Science.gov

Sample records for computer generated forces

  1. The effect of swimmer's hand/forearm acceleration on propulsive forces generation using computational fluid dynamics.

    PubMed

    Rouboa, Abel; Silva, António; Leal, Luís; Rocha, Jorge; Alves, Francisco

    2006-01-01

    Propulsive forces generated by swimmers hand/forearm, have been studied through experimental tests. However, there are serious doubts as to whether forces quantified in this way are accurate enough to be meaningful. In order to solve some experimental problems, some numerical techniques have been proposed using Computational Fluid Dynamics (CFD). The main purpose of the present work was threefold. First, disseminate the use of CFD as a new tool in swimming research. Second, apply the CFD method in the calculation of drag and lift coefficients resulting from the numerical resolution equations of the flow around the swimmers hand/forearm using the steady flow conditions. Third, evaluate the effect of hand/forearm acceleration on drag and lift coefficients. For these purposes three, two-dimensional (2D), models of a right male hand/forearm were studied. A frontal model (theta = 90 degrees, Phi = 90 degrees) and two lateral models, one with the thumb as leading edge (theta = 0 degrees, = 90 degrees), and the other with the small finger as the leading edge (theta = 0 degrees, Phi = 180 degrees). The governing system of equations considered was the incompressible Reynolds averaged Navier-Stokes equations with the standard k-epsilon model. The main results reported that, under the steady-state flow condition, the drag coefficient was the one that contributes more for propulsion, and was almost constant for the whole range of velocities, with a maximum value of 1.16 (Cd = 1.16). This is valid when the orientation of the hand/forearm is plane and the model is perpendicular to the direction of the flow. Under the hand /forearm acceleration condition, the measured values for propulsive forces calculation were approximately 22.5% (54.440 N) higher than the forces produced under the steady flow condition (44.428 N). By the results, pointed out, we can conclude that: (i) CFD can be considered an interesting new approach for hydrodynamic forces calculation on swimming, (ii) the

  2. Achieving realistic performance and decison-making capabilities in computer-generated air forces

    NASA Astrophysics Data System (ADS)

    Banks, Sheila B.; Stytz, Martin R.; Santos, Eugene, Jr.; Zurita, Vincent B.; Benslay, James L., Jr.

    1997-07-01

    For a computer-generated force (CGF) system to be useful in training environments, it must be able to operate at multiple skill levels, exhibit competency at assigned missions, and comply with current doctrine. Because of the rapid rate of change in distributed interactive simulation (DIS) and the expanding set of performance objectives for any computer- generated force, the system must also be modifiable at reasonable cost and incorporate mechanisms for learning. Therefore, CGF applications must have adaptable decision mechanisms and behaviors and perform automated incorporation of past reasoning and experience into its decision process. The CGF must also possess multiple skill levels for classes of entities, gracefully degrade its reasoning capability in response to system stress, possess an expandable modular knowledge structure, and perform adaptive mission planning. Furthermore, correctly performing individual entity behaviors is not sufficient. Issues related to complex inter-entity behavioral interactions, such as the need to maintain formation and share information, must also be considered. The CGF must also be able to acceptably respond to unforeseen circumstances and be able to make decisions in spite of uncertain information. Because of the need for increased complexity in the virtual battlespace, the CGF should exhibit complex, realistic behavior patterns within the battlespace. To achieve these necessary capabilities, an extensible software architecture, an expandable knowledge base, and an adaptable decision making mechanism are required. Our lab has addressed these issues in detail. The resulting DIS-compliant system is called the automated wingman (AW). The AW is based on fuzzy logic, the common object database (CODB) software architecture, and a hierarchical knowledge structure. We describe the techniques we used to enable us to make progress toward a CGF entity that satisfies the requirements presented above. We present our design and

  3. Force propagation and force generation in cells.

    PubMed

    Jonas, Oliver; Duschl, Claus

    2010-09-01

    Determining how forces are produced by and propagated through the cytoskeleton (CSK) of the cell is of great interest as dynamic processes of the CSK are intimately correlated with many molecular signaling pathways. We are presenting a novel approach for integrating measurements on cell elasticity, transcellular force propagation, and cellular force generation to obtain a comprehensive description of dynamic and mechanical properties of the CSK under force loading. This approach uses a combination of scanning force microscopy (SFM) and Total Internal Reflection Fluorescence (TIRF) microscopy. We apply well-defined loading schemes onto the apical cell membrane of fibroblasts using the SFM and simultaneously use TIRF microscopy to image the topography of the basal cell membrane. The locally distinct changes of shape and depth of the cytoskeletal imprints onto the basal membrane are interpreted as results of force propagation through the cytoplasm. This observation provides evidence for the tensegrity model and demonstrates the usefulness of our approach that does not depend on potentially disturbing marker compounds. We confirm that the actin network greatly determines cell stiffness and represents the substrate that mediates force transduction through the cytoplasm of the cell. The latter is an essential feature of tensegrity. Most importantly, our new finding that, both intact actin and microtubule networks are required for enabling the cell to produce work, can only be understood within the framework of the tensegrity model. We also provide, for the first time, a direct measurement of the cell's mechanical power output under compression at two femtowatts. PMID:20607861

  4. A polygonal method for haptic force generation

    SciTech Connect

    Anderson, T. |

    1996-12-31

    Algorithms for computing forces and associated surface deformations (graphical and physical) are given, which, together with a force feedback device can be used to haptically display virtual objects. The Bendable Polygon algorithm, created at Sandia National Labs and the University of New Mexico, for visual rendering of computer generated surfaces is also presented. An implementation using the EIGEN virtual reality environment, and the PHANToM (Trademark) haptic interface, is reported together with suggestions for future research.

  5. The fifth generation computer

    SciTech Connect

    Moto-Oka, T.; Kitsuregawa, M.

    1985-01-01

    The leader of Japan's Fifth Generation computer project, known as the 'Apollo' project, and a young computer scientist elucidate in this book the process of how the idea came about, international reactions, the basic technology, prospects for realization, and the abilities of the Fifth Generation computer. Topics considered included forecasting, research programs, planning, and technology impacts.

  6. Force Generation by Flapping Foils

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, P. R.; Donnelly, M.

    1996-11-01

    Aquatic animals like fish use flapping caudal fins to produce axial and cross-stream forces. During WW2, German scientists had built and tested an underwater vehicle powered by similar flapping foils. We have examined the forces produced by a pair of flapping foils. We have examined the forced produced by a pair of flapping foils attached to the tail end of a small axisymmetric cylinder. The foils operate in-phase (called waving), or in anti-phase (called clapping). In a low-speed water tunnel, we have undertaken time-dependent measurements of axial and cross-stream forces and moments that are exerted by the vortex shedding process over the entire body. Phase-matched LDV measurements of vorticity-velocity vectors, as well as limited flow visualization of the periodic vortex shedding process have also been carried out. The direction of the induced velocity within a pair of shed vortices determines the nature of the forces produced, viz., thrust or drag or cross-stream forces. The clapping mode produces a widely dispersed symmetric array of vortices which results in axial forces only (thrust and rag). On the other hand, the vortex array is staggered in the waving mode and cross-stream (maneuvering) forces are then generated.

  7. Next-generation computers

    SciTech Connect

    Torrero, E.A.

    1985-01-01

    Developments related to tomorrow's computers are discussed, taking into account advances toward the fifth generation in Japan, the challenge to U.S. supercomputers, plans concerning the creation of supersmart computers for the U.S. military, a U.S. industry response to the Japanese challenge, a survey of U.S. and European research, Great Britain, the European Common Market, codifying human knowledge for machine reading, software engineering, the next-generation softwave, plans for obtaining the million-transistor chip, and fabrication issues for next-generation circuits. Other topics explored are related to a status report regarding artificial intelligence, an assessment of the technical challenges, aspects of sociotechnology, and defense advanced research projects. Attention is also given to expert systems, speech recognition, computer vision, function-level programming and automated programming, computing at the speed limit, VLSI, and superpower computers.

  8. The vector of jaw muscle force as determined by computer-generated three dimensional simulation: a test of Greaves' model.

    PubMed

    Clausen, Philip; Wroe, Stephen; McHenry, Colin; Moreno, Karen; Bourke, Jason

    2008-11-14

    We present results from a detailed three-dimensional finite element analysis of the cranium and mandible of the Australian dingo (Canis lupus dingo) during a range of feeding activities and compare results with predictions based on two-dimensional methodology [Greaves, W.S., 2000. Location of the vector of jaw muscle force in mammals. Journal of Morphology 243, 293-299]. Greaves showed that the resultant muscle vector intersects the mandible line slightly posterior to the lower third molar (m3). Our work demonstrates that this is qualitatively correct, although the actual point is closer to the jaw joint. We show that it is theoretically possible for the biting side of the mandible to dislocate during unilateral biting; however, the bite point needs to be posterior to m3. Simulations show that reduced muscle activation on the non-biting side can considerably diminish the likelihood of dislocation with only a minor decrease in bite force during unilateral biting. By modulating muscle recruitment the animal may be able to maximise bite force whilst minimising the risk of dislocation. PMID:18838138

  9. Force generation by cellular motors.

    PubMed

    Wanka, Friedrich; Van Zoelen, Everardus J J

    2003-01-01

    Cell motility processes in non-muscle cells depend on the activity of motor proteins that bind to either microtubules or actin filaments. From presently available data it must be concluded that the driving force is generated by transient interaction of the respective motors with microtubules or actin filaments which then activates the binding and hydrolysis of ATP. This reaction results in an abrupt discharge of the motor molecule, the direction of which is determined by the spatial orientation of its binding to the helical and polar vehicle. The latter is thereby propelled in its length direction and simultaneously undergoes an axial rotation, while the expelled motor exerts an oppositely directed current in the surrounding fluid, comparable to jet propulsion. Force production, propulsion velocities and energy requirements known from in vitro studies comply with those derived from the theory. The theory opens new ways for the understanding of cellular activities such as particle transport, mitosis and morphodynamics. PMID:14668925

  10. Computer generated holographic microtags

    DOEpatents

    Sweatt, W.C.

    1998-03-17

    A microlithographic tag comprising an array of individual computer generated holographic patches having feature sizes between 250 and 75 nanometers is disclosed. The tag is a composite hologram made up of the individual holographic patches and contains identifying information when read out with a laser of the proper wavelength and at the proper angles of probing and reading. The patches are fabricated in a steep angle Littrow readout geometry to maximize returns in the -1 diffracted order. The tags are useful as anti-counterfeiting markers because of the extreme difficulty in reproducing them. 5 figs.

  11. Computer generated holographic microtags

    DOEpatents

    Sweatt, William C.

    1998-01-01

    A microlithographic tag comprising an array of individual computer generated holographic patches having feature sizes between 250 and 75 nanometers. The tag is a composite hologram made up of the individual holographic patches and contains identifying information when read out with a laser of the proper wavelength and at the proper angles of probing and reading. The patches are fabricated in a steep angle Littrow readout geometry to maximize returns in the -1 diffracted order. The tags are useful as anti-counterfeiting markers because of the extreme difficulty in reproducing them.

  12. Augmented Computer Mouse Would Measure Applied Force

    NASA Technical Reports Server (NTRS)

    Li, Larry C. H.

    1993-01-01

    Proposed computer mouse measures force of contact applied by user. Adds another dimension to two-dimensional-position-measuring capability of conventional computer mouse; force measurement designated to represent any desired continuously variable function of time and position, such as control force, acceleration, velocity, or position along axis perpendicular to computer video display. Proposed mouse enhances sense of realism and intuition in interaction between operator and computer. Useful in such applications as three-dimensional computer graphics, computer games, and mathematical modeling of dynamics.

  13. Parallel computation with the force

    NASA Technical Reports Server (NTRS)

    Jordan, H. F.

    1985-01-01

    A methodology, called the force, supports the construction of programs to be executed in parallel by a force of processes. The number of processes in the force is unspecified, but potentially very large. The force idea is embodied in a set of macros which produce multiproceossor FORTRAN code and has been studied on two shared memory multiprocessors of fairly different character. The method has simplified the writing of highly parallel programs within a limited class of parallel algorithms and is being extended to cover a broader class. The individual parallel constructs which comprise the force methodology are discussed. Of central concern are their semantics, implementation on different architectures and performance implications.

  14. Computer-generated speech

    SciTech Connect

    Aimthikul, Y.

    1981-12-01

    This thesis reviews the essential aspects of speech synthesis and distinguishes between the two prevailing techniques: compressed digital speech and phonemic synthesis. It then presents the hardware details of the five speech modules evaluated. FORTRAN programs were written to facilitate message creation and retrieval with four of the modules driven by a PDP-11 minicomputer. The fifth module was driven directly by a computer terminal. The compressed digital speech modules (T.I. 990/306, T.S.I. Series 3D and N.S. Digitalker) each contain a limited vocabulary produced by the manufacturers while both the phonemic synthesizers made by Votrax permit an almost unlimited set of sounds and words. A text-to-phoneme rules program was adapted for the PDP-11 (running under the RSX-11M operating system) to drive the Votrax Speech Pac module. However, the Votrax Type'N Talk unit has its own built-in translator. Comparison of these modules revealed that the compressed digital speech modules were superior in pronouncing words on an individual basis but lacked the inflection capability that permitted the phonemic synthesizers to generate more coherent phrases. These findings were necessarily highly subjective and dependent on the specific words and phrases studied. In addition, the rapid introduction of new modules by manufacturers will necessitate new comparisons. However, the results of this research verified that all of the modules studied do possess reasonable quality of speech that is suitable for man-machine applications. Furthermore, the development tools are now in place to permit the addition of computer speech output in such applications.

  15. An Improved Computational Technique for Calculating Electromagnetic Forces and Power Absorptions Generated in Spherical and Deformed Body in Levitation Melting Devices

    NASA Technical Reports Server (NTRS)

    Zong, Jin-Ho; Szekely, Julian; Schwartz, Elliot

    1992-01-01

    An improved computational technique for calculating the electromagnetic force field, the power absorption and the deformation of an electromagnetically levitated metal sample is described. The technique is based on the volume integral method, but represents a substantial refinement; the coordinate transformation employed allows the efficient treatment of a broad class of rotationally symmetrical bodies. Computed results are presented to represent the behavior of levitation melted metal samples in a multi-coil, multi-frequency levitation unit to be used in microgravity experiments. The theoretical predictions are compared with both analytical solutions and with the results or previous computational efforts for the spherical samples and the agreement has been very good. The treatment of problems involving deformed surfaces and actually predicting the deformed shape of the specimens breaks new ground and should be the major usefulness of the proposed method.

  16. An improved computational technique for calculating electromagnetic forces and power absorptions generated in spherical and deformed body in levitation melting devices

    NASA Technical Reports Server (NTRS)

    Zong, Jin-Ho; Szekely, Julian; Schwartz, Elliot

    1992-01-01

    An improved computational technique for calculating the electromagnetic force field, the power absorption and the deformation of an electromagnetically levitated metal sample is described. The technique is based on the volume integral method, but represents a substantial refinement; the coordinate transformation employed allows the efficient treatment of a broad class of rotationally symmetrical bodies. Computed results are presented to represent the behavior of levitation melted metal samples in a multi-coil, multi-frequency levitation unit to be used in microgravity experiments. The theoretical predictions are compared with both analytical solutions and with the results of previous computational efforts for the spherical samples and the agreement has been very good. The treatment of problems involving deformed surfaces and actually predicting the deformed shape of the specimens breaks new ground and should be the major usefulness of the proposed method.

  17. Keratocytes generate traction forces in two phases.

    PubMed

    Burton, K; Park, J H; Taylor, D L

    1999-11-01

    Forces generated by goldfish keratocytes and Swiss 3T3 fibroblasts have been measured with nanonewton precision and submicrometer spatial resolution. Differential interference contrast microscopy was used to visualize deformations produced by traction forces in elastic substrata, and interference reflection microscopy revealed sites of cell-substratum adhesions. Force ranged from a few nanonewtons at submicrometer spots under the lamellipodium to several hundred nanonewtons under the cell body. As cells moved forward, centripetal forces were applied by lamellipodia at sites that remained stationary on the substratum. Force increased and abruptly became lateral at the boundary of the lamellipodium and the cell body. When the cell retracted at its posterior margin, cell-substratum contact area decreased more rapidly than force, so that stress (force divided by area) increased as the cell pulled away. An increase in lateral force was associated with widening of the cell body. These mechanical data suggest an integrated, two-phase mechanism of cell motility: (1) low forces in the lamellipodium are applied in the direction of cortical flow and cause the cell body to be pulled forward; and (2) a component of force at the flanks pulls the rear margins forward toward the advancing cell body, whereas a large lateral component contributes to detachment of adhesions without greatly perturbing forward movement. PMID:10564269

  18. Stacking trilayers to increase force generation

    NASA Astrophysics Data System (ADS)

    Farajollahi, Meisam; Ebrahimi Takallo, Saeede; Woehling, Vincent; Fannir, Adelyne; Plesse, Cédric; Vidal, Frédéric; Sassani, Farrokh; Madden, John D. W.

    2015-04-01

    Trilayer actuators enable large mechanical amplification, but at the expense of force. Thicker trilayers can generate more force, but displacement drops. Ideally of course a combination of high force and large displacement is desirable. In this work we explore the stacking of trilayers driven by conducting polymers in order to combine large force and reasonable deflection. Trilayer actuators operating in air are simulated using the finite element method. Force generated and the maximum beam deflection of individual and multiple stacked trilayers are studied in terms of the interface condition of the neighboring layers and the length of the auxiliary trilayer. The best performance is obtained when trilayers are able to slide with respect to each other so forces can add without impeding displacement. This case will require low friction and uniformity among the trilayers. Bonding of stacked trilayers along their entire length increases force, but dramatically reduces displacement. An alternative which leads to moderate displacements with increased force is the use of a long and a short trilayer that are bonded.

  19. Minimizing forced outage risk in generator bidding

    NASA Astrophysics Data System (ADS)

    Das, Dibyendu

    Competition in power markets has exposed the participating companies to physical and financial uncertainties. Generator companies bid to supply power in a day-ahead market. Once their bids are accepted by the ISO they are bound to supply power. A random outage after acceptance of bids forces a generator to buy power from the expensive real-time hourly spot market and sell to the ISO at the set day-ahead market clearing price, incurring losses. A risk management technique is developed to assess this financial risk associated with forced outages of generators and then minimize it. This work presents a risk assessment module which measures the financial risk of generators bidding in an open market for different bidding scenarios. The day-ahead power market auction is modeled using a Unit Commitment algorithm and a combination of Normal and Cauchy distributions generate the real time hourly spot market. Risk profiles are derived and VaRs are calculated at 98 percent confidence level as a measure of financial risk. Risk Profiles and VaRs help the generators to analyze the forced outage risk and different factors affecting it. The VaRs and the estimated total earning for different bidding scenarios are used to develop a risk minimization module. This module will develop a bidding strategy of the generator company such that its estimated total earning is maximized keeping the VaR below a tolerable limit. This general framework of a risk management technique for the generating companies bidding in competitive day-ahead market can also help them in decisions related to building new generators.

  20. Do centrioles generate a polar ejection force?

    PubMed

    Wells, Jonathan

    2005-01-01

    A microtubule-dependent polar ejection force that pushes chromosomes away from spindle poles during prometaphase is observed in animal cells but not in the cells of higher plants. Elongating microtubules and kinesin-like motor molecules have been proposed as possible causes, but neither accounts for all the data. In the hypothesis proposed here a polar ejection force is generated by centrioles, which are found in animals but not in higher plants. Centrioles consist of nine microtubule triplets arranged like the blades of a tiny turbine. Instead of viewing centrioles through the spectacles of molecular reductionism and neo-Darwinism, this hypothesis assumes that they are holistically designed to be turbines. Orthogonally oriented centriolar turbines could generate oscillations in spindle microtubules that resemble the motion produced by a laboratory vortexer. The result would be a microtubule-mediated ejection force tending to move chromosomes away from the spindle axis and the poles. A rise in intracellular calcium at the onset of anaphase could regulate the polar ejection force by shutting down the centriolar turbines, but defective regulation could result in an excessive force that contributes to the chromosomal instability characteristic of most cancer cells. PMID:15889341

  1. Force Generation upon T Cell Receptor Engagement

    PubMed Central

    Husson, Julien; Chemin, Karine; Bohineust, Armelle; Hivroz, Claire; Henry, Nelly

    2011-01-01

    T cells are major players of adaptive immune response in mammals. Recognition of an antigenic peptide in association with the major histocompatibility complex at the surface of an antigen presenting cell (APC) is a specific and sensitive process whose mechanism is not fully understood. The potential contribution of mechanical forces in the T cell activation process is increasingly debated, although these forces are scarcely defined and hold only limited experimental evidence. In this work, we have implemented a biomembrane force probe (BFP) setup and a model APC to explore the nature and the characteristics of the mechanical forces potentially generated upon engagement of the T cell receptor (TCR) and/or lymphocyte function-associated antigen-1 (LFA-1). We show that upon contact with a model APC coated with antibodies towards TCR-CD3, after a short latency, the T cell developed a timed sequence of pushing and pulling forces against its target. These processes were defined by their initial constant growth velocity and loading rate (force increase per unit of time). LFA-1 engagement together with TCR-CD3 reduced the growing speed during the pushing phase without triggering the same mechanical behavior when engaged alone. Intracellular Ca2+ concentration ([Ca2+]i) was monitored simultaneously to verify the cell commitment in the activation process. [Ca2+]i increased a few tens of seconds after the beginning of the pushing phase although no strong correlation appeared between the two events. The pushing phase was driven by actin polymerization. Tuning the BFP mechanical properties, we could show that the loading rate during the pulling phase increased with the target stiffness. This indicated that a mechanosensing mechanism is implemented in the early steps of the activation process. We provide here the first quantified description of force generation sequence upon local bidimensional engagement of TCR-CD3 and discuss its potential role in a T cell mechanically

  2. The mechanics of force generation by kinesin.

    PubMed Central

    Howard, J

    1995-01-01

    Several laboratories have developed highly sensitive mechanical techniques for studying the movement of purified motor proteins along their associated filaments. The aim of these experiments is to test models for force generation, such as the powerstroke model and "ratchet" or diffusional models, by 1) directly visualizing the path on the filament along which the motor moves, 2) measuring the force exerted by the motor against the filament, and 3) characterizing the passive mechanical properties (elasticity) of the motor. This paper focuses on recently published work on the microtubule-based motor kinesin taking this mechanical approach. Related work on myosin is mentioned for comparison. PMID:7787085

  3. Force generation in a regrowing eukaryotic flagellum

    NASA Astrophysics Data System (ADS)

    Polin, Marco; Bruneau, Bastien; Johnson, Thomas; Goldstein, Raymond

    2012-02-01

    Flagella are whip-like organelles with a complex internal structure, the axoneme, highly conserved across eukaryotic species. The highly regulated activity of motor proteins arranged along the axoneme moves the flagellum in the surrounding fluid, generating forces that can be used for swimming or fluid propulsion. Although our understanding of the general mechanism behind flagellar motion is well established, the details of its implementation in a real axoneme is still poorly understood. Here we explore the inner working of the eukaryotic flagellum using a uniflagellated mutant of the unicellular green alga Chlamydomonas reinhardtii to investigate in detail the force and power generated by a moving flagellum during axonemal regrowth after deflagellation. These experiments will contribute to our understanding of the inner working of the eukaryotic flagellum.

  4. Computer-based structure generation

    NASA Astrophysics Data System (ADS)

    Korytko, Andrey A.

    The program HOUDINI has been designed to construct all structures consistent with structural implications of spectroscopic and other properties of an unknown molecule. With the advent of HOUDINI, a new method of computer structure generation, called convergent structure generation, has been developed that addresses the limitations of earlier methods. Several features of HOUDINI are noteworthy: an integrated application of the collective substructural information; the use of parallel atom groups for a highly efficient handling of alternative substructural inferences; and a managed structure generation procedure designed to build required structural features early in the process. A number of complex structure elucidation problems were solved using the HOUDINI-based comprehensive structure elucidation system. The program performance suggests that convergent structure generation is effective in solving structure problems where much of the input to the structure generator is highly ambiguous, i.e., expressed as families of alternative substructural inferences.

  5. Experimental study of radiometric forces with comparison to computational results

    NASA Astrophysics Data System (ADS)

    Selden, Nathaniel P.

    A study of the radiometric forces on heated plates has been conducted both experimentally and computationally. The experiments were carried out at USC in two vacuum chambers up to a maximum pressure of 6 Pa for various carrier gases. The computations were performed with both the DSMC and ES-BGK methods for a 2-D gas flow over a comparable range of pressures. It is shown that the radiometric devices provide maximum force at a Knudsen number approximating 0.1. Of the various gases tested, helium provides the largest peak force. Qualitatively, the experimental data and computational results are similar. A lack of experimental data on gas-surface accommodation and flow three-dimensionality yields up to a 40% difference in the magnitude of the measured and computed forces, but it is shown that this discrepancy can be used to predict accommodation values. Comparison of four geometric configurations has shown that the effect of the area is significant at pressures up to where the force is maximum. It is also demonstrated that the size of the chamber in which the radiometer resides is of primary importance, where the chamber dimensions are inversely related to the generated force. Finally, simulation of multi-vane configurations have shown that the optimal spacing of vanes can be tailored for specific uses; for maximum force production a tight spacing should be used, while maximum efficiency requires spacing on the order of a vane dimension. While the results so far are encouraging, they are far from complete. Further improvements would include: a new experimental setup to reduce uncertainty with highly accurate temperature control and measurement, an in situ way to prepare the surface as well as measure its cleanliness, and an in depth iterative computational study observing the impact of multiple radiometer vanes at numerous seperations.

  6. Control Strategies for Accurate Force Generation and Relaxation.

    PubMed

    Ohtaka, Chiaki; Fujiwara, Motoko

    2016-10-01

    Characteristics and motor strategies for force generation and force relaxation were examined using graded tasks during isometric force control. Ten female college students (M age = 20.2 yr., SD = 1.1) were instructed to accurately control the force of isometric elbow flexion using their right arm to match a target force level as quickly as possible. They performed: (1) a generation task, wherein they increased their force from 0% maximum voluntary force to 20% maximum voluntary force (0%-20%), 40% maximum voluntary force (0%-40%), or 60% maximum voluntary force (0%-60%) and (2) and a relaxation task, in which they decreased their force from 60% maximum voluntary force to 40% maximum voluntary force (60%-40%), 20% maximum voluntary force (60%-20%), or to 0% maximum voluntary force (60%-0%). Produced force parameters of point of accuracy (force level, error), quickness (reaction time, adjustment time, rate of force development), and strategy (force wave, rate of force development) were analyzed. Errors of force relaxation were all greater, and reaction times shorter, than those of force generation. Adjustment time depended on the magnitude of force and peak rates of force development and force relaxation differed. Controlled relaxation of force is more difficult with low magnitude of force control. PMID:27555365

  7. Interhemispheric connectivity during bimanual isometric force generation

    PubMed Central

    Long, Jinyi; Tazoe, Toshiki; Soteropoulos, Demetris S.

    2015-01-01

    Interhemispheric interactions through the corpus callosum play an important role in the control of bimanual forces. However, the extent to which physiological connections between primary motor cortices are modulated during increasing levels of bimanual force generation in intact humans remains poorly understood. Here we studied coherence between electroencephalographic (EEG) signals and the ipsilateral cortical silent period (iSP), two well-known measures of interhemispheric connectivity between motor cortices, during unilateral and bilateral 10%, 40%, and 70% of maximal isometric voluntary contraction (MVC) into index finger abduction. We found that EEG-EEG coherence in the alpha frequency band decreased while the iSP area increased during bilateral compared with unilateral 40% and 70% but not 10% of MVC. Decreases in coherence in the alpha frequency band correlated with increases in the iSP area, and subjects who showed this inverse relation were able to maintain more steady bilateral muscle contractions. To further examine the relationship between the iSP and coherence we electrically stimulated the ulnar nerve at the wrist at the alpha frequency. Electrical stimulation increased coherence in the alpha frequency band and decreased the iSP area during bilateral 70% of MVC. Altogether, our findings demonstrate an inverse relation between alpha oscillations and the iSP during strong levels of bimanual force generation. We suggest that interactions between neural pathways mediating alpha oscillatory activity and transcallosal inhibition between motor cortices might contribute to the steadiness of strong bilateral isometric muscle contractions in intact humans. PMID:26538610

  8. FAST MOLECULAR SOLVATION ENERGETICS AND FORCE COMPUTATION.

    PubMed

    Bajaj, Chandrajit; Zhao, Wenqi

    2010-01-20

    The total free energy of a molecule includes the classical molecular mechanical energy (which is understood as the free energy in vacuum) and the solvation energy which is caused by the change of the environment of the molecule (solute) from vacuum to solvent. The solvation energy is important to the study of the inter-molecular interactions. In this paper we develop a fast surface-based generalized Born method to compute the electrostatic solvation energy along with the energy derivatives for the solvation forces. The most time-consuming computation is the evaluation of the surface integrals over an algebraic spline molecular surface (ASMS) and the fast computation is achieved by the use of the nonequispaced fast Fourier transform (NFFT) algorithm. The main results of this paper involve (a) an efficient sampling of quadrature points over the molecular surface by using nonlinear patches, (b) fast linear time estimation of energy and inter-molecular forces, (c) error analysis, and (d) efficient implementation combining fast pairwise summation and the continuum integration using nonlinear patches. PMID:20200598

  9. 48 CFR 53.105 - Computer generation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Computer generation. 53...) CLAUSES AND FORMS FORMS General 53.105 Computer generation. (a) Agencies may computer-generate the... be computer generated by the public. Unless prohibited by agency regulations, forms prescribed...

  10. 48 CFR 53.105 - Computer generation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 2 2011-10-01 2011-10-01 false Computer generation. 53...) CLAUSES AND FORMS FORMS General 53.105 Computer generation. (a) Agencies may computer-generate the... be computer generated by the public. Unless prohibited by agency regulations, forms prescribed...

  11. Computer-Generated Feedback on Student Writing

    ERIC Educational Resources Information Center

    Ware, Paige

    2011-01-01

    A distinction must be made between "computer-generated scoring" and "computer-generated feedback". Computer-generated scoring refers to the provision of automated scores derived from mathematical models built on organizational, syntactic, and mechanical aspects of writing. In contrast, computer-generated feedback, the focus of this article, refers…

  12. Computational studies of lobed forced mixer flows

    NASA Astrophysics Data System (ADS)

    Hu, H.; Wu, S. S.; Yu, S. C. M.

    1998-03-01

    Full Navier-Stokes Analyses have been conducted for the flows behind the trailing edge of a lobed forced mixer. The governing equations are derived from the time-dependent compressible Navier-Stokes equations and discretized in the finite-difference form. A simple two-layer eddy viscosity model has also been used to account for the turbulence. Computed results are compared with some of the velocity measurements using a laser-Doppler anemometer (Yu and Yip (1997)). In general, good agreement can be obtained in the streamwise mean velocity distribution but the decay of the streamwise circulation is underpredicted. Some suggestions to the discrepancy are proposed.

  13. Age-Related Corresponding Relationships of Controlled Force Exertion Measured by a Computer-Generated Sinusoidal and Quasi-Random Display

    ERIC Educational Resources Information Center

    Nagasawa, Yoshinori; Demura, Shinichi

    2011-01-01

    This study examined age-group corresponding relationships of the controlled force exertion based on sinusoidal and quasi-random waveforms in 175 right-handed male adults aged 20 to 86 years. The subjects were divided into 3 groups based on age-level: 53 young (mean age 24.6, SD = 3.3 years), 71 middle aged (mean age 44.3, SD = 8.7 years), and 51…

  14. Determinants of contractile forces generated in disorganized actomyosin bundles.

    PubMed

    Kim, Taeyoon

    2015-04-01

    Actomyosin machinery is a fundamental engine consisting mostly of actin filaments, molecular motors, and passive cross-linkers, generating mechanical forces required for biological processes of non-muscle cells such as cell migration, cytokinesis, and morphogenesis. Although the molecular and physical properties of key elements in the actomyosin machinery have been characterized well, it still remains unclear how macroscopic force buildup and dissipation in actomyosin networks and bundles depend on the microscopic properties of individual cytoskeletal components and their local interactions. To bridge such a gap between macroscopic and microscopic scales, we have developed a three-dimensional computational model of actomyosin bundles clamped to an elastic substrate with minimal components: actin filaments, passive cross-linkers, and active motors. Our model accounts for several key features neglected by previous studies despite their significance for force generation, such as realistic structure and kinetics of the motors. Using the model, we systematically investigated how net tension in actomyosin bundles is governed via interplay between motors and cross-linkers. We demonstrated motors can generate large tension on a bundle in the absence of cross-linkers in a very inefficient, unstable manner. Cross-linkers help motors to generate their maximum potential forces as well as enhance overall connectivity, leading to much higher efficiency and stability. We showed further that the cross-linkers behave as a molecular clutch with tunable friction which has quite distinct effects on net tension depending on their cross-linking angles. We also examined the source of symmetry breaking between tensile and compressive forces during tension generation process and discussed how the length and dynamics of actin filaments and the stiffness of the elastic substrate can affect the generated tension. PMID:25103419

  15. Curvature recognition and force generation in phagocytosis

    PubMed Central

    2010-01-01

    Background The uptake of particles by actin-powered invagination of the plasma membrane is common to protozoa and to phagocytes involved in the immune response of higher organisms. The question addressed here is how a phagocyte may use geometric cues to optimize force generation for the uptake of a particle. We survey mechanisms that enable a phagocyte to remodel actin organization in response to particles of complex shape. Results Using particles that consist of two lobes separated by a neck, we found that Dictyostelium cells transmit signals concerning the curvature of a surface to the actin system underlying the plasma membrane. Force applied to a concave region can divide a particle in two, allowing engulfment of the portion first encountered. The phagosome membrane that is bent around the concave region is marked by a protein containing an inverse Bin-Amphiphysin-Rvs (I-BAR) domain in combination with an Src homology (SH3) domain, similar to mammalian insulin receptor tyrosine kinase substrate p53. Regulatory proteins enable the phagocyte to switch activities within seconds in response to particle shape. Ras, an inducer of actin polymerization, is activated along the cup surface. Coronin, which limits the lifetime of actin structures, is reversibly recruited to the cup, reflecting a program of actin depolymerization. The various forms of myosin-I are candidate motor proteins for force generation in particle uptake, whereas myosin-II is engaged only in retracting a phagocytic cup after a switch to particle release. Thus, the constriction of a phagocytic cup differs from the contraction of a cleavage furrow in mitosis. Conclusions Phagocytes scan a particle surface for convex and concave regions. By modulating the spatiotemporal pattern of actin organization, they are capable of switching between different modes of interaction with a particle, either arresting at a concave region and applying force in an attempt to sever the particle there, or extending the cup

  16. Computer generation of random deviates.

    PubMed

    Cormack, J; Shuter, B

    1991-06-01

    The need for random deviates arises in many scientific applications, such as the simulation of physical processes, numerical evaluation of complex mathematical formulae and the modeling of decision processes. In medical physics, Monte Carlo simulations have been used in radiology, radiation therapy and nuclear medicine. Specific instances include the modelling of x-ray scattering processes and the addition of random noise to images or curves in order to assess the effects of various processing procedures. Reliable sources of random deviates with statistical properties indistinguishable from true random deviates are a fundamental necessity for such tasks. This paper provides a review of computer algorithms which can be used to generate uniform random deviates and other distributions of interest to medical physicists, along with a few caveats relating to various problems and pitfalls which can occur. Source code listings for the generators discussed (in FORTRAN, Turbo-PASCAL and Data General ASSEMBLER) are available on request from the authors. PMID:1747086

  17. Force Generation by Membrane-Associated Myosin-I

    PubMed Central

    Pyrpassopoulos, Serapion; Arpağ, Göker; Feeser, Elizabeth A.; Shuman, Henry; Tüzel, Erkan; Ostap, E. Michael

    2016-01-01

    Vertebrate myosin-IC (Myo1c) is a type-1 myosin that links cell membranes to the cytoskeleton via its actin-binding motor domain and its phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2)-binding tail domain. While it is known that Myo1c bound to PtdIns(4,5)P2 in fluid-lipid bilayers can propel actin filaments in an unloaded motility assay, its ability to develop forces against external load on actin while bound to fluid bilayers has not been explored. Using optical tweezers, we measured the diffusion coefficient of single membrane-bound Myo1c molecules by force-relaxation experiments, and the ability of ensembles of membrane-bound Myo1c molecules to develop and sustain forces. To interpret our results, we developed a computational model that recapitulates the basic features of our experimental ensemble data and suggests that Myo1c ensembles can generate forces parallel to lipid bilayers, with larger forces achieved when the myosin works away from the plane of the membrane or when anchored to slowly diffusing regions. PMID:27156719

  18. Fourth-Generation Computer Languages: An Overview.

    ERIC Educational Resources Information Center

    Ricks, John

    1988-01-01

    Points out that mainframe computer users today can make their requirements known to the computer in simple English. Provides a listing of fourth generation computer language advantages over third generation languages. Summarizes a program to streamline faculty records on a mainframe computer. (MVL)

  19. 48 CFR 53.105 - Computer generation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 2 2012-10-01 2012-10-01 false Computer generation. 53...) CLAUSES AND FORMS FORMS General 53.105 Computer generation. (a) The forms prescribed by this part may be computer generated—without exception approval (see 53.103), provided— (1) There is no change to the...

  20. 48 CFR 53.105 - Computer generation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 2 2014-10-01 2014-10-01 false Computer generation. 53...) CLAUSES AND FORMS FORMS General 53.105 Computer generation. (a) The forms prescribed by this part may be computer generated—without exception approval (see 53.103), provided— (1) There is no change to the...

  1. 48 CFR 53.105 - Computer generation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 2 2013-10-01 2013-10-01 false Computer generation. 53...) CLAUSES AND FORMS FORMS General 53.105 Computer generation. (a) The forms prescribed by this part may be computer generated—without exception approval (see 53.103), provided— (1) There is no change to the...

  2. Pump instability phenomena generated by fluid forces

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.

    1985-01-01

    Rotor dynamic behavior of high energy centrifugal pumps is significantly affected by two types of fluid forces; one due to the hydraulic interaction of the impeller with the surrounding volute or diffuser and the other due to the effect of the wear rings. The available data on these forces is first reviewed. A simple one degree-of-freedom system containing these forces is analytically solved to exhibit the rotor dynamic effects. To illustrate the relative magnitude of these phenomena, an example of a multistage boiler feed pump is worked out. It is shown that the wear ring effects tend to suppress critical speed and postpone instability onset. But the volute-impeller forces tend to lower the critical speed and the instability onset speed. However, for typical boiler feed pumps under normal running clearances, the wear ring effects are much more significant than the destabilizing hydraulic interaction effects.

  3. A piezo inertial force generator optimized for high force and low frequency

    NASA Astrophysics Data System (ADS)

    Konstanzer, Peter; Jänker, Peter; Storm, Stefan

    2007-08-01

    In this paper, a novel piezo inertial force generator optimized for high forces, high endurance and low frequency is discussed. The underlying innovative technology makes use of piezoceramic d33 multilayer monolithic actuators embedded into a GFRP host structure in a leaf-spring bending configuration. Dynamic amplification of the control forces is achieved by means of a near-resonance condition. The smart force generator actuation capability is completely embedded into its leaf-spring structure. With a 4 kg inertial mass, the force generator is capable of providing control forces of ± 800 N at frequencies around 26 Hz, where endurance tests show reliability for more than 1000 operational hours. Force generators are designed, and hardware prototypes manufactured and tested with respect to performance and endurance.

  4. FUNCTION GENERATOR FOR ANALOGUE COMPUTERS

    DOEpatents

    Skramstad, H.K.; Wright, J.H.; Taback, L.

    1961-12-12

    An improved analogue computer is designed which can be used to determine the final ground position of radioactive fallout particles in an atomic cloud. The computer determines the fallout pattern on the basis of known wind velocity and direction at various altitudes, and intensity of radioactivity in the mushroom cloud as a function of particle size and initial height in the cloud. The output is then displayed on a cathode-ray tube so that the average or total luminance of the tube screen at any point represents the intensity of radioactive fallout at the geographical location represented by that point. (AEC)

  5. Building blocks (fifth-generation computers)

    SciTech Connect

    Feigenbaum, E.A.; Hayes-roth, F.; Waltz, D.L.; Reddy, R.; Zue, V.; Kanade, T.

    1983-11-01

    Major areas of artificial intelligence (AI) research as it impacts on next-generation computing are explored in five short, related articles. The first article provides an overview of the background and current goals of AI. The remaining four discuss, in turn: the codification of human knowledge for machine reading; helping computers understand natural languages; continuous speech recognition; and computer vision with imperfect inputs.

  6. Instructional Uses of the Computer: Program Force

    ERIC Educational Resources Information Center

    Ostrander, P.

    1975-01-01

    Describes a program which simulates motion in two dimensions of a point mass subject to a force which is a function of position, velocity, or time. Sample applications are noted and a source of a complete list of applications and programs is given. (GH)

  7. The Distribution of Active Force Generators Controls Mitotic Spindle Position

    NASA Astrophysics Data System (ADS)

    Grill, Stephan W.; Howard, Jonathon; Schäffer, Erik; Stelzer, Ernst H. K.; Hyman, Anthony A.

    2003-07-01

    During unequal cell divisions a mitotic spindle is eccentrically positioned before cell cleavage. To determine the basis of the net force imbalance that causes spindle displacement in one-cell Caenorhabditis elegans embryos, we fragmented centrosomes with an ultraviolet laser. Analysis of the mean and variance of fragment speeds suggests that the force imbalance is due to a larger number of force generators pulling on astral microtubules of the posterior aster relative to the anterior aster. Moreover, activation of heterotrimeric guanine nucleotide-binding protein (G protein) α subunits is required to generate these astral forces.

  8. CHARMM additive and polarizable force fields for biophysics and computer-aided drug design

    PubMed Central

    Vanommeslaeghe, K.

    2014-01-01

    Background Molecular Mechanics (MM) is the method of choice for computational studies of biomolecular systems owing to its modest computational cost, which makes it possible to routinely perform molecular dynamics (MD) simulations on chemical systems of biophysical and biomedical relevance. Scope of Review As one of the main factors limiting the accuracy of MD results is the empirical force field used, the present paper offers a review of recent developments in the CHARMM additive force field, one of the most popular bimolecular force fields. Additionally, we present a detailed discussion of the CHARMM Drude polarizable force field, anticipating a growth in the importance and utilization of polarizable force fields in the near future. Throughout the discussion emphasis is placed on the force fields’ parametrization philosophy and methodology. Major Conclusions Recent improvements in the CHARMM additive force field are mostly related to newly found weaknesses in the previous generation of additive force fields. Beyond the additive approximation is the newly available CHARMM Drude polarizable force field, which allows for MD simulations of up to 1 microsecond on proteins, DNA, lipids and carbohydrates. General Significance Addressing the limitations ensures the reliability of the new CHARMM36 additive force field for the types of calculations that are presently coming into routine computational reach while the availability of the Drude polarizable force fields offers a model that is an inherently more accurate model of the underlying physical forces driving macromolecular structures and dynamics. PMID:25149274

  9. The generation of side force by distributed suction

    NASA Astrophysics Data System (ADS)

    Roberts, Leonard; Hong, John

    1993-05-01

    This report provides an approximate analysis of the generation of side force on a cylinder placed horizontal to the flow direction by the application of distributed suction on the rearward side of the cylinder. Relationships are derived between the side force coefficients and the required suction coefficients necessary to maintain attached flow on one side of the cylinder, thereby inducing circulation around the cylinder and a corresponding side force.

  10. Force generation by the growth of amyloid aggregates

    PubMed Central

    Herling, Therese W.; Garcia, Gonzalo A.; Michaels, Thomas C. T.; Grentz, Wolfgang; Dean, James; Shimanovich, Ulyana; Gang, Hongze; Müller, Thomas; Kav, Batuhan; Terentjev, Eugene M.; Dobson, Christopher M.; Knowles, Tuomas P. J.

    2015-01-01

    The generation of mechanical forces are central to a wide range of vital biological processes, including the function of the cytoskeleton. Although the forces emerging from the polymerization of native proteins have been studied in detail, the potential for force generation by aberrant protein polymerization has not yet been explored. Here, we show that the growth of amyloid fibrils, archetypical aberrant protein polymers, is capable of unleashing mechanical forces on the piconewton scale for individual filaments. We apply microfluidic techniques to measure the forces released by amyloid growth for two systems: insulin and lysozyme. The level of force measured for amyloid growth in both systems is comparable to that observed for actin and tubulin, systems that have evolved to generate force during their native functions and, unlike amyloid growth, rely on the input of external energy in the form of nucleotide hydrolysis for maximum force generation. Furthermore, we find that the power density released from growing amyloid fibrils is comparable to that of high-performance synthetic polymer actuators. These findings highlight the potential of amyloid structures as active materials and shed light on the criteria for regulation and reversibility that guide molecular evolution of functional polymers. PMID:26195762

  11. BMEWS Radar Beam Generation and Projection Clear Air Force ...

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

    BMEWS Radar Beam Generation and Projection - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  12. Effects of inorganic phosphate on endothermic force generation in muscle.

    PubMed

    Ranatunga, K W

    1999-07-01

    Using a rapid (ca. 0.2 ms) laser temperature jump technique, the rate of endothermic force generation was examined in single-skinned (rabbit psoas) muscle fibres when they were exposed to different levels of inorganic phosphate (a product released during ATP hydrolysis in active muscle). The steady force is reduced by increased phosphate but the apparent rate constant of force generation induced by a standard temperature jump (from ca. 9 degrees C to ca. 12 degrees C) increases two- to threefold when the phosphate added is increased from zero to ca. 25 mM. The increase in the apparent rate constant also exhibits saturation at higher phosphate levels and the relation is hyperbolic. Detailed examination of the data, particularly in relation to our pressure release experiments, leads to a scheme for the molecular steps involved in phosphate release and force generation in active muscle fibres, where phosphate release from attached cross-bridges involves three reversible and sequentially faster molecular steps. Step one is a moderately slow, pre-force generation step that probably represents a transition of cross-bridges from non-specific to stereospecific attached states. Step two is moderately fast and represents endothermic cross-bridge force generation (temperature sensitive) and step three is a very rapid phosphate release. Such a scheme accommodates findings from a variety of different studies, including pressure perturbation experiments and other studies where the effect of phosphate on muscle force was studied. PMID:10445293

  13. Optimal Force Generation with Fluid-Structure Interactions

    NASA Astrophysics Data System (ADS)

    Peng, Diing-wen

    Typical computational and experimental methods are unsuitable for studying large scale optimization problems involving complex fluid structure interactions, primarily due to their time-consuming nature. A novel experimental approach is proposed here that provides a high-fidelity and efficient alternative to discover optimal parameters arising from the passive interaction between structural elasticity and fluid dynamic forces. This approach utilizes motors, force transducers, and active controllers to emulate the effects of elasticity, eliminating the physical need to replace structural components in the experiment. A clustering genetic algorithm is then used to tune the structural parameters to achieve desired optimality conditions, resulting in approximated global optimal regions within the search bound. A prototype fluid-structure interaction experiment inspired by the lift generation of flapping wing insects is presented to highlight the capabilities of this approach. The experiment aims to maximize the average lift on a sinusoidally translating plate, by optimizing the damping ratio and natural frequency of the plate's elastic pitching dynamics. Reynolds number, chord length, and stroke length are varied between optimizations to explore their relationships to the optimal structural parameters. The results reveal that only limited ranges of stroke lengths are conducive to lift generation; there also exists consistent trends between optimal stroke length, natural frequency, and damping ratio. The measured lift, pitching angle, and torque on the plate for optimal scenarios exhibit the same frequency as the translation frequency, and the phase angles of the optimal structural parameters at this frequency are found to be independent of the stroke length. This critical phase can be then characterized by a linear function of the chord length and Reynolds number. Particle image velocimetry measurements are acquired for the kinematics generated with optimal and

  14. Turbofan noise generation. Volume 2: Computer programs

    NASA Technical Reports Server (NTRS)

    Ventres, C. S.; Theobald, M. A.; Mark, W. D.

    1982-01-01

    The use of a package of computer programs developed to calculate the in duct acoustic mods excited by a fan/stator stage operating at subsonic tip speed is described. The following three noise source mechanisms are included: (1) sound generated by the rotor blades interacting with turbulence ingested into, or generated within, the inlet duct; (2) sound generated by the stator vanes interacting with the turbulent wakes of the rotor blades; and (3) sound generated by the stator vanes interacting with the velocity deficits in the mean wakes of the rotor blades. The computations for three different noise mechanisms are coded as three separate computer program packages. The computer codes are described by means of block diagrams, tables of data and variables, and example program executions; FORTRAN listings are included.

  15. Computation of unbalanced radial force in permanent magnet motors

    SciTech Connect

    Salon, S.J.; Howe, M.; Slavik, C.J.; DeBortoli, M.J.; Nevins, R.J.

    1998-10-01

    Nonuniformity in magnet strength in permanent magnet motors results in a vibration-inducing unbalanced force acting on the rotor. This force is the difference of two large numbers and as such is difficult to determine precisely with numerical models. In this paper, a permanent magnet motor with unbalanced magnets is analyzed by the finite element method. Three different techniques for computing the net force on the rotor, including a recently developed field-correction approach, are compared. Sensitivities of the techniques to computational limitations and finite element mesh characteristics are discussed.

  16. Computer-Generated Movies for Mission Planning

    NASA Technical Reports Server (NTRS)

    Roberts, P. H., Jr.; vanDillen, S. L.

    1973-01-01

    Computer-generated movies help the viewer to understand mission dynamics and get quantitative details. Sample movie frames demonstrate the uses and effectiveness of movies in mission planning. Tools needed for movie-making include computer programs to generate images on film and film processing to give the desired result. Planning scenes to make an effective product requires some thought and experience. Viewpoints and timing are particularly important. Lessons learned so far and problems still encountered are discussed.

  17. Protrusion force microscopy reveals oscillatory force generation and mechanosensing activity of human macrophage podosomes

    NASA Astrophysics Data System (ADS)

    Labernadie, Anna; Bouissou, Anaïs; Delobelle, Patrick; Balor, Stéphanie; Voituriez, Raphael; Proag, Amsha; Fourquaux, Isabelle; Thibault, Christophe; Vieu, Christophe; Poincloux, Renaud; Charrière, Guillaume M.; Maridonneau-Parini, Isabelle

    2014-11-01

    Podosomes are adhesion structures formed in monocyte-derived cells. They are F-actin-rich columns perpendicular to the substrate surrounded by a ring of integrins. Here, to measure podosome protrusive forces, we designed an innovative experimental setup named protrusion force microscopy (PFM), which consists in measuring by atomic force microscopy the deformation induced by living cells onto a compliant Formvar sheet. By quantifying the heights of protrusions made by podosomes onto Formvar sheets, we estimate that a single podosome generates a protrusion force that increases with the stiffness of the substratum, which is a hallmark of mechanosensing activity. We show that the protrusive force generated at podosomes oscillates with a constant period and requires combined actomyosin contraction and actin polymerization. Finally, we elaborate a model to explain the mechanical and oscillatory activities of podosomes. Thus, PFM shows that podosomes are mechanosensing cell structures exerting a protrusive force.

  18. Protrusion force microscopy reveals oscillatory force generation and mechanosensing activity of human macrophage podosomes.

    PubMed

    Labernadie, Anna; Bouissou, Anaïs; Delobelle, Patrick; Balor, Stéphanie; Voituriez, Raphael; Proag, Amsha; Fourquaux, Isabelle; Thibault, Christophe; Vieu, Christophe; Poincloux, Renaud; Charrière, Guillaume M; Maridonneau-Parini, Isabelle

    2014-01-01

    Podosomes are adhesion structures formed in monocyte-derived cells. They are F-actin-rich columns perpendicular to the substrate surrounded by a ring of integrins. Here, to measure podosome protrusive forces, we designed an innovative experimental setup named protrusion force microscopy (PFM), which consists in measuring by atomic force microscopy the deformation induced by living cells onto a compliant Formvar sheet. By quantifying the heights of protrusions made by podosomes onto Formvar sheets, we estimate that a single podosome generates a protrusion force that increases with the stiffness of the substratum, which is a hallmark of mechanosensing activity. We show that the protrusive force generated at podosomes oscillates with a constant period and requires combined actomyosin contraction and actin polymerization. Finally, we elaborate a model to explain the mechanical and oscillatory activities of podosomes. Thus, PFM shows that podosomes are mechanosensing cell structures exerting a protrusive force. PMID:25385672

  19. Force-generation and dynamic instability of microtubule bundles

    PubMed Central

    Laan, Liedewij; Husson, Julien; Munteanu, E. Laura; Kerssemakers, Jacob W. J.; Dogterom, Marileen

    2008-01-01

    Individual dynamic microtubules can generate pushing or pulling forces when their growing or shrinking ends are in contact with cellular objects such as the cortex or chromosomes. These microtubules can operate in parallel bundles, for example when interacting with mitotic chromosomes. Here, we investigate the force-generating capabilities of a bundle of growing microtubules and study the effect that force has on the cooperative dynamics of such a bundle. We used an optical tweezers setup to study microtubule bundles growing against a microfabricated rigid barrier in vitro. We show that multiple microtubules can generate a pushing force that increases linearly with the number of microtubules present. In addition, the bundle can cooperatively switch to a shrinking state, due to a force-induced coupling of the dynamic instability of single microtubules. In the presence of GMPCPP, bundle catastrophes no longer occur, and high bundle forces are reached more effectively. We reproduce the observed behavior with a simple simulation of microtubule bundle dynamics that takes into account previously measured force effects on single microtubules. Using this simulation, we also show that a constant compressive force on a growing bundle leads to oscillations in bundle length that are of potential relevance for chromosome oscillations observed in living cells. PMID:18577596

  20. Computer-Based Arithmetic Test Generation

    ERIC Educational Resources Information Center

    Trocchi, Robert F.

    1973-01-01

    The computer can be a welcome partner in the instructional process, but only if there is man-machine interaction. Man should not compromise system design because of available hardware; the computer must fit the system design for the result to represent an acceptable solution to instructional technology. The Arithmetic Test Generator system fits…

  1. Land of the Rising Fifth Generation Computer.

    ERIC Educational Resources Information Center

    Feigenbaum, Edward; McCorduck, Pamela

    1983-01-01

    Discusses a major, national plan (Fifth Generation Computer Systems) for Japan to become number one in the computer industry by the latter half of the 1990s. Includes comments on the likely success of and problems associated with the plan supported by Japan's Ministery of International Trade and Industry. (JN)

  2. Force Generation by Endocytic Actin Patches in Budding Yeast

    PubMed Central

    Carlsson, Anders E.; Bayly, Philip V.

    2014-01-01

    Membrane deformation during endocytosis in yeast is driven by local, templated assembly of a sequence of proteins including polymerized actin and curvature-generating coat proteins such as clathrin. Actin polymerization is required for successful endocytosis, but it is not known by what mechanisms actin polymerization generates the required pulling forces. To address this issue, we develop a simulation method in which the actin network at the protein patch is modeled as an active gel. The deformation of the gel is treated using a finite-element approach. We explore the effects and interplay of three different types of force driving invagination: 1), forces perpendicular to the membrane, generated by differences between actin polymerization rates at the edge of the patch and those at the center; 2), the inherent curvature of the coat-protein layer; and 3), forces parallel to the membrane that buckle the coat protein layer, generated by an actomyosin contractile ring. We find that with optimistic estimates for the stall stress of actin gel growth and the shear modulus of the actin gel, actin polymerization can generate almost enough force to overcome the turgor pressure. In combination with the other mechanisms, actin polymerization can the force over the critical value. PMID:24739159

  3. Isoforms Confer Characteristic Force Generation and Mechanosensation by Myosin II Filaments

    PubMed Central

    Stam, Samantha; Alberts, Jon; Gardel, Margaret L.; Munro, Edwin

    2015-01-01

    Myosin II isoforms with varying mechanochemistry and filament size interact with filamentous actin (F-actin) arrays to generate contractile forces in muscle and nonmuscle cells. How myosin II force production is shaped by isoform-specific motor properties and environmental stiffness remains poorly understood. Here, we used computer simulations to analyze force production by an ensemble of myosin motors against an elastically tethered actin filament. We found that force output depends on two timescales: the duration of F-actin attachment, which varies sharply with the ensemble size, motor duty ratio, and external load; and the time to build force, which scales with the ensemble stall force, gliding speed, and environmental stiffness. Although force-dependent kinetics were not required to sense changes in stiffness, the myosin catch bond produced positive feedback between the attachment time and force to trigger switch-like transitions from transient attachments, generating small forces, to high-force-generating runs. Using parameters representative of skeletal muscle myosin, nonmuscle myosin IIB, and nonmuscle myosin IIA revealed three distinct regimes of behavior, respectively: 1) large assemblies of fast, low-duty ratio motors rapidly build stable forces over a large range of environmental stiffness; 2) ensembles of slow, high-duty ratio motors serve as high-affinity cross-links with force buildup times that exceed physiological timescales; and 3) small assemblies of low-duty ratio motors operating at intermediate speeds are poised to respond sharply to changes in mechanical context—at low force or stiffness, they serve as low-affinity cross-links, but they can transition to force production via the positive-feedback mechanism described above. Together, these results reveal how myosin isoform properties may be tuned to produce force and respond to mechanical cues in their environment. PMID:25902439

  4. CATGEN: A Computer Assisted Test Generator.

    ERIC Educational Resources Information Center

    McCallum, L. W.

    1985-01-01

    Procedures for generating multiple-choice exams in psychology using the Apple IIe computer and the Applewriter II text editing software are described. The model is simple to use and provides flexibility in sequencing the choice of items from an instructor generated pool. (Author/RM)

  5. Detecting photographic and computer generated composites

    NASA Astrophysics Data System (ADS)

    Conotter, V.; Cordin, L.

    2011-03-01

    Nowadays, sophisticated computer graphics editors lead to a significant increase in the photorealism of images. Thus, computer generated (CG) images result to be convincing and hard to be distinguished from real ones at a first glance. Here, we propose an image forensics technique able to automatically detect local forgeries, i.e., objects generated via computer graphics software inserted in natural images, and vice versa. We develop a novel hybrid classifier based on wavelet based features and sophisticated pattern noise statistics. Experimental results show the effectiveness of the proposed approach.

  6. Nuclear Forces and High-Performance Computing: The Perfect Match

    SciTech Connect

    Luu, T; Walker-Loud, A

    2009-06-12

    High-performance computing is now enabling the calculation of certain nuclear interaction parameters directly from Quantum Chromodynamics, the quantum field theory that governs the behavior of quarks and gluons and is ultimately responsible for the nuclear strong force. We briefly describe the state of the field and describe how progress in this field will impact the greater nuclear physics community. We give estimates of computational requirements needed to obtain certain milestones and describe the scientific and computational challenges of this field.

  7. Schedule-Report-Generator Computer Program

    NASA Technical Reports Server (NTRS)

    Collazo, Fernando F.

    1990-01-01

    Schedule Report Generator provides simple method for generating periodic schedule reports. Enables engineering manager to monitor tasks assigned to staff members on weekly basis. Sorts three types of reports by use of one or more data fields as sorting keys. Schedule Organizer (SO) (COSMIC program MSC-21525), Schedule Tracker (ST) (COSMIC program MSC-21526), and Schedule Report Generator (SRG) computer programs manipulating data-base files in ways advantageous in scheduling. Written in PL/1 and DEC Command Language (DCL).

  8. Computation of ground reaction force using Zero Moment Point.

    PubMed

    Dijkstra, Erik J; Gutierrez-Farewik, Elena M

    2015-11-01

    Motion analysis is a common clinical assessment and research tool that uses a camera system or motion sensors and force plates to collect kinematic and kinetic information of a subject performing an activity of interest. The use of force plates can be challenging and sometimes even impossible. Over the past decade, several computational methods have been developed that aim to preclude the use of force plates. Useful in particular for predictive simulations, where a new motion or change in control strategy inherently means different external contact loads. These methods, however, often depend on prior knowledge of common observed ground reaction force (GRF) patterns, are computationally expensive, or difficult to implement. In this study, we evaluated the use of the Zero Moment Point as a computationally inexpensive tool to obtain the GRFs for normal human gait. The method was applied on ten healthy subjects walking in a motion analysis laboratory and predicted GRFs are evaluated against the simultaneously measured force plate data. Apart from the antero-posterior forces, GRFs are well-predicted and errors fall within the error ranges from other published methods. Joint extension moments were underestimated at the ankle and hip but overestimated at the knee, attributable to the observed discrepancy in the predicted application points of the GRFs. The computationally inexpensive method evaluated in this study can reasonably well predict the GRFs for normal human gait without using prior knowledge of common gait kinetics. PMID:26482731

  9. Next generation distributed computing for cancer research.

    PubMed

    Agarwal, Pankaj; Owzar, Kouros

    2014-01-01

    Advances in next generation sequencing (NGS) and mass spectrometry (MS) technologies have provided many new opportunities and angles for extending the scope of translational cancer research while creating tremendous challenges in data management and analysis. The resulting informatics challenge is invariably not amenable to the use of traditional computing models. Recent advances in scalable computing and associated infrastructure, particularly distributed computing for Big Data, can provide solutions for addressing these challenges. In this review, the next generation of distributed computing technologies that can address these informatics problems is described from the perspective of three key components of a computational platform, namely computing, data storage and management, and networking. A broad overview of scalable computing is provided to set the context for a detailed description of Hadoop, a technology that is being rapidly adopted for large-scale distributed computing. A proof-of-concept Hadoop cluster, set up for performance benchmarking of NGS read alignment, is described as an example of how to work with Hadoop. Finally, Hadoop is compared with a number of other current technologies for distributed computing. PMID:25983539

  10. Next Generation Distributed Computing for Cancer Research

    PubMed Central

    Agarwal, Pankaj; Owzar, Kouros

    2014-01-01

    Advances in next generation sequencing (NGS) and mass spectrometry (MS) technologies have provided many new opportunities and angles for extending the scope of translational cancer research while creating tremendous challenges in data management and analysis. The resulting informatics challenge is invariably not amenable to the use of traditional computing models. Recent advances in scalable computing and associated infrastructure, particularly distributed computing for Big Data, can provide solutions for addressing these challenges. In this review, the next generation of distributed computing technologies that can address these informatics problems is described from the perspective of three key components of a computational platform, namely computing, data storage and management, and networking. A broad overview of scalable computing is provided to set the context for a detailed description of Hadoop, a technology that is being rapidly adopted for large-scale distributed computing. A proof-of-concept Hadoop cluster, set up for performance benchmarking of NGS read alignment, is described as an example of how to work with Hadoop. Finally, Hadoop is compared with a number of other current technologies for distributed computing. PMID:25983539

  11. A simulated force generator with an adaptive command structure

    NASA Astrophysics Data System (ADS)

    Hanes, P. Jeff

    2006-05-01

    The Force Laydown Automated Generator (FLAG) is a script-driven behavior model that automatically creates military formations from the platoon level up to division level for use in simulations built on the FLAMES simulation framework. The script allows users to define formation command structure, command relationships, vehicle type and equipment, and behaviors. We have used it to automatically generate more than 3000 units in a single simulation. Currently, FLAG is used in the Air Force Research Laboratory Munitions Directorate (AFRL/MN) to assist their Comprehensive Analysis Process (CAP). It produces a reasonable threat laydown of red forces for testing their blue concept weapons. Our success in the application of FLAG leads us to believe that it offers an invaluable potential for use in training environments and other applications that need a large number of reactive, adaptive forces - red or blue.

  12. Direct measurement of the forces generated by an undulatory microswimmer

    NASA Astrophysics Data System (ADS)

    Schulman, Rafael; Backholm, Matilda; Ryu, William; Dalnoki-Veress, Kari

    2014-11-01

    C. elegans is a millimeter-sized nematode which has served as a model organism in biology for several decades, primarily due to its simple anatomy. Employing an undulatory form of locomotion, this worm is capable of propelling itself through various media. Using a micropipette deflection technique, in conjunction with high speed imaging, we directly measure the time-varying forces generated by C. elegans. We observe excellent agreement between our measured forces and the predictions of resistive force theory, through which we determine the drag coefficients of the worm. We also perform the direct force measurements at controlled distances from a single solid boundary as well as between two solid boundaries. We extract the drag coefficients of the worm to quantify the influence of the boundary on the swimming and the hydrodynamic forces involved.

  13. Force generation by orthodontic samarium-cobalt magnets.

    PubMed

    von Fraunhofer, J A; Bonds, P W; Johnson, B E

    1992-01-01

    The use of samarium-cobalt (Sm-Co) magnets for light force application is a relatively new concept in orthodontic tooth movement. This study reports on the forces generated by these magnets. Magnets were attached to aluminum rods mounted in a universal testing machine. The magnets were initially separated by 10 mm were moved toward each other at 2.5mm/min in repulsion or attraction, depending upon the magnetic pole orientation. The magnets were also positioned initially in contact and then moved apart at a rate of 2.5mm/min, again producing repulsion or attraction, depending upon the pole orientation. The Sm-Co magnets exhibit very large forces when in close approximation but forces decrease markedly at separations greater than 2mm. The force, P, generated between magnets is determined by their separation, d, and follows the relationship P = dn. At magnet separations of 0 to 2mm, the exponent n is equal to -0.4; at separations of 2mm to 7mm, exponent n equals -2.1 for both attraction and repulsion. Thus the classic Coulomb law of magnetic force was followed only at magnet separations of greater than 2mm. Force-separation behavior and the high cost of these magnets may not justify their routine clinical use. PMID:1416238

  14. Computer Program For Generation Of Surface Grids

    NASA Technical Reports Server (NTRS)

    Ching, Raymond; Pierce, Lawrence

    1993-01-01

    S3D is useful computer program for generation of grids on surfaces of bodies having complicated shapes. Product of integration of robust and widely applicable interpolation technique with latest in computer-workstation technology. Incorporates highly efficient and easy-to-use graphical-interface software, enables real-time and interactive analyses of surface-geometry data and facilitates construction of surface grids.

  15. Aeroacoustics. [analysis of properties of sound generated by aerodynamic forces

    NASA Technical Reports Server (NTRS)

    Goldstein, M., E.

    1974-01-01

    An analysis was conducted to determine the properties of sound generated by aerodynamic forces or motions originating in a flow, such as the unsteady aerodynamic forces on propellers or by turbulent flows around an aircraft. The acoustics of moving media are reviewed and mathematical models are developed. Lighthill's acoustic analogy and the application to turbulent flows are analyzed. The effects of solid boundaries are calculated. Theories based on the solution of linearized vorticity and acoustic field equations are explained. The effects of nonuniform mean flow on the generation of sound are reported.

  16. Motility, Force Generation, and Energy Consumption of Unicellular Parasites.

    PubMed

    Hochstetter, Axel; Pfohl, Thomas

    2016-07-01

    Motility is a key factor for pathogenicity of unicellular parasites, enabling them to infiltrate and evade host cells, and perform several of their life-cycle events. State-of-the-art methods of motility analysis rely on a combination of optical tweezers with high-resolution microscopy and microfluidics. With this technology, propulsion forces, energies, and power generation can be determined so as to shed light on the motion mechanisms, chemotactic behavior, and specific survival strategies of unicellular parasites. With these new tools in hand, we can elucidate the mechanisms of motility and force generation of unicellular parasites, and identify ways to manipulate and eventually inhibit them. PMID:27157805

  17. Generation of extreme ultraviolet vortex beams using computer generated holograms.

    PubMed

    Terhalle, Bernd; Langner, Andreas; Päivänranta, Birgit; Guzenko, Vitaliy A; David, Christian; Ekinci, Yasin

    2011-11-01

    We fabricate computer generated holograms for the generation of phase singularities at extreme ultraviolet (EUV) wavelengths using electron beam lithography and demonstrate their ability to generate optical vortices in the nonzero diffraction orders. To this end, we observe the characteristic intensity distribution of the vortex beam and verify the helical phase structure interferometrically. The presented method forms the basis for further studies on singular light fields in the EUV frequency range, i.e., in EUV interference lithography. Since the method is purely achromatic, it may also find applications in various fields of x ray optics. PMID:22048345

  18. Evaluation of force generation mechanisms in natural, passive hydraulic actuators

    NASA Astrophysics Data System (ADS)

    Le Duigou, A.; Castro, M.

    2016-01-01

    Pine cones are well known natural actuators that can move their scales upon humidity gradient. The mechanism manifests itself through a displacement easily observable by the naked eye, but coupled with stress generation. In ancient Egypt, wooden wedges were used to break soft blocks of stone by the generated swelling stress. The purpose of the present study is to evaluate the ability of pine cone scales to generate forces while being wetted. In our experiments, a blocking force of around 3N is measured depending on the position on the pine cone where the scales are extracted. A fairly good agreement is obtained when theoretical results based on bimetallic strip systems are compared with experimental data, even if overestimation is observed arising from the input data considered for dry tissues. Inspired by a simplified pine cone microstructure, a biocomposite analogue is manufactured and tested. Although an adequate blocking force can be generated, it has a lower value compared to natural pine cones which benefit from optimized swelling tissue content and interfacial bond strength between them. This study provides new insights to understand the generation of force by pine cones as well as to develop novel biocomposite functionalities.

  19. Evaluation of force generation mechanisms in natural, passive hydraulic actuators

    PubMed Central

    Le Duigou, A.; Castro, M.

    2016-01-01

    Pine cones are well known natural actuators that can move their scales upon humidity gradient. The mechanism manifests itself through a displacement easily observable by the naked eye, but coupled with stress generation. In ancient Egypt, wooden wedges were used to break soft blocks of stone by the generated swelling stress. The purpose of the present study is to evaluate the ability of pine cone scales to generate forces while being wetted. In our experiments, a blocking force of around 3N is measured depending on the position on the pine cone where the scales are extracted. A fairly good agreement is obtained when theoretical results based on bimetallic strip systems are compared with experimental data, even if overestimation is observed arising from the input data considered for dry tissues. Inspired by a simplified pine cone microstructure, a biocomposite analogue is manufactured and tested. Although an adequate blocking force can be generated, it has a lower value compared to natural pine cones which benefit from optimized swelling tissue content and interfacial bond strength between them. This study provides new insights to understand the generation of force by pine cones as well as to develop novel biocomposite functionalities. PMID:26726792

  20. Evaluation of force generation mechanisms in natural, passive hydraulic actuators.

    PubMed

    Le Duigou, A; Castro, M

    2016-01-01

    Pine cones are well known natural actuators that can move their scales upon humidity gradient. The mechanism manifests itself through a displacement easily observable by the naked eye, but coupled with stress generation. In ancient Egypt, wooden wedges were used to break soft blocks of stone by the generated swelling stress. The purpose of the present study is to evaluate the ability of pine cone scales to generate forces while being wetted. In our experiments, a blocking force of around 3N is measured depending on the position on the pine cone where the scales are extracted. A fairly good agreement is obtained when theoretical results based on bimetallic strip systems are compared with experimental data, even if overestimation is observed arising from the input data considered for dry tissues. Inspired by a simplified pine cone microstructure, a biocomposite analogue is manufactured and tested. Although an adequate blocking force can be generated, it has a lower value compared to natural pine cones which benefit from optimized swelling tissue content and interfacial bond strength between them. This study provides new insights to understand the generation of force by pine cones as well as to develop novel biocomposite functionalities. PMID:26726792

  1. Diffusible crosslinkers generate directed forces in microtubule networks.

    PubMed

    Lansky, Zdenek; Braun, Marcus; Lüdecke, Annemarie; Schlierf, Michael; ten Wolde, Pieter Rein; Janson, Marcel E; Diez, Stefan

    2015-03-12

    Cytoskeletal remodeling is essential to eukaryotic cell division and morphogenesis. The mechanical forces driving the restructuring are attributed to the action of molecular motors and the dynamics of cytoskeletal filaments, which both consume chemical energy. By contrast, non-enzymatic filament crosslinkers are regarded as mere friction-generating entities. Here, we experimentally demonstrate that diffusible microtubule crosslinkers of the Ase1/PRC1/Map65 family generate directed microtubule sliding when confined between partially overlapping microtubules. The Ase1-generated forces, directly measured by optical tweezers to be in the piconewton-range, were sufficient to antagonize motor-protein driven microtubule sliding. Force generation is quantitatively explained by the entropic expansion of confined Ase1 molecules diffusing within the microtubule overlaps. The thermal motion of crosslinkers is thus harnessed to generate mechanical work analogous to compressed gas propelling a piston in a cylinder. As confinement of diffusible proteins is ubiquitous in cells, the associated entropic forces are likely of importance for cellular mechanics beyond cytoskeletal networks. PMID:25748652

  2. Optical Interconnection Via Computer-Generated Holograms

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Zhou, Shaomin

    1995-01-01

    Method of free-space optical interconnection developed for data-processing applications like parallel optical computing, neural-network computing, and switching in optical communication networks. In method, multiple optical connections between multiple sources of light in one array and multiple photodetectors in another array made via computer-generated holograms in electrically addressed spatial light modulators (ESLMs). Offers potential advantages of massive parallelism, high space-bandwidth product, high time-bandwidth product, low power consumption, low cross talk, and low time skew. Also offers advantage of programmability with flexibility of reconfiguration, including variation of strengths of optical connections in real time.

  3. CGI delay compensation. [Computer Generated Image

    NASA Technical Reports Server (NTRS)

    Mcfarland, R. E.

    1986-01-01

    Computer-generated graphics in real-time helicopter simulation produces objectionable scene-presentation time delays. In the flight simulation laboratory at Ames Research Center, it has been determined that these delays have an adverse influence on pilot performance during agressive tasks such as nap of the earth (NOE) maneuvers. Using contemporary equipment, computer generated image (CGI) time delays are an unavoidable consequence of the operations required for scene generation. However, providing that magnitude distortions at higher frequencies are tolerable, delay compensation is possible over a restricted frequency range. This range, assumed to have an upper limit of perhaps 10 or 15 rad/sec, conforms approximately to the bandwidth associated with helicopter handling qualities research. A compensation algorithm is introduced here and evaluated in terms of tradeoffs in frequency responses. The algorithm has a discrete basis and accommodates both a large, constant transport delay interval and a periodic delay interval, as associated with asynchronous operations.

  4. Crouched posture maximizes ground reaction forces generated by muscles.

    PubMed

    Hoang, Hoa X; Reinbolt, Jeffrey A

    2012-07-01

    Crouch gait decreases walking efficiency due to the increased knee and hip flexion during the stance phase of gait. Crouch gait is generally considered to be disadvantageous for children with cerebral palsy; however, a crouched posture may allow biomechanical advantages that lead some children to adopt a crouch gait. To investigate one possible advantage of crouch gait, a musculoskeletal model created in OpenSim was placed in 15 different postures from upright to severe crouch during initial, middle, and final stance of the gait cycle for a total of 45 different postures. A series of optimizations was performed for each posture to maximize transverse plane ground reaction forces in the eight compass directions by modifying muscle forces acting on the model. We compared the force profile areas across all postures. Larger force profile areas were allowed by postures from mild crouch (for initial stance) to crouch (for final stance). The overall ability to generate larger ground reaction force profiles represents a mechanical advantage of a crouched posture. This increase in muscle capacity while in a crouched posture may allow a patient to generate new movements to compensate for impairments associated with cerebral palsy, such as motor control deficits. PMID:22542242

  5. Quantifying cell-generated mechanical forces within living embryonic tissues

    PubMed Central

    Campàs, Otger; Mammoto, Tadanori; Hasso, Sean; Sperling, Ralph A; O’Connell, Daniel; Bischof, Ashley G; Maas, Richard; Weitz, David A; Mahadevan, Lakshminarayanan; Ingber, Donald E

    2014-01-01

    Cell-generated mechanical forces play a critical role during tissue morphogenesis and organ formation in the embryo. However, little is known about how these forces shape embryonic organs, mainly because it has not been possible to measure cellular forces within developing three-dimensional (3D) tissues in vivo. Here we present a method to quantify cell-generated mechanical stresses that are exerted locally within living embryonic tissues using fluorescent, cell-sized, oil microdroplets with defined mechanical properties and coated with surface integrin or cadherin receptor ligands. After introducing a droplet between cells in a tissue, local stresses are determined from the droplet shape deformations, which are obtained via fluorescence microscopy and computerized image analysis. Using this method, we quantify the anisotropic stresses generated by mammary epithelial cells cultured within 3D aggregates and confirm that these stresses (3.4 nN/µm2) are dependent on myosin II activity and more than two-fold larger than the stresses generated by cells of embryonic tooth mesenchyme when analyzed within similar cultured aggregates or in developing whole mouse mandibles. PMID:24317254

  6. Computer-generated electrically switchable holographic composites

    NASA Astrophysics Data System (ADS)

    Nelson, Arthur R.; Chen, Tony; Jauniskis, Linas; Domash, Lawrence H.

    1995-04-01

    Electrically switched holographic composites (ESHC) based on Polaroid photopolymer materials were described previously using optically generated holograms. These techniques have now been extended to include computer generated holograms. A highly accurate laser writing engine was utilized to write multi-phase level diffractive gratings in Polaroid type DMP-128 photopolymer film. After compositing with liquid crystals and applying an electric field, the diffraction efficiency of the elements could be switched or tuned continuously over approximately a 100:1 range of diffraction efficiencies, opening a new range of interconnect applications.

  7. Managing turbine-generator outages by computer

    SciTech Connect

    Reinhart, E.R.

    1997-09-01

    This article describes software being developed to address the need for computerized planning and documentation programs that can help manage outages. Downsized power-utility companies and the growing demand for independent, competitive engineering and maintenance services have created a need for a computer-assisted planning and technical-direction program for turbine-generator outages. To meet this need, a software tool is now under development that can run on a desktop or laptop personal computer to assist utility personnel and technical directors in outage planning. Total Outage Planning Software (TOPS), which runs on Windows, takes advantage of the mass data storage available with compact-disc technology by archiving the complete outage documentation on CD. Previous outage records can then be indexed, searched, and viewed on a computer with the click of a mouse. Critical-path schedules, parts lists, parts order tracking, work instructions and procedures, custom data sheets, and progress reports can be generated by computer on-site during an outage.

  8. Computer-generated mineral commodity deposit maps

    USGS Publications Warehouse

    Schruben, Paul G.; Hanley, J. Thomas

    1983-01-01

    This report describes an automated method of generating deposit maps of mineral commodity information. In addition, it serves as a user's manual for the authors' mapping system. Procedures were developed which allow commodity specialists to enter deposit information, retrieve selected data, and plot deposit symbols in any geographic area within the conterminous United States. The mapping system uses both micro- and mainframe computers. The microcomputer is used to input and retrieve information, thus minimizing computing charges. The mainframe computer is used to generate map plots which are printed by a Calcomp plotter. Selector V data base system is employed for input and retrieval on the microcomputer. A general mapping program (Genmap) was written in FORTRAN for use on the mainframe computer. Genmap can plot fifteen symbol types (for point locations) in three sizes. The user can assign symbol types to data items interactively. Individual map symbols can be labeled with a number or the deposit name. Genmap also provides several geographic boundary file and window options.

  9. High Resolution Traction Force Microscopy Based on Experimental and Computational Advances

    PubMed Central

    Sabass, Benedikt; Gardel, Margaret L.; Waterman, Clare M.; Schwarz, Ulrich S.

    2008-01-01

    Cell adhesion and migration crucially depend on the transmission of actomyosin-generated forces through sites of focal adhesion to the extracellular matrix. Here we report experimental and computational advances in improving the resolution and reliability of traction force microscopy. First, we introduce the use of two differently colored nanobeads as fiducial markers in polyacrylamide gels and explain how the displacement field can be computationally extracted from the fluorescence data. Second, we present different improvements regarding standard methods for force reconstruction from the displacement field, which are the boundary element method, Fourier-transform traction cytometry, and traction reconstruction with point forces. Using extensive data simulation, we show that the spatial resolution of the boundary element method can be improved considerably by splitting the elastic field into near, intermediate, and far field. Fourier-transform traction cytometry requires considerably less computer time, but can achieve a comparable resolution only when combined with Wiener filtering or appropriate regularization schemes. Both methods tend to underestimate forces, especially at small adhesion sites. Traction reconstruction with point forces does not suffer from this limitation, but is only applicable with stationary and well-developed adhesion sites. Third, we combine these advances and for the first time reconstruct fibroblast traction with a spatial resolution of ∼1 μm. PMID:17827246

  10. Electromagnetic forces in the air gap of a permanent magnet linear generator at no load

    NASA Astrophysics Data System (ADS)

    Nilsson, K.; Danielsson, O.; Leijon, M.

    2006-02-01

    The basis for the work is the slow speed energy conversion of ocean wave energy into electricity using a direct-drive three-phase permanent magnetized linear generator. One of several important issues is the normal forces in the air gap, which is critical when designing the support structure of the generator. The electromagnetic forces in the air gap have been analyzed using Maxwell stress tensor method implemented in a two- dimensional finite element code. Simplified analytic calculations are made in order to validate the results from the extensive computer calculations. The normal electromagnetic forces in the air gap, Fδ, are analyzed for a two-sided linear generator at no load. An unstable condition of the global force on the piston occurs due to the fast increasing normal force as the air gap width decreases. A horizontal displacement of the piston from a neutral position with 3 mm air gap on both sides produces a resulting horizontal force on the piston, increasing with the displacement. A displacement of 1 mm gives a resulting horizontal force on the piston of 5.5 kN per pole and meter of core length, which is increased to 9 kN per pole and meter of core length for a displacement of 1.5 mm. Furthermore, the normal force varies due to cogging as the piston moves vertically. At a constant air gap width of 3 mm the normal forces per pole are varying between 9.9 and 11.3 kN/m of core length as the piston is moving from one pole to the next.

  11. Computational optical palpation: micro-scale force mapping using finite-element methods (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wijesinghe, Philip; Sampson, David D.; Kennedy, Brendan F.

    2016-03-01

    Accurate quantification of forces, applied to, or generated by, tissue, is key to understanding many biomechanical processes, fabricating engineered tissues, and diagnosing diseases. Many techniques have been employed to measure forces; in particular, tactile imaging - developed to spatially map palpation-mimicking forces - has shown potential in improving the diagnosis of cancer on the macro-scale. However, tactile imaging often involves the use of discrete force sensors, such as capacitive or piezoelectric sensors, whose spatial resolution is often limited to 1-2 mm. Our group has previously presented a type of tactile imaging, termed optical palpation, in which the change in thickness of a compliant layer in contact with tissue is measured using optical coherence tomography, and surface forces are extracted, with a micro-scale spatial resolution, using a one-dimensional spring model. We have also recently combined optical palpation with compression optical coherence elastography (OCE) to quantify stiffness. A main limitation of this work, however, is that a one-dimensional spring model is insufficient in describing the deformation of mechanically heterogeneous tissue with uneven boundaries, generating significant inaccuracies in measured forces. Here, we present a computational, finite-element method, which we term computational optical palpation. In this technique, by knowing the non-linear mechanical properties of the layer, and from only the axial component of displacement measured by phase-sensitive OCE, we can estimate, not only the axial forces, but the three-dimensional traction forces at the layer-tissue interface. We use a non-linear, three-dimensional model of deformation, which greatly increases the ability to accurately measure force and stiffness in complex tissues.

  12. First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning Using Satellite Data

    NASA Technical Reports Server (NTRS)

    Christopher, Sundar A.; Kliche, Donna A.; Chou, Joyce; Welch, Ronald M.

    1996-01-01

    Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

  13. First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning using Satellite Data

    NASA Technical Reports Server (NTRS)

    Chistopher, Sundar A.; Kliche, Donna V.; Chou, Joyce; Welch, Ronald M.

    1996-01-01

    Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

  14. Computer-Generated Holographic Matched Filters

    NASA Astrophysics Data System (ADS)

    Butler, Steven Frank

    This dissertation presents techniques for the use of computer-generated holograms (CGH) for matched filtering. An overview of the supporting technology is provided. Included are techniques for modifying existing CGH algorithms to serve as matched filters in an optical correlator. It shows that matched filters produced in this fashion can be modified to improve the signal-to-noise and efficiency over that possible with conventional holography. The effect and performance of these modifications are demonstrated. In addition, a correction of film non-linearity in continuous -tone filter production is developed. Computer simulations provide quantitative and qualitative demonstration of theoretical principles, with specific examples validated in optical hardware. Conventional and synthetic holograms, both bleached and unbleached, are compared.

  15. Pulling together: Tissue-generated forces that drive lumen morphogenesis.

    PubMed

    Navis, Adam; Nelson, Celeste M

    2016-07-01

    Mechanical interactions are essential for bending and shaping tissues during morphogenesis. A common feature of nearly all internal organs is the formation of a tubular network consisting of an epithelium that surrounds a central lumen. Lumen formation during organogenesis requires precisely coordinated mechanical and biochemical interactions. Whereas many genetic regulators of lumen formation have been identified, relatively little is known about the mechanical cues that drive lumen morphogenesis. Lumens can be shaped by a variety of physical behaviors including wrapping a sheet of cells around a hollow core, rearranging cells to expose a lumenal cavity, or elongating a tube via cell migration, though many of the details underlying these movements remain poorly understood. It is essential to define how forces generated by individual cells cooperate to produce the tissue-level forces that drive organogenesis. Transduction of mechanical forces relies on several conserved processes including the contraction of cytoskeletal networks or expansion of lumens through increased fluid pressure. The morphogenetic events that drive lumen formation serve as a model for similar mechanical processes occurring throughout development. To understand how lumenal networks arise, it will be essential to investigate how biochemical and mechanical processes integrate to generate complex structures from comparatively simple interactions. PMID:26778757

  16. 48 CFR 52.253-1 - Computer Generated Forms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 2 2014-10-01 2014-10-01 false Computer Generated Forms....253-1 Computer Generated Forms. As prescribed in FAR 53.111, insert the following clause: Computer... by the Federal Acquisition Regulation (FAR) may be submitted on a computer generated version of...

  17. 48 CFR 52.253-1 - Computer Generated Forms.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Computer Generated Forms....253-1 Computer Generated Forms. As prescribed in FAR 53.111, insert the following clause: Computer... by the Federal Acquisition Regulation (FAR) may be submitted on a computer generated version of...

  18. 48 CFR 52.253-1 - Computer Generated Forms.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 2 2011-10-01 2011-10-01 false Computer Generated Forms....253-1 Computer Generated Forms. As prescribed in FAR 53.111, insert the following clause: Computer... by the Federal Acquisition Regulation (FAR) may be submitted on a computer generated version of...

  19. 48 CFR 52.253-1 - Computer Generated Forms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 2 2012-10-01 2012-10-01 false Computer Generated Forms....253-1 Computer Generated Forms. As prescribed in FAR 53.111, insert the following clause: Computer... by the Federal Acquisition Regulation (FAR) may be submitted on a computer generated version of...

  20. 48 CFR 52.253-1 - Computer Generated Forms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 2 2013-10-01 2013-10-01 false Computer Generated Forms....253-1 Computer Generated Forms. As prescribed in FAR 53.111, insert the following clause: Computer... by the Federal Acquisition Regulation (FAR) may be submitted on a computer generated version of...

  1. Computer modeling of thermoelectric generator performance

    NASA Technical Reports Server (NTRS)

    Chmielewski, A. B.; Shields, V.

    1982-01-01

    Features of the DEGRA 2 computer code for simulating the operations of a spacecraft thermoelectric generator are described. The code models the physical processes occurring during operation. Input variables include the thermoelectric couple geometry and composition, the thermoelectric materials' properties, interfaces and insulation in the thermopile, the heat source characteristics, mission trajectory, and generator electrical requirements. Time steps can be specified and sublimation of the leg and hot shoe is accounted for, as are shorts between legs. Calculations are performed for conduction, Peltier, Thomson, and Joule heating, the cold junction can be adjusted for solar radition, and the legs of the thermoelectric couple are segmented to enhance the approximation accuracy. A trial run covering 18 couple modules yielded data with 0.3% accuracy with regard to test data. The model has been successful with selenide materials, SiGe, and SiN4, with output of all critical operational variables.

  2. The Shuttle Mission Simulator computer generated imagery

    NASA Technical Reports Server (NTRS)

    Henderson, T. H.

    1984-01-01

    Equipment available in the primary training facility for the Space Transportation System (STS) flight crews includes the Fixed Base Simulator, the Motion Base Simulator, the Spacelab Simulator, and the Guidance and Navigation Simulator. The Shuttle Mission Simulator (SMS) consists of the Fixed Base Simulator and the Motion Base Simulator. The SMS utilizes four visual Computer Generated Image (CGI) systems. The Motion Base Simulator has a forward crew station with six-degrees of freedom motion simulation. Operation of the Spacelab Simulator is planned for the spring of 1983. The Guidance and Navigation Simulator went into operation in 1982. Aspects of orbital visual simulation are discussed, taking into account the earth scene, payload simulation, the generation and display of 1079 stars, the simulation of sun glare, and Reaction Control System jet firing plumes. Attention is also given to landing site visual simulation, and night launch and landing simulation.

  3. Podosome rings generate forces that drive saltatory osteoclast migration

    PubMed Central

    Hu, Shiqiong; Planus, Emmanuelle; Georgess, Dan; Place, Christophe; Wang, Xianghui; Albiges-Rizo, Corinne; Jurdic, Pierre; Géminard, Jean-Christophe

    2011-01-01

    Podosomes are dynamic, actin-containing adhesion structures that collectively self-organize as rings. In this study, we first show by observing osteoclasts plated on bead-seeded soft substrates that podosome assemblies, such as rings, are involved in tension forces. During the expansion of a podosome ring, substrate displacement is oriented outward, suggesting that podosomal structures push the substrate away. To further elucidate the function of forces generated by podosomes, we analyze osteoclast migration. Determining the centers of mass of the whole cell (G) and of actin (P), we demonstrate that osteoclasts migrate by “jumps” and that the trajectories of G and P are strongly correlated. The velocity of the center of mass as a function of time reveals that osteoclasts rapidly catch up with podosomal structures in a periodic pattern. We conclude that actin dynamics inside the cell are not only correlated with cell migration, but drive it. PMID:21737683

  4. Direct computation of parameters for accurate polarizable force fields

    SciTech Connect

    Verstraelen, Toon Vandenbrande, Steven; Ayers, Paul W.

    2014-11-21

    We present an improved electronic linear response model to incorporate polarization and charge-transfer effects in polarizable force fields. This model is a generalization of the Atom-Condensed Kohn-Sham Density Functional Theory (DFT), approximated to second order (ACKS2): it can now be defined with any underlying variational theory (next to KS-DFT) and it can include atomic multipoles and off-center basis functions. Parameters in this model are computed efficiently as expectation values of an electronic wavefunction, obviating the need for their calibration, regularization, and manual tuning. In the limit of a complete density and potential basis set in the ACKS2 model, the linear response properties of the underlying theory for a given molecular geometry are reproduced exactly. A numerical validation with a test set of 110 molecules shows that very accurate models can already be obtained with fluctuating charges and dipoles. These features greatly facilitate the development of polarizable force fields.

  5. Magnetic resonance force microscopy and a solid state quantum computer.

    SciTech Connect

    Pelekhov, D. V.; Martin, I.; Suter, A.; Reagor, D. W.; Hammel, P. C.

    2001-01-01

    A Quantum Computer (QC) is a device that utilizes the principles of Quantum Mechanics to perform computations. Such a machine would be capable of accomplishing tasks not achievable by means of any conventional digital computer, for instance factoring large numbers. Currently it appears that the QC architecture based on an array of spin quantum bits (qubits) embedded in a solid-state matrix is one of the most promising approaches to fabrication of a scalable QC. However, the fabrication and operation of a Solid State Quantum Computer (SSQC) presents very formidable challenges; primary amongst these are: (1) the characterization and control of the fabrication process of the device during its construction and (2) the readout of the computational result. Magnetic Resonance Force Microscopy (MRFM)--a novel scanning probe technique based on mechanical detection of magnetic resonance-provides an attractive means of addressing these requirements. The sensitivity of the MRFM significantly exceeds that of conventional magnetic resonance measurement methods, and it has the potential for single electron spin detection. Moreover, the MRFM is capable of true 3D subsurface imaging. These features will make MRFM an invaluable tool for the implementation of a spin-based QC. Here we present the general principles of MRFM operation, the current status of its development and indicate future directions for its improvement.

  6. The tension mounts: Stress fibers as force-generating mechanotransducers

    PubMed Central

    Wittchen, Erika S.

    2013-01-01

    Stress fibers (SFs) are often the most prominent cytoskeletal structures in cells growing in tissue culture. Composed of actin filaments, myosin II, and many other proteins, SFs are force-generating and tension-bearing structures that respond to the surrounding physical environment. New work is shedding light on the mechanosensitive properties of SFs, including that these structures can respond to mechanical tension by rapid reinforcement and that there are mechanisms to repair strain-induced damage. Although SFs are superficially similar in organization to the sarcomeres of striated muscle, there are intriguing differences in their organization and behavior, indicating that much still needs to be learned about these structures. PMID:23295347

  7. Computer graphics of center of masticatory forces in complete dentures.

    PubMed

    Ogata, K; Kawahara, K; Kishimoto, E; Ogata, S

    1995-01-01

    1. INTRODUCTION. In dental education, it is valuable to show visually the differences between a good-fitting and an ill-fitting complete denture. A vector of masticatory forces across all the teeth of the denture is available to estimate the capability of the denture. The vector is simple while the forces exerted on a denture are very complex. A vector has only two factors, the point of application (center of force) and the magnitude. Because a complete denture acts as a unit, we can obtain the vector from electrical signals detected by transducers installed in the denture base. The aim of this study was to develop software which is able to show visually to dental students, the differences between the vectors of the dentures of three representative complete denture wearers. 2. METHODS. Three subjects, each with either a good, a moderate or an ill-fitting complete denture, were selected. Subject 1 could use the denture very comfortably during experiment. Subject 2 was uncomfortable at the insertion of the new denture, but after adaptations to the denture he could use it very well. Subject 3 had been uncomfortable during the experiment. A bottom complete denture was divided into upper and lower parts. These were connected by the four force-detecting units which were embedded in approximately the first premolar and second molar regions on both sides of the denture. The electric signals from these units during the chewing of peanuts and raisins (sampling time period: 30 msec) were recorded as digital signals and processed using the computer (Macintosh IIcx, Apple Computer) with the A/D converter (Lab-NB), National Instruments). Center and magnitudes of masticatory force were calculated from all sampling points using our newly developed software scripted by ¿C¿ (MPW C, Apple Computer). On the other hand, a tracing of the external shape of the dentition of the denture was made using the project (V-12, NIKON). The tracing of the dentition, with center and magnitude of

  8. Myofilament spacing and force generation in intact frog muscle fibres.

    PubMed Central

    Bagni, M A; Cecchi, G; Colomo, F

    1990-01-01

    1. The relation between sarcomere length and steady tetanic tension was determined at 10-12 degrees C for 70-80 microns long length-clamped segments of single fibres isolated from the tibialis anterior muscle of the frog, in normal and hypertonic or hypotonic Ringer solutions. 2. The tension depression and potentiation observed in hypertonic and hypotonic Ringers solutions varied with sarcomere length, so that, as opposed to myofilament overlap predictions, the optimum length for tension development was shorter in hypertonic Ringer solution and longer in hypotonic Ringer solution than in normal Ringer solution. As the fibres were stretched from 1.96 to 2.24 microns sarcomere length, both tension depression in hypertonic Ringer solution and tension potentiation in hypotonic Ringer solution increased by 9 and 5%, respectively. 3. Within this range of sarcomere lengths the length-stiffness relation in hypotonic and in hypertonic Ringer solutions exhibit little or no change relative to that in normal Ringer solution. 4. The results indicate that separation between the thick and the thin myofilaments influences the mechanism of force generation. There is an optimum interfilament distance (10-12 nm surface to surface between the thick and the thin filaments) for tension production. In isotonic Ringer solution, this corresponds to the interfilament distance at sarcomere lengths around 2.10 microns. The force per attached cross-bridge, rather than their number, appears to decrease as the interfilament distance is brought above or below the optimum length. Even if this effect is moderate in isotonic Ringer solution, it should be taken into account in models of the force-generation mechanism. PMID:2086776

  9. Force Generation, Polymerization Dynamics and Nucleation of Actin Filaments

    NASA Astrophysics Data System (ADS)

    Wang, Ruizhe

    We study force generation and actin filament dynamics using stochastic and deterministic methods. First, we treat force generation of bundled actin filaments by polymerization via molecular-level stochastic simulations. In the widely-used Brownian Ratchet model, actin filaments grow freely whenever the tip-obstacle gap created by thermal fluctuation exceeds the monomer size. We name this model the Perfect Brownian Ratchet (PBR) model. In the PBR model, actin monomer diffusion is treated implicitly. We perform a series of simulations based on the PBR, in which obstacle motion is treated explicitly; in most previous studies, obstacle motion has been treated implicitly. We find that the cooperativity of filaments is generally weak in the PBR model, meaning that more filaments would grow more slowly given the same force per filament. Closed-form formulas are also developed, which match the simulation results. These portable and accurate formulas provide guidance for experiments and upper and lower bounds for theoretical analyses. We also studied a variation of the PBR, called the Diffusing Brownian Ratchet (DBR) model, in which both actin monomer and obstacle diffusion are treated explicitly. We find that the growth rate of multiple filaments is even lower, compared with that in PBR. This finding challenges the widely-accepted PBR assumption and suggests that pushing the study of actin dynamics down to the sub-nanometer level yields new insights. We subsequently used a rate equation approach to model the effect of local depletion of actin monomers on the nucleation of actin filaments on biomimetic beads, and how the effect is regulated by capping protein (CP). We find that near the bead surface, a higher CP concentration increases local actin concentration, which leads to an enhanced activities of actin filaments' nucleation. Our model analysis matches the experimental results and lends support to an important but undervalued hypothesis proposed by Carlier and

  10. Using lateral capillary forces to compute by self-assembly

    PubMed Central

    Rothemund, Paul W. K.

    2000-01-01

    Investigations of DNA computing have highlighted a fundamental connection between self-assembly (SA) and computation: in principle, any computation can be performed by a suitable self-assembling system. In practice, exploration of this connection is limited by our ability to control the geometry and specificity of binding interactions. Recently, a system has been developed that uses surface tension to assemble plastic tiles according to shape complementarity and likeness of wetting [Bowden, N., Terfort, A., Carbeck, J. & Whitesides, G. M. (1997) Science 276, 233–235]. Here the capacity of this system to compute by SA is explored. Tiles were prepared to test the system's ability to generate three structures of increasing complexity: a periodic checkerboard tiling, an aperiodic Penrose tiling, and a computational tiling that simulates a one-dimensional cellular automaton. Matching rules for these tilings were enforced by coating tiles with patterns of hydrophobic and hydrophilic patches or wetting codes. Energetic, kinetic, and mechanistic details of SA explain differences between experimental structures and mathematically ideal ones. In particular, the growth mechanism observed appears incompatible with computations that make use of a chosen input. PMID:10655471

  11. Computer Generated Inputs for NMIS Processor Verification

    SciTech Connect

    J. A. Mullens; J. E. Breeding; J. A. McEvers; R. W. Wysor; L. G. Chiang; J. R. Lenarduzzi; J. T. Mihalczo; J. K. Mattingly

    2001-06-29

    Proper operation of the Nuclear Identification Materials System (NMIS) processor can be verified using computer-generated inputs [BIST (Built-In-Self-Test)] at the digital inputs. Preselected sequences of input pulses to all channels with known correlation functions are compared to the output of the processor. These types of verifications have been utilized in NMIS type correlation processors at the Oak Ridge National Laboratory since 1984. The use of this test confirmed a malfunction in a NMIS processor at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) in 1998. The NMIS processor boards were returned to the U.S. for repair and subsequently used in NMIS passive and active measurements with Pu at VNIIEF in 1999.

  12. Evidence for an electrostatic mechanism of force generation by the bacteriophage T4 DNA packaging motor

    NASA Astrophysics Data System (ADS)

    Migliori, Amy D.; Keller, Nicholas; Alam, Tanfis I.; Mahalingam, Marthandan; Rao, Venigalla B.; Arya, Gaurav; Smith, Douglas E.

    2014-06-01

    How viral packaging motors generate enormous forces to translocate DNA into viral capsids remains unknown. Recent structural studies of the bacteriophage T4 packaging motor have led to a proposed mechanism wherein the gp17 motor protein translocates DNA by transitioning between extended and compact states, orchestrated by electrostatic interactions between complimentarily charged residues across the interface between the N- and C-terminal subdomains. Here we show that site-directed alterations in these residues cause force dependent impairments of motor function including lower translocation velocity, lower stall force and higher frequency of pauses and slips. We further show that the measured impairments correlate with computed changes in free-energy differences between the two states. These findings support the proposed structural mechanism and further suggest an energy landscape model of motor activity that couples the free-energy profile of motor conformational states with that of the ATP hydrolysis cycle.

  13. Using GPUs to Meet Next Generation Weather Model Computational Requirements

    NASA Astrophysics Data System (ADS)

    Govett, M.; Hart, L.; Henderson, T.; Middlecoff, J.; Tierney, C.

    2008-12-01

    Weather prediction goals within the Earth Science Research Laboratory at NOAA require significant increases in model resolution (~1 km) and forecast durations (~60 days) to support expected requirements in 5 years or less. However, meeting these goals will likely require at least 100k dedicated cores. Few systems will exist that could even run such a large problem, much less house a facility that could provide the necessary power and cooling requirements. To meet our goals we are exploring alternative technologies, including Graphics Processing Units (GPU), that could provide significantly more computational performance and reduced power and cooling requirements, at a lower cost than traditional high-performance computing solutions. Our current global numerical weather prediction model, the Flow following finite-volume Isocahedral Model (FIM, http://fim.noaa.gov), is still early in its development but is already demonstrating good fidelity and excellent scalability to 1000s of cores. The icosahedral grid has several complexities not present in more traditional Cartesian grids including polygons with different numbers of sides (five and six) and non-trivial computation of locations of neighboring grid cells. FIM uses an indirect addressing scheme that yields very compact code despite these complexities. We have extracted computational kernels that encompass functions likely to take the most time at higher resolutions including all that have horizontal dependencies. Kernels implement equations for computing anti-diffusive flux-corrected transport across cell edges, calculating forcing terms and time-step differencing, and re-computing time-dependent vertical coordinates. We are extending these kernels to explore performance of GPU-specific optimizations. We will present initial performance results from the computational kernels of the FIM model, as well as the challenges related to porting code with indirect memory references to the NVIDIA GPUs. Results of this

  14. Ionospheric signatures of acoustic waves generated by transient tropospheric forcing

    NASA Astrophysics Data System (ADS)

    Zettergren, M. D.; Snively, J. B.

    2013-10-01

    Acoustic waves generated by tropospheric sources may attain significant amplitudes in the thermosphere and overlying ionosphere. Although they are weak precursors to gravity waves in the mesosphere below, acoustic waves may achieve temperature and vertical wind perturbations on the order of approximately tens of Kelvin and m/s throughout the E and F regions. Their perturbations to total electron content are predicted to be detectable by ground-based radar and GPS receivers; they also drive field-aligned currents that may be detectable in situ via magnetometers. Although transient and short lived, ionospheric signatures of acoustic waves may provide new and quantitative insight into the forcing of the upper atmosphere from below.

  15. Regulation of the basement membrane by epithelia generated forces

    PubMed Central

    Tanner, Kandice

    2012-01-01

    Tumor metastasis involves a progressive loss of tissue architecture and dissolution of structural boundaries between the epithelium and connective tissue. The basement membrane (BM), a specialized network of extracellular matrix proteins forms a barrier that physically restricts pre- invasive lesions such that they remain as local insults. The BM is not a static structure, but one that is constantly regenerated and remodeled in the adult organism. Matrix organization also regulates cell function. Thus alterations in the balance of synthesis, remodeling and proteolytic degradation of the extracellular matrix proteins may contribute to a loss of structural integrity. However, the de novo assembly and maintenance of the complex structural properties of in vivo basement membranes remain elusive. Here, this paper highlights the current understanding on the structural properties and the establishment of the BM, and discusses the potential role of self-generated forces in adult tissue remodeling and the maintenance of the BM as a malignancy suppressor. PMID:23196920

  16. Cooperative Force Generation of KIF1A Brownian Motors

    NASA Astrophysics Data System (ADS)

    Oriola, David; Casademunt, Jaume

    2013-07-01

    KIF1A is a kinesin motor protein that can work processively in a monomeric (single-headed) form by using a noise-driven ratchet mechanism. Here, we show that the combination of a passive diffusive state and finite-time kinetics of adenosine triphosphate hydrolysis provides a powerful mechanism of cooperative force generation, implying for instance that ˜10 monomeric KIF1As can team up to become ˜100 times stronger than a single one. Consequently, we propose that KIF1A could outperform conventional (double-headed) kinesin collectively and thus explain its specificity in axonal trafficking. We elucidate the cooperativity mechanism with a lattice model that includes multiparticle transitions.

  17. Force and motion generation of molecular motors: A generic description

    NASA Astrophysics Data System (ADS)

    Jülicher, Frank

    We review the properties of biological motor proteins which move along linear filaments that are polar and periodic. The physics of the operation of such motors can be described by simple stochastic models which are coupled to a chemical reaction. We analyze the essential features of force and motion generation and discuss the general properties of single motors in the framework of two-state models. Systems which contain large numbers of motors such as muscles and flagella motivate the study of many interacting motors within the framework of simple models. In this case, collective effects can lead to new types of behaviors such as dynamic instabilities of the steady states and oscillatory motion.

  18. Generation of random numbers on graphics processors: forced indentation in silico of the bacteriophage HK97.

    PubMed

    Zhmurov, A; Rybnikov, K; Kholodov, Y; Barsegov, V

    2011-05-12

    The use of graphics processing units (GPUs) in simulation applications offers a significant speed gain as compared to computations on central processing units (CPUs). Many simulation methods require a large number of independent random variables generated at each step. We present two approaches for implementation of random number generators (RNGs) on a GPU. In the one-RNG-per-thread approach, one RNG produces a stream of random numbers in each thread of execution, whereas the one-RNG-for-all-threads method builds on the ability of different threads to communicate, thus, sharing random seeds across an entire GPU device. We used these approaches to implement Ran2, Hybrid Taus, and Lagged Fibonacci algorithms on a GPU. We profiled the performance of these generators in terms of the computational time, memory usage, and the speedup factor (CPU time/GPU time). These generators have been incorporated into the program for Langevin simulations of biomolecules fully implemented on the GPU. The ∼250-fold computational speedup on the GPU allowed us to carry out single-molecule dynamic force measurements in silico to explore the mechanical properties of the bacteriophage HK97 in the experimental subsecond time scale. We found that the nanomechanical response of HK97 depends on the conditions of force application, including the rate of change and geometry of the mechanical perturbation. Hence, using the GPU-based implementation of RNGs, presented here, in conjunction with Langevin simulations, makes it possible to directly compare the results of dynamic force measurements in vitro and in silico. PMID:21194190

  19. Computational Catalysis Using the Artificial Force Induced Reaction Method.

    PubMed

    Sameera, W M C; Maeda, Satoshi; Morokuma, Keiji

    2016-04-19

    The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately

  20. Wavefront reconstruction using computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Schulze, Christian; Flamm, Daniel; Schmidt, Oliver A.; Duparré, Michael

    2012-02-01

    We propose a new method to determine the wavefront of a laser beam, based on modal decomposition using computer-generated holograms (CGHs). Thereby the beam under test illuminates the CGH with a specific, inscribed transmission function that enables the measurement of modal amplitudes and phases by evaluating the first diffraction order of the hologram. Since we use an angular multiplexing technique, our method is innately capable of real-time measurements of amplitude and phase, yielding the complete information about the optical field. A measurement of the Stokes parameters, respectively of the polarization state, provides the possibility to calculate the Poynting vector. Two wavefront reconstruction possibilities are outlined: reconstruction from the phase for scalar beams and reconstruction from the Poynting vector for inhomogeneously polarized beams. To quantify single aberrations, the reconstructed wavefront is decomposed into Zernike polynomials. Our technique is applied to beams emerging from different kinds of multimode optical fibers, such as step-index, photonic crystal and multicore fibers, whereas in this work results are exemplarily shown for a step-index fiber and compared to a Shack-Hartmann measurement that serves as a reference.

  1. Effect of gust on force generation around a robotic hummingbird wing

    NASA Astrophysics Data System (ADS)

    Marquez, Eloy; Tian, Ruijun; Shu, Fangjun

    2012-11-01

    Among the computational, theoretical and experimental studies on the high efficiency flapping flight, many are focused on the mystery of hovering. Most of these studies were conducted under steady in flow conditions. However, real-life ornithopters in the field have to routinely tackle gust and directional changes of the wind. These sudden perturbations could produce significant effect on humming bird hovering due to the small Reynolds numbers. Our experimental work was performed in a water channel using a two degree-of-freedom humming bird model. The dynamic response of the hovering motion to gust from different directions was investigated. PIV was used to measure the effect of the gust on the surrounding flow field including vortex evolution. In addition, a six-component force/torque sensor was used to measure the real-time lift and drag forces generated by the wing with and without gust. Results show that gust changes the magnitude of lift force in one stroke. However, the time-averaged lift force keeps approximately constant. Supported by Army High Performance Computing Center.

  2. F-actin cross-linking enhances the stability of force generation in disordered actomyosin networks

    NASA Astrophysics Data System (ADS)

    Jung, Wonyeong; Murrell, Michael P.; Kim, Taeyoon

    2015-12-01

    Myosin molecular motors and actin cross-linking proteins (ACPs) are known to mediate the generation and transmission of mechanical forces within the cortical F-actin cytoskeleton that drive major cellular processes such as cell division and migration. However, how motors and ACPs interact collectively over diverse timescales to modulate the time-dependent mechanical properties of the cytoskeleton remains unclear. In this study, we present a three-dimensional agent-based computational model of the cortical actomyosin network to quantitatively determine the effects of motor activity and the density and kinetics of ACPs on the accumulation and maintenance of mechanical tension within a disordered actomyosin network. We found that motors accumulate large stress quickly by behaving as temporary cross-linkers although this stress is relaxed over time unless there are sufficient passive ACPs to stabilize the network. Stabilization by ACPs helps motors to generate forces up to their maximum potential, leading to significant enhancement of the efficiency and stability of stress generation. Thus, we demonstrated that the force-dependent kinetics of ACP dissociation plays a critical role for the accumulation and sustainment of stress and the structural remodeling of networks.

  3. Molecular step(s) of force generation: temperature-perturbation experiments on muscle fibres.

    PubMed

    Ranatunga, K W; Coupland, M E

    2003-01-01

    The steady active muscle force is reduced, but the force generation induced by a standard temperature jump becomes 2-3 fold faster with increased inorganic phosphate level, [Pi]. The increase in the rate of force generation also exhibits saturation at higher [Pi] levels and the relation is hyperbolic. These observations are consistent with a kinetic scheme where rapid Pi release by actomyosin crossbridges in muscle is preceded by the force generation step. Such a scheme accounts for the sigmoidal temperature dependence of steady active force and its sensitivity to [Pi]. The [Pi] dependence of force recovery after stretch (positive strain) is also hyperbolic, suggesting that the "pre Pi-release force generation step" is strain-sensitive--as expected. However, length-release (negative strain) force transients are not [Pi] sensitive indicating an asymmetry, but its significance and also the kinetic step underlying force recovery from negative strain remain unclear. PMID:15098690

  4. Explorations in Space and Time: Computer-Generated Astronomy Films

    ERIC Educational Resources Information Center

    Meeks, M. L.

    1973-01-01

    Discusses the use of the computer animation technique to travel through space and time and watch models of astronomical systems in motion. Included is a list of eight computer-generated demonstration films entitled Explorations in Space and Time.'' (CC)

  5. Computer graphics techniques and computer-generated movies

    NASA Astrophysics Data System (ADS)

    Holzman, Robert E.; Blinn, James F.

    1988-04-01

    The JPL Computer Graphics Laboratory (CGL) has been using advanced computer graphics for more than ten years to simulate space missions and related activities. Applications have ranged from basic computer graphics used interactively to allow engineers to study problems, to sophisticated color graphics used to simulate missions and produce realistic animations and stills for use by NASA and the scientific press. In addition, the CGL did the computer animation for ``Cosmos'', a series of general science programs done for Public Television in the United States by Carl Sagan and shown world-wide. The CGL recently completed the computer animation for ``The Mechanical Universe'', a series of fifty-two half-hour elementary physics lectures, led by Professor David Goodstein of the California Institute of Technology, and now being shown on Public Television in the US. For this series, the CGL produced more than seven hours of computer animation, averaging approximately eight minutes and thirty seconds of computer animation per half-hour program. Our aim at the JPL Computer Graphics Laboratory (CGL) is the realistic depiction of physical phenomena, that is, we deal primarily in ``science education'' rather than in scientific research. Of course, our attempts to render physical events realistically often require the development of new capabilities through research or technology advances, but those advances are not our primary goal.

  6. A method of billing third generation computer users

    NASA Technical Reports Server (NTRS)

    Anderson, P. N.; Hyter, D. R.

    1973-01-01

    A method is presented for charging users for the processing of their applications on third generation digital computer systems is presented. For background purposes, problems and goals in billing on third generation systems are discussed. Detailed formulas are derived based on expected utilization and computer component cost. These formulas are then applied to a specific computer system (UNIVAC 1108). The method, although possessing some weaknesses, is presented as a definite improvement over use of second generation billing methods.

  7. Task III: Development of an Effective Computational Methodology for Body Force Representation of High-speed Rotor 37

    NASA Technical Reports Server (NTRS)

    Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)

    2003-01-01

    A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.

  8. Force Generation by Molecular-Motor-Powered Microtubule Bundles; Implications for Neuronal Polarization and Growth

    PubMed Central

    Jakobs, Maximilian; Franze, Kristian; Zemel, Assaf

    2015-01-01

    The heavily cross-linked microtubule (MT) bundles found in neuronal processes play a central role in the initiation, growth and maturation of axons and dendrites; however, a quantitative understanding of their mechanical function is still lacking. We here developed computer simulations to investigate the dynamics of force generation in 1D bundles of MTs that are cross-linked and powered by molecular motors. The motion of filaments and the forces they exert are investigated as a function of the motor type (unipolar or bipolar), MT density and length, applied load, and motor connectivity. We demonstrate that only unipolar motors (e.g., kinesin-1) can provide the driving force for bundle expansion, while bipolar motors (e.g., kinesin-5) oppose it. The force generation capacity of the bundles is shown to depend sharply on the fraction of unipolar motors due to a percolation transition that must occur in the bundle. Scaling laws between bundle length, force, MT length and motor fraction are presented. In addition, we investigate the dynamics of growth in the presence of a constant influx of MTs. Beyond a short equilibration period, the bundles grow linearly in time. In this growth regime, the bundle extends as one mass forward with most filaments sliding with the growth velocity. The growth velocity is shown to be dictated by the inward flux of MTs, to inversely scale with the load and to be independent of the free velocity of the motors. These findings provide important molecular-level insights into the mechanical function of the MT cytoskeleton in normal axon growth and regeneration after injury. PMID:26617489

  9. Improved finite-difference computation of the van der Waals force: One-dimensional case

    SciTech Connect

    Pinto, Fabrizio

    2009-10-15

    We present an improved demonstration of the calculation of Casimir forces in one-dimensional systems based on the recently proposed numerical imaginary frequency Green's function computation approach. The dispersion force on two thick lossy dielectric slabs separated by an empty gap and placed within a perfectly conducting cavity is obtained from the Green's function of the modified Helmholtz equation by means of an ordinary finite-difference method. In order to demonstrate the possibility to develop algorithms to explore complex geometries in two and three dimensions to higher order in the mesh spacing, we generalize existing classical electromagnetism algebraic methods to generate the difference equations for dielectric boundaries not coinciding with any grid points. Diagnostic tests are presented to monitor the accuracy of our implementation of the method and follow-up applications in higher dimensions are introduced.

  10. Compensation for Transport Delays Produced by Computer Image Generation Systems. Cooperative Training Series.

    ERIC Educational Resources Information Center

    Ricard, G. L.; And Others

    The cooperative Navy/Air Force project described is aimed at the problem of image-flutter encountered when visual displays that present computer generated images are used for the simulation of certain flying situations. Two experiments are described which extend laboratory work on delay compensation schemes to the simulation of formation flight in…

  11. Explicit Polarization: A Quantum Mechanical Framework for Developing Next Generation Force Fields

    PubMed Central

    2015-01-01

    Conspectus Molecular mechanical force fields have been successfully used to model condensed-phase and biological systems for a half century. By means of careful parametrization, such classical force fields can be used to provide useful interpretations of experimental findings and predictions of certain properties. Yet, there is a need to further improve computational accuracy for the quantitative prediction of biomolecular interactions and to model properties that depend on the wave functions and not just the energy terms. A new strategy called explicit polarization (X-Pol) has been developed to construct the potential energy surface and wave functions for macromolecular and liquid-phase simulations on the basis of quantum mechanics rather than only using quantum mechanical results to fit analytic force fields. In this spirit, this approach is called a quantum mechanical force field (QMFF). X-Pol is a general fragment method for electronic structure calculations based on the partition of a condensed-phase or macromolecular system into subsystems (“fragments”) to achieve computational efficiency. Here, intrafragment energy and the mutual electronic polarization of interfragment interactions are treated explicitly using quantum mechanics. X-Pol can be used as a general, multilevel electronic structure model for macromolecular systems, and it can also serve as a new-generation force field. As a quantum chemical model, a variational many-body (VMB) expansion approach is used to systematically improve interfragment interactions, including exchange repulsion, charge delocalization, dispersion, and other correlation energies. As a quantum mechanical force field, these energy terms are approximated by empirical functions in the spirit of conventional molecular mechanics. This Account first reviews the formulation of X-Pol, in the full variationally correct version, in the faster embedded version, and with systematic many-body improvements. We discuss illustrative

  12. Explicit polarization: a quantum mechanical framework for developing next generation force fields.

    PubMed

    Gao, Jiali; Truhlar, Donald G; Wang, Yingjie; Mazack, Michael J M; Löffler, Patrick; Provorse, Makenzie R; Rehak, Pavel

    2014-09-16

    Conspectus Molecular mechanical force fields have been successfully used to model condensed-phase and biological systems for a half century. By means of careful parametrization, such classical force fields can be used to provide useful interpretations of experimental findings and predictions of certain properties. Yet, there is a need to further improve computational accuracy for the quantitative prediction of biomolecular interactions and to model properties that depend on the wave functions and not just the energy terms. A new strategy called explicit polarization (X-Pol) has been developed to construct the potential energy surface and wave functions for macromolecular and liquid-phase simulations on the basis of quantum mechanics rather than only using quantum mechanical results to fit analytic force fields. In this spirit, this approach is called a quantum mechanical force field (QMFF). X-Pol is a general fragment method for electronic structure calculations based on the partition of a condensed-phase or macromolecular system into subsystems ("fragments") to achieve computational efficiency. Here, intrafragment energy and the mutual electronic polarization of interfragment interactions are treated explicitly using quantum mechanics. X-Pol can be used as a general, multilevel electronic structure model for macromolecular systems, and it can also serve as a new-generation force field. As a quantum chemical model, a variational many-body (VMB) expansion approach is used to systematically improve interfragment interactions, including exchange repulsion, charge delocalization, dispersion, and other correlation energies. As a quantum mechanical force field, these energy terms are approximated by empirical functions in the spirit of conventional molecular mechanics. This Account first reviews the formulation of X-Pol, in the full variationally correct version, in the faster embedded version, and with systematic many-body improvements. We discuss illustrative examples

  13. The RANDOM computer program: A linear congruential random number generator

    NASA Technical Reports Server (NTRS)

    Miles, R. F., Jr.

    1986-01-01

    The RANDOM Computer Program is a FORTRAN program for generating random number sequences and testing linear congruential random number generators (LCGs). The linear congruential form of random number generator is discussed, and the selection of parameters of an LCG for a microcomputer described. This document describes the following: (1) The RANDOM Computer Program; (2) RANDOM.MOD, the computer code needed to implement an LCG in a FORTRAN program; and (3) The RANCYCLE and the ARITH Computer Programs that provide computational assistance in the selection of parameters for an LCG. The RANDOM, RANCYCLE, and ARITH Computer Programs are written in Microsoft FORTRAN for the IBM PC microcomputer and its compatibles. With only minor modifications, the RANDOM Computer Program and its LCG can be run on most micromputers or mainframe computers.

  14. Third Generation Educational Use of Computer Games

    ERIC Educational Resources Information Center

    Egenfeldt-Nielsen, Simon

    2007-01-01

    This article outlines the characteristics and problems related to edutainment and of the associated research studies demonstrating that learning outcomes looks promising. The article suggests that we are moving towards a new generation of educational use of games that is more inclusive. This new generation relies on constructivist learning…

  15. 2nd Generation QUATARA Flight Computer Project

    NASA Technical Reports Server (NTRS)

    Falker, Jay; Keys, Andrew; Fraticelli, Jose Molina; Capo-Iugo, Pedro; Peeples, Steven

    2015-01-01

    Single core flight computer boards have been designed, developed, and tested (DD&T) to be flown in small satellites for the last few years. In this project, a prototype flight computer will be designed as a distributed multi-core system containing four microprocessors running code in parallel. This flight computer will be capable of performing multiple computationally intensive tasks such as processing digital and/or analog data, controlling actuator systems, managing cameras, operating robotic manipulators and transmitting/receiving from/to a ground station. In addition, this flight computer will be designed to be fault tolerant by creating both a robust physical hardware connection and by using a software voting scheme to determine the processor's performance. This voting scheme will leverage on the work done for the Space Launch System (SLS) flight software. The prototype flight computer will be constructed with Commercial Off-The-Shelf (COTS) components which are estimated to survive for two years in a low-Earth orbit.

  16. Force and power generating mechanism(s) in active muscle as revealed from temperature perturbation studies.

    PubMed

    Ranatunga, K W

    2010-10-01

    The basic characteristics of the process of force and power generation in active muscle that have emerged from temperature studies are examined. This is done by reviewing complementary findings from temperature-dependence studies and rapid temperature-jump (T-jump) experiments and from intact and skinned fast mammalian muscle fibres. In isometric muscle, a small T-jump leads to a characteristic rise in force showing that crossbridge force generation is endothermic (heat absorbed) and associated with increased entropy (disorder). The sensitivity of the T-jump force generation to added inorganic phosphate (Pi) indicates that a T-jump enhances an early step in the actomyosin (crossbridge) ATPase cycle before Pi-release. During muscle lengthening when steady force is increased, the T-jump force generation is inhibited. Conversely, during shortening when steady force is decreased, the T-jump force generation is enhanced in a velocity-dependent manner, showing that T-jump force generation is strain sensitive. Within the temperature range of ∼5–35◦C, the temperature dependence of steady active force is sigmoidal both in isometric and in shortening muscle. However, in shortening muscle, the endothermic character of force generation becomes more pronounced with increased velocity and this can, at least partly, account for the marked increase with warming of the mechanical power output of active muscle. PMID:20660565

  17. Reliability of computer-generated prediction tracing.

    PubMed

    Cangialosi, T J; Chung, J M; Elliott, D F; Meistrell, M E

    1995-01-01

    The reliability of a commercially available computer prediction program (Quick Ceph II) was evaluated using pretreatment and posttreatment cephalograms of 30 patients who were treated during an active period of growth. The computer prediction was compared with the actual treatment result, and the growth forecast with the computer program was compared with the growth forecast using a manual method. Using paired student's t-tests, predictions for 5 of the 10 variables measured were found to be statistically reliable. Comparing the relative accuracy of growth prediction in terms of absolute values, the computer came closer to the actual result in four of the nine variables, while the manual method came closer in three variables. Predictions for the other two variables were virtually the same using both methods. The manual method of prediction was sufficient to give a reasonably good graphic representation of growth changes to create a VTO. However, the computer offers the added advantages of quicker access to information and somewhat greater accuracy in producing the tracing, as well as its use in patient education. PMID:7486242

  18. User's Manual for FOMOCO Utilities-Force and Moment Computation Tools for Overset Grids

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Buning, Pieter G.

    1996-01-01

    In the numerical computations of flows around complex configurations, accurate calculations of force and moment coefficients for aerodynamic surfaces are required. When overset grid methods are used, the surfaces on which force and moment coefficients are sought typically consist of a collection of overlapping surface grids. Direct integration of flow quantities on the overlapping grids would result in the overlapped regions being counted more than once. The FOMOCO Utilities is a software package for computing flow coefficients (force, moment, and mass flow rate) on a collection of overset surfaces with accurate accounting of the overlapped zones. FOMOCO Utilities can be used in stand-alone mode or in conjunction with the Chimera overset grid compressible Navier-Stokes flow solver OVERFLOW. The software package consists of two modules corresponding to a two-step procedure: (1) hybrid surface grid generation (MIXSUR module), and (2) flow quantities integration (OVERINT module). Instructions on how to use this software package are described in this user's manual. Equations used in the flow coefficients calculation are given in Appendix A.

  19. Designing Interaction for Next Generation Personal Computing

    NASA Astrophysics Data System (ADS)

    de Michelis, Giorgio; Loregian, Marco; Moderini, Claudio; Marti, Patrizia; Colombo, Cesare; Bannon, Liam; Storni, Cristiano; Susani, Marco

    Over two decades of research in the field of Interaction Design and Computer Supported Cooperative Work convinced us that the current design of workstations no longer fits users’ needs. It is time to design new personal computers based on metaphors alternative to the desktop one. With this SIG, we are seeking to involve international HCI professionals into the challenges of designing products that are radically new and tackling the many different issues of modern knowledge workers. We would like to engage a wider cross-section of the community: our focus will be on issues of development and participation and the impact of different values in our work.

  20. Generating and Transforming by a Computer without a Dictionary.

    ERIC Educational Resources Information Center

    Ornan, Uzzi

    1978-01-01

    The ability of the computer to generate output not included in the input may be used for linguistic as well as for computational input. The ability to accept linguistic data and process it according to a certain program seems to be a promising field for investigation. Progress in this field may strengthen the assumption that the computer can be…

  1. Computer-Generated Diagrams for the Classroom.

    ERIC Educational Resources Information Center

    Carle, Mark A.; Greenslade, Thomas B., Jr.

    1986-01-01

    Describes 10 computer programs used to draw diagrams usually drawn on chalkboards, such as addition of three vectors, vector components, range of a projectile, lissajous figures, beats, isotherms, Snell's law, waves passing through a lens, magnetic field due to Helmholtz coils, and three curves. Several programming tips are included. (JN)

  2. Generating dynamic simulations of movement using computed muscle control.

    PubMed

    Thelen, Darryl G; Anderson, Frank C; Delp, Scott L

    2003-03-01

    Computation of muscle excitation patterns that produce coordinated movements of muscle-actuated dynamic models is an important and challenging problem. Using dynamic optimization to compute excitation patterns comes at a large computational cost, which has limited the use of muscle-actuated simulations. This paper introduces a new algorithm, which we call computed muscle control, that uses static optimization along with feedforward and feedback controls to drive the kinematic trajectory of a musculoskeletal model toward a set of desired kinematics. We illustrate the algorithm by computing a set of muscle excitations that drive a 30-muscle, 3-degree-of-freedom model of pedaling to track measured pedaling kinematics and forces. Only 10 min of computer time were required to compute muscle excitations that reproduced the measured pedaling dynamics, which is over two orders of magnitude faster than conventional dynamic optimization techniques. Simulated kinematics were within 1 degrees of experimental values, simulated pedal forces were within one standard deviation of measured pedal forces for nearly all of the crank cycle, and computed muscle excitations were similar in timing to measured electromyographic patterns. The speed and accuracy of this new algorithm improves the feasibility of using detailed musculoskeletal models to simulate and analyze movement. PMID:12594980

  3. Field measurement of basal forces generated by erosive debris flows

    USGS Publications Warehouse

    McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

    2013-01-01

    It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris‒flow events that incised bedrock. Over the 4 year monitoring period, 11 debris‒flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris‒flow events had a large‒magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time‒averaged mean force), high‒frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time‒averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~ 20 times the median bed sediment grain size, no significant fluctuations about the time‒averaged mean force were measured, indicating that a thin layer of sediment (~ 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse‒grained granular surges and water‒rich, intersurge flow had very similar basal force distributions despite

  4. The next generation of command post computing

    NASA Astrophysics Data System (ADS)

    Arnold, Ross D.; Lieb, Aaron J.; Samuel, Jason M.; Burger, Mitchell A.

    2015-05-01

    The future of command post computing demands an innovative new solution to address a variety of challenging operational needs. The Command Post of the Future is the Army's primary command and control decision support system, providing situational awareness and collaborative tools for tactical decision making, planning, and execution management from Corps to Company level. However, as the U.S. Army moves towards a lightweight, fully networked battalion, disconnected operations, thin client architecture and mobile computing become increasingly essential. The Command Post of the Future is not designed to support these challenges in the coming decade. Therefore, research into a hybrid blend of technologies is in progress to address these issues. This research focuses on a new command and control system utilizing the rich collaboration framework afforded by Command Post of the Future coupled with a new user interface consisting of a variety of innovative workspace designs. This new system is called Tactical Applications. This paper details a brief history of command post computing, presents the challenges facing the modern Army, and explores the concepts under consideration for Tactical Applications that meet these challenges in a variety of innovative ways.

  5. SRG - SCHEDULE REPORT GENERATOR COMPUTER PROGRAM

    NASA Technical Reports Server (NTRS)

    Collazo, F. F.

    1994-01-01

    The Schedule Organizer, SO (COSMIC Program MSC-21525), Schedule Tracker, ST (COSMIC Program MSC-21526), and Schedule Report Generator, SRG, are programs that manipulate data base files in ways that are advantageous to scheduling applications. Originally designed for the Space Shuttle flight schedule, the program can be easily modified for other scheduling situations. Schedule Organizer provides a simple method for generating distribution lists. These distribution lists contain readers' names for each task schedule defined by the input files. Schedule Tracker provides an effective method for tracking tasks that are 'past due' and/or 'near term'. ST generates reports for each responsible staff member with one or more assigned tasks that fall within the two listed categories. This enables an engineering manager to monitor tasks assigned to staff by running ST on a weekly basis. ST only lists tasks on reports that have become past due or are schedule for recent completion (near term). Schedule Reports Generator provides a simple method for generating periodic schedule reports. SRG enables an engineering manager to monitor tasks assigned to staff members on a weekly basis. SRG sorts three types of reports using one or more data fields as sort keys. One type is sorted using the calendar year as the primary key and the end date as the secondary key. Another type is sorted by flight number. A third type of report, Waterfall plots, is also generated by SRG using the end date as the sorting key. SRG requires as input a single file or two concatenated files with up to 400 single line entries. The user constructs the input file by using the LSE editor VAX utility prior to the execution of the program. The user is able to modify the current functional description text lines just displayed. ST and SRG use the same data base file as input. The common data base file has a maximum number of 400 entries. The time span of all three programs is nineteen months. Both of these maximum

  6. Computation of ion drag force on a static spherical dust grain immersed in rf discharges

    SciTech Connect

    Ikkurthi, V. R.; Melzer, A.; Matyash, K.; Schneider, R.

    2009-04-15

    The ion drag force on static spherical dust grains located in an argon rf discharge under typical laboratory experiment conditions has been computed using a three-dimensional particle-particle-particle-mesh code. Elastic and inelastic collisions have been included in the current model to obtain realistic rf discharge plasma conditions. The ion drag has been computed for various sizes of dust placed at different locations in the rf discharge under different gas pressures. The orbital drag force is typically found larger than the collection drag force. Ion-neutral collisions increase flux to the dust and hence the total drag force for collisional case is found larger than the collisionless case. Within the pressure range investigated, the drag forces do not vary much with pressure. The size dependence of the drag force is nonlinear and agrees well with the forces computed from the analytical models.

  7. The role of the cytoskeleton in cellular force generation in 2D and 3D environments

    NASA Astrophysics Data System (ADS)

    Kraning-Rush, Casey M.; Carey, Shawn P.; Califano, Joseph P.; Smith, Brooke N.; Reinhart-King, Cynthia A.

    2011-02-01

    To adhere and migrate, cells generate forces through the cytoskeleton that are transmitted to the surrounding matrix. While cellular force generation has been studied on 2D substrates, less is known about cytoskeletal-mediated traction forces of cells embedded in more in vivo-like 3D matrices. Recent studies have revealed important differences between the cytoskeletal structure, adhesion, and migration of cells in 2D and 3D. Because the cytoskeleton mediates force, we sought to directly compare the role of the cytoskeleton in modulating cell force in 2D and 3D. MDA-MB-231 cells were treated with agents that perturbed actin, microtubules, or myosin, and analyzed for changes in cytoskeletal organization and force generation in both 2D and 3D. To quantify traction stresses in 2D, traction force microscopy was used; in 3D, force was assessed based on single cell-mediated collagen fibril reorganization imaged using confocal reflectance microscopy. Interestingly, even though previous studies have observed differences in cell behaviors like migration in 2D and 3D, our data indicate that forces generated on 2D substrates correlate with forces within 3D matrices. Disruption of actin, myosin or microtubules in either 2D or 3D microenvironments disrupts cell-generated force. These data suggest that despite differences in cytoskeletal organization in 2D and 3D, actin, microtubules and myosin contribute to contractility and matrix reorganization similarly in both microenvironments.

  8. Crafting a Balanced System of Assessment in Wisconsin. Recommendations of the Next Generation Assessment Task Force

    ERIC Educational Resources Information Center

    Wisconsin Department of Public Instruction, 2009

    2009-01-01

    The Next Generation Assessment Task Force was convened to formulate Wisconsin's path forward. Task force members listened to leaders from business and technology sectors as well as leaders from PK-12 and higher education. This summary shares the process, definitions, assumptions, and recommendations of the task force. This paper aims to use these…

  9. Method of generating and measuring static small force using down-slope component of gravity

    NASA Astrophysics Data System (ADS)

    Fujii, Yusaku

    2007-06-01

    A method of generating and measuring static small forces at the micro-Newton level is proposed. In the method, the down-slope component of gravity acting on a mass on an inclined plane is used as a static force. To realize a linear motion of the mass with a small friction, an aerostatic linear bearing is used. The forces acting on the mass, such as the down-slope component of gravity and the dynamic frictional force, are determined by the levitation mass method. In an experiment, a static small force of approximately 183μN is generated and measured with a standard uncertainty of approximately 2μN.

  10. Horse chestnut extract induces contraction force generation in fibroblasts through activation of Rho/Rho kinase.

    PubMed

    Fujimura, Tsutomu; Moriwaki, Shigeru; Hotta, Mitsuyuki; Kitahara, Takashi; Takema, Yoshinori

    2006-06-01

    Contraction forces generated by non-muscle cells such as fibroblasts play important roles in determining cell morphology, vasoconstriction, and/or wound healing. However, few factors that induce cell contraction forces are known, such as lysophosphatidic acid and thrombin. Our study analyzed various plant extracts for ingredients that induce generation of cell contraction forces in fibroblasts populating collagen gels. We found that an extract of Horse chestnut (Aesculus hippocastanum) is able to induce such contraction forces in fibroblasts. The involvement of actin polymerization and stress fiber formation in the force generation was suggested by inhibition of this effect by cytochalasin D and by Rhodamine phalloidin. Rho kinase inhibitors (Y27632 and HA1077) and a Rho inhibitor (exoenzyme C3) significantly inhibited the force generation induced by the Horse chestnut extract. H7, which inhibits Rho kinase as well as other protein kinases, also significantly inhibited induction of force generation. However, inhibitors of other protein kinases such as myosin light chain kinase (ML-9), protein kinase C (Calphostin), protein kinase A (KT5720), and tyrosine kinase (Genistein, Herbimycin A) had no effect on force generation induced by Horse chestnut extract. These results suggest that the Horse chestnut extract induces generation of contraction forces in fibroblasts through stress fiber formation followed by activation of Rho protein and Rho kinase but not myosin light chain kinase or other protein kinases. PMID:16754996

  11. Scattered field generation and optical forces in transformation optics

    NASA Astrophysics Data System (ADS)

    Novitsky, A. V.

    2016-04-01

    In this paper we develop an approach for making various scattered electromagnetic fields on the transformation-optics ground. To do so, we use the a special coordinate transformation from the a vacuum virtual space to physical space, which changes the boundary of the scattering device upon transformation. We explore this approach for small scatterers compared with radiation wavelength, which allows us to predict the arbitrarily directed optical forces. Obtaining scattered fields and optical forces can be useful in nano-optics and optical micromanipulation.

  12. A body-force based method to generate supersonic equilibrium turbulent boundary layer profiles

    NASA Astrophysics Data System (ADS)

    Waindim, M.; Gaitonde, D. V.

    2016-01-01

    We further develop a simple counterflow body force-based approach to generate an equilibrium spatially developing turbulent boundary layer suitable for Direct Numerical Simulations (DNS) or Large Eddy Simulations (LES) of viscous-inviscid interactions. The force essentially induces a small separated region in an incoming specified laminar boundary layer. The resulting unstable shear layer then transitions and breaks down to yield the desired unsteady profile. The effects of wall thermal conditions are explored to demonstrate the capability of the method for both fixed wall and adiabatic wall conditions. We then describe an efficient method to select parameters that ensure transition by examining precursor signatures using generalized stability variables. These precursors are shown to be evident in a computational domain spanning only a small region around the trip and can also be detected using 2D simulations. Finally, the method is tested for different Mach numbers ranging from 1.7 to 2.9, with emphasis on flow field surveys, Reynolds stresses, and energy spectra. These results provide guidance on boundary conditions for desired boundary layer thickness at each Mach number. The consequences of using a much lower Reynolds number in computation relative to experiment are evident at the higher Mach number, where a self sustaining turbulent boundary layer is more difficult to obtain.

  13. Force generation by kinesin and myosin cytoskeletal motor proteins.

    PubMed

    Kull, F Jon; Endow, Sharyn A

    2013-01-01

    Kinesins and myosins hydrolyze ATP, producing force that drives spindle assembly, vesicle transport and muscle contraction. How do motors do this? Here we discuss mechanisms of motor force transduction, based on their mechanochemical cycles and conformational changes observed in crystal structures. Distortion or twisting of the central β-sheet - proposed to trigger actin-induced Pi and ADP release by myosin, and microtubule-induced ADP release by kinesins - is shown in a movie depicting the transition between myosin ATP-like and nucleotide-free states. Structural changes in the switch I region form a tube that governs ATP hydrolysis and Pi release by the motors, explaining the essential role of switch I in hydrolysis. Comparison of the motor power strokes reveals that each stroke begins with the force-amplifying structure oriented opposite to the direction of rotation or swing. Motors undergo changes in their mechanochemical cycles in response to small-molecule inhibitors, several of which bind to kinesins by induced fit, trapping the motors in a state that resembles a force-producing conformation. An unusual motor activator specifically increases mechanical output by cardiac myosin, potentially providing valuable information about its mechanism of function. Further study is essential to understand motor mechanochemical coupling and energy transduction, and could lead to new therapies to treat human disease. PMID:23487037

  14. Generating distributed forcing fields for spatial hydrologic modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spatial hydrologic modeling requires the development of distributed forcing fields of weather and precipitation. This is particularly difficult in mountainous regions of the western US, where measurement sites are limited and the landscape is dominated by complex terrain and variations in vegetatio...

  15. Force generation by kinesin and myosin cytoskeletal motor proteins

    PubMed Central

    Kull, F. Jon; Endow, Sharyn A.

    2013-01-01

    Summary Kinesins and myosins hydrolyze ATP, producing force that drives spindle assembly, vesicle transport and muscle contraction. How do motors do this? Here we discuss mechanisms of motor force transduction, based on their mechanochemical cycles and conformational changes observed in crystal structures. Distortion or twisting of the central β-sheet – proposed to trigger actin-induced Pi and ADP release by myosin, and microtubule-induced ADP release by kinesins – is shown in a movie depicting the transition between myosin ATP-like and nucleotide-free states. Structural changes in the switch I region form a tube that governs ATP hydrolysis and Pi release by the motors, explaining the essential role of switch I in hydrolysis. Comparison of the motor power strokes reveals that each stroke begins with the force-amplifying structure oriented opposite to the direction of rotation or swing. Motors undergo changes in their mechanochemical cycles in response to small-molecule inhibitors, several of which bind to kinesins by induced fit, trapping the motors in a state that resembles a force-producing conformation. An unusual motor activator specifically increases mechanical output by cardiac myosin, potentially providing valuable information about its mechanism of function. Further study is essential to understand motor mechanochemical coupling and energy transduction, and could lead to new therapies to treat human disease. PMID:23487037

  16. Device for synthetizing computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Svoboda, Jakub; Fiala, Pavel

    2009-05-01

    According to the needs of creating holograms of 3D computer models, an original device for synthetizing non focused holograms has been designed and manufactured. The device composes holographic masters by projecting series of 2D views of a subject. These views are displayed by a SLM and projected through a special designed objective. The hologram is then subsequently recorded near the plane of the output pupil of the writing objective. The 3D holographic stereogram is then made by the H1-H2 copying. The main goal of the device is to create rainbow single parallax hologram masters. However, the device is able to write the holo-pixels in x-y directions, which allows us to use both parallaxes. This is used for the research in the field of RGB rainbow masters, reflection hologram masters and implementation of kinetics to the final stereogram. In this paper, the method and the design of the recording device is presented.

  17. ADGEN: ADjoint GENerator for computer models

    SciTech Connect

    Worley, B.A.; Pin, F.G.; Horwedel, J.E.; Oblow, E.M.

    1989-05-01

    This paper presents the development of a FORTRAN compiler and an associated supporting software library called ADGEN. ADGEN reads FORTRAN models as input and produces and enhanced version of the input model. The enhanced version reproduces the original model calculations but also has the capability to calculate derivatives of model results of interest with respect to any and all of the model data and input parameters. The method for calculating the derivatives and sensitivities is the adjoint method. Partial derivatives are calculated analytically using computer calculus and saved as elements of an adjoint matrix on direct assess storage. The total derivatives are calculated by solving an appropriate adjoint equation. ADGEN is applied to a major computer model of interest to the Low-Level Waste Community, the PRESTO-II model. PRESTO-II sample problem results reveal that ADGEN correctly calculates derivatives of response of interest with respect to 300 parameters. The execution time to create the adjoint matrix is a factor of 45 times the execution time of the reference sample problem. Once this matrix is determined, the derivatives with respect to 3000 parameters are calculated in a factor of 6.8 that of the reference model for each response of interest. For a single 3000 for determining these derivatives by parameter perturbations. The automation of the implementation of the adjoint technique for calculating derivatives and sensitivities eliminates the costly and manpower-intensive task of direct hand-implementation by reprogramming and thus makes the powerful adjoint technique more amenable for use in sensitivity analysis of existing models. 20 refs., 1 fig., 5 tabs.

  18. Brute force meets Bruno force in parameter optimisation: introduction of novel constraints for parameter accuracy improvement by symbolic computation.

    PubMed

    Nakatsui, M; Horimoto, K; Lemaire, F; Ürgüplü, A; Sedoglavic, A; Boulier, F

    2011-09-01

    Recent remarkable advances in computer performance have enabled us to estimate parameter values by the huge power of numerical computation, the so-called 'Brute force', resulting in the high-speed simultaneous estimation of a large number of parameter values. However, these advancements have not been fully utilised to improve the accuracy of parameter estimation. Here the authors review a novel method for parameter estimation using symbolic computation power, 'Bruno force', named after Bruno Buchberger, who found the Gröbner base. In the method, the objective functions combining the symbolic computation techniques are formulated. First, the authors utilise a symbolic computation technique, differential elimination, which symbolically reduces an equivalent system of differential equations to a system in a given model. Second, since its equivalent system is frequently composed of large equations, the system is further simplified by another symbolic computation. The performance of the authors' method for parameter accuracy improvement is illustrated by two representative models in biology, a simple cascade model and a negative feedback model in comparison with the previous numerical methods. Finally, the limits and extensions of the authors' method are discussed, in terms of the possible power of 'Bruno force' for the development of a new horizon in parameter estimation. PMID:22010755

  19. Integrated Analysis of Contractile Kinetics, Force Generation, and Electrical Activity in Single Human Stem Cell-Derived Cardiomyocytes.

    PubMed

    Kijlstra, Jan David; Hu, Dongjian; Mittal, Nikhil; Kausel, Eduardo; van der Meer, Peter; Garakani, Arman; Domian, Ibrahim J

    2015-12-01

    The quantitative analysis of cardiomyocyte function is essential for stem cell-based approaches for the in vitro study of human cardiac physiology and pathophysiology. We present a method to comprehensively assess the function of single human pluripotent stem cell-derived cardiomyocyte (hPSC-CMs) through simultaneous quantitative analysis of contraction kinetics, force generation, and electrical activity. We demonstrate that statistical analysis of movies of contracting hPSC-CMs can be used to quantify changes in cellular morphology over time and compute contractile kinetics. Using a biomechanical model that incorporates substrate stiffness, we calculate cardiomyocyte force generation at single-cell resolution and validate this approach with conventional traction force microscopy. The addition of fluorescent calcium indicators or membrane potential dyes allows the simultaneous analysis of contractility and calcium handling or action potential morphology. Accordingly, our approach has the potential for broad application in the study of cardiac disease, drug discovery, and cardiotoxicity screening. PMID:26626178

  20. Integrated Analysis of Contractile Kinetics, Force Generation, and Electrical Activity in Single Human Stem Cell-Derived Cardiomyocytes

    PubMed Central

    Kijlstra, Jan David; Hu, Dongjian; Mittal, Nikhil; Kausel, Eduardo; van der Meer, Peter; Garakani, Arman; Domian, Ibrahim J.

    2015-01-01

    Summary The quantitative analysis of cardiomyocyte function is essential for stem cell-based approaches for the in vitro study of human cardiac physiology and pathophysiology. We present a method to comprehensively assess the function of single human pluripotent stem cell-derived cardiomyocyte (hPSC-CMs) through simultaneous quantitative analysis of contraction kinetics, force generation, and electrical activity. We demonstrate that statistical analysis of movies of contracting hPSC-CMs can be used to quantify changes in cellular morphology over time and compute contractile kinetics. Using a biomechanical model that incorporates substrate stiffness, we calculate cardiomyocyte force generation at single-cell resolution and validate this approach with conventional traction force microscopy. The addition of fluorescent calcium indicators or membrane potential dyes allows the simultaneous analysis of contractility and calcium handling or action potential morphology. Accordingly, our approach has the potential for broad application in the study of cardiac disease, drug discovery, and cardiotoxicity screening. PMID:26626178

  1. Computer simulations reveal complex distribution of haemodynamic forces in a mouse retina model of angiogenesis

    PubMed Central

    Bernabeu, Miguel O.; Jones, Martin L.; Nielsen, Jens H.; Krüger, Timm; Nash, Rupert W.; Groen, Derek; Schmieschek, Sebastian; Hetherington, James; Gerhardt, Holger; Franco, Claudio A.; Coveney, Peter V.

    2014-01-01

    There is currently limited understanding of the role played by haemodynamic forces on the processes governing vascular development. One of many obstacles to be overcome is being able to measure those forces, at the required resolution level, on vessels only a few micrometres thick. In this paper, we present an in silico method for the computation of the haemodynamic forces experienced by murine retinal vasculature (a widely used vascular development animal model) beyond what is measurable experimentally. Our results show that it is possible to reconstruct high-resolution three-dimensional geometrical models directly from samples of retinal vasculature and that the lattice-Boltzmann algorithm can be used to obtain accurate estimates of the haemodynamics in these domains. We generate flow models from samples obtained at postnatal days (P) 5 and 6. Our simulations show important differences between the flow patterns recovered in both cases, including observations of regression occurring in areas where wall shear stress (WSS) gradients exist. We propose two possible mechanisms to account for the observed increase in velocity and WSS between P5 and P6: (i) the measured reduction in typical vessel diameter between both time points and (ii) the reduction in network density triggered by the pruning process. The methodology developed herein is applicable to other biomedical domains where microvasculature can be imaged but experimental flow measurements are unavailable or difficult to obtain. PMID:25079871

  2. Structural Optimization of a Force Balance Using a Computational Experiment Design

    NASA Technical Reports Server (NTRS)

    Parker, P. A.; DeLoach, R.

    2002-01-01

    This paper proposes a new approach to force balance structural optimization featuring a computational experiment design. Currently, this multi-dimensional design process requires the designer to perform a simplification by executing parameter studies on a small subset of design variables. This one-factor-at-a-time approach varies a single variable while holding all others at a constant level. Consequently, subtle interactions among the design variables, which can be exploited to achieve the design objectives, are undetected. The proposed method combines Modern Design of Experiments techniques to direct the exploration of the multi-dimensional design space, and a finite element analysis code to generate the experimental data. To efficiently search for an optimum combination of design variables and minimize the computational resources, a sequential design strategy was employed. Experimental results from the optimization of a non-traditional force balance measurement section are presented. An approach to overcome the unique problems associated with the simultaneous optimization of multiple response criteria is described. A quantitative single-point design procedure that reflects the designer's subjective impression of the relative importance of various design objectives, and a graphical multi-response optimization procedure that provides further insights into available tradeoffs among competing design objectives are illustrated. The proposed method enhances the intuition and experience of the designer by providing new perspectives on the relationships between the design variables and the competing design objectives providing a systematic foundation for advancements in structural design.

  3. Computing the Casimir force using regularized boundary integral equations

    NASA Astrophysics Data System (ADS)

    Kilen, Isak; Jakobsen, Per Kristen

    2014-11-01

    In this paper we use a novel regularization procedure to reduce the calculation of the Casimir force for 2D scalar fields between compact objects to the solution of a classical integral equation defined on the boundaries of the objects. The scalar fields are subject to Dirichlet boundary conditions on the object boundaries. We test the integral equation by comparing with what we get for parallel plates, concentric circles and adjacent circles using mode summation and the functional integral method. We show how symmetries in the shapes and configuration of boundaries can easily be incorporated into our method and that it leads to fast evaluation of the Casimir force for symmetric situations.

  4. Generate rigorous pyrolysis models for olefins production by computer

    SciTech Connect

    Klein, M.T.; Broadbelt, L.J.; Grittman, D.H.

    1997-04-01

    With recent advances in the automation of the model-building process for large networks of kinetic equations, it may become feasible to generate computer pyrolysis models for naphthas and gas oil feedstocks. The potential benefit of a rigorous mechanistic model for these relatively complex liquid feedstocks is great, due to diverse characterizations and yield spectrums. An ethane pyrolysis example is used to illustrate the computer generation of reaction mechanism models.

  5. New Generation General Purpose Computer (GPC) compact IBM unit

    NASA Technical Reports Server (NTRS)

    1991-01-01

    New Generation General Purpose Computer (GPC) compact IBM unit replaces a two-unit earlier generation computer. The new IBM unit is documented in table top views alone (S91-26867, S91-26868), with the onboard equipment it supports including the flight deck CRT screen and keypad (S91-26866), and next to the two earlier versions it replaces (S91-26869).

  6. Computer-Generated Phase Diagrams for Binary Mixtures.

    ERIC Educational Resources Information Center

    Jolls, Kenneth R.; And Others

    1983-01-01

    Computer programs that generate projections of thermodynamic phase surfaces through computer graphics were used to produce diagrams representing properties of water and steam and the pressure-volume-temperature behavior of most of the common equations of state. The program, program options emphasizing thermodynamic features of interest, and…

  7. Molecular interactions and residues involved in force generation in the T4 viral DNA packaging motor.

    PubMed

    Migliori, Amy D; Smith, Douglas E; Arya, Gaurav

    2014-12-12

    Many viruses utilize molecular motors to package their genomes into preformed capsids. A striking feature of these motors is their ability to generate large forces to drive DNA translocation against entropic, electrostatic, and bending forces resisting DNA confinement. A model based on recently resolved structures of the bacteriophage T4 motor protein gp17 suggests that this motor generates large forces by undergoing a conformational change from an extended to a compact state. This transition is proposed to be driven by electrostatic interactions between complementarily charged residues across the interface between the N- and C-terminal domains of gp17. Here we use atomistic molecular dynamics simulations to investigate in detail the molecular interactions and residues involved in such a compaction transition of gp17. We find that although electrostatic interactions between charged residues contribute significantly to the overall free energy change of compaction, interactions mediated by the uncharged residues are equally if not more important. We identify five charged residues and six uncharged residues at the interface that play a dominant role in the compaction transition and also reveal salt bridging, van der Waals, and solvent hydrogen-bonding interactions mediated by these residues in stabilizing the compact form of gp17. The formation of a salt bridge between Glu309 and Arg494 is found to be particularly crucial, consistent with experiments showing complete abrogation in packaging upon Glu309Lys mutation. The computed contributions of several other residues are also found to correlate well with single-molecule measurements of impairments in DNA translocation activity caused by site-directed mutations. PMID:25311860

  8. Modulation of local field potential power of the subthalamic nucleus during isometric force generation in patients with Parkinson's disease.

    PubMed

    Florin, E; Dafsari, H S; Reck, C; Barbe, M T; Pauls, K A M; Maarouf, M; Sturm, V; Fink, G R; Timmermann, L

    2013-06-14

    Investigations of local field potentials of the subthalamic nucleus of patients with Parkinson's disease have provided evidence for pathologically exaggerated oscillatory beta-band activity (13-30 Hz) which is amenable to physiological modulation by, e.g., voluntary movement. Previous functional magnetic resonance imaging studies in healthy controls have provided evidence for an increase of subthalamic nucleus blood-oxygenation-level-dependant signal in incremental force generation tasks. However, the modulation of neuronal activity by force generation and its relationship to peripheral feedback remain to be elucidated. We hypothesised that beta-band activity in the subthalamic nucleus is modulated by incremental force generation. Subthalamic nucleus local field potentials were recorded intraoperatively in 13 patients with Parkinson's disease (37 recording sites) during rest and five incremental isometric force generation conditions of the arm with applied loads of 0-400 g (in 100-g increments). Repeated measures analysis of variance (ANOVA) revealed a modulation of local field potential (LFP) power in the upper beta-band (in 24-30 Hz; F(₃.₀₄₂)=4.693, p=0.036) and the gamma-band (in 70-76 Hz; F(₄)=4.116, p=0.036). Granger-causality was computed with the squared partial directed coherence and showed no significant modulation during incremental isometric force generation. Our findings indicate that the upper beta- and gamma-band power of subthalamic nucleus local field potentials are modulated by the physiological task of force generation in patients with Parkinson's disease. This modulation seems to be not an effect of a modulation of peripheral feedback. PMID:23454540

  9. Fin geometry for minimum entropy generation in forced convection

    NASA Astrophysics Data System (ADS)

    Poulikakos, D.; Bejan, A.

    1982-11-01

    This paper establishes a theoretical framework for the minimization of entropy generation (the waste of exergy, or useful energy) in extended surfaces (fins). The entropy generation rate formula for a general fin is derived first. Based on this general result, analytical methods and graphic results are developed for selecting the optimum dimensions of pin fins, rectangular plate fins, plate fins with trapezoidal cross section, and triangular plate fins with rectangular cross section.

  10. Compressive force generation by a bundle of living biofilaments

    NASA Astrophysics Data System (ADS)

    Ramachandran, Sanoop; Ryckaert, Jean-Paul

    2013-08-01

    To study the compressional forces exerted by a bundle of living stiff filaments pressing on a surface, akin to the case of an actin bundle in filopodia structures, we have performed particulate molecular dynamics simulations of a grafted bundle of parallel living (self-assembling) filaments, in chemical equilibrium with a solution of their constitutive monomers. Equilibrium is established as these filaments, grafted at one end to a wall of the simulation box, grow at their chemically active free end, and encounter the opposite confining wall of the simulation box. Further growth of filaments requires bending and thus energy, which automatically limit the populations of longer filaments. The resulting filament sizes distribution and the force exerted by the bundle on the obstacle are analyzed for different grafting densities and different sub- or supercritical conditions, these properties being compared with the predictions of the corresponding ideal confined bundle model. In this analysis, non-ideal effects due to interactions between filaments and confinement effects are singled out. For all state points considered at the same temperature and at the same gap width between the two surfaces, the force per filament exerted on the opposite wall appears to be a function of a rescaled free monomer density hat{ρ }_1^eff. This quantity can be estimated directly from the characteristic length of the exponential filament size distribution P observed in the size domain where these grafted filaments are not in direct contact with the wall. We also analyze the dynamics of the filament contour length fluctuations in terms of effective polymerization (U) and depolymerization (W) rates, where again it is possible to disentangle non-ideal and confinement effects.

  11. Fifth Generation Computer-Assisted Career Guidance Systems.

    ERIC Educational Resources Information Center

    Carson, Andrew D.; Cartwright, Glenn F.

    1997-01-01

    Emerging "fifth-generation" computer-assisted career guidance systems include Internet-based resources such as listservs and Web sites. Obstacles to fifth-generation systems include confidentiality, counselor resistance, and lack of training. Counselors can aid their development by authoring, collaborating, evaluating, and advocating for equal…

  12. Tablet Computers on Trial: A Transformative Force in Education?

    ERIC Educational Resources Information Center

    Kjartansdóttir, Skúlína Hlíf; Jakobsdóttir, Sólveig

    2013-01-01

    In this paper we present the results of an evaluation study of a development project for the introduction and use of tablet computers (iPads) at the lower secondary level in Nordlinga school, a compulsory school in Reykjavík. In the study, we assess the impact of the use of tablet computers on instruction and students' learning in grades 9 to 10,…

  13. Internal waves generated by unsteady impulsive forcing - numerical simulations

    NASA Astrophysics Data System (ADS)

    Paoletti, Matthew; Shipley, Kara; Brandt, Alan

    2014-11-01

    Numerical simulations of the generation of internal waves by an unsteady impulse are presented. While extensive work has examined the generation of internal waves by steady flow, such as winds over mountains, or periodic flow, an example being tidal flow over bathymetry, internal waves can also be generated by transient events like those produced by local instabilities. The studies presented here focus on the generation of internal waves by the release of a patch of miscible fluid of constant density into a stably stratified water column. The fluid descends owing to its initial momentum, spreads in the lateral direction, and vertically displaces the isopycnals, leading to the generation of internal waves. The transfer of energy from the impulse to the internal wave field is characterized by the energy flux of the radiated internal waves. While the impulse is initially axisymmetric, the effects of the three-dimensional nature of the turbulent evolution are examined by comparing the results of two-dimensional and three-dimensional numerical simulations. Supported by the Office of Navel Research.

  14. Applying the cost of generating force hypothesis to uphill running

    PubMed Central

    Taboga, Paolo; Kram, Rodger

    2014-01-01

    Historically, several different approaches have been applied to explain the metabolic cost of uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of uphill running, based upon our understanding of level running energetics and ground reaction forces during uphill running. In contrast to the vertical efficiency approach, we propose that during incline running at a certain velocity, the forces (and hence metabolic energy) required for braking and propelling the body mass parallel to the running surface are less than during level running. Based on this idea, we propose that the metabolic rate during uphill running can be predicted by a model, which posits that (1) the metabolic cost of perpendicular bouncing remains the same as during level running, (2) the metabolic cost of running parallel to the running surface decreases with incline, (3) the delta efficiency of producing mechanical power to lift the COM vertically is constant, independent of incline and running velocity, and (4) the costs of leg and arm swing do not change with incline. To test this approach, we collected ground reaction force (GRF) data for eight runners who ran thirty 30-second trials (velocity: 2.0–3.0 m/s; incline: 0–9°). We also measured the metabolic rates of eight different runners for 17, 7-minute trials (velocity: 2.0–3.0 m/s; incline: 0–8°). During uphill running, parallel braking GRF approached zero for the 9° incline trials. Thus, we modeled the metabolic cost of parallel running as exponentially decreasing with incline. With that assumption, best-fit parameters for the metabolic rate data indicate that the efficiency of producing mechanical power to lift the center of mass vertically was independent of incline and running velocity, with a value of ∼29%. The

  15. Applying the cost of generating force hypothesis to uphill running.

    PubMed

    Hoogkamer, Wouter; Taboga, Paolo; Kram, Rodger

    2014-01-01

    Historically, several different approaches have been applied to explain the metabolic cost of uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of uphill running, based upon our understanding of level running energetics and ground reaction forces during uphill running. In contrast to the vertical efficiency approach, we propose that during incline running at a certain velocity, the forces (and hence metabolic energy) required for braking and propelling the body mass parallel to the running surface are less than during level running. Based on this idea, we propose that the metabolic rate during uphill running can be predicted by a model, which posits that (1) the metabolic cost of perpendicular bouncing remains the same as during level running, (2) the metabolic cost of running parallel to the running surface decreases with incline, (3) the delta efficiency of producing mechanical power to lift the COM vertically is constant, independent of incline and running velocity, and (4) the costs of leg and arm swing do not change with incline. To test this approach, we collected ground reaction force (GRF) data for eight runners who ran thirty 30-second trials (velocity: 2.0-3.0 m/s; incline: 0-9°). We also measured the metabolic rates of eight different runners for 17, 7-minute trials (velocity: 2.0-3.0 m/s; incline: 0-8°). During uphill running, parallel braking GRF approached zero for the 9° incline trials. Thus, we modeled the metabolic cost of parallel running as exponentially decreasing with incline. With that assumption, best-fit parameters for the metabolic rate data indicate that the efficiency of producing mechanical power to lift the center of mass vertically was independent of incline and running velocity, with a value of ∼29%. The metabolic

  16. Computer program for the transient analysis of radioisotope thermoelectric generators.

    NASA Technical Reports Server (NTRS)

    Eggers, P. E.; Ridihalgh, J. L.

    1972-01-01

    A computer program is described which represents a comprehensive analytical tool providing the capability for predicting the output power and temperature profile of an arbitrary radioisotope thermoelectric generator (RTG) design in the presence of time-dependent operating conditions. The approach taken involves the merging of three existing computer programs - namely, an RTG weight optimization design program, a thermoelectric analysis program, and a nodal heat-transfer computer program. A total of seven transient conditions are included in the computer program as the principal transients affecting long- and short-term performance characteristics of RTGs. This computer program is unique in that it designs an optimum RTG, generates a thermal model or analog and performs heat-transfer analysis of the RTG under user-specified transient conditions.

  17. Synthetic mechanobiology: engineering cellular force generation and signaling.

    PubMed

    Hughes, Jasmine Hannah; Kumar, Sanjay

    2016-08-01

    Mechanobiology seeks to understand and control mechanical and related biophysical communication between cells and their surroundings. While experimental efforts in this field have traditionally emphasized manipulation of the extracellular force environment, a new suite of approaches has recently emerged in which cell phenotype and signaling are controlled by directly engineering the cell itself. One route is to control cell behavior by modulating gene expression using conditional promoters. Alternatively, protein activity can be actuated directly using synthetic protein ligands, chemically induced protein dimerization, optogenetic strategies, or functionalized magnetic nanoparticles. Proof-of-principle studies are already demonstrating the translational potential of these approaches, and future technological development will permit increasingly precise control over cell mechanobiology and improve our understanding of the underlying signaling events. PMID:27023733

  18. Force-free magnetic fields - Generating functions and footpoint displacements

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Verma, Ritu

    1991-01-01

    This paper presents analytic and numerical calculations that explore equilibrium sequences of bipolar force-free magnetic fields in relation to displacments of their magnetic footpoints. It is shown that the appearance of magnetic islands - sometimes interpreted as marking the loss of equilibrium in models of the solar atmosphere - is likely associated only with physically unrealistic footpoint displacements such as infinite separation or 'tearing' of the model photosphere. The work suggests that the loss of equilibrium in bipolar configurations, sometimes proposed as a mechanism for eruptive solar events, probably requires either fully three-dimensional field configurations or nonzero plasma pressure. The results apply only to fields that are strictly bipolar, and do not rule out equilibrium loss in more complex structures such as quadrupolar fields.

  19. Computer generated K indices adopted by the British Geological Survey

    NASA Astrophysics Data System (ADS)

    Clark, T. D. G.

    1992-04-01

    On 1 January 1991 the British Geological Survey adopted a computer method for generating K indices from its three geomagnetic observatories. This replaced the traditional handscaling method, resulting in saving of staff time. Other advantages are the ability to distribute K indices to users in real time and the fact that there will not be any change in bias of the K index caused by a change of handscaler in future. The computer algorithm is described. The results of a comparison between the computed and handscaled K indices are presented, which show the computer method to be compatible with handscaling.

  20. Local Lorentz force flowmeter at a continuous caster model using a new generation multicomponent force and torque sensor

    NASA Astrophysics Data System (ADS)

    Hernández, Daniel; Schleichert, Jan; Karcher, Christian; Fröhlich, Thomas; Wondrak, Thomas; Timmel, Klaus

    2016-06-01

    Lorentz force velocimetry is a non-invasive velocity measurement technique for electrical conductive liquids like molten steel. In this technique, the metal flow interacts with a static magnetic field generating eddy currents which, in turn, produce flow-braking Lorentz forces within the fluid. These forces are proportional to the electrical conductivity and to the velocity of the melt. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied static magnetic field which is in our case a permanent magnet. In this paper we will present a new multicomponent sensor for the local Lorentz force flowmeter (L2F2) which is able to measure simultaneously all three components of the force as well as all three components of the torque. Therefore, this new sensor is capable of accessing all three velocity components at the same time in the region near the wall. In order to demonstrate the potential of this new sensor, it is used to identify the 3-dimensional velocity field near the wide face of the mold of a continuous caster model available at the Helmholtz-Zentrum Dresden-Rossendorf. As model melt, the eutectic alloy GaInSn is used.

  1. Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps).

    PubMed

    Bishop, Kristin L

    2007-08-01

    Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a

  2. Generation of mechanical force by grafted polyelectrolytes in an electric field

    NASA Astrophysics Data System (ADS)

    Brilliantov, N. V.; Budkov, Yu. A.; Seidel, C.

    2016-03-01

    We study theoretically and by means of molecular dynamics (MD) simulations the generation of mechanical force by grafted polyelectrolytes in an external electric field, which favors its adsorption on the grafting plane. The force arises in deformable bodies linked to the free end of the chain. Varying the field, one controls the length of the nonadsorbed part of the chain and hence the deformation of the target body, i.e., the arising force too. We consider target bodies with a linear force-deformation relation and with a Hertzian one. While the first relation models a coiled Gaussian chain, the second one describes the force response of a squeezed colloidal particle. The theoretical dependences of generated force and compression of the target body on an applied field agree very well with the results of MD simulations. The analyzed phenomenon may play an important role in future nanomachinery, e.g., it may be used to design nanovices to fix nanosized objects.

  3. Next-Generation Force Fields from Symmetry-Adapted Perturbation Theory.

    PubMed

    McDaniel, Jesse G; Schmidt, J R

    2016-05-27

    Symmetry-adapted perturbation theory (SAPT) provides a unique set of advantages for parameterizing next-generation force fields from first principles. SAPT provides a direct, basis-set superposition error free estimate of molecular interaction energies, a physically intuitive energy decomposition, and a seamless transition to an asymptotic picture of intermolecular interactions. These properties have been exploited throughout the literature to develop next-generation force fields for a variety of applications, including classical molecular dynamics simulations, crystal structure prediction, and quantum dynamics/spectroscopy. This review provides a brief overview of the formalism and theory of SAPT, along with a practical discussion of the various methodologies utilized to parameterize force fields from SAPT calculations. It also highlights a number of applications of SAPT-based force fields for chemical systems of particular interest. Finally, the review ends with a brief outlook on the future opportunities and challenges that remain for next-generation force fields based on SAPT. PMID:27070322

  4. Next-Generation Force Fields from Symmetry-Adapted Perturbation Theory

    NASA Astrophysics Data System (ADS)

    McDaniel, Jesse G.; Schmidt, J. R.

    2016-05-01

    Symmetry-adapted perturbation theory (SAPT) provides a unique set of advantages for parameterizing next-generation force fields from first principles. SAPT provides a direct, basis-set superposition error free estimate of molecular interaction energies, a physically intuitive energy decomposition, and a seamless transition to an asymptotic picture of intermolecular interactions. These properties have been exploited throughout the literature to develop next-generation force fields for a variety of applications, including classical molecular dynamics simulations, crystal structure prediction, and quantum dynamics/spectroscopy. This review provides a brief overview of the formalism and theory of SAPT, along with a practical discussion of the various methodologies utilized to parameterize force fields from SAPT calculations. It also highlights a number of applications of SAPT-based force fields for chemical systems of particular interest. Finally, the review ends with a brief outlook on the future opportunities and challenges that remain for next-generation force fields based on SAPT.

  5. Numerical simulations of current generation and dynamo excitation in a mechanically forced turbulent flow.

    PubMed

    Bayliss, R A; Forest, C B; Nornberg, M D; Spence, E J; Terry, P W

    2007-02-01

    The role of turbulence in current generation and self-excitation of magnetic fields has been studied in the geometry of a mechanically driven, spherical dynamo experiment, using a three-dimensional numerical computation. A simple impeller model drives a flow that can generate a growing magnetic field, depending on the magnetic Reynolds number Rm=micro0sigmaVa and the fluid Reynolds number Re=Vanu of the flow. For Re<420, the flow is laminar and the dynamo transition is governed by a threshold of Rmcrit=100, above which a growing magnetic eigenmode is observed that is primarily a dipole field transverse to the axis of symmetry of the flow. In saturation, the Lorentz force slows the flow such that the magnetic eigenmode becomes marginally stable. For Re>420 and Rm approximately 100 the flow becomes turbulent and the dynamo eigenmode is suppressed. The mechanism of suppression is a combination of a time varying large-scale field and the presence of fluctuation driven currents (such as those predicted by the mean-field theory), which effectively enhance the magnetic diffusivity. For higher Rm, a dynamo reappears; however, the structure of the magnetic field is often different from the laminar dynamo. It is dominated by a dipolar magnetic field aligned with the axis of symmetry of the mean-flow, which is apparently generated by fluctuation-driven currents. The magnitude and structure of the fluctuation-driven currents have been studied by applying a weak, axisymmetric seed magnetic field to laminar and turbulent flows. An Ohm's law analysis of the axisymmetric currents allows the fluctuation-driven currents to be identified. The magnetic fields generated by the fluctuations are significant: a dipole moment aligned with the symmetry axis of the mean-flow is generated similar to those observed in the experiment, and both toroidal and poloidal flux expulsion are observed. PMID:17358418

  6. Characteristics and computer model simulation of magnetic damping forces in maglev systems

    SciTech Connect

    He, J.L.; Rote, D.M.; Chen, S.S.

    1994-05-01

    This report discusses the magnetic damping force in electrodynamic suspension (EDS) maglev systems. The computer model simulations, which combine electrical system equations with mechanical motion equations on the basis of dynamic circuit theory, were conducted for a loop-shaped coil guideway. The intrinsic damping characteristics of the EDS-type guideway are investigated, and the negative damping phenomenon is confirmed by the computer simulations. The report also presents a simple circuit model to aid in understanding damping-force characteristics.

  7. Changes in muscle activation and force generation patterns during cycling movements because of low-intensity squat training with slow movement and tonic force generation.

    PubMed

    Tanimoto, Michiya; Arakawa, Hiroshi; Sanada, Kiyoshi; Miyachi, Motohiko; Ishii, Naokata

    2009-11-01

    Our previous studies showed that relatively low-load (approximately 50-60% 1 repetition maximum [1RM]) resistance training with slow movement and tonic force generation (LST) significantly increased muscle size and strength. However, LST is a very specific movement that differs from natural movements associated with sport activities and activities of daily life, and therefore, it might have some unfavorable effects on dynamic sport movement. We investigated the effects of LST on muscle activity and force generation patterns during cycling movement as a representative dynamic sports movement. Twenty-four healthy young men who were not in the habit of bicycle riding and did not have a history of regular resistance training were randomly assigned to the LST (approximately 60% 1RM load, 3-second lifting, and 3-second lowering movement without a relaxing phase: n = 8), a high-intensity exercise at normal speed (HM) group (85% 1RM load, 1-second lifting, 1-second lowering, and 1-second relaxed movement: n = 8), or sedentary control (CON, n = 8) group. Subjects in the training groups performed vertical squats by the assigned method. Exercise sessions consisted of 3 sets and were performed twice a week for 13 weeks. Pre- and posttraining muscle activation and force generation patterns during the cycling movements were evaluated by the coefficient of variation (CV) of the rectified electromyographic (EMG) wave from the vastus lateralis and CV of pedaling force. Both the CV of the rectified EMG and of pedaling force decreased significantly in the LST group (-21 and -18%, p < 0.05, respectively), whereas there were no significant changes in either the HN or the CON group. This decrease in CV in the LST group could mean that muscle activity and force generation during cycling movement have become more tonic. This result following LST may have an unfavorable effect on cycling movement and other dynamic sports movements. PMID:19826286

  8. Computer generated hologram from point cloud using graphics processor.

    PubMed

    Chen, Rick H-Y; Wilkinson, Timothy D

    2009-12-20

    Computer generated holography is an extremely demanding and complex task when it comes to providing realistic reconstructions with full parallax, occlusion, and shadowing. We present an algorithm designed for data-parallel computing on modern graphics processing units to alleviate the computational burden. We apply Gaussian interpolation to create a continuous surface representation from discrete input object points. The algorithm maintains a potential occluder list for each individual hologram plane sample to keep the number of visibility tests to a minimum. We experimented with two approximations that simplify and accelerate occlusion computation. It is observed that letting several neighboring hologram plane samples share visibility information on object points leads to significantly faster computation without causing noticeable artifacts in the reconstructed images. Computing a reduced sample set via nonuniform sampling is also found to be an effective acceleration technique. PMID:20029585

  9. Tensioning the helix: a mechanism for force generation in twining plants

    PubMed Central

    Isnard, Sandrine; Cobb, Alexander R.; Holbrook, N.Michele; Zwieniecki, Maciej; Dumais, Jacques

    2009-01-01

    Twining plants use their helical stems to clasp supports and to generate a squeezing force, providing stability against gravity. To elucidate the mechanism that allows force generation, we measured the squeezing forces exerted by the twiner Dioscorea bulbifera while following its growth using time-lapse photography. We show that the development of the squeezing force is accompanied by stiffening of the stem and the expansion of stipules at the leaf base. We use a simple thin rod model to show that despite their small size and sparse distribution, stipules impose a stem deformation sufficient to account for the measured squeezing force. We further demonstrate that tensioning of the stem helix, although counter-intuitive, is the most effective mechanism for generating large squeezing forces in twining plants. Our observations and model point to a general mechanism for the generation of the twining force: a modest radial stem expansion during primary growth, or the growth of lateral structures such as leaf bases, causes a delayed stem tensioning that creates the squeezing forces necessary for twining plants to ascend their supports. Our study thus provides the long-sought answer to the question of how twining plants ascend smooth supports without the use of adhesive or hook-like structures. PMID:19386656

  10. Compliant tactile sensor for generating a signal related to an applied force

    NASA Technical Reports Server (NTRS)

    Torres-Jara, Eduardo (Inventor)

    2012-01-01

    Tactile sensor. The sensor includes a compliant convex surface disposed above a sensor array, the sensor array adapted to respond to deformation of the convex surface to generate a signal related to an applied force vector.

  11. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  12. Pseudo-random number generator for the Sigma 5 computer

    NASA Technical Reports Server (NTRS)

    Carroll, S. N.

    1983-01-01

    A technique is presented for developing a pseudo-random number generator based on the linear congruential form. The two numbers used for the generator are a prime number and a corresponding primitive root, where the prime is the largest prime number that can be accurately represented on a particular computer. The primitive root is selected by applying Marsaglia's lattice test. The technique presented was applied to write a random number program for the Sigma 5 computer. The new program, named S:RANDOM1, is judged to be superior to the older program named S:RANDOM. For applications requiring several independent random number generators, a table is included showing several acceptable primitive roots. The technique and programs described can be applied to any computer having word length different from that of the Sigma 5.

  13. Parallel grid generation algorithm for distributed memory computers

    NASA Technical Reports Server (NTRS)

    Moitra, Stuti; Moitra, Anutosh

    1994-01-01

    A parallel grid-generation algorithm and its implementation on the Intel iPSC/860 computer are described. The grid-generation scheme is based on an algebraic formulation of homotopic relations. Methods for utilizing the inherent parallelism of the grid-generation scheme are described, and implementation of multiple levELs of parallelism on multiple instruction multiple data machines are indicated. The algorithm is capable of providing near orthogonality and spacing control at solid boundaries while requiring minimal interprocessor communications. Results obtained on the Intel hypercube for a blended wing-body configuration are used to demonstrate the effectiveness of the algorithm. Fortran implementations bAsed on the native programming model of the iPSC/860 computer and the Express system of software tools are reported. Computational gains in execution time speed-up ratios are given.

  14. Generative Representations for Computer-Automated Design Systems

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.

    2004-01-01

    With the increasing computational power of Computers, software design systems are progressing from being tools for architects and designers to express their ideas to tools capable of creating designs under human guidance. One of the main limitations for these computer-automated design programs is the representation with which they encode designs. If the representation cannot encode a certain design, then the design program cannot produce it. Similarly, a poor representation makes some types of designs extremely unlikely to be created. Here we define generative representations as those representations which can create and reuse organizational units within a design and argue that reuse is necessary for design systems to scale to more complex and interesting designs. To support our argument we describe GENRE, an evolutionary design program that uses both a generative and a non-generative representation, and compare the results of evolving designs with both types of representations.

  15. Generative Representations for Computer-Automated Evolutionary Design

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.

    2006-01-01

    With the increasing computational power of computers, software design systems are progressing from being tools for architects and designers to express their ideas to tools capable of creating designs under human guidance. One of the main limitations for these computer-automated design systems is the representation with which they encode designs. If the representation cannot encode a certain design, then the design system cannot produce it. To be able to produce new types of designs, and not just optimize pre-defined parameterizations, evolutionary design systems must use generative representations. Generative representations are assembly procedures, or algorithms, for constructing a design thereby allowing for truly novel design solutions to be encoded. In addition, by enabling modularity, regularity and hierarchy, the level of sophistication that can be evolved is increased. We demonstrate the advantages of generative representations on two different design domains: the evolution of spacecraft antennas and the evolution of 3D objects.

  16. New Generations: Sequencing Machines and Their Computational Challenges

    PubMed Central

    Schwartz, David C.; Waterman, Michael S.

    2011-01-01

    New generation sequencing systems are changing how molecular biology is practiced. The widely promoted $1000 genome will be a reality with attendant changes for healthcare, including personalized medicine. More broadly the genomes of many new organisms with large samplings from populations will be commonplace. What is less appreciated is the explosive demands on computation, both for CPU cycles and storage as well as the need for new computational methods. In this article we will survey some of these developments and demands. PMID:22121326

  17. Installation of new Generation General Purpose Computer (GPC) compact unit

    NASA Technical Reports Server (NTRS)

    1991-01-01

    In the Kennedy Space Center's (KSC's) Orbiter Processing Facility (OPF) high bay 2, Spacecraft Electronics technician Ed Carter (right), wearing clean suit, prepares for (26864) and installs (26865) the new Generation General Purpose Computer (GPC) compact IBM unit in Atlantis', Orbiter Vehicle (OV) 104's, middeck avionics bay as Orbiter Systems Quality Control technician Doug Snider looks on. Both men work for NASA contractor Lockheed Space Operations Company. All three orbiters are being outfitted with the compact IBM unit, which replaces a two-unit earlier generation computer.

  18. Computation and Visualization of Casimir Forces in Arbitrary Geometries: Nonmonotonic Lateral-Wall Forces and the Failure of Proximity-Force Approximations

    SciTech Connect

    Rodriguez, Alejandro; Ibanescu, Mihai; Joannopoulos, J. D.; Johnson, Steven G.; Iannuzzi, Davide; Capasso, Federico

    2007-08-24

    We present a method of computing Casimir forces for arbitrary geometries, with any desired accuracy, that can directly exploit the efficiency of standard numerical-electromagnetism techniques. Using the simplest possible finite-difference implementation of this approach, we obtain both agreement with past results for cylinder-plate geometries, and also present results for new geometries. In particular, we examine a pistonlike problem involving two dielectric and metallic squares sliding between two metallic walls, in two and three dimensions, respectively, and demonstrate nonadditive and nonmonotonic changes in the force due to these lateral walls.

  19. Computation and visualization of Casimir forces in arbitrary geometries: nonmonotonic lateral-wall forces and the failure of proximity-force approximations.

    PubMed

    Rodriguez, Alejandro; Ibanescu, Mihai; Iannuzzi, Davide; Capasso, Federico; Joannopoulos, J D; Johnson, Steven G

    2007-08-24

    We present a method of computing Casimir forces for arbitrary geometries, with any desired accuracy, that can directly exploit the efficiency of standard numerical-electromagnetism techniques. Using the simplest possible finite-difference implementation of this approach, we obtain both agreement with past results for cylinder-plate geometries, and also present results for new geometries. In particular, we examine a pistonlike problem involving two dielectric and metallic squares sliding between two metallic walls, in two and three dimensions, respectively, and demonstrate nonadditive and nonmonotonic changes in the force due to these lateral walls. PMID:17930932

  20. Inlet distortion generated forced response of a low-aspect-ratio transonic fan

    SciTech Connect

    Manwaring, S.R.; Lorence, C.B.; Wadia, A.R.; Rabe, D.C.

    1997-10-01

    This paper describes a portion of an experimental and computational program (ADLARF), which incorporates, for the first time, measurements of all aspects of the forced response of an airfoil row, i.e., the flow defect, the unsteady pressure loadings, and the vibratory response. The purpose of this portion was to extend the knowledge of the unsteady aerodynamics associated with a low-aspect-ratio transonic fan where the flow defects were generated by inlet distortions. Measurements of screen distortion patterns were obtained with total pressure rakes and casing static pressures. The unsteady pressure loadings on the blade were determined from high response pressure transducers. The resulting blade vibrations were measured with strain gages. The steady flow was analyzed using a three-dimensional Navier-Stokes solver while the unsteady flow was determined with a quasi-three-dimensional linearized Euler solver. Experimental results showed that the distortions had strong vortical, moderate entropic, and weak acoustic parts. The three-dimensional Navier-Stokes analyses showed that the steady flow is predominantly two-dimensional, with radially outward flow existing only in the blade surface boundary layers downstream of shocks and in the aft part of the suction surface. At near resonance conditions, the strain gage data showed blade-to-blade motion variations and thus, linearized unsteady Euler solutions showed poorer agreement with the unsteady loading data than comparisons at off-resonance speeds. Data analysis showed that entropic waves generated unsteady loadings comparable to vortical waves in the blade regions where shocks existed.

  1. Enhancing student achievement through computer-generated homework

    NASA Astrophysics Data System (ADS)

    Milkent, Marlene M.; Roth, Wolff-Michael

    The purpose of this study was to investigate the effects of interactive computer-generated homework on student achievement. Of two sections of Physical Science I, one received homework via the computer; the other received printed, equivalent homework assignments. The results of this study indicate that the use of drill-and-practice computer homework minimizes differences among students with a corresponding decrease in the correlation between posttest scores and entry-level combined ACT science and mathematics scores. The results also support the basic assumption of mastery learning that appropriate instruction will decrease the relationship between aptitude and achievement.

  2. A general method for computing the total solar radiation force on complex spacecraft structures

    NASA Technical Reports Server (NTRS)

    Chan, F. K.

    1981-01-01

    The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total force arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-radiation.

  3. Computation of forced laminar convection in rotating cavities

    NASA Astrophysics Data System (ADS)

    Chew, J. W.

    1985-05-01

    Finite difference solutions are presented for forced laminar convection in a rotating cylindrical cavity with radial outflow. This forms a simple model of the cooling flow between two compressor disks in a gas turbine engine. If the fluid enters the cavity from a uniform radial source, it is shown that the local Nusselt number changes from that of a 'free disk' near the center of the cavity to that for Ekman layer flow at larger radii. With an axial inlet, the flow, and consequently, the heat transfer, is more complex. If vortex breakdown occurs, then the results are very similar to those for the radial inlet case, but otherwise a wall jet forms on the downstream disk, and the heat transfer from this disk may be several times that for the upstream disk. Variation of mean Nusselt number with rotational speed is qualitatively similar to previously published experimental measurements in turbulent flow. The effect of Prandtl number on heat transfer has also been demonstrated.

  4. High-Force Generation Is a Conserved Property of Type IV Pilus Systems▿

    PubMed Central

    Clausen, Martin; Jakovljevic, Vladimir; Søgaard-Andersen, Lotte; Maier, Berenike

    2009-01-01

    The type IV pilus (T4P) system of Neisseria gonorrhoeae is the strongest linear molecular motor reported to date, but it is unclear whether high-force generation is conserved between bacterial species. Using laser tweezers, we found that the average stalling force of single-pilus retraction in Myxococcus xanthus of 149 ± 14 pN exceeds the force generated by N. gonorrhoeae. Retraction velocities including a bimodal distribution were similar between M. xanthus and N. gonorrhoeae, but force-dependent directional switching was not. Force generation by pilus retraction is energized by the ATPase PilT. Surprisingly, an M. xanthus mutant lacking PilT apparently still retracted T4P, although at a reduced frequency. The retraction velocity was comparable to the high-velocity mode in the wild type at low forces but decreased drastically when the force increased, with an average stalling force of 70 ± 10 pN. Thus, M. xanthus harbors at least two different retraction motors. Our results demonstrate that the major physical properties are conserved between bacteria that are phylogenetically distant and pursue very different lifestyles. PMID:19429611

  5. Method of generating and measuring static small force using down-slope component of gravity.

    PubMed

    Fujii, Yusaku

    2007-06-01

    A method of generating and measuring static small forces at the micro-Newton level is proposed. In the method, the down-slope component of gravity acting on a mass on an inclined plane is used as a static force. To realize a linear motion of the mass with a small friction, an aerostatic linear bearing is used. The forces acting on the mass, such as the down-slope component of gravity and the dynamic frictional force, are determined by the levitation mass method. In an experiment, a static small force of approximately 183 microN is generated and measured with a standard uncertainty of approximately 2 microN. PMID:17614648

  6. Measurement of contractile forces generated by individual fibroblasts on self-standing fiber scaffolds.

    PubMed

    Jeon, Hojeong; Kim, Eunpa; Grigoropoulos, Costas P

    2011-02-01

    Contractility of cells in wound site is important to understand pathological wound healing and develop therapeutic strategies. In particular, contractile force generated by cells is a basic element for designing artificial three-dimensional cell culture scaffolds. Direct assessment of deformation of three-dimensional structured materials has been used to calculate contractile forces by averaging total forces with respect to the cell population number. However, macroscopic methods have offered only lower bounds of contractility due to experimental assumptions and the large variance of the spatial and temporal cell response. In the present study, cell contractility was examined microscopically in order to measure contractile forces generated by individual cells on self-standing fiber scaffolds that were fabricated via femtosecond laser-induced two-photon polymerization. Experimental assumptions and calculation errors that arose in previous studies of macroscopic and microscopic contractile force measurements could be reduced by adopting a columnar buckling model on individual, standing fiber scaffolds. Via quantifying eccentric critical loads for the buckling of fibers with various diameters, contractile forces of single cells were calculated in the range between 30-116 nN. In the present study, a force magnitude of approximately 200 nN is suggested as upper bound of the contractile force exerted by single cells. In addition, contractile forces by multiple cells on a single fiber were calculated in the range between 241-709 nN. PMID:20862610

  7. Possibility of generating a 4-neutron resonance with a T =3 /2 isospin 3-neutron force

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Lazauskas, R.; Carbonell, J.; Kamimura, M.

    2016-04-01

    We consider the theoretical possibility of generating a narrow resonance in the 4-neutron system as suggested by a recent experimental result. To that end, a phenomenological T =3 /2 3-neutron force is introduced, in addition to a realistic N N interaction. We inquire what the strength should be of the 3 n force to generate such a resonance. The reliability of the 3-neutron force in the T =3 /2 channel is examined, by analyzing its consistency with the low-lying T =1 states of 4H,4He, and 4Li and the 3H+n scattering. The ab initio solution of the 4 n Schrödinger equation is obtained using the complex scaling method with boundary conditions appropriate to the four-body resonances. We find that to generate narrow 4 n resonant states a remarkably attractive 3 N force in the T =3 /2 channel is required.

  8. An Improved Optical Tweezers Assay for Measuring the Force Generation of Single Kinesin Molecules

    PubMed Central

    Nicholas, Matthew P.; Rao, Lu; Gennerich, Arne

    2014-01-01

    Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments. PMID:24633799

  9. Robustness of muscle synergies underlying three-dimensional force generation at the hand in healthy humans

    PubMed Central

    Rymer, William Z.; Beer, Randall F.

    2012-01-01

    Previous studies using advanced matrix factorization techniques have shown that the coordination of human voluntary limb movements may be accomplished using combinations of a small number of intermuscular coordination patterns, or muscle synergies. However, the potential use of muscle synergies for isometric force generation has been evaluated mostly using correlational methods. The results of such studies suggest that fixed relationships between the activations of pairs of muscles are relatively rare. There is also emerging evidence that the nervous system uses independent strategies to control movement and force generation, which suggests that one cannot conclude a priori that isometric force generation is accomplished by combining muscle synergies, as shown in movement control. In this study, we used non-negative matrix factorization to evaluate the ability of a few muscle synergies to reconstruct the activation patterns of human arm muscles underlying the generation of three-dimensional (3-D) isometric forces at the hand. Surface electromyographic (EMG) data were recorded from eight key elbow and shoulder muscles during 3-D force target-matching protocols performed across a range of load levels and hand positions. Four synergies were sufficient to explain, on average, 95% of the variance in EMG datasets. Furthermore, we found that muscle synergy composition was conserved across biomechanical task conditions, experimental protocols, and subjects. Our findings are consistent with the view that the nervous system can generate isometric forces by assembling a combination of a small number of muscle synergies, differentially weighted according to task constraints. PMID:22279190

  10. Computational ligand-based rational design: Role of conformational sampling and force fields in model development.

    PubMed

    Shim, Jihyun; Mackerell, Alexander D

    2011-05-01

    A significant number of drug discovery efforts are based on natural products or high throughput screens from which compounds showing potential therapeutic effects are identified without knowledge of the target molecule or its 3D structure. In such cases computational ligand-based drug design (LBDD) can accelerate the drug discovery processes. LBDD is a general approach to elucidate the relationship of a compound's structure and physicochemical attributes to its biological activity. The resulting structure-activity relationship (SAR) may then act as the basis for the prediction of compounds with improved biological attributes. LBDD methods range from pharmacophore models identifying essential features of ligands responsible for their activity, quantitative structure-activity relationships (QSAR) yielding quantitative estimates of activities based on physiochemical properties, and to similarity searching, which explores compounds with similar properties as well as various combinations of the above. A number of recent LBDD approaches involve the use of multiple conformations of the ligands being studied. One of the basic components to generate multiple conformations in LBDD is molecular mechanics (MM), which apply an empirical energy function to relate conformation to energies and forces. The collection of conformations for ligands is then combined with functional data using methods ranging from regression analysis to neural networks, from which the SAR is determined. Accordingly, for effective application of LBDD for SAR determinations it is important that the compounds be accurately modelled such that the appropriate range of conformations accessible to the ligands is identified. Such accurate modelling is largely based on use of the appropriate empirical force field for the molecules being investigated and the approaches used to generate the conformations. The present chapter includes a brief overview of currently used SAR methods in LBDD followed by a more

  11. Computational ligand-based rational design: Role of conformational sampling and force fields in model development

    PubMed Central

    Shim, Jihyun; MacKerell, Alexander D.

    2011-01-01

    A significant number of drug discovery efforts are based on natural products or high throughput screens from which compounds showing potential therapeutic effects are identified without knowledge of the target molecule or its 3D structure. In such cases computational ligand-based drug design (LBDD) can accelerate the drug discovery processes. LBDD is a general approach to elucidate the relationship of a compound's structure and physicochemical attributes to its biological activity. The resulting structure-activity relationship (SAR) may then act as the basis for the prediction of compounds with improved biological attributes. LBDD methods range from pharmacophore models identifying essential features of ligands responsible for their activity, quantitative structure-activity relationships (QSAR) yielding quantitative estimates of activities based on physiochemical properties, and to similarity searching, which explores compounds with similar properties as well as various combinations of the above. A number of recent LBDD approaches involve the use of multiple conformations of the ligands being studied. One of the basic components to generate multiple conformations in LBDD is molecular mechanics (MM), which apply an empirical energy function to relate conformation to energies and forces. The collection of conformations for ligands is then combined with functional data using methods ranging from regression analysis to neural networks, from which the SAR is determined. Accordingly, for effective application of LBDD for SAR determinations it is important that the compounds be accurately modelled such that the appropriate range of conformations accessible to the ligands is identified. Such accurate modelling is largely based on use of the appropriate empirical force field for the molecules being investigated and the approaches used to generate the conformations. The present chapter includes a brief overview of currently used SAR methods in LBDD followed by a more

  12. Advanced Computer Image Generation Techniques Exploiting Perceptual Characteristics. Final Report.

    ERIC Educational Resources Information Center

    Stenger, Anthony J.; And Others

    This study suggests and identifies computer image generation (CIG) algorithms for visual simulation that improve the training effectiveness of CIG simulators and identifies areas of basic research in visual perception that are significant for improving CIG technology. The first phase of the project entailed observing three existing CIG simulators.…

  13. Decluttering Methods for Computer-Generated Graphic Displays

    NASA Technical Reports Server (NTRS)

    Schultz, E. Eugene, Jr.

    1986-01-01

    Symbol simplification and contrasting enhance viewer's ability to detect particular symbol. Report describes experiments designed to indicate how various decluttering methods affect viewer's abilities to distinguish essential from nonessential features on computer-generated graphic displays. Results indicate partial removal of nonessential graphic features through symbol simplification effective in decluttering as total removal of nonessential graphic features.

  14. Computer-Generated Geometry Instruction: A Preliminary Study

    ERIC Educational Resources Information Center

    Kang, Helen W.; Zentall, Sydney S.

    2011-01-01

    This study hypothesized that increased intensity of graphic information, presented in computer-generated instruction, could be differentially beneficial for students with hyperactivity and inattention by improving their ability to sustain attention and hold information in-mind. To this purpose, 18 2nd-4th grade students, recruited from general…

  15. SNAP: A computer program for generating symbolic network functions

    NASA Technical Reports Server (NTRS)

    Lin, P. M.; Alderson, G. E.

    1970-01-01

    The computer program SNAP (symbolic network analysis program) generates symbolic network functions for networks containing R, L, and C type elements and all four types of controlled sources. The program is efficient with respect to program storage and execution time. A discussion of the basic algorithms is presented, together with user's and programmer's guides.

  16. An Empirical Generative Framework for Computational Modeling of Language Acquisition

    ERIC Educational Resources Information Center

    Waterfall, Heidi R.; Sandbank, Ben; Onnis, Luca; Edelman, Shimon

    2010-01-01

    This paper reports progress in developing a computer model of language acquisition in the form of (1) a generative grammar that is (2) algorithmically learnable from realistic corpus data, (3) viable in its large-scale quantitative performance and (4) psychologically real. First, we describe new algorithmic methods for unsupervised learning of…

  17. The Application of Computer Musculoskeletal Modeling and Simulation to Investigate Compressive Tibiofemoral Force and Muscle Functions in Obese Children

    PubMed Central

    2013-01-01

    This study aimed to utilize musculoskeletal modelling and simulation to investigate the compressive tibiofemoral force and individual muscle function in obese children. We generated a 3D muscle-driven simulation of eight obese and eight normal-weight boys walking at their self-selected speed. The compressive tibiofemoral force and individual muscle contribution to the support and progression accelerations of center of mass (COM) were computed for each participant based on the subject-specific model. The simulated results were verified by comparing them to the experimental kinematics and EMG data. We found a linear relationship between the average self-selected speed and the normalized peak compressive tibiofemoral force (R2 = 0.611). The activity of the quadriceps contributed the most to the peak compressive tibiofemoral force during the stance phase. Obese children and nonobese children use similar muscles to support and accelerate the body COM, but nonobese children had significantly greater contributions of individual muscles. The obese children may therefore adopt a compensation strategy to avoid increasing joint loads and muscle requirements during walking. The absolute compressive tibiofemoral force and muscle forces were still greater in obese children. The long-term biomechanical adaptations of the musculoskeletal system to accommodate the excess body weight during walking are a concern. PMID:24288573

  18. Fully computed holographic stereogram based algorithm for computer-generated holograms with accurate depth cues.

    PubMed

    Zhang, Hao; Zhao, Yan; Cao, Liangcai; Jin, Guofan

    2015-02-23

    We propose an algorithm based on fully computed holographic stereogram for calculating full-parallax computer-generated holograms (CGHs) with accurate depth cues. The proposed method integrates point source algorithm and holographic stereogram based algorithm to reconstruct the three-dimensional (3D) scenes. Precise accommodation cue and occlusion effect can be created, and computer graphics rendering techniques can be employed in the CGH generation to enhance the image fidelity. Optical experiments have been performed using a spatial light modulator (SLM) and a fabricated high-resolution hologram, the results show that our proposed algorithm can perform quality reconstructions of 3D scenes with arbitrary depth information. PMID:25836429

  19. Using DSMC to compute the force on a particle in a rarefied gas flow.

    SciTech Connect

    Gallis, Michail A.; Rader, Daniel John; Torczynski, John Robert

    2002-06-01

    An approach is presented to compute the force on a spherical particle in a rarefied flow of a monatomic gas. This approach relies on the development of a Green's function that describes the force on a spherical particle in a delta-function molecular velocity distribution function. The gas-surface interaction model in this development allows incomplete accommodation of energy and tangential momentum. The force from an arbitrary molecular velocity distribution is calculated by computing the moment of the force Green's function in the same way that other macroscopic variables are determined. Since the molecular velocity distribution function is directly determined in the DSMC method, the force Green's function approach can be implemented straightforwardly in DSMC codes. A similar approach yields the heat transfer to a spherical particle in a rarefied gas flow. The force Green's function is demonstrated by application to two problems. First, the drag force on a spherical particle at arbitrary temperature and moving at arbitrary velocity through an equilibrium motionless gas is found analytically and numerically. Second, the thermophoretic force on a motionless particle in a motionless gas with a heat flux is found analytically and numerically. Good agreement is observed in both situations.

  20. Molecular interaction forces generated during protein adsorption to well-defined polymer brush surfaces.

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2015-03-17

    The molecular interaction forces generated during the adsorption of proteins to surfaces were examined by the force-versus-distance (f-d) curve measurements of atomic force microscopy using probes modified with appropriate molecules. Various substrates with polymer brush layers bearing zwitterionic, cationic, anionic, and hydrophobic groups were systematically prepared by surface-initiated atom transfer radical polymerization. Surface interaction forces on these substrates were analyzed by the f-d curve measurements using probes with the same polymer brush layer as the substrate. Repulsive forces, which decreased depending on the ionic strength, were generated between cationic or anionic polyelectrolyte brush layers; these were considered to be electrostatic interaction forces. A strong adhesive force was detected between hydrophobic polymer brush layers during retraction; this corresponded to the hydrophobic interaction between two hydrophobic polymer layers. In contrast, no significant interaction forces were detected between zwitterionic polymer brush layers. Direct interaction forces between proteins and polymer brush layers were then quantitatively evaluated by the f-d curve measurements using protein-immobilized probes consisting of negatively charged albumin and positively charged lysozyme under physiological conditions. In addition, the amount of protein adsorbed on the polymer brush layer was quantified by surface plasmon resonance measurements. Relatively large amounts of protein adsorbed to the polyelectrolyte brush layers with opposite charges. It was considered that the detachment of the protein after contact with the polymer brush layer hardly occurred due to salt formation at the interface. Both proteins adsorbed significantly on the hydrophobic polymer brush layer, which was due to hydrophobic interactions at the interface. In contrast, the zwitterionic polymer brush layer exhibited no significant interaction force with proteins and suppressed

  1. A Novel 3D Fibril Force Assay Implicates Src in Tumor Cell Force Generation in Collagen Networks

    PubMed Central

    Polackwich, Robert J.; Koch, Daniel; Arevalo, Richard; Miermont, Anne M.; Jee, Kathleen J.; Lazar, John; Urbach, Jeffrey; Mueller, Susette C.; McAllister, Ryan G.

    2013-01-01

    New insight into the biomechanics of cancer cell motility in 3D extracellular matrix (ECM) environments would significantly enhance our understanding of aggressive cancers and help identify new targets for intervention. While several methods for measuring the forces involved in cell-matrix interactions have been developed, previous to this study none have been able to measure forces in a fibrillar environment. We have developed a novel assay for simultaneously measuring cell mechanotransduction and motility in 3D fibrillar environments. The assay consists of a controlled-density fibrillar collagen gel atop a controlled-stiffness polyacrylamide (PAA) surface. Forces generated by living cells and their migration in the 3D collagen gel were measured with the 3D motion of tracer beads within the PAA layer. Here, this 3D fibril force assay is used to study the role of the invasion-associated protein kinase Src in mechanotransduction and motility. Src expression and activation are linked with proliferation, invasion, and metastasis, and have been shown to be required in 2D for invadopodia membranes to direct and mediate invasion. Breast cancer cell line MDA-MD-231 was stably transfected with GFP-tagged constitutively active Src or wild-type Src. In 3D fibrillar collagen matrices we found that, relative to wild-type Src, constitutively active Src: 1) increased the strength of cell-induced forces on the ECM, 2) did not significantly change migration speed, and 3) increased both the duration and the length, but not the number, of long membrane protrusions. Taken together, these results support the hypothesis that Src controls invasion by controlling the ability of the cell to form long lasting cellular protrusions to enable penetration through tissue barriers, in addition to its role in promoting invadopodia matrix-degrading activity. PMID:23536784

  2. Shortening actin filaments cause force generation in actomyosin network to change from contractile to extensile

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Gardel, Margaret

    Motor proteins in conjunction with filamentous proteins convert biochemical energy into mechanical energy which serves a number of cellular processes including cell motility, force generation and intracellular cargo transport. In-vitro experiments suggest that the forces generated by kinesin motors on microtubule bundles are extensile in nature whereas myosin motors on actin filaments are contractile. It is not clear how qualitatively similar systems can show completely different behaviors in terms of the nature of force generation. In order to answer this question, we carry out in vitro experiments where we form quasi 2D filamentous actomyosin networks and vary the length of actin filaments by adding capping protein. We show that when filaments are much shorter than their typical persistence length (approximately 10 microns), the forces generated are extensile and we see active nematic defect propagation, as seen in the microtubule-kinesin system. Based on this observation, we claim that the rigidity of rods plays an important role in dictating the nature of force generation in such systems. In order to understand this transition, we selectively label individual filaments and find that longer filaments show considerable bending and buckling, making them difficult to slide and extend along their length.

  3. Mechanisms of force generation by end-on kinetochore-microtubule attachments

    PubMed Central

    Joglekar, Ajit P.; Bloom, Kerry S.; Salmon, E. D.

    2010-01-01

    Generation of motile force is one of the main functions of the eukaryotic kinetochore during cell division. In recent years, the KMN network of proteins (Ndc80 complex, Mis12 complex and KNL-1 complex) has emerged as a highly conserved core microtubule-binding complex at the kinetochore. It plays a major role in coupling force generation to microtubule plus-end polymerization and depolymerization. In this review, we discuss current theoretical mechanisms of force generation, and then focus on emerging information about mechanistic contributions from the Ndc80 complex in eukaryotes, and the microtubule-binding Dam1/DASH complex from fungi. New information has also become available from super-resolution light microscopy on the protein architecture of the kinetochore-microtubule attachment site in both budding yeast and humans, which provides further insight into the mechanism of force generation. We briefly discuss potential contributions of motors, other microtubule-associated proteins, and microtubule depolymerases. Using the above evidence, we present speculative models of force generation at the kinetochore. PMID:20061128

  4. Very low force-generating ability and unusually high temperature dependency in hummingbird flight muscle fibers.

    PubMed

    Reiser, Peter J; Welch, Kenneth C; Suarez, Raul K; Altshuler, Douglas L

    2013-06-15

    Hummingbird flight muscle is estimated to have among the highest mass-specific power output among vertebrates, based on aerodynamic models. However, little is known about the fundamental contractile properties of their remarkable flight muscles. We hypothesized that hummingbird pectoralis fibers generate relatively low force when activated in a tradeoff for high shortening speeds associated with the characteristic high wingbeat frequencies that are required for sustained hovering. Our objective was to measure maximal force-generating ability (maximal force/cross-sectional area, Po/CSA) in single, skinned fibers from the pectoralis and supracoracoideus muscles, which power the wing downstroke and upstroke, respectively, in hummingbirds (Calypte anna) and in another similarly sized species, zebra finch (Taeniopygia guttata), which also has a very high wingbeat frequency during flight but does not perform a sustained hover. Mean Po/CSA in hummingbird pectoralis fibers was very low - 1.6, 6.1 and 12.2 kN m(-2), at 10, 15 and 20°C, respectively. Po/CSA in finch pectoralis fibers was also very low (for both species, ~5% of the reported Po/CSA of chicken pectoralis fast fibers at 15°C). Q10-force (force generated at 20°C/force generated at 10°C) was very high for hummingbird and finch pectoralis fibers (mean=15.3 and 11.5, respectively) compared with rat slow and fast fibers (1.8 and 1.9, respectively). Po/CSA in hummingbird leg fibers was much higher than in pectoralis fibers at each temperature, and the mean Q10-force was much lower. Thus, hummingbird and finch pectoralis fibers have an extremely low force-generating ability compared with other bird and mammalian limb fibers, and an extremely high temperature dependence of force generation. However, the extrapolated maximum force-generating ability of hummingbird pectoralis fibers in vivo (~48 kN m(-2)) is substantially higher than the estimated requirements for hovering flight of C. anna. The unusually low Po

  5. Kinesin force generation measured using a centrifuge microscope sperm-gliding motility assay.

    PubMed Central

    Hall, K; Cole, D; Yeh, Y; Baskin, R J

    1996-01-01

    To measure force generation and characterize the relationship between force and velocity in kinesin-driven motility we have developed a centrifuge microscope sperm-gliding motility assay. The average (extrapolated) value of maximum isometric force at low kinesin density was 0.90 +/- 0.14 pN. Furthermore, in the experiments at low kinesin density, sperm pulled off before stall at forces between 0.40 and 0.75 pN. To further characterize our kinesin-demembranated sperm assay we estimated maximum isometric force using a laser trap-based assay. At low kinesin density, 4.34 +/- 1.5 pN was the maximum force. Using values of axoneme stiffness available from other studies, we concluded that, in our centrifuge microscope-based assay, a sperm axoneme functions as a lever arm, magnifying the centrifugal force and leading to pull-off before stall. In addition, drag of the distal portion of the axoneme is increased by the centrifugal force (because the axoneme is rotated into closer proximity to the glass surface) and represents an additional force that the kinesin motor must overcome. Images FIGURE 1 FIGURE 9 FIGURE 10 PMID:8968616

  6. Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.

    PubMed

    Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M

    2016-09-21

    We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model. PMID:27420398

  7. Computational model for noncontact atomic force microscopy: energy dissipation of cantilever

    NASA Astrophysics Data System (ADS)

    Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M.

    2016-09-01

    We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model.

  8. Generation of optical vortex based on computer-generated holographic gratings by photolithography

    NASA Astrophysics Data System (ADS)

    Li, Shaoxiang; Wang, Zhenwei

    2013-09-01

    The Laguerre-Gaussian beam is a typical example of the optical vortices, which can be generated by computer-generated holograms (CGHs) with the topological charge controlled. Here, we fabricated transmission-amplitude CGH gratings (up to 100 lines per millimeter) on metal film by photolithography technique. Such CGH grating grooves feature high resolution and fine smoothness, so that the gratings can be used to generate Laguerre-Gaussian beam with perfect mode. They are also applicable for the generation of femtosecond optical vortices due to the high damage threshold of the metal film.

  9. Comparative assessment of forces generated during simulated alignment with self-ligating and conventional brackets.

    PubMed

    Pandis, Nikolaos; Eliades, Theodore; Bourauel, Christoph

    2009-12-01

    The objectives of this study were to comparatively assess the magnitude and direction of forces and moments generated from different bracket systems, during the initial levelling and alignment stage of orthodontic treatment. Three types of brackets were used: Orthos2 (Ormco), Damon2 (Ormco), and In-Ovation R (GAC). The brackets were bonded on resin replicas models of a patient's crowded mandibular arch, and a 0.014 inch Damon archform CuNiTi (Ormco) wire was inserted. The model was mounted on the Orthodontic Measurement and Simulation System (OMSS) and six static measurements were taken at the initial crowded state per bracket for the lateral incisor, canine, and first premolar. A total of 10 repetitions were performed for each measurement, with new brackets and archwires used for each trial. The forces and moments generated were registered directly on the OMSS software and were statistically analyzed using a one-way analysis of variance separately for each dental arch location and force component. Group differences were further analyzed with Tukey's post hoc comparisons test at the 0.05 significance level. The lingually inclined, crowded lateral incisor presented an extrusive and buccal movement and showed the lowest force in the vertical direction, whereas the self-ligating group of brackets generated the highest force in the buccolingual direction. The moments applied by the three bracket systems followed the general trend shown for forces; in the vertical axis, the self-ligating brackets exerted lower forces than their conventional counterpart. This was modified in the buccolingual direction where, in most instances, the self-ligating appliances applied higher moments compared with the conventional bracket. In most cases, the magnitude of forces and moments ranged between 30-70 cN and 2-6 N mm, respectively. However, maximum forces and moments developed at the lateral incisor were almost four times higher than the average. PMID:19349418

  10. Influence of stator slots on the development of noise-generating magnetic force waves

    NASA Astrophysics Data System (ADS)

    Wachta, B.

    The calculation of noise in electrical machines is important in the design of these machines. It is shown that the magnetic anisotropy of a laminated stator core caused by stator slots has a substantial effect on the force waves acting on the yoke. The force waves are described simply using a modulation function and the Fourier coefficients of the waves. The effects of the amplitude of the magnetic force waves are discussed, and the effectiveness of stator slot skewing is determined. It is shown that subharmonics can be generated by the slotting (affecting the harmonic number of the force waves), and that for specific harmonic numbers, a reversal in the direction of rotation of force waves takes place. The effectiveness of the method is substantiated by a practical example.

  11. A system to generate simultaneous forced oscillation and continuous positive airway pressure.

    PubMed

    Farré, R; Rotger, M; Montserrat, J M; Navajas, D

    1997-06-01

    Assessment of airway obstruction in patients with obstructive sleep apnoea (OSA) subjected to continuous positive airway pressure (CPAP) may be carried out using the forced oscillation technique (FOT). To facilitate routine application of forced oscillation (FO) in sleep studies, our aim was to design a system capable of generating CPAP and applying FOT simultaneously. We constructed a prototype CPAP + FO generator by connecting a specially designed electromagnetic valve in parallel with a conventional blower. The capacity of the prototype to generate forced oscillation (5 Hz +/- 1 hPa) was tested by connecting it to a model simulating spontaneous breathing. The response of the prototype for target CPAPs of 5, 10 and 15 hPa and imposed sinusoidal breathing with peak flow up to 0.75 L x s(-1) was excellent when compared with that reported for commercially available CPAP generators. The applicability of the prototype was tested by applying it to assess airway obstruction in four patients with OSA during sleep. We conclude that the generator designed is able to apply continuous positive airway pressure and forced oscillation simultaneously. The system could be useful for automatic and noninvasive assessment of airway obstruction in patients with obstructive sleep apnoea subjected to continuous positive airway pressure. Future development of the generator may be helpful in implementing a set-up for automatic titration of continuous positive airway pressure. PMID:9192942

  12. Force generation by muscle fibers in rigor: a laser temperature-jump study.

    PubMed

    Davis, J S; Harrington, W F

    1987-02-01

    A clear prediction of the helix-coil model for force generation in muscle is that force should be produced when the equilibrium (helix-coil) of a rigor (or activated) fiber is perturbed by a temperature jump near the melting temperature of the light meromyosin/heavy meromyosin hinge. An infrared, iodine-photodissociation laser was used to heat the fibers by approximately equal to 5 degrees C in under 1 mus. Under ionic conditions where rigor bridges are predominantly associated with the thick filament backbone, an abrupt drop in tension typical of normal thermoelastic expansion was seen. A similar response was observed below 41 degrees C for thick filament-released rigor bridges. Above this temperature, a rubber-like thermoelastic response was obtained typical of a helix-coil transition. At temperatures near 50 degrees C, the amount of force generated by a rigor fiber was large and comparable to that seen for an activated fiber at 5 degrees C. The relaxation spectra of force generation obtained for both systems (rigor and activated) show a step change followed by a biexponential kinetic process. The reciprocal relaxation times and amplitudes for these individual processes in activated and rigor fibers differ only by factors of 2-4. Force generation in the rigor muscle appears to arise from melting in the subfragment 2 hinge region of the myosin molecule since binding of subfragment 2 to the thick filament backbone inhibits force production. No significant force generation was observed following temperature jumps of relaxed fibers. PMID:3469654

  13. The use of computer vision and force sensing for tight tolerance assembly

    SciTech Connect

    Bayliss, J.D.

    1993-05-19

    Computer vision and force control provide feedback for robot manipulation during the assembly of objects. Both techniques have weaknesses, but their complementary strengths enable them to work well together, achieving assembly with tight tolerances. For instance, camera resolution limits the accuracy of computer vision, but it can locate approximately where the part should be placed and is an excellent choice for coarse placement of the part. Force control senses the force induced by object contact and if used extensively could damage a delicate part, but when used for fine placement of an object, it compensates for the error in coarse placement. It is our goal to utilize the best features of force sensing and computer vision to reduce the error in placement of an object. The results of placing a peg in a 0.15mm tolerance hole with different camera resolutions will be presented. We have chosen to use computer vision to move the peg as close to its correct placement point as possible and force control to make minor adjustments, achieving the correct positioning of the peg.

  14. Source Term Model for Vortex Generator Vanes in a Navier-Stokes Computer Code

    NASA Technical Reports Server (NTRS)

    Waithe, Kenrick A.

    2004-01-01

    A source term model for an array of vortex generators was implemented into a non-proprietary Navier-Stokes computer code, OVERFLOW. The source term models the side force created by a vortex generator vane. The model is obtained by introducing a side force to the momentum and energy equations that can adjust its strength automatically based on the local flow. The model was tested and calibrated by comparing data from numerical simulations and experiments of a single low profile vortex generator vane on a flat plate. In addition, the model was compared to experimental data of an S-duct with 22 co-rotating, low profile vortex generators. The source term model allowed a grid reduction of about seventy percent when compared with the numerical simulations performed on a fully gridded vortex generator on a flat plate without adversely affecting the development and capture of the vortex created. The source term model was able to predict the shape and size of the stream-wise vorticity and velocity contours very well when compared with both numerical simulations and experimental data. The peak vorticity and its location were also predicted very well when compared to numerical simulations and experimental data. The circulation predicted by the source term model matches the prediction of the numerical simulation. The source term model predicted the engine fan face distortion and total pressure recovery of the S-duct with 22 co-rotating vortex generators very well. The source term model allows a researcher to quickly investigate different locations of individual or a row of vortex generators. The researcher is able to conduct a preliminary investigation with minimal grid generation and computational time.

  15. The myofilament elasticity and its effect on kinetics of force generation by the myosin motor.

    PubMed

    Piazzesi, Gabriella; Dolfi, Mario; Brunello, Elisabetta; Fusi, Luca; Reconditi, Massimo; Bianco, Pasquale; Linari, Marco; Lombardi, Vincenzo

    2014-06-15

    The half-sarcomere is the functional unit of striated muscle, in which, according to a "linear" mechanical model, myosin motors are parallel force generators with an average strain s acting between the opposing myosin and actin filaments that behave as a series elastic element with compliance Cf. Thus the definition of the mechanism of force generation by myosin motors in muscle requires integration of the crystallographic model of the working stroke with the mechanical constraints provided by the organization of motors in the half-sarcomere. The relation between half-sarcomere compliance and force (Chs-T) during the development of isometric contraction deviates, at low forces, from that predicted by the linear model, indicating the presence of an elastic element in parallel with the myosin motors, which may influence the estimate of s. A working stroke model, kinetically constrained by the early phase of the isotonic velocity transient following a force step, predicts that the rate of quick force recovery following a length step is reduced to the observed value by a Cf of 12.6nm/MPa. With this value of Cf, the fit of Chs-T relation during the isometric force rise gives s=1.8-1.9nm, similar to the values estimated using the linear model. PMID:24631572

  16. Forces and moments generated by the human arm: Variability and control

    PubMed Central

    Xu, Y; Terekhov, AV; Latash, ML; Zatsiorsky, VM

    2012-01-01

    This is an exploratory study of the accurate endpoint force vector production by the human arm in isometric conditions. We formulated three common-sense hypotheses and falsified them in the experiment. The subjects (n=10) exerted static forces on the handle in eight directions in a horizontal plane for 25 seconds. The forces were of 4 magnitude levels (10 %, 20%, 30% and 40% of individual MVC). The torsion moment on the handle (grasp moment) was not specified in the instruction. The two force components and the grasp moment were recorded, and the shoulder, elbow, and wrist joint torques were computed. The following main facts were observed: (a) While the grasp moment was not prescribed by the instruction, it was always produced. The moment magnitude and direction depended on the instructed force magnitude and direction. (b) The within-trial angular variability of the exerted force vector (angular precision) did not depend on the target force magnitude (a small negative correlation was observed). (c) Across the target force directions, the variability of the exerted force magnitude and directional variability exhibited opposite trends: In the directions where the variability of force magnitude was maximal, the directional variability was minimal and vice versa. (d) The time profiles of joint torques in the trials were always positively correlated, even for the force directions where flexion torque was produced at one joint and extension torque was produced at the other joint. (e) The correlations between the grasp moment and the wrist torque were negative across the tasks and positive within the individual trials. (f) In static serial kinematic chains, the pattern of the joint torques distribution could not be explained by an optimization cost function additive with respect to the torques. Plans for several future experiments have been suggested. PMID:23080084

  17. A computer-based tool for generation of progress notes.

    PubMed Central

    Campbell, K. E.; Wieckert, K.; Fagan, L. M.; Musen, M. A.

    1993-01-01

    IVORY, a computer-based tool that uses clinical findings as the basic unit for composing progress notes, generates progress notes more efficiently than does a character-based word processor. IVORY's clinical findings are contained within a structured vocabulary that we developed to support generation of both prose progress notes and SNOMED III codes. Observational studies of physician participation in the development of IVORY's structured vocabulary have helped us to identify areas where changes are required before IVORY will be acceptable for routine clinical use. PMID:8130479

  18. The actin crosslinking protein palladin modulates force generation and mechanosensitivity of tumor associated fibroblasts

    PubMed Central

    Azatov, Mikheil; Goicoechea, Silvia M.; Otey, Carol A.; Upadhyaya, Arpita

    2016-01-01

    Cells organize actin filaments into higher-order structures by regulating the composition, distribution and concentration of actin crosslinkers. Palladin is an actin crosslinker found in the lamellar actin network and stress fibers, which are critical for mechanosensing of the environment. Palladin also serves as a molecular scaffold for α-actinin, another key actin crosslinker. By virtue of its close interactions with actomyosin structures in the cell, palladin may play an important role in cell mechanics. However, the role of palladin in cellular force generation and mechanosensing has not been studied. Here, we investigate the role of palladin in regulating the plasticity of the actin cytoskeleton and cellular force generation in response to alterations in substrate stiffness. Traction force microscopy revealed that tumor-associated fibroblasts generate larger forces on substrates of increased stiffness. Contrary to expectations, knocking down palladin increased the forces generated by cells and inhibited their ability to sense substrate stiffness for very stiff gels. This was accompanied by significant differences in actin organization, adhesion dynamics and altered myosin organization in palladin knock-down cells. Our results suggest that actin crosslinkers such as palladin and myosin motors coordinate for optimal cell function and to prevent aberrant behavior as in cancer metastasis. PMID:27353427

  19. Image quality evaluation and control of computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Hiroshi; Yamaguchi, Takeshi; Uetake, Hiroki

    2016-03-01

    Image quality of the computer-generated holograms are usually evaluated subjectively. For example, the re- constructed image from the hologram is compared with other holograms, or evaluated by the double-stimulus impairment scale method to compare with the original image. This paper proposes an objective image quality evaluation of a computer-generated hologram by evaluating both diffraction efficiency and peak signal-to-noise ratio. Theory and numerical experimental results are shown on Fourier transform transmission hologram of both amplitude and phase modulation. Results without the optimized random phase show that the amplitude transmission hologram gives better peak signal-to noise ratio, but the phase transmission hologram provides about 10 times higher diffraction efficiency to the amplitude type. As an optimized phase hologram, Kinoform is evaluated. In addition, we investigate to control image quality by non-linear operation.

  20. Behavioral personal digital assistants: The seventh generation of computing.

    PubMed

    Stephens, K R; Hutchison, W R

    1992-01-01

    Skinner (1985) described two divergent approaches to developing computer systems that would behave with some approximation to intelligence. The first approach, which corresponds to the mainstream of artificial intelligence and expert systems, models intelligence as a set of production rules that incorporate knowledge and a set of heuristics for inference and symbol manipulation. The alternative is a system that models the behavioral repertoire as a network of associations between antecedent stimuli and operants, and adapts when supplied with reinforcement. The latter approach is consistent with developments in the field of "neural networks." The authors describe how an existing adaptive network software system, based on behavior analysis and developed since 1983, can be extended to provide a new generation of software systems capable of acquiring verbal behavior. This effort will require the collaboration of the academic and commercial sectors of the behavioral community, but the end result will enable a generational change in computer systems and support for behavior analytic concepts. PMID:22477053

  1. A computer aided design procedure for generating gear teeth

    NASA Technical Reports Server (NTRS)

    Chang, S. H.; Huston, R. L.; Coy, J. J.

    1984-01-01

    A procedure for computer aided design (CAD) of gear teeth is presented. It is developed for generated teeth fabricated by a hob cutter or a shaper. It provides a means for analytically and numerically determining the tooth profile, given the cutter profile. An illustrative example with involute tooth profiles is given. Application with non-standard profiles and with bevel, spiral bevel, and hypoid gears is discussed.

  2. An optical pattern classification using computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Kajiki, Yoshinori; Matsushita, Kenji; Shimizu, Eiji

    1990-07-01

    An optical pattern classification system is proposed which performs weighting and summation by the optical system using computer-generated holograms (CGHs). The system makes it possible to simplify the structure and to improve the processing speed. A trainable pattern classification system which performs weight modification by using a CGH matrix and a dot matrix liquid crystal display (LCD) as a shutter array is proposed. The trainable pattern classifier using a CGH matrix and LCD is described, and the experimental results are presented.

  3. Extrusion of transmitter, water and ions generates forces to close fusion pore.

    PubMed

    Tajparast, M; Glavinović, M I

    2009-05-01

    During exocytosis the fusion pore opens rapidly, then dilates gradually, and may subsequently close completely, but what controls its dynamics is not well understood. In this study we focus our attention on forces acting on the pore wall, and which are generated solely by the passage of transmitter, ions and water through the open fusion pore. The transport through the charged cylindrical nano-size pore is simulated using a coupled system of Poisson-Nernst-Planck and Navier-Stokes equations and the forces that act radially on the wall of the fusion pore are then estimated. Four forces are considered: a) inertial force, b) pressure, c) viscotic force, and d) electrostatic force. The inertial and viscotic forces are small, but the electrostatic force and the pressure are typically significant. High vesicular pressure tends to open the fusion pore, but the pressure induced by the transport of charged particles (glutamate, ions), which is predominant when the pore wall charge density is high tends to close the pore. The electrostatic force, which also depends on the charge density on the pore wall, is weakly repulsive before the pore dilates, but becomes attractive and pronounced as the pore dilates. Given that the vesicular concentration of free transmitter can change rapidly due to the release, or owing to the dissociation from the gel matrix, we evaluated how much and how rapidly a change of the vesicular K(+)-glutamate(-) concentration affects the concentration of glutamate(-) and ions in the pore and how such changes alter the radial force on the wall of the fusion pore. A step-like rise of the vesicular K(+)-glutamate(-) concentration leads to a chain of events. Pore concentration (and efflux) of both K(+) and glutamate(-) rise reaching their new steady-state values in less than 100 ns. Interestingly within a similar time interval the pore concentration of Na(+) also rises, whereas that of Cl(-) diminishes, although their extra-cellular concentration does not

  4. Hardware architecture for full analytical Fraunhofer computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Pang, Zhi-Yong; Xu, Zong-Xi; Xiong, Yi; Chen, Biao; Dai, Hui-Min; Jiang, Shao-Ji; Dong, Jian-Wen

    2015-09-01

    Hardware architecture of parallel computation is proposed for generating Fraunhofer computer-generated holograms (CGHs). A pipeline-based integrated circuit architecture is realized by employing the modified Fraunhofer analytical formulism, which is large scale and enables all components to be concurrently operated. The architecture of the CGH contains five modules to calculate initial parameters of amplitude, amplitude compensation, phases, and phase compensation, respectively. The precalculator of amplitude is fully adopted considering the "reusable design" concept. Each complex operation type (such as square arithmetic) is reused only once by means of a multichannel selector. The implemented hardware calculates an 800×600 pixels hologram in parallel using 39,319 logic elements, 21,074 registers, and 12,651 memory bits in an Altera field-programmable gate array environment with stable operation at 50 MHz. Experimental results demonstrate that the quality of the images reconstructed from the hardware-generated hologram can be comparable to that of a software implementation. Moreover, the calculation speed is approximately 100 times faster than that of a personal computer with an Intel i5-3230M 2.6 GHz CPU for a triangular object.

  5. Binary encoded computer generated holograms for temporal phase shifting.

    PubMed

    Amphawan, Angela

    2011-11-01

    The trend towards real-time optical applications predicates the need for real-time interferometry. For real-time interferometric applications, rapid processing of computer generated holograms is crucial as the intractability of rapid phase changes may compromise the input to the system. This paper introduces the design of a set of binary encoded computer generated holograms (CGHs) for real-time five-frame temporal phase shifting interferometry using a binary amplitude spatial light modulator. It is suitable for portable devices with constraints in computational power. The new set of binary encoded CGHs is used for measuring the phase of the generated electric field for a real-time selective launch in multimode fiber. The processing time for the new set of CGHs was reduced by up to 65% relative to the original encoding scheme. The results obtained from the new interferometric technique are in good agreement with the results obtained by phase shifting by means of a piezo-driven flat mirror. PMID:22109188

  6. Computational power and generative capacity of genetic systems.

    PubMed

    Igamberdiev, Abir U; Shklovskiy-Kordi, Nikita E

    2016-01-01

    Semiotic characteristics of genetic sequences are based on the general principles of linguistics formulated by Ferdinand de Saussure, such as the arbitrariness of sign and the linear nature of the signifier. Besides these semiotic features that are attributable to the basic structure of the genetic code, the principle of generativity of genetic language is important for understanding biological transformations. The problem of generativity in genetic systems arises to a possibility of different interpretations of genetic texts, and corresponds to what Alexander von Humboldt called "the infinite use of finite means". These interpretations appear in the individual development as the spatiotemporal sequences of realizations of different textual meanings, as well as the emergence of hyper-textual statements about the text itself, which underlies the process of biological evolution. These interpretations are accomplished at the level of the readout of genetic texts by the structures defined by Efim Liberman as "the molecular computer of cell", which includes DNA, RNA and the corresponding enzymes operating with molecular addresses. The molecular computer performs physically manifested mathematical operations and possesses both reading and writing capacities. Generativity paradoxically resides in the biological computational system as a possibility to incorporate meta-statements about the system, and thus establishes the internal capacity for its evolution. PMID:26829769

  7. Turbofan forced mixer-nozzle internal flowfield. Volume 2: Computational fluid dynamic predictions

    NASA Technical Reports Server (NTRS)

    Werle, M. J.; Vasta, V. N.

    1982-01-01

    A general program was conducted to develop and assess a computational method for predicting the flow properties in a turbofan forced mixed duct. The detail assessment of the resulting computer code is presented. It was found that the code provided excellent predictions of the kinematics of the mixing process throughout the entire length of the mixer nozzle. The thermal mixing process between the hot core and cold fan flows was found to be well represented in the low speed portion of the flowfield.

  8. Fracture resistance of computer-aided design/computer-aided manufacturing-generated composite resin-based molar crowns.

    PubMed

    Harada, Akio; Nakamura, Keisuke; Kanno, Taro; Inagaki, Ryoichi; Örtengren, Ulf; Niwano, Yoshimi; Sasaki, Keiichi; Egusa, Hiroshi

    2015-04-01

    The aim of this study was to investigate whether different fabrication processes, such as the computer-aided design/computer-aided manufacturing (CAD/CAM) system or the manual build-up technique, affect the fracture resistance of composite resin-based crowns. Lava Ultimate (LU), Estenia C&B (EC&B), and lithium disilicate glass-ceramic IPS e.max press (EMP) were used. Four types of molar crowns were fabricated: CAD/CAM-generated composite resin-based crowns (LU crowns); manually built-up monolayer composite resin-based crowns (EC&B-monolayer crowns); manually built-up layered composite resin-based crowns (EC&B-layered crowns); and EMP crowns. Each type of crown was cemented to dies and the fracture resistance was tested. EC&B-layered crowns showed significantly lower fracture resistance compared with LU and EMP crowns, although there was no significant difference in flexural strength or fracture toughness between LU and EC&B materials. Micro-computed tomography and fractographic analysis showed that decreased strength probably resulted from internal voids in the EC&B-layered crowns introduced by the layering process. There was no significant difference in fracture resistance among LU, EC&B-monolayer, and EMP crowns. Both types of composite resin-based crowns showed fracture loads of >2000 N, which is higher than the molar bite force. Therefore, CAD/CAM-generated crowns, without internal defects, may be applied to molar regions with sufficient fracture resistance. PMID:25683749

  9. Effort minimization and synergistic muscle recruitment for three-dimensional force generation

    PubMed Central

    Borzelli, Daniele; Berger, Denise J.; Pai, Dinesh K.; d'Avella, Andrea

    2013-01-01

    To generate a force at the hand in a given spatial direction and with a given magnitude the central nervous system (CNS) has to coordinate the recruitment of many muscles. Because of the redundancy in the musculoskeletal system, the CNS can choose one of infinitely many possible muscle activation patterns which generate the same force. What strategies and constraints underlie such selection is an open issue. The CNS might optimize a performance criterion, such as accuracy or effort. Moreover, the CNS might simplify the solution by constraining it to be a combination of a few muscle synergies, coordinated recruitment of groups of muscles. We tested whether the CNS generates forces by minimum effort recruitment of either individual muscles or muscle synergies. We compared the activation of arm muscles observed during the generation of isometric forces at the hand across multiple three-dimensional force targets with the activation predicted by either minimizing the sum of squared muscle activations or the sum of squared synergy activations. Muscle synergies were identified from the recorded muscle pattern using non-negative matrix factorization. To perform both optimizations we assumed a linear relationship between rectified and filtered electromyographic (EMG) signal which we estimated using multiple linear regressions. We found that the minimum effort recruitment of synergies predicted the observed muscle patterns better than the minimum effort recruitment of individual muscles. However, both predictions had errors much larger than the reconstruction error obtained by the synergies, suggesting that the CNS generates three-dimensional forces by sub-optimal recruitment of muscle synergies. PMID:24391581

  10. Automatic generation of computable implementation guides from clinical information models.

    PubMed

    Boscá, Diego; Maldonado, José Alberto; Moner, David; Robles, Montserrat

    2015-06-01

    Clinical information models are increasingly used to describe the contents of Electronic Health Records. Implementation guides are a common specification mechanism used to define such models. They contain, among other reference materials, all the constraints and rules that clinical information must obey. However, these implementation guides typically are oriented to human-readability, and thus cannot be processed by computers. As a consequence, they must be reinterpreted and transformed manually into an executable language such as Schematron or Object Constraint Language (OCL). This task can be difficult and error prone due to the big gap between both representations. The challenge is to develop a methodology for the specification of implementation guides in such a way that humans can read and understand easily and at the same time can be processed by computers. In this paper, we propose and describe a novel methodology that uses archetypes as basis for generation of implementation guides. We use archetypes to generate formal rules expressed in Natural Rule Language (NRL) and other reference materials usually included in implementation guides such as sample XML instances. We also generate Schematron rules from NRL rules to be used for the validation of data instances. We have implemented these methods in LinkEHR, an archetype editing platform, and exemplify our approach by generating NRL rules and implementation guides from EN ISO 13606, openEHR, and HL7 CDA archetypes. PMID:25910958