excavation force appear efforts leading to deformation of the entire assembly. Application of finite element method in the optimization of components leads to economic growth, to increase the reliability and durability of the studied machine parts thus the machine. It is obvious usefulness of knowledge the state of mechanical tensions that the designed piece or the assembly not to break under the action of tensions that must cope during operation. In the course of excavation work on all bucket cutting force components, the first coming into contact with the material being excavated cutting edge. Therefore in the study with finite element analysis is retained only cutting edge. To study the field of stress and strain on the cutting edge will be created geometric patterns for each type of cup this will be subject to static analysis. The geometric design retains the cutting edge shape and on this on the tooth cassette location will apply an areal force on the abutment tooth. The cutting edge real pattern is subjected to finite element study for the worst case of rock cutting by symmetrical and asymmetrical cups whose profile is different. The purpose of this paper is to determine the displacement and tensions field for both profiles considering the maximum force applied on the cutting edge and the depth of the cutting is equal with the width of the cutting edge of the tooth. It will consider the worst case when on the structure will act both the tangential force and radial force on the bucket profile. For determination of stress and strain field on the form design of cutting edge profile will apply maximum force assuming uniform distribution and on the edge surface force will apply a radial force. After geometric patterns discretization on the cutting knives and determining stress field, can be seen that at the rectangular profile appears the "clogging" phenomenon of the cutting edge and at the polygonal profile the point of application remains constant without going inside. From the finite element method done in this paper it can be concluded that the polygonal profiles made of dihedral angles are much more durable and asymmetric cups tend to have uniform tension along the entire perimeter.

Lorentz-like force emerging from kinematic interactions between electrons and nuclei in molecules: A quantum mechanical origin of symmetry breaking that can trigger molecular chirality.

PubMed

Takatsuka, Kazuo

2017-02-28

The Longuet-Higgins (Berry) phase arising from nonadiabatic dynamics and the Aharonov-Bohm phase associated with the dynamics of a charged particle in the electromagnetic vector potential are well known to be individually a manifestation of a class of the so-called geometrical phase. We herein discuss another similarity between the force working on a charged particle moving in a magnetic field, the Lorentz force, and a force working on nuclei while passing across a region where they have a strong quantum mechanical kinematic (nonadiabatic) coupling with electrons in a molecule. This kinematic force is indeed akin to the Lorentz force in that its magnitude is proportional to the velocity of the relevant nuclei and works in the direction perpendicular to its translational motion. Therefore this Lorentz-like nonadiabatic force is realized only in space of more or equal to three dimensions, thereby highlighting a truly multi-dimensional effect of nonadiabatic interaction. We investigate its physical significance qualitatively in the context of breaking of molecular spatial symmetry, which is not seen otherwise without this force. This particular symmetry breaking is demonstrated in application to a coplanar collision between a planar molecule and an atom sharing the same plane. We show that the atom is guided by this force to the direction out from the plane, resulting in a configuration that distinguishes one side of the mirror plane from the other. This can serve as a trigger for the dynamics towards molecular chirality.

Symmetry breaking in actin gels - Implications for cellular motility

NASA Astrophysics Data System (ADS)

John, Karin; Peyla, Philippe; Misbah, Chaouqi

2007-03-01

The physical origin of cell motility is not fully understood. Recently minimal model systems have shown, that polymerizing actin itself can produce a motile force, without the help of motor proteins. Pathogens like Shigella or Listeria use actin to propel themselves forward in their host cell. The same process can be mimicked with polystyrene beads covered with the activating protein ActA, which reside in a solution containing actin monomers. ActA induces the growth of an actin gel at the bead surface. Initially the gel grows symmetrically around the bead until a critical size is reached. Subsequently one observes a symmetry breaking and the gel starts to grow asymmetrically around the bead developing a tail of actin at one side. This symmetry breaking is accompanied by a directed movement of the bead, with the actin tail trailing behind the bead. Force generation relies on the combination of two properties: growth and elasticity of the actin gel. We study this phenomenon theoretically within the framework of a linear elasticity theory and linear flux-force relationships for the evolution of an elastic gel around a hard sphere. Conditions for a parity symmetry breaking are identified analytically and illustrated numerically with the help of a phasefield model.

reaxFF Reactive Force Field for Disulfide Mechanochemistry, Fitted to Multireference ab Initio Data.

PubMed

Müller, Julian; Hartke, Bernd

2016-08-09

Mechanochemistry, in particular in the form of single-molecule atomic force microscopy experiments, is difficult to model theoretically, for two reasons: Covalent bond breaking is not captured accurately by single-determinant, single-reference quantum chemistry methods, and experimental times of milliseconds or longer are hard to simulate with any approach. Reactive force fields have the potential to alleviate both problems, as demonstrated in this work: Using nondeterministic global parameter optimization by evolutionary algorithms, we have fitted a reaxFF force field to high-level multireference ab initio data for disulfides. The resulting force field can be used to reliably model large, multifunctional mechanochemistry units with disulfide bonds as designed breaking points. Explorative calculations show that a significant part of the time scale gap between AFM experiments and dynamical simulations can be bridged with this approach.

Finite element analysis of stress-breaking attachments on maxillary implant-retained overdentures.

PubMed

Tanino, Fuminori; Hayakawa, Iwao; Hirano, Shigezo; Minakuchi, Shunsuke

2007-01-01

The purpose of this study was to examine the effect of stress-breaking attachments at the connections between maxillary palateless overdentures and implants. Three-dimensional finite element models were used to reproduce an edentulous human maxilla with an implant-retained overdenture. Two-implant models (in the canine tooth positions on both sides) and four-implant models (in the canine and second premolar tooth positions on both sides) were examined. Stress-breaking material connecting the implants and denture was included around each abutment. Axial loads of 100 N were applied to the occlusal surface at the left first molar tooth positions. In each model, the influence of the stress-breaking attachments was compared by changing the elastic modulus from 1 to 3,000 MPa and the thickness of the stress-breaking material from 1 to 3 mm. Maximum stress at the implant-bone interface and stress at the cortical bone surface just under the loading point were calculated. In all models, maximum stress at the implant-bone interface with implants located in the canine tooth position was generated at the peri-implant bone on the loading side. As the elastic modulus of the stress-breaking materials increased, the stress increased at the implant-bone interface and decreased at the cortical bone surface. Moreover, stress at the implant-bone interface with 3-mm-thick stress-breaking material was smaller than that with 1-mm-thick material. Within the limitations of this experiment, stress generated at the implant-bone interface could be controlled by altering the elastic modulus and thickness of the stress-breaking materials.

γ-PGA and MTGase improve the formation of ε-(γ-glutamyl) lysine cross-links within hairtail (Trichiurus haumela) surimi protein.

PubMed

Hu, Yaqin; Shao, Ying; Wu, Chunhua; Yuan, Chunhong; Ishimura, Gakushi; Liu, Wenjuan; Chen, Shiguo

2018-03-01

The present study investigated the mechanism of ε-(γ-glutamyl) lysine cross-links within hairtail (Trichiurus haumela) surimi protein via γ-polyglutamic acid (γ-PGA) and MTGase. The results indicated that the addition of MTGase and γ-PGA markedly improved the gelation properties of hairtail surimi protein, including its maximum breaking force and deformation, water holding capacity and gel strength. The maximum improvements were achieved by adding 0.5units MTGase/g meat paste in combination with 0.06% γ-PGA. SDS-PAGE showed that the band intensity of cross-linked proteins increased, whereas that of myosin heavy chain decreased after treatments. Further scanning electron microscopy (SEM) analysis showed the formation of a denser gel matrix, which was caused by much stronger and more inter- and intra-molecular cross-linking of proteins, via MTGase catalysing ε-(γ-glutamyl) lysine cross-links formed between lysine residues in the gel protein and glutamic residues in the hydrolytic γ-PGA. The results provide reliable guidance for the improvement of hairtail surimi protein gelation properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Flow and turbulence structure in a hypertidal estuary with the world's biggest tidal bore

NASA Astrophysics Data System (ADS)

Tu, Junbiao; Fan, Daidu

2017-04-01

Turbulent and flow structure associated with breaking tidal bores are deliberately investigated on the basis of field measurements. High-resolution velocity and hydrographic data are collected in the middle Qiantang Estuary by a vertical array of acoustic Doppler velocimeters and optical backscatter sensors, collaborated with a bottom-mounted acoustic Doppler current profiler. Besides obvious variations in diurnal and spring-neap tidal cycles, the estuarine dynamics is featured by extreme asymmetry in flood and ebb tides. The flood tide is abnormally accelerated to generate tidal bores at the first 10 min or more, with breaking or undular configurations at the front. The occurrence of peak flow velocity, turbulent kinetic energy (TKE), and TKE dissipation rate (ɛ) is definitely associated with breaking bores, with their values several times to 2 orders of magnitude larger than the corresponding secondary peak values during the maximum ebb flows. Flow and turbulence dynamics are significantly affected by the tidal-bore Froude number. A sandwich ɛ structure is clear exhibited with the maximum value at the surface, secondary maximum near the bed, and the minimum at the intermediate. Dual TKE sources are indicated by an approximate local balance between shear production and dissipation near the bottom, and a top-down TKE dissipation using the modified Froude scaling in the vertical water column. The highly elevated dissipation by breaking bores is comparable to that by intense breaking waves in the surf zone, and the former potentially penetrates the entire water column to produce extreme sediment-resuspension events in combination with intense bottom shear stress.

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

Analysis of force profile during a maximum voluntary isometric contraction task.

PubMed

Househam, Elizabeth; McAuley, John; Charles, Thompson; Lightfoot, Timothy; Swash, Michael

2004-03-01

This study analyses maximum voluntary isometric contraction (MVIC) and its measurement by recording the force profile during maximal-effort, 7-s hand-grip contractions. Six healthy subjects each performed three trials repeated at short intervals to study variation from fatigue. These three trials were performed during three separate sessions at daily intervals to look at random variation. A pattern of force development during a trial was identified. An initiation phase, with or without an initiation peak, was followed by a maintenance phase, sometimes with secondary pulses and an underlying decline in force. Of these three MVIC parameters, maximum force during the maintenance phase showed less random variability compared to intertrial fatigue variability than did maximum force during the initiation phase or absolute maximum force. Analysis of MVIC as a task, rather than a single, maximal value reveals deeper levels of motor control in its generation. Thus, force parameters other than the absolute maximum force may be better suited to quantification of muscle performance in health and disease.

Design Spectrum Analysis in NASTRAN

NASA Technical Reports Server (NTRS)

Butler, T. G.

1984-01-01

The utility of Design Spectrum Analysis is to give a mode by mode characterization of the behavior of a design under a given loading. The theory of design spectrum is discussed after operations are explained. User instructions are taken up here in three parts: Transient Preface, Maximum Envelope Spectrum, and RMS Average Spectrum followed by a Summary Table. A single DMAP ALTER packet will provide for all parts of the design spectrum operations. The starting point for getting a modal break-down of the response to acceleration loading is the Modal Transient rigid format. After eigenvalue extraction, modal vectors need to be isolated in the full set of physical coordinates (P-sized as opposed to the D-sized vectors in RF 12). After integration for transient response the results are scanned over the solution time interval for the peak values and for the times that they occur. A module called SCAN was written to do this job, that organizes these maxima into a diagonal output matrix. The maximum amplifier in each mode is applied to the eigenvector of each mode which then reveals the maximum displacements, stresses, forces and boundary reactions that the structure will experience for a load history, mode by mode. The standard NASTRAN output processors have been modified for this task. It is required that modes be normalized to mass.

Numerical study on air-structure coupling dynamic characteristics of the axial fan blade

NASA Astrophysics Data System (ADS)

Chen, Q. G.; Xie, B.; Li, F.; Gu, W. G.

2013-12-01

In order to understand the dynamic characteristics of the axial-flow fan blade due to the effect of rotating stress and the action of unsteady aerodynamic forces caused by the airflow, a numerical simulation method for air-structure coupling in an axial-flow fan with fixed rear guide blades was performed. The dynamic characteristics of an axial-flow fan rotating blade were studied by using the two-way air-structure coupling method. Based on the standard k-ε turbulence model, and using weak coupling method, the preceding six orders modal parameters of the rotating blade were obtained, and the distributions of stress and strain on the rotating blade were presented. The results show that the modal frequency from the first to the sixth order is 3Hz higher than the modal frequency without considering air-structure coupling interaction; the maximum stress and the maximum strain are all occurred in the vicinity of root area of the blade no matter the air-structure coupling is considered or not, thus, the blade root is the dangerous location subjected to fatigue break; the position of maximum deformation is at the blade tip, so the vibration of the blade tip is significant. This study can provide theoretical references for the further study on the strength analysis and mechanical optimal design.

Modeling single molecule junction mechanics as a probe of interface bonding

NASA Astrophysics Data System (ADS)

Hybertsen, Mark S.

2017-03-01

Using the atomic force microscope based break junction approach, applicable to metal point contacts and single molecule junctions, measurements can be repeated thousands of times resulting in rich data sets characterizing the properties of an ensemble of nanoscale junction structures. This paper focuses on the relationship between the measured force extension characteristics including bond rupture and the properties of the interface bonds in the junction. A set of exemplary model junction structures has been analyzed using density functional theory based calculations to simulate the adiabatic potential surface that governs the junction elongation. The junction structures include representative molecules that bond to the electrodes through amine, methylsulfide, and pyridine links. The force extension characteristics are shown to be most effectively analyzed in a scaled form with maximum sustainable force and the distance between the force zero and force maximum as scale factors. Widely used, two parameter models for chemical bond potential energy versus bond length are found to be nearly identical in scaled form. Furthermore, they fit well to the present calculations of N-Au and S-Au donor-acceptor bonds, provided no other degrees of freedom are allowed to relax. Examination of the reduced problem of a single interface, but including relaxation of atoms proximal to the interface bond, shows that a single-bond potential form renormalized by an effective harmonic potential in series fits well to the calculated results. This allows relatively accurate extraction of the interface bond energy. Analysis of full junction models shows cooperative effects that go beyond the mechanical series inclusion of the second bond in the junction, the spectator bond that does not rupture. Calculations for a series of diaminoalkanes as a function of molecule length indicate that the most important cooperative effect is due to the interactions between the dipoles induced by the donor-acceptor bond formation at the junction interfaces. The force extension characteristic of longer molecules such as diaminooctane, where the dipole interaction effects drop to a negligible level, accurately fit to the renormalized single-bond potential form. The results suggest that measured force extension characteristics for single molecule junctions could be analyzed with a modified potential form that accounts for the energy stored in deformable mechanical components in series.

Modeling single molecule junction mechanics as a probe of interface bonding

DOE PAGES

Hybertsen, Mark S.

2017-03-07

Using the atomic force microscope based break junction approach, applicable to metal point contacts and single molecule junctions, measurements can be repeated thousands of times resulting in rich data sets characterizing the properties of an ensemble of nanoscale junction structures. This paper focuses on the relationship between the measured force extension characteristics including bond rupture and the properties of the interface bonds in the junction. We analyzed a set of exemplary model junction structures using density functional theory based calculations to simulate the adiabatic potential surface that governs the junction elongation. The junction structures include representative molecules that bond tomore » the electrodes through amine, methylsulfide, and pyridine links. The force extension characteristics are shown to be most effectively analyzed in a scaled form with maximum sustainable force and the distance between the force zero and force maximum as scale factors. Widely used, two parameter models for chemical bond potential energy versus bond length are found to be nearly identical in scaled form. Furthermore, they fit well to the present calculations of N–Au and S–Au donor-acceptor bonds, provided no other degrees of freedom are allowed to relax. Examination of the reduced problem of a single interface, but including relaxation of atoms proximal to the interface bond, shows that a single-bond potential form renormalized by an effective harmonic potential in series fits well to the calculated results. This, then, allows relatively accurate extraction of the interface bond energy. Analysis of full junction models shows cooperative effects that go beyond the mechanical series inclusion of the second bond in the junction, the spectator bond that does not rupture. Calculations for a series of diaminoalkanes as a function of molecule length indicate that the most important cooperative effect is due to the interactions between the dipoles induced by the donor-acceptor bond formation at the junction interfaces. The force extension characteristic of longer molecules such as diaminooctane, where the dipole interaction effects drop to a negligible level, accurately fit to the renormalized single-bond potential form. Our results suggest that measured force extension characteristics for single molecule junctions could be analyzed with a modified potential form that accounts for the energy stored in deformable mechanical components in series.« less

Modeling single molecule junction mechanics as a probe of interface bonding

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

Hybertsen, Mark S.

Using the atomic force microscope based break junction approach, applicable to metal point contacts and single molecule junctions, measurements can be repeated thousands of times resulting in rich data sets characterizing the properties of an ensemble of nanoscale junction structures. This paper focuses on the relationship between the measured force extension characteristics including bond rupture and the properties of the interface bonds in the junction. We analyzed a set of exemplary model junction structures using density functional theory based calculations to simulate the adiabatic potential surface that governs the junction elongation. The junction structures include representative molecules that bond tomore » the electrodes through amine, methylsulfide, and pyridine links. The force extension characteristics are shown to be most effectively analyzed in a scaled form with maximum sustainable force and the distance between the force zero and force maximum as scale factors. Widely used, two parameter models for chemical bond potential energy versus bond length are found to be nearly identical in scaled form. Furthermore, they fit well to the present calculations of N–Au and S–Au donor-acceptor bonds, provided no other degrees of freedom are allowed to relax. Examination of the reduced problem of a single interface, but including relaxation of atoms proximal to the interface bond, shows that a single-bond potential form renormalized by an effective harmonic potential in series fits well to the calculated results. This, then, allows relatively accurate extraction of the interface bond energy. Analysis of full junction models shows cooperative effects that go beyond the mechanical series inclusion of the second bond in the junction, the spectator bond that does not rupture. Calculations for a series of diaminoalkanes as a function of molecule length indicate that the most important cooperative effect is due to the interactions between the dipoles induced by the donor-acceptor bond formation at the junction interfaces. The force extension characteristic of longer molecules such as diaminooctane, where the dipole interaction effects drop to a negligible level, accurately fit to the renormalized single-bond potential form. Our results suggest that measured force extension characteristics for single molecule junctions could be analyzed with a modified potential form that accounts for the energy stored in deformable mechanical components in series.« less

Final Environmental Assessment: For Construction of a Security Forces Complex on Eglin Air Force Base, FL

DTIC Science & Technology

2005-05-01

form of weapons cleaning products and wastes. State of Florida and Air Force regulations have been implemented 05/31/05 Final Environmental Assessment...Forces Complex will generate hazardous materials in the form of weapons cleaning products and wastes. Break-Free CLP Liquid is a cleaner, lubricant

Orbitally shaken shallow fluid layers. I. Regime classification

NASA Astrophysics Data System (ADS)

Alpresa, Paola; Sherwin, Spencer; Weinberg, Peter; van Reeuwijk, Maarten

2018-03-01

Orbital shakers are simple devices that provide mixing, aeration, and shear stress at multiple scales and high throughput. For this reason, they are extensively used in a wide range of applications from protein production to bacterial biofilms and endothelial cell experiments. This study focuses on the behaviour of orbitally shaken shallow fluid layers in cylindrical containers. In order to investigate the behaviour over a wide range of different conditions, a significant number of numerical simulations are carried out under different configuration parameters. We demonstrate that potential theory—despite the relatively low Reynolds number of the system—describes the free-surface amplitude well and the velocity field reasonably well, except when the forcing frequency is close to a natural frequency and resonance occurs. By classifying the simulations into non-breaking, breaking, and breaking with part of the bottom uncovered, it is shown that the onset of wave breaking is well described by Δh/(2R) = 0.7Γ, where Δh is the free-surface amplitude, R is the container radius, and Γ is the container aspect ratio; Δh can be well approximated using the potential theory. This result is in agreement with standard wave breaking theories although the significant inertial forcing causes wave breaking at lower amplitudes.

Stabilising the Herpes Simplex Virus capsid by DNA packaging

NASA Astrophysics Data System (ADS)

Wuite, Gijs; Radtke, Kerstin; Sodeik, Beate; Roos, Wouter

2009-03-01

Three different types of Herpes Simplex Virus type 1 (HSV-1) nuclear capsids can be distinguished, A, B and C capsids. These capsids types are, respectively, empty, contain scaffold proteins, or hold DNA. We investigate the physical properties of these three capsids by combining biochemical and nanoindentation techniques. Atomic Force Microscopy (AFM) experiments show that A and C capsids are mechanically indistinguishable whereas B capsids already break at much lower forces. By extracting the pentamers with 2.0 M GuHCl or 6.0 M Urea we demonstrate an increased flexibility of all three capsid types. Remarkably, the breaking force of the B capsids without pentamers does not change, while the modified A and C capsids show a large drop in their breaking force to approximately the value of the B capsids. This result indicates that upon DNA packaging a structural change at or near the pentamers occurs which mechanically reinforces the capsids structure. The reported binding of proteins UL17/UL25 to the pentamers of the A and C capsids seems the most likely candidate for such capsids strengthening. Finally, the data supports the view that initiation of DNA packaging triggers the maturation of HSV-1 capsids.

Investigation on CWR longitudinal restraint behavior in winter rail break and summer destressing operations.

DOT National Transportation Integrated Search

1997-08-01

This report presents the results of investigations on the rail anchor/fastener effects on rail movement and the resulting rail force distribution in continuous welded rail (CWR) track during rail breaks and destressing operations. Two types of tests ...

Learning to perceive haptic distance-to-break in the presence of friction.

PubMed

Altenhoff, Bliss M; Pagano, Christopher C; Kil, Irfan; Burg, Timothy C

2017-02-01

Two experiments employed attunement and calibration training to investigate whether observers are able to identify material break points in compliant materials through haptic force application. The task required participants to attune to a recently identified haptic invariant, distance-to-break (DTB), rather than haptic stimulation not related to the invariant, including friction. In the first experiment participants probed simulated force-displacement relationships (materials) under 3 levels of friction with the aim of pushing as far as possible into the materials without breaking them. In a second experiment a different set of participants pulled on the materials. Results revealed that participants are sensitive to DTB for both pushing and pulling, even in the presence of varying levels of friction, and this sensitivity can be improved through training. The results suggest that the simultaneous presence of friction may assist participants in perceiving DTB. Potential applications include the development of haptic training programs for minimally invasive (laparoscopic) surgery to reduce accidental tissue damage. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

A comparison of the reliability of make versus break testing in measuring palmar abduction strength of the thumb.

PubMed

Lim, J X; Toh, R X; Chook, S K H; Sebastin, S J; Karjalainen, T

2014-06-01

Previous studies have established the role of quantitative measurements of palmar abduction strength of the thumb (PAST). This study compares the reliability of the 'make' versus the 'break' test in measuring PAST in healthy volunteers. In a 'make' test, the body part being tested is positioned at the start of its range of motion and the participant is asked to exert his/her maximal force. In a 'break' test, increasing force is applied to a body part after it has completed its range of motion, until the joint being tested gives way. PAST was measured in both hands in 100 healthy volunteers using a handheld device. Two examiners measured PAST using both the 'make' and 'break' test to determine inter-rater reliability. The tests were repeated in 30 volunteers 6 weeks after the initial testing to determine intra-rater reliability. Our results showed that the 'make' test has better inter and intra-rater reliability.

Analysis of the bite force and mechanical design of the feeding mechanism of the durophagous horn shark Heterodontus francisci.

PubMed

Huber, Daniel R; Eason, Thomas G; Hueter, Robert E; Motta, Philip J

2005-09-01

Three-dimensional static equilibrium analysis of the forces generated by the jaw musculature of the horn shark Heterodontus francisci was used to theoretically estimate the maximum force distributions and loadings on its jaws and suspensorium during biting. Theoretical maximum bite force was then compared with bite forces measured (1) voluntarily in situ, (2) in restrained animals and (3) during electrical stimulation of the jaw adductor musculature of anesthetized sharks. Maximum theoretical bite force ranged from 128 N at the anteriormost cuspidate teeth to 338 N at the posteriormost molariform teeth. The hyomandibula, which connects the posterior margin of the jaws to the base of the chondrocranium, is loaded in tension during biting. Conversely, the ethmoidal articulation between the palatal region of the upper jaw and the chondrocranium is loaded in compression, even during upper jaw protrusion, because H. francisci's upper jaw does not disarticulate from the chondrocranium during prey capture. Maximum in situ bite force averaged 95 N for free-swimming H. francisci, with a maximum of 133 N. Time to maximum force averaged 322 ms and was significantly longer than time away from maximum force (212 ms). Bite force measurements from restrained individuals (187 N) were significantly greater than those from free-swimming individuals (95 N) but were equivalent to those from both theoretical (128 N) and electrically stimulated measurements (132 N). The mean mass-specific bite of H. francisci was greater than that of many other vertebrates and second highest of the cartilaginous fishes that have been studied. Measuring bite force on restrained sharks appears to be the best indicator of maximum bite force. The large bite forces and robust molariform dentition of H. francisci correspond to its consumption of hard prey.

Plasmonic Spherical Heterodimers: Reversal of Optical Binding Force Based on the Forced Breaking of Symmetry.

PubMed

Mahdy, M R C; Danesh, Md; Zhang, Tianhang; Ding, Weiqiang; Rivy, Hamim Mahmud; Chowdhury, Ariful Bari; Mehmood, M Q

2018-02-16

The stimulating connection between the reversal of near-field plasmonic binding force and the role of symmetry-breaking has not been investigated comprehensively in the literature. In this work, the symmetry of spherical plasmonic heterodimer-setup is broken forcefully by shining the light from a specific side of the set-up instead of impinging it from the top. We demonstrate that for the forced symmetry-broken spherical heterodimer-configurations: reversal of lateral and longitudinal near-field binding force follow completely distinct mechanisms. Interestingly, the reversal of longitudinal binding force can be easily controlled either by changing the direction of light propagation or by varying their relative orientation. This simple process of controlling binding force may open a novel generic way of optical manipulation even with the heterodimers of other shapes. Though it is commonly believed that the reversal of near-field plasmonic binding force should naturally occur for the presence of bonding and anti-bonding modes or at least for the Fano resonance (and plasmonic forces mostly arise from the surface force), our study based on Lorentz-force dynamics suggests notably opposite proposals for the aforementioned cases. Observations in this article can be very useful for improved sensors, particle clustering and aggregation.

Doing it All: Security Forces--The USAF Coin Force

DTIC Science & Technology

2009-06-01

Joseph L. III, Capt William M. Dains , and Capt David T. Watts, “Air Force Breaks New Ground at Camp Bucca, Iraq.” Military Police Bulletin, PB 19- 05-2...October 2005, http://www.wood.army.mil/MPBULLETIN/pdfs/Oct%2005/ Romano- Dains -Watts.pdf (accessed 30 Dec 08). SAFESIDE: Final Report. US Air Force

Absolute negative mobility in the anomalous diffusion

NASA Astrophysics Data System (ADS)

Chen, Ruyin; Chen, Chongyang; Nie, Linru

2017-12-01

Transport of an inertial Brownian particle driven by the multiplicative Lévy noise was investigated here. Numerical results indicate that: (i) The Lévy noise is able to induce absolute negative mobility (ANM) in the system, while disappearing in the deterministic case; (ii) the ANM can occur in the region of superdiffusion while disappearing in the region of normal diffusion, and the appropriate stable index of the Lévy noise makes the particle move along the opposite direction of the bias force to the maximum degree; (iii) symmetry breaking of the Lévy noise also causes the ANM effect. In addition, the intrinsic physical mechanism and conditions for the ANM to occur are discussed in detail. Our results have the implication that the Lévy noise plays an important role in the occurrence of the ANM phenomenon.

Kinematics and Kinetics of Taekwon-do Side Kick

PubMed Central

Wąsik, Jacek

2011-01-01

The aim of the paper is to present an analysis of the influence of selected kinematic factors on the side kick technique. This issue is especially important in the traditional version of taekwon-do, in which a single strike may reveal the winner. Six taekwon-do (International Taekwon-do Federation) athletes were asked to participate in this case study. Generally accepted criteria of sports technique biomechanical analysis were adhered to. The athletes executed a side kick three times (in Taekwon-do terminology referred to as yop chagi) in a way which they use the kick in board breaking. The obtained data were used to determine the mean velocity changes in the function of relative extension length of the kicking leg. The maximum knee and foot velocities in the Cartesian coordinate system were determined. The leg lifting time and the duration of kick execution as well as the maximum force which the standing foot exerted on the ground were also determined. On the basis of the obtained values, mean values and standard deviations were calculated. The correlation dependence (r=0.72) shows that greater knee velocity affects the velocity which the foot develops as well as the fact that the total time of kick execution depends on the velocity which the knee (r = −0.59) and the foot (r = − 0.86) develop in the leg lifting phase. The average maximum speed was obtained at the length of the leg equal to 82% of the maximum length of the fully extended leg. This length can be considered the optimum value for achieving the maximum dynamics of the kick. PMID:23486086

The biomechanical effects of variation in the maximum forces exerted by trunk muscles on the joint forces and moments in the lumbar spine: a finite element analysis.

PubMed

Kim, K; Lee, S K; Kim, Y H

2010-10-01

The weakening of trunk muscles is known to be related to a reduction of the stabilization function provided by the muscles to the lumbar spine; therefore, strengthening deep muscles might reduce the possibility of injury and pain in the lumbar spine. In this study, the effect of variation in maximum forces of trunk muscles on the joint forces and moments in the lumbar spine was investigated. Accordingly, a three-dimensional finite element model of the lumbar spine that included the trunk muscles was used in this study. The variation in maximum forces of specific muscle groups was then modelled, and joint compressive and shear forces, as well as resultant joint moments, which were presumed to be related to spinal stabilization from a mechanical viewpoint, were analysed. The increase in resultant joint moments occurred owing to decrease in maximum forces of the multifidus, interspinales, intertransversarii, rotatores, iliocostalis, longissimus, psoas, and quadratus lumborum. In addition, joint shear forces and resultant joint moments were reduced as the maximum forces of deep muscles were increased. These results from finite element analysis indicate that the variation in maximum forces exerted by trunk muscles could affect the joint forces and joint moments in the lumbar spine.

Force Structure: Better Information Needed to Support Air Force A-10 and Other Future Divestment Decisions

DTIC Science & Technology

2016-08-01

estimate should have a standardized structure that breaks costs into discrete elements with sufficient detail to ensure that cost elements are...FORCE STRUCTURE Better Information Needed to Support Air Force A-10 and Other Future Divestment Decisions Report...Accountability Office Highlights of GAO-16-816, a report to congressional committees August 2016 FORCE STRUCTURE Better Information Needed to Support

Improving Short Wave Breaking Behavior In Surfbeat Models

NASA Astrophysics Data System (ADS)

Roelvink, J.; Daly, C.; Vandongeren, A. R.; van Thiel de Vries, J.; McCall, R.

2009-12-01

In present surfzone modeling three approaches are widely applied: short-wave resolving models, ‘surfbeat’ models, which resolve wave energy modulations on the time-scale of wave groups and their associated infragravity waves, and wave averaged models. In all three approaches, wave breaking is a process that is highly schematized and governed by several empirical coefficients. In this presentation we will focus on the breaking process in ‘surfbeat’ models, such as XBeach (Roelvink et al, 2009). These models need to describe the short wave dissipation by breaking as a function of the slowly-varying short wave energy or wave height. The model usually applied is that by Roelvink (1993), which combines a probability that waves are breaking as function of wave heigth over water depth ratio H/h with a bore-type dissipation formulation similar to that by Battjes and Janssen (1978). A drawback of such a formulation is that there is no ‘memory’ in the breaking process, and the amount of breaking instantly varies with the water depth (though the wave height itself does have a memory). For cases with bichromatic waves, or for long-period swell, this does not reflect reality enough: waves that start breaking do not instantly stop breaking once the water depth increases, but continue until some lower threshold is reached. This concept was captured in Dally’s (1992) wave-by-wave approach, where individual waves are tracked in a probabilistic setting. We have now implemented a similar formulation in XBeach, where the property that waves are breaking is tracked; it is switched on when H/h exceeds a first criterion; this property is propagated using an advection equation and when H/h gets below a second criterion breaking is switched off. This formulation can do two things the previous one can’t: maintain groupiness inside the surf zone and have a maximum of wave breaking in the trough after a steep bar, as was observed for instance in Arcilla et al’s (1994) test 1C. Obviously this has important consequences for the forcing of both long waves and mean currents. In our presentation we will show results of comparisons of both formulations. References. Arcilla, A.S., Roelvink, J.A., O'Connor, B.A. Reniers, A., and Jimenez. J.A. The Delta Flume '93 Experiment. Coastal Dynamics '94. Arcilla, Stive and Kraus (eds), ASCE, New York, pp. 488-502. Battjes, J.A. and J.P.F.M. Janssen, (1978), Energy loss and set-up due to breaking in random waves, Proc. 16th Int. Coastal Eng. Conf., Hamburg, vol. 1: 569-587. Dally, W.R. (1992) Random breaking waves: Field verification of a wave-by-wave algorithm for engineering application. Coastal Engineering, Volume 16, Issue 4, March 1992, Pages 369-397. Roelvink, Dano, Ad Reniers, Ap van Dongeren, Jaap van Thiel de Vries, Robert McCall, Jamie Lescinski. Modelling storm impacts on beaches, dunes and barrier islands, Coast. Eng. (2009), doi:10.1016/j.coastaleng.2009.08.006 Roelvink, J.A. Dissipation in random wave groups incident on a beach. Coastal Eng., 19 (1993) pp. 127-150.

Gravity Wave Breaking over the Central Alps: Role of Complex Terrain.

NASA Astrophysics Data System (ADS)

Jiang, Qingfang; Doyle, James D.

2004-09-01

The characteristics of gravity waves excited by the complex terrain of the central Alps during the intensive observational period (IOP) 8 of the Mesoscale Alpine Programme (MAP) is studied through the analysis of aircraft in situ measurements, GPS dropsondes, radiosondes, airborne lidar data, and numerical simulations.Mountain wave breaking occurred over the central Alps on 21 October 1999, associated with wind shear, wind turning, and a critical level with Richardson number less than unity just above the flight level (5.7 km) of the research aircraft NCAR Electra. The Electra flew two repeated transverses across the Ötztaler Alpen, during which localized turbulence was sampled. The observed maximum vertical motion was 9 m s-1, corresponding to a turbulent kinetic energy (TKE) maximum of 10.5 m2 s-2. Spectrum analysis indicates an inertia subrange up to 5-km wavelength and multiple energy-containing spikes corresponding to a wide range of wavelengths.Manual analysis of GPS dropsonde data indicates the presence of strong flow descent and a downslope windstorm over the lee slope of the Ötztaler Alpen. Farther downstream, a transition occurs across a deep hydraulic jump associated with the ascent of isentropes and local wind reversal. During the first transverse, the turbulent region is convectively unstable as indicated by a positive sensible heat flux within the turbulent portion of the segment. The TKE derived from the flight-level data indicates multiple narrow spikes, which match the patterns shown in the diagnosed buoyancy production rate of TKE. The turbulence is nonisotropic with the major TKE contribution from the -wind component. The convectively unstable zone is advected downstream during the second transverse and the turbulence becomes much stronger and more isotropic.The downslope windstorm, flow descent, and transition to turbulence through a hydraulic jump are captured by a real-data Coupled Ocean Atmosphere Mesoscale Predition System (COAMPS) simulation. Several idealized simulations are performed motivated by the observations of multiscale waves forced by the complex terrain underneath. The simulations indicate that multiscale terrain promotes wave breaking, increases mountain drag, and enhances the downslope winds and TKE generation.

Mechanical strength of laser-welded cobalt-chromium alloy.

PubMed

Baba, N; Watanabe, I; Liu, J; Atsuta, M

2004-05-15

The purpose of this study was to investigate the effect of the output energy of laser welding and welding methods on the joint strength of cobalt-chromium (Co-Cr) alloy. Two types of cast Co-Cr plates were prepared, and transverse sections were made at the center of the plate. The cut surfaces were butted against one another, and the joints welded with a laser-welding machine at several levels of output energy with the use of two methods. The fracture force required to break specimens was determined by means of tensile testing. For the 0.5-mm-thick specimens, the force required to break the 0.5-mm laser-welded specimens at currents of 270 and 300 A was not statistically different (p > 0.05) from the results for the nonwelded control specimens. The force required to break the 1.0-mm specimens double-welded at a current of 270 A was the highest value among the 1.0-mm laser-welded specimens. The results suggested that laser welding under the appropriate conditions improved the joint strength of cobalt- chromium alloy. Copyright 2004 Wiley Periodicals, Inc.

Breaking the Yardstick: The Dangers of Market-based Governance (Defense Horizons, Number 67, May 2009)

DTIC Science & Technology

2009-05-01

the implementation of free market forces, more efficient and effective use of resources can be obtained,” which the Defense Science Board asserted...actually slower, less effective, and costlier. This is, in part, because the Breaking the Yardstick: The Dangers of Market -based Governance by Don...2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Breaking the Yardstick: The Dangers of Market -based Governance

Dietary Wolffia arrhiza meal as a substitute for soybean meal: its effects on the productive performance and egg quality of laying Japanese quails.

PubMed

Suppadit, Tawadchai; Jaturasitha, Sanchai; Sunthorn, Napassawan; Poungsuk, Pukkapong

2012-10-01

Wolffia arrhiza meal (WAM) was evaluated as a protein replacement for soybean meal (SBM) in the diet of laying Japanese quails. A total of 480 4-week-old laying quails were randomly allocated to form six groups in a completely randomized design. Each group contained four replicates, with 20 quails per replicate. WAM was incorporated into the diets at levels of 0, 4.00, 8.00, 12.0, 16.0 and 20.0%. The results showed that feed intake per bird per day, daily egg-laying rate, feed cost per 100 egg weight, egg width, egg length, egg weight, eggshell thickness, yolk height and shell quality characteristics in terms of breaking time, Young's modulus, work, maximum force, fracturability, breaking stress, stiffness and power showed no statistically significant differences (P > 0.05) among the 0 to 16.0% levels of WAM. However, these performance measures were significantly lower with 20.0% WAM in the formulated ration (P < 0.05). Mortality showed no significant differences among dietary treatments (P > 0.05). The color intensity of the yolk increased as SBM was replaced with increasing amounts of WAM (P < 0.05). In conclusion, WAM could be successfully used in place of SBM. However, the amount used should not exceed 16.0%.

77 FR 23667 - Department of Defense Task Force on the Care, Management, and Transition of Recovering Wounded...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-20

... CONTACT: Mail Delivery service through Recovering Warrior Task Force, Hoffman Building II, 200 Stovall St... Review of Non- Medical Case Management. 9:30-9:45 a.m. Break. 9:45-10:45 a.m. Task Force Recommendation... Task Force through the contact information in FOR FURTHER INFORMATION CONTACT, and this individual will...

Breaking tester for examining strength of consolidated starch

NASA Astrophysics Data System (ADS)

Stasiak, Mateusz; Molenda, Marek; Bańda, Maciej; Wiącek, Joanna; Dobrzański, Bohdan; Parafiniuk, Piotr

2017-04-01

A new method based on the measurement of force required to break by bending a vertical column of consolidated powder was elaborated, and its results were compared with the ones obtained from the Jenike shear test. A new apparatus was built based on a vertical cylindrical chamber divided into two cylinders connected with a horizontal hinge. The apparatus was tested with samples of potato, maize and wheat starches with moisture content of 6, 12 and 17% and with the addition of a lubricant. Results of testing revealed significant differences in measured force required to rotate the upper part of the cylinder away from the lower one. The average force varied from 0.138 N for maize starch to 0.143 N for potato starch, while, for various moisture contents, the measured force varied from 0.135 N for 6% to 0.143 N for 17% mc. The results were compared with the results of a direct shear test.

A Two-Step Integrated Theory of Everything (TOE)

NASA Astrophysics Data System (ADS)

Colella, Antonio

2017-01-01

Two opposing TOE visions are my Two-Step (physics/math) and Hawking's single math step. My Two-Step should replace the single step because of the latter's near zero results after a century of attempts. My physics step had 3 goals. First ``Everything'' was defined as 20 interrelated amplified theories (e.g. string, Higgs forces, spontaneous symmetry breaking, particle decays, dark matter, dark energy, stellar black holes) and their intimate physical interrelationships. Amplifications of Higgs forces theory (e.g. matter particles and their associated Higgs forces were one and inseparable, spontaneous symmetry breaking was bidirectional and caused by high temperatures not Higgs forces, and sum of 8 Higgs forces of 8 permanent matter particles was dark energy) were key to my Two-Step TOE. The second goal answered all outstanding physics questions: what were Higgs forces, dark energy, dark matter, stellar black holes, our universe's creation, etc.? The third goal provided correct inputs for the two part second math step, an E8 Lie algebra for particles and an N-body cosmology simulation (work in progress). Scientific advancement occurs only if the two opposing TOEs are openly discussed/debated.

Semester and Event-Specific Motives for Alcohol Use During Spring Break: Associated Protective Strategies and Negative Consequences

PubMed Central

Patrick, Megan E.; Lewis, Melissa A.; Lee, Christine M.; Maggs, Jennifer L.

2012-01-01

Motives surrounding alcohol use behavior are important for understanding college student drinking. However, no previous research has addressed how motives for and against drinking during specific events associated with high-risk drinking, such as Spring Break, may differ from motives for and against drinking during the regular semester. Further, we examine the extent to which semester and Spring Break motives are associated with alcohol use, protective behavioral strategies (PBS), and consequences. Participants were college students (N = 261; 55% women) who provided data both immediately prior to (Wave 1) and after (Wave 2) Spring Break. Fun/Social motives for drinking were greater for Spring Break, and Driving motives against drinking were lower for Spring Break, compared to semester drinking. Relax and Image motives for drinking and Physical/Behavioral motives for not drinking during Spring Break did not differ from semester motives. Spring Break motives for and against drinking were associated with total drinks, maximum drinks, PBS, and experienced negative consequences during Spring Break. Students’ specific motives regarding drinking during Spring Break predict high-risk drinking and may be utilized in creating salient event-specific interventions. PMID:23384451

Bond breaking in epoxy systems: A combined QM/MM approach

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

Barr, Stephen A.; Ecker, Allison M.; Berry, Rajiv J., E-mail: Rajiv.Berry@us.af.mil

2016-06-28

A novel method to combine quantum mechanics (QM) and molecular mechanics has been developed to accurately and efficiently account for covalent bond breaking in polymer systems under high strain without the use of predetermined break locations. Use of this method will provide a better fundamental understanding of the mechano-chemical origins of fracture in thermosets. Since classical force fields cannot accurately account for bond breaking, and QM is too demanding to simulate large systems, a hybrid approach is required. In the method presented here, strain is applied to the system using a classical force field, and all bond lengths are monitored.more » When a bond is stretched past a threshold value, a zone surrounding the bond is used in a QM energy minimization to determine which, if any, bonds break. The QM results are then used to reconstitute the system to continue the classical simulation at progressively larger strain until another QM calculation is triggered. In this way, a QM calculation is only computed when and where needed, allowing for efficient simulations. A robust QM method for energy minimization has been determined, as well as appropriate values for the QM zone size and the threshold bond length. Compute times do not differ dramatically from classical molecular mechanical simulations.« less

Impacts of Space Shuttle thermal protection system tile on F-15 aircraft vertical tile

NASA Technical Reports Server (NTRS)

Ko, W. L.

1985-01-01

Impacts of the space shuttle thermal protection system (TPS) tile on the leading edge and the side of the vertical tail of the F-15 aircraft were analyzed under different TPS tile orientations. The TPS tile-breaking tests were conducted to simulate the TPS tile impacts. It was found that the predicted tile impact forces compare fairly well with the tile-breaking forces, and the impact forces exerted on the F-15 aircraft vertical tail were relatively low because a very small fraction of the tile kinetic energy was dissipated in the impact, penetration, and fracture of the tile. It was also found that the oblique impact of the tile on the side of the F-15 aircraft vertical tail was unlikely to dent the tail surface.

Central Atlantic Break-up: A competition between CAMP Hotspot and thinning rate.

NASA Astrophysics Data System (ADS)

Sapin, F.; Maurin, T.

2017-12-01

The break-up of the Central Atlantic is known to have ended at about 190Myrs while the CAMP (Central Atlantic Magmatic Province) was still active. Several seismic lines, acquired recently in the deep offshore Senegal and Mauritanian domain, provide detailed images of continent-ocean transition and the oceanic crust architecture. Their interpretation is the opportunity to describe the progressive interaction between the hot spot activity, the architecture and timing of break up and the oceanic crust production. In the North, seismic data and gravity/magnetic inversions suggest an extremely thinned continental crust with possible mantle exhumation. In the South, the continental crust is thick and the transition to oceanic crust is sharp. In addition, three oceanic crust facies were described along the margin in an extremely slow spreading ridge setting ( 0.8cm/yr during the first 20Myrs): facies (1) with a poorly imaged Moho and a strongly faulted thin oceanic crust or exhumed mantle; facies (2) with an extensively faulted 6km thick oceanic crust; facies (3) with abnormally thick (9km) oceanic crust marked by SDR-type reflections. They are diachronous from North to South and the two first one disappear southwards and (facies 3) being younger toward the North. Only a single very thick oceanic crust (12-14km) remains in front of the Guinea Plateau. We concluded that, in the South, the break-up had been forced through a thick or thickened continental crust due to the remnant activity of the CAMP Hotspot. In the North, the magmatic pulse arrived far after the break-up during the spreading and the thinning of the continental crust could lead to hyper extension. This evolution emphasizes that the architecture, and thus processes leading to the break-up can vary a lot considering the influence of thermal vertical forces (mantle dynamics/hotspot/magmatism) and mechanical horizontal forces (plate movement/faulting/spreading), both of them being necessary for a rift to succeed.

Comparison of Maximum Stretch Forces between Femtosecond Laser-Assisted Capsulotomy and Continuous Curvilinear Capsulorhexis

PubMed Central

Ichikawa, Kei; Tanaka, Yoshiki; Kato, Yukihito; Horai, Rie; Tamaoki, Akeno; Ichikawa, Kazuo

2017-01-01

The current study reports comparing the postoperative mechanical properties of the anterior capsule between femtosecond laser capsulotomy (FLC) and continuous curvilinear capsulorhexis (CCC) of variable size and shape in porcine eyes. All CCCs were created using capsule forceps. Irregular or eccentric CCCs were also created to simulate real cataract surgery. For FLC, capsulotomies 5.3 mm in diameter were created using the LenSx® (Alcon) platform. Fresh porcine eyes were used in all experiments. The edges of the capsule openings were pulled at a constant speed using two L-shaped jigs. Stretch force and distance were recorded over time, and the maximum values in this regard were defined as those that were recorded when the capsule broke. There was no difference in maximum stretch force between CCC and FLC. There were no differences in circularity between FLC and same-sized CCC. However, same-sized CCC did show significantly higher maximum stretch forces than FLC. Teardrop-shaped CCC showed lower maximum stretch forces than same-sized CCC and FLC. Heart-shaped CCC showed lower maximum stretch forces than same-sized CCC. Conclusively, while capsule edge strength after CCC varied depending on size or irregularities, FLC had the advantage of stable maximum stretch forces. PMID:28210504

Comparison of Maximum Stretch Forces between Femtosecond Laser-Assisted Capsulotomy and Continuous Curvilinear Capsulorhexis.

PubMed

Takagi, Mari; Kojima, Takashi; Ichikawa, Kei; Tanaka, Yoshiki; Kato, Yukihito; Horai, Rie; Tamaoki, Akeno; Ichikawa, Kazuo

2017-01-01

The current study reports comparing the postoperative mechanical properties of the anterior capsule between femtosecond laser capsulotomy (FLC) and continuous curvilinear capsulorhexis (CCC) of variable size and shape in porcine eyes. All CCCs were created using capsule forceps. Irregular or eccentric CCCs were also created to simulate real cataract surgery. For FLC, capsulotomies 5.3 mm in diameter were created using the LenSx® (Alcon) platform. Fresh porcine eyes were used in all experiments. The edges of the capsule openings were pulled at a constant speed using two L-shaped jigs. Stretch force and distance were recorded over time, and the maximum values in this regard were defined as those that were recorded when the capsule broke. There was no difference in maximum stretch force between CCC and FLC. There were no differences in circularity between FLC and same-sized CCC. However, same-sized CCC did show significantly higher maximum stretch forces than FLC. Teardrop-shaped CCC showed lower maximum stretch forces than same-sized CCC and FLC. Heart-shaped CCC showed lower maximum stretch forces than same-sized CCC. Conclusively, while capsule edge strength after CCC varied depending on size or irregularities, FLC had the advantage of stable maximum stretch forces.

Near-infrared spectroscopic analysis of the breaking force of extended-release matrix tablets prepared by roller-compaction: influence of plasticizer levels and sintering temperature.

PubMed

Dave, Vivek S; Fahmy, Raafat M; Hoag, Stephen W

2015-06-01

The aim of this study was to investigate the feasibility of near-infrared (NIR) spectroscopy for the determination of the influence of sintering temperature and plasticizer levels on the breaking force of extended-release matrix tablets prepared via roller-compaction. Six formulations using theophylline as a model drug, Eudragit® RL PO or Eudragit® RS PO as a matrix former and three levels of TEC (triethyl citrate) as a plasticizer were prepared. The powder blend was roller compacted using a fixed roll-gap of 1.5 mm, feed screw speed to roller speed ratio of 5:1 and roll pressure of 4 MPa. The granules, after removing fines, were compacted into tablets on a Stokes B2 rotary tablet press at a compression force of 7 kN. The tablets were thermally treated at different temperatures (Room Temperature, 50, 75 and 100 °C) for 5 h. These tablets were scanned in reflectance mode in the wavelength range of 400-2500 nm and were evaluated for breaking force. Tablet breaking force significantly increased with increasing plasticizer levels and with increases in the sintering temperature. An increase in tablet hardness produced an upward shift (increase in absorbance) in the NIR spectra. The principle component analysis (PCA) of the spectra was able to distinguish samples with different plasticizer levels and sintering temperatures. In addition, a 9-factor partial least squares (PLS) regression model for tablets containing Eudragit® RL PO had an r(2) of 0.9797, a standard error of calibration of 0.6255 and a standard error of cross validation (SECV) of 0.7594. Similar analysis of tablets containing Eudragit® RS PO showed an r(2) of 0.9831, a standard error of calibration of 0.9711 and an SECV of 1.192.

Gender-related functional connectivity and craving during gaming and immediate abstinence during a mandatory break: Implications for development and progression of internet gaming disorder.

PubMed

Dong, Guangheng; Wang, Ziliang; Wang, Yifan; Du, Xiaoxia; Potenza, Marc N

2018-04-20

Although males more frequently develop Internet gaming disorder (IGD) as compared with females, few studies have examined gender-related neurocognitive differences in IGD. TASK AND DESIGN: fMRI and subjective data were collected from 119 subjects (IGD, male 29, female 25; recreational game use (RGU), male 34, female 31) when they were actively playing games and during a forced mandatory break. Analyses investigating effects of group (IGD, RGU) and gender (male, female) on the functional connectivity (FC) of executive control and reward systems linked to the dorsolateral prefrontal cortex (DLPFC) and striatum, respectively, were performed. Correlations between FC and subjective craving measures were also calculated. Gaming-group-by-gender interactions were observed. During gaming in males but not in females, the FC between the DLPFC and superior frontal gyrus was relatively decreased, and that between the striatum and thalamus was relatively increased. During the mandatory break, changes in the FC between DLPFC and superior frontal gyrus and the FC between the striatum and thalamus varied by gender with greater RGU-IGD differences observed in females. Significant correlations between FC and self-reported craving were observed. During both gaming and a forced mandatory break, brain regions implicated in executive control and reward processing showed changes in FC that varied by gender. Brain regions implicated in executive control showed differential FC in males during gaming, and FC during the forced mandatory break appeared relevant to both genders, and perhaps particularly for females. The findings suggest possible neural mechanisms for why males appear more likely to develop IGD, and why it may be particularly difficult for individuals with IGD to cease gaming. Copyright © 2018. Published by Elsevier Inc.

Slide Release Device. Shuttle Orbiter/External Tank Forward Attachment

NASA Technical Reports Server (NTRS)

1981-01-01

A prototype release mechanism is discussed which is interchangeable with the existing orbiter/external tank separation bolt and offers reduced weight, shock, and cost. The components are reuseable. The unit takes maximum advantage of the shank diameter and installs in the monoball just as does the shear bolt, by threading in the completely assembled condition. Actuation is different, in that instead of axially breaking the shank by very high pressure (on the order of 60,000 psi) using a very large force (over 235, 000 pounds), this mechanism releases the shank by cross-axis movement against a lubricated surface. Once free, the shank is driven out of the monoball by an axially precompressed spring. Final weight can be as low as 30 pounds, and the cartridge contains less than one gram of powder. The components show no significant wear after eleven actuations under load.

BIOMECHANICS. Jumping on water: Surface tension-dominated jumping of water striders and robotic insects.

PubMed

Koh, Je-Sung; Yang, Eunjin; Jung, Gwang-Pil; Jung, Sun-Pill; Son, Jae Hak; Lee, Sang-Im; Jablonski, Piotr G; Wood, Robert J; Kim, Ho-Young; Cho, Kyu-Jin

2015-07-31

Jumping on water is a unique locomotion mode found in semi-aquatic arthropods, such as water striders. To reproduce this feat in a surface tension-dominant jumping robot, we elucidated the hydrodynamics involved and applied them to develop a bio-inspired impulsive mechanism that maximizes momentum transfer to water. We found that water striders rotate the curved tips of their legs inward at a relatively low descending velocity with a force just below that required to break the water surface (144 millinewtons/meter). We built a 68-milligram at-scale jumping robotic insect and verified that it jumps on water with maximum momentum transfer. The results suggest an understanding of the hydrodynamic phenomena used by semi-aquatic arthropods during water jumping and prescribe a method for reproducing these capabilities in artificial systems. Copyright © 2015, American Association for the Advancement of Science.

Optimal braking studies

NASA Technical Reports Server (NTRS)

Pazdera, J. S.

1972-01-01

To brake in minimum distance, the tire slip must be controlled to ride the peak of the mu-slip curve so that maximum ground force is developed between tire and pavement. The resulting control system differs from antiskid systems which react to impending wheel lockup. A simplified model is presented to permit development of a sound control strategy. Liapunov techniques are used to derive a peak riding adaptive controller applicable to each wheel of a breaking vehicle. The controller is applied to a more sophisticated model of a braking airplane with strut bending dynamics included. Simulation results verify the peak riding property of the controller and the rapid adaption of the controller to extreme runway conditions. The effect of actuator dynamics, perturbation frequency, type and location of sensors, absence of a free wheel, and a method in which the pilot's braking commands can be interfaced with the peak riding system are also considered.

Implementation Learning and Forgetting Curve to Scheduling in Garment Industry

NASA Astrophysics Data System (ADS)

Muhamad Badri, Huda; Deros, Baba Md; Syahri, M.; Saleh, Chairul; Fitria, Aninda

2016-02-01

The learning curve shows the relationship between time and the cumulative number of units produced which using the mathematical description on the performance of workers in performing repetitive works. The problems of this study is level differences in the labors performance before and after the break which affects the company's production scheduling. The study was conducted in the garment industry, which the aims is to predict the company production scheduling using the learning curve and forgetting curve. By implementing the learning curve and forgetting curve, this paper contributes in improving the labors performance that is in line with the increase in maximum output 3 hours productive before the break are 15 unit product with learning curve percentage in the company is 93.24%. Meanwhile, the forgetting curve improving maximum output 3 hours productive after the break are 11 unit product with the percentage of forgetting curve in the company is 92.96%. Then, the obtained 26 units product on the productive hours one working day is used as the basic for production scheduling.

Kinetics of the head-neck complex in low-speed rear impact.

PubMed

Stemper, Brian D; Yoganandan, Naryan; Pintar, Frank A

2003-01-01

A comprehensive characterization of the biomechanics of the cervical spine in rear impact will lead to an understanding of the mechanisms of whiplash injury. Cervical kinematics have been experimentally described using human volunteers, full-body cadaver specimens, and isolated and intact head-neck specimens. However, forces and moments at the cervico-thoracic junction have not been clearly delineated. An experimental investigation was performed using ten intact head-neck complexes to delineate the loading at the base of the cervical spine and angular acceleration of the head in whiplash. A pendulum-minisled apparatus was used to simulate whiplash acceleration of the thorax at four impact severities. Lower neck loads were measured using a six-axis load cell attached between the minisled and head-neck specimens, and head angular motion was measured with an angular rate sensor attached to the lateral side of the head. Shear and axial force, extension moment, and head angular acceleration increased with impact severity. Shear force was significantly larger than axial force (p < 0.0001). Shear force reached its maximum value at 46 msec. Maximum extension moment occurred between 7 and 22 msec after maximum shear force. Maximum angular acceleration of the head occurred 2 to 18 msec later. Maximum axial force occurred last (106 msec). All four kinetic components reached maximum values during cervical S-curvature, with maximum shear force and extension moment occurring before the attainment of maximum S-curvature. Results of the present investigation indicate that shear force and extension moment at the cervico-thoracic junction drive the non-physiologic cervical S-curvature responsible for whiplash injury and underscore the importance of understanding cervical kinematics and the underlying kinetics.

Fluid surface behavior in low gravity. Center discretionary fund no. 83-21

NASA Technical Reports Server (NTRS)

Leslie, F.; Gans, R. F.; Schafer, C.

1985-01-01

Measurements of rotating equilibrium bubble shapes in the low-gravity environment of a free-falling aircraft are presented. Emphasis is placed on bubbles which intersect the container boundaries. These data are compared with theoretical profiles derived from Laplace's formula and are in good agreement with the measurements. Two types of instability are explored. The first occurs when the baffle spacing is too large for the bubble to intersect both the top and bottom boundaries. The second occurs when the hydrostatic pressure beneath a displaced free surface does not compensate for pressure change due to capillary forces. The interface shape depends on the contact angle, the radius of intersection with container, and the parameter F which is a measure of the relative importance of centrifugal force to surface tension. For isolated bubbles, F has a maximum value of 1/2. A further increase in F causes the bubble to break contact with the axis of rotation. For large values of F, the bubble becomes more cylindrical and the capillary rise occurs over a thinner layer so that the small radius of curvature can generate enough pressure drop to balance the increased hydrostatic contribution.

Core break-off mechanism

NASA Technical Reports Server (NTRS)

Myrick, Thomas M. (Inventor)

2003-01-01

A mechanism for breaking off and retaining a core sample of a drill drilled into a ground substrate has an outer drill tube and an inner core break-off tube sleeved inside the drill tube. The break-off tube breaks off and retains the core sample by a varying geometric relationship of inner and outer diameters with the drill tube. The inside diameter (ID) of the drill tube is offset by a given amount with respect to its outer diameter (OD). Similarly, the outside diameter (OD) of the break-off tube is offset by the same amount with respect to its inner diameter (ID). When the break-off tube and drill tube are in one rotational alignment, the two offsets cancel each other such that the drill can operate the two tubes together in alignment with the drill axis. When the tubes are rotated 180 degrees to another positional alignment, the two offsets add together causing the core sample in the break-off tube to be displaced from the drill axis and applying shear forces to break off the core sample.

Does combined strength training and local vibration improve isometric maximum force? A pilot study.

PubMed

Goebel, Ruben; Haddad, Monoem; Kleinöder, Heinz; Yue, Zengyuan; Heinen, Thomas; Mester, Joachim

2017-01-01

The aim of the study was to determine whether a combination of strength training (ST) and local vibration (LV) improved the isometric maximum force of arm flexor muscles. ST was applied to the left arm of the subjects; LV was applied to the right arm of the same subjects. The main aim was to examine the effect of LV during a dumbbell biceps curl (Scott Curl) on isometric maximum force of the opposite muscle among the same subjects. It is hypothesized, that the intervention with LV produces a greater gain in isometric force of the arm flexors than ST. Twenty-seven collegiate students participated in the study. The training load was 70% of the individual 1 RM. Four sets with 12 repetitions were performed three times per week during four weeks. The right arm of all subjects represented the vibration trained body side (VS) and the left arm served as the traditional trained body side (TTS). A significant increase of isometric maximum force in both body sides (Arms) occurred. VS, however, significantly increased isometric maximum force about 43% in contrast to 22% of the TTS. The combined intervention of ST and LC improves isometric maximum force of arm flexor muscles. III.

Extended healing validation of an artificial tendon to connect the quadriceps muscle to the Tibia: 180-day study.

PubMed

Melvin, Alan J; Litsky, Alan S; Mayerson, Joel L; Stringer, Keith; Juncosa-Melvin, Natalia

2012-07-01

Whenever a tendon or its bone insertion is disrupted or removed, existing surgical techniques provide a temporary connection or scaffolding to promote healing, but the interface of living to non-living materials soon breaks down under the stress of these applications, if it must bear the load more than acutely. Patients are thus disabled whose prostheses, defect size, or mere anatomy limit the availability or outcomes of such treatments. Our group developed the OrthoCoupler™ device to join skeletal muscle to prosthetic or natural structures without this interface breakdown. In this study, the goat knee extensor mechanism (quadriceps tendon, patella, and patellar tendon) was removed from the right hind limb in 16 goats. The device connected the quadriceps muscle to a stainless steel bone plate on the tibia. Mechanical testing and histology specimens were collected from each operated leg and contralateral unoperated control legs at 180 days. Maximum forces in the operated leg (vs. unoperated) were 1,400 ± 93 N (vs. 1,179 ± 61 N), linear stiffnesses were 33 ± 3 N/mm (vs. 37 ± 4 N/mm), and elongations at failure were 92.1 ± 5.3 mm (vs. 68.4 ± 3.8 mm; mean ± SEM). Higher maximum forces (p = 0.02) and elongations at failure (p=0.008) of legs with the device versus unoperated controls were significant; linear stiffnesses were not (p=0.3). We believe this technology will yield improved procedures for clinical challenges in orthopedic oncology, revision arthroplasty, tendon transfer, and tendon injury reconstruction. Copyright © 2011 Orthopaedic Research Society.

Stress analysis in patella by three-dimensional photoelasticity

NASA Astrophysics Data System (ADS)

Chen, Riqi; Zhang, Jianxing; Jiang, Kunsheng

1991-12-01

In this paper, stress distribution in patella was studied by 3-D photoelastic experiments and finite element calculations. The experimental conditions were in good agreement with that of body mechanics: (1) The ratios of m. quadriceps femoris force FQ to lig. patella force FP were 1.03 - 1.42. (2) The angles between FQ and FP were 8.4 degree(s) - 18.7 degree(s). (3) The ratio of modulus of elasticity for epoxy resin and silicon rubber matched that for patella and cartilage, i.e., 145:1. The principal stresses and their path line, normal stresses, and contact stresses between patella and ossis femoris were determined in various flexion angles (15 degree(s), 30 degree(s), 45 degree(s), 60 degree(s), 75 degree(s), 90 degree(s)). Two of the correlations were: (1) Maximum principal stress in the front of patella; (sigma) max equals 35.8Wexp(0.024(alpha) ) KPa. (2) Maximum contact stress between patella and ossis femoris; (sigma) max equals -(6.86 - 0.14(alpha) + 0.02(alpha) 2)W KPa where W was body weight subjected by a single foot. It was proved that the transverse break of patella resulted from the case that the principle stress in the front of patella exceeded ultimate tensile strength. And Tension Band Wiring (TBW) therapy conformed to the law of physiological stress field. A modified K-needles position in TBW therapy was suggested. These results are useful for further research of human patella mechanics and recovery therapy. No similar result has been found in American MEDLIN Data Bank.

Muscle Force-Velocity Relationships Observed in Four Different Functional Tests.

PubMed

Zivkovic, Milena Z; Djuric, Sasa; Cuk, Ivan; Suzovic, Dejan; Jaric, Slobodan

2017-02-01

The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force-velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles.

Parametric Study on Responses of a Self-Anchored Suspension Bridge to Sudden Breakage of a Hanger

PubMed Central

Jiang, Meng; Huang, Cailiang

2014-01-01

The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause the collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of an actual self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger causes violent vibration and large changes in internal forces of the bridge. In the process of the vibration, the maximum tension of hanger produced by breakage of a hanger exceeds 2.22 times its initial value, and the reaction forces of the bearings increase by more than 1.86 times the tension of the broken hanger. Based on the actual bridge, the influences of some factors including flexural stiffness of girder, torsion stiffness of girder, flexural stiffness of main cable, weight of girder, weight of main cable, span to sag ratio of main cable, distance of hangers, span length, and breakage time of hanger on the dynamic responses are studied in detail, and the influencing extent of the factors is presented. PMID:25045734

Parametric study on responses of a self-anchored suspension bridge to sudden breakage of a hanger.

PubMed

Qiu, Wenliang; Jiang, Meng; Huang, Cailiang

2014-01-01

The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause the collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of an actual self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger causes violent vibration and large changes in internal forces of the bridge. In the process of the vibration, the maximum tension of hanger produced by breakage of a hanger exceeds 2.22 times its initial value, and the reaction forces of the bearings increase by more than 1.86 times the tension of the broken hanger. Based on the actual bridge, the influences of some factors including flexural stiffness of girder, torsion stiffness of girder, flexural stiffness of main cable, weight of girder, weight of main cable, span to sag ratio of main cable, distance of hangers, span length, and breakage time of hanger on the dynamic responses are studied in detail, and the influencing extent of the factors is presented.

RAPID RESCUE: BREAKING THE MOLD OF ROUTINE CONTINGENCY RESPONSE FOR PERSONNEL RECOVERY

DTIC Science & Technology

2016-10-23

ultimately lead to timelier response and greater economy of force for an already critically strained Air Force core function. 1 INTRODUCTION...achieve economy of force. When an OPLAN calls for PR, a capability is requested rather than individual unit. The existing UTCs are too rigid and...the combatant commander and operational planners to achieve unity and economy of force without exceeding PR capacity.61 Tactical Employment

Breaking the Status Quo: Information and the Future Force

DTIC Science & Technology

2012-03-12

Bonds. Hollywood rolled out Movietone news releases before every cinema offering, and stalwarts such as Frank Capra produced films destined to stir...report commissioned by the French Joint Forces Centre for Concept Development, Doctrine, and Experimentation – recommended that France adopt this

A preliminary study to find a possible association between occlusal wear and maximum bite force in humans.

PubMed

Jain, Veena; Mathur, Vijay Prakash; Kumar, Abhishek

2013-01-01

The objective of the study was to investigate whether moderate-to-severe attrition is associated with maximum bite force in the first molar region. Maximum bite force in the first molar region was measured for a total of 60 subjects having moderate-to-severe attrition of occlusal surface (experimental group) using a specially-designed piezoelectric sensor based bite force measuring device. An equal number of age, gender, height and weight matched controls (control group) were also subjected to bite force measurement for comparison. The maximum bite force was found to be significantly lower (p < 0.05) in the experimental group [480.32 (153.40)] as compared to the controls [640.63 (148.90)]. While analyzing the possible etiology for occlusal wear mainly two reasons were elicited, i.e. history of parafunctional habits like use of known abrasive tooth powder (sub-group A) and Bruxism (sub-group B). However, there were many subjects in which no known definite etiological factors be attributed to occlusal wear (sub-group C). On analysing further with respect to the possibly correlated etiological factors with maximum bite force, no significant difference was found within the experimental sub-group. However, all three experimental sub-groups had significantly lower maximum bite force as compared to age, gender and BMI matched controls. A significantly lower maximum bite force was found to be associated with moderate-to-severe attrition as compared to subjects without attrition. However, no specific relation could be found between bite force and possible etiological factors like history of parafunctional habits, history of use of known abrasive tooth powder, etc.

Novel platens to measure the hardness of a pentagonal shaped tablet.

PubMed

Malladi, Jaya; Sidik, Kurex; Wu, Sutan; McCann, Ryan; Dougherty, Jeffrey; Parab, Prakash; Carragher, Thomas

2017-03-01

Tablet hardness, a measure of the breaking force of a tablet, is based on numerous factors. These include the shape of the tablet and the mode of the application of force. For instance, when a pentagonal-shaped tablet was tested with a traditional hardness tester with flat platens, there was a large variation in hardness measurements. This was due to the propensity of vertices of the tablet to crush, referred to as an "improper break". This article describes a novel approach to measure the hardness of pentagonal-shaped tablets using modified platens. The modified platens have more uniform loading than flat platens. This is because they reduce loading on the vertex of the pentagon and apply forces on tablet edges to generate reproducible tablet fracture. The robustness of modified platens was assessed using a series of studies, which included feasibility and Gauge Repeatability & Reproducibility (R&R) studies. A key finding was that improper breaks, generated frequently with a traditional hardness tester using flat platens, were eliminated. The Gauge R&R study revealed that the tablets tested with novel platens generated consistent values in hardness measurements, independent of batch, hardness level, and day of testing, operator and tablet dosage strength.

Nature's technical ceramic: the avian eggshell

PubMed Central

Hahn, Eric N.; Sherman, Vincent R.; Pissarenko, Andrei; Rohrbach, Samuel D.; Fernandes, Daniel J.

2017-01-01

Avian eggshells may break easily when impacted at a localized point; however, they exhibit impressive resistance when subjected to a well-distributed compressive load. For example, a common demonstration of material strength is firmly squeezing a chicken egg along its major axis between one's hands without breaking it. This research provides insight into the underlying mechanics by evaluating both macroscopic and microstructural features. Eggs of different size, varying from quail (30 mm) to ostrich (150 mm), are investigated. Compression experiments were conducted along the major axis of the egg using force-distributing rubber cushions between steel plates and the egg. The force at failure increases with egg size, reaching loads upwards of 5000 N for ostrich eggs. The corresponding strength, however, decreases with increasing shell thickness (intimately related to egg size); this is rationalized by a micro-defects model. Failure occurs by axial splitting parallel to the loading direction—the result of hoop tensile stresses due to the applied compressive load. Finite-element analysis is successfully employed to correlate the applied compressive force to tensile breaking strength for the eggs, and the influence of geometric ratio and microstructural heterogeneities on the shell's strength and fracture toughness is established. PMID:28123095

Exploiting Acoustic and Syntactic Features for Automatic Prosody Labeling in a Maximum Entropy Framework

PubMed Central

Sridhar, Vivek Kumar Rangarajan; Bangalore, Srinivas; Narayanan, Shrikanth S.

2009-01-01

In this paper, we describe a maximum entropy-based automatic prosody labeling framework that exploits both language and speech information. We apply the proposed framework to both prominence and phrase structure detection within the Tones and Break Indices (ToBI) annotation scheme. Our framework utilizes novel syntactic features in the form of supertags and a quantized acoustic–prosodic feature representation that is similar to linear parameterizations of the prosodic contour. The proposed model is trained discriminatively and is robust in the selection of appropriate features for the task of prosody detection. The proposed maximum entropy acoustic–syntactic model achieves pitch accent and boundary tone detection accuracies of 86.0% and 93.1% on the Boston University Radio News corpus, and, 79.8% and 90.3% on the Boston Directions corpus. The phrase structure detection through prosodic break index labeling provides accuracies of 84% and 87% on the two corpora, respectively. The reported results are significantly better than previously reported results and demonstrate the strength of maximum entropy model in jointly modeling simple lexical, syntactic, and acoustic features for automatic prosody labeling. PMID:19603083

Muscle Force-Velocity Relationships Observed in Four Different Functional Tests

PubMed Central

Zivkovic, Milena Z.; Djuric, Sasa; Cuk, Ivan; Suzovic, Dejan; Jaric, Slobodan

2017-01-01

Abstract The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force–velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles. PMID:28469742

Big Jump of Record Warm Global Mean Surface Temperature in 2014-2016 Related to Unusually Large Oceanic Heat Releases

NASA Astrophysics Data System (ADS)

Yin, Jianjun; Overpeck, Jonathan; Peyser, Cheryl; Stouffer, Ronald

2018-01-01

A 0.24°C jump of record warm global mean surface temperature (GMST) over the past three consecutive record-breaking years (2014-2016) was highly unusual and largely a consequence of an El Niño that released unusually large amounts of ocean heat from the subsurface layer of the northwestern tropical Pacific. This heat had built up since the 1990s mainly due to greenhouse-gas (GHG) forcing and possible remote oceanic effects. Model simulations and projections suggest that the fundamental cause, and robust predictor of large record-breaking events of GMST in the 21st century, is GHG forcing rather than internal climate variability alone. Such events will increase in frequency, magnitude, and duration, as well as impact, in the future unless GHG forcing is reduced.

Changes in maximum bite force related to extension of the head.

PubMed

Hellsing, E; Hagberg, C

1990-05-01

The maximum bite force and position of the hyoid bone during natural and extended head posture were studied in 15 adults. All participants had normal occlusions and full dentitions. In addition, there were no signs or symptoms of craniomandibular disorders. The bite force was measured with a bite force sensor placed between the first molars. Six registrations of gradually increasing bite force up to a maximum were made with randomized natural and extended head postures. With one exception, the mean maximum bite force value was found to be higher for every subject with extended head posture compared to natural head posture. The sample mean was 271.6 Newton in natural head posture and 321.5 Newton with 20 degrees extension. With changed head posture, the cephalometric measurements pointed towards a changed position of the hyoid bone in relation to the mandible and pharyngeal airway. The cephalometric changes in the position of the hyoid bone could be due to a changed interplay between the elevator and depressor muscle groups. This was one factor which could have influenced the registered maximum bite force.

Pulling monatomic gold wires with single molecules: an Ab initio simulation.

PubMed

Krüger, Daniel; Fuchs, Harald; Rousseau, Roger; Marx, Dominik; Parrinello, Michele

2002-10-28

Car-Parrinello molecular dynamics simulations demonstrate that pulling a single thiolate molecule anchored on a stepped gold surface does not preferentially break the sulfur-gold chemical bond. Instead, it is found that this process leads to the formation of a monoatomic gold nanowire, followed by breaking a gold-gold bond with a rupture force of about 1.2 nN. The simulations also indicate that previous single-molecule thiolate-gold and gold-gold rupture experiments both probe the same phenomenon, namely, the breaking of a gold-gold bond within a gold nanowire.

Downhill Cycling Symmetry Breaking: How the Rider Foils Experiment

ERIC Educational Resources Information Center

Abu, Yuval Ben; Wolfson, Ira; Bran, Gil; Yizhaq, Hezi

2017-01-01

In high-school teaching of mechanics, we deal, among other things, with the nature of static and kinetic friction, forces that are proportional to the normal force. Under the influence of frictional forces, a body moves down a rough sloped decline at a fixed rate of acceleration that is independent of its mass. This situation does not apply to…

Breaking through the bandwidth barrier in distributed fiber vibration sensing by sub-Nyquist randomized sampling

NASA Astrophysics Data System (ADS)

Zhang, Jingdong; Zhu, Tao; Zheng, Hua; Kuang, Yang; Liu, Min; Huang, Wei

2017-04-01

The round trip time of the light pulse limits the maximum detectable frequency response range of vibration in phase-sensitive optical time domain reflectometry (φ-OTDR). We propose a method to break the frequency response range restriction of φ-OTDR system by modulating the light pulse interval randomly which enables a random sampling for every vibration point in a long sensing fiber. This sub-Nyquist randomized sampling method is suits for detecting sparse-wideband- frequency vibration signals. Up to MHz resonance vibration signal with over dozens of frequency components and 1.153MHz single frequency vibration signal are clearly identified for a sensing range of 9.6km with 10kHz maximum sampling rate.

Psychophysical basis for maximum pushing and pulling forces: A review and recommendations.

PubMed

Garg, Arun; Waters, Thomas; Kapellusch, Jay; Karwowski, Waldemar

2014-03-01

The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers. At present it is not clear whether pushing or pulling should be favored. Similarly, it is not clear what handle heights would be optimal for pushing and pulling. Epidemiological studies are needed to determine relationships between psychophysically determined maximum acceptable pushing and pulling forces and risk of musculoskeletal injuries, in particular to low back and shoulders.

Psychophysical basis for maximum pushing and pulling forces: A review and recommendations

PubMed Central

Garg, Arun; Waters, Thomas; Kapellusch, Jay; Karwowski, Waldemar

2015-01-01

The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers. At present it is not clear whether pushing or pulling should be favored. Similarly, it is not clear what handle heights would be optimal for pushing and pulling. Epidemiological studies are needed to determine relationships between psychophysically determined maximum acceptable pushing and pulling forces and risk of musculoskeletal injuries, in particular to low back and shoulders. PMID:26664045

Intramuscular fiber conduction velocity, isometric force and explosive performance.

PubMed

Methenitis, Spyridon; Terzis, Gerasimos; Zaras, Nikolaos; Stasinaki, Angeliki-Nikoletta; Karandreas, Nikolaos

2016-06-01

Conduction of electrical signals along the surface of muscle fibers is acknowledged as an essential neuromuscular component which is linked with muscle force production. However, it remains unclear whether muscle fiber conduction velocity (MFCV) is also linked with explosive performance. The aim of the present study was to investigate the relationship between vastus lateralis MFCV and countermovement jumping performance, the rate of force development and maximum isometric force. Fifteen moderately-trained young females performed countermovement jumps as well as an isometric leg press test in order to determine the rate of force development and maximum isometric force. Vastus lateralis MFCV was measured with intramuscular microelectrodes at rest on a different occasion. Maximum MFCV was significantly correlated with maximum isometric force (r = 0.66, p < 0.01), nevertheless even closer with the leg press rate of force development at 100 ms, 150 ms, 200 ms, and 250 ms (r = 0.85, r = 0.89, r = 0.91, r = 0.92, respectively, p < 0.01). Similarly, mean MFCV and type II MFCV were better correlated with the rate of force development than with maximum isometric leg press force. Lower, but significant correlations were found between mean MFCV and countermovement jump power (r = 0.65, p < 0.01). These data suggest that muscle fiber conduction velocity is better linked with the rate of force development than with isometric force, perhaps because conduction velocity is higher in the larger and fastest muscle fibers which are recognized to contribute to explosive actions.

All-Water-Jet Coal Excavator

NASA Technical Reports Server (NTRS)

Gangal, M. D.

1985-01-01

Version of jaw miner operates without mechanical cutting and crushing. Forward-pointing jets of water dislodge and break up coal. Rearward-pointing jets further break up coal and force particles into slurry chamber. Oscillatingjet mechanism itself stays within "jaw" structure and protected from wear and tear associated with coal handling. All-jet machine generates even less dust than anger, therefore poses lesser explosion or health hazard.

Balance between cell-substrate adhesion and myosin contraction determines the frequency of motility initiation in fish keratocytes.

PubMed

Barnhart, Erin; Lee, Kun-Chun; Allen, Greg M; Theriot, Julie A; Mogilner, Alex

2015-04-21

Cells are dynamic systems capable of spontaneously switching among stable states. One striking example of this is spontaneous symmetry breaking and motility initiation in fish epithelial keratocytes. Although the biochemical and mechanical mechanisms that control steady-state migration in these cells have been well characterized, the mechanisms underlying symmetry breaking are less well understood. In this work, we have combined experimental manipulations of cell-substrate adhesion strength and myosin activity, traction force measurements, and mathematical modeling to develop a comprehensive mechanical model for symmetry breaking and motility initiation in fish epithelial keratocytes. Our results suggest that stochastic fluctuations in adhesion strength and myosin localization drive actin network flow rates in the prospective cell rear above a critical threshold. Above this threshold, high actin flow rates induce a nonlinear switch in adhesion strength, locally switching adhesions from gripping to slipping and further accelerating actin flow in the prospective cell rear, resulting in rear retraction and motility initiation. We further show, both experimentally and with model simulations, that the global levels of adhesion strength and myosin activity control the stability of the stationary state: The frequency of symmetry breaking decreases with increasing adhesion strength and increases with increasing myosin contraction. Thus, the relative strengths of two opposing mechanical forces--contractility and cell-substrate adhesion--determine the likelihood of spontaneous symmetry breaking and motility initiation.

X-1 research aircraft landing on lakebed

NASA Technical Reports Server (NTRS)

1947-01-01

The first of the rocket-powered research aircraft, the X-1 (originally designated the XS-1), was a bullet-shaped airplane that was built by the Bell Aircraft Company for the US Air Force and the National Advisory Committee on Aeronautics (NACA). The mission of the X-1 was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier'. The first of the three X-1s was glide-tested at Pinecastle Air Force Base, FL, in early 1946. The first powered flight of the X-1 was made on Dec. 9, 1946, at Edwards Air Force Base with Chalmers Goodlin, a Bell test pilot, at the controls. On Oct. 14, 1947, with USAF Captain Charles 'Chuck' Yeager as pilot, the aircraft flew faster than the speed of sound for the first time. Captain Yeager ignited the four-chambered XLR-11 rocket engines after being air-launched from under the bomb bay of a B-29 at 21,000 ft. The 6,000-lbthrust ethyl alcohol/liquid oxygen burning rockets, built by Reaction Motors, Inc., pushed him up to a speed of 700 mph in level flight. Captain Yeager was also the pilot when the X-1 reached its maximum speed of 957 mph. Another USAF pilot. Lt. Col. Frank Everest, Jr., was credited with taking the X-1 to its maximum altitude of 71,902 ft. Eighteen pilots in all flew the X-1s. The number three plane was destroyed in a fire before ever making any powered flights. A single-place monoplane, the X-1 was 31 ft long, 10 ft high, and had a wingspan of 29 ft. It weighed 4,900 lb and carried 8,200 lb of fuel. It had a flush cockpit with a side entrance and no ejection seat. This roughly 30-second video clip shows the X-1 landing on Rogers Dry Lakebed followed by the safety chase aircraft.

An investigation of rugby scrimmaging posture and individual maximum pushing force.

PubMed

Wu, Wen-Lan; Chang, Jyh-Jong; Wu, Jia-Hroung; Guo, Lan-Yuen

2007-02-01

Although rugby is a popular contact sport and the isokinetic muscle torque assessment has recently found widespread application in the field of sports medicine, little research has examined the factors associated with the performance of game-specific skills directly by using the isokinetic-type rugby scrimmaging machine. This study is designed to (a) measure and observe the differences in the maximum individual pushing forward force produced by scrimmaging in different body postures (3 body heights x 2 foot positions) with a self-developed rugby scrimmaging machine and (b) observe the variations in hip, knee, and ankle angles at different body postures and explore the relationship between these angle values and the individual maximum pushing force. Ten national rugby players were invited to participate in the examination. The experimental equipment included a self-developed rugby scrimmaging machine and a 3-dimensional motion analysis system. Our results showed that the foot positions (parallel and nonparallel foot positions) do not affect the maximum pushing force; however, the maximum pushing force was significantly lower in posture I (36% body height) than in posture II (38%) and posture III (40%). The maximum forward force in posture III (40% body height) was also slightly greater than for the scrum in posture II (38% body height). In addition, it was determined that hip, knee, and ankle angles under parallel feet positioning are factors that are closely negatively related in terms of affecting maximum pushing force in scrimmaging. In cross-feet postures, there was a positive correlation between individual forward force and hip angle of the rear leg. From our results, we can conclude that if the player stands in an appropriate starting position at the early stage of scrimmaging, it will benefit the forward force production.

Micromechanical measurements of the effect of surfactants on cyclopentane hydrate shell properties.

PubMed

Brown, Erika P; Koh, Carolyn A

2016-01-07

Investigating the effect of surfactants on clathrate hydrate growth and morphology, especially particle shell strength and cohesion force, is critical to advancing new strategies to mitigate hydrate plug formation. In this study, dodecylbenzenesulfonic acid and polysorbate 80 surfactants were included during the growth of cyclopentane hydrates at several concentrations above and below the critical micelle concentration. A novel micromechanical method was applied to determine the force required to puncture the hydrate shell using a glass cantilever (with and without surfactants), with annealing times ranging from immediately after the hydrate nucleated to 90 minutes after formation. It was shown that the puncture force was decreased by the addition of both surfactants up to a maximum of 79%. Over the entire range of annealing times (0-90 minutes), the thickness of the hydrate shell was also measured. However, there was no clear change in shell thickness with the addition of surfactants. The growth rate of the hydrate shell was found to vary less than 15% with the addition of surfactants. The cohesive force between two hydrate particles was measured for each surfactant and found to be reduced by 28% to 78%. Interfacial tension measurements were also performed. Based on these results, microscopic changes to the hydrate shell morphology (due to the presence of surfactants) were proposed to cause the decrease in the force required to break the hydrate shell, since no macroscopic morphology changes were observed. Understanding the hydrate shell strength can be critical to reducing the capillary bridge interaction between hydrate particles or controlling the release of unconverted water from the interior of the hydrate particle, which can cause rapid hydrate conversion.

Evaluation of recovery in lip closing pressure and occlusal force and contact area after orthognathic surgery.

PubMed

Ueki, Koichiro; Moroi, Akinori; Sotobori, Megumi; Ishihara, Yuri; Marukawa, Kohei; Iguchi, Ran; Kosaka, Akihiko; Ikawa, Hiroumi; Nakazawa, Ryuichi; Higuchi, Masatoshi

2014-10-01

The purpose of this study was to evaluate the relationship between lip closing force, occlusal contact area and occlusal force after orthognathic surgery in skeletal Class III patients. The subjects consisted of 54 patients (28 female and 26 male) diagnosed with mandibular prognathism who underwent sagittal split ramus osteotomy with and without Le Fort I osteotomy. Maximum and minimum lip closing forces, occlusal contact area and occlusal force were measured pre-operatively, 6 months and 1 year post-operative. Maximum and minimum lip closing forces, occlusal contact area and occlusal force increased with time after surgery, however a significant increase was not found in the occlusal contact area in women. In increased ratio (6 months/pre-operative and 1 year/pre-operative), the maximum lip closing force was significantly correlated with the occlusal contact area (P < 0.0001). This study suggested that orthognathic surgery could improve the occlusal force, contact area and lip closing force, and an increase ratio in maximum lip closing force was associated with an increased ratio in occlusal contact area. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Three-dimensional force measurements with mandibular overdentures connected to implants by ball-shaped retentive anchors. A clinical study.

PubMed

Mericske-Stern, R

1998-01-01

The purpose of this in vivo study was to determine maximum and functional forces simultaneously in three dimensions on mandibular implants supporting overdentures. The anchorage system for overdenture connection was the ball-shaped retentive anchor. Five edentulous patients, each with two mandibular ITI implants, were selected as test subjects. A novel miniaturized piezo-electric force transducer was developed for specific use with ITI implants. Force magnitudes and directions were registered under various test conditions by means of electrostatic plotter records. The test modalities were maximum biting in centric occlusion, maximum biting on a bite plate, grinding, and chewing bread. Maximum forces measured in centric occlusion and on the ipsilateral implant when using a bite plate were slightly increased in vertical and backward-forward dimension (z-, y-axis) compared to the lateral-medial direction (x-axis). On the contralateral implant, equally low values were found in all three dimensions. This may be the effect of a nonsplinted anchorage device. With the use of a bite plate, force magnitudes on the ipsilateral implant were significantly higher on the z- and y-axis than mean maximum forces in centric occlusion (P < .001). Chewing and grinding resulted in lower forces compared to maximum biting, particularly in the vertical direction. The transverse force component in backward-forward direction, however, reached magnitudes that exceeded the vertical component by 100% to 300% during chewing function. This chewing pattern had not been observed in previous investigations with bars and telescopes, and therefore appears to be specific for retentive ball anchors. The prevalent or exclusive force direction registered on both implants in the vertical direction was downward under all test conditions. In the transverse direction during maximum biting the forward direction was more frequently registered, while no obvious prevalence of transverse force direction was observed during chewing and grinding.

Limitations to maximum running speed on flat curves.

PubMed

Chang, Young-Hui; Kram, Rodger

2007-03-01

Why is maximal running speed reduced on curved paths? The leading explanation proposes that an increase in lateral ground reaction force necessitates a decrease in peak vertical ground reaction force, assuming that maximum leg extension force is the limiting factor. Yet, no studies have directly measured these forces or tested this critical assumption. We measured maximum sprint velocities and ground reaction forces for five male humans sprinting along a straight track and compared them to sprints along circular tracks of 1, 2, 3, 4 and 6 m radii. Circular track sprint trials were performed either with or without a tether that applied centripetal force to the center of mass. Sprinters generated significantly smaller peak resultant ground reaction forces during normal curve sprinting compared to straight sprinting. This provides direct evidence against the idea that maximum leg extension force is always achieved and is the limiting factor. Use of the tether increased sprint speed, but not to expected values. During curve sprinting, the inside leg consistently generated smaller peak forces compared to the outside leg. Several competing biomechanical constraints placed on the stance leg during curve sprinting likely make the inside leg particularly ineffective at generating the ground reaction forces necessary to attain maximum velocities comparable to straight path sprinting. The ability of quadrupeds to redistribute function across multiple stance legs and decouple these multiple constraints may provide a distinct advantage for turning performance.

The Use of Force Sensors and a Computer System to Introduce the Concept of Inertia at a School

ERIC Educational Resources Information Center

Bogacz, Bogdan F.; Pedziwiatr, Antoni T.

2014-01-01

A classical experiment used to introduce the concept of body inertia, breaking of a thread below and above a hanging weight, is described mathematically and presented in a new way, using force sensors and a computer system.

Sensitivity analysis of primary resonances and bifurcations of a controlled piecewise-smooth system with negative stiffness

NASA Astrophysics Data System (ADS)

Huang, Dongmei; Xu, Wei

2017-11-01

In this paper, the combination of the cubic nonlinearity and time delay is proposed to improve the performance of a piecewise-smooth (PWS) system with negative stiffness. Dynamical properties, feedback control performance and symmetry-breaking bifurcation are mainly considered for a PWS system with negative stiffness under nonlinear position and velocity feedback control. For the free vibration system, the homoclinic-like orbits are firstly derived. Then, the amplitude-frequency response of the controlled system is obtained analytically in aspect of the Lindstedt-Poincaré method and the method of multiple scales, which is also verified through the numerical results. In this regard, a softening-type behavior, which directly leads to the multi-valued responses, is illustrated over the negative position feedback. Especially, the five-valued responses in which three branches of them are stable are found. And complex multi-valued characteristics are also observed in the force-amplitude responses. Furthermore, for explaining the effectiveness of feedback control, the equivalent damping and stiffness are also introduced. Sensitivity of the system response to the feedback gain and time delay is comprehensively considered and interesting dynamical properties are found. Relatively, from the perspective of suppressing the maximum amplitude and controlling the resonance stability, the selection of the feedback parameters is discussed. Finally, the symmetry-breaking bifurcation and chaotic motion are considered.

Eight-Week Vibration Training of the Elbow Flexors by Force Modulation: Effects on Dynamic and Isometric Strength.

PubMed

Xu, Lin; Cardinale, Marco; Rabotti, Chiara; Beju, Bogdan; Mischi, Massimo

2016-03-01

Vibration exercise (VE) has been suggested as an effective method to improve strength and power capabilities. However, the underlying mechanisms in response to VE are still unclear. A pulley-like VE system, characterized by sinusoidal force applications has been developed and tested for proof of concept in a previous study. The aim of this study was to evaluate the effects of such force modulation on elbow flexors strength and compare it with conventional methods. Forty subjects were randomly divided into 4 groups of 10: the vibration group (VG), the no-vibration group (NVG), the dumbbell group (DG), and the control group (CG). Biceps curl exercises were used to train the elbow flexors 2 times a week for 8 weeks. Subjects in the VG were trained using a ramp-up baseline with superimposed 30 Hz sinusoidal vibration whereas the subjects in the NVG were trained using the same baseline but without vibration. Subjects in the DG were trained using dumbbells, and the subjects in the CG were not trained. The isometric break force (IBF) and 1 repetition maximum (1RM) of the subject's dominant arm were assessed before and after the 8-week training period. The VG achieved 1RM improvement (22.7%) larger than the NVG (10.8%) and comparable with the DG (22.3%). Differences in IBF gains following the training period among the training groups were found to be not significant. Our results support the inclusion of the proposed VE in strength training programs aimed at improving dynamic strength on the elbow flexors.

Evaluation of pliers' grip spans in the maximum gripping task and sub-maximum cutting task.

PubMed

Kim, Dae-Min; Kong, Yong-Ku

2016-12-01

A total of 25 males participated to investigate the effects of the grip spans of pliers on the total grip force, individual finger forces and muscle activities in the maximum gripping task and wire-cutting tasks. In the maximum gripping task, results showed that the 50-mm grip span had significantly higher total grip strength than the other grip spans. In the cutting task, the 50-mm grip span also showed significantly higher grip strength than the 65-mm and 80-mm grip spans, whereas the muscle activities showed a higher value at 80-mm grip span. The ratios of cutting force to maximum grip strength were also investigated. Ratios of 30.3%, 31.3% and 41.3% were obtained by grip spans of 50-mm, 65-mm, and 80-mm, respectively. Thus, the 50-mm grip span for pliers might be recommended to provide maximum exertion in gripping tasks, as well as lower maximum-cutting force ratios in the cutting tasks.

Laser-tissue soldering with biodegradable polymer films in vitro: film surface morphology and hydration effects.

PubMed

Sorg, B S; Welch, A J

2001-01-01

Previous research introduced the concept of using biodegradable polymer film reinforcement of a liquid albumin solder for improvement of the tensile strength of repaired incisions in vitro. In this study, the effect of creating small pores in the PLGA films on the weld breaking strength is studied. Additionally, the effect of hydration on the strength of the reinforced welds is investigated. A 50%(w/v) bovine serum albumin solder with 0.5 mg/mL Indocyanine Green dye was used to repair an incision in bovine aorta. The solder was coagulated with an 806-nm CW diode laser. A poly(DL-lactic-co-glycolic acid) (PLGA) film was used to reinforce the solder (the controls had solder but no reinforcement). Breaking strengths were measured acutely and after hydration in saline for 1 and 2 days. The data were analyzed by ANOVA (P < 0.05) and multiple comparisons of means were performed using the Newman-Keuls test. The creation of pores in the PLGA films qualitatively improved the film flexibility without having an apparent adverse effect on the breaking strength, while the actual technique of applying the film and solder had more of an effect. The acute maximum average breaking strengths of some of the film reinforced specimens (114.7 g-134.4 g) were significantly higher (P < 0.05) than the acute maximum average breaking strength of the unreinforced control specimens (68.3 g). Film reinforced specimens were shown to have a statistically significantly higher breaking strength than unreinforced controls after 1- and 2-day hydration. Reinforcement of liquid albumin solders in laser-assisted incision repair appears to have advantages over conventional methods that do not reinforce the cohesive strength of the solder in terms of acute breaking strength and after immersion in moist environments for short periods of time. Using a film with the solder applied to one surface only may be advantageous over other techniques.

Determination of the Maximum Control Forces and Attainable Quickness in the Operation of Airplane Controls

NASA Technical Reports Server (NTRS)

Hertel, Heinrich

1930-01-01

This report is intended to furnish bases for load assumptions in the designing of airplane controls. The maximum control forces and quickness of operation are determined. The maximum forces for a strong pilot with normal arrangement of the controls is taken as 1.25 times the mean value obtained from tests with twelve persons. Tests with a number of persons were expected to show the maximum forces that a man of average strength can exert on the control stick in operating the elevator and ailerons and also on the rudder bar. The effect of fatigue, of duration and of the nature (static or dynamic) of the force, as also the condition of the test subject (with or without belt) were also considered.

Dimer motion on a periodic substrate: spontaneous symmetry breaking and absolute negative mobility.

PubMed

Speer, David; Eichhorn, Ralf; Evstigneev, Mykhaylo; Reimann, Peter

2012-06-01

We consider two coupled particles moving along a periodic substrate potential with negligible inertia effects (overdamped limit). Even when the particles are identical and the substrate spatially symmetric, a sinusoidal external driving of appropriate amplitude and frequency may lead to spontaneous symmetry breaking in the form of a permanent directed motion of the dimer. Thermal noise restores ergodicity and thus zero net velocity, but entails arbitrarily fast diffusion of the dimer for sufficiently weak noise. Moreover, upon application of a static bias force, the dimer exhibits a motion opposite to that force (absolute negative mobility). The key requirement for all these effects is a nonconvex interaction potential of the two particles.

Anthocyanin yield and skin softening during maceration, as affected by vineyard row orientation and grape ripeness of Vitis vinifera L. cv. Shiraz.

PubMed

Giacosa, Simone; Marengo, Fabio; Guidoni, Silvia; Rolle, Luca; Hunter, Jacobus J

2015-05-01

Anthocyanin and mechanical properties were evaluated on Shiraz grapes, picked from both sides of North-South and East-West vineyard row orientations at two harvest dates. Wines were made from each combination. The evaluation and evolution of crushed skin mechanical properties during maceration-fermentation, as also affected by grape ripeness, are shown for the first time. No significant differences in anthocyanin content were found in the grapes between the two vineyard row orientations. However, a significant decrease in anthocyanins and berry skin break force (also referred as skin hardness or strength) was found between the two harvest dates. During maceration, a reduction in the crushed berry skin break force of more than 15% occurred. The intact berries and macerated skins showed similarity in skin break energy values. The anthocyanin profile of the grapes and of the wines prominently displayed malvidin forms, changed mainly by the ripeness level of the grapes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Verification and Validation of the Coastal Modeling System. Report 3: CMS-Flow: Hydrodynamics

DTIC Science & Technology

2011-12-01

Jansen (1978) Spectrum TMA Directional spreading distribution Cosine Power Directional spreading parameter γ 3.3 Bottom friction Off (default...Ramp duration 3 hr The wave breaking formula applied was Battjes and Jansen (1978) because it is the recommended wave breaking formula when using...Li, Z.H., K.D. Nguyen , J.C. Brun-Cottan and J.M. Martin. 1994. Numerical simulation of the turbidity maximum transport in the Gironde Estuary (France

Effect of bending stiffness on the peeling behavior of an elastic thin film on a rigid substrate.

PubMed

Peng, Zhilong; Chen, Shaohua

2015-04-01

Inspired by the experimental observation that the maximum peeling force of elastic films on rigid substrates does not always emerge at the steady-state peeling stage, but sometimes at the initial one, a theoretical model is established in this paper, in which not only the effect of the film's bending stiffness on the peeling force is considered, but also the whole peeling process, from the initiation of debonding to the steady-state stage, is characterized. Typical peeling force-displacement curves and deformed profiles of the film reappear for the whole peeling process. For the case of a film with relatively large bending stiffness, the maximum peeling force is found arising at the initial peeling stage and the larger the stiffness of the film, the larger the maximum peeling force is. With the peeling distance increasing, the peeling force is reduced from the maximum to a constant at the steady-state stage. For the case of a film with relatively small stiffness, the peeling force increases monotonically at the initial stage and then achieves a constant as the maximum at the steady-state stage. Furthermore, the peeling forces in the steady-state stage are compared with those of the classical Kendall model. All the theoretical predictions agree well with the existing experimental and numerical observations, from which the maximum peeling force can be predicted precisely no matter what the stiffness of the film is. The results in this paper should be very helpful in the design and assessment of the film-substrate interface.

The Chemical Structure and Acid Deterioration of Paper.

ERIC Educational Resources Information Center

Hollinger, William K., Jr.

1984-01-01

Describes the chemical structure of paper, including subatomic particles, atoms and molecules, and the forces that bond atoms into molecules, molecules into chains, chains into sheets, and sheets into layers. Acid is defined, and the deleterious role of acid in breaking the forces that bond atoms into molecules is detailed. (EJS)

Services Training Manager’s Guide.

DTIC Science & Technology

1986-04-01

and Cookies 27906-Dr-Air Force Food Service Program-Vegetable Preparation 27954-DF-Air Force Food Service Program-Mission Support Meals 28003-DF-USAF...Quality Audit Program 28246-DF-Sweet Doughs 59 *. 282 50-DY-Quick Breads 38712-DY-Hamburger Sandwich, The 39420-DYP-Give Your Eggs a Break3 39421-DY

Force-displacement differences in the lower extremities of young healthy adults between drop jumps and drop landings.

PubMed

Hackney, James M; Clay, Rachel L; James, Meredith

2016-10-01

We measured ground reaction force and lower extremity shortening in ten healthy, young adults in order to compare five trials of drop jumps to drop landings. Our dependent variable was the percentage of displacement (shortening) between the markers on the ASIS and second metatarsal heads on each LE, relative to the maximum shortening (100% displacement) for that trial at the point of greatest ground reaction force. We defined this as "percent displacement at maximum force" (%dFmax). The sample mean %dFmax was 0.73%±0.14% for the drop jumps, and 0.47%±0.09% for the drop landings. The mean within-subject difference score was 0.26%±0.20%. Two-tailed paired t test comparing %dFmax between the drop jump and drop landing yielded P=0.002. For all participants in this study, the %dFmax was greater in drop jumps than in drop landings. This indicates that in drop jumps, the point of maximum force and of maximum shortening was nearly simultaneous, compared to drop landings, where the point of maximum shortening followed that of maximum force by a greater proportion. This difference in force to displacement behavior is explained by linear spring behavior in drop jumps, and linear damping behavior in drop landings. Copyright © 2016 Elsevier B.V. All rights reserved.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

USGS Publications Warehouse

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

2012-01-01

Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from and . Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Reducing the data: Analysis of the role of vascular geometry on blood flow patterns in curved vessels

NASA Astrophysics Data System (ADS)

Alastruey, Jordi; Siggers, Jennifer H.; Peiffer, Véronique; Doorly, Denis J.; Sherwin, Spencer J.

2012-03-01

Three-dimensional simulations of blood flow usually produce such large quantities of data that they are unlikely to be of clinical use unless methods are available to simplify our understanding of the flow dynamics. We present a new method to investigate the mechanisms by which vascular curvature and torsion affect blood flow, and we apply it to the steady-state flow in single bends, helices, double bends, and a rabbit thoracic aorta based on image data. By calculating forces and accelerations in an orthogonal coordinate system following the centreline of each vessel, we obtain the inertial forces (centrifugal, Coriolis, and torsional) explicitly, which directly depend on vascular curvature and torsion. We then analyse the individual roles of the inertial, pressure gradient, and viscous forces on the patterns of primary and secondary velocities, vortical structures, and wall stresses in each cross section. We also consider cross-sectional averages of the in-plane components of these forces, which can be thought of as reducing the dynamics of secondary flows onto the vessel centreline. At Reynolds numbers between 50 and 500, secondary motions in the directions of the local normals and binormals behave as two underdamped oscillators. These oscillate around the fully developed state and are coupled by torsional forces that break the symmetry of the flow. Secondary flows are driven by the centrifugal and torsional forces, and these are counterbalanced by the in-plane pressure gradients generated by the wall reaction. The viscous force primarily opposes the pressure gradient, rather than the inertial forces. In the axial direction, and depending on the secondary motion, the curvature-dependent Coriolis force can either enhance or oppose the bulk of the axial flow, and this shapes the velocity profile. For bends with little or no torsion, the Coriolis force tends to restore flow axisymmetry. The maximum circumferential and axial wall shear stresses along the centreline correlate well with the averaged in-plane pressure gradient and the radial displacement of the peak axial velocity, respectively. We conclude with a discussion of the physiological implications of these results.

Fragmentation of an elastica

NASA Astrophysics Data System (ADS)

Vandenberghe, Nicolas; Villermaux, Emmanuel

2009-03-01

When a thin rod is submitted to an axial force greater than its critical buckling load it takes the shape of an elastica. As the load further increases, a rod made of a brittle material breaks suddenly. More than two fragments may be formed during this fragmentation. In this work we discuss the sequence of events that lead to the final broken state with two or more fragments. We show that the criterion for breaking is not trivial. In particular, we investigate the effect of the duration of the loading and we show that at a given load the waiting time before breaking is broadly distributed. We discuss the consequences of the time delayed breaking on the distributions of fragment sizes and fragment numbers.

Dependence of Wave-Breaking Statistics on Wind Stress and Wave Development

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Atakturk, Serhad S.

1992-01-01

Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m/s. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events. Wave forcing as measured by wind stress (or friction velocity, u(sub *), squared) and by inverse wave age, u(sub *)/Cp where Cp is the phase velocity of the waves at the peak of the frequency spectrum, were found to be good prerictors of percentage of breaking crests. When combined in a two parameter regression, those two variables gave small standard deviation and had a high correlation coefficient (66 percent). The combination of u(sub *)(exp 2) and u(sub *)/Cp can be understood in physical terms. Furthermore, for the larger values of u(sub *)(exp 2) the dependence of wave braking and wave age was stronger than at the low end of the values u(sub *)(exp 2) and u(sub *)/Cp. Thus, both the level of wave development as determined by inverse wave age, which we may term relative wind effectiveness for wave forcing and the wind forcing on the water surface determine the incidence of wave breaking. Substituting U(sub 10)(sup 3.75) (which is the dependence of whitecap cover found by Monahan and coworkers) an equivalent correlation was found to the prediction by u(sub *)(exp 2). Slightly better standard deviation value and higher correlation coefficient were found by using a Reynolds number as predictor. A two-parameter regression involving u(sub *)(exp 2) and a Reynold's number proposed by Toba and his colleagues which relates u(sub *)(exp 2) and peak wave frequency, improves the correlation even more but is less easy to interpret in physical terms. The equivalent percentage of breaking crests obtained in our previous study was reported at 8.6 percent for a short record obtained at U(sub 10N) of about 6 m/s. Typical values in the current study for similar conditions are 6 percent, which is consistent with the previous study in view of the scatter. In that study we did not have a video recording system, so the observed breaking may include more of the micro-scaic breaking events, and the value, 8.6 percent, is well within the range of highly probable sampling variability.

Symmetry breaking and singularity structure in Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Commeford, K. A.; Garcia-March, M. A.; Ferrando, A.; Carr, Lincoln D.

2012-08-01

We determine the trajectories of vortex singularities that arise after a single vortex is broken by a discretely symmetric impulse in the context of Bose-Einstein condensates in a harmonic trap. The dynamics of these singularities are analyzed to determine the form of the imprinted motion. We find that the symmetry-breaking process introduces two effective forces: a repulsive harmonic force that causes the daughter trajectories to be ejected from the parent singularity and a Magnus force that introduces a torque about the axis of symmetry. For the analytical noninteracting case we find that the parent singularity is reconstructed from the daughter singularities after one period of the trapping frequency. The interactions between singularities in the weakly interacting system do not allow the parent vortex to be reconstructed. Analytic trajectories were compared to the actual minima of the wave function, showing less than 0.5% error for an impulse strength of v=0.00005. We show that these solutions are valid within the impulse regime for various impulse strengths using numerical integration of the Gross-Pitaevskii equation. We also show that the actual duration of the symmetry-breaking potential does not significantly change the dynamics of the system as long as the strength is below v=0.0005.

Supramolecular Systems and Chemical Reactions in Single-Molecule Break Junctions.

PubMed

Li, Xiaohui; Hu, Duan; Tan, Zhibing; Bai, Jie; Xiao, Zongyuan; Yang, Yang; Shi, Jia; Hong, Wenjing

2017-04-01

The major challenges of molecular electronics are the understanding and manipulation of the electron transport through the single-molecule junction. With the single-molecule break junction techniques, including scanning tunneling microscope break junction technique and mechanically controllable break junction technique, the charge transport through various single-molecule and supramolecular junctions has been studied during the dynamic fabrication and continuous characterization of molecular junctions. This review starts from the charge transport characterization of supramolecular junctions through a variety of noncovalent interactions, such as hydrogen bond, π-π interaction, and electrostatic force. We further review the recent progress in constructing highly conductive molecular junctions via chemical reactions, the response of molecular junctions to external stimuli, as well as the application of break junction techniques in controlling and monitoring chemical reactions in situ. We suggest that beyond the measurement of single molecular conductance, the single-molecule break junction techniques provide a promising access to study molecular assembly and chemical reactions at the single-molecule scale.

Force and Conductance Spectroscopy of Single Molecule Junctions

NASA Astrophysics Data System (ADS)

Frei, Michael

Investigation of mechanical properties of single molecule junctions is crucial to develop an understanding and enable control of single molecular junctions. This work presents an experimental and analytical approach that enables the statistical evaluation of force and simultaneous conductance data of metallic atomic point contacts and molecular junctions. A conductive atomic force microscope based break junction technique is developed to form single molecular junctions and collect conductance and force data simultaneously. Improvements of the optical components have been achieved through the use of a super-luminescent diode, enabling tremendous increases in force resolution. An experimental procedure to collect data for various molecular junctions has been developed and includes deposition, calibration, and analysis methods. For the statistical analysis of force, novel approaches based on two dimensional histograms and a direct force identification method are presented. The two dimensional method allows for an unbiased evaluation of force events that are identified using corresponding conductance signatures. This is not always possible however, and in these situations, the force based identification of junction rearrangement events is an attractive alternative method. This combined experimental and analytical approach is then applied to three studies: First, the impact of molecular backbones to the mechanical behavior of single molecule junctions is investigated and it is found that junctions formed with identical linkers but different backbone structure result in junctions with varying breaking forces. All molecules used show a clear molecular signature and force data can be evaluated using the 2D method. Second, the effects of the linker group used to attach molecules to gold electrodes are investigated. A study of four alkane molecules with different linkers finds a drastic difference in the evolution of donor-acceptor and covalently bonded molecules respectively. In fact, the covalent bond is found to significantly distort the metal electrode rearrangement such that junction rearrangement events can no longer be identified with a clean and well defined conductance signature. For this case, the force based identification process is used. Third, results for break junction measurements with different metals are presented. It is found that silver and palladium junctions rupture with forces different from those of gold contacts. In the case of silver experiments in ambient conditions, we can also identify oxygen impurities in the silver contact formation process, leading to force and conductance measurements of silver-oxygen structures. For the future, this work provides an experimental and analytical foundation that will enable insights into single molecule systems not previously accessible.

Rheology of granular materials composed of crushable particles.

PubMed

Nguyen, Duc-Hanh; Azéma, Émilien; Sornay, Philippe; Radjaï, Farhang

2018-04-11

We investigate sheared granular materials composed of crushable particles by means of contact dynamics simulations and the bonded-cell model for particle breakage. Each particle is paved by irregular cells interacting via cohesive forces. In each simulation, the ratio of the internal cohesion of particles to the confining pressure, the relative cohesion, is kept constant and the packing is subjected to biaxial shearing. The particles can break into two or more fragments when the internal cohesive forces are overcome by the action of compressive force chains between particles. The particle size distribution evolves during shear as the particles continue to break. We find that the breakage process is highly inhomogeneous both in the fragment sizes and their locations inside the packing. In particular, a number of large particles never break whereas a large number of particles are fully shattered. As a result, the packing keeps the memory of its initial particle size distribution, whereas a power-law distribution is observed for particles of intermediate size due to consecutive fragmentation events whereby the memory of the initial state is lost. Due to growing polydispersity, dense shear bands are formed inside the packings and the usual dilatant behavior is reduced or cancelled. Hence, the stress-strain curve no longer passes through a peak stress, and a progressive monotonic evolution towards a pseudo-steady state is observed instead. We find that the crushing rate is controlled by the confining pressure. We also show that the shear strength of the packing is well expressed in terms of contact anisotropies and force anisotropies. The force anisotropy increases while the contact orientation anisotropy declines for increasing internal cohesion of the particles. These two effects compensate each other so that the shear strength is nearly independent of the internal cohesion of particles.

Attributing Changing Rates of Temperature Record Breaking to Anthropogenic Influences

NASA Astrophysics Data System (ADS)

King, Andrew D.

2017-11-01

Record-breaking temperatures attract attention from the media, so understanding how and why the rate of record breaking is changing may be useful in communicating the effects of climate change. A simple methodology designed for estimating the anthropogenic influence on rates of record breaking in a given time series is proposed here. The frequency of hot and cold record-breaking temperature occurrences is shown to be changing due to the anthropogenic influence on the climate. Using ensembles of model simulations with and without human-induced forcings, it is demonstrated that the effect of climate change on global record-breaking temperatures can be detected as far back as the 1930s. On local scales, a climate change signal is detected more recently at most locations. The anthropogenic influence on the increased occurrence of hot record-breaking temperatures is clearer than it is for the decreased occurrence of cold records. The approach proposed here could be applied in rapid attribution studies of record extremes to quantify the influence of climate change on the rate of record breaking in addition to the climate anomaly being studied. This application is demonstrated for the global temperature record of 2016 and the Central England temperature record in 2014.

Large-scale Vortex Generation and Evolution in Short-crested Isolated Wave Breaking

NASA Astrophysics Data System (ADS)

Derakhti, M.; Kirby, J. T., Jr.

2016-12-01

Peregrine (1999), in discussing the effect of localization of wave energy dissipation as a generation mechanism for vorticity at the scale of individual waves, spurred a wave of study of vorticity dynamics and mixing processes in the wave-driven ocean. In deep water, the limited depth of penetration of breaking effects leads to the conceptual forcing of a "smoke-ring" resulting from the localized cross-section of impulsive forcing (Pizzo and Melville, 2013). In shallow water, depth limitations favor the generation of a quasi-two-dimensional field of vertical vortex structures, with a resulting inverse cascade of energy to low wavenumbers and the evolution of flows such as transient rip currents (Johnson and Pattiaratchi, 2006). In this study, we are examining a more detailed picture of the vorticity field evolving during a localized breaking event, with particular interest in the span from deep water to shallow water, with special attention to the transition from weak to strong bottom control. Using an LES/VOF model (Derakhti and Kirby, 2014), we examine the evolution of coherent vortex structures whose initial scales are determined by the width of the breaking region, and are much larger than the locally-controlled reverse horseshoe structures seen in typical studies of along-crest uniform breaking. We study the persistence of three-dimensionality of these structures and their contribution to the development of depth-integrated vertical vorticity, and comment on the suitability of 2D or quasi-3D models to represent nearshore flow fields.

Myoelectric activation and kinetics of different plyometric push-up exercises.

PubMed

García-Massó, Xavier; Colado, Juan C; González, Luis M; Salvá, Pau; Alves, Joao; Tella, Víctor; Triplett, N Travis

2011-07-01

The kinetic and myoelectric differences between 3 types of plyometric push-ups were investigated. Twenty-seven healthy, physically active men served as subjects and completed both familiarization and testing sessions. During these sessions, subjects performed 2 series of 3 plyometric push-up variations in a counterbalanced order according to the following techniques: Countermovement push-ups (CPUs) were push-ups performed with the maximum speed of movement; jump push-ups (JPUs) were similar to clapping push-ups; and fall push-ups (FPUs) required kneeling subjects to drop and then attempt to return to their initial position. Vertical ground reaction forces were determined by using a force plate. Myoelectric activity was recorded by means of electromyography. Impact force and impact rate of force development were significantly (p < 0.05) higher for FPUs than for JPUs. The maximum rate of force development was higher for CPUs (p < 0.05) than for JPUs, and the maximum force was higher for the CPUs than for the FPUs (p < 0.05). There were differences among exercises for the mean muscle activation of the pectoralis major (PM; p < 0.001), triceps brachii (p < 0.001), external oblique (p < 0.005) and anterior deltoid (p < 0.001), and in the maximum muscle activation of the PM (p < 0.001). Plyometric push-ups with countermovement achieved a higher maximum force and rate of force and did not cause impact forces. Thus, this type of push-up exercise may be regarded as the best for improving explosive force. The FPU exercise achieved higher levels of muscular activation in the agonist and synergist muscle groups, and greater impact forces and impact force development rates.

Adhesive behavior of micro/nano-textured surfaces

NASA Astrophysics Data System (ADS)

Zhang, Yuyan; Wang, Xiaoli; Li, Hanqing; Wang, Ben

2015-02-01

A numerical model of the adhesive contact between a rigid smooth sphere and an elastic textured surface based on the Lennard-Jones interatomic potential law and the Hamaker summation method is established. Textures are considered by introducing the texture height distribution into the gap equation. Simulation results show that the pull-off force on textured surfaces decreases compared to that on smooth surfaces. Furthermore, effects of sphere-shaped textures on reducing adhesion are more obvious than cylinder-shaped or cube-shaped textures when the coverage area ratio, maximum height and interval of textures are fixed. For surfaces with sphere-shaped textures, variation trends of the mean pull-off force with texture density are not monotonous, and there exists a certain range of texture densities in which the mean pull-off force is small and its variation is insignificant. In addition, the pull-off force depends also on the maximum height and radius of textures. On one hand, if the texture radius is fixed, larger maximum height results in smaller pull-off force, and if the maximum height is fixed, the pull-off force tends to increase almost linearly with increases in texture radius. On the other hand, if the height-diameter ratio of textures is fixed, the pull-off force reaches a minimum at an optimum texture radius or maximum height.

Afghanistan: Post-War Governance, Security, and U.S. Policy

DTIC Science & Technology

2008-08-08

2008 prison break in Qandahar (several hundred Taliban captives were freed, as part of an emptying of the 1,200 inmates there); (7) the reported 40...more close involvement by U.S. forces, and that the force is ethnically integrated in each unit. The naming of a Pashtun, Abdul Rahim Wardak, as

Nonequilibrium dynamics of probe filaments in actin-myosin networks

NASA Astrophysics Data System (ADS)

Gladrow, J.; Broedersz, C. P.; Schmidt, C. F.

2017-08-01

Active dynamic processes of cells are largely driven by the cytoskeleton, a complex and adaptable semiflexible polymer network, motorized by mechanoenzymes. Small dimensions, confined geometries, and hierarchical structures make it challenging to probe dynamics and mechanical response of such networks. Embedded semiflexible probe polymers can serve as nonperturbing multiscale probes to detect force distributions in active polymer networks. We show here that motor-induced forces transmitted to the probe polymers are reflected in nonequilibrium bending dynamics, which we analyze in terms of spatial eigenmodes of an elastic beam under steady-state conditions. We demonstrate how these active forces induce correlations among the mode amplitudes, which furthermore break time-reversal symmetry. This leads to a breaking of detailed balance in this mode space. We derive analytical predictions for the magnitude of resulting probability currents in mode space in the white-noise limit of motor activity. We relate the structure of these currents to the spatial profile of motor-induced forces along the probe polymers and provide a general relation for observable currents on two-dimensional hyperplanes.

Columnar-to-Equiaxed Transition and Equiaxed Grain Alignment in Directionally Solidified Ni3Al Alloy Under an Axial Magnetic Field

NASA Astrophysics Data System (ADS)

Liu, Huan; Xuan, Weidong; Xie, Xinliang; Li, Chuanjun; Wang, Jiang; Yu, Jianbo; Li, Xi; Zhong, Yunbo; Ren, Zhongming

2017-09-01

The effect of an axial magnetic field on the solidification structure in directionally solidified Ni-21.5Al-0.4Zr-0.1B (at. pct) alloy was investigated. The experimental results indicated that the application of a high magnetic field caused the deformation of dendrites and the occurrence of columnar-to-equiaxed transition (CET). The magnetic field tended to orient the 〈001〉 crystal direction of the equiaxed grains along the magnetic field direction. The bulk solidification experiment under a high magnetic field showed that the crystal exhibited magnetic crystalline anisotropy. Further, the thermoelectric (TE) magnetic force and TE magnetic convention were analyzed by three-dimensional (3-D) numerical simulations. The results showed that the maximum value of TE magnetic force localized in the vicinity of the secondary dendrite arm root, which should be responsible for the dendrite break and CET. Based on the high-temperature creep mechanism, a simple model was proposed to describe the magnetic field intensity needed for CET: B ≥ kG^{ - 1.5} R^{1.25} . The model is in good agreement with the experiment results. The experimental results should be attributed to the combined action of TE magnetic effects and the magnetic moment.

High-Speed Wind-Tunnel Investigation of the Longitudinal Stability and Control Characteristics of a 0.10-Scale Model of the Grumman XF9F-2 Airplane, TED No. NACA DE301

NASA Technical Reports Server (NTRS)

Polhamus, Edward C.; King, Thomas J., Jr.

1948-01-01

An investigation was made in the Langley high-speed 7-by 10-foot tunnel to determine the high-speed longitudinal stability end con&o1 characteristics of a 0.01-scale model of the Grumman XF9F-2 airplane in the Mach number range from 0.40 to 0.85. The results indicated that the lift and drag force breaks occurred at a Mach number of about 0.76. The aerodynamic-center position moved rearward after the force break and control position stability was present for all Mach numbers up to a Mach number of 0.80.

Investigation, sensitivity analysis, and multi-objective optimization of effective parameters on temperature and force in robotic drilling cortical bone.

PubMed

Tahmasbi, Vahid; Ghoreishi, Majid; Zolfaghari, Mojtaba

2017-11-01

The bone drilling process is very prominent in orthopedic surgeries and in the repair of bone fractures. It is also very common in dentistry and bone sampling operations. Due to the complexity of bone and the sensitivity of the process, bone drilling is one of the most important and sensitive processes in biomedical engineering. Orthopedic surgeries can be improved using robotic systems and mechatronic tools. The most crucial problem during drilling is an unwanted increase in process temperature (higher than 47 °C), which causes thermal osteonecrosis or cell death and local burning of the bone tissue. Moreover, imposing higher forces to the bone may lead to breaking or cracking and consequently cause serious damage. In this study, a mathematical second-order linear regression model as a function of tool drilling speed, feed rate, tool diameter, and their effective interactions is introduced to predict temperature and force during the bone drilling process. This model can determine the maximum speed of surgery that remains within an acceptable temperature range. Moreover, for the first time, using designed experiments, the bone drilling process was modeled, and the drilling speed, feed rate, and tool diameter were optimized. Then, using response surface methodology and applying a multi-objective optimization, drilling force was minimized to sustain an acceptable temperature range without damaging the bone or the surrounding tissue. In addition, for the first time, Sobol statistical sensitivity analysis is used to ascertain the effect of process input parameters on process temperature and force. The results show that among all effective input parameters, tool rotational speed, feed rate, and tool diameter have the highest influence on process temperature and force, respectively. The behavior of each output parameters with variation in each input parameter is further investigated. Finally, a multi-objective optimization has been performed considering all the aforementioned parameters. This optimization yielded a set of data that can considerably improve orthopedic osteosynthesis outcomes.

Transient etiolation: protochlorophyll(ide) and chlorophyll forms in differentiating plastids of closed and breaking leaf buds of horse chestnut (Aesculus hippocastanum).

PubMed

Solymosi, Katalin; Bóka, Károly; Böddi, Béla

2006-08-01

An accompanying paper reports the accumulation of photoactive protochlorophyllide (Pchlide) in the innermost leaf primordia of buds of many tree species. In this paper, we describe plastid differentiation, changes in pigment concentrations and spectral properties of bud scales and leaf primordia of horse chestnut (Aesculus hippocastanum L.) from January until the end of bud break in April. The bud scales contained plastids with grana, stroma thylakoids characteristic of chloroplasts and large dense bodies within the stroma. In January, proplastids and young chloroplasts were present in the leaf primordia, and the fluorescence spectra of the primordia were similar to those of green leaves except for a minor band at 630 nm, indicative of a protochlorophyll(ide). During bud break, the pigment concentrations of the green bud scales and the outermost leaf primordia increased, and Pchlide forms with emission maxima at 633, 644 and 655 nm accumulated in the middle and innermost leaf primordia. Depending on the position of the leaf primordia within the bud, their plastids and their pigment concentrations varied. Etio-chloroplasts with prolamellar bodies (PLBs) and prothylakoids with developing grana were observed in the innermost leaves. Besides the above-mentioned Pchlide forms, the middle and innnermost leaf primordia contained only a Chl band with an emission maximum at 686 nm. The outermost leaf primordia contained etio-chloroplasts with well-developed grana and small, narrow-type PLBs. These outermost leaves contained only chlorophyll forms like the mature green leaves. No Pchlide accumulation was observed after bud break, indicating that etiolation of the innermost and middle leaves is transient. The Pchlide forms and the plastid types of the primordia in buds grown in nature were similar to those of leaves of dark-germinated seedlings and to those of the leaf primordia of dark-forced buds. We conclude that transient etiolation occurs under natural conditions. The formation of PLBs and etio-chloroplasts and the accumulation of the light-dependent NADPH:protochlorophyllide oxidoreductase are involved in the natural greening process and ontogenesis of young leaf primordia of horse chestnut buds.

Judgements about the relation between force and trajectory variables in verbally described ballistic projectile motion.

PubMed

White, Peter A

2013-01-01

How accurate are explicit judgements about familiar forms of object motion, and how are they made? Participants judged the relations between force exerted in kicking a soccer ball and variables that define the trajectory of the ball: launch angle, maximum height attained, and maximum distance reached. Judgements tended to conform to a simple heuristic that judged force tends to increase as maximum height and maximum distance increase, with launch angle not being influential. Support was also found for the converse prediction, that judged maximum height and distance tend to increase as the amount of force described in the kick increases. The observed judgemental tendencies did not resemble the objective relations, in which force is a function of interactions between the trajectory variables. This adds to a body of research indicating that practical knowledge based on experiences of actions on objects is not available to the processes that generate judgements in higher cognition and that such judgements are generated by simple rules that do not capture the objective interactions between the physical variables.

Nuclear Symmetry Energy and the Breaking of the Isospin Symmetry: How Do They Reconcile with Each Other?

NASA Astrophysics Data System (ADS)

Roca-Maza, X.; Colò, G.; Sagawa, H.

2018-05-01

We analyze and propose a solution to the apparent inconsistency between our current knowledge of the equation of state of asymmetric nuclear matter, the energy of the isobaric analog state (IAS) in a heavy nucleus such as 208Pb, and the isospin symmetry breaking forces in the nuclear medium. This is achieved by performing state-of-the-art Hartree-Fock plus random phase approximation calculations of the IAS that include all isospin symmetry breaking contributions. To this aim, we propose a new effective interaction that is successful in reproducing the IAS excitation energy without compromising other properties of finite nuclei.

Nuclear Symmetry Energy and the Breaking of the Isospin Symmetry: How Do They Reconcile with Each Other?

PubMed

Roca-Maza, X; Colò, G; Sagawa, H

2018-05-18

We analyze and propose a solution to the apparent inconsistency between our current knowledge of the equation of state of asymmetric nuclear matter, the energy of the isobaric analog state (IAS) in a heavy nucleus such as ^{208}Pb, and the isospin symmetry breaking forces in the nuclear medium. This is achieved by performing state-of-the-art Hartree-Fock plus random phase approximation calculations of the IAS that include all isospin symmetry breaking contributions. To this aim, we propose a new effective interaction that is successful in reproducing the IAS excitation energy without compromising other properties of finite nuclei.

Main steam-line break core shroud loading calculations for BWRs

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

Shoop, U.; Feltus, M.A.; Baratta, A.J.

1995-12-31

In July 1994, the U.S. Nuclear regulatory Commission sent out Generic Letter 94-03 to all boiling water reactors in the United States, informing them of intergranular stress corrosion cracking of core shrouds found in 2 reactors. The letter directed all to perform safety analysis of the BWR units. Penn State performed scoping calculations to determine the forces experienced by the core shroud during a main-stream line break transient.

Hand digit control in children: motor overflow in multi-finger pressing force vector space during maximum voluntary force production.

PubMed

Shim, Jae Kun; Karol, Sohit; Hsu, Jeffrey; de Oliveira, Marcio Alves

2008-04-01

The aim of this study was to investigate the contralateral motor overflow in children during single-finger and multi-finger maximum force production tasks. Forty-five right handed children, 5-11 years of age produced maximum isometric pressing force in flexion or extension with single fingers or all four fingers of their right hand. The forces produced by individual fingers of the right and left hands were recorded and analyzed in four-dimensional finger force vector space. The results showed that increases in task (right) hand finger forces were linearly associated with non-task (left) hand finger forces. The ratio of the non-task hand finger force magnitude to the corresponding task hand finger force magnitude, termed motor overflow magnitude (MOM), was greater in extension than flexion. The index finger flexion task showed the smallest MOM values. The similarity between the directions of task hand and non-task hand finger force vectors in four-dimensional finger force vector space, termed motor overflow direction (MOD), was the greatest for index and smallest for little finger tasks. MOM of a four-finger task was greater than the sum of MOMs of single-finger tasks, and this phenomenon was termed motor overflow surplus. Contrary to previous studies, no single-finger or four-finger tasks showed significant changes of MOM or MOD with the age of children. We conclude that the contralateral motor overflow in children during finger maximum force production tasks is dependent upon the task fingers and the magnitude and direction of task finger forces.

Evaluation of Bite Force After Open Reduction and Internal Fixation Using Microplates

PubMed Central

Kumar, S Tharani; Saraf, Saurabh; Devi, S Prasanna

2013-01-01

The primary aim of this study is to determine maximum bite force in molar and incisor regions of healthy individuals, to evaluate the bite force after open reduction and internal fixation of mandibular fractures using micro plates, for a period of up to 6 weeks and to determine the rate of recovery of maximum bite force in an Indian population. PMID:24910656

Child Trafficking: A Hindrance to the Girl-Child Education

ERIC Educational Resources Information Center

Aibangbe, Mary O.

2015-01-01

Child trafficking continues to pose a major hindrance to the freedom and educational development of the girl-child in Nigeria. Most of the girls trafficked are forced into prostitution, forced labour and in some cases as human sacrifice. Some families support this trend because they see it as a means to break the yoke of economic hardship. The…

Effect of combined actions of hip adduction/abduction on the force generation and maintenance of pelvic floor muscles in healthy women

PubMed Central

Amorim, Amanda C.; Cacciari, Licia P.; Passaro, Anice C.; Silveira, Simone R. B.; Amorim, Cesar F.; Loss, Jefferson F.

2017-01-01

Pelvic floor muscle (PFM) force and coordination are related to urinary incontinence severity and to sexual satisfaction. Health professionals frequently combine classic PFM exercises with hip adduction/abduction contraction to treat these disorders, but the real benefits of this practice are still unknown. Based on a theoretical anatomy approach whereby the levator ani muscle is inserted into the obturator internus myofascia and in which force generated by hip movements should increase the contraction quality of PFMs, our aim was to investigate the effects of isometric hip adduction and abduction on PFM force generation. Twenty healthy, nulliparous women were evaluated using two strain-gauge dynamometers (one cylinder-like inside the vaginal cavity, and the other measuring hip adduction/abduction forces around both thighs) while performing three different tasks: (a) isolated PFM contraction; (b) PFM contraction combined with hip adduction (30% and 50% maximum hip force); and (c) PFM contraction combined with hip abduction (30% and 50% maximum hip force). Data were sampled at 100Hz and subtracted from the offset if existent. We calculated a gradient between the isolated PFM contraction and each hip condition (Δ Adduction and Δ Abduction) for all variables: Maximum force (N), instant of maximum-force occurrence (s), mean force in an 8-second window (N), and PFM force loss (N.s). We compared both conditions gradients in 30% and 50% by paired t-tests. All variables did not differ between hip conditions both in 30% and 50% of maximum hip force (p>.05). PFM contraction combined with isometric hip abduction did not increase vaginal force in healthy and nulliparous women compared to PFM contraction combined with isometric hip adduction. Therefore, so far, the use of hip adduction or abduction in PFM training and treatments are not justified for improving PFM strength and endurance. PMID:28542276

Effect of combined actions of hip adduction/abduction on the force generation and maintenance of pelvic floor muscles in healthy women.

PubMed

Amorim, Amanda C; Cacciari, Licia P; Passaro, Anice C; Silveira, Simone R B; Amorim, Cesar F; Loss, Jefferson F; Sacco, Isabel C N

2017-01-01

Pelvic floor muscle (PFM) force and coordination are related to urinary incontinence severity and to sexual satisfaction. Health professionals frequently combine classic PFM exercises with hip adduction/abduction contraction to treat these disorders, but the real benefits of this practice are still unknown. Based on a theoretical anatomy approach whereby the levator ani muscle is inserted into the obturator internus myofascia and in which force generated by hip movements should increase the contraction quality of PFMs, our aim was to investigate the effects of isometric hip adduction and abduction on PFM force generation. Twenty healthy, nulliparous women were evaluated using two strain-gauge dynamometers (one cylinder-like inside the vaginal cavity, and the other measuring hip adduction/abduction forces around both thighs) while performing three different tasks: (a) isolated PFM contraction; (b) PFM contraction combined with hip adduction (30% and 50% maximum hip force); and (c) PFM contraction combined with hip abduction (30% and 50% maximum hip force). Data were sampled at 100Hz and subtracted from the offset if existent. We calculated a gradient between the isolated PFM contraction and each hip condition (Δ Adduction and Δ Abduction) for all variables: Maximum force (N), instant of maximum-force occurrence (s), mean force in an 8-second window (N), and PFM force loss (N.s). We compared both conditions gradients in 30% and 50% by paired t-tests. All variables did not differ between hip conditions both in 30% and 50% of maximum hip force (p>.05). PFM contraction combined with isometric hip abduction did not increase vaginal force in healthy and nulliparous women compared to PFM contraction combined with isometric hip adduction. Therefore, so far, the use of hip adduction or abduction in PFM training and treatments are not justified for improving PFM strength and endurance.

Force-Velocity Relationship of Upper Body Muscles: Traditional Versus Ballistic Bench Press.

PubMed

García-Ramos, Amador; Jaric, Slobodan; Padial, Paulino; Feriche, Belén

2016-04-01

This study aimed to (1) evaluate the linearity of the force-velocity relationship, as well as the reliability of maximum force (F0), maximum velocity (V0), slope (a), and maximum power (P0); (2) compare these parameters between the traditional and ballistic bench press (BP); and (3) determine the correlation of F0 with the directly measured BP 1-repetition maximum (1RM). Thirty-two men randomly performed 2 sessions of traditional BP and 2 sessions of ballistic BP during 2 consecutive weeks. Both the maximum and mean values of force and velocity were recorded when loaded by 20-70% of 1RM. All force-velocity relationships were strongly linear (r > .99). While F0 and P0 were highly reliable (ICC: 0.91-0.96, CV: 3.8-5.1%), lower reliability was observed for V0 and a (ICC: 0.49-0.81, CV: 6.6-11.8%). Trivial differences between exercises were found for F0 (ES: < 0.2), however the a was higher for the traditional BP (ES: 0.68-0.94), and V0 (ES: 1.04-1.48) and P0 (ES: 0.65-0.72) for the ballistic BP. The F0 strongly correlated with BP 1RM (r: 0.915-0.938). The force-velocity relationship is useful to assess the upper body maximal capabilities to generate force, velocity, and power.

Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter.

PubMed

Takesono, Satoshi; Onodera, Masayuki; Toda, Kiyoshi; Yoshida, Masanori; Yamagiwa, Kazuaki; Ohkawa, Akira

2006-03-01

This study examined a stirred-tank fermenter (STF) containing low-viscosity foaming liquids with an agitation impeller and foam-breaking impeller mounted on the same shaft. Results showed that the performance of the foam-breaking impeller can be improved by changing a conventional six-blade turbine impeller into a rod impeller as the agitation impeller. The volumetric oxygen-transfer coefficient, kLa, in the mechanical foam-control method (MFM) using a six-blade vaned disk as the foam-breaking impeller in the STF with the rod impeller was approximately five times greater than that of the chemical foam-control method (CFM) adding an anti-foaming agent in the STF with the six-blade turbine impeller. Application of the present method to the cultivation of Saccharomyces cerevisiae K-7 demonstrated that the cultivation time up to the maximum cell concentration was remarkably shorter than that achieved using a conventional CFM.

Application of a planetary wave breaking parameterization to stratospheric circulation statistics

NASA Technical Reports Server (NTRS)

Randel, William J.; Garcia, Rolando R.

1994-01-01

The planetary wave parameterization scheme developed recently by Garcia is applied to statospheric circulation statistics derived from 12 years of National Meteorological Center operational stratospheric analyses. From the data a planetary wave breaking criterion (based on the ratio of the eddy to zonal mean meridional potential vorticity (PV) gradients), a wave damping rate, and a meridional diffusion coefficient are calculated. The equatorward flank of the polar night jet during winter is identified as a wave breaking region from the observed PV gradients; the region moves poleward with season, covering all high latitudes in spring. Derived damping rates maximize in the subtropical upper stratosphere (the 'surf zone'), with damping time scales of 3-4 days. Maximum diffusion coefficients follow the spatial patterns of the wave breaking criterion, with magnitudes comparable to prior published estimates. Overall, the observed results agree well with the parameterized calculations of Garcia.

[Reinforcement for overdentures on abutment teeth].

PubMed

Osada, Tomoko

2006-04-01

This study investigated the effect of the position of reinforcement wires, differences in artificial teeth, and framework designs on the breaking strength of overdentures. The basal surfaces of composite resin teeth and acrylic resin teeth were removed using a carbide bur. A reinforcement wire or a wrought palatal bar was embedded near the occlusal surface or basal surface. Four types of framework structures were designed : conventional skeleton (skeleton), housing with skeleton (housing), housing plus short metal backing (metal backing), and housing plus long metal backing (double structure). After the wires, bars, and frameworks were sand-blasted with 50 microm Al(2)O(3) powder, they were primed with a metal primer and embedded in a heat-polymerized denture base resin. The breaking strengths (N) and maximum stiffness (N/mm) of two-week aged (37 degrees C) specimens were measured using a bending test (n=8). All data obtained at a crosshead speed of 2.0 mm/min were analyzed by ANOVA/Tukey's test (alpha=0.01). There were no statistical differences between the two kinds of artificial teeth (p>0.01). The wrought palatal bar had significantly higher strength than the reinforcement wire (p<0.01). Greater strengths were found for specimens with frameworks than those without frameworks (p<0.01). The breaking strength of the wrought palatal bar embedded near the occlusal surface was higher than that on the basal surface (p>0.01). The breaking strength and maximum stiffness of the double structure framework were significantly greater (p<0.01) than those of the conventional frameworks. The breaking strengths of overdentures were influenced by the size and position of the reinforcement wires. Double structure frameworks are recommended for overdentures to promote a long-term prognosis without denture breakage.

The Role of the Isospin 3/2 Component in Elastic Neutron-Deuteron Scattering and in the Deuteron Breakup Reaction

NASA Astrophysics Data System (ADS)

Witała, H.; Golak, J.; Skibiński, R.; Topolnicki, K.; Kamada, H.

We discuss the importance of the three-nucleon isospin T = 3/2 component in elastic neutron-deuteron scattering and in the deuteron breakup reaction. The contribution of this amplitude originates from charge-independence breaking of the nucleon-nucleon potential. We study the magnitude of that contribution to the elastic scattering and breakup observables, taking the Av18 nucleon-nucleon potential alone or combined with the Urbana IX three-nucleon force as well as the locally regularized chiral N4LO nucleon-nucleon potential alone or supplemented by the chiral N2LO three-nucleon force. We find that the isospin T = 3/2 component is important for the breakup reaction and the proper treatment of charge-independence breaking in this case requires the inclusion of the 1S 0 state with isospin T = 3/2. For neutron-deuteron elastic scattering the T = 3/2 contributions are insignificant and charge-independence breaking can be accounted for by neglecting T = 3/2 component and using the effective t-matrix generated with the so-called “2/3 ‑ 1/3″ rule.

Polyad breaking phenomenon associated with a local-to-normal mode transition and suitability to estimate force constants

NASA Astrophysics Data System (ADS)

Bermúdez-Montaña, M.; Lemus, R.; Castaños, O.

2017-12-01

In a system of two interacting harmonic oscillators a local-to-normal mode transition is manifested as a polyad breaking phenomenon. This phenomenon is associated with the suitability to estimate zeroth-order force constants in the framework of a local mode description. This transition is also exhibited in two interacting Morse oscillators. To study this case, an appropriate parameterisation going from a molecule with local mode behaviour (H2O) to a molecule presenting a normal mode behaviour (CO2) is introduced. Concepts from quantum mechanics like fidelity, entropy and probability density, as well from nonlinear classical mechanics like Poincaré sections are used to detect the transition region. It is found that fidelity and entropy are sensitive complementary properties to detect the local-to-normal transition. Poincaré sections allow the local-to-normal transition to be detected through the appearance of chaos as a consequence of the polyad breaking phenomenon. In addition, two kinds of avoided energy crossings are identified in accordance with the different regions of the spectrum.

CFD Applications in Support of the Space Shuttle Risk Assessment

NASA Technical Reports Server (NTRS)

Baum, Joseph D.; Mestreau, Eric; Luo, Hong; Sharov, Dmitri; Fragola, Joseph; Loehner, Rainald; Cook, Steve (Technical Monitor)

2000-01-01

The paper describes a numerical study of a potential accident scenario of the space shuttle, operating at the same flight conditions as flight 51L, the Challenger accident. The interest in performing this simulation is derived by evidence that indicates that the event itself did not exert large enough blast loading on the shuttle to break it apart. Rather, the quasi-steady aerodynamic loading on the damaged, unbalance vehicle caused the break-up. Despite the enormous explosive potential of the shuttle total fuel load (both liquid and solid), the post accident explosives working group estimated the maximum energy involvement to be equivalent to about five hundreds of pounds of TNT. This understanding motivated the simulation described here. To err on the conservative side, we modeled the event as an explosion, and used the maximum energy estimate. We modeled the transient detonation of a 500 lbs spherical charge of TNT, placed at the main engine, and the resulting blast wave propagation about the complete stack. Tracking of peak pressures and impulses at hundreds of locations on the vehicle surface indicate that the blast load was insufficient to break the vehicle, hence demonstrating likely crew survivability through such an event.

Transient response of multidegree-of-freedom linear systems to forcing functions with inequality constraints

NASA Technical Reports Server (NTRS)

Michalopoulos, C. D.

1974-01-01

Optimal control theory is applied to analyze the transient response of discrete linear systems to forcing functions with unknown time dependence but having known bounds. Particular attention is given to forcing functions which include: (1) maximum displacement of any given mass element, (2) maximum relative displacement of any two adjacent masses, and (3) maximum acceleration of a given mass. Linear mechanical systems with an arbitrary number of degrees of freedom and only one forcing function acting are considered. In the general case, the desired forcing function is found to be a function that switches from the upper-to-lower bound and vice-versa at certain moments of time. A general procedure for finding such switching times is set forth.

Comparative study on protein cross-linking and gel enhancing effect of microbial transglutaminase on surimi from different fish.

PubMed

Chanarat, Sochaya; Benjakul, Soottawat; H-Kittikun, Aran

2012-03-15

Microbial transglutaminase (MTGase) has been used to increase the gel strength of surimi. Nevertheless, its effectiveness varies with fish species. The aim of this study was to elucidate the effect of MTGase at different levels on protein cross-linking and gel property of surimi from threadfin bream, Indian mackerel and sardine in the presence and absence of endogenous transglutaminase. Breaking force of all surimi gels increased as MTGase levels (0-0.6 U g⁻¹) increased except for threadfin bream surimi gel, where the breaking force decreased at 0.6 U g⁻¹ (P < 0.05). In the presence of EDTA, the gel strengthening effect was lower, suggesting the combined effect of endogenous transglutaminase with MTGase. With the addition of MTGase, the gel with the highest increase in breaking force showed highest decrease in myosin heavy chain. When cross-linking activity of MTGase on natural actomyosin (NAM) was determined, the highest decreasing rate in ε-amino group content with the concomitant increased formation of cross-linked proteins was found in NAM from threadfin bream. The reactivity of muscle proteins toward MTGase-induced cross-linking was in agreement with surimi gel strengthening. The composition and properties of muscle proteins of varying fish species more likely determined protein cross-linking induced by MTGase, thereby affecting their gel properties.

Simulation of air-bag impact on an eye with transsclerally fixated posterior chamber intraocular lens using finite element analysis.

PubMed

Uchio, Eiichi; Kadonosono, Kazuaki; Matsuoka, Yasuhiro; Goto, Satoru

2004-02-01

To determine the physical and mechanical conditions of an impacting air bag that would rupture an eye with a transsclerally fixated posterior chamber intraocular lens (IOL). Numerical simulation study on a computer. Simulations in a model human eye were performed with a computer using the finite element analysis program PAM-CRASH (Nihon ESI). The air bag was set to impact the surface of an eye with a transsclerally fixated posterior chamber IOL at various velocities. The tensile force limit of a 10-1 polypropylene suture was assumed to be 0.16 N, which is specified in the U.S. Pharmacopeia XXII. At the lowest velocity of 20.0 m/s, 10-0 polypropylene sutures were not likely to break. Sutures fixating the IOL might break and a corneoscleral incision was likely to open after 0.3 second at the medium impacting velocity (30 m/s). Suture rupture was very likely at the highest velocity (40 m/s) since the tensile force on the sutures continuously exceeded the breaking force after the impact. In an eye with a transsclerally fixated posterior chamber IOL, severe ocular trauma can be caused by an air bag at high velocity. Small individuals such as elderly women are at greater risk for air-bag ocular injury. Further research on modifying air-bag design and deployment is important to minimize the risk for ocular injury.

Modulations of Foot and Ankle Frontal Kinematics for Breaking and Propulsive Movement Characteristics during Side-Step Cutting with Varying Midsole Thicknesses

PubMed Central

Lin, Yi-Jia; Lee, Shih-Chi; Chang, Chao-Chin; Liu, Tsung-Han

2018-01-01

This study is aimed at determining the effects of midsole thickness on movement characteristic during side cutting movement. Fifteen athletes performed side-step cutting while wearing shoes with varying midsole thicknesses. Temporal-spatial and ground reaction force variables as well as foot and ankle frontal kinematics were used to describe breaking and propulsive movement characteristics and modulation strategies. Regardless of midsole thickness, temporal-spatial variables and breaking and propulsive force during side cutting were statistically unchanged. Significantly greater peaks of ankle inversion and plantarflexion with a thicker sole and greater midtarsal pronation with a thinner sole were observed. Current results demonstrated that hypotheses formed solely based on material testing were insufficient to understand the adaptations in human movement because of the redundancy of the neuromusculoskeletal system. Participants were able to maintain temporal-spatial performance during side cutting while wearing shoes with midsoles of varying thicknesses. Increased pronation for a thinner sole might help reduce the force of impact but might be associated with an increased risk of excessive stress on soft tissue. Increased peak of ankle inversion and plantarflexion for a thicker sole may be unfavorable for the stability of ankle joint. Information provided in human movement testing is crucial for understanding factors associated with movement characteristics and injury and should be considered in the future development of shoe design. PMID:29854000

Functional Evaluation and Characterization of a Newly Developed Silicone Oil-Free Prefillable Syringe System

PubMed Central

Yoshino, Keisuke; Nakamura, Koji; Yamashita, Arisa; Abe, Yoshihiko; Iwasaki, Kazuhiro; Kanazawa, Yukie; Funatsu, Kaori; Yoshimoto, Tsuyoshi; Suzuki, Shigeru

2014-01-01

The functionality of a newly developed silicone oil-free (SOF) syringe system, of which the plunger stopper is coated by a novel coating technology (i-coating™), was assessed. By scanning electron microscopy observations and other analysis, it was confirmed that the plunger stopper surface was uniformly covered with the designed chemical composition. A microflow imaging analysis showed that the SOF system drastically reduced both silicone oil (SO) doplets and oil-induced aggregations in a model protein formulation, whereas a large number of subvisible particles and protein aggregations were formed when a SO system was used. Satisfactory container closure integrity (CCI) was confirmed by means of dye and microorganism penetration studies. Furthermore, no significant difference between the break loose and gliding forces was observed in the former, and stability studies revealed that the SOF system could perfectly show the aging independence in break loose force observed in the SO system. The results suggest that the introduced novel SOF system has a great potential and represents an alternative that can achieve very low subvisible particles, secure CCI, and the absence of a break loose force. In particular, no risk of SO-induced aggregation can bring additional value in the highly sensitive biotech drug market. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1520–1528, 2014 PMID:24643749

Validity and reliability of the abdominal test and evaluation systems tool (ABTEST) to accurately measure abdominal force.

PubMed

Glenn, Jordan M; Galey, Madeline; Edwards, Abigail; Rickert, Bradley; Washington, Tyrone A

2015-07-01

Ability to generate force from the core musculature is a critical factor for sports and general activities with insufficiencies predisposing individuals to injury. This study evaluated isometric force production as a valid and reliable method of assessing abdominal force using the abdominal test and evaluation systems tool (ABTEST). Secondary analysis estimated 1-repetition maximum on commercially available abdominal machine compared to maximum force and average power on ABTEST system. This study utilized test-retest reliability and comparative analysis for validity. Reliability was measured using test-retest design on ABTEST. Validity was measured via comparison to estimated 1-repetition maximum on a commercially available abdominal device. Participants applied isometric, abdominal force against a transducer and muscular activation was evaluated measuring normalized electromyographic activity at the rectus-abdominus, rectus-femoris, and erector-spinae. Test, re-test force production on ABTEST was significantly correlated (r=0.84; p<0.001). Mean electromyographic activity for the rectus-abdominus (72.93% and 75.66%), rectus-femoris (6.59% and 6.51%), and erector-spinae (6.82% and 5.48%) were observed for trial-1 and trial-2, respectively. Significant correlations for the estimated 1-repetition maximum were found for average power (r=0.70, p=0.002) and maximum force (r=0.72, p<0.001). Data indicate the ABTEST can accurately measure rectus-abdominus force isolated from hip-flexor involvement. Negligible activation of erector-spinae substantiates little subjective effort among participants in the lower back. Results suggest ABTEST is a valid and reliable method of evaluating abdominal force. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

The inducement of planetary boundary layer mass convergence associated with varying vorticity beneath tropospheric wind maximum

NASA Technical Reports Server (NTRS)

Johnson, D. R.

1984-01-01

The effects of the vorticity distribution are applied to study planetary boundary layer mass convergence beneath free tropospheric wind maximum. For given forcing by viscous and pressure gradient forces beneath a wind maximum, boundary layer cross stream mass transport is increased by anticyclonic vorticity on the right flank and decreased by cyclonic vorticity on the left flank. Such frictionally forced mass transport induces boundary layer mass convergence beneath the relative wind maximum. This result is related to the empirical rule that the most intense convection and severe weather frequently develop beneath the 500 mb zero relative vorticity isopleth.

Breastfeeding policy: a globally comparative analysis.

PubMed

Heymann, Jody; Raub, Amy; Earle, Alison

2013-06-01

To explore the extent to which national policies guaranteeing breastfeeding breaks to working women may facilitate breastfeeding. An analysis was conducted of the number of countries that guarantee breastfeeding breaks, the daily number of hours guaranteed, and the duration of guarantees. To obtain current, detailed information on national policies, original legislation as well as secondary sources on 182 of the 193 Member States of the United Nations were examined. Regression analyses were conducted to test the association between national policy and rates of exclusive breastfeeding while controlling for national income level, level of urbanization, female percentage of the labour force and female literacy rate. Breastfeeding breaks with pay are guaranteed in 130 countries (71%) and unpaid breaks are guaranteed in seven (4%). No policy on breastfeeding breaks exists in 45 countries (25%). In multivariate models, the guarantee of paid breastfeeding breaks for at least 6 months was associated with an increase of 8.86 percentage points in the rate of exclusive breastfeeding (P < 0.05). A greater percentage of women practise exclusive breastfeeding in countries where laws guarantee breastfeeding breaks at work. If these findings are confirmed in longitudinal studies, health outcomes could be improved by passing legislation on breastfeeding breaks in countries that do not yet ensure the right to breastfeed.

Comparisons of maximum deformation and failure forces at the implant–abutment interface of titanium implants between titanium-alloy and zirconia abutments with two levels of marginal bone loss

PubMed Central

2013-01-01

Background Zirconia materials are known for their optimal aesthetics, but they are brittle, and concerns remain about whether their mechanical properties are sufficient for withstanding the forces exerted in the oral cavity. Therefore, this study compared the maximum deformation and failure forces of titanium implants between titanium-alloy and zirconia abutments under oblique compressive forces in the presence of two levels of marginal bone loss. Methods Twenty implants were divided into Groups A and B, with simulated bone losses of 3.0 and 1.5 mm, respectively. Groups A and B were also each divided into two subgroups with five implants each: (1) titanium implants connected to titanium-alloy abutments and (2) titanium implants connected to zirconia abutments. The maximum deformation and failure forces of each sample was determined using a universal testing machine. The data were analyzed using the nonparametric Mann–Whitney test. Results The mean maximum deformation and failure forces obtained the subgroups were as follows: A1 (simulated bone loss of 3.0 mm, titanium-alloy abutment) = 540.6 N and 656.9 N, respectively; A2 (simulated bone loss of 3.0 mm, zirconia abutment) = 531.8 N and 852.7 N; B1 (simulated bone loss of 1.5 mm, titanium-alloy abutment) = 1070.9 N and 1260.2 N; and B2 (simulated bone loss of 1.5 mm, zirconia abutment) = 907.3 N and 1182.8 N. The maximum deformation force differed significantly between Groups B1 and B2 but not between Groups A1 and A2. The failure force did not differ between Groups A1 and A2 or between Groups B1 and B2. The maximum deformation and failure forces differed significantly between Groups A1 and B1 and between Groups A2 and B2. Conclusions Based on this experimental study, the maximum deformation and failure forces are lower for implants with a marginal bone loss of 3.0 mm than of 1.5 mm. Zirconia abutments can withstand physiological occlusal forces applied in the anterior region. PMID:23688204

Occlusal force, electromyographic activity of masticatory muscles and mandibular flexure of subjects with different facial types

PubMed Central

CUSTODIO, William; GOMES, Simone Guimarães Farias; FAOT, Fernanda; GARCIA, Renata Cunha Matheus Rodrigues; DEL BEL CURY, Altair Antoninha

2011-01-01

Objective The aim of this study was to evaluate whether vertical facial patterns influence maximal occlusal force (MOF), masticatory muscle electromyographic (EMG) activity, and medial mandibular flexure (MMF). Material and Methods Seventy-eight dentate subjects were divided into 3 groups by Ricketts's analysis: brachyfacial, mesofacial and dolychofacial. Maximum occlusal force in the molar region was bilaterally measured with a force transducer. The electromyographic activities of the masseter and anterior temporal muscles were recorded during maximal voluntary clenching. Medial mandibular flexure was calculated by subtracting the intermolar distance of maximum opening or protrusion from the distance in the rest position. The data were analyzed using ANOVA followed by Tukey's HSD test. The significance level was set at 5%. Results Data on maximum occlusal force showed that shorter faces had higher occlusal forces (P<0.0001). Brachyfacial subjects presented higher levels of masseter electromyographic activity and medial mandibular flexure, followed by the mesofacial and dolychofacial groups. Additionally, dolychofacial subjects showed significantly lower electromyographic temporalis activities (P<0.05). Conclusion Within the limitations of the study, it may be concluded that maximum occlusal force, masticatory muscle activity and medial mandibular flexure were influenced by the vertical facial pattern. PMID:21655772

Offshore geology and geomorphology from Point Piedras Blancas to Pismo Beach, San Luis Obispo County, California

USGS Publications Warehouse

Watt, Janet Tilden; Johnson, Samuel Y.; Hartwell, Stephen R.; Roberts, Michelle

2015-01-01

Sea level was approximately 120 to 130 m lower during the Last Glacial Maximum (about 21 ka). This approximate depth corresponds to the modern shelf break, a lateral change from the gently dipping (0.8° to 1.0°) outer shelf to the slightly more steeply dipping (about 1.5° to 2.5°) upper slope in the central and northern parts of the map area. South of Point San Luis in San Luis Bay, deltaic deposits offshore of the mouth of the Santa Maria River (11 km south of the map area) have prograded across the shelf break and now form a continuous low-angle (about 0.8°) ramp that extends to water depths of more than 160 m. The shelf break defines the landward boundary of slope deposits. North of Estero Bay, the shelf break is characterized by a distinctly sharp slope break that is mapped as a landslide headscarp above landslide deposits. Multibeam imagery and seismic-reflection profiles across this part of the shelf break show evidence of slope failure, such as slumping, sliding, and soft-sediment deformation, along the entire length of the scarp. Notably, this shelf-break scarp corresponds to a west splay of the Hosgri Fault that dies out just north of the scarp, suggesting that faulting is controlling the location (and instability) of the shelf break in this area.

Maximum Bite Force Analysis in Different Age Groups

PubMed Central

Takaki, Patricia; Vieira, Marilena; Bommarito, Silvana

2014-01-01

Introduction Maximum bite force (MBF) is the maximum force performed by the subject on the fragmentation of food, directly related with the mastication and determined by many factors. Objective Analyze the MBF of subjects according to age groups. Methods One hundred individuals from the city of São Paulo were equally divided according to age groups and gender. Each individual submitted to a myotherapy evaluation composed of anthropometric measurements of height and weight to obtain body mass index (BMI), using a tape and a digital scale (Magna, G-life, São Paulo), and a dental condition and maximum bite force evaluation, using a digital dynamometer model DDK/M (Kratos, São Paulo, Brazil), on Newton scale. The dental and bite force evaluations were monitored by a professional from the area. Analysis of variance was used with MBF as a dependent variable, age group and gender as random factors, and BMI as a control variable. Results Till the end of adolescence, it was possible to observe a decrease in MBF in both sexes, with the male force greater than the female force. In young adults, the female force became greater the males, then decreased in adulthood. There was no correlation between MBF and BMI. Conclusion There are MBF variations that characterizes the human development stages, according to age groups. PMID:25992105

Dependence of Some Mechanical Properties of Elastic Bands on the Length and Load Time

ERIC Educational Resources Information Center

Triana, C. A.; Fajardo, F.

2012-01-01

We present a study of the maximum stress supported by elastics bands of nitrile as a function of the natural length and the load time. The maximum tension of rupture and the corresponding variation in length were found by measuring the elongation of an elastic band when a mass is suspended from its free end until it reaches the breaking point. The…

Biomechanical characteristics of bioabsorbable magnesium-based (MgYREZr-alloy) interference screws with different threads.

PubMed

Ezechieli, Marco; Ettinger, Max; König, Carolin; Weizbauer, Andreas; Helmecke, Patrick; Schavan, Robert; Lucas, Arne; Windhagen, Henning; Becher, Christoph

2016-12-01

Degradable magnesium implants have received increasing interest in recent years. In anterior cruciate ligament reconstruction surgery, the well-known osteoconductive effects of biodegradable magnesium alloys may be useful. The aim of this study was to examine whether interference screws made of MgYREZr have comparable biomechanical properties to commonly used biodegradable screws and whether a different thread on the magnesium screw has an influence on the fixation strength. Five magnesium (MgYREZr-alloy) screws were tested per group. Three different groups with variable thread designs (Designs 1, 2, and 3) were produced and compared with the commercially available bioabsorbable Bioacryl rapid polylactic-co-glycolic acid screw Milagro ® . In vitro testing was performed in synthetic bone using artificial ligament fixed by an interference screw. The constructs were pretensioned with a constant load of 60 N for 30 s followed by 500 cycles between 60 N and 250 N at 1 Hz. Construct displacements between the 1st and 20th and the 21st and 500th cycles were recorded. After a 30 s break, a maximum load to failure test was performed at 1 mm/s measuring the maximum pull-out force. The maximum loads to failure of all three types of magnesium interference screws (Design 1: 1,092 ± 133.7 N; Design 2: 1,014 ± 103.3 N; Design 3: 1,001 ± 124 N) were significantly larger than that of the bioabsorbable Milagro ® interference screw (786.8 ± 62.5 N) (p < 0.05). However, the greatest maximum load was found with magnesium screw Design 1. Except for a significant difference between Designs 1 and 2, there were no further significant differences among the four groups in displacement after the 20th cycle. Biomechanical testing showed higher pull-out forces for magnesium compared with a commercial polymer screw. Hence, they suggest better stability and are a potential alternative. The thread geometry does not significantly influence the stability provided by the magnesium implants. This study shows the first promising results of a degradable material, which may be a clinical alternative in the future.

Break-up of droplets in a concentrated emulsion flowing through a narrow constriction

NASA Astrophysics Data System (ADS)

Kim, Minkyu; Rosenfeld, Liat; Tang, Sindy; Tang Lab Team

2014-11-01

Droplet microfluidics has enabled a wide range of high throughput screening applications. Compared with other technologies such as robotic screening technology, droplet microfluidics has 1000 times higher throughput, which makes the technology one of the most promising platforms for the ultrahigh throughput screening applications. Few studies have considered the throughput of the droplet interrogation process, however. In this research, we show that the probability of break-up increases with increasing flow rate, entrance angle to the constriction, and size of the drops. Since single drops do not break at the highest flow rate used in the system, break-ups occur primarily from the interactions between highly packed droplets close to each other. Moreover, the probabilistic nature of the break-up process arises from the stochastic variations in the packing configuration. Our results can be used to calculate the maximum throughput of the serial interrogation process. For 40 pL-drops, the highest throughput with less than 1% droplet break-up was measured to be approximately 7,000 drops per second. In addition, the results are useful for understanding the behavior of concentrated emulsions in applications such as mobility control in enhanced oil recovery.

Correlation of Descriptive Analysis and Instrumental Puncture Testing of Watermelon Cultivars.

PubMed

Shiu, J W; Slaughter, D C; Boyden, L E; Barrett, D M

2016-06-01

The textural properties of 5 seedless watermelon cultivars were assessed by descriptive analysis and the standard puncture test using a hollow probe with increased shearing properties. The use of descriptive analysis methodology was an effective means of quantifying watermelon sensory texture profiles for characterizing specific cultivars' characteristics. Of the 10 cultivars screened, 71% of the variation in the sensory attributes was measured using the 1st 2 principal components. Pairwise correlation of the hollow puncture probe and sensory parameters determined that initial slope, maximum force, and work after maximum force measurements all correlated well to the sensory attributes crisp and firm. These findings confirm that maximum force correlates well with not only firmness in watermelon, but crispness as well. The initial slope parameter also captures the sensory crispness of watermelon, but is not as practical to measure in the field as maximum force. The work after maximum force parameter is thought to reflect cellular arrangement and membrane integrity that in turn impact sensory firmness and crispness. Watermelon cultivar types were correctly predicted by puncture test measurements in heart tissue 87% of the time, although descriptive analysis was correct 54% of the time. © 2016 Institute of Food Technologists®

Effect of field cooling heights on the levitation force of pure and starch/polystyrene/MWCNT added bulk MgB2 superconductors

NASA Astrophysics Data System (ADS)

Tripathi, D.; Dey, T. K.

2014-12-01

A series of MgB2 pellets with and without addition of carbon from different sources (viz. starch, polystyrene and carbon nanotubes) have been synthesized by solid state reaction under argon atmosphere. XRD analysis indicates a decrease in lattice parameters of MgB2 with addition of starch, polystyrene (PS) and MWCNT and confirms substitution of carbon in boron sites. The presence of nanosized carbon inclusions between the grain boundaries in the present set of samples is evident in TEM photographs. Resistivity data confirms a decrease in superconducting transition temperature (Tc0) for MgB2 doped with starch/PS/MWCNT. The effect of different field cooling heights (HIFC) at 20 K on maximum levitation force (FMLF) and maximum attractive force (FMAF) of pure MgB2 and MgB2 doped with starch/PS/MWCNT have been investigated. Except for MWCNT, doping of starch and PS in MgB2 is found to improve FMLF and FMAF and the best result is obtained for MgB2 doped with 1 wt.% PS. Levitation force measured as a function of decreasing initial field cooling height indicates exponential dependence of both maximum levitation force (FMLF) and maximum attractive force (FMAF). However, the gap distance between PM and the sample (H0AF and HMAF) corresponding to maximum attractive force (FMAF) and zero attractive force (F0AF) varies linearly and their difference remains constant. This constancy in (HMAF - H0AF) is understood in terms of constant reduction rate of magnetic flux density between H0AF and HMAF.

Tethered swimming can be used to evaluate force contribution for short-distance swimming performance.

PubMed

Morouço, Pedro G; Marinho, Daniel A; Keskinen, Kari L; Badillo, Juan J; Marques, Mário C

2014-11-01

The purpose of this study was two-fold: (a) to compare stroke and the physiological responses between maximal tethered and free front crawl swimming and (b) to evaluate the contribution of force exertion for swimming performance over short distances. A total of 34 male swimmers, representing various levels of competitive performance, participated in this study. Each participant was tested in both a 30-second maximal tethered swimming test and a 50-m free swimming test. The tethered force parameters, the swimming speed, stroke (stroke rate [SR]), and the physiological responses (increase in blood lactate concentration [ΔBLa], heart rate, and rate of perceived exertion) were recorded and calculated. The results showed no differences in stroke and the physiological responses between tethered and free swimming, with a high level of agreement for the SR and ΔBLa. A strong correlation was obtained between the maximum impulse of force per stroke and the speed (r = 0.91; p < 0.001). Multiple regression analysis revealed that the maximum impulse and SR in the tethered condition explained 84% of the free swimming performance. The relationship between the swimming speed and maximum force tended to be nonlinear, whereas linear relationships were observed with the maximum impulse. This study demonstrates that tethered swimming does not significantly alter stroke and the physiological responses compared with free swimming, and that the maximum impulse per stroke should be used to evaluate the balance between force and the ability to effectively apply force during sprint swimming. Consequently, coaches can rely on tethered forces to identify strength deficits and improve swimming performance over short distances.

Force and Directional Force Modulation Effects on Accuracy and Variability in Low-Level Pinch Force Tracking.

PubMed

Park, Sangsoo; Spirduso, Waneen; Eakin, Tim; Abraham, Lawrence

2018-01-01

The authors investigated how varying the required low-level forces and the direction of force change affect accuracy and variability of force production in a cyclic isometric pinch force tracking task. Eighteen healthy right-handed adult volunteers performed the tracking task over 3 different force ranges. Root mean square error and coefficient of variation were higher at lower force levels and during minimum reversals compared with maximum reversals. Overall, the thumb showed greater root mean square error and coefficient of variation scores than did the index finger during maximum reversals, but not during minimum reversals. The observed impaired performance during minimum reversals might originate from history-dependent mechanisms of force production and highly coupled 2-digit performance.

The oceanic boundary layer driven by wave breaking with stochastic variability. Part 1. Direct numerical simulations

NASA Astrophysics Data System (ADS)

Sullivan, Peter P.; McWilliams, James C.; Melville, W. Kendall

2004-05-01

We devise a stochastic model for the effects of breaking waves and fit its distribution functions to laboratory and field data. This is used to represent the space time structure of momentum and energy forcing of the oceanic boundary layer in turbulence-resolving simulations. The aptness of this breaker model is evaluated in a direct numerical simulation (DNS) of an otherwise quiescent fluid driven by an isolated breaking wave, and the results are in good agreement with laboratory measurements. The breaker model faithfully reproduces the bulk features of a breaking event: the mean kinetic energy decays at a rate approaching t(-1) , and a long-lived vortex (eddy) is generated close to the water surface. The long lifetime of this vortex (more than 50 wave periods) makes it effective in energizing the surface region of oceanic boundary layers. Next, a comparison of several different DNS of idealized oceanic boundary layers driven by different surface forcing (i.e. constant current (as in Couette flow), constant stress, or a mixture of constant stress plus stochastic breakers) elucidates the importance of intermittent stress transmission to the underlying currents. A small amount of active breaking, about 1.6% of the total water surface area at any instant in time, significantly alters the instantaneous flow patterns as well as the ensemble statistics. Near the water surface a vigorous downwelling upwelling pattern develops at the head and tail of each three-dimensional breaker. This enhances the vertical velocity variance and generates both negative- and positive-signed vertical momentum flux. Analysis of the mean velocity and scalar profiles shows that breaking effectively increases the surface roughness z_o by more than a factor of 30; for our simulations z_o/lambda {≈} 0.04 to 0.06, where lambda is the wavelength of the breaking wave. Compared to a flow driven by a constant current, the extra mixing from breakers increases the mean eddy viscosity by more than a factor of 10 near the water surface. Breaking waves alter the usual balance of production and dissipation in the turbulent kinetic energy (TKE) budget; turbulent and pressure transports and breaker work are important sources and sinks in the budget. We also show that turbulent boundary layers driven by constant current and constant stress (i.e. with no breaking) differ in fundamental ways. The additional freedom provided by a constant-stress boundary condition permits finite velocity variances at the water surface, so that flows driven by constant stress mimic flows with weakly and statistically homogeneous breaking waves.

Nature's Mechanisms for Tough, Self-healing Polymers and Polymer Adhesives

NASA Astrophysics Data System (ADS)

Hansma, Paul

2007-03-01

Spider silk^2 and the natural polymer adhesives in abalone shells^3 and bone^4,5 can give us insights into nature's mechanisms for tough, self-healing polymers and polymer adhesives. The natural polymer adhesives in biomaterials have been optimized by evolution. An optimized polymer adhesive has five characteristics. 1) It holds together the strong elements of the composite. 2) It yields just before the strong elements would otherwise break. 3) It dissipates large amounts of energy as it yields. 4) It self heals after it yields. 5) It takes just a few percent by weight. Both natural polymer adhesives and silk rely on sacrificial bonds and hidden length for toughness and self-healing.^6 A relatively large energy, of order 100eV, is required to stretch a polymer molecule after a weak bond, a sacrificial bond, breaks and liberates hidden length, which was previously hidden, typically in a loop or folded domain, from whatever was stretching the polymer. The bond is called sacrificial if it breaks at forces well below the forces that could otherwise break the polymer backbone, typically greater than 1nN. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby also providing a ``self-healing'' property to the material.^2-4 Individual polymer adhesive molecules based on sacrificial bonds and hidden length can supply forces of order 300pN over distances of 100s of nanometers. Model calculations show that a few percent by weight of adhesives based on these principles could be optimized adhesives for high performance composite materials including nanotube and graphene sheet composites. ^2N. Becker, E. Oroudjev, S. Mutz et al., Nature Materials 2 (4), 278 (2003). ^3B. L. Smith, T. E. Schaffer, M. Viani et al., Nature 399 (6738), 761 (1999). ^4J. B. Thompson, J. H. Kindt, B. Drake et al., Nature 414 (6865), 773 (2001). ^5G. E. Fantner, T. Hassenkam, J. H. Kindt et al., Nature Materials 4, 612 (2005). ^6G. E. Fantner, E. Oroudjev, G. Schitter et al., Biophysical Journal 90 (4), 1411 (2006).

An Asymptotic and Stochastic Theory for the Effects of Surface Gravity Waves on Currents and Infragravity Waves

NASA Astrophysics Data System (ADS)

McWilliams, J. C.; Lane, E.; Melville, K.; Restrepo, J.; Sullivan, P.

2004-12-01

Oceanic surface gravity waves are approximately irrotational, weakly nonlinear, and conservative, and they have a much shorter time scale than oceanic currents and longer waves (e.g., infragravity waves) --- except where the primary surface waves break. This provides a framework for an asymptotic theory, based on separation of time (and space) scales, of wave-averaged effects associated with the conservative primary wave dynamics combined with a stochastic representation of the momentum transfer and induced mixing associated with non-conservative wave breaking. Such a theory requires only modest information about the primary wave field from measurements or operational model forecasts and thus avoids the enormous burden of calculating the waves on their intrinsically small space and time scales. For the conservative effects, the result is a vortex force associated with the primary wave's Stokes drift; a wave-averaged Bernoulli head and sea-level set-up; and an incremental material advection by the Stokes drift. This can be compared to the "radiation stress" formalism of Longuet-Higgins, Stewart, and Hasselmann; it is shown to be a preferable representation since the radiation stress is trivial at its apparent leading order. For the non-conservative breaking effects, a population of stochastic impulses is added to the current and infragravity momentum equations with distribution functions taken from measurements. In offshore wind-wave equilibria, these impulses replace the conventional surface wind stress and cause significant differences in the surface boundary layer currents and entrainment rate, particularly when acting in combination with the conservative vortex force. In the surf zone, where breaking associated with shoaling removes nearly all of the primary wave momentum and energy, the stochastic forcing plays an analogous role as the widely used nearshore radiation stress parameterizations. This talk describes the theoretical framework and presents some preliminary solutions using it. McWilliams, J.C., J.M. Restrepo, & E.M. Lane, 2004: An asymptotic theory for the interaction of waves and currents in coastal waters. J. Fluid Mech. 511, 135-178. Sullivan, P.P., J.C. McWilliams, & W.K. Melville, 2004: The oceanic boundary layer driven by wave breaking with stochastic variability. J. Fluid Mech. 507, 143-174.

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

NASA Astrophysics Data System (ADS)

Manoj, M. G.; Devara, P. C. S.; Safai, P. D.; Goswami, B. N.

2011-12-01

While some long breaks of monsoon intraseasonal oscillations (MISOs) are followed by active spells (BFA), some others are not (BNFA). The circulation during BFA (BNFA) cases helps (prevents) accumulation of absorbing aerosols over central India (CI) resulting in almost three times larger Aerosol Index (AI) over CI, during BFA cases compared to BNFA cases. A seminal role played by the absorbing aerosols in the transition from break to active spells is unraveled through modification of the north-south temperature gradient at lower levels. The meridional gradient of temperature at low level (∆ T) between aerosol-rich CI and pristine equatorial Indian Ocean is large (>6°C) and sustains for long time (>10 days) during BFA leading to significant moisture convergence to CI. The stability effect arising from surface cooling by the aerosols is overcome by the enhanced moisture convergence creating a moist static unstable atmosphere conducive for the large-scale organized convection over the CI region leading to the resurgence of active spells. The moisture convergence induced by ∆ T was also able to overcome possible aerosol indirect effect (Twomey effect) and initiate deep convection and transition to active condition. During BNFA cases, however the maximum ∆ T, which was weaker than the BFA cases by more than 1.5°C, could not sustain required moisture convergence and failed to lead to a sustained active spell. Using data from MODIS (MODerate resolution Imaging Spectroradiometer) onboard Terra and several other input parameters from various satellites for the period 2000-2009, the aerosol induced radiative forcing representative of two regions—the CI to the north and the pristine ocean to the south—were estimated and support the differences in observed ∆ T during the two cases. Our results highlight the need for proper inclusion of absorbing aerosols in dynamical models for simulation of the observed variability of MISOs and their extended range prediction.

Numerical experiments on breaking waves on contrasting beaches using a two-phase flow approach

NASA Astrophysics Data System (ADS)

Bakhtyar, R.; Barry, D. A.; Kees, C. E.

2012-11-01

A mechanistic understanding of beach environments needs to account for interactions of oceanic forcing and beach materials, in particular the role of waves on the evolution of the beach profile. A fully coupled two-phase flow model was used to simulate nearshore fluid-sediment turbulent flow in the cross-shore direction. It includes the Reynolds-Averaged Navier-Stokes equations and turbulent stress closures for each phase, and accounts for inter-granular stresses. The model has previously been validated using laboratory-scale data, so the results are likely more reliable for that scale. It was used to simulate wave breaking and the ensuing hydrodynamics and sediment transport processes in the surf/swash zones. Numerical experiments were conducted to investigate the effects of varying beach and wave characteristics (e.g., beach slope, sediment grain size, wave periods and heights) on the foreshore profile changes. Spilling and plunging breakers occur on dissipative and intermediate beaches, respectively. The impact of these wave/beach types on nearshore zone hydrodynamics and beach morphology was determined. The numerical results showed that turbulent kinetic energy, sediment concentrations and transport rate are greater on intermediate than on dissipative beaches. The results confirmed that wave energy, beach grain size and bed slope are main factors for sediment transport and beach morphodynamics. The location of the maximum sediment transport is near the breaking point for both beach types. Coarse- and fine-sand beaches differ significantly in their erosive characteristics (e.g., foreshore profile evolutions are erosive and accretionary on the fine and coarse sand beaches, respectively). In addition, a new parameter (based on main driving factors) is proposed that can characterize the sediment transport in the surf and swash zones. The results are consistent with existing physical observations, suggesting that the two-phase flow model is suitable for the simulation of hyper-concentrated mixed water-sediment flows in the nearshore. The model thus has potential as a useful tool for investigating interactions between nearshore hydrodynamics and beach morphology.

Sensory and Quality Evaluation of Traditional Compared with Power Ultrasound Processed Corn (Zea Mays) Tortilla Chips.

PubMed

Janve, Bhaskar; Yang, Wade; Sims, Charles

2015-06-01

Power ultrasound reduces the traditional corn steeping time from 18 to 1.5 h during tortilla chips dough (masa) processing. This study sought to examine consumer (n = 99) acceptability and quality of tortilla chips made from the masa by traditional compared with ultrasonic methods. Overall appearance, flavor, and texture acceptability scores were evaluated using a 9-point hedonic scale. The baked chips (process intermediate) before and after frying (finished product) were analyzed using a texture analyzer and machine vision. The texture values were determined using the 3-point bend test using breaking force gradient (BFG), peak breaking force (PBF), and breaking distance (BD). The fracturing properties determined by the crisp fracture support rig using fracture force gradient (FFG), peak fracture force (PFF), and fracture distance (FD). The machine vision evaluated the total surface area, lightness (L), color difference (ΔE), Hue (°h), and Chroma (C*). The results were evaluated by analysis of variance and means were separated using Tukey's test. Machine vision values of L, °h, were higher (P < 0.05) and ΔE was lower (P < 0.05) for fried and L, °h were significantly (P < 0.05) higher for baked chips produced from ultra-sonication as compare to traditional. Baked chips texture for ultra-sonication was significantly higher (P < 0.05) on BFG, BPD, PFF, and FD. Fried tortilla chips texture were higher significantly (P < 0.05) in BFG and PFF for ultra-sonication than traditional processing. However, the instrumental differences were not detected in sensory analysis, concluding possibility of power ultrasound as potential tortilla chips processing aid. © 2015 Institute of Food Technologists®

Relationship between occlusal force and falls among community-dwelling elderly in Japan: a cross-sectional correlative study.

PubMed

Eto, Maki; Miyauchi, Shinji

2018-05-09

Falls may cause serious health conditions among older population. Fall-related physical factors are thought to be associated with occlusal conditions. However, few studies examined the relationship between occlusal force and falls. To identify the association between occlusal force and falls among community-dwelling elderly individuals in Japan, public health nurses conducted a cross-sectional descriptive study. We performed extensive physical assessments of five items: maximum occlusal force, handgrip strength, maximal knee extensor strength, one-leg standing time with eyes open and body sway. We also conducted a questionnaire survey concerning the participants' demographic characteristics, health status and fall experience during the past year. Mean scores and standard deviations were calculated for age and the total points of the index of activities of daily living. Associations were examined using Mann-Whitney tests and logistic regression. We examined 159 community-dwelling people aged ≥65 years, who were independent and active, including 38 participants (24.5%) with experience of falls in the past year. Maximum occlusal force had significant correlation with handgrip strength, maximal knee extensor strength, and one-leg standing time and body sway (P < .05, respectively). We found weak associations between participants with and without a history of falls in terms of the five physical measurements. Logistic regression analysis showed that fall experience was significantly associated with maximum occlusal force (P = 0.004). This is the first study, led by public health nursing researchers, to examine the associations between maximum occlusal force and falls among community-dwelling elderly in Japan. The results showed that maximum occlusal force was significantly related to the other four extensive physical assessments, and might also suggest that maximum occlusal force assessment by public health nurses could contribute to more sophisticated and precise prediction of fall risks among the community-dwelling elderly. The latest occlusal force measurement device is non-invasive and easy to use. Public health nurses can introduce it at periodical community health checkup assembly events, which might contribute to raising awareness among community-dwelling elderly individuals and public health nurses about fall prevention and prediction.

X-1 launch from B-29 mothership

NASA Technical Reports Server (NTRS)

1947-01-01

The first of the rocket-powered research aircraft, the X-1 (originally designated the XS-1), was a bullet-shaped airplane that was built by the Bell Aircraft Company for the US Air Force and the National Advisory Committee on Aeronautics (NACA). The mission of the X-1 was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier'. The first of the three X-1s was glide-tested at Pinecastle Air Force Base, FL, in early 1946. The first powered flight of the X-1 was made on Dec. 9, 1946, at Edwards Air Force Base with Chalmers Goodlin, a Bell test pilot, at the controls. On Oct. 14, 1947, with USAF Captain Charles 'Chuck' Yeager as pilot, the aircraft flew faster than the speed of sound for the first time. Captain Yeager ignited the four-chambered XLR-11 rocket engines after being air-launched from under the bomb bay of a B-29 at 21,000 ft. The 6,000-lb thrust ethyl alcohol/liquid oxygen burning rockets, built by Reaction Motors, Inc., pushed him up to a speed of 700 mph in level flight. Captain Yeager was also the pilot when the X-1 reached its maximum speed of 957 mph. Another USAF pilot. Lt. Col. Frank Everest, Jr., was credited with taking the X-1 to its maximum altitude of 71,902 ft. Eighteen pilots in all flew the X-1s. The number three plane was destroyed in a fire before ever making any powered flights. A single-place monoplane, the X-1 was 31 ft long, 10 ft high, and had a wingspan of 29 ft. It weighed 4,900 lb and carried 8,200 lb of fuel. It had a flush cockpit with a side entrance and no ejection seat. This roughly 30-second video clip shows the X-1 launched from a B-29, ignition of the XLR-11 rocket engine, and the succeeding flight, including a roll. At one point, the video shows observers of the flight from the ground.

Evolutionary and ecological forces influencing population diversification in Bornean montane passerines.

PubMed

Chua, Vivien L; Smith, Brian Tilston; Burner, Ryan C; Rahman, Mustafa Abdul; Lakim, Maklarin; Prawiradilaga, Dewi M; Moyle, Robert G; Sheldon, Frederick H

2017-08-01

The mountains of Borneo are well known for their high endemicity and historical role in preserving Southeast Asian rainforest biodiversity, but the diversification of populations inhabiting these mountains is poorly studied. Here we examine the genetic structure of 12 Bornean montane passerines by comparing complete mtDNA ND2 gene sequences of populations spanning the island. Maximum likelihood and Bayesian phylogenetic trees and haplotype networks are examined for common patterns that might signal important historical events or boundaries to dispersal. Morphological and ecological characteristics of each species are also examined using phylogenetic generalized least-squares (PGLS) for correlation with population structure. Populations in only four of the 12 species are subdivided into distinct clades or haplotype groups. Although this subdivision occurred at about the same time in each species (ca. 0.6-0.7Ma), the spatial positioning of the genetic break differs among the species. In two species, northeastern populations are genetically divergent from populations elsewhere on the island. In the other two species, populations in the main Bornean mountain chain, including the northeast, are distinct from those on two isolated peaks in northwestern Borneo. We suggest different historical forces played a role in shaping these two distributions, despite commonality in timing. PGLS analysis showed that only a single characteristic-hand-wing index-is correlated with population structure. Birds with longer wings, and hence potentially more dispersal power, have less population structure. To understand historical forces influencing montane population structure on Borneo, future studies must compare populations across the entirety of Sundaland. Copyright © 2017 Elsevier Inc. All rights reserved.

Breaking rocks made easy: subcritical processes and tectonic predesign

NASA Astrophysics Data System (ADS)

Voigtlaender, Anne; Krautblatter, Michael

2017-04-01

In geomorphic studies, to change in landforms, e.g. by rock slope failure, fluvial or glacial erosion, a threshold is commonly assumed, which is crossed either by an increase in external driving or a decrease of internal resisting forces, respectively. If the threshold is crossed, bedrock breaks and slope fails, rivers incise and glaciers plug and sew their bed. Here we put forward a focus on the decrease of the resisting forces, as an increase in the driving forces, to match the strength of bedrock, is not that likely. We suggest that the degradation of resisting forces of bedrock can be better explained by subcritical processes like creep, fatigue and stress corrosion interplaying with tectonic predesign. Both concepts, subcritical processes and tectonic predesign have been issued in the last century, but have not been widely accepted nor have their assumptions been explicitly stressed in recent case studies. Moreover both concepts profit especially on scale issues if merged. Subcritical crack growth, includes different mechanisms promoting fractures well below the ultimate strength. Single infinitesimal but irreversible damage and deformations are induced in the material over time. They interact with inherent microstructural flaws and low applied stresses, limiting local strength and macroscopic behavior of bedrock. This reissues the concept of tectonic predesigned, as proposed by A.E. Scheidegger, which not only encompasses structural features that determine the routing of drainage patterns and shear planes, e.g. joints, faults and foliations, but also the (neo)tectonic stress-field and the (in-situ) strain state of bedrocks and mountains. Combining subcritical processes and tectonic predesign we can better explain, why and where we see a dissected, eroded and geomorphic divers' landscape. In this conceptual framework actual magnitudes of the driving forces are accounted for and so is the nature of the bedrock material, to better understand the trajectories of the forms we study, and break rocks easily.

Isospin-symmetry breaking in masses of N ≃ Z nuclei

NASA Astrophysics Data System (ADS)

Bączyk, P.; Dobaczewski, J.; Konieczka, M.; Satuła, W.; Nakatsukasa, T.; Sato, K.

2018-03-01

Effects of the isospin-symmetry breaking (ISB) beyond mean-field Coulomb terms are systematically studied in nuclear masses near the N = Z line. The Coulomb exchange contributions are calculated exactly. We use extended Skyrme energy density functionals (EDFs) with proton-neutron-mixed densities, to which we add new terms breaking the isospin symmetry. Two parameters associated with the new terms are determined by fitting mirror and triplet displacement energies (MDEs and TDEs) of isospin multiplets. The new EDFs reproduce MDEs for the T = 1/2 doublets and T = 1 triplets, and TDEs for the T = 1 triplets. Relative strengths of the obtained isospin-symmetry-breaking terms are not consistent with the differences in the NN scattering lengths, ann, app, and anp. Based on low-energy experimental data, it seems thus impossible to delineate the strong-force ISB effects from beyond-mean-field Coulomb-energy corrections.

[Cleavage time for a hydrogen bond under a load].

PubMed

Bespalov, S V; Tolpygo, K B

1993-01-01

Statistics of the hydrogen bond formation and break in a bundle of actin and myosin filaments realizing the attractive force in the sarcomere of a muscle is studied. Purely mechanical problem of the attractive-force formation and motion of myosin heads and action globules under their action is supplemented by accounting for the irreversible processes: 1. Thermal de-excitation of the latter in the chain of hydrogen bond during the elementary act of the ATP energy use resulting in fixing the extended actin filament. 2. Break of the hydrogen bonds, realizing this fixing, due to thermal fluctuations for the time tau. The average life-time turns out to be the order of time necessary for the movement of z-membrane sarcomere for the value of action filament extension delta 1, which is necessary for the process of muscle contraction to be continued.

Electrostatic Manipulation of Graphene On Graphite

NASA Astrophysics Data System (ADS)

Untiedt, Carlos; Rubio-Verdu, Carmen; Saenz-Arce, Giovanni; Martinez-Asencio, Jesús; Milan, David C.; Moaied, Mohamed; Palacios, Juan J.; Caturla, Maria Jose

2015-03-01

Here we report the use of a Scanning Tunneling Microscope (STM) under ambient and vacuum conditions to study the controlled exfoliation of the last layer of a graphite surface when an electrostatic force is applied from a STM tip. In this work we have focused on the study of two parameters: the applied voltage needed to compensate the graphite interlayer attractive force and the one needed to break atomic bonds to produce folded structures. Additionally, we have studied the influence of edge structure in the breaking geometry. Independently of the edge orientation the graphite layer is found to tear through the zig-zag direction and the lifled layer shows a zig-zag folding direction. Molecular Dinamics simulations and DFT calculations have been performed to understand our results, showing a strong correlation with the experiments. Comunidad Valenciana through Prometeo project.

A new approach to assess COPD by identifying lung function break-points

PubMed Central

Eriksson, Göran; Jarenbäck, Linnea; Peterson, Stefan; Ankerst, Jaro; Bjermer, Leif; Tufvesson, Ellen

2015-01-01

Purpose COPD is a progressive disease, which can take different routes, leading to great heterogeneity. The aim of the post-hoc analysis reported here was to perform continuous analyses of advanced lung function measurements, using linear and nonlinear regressions. Patients and methods Fifty-one COPD patients with mild to very severe disease (Global Initiative for Chronic Obstructive Lung Disease [GOLD] Stages I–IV) and 41 healthy smokers were investigated post-bronchodilation by flow-volume spirometry, body plethysmography, diffusion capacity testing, and impulse oscillometry. The relationship between COPD severity, based on forced expiratory volume in 1 second (FEV1), and different lung function parameters was analyzed by flexible nonparametric method, linear regression, and segmented linear regression with break-points. Results Most lung function parameters were nonlinear in relation to spirometric severity. Parameters related to volume (residual volume, functional residual capacity, total lung capacity, diffusion capacity [diffusion capacity of the lung for carbon monoxide], diffusion capacity of the lung for carbon monoxide/alveolar volume) and reactance (reactance area and reactance at 5Hz) were segmented with break-points at 60%–70% of FEV1. FEV1/forced vital capacity (FVC) and resonance frequency had break-points around 80% of FEV1, while many resistance parameters had break-points below 40%. The slopes in percent predicted differed; resistance at 5 Hz minus resistance at 20 Hz had a linear slope change of −5.3 per unit FEV1, while residual volume had no slope change above and −3.3 change per unit FEV1 below its break-point of 61%. Conclusion Continuous analyses of different lung function parameters over the spirometric COPD severity range gave valuable information additional to categorical analyses. Parameters related to volume, diffusion capacity, and reactance showed break-points around 65% of FEV1, indicating that air trapping starts to dominate in moderate COPD (FEV1 =50%–80%). This may have an impact on the patient’s management plan and selection of patients and/or outcomes in clinical research. PMID:26508849

DefenseLink.mil - Special Report: Battle of the Bulge

Science.gov Websites

World War II in a final desperate attempt to break and defeat Allied forces. The ensuing battle, fought the largest land battle involving American Forces in World War II. More than a million Allied troops lines of the Battle of the Bulge during World War II. The now 86-year-old returned to one of his former

Facilitating working mothers' ability to breastfeed: global trends in guaranteeing breastfeeding breaks at work, 1995-2014.

PubMed

Atabay, Efe; Moreno, Gonzalo; Nandi, Arijit; Kranz, Gabriella; Vincent, Ilona; Assi, Tina-Marie; Winfrey, Elise Marie Vaughan; Earle, Alison; Raub, Amy; Heymann, S Jody

2015-02-01

Mothers who work away from home tend to stop breastfeeding earlier than their nonworking counterparts due to workplace barriers. Barriers to breastfeeding discriminate against women and may lead to inequities in children's health outcomes. Guaranteeing paid breastfeeding breaks at work is 1 mechanism that can improve mothers' opportunity to breastfeed in the workplace. This study aimed to assess the trends in the share of countries guaranteeing breastfeeding breaks in the workplace and paid maternal leave that lasts until the infant is 6 months old (the World Health Organization recommended duration for exclusive breastfeeding), between 1995 and 2014. Legislation and secondary source data were collected and reviewed for 193 United Nations member states. Legislation was analyzed for content on breastfeeding breaks and maternal leave guarantees. Fifty-one countries (26.7%) in 2014 did not guarantee breastfeeding breaks in any form and 4 countries provided only unpaid breaks or breaks that did not cover the first 6 months of life; since 1995, around 15 countries (10.2%) legislated for such a policy. In 2014, out of 55 countries that did not guarantee paid breastfeeding breaks for the first 6 months after birth, 7 countries guaranteed paid maternal leave for the same duration; 48 countries (25.1%) provided neither paid maternal leave nor paid breastfeeding breaks. Progress in the number of countries guaranteeing breastfeeding breaks at work is modest. Adopting measures to facilitate breastfeeding at work can be a critical opportunity for countries to increase breastfeeding rates among the growing number of women in the labor force. © The Author(s) 2014.

Multiple joint muscle function with ageing: the force-velocity and power-velocity relationships in young and older men.

PubMed

Allison, Sarah J; Brooke-Wavell, Katherine; Folland, Jonathan P

2013-05-01

Whilst extensive research has detailed the loss of muscle strength with ageing for isolated single joint actions, there has been little attention to power production during more functionally relevant multiple joint movements. The extent to which force or velocity are responsible for the loss in power with ageing is also equivocal. The aim of this study was to evaluate the contribution of force and velocity to the differences in power with age by comparing the force-velocity and power-velocity relationships in young and older men during a multiple joint leg press movement. Twenty-one older men (66 ± 3 years) and twenty-three young men (24 ± 2 years) completed a series of isometric (maximum and explosive) and dynamic contractions on a leg press dynamometer instrumented to record force and displacement. The force-velocity relationship was lower for the older men as reflected by their 19 % lower maximum isometric strength (p < 0.001). Explosive isometric strength (peak rate of force development) was 21 % lower for the older men (p < 0.05) but was similar between groups when normalised to maximum strength (p = 0.58). The power-velocity relationship was lower for the older men as shown by reduced maximum power (-28 %, p < 0.001) and lower force (-20 %, p < 0.001) and velocity (-11 %, p < 0.05). Whilst force and velocity were lower in older men, the decrement in force was greater and therefore the major explanation for the attenuation of power during a functionally relevant multiple joint movement.

Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel.

PubMed

Guo, Yanjun; Hu, Jincheng; Li, Jin; Jiang, Laizhu; Liu, Tianwei; Wu, Yanping

2014-09-12

The effect of annealing temperature (1000-1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and potentiostatic critical pitting temperature (CPT). The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP). The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN) of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN.

Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel

PubMed Central

Guo, Yanjun; Hu, Jincheng; Li, Jin; Jiang, Laizhu; Liu, Tianwei; Wu, Yanping

2014-01-01

The effect of annealing temperature (1000–1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and potentiostatic critical pitting temperature (CPT). The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP). The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN) of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN. PMID:28788201

Response of discrete linear systems to forcing functions with inequality constraints.

NASA Technical Reports Server (NTRS)

Michalopoulos, C. D.; Riley, T. A.

1972-01-01

An analysis is made of the maximum response of discrete, linear mechanical systems to arbitrary forcing functions which lie within specified bounds. Primary attention is focused on the complete determination of the forcing function which will engender maximum displacement to any particular mass element of a multi-degree-of-freedom system. In general, the desired forcing function is found to be a bang-bang type function, i.e., a function which switches from the maximum to the minimum bound and vice-versa at certain instants of time. Examples of two-degree-of-freedom systems, with and without damping, are presented in detail. Conclusions are drawn concerning the effect of damping on the switching times and the general procedure for finding these times is discussed.

CT-derived indices of canine osteosarcoma-affected antebrachial strength.

PubMed

Garcia, Tanya C; Steffey, Michele A; Zwingenberger, Allison L; Daniel, Leticia; Stover, Susan M

2017-05-01

To improve the prediction of fractures in dogs with bone tumors of the distal radius by identifying computed tomography (CT) indices that correlate with antebrachial bone strength and fracture location. Prospective experimental study. Dogs with antebrachial osteosarcoma (n = 10), and normal cadaver bones (n=9). Antebrachia were imaged with quantitative CT prior to biomechanical testing to failure. CT indices of structural properties were compared to yield force and maximum force using Pearson correlation tests. Straight beam failure (Fs), axial rigidity, curved beam failure (Fc), and craniocaudal bending moment of inertia (MOICrCd) CT indices most highly correlated (0.77 > R > 0.57) with yield and maximum forces when iOSA-affected and control bones were included in the analysis. Considering only OSA-affected bones, Fs, Fc, and axial rigidity correlated highly (0.85 > R > 0.80) with maximum force. In affected bones, the location of minimum axial rigidity and maximum MOICrCd correlated highly (R > 0.85) with the actual fracture location. CT-derived axial rigidity, Fs, and MOICrCd have strong linear relationships with yield and maximum force. These indices should be further evaluated prospectively in OSA-affected dogs that do, and do not, experience pathologic fracture. © 2017 The American College of Veterinary Surgeons.

Pneumatic Control Device for the Pershing 2 Adaption Kit

DTIC Science & Technology

1979-03-14

forward force to main- tain a pressure seal (this, versus an-I6-to 25 pound maximum reverse .force component due to pressure). In all probability, initial...stem forward force to main- tain a pressure seal (this, versus an 48-to-25-pound maximum " reverse.force, component due-topressue). In-all probability...PII Li L! Ramn Eniern Inc Contrato . 2960635 GAS GENERATOR COMPATIBILITY U TEST REPORT 1.j Requirement s The requirements for the Pershing II, Phase I

Psychophysically determined forces of dynamic pushing for female industrial workers: Comparison of two apparatuses.

PubMed

Ciriello, Vincent M; Maikala, Rammohan V; Dempsey, Patrick G; O'Brien, Niall V

2010-01-01

Using psychophysics, the maximum acceptable forces for pushing have been previously developed using a magnetic particle brake (MPB) treadmill at the Liberty Mutual Research Institute for Safety. The objective of this study was to investigate the reproducibility of maximum acceptable initial and sustained forces while performing a pushing task at a frequency of 1min(-1) both on a MPB treadmill and on a high-inertia pushcart. This is important because our pushing guidelines are used extensively as a ergonomic redesign strategy and we would like the information to be as applicable as possible to cart pushing. On two separate days, nineteen female industrial workers performed a 40-min MPB treadmill pushing task and a 2-hr pushcart task, in the context of a larger experiment. During pushing, the subjects were asked to select a workload they could sustain for 8h without "straining themselves or without becoming unusually tired, weakened, overheated or out of breath." The results demonstrated that maximum acceptable initial and sustained forces of pushing determined on the high inertia pushcart were 0.8% and 2.5% lower than the MPB treadmill. The results also show that the maximum acceptable sustained force of the MPB treadmill task was 0.5% higher than the maximum acceptable sustained force of Snook and Ciriello (1991). Overall, the findings confirm that the existing pushing data developed by the Liberty Mutual Research Institute for Safety still provides an accurate estimate of maximal acceptable forces for the selected combination of distance and frequency of push for female industrial workers.

Detection of DNA damage induced in vivo by a cross-linking agent with a circular channel crucible oscillating viscometer.

PubMed

Balbi, C; Abelmoschi, M L; Roner, R; Giaretti, W; Parodi, S; Santi, L

1985-11-01

DNA damage induced in vivo by the cross-linking agent mitomycin C (MMC) was investigated with a new oscillating crucible viscometer. Viscosity was measured by lysing rat liver nuclei in an alkaline lysing solution (pH 12.5; 25 degrees C). In control samples the viscosity increased very slowly with time, reaching a plateau only after 10-12 h. The process was accelerated and the maximum viscosity was decreased by alkaline single-stranded breaks arising from methylation and subsequent depurination of DNA in vitro with dimethylsulphate (DMS). MMC, when given alone, had no evident effect on the time needed for reaching plateau viscosity but it induced a small increase in maximum viscosity. When MMC was given in association with DMS, the time of disentanglement remained unchanged (accelerated) but maximum viscosity was increased in a dose dependent way. We conclude that these data clearly confirm that the slow steady increase of the viscosity of control DNA with time reflects mainly the process of unwinding of the two strands. The speed of this process seems to depend only from the number of unwinding points in DNA (breaks).

Laryngeal Force Sensor: Quantifying Extralaryngeal Complications after Suspension Microlaryngoscopy.

PubMed

Feng, Allen L; Song, Phillip C

2018-04-01

Objectives To develop a novel sensor capable of dynamically analyzing the force exerted during suspension microlaryngoscopy and to examine the relationship between force and postoperative tongue complications. Study Design Prospective observational study. Setting Academic tertiary care center. Methods The laryngeal force sensor is a designed for use during microphonosurgery. Prospectively enrolled patients completed pre- and postoperative surveys to assess the development of tongue-related symptoms (dysgeusia, pain, paresthesia, and paresis) or dysphagia (10-item Eating Assessment Tool [EAT-10]). To prevent operator bias, surgeons were blinded to the force recordings during surgery. Results Fifty-six patients completed the study. Of these, 20 (36%) developed postoperative tongue symptoms, and 12 (21%) had abnormal EAT-10 scores. The mean maximum force across all procedures was 164.7 N (95% CI, 141.0-188.4; range, 48.5-402.6), while the mean suspension time was 34.3 minutes (95% CI, 27.4-41.2; range, 7.1-108.1). Multiple logistic regression showed maximum force (odds ratio, 1.15; 95% CI, 1.02-1.29; P = .019) and female sex (30.1%; 95% CI, 22.7%-37.5%; P < .001) as significant predictors for the development of tongue-related symptoms. The only significant predictor of an abnormal postoperative EAT-10 score was an increased maximum force (odds ratio, 1.03; 95% CI, 1.00-1.06; P = .045). Conclusions The laryngeal force sensor is capable of providing dynamic force measurements throughout suspension microlaryngoscopy. An increase in maximum force during surgery may be a significant predictor for the development of tongue-related symptoms and an abnormal EAT-10 score. Female patients may also be at greater risk for developing postoperative tongue symptoms.

Parity-Time Symmetry Breaking in Spin Chains.

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

Galda, Alexey; Vinokur, Valerii M.

We investigate nonequilibrium phase transitions in classical Heisenberg spin chains associated with spontaneous breaking of parity-time (PT) symmetry of the system under the action of Slonczewski spin-transfer torque (STT) modeled by an applied imaginary magnetic field. We reveal the STT-driven PT symmetry-breaking phase transition between the regimes of precessional and exponentially damped spin dynamics and show that its several properties can be derived from the distribution of zeros of the system's partition function, the approach first introduced by Yang and Lee for studying equilibrium phase transitions in Ising spin chains. The physical interpretation of imaginary magnetic field as describing themore » action of nonconservative forces opens the possibility of direct observations of Lee-Yang zeros in nonequilibrium physical systems.« less

Parity-time symmetry breaking in spin chains

NASA Astrophysics Data System (ADS)

Galda, Alexey; Vinokur, Valerii M.

2018-05-01

We investigate nonequilibrium phase transitions in classical Heisenberg spin chains associated with spontaneous breaking of parity-time (PT ) symmetry of the system under the action of Slonczewski spin-transfer torque (STT) modeled by an applied imaginary magnetic field. We reveal the STT-driven PT symmetry-breaking phase transition between the regimes of precessional and exponentially damped spin dynamics and show that its several properties can be derived from the distribution of zeros of the system's partition function, the approach first introduced by Yang and Lee for studying equilibrium phase transitions in Ising spin chains. The physical interpretation of imaginary magnetic field as describing the action of nonconservative forces opens the possibility of direct observations of Lee-Yang zeros in nonequilibrium physical systems.

Limitations of differential electrophoresis for measuring colloidal forces: a Brownian dynamics study.

PubMed

Holtzer, Gretchen L; Velegol, Darrell

2005-10-25

Differential electrophoresis experiments are often used to measure subpiconewton forces between two spheres of a heterodoublet. The experiments have been interpreted by solving the electrokinetic equations to obtain a simple Stokes law-type equation. However, for nanocolloids, the effects of Brownian motion alter the interpretation: (1) Brownian translation changes the rate of axial separation. (2) Brownian rotation reduces the alignment of the doublet with the applied electric field. (3) Particles can reaggregate by Brownian motion after they break, forming either heterodoublets or homodoublets, and because homodoublets cannot be broken by differential electrophoresis, this effectively terminates the experiment. We tackle points 1 and 2 using Brownian dynamics simulations (BDS) with electrophoresis as an external force, accounting for convective translation and rotation as well as Brownian translation and rotation. Our simulations identify the lower particle size limit of differential electrophoresis to be about 1 microm for desired statistical accuracy. Furthermore, our simulations predict that particles around 10 nm in size and at ambient conditions will break primarily by Brownian motion, with a negligible effect due to the electric field.

Breaking Gravity Waves Over Large-Scale Topography

NASA Astrophysics Data System (ADS)

Doyle, J. D.; Shapiro, M. A.

2002-12-01

The importance of mountain waves is underscored by the numerous studies that document the impact on the atmospheric momentum balance, turbulence generation, and the creation of severe downslope winds. As stably stratified air is forced to rise over topography, large amplitude internal gravity waves may be generated that propagate vertically, amplify and breakdown in the upper troposphere and lower stratosphere. Many of the numerical studies reported on in the literature have used two- and three-dimensional models with simple, idealized initial states to examine gravity wave breaking. In spite of the extensive previous work, many questions remain regarding gravity wave breaking in the real atmosphere. Outstanding issues that are potentially important include: turbulent mixing and wave overturning processes, mountain wave drag, downstream effects, and the mesoscale predictability of wave breaking. The current limit in our knowledge of gravity wave breaking can be partially attributed to lack of observations. During the Fronts and Atlantic Storm-Track Experiment (FASTEX), a large amplitude gravity wave was observed in the lee of Greenland on 29 January 1997. Observations taken collected during FASTEX presented a unique opportunity to study topographically forced gravity wave breaking and to assess the ability of high-resolution numerical models to predict the structure and evolution of such phenomena. Measurements from the NOAA G-4 research aircraft and high-resolution numerical simulations are used to study the evolution and dynamics of the large-amplitude gravity wave event that took place during the FASTEX. Vertical cross section analysis of dropwindsonde data, with 50-km horizontal spacing, indicates the presence of a large amplitude breaking gravity wave that extends from above the 150-hPa level to 500 hPa. Flight-level data indicate a horizontal shear of over 10-3 s-1 across the breaking wave with 25 K potential temperature perturbations. This breaking wave may have important implications for momentum flux parameterization in mesoscale models, stratospheric-tropospheric exchange dynamics as well as the dynamic sources and sinks of the ozone budget. Additionally, frequent breaking waves over Greenland are a known commercial and military aviation hazard. NRL's nonhydrostatic COAMPS^{TM}$ model is used with four nested grids with horizontal resolutions of 45 km, 15 km, 5 km and 1.67 km and 65 vertical levels to simulate the gravity wave event. The model simulation captures the temporal evolution and horizontal structure of the wave. However, the model underestimates the vertical amplitude of the wave. The model simulation suggests that the breaking wave may be triggered as a consequence of vertically propagating internal gravity waves emanating from katabatic flow near the extreme slopes of eastern Greenland. Additionally, a number of simulations that make use of a horizontally homogeneous initial state and both idealized and actual Greenland topography are performed. These simulations highlight the sensitivity of gravity wave amplification and breaking to the planetary rotation, slope of the Greenland topography, representation of turbulent mixing, and surface processes.

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2014 CFR

2014-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

Functional sensibility assessment. Part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release.

PubMed

Hsu, Hsiu-Yun; Kuo, Li-Chieh; Chiu, Haw-Yen; Jou, I-Ming; Su, Fong-Chin

2009-11-01

Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom-designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity. Based on these tests, five force-related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes-Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Handgrip fatiguing exercise can provide objective assessment of cancer-related fatigue: a pilot study.

PubMed

Veni, T; Boyas, S; Beaune, B; Bourgeois, H; Rahmani, A; Landry, S; Bochereau, A; Durand, S; Morel, B

2018-06-24

As a subjective symptom, cancer-related fatigue is assessed via patient-reported outcomes. Due to the inherent bias of such evaluation, screening and treatment for cancer-related fatigue remains suboptimal. The purpose is to evaluate whether objective cancer patients' hand muscle mechanical parameters (maximal force, critical force, force variability) extracted from a fatiguing handgrip exercise may be correlated to the different dimensions (physical, emotional, and cognitive) of cancer-related fatigue. Fourteen women with advanced breast cancer, still under or having previously received chemotherapy within the preceding 3 months, and 11 healthy women participated to the present study. Cancer-related fatigue was first assessed through the EORTC QLQ-30 and its fatigue module. Fatigability was then measured during 60 maximal repeated handgrip contractions. The maximum force, critical force (asymptote of the force-time evolution), and force variability (root mean square of the successive differences) were extracted. Multiple regression models were performed to investigate the influence of the force parameters on cancer-related fatigue's dimensions. The multiple linear regression analysis evidenced that physical fatigue was best explained by maximum force and critical force (r = 0.81; p = 0.029). The emotional fatigue was best explained by maximum force, critical force, and force variability (r = 0.83; p = 0.008). The cognitive fatigue was best explained by critical force and force variability (r = 0.62; p = 0.035). The handgrip maximal force, critical force, and force variability may offer objective measures of the different dimensions of cancer-related fatigue and could provide a complementary approach to the patient reported outcomes.

Selective deficits of grip force control during object manipulation in patients with reduced sensibility of the grasping digits.

PubMed

Nowak, Dennis A; Hermsdörfer, Joachim

2003-09-01

Persons with impaired manual sensibility frequently report problems to use the hand in manipulative tasks, such as using tools or buttoning a shirt. At least two control processes determine grip forces during voluntary object manipulation. Anticipatory force control specifies the motor commands on the basis of predictions about physical object properties and the consequences of our own actions. Feedback sensory information from the grasping digits, representing mechanical events at the skin-object interface, automatically modifies grip force according to the actual loading requirements and updates sensorimotor memories to support anticipatory grip force control. We investigated grip force control in nine patients with moderately impaired tactile sensibility of the grasping digits and in nine sex- and age-matched healthy controls lifting and holding an instrumented object. In healthy controls grip force was adequately scaled to the weight of the object to be lifted. The grip force was programmed to smoothly change in parallel with load force over the entire lifting movement. In particular, the grip force level was regulated in an economical way to be always slightly higher than the minimum required to prevent the object slipping. The temporal coupling between the grip and load force profiles achieved a high precision with the maximum grip and load forces coinciding closely in time. For the temporal regulation of the grip force profile patients with impaired tactile sensibility maintained the close co-ordination between proximal arm muscles, responsible for the lifting movement and the fingers stabilising the grasp. Maximum grip force coincided with maximum acceleration of the lifting movement. However, patients employed greater maximum grip forces and greater grip forces to hold the object unsupported when compared with controls. Our results give further evidence to the suggestion that during manipulation of objects with known physical properties the anticipatory temporal regulation of the grip force profile is centrally processed and less under sensory feedback control. In contrast, sensory afferent information from the grasping fingers plays a dominant role for the efficient scaling of the grip force level according to actual loading requirements.

Ways of increasing muscular activity by means of isometric muscular exertion

NASA Technical Reports Server (NTRS)

Kovalik, A. V.

1980-01-01

The effect of isometric muscular exertion on the human body was investigated by having subjects perform basic movements in a sitting position in the conventional manner with additional muscle tension at 50% maximum force and at maximum force. The pulse, arterial pressure, skin temperature, respiratory rate, minute respiratory volume and electrical activity of the muscles involved were all measured. Performance of the exercises with maximum muscular exertion for 20 sec and without movement resulted in the greatest shifts in these indices; in the conventional manner substantial changes did not occur; and with isometric muscular exertion with 50% maximum force with and without movement, optimal functional shifts resulted. The latter is recommended for use in industrial exercises for the prevention of hypodynamia. Ten exercises are suggested.

Screw-in forces during instrumentation by various file systems.

PubMed

Ha, Jung-Hong; Kwak, Sang Won; Kim, Sung-Kyo; Kim, Hyeon-Cheol

2016-11-01

The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems. Forty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS- k , DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%. Reciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest ( p < 0.05). Geometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended.

Design and optimization of a modal- independent linear ultrasonic motor.

PubMed

Zhou, Shengli; Yao, Zhiyuan

2014-03-01

To simplify the design of the linear ultrasonic motor (LUSM) and improve its output performance, a method of modal decoupling for LUSMs is proposed in this paper. The specific embodiment of this method is decoupling of the traditional LUSM stator's complex vibration into two simple vibrations, with each vibration implemented by one vibrator. Because the two vibrators are designed independently, their frequencies can be tuned independently and frequency consistency is easy to achieve. Thus, the method can simplify the design of the LUSM. Based on this method, a prototype modal- independent LUSM is designed and fabricated. The motor reaches its maximum thrust force of 47 N, maximum unloaded speed of 0.43 m/s, and maximum power of 7.85 W at applied voltage of 200 Vpp. The motor's structure is then optimized by controlling the difference between the two vibrators' resonance frequencies to reach larger output speed, thrust, and power. The optimized results show that when the frequency difference is 73 Hz, the output force, speed, and power reach their maximum values. At the input voltage of 200 Vpp, the motor reaches its maximum thrust force of 64.2 N, maximum unloaded speed of 0.76 m/s, maximum power of 17.4 W, maximum thrust-weight ratio of 23.7, and maximum efficiency of 39.6%.

A Methodology for Modeling the Flow of Military Personnel Across Air Force Active and Reserve Components

DTIC Science & Technology

2016-01-01

user, the model will use surplus inventory in one category to fill shortfalls in other categories. The TFBL model also has the capability to allow...the total force. As shown in Table 2.1, we used five-character AFSCs (four digits plus the suffix) to break out pilots in the current force as...Training Unit 4th digit Suffix 4th digit Suffix 4th digit 4th digit 2 or 3 Matches a specific aircraft designation 3 Does not match a specific

Shock-Absorbing Effects of Various Padding Conditions in Improving Efficacy of Wrist Guards

PubMed Central

Hwang, Il-Kyu; Kim, Kyu-Jung

2004-01-01

The use of wrist guards has limited efficacy in preventing wrist injuries during falling in many sports activities. The objectives of this study were to measure the ground reaction force of the hand under simulated impact of the forearm and hand complex with different padding conditions of wrist guards and to analyze their impact force attenuation and maximum energy absorption for improved functional efficiency. A total of 15 subjects, wearing a commercial wrist guard, participated in a cable-released hand impact experiment to test four different conditions on the volar aspect of the hand, which include a wrist guard without a volar splint (bare hand), with a volar splint (normal use), with a volar splint and additional viscoelastic polymeric padding, and a volar splint and additional air cell padding. The ground reaction force and acceleration of the hand were measured using a force platform mounted on an anti-vibration table and a miniature accelerometer, respectively. Additional padding on the bare hand could substantially improve the maximum energy absorption by more than 39%, with no differences with each other. However, only the air cell padding could simultaneously improve the impact force attenuation by 32% compared with the bare hand impact without compromising the maximum energy absorption. It is recommended that common wrist guard design should provide more compliant padding in the volar aspect to improve the impact force attenuation through optimal material selection and design. Key Points The controversial efficacy of wrist guards in preventing wrist injuries during falling was tested through investigation of their impact force attenuation and maximum energy absorption from the measured ground reaction force of the hand under simulated impact of the forearm and hand complex with four different padding conditions of wrist guards: a wrist guard without a volar splint (bare hand), with a volar splint (normal use), with a volar splint and additional viscoelastic polymeric padding, and a volar splint and additional air cell padding. In general, padding on the bare hand could improve the maximum energy absorption by more than 39%, while only the air cell padding could simultaneously attenuate the peak impact force by 32% without compromising the maximum energy absorption. Common wrist guard design requires more compliant padding in the volar aspect to improve the impact force attenuation, which should be done through optimal material selection and design. PMID:24497817

Effect of occlusal splint therapy on maximum bite force in individuals with moderate to severe attrition of teeth.

PubMed

Jain, Veena; Mathur, Vijay Prakash; Abhishek, Kumar; Kothari, Mohit

2012-10-01

The purpose of the pilot study was to determine the effect of restoring lost occlusal vertical dimension (OVD) due to attrition on maximum bite force in humans. A total of 124 subjects in age range of 25-40 years, with moderate to severe attrition, having full complement of teeth were screened according to inclusion and exclusion criteria. After consent, occlusal vertical dimension was assessed by employing mechanical and physiological methods in the experimental group and a maxillary canine guided hard splint was fabricated for each subjects fulfilling inclusion criteria and with positive consent (78). Bite force in experimental group was measured before, immediately after delivery of splint and subsequently at an interval of four, eight, and twelve weeks. Due loss during follow up, only 50 subjects could be available for bite force recording till 12 weeks. Bite force of age, gender, height and weight matched controls with no signs of attrition was also measured for comparison. Bite force of the experimental group was found to be significantly less than the matched controls (P=0.000) initially. After delivery of splint, bite force values increased progressively till twelve weeks. However comparison of bite force values of experimental group with control group showed no significant difference at end of eight (P=0.008) and twelve weeks (P=0.162). It was concluded that maximum bite force increases with restoration of lost vertical using splint therapy. A time period of 8-12 weeks is required to restore the maximum bite force value approximately similar to matched controls. Copyright © 2012 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

A Novel Technique to Measure In Vivo Uterine Suspensory Ligament Stiffness

PubMed Central

Smith, Tovia M.; Luo, Jiajia; Hsu, Yvonne; Ashton-Miller, James A.; Delancey, John O.L.

2013-01-01

Objective To describe a new computer-controlled research apparatus for measuring in vivo uterine ligament force-displacement behavior and stiffness and to present pilot data in women with and without prolapse. Study Design Seventeen women with varying uterine support underwent testing in the operating room (OR) after anesthetic induction. A tripod-mounted computer-controlled linear servoactuator was used to quantify force-displacement behavior of the cervix and supporting ligaments. The servoactuator applied a caudally-directed force to a tenaculum at 4 mm/s velocity until the traction force reached 17.8N (4 lbs.). Cervix location on POP-Q in clinic, in the OR at rest, and with minimal force (<1.1N), and maximum force (17.8N) was recorded. Ligament “stiffness” between minimum and maximum force was calculated. Results The mean (SD) subject age was 54.5 (12.7) years, parity 2.9 (1.1), BMI 29.0 (4.3) kg/m2, and POP-Q point C −3.1 (3.9) cm. POP-Q point C was most strongly correlated with cervix location at maximum force (r=+0.68, p=.003) and at rest (r=+0.62, p=.009). Associations between cervix location at minimum force (r=+0.46, p=.059) and ligament stiffness (r= −0.44,p=.079) were not statistically significant. Cervix location in the OR with minimal traction lay below the lowest point found on POP-Q for 13 women. Conclusions POP-Q point C was strongly correlated with cervix location at rest and at maximum traction force; however only 19% of the variation in POP-Q point C location was explained by ligament stiffness. The cervix location in the OR at minimal traction lay below POP-Q point C value in ¾ of women. PMID:23747493

The effect of paleotopography on lithic distribution and facies associations of small volume ignimbrites: the WTT Cupa (Roccamonfina volcano, Italy)

NASA Astrophysics Data System (ADS)

Giordano, Guido

1998-12-01

The distribution of lithic clasts within two trachytic, small volume, pumiceous ignimbrites are described from the Quaternary `White Trachytic Tuff Cupa' formation of Roccamonfina volcano, Italy. The ignimbrites show a downslope grading of lithics, with a maximum size where there is a major break in the volcano's slope, rather than at proximal locations. This is also the location where ignimbrites are thickest and most massive. The break in slope is interpreted to have reduced flow capacity and velocity, increasing the sedimentation rate, so that massive ignimbrite formed by hindered settling sedimentation. Ignimbrite Cc, exhibits no vertical grading of lithics, though it does show downslope grading with maximum size at the major break in slope and a rapid decrease further downslope. Ignimbrite Cc thins away from the break in slope, and shows an upward fining of the grain size within the topmost few decimeters of the unit. The ignimbrite is stratified proximally, and grades to massive facies at the break in slope, and distally to stratified facies with numerous inverse-graded beds. The simplest mechanism accounting for these downslope variations is progressive aggradation from a quasi-steady, nonuniform pyroclastic density current. The changes in deposit thickness and facies are interpreted to record downcurrent changes in sedimentation rate. The upward fining reflects waning flow. Inversely graded, bedded depositional facies in distal areas is interpreted to reflect flow unsteadiness and a decrease in suspended sediment load. Ignimbrite Cd shows vertical, as well as downslope grading of lithics. This characteristic, coupled with the widespread massive facies of the deposit and the tabular unit geometry are features that can be reconciled with both the debris flow/plug analogy for pyroclastic flows ( Sparks, 1976) and the progressive aggradation model ( Branney and Kokelaar, 1992). However, none of them appears to satisfy completely the field evidences, implying that when dealing with massive ignimbrites, other evidence than lithic grading needs to be presented to better understand the related transport and depositional processes.

An Experimental Study of Droplets Produced by a Plunging Breakers

NASA Astrophysics Data System (ADS)

Erinin, Martin; Wang, Dan; Towle, David; Liu, Xinan; Duncan, James

2016-11-01

In this study, the production of droplets by a mechanically generated plunging breaking water wave is investigated in a wave tank. The breaker, with an amplitude of 0.070 m, is generated repeatedly with a programmable wave maker by using a dispersively focused wave packet (average frequency 1.15 Hz). The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a cinematic digital in-line holographic system positioned at 30 locations along a horizontal plane that is 1 cm above the maximum wave crest height. This measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d >100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the breaking wave is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. The support of the National Science Foundation under Grant OCE0751853 from the Division of Ocean Sciences is gratefully acknowledged.

Tunneling STM/STS and break-junction spectroscopy of the layered nitro-chloride superconductors MNCl (M = Ti, Hf, Zr)

NASA Astrophysics Data System (ADS)

Ekino, Toshikazu; Sugimoto, Akira; Gabovich, Alexander M.; Zheng, Zhanfeng; Zhang, Shuai; Yamanaka, Shoji

2014-05-01

The layered superconductors β-MNCl with the critical temperatures Tc = 14 K (M = Zr) - 25 K (M = Hf) were investigated by means of scanning-tunneling microscopy/spectroscopy and break-junction tunneling spectroscopy. The STM/STS was used to investigate the surface electronic structures in nanometer length scale, while the BJTS was employed to precisely determine the gap characteristics. Both techniques consistently clarified the unusually large size of the superconducting gap. Wide gap distributions with large-scale maximum gap values were also revealed in α-KyTiNCl with a different crystal structure.

Design of load-to-failure tests of high-voltage insulation breaks for ITER's cryogenic network

NASA Astrophysics Data System (ADS)

Langeslag, S. A. E.; Rodriguez Castro, E.; Aviles Santillana, I.; Sgobba, S.; Foussat, A.

2015-12-01

The development of new generation superconducting magnets for fusion research, such as the ITER experiment, is largely based on coils wound with so-called cable-in-conduit conductors. The concept of the cable-in-conduit conductor is based on a direct cooling principle, by supercritical helium, flowing through the central region of the conductor, in close contact with the superconducting strands. Consequently, a direct connection exists between the electrically grounded helium coolant supply line and the highly energised magnet windings. Various insulated regions, constructed out of high-voltage insulation breaks, are put in place to isolate sectors with different electrical potential. In addition to high voltages and significant internal helium pressure, the insulation breaks will experience various mechanical forces resulting from differential thermal contraction phenomena and electro-magnetic loads. Special test equipment was designed, prepared and employed to assess the mechanical reliability of the insulation breaks. A binary test setup is proposed, where mechanical failure is assumed when leak rate of gaseous helium exceeds 10-9·Pa·m3/s. The test consists of a load-to-failure insulation break charging, in tension, while immersed in liquid nitrogen at the temperature of 77 K. Leak tightness during the test is monitored by measuring the leak rate of the gaseous helium, directly surrounding the insulation break, with respect to the existing vacuum inside the insulation break. The experimental setup is proven effective, and various insulation breaks performed beyond expectations.

Two pad axially grooved hydrostatic bearing

NASA Technical Reports Server (NTRS)

San Andres, Luis A. (Inventor)

1995-01-01

A hydrostatic bearing having two axial grooves on opposite sides of the bearing for breaking the rotational symmetry in the dynamic force coefficients thus reducing the whirl frequency ratio and increasing the damping and stiffness of the hydrostatic bearing.

Nonlinear electronic stopping power of channeled slow light ions in ZnSe: Evidence of energy loss caused by formation and breaking of chemical bond

NASA Astrophysics Data System (ADS)

Li, Chang-kai; Wang, Feng; Gao, Cong-Zhang; Liao, Bin; Ouyang, Xiao-ping; Zhang, Feng-Shou

2018-07-01

Electronic stopping power of helium ions in a semiconductor material ZnSe has been investigated through non-adiabatic dynamics simulations at energies of a few keV under channeling condition. The stopping power is predicted to be proportional to velocity for the trajectory along middle axis of a 〈 1 1 0 〉 channel, as expected for the linear response theory accounts for election-hole pair creation. While for the off-center channeling trajectory, a counterintuitive of electronic stopping power versus velocity is observed. Our study, presented herein, finds a non-trivial connection between charge transfer and the force experienced by the projectile. Charge transfer can produce, throughout the collision process, additional force by continuously forming and breaking instantaneous chemical bonds between the projectile and the neighboring host atoms.

Velocity of sarcomere shortening in rat cardiac muscle: relationship to force, sarcomere length, calcium and time.

PubMed

Daniels, M; Noble, M I; ter Keurs, H E; Wohlfart, B

1984-10-01

The relation between force and velocity was determined in sixteen trabeculae of rat right ventricle as a function of time during a twitch, of sarcomere length and of external Ca2+ concentration, [Ca2+]o. The trabeculae were studied in modified Krebs-Henseleit solution at 25 degrees C. Force was measured with a semiconductor strain gauge. Sarcomere length was measured with a laser diffraction system. A servomotor system was used in which control could be switched between sarcomere length, muscle length and force. Force-velocity relations were derived from load clamps and from contractions in which sarcomere length was initially held constant followed by a quick release and slower release of the sarcomeres at controlled velocity. Force-velocity relations were fitted by Hill's equation (Hill, 1938), (Po-P) b = (P+a) V, where P = force, V = velocity, Po = isometric force in mN/mm2 and a and b are constants. For [Ca2+]o = 2.5 mM, with both interventions the values (mean +/- S.D.) were: b = 1.00 +/- 0.45 micron/s; a = 9.52 +/- 5.60 mN/mm2; Vo measured = 13.6 +/- 3.0 micron/s; Vo calculated = 13.4 +/- 3.4 micron/s; Po measured = 96.5 +/- 25.0 mN/mm2; Po calculated = 119.3 +/- 34.5 mN/mm2. Vo rose with [Ca2+]o to a maximum at [Ca2+]o = 1.2 mM when Po was about 50% of maximum, while Po rose with [Ca2+]o to a maximum at above 2.5 mM. Vo rose with time during the twitch to a maximum at 25 ms following onset of contraction; Po was then about 50% of the maximum that was obtained at 120 ms. Vo increased with sarcomere length from zero at a sarcomere length of 1.6 micron to a maximum at 1.85 micron. Between 1.85 micron and 2.3 micron, Vo was constant. At 1.85 micron, Po was about 60% of maximum Po. These results are compatible with the hypothesis that Vo is more sensitive than Po to the amount of Ca2+ bound to the contractile proteins, and that Vo reaches a maximal value with an amount of Ca2+ bound to the contractile proteins at which Po has obtained only about 50% of its maximal value.

Mean-field studies of time reversal breaking states in super-heavy nuclei with the Gogny force

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

Robledo, L. M., E-mail: luis.robledo@uam.es

2015-10-15

Recent progress on the description of time reversal breaking (odd mass and multi-quasiparticle excitation) states in super-heavy nuclei within a mean field framework and using several flavors of the Gogny interaction is reported. The study includes ground and excited states in selected odd mass isotopes of nobelium and mendelevium as well as high K isomeric states in {sup 254}No. These are two and four-quasiparticle excitations that are treated in the same self-consistent HFB plus blocking framework as the odd mass states.

Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design

NASA Technical Reports Server (NTRS)

Davis, Roger L.; Dannenhoffer, John F., III; Clark, John P.

2010-01-01

New ideas are forthcoming to break existing bottlenecks in using CFD during design. CAD-based automated grid generation. Multi-disciplinary use of embedded, overset grids to eliminate complex gridding problems. Use of time-averaged detached-eddy simulations as norm instead of "steady" RANS to include effects of self-excited unsteadiness. Combined GPU/Core parallel computing to provide over an order of magnitude increase in performance/price ratio. Gas-turbine applications are shown here but these ideas can be used for other Air Force, Navy, and NASA applications.

The NASA Ames Hypervelocity Free Flight Aerodynamic Facility: Experimental Simulation of the Atmospheric Break-Up of Meteors

NASA Technical Reports Server (NTRS)

Wilder, M. C.; Bogdanoff, D. W.

2015-01-01

The Hypervelocity Free Flight Aerodynamic Facility at NASA Ames Research Center provides a potential platform for the experimental simulation of meteor breakup at conditions that closely match full-scale entry condition for select parameters. The poster describes the entry environment simulation capabilities of the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center and provides example images of the fragmentation of a hypersonic projectile for which break-up was initiated by mechanical forces (impact with a thin polymer diaphragm).

Finite element Analysis of Semi-Grouting Sleeve Connection Member Based on ABAQUS

NASA Astrophysics Data System (ADS)

Bao, Longsheng; Fan, Qianyu; Wang, Ling

2018-05-01

This paper use investigates the force transfer mechanism and failure form of semi-grouting sleeve members under axial load, analyze the weak points of structural bearing capacity and verify the reliability of the connection of steel bars through finite element analysis software. The results show that adding the axial load to semi-grouting sleeve forms a 45°oblique compression zone, which help to transfer stress between reinforcement, grouting material and sleeve. Because the maximum stress of sleeve doesn’t reach its tensile resistance and the deformation of the sleeve is located at the junction of the grouting and the threaded section when the stress value of steel bars at each end of the semi-grouting sleeve reach its ultimate tensile strength, we conclude that the semi-grouting sleeve members can meet the construction quality requirements and be used to connect the steel bars at the joints of the assembled structures. It is necessary to avoid breaking down, since the deformation section will accumulate large plastic deformation during the processing of the sleeve.

Flexible printed circuit board actuators

NASA Astrophysics Data System (ADS)

Lee, Junseok; Cha, Youngsu

2017-12-01

Out-of-plane actuators are made possible by the breaking of planar symmetry. In this paper, we present a thin-film out-of-plane electrostatic actuator for a flexible printed circuit board (FPCB) that can be fabricated with a single step of the conventional manufacturing process. No other components are required for actuation except a single sheet of the FPCB, and it works based on the planar asymmetry resulting from asymmetrically patterned top and bottom electrodes on each side of the polyimide film. With the structural asymmetry, the application of a high voltage in the order of kilovolts results in the asymmetry of the electric fields and the body force density, which generates the bending moment that leads to macroscopic deformations. We applied the finite element method to examine the asymmetry induced by the difference in the electrodes. In the experiment, the displacement responses to step input and square wave input of various frequencies were analyzed. It was found that our actuator constitutes an underdamped system, exhibiting resonance characteristics. The maximum oscillatory amplitude was determined at resonance, and the relationship between the displacement and the applied voltage was investigated.

Flaxseed flour (Linum usitatissinum) consumption improves bone quality and decreases the adipocyte area of lactating rats in the post-weaning period.

PubMed

Ribeiro, Danielle Cavalcante; Pereira, Aline D'Avila; da Silva, Paula Cristina Alves; dos Santos, Aline de Sousa; de Santana, Fernanda Carvalho; Boueri, Bianca Ferolla da Camara; Pessanha, Carolina Ribeiro; de Abreu, Maíra Duque Coutinho; Mancini-Filho, Jorge; da Silva, Eduardo Moreira; do Nascimento-Saba, Celly Cristina Alves; da Costa, Carlos Alberto Soares; Boaventura, Gilson Teles

2016-01-01

The aim of this work was to evaluate the effects of flaxseed flour in the intake on adiposity and femur structure of the lactating rats during the post-weaning period. After weaning, the lactating rats were divided into control (C, n = 6) and experimental (F, n = 6) groups treated with a diet containing flaxseed flour. Serum hormone and fatty acids composition, morphology of intra-abdominal adipocytes, computed tomography and biomechanical analyses of femur were determined. Food intake, body mass and hormone analysis have shown similar results. The F group showed the following (p < 0.05): lower arachidonic acid (-60%), total polyunsaturated fatty acids (-30%) and retroperitoneal adipocytes (-36%) area. Higher radiodensity of femoral head region (+29%) and higher maximum force (+18%), breaking strength (+18%) and rigidity (+31%). Fatty acid composition of flaxseed flour decreased the area of adipocytes and improved the bone quality, which may be associated with lower serum levels of arachidonic acid levels, during the post-weaning period.

Inulin and erythritol as sucrose replacers in short-dough cookies: sensory, fracture, and acoustic properties.

PubMed

Laguna, Laura; Primo-Martín, Cristina; Salvador, Ana; Sanz, Teresa

2013-05-01

The effect of sucrose replacement by erythritol and inulin was studied in short-dough cookies using instrumental and sensory analysis. Two levels of replacement were used (25% and 50% of total sucrose content). Descriptive sensory analysis showed that the sucrose replacement affects visual and texture cookies characteristics, being the differences perceived by mouth greater than by hand. In general, sucrose substitutes produced a less crispy cookie and lower consumer acceptability, with the exception of 25% sucrose replacement by inulin. Matrix aeration attributes such as open and crumbly obtained by trained panel were important properties, and correlated positively with consumer acceptance and negatively with maximum force at break (hardness). Inulin cookies sensory properties were more similar to the control than the erythritol cookies. Also, consumer overall acceptance decreased significantly with sucrose replacement by erythritol. The analysis of texture and sound revealed that inulin cookies were softer whereas erythritol cookies were harder in comparison with control cookies; despite this difference, inulin cookies had similar sound characteristics to erythritol cookies. © 2013 Institute of Food Technologists®

A Transonic Wind-Tunnel Investigation of a Seaplane Configuration having a 40 Deg Sweptback Wing, TED No. NACA DE 387

NASA Technical Reports Server (NTRS)

Hieser, Gerald; Kudlacik, Louis; Gray, W. H.

1956-01-01

During the course of an aerodynamic loads investigation of a model of the Martin XP6M-1 flying boat in the.Langley 16-foot transonic tunnel, longitudinal-aerodynamic-performance information was obtained. Data were obtained at speeds up to and exceeding those anticipated for the seaplane in level flight and included the Mach number range from 0.84. to 1.09. The angle of attack was varied from -2deg to 6deg and the average Reynolds number, based on wing mean aerodyn&ic chord, was about 3.7 x 10(exp 6). This seaplane, although not designed to maintain level flight at Mach numbers beyond the force break, was found to have a transonic drag-rise coefficient of 0.0728, with an accompanying drag-rise Mach number of about 0.85. A large portion of the.drag rise and the relatively low value of drag-rise Mach number result from the axial coincidence of the maximum areas of the principal airplane components.

Relative contributions of occlusion, maximum bite force, and chewing cycle kinematics to masticatory performance.

PubMed

Lepley, Casey R; Throckmorton, Gaylord S; Ceen, Richard F; Buschang, Peter H

2011-05-01

The purpose of this study was to explore the contributions of occlusion, maximum bite force, and chewing cycle kinematics to masticatory performance. A prospective cross-sectional study was performed on 30 subjects with Class I occlusion. Masticatory performance was measured with the test food Cuttersil (Heraeus Kulzer, South Bend, Ind) and the fractional-sieve technique. Blu-Mousse (Parkell Biomaterials, Farmingdale, NY) bite registrations were used to measure occlusal contact areas. The American Board of Orthodontics occlusal discrepancies were measured on the subjects' dental models. Maximum bite forces were recorded with a custom transducer, and 3-dimensional chewing cycle kinematics were tracked with an opto-electric computer system and Optotrak software (Northern Digital, Waterloo, Ontario, Canada). Masticatory performance was most closely correlated with occlusal contact area, indicating larger contact areas in subjects with better performance. Occlusal contact area and occlusal discrepancies were also related to bite force and chewing cycle kinematics. Maximum bite force was positively related with masticatory performance. Although masticatory performance is related, both directly and indirectly, to a number of morphologic and functional factors, it is most closely related to occlusal factors. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Development of a novel precision instrument for high-resolution simultaneous normal and shear force measurements between small planar samples

NASA Astrophysics Data System (ADS)

Lundstrom, Troy; Clark, William; Jalili, Nader

2017-05-01

In the design and development of end effector pads for silicon wafer handling robots, it is imperative that the static friction/adhesion force properties of the pads with respect to a variety of planar surfaces be characterized. In this work, the overall design, calibration, and data acquisition procedure of an instrument developed for performing these measurements on small (<10 mm × 10 mm) planar samples is presented. This device was used to perform adhesion/maximum shear force measurements on polydimethylsiloxane, a silicon wafer, and custom carbon nanotubes forest surfaces. The device was successfully able to measure an effective, mean profile adhesion force of 715 μN between a silicon wafer and a polydimethylsiloxane (2.768 × 10-6 m2) sample. In addition, a nonlinear maximum shear over normal force relationship was also measured between custom carbon nanotubes forest and the silicon wafer surfaces. The maximum shear over a normal force coefficient was found to decrease with increasing initial normal force. Currently, there are numerous devices for measuring normal/shear forces at the nano/micro- and macroscales; however, this device allows for the consistent measurement of these same types of forces on components with surface dimensions ranging from 0.1 mm to 10 mm.

Formation of Maximum Eddy Current Force by Non Ferrous Materials

NASA Astrophysics Data System (ADS)

Kader, M. M. A.; Razali, Z. B.; Yasin, N. S. M.; Daud, M. H.

2018-03-01

This project is concerned with the study of eddy current effects on various materials such as aluminum, copper and magnesium. Two types of magnets used in this study; magnetic ferrite (ZnFe+2O4) and magnetic neodymium (NdFeBN42). Eddy current force will be exerted to these materials due to current flows along the magnet. This force depends on the type of magnet, type of material and the gap between the magnet and the material or between the two magnets. The results show that at constant magnet to material gap, the eddy current force decreases as the magnet to magnet gap increases. Similarly, at constant magnet to magnet gap, the eddy current force decreases as the magnet to material gap increases. The minimum force was achieved when the gap of magnet to material is maximum, similarly to the gap of magnet to magnet. The weakest force was between Copper and Neodymium at a magnet to material gap of 20 mm and magnet to magnet gap of 40 mm; the eddy current force was 0.00048 N. The strongest force (maximum) was between Magnesium and Ferrite and 0.42273 N at a magnet to material gap of 3 mm and magnet to magnet gap of 5 mm.

Muscular Strength Is Associated with Higher Intraocular Pressure in Physically Active Males.

PubMed

Vera, Jesús; Jiménez, Raimundo; García-Ramos, Amador; Cárdenas, David

2018-02-01

The positive association between intraocular pressure (IOP) and relative maximum force may have relevance for exercise recommendations when IOP is a concern. The relationship between exercise and IOP has been approached in several studies. However, the influence of muscle function on IOP remains underexplored. This study aimed to determine the relationship between the maximal mechanical capabilities of muscles to generate force, velocity, and power with IOP. Sixty-five physically active males participated in this cross-sectional study. Baseline IOP measures were obtained by rebound tonometry, and participants performed an incremental loading test in the ballistic bench press. Baseline IOP showed a strong positive correlation with relative maximum force (r65 = 0.85, P < .001) relative maximum power (r65 = 0.85, P < .001), and relative one-repetition maximum (r65 = 0.91, P < .001). Also, a moderate positive association was obtained between baseline IOP and maximum force (r65 = 0.74, P < .001), maximum power (r65 = 0.72, P < .001), and maximum dynamic strength (r65 = 0.80, P < .001). No significant correlations between IOP and maximal velocity were obtained (all P > .05). There is a positive association between greater upper-body power and strength with higher baseline IOP, which might have important implications in the management of ocular health and especially in individuals constantly involved in resistance training programs (e.g., military personnel, weightlifters). The possible protective effect of high fitness level on the acute IOP response to strength exercise needs to be addressed in future studies.

Simulating Bubble Plumes from Breaking Waves with a Forced-Air Venturi

NASA Astrophysics Data System (ADS)

Long, M. S.; Keene, W. C.; Maben, J. R.; Chang, R. Y. W.; Duplessis, P.; Kieber, D. J.; Beaupre, S. R.; Frossard, A. A.; Kinsey, J. D.; Zhu, Y.; Lu, X.; Bisgrove, J.

2017-12-01

It has been hypothesized that the size distribution of bubbles in subsurface seawater is a major factor that modulates the corresponding size distribution of primary marine aerosol (PMA) generated when those bubbles burst at the air-water interface. A primary physical control of the bubble size distribution produced by wave breaking is the associated turbulence that disintegrates larger bubbles into smaller ones. This leads to two characteristic features of bubble size distributions: (1) the Hinze scale which reflects a bubble size above which disintegration is possible based on turbulence intensity and (2) the slopes of log-linear regressions of the size distribution on either side of the Hinze scale that indicate the state of plume evolution or age. A Venturi with tunable seawater and forced air flow rates was designed and deployed in an artificial PMA generator to produce bubble plumes representative of breaking waves. This approach provides direct control of turbulence intensity and, thus, the resulting bubble size distribution characterizable by observations of the Hinze scale and the simulated plume age over a range of known air detrainment rates. Evaluation of performance in different seawater types over the western North Atlantic demonstrated that the Venturi produced bubble plumes with parameter values that bracket the range of those observed in laboratory and field experiments. Specifically, the seawater flow rate modulated the value of the Hinze scale while the forced-air flow rate modulated the plume age parameters. Results indicate that the size distribution of sub-surface bubbles within the generator did not significantly modulate the corresponding number size distribution of PMA produced via bubble bursting.

A laser-induced pulsed water jet for layer-selective submucosal dissection of the esophagus

PubMed Central

Sato, C; Yamada, M; Nakagawa, A; Yamamoto, H; Fujishima, F; Tominaga, T; Satomi, S; Ohuchi, N

2016-01-01

Background and aims: Conventional water jet devices have been used for injecting fluid to lift up lesions during endoscopic submucosal dissection or endoscopic mucosal resection procedures. However, these devices cannot dissect the submucosal layer effectively. Here we aim to elucidate the dissection capability of a laser-induced pulsed water jet and to clarify the mechanism of dissection with layer selectivity. Materials (Subjects) and methods: Pulsed water jets were ejected from a stainless nozzle by accelerating saline using the energy of a pulsed holmium: yttrium-aluminum-garnet laser. The impact force (strength) of the jet was evaluated using a force meter. Injection of the pulsed jet into the submucosal layer was documented by high-speed imaging. The physical properties of the swine esophagus were evaluated by measuring the breaking strength. Submucosal dissection of the swine esophagus was performed and the resection bed was evaluated histologically. Results: Submucosal dissection of the esophagus was accomplished at an impact force of 1.11–1.47 N/pulse (laser energy: 1.1–1.5 J/pulse; standoff distance: 60 mm). Histological specimens showed clear dissection at the submucosal layer without thermal injury. The mean static breaking strength of the submucosa (0.11 ± 0.04 MPa) was significantly lower than that of the mucosa (1.32 ± 0.18 MPa), and propria muscle (1.45 ± 0.16 MPa). Conclusions: The pulsed water jet device showed potential for achieving selective submucosal dissection. It could achieve mucosal, submucosal, and muscle layer selectivity owing to the varied breaking strengths. PMID:27853343

How to best smash a snail: the effect of tooth shape on crushing load

PubMed Central

Crofts, S. B.; Summers, A. P.

2014-01-01

Organisms that are durophagous, hard prey consumers, have a diversity of tooth forms. To determine why we see this variation, we tested whether some tooth forms break shells better than others. We measured the force needed with three series of aluminium tooth models, which varied in concavity and the morphology of a stress concentrating cusp, to break a shell. We created functionally identical copies of two intertidal snail shells: the thicker shelled Nucella ostrina and the more ornamented Nucella lamellosa using a three-dimensional printer. In this way, we reduced variation in material properties between test shells, allowing us to test only the interaction of the experimental teeth with the two shell morphologies. We found that for all tooth shapes, thicker shells are harder to break than the thinner shells and that increased ornamentation has no discernible effect. Our results show that for both shell morphologies, domed and flat teeth break shells better than cupped teeth, and teeth with tall or skinny cusps break shells best. While our results indicate that there is an ideal tooth form for shell breaking, we do not see this shape in nature. This suggests a probable trade-off between tooth function and the structural integrity of the tooth. PMID:24430124

Gravity brake

DOEpatents

Lujan, Richard E.

2001-01-01

A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

Association of spinal deformity and pelvic tilt with gait asymmetry in adolescent idiopathic scoliosis patients: Investigation of ground reaction force.

PubMed

Park, Yang Sun; Lim, Young Tae; Koh, Kyung; Kim, Jong Moon; Kwon, Hyun Joon; Yang, Ji Seung; Shim, Jae Kun

2016-07-01

Adolescent idiopathic scoliosis is a prevalent orthopedic problem in children ages 10 to 16years. Although genetic, physiological and biomechanical factors are considered to contribute to the onset and progression of adolescent idiopathic scoliosis, the underlying mechanisms are not yet clear. The purpose of this study was to investigate the association between spinal deformity and inter-leg ground reaction force asymmetry during walking in adolescent idiopathic scoliosis patients. Fourteen patients (3 males and 11 females) participated in this study. Maximum Cobb's angle, adjusted Cobb's angle, and pelvic tilt were calculated from X-ray images. Asymmetry indices between legs were also calculated from ground reaction force magnitude and time variables from their preferred speed walking. Pearson coefficients of correlation were used to investigate associations of asymmetry indices with angle variables. Asymmetry indices of ground reaction force magnitudes positively correlated with adjusted Cobb's angle and maximum Cobb's angle mainly during the peak of braking phase, average of braking phase, while asymmetry indices of ground reaction force time variables showed no significant correlation with adjusted or maximum Cobb's angle. In contrast, asymmetry indices of ground reaction force time variables positively correlated with pelvic tilt during stance phase. We concluded that the spinal deformity of adolescent idiopathic scoliosis patients estimated using the maximum and adjusted Cobb's angles is generally associated with greater asymmetry of ground reaction force magnitudes in walking, while the pelvic tilt is associated with the greater asymmetry of ground reaction force time variables. Copyright © 2016 Elsevier Ltd. All rights reserved.

Anisotropic mechanoresponse of energetic crystallites: a quantum molecular dynamics study of nano-collision

NASA Astrophysics Data System (ADS)

Li, Ying; Kalia, Rajiv K.; Misawa, Masaaki; Nakano, Aiichiro; Nomura, Ken-Ichi; Shimamura, Kohei; Shimojo, Fuyuki; Vashishta, Priya

2016-05-01

At the nanoscale, chemistry can happen quite differently due to mechanical forces selectively breaking the chemical bonds of materials. The interaction between chemistry and mechanical forces can be classified as mechanochemistry. An example of archetypal mechanochemistry occurs at the nanoscale in anisotropic detonating of a broad class of layered energetic molecular crystals bonded by inter-layer van der Waals (vdW) interactions. Here, we introduce an ab initio study of the collision, in which quantum molecular dynamic simulations of binary collisions between energetic vdW crystallites, TATB molecules, reveal atomistic mechanisms of anisotropic shock sensitivity. The highly sensitive lateral collision was found to originate from the twisting and bending to breaking of nitro-groups mediated by strong intra-layer hydrogen bonds. This causes the closing of the electronic energy gap due to an inverse Jahn-Teller effect. On the other hand, the insensitive collisions normal to multilayers are accomplished by more delocalized molecular deformations mediated by inter-layer interactions. Our nano-collision studies provide a much needed atomistic understanding for the rational design of insensitive energetic nanomaterials and the detonation synthesis of novel nanomaterials.At the nanoscale, chemistry can happen quite differently due to mechanical forces selectively breaking the chemical bonds of materials. The interaction between chemistry and mechanical forces can be classified as mechanochemistry. An example of archetypal mechanochemistry occurs at the nanoscale in anisotropic detonating of a broad class of layered energetic molecular crystals bonded by inter-layer van der Waals (vdW) interactions. Here, we introduce an ab initio study of the collision, in which quantum molecular dynamic simulations of binary collisions between energetic vdW crystallites, TATB molecules, reveal atomistic mechanisms of anisotropic shock sensitivity. The highly sensitive lateral collision was found to originate from the twisting and bending to breaking of nitro-groups mediated by strong intra-layer hydrogen bonds. This causes the closing of the electronic energy gap due to an inverse Jahn-Teller effect. On the other hand, the insensitive collisions normal to multilayers are accomplished by more delocalized molecular deformations mediated by inter-layer interactions. Our nano-collision studies provide a much needed atomistic understanding for the rational design of insensitive energetic nanomaterials and the detonation synthesis of novel nanomaterials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08769d

Parenchymal asbestosis due to primary asbestos exposure among ship-breaking workers: report of the first cases from Bangladesh.

PubMed

Muralidhar, Venkiteswaran; Ahasan, Md Faizul; Khan, Ahad Mahmud

2017-11-03

We report for the first time asbestosis among ship-breaking workers of Sitakunda in Bangladesh who were exposed to asbestos during ship-based and beach-based operations for at least 10 years. Asbestosis was present among 35% of workers. Years of work (>20) and forced vital capacity (<80% of predicted) were significantly associated with the disease. Currently, global ship-breaking operations are mainly concentrated in the Indian subcontinent, and Bangladesh has the majority share. Ninety per cent of domestic steel is produced in the ship-breaking operations in Bangladesh and is an important contributor to the economy. It also gives employment to more than 100 000 people. It is imperative to medically check up all the workers for benign and malignant diseases causally related to asbestos among these vulnerable population of workers. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Numerical study of wind over breaking waves and generation of spume droplets

NASA Astrophysics Data System (ADS)

Yang, Zixuan; Tang, Shuai; Dong, Yu-Hong; Shen, Lian

2017-11-01

We present direct numerical simulation (DNS) results on wind over breaking waves. The air and water are simulated as a coherent system. The air-water interface is captured using a coupled level-set and volume-of-fluid method. The initial condition for the simulation is fully-developed wind turbulence over strongly-forced steep waves. Because wave breaking is an unsteady process, we use ensemble averaging of a large number of runs to obtain turbulence statistics. The generation and transport of spume droplets during wave breaking is also simulated. The trajectories of sea spray droplets are tracked using a Lagrangian particle tracking method. The generation of droplets is captured using a kinematic criterion based on the relative velocity of fluid particles of water with respect to the wave phase speed. From the simulation, we observe that the wave plunging generates a large vortex in air, which makes an important contribution to the suspension of sea spray droplets.

United States Air Force Graduate Student Research Program for 1990. Program Management Report

DTIC Science & Technology

1992-06-05

were extensively studied using pencil lead breaks in a center notch. For the fatigue studies center crack samples of 2024 - T351 aluminum were used...Research Program (SFRP) provides opportunities for research in the physical sciences, engineering, and life sciences. The program has been effective ...positive effect on teaching. (WRDC/FDL) Several mentioned the opportunity for introduction to research interests of the Air Force and the opportunity to work

Low Frequency Ocean Ambient Noise: Measurements and Theory,

DTIC Science & Technology

1987-12-14

entrained gas bubbles which result from wave breaking and which are forced by intense velocity of the gravity-capil- lary waves. For wind speeds with a...ternal force acting on the volume and has a dipole character. These two terms could be important in the incorporation of entrained bubble oscil- lation and...Applied Research Lab, Penn. State Univ., State College, PA 16804 Mellen, R.H., 1987: private communication. Minnaert, M., 1933: ’ Musical Air-Bubbles

Perception Is Reality: Special Operations Forces In the Gray Zone

DTIC Science & Technology

2016-06-01

politics, policy, bureaucracy, and military action is complex, for simplicity this research assumes all players are rational actors who will maximize...Gray Zone—the primary tool being Special Operation Forces (SOF). This research finds that policymakers and others outside of SOF have often misapplied...effect on the ability of the Unites States to reach its foreign policy goals. This research analyzes U.S. SOF employment in the Gray Zone, breaking down

Breaking the Change Barrier: A 40 Year Analysis of Air Force Pilot Retention Solutions

DTIC Science & Technology

national defense. A problem/solution research methodology using the organizational management theory of path dependence explored the implications of the...exodus is to start the incentive process earlier in the career and prior to the final decision to separate. Path dependent analysis indicates all prior... incentive options and personal involvement in the overall process. The Air Force can annually budget and forecast incentive requirements and personnel

Efficiency and Safety: The Best Time to Valve a Plaster Cast.

PubMed

Steiner, Samuel R H; Gendi, Kirollos; Halanski, Matthew A; Noonan, Kenneth J

2018-04-18

The act of applying, univalving, and spreading a plaster cast to accommodate swelling is commonly performed; however, cast saws can cause thermal and/or abrasive injury to the patient. This study aims to identify the optimal time to valve a plaster cast so as to reduce the risk of cast-saw injury and increase spreading efficiency. Plaster casts were applied to life-sized pediatric models and were univalved at set-times of 5, 8, 12, or 25 minutes. Outcome measures included average and maximum force applied during univalving, blade-to-skin touches, cut time, force needed to spread, number of spread attempts, spread completeness, spread distance, saw blade temperature, and skin surface temperature. Casts allowed to set for ≥12 minutes had significantly fewer blade-to-skin touches compared with casts that set for <12 minutes (p < 0.001). For average and maximum saw blade force, no significant difference was observed between individual set-times. However, in a comparison of the shorter group (<12 minutes) and the longer group (≥12 minutes), the longer group had a higher average force (p = 0.009) but a lower maximum force (p = 0.036). The average temperature of the saw blade did not vary between groups. The maximum force needed to "pop," or spread, the cast was greater for the 5-minute and 8-minute set-times. Despite requiring more force to spread the cast, 0% of attempts at 5 minutes and 54% of attempts at 8 minutes were successful in completely spreading the cast, whereas 100% of attempts at 12 and 25 minutes were successful. The spread distance was greatest for the 12-minute set-time at 5.7 mm. Allowing casts to set for 12 minutes is associated with decreased blade-to-skin contact, less maximum force used with the saw blade, and a more effective spread. Adherence to the 12-minute interval could allow for fewer cast-saw injuries and more effective spreading.

Modeling the Transport and Radiative Forcing of Taklimakan Dust over the Tibetan Plateau: A case study in the summer of 2006

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

Chen, Siyu; Huang, J.; Zhao, Chun

2013-01-30

The Weather Research and Forecasting model with chemistry (WRF-Chem) is used to investigate an intense dust storm event during 26 to 30 July 2006 that originated over the Taklimakan Desert (TD) and transported to the northern slope of Tibetan Plateau (TP). The dust storm is initiated by the approach of a strong cold frontal system over the TD. In summer, the meridional transport of TD dust to the TP is favored by the thermal effect of the TP and the weakening of the East Asian westerly winds. During this dust storm, the transport of TD dust over the TP ismore » further enhanced by the passage of the cold front. As a result, TD dust breaks through the planetary boundary layer and extends to the upper troposphere over the northern TP. TD dust flux arrived at the TP with a value of 6.6 Gg/day in this 5 day event but decays quickly during the southward migration over the TP due to dry deposition. The simulations show that TD dust cools the atmosphere near the surface and heats the atmosphere above with a maximum heating rate of 0.11 K day-1 at ~7 km over the TP. The event-averaged net radiative forcings of TD dust over the TP are -3.97, 1.61, and -5.58 Wm-2 at the top of the atmosphere (TOA), in the atmosphere, and at the surface, respectively. The promising performance of WRF-Chem in simulating dust and its radiative forcing provides confidence for use in further investigation of climatic impact of TD dust over the TP.« less

An Experimental Study Comparing Droplet Production by a Strong Plunging and a Weak Spilling Breaking Water Waves

NASA Astrophysics Data System (ADS)

Erinin, Martin; Wang, Dan; Towle, David; Liu, Xinan; Duncan, James

2017-11-01

In this study, the production of droplets by two mechanically generated breaking water waves is investigated in a wave tank. A strong plunging breaker and weak spilling breaker are generated repeatedly with a programmable wave maker by using two dispersively focused wave packets with the same wave maker motion profile shape (average frequency 1.15 Hz) and two overall amplitude factors. The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a high speed (650 Hz) cinematic digital in-line holographic system positioned at various locations along a horizontal plane that is 1 cm above the maximum wave crest height. The measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d >100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the two breaking waves is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. The support of the National Science Foundation under Grant OCE0751853 from the Division of Ocean Sciences is gratefully acknowledged.

Evaluation of gait kinetics in puppies with coxofemoral joint laxity

PubMed Central

Lopez, Mandi J.; Quinn, Margaret M.; Markel, Mark D.

2007-01-01

Objective To characterize ground reaction forces (GRFs) and determine whether there were correlations between forces and passive coxofemoral joint laxity in puppies. Animals Fifty-one 16-week-old hound-breed dogs. Procedure Force-plate gait evaluation and distraction radiographic imaging were performed. Ground reaction forces evaluated included x (mediolateral), y (craniocaudal breaking and propulsion), and z (vertical) peak force and impulse. Z-plane limb loading and unloading rates, loading interval, and weight distribution and y-plane stance time breaking and propulsion percentages were calculated. One-way ANOVA with the Duncan multiple range test was used to evaluate differences in gait variables among limbs. The relationships of left, right, highest, and mean distraction index (DI) with individual limb data of each dog were evaluated with the Spearman rank correlation. Left and right DIs were compared by means of linear regression analysis. Results Mean ± SEM DI was 0.67 ± 0.02. Left and right DIs were strongly correlated, but there were no significant relationships between DIs and gait variables. Most fore- and hind limb gait variables differed significantly, whereas paired fore- and hind limb gait variables did not. Asymmetry was most pronounced in the x- and y-planes. Conclusions and Clinical Relevance GRFs were consistent with those of clinically normal mature dogs, supporting an absence of association between GRF and DI in young dogs. The GRFs and elucidation of the relationship between GRFs and DI may be useful for future studies in immature dogs. PMID:16454627

A model for wave control on coral breakage and species distribution in the Hawaiian Islands

USGS Publications Warehouse

Storlazzi, C.D.; Brown, E.K.; Field, M.E.; Rodgers, K.; Jokiel, P.L.

2005-01-01

The fringing reef off southern Molokai, Hawaii, is currently being studied as part of a multi-disciplinary project led by the US Geological Survey. As part of this study, modeling and field observations were utilized to help understand the physical controls on reef morphology and the distribution of different coral species. A model was developed that calculates wave-induced hydrodynamic forces on corals of a specific form and mechanical strength. From these calculations, the wave conditions under which specific species of corals would either be stable or would break due to the imposed wave-induced forces were determined. By combining this hydrodynamic force-balance model with various wave model output for different oceanographic conditions experienced in the study area, we were able to map the locations where specific coral species should be stable (not subject to frequent breakage) in the study area. The combined model output was then compared with data on coral species distribution and coral cover at 12 sites along Molokai's south shore. Observations and modeling suggest that the transition from one coral species to another may occur when the ratio of the coral colony's mechanical strengths to the applied (wave-induced) forces may be as great as 5:1, and not less than 1:1 when corals would break. This implies that coral colony's mechanical strength and wave-induced forces may be important in defining gross coral community structure over large (orders of 10's of meters) spatial scales. ?? Springer-Verlag 2004.

[Ex Vivo Testing of Mechanical Properties of Canine Metacarpal/Metatarsal Bones after Simulated Implant Removal].

PubMed

Srnec, R; Fedorová, P; Pěnčík, J; Vojtová, L; Sedlinská, M; Nečas, A

2016-01-01

PURPOSE OF THE STUDY In a long-term perspective, it is better to remove implants after fracture healing. However, subsequent full or excessive loading of an extremity may result in refracture, and the bone with holes after screw removal may present a site with predilection for this. The aim of the study was to find ways of how to decrease risk factors for refracture in such a case. This involved support to the mechanical properties of a bone during its remodelling until defects following implant removal are repaired, using a material tolerated by bone tissue and easy to apply. It also included an assessment of the mechanical properties of a bone after filling the holes in it with a newly developed biodegradable polymer-composite gel ("bone paste"). The composite also has a prospect of being used to repair bony defects produced by pathological processes. MATERIAL AND METHODS Experiments were carried out on intact weight-bearing small bones in dogs. A total of 27 specimens of metacarpal/metatarsal bones were used for ex vivo testing. They were divided into three groups: K1 (n = 9) control undamaged bones; K2 (n = 9) control bones with iatrogenic damage simulating holes left after cortical screw removal; EXP (n = 9) experimental specimens in which simulated holes in bone were filled with the biodegradable self-hardening composite. The bone specimens were subjected to three-point bending in the caudocranial direction by a force acting parallel to the direction of drilling in their middiaphyses. The value of maximum load achieved (N) and the corresponding value of a vertical displacement (mm) were recorded in each specimen, then compared and statistically evaluated. RESULTS On application of a maximum load (N), all bone specimens broke in the mid-part of their diaphyses. In group K1 the average maximum force of 595.6 ± 79.5 N was needed to break the bone; in group K2 it was 347.6 ± 58.6 N; and in group EXP it was 458.3 ± 102.7 N. The groups with damaged bones, K2 and EXP, were compared and the difference was found to be statistically significant (p ≤ 0.05). CONCLUSIONS The recently developed biodegradable polymer-composite gel is easy and quick to apply to any defect, regardless of its shape, in bone tissue. The ex vivo mechanical tests on canine short bones showed that the composite applied to defects, which simulated holes left after screw removal, provided sufficient mechanical support to the bone architecture. The results of measuring maximum loading forces were statistically significant. However, before the composite could be recommended for use in veterinary or human medical practice, thorough pre-clinical studies will be required. fracture fixation, mechanical testing, bone plate, cortical screw, refracture.

Variability and Dynamics of the Yucatan Upwelling: High-Resolution Simulations

NASA Astrophysics Data System (ADS)

Jouanno, J.; Pallàs-Sanz, E.; Sheinbaum, J.

2018-02-01

The Yucatan shelf in the southern Gulf of Mexico is under the influence of an upwelling that uplifts cool and nutrient rich waters over the continental shelf. The analysis of a set of high-resolution (Δx = Δy ≈ 2.8 km) simulations of the Gulf of Mexico shows two dominant modes of variability of the Yucatan upwelling system: (1) a low-frequency mode related to variations in position and intensity of the Loop Current along the shelf, with upwelling intensified when the Loop Current is strong and approaches to the Yucatan shelf break and (2) a high-frequency mode with peak frequency in the 6-10 days band related to wind-forced coastal waves that force vertical velocities along the eastern Yucatan shelf break. To first order, the strength and position of the Loop Current are found to control the intensity of the upwelling, but we show that high-frequency winds also contribute (˜17%) to a net input of cool waters (<22.5°C) on the Yucatan shelf. Finally, although more observational studies are needed to corroborate the topographic character of the Yucatan upwelling system, this study reveals the key role played by a notch along the Yucatan shelf break: a sensitivity simulation without the notch shows a 55% reduction of the upwelling.

Characterizing Droplet Formation from Non-Linear Slosh in a Propellant Tank

NASA Technical Reports Server (NTRS)

Brodnick, Jacob; Yang, Hong; West, Jeffrey

2015-01-01

The Fluid Dynamics Branch (ER42) at the Marshall Space Flight Center (MSFC) was tasked with characterizing the formation and evolution of liquid droplets resulting from nonlinear propellant slosh in a storage tank. Lateral excitation of propellant tanks can produce high amplitude nonlinear slosh waves through large amplitude excitations and or excitation frequencies near a resonance frequency of the tank. The high amplitude slosh waves become breaking waves upon attaining a certain amplitude or encountering a contracting geometry such as the upper dome section of a spherical tank. Inherent perturbations in the thinning regions of breaking waves result in alternating regions of high and low pressure within the fluid. Droplets form once the force from the local pressure differential becomes larger than the force maintaining the fluid interface shape due to surface tension. Droplets released from breaking waves in a pressurized tank may lead to ullage collapse given the appropriate conditions due to the increased liquid surface area and thus heat transfer between the fluids. The goal of this project is to create an engineering model that describes droplet formation as a function of propellant slosh for use in the evaluation of ullage collapse during a sloshing event. The Volume of Fluid (VOF) model in the production level Computational Fluid Dynamics (CFD) code Loci-Stream was used to predict droplet formation from breaking waves with realistic surface tension characteristics. Various excitation frequencies and amplitudes were investigated at multiple fill levels for a single storage tank to create the engineering model of droplet formation from lateral propellant slosh.

A metabolic basis for impaired muscle force production and neuromuscular compensation during sprint cycling.

PubMed

Bundle, Matthew W; Ernst, Carrie L; Bellizzi, Matthew J; Wright, Seth; Weyand, Peter G

2006-11-01

For both different individuals and modes of locomotion, the external forces determining all-out sprinting performances fall predictably with effort duration from the burst maximums attained for 3 s to those that can be supported aerobically as trial durations extend to roughly 300 s. The common time course of this relationship suggests a metabolic basis for the decrements in the force applied to the environment. However, the mechanical and neuromuscular responses to impaired force production (i.e., muscle fatigue) are generally considered in relation to fractions of the maximum force available, or the maximum voluntary contraction (MVC). We hypothesized that these duration-dependent decrements in external force application result from a reliance on anaerobic metabolism for force production rather than the absolute force produced. We tested this idea by examining neuromuscular activity during two modes of sprint cycling with similar external force requirements but differing aerobic and anaerobic contributions to force production: one- and two-legged cycling. In agreement with previous studies, we found greater peak per leg aerobic metabolic rates [59% (+/-6 SD)] and pedal forces at VO2 peak [30% (+/-9)] during one- vs. two-legged cycling. We also determined downstroke pedal forces and neuromuscular activity by surface electromyography during 15 to 19 all-out constant load sprints lasting from 12 to 400 s for both modes of cycling. In support of our hypothesis, we found that the greater reliance on anaerobic metabolism for force production induced compensatory muscle recruitment at lower pedal forces during two- vs. one-legged sprint cycling. We conclude that impaired muscle force production and compensatory neuromuscular activity during sprinting are triggered by a reliance on anaerobic metabolism for force production.

Mechanical model for a collagen fibril pair in extracellular matrix.

PubMed

Chan, Yue; Cox, Grant M; Haverkamp, Richard G; Hill, James M

2009-04-01

In this paper, we model the mechanics of a collagen pair in the connective tissue extracellular matrix that exists in abundance throughout animals, including the human body. This connective tissue comprises repeated units of two main structures, namely collagens as well as axial, parallel and regular anionic glycosaminoglycan between collagens. The collagen fibril can be modeled by Hooke's law whereas anionic glycosaminoglycan behaves more like a rubber-band rod and as such can be better modeled by the worm-like chain model. While both computer simulations and continuum mechanics models have been investigated for the behavior of this connective tissue typically, authors either assume a simple form of the molecular potential energy or entirely ignore the microscopic structure of the connective tissue. Here, we apply basic physical methodologies and simple applied mathematical modeling techniques to describe the collagen pair quantitatively. We found that the growth of fibrils was intimately related to the maximum length of the anionic glycosaminoglycan and the relative displacement of two adjacent fibrils, which in return was closely related to the effectiveness of anionic glycosaminoglycan in transmitting forces between fibrils. These reveal the importance of the anionic glycosaminoglycan in maintaining the structural shape of the connective tissue extracellular matrix and eventually the shape modulus of human tissues. We also found that some macroscopic properties, like the maximum molecular energy and the breaking fraction of the collagen, were also related to the microscopic characteristics of the anionic glycosaminoglycan.

Analytical solution of the problem of acceleration of cargo by a bridge crane with constant acceleration at elimination of swings of a cargo rope

NASA Astrophysics Data System (ADS)

Korytov, M. S.; Shcherbakov, V. S.; Titenko, V. V.

2018-01-01

Limitation of the swing of the bridge crane cargo rope is a matter of urgency, as it can significantly improve the efficiency and safety of the work performed. In order to completely dampen the pendulum swing after the break-up of a bridge or a bridge-crane freight cart to maximum speed, it is necessary, in the normal repulsion control of the electric motor, to split the process of dispersion into a minimum of three gaps. For a dynamic system of swinging of a bridge crane on a flexible cable hanger in a separate vertical plane, an analytical solution was obtained to determine the temporal dependence of the cargo rope angle relative to the gravitational vertical when the cargo suspension point moves with constant acceleration. The resulting analytical dependence of the cargo rope angle and its first derivative can break the process of dispersing the cargo suspension point into three stages of dispersal and braking with various accelerations and enter maximum speed of movement of the cargo suspension point. In doing so, the condition of eliminating the swings of the cargo rope relative to the gravitational vertical is fulfilled. Provides examples of the maximum speed output constraints-to-time when removing the rope swing.

A Comparison of 2 Current-Issue Army Boots, 5 Prototype Military Boots, and 5 Commercial Hiking Boots: Performance, Efficiency, Biomechanics, Comfort and Injury

DTIC Science & Technology

1999-11-01

Maximum force (N) on the ankle, knee and hip while walking at 3.5 mph 51 23. Maximum heel- strike force (N) while walking at 3.5 mph ^.ർ 24...to first force peak while running at 6.5 mph ’.""."..62 34. Variables relating to force low point between the heel- strike and push-off peak...was lower peak deceleration and lower peak pressure at the heel than at the forefoot . In the second phase of their research, Hamill and Bensel (7, 8

The Decompression Sickness and Venous Gas Emboli Consequences of Air Breaks During 100% Oxygen Prebreathe

NASA Technical Reports Server (NTRS)

Conkin, J.; Gernhardt, M. L.; Powell, M. R.

2004-01-01

Not enough is known about the increased risk of hypobaric decompression sickness (DCS) and production of venous (VGE) and arterial (AGE) gas emboli following an air break in an otherwise normal 100% resting oxygen (O2) prebreathe (PB), and certainly a break in PB when exercise is used to accelerate nitrogen (N2) elimination from the tissues. Current Aeromedical Flight Rules at the Johnson Space Center about additional PB payback times are untested, possibly too conservative, and therefore not optimized for operational use. A 10 min air break at 90 min into a 120 min PB that includes initial dual-cycle ergometry for 10 min will show a measurable increase in the risk of DCS and VGE after ascent to 4.3 psia compared to a 10 min break at 15 min into the PB, or when there is no break in PB. Data collection with humans begins in 2005, but here we first evaluate the hypothesis using three models of tissue N2 kinetics: Model I is a simple single half-time compartment exponential model, Model II is a three compartment half-time exponential model, and Model III is a variable half-time compartment model where the percentage of maximum O2 consumption for the subject during dual-cycle ergometry exercise defines the half-time compartment. Model I with large rate constants to simulate an exercise effect always showed a late break in PB had the greatest consequence. Model II showed an early break had the greatest consequence. Model III showed there was no difference between early or late break in exercise PB. Only one of these outcomes will be observed when humans are tested. Our results will favor one of these models, and so advance our understanding of tissue N2 kinetics, and of altitude DCS after an air break in PB.

Intraplate compressional deformation in West-Congo and the Congo basin: related to ridge-puch from the South Atlantic spreading ridge?

NASA Astrophysics Data System (ADS)

Delvaux, Damien; Everaerts, Michel; Kongota Isasi, Elvis; Ganza Bamulezi, Gloire

2016-04-01

After the break-up and separation of South America from Africa and the initiation of the South-Atlantic mid-oceanic ridge in the Albian, at about 120 Ma, ridge-push forces started to build-up in the oceanic lithosphere and were transmitted to the adjacent continental plates. This is particularly well expressed in the passive margin and continental interior of Central Africa. According to the relations of Wiens and Stein (1985) between ridge-push forces and basal drag in function of the lithospheric age of oceanic plates, the deviatoric stress reaches a compressional maximum between 50 and 100, Ma after the initiation of the spreading ridge, so broadly corresponding to the Paleocene in this case (~70-20 Ma). Earthquake focal mechanism data show that the West-Congo margin and a large part of the Congo basin are still currently under compressional stresses with an horizontal compression parallel to the direction of the active transform fracture zones. We studied the fracture network along the Congo River in Kinshasa and Brazzaville which affect Cambrian sandstones and probably also the late Cretaceous-Paleocene sediments. Their brittle tectonic evolution is compatible with the buildup of ridge-push forces related to the South-Atlantic opening. Further inland, low-angle reverse faults are found affecting Jurassic to Middle Cretaceous cores from the Samba borehole in the Congo basin and strike-slip movements are recorded as a second brittle phase in the Permian cores of the Dekese well, at the southern margin of the Congo basin. An analysis of the topography and river network of the Congo basin show the development of low-amplitude (50-100 m) long wavelengths (100-300 km) undulations that can be interpreted as lithospheric buckling in response to the compressional intraplate stress field generated by the Mid-Atlantic ridge-push. Wiens, D.A., Stein, S., 1985. Implications of oceanic intraplate seismicity for plate stresses, driving forces and theology. Tectonophysics 1166, 143-162.

Gas transfer under high wind and its dependence on wave breaking and sea state

NASA Astrophysics Data System (ADS)

Brumer, Sophia; Zappa, Christopher; Fairall, Christopher; Blomquist, Byron; Brooks, Ian; Yang, Mingxi

2016-04-01

Quantifying greenhouse gas fluxes on regional and global scales relies on parameterizations of the gas transfer velocity K. To first order, K is dictated by wind speed (U) and is typically parameterized as a non-linear functions of U. There is however a large spread in K predicted by the traditional parameterizations at high wind speed. This is because a large variety of environmental forcing and processes (Wind, Currents, Rain, Waves, Breaking, Surfactants, Fetch) actually influence K and wind speed alone cannot capture the variability of air-water gas exchange. At high wind speed especially, breaking waves become a key factor to take into account when estimating gas fluxes. The High Wind Gas exchange Study (HiWinGS) presents the unique opportunity to gain new insights on this poorly understood aspects of air-sea interaction under high winds. The HiWinGS cruise took place in the North Atlantic during October and November 2013. Wind speeds exceeded 15 m s-1 25% of the time, including 48 hrs with U10 > 20 m s-1. Continuous measurements of turbulent fluxes of heat, momentum, and gas (CO2, DMS, acetone and methanol) were taken from the bow of the R/V Knorr. The wave field was sampled by a wave rider buoy and breaking events were tracked in visible imagery was acquired from the port and starboard side of the flying bridge during daylight hours at 20Hz. Taking advantage of the range of physical forcing and wave conditions sampled during HiWinGS, we test existing parameterizations and explore ways of better constraining K based on whitecap coverage, sea state and breaking statistics contrasting pure windseas to swell dominated periods. We distinguish between windseas and swell based on a separation algorithm applied to directional wave spectra for mixed seas, system alignment is considered when interpreting results. The four gases sampled during HiWinGS ranged from being mostly waterside controlled to almost entirely airside controlled. While bubble-mediated transfer appears to be small for moderately soluble gases like DMS, the importance of wave breaking turbulence transport has yet to be determined for all gases regardless of their solubility. This will be addressed by correlating measured K to estimates of active whitecap fraction (WA) and turbulent kinetic energy dissipation rate (ɛ). WA and ɛ are estimated from moments of the breaking crest length distribution derived from the imagery, focusing on young seas, when it is likely that large-scale breaking waves (i.e., whitecapping) will dominate the ɛ.

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2012 CFR

2012-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2013 CFR

2013-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2014 CFR

2014-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2011 CFR

2011-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

Estimation of additive forces and moments for supersonic inlets

NASA Technical Reports Server (NTRS)

Perkins, Stanley C., Jr.; Dillenius, Marnix F. E.

1991-01-01

A technique for estimating the additive forces and moments associated with supersonic, external compression inlets as a function of mass flow ratio has been developed. The technique makes use of a low order supersonic paneling method for calculating minimum additive forces at maximum mass flow conditions. A linear relationship between the minimum additive forces and the maximum values for fully blocked flow is employed to obtain the additive forces at a specified mass flow ratio. The method is applicable to two-dimensional inlets at zero or nonzero angle of attack, and to axisymmetric inlets at zero angle of attack. Comparisons with limited available additive drag data indicate fair to good agreement.

Finger tapping ability in healthy elderly and young adults.

PubMed

Aoki, Tomoko; Fukuoka, Yoshiyuki

2010-03-01

The maximum isometric force production capacity of the fingers decreases with age. However, little information is available on age-related changes in dynamic motor capacity of individual fingers. The purpose of this study was to compare the dynamic motor function of individual fingers between elderly and young adults using rapid single-finger and double-finger tapping. Fourteen elderly and 14 young adults performed maximum frequency tapping by the index, middle, ring, or little finger (single-finger tapping) and with alternate movements of the index-middle, middle-ring, or ring-little finger-pair (double-finger tapping). The maximum pinch force between the thumb and each finger, tactile sensitivity of each fingertip, and time taken to complete a pegboard test were also measured. Compared with young subjects, the older subjects had significantly slower tapping rates in all fingers and finger-pairs in the tapping tasks. The age-related decline was also observed in the tactile sensitivities of all fingers and in the pegboard test. However, there was no group difference in the pinch force of any finger. The tapping rate of each finger did not correlate with the pinch force or tactile sensitivity for the corresponding finger in the elderly subjects. Maximum rate of finger tapping was lower in the elderly adults compared with the young adults. The decline of finger tapping ability in elderly adults seems to be less affected by their maximum force production capacities of the fingers as well as tactile sensitivities at the tips of the fingers.

Verbs in the lexicon: Why is hitting easier than breaking?

PubMed

McKoon, Gail; Love, Jessica

2011-11-01

Adult speakers use verbs in syntactically appropriate ways. For example, they know implicitly that the boy hit at the fence is acceptable but the boy broke at the fence is not. We suggest that this knowledge is lexically encoded in semantic decompositions. The decomposition for break verbs (e.g. crack, smash) is hypothesized to be more complex than that for hit verbs (e.g. kick, kiss). Specifically, the decomposition of a break verb denotes that "an entity changes state as the result of some external force" whereas the decomposition for a hit verb denotes only that "an entity potentially comes in contact with another entity." In this article, verbs of the two types were compared in a lexical decision experiment - Experiment 1 - and they were compared in sentence comprehension experiments with transitive sentences (e.g. the car hit the bicycle and the car broke the bicycle) - Experiments 2 and 3. In Experiment 1, processing times were shorter for the hit than the break verbs and in Experiments 2 and 3, processing times were shorter for the hit sentences than the break sentences, results that are in accord with the complexities of the postulated semantic decompositions.

The Record Los Angeles Heat Event of September 2010: 1. Synoptic-Scale-Meso-β-Scale Analyses of Interactive Planetary Wave Breaking, Terrain- and Coastal-Induced Circulations

NASA Astrophysics Data System (ADS)

Kaplan, Michael L.; Tilley, Jeffrey S.; Hatchett, Benjamin J.; Smith, Craig M.; Walston, Joshua M.; Shourd, Kacie N.; Lewis, John M.

2017-10-01

On 27 September 2010 the Los Angeles Civic Center reached its all-time record maximum temperature of 45°C before 1330 local daylight time with several other regional stations observing all-time record breaking heat early in that afternoon. This record event is associated with a general circulation pattern predisposed to hemispheric wave breaking. Three days before the event, wave breaking organizes complex terrain- and coastal-induced processes that lead to isentropic surface folding into the Los Angeles Basin. The first wave break occurs over the western two thirds of North America leading to trough elongation across the southwestern U.S. Collocated with this trough is an isentropic potential vorticity filament that is the locus of a thermally indirect circulation central to warming and associated thickness increases and ridging westward across the Great Basin. In response to this circulation, two subsynoptic wave breaks are triggered along the Pacific coast. The isentropic potential vorticity filament is coupled to the breaking waves and the interaction produces a subsynoptic low-pressure center and a deep vortex aloft over the southeastern California desert. This coupling leads to advection of an elevated mixed layer over Point Conception the night before the record-breaking heat that creates a coastally trapped low-pressure area southwest of Los Angeles. The two low-pressure centers create a low-level pressure gradient and east-southeasterly jet directed offshore over the Los Angeles Basin by sunrise on 27 September. This allows the advection of low-level warm air from the inland terrain toward the coastally trapped disturbance and descending circulation resulting in record heating.

Inter-individual similarities and variations in muscle forces acting on the ankle joint during gait.

PubMed

Błażkiewicz, Michalina; Wiszomirska, Ida; Kaczmarczyk, Katarzyna; Naemi, Roozbeh; Wit, Andrzej

2017-10-01

Muscle forces acting over the ankle joint play an important role in the forward progression of the body during gait. Yet despite the importance of ankle muscle forces, direct in-vivo measurements are neither possible nor practical. This makes musculoskeletal simulation useful as an indirect technique to quantify the muscle forces at work during locomotion. The purpose of this study was to: 1) identify the maximum peaks of individual ankle muscle forces during gait; 2) investigate the order over which the muscles are sorted based on their maximum peak force. Three-dimensional kinematics and ground reaction forces were measured during the gait of 10 healthy subjects, and the data so obtained were input into the musculoskeletal model distributed with the OpenSim software. In all 10 individuals we observed that the soleus muscle generated the greatest strength both in dynamic (1856.1N) and isometric (3549N) conditions, followed by the gastrocnemius in dynamic conditions (1232.5N). For all other muscles, however, the sequence looks different across subjects, so the k-means clustering method was used to obtain one main order over which the muscles' peak-forces are sorted. The results indicate a common theme, with some variations in the maximum peaks of ankle muscle force across subjects. Copyright © 2017 Elsevier B.V. All rights reserved.

Ergonomic evaluation of a mechanical anastomotic stapler used by Japanese surgeons.

PubMed

Kono, Emiko; Tada, Mitsunori; Kouchi, Makiko; Endo, Yui; Tomizawa, Yasuko; Matsuo, Tomoko; Nomura, Sachiyo

2014-06-01

The satisfaction rating of currently available mechanical staplers for Japanese surgeons with small hands is low. To identify the issue, we examined the relationship of hand dimensions and grip force with the operation force of a mechanical circular stapler. Hand dimensions and grip force were measured in 113 Japanese surgeons (52 men and 61 women). We then evaluated the relationship between grip width and the operation force required to push the lever of the stapler, at three points on the lever, using a digital force gauge. The optimal grip width of the dominant hand was 62.5 ± 8.5 mm for men and 55.5 ± 5.9 mm for women (p < 0.001). The maximum grip force of the dominant hand was 44.2 ± 6.1 kg for men and 29.7 ± 4.5 kg for women (p < 0.001) and the maximum operation force required to push the lever 7.0, 45.0, and 73.0 mm from the end of the lever was 21.8, 28.6, and 42.4 kg, respectively. To our knowledge, this is the first ergonomic study of a surgical stapler to be conducted in Asia. Firing the stapler by gripping the proximal side of the lever is physically impossible for most Japanese women surgeons since the required operation force exceeds the maximum grip force, which probably accounts for the stress perceived by these women.

Biomechanical comparison of two intraoperative mobilization techniques for maxillary distraction osteogenesis: Down-fracture versus non-down-fracture.

PubMed

Yang, Lili; Suzuki, Eduardo Yugo; Suzuki, Boonsiva

2014-01-01

The purpose of this study was to compare the distraction forces and the biomechanical effects between two different intraoperative surgical procedures (down-fracture [DF] and non-DF [NDF]) for maxillary distraction osteogenesis. Eight patients were assigned into two groups according to the surgical procedure: DF, n = 6 versus NDF, n = 2. Lateral cephalograms taken preoperatively (T1), immediately after removal of the distraction device (T2), and after at least a 6 months follow-up period (T3) were analyzed. Assessment of distraction forces was performed during the distraction period. The Mann-Whitney U-test was used to compare the difference in the amount of advancement, the maximum distraction force and the amount of relapse. Although a significantly greater amount of maxillary movement was observed in the DF group (median 9.5 mm; minimum-maximum 7.9-14.1 mm) than in the NDF group (median 5.9 mm; minimum-maximum 4.4-7.6 mm), significantly lower maximum distraction forces were observed in the DF (median 16.4 N; minimum-maximum 15.1-24.6 N) than in the NDF (median 32.9 N; minimum-maximum 27.6-38.2 N) group. A significantly greater amount of dental anchorage loss was observed in the NDF group. Moreover, the amount of relapse observed in the NDF group was approximately 3.5 times greater than in the DF group. In this study, it seemed that, the use of the NDF procedure resulted in lower levels of maxillary mobility at the time of the maxillary distraction, consequently requiring greater amounts of force to advance the maxillary bone. Moreover, it also resulted in a reduced amount of maxillary movement, a greater amount of dental anchorage loss and poor treatment stability.

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces - A velocity-rate-controlled, pressure-bias-modulated system

NASA Technical Reports Server (NTRS)

Stubbs, S. M.; Tanner, J. A.

1976-01-01

During maximum braking the average ratio of drag-force friction coefficient developed by the antiskid system to maximum drag-force friction coefficient available at the tire/runway interface was higher on dry surfaces than on wet surfaces. The gross stopping power generated by the brake system on the dry surface was more than twice that obtained on the wet surfaces. With maximum braking applied, the average ratio of side-force friction coefficient developed by the tire under antiskid control to maximum side-force friction available at the tire/runway interface of a free-rolling yawed tire was shown to decrease with increasing yaw angle. Braking reduced the side-force friction coefficient on a dry surface by 75 percent as the wheel slip ratio was increased to 0.3; on a flooded surface the coefficient dropped to near zero for the same slip ratio. Locked wheel skids were observed when the tire encountered a runway surface transition from dry to flooded, due in part to the response time required for the system to sense abrupt changes in the runway friction; however, the antiskid system quickly responded by reducing brake pressure and cycling normally during the remainder of the run on the flooded surface.

53rd Annual Fuze Conference - Next Generation Fuzing - Maximum Advantage for the Warfighter

DTIC Science & Technology

2009-05-21

Time Engineering AB 3:00 pm BREAK 3:20 pm Advances In Thermal Batteries For Fuzing David E. Harney, Advanced Thermal Batteries , Inc...Currently teaming and collaborating with Advanced Thermal Batteries • and Omnitek Partners to develop an improved thermal battery. • Current

Breaking a virus: Identifying molecular level failure modes of a viral capsid by multiscale modeling

NASA Astrophysics Data System (ADS)

Krishnamani, V.; Globisch, C.; Peter, C.; Deserno, M.

2016-10-01

We use coarse-grained (CG) simulations to study the deformation of empty Cowpea Chlorotic Mottle Virus (CCMV) capsids under uniaxial compression, from the initial elastic response up to capsid breakage. Our CG model is based on the MARTINI force field and has been amended by a stabilizing elastic network, acting only within individual proteins, that was tuned to capture the fluctuation spectrum of capsid protein dimers, obtained from all atom simulations. We have previously shown that this model predicts force-compression curves that match AFM indentation experiments on empty CCMV capsids. Here we investigate details of the actual breaking events when the CCMV capsid finally fails. We present a symmetry classification of all relevant protein contacts and show that they differ significantly in terms of stability. Specifically, we show that interfaces which break readily are precisely those which are believed to form last during assembly, even though some of them might share the same contacts as other non-breaking interfaces. In particular, the interfaces that form pentamers of dimers never break, while the virtually identical interfaces within hexamers of dimers readily do. Since these units differ in the large-scale geometry and, most noticeably, the cone-angle at the center of the 5- or 6-fold vertex, we propose that the hexameric unit fails because it is pre-stressed. This not only suggests that hexamers of dimers form less frequently during the early stages of assembly; it also offers a natural explanation for the well-known β-barrel motif at the hexameric center as a post-aggregation stabilization mechanism. Finally, we identify those amino acid contacts within all key protein interfaces that are most persistent during compressive deformation of the capsid, thereby providing potential targets for mutation studies aiming to elucidate the key contacts upon which overall stability rests.

Convective wave breaking in the KdV equation

NASA Astrophysics Data System (ADS)

Brun, Mats K.; Kalisch, Henrik

2018-03-01

The KdV equation is a model equation for waves at the surface of an inviscid incompressible fluid, and it is well known that the equation describes the evolution of unidirectional waves of small amplitude and long wavelength fairly accurately if the waves fall into the Boussinesq regime. The KdV equation allows a balance of nonlinear steepening effects and dispersive spreading which leads to the formation of steady wave profiles in the form of solitary waves and cnoidal waves. While these wave profiles are solutions of the KdV equation for any amplitude, it is shown here that there for both the solitary and the cnoidal waves, there are critical amplitudes for which the horizontal component of the particle velocity matches the phase velocity of the wave. Solitary or cnoidal solutions of the KdV equation which surpass these amplitudes feature incipient wave breaking as the particle velocity exceeds the phase velocity near the crest of the wave, and the model breaks down due to violation of the kinematic surface boundary condition. The condition for breaking can be conveniently formulated as a convective breaking criterion based on the local Froude number at the wave crest. This breaking criterion can also be applied to time-dependent situations, and one case of interest is the development of an undular bore created by an influx at a lateral boundary. It is shown that this boundary forcing leads to wave breaking in the leading wave behind the bore if a certain threshold is surpassed.

Measuring the Strength of the Horned Passalus Beetle, Odontotaenius disjunctus: Revisiting an Old Topic with Modern Technology

PubMed Central

Davis, Andrew K.; Attarha, Barrett; Piefke, Taylor J.

2013-01-01

Over a century ago, a pioneering researcher cleverly devised a means to measure how much weight the horned passalus beetle, Odontotaenius disjunctus (Illiger) (Coleoptera: Passalidae), could pull using a series of springs, pulleys, and careful observation. The technology available in modern times now allows for more rigorous data collection on this topic, which could have a number of uses in scientific investigations. In this study, an apparatus was constructed using a dynamometer and a data logger in an effort to ascertain the pulling strength of this species. By allowing beetles to pull for 10 min, each beetle's mean and maximum pulling force (in Newtons) were obtained for analyses, and whether these measures are related was determined. Then, whether factors such as body length, thorax size, horn size, or gender affect either measure of strength was investigated. Basic body measurements, including horn size, of males versus females were compared. The measurements of 38 beetles (20 females, 18 males) showed there was no difference in overall body length between sexes, but females had greater girth (thorax width) than males, which could translate into larger muscle mass. A total of 21 beetles (10 females, 11 males) were tested for pulling strength. The grand mean pulling force was 0.14 N, and the grand mean maximum was 0.78 N. Despite the fact that beetles tended to pull at 20% of their maximum capacity most of the time, and that maximum force was over 5 times larger than the mean force, the 2 measures were highly correlated, suggesting they may be interchangeable for research purposes. Females had twice the pulling strength (both maximum and mean force) as males in this species overall, but when the larger thorax size of females was considered, the effect of gender was not significant. Beetle length was not a significant predictor of pulling force, but horn size was associated with maximum force. The best predictor of both measures of strength appeared to be thorax size. There are a multitude of interesting scientific questions that could be addressed using data on beetle pulling strength, and this project serves as a starting point for such work. PMID:24735074

Order statistics inference for describing topological coupling and mechanical symmetry breaking in multidomain proteins

NASA Astrophysics Data System (ADS)

Kononova, Olga; Jones, Lee; Barsegov, V.

2013-09-01

Cooperativity is a hallmark of proteins, many of which show a modular architecture comprising discrete structural domains. Detecting and describing dynamic couplings between structural regions is difficult in view of the many-body nature of protein-protein interactions. By utilizing the GPU-based computational acceleration, we carried out simulations of the protein forced unfolding for the dimer WW - WW of the all-β-sheet WW domains used as a model multidomain protein. We found that while the physically non-interacting identical protein domains (WW) show nearly symmetric mechanical properties at low tension, reflected, e.g., in the similarity of their distributions of unfolding times, these properties become distinctly different when tension is increased. Moreover, the uncorrelated unfolding transitions at a low pulling force become increasingly more correlated (dependent) at higher forces. Hence, the applied force not only breaks "the mechanical symmetry" but also couples the physically non-interacting protein domains forming a multi-domain protein. We call this effect "the topological coupling." We developed a new theory, inspired by order statistics, to characterize protein-protein interactions in multi-domain proteins. The method utilizes the squared-Gaussian model, but it can also be used in conjunction with other parametric models for the distribution of unfolding times. The formalism can be taken to the single-molecule experimental lab to probe mechanical cooperativity and domain communication in multi-domain proteins.

Tidal Impacts on Oceanographic and Sea-ice Processes in the Southern Ocean

NASA Astrophysics Data System (ADS)

Padman, L.; Muench, R. D.; Howard, S.; Mueller, R.

2008-12-01

We review recent field and modeling results that demonstrate the importance of tides in establishing the oceanographic and sea-ice conditions in the boundary regions of the Southern Ocean. The tidal component dominates the total oceanic kinetic energy throughout much of the circum-Antarctic seas. This domination is especially pronounced over the continental slope and shelf including the sub-ice-shelf cavities. Tides provide most of the energy that forces diapycnal mixing under ice shelves and thereby contributes to basal melting. The resulting Ice Shelf Water is a significant component of the Antarctic Bottom Water (AABW) filling much of the deep global ocean. Tides exert significant divergent forcing on sea ice along glacial ice fronts and coastal regions, contributing to creation and maintenance of the coastal polynyas where much of the High Salinity Shelf Water component of AABW is formed. Additional tidally forced ice divergence along the shelf break and upper slope significantly impacts area-averaged ice growth and upper-ocean salinity. Tidally forced cross- slope advection, and mixing by the benthic stress associated with tidal currents along the shelf break and upper slope, strongly influence the paths, volume fluxes and hydrographic properties of benthic outflows of dense water leaving the continental shelf. These outflows provide primary source waters for the AABW. These results confirm that general ocean circulation and coupled ocean/ice/atmosphere climate models must incorporate the impacts of tides.

Optimal flapping wing for maximum vertical aerodynamic force in hover: twisted or flat?

PubMed

Phan, Hoang Vu; Truong, Quang Tri; Au, Thi Kim Loan; Park, Hoon Cheol

2016-07-08

This work presents a parametric study, using the unsteady blade element theory, to investigate the role of twist in a hovering flapping wing. For the investigation, a flapping-wing system was developed to create a wing motion of large flapping amplitude. Three-dimensional kinematics of a passively twisted wing, which is capable of creating a linearly variable geometric angle of attack (AoA) along the wingspan, was measured during the flapping motion and used for the analysis. Several negative twist or wash-out configurations with different values of twist angle, which is defined as the difference in the average geometric AoAs at the wing root and the wing tip, were obtained from the measured wing kinematics through linear interpolation and extrapolation. The aerodynamic force generation and aerodynamic power consumption of these twisted wings were obtained and compared with those of flat wings. For the same aerodynamic power consumption, the vertical aerodynamic forces produced by the negatively twisted wings are approximately 10%-20% less than those produced by the flat wings. However, these twisted wings require approximately 1%-6% more power than flat wings to produce the same vertical force. In addition, the maximum-force-producing twisted wing, which was found to be the positive twist or wash-in configuration, was used for comparison with the maximum-force-producing flat wing. The results revealed that the vertical aerodynamic force and aerodynamic power consumption of the two types of wings are almost identical for the hovering condition. The power loading of the positively twisted wing is only approximately 2% higher than that of the maximum-force-producing flat wing. Thus, the flat wing with proper wing kinematics (or wing rotation) can be regarded as a simple and efficient candidate for the development of hovering flapping-wing micro air vehicle.

Comparison of the Force-, Velocity- and Power-Time Curves Between the Concentric-Only and Eccentric-Concentric Bench Press Exercises.

PubMed

Pérez-Castilla, Alejandro; Comfort, Paul; McMahon, John J; Pestaña-Melero, Francisco Luis; García-Ramos, Amador

2018-01-17

The aim of this study was to compare the temporal and mechanical variables between the concentric-only and eccentric-concentric bench press (BP) variants. Twenty-one men (age: 22.0±4.2 years, body mass: 73.4±7.7 kg, height: 177.2±8.0 cm; one-repetition maximum [1RM]: 1.12±0.12 kg⋅kg) were evaluated during the concentric-only and eccentric-concentric BP variants using 80% 1RM. Temporal (concentric phase duration, propulsive phase duration, and time to reach the maximum values of force, velocity, and power) and mechanical variables (force, velocity, and power), determined using a linear velocity transducer, were compared between both BP variants. All temporal variables were significantly lower during the eccentric-concentric BP compared to the concentric-only BP (P < 0.05; effect size [ES] range: 0.80-2.52). Maximum force as well as the mean values of velocity and power were significantly higher for the eccentric-concentric BP compared to the concentric-only BP (all P < 0.001; ES range: 2.87-3.58). However, trivial to small differences between both BP variants were observed for mean force (ES: 0.00-0.36) as well as for maximum velocity (ES: 0.40) and power (ES: 0.41). The stretch-shortening cycle (i.e., eccentric-concentric BP) mainly enhanced force production at the early portion of the concentric phase, but this potentiation effect gradually reduced over the latter part of the movement. Finally, force was higher for the concentric-only BP during 49% of the concentric phase duration. These results suggest that both BP variants should be included during resistance training programs in order to optimize force output at different points of the concentric phase.

Force sensitive carbon nanotube arrays for biologically inspired airflow sensing

NASA Astrophysics Data System (ADS)

Maschmann, Matthew R.; Dickinson, Ben; Ehlert, Gregory J.; Baur, Jeffery W.

2012-09-01

The compressive electromechanical response of aligned carbon nanotube (CNT) arrays is evaluated for use as an artificial hair sensor (AHS) transduction element. CNT arrays with heights of 12, 75, and 225 µm are examined. The quasi-static and dynamic sensitivity to force, response time, and signal drift are examined within the range of applied stresses predicted by a mechanical model applicable to the conceptual CNT array-based AHS (0-1 kPa). Each array is highly sensitive to compressive loading, with a maximum observed gauge factor of 114. The arrays demonstrate a repeatable response to dynamic cycling after a break-in period of approximately 50 cycles. Utilizing a four-wire measurement electrode configuration, the change in contact resistance between the array and the electrodes is observed to dominate the electromechanical response of the arrays. The response time of the CNT arrays is of the order of 10 ms. When the arrays are subjected to constant stress, mechanical creep is observed that results in a signal drift that generally diminishes the responsiveness of the arrays, particularly at stress approaching 1 kPa. The results of this study serve as a preliminary proof of concept for utilizing CNT arrays as a transduction mechanism for a proposed artificial hair sensor. Such a low profile and light-weight flow sensor is expected to have application in a number of applications including navigation and state awareness of small air vehicles, similar in function to natural hair cell receptors utilized by insects and bats.

A stochastic model for soft tissue failure using acoustic emission data.

PubMed

Sánchez-Molina, D; Martínez-González, E; Velázquez-Ameijide, J; Llumà, J; Rebollo Soria, M C; Arregui-Dalmases, C

2015-11-01

The strength of soft tissues is due mainly to collagen fibers. In most collagenous tissues, the arrangement of the fibers is random, but has preferred directions. The random arrangement makes it difficult to make deterministic predictions about the starting process of fiber breaking under tension. When subjected to tensile stress the fibers are progressively straighten out and then start to be stretched. At the beginning of fiber breaking, some of the fibers reach their maximum tensile strength and break down while some others remain unstressed (this latter fibers will assume then bigger stress until they eventually arrive to their failure point). In this study, a sample of human esophagi was subjected to a tensile breaking of fibers, up to the complete failure of the specimen. An experimental setup using Acoustic Emission to detect the elastic energy released is used during the test to detect the location of the emissions and the number of micro-failures per time unit. The data were statistically analyzed in order to be compared to a stochastic model which relates the level of stress in the tissue and the probability of breaking given the number of previously broken fibers (i.e. the deterioration in the tissue). The probability of a fiber breaking as the stretch increases in the tissue can be represented by a non-homogeneous Markov process which is the basis of the stochastic model proposed. This paper shows that a two-parameter model can account for the fiber breaking and the expected distribution for ultimate stress is a Fréchet distribution. Copyright © 2015 Elsevier Ltd. All rights reserved.

Secure RFID tag or sensor with self-destruction mechanism upon tampering

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

Nekoogar, Faranak; Dowla, Farid; Twogood, Richard

A circuit board anti-tamper mechanism comprises a circuit board having a frangible portion, a trigger having a trigger spring, a trigger arming mechanism actuated by the trigger wherein the trigger arming mechanism is initially non-actuated, a force producing mechanism, a latch providing mechanical communication between the trigger arming mechanism and the force producing mechanism, wherein the latch initially retains the force producing mechanism in a refracted position. Arming pressure applied to the trigger sufficient to overcome the trigger spring force will actuate the trigger arming mechanism, causing the anti-tamper mechanism to be armed. Subsequent tampering with the anti-tamper mechanism resultsmore » in a decrease of pressure on the trigger below the trigger spring force, thereby causing the trigger arming mechanism to actuate the latch, thereby releasing the force producing mechanism to apply force to the frangible portion of the circuit board, thereby breaking the circuit board.« less

Hydrodynamic analysis of floating platform for special purposes under complex water environment

NASA Astrophysics Data System (ADS)

Ma, Guang-ying; Yao, Yun-long

2018-03-01

This article studied a new floating offshore platform for special purposes, which was assembled by standard floating modules. By using ANSYS AQWA software, the hydrodynamic model of the platform was established. The time history responses of the platform motions and the cable tension forces were calculate under complex water environments, such as wind, wave, current and mooring. The results showed that the tension of the four cables are far less than the breaking tension of the cable, so that the cable will not break. This study can be referenced by the relevant researchers and engineers.

Dynamic Torque and Vertical Force Analysis during Nickel-titanium Rotary Root Canal Preparation with Different Modes of Reciprocal Rotation.

PubMed

Tokita, Daisuke; Ebihara, Arata; Nishijo, Miki; Miyara, Kana; Okiji, Takashi

2017-10-01

The purpose of the present study was to compare 2 modes of reciprocal movement (torque-sensitive and time-dependent reciprocal rotation) with continuous rotation in terms of torque and apical force generation during nickel-titanium rotary root canal instrumentation. A custom-made automated root canal instrumentation and torque/force analyzing device was used to prepare simulated canals in resin blocks and monitor the torque and apical force generated in the blocks during preparation. Experimental groups (n = 7, each) consisted of (1) torque-sensitive reciprocal rotation with torque-sensitive vertical movement (group TqR), (2) time-dependent reciprocal rotation with time-dependent vertical movement (group TmR), and (3) continuous rotation with time-dependent vertical movement (group CR). The canals were instrumented with TF Adaptive SM1 and SM2 rotary files (SybronEndo, Orange, CA), and the torque and apical force were measured during instrumentation with SM2. The mean and maximum torque and apical force values were statistically analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The recordings showed intermittent increases of upward apical force and clockwise torque, indicating the generation and release of screw-in forces. The maximum upward apical force values in group TmR were significantly smaller than those in group CR (P < .05). The maximum torque values in clockwise and counterclockwise directions in groups TqR and TmR were significantly smaller than those in group CR (P < .05). Under the present experimental conditions using TF Adaptive instruments, both torque-sensitive and time-dependent reciprocal rotation generated significantly lower maximum torque and may have advantages in reducing stress generation caused by screw-in forces when compared with continuous rotation. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Temporal characterization of the wave-breaking flash in a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Miao, Bo; Feder, Linus; Goers, Andrew; Hine, George; Salehi, Fatholah; Wahlstrand, Jared; Woodbury, Daniel; Milchberg, Howard

2017-10-01

Wave-breaking injection of electrons into a relativistic plasma wake generated in near-critical density plasma by sub-terawatt laser pulses generates an intense ( 1 μJ) and ultra-broadband (Δλ 300 nm) radiation flash. In this work we demonstrate the spectral coherence of this radiation and measure its temporal width using single-shot supercontinuum spectral interferometry (SSSI). The measured temporal width is limited by measurement resolution to 50 fs. Spectral coherence is corroborated by PIC simulations which show that the spatial extent of the acceleration trajectory at the trapping region is small compared to the radiation center wavelength. To our knowledge, this is the first temporal and coherence characterization of wave-breaking radiation. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

Short-term sandbar variability based on video imagery: Comparison between Time-Average and Time-Variance techniques

USGS Publications Warehouse

Guedes, R.M.C.; Calliari, L.J.; Holland, K.T.; Plant, N.G.; Pereira, P.S.; Alves, F.N.A.

2011-01-01

Time-exposure intensity (averaged) images are commonly used to locate the nearshore sandbar position (xb), based on the cross-shore locations of maximum pixel intensity (xi) of the bright bands in the images. It is not known, however, how the breaking patterns seen in Variance images (i.e. those created through standard deviation of pixel intensity over time) are related to the sandbar locations. We investigated the suitability of both Time-exposure and Variance images for sandbar detection within a multiple bar system on the southern coast of Brazil, and verified the relation between wave breaking patterns, observed as bands of high intensity in these images and cross-shore profiles of modeled wave energy dissipation (xD). Not only is Time-exposure maximum pixel intensity location (xi-Ti) well related to xb, but also to the maximum pixel intensity location of Variance images (xi-Va), although the latter was typically located 15m offshore of the former. In addition, xi-Va was observed to be better associated with xD even though xi-Ti is commonly assumed as maximum wave energy dissipation. Significant wave height (Hs) and water level (??) were observed to affect the two types of images in a similar way, with an increase in both Hs and ?? resulting in xi shifting offshore. This ??-induced xi variability has an opposite behavior to what is described in the literature, and is likely an indirect effect of higher waves breaking farther offshore during periods of storm surges. Multiple regression models performed on xi, Hs and ?? allowed the reduction of the residual errors between xb and xi, yielding accurate estimates with most residuals less than 10m. Additionally, it was found that the sandbar position was best estimated using xi-Ti (xi-Va) when xb was located shoreward (seaward) of its mean position, for both the first and the second bar. Although it is unknown whether this is an indirect hydrodynamic effect or is indeed related to the morphology, we found that this behavior can be explored to optimize sandbar estimation using video imagery, even in the absence of hydrodynamic data. ?? 2011 Elsevier B.V..

Polymer mechanochemistry: Up another rung

NASA Astrophysics Data System (ADS)

Craig, Stephen L.

2017-12-01

The use of mechanical force to break and build chemical bonds in polymers can enable transformations that cannot be conducted using stimuli such as light and heat. Now, an insulating polymer has been mechanically unzipped to create a semiconducting polymer with extended regions of conjugation.

Drops: The collapse of capillary jets

PubMed Central

Cordoba, Antonio; Cordoba, Diego; Fefferman, Charles; Fontelos, Marco A.

2002-01-01

The appearance of fluid filaments during the evolution of a viscous fluid jet is a commonly observed phenomenon. It is shown here that the break-up of such a jet subject to capillary forces is impossible through the collapse of a uniform filament. PMID:12172005

Flange joint system for SRF cavities utilizing high force spring clamps for low particle generation

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

None

A flange joint system for SRF cavities. The flange joint system includes a set of high force spring clamps that produce high force on the simple flanges of Superconducting Radio Frequency (SRF) cavities to squeeze conventional metallic seals. The system establishes the required vacuum and RF-tight seal with minimum particle contamination to the inside of the cavity assembly. The spring clamps are designed to stay within their elastic range while being forced open enough to mount over the flange pair. Upon release, the clamps have enough force to plastically deform metallic seal surfaces and continue to a new equilibrium sprungmore » dimension where the flanges remain held against one another with enough preload such that normal handling will not break the seal.« less

Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion.

PubMed

Gilman, Casey A; Imburgia, Michael J; Bartlett, Michael D; King, Daniel R; Crosby, Alfred J; Irschick, Duncan J

2015-01-01

One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C) is the change in extension (Δ) relative to a change in force (F) while loading a gecko's adhesive system (C = dΔ/dF). Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2-100 g). We also examined changes between juveniles and adults within a single species (Phelsuma grandis). We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic "model gecko" system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring) of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of adhesion in animals with dry adhesion systems.

Chewability testing in the development of a chewable tablet for hyperphosphatemia.

PubMed

Lanz, Michael; Baldischweiler, Jan; Kriwet, Burkhard; Schill, Jutta; Stafford, John; Imanidis, Georgios

2014-12-01

The official Pharmacopeia does not include a test procedure for the in vitro estimation of the chewability of tablets and publications in the scientific literature on this subject are rare. The purpose of this study was to evaluate a number of different test procedures for assessing chewability, starting from standard breaking force and strength testing and progressing to develop new procedures that simulate the actual chewing action on tablets. A further goal was to apply these test procedures to characterize the chewability of the novel phosphate binder PA21 in comparison with a commercially available phosphate binder chewable tablet product based on lanthanum (Fosrenol®) and a chewable tablet product containing calcium (Calcimagon®) - the latter being used as a standard for its very good chewability. For this purpose, a number of development formulations (different batches of PA21) were tested. The radial or diametrical tablet breaking force offers a poor means of assessing chewability while the axial breaking force was concluded to better reflect the effect of chewing on the tablet. Measurement of tablet behavior upon repeated loading afforded the best simulation of the actual chewing action and was found to have a good discriminating power with respect to chewability of the tested tablets, especially when the tablet was moistened with artificial saliva. The developed tests are shown to be more suitable for evaluating chewing properties of tablets than currently used Pharmacopeial tests. Following ICHQ6, which calls for specification of hardness for chewable tablets, these test procedures enabled the optimal chewability features of PA21 tablets in development to be confirmed whilst still maintaining capabilities for robust production and transportation processes.

Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations.

PubMed

Viktorinová, Ivana; Henry, Ian; Tomancak, Pavel

2017-11-01

Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs.

Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations

PubMed Central

Henry, Ian; Tomancak, Pavel

2017-01-01

Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs. PMID:29176774

Evidence for remotely triggered micro-earthquakes during salt cavern collapse

NASA Astrophysics Data System (ADS)

Jousset, P.; Rohmer, J.

2012-04-01

Micro-seismicity is a good indicator of spatio-temporal evolution of physical properties of rocks prior to catastrophic events like volcanic eruptions or landslides and may be triggered by a number of causes including dynamic characteristics of processes in play or/and external forces. Micro-earthquake triggering has been in the recent years the subject of intense research and our work contribute to showing further evidence of possible triggering of micro-earthquakes by remote large earthquakes. We show evidence of triggered micro-seismicity in the vicinity of an underground salt cavern prone to collapse by a remote M~7.2 earthquake, which occurred ~12000 kilometres away. We demonstrate the near critical state of the cavern before the collapse by means of 2D axisymmetric elastic finite-element simulations. Pressure was lowered in the cavern by pumping operations of brine out of the cavern. We demonstrate that a very small stress increase would be sufficient to break the overburden. High-dynamic broadband records reveal a remarkable time-correlation between a dramatic increase of the local high-frequency micro-seismicity rate associated with the break of the stiffest layer stabilizing the overburden and the passage of low-frequency remote seismic waves, including body, Love and Rayleigh surface waves. Stress oscillations due to the seismic waves exceeded the strength required for the rupture of the complex media made of brine and rock triggering micro-earthquakes and leading to damage of the overburden and eventually collapse of the salt cavern. The increment of stress necessary for the failure of a Dolomite layer is of the same order or magnitude as the maximum dynamic stress magnitude observed during the passage of the earthquakes waves. On this basis, we discuss the possible contribution of the Love and Rayleigh low-frequency surfaces waves.

The Aerodynamic and Dynamic Loading of a Slender Structure by an Impacting Tornado-Like Vortex: The Influence of Relative Vortex-to-Structure Size on Structural Loading

NASA Astrophysics Data System (ADS)

Strasser, Matthew N.

Structural loading produced by an impacting vortex is a hazardous phenomenon that is encountered in numerous applications ranging from the destruction of residences by tornados to the chopping of tip vortices by rotors. Adequate design of structures to resist vortex-induced structural loading necessitates study of the phenomenon that control the structural loading produced by an impacting vortex. This body of work extends the current knowledge base of vortex-structure interaction by evaluating the influence of the relative vortex-to-structure size on the structural loading that the vortex produces. A computer model is utilized to directly simulate the two-dimensional impact of an impinging vortex with a slender, cylindrical structure. The vortex's tangential velocity profile (TVP) is defined by a normalization of the Vatistas analytical (TVP) which realistically replicates the documented spectrum of measured vortex TVPs. The impinging vortex's maximum tangential velocity is fixed, and the vortex's critical radius is incremented from one to one-hundred times the structure's diameter. When the impinging vortex is small, it interacts with vortices produced on the structure by the free stream, and maximum force coefficient amplitudes vary by more than 400% when the impinging vortex impacts the structure at different times. Maximum drag and lift force coefficient amplitudes reach asymptotic values as the impinging vortex's size increases that are respectively 94.77% and 10.66% less than maximum force coefficients produced by an equivalent maximum velocity free stream. The vortex produces maximum structural loading when its path is shifted above the structure's centerline, and maximum drag and lift force coefficients are respectively up to 4.80% and 34.07% greater than maximum force coefficients produced by an equivalent-velocity free stream. Finally, the dynamic load factor (DLF) concept is used to develop a generalized methodology to assess the dynamic amplification of a structure's response to vortex loading and to assess the dynamic loading threat that tornados pose. Typical civil and residential structures will not experience significant response amplification, but responses of very flexible structures may be amplified by up to 2.88 times.

Effects of load on ground reaction force and lower limb kinematics during concentric squats.

PubMed

Kellis, Eleftherios; Arambatzi, Fotini; Papadopoulos, Christos

2005-10-01

The purpose of this study was to examine the effects of external load on vertical ground reaction force, and linear and angular kinematics, during squats. Eight males aged 22.1 +/- 0.8 years performed maximal concentric squats using loads ranging from 7 to 70% of one-repetition maximum on a force plate while linear barbell velocity and the angular kinematics of the hip, knee and ankle were recorded. Maximum, average and angle-specific values were recorded. The ground reaction force ranged from 1.67 +/- 0.20 to 3.21 +/- 0.29 times body weight and increased significantly as external load increased (P < 0.05). Bar linear velocity ranged from 0.54 +/- 0.11 to 2.50 +/- 0.50 m x s(-1) and decreased significantly with increasing external load (P < 0.05). Hip, knee and ankle angles at maximum ground reaction force were affected by external load (P < 0.05). The force-barbell velocity curves were fitted using linear models with coefficients (r2) ranging from 0.59 to 0.96. The results suggest that maximal force exertion during squat exercises is not achieved at the same position of the lower body as external load is increased. In contrast, joint velocity coordination does not change as load is increased. The force-velocity relationship was linear and independent from the set of data used for its determination.

Quantitative analysis of the thermal requirements for stepwise physical dormancy-break in seeds of the winter annual Geranium carolinianum (Geraniaceae)

PubMed Central

Gama-Arachchige, N. S.; Baskin, J. M.; Geneve, R. L.; Baskin, C. C.

2013-01-01

Background and Aims Physical dormancy (PY)-break in some annual plant species is a two-step process controlled by two different temperature and/or moisture regimes. The thermal time model has been used to quantify PY-break in several species of Fabaceae, but not to describe stepwise PY-break. The primary aims of this study were to quantify the thermal requirement for sensitivity induction by developing a thermal time model and to propose a mechanism for stepwise PY-breaking in the winter annual Geranium carolinianum. Methods Seeds of G. carolinianum were stored under dry conditions at different constant and alternating temperatures to induce sensitivity (step I). Sensitivity induction was analysed based on the thermal time approach using the Gompertz function. The effect of temperature on step II was studied by incubating sensitive seeds at low temperatures. Scanning electron microscopy, penetrometer techniques, and different humidity levels and temperatures were used to explain the mechanism of stepwise PY-break. Key Results The base temperature (Tb) for sensitivity induction was 17·2 °C and constant for all seed fractions of the population. Thermal time for sensitivity induction during step I in the PY-breaking process agreed with the three-parameter Gompertz model. Step II (PY-break) did not agree with the thermal time concept. Q10 values for the rate of sensitivity induction and PY-break were between 2·0 and 3·5 and between 0·02 and 0·1, respectively. The force required to separate the water gap palisade layer from the sub-palisade layer was significantly reduced after sensitivity induction. Conclusions Step I and step II in PY-breaking of G. carolinianum are controlled by chemical and physical processes, respectively. This study indicates the feasibility of applying the developed thermal time model to predict or manipulate sensitivity induction in seeds with two-step PY-breaking processes. The model is the first and most detailed one yet developed for sensitivity induction in PY-break. PMID:23456728

Break-up of metal tube makes one-time shock absorber, bars rebound

NASA Technical Reports Server (NTRS)

Hathaway, M.; Mc Gehee, J. R.; Zavada, E.

1964-01-01

A frangible metal tube has the capability to dissipate the energy generated when a vehicle lands with excessive velocity. The tube is so placed that, at impact, it is forced against a die and, as it fragments, energy is absorbed.

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

None

Articles include: Arizona Apache tribe set to break ground on new solar project; Native leaders give tribes a voice on White House Climate Task Force; Chaninik Wind Group Pursues Innovative Solutions to native Alaska energy challenges; and sections, Message from the Director, Tracey Lebeau; On the Horizon, Sharing Knowledge, and Building Bridges.

Parametric Symmetry Breaking in a Nonlinear Resonator

NASA Astrophysics Data System (ADS)

Leuch, Anina; Papariello, Luca; Zilberberg, Oded; Degen, Christian L.; Chitra, R.; Eichler, Alexander

2016-11-01

Much of the physical world around us can be described in terms of harmonic oscillators in thermodynamic equilibrium. At the same time, the far-from-equilibrium behavior of oscillators is important in many aspects of modern physics. Here, we investigate a resonating system subject to a fundamental interplay between intrinsic nonlinearities and a combination of several driving forces. We have constructed a controllable and robust realization of such a system using a macroscopic doubly clamped string. We experimentally observe a hitherto unseen double hysteresis in both the amplitude and the phase of the resonator's response function and present a theoretical model that is in excellent agreement with the experiment. Our work unveils that the double hysteresis is a manifestation of an out-of-equilibrium symmetry breaking between parametric phase states. Such a fundamental phenomenon, in the most ubiquitous building block of nature, paves the way for the investigation of new dynamical phases of matter in parametrically driven many-body systems and motivates applications ranging from ultrasensitive force detection to low-energy computing memory units.

Symmetry breaking and polarity establishment during mouse oocyte maturation

PubMed Central

Yi, Kexi; Rubinstein, Boris; Li, Rong

2013-01-01

Mammalian oocyte meiosis encompasses two rounds of asymmetric divisions to generate a totipotent haploid egg and, as by-products, two small polar bodies. Two intracellular events, asymmetric spindle positioning and cortical polarization, are critical to such asymmetric divisions. Actin but not microtubule cytoskeleton has been known to be directly involved in both events. Recent work has revealed a positive feedback loop between chromosome-mediated cortical activation and the Arp2/3-orchestrated cytoplasmic streaming that moves chromosomes. This feedback loop not only maintains meiotic II spindle position during metaphase II arrest, but also brings about symmetry breaking during meiosis I. Prior to an Arp2/3-dependent phase of fast movement, meiotic I spindle experiences a slow and non-directional first phase of migration driven by a pushing force from Fmn2-mediated actin polymerization. In addition to illustrating these molecular mechanisms, mathematical simulations are presented to elucidate mechanical properties of actin-dependent force generation in this system. PMID:24062576

Molecular Simulations of The Formation of Gold-Molecule-Gold Junctions

NASA Astrophysics Data System (ADS)

Wang, Huachuan

2013-03-01

We perform classical molecular simulations by combining grand canonical Monte Carlo (GCMC) sampling with molecular dynamics (MD) simulation to explore the dynamic gold nanojunctions in a Alkenedithiol (ADT) solvent. With the aid of a simple driving-spring model, which can reasonably represent the long-range elasticity of the gold electrode, the spring forces are obtained during the dynamic stretching procedure. A specific multi-time-scale double reversible reference system propagator (double-RESPA) algorithm has been designed for the metal-organic complex in MD simulations to identify the detailed metal-molecule bonding geometry at metal-molecule-metal interface. We investigate the variations of bonding sites of ADT molecules on gold nanojunctions at Au (111) surface at a constant chemical potential. Simulation results show that an Au-ADT-Au interface is formed on Au nanojunctions, bond-breaking intersection is at 1-1 bond of the monatomic chain of the cross-section, instead of at the Au-S bond. Breaking force is around 1.5 nN. These are consistent with the experimental measurements.

Symmetry breaking motion of a vortex pair in a driven cavity

NASA Astrophysics Data System (ADS)

McHugh, John; Osman, Kahar; Farias, Jason

2002-11-01

The two-dimensional driven cavity problem with an anti-symmetric sinusoidal forcing has been found to exhibit a subcritical symmetry breaking bifurcation (Farias and McHugh, Phys. Fluids, 2002). Equilibrium solutions are either a symmetric vortex pair or an asymmetric motion. The asymmetric motion is an asymmetric vortex pair at low Reynolds numbers, but merges into a three vortex motion at higher Reynolds numbers. The asymmetric solution is obtained by initiating the flow with a single vortex centered in the domain. Symmetric motion is obtained with no initial vortex, or weak initial vortex. The steady three-vortex motion occurs at a Reynolds number of approximately 3000, where the symmetric vortex pair has already gone through a Hopf bifurcation. Further two-dimensional results show that forcing with two full oscillations across the top of the cavity results in two steady vortex motions, depending on initial conditions. Three-dimensional results have even more steady solutions. The results are computational and theoretical.

Contact Control, Version 1

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

von Sternberg, Alex

The contact control code is a generalized force control scheme meant to interface with a robotic arm being controlled using the Robot Operating System (ROS). The code allows the user to specify a control scheme for each control dimension in a way that many different control task controllers could be built from the same generalized controller. The input to the code includes maximum velocity, maximum force, maximum displacement, and a control law assigned to each direction and the output is a 6 degree of freedom velocity command that is sent to the robot controller.

More Capable Warfighting Through Reduced Fuel Burden. The Defense Science Board Task Force on Improving Fuel Efficiency of Weapons Platforms

DTIC Science & Technology

2001-01-01

Date 00 Jan 2001 Report Type N/A Dates Covered (from... to) - Title and Subtitle The Defense Science Board Task Force on Improving Fuel Efficency ...equipment, people , facilities and other overhead costs) known, understood and factored into the cost of fuel, there would be proper visibility to focus...work- ES- 7 logistics shortfalls impose on operational commanders. Logistics should be played and when it breaks, wargamers must account for it rather

Twisting Plasma

NASA Image and Video Library

2016-06-08

A close-up of twisting plasma above the Sun's surface produced a nice display of turbulence by caused combative magnetic forces (June 7-8, 2016) over a day and a half. The plasma does not break away, but just spins and twists the entire period. Images were taken in extreme ultraviolet light. The mass we observed is part of a longer, darkish filament angling down from the upper left of the frame. Filaments are unstable clouds of plasma suspended above the Sun by magnetic forces. http://photojournal.jpl.nasa.gov/catalog/PIA20739

Stick balancing with reflex delay in case of parametric forcing

NASA Astrophysics Data System (ADS)

Insperger, Tamas

2011-04-01

The effect of parametric forcing on a PD control of an inverted pendulum is analyzed in the presence of feedback delay. The stability of the time-periodic and time-delayed system is determined numerically using the first-order semi-discretization method in the 5-dimensional parameter space of the pendulum's length, the forcing frequency, the forcing amplitude, the proportional and the differential gains. It is shown that the critical length of the pendulum (that can just be balanced against the time-delay) can significantly be decreased by parametric forcing even if the maximum forcing acceleration is limited. The numerical analysis showed that the critical stick length about 30 cm corresponding to the unforced system with reflex delay 0.1 s can be decreased to 18 cm with keeping maximum acceleration below the gravitational acceleration.

Climbing, Slipping and Newton's Second Law

ERIC Educational Resources Information Center

O'Shea, Michael J.

2009-01-01

A point mass model of a climber ascending a rock slope is developed. Stability of the climber is defined via the maximum possible friction force exerted by the feet of the climber on rock and the maximum possible force that the hands of the climber can support in a handhold. This model is then generalized to a somewhat more realistic extended mass…

Effects of a Short Physical Exercise Intervention on Patients with Multiple Sclerosis (MS).

PubMed

Kerling, Arno; Keweloh, Karin; Tegtbur, Uwe; Kück, Momme; Grams, Lena; Horstmann, Hauke; Windhagen, Anja

2015-07-10

The aim of this prospective randomized controlled trial was to investigate if a short-term endurance or combined endurance/resistance exercise program was sufficient to improve aerobic capacity and maximum force in adult patients (18-65 years) with multiple sclerosis (MS). All patients performed a three-month exercise program consisting of two training sessions per week, lasting 40 min each, with moderate intensity. All patients had a maximum value of 6 (low to moderate disability) on the Expanded Disability Status Scale (EDSS). One group (combined workout group (CWG); 15 females, 4 males) completed a combined endurance/resistance workout (20 min on a bicycle ergometer, followed by 20 min of resistance training), while the other group (endurance workout group (EWG); 13 females, 5 males) completed a 40 min endurance training program. Aerobic capacity was assessed as peak oxygen uptake, ventilatory anaerobic threshold, and workload expressed as Watts. Maximum force of knee and shoulder extensors and flexors was measured using isokinetic testing. Quality of life was assessed with the SF-36 questionnaire, and fatigue was measured using the Modified Fatigue Impact Scale. Both training groups increased in aerobic capacity and maximum force. EWG, as well as CWG, showed improvement in several subscales of the SF-36 questionnaire and decrease of their fatigue. A short exercise intervention increased both aerobic capacity and maximum force independent of whether endurance or combined endurance/resistance workouts were performed.

Joint mobilization forces and therapist reliability in subjects with knee osteoarthritis

PubMed Central

Tragord, Bradley S; Gill, Norman W; Silvernail, Jason L; Teyhen, Deydre S; Allison, Stephen C

2013-01-01

Objectives: This study determined biomechanical force parameters and reliability among clinicians performing knee joint mobilizations. Methods: Sixteen subjects with knee osteoarthritis and six therapists participated in the study. Forces were recorded using a capacitive-based pressure mat for three techniques at two grades of mobilization, each with two trials of 15 seconds. Dosage (force–time integral), amplitude, and frequency were also calculated. Analysis of variance was used to analyze grade differences, intraclass correlation coefficients determined reliability, and correlations assessed force associations with subject and rater variables. Results: Grade IV mobilizations produced higher mean forces (P<0.001) and higher dosage (P<0.001), while grade III produced higher maximum forces (P = 0.001). Grade III forces (Newtons) by technique (mean, maximum) were: extension 48, 81; flexion 41, 68; and medial glide 21, 34. Grade IV forces (Newtons) by technique (mean, maximum) were: extension 58, 78; flexion 44, 60; and medial glide 22, 30. Frequency (Hertz) ranged between 0.9–1.1 (grade III) and 1.4–1.6 (grade IV). Intra-clinician reliability was excellent (>0.90). Inter-clinician reliability was moderate for force and dosage, and poor for amplitude and frequency. Discussion: Force measurements were consistent with previously reported ranges and clinical constructs. Grade III and grade IV mobilizations can be distinguished from each other with differences for force and frequency being small, and dosage and amplitude being large. Intra-clinician reliability was excellent for all biomechanical parameters and inter-clinician reliability for dosage, the main variable of clinical interest, was moderate. This study quantified the applied forces among multiple clinicians, which may help determine optimal dosage and standardize care. PMID:24421632

Numerical Simulations of Upstream Propagating Solitary Waves and Wave Breaking In A Stratified Fjord

NASA Astrophysics Data System (ADS)

Stastna, M.; Peltier, W. R.

In this talk we will discuss ongoing numerical modeling of the flow of a stratified fluid over large scale topography motivated by observations in Knight Inlet, a fjord in British Columbia, Canada. After briefly surveying the work done on the topic in the past we will discuss our latest set of simulations in which we have observed the gener- ation and breaking of three different types of nonlinear internal waves in the lee of the sill topography. The first type of wave observed is a large lee wave in the weakly strat- ified main portion of the water column, The second is an upward propagating internal wave forced by topography that breaks in the strong, near-surface pycnocline. The third is a train of upstream propagating solitary waves that, in certain circumstances, form as breaking waves consisting of a nearly solitary wave envelope and a highly unsteady core near the surface. Time premitting, we will comment on the implications of these results for our long term goal of quantifying tidally driven mixing in Knight Inlet.

Janus monolayers of transition metal dichalcogenides.

PubMed

Lu, Ang-Yu; Zhu, Hanyu; Xiao, Jun; Chuu, Chih-Piao; Han, Yimo; Chiu, Ming-Hui; Cheng, Chia-Chin; Yang, Chih-Wen; Wei, Kung-Hwa; Yang, Yiming; Wang, Yuan; Sokaras, Dimosthenis; Nordlund, Dennis; Yang, Peidong; Muller, David A; Chou, Mei-Yin; Zhang, Xiang; Li, Lain-Jong

2017-08-01

Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS 2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

Simulation of condensation and liquid break-up on a micro-object with upper and lower movable walls using Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Asadollahi, Arash; Esmaeeli, Asghar

2018-05-01

In this paper, two-dimensional condensation, liquid behavior on the micro-object with moving walls, and breaking up have been investigated by the Shan and Chen multiphase Lattice Boltzmann Method (LBM), which has the ability to incorporate interactions such as fluid-fluid, and also fluid-solid. Four test cases with low, medium, high, and very high Weber numbers are investigated considering the velocity control of walls in detail. Vertical spread fraction n / h (where n is the minimum liquid thickness after deformation and h is the maximum length of liquid deformation in each time) decreases quickly indicating the liquid tendency to breakup in all cases. Except for the case of a very high Weber number, the separation will not happen and finally after fluctuation the fixed bulk of condensed liquid will be placed on the side of the micro-object. The maximum value of reaction parameter h / d becomes larger as the Weber number increases. It is shown that an increase in the Weber number leads to liquid breakup and this mechanism provides an effective way for removing the condensed liquid from micro-devices surfaces. The results by LBM reveal the liquid evolutionary behavior and breaking up over time and show that it is a controllable situation by manipulating the walls velocity. Moreover, it can be used in order to centralize and aggregate all the liquid to a specific direction.

Forcing a three-dimensional, hydrostatic, primitive-equation model for application in the surf zone: 2. Application to DUCK94

NASA Astrophysics Data System (ADS)

Newberger, P. A.; Allen, J. S.

2007-08-01

A three-dimensional primitive-equation model for application to the nearshore surf zone has been developed. This model, an extension of the Princeton Ocean Model (POM), predicts the wave-averaged circulation forced by breaking waves. All of the features of the original POM are retained in the extended model so that applications can be made to regions where breaking waves, stratification, rotation, and wind stress make significant contributions to the flow behavior. In this study we examine the effects of breaking waves and wind stress. The nearshore POM circulation model is embedded within the NearCom community model and is coupled with a wave model. This combined modeling system is applied to the nearshore surf zone off Duck, North Carolina, during the DUCK94 field experiment of October 1994. Model results are compared to observations from this experiment, and the effects of parameter choices are examined. A process study examining the effects of tidal depth variation on depth-dependent wave-averaged currents is carried out. With identical offshore wave conditions and model parameters, the strength and spatial structure of the undertow and of the alongshore current vary systematically with water depth. Some three-dimensional solutions show the development of shear instabilities of the alongshore current. Inclusion of wave-current interactions makes an appreciable difference in the characteristics of the instability.

Light dark matter, naturalness, and the radiative origin of the electroweak scale

DOE PAGES

Altmannshofer, Wolfgang; Bardeen, William A.; Bauer, Martin; ...

2015-01-09

We study classically scale invariant models in which the Standard Model Higgs mass term is replaced in the Lagrangian by a Higgs portal coupling to a complex scalar field of a dark sector. We focus on models that are weakly coupled with the quartic scalar couplings nearly vanishing at the Planck scale. The dark sector contains fermions and scalars charged under dark SU(2) × U(1) gauge interactions. Radiative breaking of the dark gauge group triggers electroweak symmetry breaking through the Higgs portal coupling. Requiring both a Higgs boson mass of 125.5 GeV and stability of the Higgs potential up tomore » the Planck scale implies that the radiative breaking of the dark gauge group occurs at the TeV scale. We present a particular model which features a long-range abelian dark force. The dominant dark matter component is neutral dark fermions, with the correct thermal relic abundance, and in reach of future direct detection experiments. The model also has lighter stable dark fermions charged under the dark force, with observable effects on galactic-scale structure. Collider signatures include a dark sector scalar boson with mass ≲ 250 GeV that decays through mixing with the Higgs boson, and can be detected at the LHC. As a result, the Higgs boson, as well as the new scalar, may have significant invisible decays into dark sector particles.« less

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

PubMed Central

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei; Unocic, Raymond R.; Guo, Daqiang; Okatan, M. Baris; Dai, Sheng; Cummings, Peter T.; Kalinin, Sergei V.; Feng, Guang; Balke, Nina

2016-01-01

Atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements are sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. The comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained. PMID:27587276

Influence of electrostatic forces on particle propulsion in the evanescent field of silver ion-exchanged waveguides.

PubMed

Gebennikov, Dmytro; Mittler, Silvia

2013-02-26

The effect of electrostatic interaction between carboxylate- and amino-functionalized polystyrene particles and a charged waveguide surface on the propulsion speed in optical tweezers is considered to be a function of the pH and ionic strength. It was shown that with the variation of the pH of the aqueous solution in which the particles were immersed, a systematic change in propulsion speed with a maximum speed could be achieved. The appearance of a maximum speed was ascribed to changes in the particle-waveguide separation as a result of the combination of two forces: Coulomb repulsion/attraction and induced dipole forces. The highest maximum speed at low ionic strength was around 12 μm/s. Changes in the ionic strength of the solution influenced the gradient of the dielectric constant near the involved surfaces and also led to a slightly reduced hydrodynamic radius of the particles. The combination of these effects subsequently increased the maximum speed to about 23 μm/s.

Time-reversal symmetry breaking with acoustic pumping of nanophotonic circuits

NASA Astrophysics Data System (ADS)

Sohn, Donggyu B.; Kim, Seunghwi; Bahl, Gaurav

2018-02-01

Achieving non-reciprocal light propagation via stimuli that break time-reversal symmetry, without magneto-optics, remains a major challenge for integrated nanophotonic devices. Recently, optomechanical microsystems in which light and vibrational modes are coupled through ponderomotive forces have demonstrated strong non-reciprocal effects through a variety of techniques, but always using optical pumping. None of these approaches has demonstrated bandwidth exceeding that of the mechanical system, and all of them require optical power; these are both fundamental and practical issues. Here, we resolve both challenges by breaking time-reversal symmetry using a two-dimensional acoustic pump that simultaneously provides a non-zero overlap integral for light-sound interaction and also satisfies the necessary phase-matching. We use this technique to produce a non-reciprocal modulator (a frequency shifting isolator) by means of indirect interband scattering. We demonstrate mode conversion asymmetry up to 15 dB and efficiency as high as 17% over a bandwidth exceeding 1 GHz.

Boost breaking in the EFT of inflation

DOE PAGES

Delacrétaz, Luca V.; Noumi, Toshifumi; Senatore, Leonardo

2017-02-17

If time-translations are spontaneously broken, so are boosts. This symmetry breaking pattern can be non-linearly realized by either just the Goldstone boson of time translations, or by four Goldstone bosons associated with time translations and boosts. Here in this paper we extend the Effective Field Theory of Multifield Inflation to consider the case in which the additional Goldstone bosons associated with boosts are light and coupled to the Goldstone boson of time translations. The symmetry breaking pattern forces a coupling to curvature so that the mass of the additional Goldstone bosons is predicted to be equal to √2H in themore » vast majority of the parameter space where they are light. This pattern therefore offers a natural way of generating self-interacting particles with Hubble mass during inflation. After constructing the general effective Lagrangian, we study how these particles mix and interact with the curvature fluctuations, generating potentially detectable non-Gaussian signals.« less

The Control of Growth Symmetry Breaking in the Arabidopsis Hypocotyl.

PubMed

Peaucelle, Alexis; Wightman, Raymond; Höfte, Herman

2015-06-29

Complex shapes in biology depend on the ability of cells to shift from isotropic to anisotropic growth during development. In plants, this growth symmetry breaking reflects changes in the extensibility of the cell walls. The textbook view is that the direction of turgor-driven cell expansion depends on the cortical microtubule (CMT)-mediated orientation of cellulose microfibrils. Here, we show that this view is incomplete at best. We used atomic force microscopy (AFM) to study changes in cell-wall mechanics associated with growth symmetry breaking within the hypocotyl epidermis. We show that, first, growth symmetry breaking is preceded by an asymmetric loosening of longitudinal, as compared to transverse, anticlinal walls, in the absence of a change in CMT orientation. Second, this wall loosening is triggered by the selective de-methylesterification of cell-wall pectin in longitudinal walls, and, third, the resultant mechanical asymmetry is required for the growth symmetry breaking. Indeed, preventing or promoting pectin de-methylesterification, respectively, increased or decreased the stiffness of all the cell walls, but in both cases reduced the growth anisotropy. Finally, we show that the subsequent CMT reorientation contributes to the consolidation of the growth axis but is not required for the growth symmetry breaking. We conclude that growth symmetry breaking is controlled at a cellular scale by bipolar pectin de-methylesterification, rather than by the cellulose-dependent mechanical anisotropy of the cell walls themselves. Such a cell asymmetry-driven mechanism is comparable to that underlying tip growth in plants but also anisotropic cell growth in animal cells. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gender, Emotion, and the Family.

ERIC Educational Resources Information Center

Brody, Leslie

Breaking with conventional wisdom, this book integrates a wealth of perspectives and research-- biological, sociocultural, developmental--to explore the nature and extent of gender differences in emotional expression and the question of how such differences come about. In the book, nurture rather than nature emerges as the stronger force in…

The Public Telecommunications Network: A Concept in Transition.

ERIC Educational Resources Information Center

Noam, Eli M.

1987-01-01

Argues that the traditional centralized model of the public telecommunication networks is being undermined by a host of centrifugal forces, and that a new and open network concept is emerging that breaks down the dichotomy between the telecommunications sector and the rest of the economy. (JD)

Reliability, Validity, and Sensitivity of a Novel Smartphone-Based Eccentric Hamstring Strength Test in Professional Football Players.

PubMed

Lee, Justin W Y; Cai, Ming-Jing; Yung, Patrick S H; Chan, Kai-Ming

2018-05-01

To evaluate the test-retest reliability, sensitivity, and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players. A total of 25 healthy male professional football players performed the Chinese University of Hong Kong (CUHK) Nordic break-point test, hamstring fatigue protocol, and isokinetic hamstring strength test. The CUHK Nordic break-point test is based on a Nordic hamstring exercise. The Nordic break-point angle was defined as the maximum point where the participant could no longer support the weight of his body against gravity. The criterion for the sensitivity test was the presprinting and postsprinting difference of the Nordic break-point angle with a hamstring fatigue protocol. The hamstring fatigue protocol consists of 12 repetitions of the 30-m sprint with 30-s recoveries between sprints. Hamstring peak torque of the isokinetic hamstring strength test was used as the criterion for validity. A high test-retest reliability (intraclass correlation coefficient = .94; 95% confidence interval, .82-.98) was found in the Nordic break-point angle measurements. The Nordic break-point angle significantly correlated with isokinetic hamstring peak torques at eccentric action of 30°/s (r = .88, r 2  = .77, P < .001). The minimal detectable difference was 8.03°. The sensitivity of the measure was good enough that a significance difference (effect size = 0.70, P < .001) was found between presprinting and postsprinting values. The CUHK Nordic break-point test is a simple, portable, quick smartphone-based method to provide reliable and accurate eccentric hamstring strength measures among male professional football players.

Hinge Moment Coefficient Prediction Tool and Control Force Analysis of Extra-300 Aerobatic Aircraft

NASA Astrophysics Data System (ADS)

Nurohman, Chandra; Arifianto, Ony; Barecasco, Agra

2018-04-01

This paper presents the development of tool that is applicable to predict hinge moment coefficients of subsonic aircraft based on Roskam’s method, including the validation and its application to predict hinge moment coefficient of an Extra-300. The hinge moment coefficients are used to predict the stick forces of the aircraft during several aerobatic maneuver i.e. inside loop, half cuban 8, split-s, and aileron roll. The maximum longitudinal stick force is 566.97 N occurs in inside loop while the maximum lateral stick force is 340.82 N occurs in aileron roll. Furthermore, validation hinge moment prediction method is performed using Cessna 172 data.

Attainment and retention of force moderation following laparoscopic resection training with visual force feedback.

PubMed

Hernandez, Rafael; Onar-Thomas, Arzu; Travascio, Francesco; Asfour, Shihab

2017-11-01

Laparoscopic training with visual force feedback can lead to immediate improvements in force moderation. However, the long-term retention of this kind of learning and its potential decay are yet unclear. A laparoscopic resection task and force sensing apparatus were designed to assess the benefits of visual force feedback training. Twenty-two male university students with no previous experience in laparoscopy underwent relevant FLS proficiency training. Participants were randomly assigned to either a control or treatment group. Both groups trained on the task for 2 weeks as follows: initial baseline, sixteen training trials, and post-test immediately after. The treatment group had visual force feedback during training, whereas the control group did not. Participants then performed four weekly test trials to assess long-term retention of training. Outcomes recorded were maximum pulling and pushing forces, completion time, and rated task difficulty. Extreme maximum pulling force values were tapered throughout both the training and retention periods. Average maximum pushing forces were significantly lowered towards the end of training and during retention period. No significant decay of applied force learning was found during the 4-week retention period. Completion time and rated task difficulty were higher during training, but results indicate that the difference eventually fades during the retention period. Significant differences in aptitude across participants were found. Visual force feedback training improves on certain aspects of force moderation in a laparoscopic resection task. Results suggest that with enough training there is no significant decay of learning within the first month of the retention period. It is essential to account for differences in aptitude between individuals in this type of longitudinal research. This study shows how an inexpensive force measuring system can be used with an FLS Trainer System after some retrofitting. Surgical instructors can develop their own tasks and adjust force feedback levels accordingly.

Sharp Transition in the Lift Force of a Fluid Flowing Past Nonsymmetrical Obstacles: Evidence for a Lift Crisis in the Drag Crisis Regime.

PubMed

Bot, Patrick; Rabaud, Marc; Thomas, Goulven; Lombardi, Alessandro; Lebret, Charles

2016-12-02

Bluff bodies moving in a fluid experience a drag force which usually increases with velocity. However in a particular velocity range a drag crisis is observed, i.e., a sharp and strong decrease of the drag force. This counterintuitive result is well characterized for a sphere or a cylinder. Here we show that, for an object breaking the up-down symmetry, a lift crisis is observed simultaneously to the drag crisis. The term lift crisis refers to the fact that at constant incidence the time-averaged transverse force, which remains small or even negative at low velocity, transitions abruptly to large positive values above a critical flow velocity. This transition is characterized from direct force measurements as well as from change in the velocity field around the obstacle.

A PC-based high temperature gas reactor simulator for Indonesian conceptual HTR reactor basic training

NASA Astrophysics Data System (ADS)

Syarip; Po, L. C. C.

2018-05-01

In planning for nuclear power plant construction in Indonesia, helium cooled high temperature reactor (HTR) is favorable for not relying upon water supply that might be interrupted by earthquake. In order to train its personnel, BATAN has cooperated with Micro-Simulation Technology of USA to develop a 200 MWt PC-based simulation model PCTRAN/HTR. It operates in Win10 environment with graphic user interface (GUI). Normal operation of startup, power maneuvering, shutdown and accidents including pipe breaks and complete loss of AC power have been conducted. A sample case of safety analysis simulation to demonstrate the inherent safety features of HTR was done for helium pipe break malfunction scenario. The analysis was done for the variation of primary coolant pipe break i.e. from 0,1% - 0,5 % and 1% - 10 % helium gas leakages, while the reactor was operated at the maximum constant power of 10 MWt. The result shows that the highest temperature of HTR fuel centerline and coolant were 1150 °C and 1296 °C respectively. With 10 kg/s of helium flow in the reactor core, the thermal power will back to the startup position after 1287 s of helium pipe break malfunction.

Effect of gender, facial dimensions, body mass index and type of functional occlusion on bite force.

PubMed

Koç, Duygu; Doğan, Arife; Bek, Bülent

2011-01-01

Some factors such as gender, age, craniofacial morphology, body structure, occlusal contact patterns may affect the maximum bite force. Thus, the purposes of this study were to determine the mean maximum bite force in individuals with normal occlusion, and to examine the effect of gender, facial dimensions, body mass index (BMI), type of functional occlusion (canine guidance and group function occlusion) and balancing side interferences on it. Thirty-four individuals aged 19-20 years-old were selected for this study. Maximum bite force was measured with strain-gauge transducers at first molar region. Facial dimensions were defined by standardized frontal photographs as follows: anterior total facial height (ATFH), bizygomathic facial width (BFW) and intergonial width (IGW). BMI was calculated using the equation weight/height². The type of functional occlusion and the balancing side interferences of the subjects were identified by clinical examination. Bite force was found to be significantly higher in men than women (p<0.05). While there was a negative correlation between the bite force and ATFH/BFW, ATFH/IGW ratios in men (p<0.05), women did not show any statistically significant correlation (p>0.05). BMI and bite force correlation was not statistically significant (p>0.05). The average bite force did not differ in subjects with canine guidance or group function occlusion and in the presence of balancing side interferences (p>0.05). Data suggest that bite force is affected by gender. However, BMI, type of functional occlusion and the presence of balancing side interferences did not exert a meaningful influence on bite force. In addition, transverse facial dimensions showed correlation with bite force in only men.

Determinant Factors of the Squat Jump in Sprinting and Jumping Athletes

PubMed Central

González-Badillo, Juan José; Jiménez-Reyes, Pedro; Ramírez-Lechuga, Jorge

2017-01-01

Abstract The aim of this study was to assess the relationship between strength variables and maximum velocity (Vmax) in the squat jump (SJ) in sprinting and jumping athletes. Thirty-two sprinting and jumping athletes of national level (25.4 ± 4.5 years; 79.4 ± 6.9 kg and 180.4 ± 6.0 cm) participated in the study. Vmax in the SJ showed significant relationships with peak force 1 (PF1) (r = 0.82, p ≤ 0.001), peak force 2 (PF2) (r = 0.68, p ≤ 0.001), PF2 by controlling for PF1 (r = 0.30, non-significant), the maximum rate of force development at peak force 1 (RFDmax1) (r = 0.62, p ≤ 0.001), mean RFD 1 (RFDmean1) (r = 0.48, p ≤ 0.01), mean RFD 2 (RFDmean2) (r = 0.70, p ≤ 0.001), force at RFDmax1 (r = 0.36, p ≤ 0.05), force at RFDmax2 (r = 0.83, p ≤ 0.001) and force at RFDmax2 by controlling for PF1 (r = 0.40, p ≤ 0.05). However, Vmax in the SJ was associated negatively with the ratio PF2/PF1 (r = -0.54, p ≤ 0.01), time at peak force 2 (Tp2) (r = -0.64, p ≤ 0.001) and maximum rate of force development at peak force 2 (RFDmax2) (r = -0.71, p ≤ 0.001). These findings indicate that the peak force achieved at the beginning of the movement (PF1) is the main predictor of performance in jumping, although the RFDmax values and the ratio PF2/PF1 are also variables to be taken into account when analyzing the determinant factors of vertical jumping. PMID:28828074

Powder fed sheared dispersal particle generator

NASA Technical Reports Server (NTRS)

Morrisette, E. L.; Bushnell, D. M. (Inventor)

1984-01-01

A particle generating system is described which is capable of breaking up agglomerations of particles and producing a cloud of uniform, submicron-sized particles at high pressure and high flow rates. This is achieved by utilizing a tubular structure which has injection microslits on is periphery to accept and disperse the desired particle feed. By suppling a carrying fluid at a pressure, of approximately twice the ambient pressure of the velocimeter's settling chamber, the microslits operate at choked flow conditions. The shearing action of this choked flow is sufficient to overcome interparticle bonding forces, thereby breaking up the agglomerates of the particles feed into individual particles.

Electronic and mechanical characteristics of stacked dimer molecular junctions.

PubMed

Magyarkuti, András; Adak, Olgun; Halbritter, Andras; Venkataraman, Latha

2018-02-15

Break-junction measurements are typically aimed at characterizing electronic properties of single molecules bound between two metal electrodes. Although these measurements have provided structure-function relationships for such devices, there is little work that studies the impact of molecule-molecule interactions on junction characteristics. Here, we use a scanning tunneling microscope based break-junction technique to study pi-stacked dimer junctions formed with two amine-terminated conjugated molecules. We show that the conductance, force and flicker noise of such dimers differ dramatically when compared with the corresponding monomer junctions and discuss the implications of these results on intra- and inter-molecular charge transport.

Associations Between Rate of Force Development Metrics and Throwing Velocity in Elite Team Handball Players: a Short Research Report

PubMed Central

Marques, Mário C.; Saavedra, Francisco J.; Abrantes, Catarina; Aidar, Felipe J.

2011-01-01

Performance assessment has become an invaluable component of monitoring participant’s development in distinct sports, yet limited and contradictory data are available in trained subjects. The purpose of this study was to examine the relationship between ball throwing velocity during a 3-step running throw in elite team handball players and selected measures of rate of force development like force, power, velocity, and bar displacement during a concentric only bench press exercise in elite male handball players. Fitteen elite senior male team handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric only bench press test with 25, 35, and 45 kg as well as having one-repetition maximum strength determined. Ball throwing velocity was evaluated with a standard 3-step running throw using a radar gun. The results of this study indicated significant associations between ball velocity and time at maximum rate of force development (0, 66; p<0.05) and rate of force development at peak force (0,56; p<0.05) only with 25kg load. The current research indicated that ball velocity was only median associated with maximum rate of force development with light loads. A training regimen designed to improve ball-throwing velocity in elite male team handball players should emphasize bench press movement using light loads. PMID:23487363

Associations between rate of force development metrics and throwing velocity in elite team handball players: a short research report.

PubMed

Marques, Mário C; Saavedra, Francisco J; Abrantes, Catarina; Aidar, Felipe J

2011-09-01

Performance assessment has become an invaluable component of monitoring participant's development in distinct sports, yet limited and contradictory data are available in trained subjects. The purpose of this study was to examine the relationship between ball throwing velocity during a 3-step running throw in elite team handball players and selected measures of rate of force development like force, power, velocity, and bar displacement during a concentric only bench press exercise in elite male handball players. Fitteen elite senior male team handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric only bench press test with 25, 35, and 45 kg as well as having one-repetition maximum strength determined. Ball throwing velocity was evaluated with a standard 3-step running throw using a radar gun. The results of this study indicated significant associations between ball velocity and time at maximum rate of force development (0, 66; p<0.05) and rate of force development at peak force (0,56; p<0.05) only with 25kg load. The current research indicated that ball velocity was only median associated with maximum rate of force development with light loads. A training regimen designed to improve ball-throwing velocity in elite male team handball players should emphasize bench press movement using light loads.

Evaluation of peak force of a manually operated chiropractic adjusting instrument with an adapter for use in animals.

PubMed

Duarte, Felipe Coutinho Kullmann; Kolberg, Carolina; Barros, Rodrigo R; Silva, Vivian G A; Gehlen, Günter; Vassoler, Jakson M; Partata, Wania A

2014-05-01

This study was designed to assess the peak force of a manually operated chiropractic adjusting instrument, the Activator Adjusting Instrument 4 (AAI 4), with an adapter for use in animals, which has a 3- to 4-fold smaller contact surface area than the original rubber tip. Peak force was determined by thrusting the AAI 4 with the adapter or the original rubber tip onto a load cell. First, the AAI 4 was applied perpendicularly by a doctor of chiropractic onto the load cell. Then, the AAI 4 was fixed in a rigid framework and applied to the load cell. This procedure was done to prevent any load on the load cell before the thrust impulse. In 2 situations, trials were performed with the AAI 4 at all force settings (settings I, II, III, and IV, minimum to maximum, respectively). A total of 50000 samples per second over a period of 3 seconds were collected. In 2 experimental protocols, the use of the adapter in the AAI 4 increased the peak force only with setting I. The new value was around 80% of the maximum value found for the AAI 4. Nevertheless, the peak force values of the AAI 4 with the adapter and with the original rubber tip in setting IV were similar. The adapter effectively determines the maximum peak force value at force setting I of AAI 4. Copyright © 2014 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

Biomechanical comparison of two intraoperative mobilization techniques for maxillary distraction osteogenesis: Down-fracture versus non-down-fracture

PubMed Central

Yang, Lili; Suzuki, Eduardo Yugo; Suzuki, Boonsiva

2014-01-01

Purposes: The purpose of this study was to compare the distraction forces and the biomechanical effects between two different intraoperative surgical procedures (down-fracture [DF] and non-DF [NDF]) for maxillary distraction osteogenesis. Materials and Methods: Eight patients were assigned into two groups according to the surgical procedure: DF, n = 6 versus NDF, n = 2. Lateral cephalograms taken preoperatively (T1), immediately after removal of the distraction device (T2), and after at least a 6 months follow-up period (T3) were analyzed. Assessment of distraction forces was performed during the distraction period. The Mann–Whitney U-test was used to compare the difference in the amount of advancement, the maximum distraction force and the amount of relapse. Results: Although a significantly greater amount of maxillary movement was observed in the DF group (median 9.5 mm; minimum-maximum 7.9-14.1 mm) than in the NDF group (median 5.9 mm; minimum-maximum 4.4-7.6 mm), significantly lower maximum distraction forces were observed in the DF (median 16.4 N; minimum-maximum 15.1-24.6 N) than in the NDF (median 32.9 N; minimum-maximum 27.6-38.2 N) group. A significantly greater amount of dental anchorage loss was observed in the NDF group. Moreover, the amount of relapse observed in the NDF group was approximately 3.5 times greater than in the DF group. Conclusions: In this study, it seemed that, the use of the NDF procedure resulted in lower levels of maxillary mobility at the time of the maxillary distraction, consequently requiring greater amounts of force to advance the maxillary bone. Moreover, it also resulted in a reduced amount of maxillary movement, a greater amount of dental anchorage loss and poor treatment stability. PMID:25593865

High temperature thermoplastic elastomers synthesized by living anionic polymerization in hydrocarbon solvent at room temperature

DOE PAGES

Schlegel, Ralf; Williams, Katherine; Voyloy, Dimitry; ...

2016-03-30

We present the synthesis and characterization of a new class of high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene (FIF) triblock copolymers. All copolymers were prepared by living anionic polymerization in benzene at room temperature. Homopolymerization and effects of additives on the glass transition temperature (T g) of polybenzofulvene (PBF) were also investigated. Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390 ± 66% from tensile tests. The stress–strain curves of FIF-10 and 14 were analyzed by a statistical molecular approach using amore » nonaffine tube model to estimate the thermoplastic elastomer behavior. Dynamic mechanical analysis showed that the softening temperature of PBF in FIF was 145 °C, much higher than that of thermoplastic elastomers with polystyrene hard blocks. Microphase separation of FIF triblock copolymers was observed by small-angle X-ray scattering, even though long-range order was not achieved under the annealing conditions employed. Additionally, the microphase separation of the resulting triblock copolymers was examined by atomic force microscopy.« less

High temperature thermoplastic elastomers synthesized by living anionic polymerization in hydrocarbon solvent at room temperature

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

Schlegel, Ralf; Williams, Katherine; Voyloy, Dimitry

We present the synthesis and characterization of a new class of high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene (FIF) triblock copolymers. All copolymers were prepared by living anionic polymerization in benzene at room temperature. Homopolymerization and effects of additives on the glass transition temperature (T g) of polybenzofulvene (PBF) were also investigated. Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390 ± 66% from tensile tests. The stress–strain curves of FIF-10 and 14 were analyzed by a statistical molecular approach using amore » nonaffine tube model to estimate the thermoplastic elastomer behavior. Dynamic mechanical analysis showed that the softening temperature of PBF in FIF was 145 °C, much higher than that of thermoplastic elastomers with polystyrene hard blocks. Microphase separation of FIF triblock copolymers was observed by small-angle X-ray scattering, even though long-range order was not achieved under the annealing conditions employed. Additionally, the microphase separation of the resulting triblock copolymers was examined by atomic force microscopy.« less

Linking the historic 2011 Mississippi River flood to coastal wetland sedimentation

USGS Publications Warehouse

Falcini, Federico; Khan, Nicole S.; Macelloni, Leonardo; Horton, Benjamin P.; Lutken, Carol B.; McKee, Karen L.; Santoleri, Rosalia; Colella, Simone; Li, Chunyan; Volpe, Gianluca; D’Emidio, Marco; Salusti, Alessandro; Jerolmack, Douglas J.

2012-01-01

Wetlands in the Mississippi River deltaic plain are deteriorating in part because levees and control structures starve them of sediment. In Spring of 2011 a record-breaking flood brought discharge on the lower Mississippi River to dangerous levels, forcing managers to divert up to 3500 m3/s-1 of water to the Atchafalaya River Basin. Here we quantify differences between the Mississippi and Atchafalaya River inundation and sediment-plume patterns using field-calibrated satellite data, and assess the impact these outflows had on wetland sedimentation. We characterize hydrodynamics and suspended sediment patterns of the Mississippi River plume using in-situ data collected during the historic flood. We show that the focused, high-momentum jet from the leveed Mississippi delivered sediment far offshore. In contrast, the plume from the Atchafalaya was more diffuse; diverted water inundated a large area; and sediment was trapped within the coastal current. Maximum sedimentation (up to several centimetres) occurred in the Atchafalaya Basin despite the larger sediment load carried by the Mississippi. Minimum accumulation occurred along the shoreline between these river sources. Our findings provide a mechanistic link between river-mouth dynamics and wetland sedimentation patterns that is relevant for plans to restore deltaic wetlands using artificial diversions.

Predicting the safe load on backpacker's arm using Lagrange multipliers method

NASA Astrophysics Data System (ADS)

Abdalla, Faisal Saleh; Rambely, Azmin Sham

2014-09-01

In this study, a technique has been suggested to reduce a backpack load by transmitting determined loads to the children arm. The purpose of this paper is to estimate school children arm muscles while load carriage as well as to determine the safe load can be carried at wrist while walking with backpack. A mathematical model, as three DOFs model, was investigated in the sagittal plane and Lagrange multipliers method (LMM) was utilized to minimize a quadratic objective function of muscle forces. The muscle forces were minimized with three different load conditions which are termed as 0-L=0 N, 1-L=21.95 N, and 2-L=43.9 N. The investigated muscles were estimated and compared to their maximum forces throughout the load conditions. Flexor and extensor muscles were estimated and the results showed that flexor muscles were active while extensor muscles showed inactivity. The estimated muscle forces were didn't exceed their maximum forces with 0-L and 1-L conditions whereas biceps and FCR muscles exceeded their maximum forces with 2-L condition. Consequently, 1-L condition is quiet safe to be carried by hand whereas 2-L condition is not. Thus to reduce the load in the backpack the transmitted load shouldn't exceed 1-L condition.

Bite force measurements with hard and soft bite surfaces.

PubMed

Serra, C M; Manns, A E

2013-08-01

Bite force has been measured by different methods and over a wide variety of designs. In several instruments, the fact that bite surface has been manufactured with stiff materials might interfere in obtaining reliable data, by a more prompt activation of inhibitory reflex mechanisms. The purpose of this study was to compare the maximum voluntary bite force measured by a digital occlusal force gauge (GM10 Nagano Keiki, Japan) between different opponent teeth, employing semi-hard or soft bite surfaces. A sample of 34 young adults with complete natural dentition was studied. The original semi-hard bite surface was exchanged by a soft one, made of leather and rubber. Maximum voluntary bite force recordings were made for each tooth group and for both bite surfaces. Statistical analyses (Student's t-test) revealed significant differences, with higher scores while using the soft surface across sexes and tooth groups (P < 0·05). Differential activation of periodontal mechanoreceptors of a specific tooth group is mainly conditioned by the hardness of the bite surface; a soft surface induces greater activation of elevator musculature, while a hard one induces inhibition more promptly. Thus, soft bite surfaces are recommended for higher reliability in maximum voluntary bite force recordings. © 2013 John Wiley & Sons Ltd.

Grip and limb force limits to turning performance in competition horses

PubMed Central

Tan, Huiling; Wilson, Alan M.

2011-01-01

Manoeuverability is a key requirement for successful terrestrial locomotion, especially on variable terrain, and is a deciding factor in predator–prey interaction. Compared with straight-line running, bend running requires additional leg force to generate centripetal acceleration. In humans, this results in a reduction in maximum speed during bend running and a published model assuming maximum limb force as a constraint accurately predicts how much a sprinter must slow down on a bend given his maximum straight-line speed. In contrast, greyhounds do not slow down or change stride parameters during bend running, which suggests that their limbs can apply the additional force for this manoeuvre. We collected horizontal speed and angular velocity of heading of horses while they turned in different scenarios during competitive polo and horse racing. The data were used to evaluate the limits of turning performance. During high-speed turns of large radius horizontal speed was lower on the bend, as would be predicted from a model assuming a limb force limit to running speed. During small radius turns the angular velocity of heading decreased with increasing speed in a manner consistent with the coefficient of friction of the hoof–surface interaction setting the limit to centripetal force to avoid slipping. PMID:21147799

Grip and limb force limits to turning performance in competition horses.

PubMed

Tan, Huiling; Wilson, Alan M

2011-07-22

Manoeuverability is a key requirement for successful terrestrial locomotion, especially on variable terrain, and is a deciding factor in predator-prey interaction. Compared with straight-line running, bend running requires additional leg force to generate centripetal acceleration. In humans, this results in a reduction in maximum speed during bend running and a published model assuming maximum limb force as a constraint accurately predicts how much a sprinter must slow down on a bend given his maximum straight-line speed. In contrast, greyhounds do not slow down or change stride parameters during bend running, which suggests that their limbs can apply the additional force for this manoeuvre. We collected horizontal speed and angular velocity of heading of horses while they turned in different scenarios during competitive polo and horse racing. The data were used to evaluate the limits of turning performance. During high-speed turns of large radius horizontal speed was lower on the bend, as would be predicted from a model assuming a limb force limit to running speed. During small radius turns the angular velocity of heading decreased with increasing speed in a manner consistent with the coefficient of friction of the hoof-surface interaction setting the limit to centripetal force to avoid slipping.

3D Numerical Simulation of the Wave and Current Loads on a Truss Foundation of the Offshore Wind Turbine During the Extreme Typhoon Event

NASA Astrophysics Data System (ADS)

Lin, C. W.; Wu, T. R.; Chuang, M. H.; Tsai, Y. L.

2015-12-01

The wind in Taiwan Strait is strong and stable which offers an opportunity to build offshore wind farms. However, frequently visited typhoons and strong ocean current require more attentions on the wave force and local scour around the foundation of the turbine piles. In this paper, we introduce an in-house, multi-phase CFD model, Splash3D, for solving the flow field with breaking wave, strong turbulent, and scour phenomena. Splash3D solves Navier-Stokes Equation with Large-Eddy Simulation (LES) for the fluid domain, and uses volume of fluid (VOF) with piecewise linear interface reconstruction (PLIC) method to describe the break free-surface. The waves were generated inside the computational domain by internal wave maker with a mass-source function. This function is designed to adequately simulate the wave condition under observed extreme events based on JONSWAP spectrum and dispersion relationship. Dirichlet velocity boundary condition is assigned at the upper stream boundary to induce the ocean current. At the downstream face, the sponge-layer method combined with pressure Dirichlet boundary condition is specified for dissipating waves and conducting current out of the domain. Numerical pressure gauges are uniformly set on the structure surface to obtain the force distribution on the structure. As for the local scour around the foundation, we developed Discontinuous Bi-viscous Model (DBM) for the development of the scour hole. Model validations were presented as well. The force distribution under observed irregular wave condition was extracted by the irregular-surface force extraction (ISFE) method, which provides a fast and elegant way to integrate the force acting on the surface of irregular structure. From the Simulation results, we found that the total force is mainly induced by the impinging waves, and the force from the ocean current is about 2 order of magnitude smaller than the wave force. We also found the dynamic pressure, wave height, and the projection area of the structure are the main factors to the total force. Detailed results and discussion are presented as well.

Biomechanical Analysis of the Closed Kinetic Chain Upper-Extremity Stability Test.

PubMed

Tucci, Helga T; Felicio, Lilian R; McQuade, Kevin J; Bevilaqua-Grossi, Debora; Camarini, Paula Maria Ferreira; Oliveira, Anamaria S

2017-01-01

The closed kinetic chain upper-extremity stability (CKCUES) test is a functional test for the upper extremity performed in the push-up position, where individuals support their body weight on 1 hand placed on the ground and swing the opposite hand until touching the hand on the ground, then switch hands and repeat the process as fast as possible for 15 s. To study scapular kinematic and kinetic measures during the CKCUES test for 3 different distances between hands. Experimental. Laboratory. 30 healthy individuals (15 male, 15 female). Participants performed 3 repetitions of the test at 3 distance conditions: original (36 in), interacromial, and 150% interacromial distance between hands. Participants completed a questionnaire on pain intensity and perceived exertion before and after the procedures. Scapular internal/external rotation, upward/downward rotation, and posterior/anterior tilting kinematics and kinetic data on maximum force and time to maximum force were measured bilaterally in all participants. Percentage of body weight on upper extremities was calculated. Data analyses were based on the total numbers of hand touches performed for each distance condition, and scapular kinematics and kinetic values were averaged over the 3 trials. Scapular kinematics, maximum force, and time to maximum force were compared for the 3 distance conditions within each gender. Significance level was set at α = .05. Scapular internal rotation, posterior tilting, and upward rotation were significantly greater in the dominant side for both genders. Scapular upward rotation was significantly greater in original distance than interacromial distance in swing phase. Time to maximum force in women was significantly greater in the dominant side. CKCUES test kinematic and kinetic measures were not different among 3 conditions based on distance between hands. However, the test might not be suitable for initial or mild-level rehabilitation due to its challenging requirements.

Familial hypertrophic cardiomyopathy: functional effects of myosin mutation R723G in cardiomyocytes.

PubMed

Kraft, Theresia; Witjas-Paalberends, E Rosalie; Boontje, Nicky M; Tripathi, Snigdha; Brandis, Almuth; Montag, Judith; Hodgkinson, Julie L; Francino, Antonio; Navarro-Lopez, Francisco; Brenner, Bernhard; Stienen, Ger J M; van der Velden, Jolanda

2013-04-01

Familial Hypertrophic Cardiomyopathy (FHC) is frequently caused by mutations in the β-cardiac myosin heavy chain (β-MyHC). To identify changes in sarcomeric function triggered by such mutations, distinguishing mutation effects from other functional alterations of the myocardium is essential. We previously identified a direct effect of mutation R723G (MyHC723) on myosin function in slow Musculus soleus fibers. Here we investigate contractile features of left ventricular cardiomyocytes of FHC-patients with the same MyHC723-mutation and compare these to the soleus data. In mechanically isolated, triton-permeabilized MyHC723-cardiomyocytes, maximum force was significantly lower but calcium-sensitivity was unchanged compared to donor. Conversely, MyHC723-soleus fibers showed significantly higher maximum force and reduced calcium-sensitivity compared to controls. Protein phosphorylation, a potential myocardium specific modifying mechanism, might account for differences compared to soleus fibers. Analysis revealed reduced phosphorylation of troponin I and T, myosin-binding-protein C, and myosin-light-chain 2 in MyHC723-myocardium compared to donor. Saturation of protein-kinaseA phospho-sites led to comparable, i.e., reduced MyHC723-calcium-sensitivity in cardiomyocytes as in M. soleus fibers, while maximum force remained reduced. Myofibrillar disarray and lower density of myofibrils, however, largely account for reduced maximum force in MyHC723-cardiomyocytes. The changes seen when phosphorylation of sarcomeric proteins in myocardium of affected patients is matched to control tissue suggest that the R723G mutation causes reduced Ca(++)-sensitivity in both cardiomyocytes and M. soleus fibers. In MyHC723-myocardium, however, hypophosphorylation can compensate for the reduced calcium-sensitivity, while maximum force generation, lowered by myofibrillar deficiency and disarray, remains impaired, and may only be compensated by hypertrophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

78 FR 74119 - Department of Defense Task Force on the Care, Management, and Transition of Recovering Wounded...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-10

... Project Technical Training Academy Briefing 11:00 a.m.-12:00 p.m. Interagency Program Office (IPO) Briefing 12:00 p.m.-1:00 p.m. Break for Lunch 1:00 p.m.-2:00 p.m. Job Training, Employment Skills Training...

On the numerical treatment of Coulomb forces in scattering problems

NASA Astrophysics Data System (ADS)

Randazzo, J. M.; Ancarani, L. U.; Colavecchia, F. D.; Gasaneo, G.; Frapiccini, A. L.

2012-11-01

We investigate the limiting procedures to obtain Coulomb interactions from short-range potentials. The application of standard techniques used for the two-body case (exponential and sharp cutoff) to the three-body break-up problem is illustrated numerically by considering the Temkin-Poet (TP) model of e-H processes.

Gas pressure in sealed electrochemical cells measured externally

NASA Technical Reports Server (NTRS)

Sherfey, J. M.

1967-01-01

Piezoresistive transducer measures gas pressure inside sealed secondary electrochemical cells without breaking the seal. This method is based on the observed fact that the force exerted by the cell faces on the clamp tightening them against the transducer is a function of the gas pressure inside the cell.

Thoughts on Designing Things To NOT Break.

ERIC Educational Resources Information Center

Klajnscek, Rich

1998-01-01

Explains aspects of the design and loading of high-ropes courses and other challenge-course equipment. Discusses the engineer's factor of safety, determined by industry standards or the level of risk considered acceptable; definitions of terms for material strength; and the forces involved in loads sustained by belay ropes and cables. (SV)

Intercollegiate Athletics Subsidies: A Regressive Tax

ERIC Educational Resources Information Center

Denhart, Matthew; Vedder, Richard

2010-01-01

For most colleges and universities in the United States, intercollegiate athletics is a losing financial proposition. The vast majority ICA departments do not break even and require subsidization from the institution as a whole. When schools are forced to heavily subsidize athletics, ICA serves to impose an "athletics tax" on other dimensions of…

Breaking the Ice: Career Development Activities for Accounting Students

ERIC Educational Resources Information Center

Kilpatrick, Bob G.; Wilburn, Nancy L.

2010-01-01

This paper describes two co-curricular career development activities, mock interviews and speed networking that we provide for accounting majors at our university. The driving force behind both activities was to increase comfort levels for students when interacting with professionals and to enhance their job interview and networking skills.…

50 CFR 229.2 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... highest tensile force which an object can withstand before breaking. Bridle means the lines connecting a... individual authorized by NMFS, or a designated contractor, to record information on marine mammal... fastened to the deck, rail, or drum, and all buoys larger than 6 inches (15.24 cm) in diameter, high flyers...

Does shoe heel design influence ground reaction forces and knee moments during maximum lunges in elite and intermediate badminton players?

PubMed

Lam, Wing-Kai; Ryue, Jaejin; Lee, Ki-Kwang; Park, Sang-Kyoon; Cheung, Jason Tak-Man; Ryu, Jiseon

2017-01-01

Lunge is one frequently executed movement in badminton and involves a unique sagittal footstrike angle of more than 40 degrees at initial ground contact compared with other manoeuvres. This study examined if the shoe heel curvature design of a badminton shoe would influence shoe-ground kinematics, ground reaction forces, and knee moments during lunge. Eleven elite and fifteen intermediate players performed five left-forward maximum lunge trials with Rounded Heel Shoe (RHS), Flattened Heel Shoe (FHS), and Standard Heel Shoes (SHS). Shoe-ground kinematics, ground reaction forces, and knee moments were measured by using synchronized force platform and motion analysis system. A 2 (Group) x 3 (Shoe) ANOVA with repeated measures was performed to determine the effects of different shoes and different playing levels, as well as the interaction of two factors on all variables. Shoe effect indicated that players demonstrated lower maximum vertical loading rate in RHS than the other two shoes (P < 0.05). Group effect revealed that elite players exhibited larger footstrike angle, faster approaching speed, lower peak horizontal force and horizontal loading rates but higher vertical loading rates and larger peak knee flexion and extension moments (P < 0.05). Analysis of Interactions of Group x Shoe for maximum and mean vertical loading rates (P < 0.05) indicated that elite players exhibited lower left maximum and mean vertical loading rates in RHS compared to FHS (P < 0.01), while the intermediate group did not show any Shoe effect on vertical loading rates. These findings indicate that shoe heel curvature would play some role in altering ground reaction force impact during badminton lunge. The differences in impact loads and knee moments between elite and intermediate players may be useful in optimizing footwear design and training strategy to minimize the potential risks for impact related injuries in badminton.

Does shoe heel design influence ground reaction forces and knee moments during maximum lunges in elite and intermediate badminton players?

PubMed Central

Cheung, Jason Tak-Man; Ryu, Jiseon

2017-01-01

Background Lunge is one frequently executed movement in badminton and involves a unique sagittal footstrike angle of more than 40 degrees at initial ground contact compared with other manoeuvres. This study examined if the shoe heel curvature design of a badminton shoe would influence shoe-ground kinematics, ground reaction forces, and knee moments during lunge. Methods Eleven elite and fifteen intermediate players performed five left-forward maximum lunge trials with Rounded Heel Shoe (RHS), Flattened Heel Shoe (FHS), and Standard Heel Shoes (SHS). Shoe-ground kinematics, ground reaction forces, and knee moments were measured by using synchronized force platform and motion analysis system. A 2 (Group) x 3 (Shoe) ANOVA with repeated measures was performed to determine the effects of different shoes and different playing levels, as well as the interaction of two factors on all variables. Results Shoe effect indicated that players demonstrated lower maximum vertical loading rate in RHS than the other two shoes (P < 0.05). Group effect revealed that elite players exhibited larger footstrike angle, faster approaching speed, lower peak horizontal force and horizontal loading rates but higher vertical loading rates and larger peak knee flexion and extension moments (P < 0.05). Analysis of Interactions of Group x Shoe for maximum and mean vertical loading rates (P < 0.05) indicated that elite players exhibited lower left maximum and mean vertical loading rates in RHS compared to FHS (P < 0.01), while the intermediate group did not show any Shoe effect on vertical loading rates. Conclusions These findings indicate that shoe heel curvature would play some role in altering ground reaction force impact during badminton lunge. The differences in impact loads and knee moments between elite and intermediate players may be useful in optimizing footwear design and training strategy to minimize the potential risks for impact related injuries in badminton. PMID:28334016

Influence of G-forces and hypodynamia on the portal system of the liver

NASA Technical Reports Server (NTRS)

Drozdova, A. V.

1975-01-01

Longitudinally and transversely applied g-forces as intolerable levels cause damage to the interlobular veins of the liver, with maximum damage caused by dorso-ventral g-force application. The portal vein system is more resilient with respect to g-forces at the limit of tolerance.

Changes in plantar loading based on shoe type and sex during a jump-landing task.

PubMed

Debiasio, Justin C; Russell, Mary E; Butler, Robert J; Nunley, James A; Queen, Robin M

2013-01-01

Metatarsal stress fractures are common in cleated-sport athletes. Previous authors have shown that plantar loading varies with footwear, sex, and the athletic task. To examine the effects of shoe type and sex on plantar loading in the medial midfoot (MMF), lateral midfoot (LMF), medial forefoot (MFF), middle forefoot (MidFF), and lateral forefoot (LFF) during a jump-landing task. Crossover study. Laboratory. Twenty-seven recreational athletes (14 men, 13 women) with no history of lower extremity injury in the last 6 months and no history of foot or ankle surgery. The athletes completed 7 jumping trials while wearing bladed-cleat, turf-cleat, and running shoes. Maximum force, contact area, contact time, and the force-time integral were analyzed in each foot region. We calculated 2 × 3 analyses of variance (α = .05) to identify shoe-condition and sex differences. We found no shoe × sex interactions, but the MMF, LMF, MFF, and LFF force-time integrals were greater in men (P < .03). The MMF maximum force was less with the bladed-cleat shoes (P = .02). Total foot and MidFF maximum force was less with the running shoes (P < .01). The MFF and LFF maximum forces were different among all shoe conditions (P < .01). Total foot contact area was less in the bladed-cleat shoes (P = .01). The MMF contact area was greatest in the running shoes (P < .01). The LFF contact area was less in the running shoes (P = .03). The MFF and LFF force-time integrals were greater with the bladed-cleat shoes (P < .01). The MidFF force-time integral was less in the running shoes (P < .01). Independent of shoe, men and women loaded the foot differently during a jump landing. The bladed cleat increased forefoot loading, which may increase the risk for forefoot injury. The type of shoe should be considered when choosing footwear for athletes returning to activity after metatarsal stress fractures.

Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

USGS Publications Warehouse

McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

2008-01-01

Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

Flood hydrology and dam-breach hydraulic analyses of four reservoirs in the Black Hills, South Dakota

USGS Publications Warehouse

Hoogestraat, Galen K.

2011-01-01

Extensive information about the construction of dams or potential downstream hazards in the event of a dam breach is not available for many small reservoirs within the Black Hills National Forest. In 2009, the U.S. Forest Service identified the need for reconnaissance-level dam-breach assessments for four of these reservoirs within the Black Hills National Forest (Iron Creek, Horsethief, Lakota, and Mitchell Lakes) with the potential to flood downstream structures. Flood hydrology and dam-breach hydraulic analyses for the four selected reservoirs were conducted by the U.S. Geological Survey in cooperation with the U.S. Forest service to estimate the areal extent of downstream inundation. Three high-flow breach scenarios were considered for cases when the dam is in place (overtopped) and when a dam break (failure) occurs: the 100-year recurrence 24-hour precipitation, 500-year recurrence peak flow, and the probable maximum precipitation. Inundation maps were developed that show the estimated extent of downstream floodwaters from simulated scenarios. Simulation results were used to determine the hazard classification of a dam break (high, significant, or low), based primarily on the potential for loss of life or property damage resulting from downstream inundation because of the flood surge.The inflow design floods resulting from the two simulated storm events (100-year 24-hour and probable maximum precipitation) were determined using the U.S. Army Corps of Engineers Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS). The inflow design flood for the 500-year recurrence peak flow was determined by using regional regression equations developed for streamflow-gaging stations with similar watershed characteristics. The step-backwater hydraulic analysis model, Hydrologic Engineering Center's River Analysis System (HEC-RAS), was used to determine water-surface profiles of in-place and dam-break scenarios for the three inflow design floods that were simulated. Inundation maps for in-place and dam-break scenarios were developed for the area downstream from the dam to the mouth of each stream.Dam-break scenarios for three of the four reservoirs assessed in this study were rated as low hazards owing to absence of permanent structures downstream from the dams. Iron Creek Lake's downstream channel to its mouth does not include any permanent structures within the inundation flood plains. For the two reservoirs with the largest watershed areas, Lakota and Mitchell Lake, the additional floodwater surge resulting from a dam break would be minor relative to the magnitude of the large flood streamflow into the reservoirs, based on the similar areal extent of inundation for the in-place and dam-break scenarios as indicated by the developed maps. A dam-break scenario at Horsethief Lake is rated as a significant hazard because of potential lives-in-jeopardy in downstream dwellings and appreciable economic loss.

Breaking Waves on the Ocean Surface

NASA Astrophysics Data System (ADS)

Schwendeman, Michael S.

In the open ocean, breaking waves are a critical mechanism for the transfer of energy, momentum, and mass between the atmosphere and the ocean. Despite much study, fundamental questions about wave breaking, such as what determines whether a wave will break, remain unresolved. Measurements of oceanic breakers, or "whitecaps," are often used to validate the hypotheses derived in simplified theoretical, numerical, or experimental studies. Real-world measurements are also used to improve the parameterizations of wave-breaking in large global models, such as those forecasting climate change. Here, measurements of whitecaps are presented using ship-based cameras, from two experiments in the North Pacific Ocean. First, a method for georectifying the camera imagery is described using the distant horizon, without additional instrumentation. Over the course of the experiment, this algorithm correctly identifies the horizon in 92% of images in which it is visible. In such cases, the calculation of camera pitch and roll is accurate to within 1 degree. The main sources of error in the final georectification are from mislabeled horizons due to clouds, rain, or poor lighting, and from vertical "heave" motions of the camera, which cannot be calculated with the horizon method. This method is used for correcting the imagery from the first experiment, and synchronizing the imagery from the second experiment to an onboard inertial motion package. Next, measurements of the whitecap coverage, W, are shown from both experiments. Although W is often used in models to represent whitecapping, large uncertainty remains in the existing parameterizations. The data show good agreement with recent measurements using the wind speed. Although wave steepness and dissipation are hypothesized to be more robust predictors of W, this is shown to not always be the case. Wave steepness shows comparable success to the wind parameterizations only when using a mean-square slope variable calculated over the equilibrium range waves and normalizing by the wave directional spread. Meanwhile, correlation of W with turbulent dissipation measurements is significantly worse, which may be due to uncertainty in the measurements or bias related to micro-breaking waves. Finally, phase-resolved, three-dimensional, measurements of the whitecaps were made from a new ship-based stereo video system. Comparison with concurrent buoy measurements indicate that the stereo data accurately reproduces the wave statistics, including the frequency spectra. The whitecaps are characterized by transient and spatially localized regions of extreme surface gradients, rather than large crest-to-trough steepnesses. It was found that whitecaps were around 10 times more likely to have extreme slopes, and 50% of the observed extreme surface slopes were in the vicinity of the breaking waves. The maximum whitecap slopes show good agreement with the Stokes 120 degree limiting crest geometry, and the whitecap crest loses much of its maximum steepness shortly after the onset of breaking. The whitecap phase speeds are consistently less than the linear or weakly nonlinear predicted phase speed, which indicate the effect of narrow-band wave groups, despite the broad-band wave spectra.

Trends in record-breaking temperatures for the conterminous United States

NASA Astrophysics Data System (ADS)

Rowe, Clinton M.; Derry, Logan E.

2012-08-01

In an unchanging climate, record-breaking temperatures are expected to decrease in frequency over time, as established records become increasingly more difficult to surpass. This inherent trend in the number of record-breaking events confounds the interpretation of actual trends in the presence of any underlying climate change. Here, a simple technique to remove the inherent trend is introduced so that any remaining trend can be examined separately for evidence of a climate change. As this technique does not use the standard definition of a broken record, our records* are differentiated by an asterisk. Results for the period 1961-2010 indicate that the number of record* low daily minimum temperatures has been significantly and steadily decreasing nearly everywhere across the United States while the number of record* high daily minimum temperatures has been predominantly increasing. Trends in record* low and record* high daily maximum temperatures are generally weaker and more spatially mixed in sign. These results are consistent with other studies examining changes expected in a warming climate.

Energy attenuation performance of impact protection worn by motorcyclists in real-world crashes.

PubMed

Albanese, Bianca; Gibson, Tom; Whyte, Tom; Meredith, Lauren; Savino, Giovanni; de Rome, Liz; Baldock, Matthew; Fitzharris, Michael; Brown, Julie

2017-05-29

Laboratory studies have demonstrated that impact protectors (IP) used in motorcycle clothing can reduce fracture severities. While crash studies have reported IP are associated with reduced likelihood of soft tissue injury, there is little evidence of their effectiveness in reducing fracture likelihood. This discrepancy might be related to IP quality. There are mandatory requirements for IP supplied with protective clothing in Europe, but not elsewhere. This study examines the energy attenuation performance of IP used by Australian riders. IP were harvested from clothing worn by crashed riders admitted to hospital. The IP were examined and energy attenuation properties were determined using EN 1621-1 test procedures. Impact injury was identified from medical records and defined as fractures, dislocations, and avulsions that occurred following impact to the rider's shoulders, elbows, hips, and/or knees. Fisher's exact test was used to examine the relationship between meeting the EN 1621-1 energy attenuation requirements and impact injury. The association between the average and maximum transmitted force, and impact injury was examined using generalized estimating equations. Motorcycle riders were recruited as part of an in-depth crash study through three hospitals in New South Wales, Australia, between 2012 and 2014. Riders were interviewed, and engineers conducted site, vehicle, and clothing inspections. Clothing was collected, or identical garments were purchased. Clothing was inspected for 62 riders. Of these, 19 wore clothing incorporating 76 IP. Twenty-six of these were impacted in the crash event. Almost all impacted IP (96%) were CE marked, and most (83%) met Level 1 energy attenuation requirements of EN 1621-1 when tested. Of the 26 impacted IP, four were associated with impact injuries, including midshaft and distal clavicle fractures and a scapula and olecranon fracture. No associations between meeting EN 1621-1 requirements and impact injury were found (p = 0.5). There was no association between average force transmitted and impact injury (95% CI: 0.91-1.24); however, as maximum force transmitted increased, the odds of impact injury increased (95% CI: 1.01-1.2). These results indicate a high probability of impact injury at 50 kN, the limit of maximum transmitted force specified in EN 1621-1. The allowable transmitted force of EN 1621-1 may be too high to effectively reduce the probability of impact injury. This is not surprising, given human tolerance levels that are reported in literature. Reducing the force limit below the reported fracture tolerance limits might be difficult with current technology. However, there is scope to reduce the EN 1621-1 maximum limit of 50 kN transmitted force. A reduction in the maximum force limit would improve rider protection and appears feasible, as 77% of tested IP recorded a maximum force <35 kN. This level of transmitted force is estimated to be associated with <20% probability of impact injury. While the performance of IP available to Australian riders is not regulated, most IP was CE marked. The results indicate a significant association between maximum transmitted force, tested according to EN 1621-1 procedures, and impact injury. Further investigation of the EN 1621-1 requirements may be warranted. This work will interest those targeting protective equipment for motorcyclists as a mechanism for reducing injury to these vulnerable road users.

Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion

PubMed Central

Gilman, Casey A.; Imburgia, Michael J.; Bartlett, Michael D.; King, Daniel R.; Crosby, Alfred J.; Irschick, Duncan J.

2015-01-01

One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C) is the change in extension (Δ) relative to a change in force (F) while loading a gecko’s adhesive system (C = dΔ/dF). Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2–100 g). We also examined changes between juveniles and adults within a single species (Phelsuma grandis). We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic “model gecko” system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring) of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of adhesion in animals with dry adhesion systems. PMID:26331621

Control system for maximum use of adhesive forces of a railway vehicle in a tractive mode

NASA Astrophysics Data System (ADS)

Spiryagin, Maksym; Lee, Kwan Soo; Yoo, Hong Hee

2008-04-01

The realization of maximum adhesive forces for a railway vehicle is a very difficult process, because it involves using tractive efforts and depends on friction characteristics in the contact zone between wheels and rails. Tractive efforts are realized by means of tractive torques of motors, and their maximum values can provide negative effects such as slip and skid. These situations usually happen when information about friction conditions is lacking. The negative processes have a major influence on wearing of contact bodies and tractive units. Therefore, many existing control systems for vehicles use an effect of a prediction of a friction coefficient between wheels and rails because measuring a friction coefficient at the moment of running vehicle movement is very difficult. One of the ways to solve this task is to use noise spectrum analysis for friction coefficient detection. This noise phenomenon has not been clearly studied and analyzed. In this paper, we propose an adhesion control system of railway vehicles based on an observer, which allows one to determine the maximum tractive torque based on the optimal adhesive force between the wheels (wheel pair) of a railway vehicle and rails (rail track) depending on weight load from a wheel to a rail, friction conditions in the contact zone, a lateral displacement of wheel set and wheel sleep. As a result, it allows a railway vehicle to be driven in a tractive mode by the maximum adhesion force for real friction conditions.

Tibiofemoral Contact Forces in the Anterior Cruciate Ligament-Reconstructed Knee.

PubMed

Saxby, David John; Bryant, Adam L; Modenese, Luca; Gerus, Pauline; Killen, Bryce A; Konrath, Jason; Fortin, Karine; Wrigley, Tim V; Bennell, Kim L; Cicuttini, Flavia M; Vertullo, Christopher; Feller, Julian A; Whitehead, Tim; Gallie, Price; Lloyd, David G

2016-11-01

To investigate differences in anterior cruciate ligament-reconstructed (ACLR) and healthy individuals in terms of the magnitude of the tibiofemoral contact forces, as well as the relative muscle and external load contributions to those contact forces, during walking, running, and sidestepping gait tasks. A computational EMG-driven neuromusculoskeletal model was used to estimate the muscle and tibiofemoral contact forces in those with single-bundle combined semitendinosus and gracilis tendon autograft ACLR (n = 104, 29.7 ± 6.5 yr, 78.1 ± 14.4 kg) and healthy controls (n = 60, 27.5 ± 5.4 yr, 67.8 ± 14.0 kg) during walking (1.4 ± 0.2 m·s), running (4.5 ± 0.5 m·s) and sidestepping (3.7 ± 0.6 m·s). Within the computational model, the semitendinosus of ACLR participants was adjusted to account for literature reported strength deficits and morphological changes subsequent to autograft harvesting. ACLR had smaller maximum total and medial tibiofemoral contact forces (~80% of control values, scaled to bodyweight) during the different gait tasks. Compared with controls, ACLR were found to have a smaller maximum knee flexion moment, which explained the smaller tibiofemoral contact forces. Similarly, compared with controls, ACLR had both a smaller maximum knee flexion angle and knee flexion excursion during running and sidestepping, which may have concentrated the articular contact forces to smaller areas within the tibiofemoral joint. Mean relative muscle and external load contributions to the tibiofemoral contact forces were not significantly different between ACLR and controls. ACLR had lower bodyweight-scaled tibiofemoral contact forces during walking, running, and sidestepping, likely due to lower knee flexion moments and straighter knee during the different gait tasks. The relative contributions of muscles and external loads to the contact forces were equivalent between groups.

Effect of the loading rate on compressive properties of goose eggs.

PubMed

Nedomová, Š; Kumbár, V; Trnka, J; Buchar, J

2016-03-01

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.

Geometric and mechanical evaluation of 3D-printing materials for skull base anatomical education and endoscopic surgery simulation - A first step to create reliable customized simulators.

PubMed

Favier, Valentin; Zemiti, Nabil; Caravaca Mora, Oscar; Subsol, Gérard; Captier, Guillaume; Lebrun, Renaud; Crampette, Louis; Mondain, Michel; Gilles, Benjamin

2017-01-01

Endoscopic skull base surgery allows minimal invasive therapy through the nostrils to treat infectious or tumorous diseases. Surgical and anatomical education in this field is limited by the lack of validated training models in terms of geometric and mechanical accuracy. We choose to evaluate several consumer-grade materials to create a patient-specific 3D-printed skull base model for anatomical learning and surgical training. Four 3D-printed consumer-grade materials were compared to human cadaver bone: calcium sulfate hemihydrate (named Multicolor), polyamide, resin and polycarbonate. We compared the geometric accuracy, forces required to break thin walls of materials and forces required during drilling. All materials had an acceptable global geometric accuracy (from 0.083mm to 0.203mm of global error). Local accuracy was better in polycarbonate (0.09mm) and polyamide (0.15mm) than in Multicolor (0.90mm) and resin (0.86mm). Resin and polyamide thin walls were not broken at 200N. Forces needed to break Multicolor thin walls were 1.6-3.5 times higher than in bone. For polycarbonate, forces applied were 1.6-2.5 times higher. Polycarbonate had a mode of fracture similar to the cadaver bone. Forces applied on materials during drilling followed a normal distribution except for the polyamide which was melted. Energy spent during drilling was respectively 1.6 and 2.6 times higher on bone than on PC and Multicolor. Polycarbonate is a good substitute of human cadaver bone for skull base surgery simulation. Thanks to short lead times and reasonable production costs, patient-specific 3D printed models can be used in clinical practice for pre-operative training, improving patient safety.

Self-energy and self-force in the space-time of a thick cosmic string

NASA Astrophysics Data System (ADS)

Khusnutdinov, N. R.; Bezerra, V. B.

2001-10-01

We calculate the self-energy and self-force for an electrically charged particle at rest in the background of Gott-Hiscock cosmic string space-time. We find the general expression for the self-energy which is expressed in terms of the S matrix of the scattering problem. The self-energy continuously falls down outward from the string's center with the maximum at the origin of the string. The self-force is repulsive for an arbitrary position of the particle. It tends to zero in the string's center and also far from the string and it has a maximum value at the string's surface. The plots of the numerical calculations of the self-energy and self-force are shown.

Recognition Imaging with a DNA Aptamer

PubMed Central

Lin, Liyun; Wang, Hongda; Liu, Yan; Yan, Hao; Lindsay, Stuart

2006-01-01

We have used a DNA-aptamer tethered to an atomic force microscope probe to carry out recognition imaging of IgE molecules attached to a mica substrate. The recognition was efficient (∼90%) and specific, being blocked by injection of IgE molecules in solution, and not being interfered with by high concentrations of a second protein. The signal/noise ratio of the recognition signal was better than that obtained with antibodies, despite the fact that the average force required to break the aptamer-protein bonds was somewhat smaller. PMID:16513776

Ply-tear webbing energy absorber

NASA Technical Reports Server (NTRS)

Stevens, G. W. H.

1972-01-01

Ply-tear webbing is essentially two plain webbings that are bound together by a portion of the warps and that can be torn apart and do work by breaking the binders. Nylon webbing were woven to range in tear force from 1 to 10 kilonewtons. This force is substantially independent of speed, which was as high as 100 m/sec in some cases. A specific energy absorption of 90 J/g was achieved in the dry state. However, lower rated webbings that absorb approximately 40 J/g are recommended for use in practice where it is acceptable.

The Value of an Independent Royal Air Force - Breaking the Oscar Wilde Paradigm in British Defence

DTIC Science & Technology

2010-06-01

discussion. 11 Ian Drury , Defence Correspondent, "Could this be the end for the RAF? Military chief refuses to rule out merger with Navy as cuts loom...However, would it provide the flexibility to be effective if a different threat emerged in ten years time? In contrast to Smith‟s thesis, Colin ...1984), 88. 25 General Rupert Smith, The Utility of Force – The Art of War in the Modern World (New York, NY: Vintage Books, 2008), 5. 26 Colin

Calculation of muscle loading and joint contact forces during the rock step in Irish dance.

PubMed

Shippen, James M; May, Barbara

2010-01-01

A biomechanical model for the analysis of dancers and their movements is described. The model consisted of 31 segments, 35 joints, and 539 muscles, and was animated using movement data obtained from a three-dimensional optical tracking system that recorded the motion of dancers. The model was used to calculate forces within the muscles and contact forces at the joints of the dancers in this study. Ground reaction forces were measured using force plates mounted in a sprung floor. The analysis procedure is generic and can be applied to any dance form. As an exemplar of the application process an Irish dance step, the rock, was analyzed. The maximum ground reaction force found was 4.5 times the dancer's body weight. The muscles connected to the Achilles tendon experienced a maximum force comparable to their maximal isometric strength. The contact force at the ankle joint was 14 times body weight, of which the majority of the force was due to muscle contraction. It is suggested that as the rock step produces high forces, and therefore the potential to cause injury, its use should be carefully monitored.

Observed changes in the characteristics of Active and Break Spells in the Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

Singh, D.; Tsiang, M.; Rajaratnam, B.; Diffenbaugh, N. S.

2013-12-01

South Asia is home to about 24% of the world's population and is one of the world's most disaster prone regions. The majority of the people in this region depend on agriculture for their livelihood. Substantial variability in the South Asian Summer Monsoon occurs on an intraseasonal timescale (30-60 day) during which it fluctuates between spells of heavy (active spells) and low rainfall (breaks or weak spells). Considering the potentially severe implications of such rainfall variations, we quantify historical changes in the active and break spell characteristics in an effort to understand how these events are likely to respond to future anthropogenic forcings using the 1degx1deg gridded rainfall dataset. We find a decreasing trend in peak season rainfall since 1951 and a statistically significant shift in the rainfall distribution, suggesting greater extremes. Consequently, our results suggest an intensification of the active spells and more frequent occurrence of break spells at the 95% significance level. To understand the cause of these changes, we explore the environmental parameters in the North Indian Ocean and the Western Pacific that influence the occurrence of such events over the core monsoon region. We use the NCEP/NCAR Reanalysis 1 (1948-present) to do a composite analysis for two periods - 1951-1980 and 1981-2011. First, we examine the energetics of the baroclinic instabilities that initiate cyclonic depressions in the northern Bay of Bengal and the net moisture flux into the region. Further, sea surface temperatures are known to influence the characteristics of active and break spells. Therefore, next, we study sea surface temperature patterns in the Bay of Bengal and the equatorial western Pacific preceding breaks. We also examine the persistence of breaks through the diabatic heating anomalies over this region.

First-principles calculation of the polarization-dependent force driving the Eg mode in bismuth under optical excitation.

NASA Astrophysics Data System (ADS)

Murray, Eamonn; Fahy, Stephen

2014-03-01

Using first principles electronic structure methods, we calculate the induced force on the Eg (zone centre transverse optical) phonon mode in bismuth immediately after absorption of polarized light. When radiation with polarization perpendicular to the c-axis is absorbed in bismuth, the distribution of excited electrons and holes breaks the three-fold rotational symmetry and leads to a net force on the atoms in the direction perpendicular to the axis. We calculate the initial excited electronic distribution as a function of photon energy and polarization and find the resulting transverse and longitudinal forces experienced by the atoms. Using the measured, temperature-dependent rate of decay of the transverse force[2], we predict the approximate amplitude of induced atomic motion in the Eg mode as a function of temperature and optical fluence. This work is supported by Science Foundation Ireland and a Marie Curie International Incoming Fellowship.

Systematic Breakdown of Amontons' Law of Friction for an Elastic Object Locally Obeying Amontons' Law

PubMed Central

Otsuki, Michio; Matsukawa, Hiroshi

2013-01-01

In many sliding systems consisting of solid object on a solid substrate under dry condition, the friction force does not depend on the apparent contact area and is proportional to the loading force. This behaviour is called Amontons' law and indicates that the friction coefficient, or the ratio of the friction force to the loading force, is constant. Here, however, using numerical and analytical methods, we show that Amontons' law breaks down systematically under certain conditions for an elastic object experiencing a friction force that locally obeys Amontons' law. The macroscopic static friction coefficient, which corresponds to the onset of bulk sliding of the object, decreases as pressure or system length increases. This decrease results from precursor slips before the onset of bulk sliding, and is consistent with the results of certain previous experiments. The mechanisms for these behaviours are clarified. These results will provide new insight into controlling friction. PMID:23545778

Influence of Emotion on the Control of Low-Level Force Production

ERIC Educational Resources Information Center

Naugle, Kelly M.; Coombes, Stephen A.; Cauraugh, James H.; Janelle, Christopher M.

2012-01-01

The accuracy and variability of a sustained low-level force contraction (2% of maximum voluntary contraction) was measured while participants viewed unpleasant, pleasant, and neutral images during a feedback occluded force control task. Exposure to pleasant and unpleasant images led to a relative increase in force production but did not alter the…

Stress-strain state of reinforced bimodulus beam on an elastic foundation

NASA Astrophysics Data System (ADS)

Beskopylny, A. N.; Kadomtseva, E. E.; Strelnikov, G. P.; Berdnik, Y. A.

2017-10-01

The paper provides the calculation theory of an arbitrary supported and arbitrary loaded reinforced beam filled with bimodulus material. The formulas determining normal stresses, bending moments, shear forces, rotation angles and a deflection of a rectangular crosssection beam reinforced with any number of bars aligned parallel to the beam axis have been obtained. The numerical study has been carried out to investigate an influence of a modulus of subgrade reaction on values of maximum normal stresses, maximum bending moments and a maximum deflection of a hinged supported beam loaded with a point force or uniform distributed load. The estimation is based on the method of initial parameters for a beam on elastic foundation and the Bubnov-Galerkin method. Values of maximum deflections, maximum bending moments and maximum stresses obtained by these methods coincide. The numerical studies show that taking into consideration the bimodulus of material leads to the necessity to calculate the strength analysis of both tensile stresses and compressive stresses.

Selective effects of different fatigue protocols on the function of upper body muscles assessed through the force-velocity relationship.

PubMed

García-Ramos, Amador; Torrejón, Alejandro; Feriche, Belén; Morales-Artacho, Antonio J; Pérez-Castilla, Alejandro; Padial, Paulino; Jaric, Slobodan

2018-02-01

This study explored the feasibility of the force-velocity relationship (F-V) to detect the acute effects of different fatigue protocols on the selective changes of the maximal capacities of upper body muscles to produce force, velocity, and power. After determining the bench press one-repetition maximum (1RM), participants' F-V relationships were assessed during the bench press throw exercise on five separate sessions after performing one of the following fatiguing protocols: 60%1RM failure, 60%1RM non-failure, 80%1RM failure, 80%1RM non-failure, and no-fatigue. In the non-failure protocols, participants performed half the maximum number of repetitions than in their respective failure protocols. The main findings revealed that (1) all F-V relationships were highly linear (median r = 0.997 and r = 0.982 for averaged across participants and individual data, respectively), (2) the fatiguing protocols were ranked based on the magnitude of power loss as follows: 60%1RM failure > 80%1RM failure > 60%1RM non-failure > 80%1RM non-failure, while (3) the assessed maximum force and velocity outputs showed a particularly prominent reduction in the protocols based on the lowest and highest levels of fatigue (i.e., 80%1RM non-failure and 60%1RM failure), respectively. The results support the use of F-V to assess the effects of fatigue on the distinctive capacities of the muscles to produce force, velocity, and power output while performing multi-joint tasks, while the assessed maximum force and velocity capacities showed a particularly prominent reduction in the protocols based on the lowest and highest levels of fatigue (i.e., 80%1RM non-failure and 60%1RM failure), respectively.

Late summer and fall wave climate in the Beaufort and Chukchi Seas, 2000-2014

NASA Astrophysics Data System (ADS)

Fan, Y.; Rogers, W.; Thomson, J.; Stopa, J.

2016-02-01

Jim Thomson, Applied Physics Laboratory, University of Washington, Seattle, WA According to IPCC, "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world." Some regions within the Arctic have warmed even more rapidly, with Alaska and western Canada's temperature rising by 3 to 4 °C (5.40 to 7.20 °F). Arctic ice is getting thinner, melting and rupturing. The polar ice cap as a whole is shrinking. Images from NASA satellites show that the area of permanent ice cover is contracting at a rate of 9 percent each decade. If this trend continues, summers in the Arctic could become ice-free by the end of the century. Arctic storms thus have the potential to create large waves in the region. Ocean waves can also penetrate remarkable distances into ice fields and impact sea-ice thermodynamics by breaking up ice floes and accelerating ice melting during the summer (Asplin et al 2012); or influencing sea-ice growth and hence the morphology of the mature ice sheet during the winter (Lange et al 1989). Waves breaking on the shore could also affect the coastlines, where melting permafrost is already making shores more vulnerable to erosion. Preliminary wave model results from four selected years suggests that the sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. In particular, larger waves are more common in years with low or late sea ice cover. Trends in amount of wave energy impinging on the ice edge, however, are inconclusive. To better understand the potential effect of surface wave on the advance/retreat of ice edges and the coastlines. 15 years (2000 to 2014) of surface wave simulations in the Arctic Ocean using WAVEWATCH III will be conducted. Wind and ice forcing are obtained from the ERA-interim global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). Wave energy flux arriving at the ice edges and land boundaries will be analyzed and histograms and fitted Weibull probability distribution functions will used to identify similarities and differences during the 15 year period. The potential effect of surface waves on ice advance/retreat and land erosion will be explored and discussed.

Co-seismic ruptures of the 12 May 2008, Ms 8.0 Wenchuan earthquake, Sichuan: East-west crustal shortening on oblique, parallel thrusts along the eastern edge of Tibet

USGS Publications Warehouse

Liu-Zeng, J.; Zhang, Z.; Wen, L.; Tapponnier, P.; Sun, Jielun; Xing, X.; Hu, G.; Xu, Q.; Zeng, L.; Ding, L.; Ji, C.; Hudnut, K.W.; van der Woerd, J.

2009-01-01

The Ms 8.0, Wenchuan earthquake, which devastated the mountainous western rim of the Sichuan basin in central China, produced a surface rupture over 200??km-long with oblique thrust/dextral slip and maximum scarp heights of ~ 10??m. It thus ranks as one of the world's largest continental mega-thrust events in the last 150??yrs. Field investigation shows clear surface breaks along two of the main branches of the NE-trending Longmen Shan thrust fault system. The principal rupture, on the NW-dipping Beichuan fault, displays nearly equal amounts of thrust and right-lateral slip. Basin-ward of this rupture, another continuous surface break is observed for over 70??km on the parallel, more shallowly NW-dipping Pengguan fault. Slip on this latter fault was pure thrusting, with a maximum scarp height of ~ 3.5??m. This is one of the very few reported instances of crustal-scale co-seismic slip partitioning on parallel thrusts. This out-of-sequence event, with distributed surface breaks on crustal mega-thrusts, highlights regional, ~ EW-directed, present day crustal shortening oblique to the Longmen Shan margin of Tibet. The long rupture and large offsets with strong horizontal shortening that characterize the Wenchuan earthquake herald a re-evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau, and require a re-assessment of seismic hazard along potentially under-rated active faults across the densely populated western Sichuan basin and mountains. ?? 2009 Elsevier B.V.

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

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

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei

In this paper, atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements aremore » sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. Finally, the comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.« less

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

DOE PAGES

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei; ...

2016-09-02

In this paper, atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements aremore » sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. Finally, the comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.« less

Superior-inferior position of patellar component affects patellofemoral kinematics and contact forces in computer simulation.

PubMed

Nakamura, Shinichiro; Tanaka, Yoshihisa; Kuriyama, Shinichi; Nishitani, Kohei; Ito, Hiromu; Furu, Moritoshi; Matsuda, Shuichi

2017-06-01

Anterior knee pain has been reported as a major postoperative complication after total knee arthroplasty, which may lead to patient dissatisfaction. Rotational alignment and the medial-lateral position correlate with patellar maltracking, which can cause knee pain postoperatively. However, the superior-inferior position of the patellar component has not been investigated. The purpose of the current study was to investigate the effects of the patellar superior-inferior position on patellofemoral kinematics and kinetics. Superior, central, and inferior models with a dome patellar component were constructed. In the superior and inferior models, the position of the patellar component translated superiorly and inferiorly, respectively, by 3mm, relative to the center model. Kinematics of the patellar component, quadriceps force, and patellofemoral contact force were calculated using a computer simulation during a squatting activity in a weight-bearing deep knee bend. In the inferior model, the flexion angle, relative to the tibial component, was the greatest among all models. The inferior model showed an 18.0%, 36.5%, and 22.7% increase in the maximum quadriceps force, the maximum medial patellofemoral force, and the maximum lateral patellofemoral force, respectively, compared with the superior model. Superior-inferior positions affected patellofemoral kinematic and kinetics. Surgeons should avoid the inferior position of the patellar component, because the inferior positioned model showed greater quadriceps and patellofemoral force, resulting in a potential risk for anterior knee pain and component loosening. Copyright © 2017. Published by Elsevier Ltd.

Do PTK2 gene polymorphisms contribute to the interindividual variability in muscle strength and the response to resistance training? A preliminary report.

PubMed

Erskine, Robert M; Williams, Alun G; Jones, David A; Stewart, Claire E; Degens, Hans

2012-04-01

The protein tyrosine kinase-2 (PTK2) gene encodes focal adhesion kinase, a structural protein involved in lateral transmission of muscle fiber force. We investigated whether single-nucleotide polymorphisms (SNPs) of the PTK2 gene were associated with various indexes of human skeletal muscle strength and the interindividual variability in the strength responses to resistance training. We determined unilateral knee extension single repetition maximum (1-RM), maximum isometric voluntary contraction (MVC) knee joint torque, and quadriceps femoris muscle specific force (maximum force per unit physiological cross-sectional area) before and after 9 wk of knee extension resistance training in 51 untrained young men. All participants were genotyped for the PTK2 intronic rs7843014 A/C and 3'-untranslated region (UTR) rs7460 A/T SNPs. There were no genotype associations with baseline measures or posttraining changes in 1-RM or MVC. Although the training-induced increase in specific force was similar for all PTK2 genotypes, baseline specific force was higher in PTK2 rs7843014 AA and rs7460 TT homozygotes than in the respective rs7843014 C- (P = 0.016) and rs7460 A-allele (P = 0.009) carriers. These associations between muscle specific force and PTK2 SNPs suggest that interindividual differences exist in the way force is transmitted from the muscle fibers to the tendon. Therefore, our results demonstrate for the first time the impact of genetic variation on the intrinsic strength of human skeletal muscle.

Analyses of Deformation and Stress of Oil-free Scroll Compressor Scroll

NASA Astrophysics Data System (ADS)

Peng, Bin; Li, Yaohong; Zhao, Shenxian

2017-12-01

The solid model of orbiting and fixed scroll is created by the Solidworks The deformation and stress of scrolls under gas force, temperature field, inertia force and the coupling field are analyzed using the Ansys software. The deformation for different thickness and height scroll tooth is investigated. The laws of deformation and stress for scrolls are gotten. The research results indicate that the stress and deformation of orbiting scroll are mainly affected by the temperature field. The maximum deformation occurs in the tooth head of scroll wrap because of the largest gas forces and the highest temperature in the tooth head of scroll wrap. The maximum stress is located in the end of the tooth, and the maximum stress of the coupling field is not the sum of loads. The scroll tooth is higher, and the deformation is bigger. The scroll tooth is thicker, and the deformation is smaller.

Potential landscape and flux field theory for turbulence and nonequilibrium fluid systems

NASA Astrophysics Data System (ADS)

Wu, Wei; Zhang, Feng; Wang, Jin

2018-02-01

Turbulence is a paradigm for far-from-equilibrium systems without time reversal symmetry. To capture the nonequilibrium irreversible nature of turbulence and investigate its implications, we develop a potential landscape and flux field theory for turbulent flow and more general nonequilibrium fluid systems governed by stochastic Navier-Stokes equations. We find that equilibrium fluid systems with time reversibility are characterized by a detailed balance constraint that quantifies the detailed balance condition. In nonequilibrium fluid systems with nonequilibrium steady states, detailed balance breaking leads directly to a pair of interconnected consequences, namely, the non-Gaussian potential landscape and the irreversible probability flux, forming a 'nonequilibrium trinity'. The nonequilibrium trinity characterizes the nonequilibrium irreversible essence of fluid systems with intrinsic time irreversibility and is manifested in various aspects of these systems. The nonequilibrium stochastic dynamics of fluid systems including turbulence with detailed balance breaking is shown to be driven by both the non-Gaussian potential landscape gradient and the irreversible probability flux, together with the reversible convective force and the stochastic stirring force. We reveal an underlying connection of the energy flux essential for turbulence energy cascade to the irreversible probability flux and the non-Gaussian potential landscape generated by detailed balance breaking. Using the energy flux as a center of connection, we demonstrate that the four-fifths law in fully developed turbulence is a consequence and reflection of the nonequilibrium trinity. We also show how the nonequilibrium trinity can affect the scaling laws in turbulence.

Study on the rheological properties and volatile release of cold-set emulsion-filled protein gels.

PubMed

Mao, Like; Roos, Yrjö H; Miao, Song

2014-11-26

Emulsion-filled protein gels (EFP gels) were prepared through a cold-set gelation process, and they were used to deliver volatile compounds. An increase in the whey protein isolate (WPI) content from 4 to 6% w/w did not show significant effect on the gelation time, whereas an increase in the oil content from 5 to 20% w/w resulted in an earlier onset of gelation. Gels with a higher WPI content had a higher storage modulus and water-holding capacity (WHC), and they presented a higher force and strain at breaking, indicating that a more compact gel network was formed. An increase in the oil content contributed to gels with a higher storage modulus and force at breaking; however, this increase did not affect the WHC of the gels, and gels with a higher oil content became more brittle, resulting in a decreased strain at breaking. GC headspace analysis showed that volatiles released at lower rates and had lower air-gel partition coefficients in EFP gels than those in ungelled counterparts. Gels with a higher WPI content had lower release rates and partition coefficients of the volatiles. A change in the oil content significantly modified the partition of volatiles at equilibrium, but it produced a minor effect on the release rate of the volatiles. The findings indicated that EFP gels could be potentially used to modulate volatile release by varying the rheological properties of the gel.

Aerosols cause intraseasonal short-term suppression of Indian monsoon rainfall.

PubMed

Dave, Prashant; Bhushan, Mani; Venkataraman, Chandra

2017-12-11

Aerosol abundance over South Asia during the summer monsoon season, includes dust and sea-salt, as well as, anthropogenic pollution particles. Using observations during 2000-2009, here we uncover repeated short-term rainfall suppression caused by coincident aerosols, acting through atmospheric stabilization, reduction in convection and increased moisture divergence, leading to the aggravation of monsoon break conditions. In high aerosol-low rainfall regions extending across India, both in deficient and normal monsoon years, enhancements in aerosols levels, estimated as aerosol optical depth and absorbing aerosol index, acted to suppress daily rainfall anomaly, several times in a season, with lags of a few days. A higher frequency of prolonged rainfall breaks, longer than seven days, occurred in these regions. Previous studies point to monsoon rainfall weakening linked to an asymmetric inter-hemispheric energy balance change attributed to aerosols, and short-term rainfall enhancement from radiative effects of aerosols. In contrast, this study uncovers intraseasonal short-term rainfall suppression, from coincident aerosol forcing over the monsoon region, leading to aggravation of monsoon break spells. Prolonged and intense breaks in the monsoon in India are associated with rainfall deficits, which have been linked to reduced food grain production in the latter half of the twentieth century.

Pretreatment of microbial sludges

DOEpatents

Rivard, Christopher J.; Nagle, Nicholas J.

1995-01-01

Methods are described for pretreating microbial sludges to break cells and disrupt organic matter. One method involves the use of sonication, and another method involves the use of shear forces. The pretreatment of sludge enhances bioconversion of the organic fraction. This allows for efficient dewatering of the sludge and reduces the cost for final disposal of the waste.

Planetary Wave Breaking and Tropospheric Forcing as Seen in the Stratospheric Sudden Warming of 2006

DTIC Science & Technology

2009-02-01

involved in this complex case ( Harnik et al. 2005). The forecasting experiments (Fig. 8) show, in this case, the importance of accurately forecasting the...Phoebus, 1992: The Navy’s operational atmospheric analysis. Wea. Forecasting, 7, 232–249. Harnik , N., R. K. Scott, and J. Perlwitz, 2005: Wave

Tuskegee Airman Lee Hayes

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

Hayes, Lee

2006-08-03

Hayes, a resident of Amagansett who worked at Brookhaven Lab as a custodian from 1958 to 1966, served in an all-black bomber squadron at Tuskegee Army Air Field in Alabama. He was among 994 precedent-breaking black soldiers at Tuskegee who passed rigorous tests between 1942 and 1946 to become pilots in the then-segregated armed forces.

77 FR 3454 - Department of Defense Task Force on the Care, Management, and Transition of Recovering Wounded...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-24

... Members Post-Operational Deployment, Dr. Richard R. Bannick 9:30-9:45 a.m. Break 9:45-10:45 a.m. OSD... 10 a.m.-12 p.m. Panel on Evidence-Based Treatment Modalities for PTSD (Program 12:00-1 p.m. Lunch 1...

Pretreatment of microbial sludges

DOEpatents

Rivard, C.J.; Nagle, N.J.

1995-01-10

Methods are described for pretreating microbial sludges to break cells and disrupt organic matter. One method involves the use of sonication, and another method involves the use of shear forces. The pretreatment of sludge enhances bioconversion of the organic fraction. This allows for efficient dewatering of the sludge and reduces the cost for final disposal of the waste.

Caught in the Middle

ERIC Educational Resources Information Center

Beem, Kate

2006-01-01

In April 2005, the board of education in the Muhlenberg School District was forced to break one of their school policies after several parents complained about a book that has been included in the school's curriculum. The book, "The Buffalo Tree," by Adam Rapp has a passage detailing how an adolescent boy becomes sexually aroused in a communal…

Tuskegee Airman Lee Hayes

ScienceCinema

Hayes, Lee

2017-12-22

Hayes, a resident of Amagansett who worked at Brookhaven Lab as a custodian from 1958 to 1966, served in an all-black bomber squadron at Tuskegee Army Air Field in Alabama. He was among 994 precedent-breaking black soldiers at Tuskegee who passed rigorous tests between 1942 and 1946 to become pilots in the then-segregated armed forces.

Catering to a Diverse Crowd

ERIC Educational Resources Information Center

Fogg, Piper

2008-01-01

Isolation and lack of services for members of minority groups can be real hurdles for colleges in small towns and rural areas that want to diversify their work forces. The chance to meet people from the same background, worship in a shared faith, or share cultural interests can make or break someone's living experience. This article describes…

Estimating severity of sideways fall using a generic multi linear regression model based on kinematic input variables.

PubMed

van der Zijden, A M; Groen, B E; Tanck, E; Nienhuis, B; Verdonschot, N; Weerdesteyn, V

2017-03-21

Many research groups have studied fall impact mechanics to understand how fall severity can be reduced to prevent hip fractures. Yet, direct impact force measurements with force plates are restricted to a very limited repertoire of experimental falls. The purpose of this study was to develop a generic model for estimating hip impact forces (i.e. fall severity) in in vivo sideways falls without the use of force plates. Twelve experienced judokas performed sideways Martial Arts (MA) and Block ('natural') falls on a force plate, both with and without a mat on top. Data were analyzed to determine the hip impact force and to derive 11 selected (subject-specific and kinematic) variables. Falls from kneeling height were used to perform a stepwise regression procedure to assess the effects of these input variables and build the model. The final model includes four input variables, involving one subject-specific measure and three kinematic variables: maximum upper body deceleration, body mass, shoulder angle at the instant of 'maximum impact' and maximum hip deceleration. The results showed that estimated and measured hip impact forces were linearly related (explained variances ranging from 46 to 63%). Hip impact forces of MA falls onto the mat from a standing position (3650±916N) estimated by the final model were comparable with measured values (3698±689N), even though these data were not used for training the model. In conclusion, a generic linear regression model was developed that enables the assessment of fall severity through kinematic measures of sideways falls, without using force plates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes.

PubMed

Yi, Kexi; Rubinstein, Boris; Unruh, Jay R; Guo, Fengli; Slaughter, Brian D; Li, Rong

2013-03-04

Polar body extrusion during oocyte maturation is critically dependent on asymmetric positioning of the meiotic spindle, which is established through migration of the meiosis I (MI) spindle/chromosomes from the oocyte interior to a subcortical location. In this study, we show that MI chromosome migration is biphasic and driven by consecutive actin-based pushing forces regulated by two actin nucleators, Fmn2, a formin family protein, and the Arp2/3 complex. Fmn2 was recruited to endoplasmic reticulum structures surrounding the MI spindle, where it nucleated actin filaments to initiate an initially slow and poorly directed motion of the spindle away from the cell center. A fast and highly directed second migration phase was driven by actin-mediated cytoplasmic streaming and occurred as the chromosomes reach a sufficient proximity to the cortex to activate the Arp2/3 complex. We propose that decisive symmetry breaking in mouse oocytes results from Fmn2-mediated perturbation of spindle position and the positive feedback loop between chromosome signal-induced Arp2/3 activation and Arp2/3-orchestrated cytoplasmic streaming that transports the chromosomes.

Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes

PubMed Central

Yi, Kexi; Rubinstein, Boris; Unruh, Jay R.; Guo, Fengli; Slaughter, Brian D.

2013-01-01

Polar body extrusion during oocyte maturation is critically dependent on asymmetric positioning of the meiotic spindle, which is established through migration of the meiosis I (MI) spindle/chromosomes from the oocyte interior to a subcortical location. In this study, we show that MI chromosome migration is biphasic and driven by consecutive actin-based pushing forces regulated by two actin nucleators, Fmn2, a formin family protein, and the Arp2/3 complex. Fmn2 was recruited to endoplasmic reticulum structures surrounding the MI spindle, where it nucleated actin filaments to initiate an initially slow and poorly directed motion of the spindle away from the cell center. A fast and highly directed second migration phase was driven by actin-mediated cytoplasmic streaming and occurred as the chromosomes reach a sufficient proximity to the cortex to activate the Arp2/3 complex. We propose that decisive symmetry breaking in mouse oocytes results from Fmn2-mediated perturbation of spindle position and the positive feedback loop between chromosome signal-induced Arp2/3 activation and Arp2/3-orchestrated cytoplasmic streaming that transports the chromosomes. PMID:23439682

Spatial heterogeneity and the evolution of sex in diploids.

PubMed

Agrawal, Aneil F

2009-07-01

Much of the theoretical work on the evolution of sex has focused on the effects of recombination. In diploids, segregation also occurs during sexual reproduction. Segregation breaks down some types of genetic associations that are not affected by recombination and thus influences the evolution of sex in ways that are not apparent from studying the evolution of recombination as a surrogate for sex. Here I examine the evolution of sex in diploids experiencing spatially heterogeneous selection. If divergent selection causes genetic differentiation, then migration can be a powerful force generating genetic associations that may not be favored by selection. An advantage to sex can arise from breaking down these associations. By examining modifiers of both sex and recombination, the model allows for a direct comparison of the forces acting on these related but different processes, illuminating the role of segregation. The model also includes inbreeding, which has been shown to be important for both segregation and recombination. I find that inbreeding affects the evolution of sex through segregation, not recombination. Several suggestions for empirical experiments are given.

Light backscatter fiber optic sensor: a new tool for predicting the stability of pork emulsions containing antioxidative potato protein hydrolysate.

PubMed

Nieto, Gema; Xiong, Youling L; Payne, Fred; Castillo, Manuel

2015-02-01

The objective of this study was to determine whether light backscatter response from fresh pork meat emulsions is correlated to final product stability indices. A specially designed fiber optic measurement system was used in combination with a miniature fiber optic spectrometer to determine the intensity of light backscatter within the wavelength range 300-1100 nm (UV/VIS/NIR) at different radial distances (2, 2.5 and 3mm) with respect to the light source in pork meat emulsions with two fat levels (15%, 30%) and two levels (0, 2.5%) of the natural antioxidant hydrolyzed potato protein (HPP). Textural parameters (hardness, deformability, cohesiveness and breaking force), cooking loss, TBARS (1, 2, 3, and 7 days of storage at 4 °C) and CIELAB color coordinates of cooked emulsions were measured. The light backscatter was directly correlated with cooking losses, color, breaking force and TBARS. The optical configuration proposed would compensate for the emulsion heterogeneity, maximizing the existing correlation between the optical signal and the emulsion quality metrics.

Increased in-shoe lateral plantar pressures with chronic ankle instability.

PubMed

Schmidt, Heather; Sauer, Lindsay D; Lee, Sae Yong; Saliba, Susan; Hertel, Jay

2011-11-01

Previous plantar pressure research found increased loads and slower loading response on the lateral aspect of the foot during gait with chronic ankle instability compared to healthy controls. The studies had subjects walking barefoot over a pressure mat and results have not been confirmed with an in-shoe plantar pressure system. Our purpose was to report in-shoe plantar pressure measures for chronic ankle instability subjects compared to healthy controls. Forty-nine subjects volunteered (25 healthy controls, 24 chronic ankle instability) for this case-control study. Subjects jogged continuously on a treadmill at 2.68 m/s (6.0 mph) while three trials of ten consecutive steps were recorded. Peak pressure, time-to-peak pressure, pressure-time integral, maximum force, time-to-maximum force, and force-time integral were assessed in nine regions of the foot with the Pedar-x in-shoe plantar pressure system (Novel, Munich, Germany). Chronic ankle instability subjects demonstrated a slower loading response in the lateral rearfoot indicated by a longer time-to-peak pressure (16.5% +/- 10.1, p = 0.001) and time-to-maximum force (16.8% +/- 11.3, p = 0.001) compared to controls (6.5% +/- 3.7 and 6.6% +/- 5.5, respectively). In the lateral midfoot, ankle instability subjects demonstrated significantly greater maximum force (318.8 N +/- 174.5, p = 0.008) and peak pressure (211.4 kPa +/- 57.7, p = 0.008) compared to controls (191.6 N +/- 74.5 and 161.3 kPa +/- 54.7). Additionally, ankle instability subjects demonstrated significantly higher force-time integral (44.1 N/s +/- 27.3, p = 0.005) and pressure-time integral (35.0 kPa/s +/- 12.0, p = 0.005) compared to controls (23.3 N/s +/- 10.9 and 24.5 kPa/s +/- 9.5). In the lateral forefoot, ankle instability subjects demonstrated significantly greater maximum force (239.9N +/- 81.2, p = 0.004), force-time integral (37.0 N/s +/- 14.9, p = 0.003), and time-to-peak pressure (51.1% +/- 10.9, p = 0.007) compared to controls (170.6 N +/- 49.3, 24.3 N/s +/- 7.2 and 43.8% +/- 4.3). Using an in-shoe plantar pressure system, chronic ankle instability subjects had greater plantar pressures and forces in the lateral foot compared to controls during jogging. These findings may have implications in the etiology and treatment of chronic ankle instability.

Kinetics of badminton lunges in four directions.

PubMed

Hong, Youlian; Wang, Shao Jun; Lam, Wing Kai; Cheung, Jason Tak Man

2014-02-01

The lunge is the most fundamental skill in badminton competitions. Fifteen university-level male badminton players performed lunge maneuvers in four directions, namely, right-forward, left-forward, right-backward, and left-backward, while wearing two different brands of badminton shoes. The test compared the kinetics of badminton shoes in performing typical lunge maneuvers. A force plate and an insole measurement system measured the ground reaction forces and plantar pressures. These measurements were compared across all lunge maneuvers. The left-forward lunge generated significantly higher first vertical impact force (2.34 ± 0.52 BW) than that of the right-backward (2.06 ± 0.60 BW) and left-backward lunges (1.78 ± 0.44 BW); higher second vertical impact force (2.44 ± 0.51 BW) than that of the left-backward lunge (2.07 ± 0.38 BW); and higher maximum anterior-posterior shear force (1.48 ± 0.36 BW) than that of the left-backward lunge (1.18 ± 0.38 BW). Compared with other lunge directions, the left-forward lunge showed higher mean maximum vertical impact anterior-posterior shear forces and their respective maximum loading rates, and the plantar pressure at the total foot and heel regions. Therefore, the left-forward lunge is a critical maneuver for badminton biomechanics and related footwear research because of the high loading magnitude generated during heel impact.

Bending stiffness, torsional stability, and insertion force of cementless femoral stems.

PubMed

Incavo, S J; Johnson, C C; Churchill, D L; Beynnon, B D

2001-04-01

In cementless total hip arthroplasty, increased femoral stem flexibility and decreased fracture propensity are desirable characteristics. The slotting and tapering of the stem have been introduced to achieve this. These features should not, however, be allowed to interfere with the ability of the distal stem to provide initial mechanical stability, especially under rotation. This study was done to investigate the ability of slotted and tapered stem designs to reduce stiffness and insertion force while still maintaining adequate torsional strength. The torsional strength, maximum insertion force, and insertional work of straight, slotted, and taper stems were measured by inserting each type into rigid polyurethane foam and torque testing to failure. Bending stiffness of each stem design was calculated using numerical methods. When compared to a straight stem, a unislot stem has similar torsional strength, maximum insertional force, and work of insertion. The bending stiffness is decreased by 19% to 82% depending on the bending direction. A trislot design decreased torque strength by 29%, maximal insertion force by 36%, and work by 11%. Bending stiffness was decreased by 74% and was not dependent on bending direction. A 0.5-mm taper decreased torque strength by 11% and insertional work by 14%. No difference was seen in maximum insertional force. We conclude that the design features studied (slots and taper) are effective in decreasing stem stiffness and reducing fracture propensity.

Acoustic Emission from Breaking a Bamboo Chopstick

NASA Astrophysics Data System (ADS)

Tsai, Sun-Ting; Wang, Li-Min; Huang, Panpan; Yang, Zhengning; Chang, Chin-De; Hong, Tzay-Ming

2016-01-01

The acoustic emission from breaking a bamboo chopstick or a bundle of spaghetti is found to exhibit similar behavior as the famous seismic laws of Gutenberg and Richter, Omori, and Båth. By the use of a force-sensing detector, we establish a positive correlation between the statistics of sound intensity and the magnitude of a tremor. We also manage to derive these laws analytically without invoking the concept of a phase transition, self-organized criticality, or fractal. Our model is deterministic and relies on the existence of a structured cross section, either fibrous or layered. This success at explaining the power-law behavior supports the proposal that geometry is sometimes more important than mechanics.

Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers.

PubMed

Roche, Stuart M; Gumucio, Jonathan P; Brooks, Susan V; Mendias, Christopher L; Claflin, Dennis R

2015-06-16

Analysis of the contractile properties of chemically skinned, or permeabilized, skeletal muscle fibers offers a powerful means by which to assess muscle function at the level of the single muscle cell. Single muscle fiber studies are useful in both basic science and clinical studies. For basic studies, single muscle fiber contractility measurements allow investigation of fundamental mechanisms of force production, and analysis of muscle function in the context of genetic manipulations. Clinically, single muscle fiber studies provide useful insight into the impact of injury and disease on muscle function, and may be used to guide the understanding of muscular pathologies. In this video article we outline the steps required to prepare and isolate an individual skeletal muscle fiber segment, attach it to force-measuring apparatus, activate it to produce maximum isometric force, and estimate its cross-sectional area for the purpose of normalizing the force produced.

Trapping and rotating of a metallic particle trimer with optical vortex

NASA Astrophysics Data System (ADS)

Shen, Z.; Su, L.; Yuan, X.-C.; Shen, Y.-C.

2016-12-01

We have experimentally observed the steady rotation of a mesoscopic size metallic particle trimer that is optically trapped by tightly focused circularly polarized optical vortex. Our theoretical analysis suggests that a large proportion of the radial scattering force pushes the metallic particles together, whilst the remaining portion provides the centripetal force necessary for the rotation. Furthermore, we have achieved the optical trapping and rotation of four dielectric particles with optical vortex. We found that, different from the metallic particles, instead of being pushed together by the radial scattering force, the dielectric particles are trapped just outside the maximum intensity ring of the focused field. The radial gradient force attracting the dielectric particles towards the maximum intensity ring provides the centripetal force for the rotation. The achieved steady rotation of the metallic particle trimer reported here may open up applications such as the micro-rotor.

Ice Action on Pairs of Cylindrical and Conical Structures,

DTIC Science & Technology

1983-09-01

correlation because the forces generated ficult to pick a distinct peak in the autospectra for between the structure and the ice sheet are af- the...against two conical structures ...... 20 24. Normalized maximum ice force versus ice velocity ................. 20 25. Normalized initial peak force...versus ice velocity .................. 21 26. Ratio of initial peak ice force to theoretical ice force versus ratio of center-to-center distance

Bite force measurement based on fiber Bragg grating sensor

NASA Astrophysics Data System (ADS)

Padma, Srivani; Umesh, Sharath; Asokan, Sundarrajan; Srinivas, Talabattula

2017-10-01

The maximum level of voluntary bite force, which results from the combined action of muscle of mastication, joints, and teeth, i.e., craniomandibular structure, is considered as one of the major indicators for the functional state of the masticatory system. Measurement of voluntary bite force provides useful data for the jaw muscle function and activity along with assessment of prosthetics. This study proposes an in vivo methodology for the dynamic measurement of bite force employing a fiber Bragg grating (FBG) sensor known as bite force measurement device (BFMD). The BFMD developed is a noninvasive intraoral device, which transduces the bite force exerted at the occlusal surface into strain variations on a metal plate. These strain variations are acquired by the FBG sensor bonded over it. The BFMD developed facilitates adjustment of the distance between the biting platform, which is essential to capture the maximum voluntary bite force at three different positions of teeth, namely incisor, premolar, and molar sites. The clinically relevant bite forces are measured at incisor, molar, and premolar position and have been compared against each other. Furthermore, the bite forces measured with all subjects are segregated according to gender and also compared against each other.

Relationships between static foot alignment and dynamic plantar loads in runners with acute and chronic stages of plantar fasciitis: a cross-sectional study

PubMed Central

Ribeiro, Ana P.; Sacco, Isabel C. N.; Dinato, Roberto C.; João, Silvia M. A.

2016-01-01

BACKGROUND: The risk factors for the development of plantar fasciitis (PF) have been associated with the medial longitudinal arch (MLA), rearfoot alignment and calcaneal overload. However, the relationships between the biomechanical variables have yet to be determined. OBJECTIVE: The goal of this study was to investigate the relationships between the MLA, rearfoot alignment, and dynamic plantar loads in runners with unilateral PF in acute and chronic phases. METHOD: Cross-sectional study which thirty-five runners with unilateral PF were evaluated: 20 in the acute phase (with pain) and 15 with previous chronic PF (without pain). The MLA index and rearfoot alignment were calculated using digital images. The contact area, maximum force, peak pressure, and force-time integral over three plantar areas were acquired with Pedar X insoles while running at 12 km/h, and the loading rates were calculated from the vertical forces. RESULTS: The multiple regression analyses indicated that both the force-time integral (R 2=0.15 for acute phase PF; R 2=0.17 for chronic PF) and maximum force (R 2=0.35 for chronic PF) over the forefoot were predicted by an elevated MLA index. The rearfoot valgus alignment predicted the maximum force over the rearfoot in both PF groups: acute (R 2=0.18) and chronic (R 2=0.45). The rearfoot valgus alignment also predicted higher loading rates in the PF groups: acute (R 2=0.19) and chronic (R 2=0.40). CONCLUSION: The MLA index and the rearfoot alignment were good predictors of plantar loads over the forefoot and rearfoot areas in runners with PF. However, rearfoot valgus was demonstrated to be an important clinical measure, since it was able to predict the maximum force and both loading rates over the rearfoot. PMID:26786073

38 CFR 8a.2 - Maximum amount of insurance.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) The maximum amount of insurance in force on any one life at one time shall not exceed the lesser of... MORTGAGE LIFE INSURANCE § 8a.2 Maximum amount of insurance. (a) Each eligible veteran is authorized up to a maximum of $90,000 in VMLI to insure his or her life during periods he or she is obligated under a...

38 CFR 8a.2 - Maximum amount of insurance.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) The maximum amount of insurance in force on any one life at one time shall not exceed the lesser of... MORTGAGE LIFE INSURANCE § 8a.2 Maximum amount of insurance. (a) Each eligible veteran is authorized up to a maximum of $90,000 in VMLI to insure his or her life during periods he or she is obligated under a...

The TSS-1R Results - the Physics of Current Collection in Magnetized Plasmas Revised

NASA Astrophysics Data System (ADS)

Papadopoulos, Konstantinos

1996-11-01

The Tethered Satellite System (TSS-1R) was deployed from the space shuttle "Columbia" (STS-75 Mission) on February 24, 1996. The satellite was deployed to a distance of 19.7 km above the shuttle. The system operated nominally over its deployment phase which lasted 5.5 hours. A defect in the tether insulation inside the orbiter caused a local discharge which led to a tether break. Data collected before and during the break revealed a host of new physics phenomena concerning the current collection by charged bodies in space moving at orbital velocities. The maximum EMF observed during the mission was 3.8 kV and the maximum current exceeded 1A. Power generation of several kW's was demonstrated. The current collected was significantly larger than expected by space charged limited flow in magnetized and even unmagnetized plasmas. For example the 1A current was collected with less than 1 kV potential instead of the 20 kV given by previous theories. The presentation will review the fascinating results of the TSS-1R and will discuss the ongoing physics analysis of the observed phenomena. *In collaboration with A. Drobot and C.L. Chang of SAIC.

Performance Evaluation of an Actuator Dust Seal for Lunar Operation

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Gaier, James R.; Handschuh, Michael; Panko, Scott; Sechkar, Ed

2013-01-01

Exploration of extraterrestrial surfaces (e.g. moon, Mars, asteroid) will require durable space mechanisms that will survive potentially dusty surface conditions in addition to the hard vacuum and extreme temperatures of space. Baseline tests with lunar simulant were recently completed at NASA GRC on a new Low-Temperature Mechanism (LTM) dust seal for space actuator application. Following are top-level findings of the tests completed to date in vacuum using NU-LHT-2M lunar-highlands simulant. A complete set of findings are found in the conclusions section.Tests were run at approximately 10-7 torr with unidirectional rotational speed of 39 RPM.Initial break-in runs were performed at atmospheric conditions with no simulant. During the break-in runs, the maximum torque observed was 16.7 lbf-in. while the maximum seal outer diameter temperature was 103F. Only 0.4 milligrams of NU-LHT-2M simulant passed through the sealshaft interface in the first 511,000 cycles while under vacuum despite a chip on the secondary sealing surface.Approximately 650,000 of a planned 1,000,000 cycles were completed in vacuum with NU-LHT-2M simulant.Upon test disassembly NU-LHT-2M was found on the secondary sealing surface.

Experimental and theoretical investigation of passive damping concepts for member forced and free vibration

NASA Technical Reports Server (NTRS)

Razzaq, Zia; Mykins, David W.

1987-01-01

Potential passive damping concepts for use in space structures are identified. The effectiveness of copper brush, wool swab, and silly putty in chamber dampers is investigated through natural vibration tests on a tubular aluminum member. The member ends have zero translation and possess partial rotational restraints. The silly putty in chamber dampers provide the maximum passive damping efficiency. Forced vibration tests are then conducted with one, two, and three damper chambers containing silly putty. Owing to the limitation of the vibrator used, the performance of these dampers could not be evaluated experimentally until the forcing function was disengaged. Nevertheless, their performance is evaluated through a forced dynamic finite element analysis conducted as a part of this investigation. The theoretical results based on experimentally obtained damping ratios indicate that the passive dampers are considerably more effective under member natural vibration than during forced vibration. Also, the maximum damping under forced vibration occurs at or near resonance.

Modeling Climate Responses to Spectral Solar Forcing on Centennial and Decadal Time Scales

NASA Technical Reports Server (NTRS)

Wen, G.; Cahalan, R.; Rind, D.; Jonas, J.; Pilewskie, P.; Harder, J.

2012-01-01

We report a series of experiments to explore clima responses to two types of solar spectral forcing on decadal and centennial time scales - one based on prior reconstructions, and another implied by recent observations from the SORCE (Solar Radiation and Climate Experiment) SIM (Spectral 1rradiance Monitor). We apply these forcings to the Goddard Institute for Space Studies (GISS) Global/Middle Atmosphere Model (GCMAM). that couples atmosphere with ocean, and has a model top near the mesopause, allowing us to examine the full response to the two solar forcing scenarios. We show different climate responses to the two solar forCing scenarios on decadal time scales and also trends on centennial time scales. Differences between solar maximum and solar minimum conditions are highlighted, including impacts of the time lagged reSponse of the lower atmosphere and ocean. This contrasts with studies that assume separate equilibrium conditions at solar maximum and minimum. We discuss model feedback mechanisms involved in the solar forced climate variations.

Supercontinent break-up: Causes and consequences

NASA Astrophysics Data System (ADS)

Li, Z. X.

2014-12-01

Supercontinent break-up has most commonly been linked to plume or superplume events, and/or supercontinent thermal insulation, but precise mechanisms are yet to be worked out. Even less know is if and what roles other factors may play. Key factors likely include gravitational force due to the continental superswell driven by both the lower-mantle superplume and continental thermal insulation, mental convention driven by the superplume and individual plumes atop the superplume, assisted by thermal/magmatic weakening of the supercontinent interior (both plume heat and thermal insulation heat). In addition, circum-supercontinent slab downwelling may not only drive the formation of the antipodal superplumes (thus the break-up of the supercontinent), the likely roll-back of the subduction system would also create extension within the supercontinent, facilitating supercontinent break-up. Consequences of supercontinent break-up include long-term sea-level rise, climatic changes due to changes in ocean circulation pattern and carbon cycle, and biodiversification. It has long been demonstrated that the existence of the supercontinent Pangea corresponds to a long-term sea-level drop, whereas the break-up of the supercontinent corresponds to a long-term sea-level rise (170 m higher than it is today). A recent analysis of Neoproterozoic sedimentary facies illustrates that the time of Neoproterozoic supercontinent Rodinia corresponds to a low in the percentage of deep marine facies occurrence, whereas the time of Rodinia break-up corresponds to a significantly higher percentage of deep marine facies occurrence. The long-tern sea-level drop during supercontinent times were likely caused by both plume/superplume dynamic topography and an older mean age of the oceanic crust, whereas long-tern sea-level rise during supercontinent break-up (720-580 Ma for Rodinia and Late Jurassic-Cretaceous for Pangea) likely corresponds to an younger mean age of the oceanic crust, massive plume-induced magmatism in the oceans, and perhaps the effect of continents drifting away from a weakening sub-supercontinent superplume.

A Microscopic View of Oil Slick Break-Up and Emulsion Formation in Breaking Waves

NASA Astrophysics Data System (ADS)

Law, J.; Shahrokhi, H.; Shaw, J. M.

1996-11-01

The hydrodynamic behaviour of oil spills in breaking waves determines the appropriateness and effectiveness of remedial measures during clean-up operations. Oil slicks either disperse as fine drops or form water in oil emulsions when exposed to breaking waves. However, there is little agreement with respect to the controlling variables or mechanisms for emulsification or dispersion and predictions are unreliable. For example, predicted energy dissipation rates in breaking waves are too low to account for the drop sizes encountered experimentally[1]. In this paper, we assess the impact of hydrodynamics and physical properties on the formation of dispersions or emulsions. The maximum stable drop size for dispersions arising from oil slicks and water in oil emulsions are shown to be controlled by Raleigh-Taylor instability or the prevalent local shear stress. Data from four experimental studies[2-5], with a broad range of physical properties were fitted quantitatively. As high shear events are intermittent, stable water in oil emulsions can be formed by dispersion inversion near the water air interface or by water entrained by gas bubbles passing through oil slicks. 1) Li & Garrett, 19th AMOP, Calgary AB, 1, 185-198 (1996). 2) Lin et al., Report CG-D-54-78, U.S. Coast Guard, Washington D.C. (1978). 3) Buist, MASc Thesis, University of Toronto (1979). 4) Wallace et al., 9th AMOP, Edmonton AB, 2, 421-429, June 10-12 (1986). 5) Ross Environmental Research Ltd., Ottawa ON, Report EE-96, (1987).

Induction of single- and double-strand breaks in plasmid DNA by monoenergetic alpha-particles with energies below the Bragg-maximum.

PubMed

Scholz, V; Weidner, J; Köhnlein, W; Frekers, D; Wörtche, H J

1997-01-01

The yield of single-strand breaks (ssb) and double-strand breaks (dsb) produced by alpha-particles at the end of their track in DNA-films was determined experimentally. Helium nuclei were accelerated to 600 keV in the 400 kV ion accelerator and scattered at a carbon target. The elastically scattered alpha-particles with energies of 344 keV and 485 keV were used to irradiate supercircular plasmid DNA in vacuo. For the dosimetry of the alpha-particles a surface barrier detector was used and the energy distribution of the alpha-particles determined. The energy loss of the particles in the DNA-layer was calculated. DNA samples were separated into the three conformational isomers using agarose gel electrophoresis. After fluorochromation the number of ssb and dsb per plasmid DNA molecule was established from the band intensities assuming the validity of Poisson statistics. Linear dose effect correlations were found for ssb and dsb per plasmid molecule. In the case of 344 keV-alpha-particles the yield of dsb was (8.6 +/- 0.9) x 10(-11) breaks/Gy x dalton. The ratio of ssb/dsb was 0.5 +/- 0.2. This is at least a factor of six larger than the ratio found in experiments with higher energy alpha-particles and from model calculations. Similar experiments with protons yielded a relative biological effectiveness (rbe) value of 2.8 for the induction of double-strand breaks by track end alpha-particles.

Water entry and exit of horizontal circular cylinders

NASA Astrophysics Data System (ADS)

Greenhow, M.; Moyo, S.

This paper describes fully nonlinear two-dimensional numerical calculations of the free-surface deformations of initially calm water caused by the forced motion of totally or partially submerged horizontal circular cylinders. The paper considers the following. (i) Totally submerged cylinders moving with constant velocity in vertical, horizontal or combined motions. Results are compared with the small-time asymptotic solution obtained by Tyvand and Milohin 1995. Their results, which are taken to third-order (which is when gravity terms first appear in the expansions), are in excellent agreement with the numerical calculations for small times; beyond this only the numerical method gives accurate results until the free surface breaks or the cylinder emerges from the free surface. Breaking can occur during exit due to strongly negative pressures arising on the cylinder surface, or during the downwards motion causing a free-surface depression which closes up rapidly, forming splashes. Downwards motion is also shown to give rise to high-frequency waves in some cases. (ii) The free-surface deformations, pressures and forces acting on a cylinder in vertical or oblique forced motion during engulfment when it submerges from being initially half-submerged. The initial stages, when the cylinder still pierces the free surface, specify the initial conditions for a separate program for a completely submerged body, thereby allowing complete engulfment to be studied. The free surface closes up violently over the top of the cylinder resulting in jet flow, which, while difficult to handle numerically, has been shown to be insignificant for the bulk flow and the cylinder pressures and forces.

An algorithm to locate optimal bond breaking points on a potential energy surface for applications in mechanochemistry and catalysis.

PubMed

Bofill, Josep Maria; Ribas-Ariño, Jordi; García, Sergio Pablo; Quapp, Wolfgang

2017-10-21

The reaction path of a mechanically induced chemical transformation changes under stress. It is well established that the force-induced structural changes of minima and saddle points, i.e., the movement of the stationary points on the original or stress-free potential energy surface, can be described by a Newton Trajectory (NT). Given a reactive molecular system, a well-fitted pulling direction, and a sufficiently large value of the force, the minimum configuration of the reactant and the saddle point configuration of a transition state collapse at a point on the corresponding NT trajectory. This point is called barrier breakdown point or bond breaking point (BBP). The Hessian matrix at the BBP has a zero eigenvector which coincides with the gradient. It indicates which force (both in magnitude and direction) should be applied to the system to induce the reaction in a barrierless process. Within the manifold of BBPs, there exist optimal BBPs which indicate what is the optimal pulling direction and what is the minimal magnitude of the force to be applied for a given mechanochemical transformation. Since these special points are very important in the context of mechanochemistry and catalysis, it is crucial to develop efficient algorithms for their location. Here, we propose a Gauss-Newton algorithm that is based on the minimization of a positively defined function (the so-called σ-function). The behavior and efficiency of the new algorithm are shown for 2D test functions and for a real chemical example.

A Study of the Use of Contact Loading to Simulate Low Velocity Impact

NASA Technical Reports Server (NTRS)

Highsmith, Alton L.

1997-01-01

Although numerous studies on the impact response of laminated composites have been conducted, there is as yet no agreement within the composites community on what parameter or parameters are adequate for quantifying the severity of an impact event. One of the more interesting approaches that has been proposed uses the maximum contact force during impact to "quantify" the severity of the impact event, provided that the impact velocity is sufficiently low. A significant advantage of this approach, should it prove to be reliable, is that quasi-static contact loading could be used to simulate low velocity impact. In principle, a single specimen, loaded quasi-statically to successively increasing contact loads could be used to map the entire spectrum of damage as a function of maximum contact force. The present study had as its objective assessing whether or not the maximum contact force during impact is a suitable parameter for characterizing an impact. The response of [+/-60/0(sub 4)/+/-60/0(sub 2)](sub s) laminates fabricated from Fiberite T300/934 graphite epoxy and subjected to quasi-static contact loading and to low velocity impact was studied. Three quasi-static contact load levels - 525 lb., 600 lb., and 675 lb. - were selected. Three impact energy levels - 1.14 ft.-lb., 2.0 ft.-lb., and 2.60 ft.-lb. - were chosen in an effort to produce impact events in which the maximum contact forces during the impact events were 525 lb., 600 lb., and 625 lb., respectively. Damage development was documented using dye-penetrant enhanced x-ray radiography. A digital image processing technique was used to obtain quantitative information about the damage zone. Although it was intended that the impact load levels produce maximum contact forces equal to those used in the quasi-static contact experiments, larger contact forces were developed during impact loading. In spite of this, the damage zones developed in impacted specimens were smaller than the damage zones developed in specimens subjected to the corresponding quasi-static contact loading. The impacted specimens may have a greater tendency to develop fiber fracture, but, at present, a quantitative assessment of fiber fracture is not available. In addressing whether or not contact force is an adequate metric for describing the severity of an impact event, the results of this study suggest that it is not. In cases where the quasi-static load level and the maximum contact force during impact were comparable, the quasi-statically loaded specimens consistently developed larger damage zones. It should be noted, however, that using quasi-static damage data to forecast the behavior of impacted material may give conservative estimates of the residual strength of impacted composites.

Plate Kinematic model of the NW Indian Ocean and derived regional stress history of the East African Margin

NASA Astrophysics Data System (ADS)

Tuck-Martin, Amy; Adam, Jürgen; Eagles, Graeme

2015-04-01

Starting with the break up of Gondwana, the northwest Indian Ocean and its continental margins in Madagascar, East Africa and western India formed by divergence of the African and Indian plates and were shaped by a complicated sequence of plate boundary relocations, ridge propagation events, and the independent movement of the Seychelles microplate. As a result, attempts to reconcile the different plate-tectonic components and processes into a coherent kinematic model have so far been unsatisfactory. A new high-resolution plate kinematic model has been produced in an attempt to solve these problems, using seafloor spreading data and rotation parameters generated by a mixture of visual fitting of magnetic isochron data and iterative joint inversion of magnetic isochron and fracture zone data. Using plate motion vectors and plate boundary geometries derived from this model, the first-order regional stress pattern was modelled for distinct phases of margin formation. The stress pattern is correlated with the tectono-stratigraphic history of related sedimentary basins. The plate kinematic model identifies three phases of spreading, from the Jurassic to the Paleogene, which resulted in the formation of three main oceanic basins. Prior to these phases, intracontinental 'Karoo' rifting episodes in the late Carboniferous to late Triassic had failed to break up Gondwana, but initiated the formation of sedimentary basins along the East African and West Madagascan margins. At the start of the first phase of spreading (183 to 133 Ma) predominantly NW - SE extension caused continental rifting that separated Madagascar/India/Antarctica from Africa. Maximum horizontal stresses trended perpendicular to the local plate-kinematic vector, and parallel to the rift axes. During and after continental break-up and subsequent spreading, the regional stress regime changed drastically. The extensional stress regime became restricted to the active spreading ridges that in turn adopted trends normal to the plate divergence vector. Away from the active ridges, compressional horizontal stresses caused by ridge-push forces were transmitted through the subsiding oceanic lithosphere, with an SH max orientation parallel to plate divergence vectors. These changes are documented by the lower Bajocian continental breakup unconformity, which can be traced throughout East African basins. At 133 Ma, the plate boundary moved from north to south of Madagascar, incorporating it into the African plate and initiating its separation from Antarctica. The orientation of the plate divergence vector however did not change markedly. The second phase (89 - 61 Ma) led to the separation of India from Madagascar, initiating a new and dramatic change in stress orientation from N-S to ENE-WSW. This led to renewed tectonic activity in the sedimentary basins of western Madagascar. In the third phase (61 Ma to present) asymmetric spreading of the Carlsberg Ridge separated India from the Seychelles and the Mascarene Plateau via the southward propagation of the Carlsberg Ridge to form the Central Indian Ridge. The anti-clockwise rotation of the independent Seychelles microplate between chrons 28n (64.13 Ma) and 26n (58.38 Ma) and the opening of the short-lived Laxmi Basin (67 Ma to abandonment within chron 28n (64.13 - 63.10 Ma)) have been further constrained by the new plate kinematic model. Along the East African margin, SH max remained in a NE - SW orientation and the sedimentary basins experienced continued thick, deep water sediment deposition. Contemporaneously, in the sedimentary basins along East African passive margin, ridge-push related maximum horizontal stresses became progressively outweighed by local gravity-driven NE-SW maximum horizontal stresses trending parallel to the margin. These stress regimes are caused by sediment loading and extensional collapse of thick sediment wedges, predominantly controlled by margin geometry. Our study successfully integrates an interpretation of paleo-stress regimes constrained by the new high resolution plate kinematic and basin history to produce a margin scale tectono-stratigraphic framework that highlights the important interplay of plate boundary forces and basin formation events along the East African margin.

Live cell imaging combined with high-energy single-ion microbeam

NASA Astrophysics Data System (ADS)

Guo, Na; Du, Guanghua; Liu, Wenjing; Guo, Jinlong; Wu, Ruqun; Chen, Hao; Wei, Junzhe

2016-03-01

DNA strand breaks can lead to cell carcinogenesis or cell death if not repaired rapidly and efficiently. An online live cell imaging system was established at the high energy microbeam facility at the Institute of Modern Physics to study early and fast cellular response to DNA damage after high linear energy transfer ion radiation. The HT1080 cells expressing XRCC1-RFP were irradiated with single high energy nickel ions, and time-lapse images of the irradiated cells were obtained online. The live cell imaging analysis shows that strand-break repair protein XRCC1 was recruited to the ion hit position within 20 s in the cells and formed bright foci in the cell nucleus. The fast recruitment of XRCC1 at the ion hits reached a maximum at about 200 s post-irradiation and then was followed by a slower release into the nucleoplasm. The measured dual-exponential kinetics of XRCC1 protein are consistent with the proposed consecutive reaction model, and the measurements obtained that the reaction rate constant of the XRCC1 recruitment to DNA strand break is 1.2 × 10-3 s-1 and the reaction rate constant of the XRCC1 release from the break-XRCC1 complex is 1.2 × 10-2 s-1.

Quantitative aspects of vibratory mobilization and break-up of non-wetting fluids in porous media

NASA Astrophysics Data System (ADS)

Deng, Wen

Seismic stimulation is a promising technology aimed to mobilize the entrapped non-wetting fluids in the subsurface. The applications include enhanced oil recovery or, alternatively, facilitation of movement of immiscible/partly-miscible gases far into porous media, for example, for CO2 sequestration. This work is devoted to detailed quantitative studies of the two basic pore-scale mechanisms standing behind seismic stimulation: the mobilization of bubbles or drops entrapped in pore constrictions by capillary forces and the break-up of continuous long bubbles or drops. In typical oil-production operations, oil is produced by the natural reservoir-pressure drive during the primary stage and by artificial water flooding at the secondary stage. Capillary forces act to retain a substantial residual fraction of reservoir oil even after water flooding. The seismic stimulation is an unconventional technology that serves to overcome capillary barriers in individual pores and liberate the entrapped oil by adding an oscillatory inertial forcing to the external pressure gradient. According to our study, the effect of seismic stimulation on oil mobilization is highly dependent on the frequencies and amplitudes of the seismic waves. Generally, the lower the frequency and the larger the amplitude, more effective is the mobilization. To describe the mobilization process, we developed two theoretical hydrodynamics-based models and justified both using computational fluid dynamics (CFD). Our theoretical models have a significant advantage over CFD in that they reduce the computational time significantly, while providing correct practical guidance regarding the required field parameters of vibroseismic stimulation, such as the amplitude and frequency of the seismic field. The models also provide important insights into the basic mechanisms governing the vibration-driven two-phase flow in constricted capillaries. In a waterflooded reservoir, oil can be recovered most efficiently by forming continuous streams from isolated droplets. The longer the continuous oil phase under a certain pressure gradient, the more easily it overcomes its capillary barrier. However, surface tension between water and oil causes the typically non-wetting oil, constituting the core phase in the channels, to break up at the pore constriction into isolated beads, which inhibits further motion. The break-up thus counteracts the mobilization. We developed a theoretical model that provides an exact quantitative description of the dynamics of the oil-snap-off process. It also formulates a purely geometric criterion that controls, based on pore geometry only, whether the oil core phase stays continuous or disintegrates into droplets. Both the theoretical model and the break-criterion have been validated against CFD simulations. The work completed elucidates the basic physical mechanisms behind the enhanced oil recovery by seismic waves and vibrations. This creates a theoretical foundation for the further development of corresponding field technologies.

Stem extension and mechanical stability of Xanthium canadense grown in an open or in a dense stand

PubMed Central

Watari, Ryoji; Nagashima, Hisae; Hirose, Tadaki

2014-01-01

Background and Aims Plants in open, uncrowded habitats typically have relatively short stems with many branches, whereas plants in crowded habitats grow taller and more slender at the expense of mechanical stability. There seems to be a trade-off between height growth and mechanical stability, and this study addresses how stand density influences stem extension and consequently plant safety margins against mechanical failure. Methods Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering. Internode dimensions and mechanical properties were measured at the metamer level, and the critical buckling height beyond which the plant elastically buckles under its own weight and the maximum lateral wind force the plant can withstand were calculated. Key Results Internodes were longer in D- than S-plants, but basal diameter did not differ significantly. Relative growth rates of internode length and diameter were negatively correlated to the volumetric solid fraction of the internode. Internode dry mass density was higher in S- than D-plants. Young's modulus of elasticity and the breaking stress were higher in lower metamers, and in D- than in S-plants. Within a stand, however, both moduli were positively related to dry mass density. The buckling safety factor, a ratio of critical buckling height to actual height, was higher in S- than in D-plants. D-plants were found to be approaching the limiting value 1. Lateral wind force resistance was higher in S- than in D-plants, and increased with growth in S-plants. Conclusions Critical buckling height increased with height growth due mainly to an increase in stem stiffness and diameter and a reduction in crown/stem mass ratio. Lateral wind force resistance was enhanced due to increased tissue strength and diameter. The increase in tissue stiffness and strength with height growth plays a crucial role in maintaining a safety margin against mechanical failure in herbaceous species that lack the capacity for secondary growth. PMID:24879768

Internal structure of inertial granular flows.

PubMed

Azéma, Emilien; Radjaï, Farhang

2014-02-21

We analyze inertial granular flows and show that, for all values of the inertial number I, the effective friction coefficient μ arises from three different parameters pertaining to the contact network and force transmission: (1) contact anisotropy, (2) force chain anisotropy, and (3) friction mobilization. Our extensive 3D numerical simulations reveal that μ increases with I mainly due to an increasing contact anisotropy and partially by friction mobilization whereas the anisotropy of force chains declines as a result of the destabilizing effect of particle inertia. The contact network undergoes topological transitions, and beyond I≃0.1 the force chains break into clusters immersed in a background "soup" of floating particles. We show that this transition coincides with the divergence of the size of fluidized zones characterized from the local environments of floating particles and a slower increase of μ with I.

Internal Structure of Inertial Granular Flows

NASA Astrophysics Data System (ADS)

Azéma, Emilien; Radjaï, Farhang

2014-02-01

We analyze inertial granular flows and show that, for all values of the inertial number I, the effective friction coefficient μ arises from three different parameters pertaining to the contact network and force transmission: (1) contact anisotropy, (2) force chain anisotropy, and (3) friction mobilization. Our extensive 3D numerical simulations reveal that μ increases with I mainly due to an increasing contact anisotropy and partially by friction mobilization whereas the anisotropy of force chains declines as a result of the destabilizing effect of particle inertia. The contact network undergoes topological transitions, and beyond I≃0.1 the force chains break into clusters immersed in a background "soup" of floating particles. We show that this transition coincides with the divergence of the size of fluidized zones characterized from the local environments of floating particles and a slower increase of μ with I.

Catch-slip bonds can be dispensable for motor force regulation during skeletal muscle contraction

NASA Astrophysics Data System (ADS)

Dong, Chenling; Chen, Bin

2015-07-01

It is intriguing how multiple molecular motors can perform coordinated and synchronous functions, which is essential in various cellular processes. Recent studies on skeletal muscle might have shed light on this issue, where rather precise motor force regulation was partly attributed to the specific stochastic features of a single attached myosin motor. Though attached motors can randomly detach from actin filaments either through an adenosine triphosphate (ATP) hydrolysis cycle or through "catch-slip bond" breaking, their respective contribution in motor force regulation has not been clarified. Here, through simulating a mechanical model of sarcomere with a coupled Monte Carlo method and finite element method, we find that the stochastic features of an ATP hydrolysis cycle can be sufficient while those of catch-slip bonds can be dispensable for motor force regulation.

Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea.

PubMed

Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C; Daniels, Chris J; Inall, Mark; Davidson, Keith

2016-01-01

The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to shelf break and oceanic stations in the study area.

Modelling the association of dengue fever cases with temperature and relative humidity in Jeddah, Saudi Arabia-A generalised linear model with break-point analysis.

PubMed

Alkhaldy, Ibrahim

2017-04-01

The aim of this study was to examine the role of environmental factors in the temporal distribution of dengue fever in Jeddah, Saudi Arabia. The relationship between dengue fever cases and climatic factors such as relative humidity and temperature was investigated during 2006-2009 to determine whether there is any relationship between dengue fever cases and climatic parameters in Jeddah City, Saudi Arabia. A generalised linear model (GLM) with a break-point was used to determine how different levels of temperature and relative humidity affected the distribution of the number of cases of dengue fever. Break-point analysis was performed to modelled the effect before and after a break-point (change point) in the explanatory parameters under various scenarios. Akaike information criterion (AIC) and cross validation (CV) were used to assess the performance of the models. The results showed that maximum temperature and mean relative humidity are most probably the better predictors of the number of dengue fever cases in Jeddah. In this study three scenarios were modelled: no time lag, 1-week lag and 2-weeks lag. Among these scenarios, the 1-week lag model using mean relative humidity as an explanatory variable showed better performance. This study showed a clear relationship between the meteorological variables and the number of dengue fever cases in Jeddah. The results also demonstrated that meteorological variables can be successfully used to estimate the number of dengue fever cases for a given period of time. Break-point analysis provides further insight into the association between meteorological parameters and dengue fever cases by dividing the meteorological parameters into certain break-points. Copyright © 2016 Elsevier B.V. All rights reserved.

Behavioral response to a just-in-time adaptive intervention (JITAI) to reduce sedentary behavior in obese adults: Implications for JITAI optimization.

PubMed

Thomas, J Graham; Bond, Dale S

2015-12-01

Just-in-time adaptive interventions (JITAIs) use mobile computers, sensors, and software analytics to automatically detect behavior and deliver tailored treatment. However, little is known about how JITAIs influence patterns of behavior or how best to design JITAIs for maximum effect. This study examined prompts and behavioral response to the B-MOBILE JITAI for reducing sedentary behavior (SB) in overweight/obese individuals. Thirty participants (83% women; 67% White, mean ± SD body mass index = 36.2 kg/m2) tested 3 conditions presented in a randomized counterbalanced order involving smartphone-based prompts for walking breaks of (a) 3 min after 30 SB min, (b) 6 min after 60 SB min, and (c) 12 min after 120 SB min. Participants carried the smartphone an average of 6.90 days during each 7-day condition, for an average of 14.94 hr per day. The 3- and 6-min conditions resulted in the greatest number of prompts, walking breaks, the best adherence to prompts, the greatest amount of daily time spent in walking breaks, and fastest adherence to prompts (ps < .01). Small but statistically significant decreases in the number of daily walking breaks, adherence to prompts, and minutes per day spent in walking breaks were observed as a function of the number of days spent in a condition (ps < .05). The B-MOBILE JITAI was effective in prompting breaks in sedentary behavior when it was most clinically relevant. Frequent prompts for small change may be an optimal strategy for shaping sedentary behavior, although more research is needed to determine how best to promote long-term adherence. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

Behavioral Response to a Just-in-Time Adaptive Intervention (JITAI) to Reduce Sedentary Behavior in Obese Adults: Implications for JITAI Optimization

PubMed Central

Thomas, J. Graham; Bond, Dale S.

2015-01-01

Objective Just-in-time adaptive interventions (JITAIs) use mobile computers, sensors, and software analytics to automatically detect behavior and deliver tailored treatment. However, little is known about how JITAIs influence patterns of behavior or how best to design JITAIs for maximum effect. Methods This study examined prompts and behavioral response to the B-MOBILE JITAI for reducing sedentary behavior (SB) in overweight/obese individuals. Thirty participants (83% women; 67% White, mean ± SD body mass index = 36.2 kg/m2) tested three conditions presented in a randomized counterbalanced order involving smartphone-based prompts for walking breaks of (1) 3-min after 30 SB min; (2) 6-min after 60 SB min; and (3) 12-min after 120 SB min. Results Participants carried the smartphone an average of 6.90 days during each 7-day condition, for an average of 14.94 hours per day. The 3- and 6-min conditions resulted in the greatest number of prompts, walking breaks, the best adherence to prompts, the greatest amount of daily time spent in walking breaks, and fastest adherence to prompts (ps < .01). Small but statistically significant decreases in the number of daily walking breaks, adherence to prompts, and minutes per day spent in walking breaks were observed as a function of the number of days spent in a condition (ps < .05). Conclusions The B-MOBILE JITAI was effective in prompting breaks in sedentary behavior when it is most clinically relevant. Frequent prompts for small change may be an optimal strategy for shaping sedentary behavior, although more research is needed to determine how best to promote long-term adherence. PMID:26651467

Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea

PubMed Central

Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C.; Daniels, Chris J.; Inall, Mark; Davidson, Keith

2016-01-01

The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to shelf break and oceanic stations in the study area. PMID:27736920

Preparing Safety Cases for Operating Outside Prescriptive Fatigue Risk Management Regulations.

PubMed

Gander, Philippa; Mangie, Jim; Wu, Lora; van den Berg, Margo; Signal, Leigh; Phillips, Adrienne

2017-07-01

Transport operators seeking to operate outside prescriptive fatigue management regulations are typically required to present a safety case justifying how they will manage the associated risk. This paper details a method for constructing a successful safety case. The method includes four elements: 1) scope (prescriptive rules and operations affected); 2) risk assessment; 3) risk mitigation strategies; and 4) monitoring ongoing risk. A successful safety case illustrates this method. It enables landing pilots in 3-pilot crews to choose the second or third in-flight rest break, rather than the regulatory requirement to take the third break. Scope was defined using a month of scheduled flights that would be covered (N = 4151). These were analyzed in the risk assessment using existing literature on factors affecting fatigue to estimate the maximum time awake at top of descent and sleep opportunities in each break. Additionally, limited data collected before the new regulations showed that pilots flying at landing chose the third break on only 6% of flights. A prospective survey comparing subjective reports (N = 280) of sleep in the second vs. third break and fatigue and sleepiness ratings at top of descent confirmed that the third break is not consistently superior. The safety case also summarized established systems for fatigue monitoring, risk assessment and hazard identification, and multiple fatigue mitigation strategies that are in place. Other successful safety cases have used this method. The evidence required depends on the expected level of risk and should evolve as experience with fatigue risk management systems builds.Gander P, Mangie J, Wu L, van den Berg M, Signal L, Phillips A. Preparing safety cases for operating outside prescriptive fatigue risk management regulations. Aerosp Med Hum Perform. 2017; 88(7):688-696.

Trichodesmium slicks associated with environmental conditions of continental shelf-break at the southwestern of the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Detoni, A. M. S.; Yunes, J. S., Sr.; Ciotti, Á. M.; Calil, P. H. R.; Tavano, V. M.

2016-02-01

Trichodesmium can accumulate high biomass, particularly in the oligotrophic regions of North and Tropical Atlantic, and North Pacific. Large Trichodesmium slicks have been reported in the South Atlantic as well, associated with the Brazil Currrent (BC) that flows southwards over the continental shelf-break. Regional variations of the width of the Brazilian continental shelf, as well as changes in the bottom topography, generate cyclonic and anti-cyclonic eddies as BC crosses the southeastern Brazil. Thus, the general conditions of the BC - characterized as a warm, saline and oligotrophic current - are expected to change not only with latitude but also by the influence of mesoscale instabilities. In this study, three oceanographic cruises were carried out to characterize the distribution of Trichodesmium along the southeastern Brazilian continental shelf-break and their relationship with temperature and upper layer nutrients concentrations. As in other oceanic regions, high concentrations of Trichodesmium (maximum 212.6 × 105 trichomes L-1) were observed in waters with temperatures between 22° C to 25° C, low nitrogen (< 2.4 μM), and moderate phosphate concentrations (> 0.08 μM), where wind speeds were low (< 11 m s-1). Generally, slicks were present where phosphate concentration in the upper 25 m was slightly higher than that of adjacent waters. Wind and hydrographic observations suggested that wind divergence at micro-regions (approximately 625 km2), as well as shelf-break dynamics can drive sporadic shelf-break upwelling, favouring Trichodesmium growth between 23° S to 28° S. Although shelf-break upwelling may occur along the entire domain of the BC flow, Trichodesmium densities were low at latitudes between 28° S to 33° S likely a result of the lower sea surface temperature.

The role of the extrinsic thoracic limb muscles in equine locomotion.

PubMed

Payne, R C; Veenman, P; Wilson, A M

2005-02-01

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.

The role of the extrinsic thoracic limb muscles in equine locomotion.

PubMed

Payne, R C; Veenman, P; Wilson, A M

2004-12-01

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.

The role of the extrinsic thoracic limb muscles in equine locomotion

PubMed Central

Payne, RC; Veenman, P; Wilson, AM

2005-01-01

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 ± 17 mm) fascicles, arranged at about 45° to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb. PMID:15730484

The role of the extrinsic thoracic limb muscles in equine locomotion

PubMed Central

Payne, R C; Veenman, P; Wilson, A M

2004-01-01

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 ± 17 mm) fascicles, arranged at about 45° to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb. PMID:15610395

Hydration history and attachment morphology regulate seed release in Chorizanthe rigida (Polygonaceae), a serotinous desert annual.

PubMed

Martínez-Berdeja, Alejandra; Torres, Mauricio; Altshuler, Douglas L; Ezcurra, Exequiel

2014-07-01

• Premise of the study: Most seed dispersal studies focus on the spatial aspects of propagule dissemination, i.e., the movement of seeds away from the mother plant. However, the timing of seed release can also be a critical variable influencing the probability of seedling survival. We used a biomechanical approach to analyze seed release in Chorizanthe rigida, a serotinous desert annual, to understand the adaptive significance of seed retention in this species.• Methods: We performed pull-to-break tests on individual propagules (i.e., involucres and achene) from newly developed and older plants, under dry and wet conditions, and recorded the breaking force. We measured the involucral base area using digital images and image processing software.• Key results: There is a positive correlation between the force required to detach an involucre and the size of its base area. The force required to detach involucres from soaked and older plants was lower than that for dry and new plants. This pattern provides a mechanism for the plant to regulate the number of involucres released in different rain events.• Conclusions: Seed release in C. rigida is mediated by propagule morphology, rainfall conditions, and age of the dry plant. These factors allow this species to cope with desert environmental variability by influencing the timing and number of seeds released. © 2014 Botanical Society of America, Inc.

Dynamical phenomena in fast sliding nanotube models

NASA Astrophysics Data System (ADS)

Zhang, X. H.; Santoro, G. E.; Tartaglino, U.; Tosatti, E.

2013-03-01

The experimentally known fact that coaxial carbon nanotubes can be forced to slide one inside the other stimulated in the past much detailed modelling of the dynamical sliding process. Molecular dynamics simulations of sliding coaxial nanotubes showed the existence of strong frictional peaks when, at large speed, one tube excites the other with a 'washboard' frequency that happens to resonate with some intrinsic vibration frequency. At some of these special speeds we discover a striking example of dynamical symmetry breaking taking place at the nanoscale. Even when both nanotubes are perfectly left-right symmetric and nonchiral, precisely in correspondence with the large peaks of sliding friction occurring at a series of critical sliding velocities, a nonzero angular momentum spontaneously appears. A detailed analysis shows that this internal angular momentum is of phonon origin, in particular arising from preferential excitation of a right polarized (or, with equal probability, of a left polarized) outer-tube 'pseudorotation' mode, thus spontaneously breaking their exact twofold right-left degeneracy. We present and discuss a detailed analysis of nonlinear continuum equations governing this phenomenon, showing the close similarity of this phenomenon with the well-known rotational instability of a forced string, which takes place under sufficiently strong periodic forcing of the string. We also point out new elements appearing in the present problem which are 'nano', in particular the involvement of Umklapp processes and the role of sliding nanofriction.

Dose-Rate Effects in Breaking DNA Strands by Short Pulses of Extreme Ultraviolet Radiation.

PubMed

Vyšín, Luděk; Burian, Tomáš; Ukraintsev, Egor; Davídková, Marie; Grisham, Michael E; Heinbuch, Scott; Rocca, Jorge J; Juha, Libor

2018-05-01

In this study, we examined dose-rate effects on strand break formation in plasmid DNA induced by pulsed extreme ultraviolet (XUV) radiation. Dose delivered to the target molecule was controlled by attenuating the incident photon flux using aluminum filters as well as by changing the DNA/buffer-salt ratio in the irradiated sample. Irradiated samples were examined using agarose gel electrophoresis. Yields of single- and double-strand breaks (SSBs and DSBs) were determined as a function of the incident photon fluence. In addition, electrophoresis also revealed DNA cross-linking. Damaged DNA was inspected by means of atomic force microscopy (AFM). Both SSB and DSB yields decreased with dose rate increase. Quantum yields of SSBs at the highest photon fluence were comparable to yields of DSBs found after synchrotron irradiation. The average SSB/DSB ratio decreased only slightly at elevated dose rates. In conclusion, complex and/or clustered damages other than cross-links do not appear to be induced under the radiation conditions applied in this study.

Observation of a Discrete Time Crystal

NASA Astrophysics Data System (ADS)

Kyprianidis, A.; Zhang, J.; Hess, P.; Becker, P.; Lee, A.; Smith, J.; Pagano, G.; Potter, A.; Vishwanath, A.; Potirniche, I.-D.; Yao, N.; Monroe, C.

2017-04-01

Spontaneous symmetry breaking is a key concept in the understanding of many physical phenomena, such as the formation of spatial crystals and the phase transition from paramagnetism to magnetic order. While the breaking of time translation symmetry is forbidden in equilibrium systems, it is possible for non-equilibrium Floquet driven systems to break a discrete time translation symmetry, and we present clear signatures of the formation of such a discrete time crystal. We apply a time periodic Hamiltonian to a chain of interacting spins under many-body localization conditions and observe the system's sub-harmonic response at twice that period. This spontaneous doubling of the periodicity is robust to external perturbations. We represent the spins with a linear chain of trapped 171Yb+ ions in an rf Paul trap, generate spin-spin interactions through spin-dependent optical dipole forces, and measure each spin using state-dependent fluorescence. This work is supported by the ARO Atomic Physics Program, the AFOSR MURI on Quantum Measurement and Verification, and the NSF Physics Frontier Center at JQI.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

NASA Astrophysics Data System (ADS)

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK' 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha's Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

Trapping of Momentum due to Low Salinity Water in the north Bay of Bengal

NASA Astrophysics Data System (ADS)

Chaudhuri, D.; Tandon, A.; Farrar, T.; Weller, R. A.; Venkatesan, R.; S, S.; MacKinnon, J. A.; D'Asaro, E. A.; Sengupta, D.

2016-02-01

We study the relation between near-surface ocean stratification and upper ocean currents (momentum) during the diurnal cycle and subseasonal "active-break cycle" of the summer monsoon in the north Bay of Bengal. We use time series of hourly observations from NIOT moorings BD08, BD09 and an INCOIS mooring near 18 N, 89 E in 2013, and data collected during two research cruises of ORV Sagar Nidhi in August-September 2014 and 2015. Our analyses are based on upper ocean profiles of temperature, salinity and density (from moorings and a shipborne underway conductivity-temperature-depth profiler), velocity (Acoustic Doppler Current Profiler), and surface forcing (meterology sensors on moored buoy and ship). Monsoon breaks are characterized by low rainfall, low wind speed (0-5 m/s) and high incident shortwave radiation, whereas active phases are marked by intense rainfall, high wind speed (8-16 m/s) and low incident sunlight. Our main findings are: (i) Net surface heat flux is positive (ocean gains heat) during break spells, and sea surface temperature (SST) rises by upto 1.5 C in 1-2 weeks. (ii) During breaks, day-night SST difference can reach 1.5C; mixed layer depth (MLD) shoals to 5m during day time, and deepens to 15-20 m by late night/early morning. (iii) During active spells, SST cools on subseasonal scales; MLD is deep (exceeding 20 m), and diurnal re-stratification is weak or absent. (iv) Once very low-salinity water (<30 psu) from rivers arrives at the moorings in late August, MLD remains shallow, and is insensitive to subseasonal changes in surface forcing. (v) Moored data and high-resolution observations from the summer 2014 and 2015 cruises reveal trapping of momentum from winds in a relatively thin surface layer when surface salinity is low and the shallow stratification is strong. Results of ingoing analyses will be presented at the meeting.

Changes in Plantar Loading Based on Shoe Type and Sex During a Jump-Landing Task

PubMed Central

DeBiasio, Justin C.; Russell, Mary E.; Butler, Robert J.; Nunley, James A.; Queen, Robin M.

2013-01-01

Context: Metatarsal stress fractures are common in cleated-sport athletes. Previous authors have shown that plantar loading varies with footwear, sex, and the athletic task. Objective: To examine the effects of shoe type and sex on plantar loading in the medial midfoot (MMF), lateral midfoot (LMF), medial forefoot (MFF), middle forefoot (MidFF), and lateral forefoot (LFF) during a jump-landing task. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Twenty-seven recreational athletes (14 men, 13 women) with no history of lower extremity injury in the last 6 months and no history of foot or ankle surgery. Main Outcome Measure(s): The athletes completed 7 jumping trials while wearing bladed-cleat, turf-cleat, and running shoes. Maximum force, contact area, contact time, and the force-time integral were analyzed in each foot region. We calculated 2 × 3 analyses of variance (α = .05) to identify shoe-condition and sex differences. Results: We found no shoe × sex interactions, but the MMF, LMF, MFF, and LFF force-time integrals were greater in men (P < .03). The MMF maximum force was less with the bladed-cleat shoes (P = .02). Total foot and MidFF maximum force was less with the running shoes (P < .01). The MFF and LFF maximum forces were different among all shoe conditions (P < .01). Total foot contact area was less in the bladed-cleat shoes (P = .01). The MMF contact area was greatest in the running shoes (P < .01). The LFF contact area was less in the running shoes (P = .03). The MFF and LFF force-time integrals were greater with the bladed-cleat shoes (P < .01). The MidFF force-time integral was less in the running shoes (P < .01). Conclusions: Independent of shoe, men and women loaded the foot differently during a jump landing. The bladed cleat increased forefoot loading, which may increase the risk for forefoot injury. The type of shoe should be considered when choosing footwear for athletes returning to activity after metatarsal stress fractures. PMID:24067149

Comparison of the force applied on oral structures during intubation attempts by novice physicians between the Macintosh direct laryngoscope, Airway Scope and C-MAC PM: a high-fidelity simulator-based study.

PubMed

Nakanishi, Taizo; Shiga, Takashi; Homma, Yosuke; Koyama, Yasuaki; Goto, Tadahiro

2016-05-23

We examined whether the use of Airway Scope (AWS) and C-MAC PM (C-MAC) decreased the force applied on oral structures during intubation attempts as compared with the force applied with the use of Macintosh direct laryngoscope (DL). Prospective cross-over study. A total of 35 novice physicians participated. We used 6 simulation scenarios based on the difficulty of intubation and intubation devices. Our primary outcome measures were the maximum force applied on the maxillary incisors and tongue during intubation attempts, measured by a high-fidelity simulator. The maximum force applied on maxillary incisors was higher with the use of the C-MAC than with the DL and AWS in the normal airway scenario (DL, 26 Newton (N); AWS, 18 N; C-MAC, 52 N; p<0.01) and the difficult airway scenario (DL, 42 N; AWS, 24 N; C-MAC, 68 N; p<0.01). In contrast, the maximum force applied on the tongue was higher with the use of the DL than with the AWS and C-MAC in both airway scenarios (DL, 16 N; AWS, 1 N; C-MAC, 7 N; p<0.01 in the normal airway scenario; DL, 12 N; AWS, 4 N; C-MAC, 7 N; p<0.01 in the difficult airway scenario). The use of C-MAC, compared with the DL and AWS, was associated with the higher maximum force applied on maxillary incisors during intubation attempts. In contrast, the use of video laryngoscopes was associated with the lower force applied on the tongue in both airway scenarios, compared with the DL. Our study was a simulation-based study, and further research on living patients would be warranted. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/