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Sample records for additional driving force

  1. Forces Driving Chaperone Action.

    PubMed

    Koldewey, Philipp; Stull, Frederick; Horowitz, Scott; Martin, Raoul; Bardwell, James C A

    2016-07-14

    It is still unclear what molecular forces drive chaperone-mediated protein folding. Here, we obtain a detailed mechanistic understanding of the forces that dictate the four key steps of chaperone-client interaction: initial binding, complex stabilization, folding, and release. Contrary to the common belief that chaperones recognize unfolding intermediates by their hydrophobic nature, we discover that the model chaperone Spy uses long-range electrostatic interactions to rapidly bind to its unfolded client protein Im7. Short-range hydrophobic interactions follow, which serve to stabilize the complex. Hydrophobic collapse of the client protein then drives its folding. By burying hydrophobic residues in its core, the client's affinity to Spy decreases, which causes client release. By allowing the client to fold itself, Spy circumvents the need for client-specific folding instructions. This mechanism might help explain how chaperones can facilitate the folding of various unrelated proteins. PMID:27293188

  2. Forces driving epithelial wound healing

    NASA Astrophysics Data System (ADS)

    Brugués, Agustí; Anon, Ester; Conte, Vito; Veldhuis, Jim H.; Gupta, Mukund; Colombelli, Julien; Muñoz, José J.; Brodland, G. Wayne; Ladoux, Benoit; Trepat, Xavier

    2014-09-01

    A fundamental feature of multicellular organisms is their ability to self-repair wounds through the movement of epithelial cells into the damaged area. This collective cellular movement is commonly attributed to a combination of cell crawling and `purse-string’ contraction of a supracellular actomyosin ring. Here we show by direct experimental measurement that these two mechanisms are insufficient to explain force patterns observed during wound closure. At early stages of the process, leading actin protrusions generate traction forces that point away from the wound, showing that wound closure is initially driven by cell crawling. At later stages, we observed unanticipated patterns of traction forces pointing towards the wound. Such patterns have strong force components that are both radial and tangential to the wound. We show that these force components arise from tensions transmitted by a heterogeneous actomyosin ring to the underlying substrate through focal adhesions. The structural and mechanical organization reported here provides cells with a mechanism to close the wound by cooperatively compressing the underlying substrate.

  3. Forces driving epithelial wound healing

    PubMed Central

    Veldhuis, Jim H.; Gupta, Mukund; Colombelli, Julien; Muñoz, José J.; Brodland, G. Wayne; Ladoux, Benoit; Trepat, Xavier

    2015-01-01

    A fundamental feature of multicellular organisms is their ability to self-repair wounds through the movement of epithelial cells into the damaged area. This collective cellular movement is commonly attributed to a combination of cell crawling and “purse-string” contraction of a supracellular actomyosin ring. Here we show by direct experimental measurement that these two mechanisms are insufficient to explain force patterns observed during wound closure. At early stages of the process, leading actin protrusions generate traction forces that point away from the wound, showing that wound closure is initially driven by cell crawling. At later stages, we observed unanticipated patterns of traction forces pointing towards the wound. Such patterns have strong force components that are both radial and tangential to the wound. We show that these force components arise from tensions transmitted by a heterogeneous actomyosin ring to the underlying substrate through focal adhesions. The structural and mechanical organization reported here provides cells with a mechanism to close the wound by cooperatively compressing the underlying substrate. PMID:27340423

  4. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  5. Unraveling Base Stacking Driving Forces in DNA.

    PubMed

    Mak, Chi H

    2016-07-01

    Base stacking is a key determinant of nucleic acid structures, but the precise origin of the thermodynamic driving force behind the stacking of nucleobases remains open. The rather mild stacking free energy measured experimentally, roughly a kcal/mol depending on the identity of the bases, is physiologically significant because while base stacking confers stability to the genome in its double helix form, the duplex also has to be unwound in order to be replicated or transcribed. A stacking free energy that is either too high or too low will over- or understabilize the genome, impacting the storage of genetic information and also its retrieval. While the molecular origin of stacking driving force has been attributed to many different sources including dispersion, electrostatics, and solvent hydrogen bonding, here we show via a systematic decomposition of the stacking free energy using large-scale computer simulations that the dominant driving force stabilizing base stacking is nonhydrophobic solvent entropy. Counteracting this is the conformational entropic penalty on the sugar-phosphate backbone against stacking, while solvent hydrogen-bonding, charge-charge interactions, and dispersive forces produce only secondary perturbations. Solvent entropic forces and DNA backbone conformational strains therefore work against each other, leading to a very mild composite stacking free energy in agreement with experiments. PMID:27045853

  6. Controlling Casimir force via coherent driving field

    NASA Astrophysics Data System (ADS)

    Ahmad, Rashid; Abbas, Muqaddar; Ahmad, Iftikhar; Qamar, Sajid

    2016-04-01

    A four level atom-field configuration is used to investigate the coherent control of Casimir force between two identical plates made up of chiral atomic media and separated by vacuum of width d. The electromagnetic chirality-induced negative refraction is obtained via atomic coherence. The behavior of Casimir force is investigated using Casimir-Lifshitz formula. It is noticed that Casimir force can be switched from repulsive to attractive and vice versa via coherent control of the driving field. This switching feature provides new possibilities of using the repulsive Casimir force in the development of new emerging technologies, such as, micro-electro-mechanical and nano-electro-mechanical systems, i.e., MEMS and NEMS, respectively.

  7. Study of scratch drive actuator force characteristics

    NASA Astrophysics Data System (ADS)

    Li, Lijie; Brown, J. Gordon; Uttamchandani, Deepak

    2002-11-01

    Microactuators are one of the key components in MEMS technology, and various designs have been realized through different fabrication processes. One type of microactuator commonly used is the scratch drive actuator (SDA) that is frequently fabricated by surface micromachining processes. An experimental investigation has been conducted on the force characteristics of SDAs fabricated using the JDSU Microsystems MUMPs process. One-, two-, three- and four-plate SDAs connected to box-springs have been designed and fabricated for these experiments using MUMPs run 44. The spring constant for the box-springs has been calculated by FEM using ANSYS software. The product of the spring constant and spring extension is used to measure the forces produced by these SDAs. It is estimated that the forces produced exceed 250 μN from a one-plate SDA and 850 μN from a four-plate SDA.

  8. Driving forces behind integration: weigh your options.

    PubMed

    Friend, P M; Meighan, S

    1994-01-01

    Collaborative relationships between hospitals and physicians can take many forms. Before you choose your strategy, consider the benefits and drawbacks of each. Many of America's hospitals and physicians are rushing to integrate their services through a variety of collaborative options. Their haste has been encouraged by many factors. Before hospitals and physicians react to the driving forces around them, they should carefully consider the pros and cons of four types of collaborative options: 1. management service organizations, 2. physician-hospital organizations, 3. practice acquisition models, 4. equity models. PMID:10133599

  9. Forces driving epithelial spreading in zebrafish gastrulation.

    PubMed

    Behrndt, Martin; Salbreux, Guillaume; Campinho, Pedro; Hauschild, Robert; Oswald, Felix; Roensch, Julia; Grill, Stephan W; Heisenberg, Carl-Philipp

    2012-10-12

    Contractile actomyosin rings drive various fundamental morphogenetic processes ranging from cytokinesis to wound healing. Actomyosin rings are generally thought to function by circumferential contraction. Here, we show that the spreading of the enveloping cell layer (EVL) over the yolk cell during zebrafish gastrulation is driven by a contractile actomyosin ring. In contrast to previous suggestions, we find that this ring functions not only by circumferential contraction but also by a flow-friction mechanism. This generates a pulling force through resistance against retrograde actomyosin flow. EVL spreading proceeds normally in situations where circumferential contraction is unproductive, indicating that the flow-friction mechanism is sufficient. Thus, actomyosin rings can function in epithelial morphogenesis through a combination of cable-constriction and flow-friction mechanisms. PMID:23066079

  10. Numerical calculations of the driving force on an Abrikosov vortex

    NASA Astrophysics Data System (ADS)

    Chen, D.-X.; Pardo, E.; Sanchez, A.

    2010-05-01

    The driving force on an Abrikosov vortex is calculated numerically from the London equation and involved energies for a vortex perpendicular to the screening current near the surface of a superconductor. Compared with previous analytical derivation of the total force, the partial magnetic, kinematic, and external forces are also obtained so that the nature of the driving force may be deeply discussed. It is shown that the force is neither a Lorentz force nor a Magnus force as often believed and that in order to get a correct result, the image effects and the work done by the applied field must be taken into account. A name of London force is suggested for the driving force. A deep understanding of the nature of the driving force on Abrikosov vortices may also be important in the study of vortex pinning and dynamics in type-II superconductors.

  11. Unmanned Turning Force Control Based on the Spindle Drive Characteristics

    NASA Astrophysics Data System (ADS)

    Huh, Kunsoo; Pak, Changho

    While the rough turning process is machining a workpiece at various cutting depth, the feedrate is usually selected based on the maximum depth of cut. Even if this selection can avoid power saturation or tool breakage, it is very conservative compared to the capacity of machine tools and can reduce the productivity significantly. Many adaptive control techniques have been reported that can adjust the feedrate to maintain the constant cutting force. However, these controllers are not very widely used in manufacturing industry because of the limitations in measuring the cutting force signals and selecting the appropriate cutting force level. In this paper, an unmanned turning process control system is proposed based on the spindle drive characteristics. A synthesized cutting force monitor is introduced to estimate the cutting force as accurately as a dynamometer does. The reference cutting force level as well as the feed-rate is selected considering the spindle motor characteristics. Because the cutting process is highly nonlinear, a fuzzy logic controller is applied to maintain the desired cutting force level. The experimental results demonstrate that the proposed system can be easily realized in CNC lathe with requiring little additional hardware.

  12. Driving forces: Slab subduction and mantle convection

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1988-01-01

    Mantle convection is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the convecting mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle convection and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar convecting systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple convection experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle convection.

  13. Inversion for the driving forces of plate tectonics

    NASA Technical Reports Server (NTRS)

    Richardson, R. M.

    1983-01-01

    Inverse modeling techniques have been applied to the problem of determining the roles of various forces that may drive and resist plate tectonic motions. Separate linear inverse problems have been solved to find the best fitting pole of rotation for finite element grid point velocities and to find the best combination of force models to fit the observed relative plate velocities for the earth's twelve major plates using the generalized inverse operator. Variance-covariance data on plate motion have also been included. Results emphasize the relative importance of ridge push forces in the driving mechanism. Convergent margin forces are smaller by at least a factor of two, and perhaps by as much as a factor of twenty. Slab pull, apparently, is poorly transmitted to the surface plate as a driving force. Drag forces at the base of the plate are smaller than ridge push forces, although the sign of the force remains in question.

  14. OSHA Laboratory Standard: Driving Force for Laboratory Safety!

    ERIC Educational Resources Information Center

    Roy, Kenneth R.

    2000-01-01

    Discusses the Occupational Safety and Health Administration's (OSHA's) Laboratory Safety Standards as the major driving force in establishing and maintaining a safe working environment for teachers and students. (Author)

  15. Vaccine Refusal a Driving Force Behind Measles Outbreaks, Study Finds

    MedlinePlus

    ... nlm.nih.gov/medlineplus/news/fullstory_157778.html Vaccine Refusal a Driving Force Behind Measles Outbreaks, Study ... than half of the cases involved unvaccinated children. Vaccine refusal was also often the culprit in whooping ...

  16. Entropic forces drive contraction of cytoskeletal networks.

    PubMed

    Braun, Marcus; Lansky, Zdenek; Hilitski, Feodor; Dogic, Zvonimir; Diez, Stefan

    2016-05-01

    The cytoskeleton is a network of interconnected protein filaments, which provide a three-dimensional scaffold for cells. Remodeling of the cytoskeleton is important for key cellular processes, such as cell motility, division, or morphogenesis. This remodeling is traditionally considered to be driven exclusively by processes consuming chemical energy, such as the dynamics of the filaments or the action of molecular motors. Here, we review two mechanisms of cytoskeletal network remodeling that are independent of the consumption of chemical energy. In both cases directed motion of overlapping filaments is driven by entropic forces, which arise from harnessing thermal energy present in solution. Entropic forces are induced either by macromolecular crowding agents or by diffusible crosslinkers confined to the regions where filaments overlap. Both mechanisms increase filament overlap length and lead to the contraction of filament networks. These force-generating mechanisms, together with the chemical energy-dependent mechanisms, need to be considered for the comprehensive quantitative picture of the remodeling of cytoskeletal networks in cells. PMID:26996935

  17. Developing pressures: fluid forces driving morphogenesis.

    PubMed

    Navis, Adam; Bagnat, Michel

    2015-06-01

    Over several decades genetic studies have unraveled many molecular mechanisms that underlie the signaling networks guiding morphogenesis, but the mechanical forces at work remain much less well understood. Accumulation of fluid within a luminal space can generate outward hydrostatic pressure capable of shaping morphogenesis at several scales, ranging from individual organs to the entire vertebrate body-plan. Here, we focus on recent work that uncovered mechanical roles for fluid secretion during morphogenesis. Identifying the roles and regulation of fluid secretion will be instrumental for understanding the mechanics of morphogenesis as well as many human diseases of complex genetic and environmental origin including secretory diarrheas and scoliosis. PMID:25698116

  18. Ocean forcing drives glacier retreat sometimes

    NASA Astrophysics Data System (ADS)

    Bassis, J. N.; Ultee, E.; Ma, Y.

    2015-12-01

    Observations show that marine-terminating glaciers respond to climate forcing nonlinearly, with periods of slow or negligible glacier advance punctuated by abrupt, rapid retreat. Once glacier retreat has initiated, glaciers can quickly stabilize with a new terminus position. Alternatively, retreat can be sustained for decades (or longer), as is the case for Columbia Glacier, Alaska where retreat initiated ~1984 and continues to this day. Surprisingly, patterns of glacier retreat show ambiguous or even contradictory correlations with atmospheric temperature and glacier surface mass balance. Despite these puzzles, observations increasingly show that intrusion of warm subsurface ocean water into fjords can lead to glacier erosion rates that can account for a substantial portion of the total mass lost from glaciers. Here we use a simplified flowline model to show that even relatively modest submarine melt rates (~100 m/a) near the terminus of grounded glaciers can trigger large increases in iceberg calving leading to rapid glacier retreat. However, the strength of the coupling between submarine melt and calving is a strong function of the geometry of the glacier (bed topography, ice thickness and glacier width). This can lead to irreversible retreat when the terminus is thick and grounded deeply beneath sea level or result in little change when the glacier is relatively thin, grounded in shallow water or pinned in a narrow fjord. Because of the strong dependence on glacier geometry, small perturbations in submarine melting can trigger glaciers in their most advanced—and geometrically precarious—state to undergo sudden retreat followed by much slower re-advance. Although many details remain speculative, our model hints that some glaciers are more sensitive than others to ocean forcing and that some of the nonlinearities of glacier response to climate change may be attributable to variations in difficult-to-detect subsurface water temperatures that need to be better

  19. Wall relaxation and the driving forces for cell expansive growth

    NASA Technical Reports Server (NTRS)

    Cosgrove, D. J.

    1987-01-01

    When water uptake by growing cells is prevented, the turgor pressure and the tensile stress in the cell wall are reduced by continued wall loosening. This process, termed in vivo stress relaxation, provides a new way to study the dynamics of wall loosening and to measure the wall yield threshold and the physiological wall extensibility. Stress relaxation experiments indicate that wall stress supplies the mechanical driving force for wall yielding. Cell expansion also requires water absorption. The driving force for water uptake during growth is created by wall relaxation, which lowers the water potential of the expanding cells. New techniques for measuring this driving force show that it is smaller than believed previously; in elongating stems it is only 0.3 to 0.5 bar. This means that the hydraulic resistance of the water transport pathway is small and that rate of cell expansion is controlled primarily by wall loosening and yielding.

  20. Sequential reconstruction of driving-forces from nonlinear nonstationary dynamics

    NASA Astrophysics Data System (ADS)

    Güntürkün, Ulaş

    2010-07-01

    This paper describes a functional analysis-based method for the estimation of driving-forces from nonlinear dynamic systems. The driving-forces account for the perturbation inputs induced by the external environment or the secular variations in the internal variables of the system. The proposed algorithm is applicable to the problems for which there is too little or no prior knowledge to build a rigorous mathematical model of the unknown dynamics. We derive the estimator conditioned on the differentiability of the unknown system’s mapping, and smoothness of the driving-force. The proposed algorithm is an adaptive sequential realization of the blind prediction error method, where the basic idea is to predict the observables, and retrieve the driving-force from the prediction error. Our realization of this idea is embodied by predicting the observables one-step into the future using a bank of echo state networks (ESN) in an online fashion, and then extracting the raw estimates from the prediction error and smoothing these estimates in two adaptive filtering stages. The adaptive nature of the algorithm enables to retrieve both slowly and rapidly varying driving-forces accurately, which are illustrated by simulations. Logistic and Moran-Ricker maps are studied in controlled experiments, exemplifying chaotic state and stochastic measurement models. The algorithm is also applied to the estimation of a driving-force from another nonlinear dynamic system that is stochastic in both state and measurement equations. The results are judged by the posterior Cramer-Rao lower bounds. The method is finally put into test on a real-world application; extracting sun’s magnetic flux from the sunspot time series.

  1. On the driving force of PAH production

    NASA Technical Reports Server (NTRS)

    Frenklach, Michael

    1989-01-01

    The kinetic factors affecting the production of polycyclic aromatic hydrocarbons (PAH) in high-temperature pyrolysis and combustion environments are analyzed. A lumped kinetic model representing polymerization-type growth by one irreversible step and two reversible steps is considered. It is shown that at high temperatures, PAH growth is controlled by the superequilibrium of hydrogen atoms; at low temperatures and low H2 concentrations, the PAH growth rate is proportional to the rate of the H-abstraction of a hydrogen atom from aromatic molecules; while at low temperatures and high H2 concentrations, it is controlled by the thermodynamics of the H-abstraction and the kinetics of acetylene addition to aromatic radicals. The presence of oxygen mainly affects the small-molecule reactions during the induction period.

  2. Pattern-formation under acoustic driving forces

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2015-07-01

    Chemical and metallurgical processes enhanced by high intensity acoustic waves, thermoacoustic engines and refrigerators, fuel rods in nuclear reactors, heat exchanger tubes, offshore and vibrating structures, solar thermal collectors, acoustic levitators, microfluidic devices, cycling, musical acoustics, blood flow through veins/arteries, hearing in the mammalian ear, carbon nanotube loudspeakers, etc. The evolution of a myriad of processes involving the oscillation of viscous fluids in the presence of solid boundaries is up to a certain extent influenced by acoustic streaming. In addition to the sound field, viscous energy dissipation at the fluid-solid boundary causes a time-independent fluid circulation, which can lead to a significant enhancement of heat, mass and momentum transfer at large oscillation amplitudes. A particularly relevant phenomenon that can be notably affected by acoustic streaming is the promotion of sound waves by temperature gradients or viceversa (thermoacoustics), which is at the basis of potentially efficient and environmental friendly engines and refrigerators that have attracted a renewed interest in the last years. In the present manuscript, historical developments and the underlying basic physics behind acoustic streaming and thermoacoustics are reviewed from an unifying perspective.

  3. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

    PubMed Central

    Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind

    2012-01-01

    Summary We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. PMID:22563531

  4. Designing Teaching Facilities: Pedagogy as the Driving Force

    ERIC Educational Resources Information Center

    Stump, Karen H.; Swensen, Jill

    2005-01-01

    Pedagogy, the art and science of teaching, should be the driving force behind the design of any teaching facility. What is taught and how it is taught should determine the size, type, and configuration of educational space. The statement seems obvious, but often miscommunication and ill-considered compromises can divert a capital project from an…

  5. Drunk Driving Among Novice Drivers, Possible Prevention with Additional Psychological Module in Driving School Curriculum

    PubMed Central

    Eensoo, Diva; Paaver, Marika; Harro, Jaanus

    2011-01-01

    Road traffic collisions caused by drunk driving pose a significant public health problem all over the world. Therefore additional preventive activities against drunk driving should be worked out. The aim of the study was to assess drunk driving in novice drivers after a psychological intervention taking into account also impulsivity, law obedience, and alcohol-related measures. An intervention study was started with 1889 car driver’s license attempters during their driving school studies. Subjects were classified as intervention group (n=1083, mean age 23.1 (SD=7.4) years), control group (n=517, mean age 22.8 (SD=7.1) years) and “lost” group (n=289, mean age 23.0 (SD=6.9) years). “Lost” group subjects had been assigned into the intervention group, but they did not participate in the intervention. Subjects of the intervention group participated in a psychological intervention on the dangers of impulsive behavior in traffic. After a three year follow-up period it appeared that in the control group and in the lost group there was a significantly higher proportion of drunk drivers than in the intervention group, 3.3% (n=17), 3.5% (n=10) and 1.5% (n=10) (p=0.026), respectively. Survival analysis confirmed that psychological intervention had a significant impact on drunk driving (p=0.015), and the impact of the intervention was persistent also in the case of higher scores in Mild social deviance. In subjects with higher scores in impulsivity measures and alcohol-related problems the impact of short psychological intervention was not sufficient for preventing drunk driving. It can be concluded that psychological intervention used during the driving school studies is an effective primary prevention activity against drunk driving. However, for drivers with high scores in impulsivity measures and alcohol-related problems, the short psychological intervention is not sufficient in reducing drunk driving behavior. PMID:22105403

  6. 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

  7. Drive frequency dependent phase imaging in piezoresponse force microscopy

    SciTech Connect

    Bo Huifeng; Kan Yi; Lu Xiaomei; Liu Yunfei; Peng Song; Wang Xiaofei; Cai Wei; Xue Ruoshi; Zhu Jinsong

    2010-08-15

    The drive frequency dependent piezoresponse (PR) phase signal in near-stoichiometric lithium niobate crystals is studied by piezoresponse force microscopy. It is clearly shown that the local and nonlocal electrostatic forces have a great contribution to the PR phase signal. The significant PR phase difference of the antiparallel domains are observed at the contact resonances, which is related to the electrostatic dominated electromechanical interactions of the cantilever and tip-sample system. Moreover, the modulation voltage induced frequency shift at higher eigenmodes could be attributed to the change of indention force depending on the modulation amplitude with a piezoelectric origin. The PR phase of the silicon wafer is also measured for comparison. It is certificated that the electrostatic interactions are universal in voltage modulated scanning probe microscopy and could be extended to other phase imaging techniques.

  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. Impact assessment of land use planning driving forces on environment

    SciTech Connect

    Chen, Longgao; Yang, Xiaoyan; Chen, Longqian; Li, Long

    2015-11-15

    Land use change may exert a negative impact on environmental quality. A state–impact–state (SIS) model describing a state transform under certain impacts has been integrated into land use planning (LUP) environmental impact assessment (LUPEA). This logical model is intuitive and easy to understand, but the exploration of impact is essential to establish the indicator system and to identify the scope of land use environmental impact when it is applied to a specific region. In this study, we investigated environmental driving forces from land use planning (LUPF), along with the conception, components, scope, and impact of LUPF. This method was illustrated by a case study in Zoucheng, China. Through the results, we concluded that (1) the LUPF on environment are impacts originated from the implementation of LUP on a regional environment, which are characterized by four aspects: magnitude, direction, action point, and its owner; (2) various scopes of LUPF on individual environmental elements based on different standards jointly define the final scope of LUPEA; (3) our case study in Zoucheng demonstrates the practicability of this proposed approach; (4) this method can be embedded into LUPEA with direction, magnitudes, and scopes of the LUPF on individual elements obtained, and the identified indicator system can be directly employed into LUPEA and (5) the assessment helps to identify key indicators and to set up a corresponding strategy to mitigate the negative impact of LUP on the environment, which are two important objectives of strategic environmental assessment (SEA) in LUP. - Highlights: • Environmental driving forces from land use planning (LUPF) are investigated and categorized. • Our method can obtains the direction, magnitudes and scopes of environmental driving forces. • The LUPEA scope is determined by the combination of various scopes of LUPF on individual elements. • LUPF assessment can be embedded into LUPEA. • The method can help to

  10. 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

  11. Force control compensation method with variable load stiffness and damping of the hydraulic drive unit force control system

    NASA Astrophysics Data System (ADS)

    Kong, Xiangdong; Ba, Kaixian; Yu, Bin; Cao, Yuan; Zhu, Qixin; Zhao, Hualong

    2016-05-01

    Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit (HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this

  12. Force control compensation method with variable load stiffness and damping of the hydraulic drive unit force control system

    NASA Astrophysics Data System (ADS)

    Kong, Xiangdong; Ba, Kaixian; Yu, Bin; Cao, Yuan; Zhu, Qixin; Zhao, Hualong

    2016-04-01

    Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit (HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this

  13. Traction-drive force transmission for telerobotic joints

    NASA Technical Reports Server (NTRS)

    Kuban, D. P.; Williams, D. M.

    1989-01-01

    The U.S. Space Station Program is providing many technological developments to meet the increasing demands of designing such a facility. One of the key areas of research is that of telerobotics for space station assembly and maintenance. Initial implementation will be teleoperated, but long-term plans call for autonomous robotics. One of the essential components for making this transition successful is the manipulator joints mechanism. Historically, teleoperated manipulators and industrial robotics have had very different mechanisms for force transmission. This is because the design objectives are almost mutually exclusive. A teleoperator must have very low friction and inertia to minimize operator fatigue; backlash and stiffness are of secondary concern. A robot, however, must have minimum backlash, and high stiffness for accurate and rapid positioning. A joint mechanism has yet to be developed that can optimize these divergent performance objectives. A joint mechanism that approaches this optimal performance was developed for NASA Langley, Automation Technology Branch. It is a traction-drive differential that uses variable preload mechanisms. The differential provides compact, dexterous motion range with a torque density similar to geared systems. The traction drive offers high stiffness and zero backlash, for good robotic performance, and the variable loading mechanism (VLM) minimizes the drive-train friction, for improved teleoperation.

  14. The thermodynamic driving force for rafting in superalloys

    SciTech Connect

    Nabarro, F.R.N.; Cress, C.M. |; Kotschy

    1996-08-01

    Eshelby`s energy-momentum tensor is used to provide an analytical expression for the driving force for rafting in the elastic regime in a superalloy with a high volume fraction of {gamma}{prime}. The structure is modelled as a simple cubic array of {gamma}{prime} cubes separated by thin sheets of {gamma}. During rafting, the {gamma}{prime} particles are constrained to remain tetragonal prisms. For tension along a cube axis, the driving force is proportional to the product of the tension {sigma}, the fractional difference {delta} of lattice parameters of {gamma}{prime} and {gamma} and the fractional difference m of their elastic constants c{sub 11} {minus} c{sub 12}. As in the calculation of Pineau for an isolated spheroid, needles are formed when this product {sigma}{delta}m is positive. Two- and three-dimensional systems behave similarly. The initial plastic strain in {gamma} is anelastic and in principle reversible. When the plastic strain exceeds m{delta}, platelets perpendicular to the stress axis are formed if the product {sigma}{delta} is negative.

  15. The chemical driving force for rafting in superalloys

    SciTech Connect

    Nabarro, F.R.N. |

    1997-08-15

    Until recently, all theories of the driving force for rafting have considered the compositions of the two phases to be fixed, although accepting that the rate of rafting might be controlled by diffusion. When plastic flow occurs, the difference in elastic constants becomes negligible. A high energy density builds up in the transverse {gamma} sheets, and rafting occurs by outward motion of the transverse interfaces, reducing the volume which has a high energy density. The analysis considers only the change in enthalpy between two states, one in which the two phases have the compositions which are in equilibrium in the absence of external stress, the external stress has been applied, but no diffusion has occurred, and one in which the two phases have the homogeneous compositions which are in equilibrium under the applied stress. The authors do not attempt to treat the intermediate configuration in which some diffusion has occurred, but the compositions of the phases are inhomogeneous.

  16. Interaction Forces Drive the Environmental Transmission of Pathogenic Protozoa

    PubMed Central

    Aubert, Dominique; Puech, Pierre-Henri; Hohweyer, Jeanne; Azas, Nadine; Villena, Isabelle

    2012-01-01

    The protozoan parasites Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (Giardia) and oocysts (Cryptosporidium and Toxoplasma), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites' surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano- to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano- to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution. PMID:22156429

  17. Molecular pathology as the driving force for personalized oncology.

    PubMed

    Oktay, Maja H; Hui, Pei

    2012-11-01

    Innovative Tissue-Based Diagnostics Philadelphia, PA, USA, 4-5 June 2012 This article focuses on the current and emerging molecular diagnostics relevant to clinical practice of oncology discussed in the session of Molecular Pathology as the Driving Force for Personalized Oncology, one of the three main themes of innovative tissue-based diagnostics with the other two being pathology in cancer drug development, and in vivo microscopy and intraoperative imaging. The session brought together seven topics and a keynote presentation in the area of precision cancer diagnosis and treatment: single gene molecular testing as the most popular cancer molecular diagnostics in current time, panel gene mutation analysis as an emerging theme for cancer therapy targeting at multiple signaling pathways, and the next-generation sequencing platform - an ultimate molecular analysis of cancer for future clinical practice. Novel tactics based on existing technology were emphasized including in vitro drug sensitivity testing and exploring immunohistochemistry in combination with histocytological assays for risk assessment of tumor metastasis and layered immunohistochemistry to predict tumor response to target cancer treatment. Clinical molecular assay development, verification and validation were among practical topics in molecular diagnostic operations. The conference was culminated by Marc Ladanyi's keynote presentation of the current and future strategies for comprehensive routine clinical genotyping of lung cancers for optimal selection of targeted therapies. PMID:23249199

  18. Self-driving capacitive cantilevers for high-frequency atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Brown, Keith A.; Yang, Benjamin H.; Westervelt, R. M.

    2012-01-01

    We demonstrate a simple way to actuate an atomic force microscope cantilever at high frequencies by electrically driving a thin-film capacitor on its surface. Capacitive driving directly actuates the vibrational mode of the cantilever, removing the effects of unwanted mechanical modes present in conventional driving systems and removing the need for a drive piezoelectric. Practical vibration amplitudes are attainable at drive voltages <5 V. We capacitively drive the first mechanical resonance of a tapping mode cantilever (243 kHz) and a high-frequency cantilever (1.5 MHz) with vibration amplitudes in agreement with our model of capacitive driving.

  19. The driving force for glide of a threading dislocation in a strained epitaxial layer on a substrate

    NASA Astrophysics Data System (ADS)

    Freund, L. B.

    T HE PROCESS of epitaxial growth of a very thin layer onto a substrate crystal is considered for the particular situation in which the layer and substrate materials have the same crystal structure and orientation but different lattice parameters. Under these conditions, the layer grows with an intrinsic elastic strain determined by the mismatch in lattice parameters. The associated stress in the crystalline layer provides a driving force for the nucleation and motion of defects, primarily dislocations. The focus here is on the glide of a dislocation extending from the free surface of the layer to the layer-substrate interface, the so-called threading dislocation. A general definition of driving force for glide of a threading dislocation is introduced on the basis of work arguments. The definition is then applied to calculate the driving force for steady motion of an isolated threading dislocation in a strained layer, and the result includes Matthews' critical thickness concept as one of its features. Next, a kinetic equation for glide of a dislocation in semiconductor materials is proposed to estimate the glide rate of a threading dislocation in these low mobility materials. Finally, for the case of cubic materials, the general definition of driving force is applied to estimate the additional driving force on a threading dislocation due to an encounter with a dislocation on an intersecting glide plane. The results indicate that this effect is significant in blocking the glide of a threading dislocation for large mismatch strains and for layer thicknesses near the critical thickness.

  20. Traction-drive force transmission for telerobotic joints

    NASA Technical Reports Server (NTRS)

    Williams, D. M.; Kuban, D. P.

    1989-01-01

    A mechanism which meets the requirements of a teleoperated manipulator and those of an autonomous robot is discussed. The mechanism is a traction-drive differential that uses variable preload mechanisms. The differential provides compact design, with dextrous motion range and torque density similar to geared systems. The traction drive offers high stiffness to backlash for good robotic performance. The variable-loading mechanism (VLM) minimizes the drive-train friction for improved teleoperation. This combination provides a mechanism to allow advanced manipulation with either teleoperated control or autonomous robotic operation. The design principles of both major components of the joint mechanism are described.

  1. Cation charge dependence of the forces driving DNA assembly.

    PubMed

    DeRouchey, Jason; Parsegian, V Adrian; Rau, Donald C

    2010-10-20

    Understanding the strength and specificity of interactions among biologically important macromolecules that control cellular functions requires quantitative knowledge of intermolecular forces. Controlled DNA condensation and assembly are particularly critical for biology, with separate repulsive and attractive intermolecular forces determining the extent of DNA compaction. How these forces depend on the charge of the condensing ion has not been determined, but such knowledge is fundamental for understanding the basis of DNA-DNA interactions. Here, we measure DNA force-distance curves for a homologous set of arginine peptides. All forces are well fit as the sum of two exponentials with 2.4- and 4.8-Å decay lengths. The shorter-decay-length force is always repulsive, with an amplitude that varies slightly with length or charge. The longer-decay-length force varies strongly with cation charge, changing from repulsion with Arg¹ to attraction with Arg². Force curves for a series of homologous polyamines and the heterogeneous protein protamine are quite similar, demonstrating the universality of these forces for DNA assembly. Repulsive amplitudes of the shorter-decay-length force are species-dependent but nearly independent of charge within each species. A striking observation was that the attractive force amplitudes for all samples collapse to a single curve, varying linearly with the inverse of the cation charge. PMID:20959102

  2. Additive CHARMM force field for naturally occurring modified ribonucleotides.

    PubMed

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D; Nilsson, Lennart

    2016-04-15

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all-atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. PMID:26841080

  3. Additive CHARMM force field for naturally occurring modified ribonucleotides

    PubMed Central

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D.

    2016-01-01

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all‐atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26841080

  4. Nonlinear forced response of electromechanical integrated toroidal drive to coupled excitation.

    PubMed

    Xu, Lizhong; Wang, Fen

    2012-01-01

    The electric excitation and the parameter excitation from mesh stiffness fluctuation are analyzed. The forced response equations of the drive system to the coupled excitations are presented. For the exciting frequencies far from and near natural frequencies, the forced responses of the drive system to the coupled excitations are investigated. Results show that the nonlinear forced responses of the drive system to the coupled excitations change periodically and unsteadily; the time period of the nonlinear forced responses depends on the frequencies of the electric excitation, the mesh parameter excitation, and the nonlinear natural frequencies of the drive system; in order to improve the dynamics performance of the drive system, the frequencies of the electric excitations should not be taken as integral multiple of the mesh parameter exciting frequency. PMID:23251105

  5. Driving forces behind the construction of an eco-compensation mechanism for wetlands in China

    NASA Astrophysics Data System (ADS)

    Wang, Changhai

    2016-09-01

    This research revealed important driving forces behind the construction of an eco-compensation mechanism for wetlands (DFEMW) in China. Using China's provincial panel data from 1978 to 2008, a fixed-effects model was used to analyze the impacts of agricultural production systems on wetlands. We identified three DFEMW as follows: the change of wetland resources and protection measures in China; declaration and implementation of the provincial Wetland Protection Ordinance; and wetland degradation by agricultural production systems, which necessitated the establishment of a wetland eco-compensation mechanism. In addition to the DFEMW, a significant positive correlation between wetland area and both rural population and gross agricultural production was identified, in addition to a negative correlation with chemical fertilizer usage, reservoir storage capacity, and irrigation area. The underlying reasons for the serious degradation and inadequate protection of wetlands were market failure and government failure; these were the driving forces behind the need to establish a wetland eco-compensation mechanism. From a governmental perspective, it has been difficult to rectify market failures in resource distribution and thus to prevent wetland degradation. Factors include conflicts of interest, lack of investment, effective special laws, a simple means to protect wetlands, and a multidisciplinary management system. Therefore, the key factor is the coordination of interest relationships between those who utilize wetlands and those who seek to minimize wetland degradation and effectively protect wetlands.

  6. Driving forces behind the construction of an eco-compensation mechanism for wetlands in China

    NASA Astrophysics Data System (ADS)

    Wang, Changhai

    2016-03-01

    This research revealed important driving forces behind the construction of an eco-compensation mechanism for wetlands (DFEMW) in China. Using China's provincial panel data from 1978 to 2008, a fixed-effects model was used to analyze the impacts of agricultural production systems on wetlands. We identified three DFEMW as follows: the change of wetland resources and protection measures in China; declaration and implementation of the provincial Wetland Protection Ordinance; and wetland degradation by agricultural production systems, which necessitated the establishment of a wetland eco-compensation mechanism. In addition to the DFEMW, a significant positive correlation between wetland area and both rural population and gross agricultural production was identified, in addition to a negative correlation with chemical fertilizer usage, reservoir storage capacity, and irrigation area. The underlying reasons for the serious degradation and inadequate protection of wetlands were market failure and government failure; these were the driving forces behind the need to establish a wetland eco-compensation mechanism. From a governmental perspective, it has been difficult to rectify market failures in resource distribution and thus to prevent wetland degradation. Factors include conflicts of interest, lack of investment, effective special laws, a simple means to protect wetlands, and a multidisciplinary management system. Therefore, the key factor is the coordination of interest relationships between those who utilize wetlands and those who seek to minimize wetland degradation and effectively protect wetlands.

  7. True polar wander and plate-driving forces

    NASA Technical Reports Server (NTRS)

    Davis, D. M.; Solomon, S. C.

    1985-01-01

    The nature of net torques applied to the lithosphere by ridge and trench forces as implied by the absence of recent true polar wander is explored. The 'ridge push' and 'trench pull' forces and the potential net torques on the global lithosphere contributed by each of these forces are discussed. It is shown that the relative magnitudes of the net torques contributed by ridge and trench forces are constrained by the absence of true polar wander during the Cenozoic and by the magnitudes of basal shear stresses on the faster moving plates. It is suggested that the lack of recent true polar wander may be due at least in part to the coincidence of a near cancellation of net torques contributed by ridge and trench forces.

  8. Self-Motion Depending on the Physicochemical Properties of Esters as the Driving Force

    ERIC Educational Resources Information Center

    Nakata, Satoshi; Matsuo, Kyoko; Kirisaka, Junko

    2007-01-01

    The self-motion of an ester boat is investigated depending on the physicochemical properties of the surface-active substance. The results show that the ester boat moves towards the higher surface tension generating as the driving force.

  9. Theory of polymer translocation through a flickering nanopore under an alternating driving force

    NASA Astrophysics Data System (ADS)

    Sarabadani, Jalal; Ikonen, Timo; Ala-Nissila, Tapio

    2015-08-01

    We develop a theory for polymer translocation driven by a time-dependent force through an oscillating nanopore. To this end, we extend the iso-flux tension propagation theory [Sarabadani et al., J. Chem. Phys. 141, 214907 (2014)] for such a setup. We assume that the external driving force in the pore has a component oscillating in time, and the flickering pore is similarly described by an oscillating term in the pore friction. In addition to numerically solving the model, we derive analytical approximations that are in good agreement with the numerical simulations. Our results show that by controlling either the force or pore oscillations, the translocation process can be either sped up or slowed down depending on the frequency of the oscillations and the characteristic time scale of the process. We also show that while in the low and high frequency limits, the translocation time τ follows the established scaling relation with respect to chain length N0, in the intermediate frequency regime small periodic, fluctuations can have drastic effects on the dynamical scaling. The results can be easily generalized for non-periodic oscillations and elucidate the role of time dependent forces and pore oscillations in driven polymer translocation.

  10. Analysis of Korean Students' International Mobility by 2-D Model: Driving Force Factor and Directional Factor

    ERIC Educational Resources Information Center

    Park, Elisa L.

    2009-01-01

    The purpose of this study is to understand the dynamics of Korean students' international mobility to study abroad by using the 2-D Model. The first D, "the driving force factor," explains how and what components of the dissatisfaction with domestic higher education perceived by Korean students drives students' outward mobility to seek foreign…

  11. Nano-rheology of hydrogels using direct drive force modulation atomic force microscopy.

    PubMed

    Nalam, Prathima C; Gosvami, Nitya N; Caporizzo, Matthew A; Composto, Russell J; Carpick, Robert W

    2015-11-01

    We present a magnetic force-based direct drive modulation method to measure local nano-rheological properties of soft materials across a broad frequency range (10 Hz to 2 kHz) using colloid-attached atomic force microscope (AFM) probes in liquid. The direct drive method enables artefact-free measurements over several decades of excitation frequency, and avoids the need to evaluate medium-induced hydrodynamic drag effects. The method was applied to measure the local mechanical properties of polyacrylamide hydrogels. The frequency-dependent storage stiffness, loss stiffness, and loss tangent (tan δ) were quantified for hydrogels having high and low crosslinking densities by measuring the amplitude and the phase response of the cantilever while the colloid was in contact with the hydrogel. The frequency bandwidth was further expanded to lower effective frequencies (0.1 Hz to 10 Hz) by obtaining force-displacement (FD) curves. Slow FD measurements showed a recoverable but highly hysteretic response, with the contact mechanical behaviour dependent on the loading direction: approach curves showed Hertzian behaviour while retraction curves fit the JKR contact mechanics model well into the adhesive regime, after which multiple detachment instabilities occurred. Using small amplitude dynamic modulation to explore faster rates, the load dependence of the storage stiffness transitioned from Hertzian to a dynamic punch-type (constant contact area) model, indicating significant influence of material dissipation coupled with adhesion. Using the appropriate contact model across the full frequency range measured, the storage moduli were found to remain nearly constant until an increase began near ∼100 Hz. The softer gels' storage modulus increased from 7.9 ± 0.4 to 14.5 ± 2.1 kPa (∼85%), and the stiffer gels' storage modulus increased from 16.3 ± 1.1 to 31.7 ± 5.0 kPa (∼95%). This increase at high frequencies may be attributed to a contribution from solvent

  12. Axial force and efficiency tests of fixed center variable speed belt drive

    NASA Technical Reports Server (NTRS)

    Bents, D. J.

    1981-01-01

    An investigation of how the axial force varies with the centerline force at different speed ratios, speeds, and loads, and how the drive's transmission efficiency is affected by these related forces is described. The tests, intended to provide a preliminary performance and controls characterization for a variable speed belt drive continuously variable transmission (CVT), consisted of the design and construction of an experimental test rig geometrically similar to the CVT, and operation of that rig at selected speed ratios and power levels. Data are presented which show: how axial forces exerted on the driver and driven sheaves vary with the centerline force at constant values of speed ratio, speed, and output power; how the transmission efficiency varies with centerline force and how it is also a function of the V belt coefficient; and the axial forces on both sheaves as normalized functions of the traction coefficient.

  13. Nonlinearly Additive Forces in Multivalent Ligand Binding to a Single Protein Revealed with Force Spectroscopy

    SciTech Connect

    Ratto, T V; Rudd, R E; Langry, K C; Balhorn, R L; McElfresh, M W

    2005-07-15

    We present evidence of multivalent interactions between a single protein molecule and multiple carbohydrates at a pH where the protein can bind four ligands. The evidence is based not only on measurements of the force required to rupture the bonds formed between ConcanavalinA (ConA) and {alpha}-D-mannose, but also on an analysis of the polymer-extension force curves to infer the polymer architecture that binds the protein to the cantilever and the ligands to the substrate. We find that although the rupture forces for multiple carbohydrate connections to a single protein are larger than the rupture force for a single connection, they do not scale additively with increasing number. Specifically, the most common rupture forces are approximately 46, 66, and 85 pN, which we argue corresponds to 1, 2, and 3 ligands being pulled simultaneously from a single protein as corroborated by an analysis of the linkage architecture. As in our previous work polymer tethers allow us to discriminate between specific and non-specific binding. We analyze the binding configuration (i.e. serial versus parallel connections) through fitting the polymer stretching data with modified Worm-Like Chain (WLC) models that predict how the effective stiffness of the tethers is affected by multiple connections. This analysis establishes that the forces we measure are due to single proteins interacting with multiple ligands, the first force spectroscopy study that establishes single-molecule multivalent binding unambiguously.

  14. Nano-rheology of hydrogels using direct drive force modulation atomic force microscopy†

    PubMed Central

    Nalam, Prathima C.; Gosvami, Nitya N.; Caporizzo, Matthew A.; Composto, Russell J.

    2016-01-01

    We present a magnetic force-based direct drive modulation method to measure local nano-rheological properties of soft materials across a broad frequency range (10 Hz to 2 kHz) using colloid-attached atomic force microscope (AFM) probes in liquid. The direct drive method enables artefact-free measurements over several decades of excitation frequency, and avoids the need to evaluate medium-induced hydrodynamic drag effects. The method was applied to measure the local mechanical properties of polyacrylamide hydrogels. The frequency-dependent storage stiffness, loss stiffness, and loss tangent (tan δ) were quantified for hydrogels having high and low crosslinking densities by measuring the amplitude and the phase response of the cantilever while the colloid was in contact with the hydrogel. The frequency bandwidth was further expanded to lower effective frequencies (0.1 Hz to 10 Hz) by obtaining force–displacement (FD) curves. Slow FD measurements showed a recoverable but highly hysteretic response, with the contact mechanical behaviour dependent on the loading direction: approach curves showed Hertzian behaviour while retraction curves fit the JKR contact mechanics model well into the adhesive regime, after which multiple detachment instabilities occurred. Using small amplitude dynamic modulation to explore faster rates, the load dependence of the storage stiffness transitioned from Hertzian to a dynamic punch-type (constant contact area) model, indicating significant influence of material dissipation coupled with adhesion. Using the appropriate contact model across the full frequency range measured, the storage moduli were found to remain nearly constant until an increase began near ∼100 Hz. The softer gels' storage modulus increased from 7.9 ± 0.4 to 14.5 ± 2.1 kPa (∼85%), and the stiffer gels' storage modulus increased from 16.3 ± 1.1 to 31.7 ± 5.0 kPa (∼95%). This increase at high frequencies may be attributed to a contribution from solvent

  15. Cancer metabolism as a central driving force of glioma pathogenesis.

    PubMed

    Masui, Kenta; Cavenee, Webster K; Mischel, Paul S

    2016-07-01

    The recent identification of distinct genetic and epigenetic features in each glioma entity is leading to a multilayered, integrated diagnostic approach combining histologic features with molecular genetic information. Somatic mutations in isocitrate dehydrogenase (IDH) and receptor tyrosine kinase (RTK) pathways are key oncogenic events in diffuse gliomas, including lower grade (grade II and III) gliomas (LGG) and the highly lethal brain tumor glioblastoma (GBM), respectively, where they reprogram the epigenome, transcriptome, and metabolome to drive tumor growth. However, the mechanisms by which these genetic aberrations are translated into the aggressive nature of gliomas through metabolic reprogramming have just begun to be unraveled. The intricate interactions between the oncogenic signaling and cancer metabolism have also been recently demonstrated. Here, we describe a set of recent discoveries on cancer metabolism driven by IDH mutation and mutations in RTK pathways, highlighting the integration of genetic mutations, metabolic reprogramming, and epigenetic shifts, potentially providing new therapeutic opportunities. PMID:27295313

  16. The Impact of Evolutionary Driving Forces on Human Complex Diseases: A Population Genetics Approach

    PubMed Central

    Saeb, Amr T. M.; Al-Naqeb, Dhekra

    2016-01-01

    Investigating the molecular evolution of human genome has paved the way to understand genetic adaptation of humans to the environmental changes and corresponding complex diseases. In this review, we discussed the historical origin of genetic diversity among human populations, the evolutionary driving forces that can affect genetic diversity among populations, and the effects of human movement into new environments and gene flow on population genetic diversity. Furthermore, we presented the role of natural selection on genetic diversity and complex diseases. Then we reviewed the disadvantageous consequences of historical selection events in modern time and their relation to the development of complex diseases. In addition, we discussed the effect of consanguinity on the incidence of complex diseases in human populations. Finally, we presented the latest information about the role of ancient genes acquired from interbreeding with ancient hominids in the development of complex diseases. PMID:27313952

  17. The Impact of Evolutionary Driving Forces on Human Complex Diseases: A Population Genetics Approach.

    PubMed

    Saeb, Amr T M; Al-Naqeb, Dhekra

    2016-01-01

    Investigating the molecular evolution of human genome has paved the way to understand genetic adaptation of humans to the environmental changes and corresponding complex diseases. In this review, we discussed the historical origin of genetic diversity among human populations, the evolutionary driving forces that can affect genetic diversity among populations, and the effects of human movement into new environments and gene flow on population genetic diversity. Furthermore, we presented the role of natural selection on genetic diversity and complex diseases. Then we reviewed the disadvantageous consequences of historical selection events in modern time and their relation to the development of complex diseases. In addition, we discussed the effect of consanguinity on the incidence of complex diseases in human populations. Finally, we presented the latest information about the role of ancient genes acquired from interbreeding with ancient hominids in the development of complex diseases. PMID:27313952

  18. Lifetime of metastable states in a Ginzburg-Landau system: Numerical simulations at large driving forces.

    PubMed

    Umantsev, A

    2016-04-01

    We developed a "brute-force" simulation method and conducted numerical "experiments" on homogeneous nucleation in an isotropic system at large driving forces (not small supersaturations) using the stochastic Ginzburg-Landau approach. Interactions in the system are described by the asymmetric (no external field), athermal (temperature-independent driving force), tangential (simple phase diagram) Hamiltonian, which has two independent "drivers" of the phase transition: supersaturation and thermal noise. We obtained the probability distribution function of the lifetime of the metastable state and analyzed its mean value as a function of the supersaturation, noise strength, and volume. We also proved the nucleation theorem in the mean-field approximation. The results allowed us to find the thermodynamic properties of the barrier state and conclude that at large driving forces the fluctuating volumes are not independent. PMID:27176373

  19. Transport and efficiency of Brownian particles in confined narrow channels with a periodic driving force

    NASA Astrophysics Data System (ADS)

    Wang, Rang; Zhou, Jia-Ning; Liu, Xue-Mei; Xiao, Hua

    2015-11-01

    Transport and efficiency of over-damped Brownian particles moving in a confined narrow channel is investigated in the presence of an oscillating force and a static load force. It is found that the average velocity increases monotonously with the unbiased external driving force, while the efficiency can be a peaked function of unbiased external force, which indicates that the unbiased external force can facilitate the efficiency of energy transformation. Moreover, the average velocity and the efficiency demonstrate complex behaviors due to the consideration of Stokes efficiency.

  20. Position and force control of a vehicle with two or more steerable drive wheels

    SciTech Connect

    Reister, D.B.; Unseren, M.A.

    1992-10-01

    When a vehicle with two or more steerable drive wheels is traveling in a circle, the motion of the wheels is constrained. The wheel translational velocity divided by the radius to the center of rotation must be the same for all wheels. When the drive wheels are controlled independently using position control, the motion of the wheels may violate the constraints and the wheels may slip. Consequently, substantial errors can occur in the orientation of the vehicle. A vehicle with N drive wheels has (N - 1) constraints and one degree of freedom. We have developed a new approach to the control of a vehicle with N steerable drive wheels. The novel aspect of our approach is the use of force control. To control the vehicle, we have one degree of freedom for the position on the circle and (N - 1) forces that can be used to reduce errors. Recently, Kankaanranta and Koivo developed a control architecture that allows the force and position degrees of freedom to be decoupled. In the work of Kankaanranta and Koivo the force is an exogenous input. We have made the force endogenous by defining the force in terms of the errors in satisfying the rigid body kinematic constraints. We have applied the control architecture to the HERMIES-III robot and have measured a dramatic reduction in error (more than a factor of 20) compared to motions without force control.

  1. Amplitude modulation atomic force microscopy, is acoustic driving in liquid quantitatively reliable?

    PubMed

    Liu, Fei; Zhao, Cunlu; Mugele, Frieder; van den Ende, Dirk

    2015-09-25

    Measuring quantitative tip-sample interaction forces in dynamic atomic force microscopy in fluids is challenging because of the strong damping of the ambient viscous medium and the fluid-mediated driving forces. This holds in particular for the commonly used acoustic excitation of the cantilever oscillation. Here we present measurements of tip-sample interactions due to conservative DLVO and hydration forces and viscous dissipation forces in aqueous electrolytes using tips with radii varying from typical 20 nm for the DLVO and hydration forces, to 1 μm for the viscous dissipation. The measurements are analyzed using a simple harmonic oscillator model, continuous beam theory with fluid-mediated excitation and thermal noise spectroscopy (TNS). In all cases consistent conservative forces, deviating less than 40% from each other, are obtained for all three approaches. The DLVO forces are even within 5% of the theoretical expectations for all approaches. Accurate measurements of dissipative forces within 15% of the predictions of macroscopic fluid dynamics require the use of TNS or continuous beam theory including fluid-mediated driving. Taking this into account, acoustic driving in liquid is quantitatively reliable. PMID:26335613

  2. Amplitude modulation atomic force microscopy, is acoustic driving in liquid quantitatively reliable?

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Zhao, Cunlu; Mugele, Frieder; van den Ende, Dirk

    2015-09-01

    Measuring quantitative tip-sample interaction forces in dynamic atomic force microscopy in fluids is challenging because of the strong damping of the ambient viscous medium and the fluid-mediated driving forces. This holds in particular for the commonly used acoustic excitation of the cantilever oscillation. Here we present measurements of tip-sample interactions due to conservative DLVO and hydration forces and viscous dissipation forces in aqueous electrolytes using tips with radii varying from typical 20 nm for the DLVO and hydration forces, to 1 μm for the viscous dissipation. The measurements are analyzed using a simple harmonic oscillator model, continuous beam theory with fluid-mediated excitation and thermal noise spectroscopy (TNS). In all cases consistent conservative forces, deviating less than 40% from each other, are obtained for all three approaches. The DLVO forces are even within 5% of the theoretical expectations for all approaches. Accurate measurements of dissipative forces within 15% of the predictions of macroscopic fluid dynamics require the use of TNS or continuous beam theory including fluid-mediated driving. Taking this into account, acoustic driving in liquid is quantitatively reliable.

  3. Experimental modeling of the effect of hurricane wind forces on driving behavior and vehicle performance.

    PubMed

    Rodriguez, Jose M; Codjoe, Julius; Osman, Osama; Ishak, Sherif; Wolshon, Brian

    2015-01-01

    While traffic planning is important for developing a hurricane evacuation plan, vehicle performance on the roads during extreme weather conditions is critical to the success of the planning process. This novel study investigates the effect of gusty hurricane wind forces on the driving behavior and vehicle performance. The study explores how the parameters of a driving simulator could be modified to reproduce wind loadings experienced by three vehicle types (passenger car, ambulance, and bus) during gusty hurricane winds, through manipulation of appropriate software. Thirty participants were then tested on the modified driving simulator under five wind conditions (ranging from normal to hurricane category 4). The driving performance measures used were heading error and lateral displacement. The results showed that higher wind forces resulted in more varied and greater heading error and lateral displacement. The ambulance had the greatest heading errors and lateral displacements, which were attributed to its large lateral surface area and light weight. Two mathematical models were developed to estimate the heading error and lateral displacements for each of the vehicle types for a given change in lateral wind force. Through a questionnaire, participants felt the different characteristics while driving each vehicle type. The findings of this study demonstrate the valuable use of a driving simulator to model the behavior of different vehicle types and to develop mathematical models to estimate and quantify driving behavior and vehicle performance under hurricane wind conditions. PMID:25902298

  4. Crack Driving Forces in a Multilayered Coating System for Ceramic Matrix Composite Substrates

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Zhu, Dongming; Miller, Robert A.

    2005-01-01

    The effects of the top coating thickness, modulus and shrinkage strains on the crack driving forces for a baseline multilayer Yttria-Stabilized-Zirconia/Mullite/Si thermal and environment barrier coating (TEBC) system for SiC/SiC ceramic matrix composite substrates are determined for gas turbine applications. The crack driving forces increase with increasing modulus, and a low modulus thermal barrier coating material (below 10 GPa) will have no cracking issues under the thermal gradient condition analyzed. Since top coating sintering increases the crack driving forces with time, highly sintering resistant coatings are desirable to maintain a low tensile modulus and maintain a low crack driving force with time. Finite element results demonstrated that an advanced TEBC system, such as ZrO2/HfO2, which possesses improved sintering resistance and high temperature stability, exhibited excellent durability. A multi-vertical cracked structure with fine columnar spacing is an ideal strain tolerant coating capable of reducing the crack driving forces to an acceptable level even with a high modulus of 50 GPa.

  5. Modeling of a High Force Density Fishbone Shaped Electrostatic Comb Drive Microactuator

    PubMed Central

    Megat Hasnan, Megat Muhammad Ikhsan; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana; Nik Ghazali, Nik Nazri

    2014-01-01

    This paper presents the design and evaluation of a high force density fishbone shaped electrostatic comb drive actuator. This comb drive actuator has a branched structure similar to a fishbone, which is intended to increase the capacitance of the electrodes and hence increase the electrostatic actuation force. Two-dimensional finite element analysis was used to simulate the motion of the fishbone shaped electrostatic comb drive actuator and compared against the performance of a straight sided electrostatic comb drive actuator. Performances of both designs are evaluated by comparison of displacement and electrostatic force. For both cases, the active area and the minimum gap distance between the two electrodes were constant. An active area of 800 × 300 μm, which contained 16 fingers of fishbone shaped actuators and 40 fingers of straight sided actuators, respectively, was used. Through simulation, improvement of drive force of the fishbone shaped electrostatic comb driver is approximately 485% higher than conventional electrostatic comb driver. These results indicate that the fishbone actuator design provides good potential for applications as high force density electrostatic microactuator in MEMS systems. PMID:25165751

  6. Rare HLA Drive Additional HIV Evolution Compared to More Frequent Alleles

    PubMed Central

    Lockhart, David W.; Listgarten, Jennifer; Maley, Stephen N.; Kadie, Carl; Learn, Gerald H.; Nickle, David C.; Heckerman, David E.; Deng, Wenjie; Brander, Christian; Ndung'u, Thumbi; Coovadia, Hoosen; Goulder, Philip J.R.; Korber, Bette T.; Walker, Bruce D.; Mullins, James I.

    2009-01-01

    Abstract HIV-1 can evolve HLA-specific escape variants in response to HLA-mediated cellular immunity. HLA alleles that are common in the host population may increase the frequency of such escape variants at the population level. When loss of viral fitness is caused by immune escape variation, these variants may revert upon infection of a new host who does not have the corresponding HLA allele. Furthermore, additional escape variants may appear in response to the nonconcordant HLA alleles. Because individuals with rare HLA alleles are less likely to be infected by a partner with concordant HLA alleles, viral populations infecting hosts with rare HLA alleles may undergo a greater amount of evolution than those infecting hosts with common alleles due to the loss of preexisting escape variants followed by new immune escape. This hypothesis was evaluated using maximum likelihood phylogenetic trees of each gene from 272 full-length HIV-1 sequences. Recent viral evolution, as measured by the external branch length, was found to be inversely associated with HLA frequency in nef (p < 0.02), env (p < 0.03), and pol (p ≤ 0.05), suggesting that rare HLA alleles provide a disproportionate force driving viral evolution compared to common alleles, likely due to the loss of preexisting escape variants during early stages postinfection. PMID:19327049

  7. Characterizing a sustainability transition: Goals, targets, trends, and driving forces

    PubMed Central

    Parris, Thomas M.; Kates, Robert W.

    2003-01-01

    Sustainable development exhibits broad political appeal but has proven difficult to define in precise terms. Recent scholarship has focused on the nature of a sustainability transition, described by the National Research Council as meeting the needs of a stabilizing future world population while reducing hunger and poverty and maintaining the planet's life-support systems. We identify a small set of goals, quantitative targets, and associated indicators that further characterize a sustainability transition by drawing on the consensus embodied in internationally negotiated agreements and plans of action. To illustrate opportunities for accelerating progress, we then examine current scholarship on the processes that influence attainment of four such goals: reducing hunger, promoting literacy, stabilizing greenhouse-gas concentrations, and maintaining fresh-water availability. We find that such analysis can often reveal “levers of change,” forces that both control the rate of positive change and are subject to policy intervention. PMID:12819346

  8. Solar Radiation as Driving Force In Early Evolution

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Peterson, David L. (Technical Monitor)

    2002-01-01

    Ultraviolet radiation (UVR) has provided an evolutionary challenge to life on Earth in that it is both an agent of mutation and as well as a selective force. Today surface fluxes of UVR vary diurnally, seasonally, etc. Still, the UVR flux was probably substantially higher during the early phases of evolution, suggesting that its role in evolution was even more prominent during this time. In this presentation, the creative role of UVR in evolution is discussed, specifically in connection with the role that UVR may have played in the evolution of early microbial ecosystems. The presentation will include discussions of the direct influence of UVR on such processes as photosynthesis and genetic damage, as well as the indirect influence of UVR as mediated through the production of reactive oxygen species. These biological effects of UVR will be viewed against the backdrop of the physical nature of the early Earth, surely a very different place then than now.

  9. Estimation of the driving force for dioxygen formation in photosynthesis.

    PubMed

    Nilsson, Håkan; Cournac, Laurent; Rappaport, Fabrice; Messinger, Johannes; Lavergne, Jérôme

    2016-01-01

    Photosynthetic water oxidation to molecular oxygen is carried out by photosystem II (PSII) over a reaction cycle involving four photochemical steps that drive the oxygen-evolving complex through five redox states Si (i = 0,…, 4). For understanding the catalytic strategy of biological water oxidation it is important to elucidate the energetic landscape of PSII and in particular that of the final S4 → S0 transition. In this short-lived chemical step the four oxidizing equivalents accumulated in the preceding photochemical events are used up to form molecular oxygen, two protons are released and at least one substrate water molecule binds to the Mn4CaO5 cluster. In this study we probed the probability to form S4 from S0 and O2 by incubating YD-less PSII in the S0 state for 2–3 days in the presence of (18)O2 and H2(16)O. The absence of any measurable (16,18)O2 formation by water-exchange in the S4 state suggests that the S4 state is hardly ever populated. On the basis of a detailed analysis we determined that the equilibrium constant K of the S4 → S0 transition is larger than 1.0 × 10(7) so that this step is highly exergonic. We argue that this finding is consistent with current knowledge of the energetics of the S0 to S4 reactions, and that the high exergonicity is required for the kinetic efficiency of PSII. PMID:26435390

  10. Hypoxia: The Force that Drives Chronic Kidney Disease

    PubMed Central

    Fu, Qiangwei; Colgan, Sean P; Shelley, Carl Simon

    2016-01-01

    In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy. PMID:26847481

  11. Hypoxia: The Force that Drives Chronic Kidney Disease.

    PubMed

    Fu, Qiangwei; Colgan, Sean P; Shelley, Carl Simon

    2016-03-01

    In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy. PMID:26847481

  12. Changing and Differentiated Urban Landscape in China: Spatiotemporal Patterns and Driving Forces.

    PubMed

    Fang, Chuanglin; Li, Guangdong; Wang, Shaojian

    2016-03-01

    Urban landscape spatiotemporal change patterns and their driving mechanisms in China are poorly understood at the national level. Here we used remote sensing data, landscape metrics, and a spatial econometric model to characterize the spatiotemporal patterns of urban landscape change and investigate its driving forces in China between 1990 and 2005. The results showed that the urban landscape pattern has experienced drastic changes over the past 15 years. Total urban area has expanded approximately 1.61 times, with a 2.98% annual urban-growth rate. Compared to previous single-city studies, although urban areas are expanding rapidly, the overall fragmentation of the urban landscape is decreasing and is more irregular and complex at the national level. We also found a stair-stepping, urban-landscape changing pattern among eastern, central, and western counties. In addition, administrative level, urban size, and hierarchy have effects on the urban landscape pattern. We also found that a combination of landscape metrics can be used to supplement our understanding of the pattern of urbanization. The changes in these metrics are correlated with geographical indicators, socioeconomic factors, infrastructure variables, administrative level factors, policy factors, and historical factors. Our results indicate that the top priority should be strengthening the management of urban planning. A compact and congregate urban landscape may be a good choice of pattern for urban development in China. PMID:26856966

  13. Intracellular and extracellular forces drive primary cilia movement.

    PubMed

    Battle, Christopher; Ott, Carolyn M; Burnette, Dylan T; Lippincott-Schwartz, Jennifer; Schmidt, Christoph F

    2015-02-01

    Primary cilia are ubiquitous, microtubule-based organelles that play diverse roles in sensory transduction in many eukaryotic cells. They interrogate the cellular environment through chemosensing, osmosensing, and mechanosensing using receptors and ion channels in the ciliary membrane. Little is known about the mechanical and structural properties of the cilium and how these properties contribute to ciliary perception. We probed the mechanical responses of primary cilia from kidney epithelial cells [Madin-Darby canine kidney-II (MDCK-II)], which sense fluid flow in renal ducts. We found that, on manipulation with an optical trap, cilia deflect by bending along their length and pivoting around an effective hinge located below the basal body. The calculated bending rigidity indicates weak microtubule doublet coupling. Primary cilia of MDCK cells lack interdoublet dynein motors. Nevertheless, we found that the organelles display active motility. 3D tracking showed correlated fluctuations of the cilium and basal body. These angular movements seemed random but were dependent on ATP and cytoplasmic myosin-II in the cell cortex. We conclude that force generation by the actin cytoskeleton surrounding the basal body results in active ciliary movement. We speculate that actin-driven ciliary movement might tune and calibrate ciliary sensory functions. PMID:25605896

  14. Intracellular and extracellular forces drive primary cilia movement

    PubMed Central

    Battle, Christopher; Ott, Carolyn M.; Burnette, Dylan T.; Lippincott-Schwartz, Jennifer; Schmidt, Christoph F.

    2015-01-01

    Primary cilia are ubiquitous, microtubule-based organelles that play diverse roles in sensory transduction in many eukaryotic cells. They interrogate the cellular environment through chemosensing, osmosensing, and mechanosensing using receptors and ion channels in the ciliary membrane. Little is known about the mechanical and structural properties of the cilium and how these properties contribute to ciliary perception. We probed the mechanical responses of primary cilia from kidney epithelial cells [Madin–Darby canine kidney-II (MDCK-II)], which sense fluid flow in renal ducts. We found that, on manipulation with an optical trap, cilia deflect by bending along their length and pivoting around an effective hinge located below the basal body. The calculated bending rigidity indicates weak microtubule doublet coupling. Primary cilia of MDCK cells lack interdoublet dynein motors. Nevertheless, we found that the organelles display active motility. 3D tracking showed correlated fluctuations of the cilium and basal body. These angular movements seemed random but were dependent on ATP and cytoplasmic myosin-II in the cell cortex. We conclude that force generation by the actin cytoskeleton surrounding the basal body results in active ciliary movement. We speculate that actin-driven ciliary movement might tune and calibrate ciliary sensory functions. PMID:25605896

  15. Tuning the driving force for exciton dissociation in single-walled carbon nanotube heterojunctions

    NASA Astrophysics Data System (ADS)

    Ihly, Rachelle; Mistry, Kevin S.; Ferguson, Andrew J.; Clikeman, Tyler T.; Larson, Bryon W.; Reid, Obadiah; Boltalina, Olga V.; Strauss, Steven H.; Rumbles, Garry; Blackburn, Jeffrey L.

    2016-06-01

    Understanding the kinetics and energetics of interfacial electron transfer in molecular systems is crucial for the development of a broad array of technologies, including photovoltaics, solar fuel systems and energy storage. The Marcus formulation for electron transfer relates the thermodynamic driving force and reorganization energy for charge transfer between a given donor/acceptor pair to the kinetics and yield of electron transfer. Here we investigated the influence of the thermodynamic driving force for photoinduced electron transfer (PET) between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives by employing time-resolved microwave conductivity as a sensitive probe of interfacial exciton dissociation. For the first time, we observed the Marcus inverted region (in which driving force exceeds reorganization energy) and quantified the reorganization energy for PET for a model SWCNT/acceptor system. The small reorganization energies (about 130 meV, most of which probably arises from the fullerene acceptors) are beneficial in minimizing energy loss in photoconversion schemes.

  16. Extracting the driving force from ozone data using slow feature analysis

    NASA Astrophysics Data System (ADS)

    Wang, Geli; Yang, Peicai; Zhou, Xiuji

    2016-05-01

    Slow feature analysis (SFA) is a recommended technique for extracting slowly varying features from a quickly varying signal. In this work, we apply SFA to total ozone data from Arosa, Switzerland. The results show that the signal of volcanic eruptions can be found in the driving force, and wavelet analysis of this driving force shows that there are two main dominant scales, which may be connected with the effect of climate mode such as North Atlantic Oscillation (NAO) and solar activity. The findings of this study represent a contribution to our understanding of the causality from observed climate data.

  17. Competition is a driving force in topographic mapping.

    PubMed

    Triplett, Jason W; Pfeiffenberger, Cory; Yamada, Jena; Stafford, Ben K; Sweeney, Neal T; Litke, Alan M; Sher, Alexander; Koulakov, Alexei A; Feldheim, David A

    2011-11-22

    Topographic maps are the primary means of relaying spatial information in the brain. Understanding the mechanisms by which they form has been a goal of experimental and theoretical neuroscientists for decades. The projection of the retina to the superior colliculus (SC)/tectum has been an important model used to show that graded molecular cues and patterned retinal activity are required for topographic map formation. Additionally, interaxon competition has been suggested to play a role in topographic map formation; however, this view has been recently challenged. Here we present experimental and computational evidence demonstrating that interaxon competition for target space is necessary to establish topography. To test this hypothesis experimentally, we determined the nature of the retinocollicular projection in Math5 (Atoh7) mutant mice, which have severely reduced numbers of retinal ganglion cell inputs into the SC. We find that in these mice, retinal axons project to the anteromedialj portion of the SC where repulsion from ephrin-A ligands is minimized and where their attraction to the midline is maximized. This observation is consistent with the chemoaffinity model that relies on axon-axon competition as a mapping mechanism. We conclude that chemical labels plus neural activity cannot alone specify the retinocollicular projection; instead axon-axon competition is necessary to create a map. Finally, we present a mathematical model for topographic mapping that incorporates molecular labels, neural activity, and axon competition. PMID:22065784

  18. Compositional gradients in photopolymer films utilizing kinetic driving forces

    NASA Astrophysics Data System (ADS)

    Cook, Clinton John

    Independent control of the surface and bulk properties is advantageous for many applications such as adhesives, release coatings, and antimicrobial films. Traditional methods for achieving independent control typically require multiple processing steps such as wet-on-wet or wet-on-dry coating methods. Independent control over the surface properties can achieved in a single step utilizing the temporal and spatial control inherent to photopolymerization. Specifically, a co-photopolymerization of monomers with different reactivities in the presence of a light gradient is capable of producing a polymer film with a surface chemistry that differs from the bulk chemistry. The light gradient, produced via the concentration of photoinitiator in the formulation, results in a reaction gradient through the film with the higher rates of reaction occurring in the high light intensity regions of the film. The preferentially reacting monomer adds at a greater rate in the high light intensity regions resulting in non-uniform consumption yielding a concentration gradient. Consequently, diffusion of the preferentially reacting monomer from the bulk to the surface of the film and a counter-diffusion of the other monomer from the surface to the bulk of the film occurs from the non-uniform monomer consumption thus producing a film with a concentration gradient through the depth of the film with the preferentially reacting monomer enriching the high light intensity regions. A variety of kinetic differences capable of producing a stratified film will be presented including inherent monomer reactivity, number of functional groups per monomer, oxygen inhibition, thiol-ene chemistry, and Norrish type two initiation. Additionally, parameters that control the degree of stratification, such as methods of varying polymerization rate and the light gradient, will be examined. Changes in surface properties (such as contact angle, surface hardness, adhesion) and bulk properties (such as mechanical

  19. Thrust and normal force characteristics analysis of linear synchronous motor for direct drive conveyer

    NASA Astrophysics Data System (ADS)

    Zhu, Yu-wu; Kim, Do-sun; Cho, Yun-hyun

    2007-12-01

    The problem in improving the high positioning precision of permanent magnet linear synchronous motor (PMLSM) for direct drive conveyer is the large detent force, which contains two components: one is the cogging force caused by the interaction between the permanent magnet (PM) and the iron core, the other is the end effect caused by the finite mover length. In this paper a force compensator in the field oriented control (FOC) algorithm is employed to reduce this detent force, so the thrust and the normal force characteristics analysis of PMLSM are of the most importance. First the characteristics of the thrust and the normal force are simulated by finite element method (FEM), and the relation of the thrust and the normal force to the q-axis current is analyzed. Then the components of detent force are defined by Fourier series using the curve fitting method, and compensated by injecting the instantaneous currents using the FOC method. Finally the dynamic characteristics of this PMLSM for direct drive conveyer are investigated, and the numerical results are reported to validate the effectiveness of this proposed method.

  20. Sustainment of Fine Particle Cloud by Means of Time-Averaged Particle Driving Force in Plasmas

    SciTech Connect

    Gohda, Takuma; Iizuka, Satoru

    2008-09-07

    We have succeeded in sustaining fine particle cloud by using a time-averaged particle driving (TAPD) method in the RF discharge plasma. The particles feel only time-averaged force when the period of pulses applied to those point-electrodes is shorter than the particle response time. The particles are transported to a middle point between two point-electrodes.

  1. Fast charge separation in a non-fullerene organic solar cell with a small driving force

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Chen, Shangshang; Qian, Deping; Gautam, Bhoj; Yang, Guofang; Zhao, Jingbo; Bergqvist, Jonas; Zhang, Fengling; Ma, Wei; Ade, Harald; Inganäs, Olle; Gundogdu, Kenan; Gao, Feng; Yan, He

    2016-07-01

    Fast and efficient charge separation is essential to achieve high power conversion efficiency in organic solar cells (OSCs). In state-of-the-art OSCs, this is usually achieved by a significant driving force, defined as the offset between the bandgap (Egap) of the donor/acceptor materials and the energy of the charge transfer (CT) state (ECT), which is typically greater than 0.3 eV. The large driving force causes a relatively large voltage loss that hinders performance. Here, we report non-fullerene OSCs that exhibit ultrafast and efficient charge separation despite a negligible driving force, as ECT is nearly identical to Egap. Moreover, the small driving force is found to have minimal detrimental effects on charge transfer dynamics of the OSCs. We demonstrate a non-fullerene OSC with 9.5% efficiency and nearly 90% internal quantum efficiency despite a low voltage loss of 0.61 V. This creates a path towards highly efficient OSCs with a low voltage loss.

  2. Design considerations of electromagnetic force in a direct drive permanent magnet brushless motor

    NASA Astrophysics Data System (ADS)

    Chen, H. S.; Tsai, M. C.

    2008-04-01

    In this paper, a numerical study of electromagnetic force associated with the width of stator teeth, width of rotor back iron, and slot opening for a ten-pole nine-slot direct drive permanent magnet brushless motor is presented. The study calculates the amplitude of the electromagnetic force on the rotating rotor by using the finite-element method. The results show that the amplitude of electromagnetic force, which may cause the noise and vibration of motors, changes with the variation of these above mentioned three factors. The relationship between the considerations of output torque and the minimization of noise and vibration is also established in this paper.

  3. Driving Force.

    ERIC Educational Resources Information Center

    Rich, Richard A.

    1998-01-01

    Discusses campus parking assessment and planning to meet the increasing demands of colleges and universities while controlling costs and reducing student and staff discontent. Explores advice for expanding parking-lot space and maintaining security. Provides a chart that shows general parking requirements for various groups based on students…

  4. Vehicle Dynamics Control of In-wheel Electric Motor Drive Vehicles Based on Averaging of Tire Force Usage

    NASA Astrophysics Data System (ADS)

    Masaki, Nobuo; Iwano, Haruo; Kamada, Takayoshi; Nagai, Masao

    For in-wheel electric motor drive vehicles, a new vehicle dynamics control which is based on the tire force usage rate is proposed. The new controller adopts non-linear optimal control could manage the interference between direct yaw-moment control and the tire force usage rate. The new control is considered total longitudinal and transverse tire force. Therefore the controller can prevent tire force saturation near tire force limit during cornering. Simulations and test runs by the custom made four wheel drive in-wheel motor electric vehicle show that higher driving stability performance compared to the performance of the same vehicle without control.

  5. Causality of global warming seen from observations: a scale analysis of driving force of the surface air temperature time series in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Yang, Peicai; Wang, Geli; Zhang, Feng; Zhou, Xiuji

    2016-05-01

    By using the slow feature analysis, we reconstructed the driving force for an observed monthly surface air temperature anomaly time series in the northern hemisphere. Wavelet transformation technique was then used to analyze the scale structure of the derived driving force and its causal relationship with global warming. Results showed that the driving force for the analyzed temperature climate system included two independent degrees of freedom which respectively represented the effects of 22-year solar cycle and Atlantic Multidecadal Oscillation on the climate. More importantly, the driving force is modulated in amplitude by signals with much longer time periods. The modulation controls the energy input to the climate system and its effect on the global warming is decisive. In addition, through analyzing phase transitions from zero to extremes of the modulating signals, we provide a projection for the future trend of the surface air temperature. In specific, in the next 45-65 years, the driving force will continue to rise which will drive the air temperature even warmer. This is a long term natural trend determined by the modulating amplitude signals, but not directly related to human activity.

  6. Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterization

    NASA Astrophysics Data System (ADS)

    Bourtsoukidis, E.; Bonn, B.; Dittmann, A.; Hakola, H.; Hellén, H.; Jacobi, S.

    2012-06-01

    Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterization is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterization that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring=0.09 ± 0.01, βsummer=0.12 ± 0.02, βautumn=0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002)< β<(0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a~critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3=0.63 ± 0.01; CCT=0.47 ± 0.02 at t=0 h for temperature) with a time shift 2-4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20 % of the measured; R2=0.31). However, the addition of an ozone dependent term improved substantially the fitting between measured and

  7. Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterisation

    NASA Astrophysics Data System (ADS)

    Bourtsoukidis, E.; Bonn, B.; Dittmann, A.; Hakola, H.; Hellén, H.; Jacobi, S.

    2012-11-01

    Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterisation is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterisation that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring = 0.09 ± 0.01, βsummer = 0.12 ± 0.02, βautumn = 0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002) < β < (0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3 = 0.63 ± 0.01; CCT = 0.47 ± 0.02 at t = 0 h for temperature) with a time shift 2-4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20% of the measured; R2 = 0.31). However, the addition of an ozone dependent term improved substantially the fitting

  8. Analyzing the Long Term Cohesive Effect of Sector Specific Driving Forces.

    PubMed

    Berman, Yonatan; Ben-Jacob, Eshel; Zhang, Xin; Shapira, Yoash

    2016-01-01

    Financial markets are partially composed of sectors dominated by external driving forces, such as commodity prices, infrastructure and other indices. We characterize the statistical properties of such sectors and present a novel model for the coupling of the stock prices and their dominating driving forces, inspired by mean reverting stochastic processes. Using the model we were able to explain the market sectors' long term behavior and estimate the coupling strength between stocks in financial markets and the sector specific driving forces. Notably, the analysis was successfully applied to the shipping market, in which the Baltic dry index (BDI), an assessment of the price of transporting the major raw materials by sea, influences the shipping financial market. We also present the analysis of other sectors-the gold mining market and the food production market, for which the model was also successfully applied. The model can serve as a general tool for characterizing the coupling between external forces and affected financial variables and therefore for estimating the risk in sectors and their vulnerability to external stress. PMID:27031230

  9. Analyzing the Long Term Cohesive Effect of Sector Specific Driving Forces

    PubMed Central

    Berman, Yonatan; Zhang, Xin; Shapira, Yoash

    2016-01-01

    Financial markets are partially composed of sectors dominated by external driving forces, such as commodity prices, infrastructure and other indices. We characterize the statistical properties of such sectors and present a novel model for the coupling of the stock prices and their dominating driving forces, inspired by mean reverting stochastic processes. Using the model we were able to explain the market sectors’ long term behavior and estimate the coupling strength between stocks in financial markets and the sector specific driving forces. Notably, the analysis was successfully applied to the shipping market, in which the Baltic dry index (BDI), an assessment of the price of transporting the major raw materials by sea, influences the shipping financial market. We also present the analysis of other sectors—the gold mining market and the food production market, for which the model was also successfully applied. The model can serve as a general tool for characterizing the coupling between external forces and affected financial variables and therefore for estimating the risk in sectors and their vulnerability to external stress. PMID:27031230

  10. A Study of the Effect of the Fringe Fields on the Electrostatic Force in Vertical Comb Drives

    PubMed Central

    Gallagher, Else; Moussa, Walied

    2014-01-01

    The equation that describes the relationship between the applied voltage and the resulting electrostatic force within comb drives is often used to assist in choosing the dimensions for their design. This paper re-examines how some of these dimensions—particularly the cross-sectional dimensions of the comb teeth—affect this relationship in vertical comb drives. The electrostatic forces in several vertical comb drives fabricated for this study were measured and compared to predictions made with four different mathematical models in order to explore the amount of complexity required within a model to accurately predict the electrostatic forces in the comb drives. PMID:25350504

  11. Dynamic tensile forces drive collective cell migration through three-dimensional extracellular matrices

    PubMed Central

    Gjorevski, Nikolce; S. Piotrowski, Alexandra; Varner, Victor D.; Nelson, Celeste M.

    2015-01-01

    Collective cell migration drives tissue remodeling during development, wound repair, and metastatic invasion. The physical mechanisms by which cells move cohesively through dense three-dimensional (3D) extracellular matrix (ECM) remain incompletely understood. Here, we show directly that migration of multicellular cohorts through collagenous matrices occurs via a dynamic pulling mechanism, the nature of which had only been inferred previously in 3D. Tensile forces increase at the invasive front of cohorts, serving a physical, propelling role as well as a regulatory one by conditioning the cells and matrix for further extension. These forces elicit mechanosensitive signaling within the leading edge and align the ECM, creating microtracks conducive to further migration. Moreover, cell movements are highly correlated and in phase with ECM deformations. Migrating cohorts use spatially localized, long-range forces and consequent matrix alignment to navigate through the ECM. These results suggest biophysical forces are critical for 3D collective migration. PMID:26165921

  12. Application of Laser Ranging and VLBI Data to a Study of Plate Tectonic Driving Forces

    NASA Technical Reports Server (NTRS)

    Solomon, S. C.

    1980-01-01

    The conditions under which changes in plate driving or resistive forces associated with plate boundary earthquakes are measurable with laser ranging or very long base interferometry were investigated. Aspects of plate forces that can be characterized by such measurements were identified. Analytic solutions for two dimensional stress diffusion in a viscoelastic plate following earthquake faulting on a finite fault, finite element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting, and quantitative constraints from modeling of global intraplate stress on the magnitude of deviatoric stress in the lithosphere are among the topics discussed.

  13. A study on tyre force distribution controls for full drive-by-wire electric vehicle

    NASA Astrophysics Data System (ADS)

    Suzuki, Yuta; Kano, Yoshio; Abe, Masato

    2014-05-01

    Feed-forward types of tyre force distribution controls with some norms for motion controls of a full drive-by-wire electric vehicle are presented. One of the norms for the distribution control introduced is minimising tyre workload and another one is minimising tyre dissipation energy due to tyre slip during vehicle motion. The effects of the distribution controls are substantiated using an experimental vehicle on a proving ground. Especially the effects of the tyre force distribution norms on improving vehicle stability and on reducing the tyre energy dissipation caused by tyre slip are investigated.

  14. Electronic structure and driving forces in β-cyclodextrin: Diclofenac inclusion complexes

    NASA Astrophysics Data System (ADS)

    Bogdan, Diana; Morari, C.

    2007-07-01

    We investigate the geometry and electronic structure for complexes of β-cyclodextrin with diclofenac using DFT calculations. The effect of solvent is explicitly taken into account. This investigation allows us to draw meaningful conclusions upon the stability of the complex and the nature of the driving forces leading to the complexation process. In particular we emphasize the role of the water, by pointing out the changes in the solvent's electronic structure for different docking geometries.

  15. Testing thermal gradient driving force for grain boundary migration using molecular dynamics simulations

    SciTech Connect

    Bai, Xian-Ming; Zhang, Yongfeng; Tonks, Michael R.

    2015-02-01

    Strong thermal gradients in low-thermal-conductivity ceramics may drive extended defects, such as grain boundaries and voids, to migrate in preferential directions. In this work, molecular dynamics simulations are conducted to study thermal gradient driven grain boundary migration and to verify a previously proposed thermal gradient driving force equation, using uranium dioxide as a model system. It is found that a thermal gradient drives grain boundaries to migrate up the gradient and the migration velocity increases under a constant gradient owing to the increase in mobility with temperature. Different grain boundaries migrate at very different rates due to their different intrinsic mobilities. The extracted mobilities from the thermal gradient driven simulations are compared with those calculated from two other well-established methods and good agreement between the three different methods is found, demonstrating that the theoretical equation of the thermal gradient driving force is valid, although a correction of one input parameter should be made. The discrepancy in the grain boundary mobilities between modeling and experiments is also discussed.

  16. Theoretical analysis of the formation driving force and decreased sensitivity for CL-20 cocrystals

    NASA Astrophysics Data System (ADS)

    Zhou, Jun-Hong; Shi, Liang-Wei; Zhang, Chao-Yang; Li, Hong-Zhen; Chen, Min-Bo; Chen, Wei-Ming

    2016-07-01

    Methods that analyze the driving force in the formation of the new energetic cocrystal are proposed in this paper. Various intermolecular interactions in the 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.05,9.03,11]dodecane (CL-20) cocrystals are compared with those in pure CL-20 and coformer crystals by atom in molecule (AIM) and Hirshfeld surface methods under the supramolecular cluster model. The driving force in the formation of the CL-20 cocrystals is analyzed. The main driving force in the formation of the cocrystal CL-20/HMX comes from the O···H interactions, that in the formation of the cocrystal CL-20/TNT from the O···H and C···O interactions, and that in the formation of the cocrystal CL-20/BTF from the N···H and N···O interactions. Other interactions in the CL-20 cocrystals only contribute to their stabilization. At the same time, the reasons for the decreased impact sensitivity of the CL-20 cocrystals are also analyzed. They are the strengthening of the intermolecular interactions, the reducing of the free space, and the changing of the surrounding of CL-20 molecule in the CL-20 cocrystals in comparison with those in the pure CL-20 crystal.

  17. Theoretical analysis of the formation driving force and decreased sensitivity for CL-20 cocrystals

    NASA Astrophysics Data System (ADS)

    Zhou, Jun-Hong; Shi, Liang-Wei; Zhang, Chao-Yang; Li, Hong-Zhen; Chen, Min-Bo; Chen, Wei-Ming

    2016-07-01

    Methods that analyze the driving force in the formation of the new energetic cocrystal are proposed in this paper. Various intermolecular interactions in the 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.05,9.03,11]dodecane (CL-20) cocrystals are compared with those in pure CL-20 and coformer crystals by atom in molecule (AIM) and Hirshfeld surface methods under the supramolecular cluster model. The driving force in the formation of the CL-20 cocrystals is analyzed. The main driving force in the formation of the cocrystal CL-20/HMX comes from the O···H interactions, that in the formation of the cocrystal CL-20/TNT from the O···H and C···O interactions, and that in the formation of the cocrystal CL-20/BTF from the N···H and N···O interactions. Other interactions in the CL-20 cocrystals only contribute to their stabilization. At the same time, the reasons for the decreased impact sensitivity of the CL-20 cocrystals are also analyzed. They are the strengthening of the intermolecular interactions, the reducing of the free space, and the changing of the surrounding of CL-20 molecule in the CL-20 cocrystals in comparison with those in the pure CL-20 crystal.

  18. Tuning the driving force for exciton dissociation in single-walled carbon nanotube heterojunctions.

    PubMed

    Ihly, Rachelle; Mistry, Kevin S; Ferguson, Andrew J; Clikeman, Tyler T; Larson, Bryon W; Reid, Obadiah; Boltalina, Olga V; Strauss, Steven H; Rumbles, Garry; Blackburn, Jeffrey L

    2016-06-01

    Understanding the kinetics and energetics of interfacial electron transfer in molecular systems is crucial for the development of a broad array of technologies, including photovoltaics, solar fuel systems and energy storage. The Marcus formulation for electron transfer relates the thermodynamic driving force and reorganization energy for charge transfer between a given donor/acceptor pair to the kinetics and yield of electron transfer. Here we investigated the influence of the thermodynamic driving force for photoinduced electron transfer (PET) between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives by employing time-resolved microwave conductivity as a sensitive probe of interfacial exciton dissociation. For the first time, we observed the Marcus inverted region (in which driving force exceeds reorganization energy) and quantified the reorganization energy for PET for a model SWCNT/acceptor system. The small reorganization energies (about 130 meV, most of which probably arises from the fullerene acceptors) are beneficial in minimizing energy loss in photoconversion schemes. PMID:27219706

  19. Facilitating Implementation of Interprofessional Collaborative Practices Into Primary Care: A Trilogy of Driving Forces.

    PubMed

    Bareil, Céline; Duhamel, Fabie; Lalonde, Lyne; Goudreau, Johanne; Hudon, Eveline; Lussier, Marie-Thérèse; Lévesque, Lise; Lessard, Sylvie; Turcotte, Alain; Lalonde, Gilles

    2015-01-01

    Implementing interprofessional collaborative practices in primary care is challenging, and research about its facilitating factors remains scarce. The goal of this participatory action research study was to better understand the driving forces during the early stage of the implementation process of a community-driven and patient-focused program in primary care titled "TRANSforming InTerprofessional cardiovascular disease prevention in primary care" (TRANSIT). Eight primary care clinics in Quebec, Canada, agreed to participate by creating and implementing an interprofessional facilitation team (IFT). Sixty-three participants volunteered to be part of an IFT, and 759 patients agreed to participate. We randomized six clinics into a supported facilitation ("supported") group, with an external facilitator (EF) and financial incentives for participants. We assigned two clinics to an unsupported facilitation ("unsupported") group, with no EF or financial incentives. After 3 months, we held one interview for the two EFs. After 6 months, we held eight focus groups with IFT members and another interview with each EF. The analyses revealed three key forces: (1) opportunity for dialogue through the IFT, (2) active role of the EF, and (3) change implementation budgets. Decision-makers designing implementation plans for interprofessional programs should ensure that these driving forces are activated. Further research should examine how these forces affect interprofessional practices and patient outcomes. PMID:26364352

  20. Quantifying the net slab pull force as a driving mechanism for plate tectonics

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.

    2004-04-01

    It has remained unclear how much of the negative buoyancy force of the slab (FB) is used to pull the trailing plate at the surface into the mantle. Here I present three-dimensional laboratory experiments to quantify the net slab pull force (FNSP) with respect to FB during subduction. Results show that FNSP increases with increasing slab length and dip up to ~8-12% of FB, making FNSP up to twice as large as the ridge push force. The remainder of FB is primarily used to drive rollback-induced mantle flow (~70%), to bend the subducting plate at the trench (~15-30%) and to overcome shear resistance between slab and mantle (0-8%).

  1. Optomechanically induced transparency in the presence of an external time-harmonic-driving force

    PubMed Central

    Ma, Jinyong; You, Cai; Si, Liu-Gang; Xiong, Hao; Li, Jiahua; Yang, Xiaoxue; Wu, Ying

    2015-01-01

    We propose a potentially valuable scheme to measure the properties of an external time-harmonic-driving force with frequency ω via investigating its interaction with the combination of a pump field and a probe field in a generic optomechanical system. We show that the spectra of both the cavity field and output field in the configuration of optomechanically induced transparency are greatly modified by such an external force, leading to many interesting linear and non-linear effects, such as the asymmetric structure of absorption in the frequency domain and the antisymmetry breaking of dispersion near ω = ωm. Furthermore, we find that our scheme can be used to measure the initial phase of the external force. More importantly, this setup may eliminate the negative impact of thermal noise on the measurement of the weak external force in virtue of the process of interference between the probe field and the external force. Finally, we show that our configuration can be employed to improve the measurement resolution of the radiation force produced by a weak ultrasonic wave. PMID:26062029

  2. How metal films de-wet substrates : identifying the kinetic pathways and energetic driving forces.

    SciTech Connect

    Thurmer, Konrad; Schmid, Andreas; Sato, Yu; Hamilton, John C.; Saa, Angela; McCarty, Kevin F.; de la Figuera, Juan; Bartelt, Norman Charles

    2008-10-01

    We study how single-crystal chromium films of uniform thickness on W(110) substrates are converted to arrays of three-dimensional (3D) Cr islands during annealing. We use low-energy electron microscopy (LEEM) to directly observe a kinetic pathway that produces trenches that expose the wetting layer. Adjacent film steps move simultaneously uphill and downhill relative to the staircase of atomic steps on the substrate. This step motion thickens the film regions where steps advance. Where film steps retract, the film thins, eventually exposing the stable wetting layer. Since our analysis shows that thick Cr films have a lattice constant close to bulk Cr, we propose that surface and interface stress provide a possible driving force for the observed morphological instability. Atomistic simulations and analytic elastic models show that surface and interface stress can cause a dependence of film energy on thickness that leads to an instability to simultaneous thinning and thickening. We observe that de-wetting is also initiated at bunches of substrate steps in two other systems, Ag/W(110) and Ag/Ru(0001). We additionally describe how Cr films are converted into patterns of unidirectional stripes as the trenches that expose the wetting layer lengthen along the W[001] direction. Finally, we observe how 3D Cr islands form directly during film growth at elevated temperature. The Cr mesas (wedges) form as Cr film steps advance down the staircase of substrate steps, another example of the critical role that substrate steps play in 3D island formation.

  3. Detailed Per-residue Energetic Analysis Explains the Driving Force for Microtubule Disassembly

    PubMed Central

    Ayoub, Ahmed T.; Klobukowski, Mariusz; Tuszynski, Jack A.

    2015-01-01

    Microtubules are long filamentous hollow cylinders whose surfaces form lattice structures of αβ-tubulin heterodimers. They perform multiple physiological roles in eukaryotic cells and are targets for therapeutic interventions. In our study, we carried out all-atom molecular dynamics simulations for arbitrarily long microtubules that have either GDP or GTP molecules in the E-site of β-tubulin. A detailed energy balance of the MM/GBSA inter-dimer interaction energy per residue contributing to the overall lateral and longitudinal structural stability was performed. The obtained results identified the key residues and tubulin domains according to their energetic contributions. They also identified the molecular forces that drive microtubule disassembly. At the tip of the plus end of the microtubule, the uneven distribution of longitudinal interaction energies within a protofilament generates a torque that bends tubulin outwardly with respect to the cylinder's axis causing disassembly. In the presence of GTP, this torque is opposed by lateral interactions that prevent outward curling, thus stabilizing the whole microtubule. Once GTP hydrolysis reaches the tip of the microtubule (lateral cap), lateral interactions become much weaker, allowing tubulin dimers to bend outwards, causing disassembly. The role of magnesium in the process of outward curling has also been demonstrated. This study also showed that the microtubule seam is the most energetically labile inter-dimer interface and could serve as a trigger point for disassembly. Based on a detailed balance of the energetic contributions per amino acid residue in the microtubule, numerous other analyses could be performed to give additional insights into the properties of microtubule dynamic instability. PMID:26030285

  4. Land use change and its driving forces in alluvial-plain oasis

    NASA Astrophysics Data System (ADS)

    Xiao, Luxiang; Zhang, Zengxiang; Chen, Xi; Luo, Geping; Wen, Qingke

    2007-11-01

    Land use change and its driving factors are hot topics of global change research, and also important topics of sustainable development. This paper selected a small area in alluvial plain oasis in Xinjiang Autonomous region of China as the study area. Using Landsat TM data of 1987, 1998 and 2004, the dynamic process of the spatial-temporal characteristics of land use changes were analyzed to improve understanding and to find the driving forces of land use changes so that sustainable land utilization could be practiced. During the 17 years salt-alkali tolerant cropland, cereal cropland, vegetable-fruit land, and shrubbery, had decreased remarkably by 78.59%, 85.95%, 92.13%, 68.43%, respectively. Cotton-liquorice land, grape-hop land, planted forest, residential area in town, residential area in village, and saline-alkaline field had increased dramatically. The increased percentage received the value of 2432.11%, 10103.18%, 889.91%, 222.45%, 96.00%, 44.18%, respectively. By the logistic regression, the main driving factors were derived for each land use type. The advance of technology (fertilizer input, irrigation quota, and animal labor et al.) and market (unit are yield net) were the main driving factors. Policy, in a higher level, influenced the land use dynamics for all the land use changes.

  5. Driving force of binding of amyloid {beta}-protein to lipid bilayers

    SciTech Connect

    Ikeda, Keisuke; Matsuzaki, Katsumi

    2008-06-06

    Amyloid {beta}-protein (A{beta}) has been reported to interact with a variety of lipid species, although the thermodynamic driving force remains unclear. We investigated the binding of A{beta}s labeled with the dye diethylaminocoumarin (DAC-A{beta}s) to lipid bilayers under various conditions. DAC-A{beta}-(1-40) electrostatically bound to anionic and cationic lipids at acidic and alkaline interfacial pH, respectively. However, at neutral pH, electroneutral A{beta} did not bind to these lipids, indicating little hydrophobic interaction between A{beta}-(1-40) and the acyl chains of lipids. In contrast, DAC-A{beta} associated with glycolipids even under electroneutral conditions. These results suggested that hydrogen-bonding as well as hydrophobic interactions with sugar groups of glycolipids drive the membrane binding of A{beta}-(1-40)

  6. Multiple Driving Forces Required for Efficient Secretion of Autotransporter Virulence Proteins*

    PubMed Central

    Drobnak, Igor; Braselmann, Esther; Clark, Patricia L.

    2015-01-01

    Autotransporter (AT) proteins are a broad class of virulence proteins from Gram-negative bacterial pathogens that require their own C-terminal transmembrane domain to translocate their N-terminal passenger across the bacterial outer membrane (OM). But given the unavailability of ATP or a proton gradient across the OM, it is unknown what energy source(s) drives this process. Here we used a combination of computational and experimental approaches to quantitatively compare proposed AT OM translocation mechanisms. We show directly for the first time that when translocation was blocked an AT passenger remained unfolded in the periplasm. We demonstrate that AT secretion is a kinetically controlled, non-equilibrium process coupled to folding of the passenger and propose a model connecting passenger conformation to secretion kinetics. These results reconcile seemingly contradictory reports regarding the importance of passenger folding as a driving force for OM translocation but also reveal that another energy source is required to initiate translocation. PMID:25670852

  7. Finite element modeling of stress in the Nazca plate - Driving forces and plate boundary earthquakes

    NASA Technical Reports Server (NTRS)

    Richardson, R. M.

    1978-01-01

    The state of stress within the Nazca plate due to plate driving forces and large plate boundary earthquakes has been analyzed by applying a finite element method using the wave front solution technique to models of the intraplate stress field in a single plate using a refined grid. Although only static elastic models have been explicitly calculated, certain limiting cases of an elastic plate over a viscous asthenosphere were also treated. A state of nearly east-west compression inferred from the source mechanism of thrust earthquakes in the interior of the plate requires ridge pushing forces. The net pulling force on the oceanic plate by the subducted slab has a maximum value comparable to pushing forces. The estimated horizontal deviatoric stress in intraplate regions, based on potential forces associated with the ridge, is on the order of a few hundred bars. The intraplate stress field in the region of the 1960 earthquake may change by a few tens of bars at most once the asthenosphere has relaxed, with changes on the order of one bar occurring at greater distances into the plate. The changes in the intraplate stress field are probably not noticeable unless the lithosphere is near failure.

  8. Role of Chemical Driving Force in Martensitic Transformations of High-Purity Fe-Cr-Ni Alloys

    NASA Astrophysics Data System (ADS)

    Behjati, P.; Najafizadeh, A.

    2011-12-01

    The main objective of the present work is to point out the respective roles of chemical driving force and stacking fault energy (SFE) in the occurrence of martensitic transformations in high-purity Fe-Cr-Ni alloys. For this purpose, the transmission electron microscope (TEM), X-ray diffractometer, thermal differential microanalyzer (TDA), and tension test were employed to report M s temperatures, austenite stacking fault energies, and driving forces for the concerned alloys. It was observed that the martensitic transformations in the studied alloys occur through the γ → ɛ → α' steps. As a remarkable result, it was shown that a low SFE, if necessary to ɛ-phase nucleation, is not a sufficient condition for nucleation of α' phase. In fact, the formation of stable α' nuclei from α' embryos occur if the required chemical driving force is provided. Also, an equation was proposed for the kinetics of spontaneous martensitic transformation as a function of driving force.

  9. Remote sensing monitoring and driving force analysis to forest and greenbelt in Zhuhai

    NASA Astrophysics Data System (ADS)

    Yuliang Qiao, Pro.

    As an important city in the southern part of Chu Chiang Delta, Zhuhai is one of the four special economic zones which are opening up to the outside at the earliest in China. With pure and fresh air and trees shading the street, Zhuhai is a famous beach port city which is near the mountain and by the sea. On the basis of Garden City, the government of Zhuhai decides to build National Forest City in 2011, which firstly should understand the situation of greenbelt in Zhuhai in short term. Traditional methods of greenbelt investigation adopt the combination of field surveying and statistics, whose efficiency is low and results are not much objective because of artificial influence. With the adventure of the information technology such as remote sensing to earth observation, especially the launch of many remote sensing satellites with high resolution for the past few years, kinds of urban greenbelt information extraction can be carried out by using remote sensing technology; and dynamic monitoring to spatial pattern evolvement of forest and greenbelt in Zhuhai can be achieved by the combination of remote sensing and GIS technology. Taking Landsat5 TM data in 1995, Landsat7 ETM+ data in 2002, CCD and HR data of CBERS-02B in 2009 as main information source, this research firstly makes remote sensing monitoring to dynamic change of forest and greenbelt in Zhuhai by using the combination of vegetation coverage index and three different information extraction methods, then does a driving force analysis to the dynamic change results in 3 months. The results show: the forest area in Zhuhai shows decreasing tendency from 1995 to 2002, increasing tendency from 2002 to 2009; overall, the forest area show a small diminution tendency from 1995 to 2009. Through the comparison to natural and artificial driving force, the artificial driving force is the leading factor to the change of forest and greenbelt in Zhuhai. The research results provide a timely and reliable scientific basis

  10. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching

    NASA Astrophysics Data System (ADS)

    Li, Jicun; Wang, Feng

    2015-11-01

    Simple non-polarizable potentials were developed for Na+, K+, Cl-, and Br- using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration.

  11. Proton-coupled electron transfers: pH-dependent driving forces? Fundamentals and artifacts.

    PubMed

    Bonin, Julien; Costentin, Cyrille; Robert, Marc; Routier, Mathilde; Savéant, Jean-Michel

    2013-09-25

    Besides its own interest, tryptophan oxidation by photogenerated Ru complexes is one of the several examples where concerted proton-electron transfer (CPET) to water as proton acceptor endowed with a pH-dependent driving force has been invoked to explain the data. Since this notion is contrary to the very basic principles of chemical physics, it was interesting to attempt uncovering the source of this contradiction with an easily accessible substrate. Careful examination of the oxidation of the tryptophan (ethyl ester derivative) bearing a NH3(+)/NH2 group showed that there is no trace of such an unconventional H2O-CPET with a pH-dependent driving force. The reaction mechanism simply consists, with both the NH3(+) acid and NH2 basic forms of the tryptophan derivative, in a rate-determining electron-transfer step followed by deprotonation steps. The same is true with the ethyl ester-methyl amide derivative of tryptophan, whose behavior is even simpler since the molecule does not bear an acid-base group. No such unconventional H2O-CPET was found with phenol, another easily accessible substrate. It may thus be inferred that the same applies to less easily available systems in which electron transfer occurs intramolecularly. These observations help to rid the road of such artificial obstacles and improve present models of H2O-CPET reactions, a landmark towards the understanding of the role of water chains in natural systems. PMID:23972082

  12. Human health and the water environment: using the DPSEEA framework to identify the driving forces of disease.

    PubMed

    Gentry-Shields, Jennifer; Bartram, Jamie

    2014-01-15

    There is a growing awareness of global forces that threaten human health via the water environment. A better understanding of the dynamic between human health and the water environment would enable prediction of the significant driving forces and effective strategies for coping with or preventing them. This report details the use of the Driving Force-Pressure-State-Exposure-Effect-Action (DPSEEA) framework to explore the linkage between water-related diseases and their significant driving forces. The DPSEEA frameworks indicate that a select group of driving forces, including population growth, agriculture, infrastructure (dams and irrigation), and climate change, is at the root cause of key global disease burdens. Construction of the DPSEEA frameworks also allows for the evaluation of public health interventions. Sanitation was found to be a widely applicable and effective intervention, targeting the driver/pressure linkage of most of the water-related diseases examined. Ultimately, the DPSEEA frameworks offer a platform for constituents in both the health and environmental fields to collaborate and commit to a common goal targeting the same driving forces. PMID:24036221

  13. Application of laser ranging and VLBI data to a study of plate tectonic driving forces. [finite element method

    NASA Technical Reports Server (NTRS)

    Solomon, S. C.

    1980-01-01

    The measurability of changes in plate driving or resistive forces associated with plate boundary earthquakes by laser rangefinding or VLBI is considered with emphasis on those aspects of plate forces that can be characterized by such measurements. Topics covered include: (1) analytic solutions for two dimensional stress diffusion in a plate following earthquake faulting on a finite fault; (2) two dimensional finite-element solutions for the global state of stress at the Earth's surface for possible plate driving forces; and (3) finite-element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting.

  14. Calculations of Alfvén wave driving forces, plasma flow, and current drive in the Tokamak Chauffage Alfvén wave experiment in Brazil (TCABR)

    NASA Astrophysics Data System (ADS)

    Amarante-Segundo, G.; Elfimov, A. G.; Galvão, R. M. O.; Ross, D. W.; Nascimento, I. C.

    2001-01-01

    The current and plasma flows driven by ponderomotive forces are calculated for tokamak plasmas, using a kinetic code in the Alfvén range of frequencies. The rf (radio frequency) ponderomotive force is expressed as a sum of a gradient part and of a wave momentum transfer force, which is proportional to wave dissipation (electron Landau damping and transit time magnetic pumping). Finally, the rf force is balanced by the viscous force in the fluid momentum response to the rf fields in the plasma. The relative magnitudes of the different forces for kinetic and global Alfvén waves with low phase velocities are explicitly calculated. It is shown that, dissipating in electrons, Alfvén waves can drive ion flow via the gradient force, which is dominated in m=0-sideband harmonic resonance induced by toroidal mode coupling. Estimates of power requirements to drive substantial poloidal flow in the Tokamak Chauffage Alfvén wave heating experiment in Brazil (TCABR) [L. Ruchko, M. C. Andrade, R. M. O. Galvão, Nucl. Fusion 30, 503 (1996)] are made.

  15. The role of biotic forces in driving macroevolution: beyond the Red Queen

    PubMed Central

    Voje, Kjetil L.; Holen, Øistein H.; Liow, Lee Hsiang; Stenseth, Nils Chr.

    2015-01-01

    A multitude of hypotheses claim that abiotic factors are the main drivers of macroevolutionary change. By contrast, Van Valen's Red Queen hypothesis is often put forward as the sole representative of the view that biotic forcing is the main evolutionary driver. This imbalance of hypotheses does not reflect our current knowledge: theoretical work demonstrates the plausibility of biotically driven long-term evolution, whereas empirical work suggests a central role for biotic forcing in macroevolution. We call for a more pluralistic view of how biotic forces may drive long-term evolution that is compatible with both phenotypic stasis in the fossil record and with non-constant extinction rates. Promising avenues of research include contrasting predictions from relevant theories within ecology and macroevolution, as well as embracing both abiotic and biotic proxies while modelling long-term evolutionary data. By fitting models describing hypotheses of biotically driven macroevolution to data, we could dissect their predictions and transcend beyond pattern description, possibly narrowing the divide between our current understanding of micro- and macroevolution. PMID:25948685

  16. The role of biotic forces in driving macroevolution: beyond the Red Queen.

    PubMed

    Voje, Kjetil L; Holen, Øistein H; Liow, Lee Hsiang; Stenseth, Nils Chr

    2015-06-01

    A multitude of hypotheses claim that abiotic factors are the main drivers of macroevolutionary change. By contrast, Van Valen's Red Queen hypothesis is often put forward as the sole representative of the view that biotic forcing is the main evolutionary driver. This imbalance of hypotheses does not reflect our current knowledge: theoretical work demonstrates the plausibility of biotically driven long-term evolution, whereas empirical work suggests a central role for biotic forcing in macroevolution. We call for a more pluralistic view of how biotic forces may drive long-term evolution that is compatible with both phenotypic stasis in the fossil record and with non-constant extinction rates. Promising avenues of research include contrasting predictions from relevant theories within ecology and macroevolution, as well as embracing both abiotic and biotic proxies while modelling long-term evolutionary data. By fitting models describing hypotheses of biotically driven macroevolution to data, we could dissect their predictions and transcend beyond pattern description, possibly narrowing the divide between our current understanding of micro- and macroevolution. PMID:25948685

  17. Anomalous yield reduction in direct-drive DT implosions due to 3He addition

    SciTech Connect

    Herrmann, Hans W; Langenbrunner, James R; Mack, Joseph M; Cooley, James H; Wilson, Douglas C; Evans, Scott C; Sedillo, Tom J; Kyrala, George A; Caldwell, Stephen E; Young, Carlton A; Nobile, Arthur; Wermer, Joseph R; Paglieri, Stephen N; Mcevoy, Aaron M; Kim, Yong Ho; Batha, Steven H; Horsfield, Colin J; Drew, Dave; Garbett, Warren; Rubery, Michael; Glebov, Vladimir Yu; Roberts, Samuel; Frenje, Johan A

    2008-01-01

    Glass capsules were imploded in direct drive on the OMEGA laser [T. R. Boehly et aI., Opt. Commun. 133, 495, 1997] to look for anomalous degradation in deuterium/tritium (DT) yield (i.e., beyond what is predicted) and changes in reaction history with {sup 3}He addition. Such anomalies have previously been reported for D/{sup 3}He plasmas, but had not yet been investigated for DT/{sup 3}He. Anomalies such as these provide fertile ground for furthering our physics understanding of ICF implosions and capsule performance. A relatively short laser pulse (600 ps) was used to provide some degree of temporal separation between shock and compression yield components for analysis. Anomalous degradation in the compression component of yield was observed, consistent with the 'factor of two' degradation previously reported by MIT at a 50% {sup 3}He atom fraction in D{sub 2} using plastic capsules [Rygg et aI., Phys. Plasmas 13, 052702 (2006)]. However, clean calculations (i.e., no fuel-shell mixing) predict the shock component of yield quite well, contrary to the result reported by MIT, but consistent with LANL results in D{sub 2}/{sup 3}He [Wilson, et aI., lml Phys: Conf Series 112, 022015 (2008)]. X-ray imaging suggests less-than-predicted compression ofcapsules containing {sup 3}He. Leading candidate explanations are poorly understood Equation-of-State (EOS) for gas mixtures, and unanticipated particle pressure variation with increasing {sup 3}He addition.

  18. CHARMM General Force Field (CGenFF): A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields

    PubMed Central

    Vanommeslaeghe, K.; Hatcher, E.; Acharya, C.; Kundu, S.; Zhong, S.; Shim, J.; Darian, E.; Guvench, O.; Lopes, P.; Vorobyov, I.; MacKerell, A. D.

    2010-01-01

    The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids and carbohydrates. In the present paper an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds. The parametrization philosophy behind the force field focuses on quality at the expense of transferability, with the implementation concentrating on an extensible force field. Statistics related to the quality of the parametrization with a focus on experimental validation are presented. Additionally, the parametrization procedure, described fully in the present paper in the context of the model systems, pyrrolidine, and 3-phenoxymethylpyrrolidine will allow users to readily extend the force field to chemical groups that are not explicitly covered in the force field as well as add functional groups to and link together molecules already available in the force field. CGenFF thus makes it possible to perform “all-CHARMM” simulations on drug-target interactions thereby extending the utility of CHARMM force fields to medicinally relevant systems. PMID:19575467

  19. Molecular dynamics simulations of grain boundary mobility in Al, Cu and γ-Fe using a symmetrical driving force

    NASA Astrophysics Data System (ADS)

    Ulomek, F.; Mohles, V.

    2014-07-01

    We present a new artificial driving force for the determination of grain boundary mobility by molecular dynamics. The new driving force is a symmetric version of the synthetic driving force formerly introduced by Janssens et al 2006 Nature Mater. 5 124-7. The new version depends on two orientation parameters instead of one. We analyze the advantages and disadvantages of these two driving force methods. Grain boundary mobilities are simulated for eight symmetric CSL tilt grain boundaries in Al, Cu and γ-Fe, and two MD potentials for each of these materials. Boundary conditions are kept as similar as possible to show the influence of the different materials and to compare to the influence of the different MD potential types on simulated GB mobilities. We find that the newly introduced artificial driving force is a slight improvement, but it cannot remove the shortcomings of the original approach. Also, it is found that the differences in calculated MD mobilities between different materials are of the same order as those between different MD potentials of any one element. Sources for such differences are identified and classified by severity.

  20. On the driving force for crack growth during thermal actuation of shape memory alloys

    NASA Astrophysics Data System (ADS)

    Baxevanis, T.; Parrinello, A. F.; Lagoudas, D. C.

    2016-04-01

    The effect of thermomechanically induced phase transformation on the driving force for crack growth in polycrystalline shape memory alloys is analyzed in an infinite center-cracked plate subjected to a thermal actuation cycle under mechanical load in plain strain. Finite element calculations are carried out to determine the mechanical fields near the static crack and the crack-tip energy release rate using the virtual crack closure technique. A substantial increase of the energy release rate - an order of magnitude for some material systems - is observed during the thermal cycle due to the stress redistribution induced by large scale phase transformation. Thus, phase transformation occurring due to thermal variations under mechanical load may result in crack growth if the crack-tip energy release rate reaches a material specific critical value.

  1. Unraveling the genetic driving forces enabling antibiotic resistance at the single cell level

    NASA Astrophysics Data System (ADS)

    Bos, Julia

    Bacteria are champions at finding ways to quickly respond and adapt to environments like the human gut, known as the epicentre of antibiotic resistance. How do they do it? Combining molecular biology tools to microfluidic and fluorescence microscopy technologies, we monitor the behavior of bacteria at the single cell level in the presence of non-toxic doses of antibiotics. By tracking the chromosome dynamics of Escherichia coli cells upon antibiotic treatment, we examine the changes in the number, localization and content of the chromosome copies within one cell compartment or between adjacent cells. I will discuss how our work pictures the bacterial genomic plasticity as a driving force in evolution and how it provides access to the mechanisms controlling the subtle balance between genetic diversity and stability in the development of antibiotic resistance.

  2. Opposing forces of aerosol cooling and El Nino drive coral bleaching on Caribbean reefs.

    PubMed

    Gill, Jennifer A; Watkinson, Andrew R; McWilliams, John P; Côté, Isabelle M

    2006-12-01

    Bleaching of corals as a result of elevated sea surface temperatures (SST) is rapidly becoming a primary source of stress for reefs globally; the scale and extent of this threat will depend on how the drivers of SST interact to influence bleaching patterns. We demonstrate how the opposing forces of the El Niño-Southern Oscillation (ENSO) and levels of atmospheric aerosols drive regional-scale patterns of coral bleaching across the Caribbean. When aerosol levels are low, bleaching is largely determined by El Niño strength, but high aerosol levels mitigate the effects of a severe El Niño. High aerosol levels, resulting principally from recent volcanic activity, have thus protected Caribbean reefs from more frequent widespread bleaching events but cannot be relied on to provide similar protection in the future. PMID:17116861

  3. Rapid Evolutionary Dynamics of Structural Disorder as a Potential Driving Force for Biological Divergence in Flaviviruses

    PubMed Central

    Ortiz, Juan F.; MacDonald, Madolyn L.; Masterson, Patrick; Uversky, Vladimir N.; Siltberg-Liberles, Jessica

    2013-01-01

    Protein structure is commonly regarded to be conserved and to dictate function. Most proteins rely on conformational flexibility to some degree. Are regions that convey conformational flexibility conserved over evolutionary time? Can changes in conformational flexibility alter protein function? Here, the evolutionary dynamics of structurally ordered and disordered (flexible) regions are investigated genome-wide in flaviviruses, revealing that the amount and location of structural disorder fluctuates highly among related proteins. Some regions are prone to shift between structured and flexible states. Increased evolutionary dynamics of structural disorder is observed for some lineages but not in others. Lineage-specific transitions of this kind could alter the conformational ensemble accessible to the same protein in different species, causing a functional change, even if the predominant function remains conserved. Thus, rapid evolutionary dynamics of structural disorder is a potential driving force for phenotypic divergence among flaviviruses. PMID:23418179

  4. Quantitative attribution of major driving forces on soil organic carbon dynamics

    NASA Astrophysics Data System (ADS)

    Wu, Yiping; Liu, Shuguang; Tan, Zhengxi

    2015-03-01

    Soil organic carbon (SOC) storage plays a major role in the global carbon cycle and is affected by many factors including land use/management changes (e.g., biofuel production-oriented changes). However, the contributions of various factors to SOC changes are not well understood and quantified. This study was designed to investigate the impacts of changing farming practices, initial SOC levels, and biological enhancement of grain production on SOC dynamics and to attribute the relative contributions of major driving forces (CO2 enrichment and farming practices) using a fractional factorial modeling design. The case study at a crop site in Iowa in the United States demonstrated that the traditional corn-soybean (CS) rotation could still accumulate SOC over this century (from 4.2 to 6.8 kg C/m2) under the current condition; whereas the continuous-corn (CC) system might have a higher SOC sequestration potential than CS. In either case, however, residue removal could reduce the sink potential substantially. Long-term simulation results also suggested that the equilibrium SOC level may vary greatly (˜5.7 to ˜11 kg C/m2) depending on cropping systems and management practices, and projected growth enhancement could make the magnitudes higher (˜7.8 to ˜13 kg C/m2). Importantly, the factorial design analysis indicated that residue management had the most significant impact (contributing 49.4%) on SOC changes, followed by CO2 Enrichment (37%), Tillage (6.2%), the combination of CO2 Enrichment-Residue removal (5.8%), and Fertilization (1.6%). In brief, this study is valuable for understanding the major forces driving SOC dynamics of agroecosystems and informative for decision-makers when seeking the enhancement of SOC sequestration potential and sustainability of biofuel production, especially in the Corn Belt region of the United States.

  5. Driving Forces of Gyrase Recognition by the Addiction Toxin CcdB*

    PubMed Central

    Simic, Mario; De Jonge, Natalie; Loris, Remy; Vesnaver, Gorazd; Lah, Jurij

    2009-01-01

    Gyrase, an essential bacterial topoisomerase, is the target of several antibiotics (e.g. quinolones) as well as of bacterial toxin CcdB. This toxin, encoded by Escherichia coli toxin-antitoxin module ccd, poisons gyrase by causing inhibition of both transcription and replication. Because the molecular driving forces of gyrase unfolding and CcdB-gyrase binding were unknown, the nature of the CcdB-gyrase recognition remained elusive. Therefore, we performed a detailed thermodynamic analysis of CcdB binding to several fragments of gyrase A subunit (GyrA) that contain the CcdB-binding site. Binding of CcdB to the shorter fragments was studied directly by isothermal titration calorimetry. Its binding to the longer GyrA59 fragment in solution is kinetically limited and was therefore investigated via urea induced unfolding of the GyrA59-CcdB complex and unbound GyrA59 and CcdB, monitored by circular dichroism spectroscopy. Model analysis of experimental data, in combination with the relevant structural information, indicates that CcdB binding to gyrase is an enthalpic process driven mainly by specific interactions between CcdB and the highly stable dimerization domain of the GyrA. The dissection of binding energetics indicates that CcdB-gyrase recognition is accompanied by opening of the tower and catalytic domain of GyrA. Such extensive structural rearrangements appear to be crucial driving forces for the functioning of the ccd toxin-antitoxin module. PMID:19465484

  6. Driving forces for import of waste for energy recovery in Sweden.

    PubMed

    Olofsson, Mattias; Sahlin, Jenny; Ekvall, Tomas; Sundberg, Johan

    2005-02-01

    Between 1996 and 2002, the Swedish import of so-called yellow waste for energy recovery increased. The import mainly consisted of separated wood waste and mixes of used wood and paper and/or plastics that was combusted in district heat production plants (DHPPs). Some mixed waste was imported to waste incineration plants for energy recovery (10% of the import of yellow waste for energy recovery in 2002). The import came primarily from Germany, the Netherlands, Norway, Denmark and Finland. We identified six underlying driving forces for this recent increase of imported waste which are outlined and their interactive issues discussed. --The energy system infrastructure, which enables high energy recovery in Sweden. --The energy taxation, where high Swedish taxes on fossil fuels make relatively expensive solid biofuels the main alternative for base load production of district heat. --The quality of the waste-derived fuels, which has been higher in the exporting countries than in Sweden. --The bans on landfilling within Europe and the shortage of waste treatment capacity. --Taxes on waste management in Europe. --Gate fee differences between exporting countries and Sweden. In the future, the overall strength of these driving forces will probably be weakened. A Swedish tax on waste incineration is being investigated. In other European countries, the ambition to reach the Kyoto targets and increase the renewable electricity production could improve the competitiveness of waste-derived fuels in comparison with fossil fuels. Swedish DHPPs using waste-derived fuels will experience higher costs after the Waste Incineration Directive is fully implemented. The uncertainty about European waste generation and treatment capacity, however, might have a large influence on the future gate fees and thus also on the yellow waste import into Sweden. PMID:15751390

  7. Driving force analysis of the agricultural water footprint in China based on the LMDI method.

    PubMed

    Zhao, Chunfu; Chen, Bin

    2014-11-01

    China's water scarcity problems have become more severe because of the unprecedented economic development and population explosion. Considering agriculture's large share of water consumption, obtaining a clear understanding of Chinese agricultural consumptive water use plays a key role in addressing China's water resource stress and providing appropriate water mitigation policies. We account for the Chinese agricultural water footprint from 1990 to 2009 based on bottom up approach. Then, the underlying driving forces are decomposed into diet structure effect, efficiency effect, economic activity effect, and population effect, and analyzed by applying a log-mean Divisia index (LMDI) model. The results reveal that the Chinese agricultural water footprint has risen from the 94.1 Gm3 in 1990 to 141 Gm3 in 2009. The economic activity effect is the largest positive contributor to promoting the water footprint growth, followed by the population effect and diet structure effect. Although water efficiency improvement as a significant negative effect has reduced overall water footprint, the water footprint decline from water efficiency improvement cannot compensate for the huge increase from the three positive driving factors. The combination of water efficiency improvement and dietary structure adjustment is the most effective approach for controlling the Chinese agricultural water footprint's further growth. PMID:25289879

  8. Theory of open-circuit voltage and the driving force of charge separation in pn-junction solar cells

    NASA Astrophysics Data System (ADS)

    Hara, Kosuke O.; Usami, Noritaka

    2013-10-01

    We have derived the formula to calculate the open-circuit voltage in a pn-junction solar cell from carrier densities by considering the driving force of charge separation without using the equation for current. The excess amount of chemical potential of charge carriers is proposed as the origin of the driving force of charge separation, and the voltage formula is derived from the gradient of excess chemical potential. The calculated voltage is shown to agree with the result of a rigorous device simulation for symmetrical pn-homojunction devices with band gaps of 0.6-1.8 eV and majority-carrier densities of 1015-1019 cm-3. The developed formula is, therefore, valid for the pn-homojunction devices, indicating that the driving force of charge separation stems from the excess chemical potential.

  9. Depletion forces drive polymer-like self-assembly in vibrofluidized granular materials†

    PubMed Central

    Nossal, Ralph

    2011-01-01

    Ranging from nano- to granular-scales, control of particle assembly can be achieved by limiting the available free space, for example by increasing the concentration of particles (“crowding”) or through their restriction to 2D environments. It is unclear, however, if self-assembly principles governing thermally-equilibrated molecules can also apply to mechanically-excited macroscopic particles in non-equilibrium steady-state. Here we show that low densities of vibrofluidized steel rods, when crowded by high densities of spheres and confined to quasi-2D planes, can self-assemble into linear polymer-like structures. Our 2D Monte Carlo simulations show similar finite sized aggregates in thermally equilibrated binary mixtures. Using theory and simulations, we demonstrate how depletion interactions create oriented “binding” forces between rigid rods to form these “living polymers.” Unlike rod-sphere mixtures in 3D that can demonstrate well-defined equilibrium phases, our mixtures confined to 2D lack these transitions because lower dimensionality favors the formation of linear aggregates, thus suppressing a true phase transition. The qualitative and quantitative agreement between equilibrium and granular patterning for these mixtures suggests that entropy maximization is the determining driving force for bundling. Furthermore, this study uncovers a previously unknown patterning behavior at both the granular and nanoscales, and may provide insights into the role of crowding at interfaces in molecular assembly. PMID:22039392

  10. Dominant Driving Forces in Human Telomere Quadruplex Binding-Induced Structural Alterations.

    PubMed

    Bončina, Matjaž; Hamon, Florian; Islam, Barira; Teulade-Fichou, Marie-Paule; Vesnaver, Gorazd; Haider, Shozeb; Lah, Jurij

    2015-06-16

    Recently various pathways of human telomere (ht) DNA folding into G-quadruplexes and of ligand binding to these structures have been proposed. However, the key issue as to the nature of forces driving the folding and recognition processes remains unanswered. In this study, structural changes of 22-mer ht-DNA fragment (Tel22), induced by binding of ions (K(+), Na(+)) and specific bisquinolinium ligands, were monitored by calorimetric and spectroscopic methods and by gel electrophoresis. Using the global model analysis of a wide variety of experimental data, we were able to characterize the thermodynamic forces that govern the formation of stable Tel22 G-quadruplexes, folding intermediates, and ligand-quadruplex complexes, and then predict Tel22 behavior in aqueous solutions as a function of temperature, salt concentration, and ligand concentration. On the basis of the above, we believe that our work sets the framework for better understanding the heterogeneity of ht-DNA folding and binding pathways, and its structural polymorphism. PMID:26083930

  11. Equal sensation curves for whole-body vibration expressed as a function of driving force

    NASA Astrophysics Data System (ADS)

    Mansfield, Neil J.; Maeda, Setsuo

    2005-06-01

    Previous studies have shown that the seated human is most sensitive to whole-body vertical vibration at about 5 Hz. Similarly, the body shows an apparent mass resonance at about 5 Hz. Considering these similarities between the biomechanical and subjective responses, it was hypothesized that, at low frequencies, subjective ratings of whole-body vibration might be directly proportional to the driving force. Twelve male subjects participated in a laboratory experiment where subjects sat on a rigid seat mounted on a shaker. The magnitude of a test stimulus was adjusted such that the subjective intensity could be matched to a reference stimulus, using a modified Bruceton test protocol. The sinusoidal reference stimulus was 8-Hz vibration with a magnitude of 0.5 m/s2 rms (or 0.25 m/s2 rms for the 1-Hz test); the sinusoidal test stimuli had frequencies of 1, 2, 4, 16, and 32 Hz. Equal sensation contours in terms of seat acceleration showed data similar to those in the literature. Equal sensation contours in terms of force showed a nominally linear response at 1, 2, and 4 Hz, but an increasing sensitivity at higher frequencies. This is in agreement with a model derived from published subjective and objective fitted data. .

  12. Driving forces for adsorption of polyols onto zeolites from aqueous solutions.

    PubMed

    Mallon, Elizabeth E; Bhan, Aditya; Tsapatsis, Michael

    2010-02-11

    Ambient temperature adsorption isotherms have been developed for C(2)-C(6) diols and triols on small (FER), medium (MWW, MFI, BEA), and large (MOR, FAU) pore zeolites as well as on ordered mesoporous materials (MCM-36, 3DOm-MFI, and SBA-15) using gravimetry. Henry's constants for diol and triol adsorption on silicalite-1 increase exponentially with carbon number demonstrating that confinement of the adsorbate in the zeolite pores is the primary driving force for adsorption. This conclusion is supported by results for propylene glycol adsorption at low coverages on materials differing in topology and chemical composition. It is shown that adsorption decreases with an increase in the adsorbent pore size, and aluminum content only has a marginal effect. Comparison of diol and triol adsorption on silicalite-1 shows that increasing the number of hydroxyl groups causes a decrease in the Henry's constant possibly due to a change of the configuration of the adsorbate in the zeolite pores, while the location of the hydroxyl groups does not have a significant effect. Overall, this study provides evidence that polyol adsorption is primarily a function of dispersion forces that are derived from the fit of the adsorbate in the adsorbent pores. These findings could have an impact on the separation and catalytic conversion of oxygenates in the processing of biomass to chemicals and fuels. PMID:20070098

  13. Dominant Driving Forces in Human Telomere Quadruplex Binding-Induced Structural Alterations

    PubMed Central

    Bončina, Matjaž; Hamon, Florian; Islam, Barira; Teulade-Fichou, Marie-Paule; Vesnaver, Gorazd; Haider, Shozeb; Lah, Jurij

    2015-01-01

    Recently various pathways of human telomere (ht) DNA folding into G-quadruplexes and of ligand binding to these structures have been proposed. However, the key issue as to the nature of forces driving the folding and recognition processes remains unanswered. In this study, structural changes of 22-mer ht-DNA fragment (Tel22), induced by binding of ions (K+, Na+) and specific bisquinolinium ligands, were monitored by calorimetric and spectroscopic methods and by gel electrophoresis. Using the global model analysis of a wide variety of experimental data, we were able to characterize the thermodynamic forces that govern the formation of stable Tel22 G-quadruplexes, folding intermediates, and ligand-quadruplex complexes, and then predict Tel22 behavior in aqueous solutions as a function of temperature, salt concentration, and ligand concentration. On the basis of the above, we believe that our work sets the framework for better understanding the heterogeneity of ht-DNA folding and binding pathways, and its structural polymorphism. PMID:26083930

  14. Associated decrements in rate of force development and neural drive after maximal eccentric exercise.

    PubMed

    Farup, J; Rahbek, S K; Bjerre, J; de Paoli, F; Vissing, K

    2016-05-01

    The present study investigated the changes in contractile rate of force development (RFD) and the neural drive following a single bout of eccentric exercise. Twenty-four subjects performed 15 × 10 maximal isokinetic eccentric knee extensor contractions. Prior to and at 24, 48, 72, 96, and 168 h during post-exercise recovery, isometric RFD (30, 50 100, and 200 ms), normalized RFD [1/6,1/2, and 2/3 of maximal voluntary contraction (MVC)] and rate of electromyography rise (RER; 30, 50, and 75 ms) were measured. RFD decreased by 28-42% peaking at 48 h (P < 0.01-P < 0.001) and remained depressed at 168 h (P < 0.05). Normalized RFD at 2/3 of MVC decreased by 22-39% (P < 0.01), peaked at 72 h and returned to baseline at 168 h. These changes in RFD were associated with a decrease in RER at 48 h-96 h (P < 0.05-P < 0.001). Accumulated changes (area under curve) revealed a greater relative decrease in accumulated RFD at 100 ms by -2727 ± 309 (%h; P < 0.05) and 200 ms by -3035 ± 271 (%h; P < 0.001) compared with MVC, which decreased, by -1956 ± 234 (%h). In conclusion, RFD and RER are both markedly reduced following a bout of maximal eccentric exercise. This association suggests that exercise-induced decrements in RFD can, in part, be explained decrements in neural drive. PMID:25944178

  15. Thermal denaturation of Bungarus fasciatus acetylcholinesterase: Is aggregation a driving force in protein unfolding?

    PubMed

    Shin, I; Wachtel, E; Roth, E; Bon, C; Silman, I; Weiner, L

    2002-08-01

    A monomeric form of acetylcholinesterase from the venom of Bungarus fasciatus is converted to a partially unfolded molten globule species by thermal inactivation, and subsequently aggregates rapidly. To separate the kinetics of unfolding from those of aggregation, single molecules of the monomeric enzyme were encapsulated in reverse micelles of Brij 30 in 2,2,4-trimethylpentane, or in large unilamellar vesicles of egg lecithin/cholesterol at various protein/micelle (vesicle) ratios. The first-order rate constant for thermal inactivation at 45 degrees C, of single molecules entrapped within the reverse micelles (0.031 min(-1)), was higher than in aqueous solution (0.007 min(-1)) or in the presence of normal micelles (0.020 min(-1)). This clearly shows that aggregation does not provide the driving force for thermal inactivation of BfAChE. Within the large unilamellar vesicles, at average protein/vesicle ratios of 1:1 and 10:1, the first-order rate constants for thermal inactivation of the encapsulated monomeric acetylcholinesterase, at 53 degrees C, were 0.317 and 0.342 min(-1), respectively. A crosslinking technique, utilizing the photosensitive probe, hypericin, showed that thermal denaturation produces a distribution of species ranging from dimers through to large aggregates. Consequently, at a protein/vesicle ratio of 10:1, aggregation can occur upon thermal denaturation. Thus, these experiments also demonstrate that aggregation does not drive the thermal unfolding of Bungarus fasciatus acetylcholinesterase. Our experimental approach also permitted monitoring of recovery of enzymic activity after thermal denaturation in the absence of a competing aggregation process. Whereas no detectable recovery of enzymic activity could be observed in aqueous solution, up to 23% activity could be obtained for enzyme sequestered in the reverse micelles. PMID:12142456

  16. Nuclear Planetology: Constraining the Driving Force in Wegener's Continental Drift Theory

    NASA Astrophysics Data System (ADS)

    Roller, G.

    2015-12-01

    Nuclear planetology [1] is a new research field, which aims at deciphering the nuclear physics processes responsible for the evolution of ultra-substellar objects and the driving force in Wegener's continental drift theory by means of Re-Os nuclear geochronometry [2]. Terrestrial Re/Os ratios observed within diamond sulphide inclusions [3], compatible with lunar r-process production ratios of Th/U≈1≈Au/Ir [4], drop from ≈0.8 to 0.2-0.05 for nucleogeochronometric ages between 2.3 Ga and 1.4 Ga [5]. It has therefore been argued [5,6] that the Re/Os fractionation is related to a change in oxygen fugacity due to the physics/chemistry of Earth's core after a possibly Fermi-pressure controlled core collapse [4]. Here, Pd/Ru, Pd/Pt, Pd/Ir, Pd/Os, Ru/Ir, Ru/Os, Pt/Ir or Pt/Os ratios from 24 published H chondrite components [7] are connected to their respective nucleogeochronometric ages to constrain an extended fossil fractionation record over 800 Ma. The following ranges are obtained: 0.06-1.04 (Pd/Ru), 0.06-0.79 (Pd/Pt), 0.06-1.76 (Pd/Os), 0.07-1.94 (Pd/Ir), 1.08-1.99 (Ru/Ir), 0.83-2.41 (Pt/Os), 0.82-2.64 (Pt/Ir). Comparing the Re/Os fractionation pattern of the diamond sulphide inclusions with these results and considering that Re is readily oxidized even at ultra-low oxygen fugacity, it may be concluded that (i) extremely reducing conditions within Earth's core basically preserve any unfractionated r-process element ratio until today; and (ii) nuclear/quantum physics processes leading to the observed ratios and fractionation pattern are ultimately the driving force in Wegener's continental drift theory. [1] Roller (2015), Abstract T34B-0407, AGU Spring Meeting. [2] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-17. [3] Smit et al. (2010), GCA 74, 3292. [4] Roller (2015), Abstract #5041, 78th Ann. Met. Soc. Meeting. [5] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-2399. [6] Roller (2015), Abstract PG34A-0283, AGU Spring Meeting. [7] Horan et al. (2009), GCA 73

  17. Direct determination of the driving forces for taurocholate uptake into rat liver plasma membrane vesicles.

    PubMed

    Duffy, M C; Blitzer, B L; Boyer, J L

    1983-10-01

    To determine directly the driving forces for bile acid entry into the hepatocyte, the uptake of [3H]taurocholic acid into rat liver plasma membrane vesicles was studied. The membrane preparation contained predominantly right-side-out vesicles, and was highly enriched in plasma membrane marker enzymes. The uptake of taurocholate at equilibrium was inversely related to medium osmolarity, indicating transport into an osmotically sensitive space. In the presence of an inwardly directed sodium gradient (NaCl or sodium gluconate), the initial rate of uptake was rapid and taurocholate was transiently accumulated at a concentration twice that at equilibrium (overshoot). Other inwardly directed cation gradients (K+, Li+, choline+) or the presence of sodium in the absence of a gradient (Na+ equilibrated) resulted in a slower initial uptake rate and did not sustain an overshoot. Bile acids inhibited sodium-dependent taurocholate uptake, whereas bromsulphthalein inhibited both sodium-dependent and sodium-independent uptake and D-glucose had no effect on uptake. Uptake was temperature dependent, with maximal overshoots occurring at 25 degrees C. Imposition of a proton gradient across the vesicle (pHo less than pHi) in the absence of a sodium gradient failed to enhance taurocholate uptake, indicating that double ion exchange (Na+-H+, OH- -anion) is unlikely. Creation of a negative intravesicular potential by altering accompanying anions or by valinomycin-induced K+-diffusion potentials did not enhance taurocholate uptake, suggesting an electroneutral transport mechanism. The kinetics of taurocholate uptake demonstrated saturability with a Michaelis constant at 52 microM and maximum velocity of 4.5 nmol X mg-1 X protein X min-1. These studies provide definitive evidence for a sodium gradient-dependent, carrier-mediated, electrically neutral transport mechanism for hepatic taurocholate uptake. These findings are consistent with a model for bile secretion in which the basolateral

  18. Direct determination of the driving forces for taurocholate uptake into rat liver plasma membrane vesicles.

    PubMed Central

    Duffy, M C; Blitzer, B L; Boyer, J L

    1983-01-01

    To determine directly the driving forces for bile acid entry into the hepatocyte, the uptake of [3H]taurocholic acid into rat liver plasma membrane vesicles was studied. The membrane preparation contained predominantly right-side-out vesicles, and was highly enriched in plasma membrane marker enzymes. The uptake of taurocholate at equilibrium was inversely related to medium osmolarity, indicating transport into an osmotically sensitive space. In the presence of an inwardly directed sodium gradient (NaCl or sodium gluconate), the initial rate of uptake was rapid and taurocholate was transiently accumulated at a concentration twice that at equilibrium (overshoot). Other inwardly directed cation gradients (K+, Li+, choline+) or the presence of sodium in the absence of a gradient (Na+ equilibrated) resulted in a slower initial uptake rate and did not sustain an overshoot. Bile acids inhibited sodium-dependent taurocholate uptake, whereas bromsulphthalein inhibited both sodium-dependent and sodium-independent uptake and D-glucose had no effect on uptake. Uptake was temperature dependent, with maximal overshoots occurring at 25 degrees C. Imposition of a proton gradient across the vesicle (pHo less than pHi) in the absence of a sodium gradient failed to enhance taurocholate uptake, indicating that double ion exchange (Na+-H+, OH- -anion) is unlikely. Creation of a negative intravesicular potential by altering accompanying anions or by valinomycin-induced K+-diffusion potentials did not enhance taurocholate uptake, suggesting an electroneutral transport mechanism. The kinetics of taurocholate uptake demonstrated saturability with a Michaelis constant at 52 microM and maximum velocity of 4.5 nmol X mg-1 X protein X min-1. These studies provide definitive evidence for a sodium gradient-dependent, carrier-mediated, electrically neutral transport mechanism for hepatic taurocholate uptake. These findings are consistent with a model for bile secretion in which the basolateral

  19. Additional interfacial force in lattice Boltzmann models for incompressible multiphase flows.

    PubMed

    Li, Q; Luo, K H; Gao, Y J; He, Y L

    2012-02-01

    The existing lattice Boltzmann models for incompressible multiphase flows are mostly constructed with two distribution functions: one is the order parameter distribution function, which is used to track the interface between different phases, and the other is the pressure distribution function for solving the velocity field. In this paper, it is shown that in these models the recovered momentum equation is inconsistent with the target one: an additional force is included in the recovered momentum equation. The additional force has the following features. First, it is proportional to the macroscopic velocity. Second, it is zero in every single-phase region but is nonzero in the interface. Therefore it can be interpreted as an interfacial force. To investigate the effects of the additional interfacial force, numerical simulations are carried out for the problem of Rayleigh-Taylor instability, droplet splashing on a thin liquid film, and the evolution of a falling droplet under gravity. Numerical results demonstrate that, with the increase of the velocity or the Reynolds number, the additional interfacial force will gradually have an important influence on the interface and affect the numerical accuracy. PMID:22463354

  20. Microstructure and mesh sensitivities of mesoscale surrogate driving force measures for transgranular fatigue cracks in polycrystals

    SciTech Connect

    Castelluccio, Gustavo M.; McDowell, David L.

    2015-05-22

    The number of cycles required to form and grow microstructurally small fatigue cracks in metals exhibits substantial variability, particularly for low applied strain amplitudes. This variability is commonly attributed to the heterogeneity of cyclic plastic deformation within the microstructure, and presents a challenge to minimum life design of fatigue resistant components. Our paper analyzes sources of variability that contribute to the driving force of transgranular fatigue cracks within nucleant grains. We also employ crystal plasticity finite element simulations that explicitly render the polycrystalline microstructure and Fatigue Indicator Parameters (FIPs) averaged over different volume sizes and shapes relative to the anticipated fatigue damage process zone. Volume averaging is necessary to both achieve description of a finite fatigue damage process zone and to regularize mesh dependence in simulations. Furthermore, results from constant amplitude remote applied straining are characterized in terms of the extreme value distributions of volume averaged FIPs. Grain averaged FIP values effectively mitigate mesh sensitivity, but they smear out variability within grains. Furthermore, volume averaging over bands that encompass critical transgranular slip planes appear to present the most attractive approach to mitigate mesh sensitivity while preserving variability within grains.

  1. Computational studies of sequence-specific driving forces in peptide self-assembly

    NASA Astrophysics Data System (ADS)

    Jeon, Joohyun

    Peptides are biopolymers made from various sequences of twenty different types of amino acids, connected by peptide bonds. There are practically an infinite number of possible sequences and tremendous possible combinations of peptide-peptide interactions. Recently, an increasing number of studies have shown a stark variety of peptide self-assembled nanomaterials whose detailed structures depend on their sequences and environmental factors; these have end uses in medical and bio-electronic applications, for example. To understand the underlying physics of complex peptide self-assembly processes and to delineate sequence specific effects, in this study, I use various simulation tools spanning all-atom molecular dynamics to simple lattice models and quantify the balance of interactions in the peptide self-assembly processes. In contrast to the existing view that peptides' aggregation propensities are proportional to the net sequence hydrophobicity and inversely proportional to the net charge, I show the more nuanced effects of electrostatic interactions, including the cooperative effects between hydrophobic and electrostatic interactions. Notably, I suggest rather unexpected, yet important roles of entropies in the small scale oligomerization processes. Overall, this study broadens our understanding of the role of thermodynamic driving forces in peptide self-assembly.

  2. [Landscape pattern change at the upper reaches of Minjiang River and its driving force].

    PubMed

    Hu, Zhibin; He, Xingyuan; Jiang, Xiaobo; Zhao, Yonghua; Hu, Yuanman; Chang, Yu; Li, Yuehui; Han, Wenquan; Liu, Miao

    2004-10-01

    The upper reaches of Minjiang River is an ecological sensitive and vulnerable area in southwest of China. It is of great significance to the ecological pattern safety in China. In this study, we analyzed the landscape pattern change through the interpretation of TM imageries in 1986, 1995 and 2000. The results showed that the matrix landscape in this area was grass landscape. Forest landscape patches were embedded in the grass landscape. The forest landscape area increased from 1986 to 1995 and decreased from 1995 to 2000. However, the number of patches of forest landscape was increasing during all the time. This suggested that the intensity of anthropogenic disturbances including harvesting, forest landscape reclaiming and excessive grazing were persistently increasing from 1986 to 2000. The ecological driving forces of the landscape change in this area were the intensified anthropogenic disturbances as a result of the population boom including the predacious harvesting of forest and excessive grazing. The natural disturbances such as the global climatic change also partly influenced the landscape change in this area. PMID:15624811

  3. Marine incursion into East Asia: a forgotten driving force of biodiversity

    PubMed Central

    Yang, Lu; Hou, Zhonge; Li, Shuqiang

    2013-01-01

    Episodic marine incursion has been a major driving force in the formation of present-day diversity. Marine incursion is considered to be one of the most productive ‘species pumps’ particularly because of its division and coalescence effects. Marine incursion events and their impacts on diversity are well documented from South America, North America and Africa; however, their history and impacts in continental East Asia largely remain unknown. Here, we propose a marine incursion scenario occurring in East Asia during the Miocene epoch, 10–17 Ma. Our molecular phylogenetic analysis of Platorchestia talitrids revealed that continental terrestrial populations (Platorchestia japonica) form a monophyletic group that is the sister group to the Northwest Pacific coastal species Platorchestia pacifica. The divergence time between the two species coincides with Middle Miocene high global sea levels. We suggest that the inland form arose as a consequence of a marine incursion event. This is the first solid case documenting the impact of marine incursion on extant biodiversity in continental East Asia. We believe that such incursion event has had major impacts on other organisms and has played an important role in the formation of biodiversity patterns in the region. PMID:23446524

  4. Whole-genome plasma sequencing reveals focal amplifications as a driving force in metastatic prostate cancer

    PubMed Central

    Ulz, Peter; Belic, Jelena; Graf, Ricarda; Auer, Martina; Lafer, Ingrid; Fischereder, Katja; Webersinke, Gerald; Pummer, Karl; Augustin, Herbert; Pichler, Martin; Hoefler, Gerald; Bauernhofer, Thomas; Geigl, Jochen B.; Heitzer, Ellen; Speicher, Michael R.

    2016-01-01

    Genomic alterations in metastatic prostate cancer remain incompletely characterized. Here we analyse 493 prostate cancer cases from the TCGA database and perform whole-genome plasma sequencing on 95 plasma samples derived from 43 patients with metastatic prostate cancer. From these samples, we identify established driver aberrations in a cancer-related gene in nearly all cases (97.7%), including driver gene fusions (TMPRSS2:ERG), driver focal deletions (PTEN, RYBP and SHQ1) and driver amplifications (AR and MYC). In serial plasma analyses, we observe changes in focal amplifications in 40% of cases. The mean time interval between new amplifications was 26.4 weeks (range: 5–52 weeks), suggesting that they represent rapid adaptations to selection pressure. An increase in neuron-specific enolase is accompanied by clonal pattern changes in the tumour genome, most consistent with subclonal diversification of the tumour. Our findings suggest a high plasticity of prostate cancer genomes with newly occurring focal amplifications as a driving force in progression. PMID:27328849

  5. Transcriptional abundance is not the single force driving the evolution of bacterial proteins

    PubMed Central

    2013-01-01

    Background Despite rapid progress in understanding the mechanisms that shape the evolution of proteins, the relative importance of various factors remain to be elucidated. In this study, we have assessed the effects of 16 different biological features on the evolutionary rates (ERs) of protein-coding sequences in bacterial genomes. Results Our analysis of 18 bacterial species revealed new correlations between ERs and constraining factors. Previous studies have suggested that transcriptional abundance overwhelmingly constrains the evolution of yeast protein sequences. This transcriptional abundance leads to selection against misfolding or misinteractions. In this study we found that there was no single factor in determining the evolution of bacterial proteins. Not only transcriptional abundance (codon adaptation index and expression level), but also protein-protein associations (PPAs), essentiality (ESS), subcellular localization of cytoplasmic membrane (SLM), transmembrane helices (TMH) and hydropathicity score (HS) independently and significantly affected the ERs of bacterial proteins. In some species, PPA and ESS demonstrate higher correlations with ER than transcriptional abundance. Conclusions Different forces drive the evolution of protein sequences in yeast and bacteria. In bacteria, the constraints are involved in avoiding a build-up of toxic molecules caused by misfolding/misinteraction (transcriptional abundance), while retaining important functions (ESS, PPA) and maintaining the cell membrane (SLM, TMH and HS). Each of these independently contributes to the variation in protein evolution. PMID:23914835

  6. Temporal-spatial patterns of wetlands changes in China and driving force analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Shuwen; Zhang, Yangzhen; Chen, Jing; Zhang, Yanhong; Gao, Zhiqiang

    2004-11-01

    Wetlands are special ecosystem lying between the terrestrial and open-water areas. Similar to forest, grass, and ocean ecosystems, wetlands take parts in protecting environments and exploring resources. In China, wetlands are undergoing significant degradation that is caused by both natural processes and human activities. In order to know the details of wetlands change so as to take suitable actions to protect wetlands, Landsat TM/ETM images are used as main data sets. Accessorial data such as topography map and China mire map are also used. In this paper, wetlands are defined as swamplands, potholes, wet meadow, riverine, lacurtrine. Three periods (1990a, 1995a, 2000a) data of wetlands in china are extracted from TM through the interactive interpretation. Applying spatial analysis function of GIS technology and statistics methods, the spatial distribution pattern and temporal changes are studied. The research results show that, during the 10 years from 1990 to 2000, wetlands area decreased largely, and spatial difference is notable. Finally, the driving forces resulting in mires changes are analyzed.

  7. Microstructure and mesh sensitivities of mesoscale surrogate driving force measures for transgranular fatigue cracks in polycrystals

    DOE PAGESBeta

    Castelluccio, Gustavo M.; McDowell, David L.

    2015-05-22

    The number of cycles required to form and grow microstructurally small fatigue cracks in metals exhibits substantial variability, particularly for low applied strain amplitudes. This variability is commonly attributed to the heterogeneity of cyclic plastic deformation within the microstructure, and presents a challenge to minimum life design of fatigue resistant components. Our paper analyzes sources of variability that contribute to the driving force of transgranular fatigue cracks within nucleant grains. We also employ crystal plasticity finite element simulations that explicitly render the polycrystalline microstructure and Fatigue Indicator Parameters (FIPs) averaged over different volume sizes and shapes relative to the anticipatedmore » fatigue damage process zone. Volume averaging is necessary to both achieve description of a finite fatigue damage process zone and to regularize mesh dependence in simulations. Furthermore, results from constant amplitude remote applied straining are characterized in terms of the extreme value distributions of volume averaged FIPs. Grain averaged FIP values effectively mitigate mesh sensitivity, but they smear out variability within grains. Furthermore, volume averaging over bands that encompass critical transgranular slip planes appear to present the most attractive approach to mitigate mesh sensitivity while preserving variability within grains.« less

  8. Driving Forces for Oppositely Charged Polyion Association in Aqueous Solutions: Enthalpic, Entropic, but Not Electrostatic.

    PubMed

    Fu, Jingcheng; Schlenoff, Joseph B

    2016-01-27

    Driving forces for association between oppositely charged biological or synthetic polymers in aqueous solution have long been identified as electrostatic in origin. This attraction is broken down into an entropic component, due to loss of counterions, and an enthalpic component, stemming from Coulombic attraction between opposite charges. While the balance between entropic and enthalpic contributions shifts according to the conditions, the presence of exotherms or endotherms on mixing, though small, are viewed as signatures of Coulombic interactions which support theories of polyelectrolyte association rooted in continuum electrostatics. Here, a head-to-head comparison is made between mechanisms based on electrostatics and those based on specific ion pairing, or ion exchange. Using a Hofmeister series of counterions for a common polycation, poly(diallyldimethylammonium), enthalpy changes on association with poly(styrenesulfonate) are shown to derive from changes in water perturbation, revealed by Raman scattering studies of water O-H vibrations. The free energy for complexation is almost completely entropic over all salt concentrations. PMID:26771205

  9. Force Sensitive Handles and Capacitive Touch Sensor for Driving a Flexible Haptic-Based Immersive System

    PubMed Central

    Covarrubias, Mario; Bordegoni, Monica; Cugini, Umberto

    2013-01-01

    In this article, we present an approach that uses both two force sensitive handles (FSH) and a flexible capacitive touch sensor (FCTS) to drive a haptic-based immersive system. The immersive system has been developed as part of a multimodal interface for product design. The haptic interface consists of a strip that can be used by product designers to evaluate the quality of a 3D virtual shape by using touch, vision and hearing and, also, to interactively change the shape of the virtual object. Specifically, the user interacts with the FSH to move the virtual object and to appropriately position the haptic interface for retrieving the six degrees of freedom required for both manipulation and modification modalities. The FCTS allows the system to track the movement and position of the user's fingers on the strip, which is used for rendering visual and sound feedback. Two evaluation experiments are described, which involve both the evaluation and the modification of a 3D shape. Results show that the use of the haptic strip for the evaluation of aesthetic shapes is effective and supports product designers in the appreciation of the aesthetic qualities of the shape. PMID:24113680

  10. Stress-triggered atavistic reprogramming (STAR) addiction: driving force behind head and neck cancer?

    PubMed Central

    Masuda, Muneyuki; Wakasaki, Takahiro; Toh, Satoshi

    2016-01-01

    Recent results of the Cancer Genome Atlas on head and neck squamous cell carcinoma (HNSCC) revealed that HNSCC lacked predominant gain-of-function mutations in oncogenes, whereas an essential role for epigenetics in oncogenesis has become apparent. In parallel, it has gained general acceptance that cancer is considered as complex adaptive system, which evolves responding environmental selective pressures. This somatic evolution appears to proceed concurrently with the acquisition of an atavistic pluripotent state (i.e., “stemness”), which is inducible by intrinsic epigenetic reprogramming program as demonstrated by induced pluripotent stem (iPS) cells. This Nobel prize-winning discovery has markedly accelerated and expanded cancer stem cell research from the point of epigenetic reprogramming. Taken together, we hypothesize that stress-triggered atavistic reprogramming (STAR) may be the major driving force of HNSCC evolution. In this perspective, we discuss the possible mechanisms of STAR in HNSCC, focusing on recent topics of epigenetic reprogramming in developmental and cancer cell biology. PMID:27429838

  11. Driving force transmission mechanism using a timing belt for an internal combustion engine

    SciTech Connect

    Abe, S.

    1987-11-24

    A driving force transmission mechanism is described comprising: a timing pulley having teeth, each of the teeth having a width perpendicular to a direction of movement of the teeth; and a timing belt engaging the timing pulley, the timing belt having teeth, each of the timing belt teeth having a width perpendicular to a direction of movement of the timing belt teeth; a width of the timing belt not being larger that a width of the timing pulley; the width of the teeth of the timing belt at dedendums of the teeth being larger than a width of engagement of the teeth of the timing belt with the teeth of the timing pulley; at least one of width end portions of the teeth of the timing pulley and width end portions of the teeth of the timing belt being cut out so that width end portions of the teeth of the timing belt at dedendums of the timing belt do not contact the teeth of the timing pulley.

  12. Driving force for indentation cracking in glass: composition, pressure and temperature dependence

    PubMed Central

    Rouxel, Tanguy

    2015-01-01

    The occurrence of damage at the surface of glass parts caused by sharp contact loading is a major issue for glass makers, suppliers and end-users. Yet, it is still a poorly understood problem from the viewpoints both of glass science and solid mechanics. Different microcracking patterns are observed at indentation sites depending on the glass composition and indentation cracks may form during both the loading and the unloading stages. Besides, we do not know much about the fracture toughness of glass and its composition dependence, so that setting a criterion for crack initiation and predicting the extent of the damage yet remain out of reach. In this study, by comparison of the behaviour of glasses from very different chemical systems and by identifying experimentally the individual contributions of the different rheological processes leading to the formation of the imprint—namely elasticity, densification and shear flow—we obtain a fairly straightforward prediction of the type and extent of the microcracks which will most likely form, depending on the physical properties of the glass. Finally, some guidelines to reduce the driving force for microcracking are proposed in the light of the effects of composition, temperature and pressure, and the areas for further research are briefly discussed. PMID:25713446

  13. Whole-genome plasma sequencing reveals focal amplifications as a driving force in metastatic prostate cancer.

    PubMed

    Ulz, Peter; Belic, Jelena; Graf, Ricarda; Auer, Martina; Lafer, Ingrid; Fischereder, Katja; Webersinke, Gerald; Pummer, Karl; Augustin, Herbert; Pichler, Martin; Hoefler, Gerald; Bauernhofer, Thomas; Geigl, Jochen B; Heitzer, Ellen; Speicher, Michael R

    2016-01-01

    Genomic alterations in metastatic prostate cancer remain incompletely characterized. Here we analyse 493 prostate cancer cases from the TCGA database and perform whole-genome plasma sequencing on 95 plasma samples derived from 43 patients with metastatic prostate cancer. From these samples, we identify established driver aberrations in a cancer-related gene in nearly all cases (97.7%), including driver gene fusions (TMPRSS2:ERG), driver focal deletions (PTEN, RYBP and SHQ1) and driver amplifications (AR and MYC). In serial plasma analyses, we observe changes in focal amplifications in 40% of cases. The mean time interval between new amplifications was 26.4 weeks (range: 5-52 weeks), suggesting that they represent rapid adaptations to selection pressure. An increase in neuron-specific enolase is accompanied by clonal pattern changes in the tumour genome, most consistent with subclonal diversification of the tumour. Our findings suggest a high plasticity of prostate cancer genomes with newly occurring focal amplifications as a driving force in progression. PMID:27328849

  14. Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells.

    PubMed

    Yang, Wenxing; Vlachopoulos, Nick; Hao, Yan; Hagfeldt, Anders; Boschloo, Gerrit

    2015-06-28

    Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E(0) = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline dye D149. The origin of this improvement was found to be the increased dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the oxidized dye with a driving force of only ∼0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to oxidized dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO(+) redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be ∼0.5 μm, which is smaller than the ∼2.8 μm found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and dyes with a minimal need of driving force for high regeneration yields. PMID:26016854

  15. Growth of whiskers from Sn surfaces: Driving forces and growth mechanisms

    NASA Astrophysics Data System (ADS)

    Chason, Eric; Jadhav, Nitin; Pei, Fei; Buchovecky, Eric; Bower, Allan

    2013-05-01

    Sn whiskers are thin filaments that grow spontaneously out of the surface of coatings on Cu and have become a critical reliability problem in Pb-free electronics. In this review, we focus on what creates the driving force for whiskers (or more rounded “hillocks”), and what determines where on the surface they will form. Experimental studies are reviewed that quantify the relationship between the Cu-Sn intermetallic (IMC) formation, stress in the layer and whisker/hillock density. Measurements of the mechanical properties show how stress relaxation in the Sn layer is intimately related to how much stress develops due to the IMC formation. Real-time scanning electron microscope (SEM)/focused ion beam (FIB) studies are described that illustrate the whisker/hillock growth process in detail. Whiskers are found to grow out of a single grain on the surface with little lateral growth while hillock growth is accompanied by extensive grain growth and crystallite rotation. Electron-backscattering detection (EBSD) shows the grain structure around where the whiskers/hillocks form, indicating that whiskers can grow out of pre-existing grains and do not require the nucleation of new grains. This has led to a picture in which stress builds up due to IMC growth and causes whiskers/hillocks to form at “weak grains”, i.e., grains that have a stress relaxation mechanism that becomes active at a lower stress than its neighbors. FEA (finite element analysis) calculations are used to simulate the evolving stress and whisker growth for several different mechanisms that may lead to “weak” grains.

  16. Crop modeling: Studying the effect of water stress on the driving forces governing plant water potential

    NASA Astrophysics Data System (ADS)

    van Emmerik, T. H. M.; Mirfenderesgi, G.; Bohrer, G.; Steele-Dunne, S. C.; Van De Giesen, N.

    2015-12-01

    Water stress is one of the most important environmental factors that influence plant water dynamics. To prevent excessive water loss and physiological damage, plants can regulate transpiration by adjusting the stomatal aperture. This enhances survival, but also reduced photosynthesis and productivity. During periods of low water availability, stomatal regulation is a trade-off between optimization of either survival or production. Water stress defence mechanisms lead to significant changes in plant dynamics, e.g. leaf and stem water content. Recent research has shown that water content in a corn canopy can change up to 30% diurnally as a result of water stress, which has a considerable influence on radar backscatter from a corn canopy [1]. This highlighted the potential of water stress detection using radar. To fully explore the potential of water stress monitoring using radar, we need to understand the driving forces governing plant water potential. For this study, the recently developed the Finite-Element Tree-Crown Hydrodynamic model version 2 (FETCH2) model is applied to a corn canopy. FETCH2 is developed to resolve the hydrodynamic processes within a plant using the porous media analogy, allowing investigation of the influence of environmental stress factors on plant dynamics such as transpiration, photosynthesis, stomatal conductance, and leaf and stem water content. The model is parameterized and evaluated using a detailed dataset obtained during a three-month field experiment in Flevoland, the Netherlands, on a corn canopy. [1] van Emmerik, T., S. Steele-Dunne, J. Judge and N. van de Giesen: "Impact of Diurnal Variation in Vegetation Water Content on Radar Backscatter of Maize During Water Stress", Geosciences and Remote Sensing, IEEE Transactions on, vol. 52, issue 7, doi: 10.1109/TGRS.2014.2386142, 2015.

  17. Driving forces of heavy metal changes in agricultural soils in a typical manufacturing center.

    PubMed

    Qiu, Menglong; Li, Fangbai; Wang, Qi; Chen, Junjian; Yang, Guoyi; Liu, Liming

    2015-05-01

    Heavy metal concentrations in 2002 and 2012 in agricultural soils in Dongguan, a manufacturing center in southern China, were analyzed to determine the impact of rapid economic development on soil pollution. The level of pollution was assessed using the Nemerow synthetic pollution index (NPI), and its changing characteristics and driving forces were analyzed using multivariate statistical and geostatistical methods. The results indicate that the mean NPI was 0.79 in 2002 and 0.84 in 2012, which indicates aggravated heavy metal contamination in the agricultural soils. The concentrations of Cd and Zn increased 54.7 and 20.8 %, respectively, whereas Hg and Pb decreased 35.3 and 24.5 %, respectively. Cr, As, Cu, and Ni remained relatively stable. The Hg and Cd concentrations were highly correlated with soil types (P < 0.01), the secondary industrial output per unit of land (P < 0.01), proportion of cereal fields (P < 0.01), proportion of vegetable fields (P < 0.01), population density (P < 0.05), and road density (P < 0.05). The Pb and As concentrations were greatly influenced by soil types (P < 0.01), river density (P < 0.01), fertilizer rate (P < 0.01), and road density (P < 0.05). Cr, Zn, Cu, and Ni concentrations were primarily driven by soil types (P < 0.01), river density (P < 0.01), and fertilizer rate (P < 0.05). PMID:25861902

  18. Oxidized cholesterol as the driving force behind the development of Alzheimer’s disease

    PubMed Central

    Gamba, Paola; Testa, Gabriella; Gargiulo, Simona; Staurenghi, Erica; Poli, Giuseppe; Leonarduzzi, Gabriella

    2015-01-01

    Alzheimer’s disease (AD), the most common neurodegenerative disorder associated with dementia, is typified by the pathological accumulation of amyloid Aβ peptides and neurofibrillary tangles (NFT) within the brain. Considerable evidence indicates that many events contribute to AD progression, including oxidative stress, inflammation, and altered cholesterol metabolism. The brain’s high lipid content makes it particularly vulnerable to oxidative species, with the consequent enhancement of lipid peroxidation and cholesterol oxidation, and the subsequent formation of end products, mainly 4-hydroxynonenal and oxysterols, respectively from the two processes. The chronic inflammatory events observed in the AD brain include activation of microglia and astrocytes, together with enhancement of inflammatory molecule and free radical release. Along with glial cells, neurons themselves have been found to contribute to neuroinflammation in the AD brain, by serving as sources of inflammatory mediators. Oxidative stress is intimately associated with neuroinflammation, and a vicious circle has been found to connect oxidative stress and inflammation in AD. Alongside oxidative stress and inflammation, altered cholesterol metabolism and hypercholesterolemia also significantly contribute to neuronal damage and to progression of AD. Increasing evidence is now consolidating the hypothesis that oxidized cholesterol is the driving force behind the development of AD, and that oxysterols are the link connecting the disease to altered cholesterol metabolism in the brain and hypercholesterolemia; this is because of the ability of oxysterols, unlike cholesterol, to cross the blood brain barrier (BBB). The key role of oxysterols in AD pathogenesis has been strongly supported by research pointing to their involvement in modulating neuroinflammation, Aβ accumulation, and cell death. This review highlights the key role played by cholesterol and oxysterols in the brain in AD pathogenesis

  19. Multi Satellites Monitoring of Land Use/Cover Change and Its Driving Forces in Kashgar Region, China

    NASA Astrophysics Data System (ADS)

    Maimaitiaili, Ayisulitan; Aji, xiaokaiti; Kondoh, Akihiko

    2016-04-01

    Multi Satellites Monitoring of Land Use/Cover Change and Its Driving Forces in Kashgar Region, China Ayisulitan Maimaitiaili1, Xiaokaiti Aji2 Akihiko Kondoh2 1Graduate School of Science, Chiba University, Japan 2Center for Environmental Remote Sensing, Chiba University The spatio-temporal changes of Land Use/Cover (LUCC) and its driving forces in Kashgar region, Xinjiang Province, China, are investigated by using satellite remote sensing and a geographical information system (GIS). Main goal of this paper is to quantify the drivers of LUCC. First, considering lack of the Land Cover (LC) map in whole study area, we produced LC map by using Landsat images. Land use information from Landsat data was collected using maximum likelihood classification method. Land use change was studied based on the change detection method of land use types. Second, because the snow provides a key water resources for stream flow, agricultural production and drinking water for sustaining large population in Kashgar region, snow cover are estimated by Spot Vegetation data. Normalized Difference Snow Index (NDSI) algorithm are applied to make snow cover map, which is used to screen the LUCC and climate change. The best agreement is found with threshold value of NDSI≥0.2 to generate multi-temporal snow cover and snowmelt maps. Third, driving forces are systematically identified by LC maps and statistical data such as climate and socio-economic data, regarding to i) the climate changes and ii) socioeconomic development that the spatial correlation among LUCC, snow cover change, climate and socioeconomic changes are quantified by using liner regression model and negative / positive trend analysis. Our results showed that water bodies, bare land and grass land have decreasing notably. By contrast, crop land and urban area have continually increasing significantly, which are dominated in study area. The area of snow/ice have fluctuated and has strong seasonal trends, total annual snow cover

  20. Thermodynamic Driving Forces for Dye Molecule Position and Orientation in Nanoconfined Solvents.

    PubMed

    Harvey, Jacob A; Thompson, Ward H

    2015-07-23

    The results of replica exchange molecular dynamics simulations of a coumarin 153 (C153) dye molecule dissolved in ethanol confined within a 2.4 nm hydrophilic amorphous silica pore are presented. The C153 dye position and orientation distributions provide insight into time-dependent fluorescence measurements in nanoconfined solvents as well as general features of chemistry in mesoporous materials. In addition to the distributions themselves, the free energy, internal energy, and entropic contributions have been calculated to explore the factors determining the distributions. The most likely location of C153 is found to be near the pore surface, but two possible hydrogen-bonding structures lead to differing orientations. Internal energy and entropy are found to be competing forces within the pore, with entropy playing a significant role with unexpected consequences. These results represent a crucial step in determining how the nanoconfining framework can affect measurements of solvation dynamics. PMID:25295835

  1. Chronic Inflammation-Related HPV: A Driving Force Speeds Oropharyngeal Carcinogenesis

    PubMed Central

    Liu, Xin; Ma, Xiangrui; Lei, Zhengge; Feng, Hao; Wang, Shasha; Cen, Xiao; Gao, Shiyu; Jiang, Yaping; Jiang, Jian; Chen, Qianming; Tang, Yajie; Tang, Yaling; Liang, Xinhua

    2015-01-01

    Oropharyngeal squamous cell carcinoma (OPSCC) has been known to be a highly aggressive disease associated with human papilloma virus (HPV) infection. To investigate the relationship between HPV and chronic inflammation in oropharyngeal carcinogenesis, we collected 140 oral mucous fresh specimens including 50 OPSCC patients, 50 cancer in situ, 30 precancerous lesions, and 10 normal oral mucous. Our data demonstrated that there was a significantly higher proportion of severe chronic inflammation in dysplastic epithelia in comparison with that in normal tissues (P<0.001). The positive rate of HPV 16 was parallel with the chronic inflammation degrees from mild to severe inflammation (P<0.05). The positive rate of HPV 16 was progressively improved with the malignant progression of oral mucous (P<0.05). In addition, CD11b+ LIN- HLA-DR-CD33+ MDSCs were a critical cell population that mediates inflammation response and immune suppression in HPV-positive OPSCC. These indicated that persistent chronic inflammation-related HPV infection might drive oropharyngeal carcinogenesis and MDSCs might pay an important role during this process. Thus, a combination of HPV infection and inflammation expression might become a helpful biomedical marker to predict oropharyngeal carcinogenesis. PMID:26193368

  2. Inertial force measurement of an actuator arm of a hard disk drive in free oscillation by numerical analysis and experiments

    NASA Astrophysics Data System (ADS)

    Gu, Bin; Shu, Dong-Wei; Fujii, Yusaku; Shi, Bao-Jun

    2008-12-01

    In this paper, inertial force of an Actuator Arm of a Hard Disk Drive (HDD) in free oscillation after an impact load is accurately measured by means of a finite element analysis and by carrying out experiments using a modified Levitation Mass Method (LMM). A 3D finite element model of an actuator arm of a HDD is modeled in ANSYS/LS-DYNA using shell elements. An impact load, which is modeled as a half sine force pulse, is applied to a mass, which is attached with the Actuator Arm. The velocity and the inertial force of the mass in free oscillation are obtained from the simulation. In the LMM method, the arm is attached to a mass, i.e. the moving part of an aerostatic linear bearing, and the total force acting on the mass is measured as the inertial force of the mass using an optical interferometer. An impact is applied to the mass with the arm by colliding it to the metal base, and the inertial force of the arm is evaluated during the free oscillation. The velocity and the inertial force of the mass are calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental and numerical results is achieved. This numerical analysis can be further used to investigate the dynamic response of the actuator arm when it is subjected to different impact load, which is modeled with half sine force pulse with different pulse widths and amplitudes.

  3. Sector trends and driving forces of global energy use and greenhouse gas emissions: focus in industry and buildings

    SciTech Connect

    Price, Lynn; Worrell, Ernst; Khrushch, Marta

    1999-09-01

    Disaggregation of sectoral energy use and greenhouse gas emissions trends reveals striking differences between sectors and regions of the world. Understanding key driving forces in the energy end-use sectors provides insights for development of projections of future greenhouse gas emissions. This report examines global and regional historical trends in energy use and carbon emissions in the industrial, buildings, transport, and agriculture sectors, with a more detailed focus on industry and buildings. Activity and economic drivers as well as trends in energy and carbon intensity are evaluated. The authors show that macro-economic indicators, such as GDP, are insufficient for comprehending trends and driving forces at the sectoral level. These indicators need to be supplemented with sector-specific information for a more complete understanding of future energy use and greenhouse gas emissions.

  4. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Tautz, Stefan

    2014-03-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Their description as an inherently quantum mechanical phenomenon was developed for single atoms and homogeneous macroscopic bodies by London, Casimir, and Lifshitz. For intermediate-sized objects like organic molecules an atomistic description is required, but explicit first principles calculations are very difficult since correlations between many interacting electrons have to be considered. Hence, semi-empirical correction schemes are often used that simplify the vdW interaction to a sum over atom-pair potentials. A similar gap exists between successful measurements of vdW and Casimir forces for single atoms on the one hand and macroscopic bodies on the other, as comparable experiments for molecules are absent. I will present experiments in which long-range vdW potentials between a series of related molecules and a metal surface have been determined experimentally. The experiments rely on the extremely sensitive force detection of an atomic force microscope in combination with its molecular manipulation capabilities. The results allow us to confirm the asymptotic force law and to quantify the non-additive part of the vdW interaction which is particularly challenging for theory. In the present case, cooperative effects account for 10% of the total interaction. This effect is of general validity in molecules and thus relevant at the intersection of chemistry, physics, biology, and materials science.

  5. Passive Joint Forces Are Tuned to Limb Use in Insects and Drive Movements without Motor Activity

    PubMed Central

    Ache, Jan M.; Matheson, Thomas

    2013-01-01

    Summary Background Limb movements are generally driven by active muscular contractions working with and against passive forces arising in muscles and other structures. In relatively heavy limbs, the effects of gravity and inertia predominate, whereas in lighter limbs, passive forces intrinsic to the limb are of greater consequence. The roles of passive forces generated by muscles and tendons are well understood, but there has been little recognition that forces originating within joints themselves may also be important, and less still that these joint forces may be adapted through evolution to complement active muscle forces acting at the same joint. Results We examined the roles of passive joint forces in insect legs with different arrangements of antagonist muscles. We first show that passive forces modify actively generated movements of a joint across its working range, and that they can be sufficiently strong to generate completely passive movements that are faster than active movements observed in natural behaviors. We further demonstrate that some of these forces originate within the joint itself. In legs of different species adapted to different uses (walking, jumping), these passive joint forces complement the balance of strength of the antagonist muscles acting on the joint. We show that passive joint forces are stronger where they assist the weaker of two antagonist muscles. Conclusions In limbs where the dictates of a key behavior produce asymmetry in muscle forces, passive joint forces can be coadapted to provide the balance needed for the effective generation of other behaviors. PMID:23871240

  6. Matching of additive and polarizable force fields for multiscale condensed phase simulations

    PubMed Central

    Baker, Christopher M.; Best, Robert B.

    2013-01-01

    Inclusion of electronic polarization effects is one of the key aspects in which the accuracy of current biomolecular force fields may be improved. The principal drawback of such approaches is the computational cost, which typically ranges from 3 – 10 times that of the equivalent additive model, and may be greater for more sophisticated treatments of polarization or other many-body effects. Here, we present a multiscale approach which may be used to enhance the sampling in simulations with polarizable models, by using the additive model as a tool to explore configuration space. We use a method based on information theory to determine the charges for an additive model that has optimal overlap with the polarizable one, and we demonstrate the feasibility of enhancing sampling via a hybrid replica exchange scheme for several model systems. An additional advantage is that, in the process, we obtain a systematic method for deriving charges for an additive model that will be the natural complement to its polarizable parent. The additive charges are found by an effective coarse-graining of the polarizable force field, rather than by ad hoc procedures. PMID:23997691

  7. The Labour Market as the Driving Force of Belgian Higher Education.

    ERIC Educational Resources Information Center

    Wielemans, Willy

    1988-01-01

    An examination of internal and external forces on Belgian higher education suggests that the system is too closely controlled by economic and political forces in the labor market, which threatens to distort university life and higher education in general. (MSE)

  8. Economy, Speed and Size Matter: Evolutionary Forces Driving Nuclear Genome Miniaturization and Expansion

    PubMed Central

    CAVALIER-SMITH, THOMAS

    2005-01-01

    • Background Nuclear genome size varies 300 000-fold, whereas transcriptome size varies merely 17-fold. In the largest genomes nearly all DNA is non-genic secondary DNA, mostly intergenic but also within introns. There is now compelling evidence that secondary DNA is functional, i.e. positively selected by organismal selection, not the purely neutral or ‘selfish’ outcome of mutation pressure. The skeletal DNA theory argued that nuclear volumes are genetically determined primarily by nuclear DNA amounts, modulated somewhat by genes affecting the degree of DNA packing or unfolding; the huge spread of nuclear genome sizes is the necessary consequence of the origin of the nuclear envelope and the nucleation of its assembly by DNA, plus the adaptively significant 300 000-fold range of cell volumes and selection for balanced growth by optimizing karyoplasmic volume ratios (essentially invariant with cell volume in growing/multiplying cells). This simple explanation of the C-value paradox is refined here in the light of new insights into the nature of heterochromatin and the nuclear lamina, the genetic control of cell volume, and large-scale eukaryote phylogeny, placing special emphasis on protist test cases of the basic principles of nuclear genome size evolution. • Genome Miniaturization and Expansion Intracellular parasites (e.g. Plasmodium, microsporidia) dwarfed their genomes by gene loss and eliminating virtually all secondary DNA. The primary driving forces for genome reduction are metabolic and spatial economy and cell multiplication speed. Most extreme nuclear shrinkage yielded genomes as tiny as 0·38 Mb (making the nuclear genome size range effectively 1·8 million-fold!) in some minute enslaved nuclei (nucleomorphs) of cryptomonads and chlorarachneans, chimaeric cells that also retain a separate normal large nucleus. The latter shows typical correlation between genome size and cell volume, but nucleomorphs do not despite co-existing in the same cell

  9. The Driving Force of the Na+/Ca2+-Exchanger during Metabolic Inhibition

    PubMed Central

    Baartscheer, Antonius; Schumacher, Cees A.; Coronel, Ruben; Fiolet, Jan W. T.

    2011-01-01

    Objective: Metabolic inhibition causes a decline in mechanical performance and, if prolonged, myocardial contracture and cell death. The decline in mechanical performance is mainly due to altered intracellular calcium handling, which is under control of the Na+/Ca2+-exchanger (NCX) The driving force of the NCX (ΔGncx) determines the activity of NCX. The aim of this study was to describe the relation between ΔGncx and calcium homeostasis during metabolic inhibition. Methods: In left ventricular rabbit myocytes, during metabolic inhibition (2 mmol/L sodium cyanide), sodium ([Na+]i), calcium ([Ca2+;]i), and action potentials were determined with SBFI, indo-1, and the patch clamp technique. Changes of ΔGncx were calculated. Results: During metabolic inhibition: The first 8 min [Na+]i remained constant, systolic calcium decreased from 532 ± 28 to 82 ± 13 nM, diastolic calcium decreased from 121 ± 12 to 36 ± 10 nM and the sarcoplasmic reticulum (SR) calcium content was depleted for 85 ± 3%. After 8 min [Na+;]i and diastolic calcium started to increase to 30 ± 1.3 mmol/L and 500 ± 31 nM after 30 min respectively. The action potential duration shortened biphasically. In the first 5 min it shortened from 225 ± 12 to 153 ± 11 ms and remained almost constant until it shortened again after 10 min. After 14 min action potential and calcium transients disappeared due to unexcitability of the myocytes. This resulted in an increased of the time average of ΔGncx from 6.2 ± 0.2 to 7.7 ± 0.3 kJ/mol during the first 3 min, where after it decreased and became negative after about 15 min. Conclusion: Metabolic inhibition caused an early increase of ΔGncx caused by shortening of the action potential. The increase of ΔGncx contributed to decrease of diastolic calcium, calcium transient amplitude, SR calcium content, and contractility. The increase of diastolic calcium started after ΔGncx became

  10. Prescription drug advertising: is it a driving force on drug pricing?

    PubMed

    Millstein, Lloyd G

    2003-01-01

    It has been shown that drug companies will sell more drugs when they use DTC advertising, but it is also true that many consumers who are suffering--unaware there is help for their symptoms--will learn from these ads that help is available. Advertising to consumers, like advertising to professionals, will continue to be one of the best methods of providing information. Of course, healthcare professionals also have the sales representatives, their colleagues, medical journals, and medical conventions as additional options for needed information. The consumer may or may not use other methods, such as the Internet, the library or friends or family, but the advertising is a starting point for a dialogue. If the DTC ad provides consumers with "information," which is different from "advertising," the drug company will be providing a worthwhile service to consumers and potential patients. No doubt consumers will begin demanding higher quality information from DTC ads and will frown upon the ads that are blatantly trying just to sell a drug. It will also reap the benefits of improved consumer awareness and patient compliance. A DTC ad that is consumer-friendly, does not use fear appeal, is educational in tone, and downplays the "hard sell" and hype will go a long way in offering important information to the casual observer. Oversight by the FDA will ensure the information meets the requirements they have set down for prescription drug advertising. That is, advertising will be truthful and fairly balanced and will meet what the government, consumers and, no doubt, the medical community wants. Attempting to control drug costs, by controlling advertising, will not be an easy task. This has an implication across all product areas, not just drugs. DTC advertising has become a lightening rod for cost containment issues, but is it alone driving demand for prescription products? I don't think so. PMID:14983621

  11. Environmental disruption of host–microbe co-adaptation as a potential driving force in evolution

    PubMed Central

    Soen, Yoav

    2014-01-01

    The microbiome is known to have a profound effect on the development, physiology and health of its host. Whether and how it also contributes to evolutionary diversification of the host is, however, unclear. Here we hypothesize that disruption of the microbiome by new stressful environments interferes with host–microbe co-adaptation, contributes to host destabilization, and can drive irreversible changes in the host prior to its genetic adaptation. This hypothesis is based on three presumptions: (1) the microbiome consists of heritable partners which contribute to the stability (canalization) of host development and physiology in frequently encountered environments, (2) upon encountering a stressful new environment, the microbiome adapts much faster than the host, and (3) this differential response disrupts cooperation, contributes to host destabilization and promotes reciprocal changes in the host and its microbiome. This dynamic imbalance relaxes as the host and its microbiome establish a new equilibrium state in which they are adapted to one another and to the altered environment. Over long time in this new environment, the changes in the microbiome contribute to the canalization of the altered state. This scenario supports stability of the adapted patterns, while promoting variability which may be beneficial in new stressful conditions, thus allowing the organism to balance stability and flexibility based on contextual demand. Additionally, interaction between heritable microbial and epigenetic/physiological changes can promote new outcomes which persist over a wide range of timescales. A sufficiently persistent stress can further induce irreversible changes in the microbiome which may permanently alter the organism prior to genetic changes in the host. Epigenetic and microbial changes therefore provide a potential infrastructure for causal links between immediate responses to new environments and longer-term establishment of evolutionary adaptations. PMID

  12. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-11-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  13. Non-additivity of molecule-surface van der Waals potentials from force measurements

    PubMed Central

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-01-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction. PMID:25424490

  14. Comparison of the driving forces of spring phenology among savanna landscapes by including combined spatial and temporal heterogeneity

    NASA Astrophysics Data System (ADS)

    Zhu, Likai; Southworth, Jane; Meng, Jijun

    2015-10-01

    Understanding spatial and temporal dynamics of land surface phenology (LSP) and its driving forces are critical for providing information relevant to short- and long-term decision making, particularly as it relates to climate response planning. With the third generation Global Inventory Monitoring and Modeling System (GIMMS3g) Normalized Difference Vegetation Index (NDVI) data and environmental data from multiple sources, we investigated the spatio-temporal changes in the start of the growing season (SOS) in southern African savannas from 1982 through 2010 and determined its linkage to environmental factors using spatial panel data models. Overall, the SOS occurs earlier in the north compared to the south. This relates in part to the differences in ecosystems, with northern areas representing high rainfall and dense tree cover (mainly tree savannas), whereas the south has lower rainfall and sparse tree cover (mainly bush and grass savannas). From 1982 to 2010, an advanced trend was observed predominantly in the tree savanna areas of the north, whereas a delayed trend was chiefly found in the floodplain of the north and bush/grass savannas of the south. Different environmental drivers were detected within tree- and grass-dominated savannas, with a critical division being represented by the 800 mm isohyet. Our results supported the importance of water as a driver in this water-limited system, specifically preseason soil moisture, in determining the SOS in these water-limited, grass-dominated savannas. In addition, the research pointed to other, often overlooked, effects of preseason maximum and minimum temperatures on the SOS across the entire region. Higher preseason maximum temperatures led to an advance of the SOS, whereas the opposite effects of preseason minimum temperature were observed. With the rapid increase in global change research, this work will prove helpful for managing savanna landscapes and key to predicting how projected climate changes will affect

  15. Comparison of the driving forces of spring phenology among savanna landscapes by including combined spatial and temporal heterogeneity.

    PubMed

    Zhu, Likai; Southworth, Jane; Meng, Jijun

    2015-10-01

    Understanding spatial and temporal dynamics of land surface phenology (LSP) and its driving forces are critical for providing information relevant to short- and long-term decision making, particularly as it relates to climate response planning. With the third generation Global Inventory Monitoring and Modeling System (GIMMS3g) Normalized Difference Vegetation Index (NDVI) data and environmental data from multiple sources, we investigated the spatio-temporal changes in the start of the growing season (SOS) in southern African savannas from 1982 through 2010 and determined its linkage to environmental factors using spatial panel data models. Overall, the SOS occurs earlier in the north compared to the south. This relates in part to the differences in ecosystems, with northern areas representing high rainfall and dense tree cover (mainly tree savannas), whereas the south has lower rainfall and sparse tree cover (mainly bush and grass savannas). From 1982 to 2010, an advanced trend was observed predominantly in the tree savanna areas of the north, whereas a delayed trend was chiefly found in the floodplain of the north and bush/grass savannas of the south. Different environmental drivers were detected within tree- and grass-dominated savannas, with a critical division being represented by the 800 mm isohyet. Our results supported the importance of water as a driver in this water-limited system, specifically preseason soil moisture, in determining the SOS in these water-limited, grass-dominated savannas. In addition, the research pointed to other, often overlooked, effects of preseason maximum and minimum temperatures on the SOS across the entire region. Higher preseason maximum temperatures led to an advance of the SOS, whereas the opposite effects of preseason minimum temperature were observed. With the rapid increase in global change research, this work will prove helpful for managing savanna landscapes and key to predicting how projected climate changes will affect

  16. MRCK-1 Drives Apical Constriction in C. elegans by Linking Developmental Patterning to Force Generation.

    PubMed

    Marston, Daniel J; Higgins, Christopher D; Peters, Kimberly A; Cupp, Timothy D; Dickinson, Daniel J; Pani, Ariel M; Moore, Regan P; Cox, Amanda H; Kiehart, Daniel P; Goldstein, Bob

    2016-08-22

    Apical constriction is a change in cell shape that drives key morphogenetic events including gastrulation and neural tube formation. Apical force-producing actomyosin networks drive apical constriction by contracting while connected to cell-cell junctions. The mechanisms by which developmental patterning regulates these actomyosin networks and associated junctions with spatial precision are not fully understood. Here we identify a myosin light-chain kinase MRCK-1 as a key regulator of C. elegans gastrulation that integrates spatial and developmental patterning information. We show that MRCK-1 is required for activation of contractile actomyosin dynamics and elevated cortical tension in the apical cell cortex of endoderm precursor cells. MRCK-1 is apically localized by active Cdc42 at the external, cell-cell contact-free surfaces of apically constricting cells, downstream of cell fate determination mechanisms. We establish that the junctional components α-catenin, β-catenin, and cadherin become highly enriched at the apical junctions of apically constricting cells and that MRCK-1 and myosin activity are required in vivo for this enrichment. Taken together, our results define mechanisms that position a myosin activator to a specific cell surface where it both locally increases cortical tension and locally enriches junctional components to facilitate apical constriction. These results reveal crucial links that can tie spatial information to local force generation to drive morphogenesis. PMID:27451898

  17. Computing the acoustic radiation force exerted on a sphere using the translational addition theorem.

    PubMed

    Silva, Glauber T; Baggio, André L; Lopes, J Henrique; Mitri, Farid G

    2015-03-01

    In this paper, the translational addition theorem for spherical functions is employed to calculate the acoustic radiation force produced by an arbitrary shaped beam on a sphere arbitrarily suspended in an inviscid fluid. The procedure is also based on the partial-wave expansion method, which depends on the beam-shape and scattering coefficients. Given a set of beam-shape coefficients (BSCs) for an acoustic beam relative to a reference frame, the translational addition theorem can be used to obtain the BSCs relative to the sphere positioned anywhere in the medium. The scattering coefficients are obtained from the acoustic boundary conditions across the sphere's surface. The method based on the addition theorem is particularly useful to avoid quadrature schemes to obtain the BSCs. We use it to compute the acoustic radiation force exerted by a spherically focused beam (in the paraxial approximation) on a silicone-oil droplet (compressible fluid sphere). The analysis is carried out in the Rayleigh (i.e., the particle diameter is much smaller than the wavelength) and Mie (i.e., the particle diameter is of the order of the wavelength or larger) scattering regimes. The obtained results show that the paraxial focused beam can only trap particles in the Rayleigh scattering regime. PMID:25768823

  18. A lateral-axis micromachined tuning fork gyroscope with torsional Z-sensing and electrostatic force-balanced driving

    NASA Astrophysics Data System (ADS)

    Guo, Z. Y.; Yang, Z. C.; Zhao, Q. C.; Lin, L. T.; Ding, H. T.; Liu, X. S.; Cui, J.; Xie, H.; Yan, G. Z.

    2010-02-01

    A single-crystal silicon-based lateral-axis tuning-fork gyroscope (TFG) with electrostatic force-balanced (EFB) driving and torsional z-sensing is presented. The EFB comb drive used in this TFG can efficiently suppress the mechanical coupling in a simple manner. The TFG structure is also optimized to further reduce the coupling. Moreover, the Coriolis acceleration-induced out-of-plane rotation of the sensing mode is detected by using bending springs and differential comb fingers. This z-sensing design has relatively high Q, so this gyroscope can work at atmospheric pressure. This TFG design has been fabricated and tested. Measured in air, the device demonstrates a sensitivity of 2.9 mV/°/s, a full range of 800° s-1 with a 0.9% nonlinearity and the noise floor of 0.035°/s/Hz1/2. This TFG design also has very low coupling, where the measured drive-to-sense coupling and sense-to-drive coupling are -45 dB and -51 dB, respectively.

  19. Risky driving among UK regular armed forces personnel: changes over time

    PubMed Central

    Sheriff, Rebecca J Syed; Forbes, Harriet J; Wessely, Simon C; Greenberg, Neil; Jones, Norman; Fertout, Mohammed; Harrison, Kate; Fear, Nicola T

    2015-01-01

    Objectives To compare the prevalence of self-reported risky driving in a sample of UK military personnel at 2 different time points (2004 and 2009), and to identify the incidence of new onset risky driving and possible determinants of becoming a new risky driver. Methods Data were used from 2 phases of a military cohort study investigating the health and well-being of UK military personnel between 2004 and 2009. Participants were included if they were undertaking regular (rather than reserve) engagements, had completed both surveys and reported being a driver at both surveys. Univariable and multivariable logistic regression analyses were performed to examine the relationship between risky driving status and sociodemographic and military characteristics. Data analysis was conducted in 2011. Results The prevalence of risky driving reduced from 18% to 14%, over an average of 3.3 years. The incidence of new onset risky driving was 7%. Predictors for becoming a new risky driver were: younger age, not being in a relationship at phase 2 and harmful alcohol use. Those deployed after 2007 were less likely to become risky drivers following deployment, compared with those deployed before 2007 (adjusted OR 0.62 (95% CI 0.40 to 0.95)). Conclusions The prevalence of becoming a risky driver appears to have reduced over time. This paper suggests a number of explanations for this reduction, including changes in the way that the UK military have dealt with road safety with the introduction of the road safety campaign (in 2007). PMID:26399573

  20. Influence of Polarization on Carbohydrate Hydration: A Comparative Study Using Additive and Polarizable Force Fields.

    PubMed

    Pandey, Poonam; Mallajosyula, Sairam S

    2016-07-14

    Carbohydrates are known to closely modulate their surrounding solvent structures and influence solvation dynamics. Spectroscopic investigations studying far-IR regions (below 1000 cm(-1)) have observed spectral shifts in the libration band (around 600 cm(-1)) of water in the presence of monosaccharides and polysaccharides. In this paper, we use molecular dynamics simulations to gain atomistic insight into carbohydrate-water interactions and to specifically highlight the differences between additive (nonpolarizable) and polarizable simulations. A total of six monosaccharide systems, α and β anomers of glucose, galactose, and mannose, were studied using additive and polarizable Chemistry at HARvard Macromolecular Mechanics (CHARMM) carbohydrate force fields. Solvents were modeled using three additive water models TIP3P, TIP4P, and TIP5P in additive simulations and polarizable water model SWM4 in polarizable simulations. The presence of carbohydrate has a significant effect on the microscopic water structure, with the effects being pronounced for proximal water molecules. Notably, disruption of the tetrahedral arrangement of proximal water molecules was observed due to the formation of strong carbohydrate-water hydrogen bonds in both additive and polarizable simulations. However, the inclusion of polarization resulted in significant water-bridge occupancies, improved ordered water structures (tetrahedral order parameter), and longer carbohydrate-water H-bond correlations as compared to those for additive simulations. Additionally, polarizable simulations also allowed the calculation of power spectra from the dipole-dipole autocorrelation function, which corresponds to the IR spectra. From the power spectra, we could identify spectral signatures differentiating the proximal and bulk water structures, which could not be captured from additive simulations. PMID:27266974

  1. Influence of Additional Tensile Force on Springback of Tube Under Rotary Draw Bending

    NASA Astrophysics Data System (ADS)

    E, Daxin; Guan, Zhiping; Chen, Jisheng

    2012-11-01

    According to the characteristics of tube under rotary draw bending, the formulae were derived to calculate the springback angles of tubes subjected to combined bending and additional tension. Especially, as the neutral layer (NL) moves to the inner concave surface of the bend, the analytical values agree very well with the experimental results. The analysis shows that the additional tensile force causes the movement of the NL toward the bending center and makes the deformation behavior under rotary draw bending or numerically controlled (NC) bending different with that under pure bending, and also it could enlarge the springback angle if taking the movement of the NL into consideration. In some range, the springback angle would increase slightly with larger wall thickness/diameter ratio and decrease with wall thinning. The investigation could provide reference for the analysis of rotary draw bending, the design of NC tube bender and the related techniques.

  2. Spatial driving forces of dominant land use/land cover transformations in the Dongjiang River watershed, Southern China.

    PubMed

    Gao, Changjun; Zhou, Ping; Jia, Peng; Liu, Zhiyong; Wei, Long; Tian, Huiling

    2016-02-01

    Information about changes in, and causes of, land use/land cover (LULC) is crucial for land use resource planning. We investigated the processes involved in LULC change (LUCC) in the Dongjiang Watershed, in Southern China, over a 15-year period to gain a better understanding of the causes of the main types of LUCC. Using a depth transition matrix and redundancy analysis (RDA), the major types and causes of LUCC for each LULC type over the past 15 years were identified. LUCC exhibited obvious net change, relatively low persistence, and high swap change. The swap changes in most LULC types were considered as a strong signal of LULC transformations. The driving forces behind swap changes were quantified and identified through RDA. The results showed that all driving forces played important roles in explaining swap changes of LULC, although the relative effects of these drivers varied widely with both LULC type and time period. Swap changes of the LULC types were generally classified into two categories. Some, e.g., built-up land and wetland, were affected mostly by landform and/or distance factors, while others, e.g., grassland and woodland, were modulated mostly by climate and/or socioeconomic factors. Selected spatial driving forces and local land use policies played important roles in explaining the dominant LUCC types, but on different timescales. These findings may improve understanding of the detailed processes involved in LUCC, landscape transformation, and the causes of LUCC in other areas with extensive LUCC and could help managers plan, design, and implement land resource management. PMID:26746657

  3. Pseudo-casimir structural force drives spinodal dewetting in nematic liquid crystals

    PubMed

    Ziherl; Podgornik; Zumer

    2000-02-01

    We analyze theoretically the fluctuation-induced force in thin nematic films subject to competing surface interactions, and we find that the force is attractive at small distances and repulsive otherwise. The results provide a consistent interpretation of a recent study of spinodal dewetting of 5CB on a silicon wafer [F. Vandenbrouck et al., Phys. Rev. Lett. 82, 2693 (1999)], implying that this experiment can be regarded as the first observation of the pseudo-Casimir effect in liquid crystals. PMID:11017485

  4. Transient-state fluctuationlike relation for the driving force on a biomolecule

    NASA Astrophysics Data System (ADS)

    Ponmurugan, M.; Vemparala, Satyavani

    2011-12-01

    In experiments and simulations the force acting on a single biomolecular system has been observed as a fluctuating quantity if the system is driven under constant velocity. We ask the question that is analogous to transient state entropy production and work fluctuation relations whether the force fluctuations observed in the single biomolecular system satisfy a transient state fluctuationlike relation, and the answer is in the affirmative. Using a constant velocity pulling steered molecular dynamics simulation study for protein unfolding, we confirm that the force fluctuations of this single biomolecular system satisfy a transient-state fluctuationlike relation (1)/(γ(T,v))ln[(Pv(+f))/(Pv(-f))]=f. Pv(±f) is the probability of positive and negative values of forces f=f⃗·n̂ for a given unfolding velocity of magnitude v and the pulling direction n⃗, n̂ is the unit vector of n⃗, and γ(T,v) is a factor that depends on initial equilibrium temperature T and the unfolding velocity. For different unfolding velocities we find that the system in the nonequilibrium pulling region displays substantial negative fluctuation in its unfolding force when velocity decreases. A negative value of force may indicate the emergence of refolding behavior during protein unfolding. We also find that γ(T,v)˜T-δvα and the system relaxation time τ(T,v)˜Tδv-(1+α), where α and δ are scaling exponents.

  5. Transferability and additivity of dihedral parameters in polarizable and nonpolarizable empirical force fields.

    PubMed

    Zgarbová, Marie; Rosnik, Andreana M; Luque, F Javier; Curutchet, Carles; Jurečka, Petr

    2015-09-30

    Recent advances in polarizable force fields have revealed that major reparameterization is necessary when the polarization energy is treated explicitly. This study is focused on the torsional parameters, which are crucial for the accurate description of conformational equilibria in biomolecules. In particular, attention is paid to the influence of polarization on the (i) transferability of dihedral terms between molecules, (ii) transferability between different environments, and (iii) additivity of dihedral energies. To this end, three polarizable force fields based on the induced point dipole model designed for use in AMBER are tested, including two recent ff02 reparameterizations. Attention is paid to the contributions due to short range interactions (1-2, 1-3, and 1-4) within the four atoms defining the dihedral angle. The results show that when short range 1-2 and 1-3 polarization interactions are omitted, as for instance in ff02, the 1-4 polarization contribution is rather small and unlikely to improve the description of the torsional energy. Conversely, when screened 1-2 and 1-3 interactions are included, the polarization contribution is sizeable and shows potential to improve the transferability of parameters between different molecules and environments as well as the additivity of dihedral terms. However, to reproduce intramolecular polarization effects accurately, further fine-tuning of the short range damping of polarization is necessary. PMID:26224547

  6. CHARMM Additive All-Atom Force Field for Acyclic Polyalcohols, Acyclic Carbohydrates and Inositol

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    Parametrization of the additive all-atom CHARMM force field for acyclic polyalcohols, acyclic carbohydrates and inositol is conducted. Initial parameters were transferred from the alkanes and hexopyranose carbohydrates, with subsequent development and optimization of parameters unique to the molecules considered in this study. Using the model compounds acetone and acetaldehyde, nonbonded parameters for carbonyls were optimized targeting quantum mechanical interaction data for solute-water pairs and pure solvent thermodynamic data. Bond and angle parameters were adjusted by comparing optimized geometries to small molecule crystal survey data and by performing vibrational analyses on acetone, acetaldehyde and glycerol. C-C-C-C, C-C-C-O, C-C-OH and O-C-C-O torsional parameters for polyol chains were fit to quantum mechanical dihedral potential energy scans comprising over 1500 RIMP2/cc-pVTZ//MP2/6-31G(d) conformations using an automated Monte Carlo simulated annealing procedure. Comparison of computed condensed-phase data, including crystal lattice parameters and densities, NMR proton-proton couplings, densities and diffusion coefficients of aqueous solutions, to experimental data validated the optimized parameters. Parameter development for these compounds proved particularly challenging because of the flexibility of the acyclic sugars and polyalcohols as well as the intramolecular hydrogen bonding between vicinal hydroxyls for all of the compounds. The newly optimized additive CHARMM force field parameters are anticipated to be of utility for atomic level of detail simulations of acyclic polyalcohols, acyclic carbohydrates and inositol in solution. PMID:20160980

  7. Dynamic model of the force driving kinesin to move along microtubule-Simulation with a model system

    NASA Astrophysics Data System (ADS)

    Chou, Y. C.; Hsiao, Yi-Feng; To, Kiwing

    2015-09-01

    A dynamic model for the motility of kinesin, including stochastic-force generation and step formation is proposed. The force driving the motion of kinesin motor is generated by the impulse from the collision between the randomly moving long-chain stalk and the ratchet-shaped outer surface of microtubule. Most of the dynamical and statistical features of the motility of kinesin are reproduced in a simulation system, with (a) ratchet structures similar to the outer surface of microtubule, (b) a bead chain connected to two heads, similarly to the stalk of the real kinesin motor, and (c) the interaction between the heads of the simulated kinesin and microtubule. We also propose an experiment to discriminate between the conventional hand-over-hand model and the dynamic model.

  8. Using special additions to preparation of the moulding mixture for casting steel parts of drive wheel type

    NASA Astrophysics Data System (ADS)

    Josan, A.; Pinca Bretotean, C.

    2015-06-01

    The paper presents the possibility of using special additions to the execution of moulding mixtures for steel castings, drive wheel type. Critical analysis of moulding technology leads to the idea that most defects appear due to using improper moulding mixture. Using a improper moulding mixture leads to penetration of steel in moulding mixture, resulting in the formation of adherences, due to inadequate refractarity of the mould and core mixtures. Using only the unique mixture to the moulding leads to increasing consumption of new sand, respectively to the increase of price of piece. Acording to the dates registered in the industrial practice is necessary to use the special additions to obtain the moulding mixtures, carbonaceous materials respectively.

  9. Binding dynamics and energetic insight into the molecular forces driving nucleotide binding by guanylate kinase.

    PubMed

    Kandeel, Mahmoud; Kitade, Yukio

    2011-01-01

    Plasmodium deoxyguanylate pathways are an attractive area of investigation for future metabolic and drug discovery studies due to their unique substrate specificities. We investigated the energetic contribution to guanylate kinase substrate binding and the forces underlying ligand recognition. In the range from 20 to 35°C, the thermodynamic profiles displayed marked decrease in binding enthalpy, while the free energy of binding showed little changes. GMP produced a large binding heat capacity change of -356 cal mol(-1) K(-1), indicating considerable conformational changes upon ligand binding. Interestingly, the calculated ΔCp was -32 cal mol(-1) K(-1), indicating that the accessible surface area is not the central change in substrate binding, and that other entropic forces, including conformational changes, are more predominant. The thermodynamic signature for GMP is inconsistent with rigid-body association, while dGMP showed more or less rigid-body association. These binding profiles explain the poor catalytic efficiency and low affinity for dGMP compared with GMP. At low temperature, the ligands bind to the receptor site under the effect of hydrophobic forces. Interestingly, by increasing the temperature, the entropic forces gradually vanish and proceed to a nonfavorable contribution, and the interaction occurs mainly through bonding, electrostatic forces, and van der Waals interactions. PMID:21360614

  10. Simulation of uphill/downhill running on a level treadmill using additional horizontal force.

    PubMed

    Gimenez, Philippe; Arnal, Pierrick J; Samozino, Pierre; Millet, Guillaume Y; Morin, Jean-Benoit

    2014-07-18

    Tilting treadmills allow a convenient study of biomechanics during uphill/downhill running, but they are not commonly available and there is even fewer tilting force-measuring treadmill. The aim of the present study was to compare uphill/downhill running on a treadmill (inclination of ± 8%) with running on a level treadmill using additional backward or forward pulling forces to simulate the effect of gravity. This comparison specifically focused on the energy cost of running, stride frequency (SF), electromyographic activity (EMG), leg and foot angles at foot strike, and ground impact shock. The main results are that SF, impact shock, and leg and foot angle parameters determined were very similar and significantly correlated between the two methods, the intercept and slope of the linear regression not differing significantly from zero and unity, respectively. The correlation of oxygen uptake (V̇O2) data between both methods was not significant during uphill running (r=0.42; P>0.05). V̇O2 data were correlated during downhill running (r=0.74; P<0.01) but there was a significant difference between the methods (bias=-2.51 ± 1.94 ml min(-1) kg(-1)). Linear regressions for EMG of vastus lateralis, biceps femoris, gastrocnemius lateralis, soleus and tibialis anterior were not different from the identity line but the systematic bias was elevated for this parameter. In conclusion, this method seems appropriate for the study of SF, leg and foot angle, impact shock parameters but is less applicable for physiological variables (EMG and energy cost) during uphill/downhill running when using a tilting force-measuring treadmill is not possible. PMID:24811045

  11. CHARMM Additive All-Atom Force Field for Aldopentofuranoses, Methyl-Aldopentofuranosides and Fructofuranose

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    An additive all-atom empirical force field for aldopentofuranoses, methyl-aldopentofuranosides (Me-aldopentofuranosides) and fructofuranose carbohydrates, compatible with existing CHARMM carbohydrate parameters, is presented. Building on existing parameters transferred from cyclic ethers and hexopyranoses, parameters were further developed using target data for complete furanose carbohydrates as well as O-methyl tetrahydrofuran. The bond and angle equilibrium parameters were adjusted to reproduce target geometries from a survey of furanose crystal structures, and dihedral parameters were fit to over 1700 quantum mechanical (QM) MP2/cc-pVTZ//MP2/6-31G(d) conformational energies. The conformational energies were for a variety of complete furanose monosaccharides, and included two-dimensional ring pucker energy surfaces. Bonded parameter optimization led to the correct description of the ring pucker for a large set of furanose compounds, while furanose-water interaction energies and distances reproduced QM HF/6-31G(d) results for a number of furanose monosaccharides, thereby validating the nonbonded parameters. Crystal lattice unit cell parameters and volumes, aqueous-phase densities, and aqueous NMR ring pucker and exocyclic data were used to validate the parameters in condensed-phase environments. Conformational sampling analysis of the ring pucker and exocyclic group showed excellent agreement with experimental NMR data, demonstrating that the conformational energetics in aqueous solution are accurately described by the optimized force field. Overall, the parameters reproduce available experimental data well and are anticipated to be of utility in future computational studies of carbohydrates, including in the context of proteins, nucleic acids and/or lipids when combined with existing CHARMM biomolecular force fields. PMID:19694450

  12. Earthworm invasion as the driving force behind plant invasion and community change in northeastern North American forests.

    PubMed

    Nuzzo, Victoria A; Maerz, John C; Blossey, Bernd

    2009-08-01

    Identification of factors that drive changes in plant community structure and contribute to decline and endangerment of native plant species is essential to the development of appropriate management strategies. Introduced species are assumed to be driving causes of shifts in native plant communities, but unequivocal evidence supporting this view is frequently lacking. We measured native vegetation, non-native earthworm biomass, and leaf-litter volume in 15 forests in the presence and absence of 3 non-native plant species (Microstegium vimineum, Alliaria petiolata, Berberis thunbergii) to assess the general impact of non-native plant and earthworm invasions on native plant communities in northeastern United States. Non-native plant cover was positively correlated with total native plant cover and non-native earthworm biomass. Earthworm biomass was negatively associated with cover of native woody and most herbaceous plants and with litter volume. Graminoid cover was positively associated with non-native earthworm biomass and non-native plant cover. These earthworm-associated responses were detected at all sites despite differences in earthworm species and abundance, composition of the native plant community, identity of invasive plant species, and geographic region. These patterns suggest earthworm invasion, rather than non-native plant invasion, is the driving force behind changes in forest plant communities in northeastern North America, including declines in native plant species, and earthworm invasions appear to facilitate plant invasions in these forests. Thus, a focus on management of invasive plant species may be insufficient to protect northeastern forest understory species. PMID:19236448

  13. Vegetation coverage change and associated driving forces in mountain areas of Northwestern Yunnan, China using RS and GIS.

    PubMed

    Peng, Jian; Liu, Yinghui; Shen, Hong; Han, Yinan; Pan, Yajing

    2012-08-01

    The dynamics of vegetation coverage and associated driving forces are one of the key issues in global environmental change. In the study, taking Lijiang County as a case, the Normalized Difference Vegetation Index was used to quantify vegetation coverage change in mountain areas of Northwestern Yunnan, China, with the application of remote sensing data and GIS technologies. And associated driving forces of vegetation coverage change were also analyzed, with a focus on land use change and elevation. The results showed that there was high vegetation coverage with a significant increase in the whole county during 1986-2002. However, due to economic development and the implementation of environmental protection polices, vegetation coverage change in the county showed distinct spatial diversity, which mainly behaved as the increasing in the northwest of the county with low human activities, and the decreasing in the south with high economic development. The results also showed that as a restrictive factor, elevation was of great signification on the spatial distribution of vegetation coverage in a broad scale; while in the county level, it was land use that determined the vegetation coverage, since the change of vegetation coverage grades in the study area was mainly associated with the change of land use types. PMID:21912871

  14. Driving forces and the influence of the buffer composition on the complexation reaction between ibuprofen and HPCD.

    PubMed

    Perlovich, German L; Skar, Merete; Bauer-Brandl, Annette

    2003-10-01

    Cyclodextrins are often used in order to increase the aqueous solubility of drug substances by complexation. In order to investigate the complexation reaction of ibuprofen and hydroxypropyl-beta-cyclodextrin, titration calorimetry was used as a direct method. The thermodynamic parameters of the complexation process (stability constant, K(11); complexation enthalpy, deltaH(c) degrees ) were obtained in two different buffer systems (citric acid/sodium-phosphate and phosphoric acid) at various pH values. Based on these data the relative contributions of the enthalpic and entropic terms of the Gibbs energy to the complexation process have been analyzed. In both buffers the enthalpic and entropic terms are of different sign and this case corresponds to a 'nonclassical' model of hydrophobic interaction. In citric buffer, the main driving force of complexation is the entropy, which increases from 60 to 67% while the pH of the solution increases from 3.2 to 8.0. However, for the phosphoric buffer the entropic term decreases from 60 to 45%, while the pH-value of the solution increases from 5.0 to 8.2, and the driving force of the complexation process changes from entropy to enthalpy. The experimental data of the present study are compared to results of other authors and discrepancies discussed in detail. PMID:14550885

  15. Relative importance of driving force and electrostatic interactions in the reduction of multihaem cytochromes by small molecules.

    PubMed

    Quintas, Pedro O; Cepeda, Andreia P; Borges, Nuno; Catarino, Teresa; Turner, David L

    2013-06-01

    Multihaem cytochromes are essential to the energetics of organisms capable of bioremediation and energy production. The haems in several of these cytochromes have been discriminated thermodynamically and their individual rates of reduction by small electron donors were characterized. The kinetic characterization of individual haems used the Marcus theory of electron transfer and assumed that the rates of reduction of each haem by sodium dithionite depend only on the driving force, while electrostatic interactions were neglected. To determine the relative importance of these factors in controlling the rates, we studied the effect of ionic strength on the redox potential and the rate of reduction by dithionite of native Methylophilus methylotrophus cytochrome c″ and three mutants at different pH values. We found that the main factor determining the rate is the driving force and that Marcus theory describes this satisfactorily. This validates the method of the simultaneous fitting of kinetic and thermodynamic data in multihaem cytochromes and opens the way for further investigation into the mechanisms of these proteins. PMID:23428398

  16. Land use changes and its driving forces in hilly ecological restoration area based on gis and rs of northern china

    PubMed Central

    Gao, Peng; Niu, Xiang; Wang, Bing; Zheng, Yunlong

    2015-01-01

    Land use change is one of the important aspects of the regional ecological restoration research. With remote sensing (RS) image in 2003, 2007 and 2012, using geographic information system (GIS) technologies, the land use pattern changes in Yimeng Mountain ecological restoration area in China and its driving force factors were studied. Results showed that: (1) Cultivated land constituted the largest area during 10 years, and followed by forest land and grass land; cultivated land and unused land were reduced by 28.43% and 44.32%, whereas forest land, water area and land for water facilities and others were increased. (2) During 2003–2007, forest land change showed the largest, followed by unused land and grass land; however, during 2008–2012, water area and land for water facilities change showed the largest, followed by grass land and unused land. (3) Land use degree was above the average level, it was in the developing period during 2003–2007 and in the degenerating period during 2008–2012. (4) Ecological Restoration Projects can greatly change the micro topography, increase vegetation coverage, and then induce significant changes in the land use distribution, which were the main driving force factors of the land use pattern change in the ecological restoration area. PMID:26047160

  17. Thermodynamic Driving Force of the γ → ɛ Transformation and Resulting MS Temperature in High-Mn Steels

    NASA Astrophysics Data System (ADS)

    Pisarik, S. T.; Van Aken, D. C.

    2016-03-01

    Two-stage transformation-induced plasticity (TRIP) behavior characterized by the martensitic transformations, γ → ɛ → α', has produced exceptional tensile strengths and work hardening rates in Fe-14 wt pct Mn alloys containing Al and Si. A regular solution model has been developed to accurately calculate Δ G γ → ɛ for a given TRIP alloy and the calculated driving force is used to determine the M S ɛ temperature. The regular solution model developed here predicted driving forces that corresponded well with reported microstructures and behavior of seven FeMnAlSiC steels from literature when considered in conjunction with nucleating defect critical size and material process history. The role of available nucleating defects of critical size, n*, has been linked to the stacking fault energy necessary to observe the γ → ɛ transformation and the M S ɛ temperature. The regular solution model provided excellent correlation between calculated M S ɛ temperatures and those measured experimentally in 89 alloys from literature and suggested n* = 4 is the critical size of a nucleating defect in annealed microstructures. Factors affecting the γ → ɛ transformation and the M S ɛ temperature have been identified as prior austenite grain size, dislocation substructure due to prior deformation, and solute segregation.

  18. Commentary: Forces That Drive the Vape Shop Industry and Implications for the Health Professions

    PubMed Central

    Sussman, Steve; Baezconde-Garbanati, Lourdes; Garcia, Robert; Barker, Dianne C.; Samet, Jonathan M.; Leventhal, Adam; Unger, Jennifer B.

    2016-01-01

    At least three factors may be driving the evolution of the vape shop industry, a rapidly growing market sector that specializes in the sales of electronic cigarettes: (1) the tobacco industry, (2) the public health sector and its diverse stakeholders, and (3) consumer demand. These influences and the responses of the vape shop sector have resulted in a rapidly changing landscape. This commentary briefly discusses these three factors and the implications for the health professions, as they address the vape shop industry and its consequences for public health. PMID:25967071

  19. Commentary: Forces That Drive the Vape Shop Industry and Implications for the Health Professions.

    PubMed

    Sussman, Steve; Baezconde-Garbanati, Lourdes; Garcia, Robert; Barker, Dianne C; Samet, Jonathan M; Leventhal, Adam; Unger, Jennifer B

    2016-09-01

    At least three factors may be driving the evolution of the vape shop industry, a rapidly growing market sector that specializes in the sales of electronic cigarettes: (1) the tobacco industry, (2) the public health sector and its diverse stakeholders, and (3) consumer demand. These influences and the responses of the vape shop sector have resulted in a rapidly changing landscape. This commentary briefly discusses these three factors and the implications for the health professions, as they address the vape shop industry and its consequences for public health. PMID:25967071

  20. Forest dynamics and its driving forces of sub-tropical forest in South China

    PubMed Central

    Ma, Lei; Lian, Juyu; Lin, Guojun; Cao, Honglin; Huang, Zhongliang; Guan, Dongsheng

    2016-01-01

    Tree mortality and recruitment are key factors influencing forest dynamics, but the driving mechanisms of these processes remain unclear. To better understand these driving mechanisms, we studied forest dynamics over a 5-year period in a 20-ha sub-tropical forest in the Dinghushan Nature Reserve, South China. The goal was to identify determinants of tree mortality/recruitment at the local scale using neighborhood analyses on some locally dominant tree species. Results show that the study plot was more dynamic than some temperate and tropical forests in a comparison to large, long-term forest dynamics plots. Over the 5-year period, mortality rates ranged from 1.67 to 12.33% per year while recruitment rates ranged from 0 to 20.26% per year. Tree size had the most consistent effect on mortality across species. Recruitment into the ≥1-cm size class consistently occurred where local con-specific density was high. This suggests that recruitment may be limited by seed dispersal. Hetero-specific individuals also influenced recruitment significantly for some species. Canopy species had low recruitment into the ≥1-cm size class over the 5-year period. In conclusion, tree mortality and recruitment for sixteen species in this plot was likely limited by seed dispersal and density-dependence. PMID:26940005

  1. Impaired Driving

    MedlinePlus

    ... Risk Factors BAC Effects Prevention Additional Resources How big is the problem? In 2014, 9,967 people ... Driving: A Threat to Everyone (October 2011) Additional Data Drunk Driving State Data and Maps Motor Vehicle ...

  2. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  3. Self-similar expansion of solar coronal mass ejections: Implications for Lorentz self-force driving

    SciTech Connect

    Subramanian, Prasad; Arunbabu, K. P.; Mauriya, Adwiteey; Vourlidas, Angelos

    2014-08-01

    We examine the propagation of several coronal mass ejections (CMEs) with well-observed flux rope signatures in the field of view of the SECCHI coronagraphs on board the STEREO satellites using the graduated cylindrical shell fitting method of Thernisien et al. We find that the manner in which they propagate is approximately self-similar; i.e., the ratio (κ) of the flux rope minor radius to its major radius remains approximately constant with time. We use this observation of self-similarity to draw conclusions regarding the local pitch angle (γ) of the flux rope magnetic field and the misalignment angle (χ) between the current density J and the magnetic field B. Our results suggest that the magnetic field and current configurations inside flux ropes deviate substantially from a force-free state in typical coronagraph fields of view, validating the idea of CMEs being driven by Lorentz self-forces.

  4. Self-similar Expansion of Solar Coronal Mass Ejections: Implications for Lorentz Self-force Driving

    NASA Astrophysics Data System (ADS)

    Subramanian, Prasad; Arunbabu, K. P.; Vourlidas, Angelos; Mauriya, Adwiteey

    2014-08-01

    We examine the propagation of several coronal mass ejections (CMEs) with well-observed flux rope signatures in the field of view of the SECCHI coronagraphs on board the STEREO satellites using the graduated cylindrical shell fitting method of Thernisien et al. We find that the manner in which they propagate is approximately self-similar; i.e., the ratio (κ) of the flux rope minor radius to its major radius remains approximately constant with time. We use this observation of self-similarity to draw conclusions regarding the local pitch angle (γ) of the flux rope magnetic field and the misalignment angle (χ) between the current density J and the magnetic field B. Our results suggest that the magnetic field and current configurations inside flux ropes deviate substantially from a force-free state in typical coronagraph fields of view, validating the idea of CMEs being driven by Lorentz self-forces.

  5. Dominant Driving Force for Protein Folding -- A Result from Analyzing the Statistical Potential

    NASA Astrophysics Data System (ADS)

    Li, Hao; Tang, Chao; Wingreen, Ned

    1997-03-01

    In a statistical approach, the energy of a particular substructure in proteins is related to its number of appearance in the protein structure data bank via a Boltzmann factor. Such knowledge based potentials are widely used in protein structure prediction. A well known example is the inter-residue contact energies between different types of amino acids -- a 20× 20 matrix derived by Miyazawa and Jernigan (MJ). We have analyzed the MJ matrix using the method of eigenvalue decomposition. We find that the MJ matrix can be accurately reconstructed by using only the two largest eigenvalues and the corresponding eigenvectors. The matrix elements can be simply expressed as M_ij=C_0+C_1(q_i+q_j)+C_2q_iq_j, with C's constants, and 20 q values associated with 20 amino acids. We find that this regularity is due to hydrophobic force and a force of demixing, the latter obeying Hildebrand's solubility theory for simple liquids.

  6. Both contractile axial and lateral traction force dynamics drive amoeboid cell motility

    PubMed Central

    Bastounis, Effie; Meili, Ruedi; Álvarez-González, Begoña; Francois, Joshua; del Álamo, Juan C.; Lasheras, Juan C.

    2014-01-01

    Chemotaxing Dictyostelium discoideum cells adapt their morphology and migration speed in response to intrinsic and extrinsic cues. Using Fourier traction force microscopy, we measured the spatiotemporal evolution of shape and traction stresses and constructed traction tension kymographs to analyze cell motility as a function of the dynamics of the cell’s mechanically active traction adhesions. We show that wild-type cells migrate in a step-wise fashion, mainly forming stationary traction adhesions along their anterior–posterior axes and exerting strong contractile axial forces. We demonstrate that lateral forces are also important for motility, especially for migration on highly adhesive substrates. Analysis of two mutant strains lacking distinct actin cross-linkers (mhcA− and abp120− cells) on normal and highly adhesive substrates supports a key role for lateral contractions in amoeboid cell motility, whereas the differences in their traction adhesion dynamics suggest that these two strains use distinct mechanisms to achieve migration. Finally, we provide evidence that the above patterns of migration may be conserved in mammalian amoeboid cells. PMID:24637328

  7. Single molecule compression reveals intra-protein forces drive cytotoxin pore formation

    PubMed Central

    Czajkowsky, Daniel M; Sun, Jielin; Shen, Yi; Shao, Zhifeng

    2015-01-01

    Perfringolysin O (PFO) is a prototypical member of a large family of pore-forming proteins that undergo a significant reduction in height during the transition from the membrane-assembled prepore to the membrane-inserted pore. Here, we show that targeted application of compressive forces can catalyze this conformational change in individual PFO complexes trapped at the prepore stage, recapitulating this critical step of the spontaneous process. The free energy landscape determined from these measurements is in good agreement with that obtained from molecular dynamics simulations showing that an equivalent internal force is generated by the interaction of the exposed hydrophobic residues with the membrane. This hydrophobic force is transmitted across the entire structure to produce a compressive stress across a distant, otherwise stable domain, catalyzing its transition from an extended to compact conformation. Single molecule compression is likely to become an important tool to investigate conformational transitions in membrane proteins. DOI: http://dx.doi.org/10.7554/eLife.08421.001 PMID:26652734

  8. Pressure perturbations from geologic carbon sequestration: Area-of-review boundaries and borehole leakage driving forces

    SciTech Connect

    Nicot, J.-P.; Oldenburg, C.M.; Bryant, S.L.; Hovorka, S.D.

    2009-07-01

    We investigate the possibility that brine could be displaced upward into potable water through wells. Because of the large volumes of CO2 to be injected, the influence of the zone of elevated pressure on potential conduits such as well boreholes could extend many kilometers from the injection site-farther than the CO2 plume itself. The traditional approach to address potential brine leakage related to fluid injection is to set an area of fixed radius around the injection well/zone and to examine wells and other potentially open pathways located in the ''Area-of-Review'' (AoR). This suggests that the AoR eeds to be defined in terms of the potential for a given pressure perturbation to drive upward fluid flow in any given system rather than on some arbitrary pressure rise. We present an analysis that focuses on the changes in density/salinity of the fluids in the potentially leaking wellbore.

  9. Line tension at lipid phase boundaries as driving force for HIV fusion peptide-mediated fusion

    NASA Astrophysics Data System (ADS)

    Yang, Sung-Tae; Kiessling, Volker; Tamm, Lukas K.

    2016-04-01

    Lipids and proteins are organized in cellular membranes in clusters, often called `lipid rafts'. Although raft-constituent ordered lipid domains are thought to be energetically unfavourable for membrane fusion, rafts have long been implicated in many biological fusion processes. For the case of HIV gp41-mediated membrane fusion, this apparent contradiction can be resolved by recognizing that the interfaces between ordered and disordered lipid domains are the predominant sites of fusion. Here we show that line tension at lipid domain boundaries contributes significant energy to drive gp41-fusion peptide-mediated fusion. This energy, which depends on the hydrophobic mismatch between ordered and disordered lipid domains, may contribute tens of kBT to fusion, that is, it is comparable to the energy required to form a lipid stalk intermediate. Line-active compounds such as vitamin E lower line tension in inhomogeneous membranes, thereby inhibit membrane fusion, and thus may be useful natural viral entry inhibitors.

  10. What drives interannual variability of hypoxia in Chesapeake Bay: Climate forcing versus nutrient loading?

    NASA Astrophysics Data System (ADS)

    Li, Ming; Lee, Younjoo J.; Testa, Jeremy M.; Li, Yun; Ni, Wenfei; Kemp, W. Michael; Di Toro, Dominic M.

    2016-03-01

    Oxygen depletion in estuaries is a worldwide problem with detrimental effects on many organisms. Although nutrient loading has been stabilized for a number of these systems, seasonal hypoxia persists and displays large year-to-year variations, with larger hypoxic volumes in wetter years and smaller hypoxic volumes in drier years. Data analysis points to climate as a driver of interannual hypoxia variability, but nutrient inputs covary with freshwater flow. Here we report an oxygen budget analysis of Chesapeake Bay to quantify relative contributions of physical and biogeochemical processes. Vertical diffusive flux declines with river discharge, whereas longitudinal advective flux increases with river discharge, such that their total supply of oxygen to bottom water is relatively unchanged. However, water column respiration exhibits large interannual fluctuations and is correlated with primary production and hypoxic volume. Hence, the model results suggest that nutrient loading is the main mechanism driving interannual hypoxia variability in Chesapeake Bay.

  11. Line tension at lipid phase boundaries as driving force for HIV fusion peptide-mediated fusion.

    PubMed

    Yang, Sung-Tae; Kiessling, Volker; Tamm, Lukas K

    2016-01-01

    Lipids and proteins are organized in cellular membranes in clusters, often called 'lipid rafts'. Although raft-constituent ordered lipid domains are thought to be energetically unfavourable for membrane fusion, rafts have long been implicated in many biological fusion processes. For the case of HIV gp41-mediated membrane fusion, this apparent contradiction can be resolved by recognizing that the interfaces between ordered and disordered lipid domains are the predominant sites of fusion. Here we show that line tension at lipid domain boundaries contributes significant energy to drive gp41-fusion peptide-mediated fusion. This energy, which depends on the hydrophobic mismatch between ordered and disordered lipid domains, may contribute tens of kBT to fusion, that is, it is comparable to the energy required to form a lipid stalk intermediate. Line-active compounds such as vitamin E lower line tension in inhomogeneous membranes, thereby inhibit membrane fusion, and thus may be useful natural viral entry inhibitors. PMID:27113279

  12. CHARMM Additive All-Atom Force Field for Phosphate and Sulfate Linked to Carbohydrates

    PubMed Central

    Mallajosyula, Sairam S.; Guvench, Olgun; Hatcher, Elizabeth; MacKerell, Alexander D.

    2012-01-01

    Presented is an extension of the CHARMM additive all-atom carbohydrate force field to enable the modeling of phosphate and sulfate linked to carbohydrates. The parameters are developed in a hierarchical fashion using model compounds containing the key atoms in the full carbohydrates. Target data for parameter optimization included full two-dimensional energy surfaces defined by the glycosidic dihedral angle pairs in the phosphate/sulfate model compound analogs of hexopyranose monosaccharide phosphates and sulfates, as determined by quantum mechanical (QM) MP2/cc-pVTZ single point energies on MP2/6-31+G(d) optimized structures. In order to achieve balanced, transferable dihedral parameters for the dihedral angles, surfaces for all possible anomeric and conformational states were included during the parametrization process. In addition, to model physiologically relevant systems both the mono- and di-anionic charged states were studied for the phosphates. This resulted in over 7000 MP2/cc-pVTZ//MP2/6-31G+(d) model compound conformational energies which, supplemented with QM geometries, were the main target data for the parametrization. Parameters were validated against crystals of relevant monosaccharide derivatives obtained from the Cambridge Structural Database (CSD) and larger systems, namely inositol-(tri/tetra/penta) phosphates non-covalently bound to the pleckstrin homology (PH) domain and oligomeric chondroitin sulfate in solution and in complex with cathepsin K protein. PMID:22685386

  13. Stability enhancement and fuel economy of the 4-wheel-drive hybrid electric vehicles by optimal tyre force distribution

    NASA Astrophysics Data System (ADS)

    Goodarzi, Avesta; Mohammadi, Masoud

    2014-04-01

    In this paper, vehicle stability control and fuel economy for a 4-wheel-drive hybrid vehicle are investigated. The integrated controller is designed within three layers. The first layer determines the total yaw moment and total lateral force made by using an optimal controller method to follow the desired dynamic behaviour of a vehicle. The second layer determines optimum tyre force distribution in order to optimise tyre usage and find out how the tyres should share longitudinal and lateral forces to achieve a target vehicle response under the assumption that all four wheels can be independently steered, driven, and braked. In the third layer, the active steering, wheel slip, and electrical motor torque controllers are designed. In the front axle, internal combustion engine (ICE) is coupled to an electric motor (EM). The control strategy has to determine the power distribution between ICE and EM to minimise fuel consumption and allowing the vehicle to be charge sustaining. Finally, simulations performed in MATLAB/SIMULINK environment show that the proposed structure could enhance the vehicle stability and fuel economy in different manoeuvres.

  14. Complete canthi removal reveals that forces from the amnioserosa alone are sufficient to drive dorsal closure in Drosophila

    PubMed Central

    Wells, Adrienne R.; Zou, Roger S.; Tulu, U. Serdar; Sokolow, Adam C.; Crawford, Janice M.; Edwards, Glenn S.; Kiehart, Daniel P.

    2014-01-01

    Drosophila's dorsal closure provides an excellent model system with which to analyze biomechanical processes during morphogenesis. During native closure, the amnioserosa, flanked by two lateral epidermal sheets, forms an eye-shaped opening with canthi at each corner. The dynamics of amnioserosa cells and actomyosin purse strings in the leading edges of epidermal cells promote closure, whereas the bulk of the lateral epidermis opposes closure. Canthi maintain purse string curvature (necessary for their dorsalward forces), and zipping at the canthi shortens leading edges, ensuring a continuous epithelium at closure completion. We investigated the requirement for intact canthi during closure with laser dissection approaches. Dissection of one or both canthi resulted in tissue recoil and flattening of each purse string. After recoil and a temporary pause, closure resumed at approximately native rates until slowing near the completion of closure. Thus the amnioserosa alone can drive closure after dissection of one or both canthi, requiring neither substantial purse string curvature nor zipping during the bulk of closure. How the embryo coordinates multiple, large forces (each of which is orders of magnitude greater than the net force) during native closure and is also resilient to multiple perturbations are key extant questions. PMID:25253724

  15. Specific sine-Gordon soliton dynamics in the presence of external driving forces

    NASA Astrophysics Data System (ADS)

    Reinisch, Gilbert; Fernandez, Jean Claude

    1981-07-01

    We consider the acceleration of a single sine-Gordon (SG) soliton kink wave by an external time-dependent force χ(t), first without any dissipation, and then in the presence of a weak damping effect. We use the method of Fogel, Trullinger, Bishop, and Krumhansl [FTBK,

    Phys. Rev. B 45, 1578 (1977)]
    which consists in perturbing the SG equation about its kink solution and solving the resulting linear inhomogeneous equation for the perturbation function by expanding it in the complete set of eigenfunctions of the Schrödinger operator with potential 1-2 2x. Our results concerning the accelerated soliton dynamics strongly disagree with the FTBK conclusion that the soliton should undergo an acceleration proportional to χ (this is the so-called Newtonian dynamical behavior of SG soliton, which is also predicted by all existing perturbation theories dealing with the perturbed SG equation). On the contrary, we find that this Newtonian acceleration is exactly balanced by a reaction effect of the continuous phonon spectrum excited by the external force χ, upon the moving kink, so that there is no soliton acceleration at all within the frame of this linear perturbation theory, i.e., for small time values. Actually, we show by the simple example of a static external force that the acceleration of an initially static kink is a higher-order effect (proportional to χt2, where t is the time, instead of being constant and proportional to χ). We emphasize that this last result has already been checked by numerical experiments and show, both by theory and by numerical simulations, that it does not qualitatively change when a small damping effect is taken into account.

  16. Inherent Driving Force for Charge Separation in Curved Stacks of Oligothiophenes

    SciTech Connect

    Wu, Qin

    2015-01-30

    Coexistence of high local charge mobility and an energy gradient can lead to efficient free charge carrier generation from geminate charge transfer states at the donor–acceptor interface in bulk heterojunction organic photovoltaics. It is, however, not clear what polymer microstructures can support such coexistence. Using recent methods from density functional theory, we propose that a stack of similarly curved oligothiophene chains can deliver the requirements for efficient charge separation. Curved stacks are stable because of the polymer’s strong π-stacking ability and because backbone torsions are flexible in neutral chains. However, energy of a charge in a polymer chain has remarkably stronger dependence on torsions. The trend of increasing planarity in curved stacks effectively creates an energy gradient that drives charge in one direction. The curvature of these partially ordered stacks is found to beneficially interact with fullerenes for charge separation. The curved stacks, therefore, are identified as possible building blocks for interfacial structures that lead to efficient free carrier generation in high-performing organic photovoltaic systems.

  17. Driving force for crystallization of anionic lipid membranes revealed by atomistic simulations.

    PubMed

    Qiao, Bao Fu; Olvera de la Cruz, Monica

    2013-05-01

    Crystalline vesicles are promising nanomaterials due to their mechanical stability in various environments. To control their fabrication, it is essential to understand the effects of different experimental conditions on crystallization. Here we perform atomistic molecular dynamics simulations of anionic lipid membranes of 1,2-dilauroyl-sn-glycero-3-phosphol-L-serine. In the presence of Na(+) monovalent counterions, we access the phase transition from the liquid-like disordered liquid-crystalline phase to the ordered gel phase by lowering the temperature of the system. The phase transition is conclusively evidenced by the scattering structure factor. Quantitative calculations show that the enhancement of the intertail van der Waals interaction (about -6 k(B)T) plays a dominant role in driving the phase transition rather than the increase in the cohesive interaction (-0.5 k(B)T) between lipids and counterions. Meanwhile, in the presence of multivalent counterions of Zn(2+) or La(3+) the gel phase is found throughout the temperature range investigated. Moreover, the van der Waals interaction per hydrocarbon group is ∼20% stronger in the gel phase (∼ -1.8 k(B)T regardless of the counterions) than in the liquid-crystalline phase (-1.5 k(B)T). PMID:23565965

  18. Inherent Driving Force for Charge Separation in Curved Stacks of Oligothiophenes

    DOE PAGESBeta

    Wu, Qin

    2015-01-30

    Coexistence of high local charge mobility and an energy gradient can lead to efficient free charge carrier generation from geminate charge transfer states at the donor–acceptor interface in bulk heterojunction organic photovoltaics. It is, however, not clear what polymer microstructures can support such coexistence. Using recent methods from density functional theory, we propose that a stack of similarly curved oligothiophene chains can deliver the requirements for efficient charge separation. Curved stacks are stable because of the polymer’s strong π-stacking ability and because backbone torsions are flexible in neutral chains. However, energy of a charge in a polymer chain has remarkablymore » stronger dependence on torsions. The trend of increasing planarity in curved stacks effectively creates an energy gradient that drives charge in one direction. The curvature of these partially ordered stacks is found to beneficially interact with fullerenes for charge separation. The curved stacks, therefore, are identified as possible building blocks for interfacial structures that lead to efficient free carrier generation in high-performing organic photovoltaic systems.« less

  19. Line tension at lipid phase boundaries as driving force for HIV fusion peptide-mediated fusion

    PubMed Central

    Yang, Sung-Tae; Kiessling, Volker; Tamm, Lukas K.

    2016-01-01

    Lipids and proteins are organized in cellular membranes in clusters, often called ‘lipid rafts'. Although raft-constituent ordered lipid domains are thought to be energetically unfavourable for membrane fusion, rafts have long been implicated in many biological fusion processes. For the case of HIV gp41-mediated membrane fusion, this apparent contradiction can be resolved by recognizing that the interfaces between ordered and disordered lipid domains are the predominant sites of fusion. Here we show that line tension at lipid domain boundaries contributes significant energy to drive gp41-fusion peptide-mediated fusion. This energy, which depends on the hydrophobic mismatch between ordered and disordered lipid domains, may contribute tens of kBT to fusion, that is, it is comparable to the energy required to form a lipid stalk intermediate. Line-active compounds such as vitamin E lower line tension in inhomogeneous membranes, thereby inhibit membrane fusion, and thus may be useful natural viral entry inhibitors. PMID:27113279

  20. Predation risk as a driving force for sexual segregation: a cross-population comparison.

    PubMed

    Croft, Darren P; Morrell, Lesley J; Wade, Amy S; Piyapong, Chantima; Ioannou, Christos C; Dyer, John R G; Chapman, Ben B; Wong, Yan; Krause, Jens

    2006-06-01

    Sexual segregation is widespread throughout the animal kingdom. Although a number of hypotheses have been proposed to account for observed patterns, the generality of the mechanisms remains debated. One possible reason for this is the focus on segregation patterns in large mammals such as ungulates, where the majority of studies are descriptions of a single population. Here, we present the results of a cross‐population comparison of patterns of sexual segregation in the Trinidadian guppy, Poecilia reticulata. We relate observed patterns to experimental quantification of predation risk and sexual harassment of females by males in eight populations. We find that the degree of segregation increases with predation risk, with deeper waters becoming increasingly female biased. Furthermore, we observed that levels of male harassment are lower in deeper water but only in those rivers that contain major guppy predators. We conclude that sexual segregation in guppies is consistent with the predation risk hypothesis: sexual segregation results from a combination of predation risk driving males (the more vulnerable sex) into less risky habitats and females gaining benefits of reduced sexual harassment by remaining in high‐predation environments. PMID:16649156

  1. Driving force dependence of charge separation and recombination processes in dyads of nucleotides and strongly electron-donating oligothiophenes.

    PubMed

    Lin, Shih-Hsun; Fujitsuka, Mamoru; Ishikawa, Mayuka; Majima, Tetsuro

    2014-10-23

    Charge transfer in DNA has attracted great attention of scientists because of its importance in biological processes. However, our knowledge on excess-electron transfer in DNA still remains limited in comparison to numerous studies of hole transfer in DNA. To clarify the dynamics of excess-electron transfer in DNA by photochemical techniques, new electron-donating photosensitizers should be developed. Herein, a terthiophene and two 3,4-ethylenedioxythiophene oligomers were used as photosensitizers in dyads including natural nucleobases as electron acceptors. The charge separation and recombination processes in the dyads were investigated by femtosecond laser flash photolysis, and the driving force dependence of these rate constants was discussed on the basis of the Marcus theory. From this study, the conformation effect on charge recombination process was found. We expect that 3,4-ethylenedioxythiophene oligomers are useful in investigation of excess-electron-transfer dynamics in DNA. PMID:25265410

  2. Research Problems Associated with Limiting the Applied Force in Vibration Tests and Conducting Base-Drive Modal Vibration Tests

    NASA Technical Reports Server (NTRS)

    Scharton, Terry D.

    1995-01-01

    The intent of this paper is to make a case for developing and conducting vibration tests which are both realistic and practical (a question of tailoring versus standards). Tests are essential for finding things overlooked in the analyses. The best test is often the most realistic test which can be conducted within the cost and budget constraints. Some standards are essential, but the author believes more in the individual's ingenuity to solve a specific problem than in the application of standards which reduce problems (and technology) to their lowest common denominator. Force limited vibration tests and base-drive modal tests are two examples of realistic, but practical testing approaches. Since both of these approaches are relatively new, a number of interesting research problems exist, and these are emphasized herein.

  3. RUNX2 and the PI3K/AKT axis reciprocal activation as a driving force for tumor progression.

    PubMed

    Cohen-Solal, Karine A; Boregowda, Rajeev K; Lasfar, Ahmed

    2015-01-01

    From the first reported role of the transcription factor RUNX2 in osteoblast and chondrocyte differentiation and migration to its involvement in promigratory/proinvasive behavior of breast, prostate, and thyroid cancer cells, osteosarcoma, or melanoma cells, RUNX2 currently emerges as a key player in metastasis. In this review, we address the interaction of RUNX2 with the PI3K/AKT signaling pathway, one of the critical axes controlling cancer growth and metastasis. AKT, either by directly phosphorylating/activating RUNX2 or phosphorylating/inactivating regulators of RUNX2 stability or activity, contributes to RUNX2 transcriptional activity. Reciprocally, the activation of the PI3K/AKT pathway by RUNX2 regulation of its different components has been described in non-transformed and transformed cells. This mutual activation in the context of cancer cells exhibiting constitutive AKT activation and high levels of RUNX2 might constitute a major driving force in tumor progression and aggressiveness. PMID:26204939

  4. Energetic driving force for preferential binding of self-interstitial atoms to Fe grain boundaries over vacancies

    SciTech Connect

    Tschopp, Mark A.; Horstemeyer, Mark; Gao, Fei; Sun, Xin; Khaleel, Mohammad A.

    2011-05-02

    Molecular dynamics simulations of 50 Fe grain boundaries were used to understand their interaction with vacancies and self-interstitial atoms at all atomic positions within 20 °A of the boundary, which is important for designing radiation-resistant polycrystalline materials. Site-to-site variation within the boundary of both vacancy and self-interstitial formation energies is substantial, with the majority of sites having lower formation energies than in the bulk. Comparing the vacancy and self-interstitial atom binding energies for each site shows that there is an energetic driving force for interstitials to preferentially bind to grain boundary sites over vacancies. Furthermore, these results provide a valuable dataset for quantifying uncertainty bounds for various grain boundary types at the nanoscale, which can be propagated to higher scale simulations of microstructure evolution.

  5. Opposing forces of aerosol cooling and El Niño drive coral bleaching on Caribbean reefs

    PubMed Central

    Gill, Jennifer A.; Watkinson, Andrew R.; McWilliams, John P.; Côté, Isabelle M.

    2006-01-01

    Bleaching of corals as a result of elevated sea surface temperatures (SST) is rapidly becoming a primary source of stress for reefs globally; the scale and extent of this threat will depend on how the drivers of SST interact to influence bleaching patterns. We demonstrate how the opposing forces of the El Niño–Southern Oscillation (ENSO) and levels of atmospheric aerosols drive regional-scale patterns of coral bleaching across the Caribbean. When aerosol levels are low, bleaching is largely determined by El Niño strength, but high aerosol levels mitigate the effects of a severe El Niño. High aerosol levels, resulting principally from recent volcanic activity, have thus protected Caribbean reefs from more frequent widespread bleaching events but cannot be relied on to provide similar protection in the future. PMID:17116861

  6. Mining spatial information to investigate the evolution of karst rocky desertification and its human driving forces in Changshun, China.

    PubMed

    Xu, Erqi; Zhang, Hongqi; Li, Mengxian

    2013-08-01

    The processes of karst rocky desertification (KRD) have been found to cause the most severe environmental degradation in southwestern China. Understanding the driving forces that cause KRD is essential for managing and restoring the areas that it impacts. Studies of the human driving forces of KRD are limited to the county level, a specific administrative unit in China; census data are acquired at this scale, which can lead to scale biases. Changshun County is studied here as a representative area and anthropogenic influences in the county are accounted for by using Euclidean distances for the proximity to roads and settlements. We propose a standard coefficient of human influence (SOI) that standardizes the Euclidean distances for different KRD transformations to compare the effects of human activities in different areas. In Changshun County, the individual influences of roads and settlements share similar characteristics. The SOIs of improved KRD transformation types are almost negative, but the SOIs of deteriorated types are nearly positive except for one form of KRD turning to the extremely severe KRD. The results indicated that the distribution and evolution of the KRD areas from 2000 to 2010 in Changshun were affected positively by human activities (e.g., KRD restoration projects) and also negatively (e.g., by intense and irrational land use). Our results demonstrate that the spatial techniques and SOI used in this study can effectively incorporate information concerning human influences and internal KRD transformations. This provides a suitable approach for studying the relationships between human activities and KRD processes at fine scales. PMID:23685367

  7. [Land use change dynamics and driving forces of the vulnerable ecological region in northwestern Shanxi Province, China].

    PubMed

    Li, Xiu-Fen; Liu, Li-Min; Qi, Xin; Zhang, Jin-Xin; Zhao, Tong-Bin; Wang, Yi; Liu, Xue-Fen; Zhou, Yong-Bin

    2014-10-01

    By using remote sensing and GIS technology, this paper collected land use information of 1980, 1990, 2000 and 2010 and the relevant statistical data, and analyzed the characteristics of land use change and its driving forces in northwestern Shanxi Province, the typical ecological fragile area. The results showed that there were significant changes in land use patterns in the past 30 years. During 1980-1990, 1990-2000 and 2000-2010 periods, the area of farmland decreased continuously, while the areas of grassland and woodland experienced increase-decrease-increase and decrease-increase-decrease patterns of change, respectively. The areas of industrial and resident lands increased continuously, but the water body and unused land decreased. The farmland was mainly transformed to grassland and woodland, and the areas of industrial and resident lands increased from the farmland. The lost area of water body was transformed to grassland and farmland. The decrease of unused land was due to the implementation of ecological engineering and urban ex-panding. In general, the changes of land use types were significantly higher before 2000 than after 2000. The industrial and resident lands, unused land and grassland changed drastically. The relationships between land use types and driving forces indicated that population pressure and economic development led to the changes of industrial land and farmland; policy of forestry ecological engi- neering drove the changes of woodland and grassland; the drought-characterized climate was the major cause inducing the decrease of water area and hindering the restoration of forest. PMID:25796906

  8. Technique of optimization of minimum temperature driving forces in the heaters of regeneration system of a steam turbine unit

    NASA Astrophysics Data System (ADS)

    Shamarokov, A. S.; Zorin, V. M.; Dai, Fam Kuang

    2016-03-01

    At the current stage of development of nuclear power engineering, high demands on nuclear power plants (NPP), including on their economy, are made. In these conditions, improving the quality of NPP means, in particular, the need to reasonably choose the values of numerous managed parameters of technological (heat) scheme. Furthermore, the chosen values should correspond to the economic conditions of NPP operation, which are postponed usually a considerable time interval from the point of time of parameters' choice. The article presents the technique of optimization of controlled parameters of the heat circuit of a steam turbine plant for the future. Its particularity is to obtain the results depending on a complex parameter combining the external economic and operating parameters that are relatively stable under the changing economic environment. The article presents the results of optimization according to this technique of the minimum temperature driving forces in the surface heaters of the heat regeneration system of the steam turbine plant of a K-1200-6.8/50 type. For optimization, the collector-screen heaters of high and low pressure developed at the OAO All-Russia Research and Design Institute of Nuclear Power Machine Building, which, in the authors' opinion, have the certain advantages over other types of heaters, were chosen. The optimality criterion in the task was the change in annual reduced costs for NPP compared to the version accepted as the baseline one. The influence on the decision of the task of independent variables that are not included in the complex parameter was analyzed. An optimization task was decided using the alternating-variable descent method. The obtained values of minimum temperature driving forces can guide the design of new nuclear plants with a heat circuit, similar to that accepted in the considered task.

  9. Tendency to occupy a statistically dominant spatial state of the flow as a driving force for turbulent transition.

    PubMed

    Chekmarev, Sergei F

    2013-03-01

    The transition from laminar to turbulent fluid motion occurring at large Reynolds numbers is generally associated with the instability of the laminar flow. On the other hand, since the turbulent flow characteristically appears in the form of spatially localized structures (e.g., eddies) filling the flow field, a tendency to occupy such a structured state of the flow cannot be ruled out as a driving force for turbulent transition. To examine this possibility, we propose a simple analytical model that treats the flow as a collection of localized spatial structures, each of which consists of elementary cells in which the behavior of the particles (atoms or molecules) is uncorrelated. This allows us to introduce the Reynolds number, associating it with the ratio between the total phase volume for the system and that for the elementary cell. Using the principle of maximum entropy to calculate the most probable size distribution of the localized structures, we show that as the Reynolds number increases, the elementary cells group into the localized structures, which successfully explains turbulent transition and some other general properties of turbulent flows. An important feature of the present model is that a bridge between the spatial-statistical description of the flow and hydrodynamic equations is established. We show that the basic assumptions underlying the model, i.e., that the particles are indistinguishable and elementary volumes of phase space exist in which the state of the particles is uncertain, are involved in the derivation of the Navier-Stokes equation. Taking into account that the model captures essential features of turbulent flows, this suggests that the driving force for the turbulent transition is basically the same as in the present model, i.e., the tendency of the system to occupy a statistically dominant state plays a key role. The instability of the flow at high Reynolds numbers can then be a mechanism to initiate structural rearrangement of

  10. Wading for food the driving force of the evolution of bipedalism?

    PubMed

    Kuliukas, Algis

    2002-01-01

    Evidence is accumulating that suggests that the large human brain is most likely to have evolved in littoral and estuarine habitats rich in naturally occurring essential fatty acids. This paper adds further weight to this view, suggesting that another key human trait, our bipedality might also be best explained as an adaptation to a water-side niche. Evidence is provided here that extant apes, although preferring to keep dry, go into water when driven to do so by hunger. The anecdotal evidence has suggested that they tend to do this bipedally. Here, a new empirical study of captive bonobos found them to exhibit 2% or less bipedality on the ground or in trees but over 90% when wading in water to collect food. The skeletal morphology of AL 288-1 ("Lucy") is shown to indicate a strong ability to abduct and adduct the femur. These traits, together with a remarkably platypelloid pelvis, have not yet been adequately explained by terrestrial or arboreal models for early bipedalism but are consistent with those expected in an ape that adopted a specialist side-to-side 'ice-skating' or sideways wading mode. It is argued that this explanation of A. afarensis locomotor morphology is more parsimonious than others which have plainly failed to produce a consensus. Microwear evidence of Australopithecus dentition is also presented as evidence that the drive for such a wading form of locomotion might well have been waterside foods. This model obtains further support from the paleo-habitats of the earliest known bipeds, which are consistent with the hypothesis that wading contributed to the adaptive pressure towards bipedality. PMID:12617279

  11. Spatial Pattern of Land Use Change and Its Driving Force in Jiangsu Province

    PubMed Central

    Du, Xindong; Jin, Xiaobin; Yang, Xilian; Yang, Xuhong; Zhou, Yinkang

    2014-01-01

    Scientific interpretation of the mechanism of land use change is important for government planning and management activities. This study analyzes the land use change in Jiangsu Province using three land use maps of 2000, 2005 and 2008. The study results show that there was a significant change in land use. The change was mainly characterized by a continuous built-up land expansion primarily at the expense of cropland loss, and the trend became increasingly rapid. There was an obvious regional difference, as most of the cropland loss or built-up land expansion took place in southern Jiangsu, where the rate of built-up land expansion was faster than in central and northern Jiangsu. Meanwhile, the spatial pattern changed remarkably; in general, the number of patches (NumP) showed a declining trend, and the mean patch size (MPS) and patch size standard deviation (PSSD) displayed increase trends. Furthermore, the relative importance of selected driven factors was identified by principal component analysis (PCA) and general linear model (GLM). The results showed that not only the relative importance of a specific driving factor may vary, but the driven factors may as well. The most important driven factor changed from urban population (UP), secondary gross domestic product (SGDP) and gross domestic product (GDP) during 2000–2005 to resident population (RP), population density (POD) and UP during 2005–2008, and the deviance explained (DE) decreased from 91.60% to 81.04%. Policies also had significant impacts on land use change, which can be divided into direct and indirect impacts. Development policies usually had indirect impacts, particularly economic development policies, which promote the economic development to cause land use change, while land management policies had direct impacts. We suggest that the government should think comprehensively and cautiously when proposing a new development strategy or plan. PMID:24646864

  12. Experiments using atmospheric forcing from a FGGE analysis to drive an upper ocean model

    NASA Technical Reports Server (NTRS)

    Camerlengo, A.

    1983-01-01

    Results are presented of a series of numerical experiments in which an upper ocean model is driven by surface heat fluxes and stress fields derived from the FGGE SOP-1 GLAS analysis/forecast system (Halem, et al., 1982). The model results show that most changes in the mixed layer height and horizontal velocity occurs in the first days. On the other hand, changes in the temperature field take a longer time to develop. In the most realistic case (real initial conditions, instantaneous forcing fields from the atmospheric analysis), the resulting changes in temperature were larger than observed and the correlation between observed and predicted changes was poor. The deficiency in the forecast of SST changes may be due to several factors: lack of sufficient ocean resolution, improper initialization, lack of feedback between the ocean and the atmosphere and the absence of transports by the strong boundary currents, and perhaps unrealistic surface fluxes of heat and momentum. Unless these problems are alleviated it is not reasonable to perform coupled atmospheric ocean forecasts.

  13. Biomechanical force in blood development: extrinsic physical cues drive pro-hematopoietic signaling

    PubMed Central

    Lee, Hyun Jung; Li, Nan; Evans, Siobahn M.; Diaz, Miguel F.; Wenzel, Pamela L.

    2013-01-01

    The hematopoietic system is dynamic during development and in adulthood, undergoing countless spatial and temporal transitions during the course of one’s life. Microenvironmental cues in the many unique hematopoietic niches differ, characterized by distinct soluble molecules, membrane-bound factors, and biophysical features that meet the changing needs of the blood system. Research from the last decade has revealed the importance of substrate elasticity and biomechanical force in determination of stem cell fate. Our understanding of the role of these factors in hematopoiesis is still relatively poor; however, the developmental origin of blood cells from the endothelium promts a model for comparison. Many endothelial mechanical sensors and second messenger systems may also determine hematopoietic stem cell fate, self renewal, and homing behaviors. Further, the intimate contact of hematopoietic cells with mechanosensitive cell types, including osteoblasts, endothelial cells, mesenchymal stem cells, and pericytes, places them in close proximity to paracrine signaling downstream of mechanical signals. The objective of this review is to present an overview of the sensors and intracellular signaling pathways activated by mechanical cues and highlight the role of mechanotransductive pathways in hematopoiesis. PMID:23850217

  14. Structural Fe(II) Oxidation in Biotite by an Ectomycorrhizal Fungi Drives Mechanical Forcing.

    PubMed

    Bonneville, Steeve; Bray, Andrew W; Benning, Liane G

    2016-06-01

    Microorganisms are essential agents of Earth's soil weathering engine who help transform primary rock-forming minerals into soils. Mycorrhizal fungi, with their vast filamentous networks in symbiosis with the roots of most plants can alter a large number of minerals via local acidification, targeted excretion of ligands, submicron-scale biomechanical forcing, and mobilization of Mg, Fe, Al, and K at the hypha-biotite interface. Here, we present experimental evidence that Paxillus involutus-a basidiomycete fungus-in ectomycorrhizal symbiosis with Scots pine (Pinus sylvestris), is able to oxidize a substantial amount of structural Fe(II) in biotite. Iron redox chemistry, quantified by X-ray absorption near edge spectra on 13 fungi-biotite sections along three distinct hypha colonizing the [001] basal plane of biotite, revealed variable but extensive Fe(II) oxidation up to ∼2 μm in depth and a Fe(III)/Fetotal ratio of up to ∼0.8. The growth of Fe(III) hydroxide implies a volumetric change and a strain within the biotite lattice potentially large enough to induce microcrack formation, which are abundant below the hypha-biotite interface. This Fe(II) oxidation also leads to the formation of a large pool of Fe(III) (i.e., structural Fe(III) and Fe(III) oxyhydroxides) within biotite that could participate in the Fe redox cycling in soils. PMID:27128742

  15. Selective pressure against horizontally acquired prokaryotic genes as a driving force of plastid evolution.

    PubMed

    Llorente, Briardo; de Souza, Flavio S J; Soto, Gabriela; Meyer, Cristian; Alonso, Guillermo D; Flawiá, Mirtha M; Bravo-Almonacid, Fernando; Ayub, Nicolás D; Rodríguez-Concepción, Manuel

    2016-01-01

    The plastid organelle comprises a high proportion of nucleus-encoded proteins that were acquired from different prokaryotic donors via independent horizontal gene transfers following its primary endosymbiotic origin. What forces drove the targeting of these alien proteins to the plastid remains an unresolved evolutionary question. To better understand this process we screened for suitable candidate proteins to recapitulate their prokaryote-to-eukaryote transition. Here we identify the ancient horizontal transfer of a bacterial polyphenol oxidase (PPO) gene to the nuclear genome of an early land plant ancestor and infer the possible mechanism behind the plastidial localization of the encoded enzyme. Arabidopsis plants expressing PPO versions either lacking or harbouring a plastid-targeting signal allowed examining fitness consequences associated with its subcellular localization. Markedly, a deleterious effect on plant growth was highly correlated with PPO activity only when producing the non-targeted enzyme, suggesting that selection favoured the fixation of plastid-targeted protein versions. Our results reveal a possible evolutionary mechanism of how selection against heterologous genes encoding cytosolic proteins contributed in incrementing plastid proteome complexity from non-endosymbiotic gene sources, a process that may also impact mitochondrial evolution. PMID:26750147

  16. Driving Forces for Bicarbonate Transport in the Cyanobacterium Synechococcus R-2 (PCC 7942).

    PubMed Central

    Ritchie, R. J.; Nadolny, C.; Larkum, AWD.

    1996-01-01

    Air-grown Synechococcus R-2 (PCC 7942) cultures grown in BG-11 medium are very alkaline (outside pH is 10.0) and use HCO3- as their inorganic carbon source. The cells showed a dependence on Na+ for photosynthesis, but low Na+ conditions (1 mol m-3) were sufficient to support saturating photosynthesis. The intracellular dissolved inorganic carbon in the light was greater than 20 mol m-3 in both low-Na+ conditions and in BG-11 medium containing the usual [Na+] (24 mol m-3, designated high-Na+ conditions). The electrochemical potential for HCO3- in the light was in excess of 25 kJ mol-1, even in high-Na+ conditions. The Na+-motive force was greater than -12 kJ mol-1 under both Na+ conditions. On thermodynamic grounds, an Na+-driven co-port process would need to have a stoichiometry of 2 or greater ([greater than or equal to]2Na+ in/HCO3-1 in), but we show that Na+ or K+ fluxes cannot be linked to HCO3- transport. Na+ and K+ fluxes were unaffected by the presence or absence of dissolved inorganic carbon. In low-Na+ conditions, Na+ fluxes are too low to support the observed net 14C-carbon fixation rate. Active transport of HCO3- hyperpolarizes (not depolarizes) the membrane potential. PMID:12226464

  17. Selective pressure against horizontally acquired prokaryotic genes as a driving force of plastid evolution

    PubMed Central

    Llorente, Briardo; de Souza, Flavio S. J.; Soto, Gabriela; Meyer, Cristian; Alonso, Guillermo D.; Flawiá, Mirtha M.; Bravo-Almonacid, Fernando; Ayub, Nicolás D.; Rodríguez-Concepción, Manuel

    2016-01-01

    The plastid organelle comprises a high proportion of nucleus-encoded proteins that were acquired from different prokaryotic donors via independent horizontal gene transfers following its primary endosymbiotic origin. What forces drove the targeting of these alien proteins to the plastid remains an unresolved evolutionary question. To better understand this process we screened for suitable candidate proteins to recapitulate their prokaryote-to-eukaryote transition. Here we identify the ancient horizontal transfer of a bacterial polyphenol oxidase (PPO) gene to the nuclear genome of an early land plant ancestor and infer the possible mechanism behind the plastidial localization of the encoded enzyme. Arabidopsis plants expressing PPO versions either lacking or harbouring a plastid-targeting signal allowed examining fitness consequences associated with its subcellular localization. Markedly, a deleterious effect on plant growth was highly correlated with PPO activity only when producing the non-targeted enzyme, suggesting that selection favoured the fixation of plastid-targeted protein versions. Our results reveal a possible evolutionary mechanism of how selection against heterologous genes encoding cytosolic proteins contributed in incrementing plastid proteome complexity from non-endosymbiotic gene sources, a process that may also impact mitochondrial evolution. PMID:26750147

  18. Investigation of Adiabatic Shear Bands in Thick-Walled Cylinders Collapsed by Electro-Magnetic Driving Forces

    NASA Astrophysics Data System (ADS)

    Lovinger, Z.; Rikanati, A.; Rittel, D.; Rosenberg, Z.

    2009-12-01

    The Thick-Walled Cylinder technique, reported in the literature, employs an explosive cylinder to create the driving force, collapsing the cylindrical sample. This experimental set-up has been established as a controlled and repeatable technique to create and study multiple adiabatic shear bands. Searching to establish a simpler experimental platform to perform large sets of experiments, we have designed an Electro-Magnetic (EM) set-up for the collapse of thick walled cylinders. The EM setup is based on a pulsed current generator using a capacitor bank system. The specimen is an assembly of coaxial cylinders, where the inner and outer cylinders, each attached to an opposite pole, are short-circuited. Upon discharge, a high current flows through the cylinders, in opposite directions, creating repulsive magnetic forces between them. This work presents the design procedure of the specimens using numerical simulations as well as some results for SS304L thick-walled specimens, using this setup. The spatial distribution of the multiple adiabatic shear bands in these experiments is in good agreement with that reported in the literature for the explosive driven experiments with SS304L specimens. Our numerical simulations show good agreement with the experimental results for both global behaviour and shear band distribution.

  19. Spatial analysis and quantification of the thermodynamic driving forces in protein-ligand binding: binding site variability.

    PubMed

    Raman, E Prabhu; MacKerell, Alexander D

    2015-02-25

    The thermodynamic driving forces behind small molecule-protein binding are still not well-understood, including the variability of those forces associated with different types of ligands in different binding pockets. To better understand these phenomena we calculate spatially resolved thermodynamic contributions of the different molecular degrees of freedom for the binding of propane and methanol to multiple pockets on the proteins Factor Xa and p38 MAP kinase. Binding thermodynamics are computed using a statistical thermodynamics based end-point method applied on a canonical ensemble comprising the protein-ligand complexes and the corresponding free states in an explicit solvent environment. Energetic and entropic contributions of water and ligand degrees of freedom computed from the configurational ensemble provide an unprecedented level of detail into the mechanisms of binding. Direct protein-ligand interaction energies play a significant role in both nonpolar and polar binding, which is comparable to water reorganization energy. Loss of interactions with water upon binding strongly compensates these contributions leading to relatively small binding enthalpies. For both solutes, the entropy of water reorganization is found to favor binding in agreement with the classical view of the "hydrophobic effect". Depending on the specifics of the binding pocket, both energy-entropy compensation and reinforcement mechanisms are observed. It is notable to have the ability to visualize the spatial distribution of the thermodynamic contributions to binding at atomic resolution showing significant differences in the thermodynamic contributions of water to the binding of propane versus methanol. PMID:25625202

  20. Spatial Analysis and Quantification of the Thermodynamic Driving Forces in Protein-Ligand Binding: Binding Site Variability

    PubMed Central

    Raman, E. Prabhu; MacKerell, Alexander D.

    2015-01-01

    The thermodynamic driving forces behind small molecule-protein binding are still not well understood, including the variability of those forces associated with different types of ligands in different binding pockets. To better understand these phenomena we calculate spatially resolved thermodynamic contributions of the different molecular degrees of freedom for the binding of propane and methanol to multiple pockets on the proteins Factor Xa and p38 MAP kinase. Binding thermodynamics are computed using a statistical thermodynamics based end-point method applied on a canonical ensemble comprising the protein-ligand complexes and the corresponding free states in an explicit solvent environment. Energetic and entropic contributions of water and ligand degrees of freedom computed from the configurational ensemble provides an unprecedented level of detail into the mechanisms of binding. Direct protein-ligand interaction energies play a significant role in both non-polar and polar binding, which is comparable to water reorganization energy. Loss of interactions with water upon binding strongly compensates these contributions leading to relatively small binding enthalpies. For both solutes, the entropy of water reorganization is found to favor binding in agreement with the classical view of the “hydrophobic effect”. Depending on the specifics of the binding pocket, both energy-entropy compensation and reinforcement mechanisms are observed. Notable is the ability to visualize the spatial distribution of the thermodynamic contributions to binding at atomic resolution showing significant differences in the thermodynamic contributions of water to the binding of propane versus methanol. PMID:25625202

  1. Medical school survival versus social responsibility: finances as a driving force.

    PubMed

    Brandt, E N

    1989-01-01

    Medical educators are an interesting group of people. They thrive on new knowledge. They get excited and enthusiastic, and readily adopt new ways when the evidence is sufficient. Yet, at the same time, they resist with great vehemence change in the way they do their business. Ask how often the curriculum structure is examined. Indeed, the function of most curriculum committees is to ensure that that does not happen. Ask how often the criteria for medical school admission are examined, especially with respect to the knowledge requirements. Ask how often the faculty discusses, or even examines, the expectations of society as they are expressed by alumni, legislators, or members of the public. Ask how often faculties try to determine strategies for dealing with all of these external forces. Are those strategies approached with the same degree of objectivity and data-gathering skills that would be used in examining new therapeutic regimens? Medical educators are talented, creative people. They have a very large appetite for information and great ambition to be as fine academicians as possible. It is those characteristics that have served them well, as students and as responsible academicians. Indeed, the great strength of medical education, in my view, is that medical schools take some very bright people called faculty and some very bright people called students, mix them together for four years, and graduate a group of very smart people who will then spend three years or more mixed up with some very bright and creative people. That is a strength that can-not lost. Will the future allow us to continue that in an equally effective manner? PMID:2734361

  2. Thermodynamic driving forces for PAH isomerization and growth during thermal treatment of polluted soils.

    PubMed

    Pope, C J; Peters, W A; Howard, J B

    2000-12-01

    For a limiting case of thermodynamic equilibrium, the importance of two classes of thermal chemical reactions that modify the structure and bioactivity of polycyclic aromatic hydrocarbons (PAH) was assessed computationally. These reactions are molecular weight (MW) growth by acetylene addition, and intramolecular rearrangement (isomerization). Temperatures (300-1100 degrees C), and the chemical environment (C(2)H(2)/H(2) molar ratios) were selected for relevancy to thermal treatment of PAH-contaminated soils under oxygen-free conditions. Molecular mechanics methods [MM3(92)] were used to compute thermochemical properties for calculation of equilibrium constants, i.e., heats of formation, standard entropies, and heat capacities for 30 PAH with empirical formulae C(14)H(10), C(16)H(10), C(18)H(10), C(18)H(12), C(20)H(10), and C(20)H(12). Included were 11 PAH containing only six-membered rings and 19 PAH containing both five- and six-membered rings. For each of these PAH the calculations predict that with increasing temperature, isomerization increases the "complexity" of the PAH mixture, i.e., the relative abundance of each PAH isomer in the mixture other than the most stable isomer, increases. Isomerization also partially transforms non-mutagens to mutagens, e.g., pyrene and benzo[e]pyrene to fluoranthene and benzo[a]pyrene, respectively, and partially converts cyclopenta[c, d]pyrene (CPEP) and chrysene, both human cell mutagens, to one and three additional human cell mutagens, respectively. Acetylene addition transforms the non-mutagens phenanthrene and pyrene to the mutagens triphenylene and CPEP, respectively. Some of the predicted PAH have been observed elsewhere among the products of aromatics pyrolysis. This study elucidates PAH reactivity for comparison with measurements, and identifies PAH reactions to be monitored and avoided in soil thermal decontamination and other waste remediation processes. PMID:11040395

  3. MECHANISM AND HYDROPHOBIC FORCES DRIVING MEMBRANE PROTEIN INSERTION OF SUBUNIT II OF CYTOCHROME BO OXIDASE

    PubMed Central

    Celebi, Nil; Dalbey, Ross E.; Yuan, Jijun

    2009-01-01

    Subunit II (CyoA) of cytochrome bo oxidase, which spans the inner membrane twice in bacteria, has several unusual features in membrane biogenesis. It is synthesized with an amino-terminal signal peptide. In addition, distinct pathways are used to insert the two ends of the protein. The amino-terminal domain is inserted by the YidC pathway whereas the large carboxyl-terminal domain is translocated by the SecYEG pathway. Insertion of the protein is also pmf-independent. In this study we examined the topogenic requirements and mechanism of insertion of CyoA in bacteria. We find that both the signal peptide and the first membrane spanning region are required for insertion of the amino-terminal periplasmic loop. The pmf-independence of insertion of the first periplasmic loop is due to the loop’s neutral net charge. We observe also that the introduction of negatively charged residues into the periplasmic loop makes insertion pmf dependent, whereas the addition of positively charged residues prevents insertion unless the pmf is abolished. Insertion of the carboxyl-terminal domain in the full-length CyoA occurs by a sequential mechanism even when the CyoA amino and carboxyl-terminal domains are swapped with other domains. However, when a long spacer peptide is added to increase the distance between the amino-terminal and carboxyl-terminal domains, insertion no longer occurs by a sequential mechanism. PMID:18155041

  4. Demonstration of non-additivity and asymmetry in the lateral Casimir force

    NASA Astrophysics Data System (ADS)

    Chiu, Hsiang-Chih

    2009-10-01

    The Casimir effect is a purely quantum mechanical phenomenon which has drawn extensive attention in the last decade. With the rapid development of modern scientific instruments, it has been demonstrated and measured with unprecedented precision. Because of its unique dependence on the separation and geometry, the Casimir force is expected to play an important role in modern nano-electro-mechanical systems. An understanding of the shape dependence of the Casimir force and its control has become a very important research topic for the future nano-technology. Since the demonstration of the lateral Casimir force in 2002 at UC Riverside, this special effect has inspired a lot of theoretical research. The asymmetry of the lateral Casimir has been predicted and exact theories which take into account diffraction-like correlation effect between the scattered zero point photons from the boundaries have been proposed. We improved the experimental setup and experimental conditions (grating period of order of the separation distance) to study these new phenomenon. In this research, we demonstrate the asymmetrical lateral Casimir force for the first time. The experimental results show very good agreement with a recently developed exact theory based on the scattering approach with no tting parameters. The measured force also show the expected deviation from the commonly used proximity force approximation. The results provide a further understanding of the shape dependence of the Casimir force and will enhance the capabilities for its application in nano technology, especially for the frictionless transmission of lateral motion.

  5. 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)

  6. Phylogenetic Analysis Supports Horizontal Transmission as a Driving Force of the Spread of Avian Bornaviruses

    PubMed Central

    Rubbenstroth, Dennis; Schmidt, Volker; Rinder, Monika; Legler, Marko; Twietmeyer, Sönke; Schwemmer, Phillip; Corman, Victor M.

    2016-01-01

    Background Avian bornaviruses are a genetically diverse group of viruses initially discovered in 2008. They are known to infect several avian orders. Bornaviruses of parrots and related species (Psittaciformes) are causative agents of proventricular dilatation disease, a chronic and often fatal neurologic disease widely distributed in captive psittacine populations. Although knowledge has considerably increased in the past years, many aspects of the biology of avian bornaviruses are still undiscovered. In particular, the precise way of transmission remains unknown. Aims and Methods In order to collect further information on the epidemiology of bornavirus infections in birds we collected samples from captive and free-ranging aquatic birds (n = 738) and Passeriformes (n = 145) in Germany and tested them for the presence of bornaviruses by PCR assays covering a broad range of known bornaviruses. We detected aquatic bird bornavirus 1 (ABBV-1) in three out of 73 sampled free-ranging mute swans (Cygnus olor) and one out of 282 free-ranging Eurasian oystercatchers (Haematopus ostralegus). Canary bornavirus 1 (CnBV-1), CnBV-2 and CnBV-3 were detected in four, six and one out of 48 captive common canaries (Serinus canaria forma domestica), respectively. In addition, samples originating from 49 bornavirus-positive captive Psittaciformes were used for determination of parrot bornavirus 2 (PaBV-2) and PaBV-4 sequences. Bornavirus sequences compiled during this study were used for phylogenetic analysis together with all related sequences available in GenBank. Results of the Study Within ABBV-1, PaBV-2 and PaBV-4, identical or genetically closely related bornavirus sequences were found in parallel in various different avian species, suggesting that inter-species transmission is frequent relative to the overall transmission of these viruses. Our results argue for an important role of horizontal transmission, but do not exclude the additional possibility of vertical transmission

  7. CD Nomenclature 2015: Human Leukocyte Differentiation Antigen Workshops as a Driving Force in Immunology.

    PubMed

    Engel, Pablo; Boumsell, Laurence; Balderas, Robert; Bensussan, Armand; Gattei, Valter; Horejsi, Vaclav; Jin, Bo-Quan; Malavasi, Fabio; Mortari, Frank; Schwartz-Albiez, Reinhard; Stockinger, Hannes; van Zelm, Menno C; Zola, Heddy; Clark, Georgina

    2015-11-15

    CD (cluster of differentiation) Ags are cell surface molecules expressed on leukocytes and other cells relevant for the immune system. CD nomenclature has been universally adopted by the scientific community and is officially approved by the International Union of Immunological Societies and sanctioned by the World Health Organization. It provides a unified designation system for mAbs, as well as for the cell surface molecules that they recognize. This nomenclature was established by the Human Leukocyte Differentiation Antigens Workshops. In addition to defining the CD nomenclature, these workshops have been instrumental in identifying and determining the expression and function of cell surface molecules. Over the past 30 y, the data generated by the 10 Human Leukocyte Differentiation Antigens Workshops have led to the characterization and formal designation of more than 400 molecules. CD molecules are commonly used as cell markers, allowing the identification and isolation of leukocyte populations, subsets, and differentiation stages. mAbs against these molecules have proven to be essential for biomedical research and diagnosis, as well as in biotechnology. More recently, they have been recognized as invaluable tools for the treatment of several malignancies and autoimmune diseases. In this article, we describe how the CD nomenclature was established, present the official updated list of CD molecules, and provide a rationale for their usefulness in the 21st century. PMID:26546687

  8. Host-specific driving force in human immunodeficiency virus type 1 evolution in vivo.

    PubMed Central

    Zhang, L; Diaz, R S; Ho, D D; Mosley, J W; Busch, M P; Mayer, A

    1997-01-01

    To investigate the process of human immunodeficiency virus type 1 (HIV-1) evolution in vivo, a total of 179 HIV-1 V3 sequences derived from cell-free plasma were determined from serial samples in three epidemiologically linked individuals (one infected blood donor and two transfusion recipients) over a maximum period of 8 years. A systematic analysis of pairwise comparisons of intrapatient sequences, both within and between each sample time point, revealed a preponderance and accumulation of nonsynonymous rather than synonymous substitutions in the V3 loop and flanking regions as they diverged over time. This strongly argues for the dominant role that positive selection for amino acid change plays in governing the pattern and process of HIV-1 env V3 evolution in vivo and nullifies hypotheses of purely neutral or mutation-driven evolution or completely chance events. In addition, different rates of evolution of HIV-1 were observed in these three different individuals infected with the same viral strain, suggesting that the degree of positive pressure for HIV-1 amino acid change is host dependent. Finally, the observed similar rate of accumulation in divergence within and between infected individuals suggests that the process of genetic divergence in the HIV epidemic proceeds regardless of host-to-host transmission events, i.e., that transmission does not reset the evolutionary clock. PMID:9032400

  9. Transdifferentiation is a driving force of regeneration in Halisarca dujardini (Demospongiae, Porifera).

    PubMed

    Borisenko, Ilya E; Adamska, Maja; Tokina, Daria B; Ereskovsky, Alexander V

    2015-01-01

    The ability to regenerate is widespread in the animal kingdom, but the regenerative capacities and mechanisms vary widely. To understand the evolutionary history of the diverse regeneration mechanisms, the regeneration processes must be studied in early-evolved metazoans in addition to the traditional bilaterian and cnidarian models. For this purpose, we have combined several microscopy techniques to study mechanisms of regeneration in the demosponge Halisarca dujardini. The objectives of this work are to detect the cells and morphogenetic processes involved in Halisarca regeneration. We show that in Halisarca there are three main sources of the new exopinacoderm during regeneration: choanocytes, archaeocytes and (rarely) endopinacocytes. Here we show that epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) occur during Halisarca regeneration. EMT is the principal mechanism during the first stages of regeneration, soon after the injury. Epithelial cells from damaged and adjacent intact choanocyte chambers and aquiferous canals assume mesenchymal phenotype and migrate into the mesohyl. Together with archaeocytes, these cells form an undifferentiated cell mass beneath of wound, which we refer to as a blastema. After the blastema is formed, MET becomes the principal mechanism of regeneration. Altogether, we demonstrate that regeneration in demosponges involves a variety of processes utilized during regeneration in other animals (e.g., cell migration, dedifferentiation, blastema formation) and points to the particular importance of transdifferentiation in this process. Further studies will be needed to uncover the molecular mechanisms governing regeneration in sponges. PMID:26336645

  10. Transdifferentiation is a driving force of regeneration in Halisarca dujardini (Demospongiae, Porifera)

    PubMed Central

    Borisenko, Ilya E.; Adamska, Maja; Tokina, Daria B.

    2015-01-01

    The ability to regenerate is widespread in the animal kingdom, but the regenerative capacities and mechanisms vary widely. To understand the evolutionary history of the diverse regeneration mechanisms, the regeneration processes must be studied in early-evolved metazoans in addition to the traditional bilaterian and cnidarian models. For this purpose, we have combined several microscopy techniques to study mechanisms of regeneration in the demosponge Halisarca dujardini. The objectives of this work are to detect the cells and morphogenetic processes involved in Halisarca regeneration. We show that in Halisarca there are three main sources of the new exopinacoderm during regeneration: choanocytes, archaeocytes and (rarely) endopinacocytes. Here we show that epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) occur during Halisarca regeneration. EMT is the principal mechanism during the first stages of regeneration, soon after the injury. Epithelial cells from damaged and adjacent intact choanocyte chambers and aquiferous canals assume mesenchymal phenotype and migrate into the mesohyl. Together with archaeocytes, these cells form an undifferentiated cell mass beneath of wound, which we refer to as a blastema. After the blastema is formed, MET becomes the principal mechanism of regeneration. Altogether, we demonstrate that regeneration in demosponges involves a variety of processes utilized during regeneration in other animals (e.g., cell migration, dedifferentiation, blastema formation) and points to the particular importance of transdifferentiation in this process. Further studies will be needed to uncover the molecular mechanisms governing regeneration in sponges. PMID:26336645

  11. Linking land cover dynamics with driving forces in mountain landscape of the Northwestern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Regos, Adrián; Ninyerola, Miquel; Moré, Gerard; Pons, Xavier

    2015-06-01

    The mountainous areas of the northwestern Iberian Peninsula have undergone intense land abandonment. In this work, we wanted to determine if the abandonment of the rural areas was the main driver of landscape dynamics in Gerês-Xurés Transboundary Biosphere Reserve (NW Iberian Peninsula), or if other factors, such as wildfires and the land management were also directly affecting these spatio-temporal dynamics. For this purpose, we used earth observation data acquired from Landsat TM and ETM + satellite sensors, complemented by ancillary data and prior field knowledge, to evaluate the land use/land cover changes in our study region over a 10-year period (2000-2010). The images were radiometrically calibrated using a digital elevation model to avoid cast- and self-shadows and different illumination effects caused by the intense topographic variations in the study area. We applied a maximum likelihood classifier, as well as other five approaches that provided insights into the comparison of thematic maps. To describe the land cover changes we addressed the analysis from a multilevel approach in three areas with different regimes of environmental protection. The possible impact of wildfires was assessed from statistical and spatially explicit fire data. Our findings suggest that land abandonment and forestry activities are the main factors causing the changes in landscape patterns. Specifically, we found a strong decrease of the 'meadows and crops' and 'sparse vegetation areas' in favor of woodlands and scrublands. In addition, the huge impact of wildfires on the Portuguese side have generated new 'rocky areas', while on the Spanish side its impact does not seem to have been a decisive factor on the landscape dynamics in recent years. We conclude rural exodus of the last century, differences in land management and fire suppression policies between the two countries and the different protection schemes could partly explain the different patterns of changes recorded in

  12. Land use/cover changes in European mountain areas: identifying links between global driving forces and local consequences

    NASA Astrophysics Data System (ADS)

    Malek, Žiga; Schröter, Dagmar; Glade, Thomas

    2013-04-01

    Minor land use/cover changes in mountain areas can aggravate the consequences of hydro-meteorological hazards such as landslides, avalanches, rockfall and flash floods. What is more, they change the provisioning of ecosystem services; also as their recovery after anthropogenic induced changes in mountains are slower or not occurring at all due to harsh climate and soil conditions. Examples of these changes are urbanization in high risk areas or deforestation on slopes. To understand the driving forces behind land use/cover changes in European mountain areas, the focus is on the two case study areas: The Val Canale valley in the Italian Alps and the Buzau valley in the Romanian Carpathians. Land use/cover changes were analyzed in the recent decades applying various remote sensing techniques, such as satellite imagery classification and visual interpretation, as well as integration of various databases (e.g. forestry, spatial planning and cadaster plans). Instead of identifying the statistical significance of particular variables (e.g. population change), the links between different driving forces of global change (e.g. political and policy changes, infrastructural plans) and local socio-economic variables were investigated further through interviewing local and regional stakeholders. The results show how both areas differ in the consequences of global changes in terms of land use/cover change. The Italian area witnessed a trajectory from a commercially active and competitive area, to an area with a large portion of abandoned commercial, customs, industrial and mining zones. These processes were accompanied by the expansion of settlements comprised mostly of secondary housing on areas with high risk, resulting in catastrophic consequences in recent flash floods and debris flows events. The Romanian site also witnessed a breakdown of local commercial and industrial activities. Together with land ownership reforms, this has resulted in the emergence of subsistence

  13. Mantle viscosity - A comparison of models from postglacial rebound and from the geoid, plate driving forces, and advected heat flux

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1991-01-01

    Models of the radial variation of effective viscosity inferred from the earth's response to surface loads associated with Pleistocene deglaciation are compared to structures inferred from models of geodynamic phenomena associated with convection: the geoid, plate-driving forces, and advected heat flux. While observations of the earth's response to surface loads do not have sufficient resolution to justify more than two viscous layers, adequately matching the observed long-wavelength geoid anomalies associated with density contrasts in the lower mantle (inferred from seismic tomography) and in the upper mantle (inferred from a model of subducted slabs) requires more structure. It is possible to explain the geoid, observed plate velocities, the advected heat flux in the lower mantle, and relative sea-level variations in oceanic regions, all with a mantle with a high-viscosity/elastic lid, an asthenospheric channel of 2 x 10 exp 19 Pa s from 100 to 400-km depth, a 6 x 10 exp 20 Pa s transition zone, and a lower mantle of 6 x 10 exp 21 Pa s. The uplift history of Australia, Fennoscandia, and Laurentia can be explained with an asthenospheric viscosity less than a factor of 10 higher. Lateral variations in lower mantle viscosity are not required. Transient creep appears to be unimportant for the recent response-to-surface loads from Pleistocene deglaciation.

  14. Solvent driving force ensures fast formation of a persistent and well-separated radical pair in plant cryptochrome.

    PubMed

    Lüdemann, Gesa; Solov'yov, Ilia A; Kubař, Tomáš; Elstner, Marcus

    2015-01-28

    The photoreceptor protein cryptochrome is thought to host, upon light absorption, a radical pair that is sensitive to very weak magnetic fields, endowing migratory birds with a magnetic compass sense. The molecular mechanism that leads to formation of a stabilized, magnetic field sensitive radical pair has despite various theoretical and experimental efforts not been unambiguously identified yet. We challenge this unambiguity through a unique quantum mechanical molecular dynamics approach where we perform electron transfer dynamics simulations taking into account the motion of the protein upon the electron transfer. This approach allows us to follow the time evolution of the electron transfer in an unbiased fashion and to reveal the molecular driving force that ensures fast electron transfer in cryptochrome guaranteeing formation of a persistent radical pair suitable for magnetoreception. We argue that this unraveled molecular mechanism is a general principle inherent to all proteins of the cryptochrome/photolyase family and that cryptochromes are, therefore, tailored to potentially function as efficient chemical magnetoreceptors. PMID:25535848

  15. Fixed negative charge and the Donnan effect: a description of the driving forces associated with brain tissue swelling and oedema.

    PubMed

    Elkin, Benjamin S; Shaik, Mohammed A; Morrison, Barclay

    2010-02-13

    Cerebral oedema or brain tissue swelling is a significant complication following traumatic brain injury or stroke that can increase the intracranial pressure (ICP) and impair blood flow. Here, we have identified a potential driver of oedema: the negatively charged molecules fixed within cells. This fixed charge density (FCD), once exposed, could increase ICP through the Donnan effect. We have shown that metabolic processes and membrane integrity are required for concealing this FCD as slices of rat cortex swelled immediately (within 30 min) following dissection if treated with 2 deoxyglucose + cyanide (2DG+CN) or Triton X-100. Slices given ample oxygen and glucose, however, did not swell significantly. We also found that dead brain tissue swells and shrinks in response to changes in ionic strength of the bathing medium, which suggests that the Donnan effect is capable of pressurizing and swelling brain tissue. As predicted, a non-ionic osmolyte, 1,2 propanediol, elicited no volume change at 2000 x 10(-3) osmoles l(-1) (Osm). Swelling data were well described by triphasic mixture theory with the calculated reference state FCD similar to that measured with a 1,9 dimethylmethylene blue assay. Taken together, these data suggest that intracellular fixed charges may contribute to the driving forces responsible for brain swelling. PMID:20047940

  16. Invasion of Nostocales (cyanobacteria) to Subtropical and Temperate Freshwater Lakes – Physiological, Regional, and Global Driving Forces

    PubMed Central

    Sukenik, Assaf; Hadas, Ora; Kaplan, Aaron; Quesada, Antonio

    2012-01-01

    Similar to the increased number of studies on invasive plants and animals in terrestrial and aquatic ecosystems, many reports were recently published on the invasion of Nostocales (cyanobacteria) to freshwater environments worldwide. Invasion and proliferation of Nostocales in new habitats have the potential to significantly alter the structure of the native community and to modify ecosystem functioning. But most importantly, they influence the water quality due to a variety of toxic compounds that some species produce. Therefore a special attention was given to the invasion and persistence of toxic cyanobacteria in many aquatic ecosystems. Here we summarize the currently published records on the invasion of two Nostocales genera, Cylindrospermopsis and Aphanizomenon, to lakes and water reservoirs in subtropical and temperate zones. These invading species possess traits thought to be common to many invasive organisms: high growth rate, high resource utilization efficiency and overall superior competitive abilities over native species when local conditions vary. Assuming that dispersion routes of cyanobacteria have not been changed much in recent decades, their recent establishment and proliferation in new habitats indicate changes in the environment under which they can exploit their physiological advantage over the native phytoplankton population. In many cases, global warming was identified as the major driving force for the invasion of Nostocales. Due to this uncontrollable trend, invasive Nostocales species are expected to maintain their presence in new habitats and further expand to new environments. In other cases, regional changes in nutrient loads and in biotic conditions were attributed to the invasion events. PMID:22408640

  17. Addition of Electrostatic Forces to EDEM with Applications to Triboelectrically Charged Particles

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Calle, Carlos; Curry, David

    2008-01-01

    Tribocharging of particles is common in many processes including fine powder handling and mixing, printer toner transport and dust extraction. In a lunar environment with its high vacuum and lack of water, electrostatic forces are an important factor to consider when designing and operating equipment. Dust mitigation and management is critical to safe and predictable performance of people and equipment. The extreme nature of lunar conditions makes it difficult and costly to carryout experiments on earth which are necessary to better understand how particles gather and transfer charge between each other and with equipment surfaces. DEM (Discrete Element Modeling) provides an excellent virtual laboratory for studying tribocharging of particles as well as for design of devices for dust mitigation and for other purposes related to handling and processing of lunar regolith. Theoretical and experimental work has been performed pursuant to incorporating screened Coulombic electrostatic forces into EDEM Tm, a commercial DEM software package. The DEM software is used to model the trajectories of large numbers of particles for industrial particulate handling and processing applications and can be coupled with other solvers and numerical models to calculate particle interaction with surrounding media and force fields. In this paper we will present overview of the theoretical calculations and experimental data and their comparison to the results of the DEM simulations. We will also discuss current plans to revise the DEM software with advanced electrodynamic and mechanical algorithms.

  18. Driving forces of individual BVOC emissions from a spruce tree in Central Germany; results from a dynamic enclosure study.

    NASA Astrophysics Data System (ADS)

    Bourtsoukidis, S.; Dittmann, A.; Jacobi, S.; Bonn, B.

    2012-04-01

    We have conducted seasonal ambient and emission measurements of a series of biogenic VOCs such as monoterpenes (MT), sesquiterpenes (SQT), isoprene, methanol, methyl chavicol and acetaldehyde. Therefore a plant enclosure technique was applied in order to investigate a Central European spruce forest and its emissions responses to meteorological and environmental parameters. A healthy ≈15m tall Norway spruce tree was selected and a vegetation enclosure technique was applied from April to November 2011. VOCs are measured by PTR-MS, while samples have also been analyzed with GC-MS (Gas Chromatography - Mass Spectrometry) techniques for intercomparison and identification of individual VOCs. E/N ratio was adjusted at 117Td[2] and the primary ion signal (H3O+) was continuously above 4×10^7cps, implying a high sensitivity to our measurements. Temperature, relative humidity, ozone, photosynthetic active radiation (PAR) and CO2 concentrations were continuously measured inside the plant cuvette. Meteorological and environmental parameters (radiation, atmospheric pressure, wind velocity, wind direction, temperature, O3, relative humidity, soil moisture, precipitation, global radiation, H2O, NO, NO2) were measured by HLUG (Hessian Agency for Environment and Geology) and DWD (German Weather Service), 50 meters away from the measuring site. In a peculiar season, which was characterized by a warm spring (temperature anomaly >40C), a wet summer (precipitation anomaly 126-150%) and an extremely dry autumn (precipitation anomaly <50%), VOC emissions were analyzed and studied in order to discern different driving forces for the individual compounds. The suggested[3] empirical beta factor for MT found to be in a reasonable range but the temperature dependency was almost double for daytime compared to nighttime measurements, suggesting that light is also influencing MT emissions. On the contrary, SQT emissions showed similar temperature dependency for both day and night measurements

  19. Volcanism of the Central Atlantic Magmatic Province as a potential driving force in the end-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Pálfy, József

    Radiometric dating suggests that eruptions in the Central Atlantic magmatic province (CAMP) are synchronous with the ˜200 Ma end-Triassic mass extinction. Although stratigraphic evidence for major flows prior to the extinction horizon is still lacking, the vast extent of the province allows the assumption of cause-and-effect relationship between volcanism and extinction, mediated by drastic environmental change. A recently recognized negative carbon isotope anomaly at the Triassic-Jurassic boundary is interpreted to reflect combined effects of volcanically derived CO2 input, methane release through dissociation of gas hydrates in a global warming episode, and a possible marine productivity crisis. Maximum duration of the Rhaetian stage is estimated as only 2 m.y., and the isotope event appears short, lasting for less than 100 k.y. A variety of marine and terrestrial fossil groups (e.g., radiolarians, corals, bivalves, and plants) experienced correlated and sudden extinction at the end of Triassic, although some groups (e.g., ammonoids and conodonts) underwent a prolonged period of declining diversity. Post-extinction faunas and floras are cosmopolitan. Biotic recovery was delayed and the earliest Hettangian is a lag phase characterized by low diversity, possibly due to sustained environmental stress. The hypothesis of CAMP as the principal driving force in the end-Triassic extinction appears more consistent with paleontological and isotopic observations than alternative models. The temporally adjacent large igneous provinces, the Siberian Traps at the Permian-Triassic boundary and the Early Jurassic Karoo-Ferrar province, are also linked to extinction events, albeit of differing magnitude.

  20. Long-term dynamics in land resource use and the driving forces in the Beressa watershed, highlands of Ethiopia.

    PubMed

    Amsalu, Aklilu; Stroosnijder, Leo; de Graaff, Jan

    2007-06-01

    Land degradation in the Ethiopian highlands is considered to be one of the major problems threatening agricultural development and food security in the country. However, knowledge about the forces driving the long-term dynamics in land resources use is limited. This research integrates biophysical information with socio-economic processes and policy changes to examine the dynamics of land resource use and farmers' livelihoods in the Beressa watershed for over 40 years during the second half of the 20th century. It was found that there have been substantial dynamics in land resource use in the area. The natural vegetation cover has been extensively cleared, although most of the cleared areas have since been replaced with plantations. Grazing land has expanded remarkably at the expense of cropland and bare land. However, the expansion of cropland was minimal over the 43-year period despite a quadrupling of the population density. Yields have not increased to compensate for the reduction in per capita cropland, and the soil quality appears to be not that good. Though the farmers perceived it otherwise, the long-term rainfall pattern has improved. In response to soil degradation, water shortage, socio-economic and policy changes, farmers have tended to gradually change from annual cropping to tree planting and livestock production to cope with the problems of soil degradation, water scarcity and smaller farms. Income diversification through the sale of wood and cattle dung is becoming a major livelihood strategy. Apparently, however, little attention has been paid to investments in soil and water conservation (SWC) and local soil fertility amendments. In particular, increased erosion and related high nutrient losses in sediments, as well as the removal of potentially available soil nutrients through the sale of manure threatens to damage agricultural sustainability in the area. PMID:16959397

  1. Mannose-Binding Lectin Inhibits the Motility of Pathogenic Salmonella by Affecting the Driving Forces of Motility and the Chemotactic Response

    PubMed Central

    Nakamura, Shuichi; Islam, Md. Shafiqul; Guo, Yijie; Ihara, Kohei; Tomioka, Rintaro; Masuda, Mizuki; Yoneyama, Hiroshi; Isogai, Emiko

    2016-01-01

    Mannose-binding lectin (MBL) is a key pattern recognition molecule in the lectin pathway of the complement system, an important component of innate immunity. MBL functions as an opsonin which enhances the sequential immune process such as phagocytosis. We here report an inhibitory effect of MBL on the motility of pathogenic bacteria, which occurs by affecting the energy source required for motility and the signaling pathway of chemotaxis. When Salmonella cells were treated with a physiological concentration of MBL, their motile fraction and free-swimming speed decreased. Rotation assays of a single flagellum showed that the flagellar rotation rate was significantly reduced by the addition of MBL. Measurements of the intracellular pH and membrane potential revealed that MBL affected a driving force for the Salmonella flagellum, the electrochemical potential difference of protons. We also found that MBL treatment increased the reversal frequency of Salmonella flagellar rotation, which interfered with the relative positive chemotaxis toward an attractive substrate. We thus propose that the motility inhibition effect of MBL may be secondarily involved in the attack against pathogens, potentially facilitating the primary role of MBL in the complement system. PMID:27104738

  2. An ANCCA/PRO2000-miR-520a-E2F2 regulatory loop as a driving force for the development of hepatocellular carcinoma.

    PubMed

    Huang, J; Yang, J; Lei, Y; Gao, H; Wei, T; Luo, L; Zhang, F; Chen, H; Zeng, Q; Guo, L

    2016-01-01

    Hepatocellular carcinoma (HCC) is one of the most common malignancies in Asia especially in China. We previously identified that ANCCA/PRO2000 as an important proliferation-associated protein predicted poor prognosis of patients with HCC. However, the molecular mechanisms of ANCCA/PRO2000 leading to hepatocarcinogenesis and progression are still obscure. In the present study, we found that ANCCA/PRO2000 overexpression in HCC specimens correlated with aggressive tumor behavior and poor survival. Furthermore, ANCCA/PRO2000 exerts strong oncogenic function in HCC and promotes cell proliferation by regulating E2F2 expression, a critical cell cycle regulator. Notably, miR-520a is an intermediate regulator between ANCCA/PRO2000 and E2F2. Mechanistically, ANCCA/PRO2000 not only interacts with E2F2 but also negatively regulates miR-520a that inhibits E2F2 to cooperatively promote in vitro and in vivo growth of HCC cells. Moreover, we demonstrated that ANCCA/PRO2000 enhances the migratory capacity of HCC cells partially by suppressing ERO1L and G3BP2 expression. Additional research identified that miR-372, as a prognostic factor for HCC, could directly target ANCCA/PRO2000. Our results suggest the ANCCA/PRO2000-miR-520a-E2F2 regulatory loop as a driving force for HCC development and ANCCA/PRO2000 as a potential therapeutic target for HCC. PMID:27239961

  3. The endothermic ATP hydrolysis and crossbridge attachment steps drive the increase of force with temperature in isometric and shortening muscle.

    PubMed

    Offer, Gerald; Ranatunga, K W

    2015-04-15

    The isometric tetanic tension of skeletal muscle increases with temperature because attached crossbridge states bearing a relatively low force convert to those bearing a higher force. It was previously proposed that the tension-generating step(s) in the crossbridge cycle was highly endothermic and was therefore itself directly targeted by changes in temperature. However, this did not explain why a rapid rise in temperature (a temperature jump) caused a much slower rate of rise of tension than a rapid length step. This led to suggestions that the step targeted by a temperature rise is not the tension-generating step but is an extra step in the attached pathway of the crossbridge cycle, perhaps located on a parallel pathway. This enigma has been a major obstacle to a full understanding of the operation of the crossbridge cycle. We have now used a previously developed mechano-kinetic model of the crossbridge cycle in frog muscle to simulate the temperature dependence of isometric tension and shortening velocity. We allowed all five steps in the cycle to be temperature-sensitive. Models with different starting combinations of enthalpy changes and activation enthalpies for the five steps were refined by downhill simplex runs and scored by their ability to fit experimental data on the temperature dependence of isometric tension and the relationship between force and shortening velocity in frog muscle. We conclude that the first tension-generating step may be weakly endothermic and that the rise of tension with temperature is largely driven by the preceding two strongly endothermic steps of ATP hydrolysis and attachment of M.ADP.Pi to actin. The refined model gave a reasonable fit to the available experimental data and after a temperature jump the overall rate of tension rise was much slower than after a length step as observed experimentally. The findings aid our understanding of the crossbridge cycle by showing that it may not be necessary to include an additional

  4. The endothermic ATP hydrolysis and crossbridge attachment steps drive the increase of force with temperature in isometric and shortening muscle

    PubMed Central

    Offer, Gerald; Ranatunga, K W

    2015-01-01

    The isometric tetanic tension of skeletal muscle increases with temperature because attached crossbridge states bearing a relatively low force convert to those bearing a higher force. It was previously proposed that the tension-generating step(s) in the crossbridge cycle was highly endothermic and was therefore itself directly targeted by changes in temperature. However, this did not explain why a rapid rise in temperature (a temperature jump) caused a much slower rate of rise of tension than a rapid length step. This led to suggestions that the step targeted by a temperature rise is not the tension-generating step but is an extra step in the attached pathway of the crossbridge cycle, perhaps located on a parallel pathway. This enigma has been a major obstacle to a full understanding of the operation of the crossbridge cycle. We have now used a previously developed mechano-kinetic model of the crossbridge cycle in frog muscle to simulate the temperature dependence of isometric tension and shortening velocity. We allowed all five steps in the cycle to be temperature-sensitive. Models with different starting combinations of enthalpy changes and activation enthalpies for the five steps were refined by downhill simplex runs and scored by their ability to fit experimental data on the temperature dependence of isometric tension and the relationship between force and shortening velocity in frog muscle. We conclude that the first tension-generating step may be weakly endothermic and that the rise of tension with temperature is largely driven by the preceding two strongly endothermic steps of ATP hydrolysis and attachment of M.ADP.Pi to actin. The refined model gave a reasonable fit to the available experimental data and after a temperature jump the overall rate of tension rise was much slower than after a length step as observed experimentally. The findings aid our understanding of the crossbridge cycle by showing that it may not be necessary to include an additional

  5. Probing into the Supramolecular Driving Force of an Amphiphilic β-Cyclodextrin Dimer in Various Solvents: Host-Guest Recognition or Hydrophilic-Hydrophobic Interaction?

    PubMed

    Bai, Yang; Fan, Xiao-dong; Yao, Hao; Yang, Zhen; Liu, Ting-ting; Zhang, Hai-tao; Zhang, Wan-bin; Tian, Wei

    2015-09-01

    Tuning of the morphology and size of supramolecular self-assemblies is of theoretical and practical significance. To date, supramolecular driving forces in different solvents remain unclear. In this study, we first synthesized an amphiphilic β-cyclodextrin (β-CD) dimer that consists of one hydrophobic ibuprofen (Ibu) and two hydrophilic β-CD moieties (i.e., Ibu-CD2). Ibu-CD2 possesses double supramolecular driving forces, namely, the host-guest recognition and hydrophilic-hydrophobic interaction. The host-guest interaction of Ibu-CD2 induced the formation of branched supramolecular polymers (SPs) in pure water, whereas the hydrophilic-hydrophobic interaction generated spherical or irregular micelles in water/organic mixtures. The SP size increased with the increase in Ibu-CD2 concentration in pure water. By contrast, the size of micelles decreased with the increase in volume ratio of water in mixtures. PMID:26301920

  6. DropBot: An open-source digital microfluidic control system with precise control of electrostatic driving force and instantaneous drop velocity measurement

    SciTech Connect

    Fobel, Ryan; Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, Ontario M5S 3E1 ; Fobel, Christian; Wheeler, Aaron R.; Donnelly Centre for Cellular and Biomolecular Research, 160 College St., Toronto, Ontario M5S 3E1; Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario M5S 3H6

    2013-05-13

    We introduce DropBot: an open-source instrument for digital microfluidics (http://microfluidics.utoronto.ca/dropbot). DropBot features two key functionalities for digital microfluidics: (1) real-time monitoring of instantaneous drop velocity (which we propose is a proxy for resistive forces), and (2) application of constant electrostatic driving forces through compensation for amplifier-loading and device capacitance. We anticipate that this system will enhance insight into failure modes and lead to new strategies for improved device reliability, and will be useful for the growing number of users who are adopting digital microfluidics for automated, miniaturized laboratory operation.

  7. DropBot: An open-source digital microfluidic control system with precise control of electrostatic driving force and instantaneous drop velocity measurement

    NASA Astrophysics Data System (ADS)

    Fobel, Ryan; Fobel, Christian; Wheeler, Aaron R.

    2013-05-01

    We introduce DropBot: an open-source instrument for digital microfluidics (http://microfluidics.utoronto.ca/dropbot). DropBot features two key functionalities for digital microfluidics: (1) real-time monitoring of instantaneous drop velocity (which we propose is a proxy for resistive forces), and (2) application of constant electrostatic driving forces through compensation for amplifier-loading and device capacitance. We anticipate that this system will enhance insight into failure modes and lead to new strategies for improved device reliability, and will be useful for the growing number of users who are adopting digital microfluidics for automated, miniaturized laboratory operation.

  8. Magnetic Force Microscopy Study of Zr2Co11 -Based Nanocrystalline Materials: Effect of Mo Addition

    DOE PAGESBeta

    Yue, Lanping; Jin, Yunlong; Zhang, Wenyong; Sellmyer, David J.

    2015-01-01

    Tmore » he addition of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr2Co11-based nanocrystalline permanent magnets. he effect of Mo addition on magnetic domain structures of melt spun nanocrystalline Zr16Co84-xMox(x=0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. he coercivity of the samples increases with the increase in Mo content (x≤1.5). he maximum energy product(BH)maxincreases with increasingxfrom 0.5 MGOe forx=0to a maximum value of 4.2 MGOe forx=1.5. he smallest domain size with a relatively short magnetic correlation length of 128 nm and largest root-mean-square phase shiftΦrmsvalue of 0.66° are observed for thex=1.5. he optimal Mo addition promotes magnetic domain structure refinement and thus leads to a significant increase in coercivity and energy product in this sample.« less

  9. Deciphering the driving forces of short-term erosion in glacially impacted landscapes, an example from the Western Alps

    NASA Astrophysics Data System (ADS)

    Glotzbach, Christoph; van der Beek, Peter; Carcaillet, Julien; Delunel, Romain

    2013-04-01

    Tectonic uplift is the main driver of long-term erosion, but climate changes can markedly affect the link between tectonics and erosion, causing transient variations in short-term erosion rate. Here we study the driving forces of short-term erosion rates in the French Western Alps as estimated from in-situ produced cosmogenic 10Be and detrital apatite fission-track thermochronology analysis of stream sediments. Short-term erosion rates from 10Be analyses vary between ~0.27 and ~1.33 mm/yr, similar to rates measured in adjacent areas of the Alps. Part of the data scales positively with elevation, while the full dataset shows a significant positive correlation with steepness index of streams and normalized geophysical relief. Mean long-term exhumation and short-term erosion rates are comparable in areas that are exhuming rapidly (>0.4 km/Myr), but short-term rates are on average two-three (and up to six) times higher than long-term rates in areas where the latter are slow (<0.4 km/Myr). These findings are supported by detrital apatite fission-track age distributions that appear to require similar variations in erosion rates. Major glaciations strongly impacted the external part of the Alps, increasing both long-term exhumation rates as well as relief (e.g. Glotzbach et al. 2011; Häuselmann et al. 2007; Valla et al.). Based on our data, it seems that glacial impact in the more slowly eroding internal part is mainly restricted to relief, which is reflected in high transient short-term erosion rates. The data further reveal that normalized steepness index and ridgeline geophysical relief are well correlated with (and could be used as proxies for) short-term erosion, in contrast to slope, corroborating studies in purely fluvial landscapes. Our study demonstrates that climate change, e.g. through occurrence of major glaciations, can markedly perturb landscapes short-term erosion patterns in regions of tectonically controlled long-term exhumation. Glotzbach C., P.A. van

  10. [Spatio-temporal change of sand-fixing function and its driving forces in desertification control ecological function area of Hunshandake, China].

    PubMed

    Shen, Lu; Tian, Mei-rong; Gao, Ji-xi; Qian, Jin-ping

    2016-01-01

    Soil erosion is an important ecological and environmental problem in Hunshandake Desert, and the sand-fixing function determines the degree of ecological security in the entire region. In order to clarify the situation of windbreak and sand fixation in Hunshandake area, and to guide the prevention and treatment of desertification on regional scale, based on the meteorological and remote sensing data, this paper quantitatively analyzed the temporal and spatial pattern of windbreak and sand fixation ability between 2000-2010 by the revised wind erosion equation (RWEQ) model, meanwhile, the driving forces for each county ( or banner) in the functional zone were analyzed with the method of principal component analysis. The results showed that there was a fluctuation of the sand fixing capacity in Hunshandake over time, generally rendering a decline trend. The coniferous forest and grassland had strong windbreak and sand fixation capacity in unit area among the various land categories. In terms of spatial distribution, the windbreak and sand fixation function in western and southeastern region was weak and needed to be strengthened with ecological restoration efforts. Through the study of the social driving forces of each administrative region in the function zone, there were 3 main social driving forces of soil erosion in the administrative functions: the intensity of input-output, the level of economic development and the level of agriculture-husbandry development. PMID:27228595

  11. Coriolis Force Mass-Flow Meter Composed of a Straight Pipe and an Additional Resonance-Vibrator

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hirohide; Tomikawa, Yoshiro

    1993-05-01

    This paper deals with a new construction for a mass-flow meter using Coriolis force, and its basic experimental results. Some Coriolis force mass-flow meters, proposed up to now, are of a twin construction of, for example, a U-type pipe or a straight-type pipe, where the mass-flow is determined by measuring the relative displacement between the pipes. Therefore, their structure is too complex. To improve this situation, the authors propose a new mass-flow meter using one straight pipe, together with an additional flexural resonance-vibrator. The experimental results prove that a mass-flow meter can be realized by such a simple construction as dealt with here.

  12. Polarization-dependent force driving the Eg mode in bismuth under optical excitation: comparison of first-principles theory with ultra-fast x-ray experiments

    NASA Astrophysics Data System (ADS)

    Fahy, Stephen; Murray, Eamonn

    2015-03-01

    Using first principles electronic structure methods, we calculate the induced force on the Eg (zone centre transverse optical) phonon mode in bismuth immediately after absorption of a ultrafast pulse of polarized light. To compare the results with recent ultra-fast, time-resolved x-ray diffraction experiments, we include the decay of the force due to carrier scattering, as measured in optical Raman scattering experiments, and simulate the optical absorption process, depth-dependent atomic driving forces, and x-ray diffraction in the experimental geometry. We find excellent agreement between the theoretical predictions and the observed oscillations of the x-ray diffraction signal, indicating that first-principles theory of optical absorption is well suited to the calculation of initial atomic driving forces in photo-excited materials following ultrafast excitation. This work is supported by Science Foundation Ireland (Grant No. 12/IA/1601) and EU Commission under the Marie Curie Incoming International Fellowships (Grant No. PIIF-GA-2012-329695).

  13. The Scrunchworm Hypothesis: Transitions Between A-DNA and B-DNA Provide the Driving Force for Genome Packaging in Double-Stranded DNA Bacteriophages

    PubMed Central

    Harvey, Stephen C.

    2015-01-01

    Double-stranded DNA bacteriophages have motors that drive the genome into preformed capsids, using the energy releas ed by hydrolysis of ATP to overcome the forces opposing DNA packaging. Viral packaging motors are the strongest of all biological motors, but it is not known how they generate these forces. Several models for the process of mechanochemical force generation have been put forward, but there is no consensus on which, if any, of these is correct. All the existing models assume that protein-generated forces drive the DNA forward. The scrunchworm hypothesis proposes that the DNA molecule is the active force-generating core of the motor, not simply a substrate on which the motor operates. The protein components of the motor dehydrate a section of the DNA, converting it from the B form to the A form and shortening it by about 23%. The proteins then rehydrate the DNA, which converts back to the B form. Other regions of the motor grip and release the DNA to capture the shortening-lengthening motions of the B→A→B cycle (“scrunching”), so that DNA is pulled into the motor and pushed forward into the capsid. This DNA-centric mechanism provides a quantitative physical explanation for the magnitude of the forces generated by viral packaging motors. It also provides a simple explanation for the fact that each of the steps in the burst cycle advances the DNA by 2.5 base pairs. The scrunchworm hypothesis is consistent with a large body of published data, and it makes four experimentally testable predictions. PMID:25486612

  14. Persistent disparities in stratospheric water vapor measurements drive large uncertainties in the radiative forcing by lower stratospheric water vapor

    NASA Astrophysics Data System (ADS)

    Hurst, D. F.; Rosenlof, K. H.; Portmann, R. W.; Voemel, H.; Schiller, C.; Smith, J. B.; Thornberry, T. D.; Rollins, A. W.; Hall, E.; Jordan, A.; Oltmans, S. J.

    2011-12-01

    Lower stratospheric water vapor is a powerful attenuator of outgoing long wave radiation, hence its strong influence on the Earth's radiation budget. The radiative forcing by lower stratospheric water vapor is, however, quite uncertain because of significant disparities in lower stratospheric water vapor measurements by different instruments. Specifically, measurement discrepancies of 0.5 to 2 ppmv H2O (15 to 60%) between several well-established aircraft- and balloon-borne instruments have now persisted for almost two decades. The Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) in April 2011 provided not only a fresh opportunity to reexamine and reevaluate these persistent measurement discrepancies, but also to compare water vapor measurements by additional aircraft-based instrumentation. Here we compare the in situ measurements of lower stratospheric water vapor by five different instruments during MACPEX. Three of these instruments (Harvard water, FISH, and NOAA CIMS) were aboard the NASA WB-57 aircraft, while two (CFH and NOAA FPH) were launched on balloons. Substantial efforts were made to coordinate aircraft and balloon measurements in space and time, such that the aircraft would reach maximum altitude en route to the balloon rendezvous point, then both aircraft and balloon would descend together. Lower stratospheric water vapor measurements during MACPEX generally fall into two groups: CFH, NOAA FPH and FISH are in good agreement, while Harvard water and NOAA CIMS agree with each other but are significantly different than the other group. Differences between the two groups range from 0.5 to 1.0 ppmv (15 to 30%), with Harvard and NOAA CIMS mixing ratios consistently higher. Though these differences seem relatively large, they are smaller than some previously observed differences between the FPH/CFH and Harvard water. For example, Harvard stratospheric water vapor measurements during the 1993 CEPEX and 2006 CR-AVE campaigns were 1.5 and 2 ppmv

  15. The Driving Forces of the Large-Scale Deformation in the India-Eurasia Collision Region: Joint Modeling of Lithosphere and Mantle Dynamics

    NASA Astrophysics Data System (ADS)

    Wang, X.; Holt, W. E.; Ghosh, A.

    2014-12-01

    The origin of the large-scale deformation of the India-Eurasia collision zone has been pursued for more than 4 decades. However, the driving forces for the largest area of continental deformation zone on earth have not been entirely resolved; the source of such driving forces remains enigmatic. One reason could be that the driving forces have to be sufficiently large to overcome the resistance of the Tibetan Plateau, created by excess gravitational potential energy (GPE) over a long time span. Another reason is that seismic experiments carried out in the Tibetan Plateau, due to the harsh natural conditions, are fewer, making it challenging to resolve high-resolution seismic structure beneath Tibet. We address this issue of driving forces in this deformation zone by quantifying the primary contributions to the lithospheric stress field. We take into account effects of topography and shallow lithosphere structure, as well as tractions originating from deeper mantle convection, in order to calculate model estimates of the total lithosphere stresses. We evaluate recent published global seismic tomographic models (P-wave, S-wave, and geodynamic models) and select a tomographic model which, when used in the semi-analytical mantle circulation model HC (Hager and O'Connell, 1981; Milner et al., 2009), provides a best fit to observations of geoid, surface motions, strain rates, and stress orientations. We use the joint modeling of lithosphere and mantle dynamics approach of Ghosh and Holt (2012) to compute the full lithosphere stresses, except that we use HC for the circulation model, which can only handle radial viscosity variations. After using the selected seismic tomographic model of SAW642AN (Panning and Romanowicz, 2006) to compute the global lithosphere stresses, we refine the calculated stresses in the India-Eurasia collision zone. Our results show that both the driving stresses from mantle convection and GPE differences contribute to the deviatoric stress field in

  16. Lessons Learned at the Idaho National Laboratory for the Entry into Force of the U.S. Additional Protocol

    SciTech Connect

    Jeffrey C. Joe; Shauna A. Hoiland

    2009-07-01

    For a number of years, the Idaho National Laboratory (INL) has been preparing for the entry into force of the U.S. Additional Protocol (AP). These preparations included attending training, participating in tabletop exercises, preparing draft declarations, developing INL-specific guidance documents, preparing for and hosting a mock complementary access visit, and preparing declarations for official submittal. All of these activities, the training materials, and software developed by other U.S. DOE national laboratories (PNNL, ORNL, LANL, and BNL) were very helpful in preparing for the entry into force of the AP. As with any endeavor of this size and complexity, however, there are always instances where even the best preparations and advanced planning do not anticipate every challenge. As the DOE's lead nuclear energy research and development facility, the INL faced many unique challenges. The majority of research conducted at the INL is nuclear fuel cycle related, most of which is not protected by the National Security Exclusion. This paper describes the lessons learned from the INL’s experience of preparing for the entry into force of the AP, specifically how translating and implementing general principles into actual activities proved to be one of many challenges, and provides general suggestions on how to respond effectively and efficiently to routine annual data calls and other AP requests.

  17. Vibrational relaxation as the driving force for wavelength conversion in the peridinin-chlorophyll a-protein.

    PubMed

    Götze, Jan P; Karasulu, Bora; Patil, Mahendra; Thiel, Walter

    2015-12-01

    We present a computationally derived energy transfer model for the peridinin-chlorophyll a-protein (PCP), which invokes vibrational relaxation in the two lowest singlet excited states rather than internal conversion between them. The model allows an understanding of the photoinduced processes without assuming further electronic states or a dependence of the 2Ag state character on the vibrational sub-state. We report molecular dynamics simulations (CHARMM22 force field) and quantum mechanics/molecular mechanics (QM/MM) calculations on PCP. In the latter, the QM region containing a single peridinin (Per) chromophore or a Per-Chl a (chlorophyll a) pair is treated by density functional theory (DFT, CAM-B3LYP) for geometries and by DFT-based multireference configuration interaction (DFT/MRCI) for excitation energies. The calculations show that Per has a bright, green light absorbing 2Ag state, in addition to the blue light absorbing 1Bu state found in other carotenoids. Both states undergo a strong energy lowering upon relaxation, leading to emission in the red, while absorbing in the blue or green. The orientation of their transition dipole moments indicates that both states are capable of excited-state energy transfer to Chl a, without preference for either 1Bu or 2Ag as donor state. We propose that the commonly postulated partial intramolecular charge transfer (ICT) character of a donating Per state can be assigned to the relaxed 1Bu state, which takes on ICT character. By assuming that both 1Bu and 2Ag are able to donate to the Chl a Q band, one can explain why different chlorophyll species in PCP exhibit different acceptor capabilities. PMID:26231454

  18. Resonance scattering and radiation force calculations for an elastic cylinder using the translational addition theorem for cylindrical wave functions

    SciTech Connect

    Mitri, F. G.

    2015-09-15

    The standard Resonance Scattering Theory (RST) of plane waves is extended for the case of any two-dimensional (2D) arbitrarily-shaped monochromatic beam incident upon an elastic cylinder with arbitrary location using an exact methodology based on Graf’s translational addition theorem for the cylindrical wave functions. The analysis is exact as it does not require numerical integration procedures. The formulation is valid for any cylinder of finite size and material that is immersed in a nonviscous fluid. Partial-wave series expansions (PWSEs) for the incident, internal and scattered linear pressure fields are derived, and the analysis is further extended to obtain generalized expressions for the on-axis and off-axis acoustic radiation force components. The wave-fields are expressed using generalized PWSEs involving the beam-shape coefficients (BSCs) and the scattering coefficients of the cylinder. The off-axial BSCs are expressed analytically in terms of an infinite PWSE with emphasis on the translational offset distance d. Numerical computations are considered for a zeroth-order quasi-Gaussian beam chosen as an example to illustrate the analysis. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. In addition, computations for the radiation force exerted on an elastic cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed.

  19. Using geoinformatics and cultural anthropology to identify links between land change, driving forces and actors in the Okavango catchment

    NASA Astrophysics Data System (ADS)

    Röder, Achim; Stellmes, Marion; Pröpper, Michael; Schneibel, Anne

    2015-04-01

    intensive uses, although the same processes are likely to occur in parts of the Okavango region in the future. Literature: Banwart, S. (2011). "Save our soils." Nature 474: 151-152. Bürgi, M., A. M. Hersperger, et al. (2004). "Driving forces of landscape change - current and new directions." Landscape Ecology 19: 857-868. Butchart, S. H. M., M. Walpole, et al. (2010). "Global Biodiversity: Indicators of Recent Declines." Science 328(5982): 1164-1168. Ellis, E. C. and N. Ramankutty (2008). "Putting people in the map: anthropogenic biomes of the world." Frontiers in Ecology and the Environment 6(8): 439-447. Foley, J. A., R. Defries, et al. (2005). "Global consequences of land use." Science 309(5734): 570-574. Geist, H. J. and E. F. Lambin (2002). "Proximate causes and underlying driving forces of tropical deforestation." BioScience 52(2): 143-150. Haub, C. (2012) World Population Data Sheet. World Population Hein, L., K. van Koppen, et al. (2006). "Spatial scales, stakeholders and the valuation of ecosystem services." Ecological Economics 57: 209-228. Hersperger, A. M., M.-P. Gennaio, et al. (2010). "Linking land change with driving forces and actors: four conceptual models." Ecology and Society 15(4): 1-17. Huang, C., L. S. Davis, et al. (2002). "An assessment of support vector machines for land cover classification." International Journal of Remote Sensing 23(4): 725-749. IPCC (2013). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. T. F. Stocker, G. Qin, G.-K. Plattneret al. Cambridge, Cambridge University Press. Jönsson, P. and L. Eklundh (2004). "TIMESAT - a program for analysing time-series of satellite sensor data." Computers and Geosciences 30(833-845). Kowalski, B., N. Azebaze, et al. (2013). "Mashare - The People." Biodiversity & Ecology 5: 121-128. Lal, R. (2013). "Climate-strategic agriculture and the water-soil-waste nexus." Journal of Plant

  20. Solvating additives drive solution-mediated electrochemistry and enhance toroid growth in non-aqueous Li-O₂ batteries.

    PubMed

    Aetukuri, Nagaphani B; McCloskey, Bryan D; García, Jeannette M; Krupp, Leslie E; Viswanathan, Venkatasubramanian; Luntz, Alan C

    2015-01-01

    Given their high theoretical specific energy, lithium-oxygen batteries have received enormous attention as possible alternatives to current state-of-the-art rechargeable Li-ion batteries. However, the maximum discharge capacity in non-aqueous lithium-oxygen batteries is limited to a small fraction of its theoretical value due to the build-up of insulating lithium peroxide (Li₂O₂), the battery's primary discharge product. The discharge capacity can be increased if Li₂O₂ forms as large toroidal particles rather than as a thin conformal layer. Here, we show that trace amounts of electrolyte additives, such as H₂O, enhance the formation of Li₂O₂ toroids and result in significant improvements in capacity. Our experimental observations and a growth model show that the solvating properties of the additives prompt a solution-based mechanism that is responsible for the growth of Li₂O₂ toroids. We present a general formalism describing an additive's tendency to trigger the solution process, providing a rational design route for electrolytes that afford larger lithium-oxygen battery capacities. PMID:25515890

  1. Solvating additives drive solution-mediated electrochemistry and enhance toroid growth in non-aqueous Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Aetukuri, Nagaphani B.; McCloskey, Bryan D.; García, Jeannette M.; Krupp, Leslie E.; Viswanathan, Venkatasubramanian; Luntz, Alan C.

    2015-01-01

    Given their high theoretical specific energy, lithium-oxygen batteries have received enormous attention as possible alternatives to current state-of-the-art rechargeable Li-ion batteries. However, the maximum discharge capacity in non-aqueous lithium-oxygen batteries is limited to a small fraction of its theoretical value due to the build-up of insulating lithium peroxide (Li2O2), the battery’s primary discharge product. The discharge capacity can be increased if Li2O2 forms as large toroidal particles rather than as a thin conformal layer. Here, we show that trace amounts of electrolyte additives, such as H2O, enhance the formation of Li2O2 toroids and result in significant improvements in capacity. Our experimental observations and a growth model show that the solvating properties of the additives prompt a solution-based mechanism that is responsible for the growth of Li2O2 toroids. We present a general formalism describing an additive’s tendency to trigger the solution process, providing a rational design route for electrolytes that afford larger lithium-oxygen battery capacities.

  2. Repeated forced swim stress has additive effects in anxiety behavior and in cathecolamine levels of adult rats exposed to deltamethrin.

    PubMed

    Habr, Soraya F; Macrini, Daclé J; Florio, Jorge C; Bernardi, Maria M

    2014-01-01

    Deltamethrin (DTM) is a type II pyrethroid insecticide that elicits autonomic and neuroendocrine responses that indicate high levels of stress, presumably caused by the neurotoxic effect of the insecticide. This study investigated the effect of DTM exposure (10 mg/kg, p.o.) and an additional stress induced in the forced swim test (FST) in behavioral tasks related to anxiety, serum corticosterone levels, and striatal neurotransmitter levels. Open field behavior and social interaction were evaluated after DTM administration (10 mg kg(-1), p.o). DTM per se reduced rearing frequency in the open field, but no alterations in locomotion frequency or immobility duration were detected. Stress increased immobility duration compared with non-stressed animals. DTM reduced social interaction and increased corticosterone levels, and these effects were enhanced in stressed animals. Mainly stress affected dopaminergic and serotoninergic activity. In anxiety behavior and in both neurotransmitters and metabolites levels it was observed an additive effect of stress in DTM treated rat data. These results indicate that DTM enhanced the anxiogenic responses and stress had an additive effect over the DTM stress. The neurochemical data did not indicate an interaction between stress and DTM exposure. The present results maybe important for implementing pyrethroid insecticide safety standards. PMID:25444720

  3. Driving Forces of Dynamic Changes in Soil Erosion in the Dahei Mountain Ecological Restoration Area of Northern China Based on GIS and RS

    PubMed Central

    Li, Xiao; Niu, Xiang; Wang, Bing; Gao, Peng; Liu, Yu

    2016-01-01

    Dynamic change in soil erosion is an important focus of regional ecological restoration research. Here, the dynamic changes of soil erosion and its driving forces in the Dahei Mountain ecological restoration area of northern China were analyzed by LANDSAT TM remote sensing captured via geographic information system (GIS) technologies during three typical periods in 2004, 2008 and 2013. The results showed the following: (1) a decrease in intensive erosion and moderate erosion areas, as well as an increase in light erosion areas, was observed during two periods: one from 2004 to 2008 and the other from 2008 to 2013. (2) Between 2004 and 2008, the variation in the range of slight erosion was the largest (24.28%), followed by light erosion and intensive erosion; between 2008 and 2013, the variation in the range of intensive erosion area was the largest (9.89%), followed by slight erosion and moderate erosion. (3) Socioeconomic impact, accompanied by natural environmental factors, was the main driving force underlying the change in soil erosion within the ecological restoration area. In particular, the socioeconomic factors of per capita forest area and land reclamation rate, as well as the natural environmental factor of terrain slope, significantly influenced soil erosion changes within the ecological restoration area. PMID:26981637

  4. Multiple G-quartet structures in pre-edited mRNAs suggest evolutionary driving force for RNA editing in trypanosomes.

    PubMed

    Leeder, W-Matthias; Hummel, Niklas F C; Göringer, H Ulrich

    2016-01-01

    Mitochondrial transcript maturation in African trypanosomes requires a U-nucleotide specific RNA editing reaction. In its most extreme form hundreds of U's are inserted into and deleted from primary transcripts to generate functional mRNAs. Unfortunately, both origin and biological role of the process have remained enigmatic. Here we report a so far unrecognized structural feature of pre-edited mRNAs. We demonstrate that the cryptic pre-mRNAs contain numerous clustered G-nt, which fold into G-quadruplex (GQ) structures. We identified 27 GQ's in the different pre-mRNAs and demonstrate a positive correlation between the steady state abundance of guide (g)RNAs and the sequence position of GQ-elements. We postulate that the driving force for selecting G-rich sequences lies in the formation of DNA/RNA hybrid G-quadruplex (HQ) structures between the pre-edited transcripts and the non-template strands of mitochondrial DNA. HQ's are transcription termination/replication initiation sites and thus guarantee an unperturbed replication of the mt-genome. This is of special importance in the insect-stage of the parasite. In the transcription-on state, the identified GQ's require editing as a GQ-resolving activity indicating a link between replication, transcription and RNA editing. We propose that the different processes have coevolved and suggest the parasite life-cycle and the single mitochondrion as evolutionary driving forces. PMID:27436151

  5. Driving force for {gamma} {yields} {var{underscore}epsilon} martensitic transformation and stacking fault energy of {gamma} in Fe-Mn binary system

    SciTech Connect

    Lee, Y.K.; Choi, C.S.

    2000-02-01

    A regular solution model for the difference of the chemical free energy between {gamma} and {var{underscore}epsilon} phases during {gamma} {yields} {var{underscore}epsilon} martensitic transformation in the Fe-Mn binary system has been reexamined and partly modified based on many articles concerning the M{sub s} and A{sub s} temperatures of Fe-Mn alloys. Using the regular solution model, the measured M{sub s} temperatures, and a thermodynamic model for the stacking fault energy (SFE) of austenite ({gamma}), the driving force for {gamma} {yields} {epsilon} martensitic transformation, and the SFE of {gamma} have been calculated. The driving force for {gamma} {yields} {epsilon} martensitic transformation increases linearly from {minus}68 to {minus}120 J/mole with increasing Mn content from 16 to 24 wt pct. The SFE of {gamma} decreases to approximately 13 at. pct Mn and then increases with increasing Mn content, which is in better agreement with Schumann's result rather than Volosevich et al.'s result.

  6. Multiple Infections with Cardinium and Two Strains of Wolbachia in The Spider Mite Tetranychus phaselus Ehara: Revealing New Forces Driving the Spread of Wolbachia

    PubMed Central

    Zhao, Dong-Xiao; Chen, Da-Song; Ge, Cheng; Gotoh, Tetsuo; Hong, Xiao-Yue

    2013-01-01

    Cytoplasmic incompatibility (CI) has been proposed as a major mechanism by which certain strains of Wolbachia to invade and persist in host populations. However, mechanisms that underlie the invasion and persistence of non-CI strains are less well understood. Here, we established a spider mite Tetranychus phaselus population multiply infected by Cardinium as well as two distinct lineages of Wolbachia, designated wCon and wOri, to study the forces driving the spread of the non-CI strain of Wolbachia wOri. Interestingly, we found that wOri provided a longevity advantage to its female hosts under ideal conditions, making wOri stay longer in this population, and then being transmitted to more offspring. Furthermore, the lifespan of uninfected females was reduced when mated with multiple-infected males. As a result, the uninfected population is attenuated by the multiple-infected males. Thus, we infer that the host age effects of multiple infection may represent sufficient forces driving the spread of wOri through the host population. PMID:23355904

  7. Driving Forces of Dynamic Changes in Soil Erosion in the Dahei Mountain Ecological Restoration Area of Northern China Based on GIS and RS.

    PubMed

    Li, Xiao; Niu, Xiang; Wang, Bing; Gao, Peng; Liu, Yu

    2016-01-01

    Dynamic change in soil erosion is an important focus of regional ecological restoration research. Here, the dynamic changes of soil erosion and its driving forces in the Dahei Mountain ecological restoration area of northern China were analyzed by LANDSAT TM remote sensing captured via geographic information system (GIS) technologies during three typical periods in 2004, 2008 and 2013. The results showed the following: (1) a decrease in intensive erosion and moderate erosion areas, as well as an increase in light erosion areas, was observed during two periods: one from 2004 to 2008 and the other from 2008 to 2013. (2) Between 2004 and 2008, the variation in the range of slight erosion was the largest (24.28%), followed by light erosion and intensive erosion; between 2008 and 2013, the variation in the range of intensive erosion area was the largest (9.89%), followed by slight erosion and moderate erosion. (3) Socioeconomic impact, accompanied by natural environmental factors, was the main driving force underlying the change in soil erosion within the ecological restoration area. In particular, the socioeconomic factors of per capita forest area and land reclamation rate, as well as the natural environmental factor of terrain slope, significantly influenced soil erosion changes within the ecological restoration area. PMID:26981637

  8. Multiple G-quartet structures in pre-edited mRNAs suggest evolutionary driving force for RNA editing in trypanosomes

    PubMed Central

    Leeder, W.-Matthias; Hummel, Niklas F. C.; Göringer, H. Ulrich

    2016-01-01

    Mitochondrial transcript maturation in African trypanosomes requires a U-nucleotide specific RNA editing reaction. In its most extreme form hundreds of U’s are inserted into and deleted from primary transcripts to generate functional mRNAs. Unfortunately, both origin and biological role of the process have remained enigmatic. Here we report a so far unrecognized structural feature of pre-edited mRNAs. We demonstrate that the cryptic pre-mRNAs contain numerous clustered G-nt, which fold into G-quadruplex (GQ) structures. We identified 27 GQ’s in the different pre-mRNAs and demonstrate a positive correlation between the steady state abundance of guide (g)RNAs and the sequence position of GQ-elements. We postulate that the driving force for selecting G-rich sequences lies in the formation of DNA/RNA hybrid G-quadruplex (HQ) structures between the pre-edited transcripts and the non-template strands of mitochondrial DNA. HQ’s are transcription termination/replication initiation sites and thus guarantee an unperturbed replication of the mt-genome. This is of special importance in the insect-stage of the parasite. In the transcription-on state, the identified GQ’s require editing as a GQ-resolving activity indicating a link between replication, transcription and RNA editing. We propose that the different processes have coevolved and suggest the parasite life-cycle and the single mitochondrion as evolutionary driving forces. PMID:27436151

  9. A piezo motor based on a new principle with high output force, rigidity and integrity: the Tuna Drive.

    PubMed

    Liu, Xiaolong; Lu, Qingyou

    2012-11-01

    We present a linear piezoelectric motor as simple as one piezoelectric scanner tube (PST) spring-clamping a central shaft at both ends with roughly equal clamping forces. The clamping points are aligned with ±X electrodes at one end and ±Y electrodes at the other end. Thus, the ±X (or ±Y) push-pull motions of the PST can cause the push-pull motions of the clamping points on the shaft (called push-pull rubbing), which reduces the total dynamic friction force at one (or the other) end of the PST. This new piezo motor advances one step by fast push-pull rubbing at one end while slowly retracting the PST followed by fast push-pull rubbing at the other end while slowly elongating the PST. Apart from the obvious advantages of simplicity, rigidity, integrity, etc., we will also show that this motor can produce a large output force, which we believe is because of the huge drop of the clamping friction force when the push-pull rubbing occurs. PMID:23206102

  10. A piezo motor based on a new principle with high output force, rigidity and integrity: The Tuna Drive

    NASA Astrophysics Data System (ADS)

    Liu, Xiaolong; Lu, Qingyou

    2012-11-01

    We present a linear piezoelectric motor as simple as one piezoelectric scanner tube (PST) spring-clamping a central shaft at both ends with roughly equal clamping forces. The clamping points are aligned with ±X electrodes at one end and ±Y electrodes at the other end. Thus, the ±X (or ±Y) push-pull motions of the PST can cause the push-pull motions of the clamping points on the shaft (called push-pull rubbing), which reduces the total dynamic friction force at one (or the other) end of the PST. This new piezo motor advances one step by fast push-pull rubbing at one end while slowly retracting the PST followed by fast push-pull rubbing at the other end while slowly elongating the PST. Apart from the obvious advantages of simplicity, rigidity, integrity, etc., we will also show that this motor can produce a large output force, which we believe is because of the huge drop of the clamping friction force when the push-pull rubbing occurs.

  11. Light-induced hydrogen bonding pattern and driving force of electron transfer in AppA BLUF domain photoreceptor.

    PubMed

    Ishikita, Hiroshi

    2008-11-01

    The AppA BLUF (blue light sensing using FAD) domain from Rhodobacter sphaeroides serves as a blue light-sensing photoreceptor. The charge separation process between Tyr-21 and flavin plays an important role in the light signaling state by transforming the dark state conformation to the light state one. By solving the linearized Poisson-Boltzmann equation, I calculated E(m) for Tyr-21, flavin, and redox-active Trp-104 and revealed the electron transfer (ET) driving energy. Rotation of the Gln-63 side chain that converts protein conformation from the dark state to the light state is responsible for the decrease of 150 mV in E(m) for Tyr-21, leading to the significantly larger ET driving energy in the light state conformation. The pK(a) values of protonation for flavin anions are essentially the same in both dark and light state crystal structures. In contrast to the ET via Tyr-21, formation of the W state results in generation of only the dark state conformation (even if the initial conformation is in the light state); this could explain why Trp-104-mediated ET deactivates the light-sensing yield and why the activity of W104A mutant is similar to that of the light-adapted native BLUF. PMID:18647748

  12. The land use change characteristics and its driving force analysis of Shiyang river basin in northwest China

    NASA Astrophysics Data System (ADS)

    Han, Tao; Xie, Yaowen; Jiang, Youyan

    2015-12-01

    In the paper, the use of 1994 and 2005 Landsat TM data monitors the land use and changes of the Shiyang river basin with remote sensing classification comparison under the support of GIS. The result shows that from 1994 to 2005, the area of farmland and settlement land increased greatly and that of grass and forest reduces obviously in this basin; Minqin which is in the lower reaches of Shiyang river basin has a serious desertification with low grass coverage degradation into desert. With a comprehensive analysis about the driving factors of nature and human, population pressure and irrational use of water resource are the key factors of the Land use change and between the natural factor and human factor, human acts leading role.

  13. Selective copper diffusion into quartz-hosted vapor inclusions: Evidence from other host minerals, driving forces, and consequences for Cu-Au ore formation

    NASA Astrophysics Data System (ADS)

    Seo, Jung Hun; Heinrich, Christoph A.

    2013-07-01

    Recent experimental studies have raised concerns that Cu concentrations in quartz-hosted fluid inclusions from magmatic-hydrothermal ore deposits do not represent pristine concentrations in the trapped fluids, but are modified by post-entrapment diffusional exchange through the host quartz. New microanalyses of fluid inclusions hosted in topaz show significantly lower Cu concentrations in vapor inclusions, compared to otherwise identical inclusions hosted by coexisting quartz, whereas coeval brine (hypersaline liquid) inclusions are very similar independent of host mineral in one sample. Sulfur is present as a major component in all vapor inclusions, as in most porphyry-related vapor inclusions, and Cu never exceeds S, but commonly matches the S content at a molar ratio of Cu:S ⩽ 2 in vapor inclusions hosted by quartz. Univalent ions with a radius smaller than ˜1 Å are known to diffuse rapidly through the channels of the quartz structure, parallel to its crystallographic c axis. Since only Cu concentrations differ between topaz- and quartz-hosted inclusions, we hypothesize that Cu+ and H+ re-equilibrate by diffusional ion exchange through these channels, while all other element concentrations remain essentially unchanged. A thermodynamic model considering charge-balanced Cu+H+ exchange and diffusive H2 re-equilibration of an initially Cu-poor but S-rich vapor inclusion with a typical rock-buffered fluid environment outside the host crystal demonstrates a strong chemical driving force for Cu+ to migrate from the surrounding rock into the fluid inclusion during cooling of the system. The driving force for Cu diffusion, against the gradient in total Cu concentration, is the abundant H+ liberated inside the inclusion by dissociation of HCl and particularly by the precipitation of CuFeS2 by reaction with the initially trapped H2S and/or SO2. Gold is not only a much larger ion, but is subject to an opposing driving force, suggesting that high concentrations of this

  14. Forced and natural carbonation of lime-based mortars with and without additives: Mineralogical and textural changes

    SciTech Connect

    Cultrone, G.

    2005-12-15

    We have studied the carbonation process in different types of mortars, with and without pozzolana or air-entraining additives, subject to a CO{sub 2}-rich atmosphere and compared the results with those of similar naturally carbonated mortars. We used X-ray diffraction technique to demonstrate that high CO{sub 2} concentrations favour a faster, more complete carbonation process with 8 days being sufficient to convert portlandite into 90 wt.% calcite. Full carbonation, however, is not reached during the life-span of the tests, not even in forced carbonation experiments. This could be due to at least one of the following phenomena: a premature drying of samples during carbonation reaction, the temperature at which the carbonation process was carried out or the reduction of pore volume occupied by newly formed calcite crystals. This last option seems to be the least probable. We observed a more prolific development of calcite crystals in the pores and fissures through which the carbonic anhydride flows. Under natural conditions, carbonation is much slower and similar levels are not reached for 6 months. These differences suggest that the carbonation process is influenced by the amount of CO{sub 2} used. Both the mineralogy and texture of mortars vary depending on the type of additive used but the speed of the portlandite-calcite transformation does not change significantly. Pozzolana produces hydraulic mortars although the quantity of calcium aluminosilicate crystals is low. The air-entraining agent significantly alters the texture of the mortars creating rounded pores and eliminating or reducing the drying cracks.

  15. Up-regulation of Rho/ROCK signaling in sarcoma cells drives invasion and increased generation of protrusive forces.

    PubMed

    Rösel, Daniel; Brábek, Jan; Tolde, Ondrej; Mierke, Claudia T; Zitterbart, Daniel P; Raupach, Carina; Bicanová, Krisýtyna; Kollmannsberger, Philip; Panková, Daniela; Vesely, Pavel; Folk, Petr; Fabry, Ben

    2008-09-01

    Tumor cell invasion is the most critical step of metastasis. Determination of the mode of invasion within the particular tumor is critical for effective cancer treatment. Protease-independent amoeboid mode of invasion has been described in carcinoma cells and more recently in sarcoma cells on treatment with protease inhibitors. To analyze invasive behavior, we compared highly metastatic sarcoma cells with parental nonmetastatic cells. The metastatic cells exhibited a functional up-regulation of Rho/ROCK signaling and, similarly to carcinoma cells, an amoeboid mode of invasion. Using confocal and traction force microscopy, we showed that an up-regulation of Rho/ROCK signaling leads to increased cytoskeletal dynamics, myosin light chain localization, and increased tractions at the leading edge of the cells and that all of these contributed to increased cell invasiveness in a three-dimensional collagen matrix. We conclude that cells of mesenchymal origin can use the amoeboid nonmesenchymal mode of invasion as their primary invading mechanism and show the dependence of ROCK-mediated amoeboid mode of invasion on the increased capacity of cells to generate force. PMID:18819929

  16. Interactions of aromatic heterocycles with water: the driving force from free-jet rotational spectroscopy and model electrostatic calculations.

    PubMed

    Maris, Assimo; Melandri, Sonia; Miazzi, Marta; Zerbetto, Francesco

    2008-06-23

    The interaction of isolated aromatic nitrogen atoms with water is explored within free jets by using rotational spectroscopy. To the existing data on diazines, we add the case of the 1:1 complex of 1,3,5-triazine and water (where water donates a proton to one of the nitrogen heterocyclic atoms to form a planar adduct). An electrostatic model based on distributed multipoles accurately reproduces the structures of the four azine-water complexes and allows us to understand the forces that stabilize these structures. The applied intermolecular potential allows us to estimate the changes in the thermodynamic functions of the complexes-compared to the separated constituents-and evaluate the temperature at which the complexes are stable under standard conditions. PMID:18470857

  17. Auto Focus and Leveling Control of Large-Scale High-Precision Scan-Stage Using Driving Force and Surface Shape of the Stage

    NASA Astrophysics Data System (ADS)

    Sakata, Koichi; Fujimoto, Hiroshi; Ohtomo, Takeshi; Saiki, Kazuaki

    The large-scale high-precision scan-stage is industrial equipment for microfabrications. The scan-stage needs not only fast and precise positioning but also the attitude control of the stage. The attitude of the stage is disturbed by the stage thrust in scanning. However, the sampling time of output is much longer than the sampling time of control input by DSP because image sensors are employed in the output encoder. It is difficult to reject the disturbances by single-rate feedback system. In this paper, we proposed the attitude control based on PTC (perfect tracking control) using driving force and surface shape of the stage. Finally, simulations and experiments are performed to show the advantages of the proposed control system.

  18. Non-tectonic base level forcings drive widespread transient incision and relief production in the waning Appalachian orogen

    NASA Astrophysics Data System (ADS)

    Prince, P. S.; Richardson, R. P.

    2012-12-01

    The development of knickpoints and steep bedrock gorges within otherwise low-relief landscapes of the Appalachian Highlands has long interested geomorphologists. While large tracts of muted Appalachian topography appear consistent with slow, steady exhumation of a thickened crustal root, active gorge development into lower-relief uplands suggests that Appalachian river systems have been re-energized to incise into bedrock and increase relief. Orogen-scale analysis of incision patterns, fluvial profiles, and surficial deposits indicate that two main sources of non-tectonic base level drop superimposed on the slowly-exhuming Appalachian landscape can explain the Cenozoic relief production observed. Along the Eastern Continental Divide on the southeast margin of the Highlands, repeated capture of headwaters of elevated, landward-draining streams of the Blue Ridge by Atlantic basin streams maintains the oversteepened slopes and bedrock gorges of the Blue Ridge Escarpment zone. Capture events induce a transient erosional response in which rapid knickpoint retreat carves deep gorges into the captured basin, ultimately adjusting topography to match the rest of the Atlantic slope. In the lower reaches of landward Appalachian rivers still following courses to the continental interior, hillslope steepening in the wake of migrating knickpoints is apparent against the backdrop of a comparatively low-relief upland. This landscape suggests that landward base level drop, possibly due to rapid, glacially-forced Plio-Pleistocene drainage rearrangement, has initiated transgressive waves of incision to adjust Highlands topography to the recently-established continental interior drainage pattern. Encroachment of both the post-rift seaward base level and the modern landward base level forces a rapid release of potential energy stored in the elevated Highlands, energizing streams to incise into bedrock without the introduction of new tectonic energy. The southern Appalachian landscape

  19. The effect of electric field geometry on the performance of electromembrane extraction systems: footprints of a third driving force along with migration and diffusion.

    PubMed

    Moazami, Hamid Reza; Hosseiny Davarani, Saied Saeed; Mohammadi, Jamil; Nojavan, Saeed; Abrari, Masoud

    2015-09-01

    The distribution of electric field vectors was first calculated for electromembrane extraction (EME) systems in classical and cylindrical electrode geometries. The results showed that supported liquid membrane (SLM) has a general field amplifying effect due to its lower dielectric constant in comparison with aqueous donor/acceptor solutions. The calculated norms of the electric field vector showed that a DC voltage of 50 V can create huge electric field strengths up to 64 kV m(-1) and 111 kV m(-1) in classical and cylindrical geometries respectively. In both cases, the electric field strength reached its peak value on the inner wall of the SLM. In the case of classical geometry, the field strength was a function of the polar position of the SLM whereas the field strength in cylindrical geometry was angularly uniform. In order to investigate the effect of the electrode geometry on the performance of real EME systems, the analysis was carried out in three different geometries including classical, helical and cylindrical arrangements using naproxen and sodium diclofenac as the model analytes. Despite higher field strength and extended cross sectional area, the helical and cylindrical geometries gave lower recoveries with respect to the classical EME. The observed decline of the signal was proved to be against the relations governing migration and diffusion processes, which means that a third driving force is involved in EME. The third driving force is the interaction between the radially inhomogeneous electric field and the analyte in its neutral form. PMID:26388374

  20. Analysis of Urban-Rural Land-Use Change during 1995-2006 and Its Policy Dimensional Driving Forces in Chongqing, China

    PubMed Central

    Long, Hualou; Wu, Xiuqin; Wang, Wenjie; Dong, Guihua

    2008-01-01

    This paper analyzes the urban-rural land-use change of Chongqing and its policy dimensional driving forces from 1995 to 2006, using high-resolution Landsat TM (Thematic Mapper) data of 1995, 2000 and 2006, and socio-economic data from both research institutes and government departments. The outcomes indicated that urban-rural land-use change in Chongqing can be characterized by two major trends: First, the non-agricultural land increased substantially from 1995 to 2006, thus causing agricultural land especially farmland to decrease continuously. Second, the aggregation index of urban settlements and rural settlements shows that local urban-rural development experienced a process of changing from aggregation (1995-2000) to decentralization (2000-2006). Chongqing is a special area getting immersed in many important policies, which include the establishment of the municipality directly under the Central Government, the building of Three Gorges Dam Project, the Western China Development Program and the Grain-for-Green Programme, and bring about tremendous influences on its land-use change. By analyzing Chongqing's land-use change and its policy driving forces, some implications for its new policy of ‘Urban-rural Integrated Reform’ are obtained. That is more attentions need to be paid to curbing excessive and idle rural housing and consolidating rural construction land, and to laying out a scientific land-use plan for its rural areas taking such rural land-use issues as farmland occupation and rural housing land management into accounts, so as to coordinate and balance the urban-rural development.

  1. Unlocking the biogeochemical black box: What drives microbial response to climate forcing in semi-arid soils?

    NASA Astrophysics Data System (ADS)

    Moravec, B. G.; McLain, J. E.; Lohse, K. A.

    2009-12-01

    Microbial mediated cycling of carbon (C) and nitrogen (N) and their loss from soils are closely linked to soil moisture and temperature. Yet, it is unclear how microbial communities will respond to climatic forcing (namely increased inter-annual precipitation variability and severe drought) and to what extent parent material controls these responses. We used Real Time Polymerase Chain Reaction (RT-PCR) and C utilization assays to determine the relative abundance and diversity of microbial populations during pre-, mid- and post-monsoon time intervals at four sites along a steep elevation gradient (temperature and precipitation range of >10°C and >50 cm, respectively) in the Santa Catalina Mountains, AZ. Contrasting parent materials (schist and granite) were paired at elevations. RT-PCR results showed large increases of bacterial and fungal biomarkers at high elevations with the onset of precipitation (pre- to mid- monsoon conditions) (as much as 824%). In contrast, bacteria biomarkers did not change at low elevation granite site as a result of the onset of precipitation whereas fungal biomarkers increased by 177% at this site. Both bacteria and fungal biomarkers increased substantially at low elevation schist sites with the onset of precipitation. Finally, C utilization assays indicated that high elevation sites had a relatively high diversity of C utilization compared to low elevation soils. We hypothesize that increased bacterial and fungal abundance in low elevation schist-derived soils relative to granite soils after the onset of monsoon rains may be a function of soil texture, with higher clay content in schist soils leading to higher soil moisture availability. Alternatively, differences in microbial responses may be due to higher C availability in schist soils compared to granite soils. Higher C utilization diversity as well as similar bacteria and fungal biomarker responses found at high elevation sites (both granite and schist soils) in response to

  2. Mediterranean coastal dune vegetation: Are disturbance and stress the key selective forces that drive the psammophilous succession?

    NASA Astrophysics Data System (ADS)

    Ciccarelli, Daniela

    2015-11-01

    Plant communities of coastal dunes are distributed along a characteristic sea-inland gradient. Generally, there is a shift from annual and short height species with small leaves in the initial successional stages to perennial tall shrubs with tough leaves in later phases. Assessing the community-weighted mean (CWM) trait values is used in plant ecology to describe ecosystem properties especially during succession. In particular, CSR (Competitive, Stress-tolerant, and Ruderal strategy) classification allows us to explore community functional shifts in terms of disturbance, stress and competition selective forces. The functional basis of the psammophilous succession was studied based on the following questions: (1) Can we circumscribe different functional types among plant species of Mediterranean coastal dunes? (2) How do CWM trait values vary along the environmental sea-inland gradient? (3) What is the relative importance of competition, stress and disturbance in the processes of plant community assembling? (4) Can we postulate that along primary successions there is generally a shift from ruderality to stress-tolerance? An explorative analysis of functional groups was performed by Non-Metric Multidimensional Scaling (NMDS) analysing nine morpho-functional traits measured for 45 taxa from 880 dune plots localised in Tuscany (central Italy, Europe). NMDS ordination showed a scattered distribution of psammophytes that could not be delimited in precise plant functional types. The first NMDS axis has been interpreted as a leaf economics axis because it was correlated to leaf area (LA) and leaf dry matter content (LDMC), while the second one was a plant size axis because of its correlation with canopy height. Along the sea-inland gradient, pioneer plant communities of upper beach were dominated by ruderals (with the lowest values of LDMC and specific leaf area - SLA), well-adapted to the harsh environmental conditions of coastal dunes. More distant from the sea, where

  3. 10-15 years of GST monitoring over mountain permafrost in Switzerland: Indicators for driving forces for permafrost evolution

    NASA Astrophysics Data System (ADS)

    Staub, Benno; Delaloye, Reynald; Hilbich, Christin; Lambiel, Christophe; Nötzli, Jeannette; Völksch, Ingo

    2013-04-01

    Ground Surface Temperatures (GST) are mainly controlled by atmospheric factors and topographical effects and represent an important standard element within the operational permafrost monitoring network PERMOS in Switzerland. Due to its shape, position and extent the Alpine arc is influenced by prevailing winds from several directions provoking a complex and highly variable pattern of precipitation in different regions of Switzerland with a general trend to a more continental climate in some inner-alpine valleys. The lower boundary for the occurrence of mountain permafrost in the Swiss Alps is located at about 2500 m asl., close to the free atmosphere where air temperatures are almost homogenous in all regions, but precipitation usually shows large regional differences regarding timing and quantity depending on the meteorological conditions. At the elevation range of mountain permafrost the ground surface remains snow-free only for about 4-5 months (between June and November) with a high temporal and spatial variability, while over the rest of the year it stays well shielded from the atmosphere (due to the high surface albedo and emissivity and low thermal conductivity of snow). Therefore, the influence of the atmosphere at this boundary layer on the ground thermal regime is well reflected by GST measurements on a very local, site-specific scale. Relative values like GST anomalies can serve as indicators describing processes of energy and heat transfer at the ground surface in a semi-quantitative way. This information is used in a signal-response analysis integrating GST with other permafrost monitoring elements that represent the permafrost response to external effects (e.g. relative changes in borehole temperatures, apparent electrical resistivities or rock glacier creep rates). To identify and quantify the dominant processes and factors controlling the response of Alpine permafrost to external forces, special consideration is devoted to the characteristics of

  4. A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

    SciTech Connect

    Nakano, Jinichiro

    2013-03-15

    Thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. Stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T0, independent of composition and temperature when the other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dGm/(RT), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the studied compositions. The obtained results revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.

  5. Variation in the Chemical Driving Force for Intragranular Nucleation in the Multi-pass Weld Metal of Ti-Containing High-Strength Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Kang, Yongjoon; Han, Kyutae; Park, Joo Hyun; Lee, Changhee

    2015-08-01

    The variation of the Mn-depleted zone (MDZ) around the inclusion during multi-pass welding of Ti-containing high-strength low-alloy (HSLA) steel was investigated by taking the changes in the impact toughness and microstructure into account. As-deposited weld metal specimens were prepared by single-pass, bead-in-groove welding, and reheated weld metal specimens were obtained by a thermal simulation technique. Two types of chemical compositions were prepared, mainly by controlling the Ti content in order to form two types of phases at inclusion/matrix interface: spinel and ilmenite. When the reheating thermal cycle is applied to the as-deposited weld metal, the MDZ depth varied depending on the inclusion surface phase; this could be explained by the competition of the homogenization effect and the dissolution effect, which occurred near the inclusion/matrix interface. In order to enhance the chemical driving force for intragranular nucleation in both as-deposited weld metal and reheated weld metal, the formation of ilmenite phase is recommended.

  6. A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

    DOE PAGESBeta

    Nakano, Jinichiro

    2013-03-15

    Thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. Stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T0, independent of composition and temperature when the other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dGm/(RT), was determined in the presence of Fe-rich and Mn-rich composition sets in eachmore » phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the studied compositions. The obtained results revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.« less

  7. The spatial-temporal patterns and the driving forces of land-use/cover change in the Dongting Lake area of the middle Yangtze River basin

    NASA Astrophysics Data System (ADS)

    Li, Rendong; Liu, Jiyuan; Zhuang, Dafang; Gao, Zhiqiang

    2004-11-01

    Dongting Lake area, located on the southern bank of the middle Yangtze River in central China, is one of the regions experiencing rapid land use change and seriously suffering from flooding disaster in the country. In this paper, a series of land-use coverage was generated through visually interpreting Landsat MSS, TM and ETM images, of 1980, 1990 and 2000 respectively. Then, the spatial-temporal characteristics and the driving forces of the land use changes were analyzed in the study area. The results show that, from 1980 to 2000, the areas of farmland, woodland and non-used land decreased, while those of built-up land, water area and grassland increased. There was a significant shifting from farmland to water or built-up area, and the large-scale reclamation from the lake ever in history has not been found since 1980. The fastest changed area was in Shishou City, Yueyang City and Jinshi City, and the slowest in the eastern and southeastern area. About 49% of the changes were caused by the adjustment of agricultural economic structure, 29.75% by the urbanization and industrialization, and 21.41% by the environmental pressure. The policy, market price and tax on land products also have definitively influences on the land-use changes.

  8. Fixed negative charge and the Donnan effect: a description of the driving forces associated with brain tissue swelling and oedema

    PubMed Central

    Elkin, Benjamin S.; Shaik, Mohammed A.; Morrison, Barclay

    2010-01-01

    Cerebral oedema or brain tissue swelling is a significant complication following traumatic brain injury or stroke that can increase the intracranial pressure (ICP) and impair blood flow. Here, we have identified a potential driver of oedema: the negatively charged molecules fixed within cells. This fixed charge density (FCD), once exposed, could increase ICP through the Donnan effect. We have shown that metabolic processes and membrane integrity are required for concealing this FCD as slices of rat cortex swelled immediately (within 30 min) following dissection if treated with 2 deoxyglucose + cyanide (2DG+CN) or Triton X-100. Slices given ample oxygen and glucose, however, did not swell significantly. We also found that dead brain tissue swells and shrinks in response to changes in ionic strength of the bathing medium, which suggests that the Donnan effect is capable of pressurizing and swelling brain tissue. As predicted, a non-ionic osmolyte, 1,2 propanediol, elicited no volume change at 2000×10−3 osmoles l−1 (Osm). Swelling data were well described by triphasic mixture theory with the calculated reference state FCD similar to that measured with a 1,9 dimethylmethylene blue assay. Taken together, these data suggest that intracellular fixed charges may contribute to the driving forces responsible for brain swelling. PMID:20047940

  9. Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors

    NASA Astrophysics Data System (ADS)

    Taylan Koparan, E.; Savaskan, B.; Guner, S. B.; Celik, S.

    2016-02-01

    We present a detailed investigation of the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB2 obtained by hot press method. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 10 wt%) of the total MgB2. Moreover, we present MgB2 bulk samples fabricated by using different production methods including hot pressing method to our knowledge. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano-boron (B) powder and Bi-2212 powder which are produced by hot press method. As a result of hot press process, compact pellet samples were manufactured. The vertical and lateral levitation force measurements were executed at the temperatures of 20, 24 and 28 K under zero-field-cooled (ZFC) and field-cooled (FC) regimes for samples with various adding levels. At 24 K and 28 K under ZFC regime, the 2 wt% Bi-2212 added sample exhibits a higher vertical levitation force than the pure sample. Bi-2212 added MgB2 samples compared to the pure sample have lower attractive force values in FC regime. The magnetic field dependence of the critical current density J c was calculated from the M-H loops for Bi-2212 added MgB2 samples. The 2 wt% Bi-2212 added sample has the best levitation and critical current density performance compared to other samples. The critical temperature ( T c ) has slightly dropped from 37.8 K for the pure MgB2 sample to 36.7 K for the 10 wt% of Bi-2212 added sample. The transition temperature slightly decreases when Bi-2212 adding level is increased.

  10. CHARMM All-Atom Additive Force Field for Sphingomyelin: Elucidation of Hydrogen Bonding and of Positive Curvature

    PubMed Central

    Venable, Richard M.; Sodt, Alexander J.; Rogaski, Brent; Rui, Huan; Hatcher, Elizabeth; MacKerell, Alexander D.; Pastor, Richard W.; Klauda, Jeffery B.

    2014-01-01

    The C36 CHARMM lipid force field has been extended to include sphingolipids, via a combination of high-level quantum mechanical calculations on small molecule fragments, and validation by extensive molecular dynamics simulations on N-palmitoyl and N-stearoyl sphingomyelin. NMR data on these two molecules from several studies in bilayers and micelles played a strong role in the development and testing of the force field parameters. Most previous force fields for sphingomyelins were developed before the availability of the detailed NMR data and relied on x-ray diffraction of bilayers alone for the validation; these are shown to be too dense in the bilayer plane based on published chain order parameter data from simulations and experiments. The present simulations reveal O-H:::O-P intralipid hydrogen bonding occurs 99% of the time, and interlipid N-H:::O=C (26-29%, depending on the lipid) and N-H:::O-H (17–19%). The interlipid hydrogen bonds are long lived, showing decay times of 50 ns, and forming strings of lipids, and leading to reorientational correlation time of nearly 100 ns. The spontaneous radius of curvature for pure N-palmitoyl sphingomyelin bilayers is estimated to be 43–100 Å, depending on the assumptions made in assigning a bending constant; this unusual positive curvature for a two-tailed neutral lipid is likely associated with hydrogen bond networks involving the NH of the sphingosine group. PMID:24988348

  11. Theoretical study of the molecular force field and vibration analysis of the hydrogen cyanide addition compound with boron tribromide.

    PubMed

    Hase, Y

    2010-01-01

    An extensive HF, MP2, B3LYP and CCSD study of the molecular structure, force field and normal vibrations has been carried out for the hydrogen cyanide compound with boron tribromide. Most of the calculations agree that the HCN-BBr(3) molecule belongs to C(3v) point group and has a N-B length of 1.55-1.70 A and a N-B-Br angle of 103-105 degrees. These calculations also have estimated the missing low-wavenumber fundamentals in the 190 (nu(5)), 150 (nu(9)) and 105 cm(-1) (nu(10)) regions, instead of the supposed fundamentals at 207, 188 and 150 cm(-1), respectively, based on the combination bands. The quantum chemical force constants, by the B3LYP/6-31G and CCSD/3-21G calculations, have been adjusted by the scaling factors to reproduce the fundamentals in the literature [3] to include the bands below 200 cm(-1) proposed in this study. Normal coordinate analysis using the scaled force constants has been performed to interpret the molecular vibrations of four isotopic molecules, HCN-(10)BBr(3), HCN-(11)BBr(3), DCN-(10)BBr(3) and DCN-(11)BBr(3). PMID:19955013

  12. Theoretical study of the molecular force field and vibration analysis of the hydrogen cyanide addition compound with boron tribromide

    NASA Astrophysics Data System (ADS)

    Hase, Y.

    2010-01-01

    An extensive HF, MP2, B3LYP and CCSD study of the molecular structure, force field and normal vibrations has been carried out for the hydrogen cyanide compound with boron tribromide. Most of the calculations agree that the HCN-BBr 3 molecule belongs to C3v point group and has a N-B length of 1.55-1.70 Å and a N-B-Br angle of 103-105°. These calculations also have estimated the missing low-wavenumber fundamentals in the 190 ( ν5), 150 ( ν9) and 105 cm -1 ( ν10) regions, instead of the supposed fundamentals at 207, 188 and 150 cm -1, respectively, based on the combination bands. The quantum chemical force constants, by the B3LYP/6-31G and CCSD/3-21G calculations, have been adjusted by the scaling factors to reproduce the fundamentals in the literature [3] to include the bands below 200 cm -1 proposed in this study. Normal coordinate analysis using the scaled force constants has been performed to interpret the molecular vibrations of four isotopic molecules, HCN- 10BBr 3, HCN- 11BBr 3, DCN- 10BBr 3 and DCN- 11BBr 3.

  13. Driving forces of researchers mobility

    PubMed Central

    Gargiulo, Floriana; Carletti, Timoteo

    2014-01-01

    Starting from the dataset of the publication corpus of the APS during the period 1955–2009, we reconstruct the individual researchers trajectories, namely the list of the consecutive affiliations for each scholar. Crossing this information with different geographic datasets we embed these trajectories in a spatial framework. Using methods from network theory and complex systems analysis we characterise these patterns in terms of topological network properties and we analyse the dependence of an academic path across different dimensions: the distance between two subsequent positions, the relative importance of the institutions (in terms of number of publications) and some socio–cultural traits. We show that distance is not always a good predictor for the next affiliation while other factors like “the previous steps” of the career of the researchers (in particular the first position) or the linguistic and historical similarity between two countries can have an important impact. Finally we show that the dataset exhibit a memory effect, hence the fate of a career strongly depends from the first two affiliations. PMID:24810800

  14. Driving forces of researchers mobility

    NASA Astrophysics Data System (ADS)

    Gargiulo, Floriana; Carletti, Timoteo

    2014-05-01

    Starting from the dataset of the publication corpus of the APS during the period 1955-2009, we reconstruct the individual researchers trajectories, namely the list of the consecutive affiliations for each scholar. Crossing this information with different geographic datasets we embed these trajectories in a spatial framework. Using methods from network theory and complex systems analysis we characterise these patterns in terms of topological network properties and we analyse the dependence of an academic path across different dimensions: the distance between two subsequent positions, the relative importance of the institutions (in terms of number of publications) and some socio-cultural traits. We show that distance is not always a good predictor for the next affiliation while other factors like ``the previous steps'' of the career of the researchers (in particular the first position) or the linguistic and historical similarity between two countries can have an important impact. Finally we show that the dataset exhibit a memory effect, hence the fate of a career strongly depends from the first two affiliations.

  15. Driving forces of researchers mobility.

    PubMed

    Gargiulo, Floriana; Carletti, Timoteo

    2014-01-01

    Starting from the dataset of the publication corpus of the APS during the period 1955-2009, we reconstruct the individual researchers trajectories, namely the list of the consecutive affiliations for each scholar. Crossing this information with different geographic datasets we embed these trajectories in a spatial framework. Using methods from network theory and complex systems analysis we characterise these patterns in terms of topological network properties and we analyse the dependence of an academic path across different dimensions: the distance between two subsequent positions, the relative importance of the institutions (in terms of number of publications) and some socio-cultural traits. We show that distance is not always a good predictor for the next affiliation while other factors like "the previous steps" of the career of the researchers (in particular the first position) or the linguistic and historical similarity between two countries can have an important impact. Finally we show that the dataset exhibit a memory effect, hence the fate of a career strongly depends from the first two affiliations. PMID:24810800

  16. Driving forces push Italian exploration

    SciTech Connect

    Steven, R.R.

    1982-03-01

    The Italian offshore is one of the most active in Europe. Although it cannot be compared with the North Sea in terms of hydrocarbon production or potential, Italy is expending a great deal of effort in order to reduce imported oil and gas from the current level of around 90% of total domestic consumption of 147 million tons of oil equivalent a year. The drilling program, major targets, and development of new oil fields are discussed briefly. (JMT)

  17. Driving forces and risk management

    EPA Science Inventory

    From a public health perspective, food safety is the overall goal and there are two distinct areas where interventions to this end can take place – either pre- or post-harvest. In pre-harvest, water quality management is the focus whereas post-harvest quality management depends ...

  18. A Driving Force in NASCAR

    ERIC Educational Resources Information Center

    Matthews, Frank J.

    2007-01-01

    Minority participation and interest in sports is legendary--depending on what sport you are talking about. Blacks have long been a major factor in the popularity of basketball and football. Tiger Woods' success has contributed to an explosion of interest in golf within the Black community. Arthur Ashe brought tennis into the Black consciousness,…

  19. Comparison of operation efficiency for the insert task when using stereoscopic images with additional lines, stereoscopic images, and a manipulator with force feedback

    NASA Astrophysics Data System (ADS)

    Matsunaga, Katsuya; Shidoji, Kazunori; Matsubara, Kenjiro

    1999-05-01

    It has been reported that operation efficiency for the teleoperations using stereoscopic video images is lower than when using the naked eye in real environments. Here, the authors tried to improve the human-machine interface of this particular system to achieve higher operation efficiency for stereoscopic video imags by adding other information. An experiment was carried out under the four following conditions: when the insert task was performed by subjects using conventional stereoscopic video imags, when the centering lines of the cylindrical objects and holes were added to the conventional stereoscopic video images, when the force feedback was provided to the system manipulator as one object touched another object, and when both of the additional centering lines and force feedback were provided. The subject's task was to inset a cylindrical object into a round hole. The completion time was measured from the time of the starting signal to the time when the object was inserted into the hole. Completion time, when additional lines were given, was shorter than when the force feedback was provided, and when no additional information was provided. It was concluded that additional visual information contributed more to the recognition of the space rather than providing additional information about surface phenomena.

  20. H2O-rich melt inclusions in fayalitic olivine from Hekla volcano: Implications for phase relationships in silicic systems and driving forces of explosive volcanism on Iceland

    NASA Astrophysics Data System (ADS)

    Portnyagin, Maxim; Hoernle, Kaj; Storm, Sonja; Mironov, Nikita; van den Bogaard, Christel; Botcharnikov, Roman

    2012-12-01

    Silicic Icelandic magmas are widely believed to contain low to moderate H2O content prior to degassing, and that their high explosivity mostly results from the interaction of the magmas with ice or meteoric water. Here we report the compositions of glass inclusions (SiO2=57-72 wt%, K2O=1.3-2.6 wt%) in Fe-rich olivines (Fo2-42) from the largest Holocene eruptions of Hekla volcano (H3 and H4) on Iceland, which preserved quenched melts with very high primary H2O contents (3.3-6.2 wt%). The silicic Hekla melts originate primarily by extensive (˜90%) crystal fractionation of H2O-poor (˜0.6 wt%) basalts and represent an end member in the systematics of terrestrial magmas because they originate at low fO2 (ΔQFM ˜-0.1 to -0.4) and have as high H2O contents as significantly more oxidized island-arc magmas (ΔQFM≥1). This demonstrates that H2O and ΔQFM do not correlate in silicic magmas from different tectonic settings, and that fO2, not H2O content, shows a major difference between silicic ocean-island (e.g., Icelandic) and island-arc magmas. Analysis of available experimental data suggests that high H2O activity and low fO2 expand the field of olivine stability in silicic melts. Low fO2 and low MgO content could also suppress crystallization of amphibole. On the basis of these results we propose that an anhydrous mineral assemblage bearing Fe-rich olivine in evolved volcanic and Skaergaard-type intrusive rocks does not imply low H2O in magmas prior to degassing but, in contrast to the commonly held view, is an indicator of H2O-rich silicic parental magmas crystallized at low fO2. Finally, the high H2O content in magma was a major driving force of the largest explosive eruptions of Hekla volcano and must be at least as important for driving silicic explosive volcanism on Iceland as magma-ice interaction.

  1. Magnetostrictive roller drive motor

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1992-01-01

    A magnetostrictive drive motor is disclosed which has a rotary drive shaft in the form of a drum which is encircled by a plurality of substantially equally spaced roller members in the form of two sets of cones which are in contact with the respective cam surfaces on the inside surface of an outer drive ring. The drive ring is attached to sets of opposing pairs of magnetostrictive rods. Each rod in a pair is mutually positioned end to end within respective energizing coils. When one of the coils in an opposing pair is energized, the energized rod expands while the other rod is caused to contract, causing the drive ring to rock, i.e., rotate slightly in either the clockwise or counterclockwise direction, depending upon which rod in a pair is energized. As the drive ring is activated in repetitive cycles in either direction, one set of drive cones attempts to roll up their respective cam surface but are pinned between the drive shaft drum and the drive ring. As the frictional force preventing sliding builds up, the cones become locked, setting up reaction forces including a tangential component which is imparted to the drive shaft drum to provide a source of motor torque. Simultaneously the other set of cones are disengaged from the drive shaft drum. Upon deactivation of the magnetostrictive rod coils, the force on the drive cones is released, causing the system to return to an initial rest position. By repetitively cycling the energization of the magnetostrictive rods, the drive shaft drum indexes in microradian rotational steps.

  2. Driving forces for metamorphic vein filling during bauxite dehydration: insights from Li and Al transfer illustrated by LIBS compositional profiles (Western Alps)

    NASA Astrophysics Data System (ADS)

    Verlaguet, Anne; Brunet, Fabrice; Goffé, Bruno; Menut, Denis; Findling, Nathaniel; Poinssot, Christophe

    2015-04-01

    In subduction zones, the significant amounts of aqueous fluid released in the course of the successive dehydration reactions occurring during prograde metamorphism are expected to strongly influence the rock rheology, as well as kinetics of metamorphic reactions and mass transfer efficiency. Mineralized veins, ubiquitous in metamorphic rocks, can be seen as preserved witnesses of fluid and mass redistribution that partly accommodate the rock deformation (lateral segregation). However, the driving forces and mechanisms of mass transfer towards fluid-filled open spaces remain somewhat unclear. The aim of this study is to investigate the vein-forming processes and the modalities of mass transfer during local fluid-rock interactions, and their links with fluid production and rock deformation, with new insights from Laser Induced Breakdown Spectroscopy (LIBS) profiles. This study focuses on karstic pockets (metre scale) of Triassic metabauxites embedded in thick carbonate units, that have been isolated from large-scale fluid flow during HP-LT Alpine metamorphism (W. Vanoise, French Alps). These rocks display several generations of metamorphic veins containing various Al-bearing minerals, which give particular insights into mass transfer processes. It is proposed that the internally-derived fluid (~13 vol% produced by successive dehydration reactions) has promoted the opening of fluid-filled open spaces (euhedral habits of vein minerals) and served as medium for diffusive mass transfer from rock to vein. Based on mineralogical and textural features, two vein types can be distinguished: (1) some veins are filled with newly formed products of either prograde (chloritoid) or retrograde (chlorite) metamorphic reactions; in this case, fluid-filled open spaces seem to offer energetically favourable nucleation/growth sites; (2) the second vein type is filled with cookeite (Li-Al-rich chlorite) or pyrophyllite, which were present in the host-rock prior to the vein formation. In

  3. Interactions between seasonality and oceanic forcing drive the phytoplankton variability in the tropical-temperate transition zone (~ 30°S) of Eastern Australia

    NASA Astrophysics Data System (ADS)

    Armbrecht, Linda H.; Schaeffer, Amandine; Roughan, Moninya; Armand, Leanne K.

    2015-04-01

    The East Australian Current (EAC) has been shown to be warming rapidly, which is expected to cause latitudinal shifts in phytoplankton abundance, distribution and composition along the east Australian coast. Yet a lack of phytoplankton information exists northward of 34°S. Here, we provide the first detailed taxonomic time-series survey (monthly sampling for about one annual cycle, 2011-2012) in the east Australian tropical-temperate transition zone (~ 30°S, upstream of the EAC separation point at ~ 31-32°S). All phytoplankton (categorised depending on their association with specific water-types) show a seasonal signal with abundance maxima (minima) during summer (winter). This seasonal signal is most pronounced in the seasonal/bloom category and least expressed by deep-water taxa, which prefer cold, saline and dense bottom water independent of the season. Different extents of EAC encroachment onto the continental shelf drive the cross-shelf phytoplankton composition and distribution, such that a weak EAC is associated with phytoplankton community being organised along 'depth' and 'distance from the coast' gradients with high phytoplankton abundances inshore. A strong EAC favours the occurrence of warm-water taxa offshore and an increase in diatom abundance on the mid-shelf (53% shelf width). We conclude that the phytoplankton community in the tropical-temperate transition zone of Eastern Australia is driven by an interaction of intrinsic seasonal cycles and primarily EAC-driven oceanic forcing. Our findings benefit studies located in Western Boundary Current systems worldwide, in which warming and strengthening of these currents are predicted to severely impact phytoplankton dynamics.

  4. The SCOPSCO deep drilling program in ancient Lake Ohrid: Unravelling the driving forces of speciation in Europe's oldest and most biodiverse lake

    NASA Astrophysics Data System (ADS)

    Wilke, Thomas; Wagner, Bernd; Albrecht, Christian; Levkov, Zlatko; Francke, Alexander; Hauffe, Torsten; Cvetkoska, Aleksandra; Jovanovska, Elena; Zhang, Xiaosen; Reed, Jane M.; Wagner-Cremer, Friederike; Stelbrink, Björn; Viehberg, Finn

    2015-04-01

    Ancient Lake Ohrid on the Balkan Peninsula constitutes the oldest and most biodiverse lake in Europe. The processes generating this extraordinary species richness with a high share of endemic taxa, however, are poorly understood. In order to unravel the geological and biological history of the lake and to study, among others, the influence of major geological and environmental events on the evolution of endemic taxa, an international research initiative - the SCOPSCO project - was launched. The project combines sedimentological, tephro-stratigraphical, seismic and paleontological (diatoms, mollusks, ostracods) studies of lake sediment cores with molecular-dating and empirical modelling approaches applied to extant taxa. Preliminary analyses of sediment core and borehole logging data from drill sites with a maximum penetration depth of 569 m below lake floor and an overall recovery of > 95 % indicate that Lake Ohrid is roughly 1.3 to 1.5 My old. Intriguingly, these data fully reinforce the results of molecular clock analyses conducted prior to the drilling operation. Moreover, the combined geological and biological studies suggest that the extraordinary biodiversity in Lake Ohrid is largely driven by 1) the long and continuous existence of the lake, 2) the lack of catastrophic events (e.g., desiccation, full glaciation or salinization) during its lifetime potentially causing massive extinctions, 3) the high buffer capacity of the lake to environmental change and/or the high resilience of its taxa, and 4) distinct turnovers in species composition over time promoting frequency dependent selection. The cumulative effect of these factors, in turn, resulted in overall low extinction rates and continuous speciation and radiation events. These findings not only shed new light on patterns and processes of evolution in Europe's oldest lake, they also show that data from sediment cores can contribute to a better understanding of the driving forces of biotic evolution

  5. Selective transport of amino acids into the gas phase: driving forces for amino acid solubilization in gas-phase reverse micelles.

    PubMed

    Fang, Yigang; Bennett, Andrew; Liu, Jianbo

    2011-01-28

    We report a study on encapsulation of various amino acids into gas-phase sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) reverse micelles, using electrospray ionization guided-ion-beam tandem mass spectrometry. Collision-induced dissociation of mass-selected reverse micellar ions with Xe was performed to probe structures of gas-phase micellar assemblies, identify solute-surfactant interactions, and determine preferential incorporation sites of amino acids. Integration into gas-phase reverse micelles depends upon amino acid hydrophobicity and charge state. For examples, glycine and protonated amino acids (such as protonated tryptophan) are encapsulated within the micellar core via electrostatic interactions; while neutral tryptophan is adsorbed in the surfactant layer. As verified using model polar hydrophobic compounds, the hydrophobic effect and solute-interface hydrogen-bonding do not provide sufficient driving force needed for interfacial solubilization of neutral tryptophan. Neutral tryptophan, with a zwitterionic structure, is intercalated at the micellar interface between surfactant molecules through complementary effects of electrostatic interactions between tryptophan backbone and AOT polar heads, and hydrophobic interactions between tryptophan side chain and AOT alkyl tails. Protonation of tryptophan could significantly improve its incorporation capacity into gas-phase reverse micelles, and displace its incorporation site from the micellar interfacial zone to the core; protonation of glycine, on the other hand, has little effect on its encapsulation capacity. Another interesting observation is that amino acids of different isoelectric points could be selectively encapsulated into, and transported by, reverse micelles from solution to the gas phase, based upon their competition for protonation and subsequent encapsulation within the micellar core. PMID:21140022

  6. Lessons learned during the training exercise for the entry into force of the U.S. additional protocol in the DOE complex

    SciTech Connect

    Boyer, Brian D

    2009-01-01

    In 2008 in anticipation of the United States bringing into force the Additional Protocol in early 2009 DOE/NNSA planned and executed training exercises in the conduct of Additional Protocol complementary access activities. Brookhaven National Laboratory and Los Alamos National Laboratory together produced the exercises designed to prepare the following types of DOE laboratories for complementary access - weapons laboratories, nuclear engineering laboratories, and science laboratories. This panel provides a forum to discuss and summarize the results and lessons learned from the 2008 exercise.

  7. Study on HCl Driving Force for the Reaction of NaCl-Maleic Acid Mixing Single Droplet Using Micro-FTIR Spectroscopy

    NASA Astrophysics Data System (ADS)

    He, Xiang; Zhang, Yunhong

    2016-04-01

    Chemical aging is the one of the most important physicochemical process in atmospheric aerosols. Mixing of sea salt and water-soluble organic components has profound effects on the volatile characteristic and evolving chemical composition of the anthropogenic origin aerosols, which are poorly understood. In this study, the chemical reaction behavior of the mixture of NaCl and maleic acid (H2MA) micron-level single droplet was investigated using a gas-flow system combined with microscopic Fourier transform infrared (micro-FTIR) spectrometer over the range of relative humidity (63˜95% RH) for the first time. The results showed that the mixture of NaCl and H2MA single droplet could react to form monosodium maleate salt (NaHMA) at the constant RH from the characterization of the FTIR. The reaction is a result of an acid displacement reaction R1, which is driven by high volatility of the HCl product. NaCl(aq)+H2MA(aq)=NaHMA(aq)+HCl(aq,g) (R1) According to the change tendency of the absorbance values of 1579 cm‑1 COO‑ stretching band of the NaHMA dependent upon reaction times at different RHs, the growth range of the trend which could lead to the faster reaction rate was obvious at lower RH. The water content of the droplet was also more likely to reduce rapidly with the loss of the RH from the absorbance changes of 3400 cm‑1H2O stretching band dependent upon reaction times. These may be due to irreversible evaporation of HCl gas which is the main driving force for this type of reaction and the NaHMA is a less hygroscopic component compared to H2MA. And the HCl gas is more likely to evaporate faster from the single droplet and promote the reaction rate and the consumption of water content at lower RH. These results could help in understanding the chemical conversion processes of water-soluble dicarboxylic acids to dicarboxylate salts, as well as the consumption of Cl in sea salt aerosols by organic acids in the atmosphere.

  8. Exploring the retention properties of CaF2 nanoparticles as possible additives for dental care application with tapping-mode atomic force microscope in liquid.

    PubMed

    Wasem, Matthias; Köser, Joachim; Hess, Sylvia; Gnecco, Enrico; Meyer, Ernst

    2014-01-13

    Amplitude-modulation atomic force microscopy (AM-AFM) is used to determine the retention properties of CaF2 nanoparticles adsorbed on mica and on tooth enamel in liquid. From the phase-lag of the forced cantilever oscillation the local energy dissipation at the detachment point of the nanoparticle was determined. This enabled us to compare different as-synthesized CaF2 nanoparticles that vary in shape, size and surface structure. CaF2 nanoparticles are candidates for additives in dental care products as they could serve as fluorine-releasing containers preventing caries during a cariogenic acid attack on the teeth. We show that the adherence of the nanoparticles is increased on the enamel substrate compared to mica, independently of the substrate roughness, morphology and size of the particles. PMID:24455460

  9. Exploring the retention properties of CaF2 nanoparticles as possible additives for dental care application with tapping-mode atomic force microscope in liquid

    PubMed Central

    Köser, Joachim; Hess, Sylvia; Gnecco, Enrico; Meyer, Ernst

    2014-01-01

    Summary Amplitude-modulation atomic force microscopy (AM-AFM) is used to determine the retention properties of CaF2 nanoparticles adsorbed on mica and on tooth enamel in liquid. From the phase-lag of the forced cantilever oscillation the local energy dissipation at the detachment point of the nanoparticle was determined. This enabled us to compare different as-synthesized CaF2 nanoparticles that vary in shape, size and surface structure. CaF2 nanoparticles are candidates for additives in dental care products as they could serve as fluorine-releasing containers preventing caries during a cariogenic acid attack on the teeth. We show that the adherence of the nanoparticles is increased on the enamel substrate compared to mica, independently of the substrate roughness, morphology and size of the particles. PMID:24455460

  10. Ultrasensitive hysteretic force sensing with parametric nonlinear oscillators

    NASA Astrophysics Data System (ADS)

    Papariello, Luca; Zilberberg, Oded; Eichler, Alexander; Chitra, R.

    2016-08-01

    We propose a method for linear detection of weak forces using parametrically driven nonlinear resonators. The method is based on a peculiar feature in the response of the resonator to a near resonant periodic external force. This feature stems from a complex interplay among the parametric drive, external force, and nonlinearities. For weak parametric drive, the response exhibits the standard Duffing-like single jump hysteresis. For stronger drive amplitudes, we find a qualitatively new double jump hysteresis which arises from stable solutions generated by the cubic Duffing nonlinearity. The additional jump exists only if the external force is present and the frequency at which it occurs depends linearly on the amplitude of the external force, permitting a straightforward ultrasensitive detection of weak forces. With state-of-the-art nanomechanical resonators, our scheme should permit force detection in the attonewton range.

  11. Characterization of New Isolates of Apricot vein clearing-associated virus and of a New Prunus-Infecting Virus: Evidence for Recombination as a Driving Force in Betaflexiviridae Evolution.

    PubMed

    Marais, Armelle; Faure, Chantal; Mustafayev, Eldar; Candresse, Thierry

    2015-01-01

    Double stranded RNAs from Prunus samples gathered from various surveys were analyzed by a deep-sequencing approach. Contig annotations revealed the presence of a potential new viral species in an Azerbaijani almond tree (Prunus amygdalus) and its genome sequence was completed. Its genomic organization is similar to that of the recently described Apricot vein clearing associated virus (AVCaV) for which two new isolates were also characterized, in a similar fashion, from two Japanese plums (Prunus salicina) from a French germplasm collection. The amino acid identity values between the four proteins encoded by the genome of the new virus have identity levels with those of AVCaV which fall clearly outside the species demarcation criteria. The new virus should therefore be considered as a new species for which the name of Caucasus prunus virus (CPrV) has been proposed. Phylogenetic relationships and nucleotide comparisons suggested that together with AVCaV, CPrV could define a new genus (proposed name: Prunevirus) in the family Betaflexiviridae. A molecular test targeting both members of the new genus was developed, allowing the detection of additional AVCaV isolates, and therefore extending the known geographical distribution and the host range of AVCaV. Moreover, the phylogenetic trees reconstructed with the amino acid sequences of replicase, movement and coat proteins of representative Betaflexiviridae members suggest that Citrus leaf blotch virus (CLBV, type member of the genus Citrivirus) may have evolved from a recombination event involving a Prunevirus, further highlighting the importance of recombination as a driving force in Betaflexiviridae evolution. The sequences reported in the present manuscript have been deposited in the GenBank database under accession numbers KM507061-KM504070. PMID:26086395

  12. Characterization of New Isolates of Apricot vein clearing-associated virus and of a New Prunus-Infecting Virus: Evidence for Recombination as a Driving Force in Betaflexiviridae Evolution

    PubMed Central

    Marais, Armelle; Faure, Chantal; Mustafayev, Eldar; Candresse, Thierry

    2015-01-01

    Double stranded RNAs from Prunus samples gathered from various surveys were analyzed by a deep-sequencing approach. Contig annotations revealed the presence of a potential new viral species in an Azerbaijani almond tree (Prunus amygdalus) and its genome sequence was completed. Its genomic organization is similar to that of the recently described Apricot vein clearing associated virus (AVCaV) for which two new isolates were also characterized, in a similar fashion, from two Japanese plums (Prunus salicina) from a French germplasm collection. The amino acid identity values between the four proteins encoded by the genome of the new virus have identity levels with those of AVCaV which fall clearly outside the species demarcation criteria. The new virus should therefore be considered as a new species for which the name of Caucasus prunus virus (CPrV) has been proposed. Phylogenetic relationships and nucleotide comparisons suggested that together with AVCaV, CPrV could define a new genus (proposed name: Prunevirus) in the family Betaflexiviridae. A molecular test targeting both members of the new genus was developed, allowing the detection of additional AVCaV isolates, and therefore extending the known geographical distribution and the host range of AVCaV. Moreover, the phylogenetic trees reconstructed with the amino acid sequences of replicase, movement and coat proteins of representative Betaflexiviridae members suggest that Citrus leaf blotch virus (CLBV, type member of the genus Citrivirus) may have evolved from a recombination event involving a Prunevirus, further highlighting the importance of recombination as a driving force in Betaflexiviridae evolution. The sequences reported in the present manuscript have been deposited in the GenBank database under accession numbers KM507061-KM504070. PMID:26086395

  13. CONTROL ROD DRIVE

    DOEpatents

    Chapellier, R.A.

    1960-05-24

    BS>A drive mechanism was invented for the control rod of a nuclear reactor. Power is provided by an electric motor and an outside source of fluid pressure is utilized in conjunction with the fluid pressure within the reactor to balance the loadings on the motor. The force exerted on the drive mechanism in the direction of scramming the rod is derived from the reactor fluid pressure so that failure of the outside pressure source will cause prompt scramming of the rod.

  14. iDriving (Intelligent Driving)

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving stylesmore » in responses to actual driving conditions to improve fuel efficiency.« less

  15. iDriving (Intelligent Driving)

    SciTech Connect

    Malikopoulos, Andreas

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving styles in responses to actual driving conditions to improve fuel efficiency.

  16. Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields.

    PubMed

    Lin, Bin; Lopes, Pedro E M; Roux, Benoît; MacKerell, Alexander D

    2013-08-28

    Kirkwood-Buff analysis was performed on aqueous solutions of N-methylacetamide and acetamide using the Chemistry at HARvard Molecular Mechanics additive and Drude polarizable all-atom force fields. Comparison of a range of properties with experimental results, including Kirkwood-Buff integrals, excess coordination numbers, solution densities, partial molar values, molar enthalpy of mixing, showed both models to be well behaved at higher solute concentrations with the Drude model showing systematic improvement at lower solution concentrations. However, both models showed difficulties reproducing experimental activity derivatives and the excess Gibbs energy, with the Drude model performing slightly better. At the molecular level, the improved agreement of the Drude model at low solute concentrations is due to increased structure in the solute-solute and solute-solvent interactions. The present results indicate that the explicit inclusion of electronic polarization leads to improved modeling of dilute solutions even when those properties are not included as target data during force field optimization. PMID:24007020

  17. Impact of 2′-hydroxyl sampling on the conformational properties of RNA: Update of the CHARMM all-atom additive force field for RNA

    PubMed Central

    Denning, Elizabeth J.; Priyakumar, U. Deva; Nilsson, Lennart; MacKerell, Alexander D.

    2011-01-01

    Here, we present an update of the CHARMM27 all-atom additive force field for nucleic acids that improves the treatment of RNA molecules. The original CHARMM27 force field parameters exhibit enhanced Watson-Crick (WC) base pair opening which is not consistent with experiment while analysis of MD simulations show the 2′-hydroxyl moiety to almost exclusively sample the O3′ orientation. Quantum mechanical studies of RNA related model compounds indicate the energy minimum associated with the O3′ orientation to be too favorable, consistent with the MD results. Optimization of the dihedral parameters dictating the energy of the 2′-hydroxyl proton targeting the QM data yielded several parameter sets, which sample both the base and O3′ orientations of the 2′-hydroxyl to varying degrees. Selection of the final dihedral parameters was based on reproduction of hydration behavior as related to a survey of crystallographic data and better agreement with experimental NMR J-coupling values. Application of the model, designated CHARMM36, to a collection of canonical and non-canonical RNA molecules reveals overall improved agreement with a range of experimental observables as compared to CHARMM27. The results also indicate the sensitivity of the conformational heterogeneity of RNA to the orientation of the 2′-hydroxyl moiety and support a model whereby the 2′-hydroxyl can enhance the probability of conformational transitions in RNA. PMID:21469161

  18. Drugged Driving

    MedlinePlus

    ... Infographics » Drugged Driving Drugged Driving Email Facebook Twitter Text Description of Infographic Top Right Figure : In 2009, ... crash than those who don't smoke. Bottom Text: Develop Social Strategies Offer to be a designated ...

  19. The Additive Impact of Group and Individual Publicly Displayed Feedback: Examining Individual Response Patterns and Response Generalization in a Safe-Driving Occupational Intervention

    ERIC Educational Resources Information Center

    Ludwig, Timothy D.; Geller, E. Scott; Clarke, Steven W.

    2010-01-01

    Additive effects of publicly posting individual feedback following group goal-setting and feedback were evaluated. The turn-signal use of pizza deliverers was studied in a multiple baseline design across two pizza stores. After baseline observations, pizza deliverers voted on a group turn-signal goal and then received 4 weeks of group feedback on…

  20. Additive and interaction effects at three amino acid positions in HLA-DQ and HLA-DR molecules drive type 1 diabetes risk

    PubMed Central

    Hu, Xinli; Deutsch, Aaron J; Lenz, Tobias L; Onengut-Gumuscu, Suna; Han, Buhm; Chen, Wei-Min; Howson, Joanna M M; Todd, John A; de Bakker, Paul I W; Rich, Stephen S; Raychaudhuri, Soumya

    2016-01-01

    Variation in the human leukocyte antigen (HLA) genes accounts for one-half of the genetic risk in type 1 diabetes (T1D). Amino acid changes in the HLA-DR and HLA-DQ molecules mediate most of the risk, but extensive linkage disequilibrium complicates the localization of independent effects. Using 18,832 case-control samples, we localized the signal to 3 amino acid positions in HLA-DQ and HLA-DR. HLA-DQβ1 position 57 (previously known; P = 1 × 10−1,355) by itself explained 15.2% of the total phenotypic variance. Independent effects at HLA-DRβ1 positions 13 (P = 1 × 10−721) and 71 (P = 1 × 10−95) increased the proportion of variance explained to 26.9%. The three positions together explained 90% of the phenotypic variance in the HLA-DRB1–HLA-DQA1–HLA-DQB1 locus. Additionally, we observed significant interactions for 11 of 21 pairs of common HLA-DRB1–HLA-DQA1–HLA-DQB1 haplotypes (P = 1.6 × 10−64). HLA-DRβ1 positions 13 and 71 implicate the P4 pocket in the antigen-binding groove, thus pointing to another critical protein structure for T1D risk, in addition to the HLA-DQ P9 pocket. PMID:26168013

  1. Competition among Li+, Na+, K+ and Rb+ Monovalent Ions for DNA in Molecular Dynamics Simulations using the Additive CHARMM36 and Drude Polarizable Force Fields

    PubMed Central

    Savelyev, Alexey; MacKerell, Alexander D.

    2015-01-01

    In the present study we report on interactions of and competition between monovalent ions for two DNA sequences in MD simulations. Efforts included the development and validation of parameters for interactions among the first-group monovalent cations, Li+, Na+, K+ and Rb+, and DNA in the Drude polarizable and additive CHARMM36 force fields (FF). The optimization process targeted gas-phase QM interaction energies of various model compounds with ions and osmotic pressures of bulk electrolyte solutions of chemically relevant ions. The optimized ionic parameters are validated against counterion condensation theory and buffer exchange-atomic emission spectroscopy measurements providing quantitative data on the competitive association of different monovalent ions with DNA. Comparison between experimental and MD simulation results demonstrates that, compared to the additive CHARMM36 model, the Drude FF provides an improved description of the general features of the ionic atmosphere around DNA and leads to closer agreement with experiment on the ionic competition within the ion atmosphere. Results indicate the importance of extended simulation systems on the order of 25 Å beyond the DNA surface to obtain proper convergence of ion distributions. PMID:25751286

  2. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    SciTech Connect

    Lee, Jumin; Cheng, Xi; Swails, Jason M.; Yeom, Min Sun; Eastman, Peter K.; Lemkul, Justin A.; Wei, Shuai; Buckner, Joshua; Jeong, Jong Cheol; Qi, Yifei; Jo, Sunhwan; Pande, Vijay S.; Case, David A.; Brooks, Charles L.; MacKerell, Alexander D.; Klauda, Jeffery B.; Im, Wonpil

    2015-11-12

    Here we report that proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find the optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules.

  3. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    PubMed Central

    2015-01-01

    Proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find the optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules. PMID:26631602

  4. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    DOE PAGESBeta

    Lee, Jumin; Cheng, Xi; Swails, Jason M.; Yeom, Min Sun; Eastman, Peter K.; Lemkul, Justin A.; Wei, Shuai; Buckner, Joshua; Jeong, Jong Cheol; Qi, Yifei; et al

    2015-11-12

    Here we report that proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find themore » optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules.« less

  5. The relaxation of intrinsic compressive stress in complementary metal-oxide-semiconductor transistors by additional N ion implantation treatment with atomic force microscope-Raman stress extraction

    NASA Astrophysics Data System (ADS)

    Liao, M.-H.; Chen, C.-H.; Chang, L.-C.; Yang, C.; Kao, S.-C.

    2012-05-01

    Based on the stress extraction and measurement by atomic force microscope-Raman technique with the nanometer level space resolution, the high compressive stress about 550 MPa on the Si active region (OD) is observed for the current complementary metal-oxide-semiconductor (CMOS) transistor. During the thermal budget for the standard manufacture process of the current CMOS transistor, the difference of thermal expansion coefficients between Si and Shallow Trench Isolation (STI) oxide results in this high compressive stress in Si OD and further degrades the electron carrier mobility seriously. In order to relax this intrinsic processed compressive stress in Si OD and try to recover this performance loss, the novel process is proposed in this work in addition to the usage of one-side pad SiN layer. With this novel process of additional N-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress about 438 MPa in Si OD can be achieved by the smaller difference of thermal expansion coefficients between Si and N-doped SiO2 STI oxide. The formation of Si-N bonding in N-doped SiO2 STI region can be monitored by Fourier transform infrared spectroscopy spectra and thermal expansion coefficients for Si, SiO2, and SiN are 2.6 ppm/K, 0.4 ppm/K, and 2.87 ppm/K, respectively. The effective relaxation of intrinsic processed compressive stress in Si OD about 112 MPa (from 550 MPa to 438 MPa) by this proposed additional N IMP treatment contributes ˜14% electron carrier mobility enhancement/recovery. The experimental electrical data agree well with the theoretical piezoelectricity calculation for the strained-Si theory.

  6. Control rod drive

    SciTech Connect

    Hawke, Basil C.

    1986-01-01

    A control rod drive uses gravitational forces to insert one or more control rods upwardly into a reactor core from beneath the reactor core under emergency conditions. The preferred control rod drive includes a vertically movable weight and a mechanism operatively associating the weight with the control rod so that downward movement of the weight is translated into upward movement of the control rod. The preferred control rod drive further includes an electric motor for driving the control rods under normal conditions, an electrically actuated clutch which automatically disengages the motor during a power failure and a decelerator for bringing the control rod to a controlled stop when it is inserted under emergency conditions into a reactor core.

  7. Pile Driving

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.

  8. Reduced Cardiac Contractile Force Due to Sympathovagal Dysfunction Mediates the Additive Hypotensive Effects of Limited-Access Regimens of Ethanol and Clonidine in Spontaneously Hypertensive Rats

    PubMed Central

    El-Mas, Mahmoud M.

    2010-01-01

    Our previous attempts to investigate the long-term hemodynamic interaction between ethanol and clonidine in telemetered spontaneously hypertensive rats (SHRs) were hampered by the lack of a sustained hypotensive response to continuous clonidine exposure. This limitation was circumvented when we adopted a limited-access clonidine (8:30 AM–4:30 PM) paradigm in a recent study. The latter paradigm was employed here to evaluate the ethanol-clonidine interaction and possible roles of myocardial function and autonomic control in this interaction. Changes in blood pressure (BP), heart rate, maximum rate of rise in BP wave (+dP/dtmax), and spectral cardiovascular autonomic profiles were measured by radiotelemetry in pair-fed SHRs receiving clonidine (150 μg/kg/day), ethanol [2.5% (w/v)], or their combination during the day for 12 weeks. Ethanol or clonidine elicited long-term decreases in BP, and their combination caused additive hypotensive response. Significant reductions in +dP/dtmax were observed upon concurrent treatment with ethanol and clonidine, in contrast to no effect for individual treatment. In addition, the combined treatment increased the high-frequency (HF) spectral band of interbeat interval (IBI-HFnu, 0.75–3 Hz) and decreased low-frequency (IBI-LFnu, 0.2–0.75 Hz) bands and IBILF/HF ratios. Clonidine-evoked reductions in plasma and urine norepinephrine and BP-LF spectral power (measure of vasomotor sympathetic tone) were not affected by ethanol. In conclusion, concurrent treatment with ethanol and clonidine shifts the sympathovagal balance toward parasympathetic dominance and elicits exaggerated hypotension as a result of a reduction in cardiac contractile force. PMID:20864507

  9. Vegetation dynamics and its driving forces from climate change and human activities in the Three-River Source Region, China from 1982 to 2012.

    PubMed

    Zhang, Ying; Zhang, Chaobin; Wang, Zhaoqi; Chen, Yizhao; Gang, Chengcheng; An, Ru; Li, Jianlong

    2016-09-01

    The Three-River Source Region (TRSR), a region with key importance to the ecological security of China, has undergone climate changes and a shift in human activities driven by a series of ecological restoration projects in recent decades. To reveal the spatiotemporal dynamics of vegetation dynamics and calculate the contributions of driving factors in the TRSR across different periods from 1982 to 2012, net primary productivity (NPP) estimated using the Carnegie-Ames-Stanford approach model was used to assess the status of vegetation. The actual effects of different climatic variation trends on interannual variation in NPP were analyzed. Furthermore, the relationships of NPP with different climate factors and human activities were analyzed quantitatively. Results showed the following: from 1982 to 2012, the average NPP in the study area was 187.37gcm(-2)yr(-1). The average NPP exhibited a fluctuation but presented a generally increasing trend over the 31-year study period, with an increase rate of 1.31gcm(-2)yr(-2). During the entire study period, the average contributions of temperature, precipitation, and solar radiation to NPP interannual variation over the entire region were 0.58, 0.73, and 0.09gcm(-2)yr(-2), respectively. Radiation was the climate factor with the greatest influence on NPP interannual variation. The factor that restricted NPP increase changed from temperature and radiation to precipitation. The average contributions of climate change and human activities to NPP interannual variation were 1.40gcm(-2)yr(-2) and -0.08gcm(-2)yr(-2), respectively. From 1982 to 2000, the general climate conditions were favorable to vegetation recovery, whereas human activities had a weaker negative impact on vegetation growth. From 2001 to 2012, climate conditions began to have a negative impact on vegetation growth, whereas human activities made a favorable impact on vegetation recovery. PMID:27135584

  10. Distracted Driving

    MedlinePlus

    ... combines all three types of distraction. 3 How big is the problem? Deaths In 2013, 3,154 ... European countries. More A CDC study analyzed 2011 data on distracted driving, including talking on a cell ...

  11. Distracted driving

    MedlinePlus

    ... stay safe with a cell phone in the car. ... for Disease Control and Prevention Injury Prevention & Control. Motor Vehicle Safety. www.cdc.gov/motorvehiclesafety/distracted_driving . Accessed May ...

  12. Driving Safely

    MedlinePlus

    ... drivers’ flexibility and coordination, and reduced driving errors. S l Hand grip strengthening to help you hold on to the steering wheel l Shoulder and upper arm flexibility exercises to make ...

  13. Force reflecting hand controller for manipulator teleoperation

    NASA Technical Reports Server (NTRS)

    Bryfogle, Mark D.

    1991-01-01

    A force reflecting hand controller based upon a six degree of freedom fully parallel mechanism, often termed a Stewart Platform, has been designed, constructed, and tested as an integrated system with a slave robot manipulator test bed. A force reflecting hand controller comprises a kinesthetic device capable of transmitting position and orientation commands to a slave robot manipulator while simultaneously representing the environmental interaction forces of the slave manipulator back to the operator through actuators driving the hand controller mechanism. The Stewart Platform was chosen as a novel approach to improve force reflecting teleoperation because of its inherently high ratio of load generation capability to system mass content and the correspondingly high dynamic bandwidth. An additional novelty of the program was to implement closed loop force and torque control about the hand controller mechanism by equipping the handgrip with a six degree of freedom force and torque measuring cell. The mechanical, electrical, computer, and control systems are discussed and system tests are presented.

  14. Force reflecting hand controller for manipulator teleoperation

    NASA Astrophysics Data System (ADS)

    Bryfogle, Mark D.

    1991-12-01

    A force reflecting hand controller based upon a six degree of freedom fully parallel mechanism, often termed a Stewart Platform, has been designed, constructed, and tested as an integrated system with a slave robot manipulator test bed. A force reflecting hand controller comprises a kinesthetic device capable of transmitting position and orientation commands to a slave robot manipulator while simultaneously representing the environmental interaction forces of the slave manipulator back to the operator through actuators driving the hand controller mechanism. The Stewart Platform was chosen as a novel approach to improve force reflecting teleoperation because of its inherently high ratio of load generation capability to system mass content and the correspondingly high dynamic bandwidth. An additional novelty of the program was to implement closed loop force and torque control about the hand controller mechanism by equipping the handgrip with a six degree of freedom force and torque measuring cell. The mechanical, electrical, computer, and control systems are discussed and system tests are presented.

  15. Head tilt during driving.

    PubMed

    Zikovitz, D C; Harris, L R

    1999-05-01

    In order to distinguish between the use of visual and gravito-inertial force reference frames, the head tilt of drivers and passengers were measured as they went around corners at various speeds. The visual curvature of the corners were thus dissociated from the magnitude of the centripetal forces (0.30-0.77 g). Drivers' head tilts were highly correlated with the visually-available estimate of the curvature of the road (r2=0.86) but not with the centripetal force (r2<0.1). Passengers' head tilts were inversely correlated with the lateral forces (r2=0.3-0.7) and seem to reflect a passive sway. The strong correlation of the tilt of drivers' heads with a visual aspect of the road ahead, supports the use of a predominantly visual reference frame for the driving task. PMID:10722313

  16. Hairless mutation: a driving force of humanization from a human–ape common ancestor by enforcing upright walking while holding a baby with both hands

    PubMed Central

    Sutou, Shizuyo

    2012-01-01

    Three major characteristics distinguish humans from other primates: bipedality, practical nakedness, and the family as a social unit. A hairless mutation introduced into the chimpanzee/human last common ancestor (CLCA) 6 million years ago (Mya) diverged hairless human and hairy chimpanzee lineages. All primates except humans can carry their babies without using their hands. A hairless mother would be forced to stand and walk upright. Her activities would be markedly limited. The male partner would have to collect food and carry it to her by hand to keep her and their baby from starving; irresponsible and selfish males could not have left their offspring. The mother would have sexually accepted her partner at any time as a reward for food. Sexual relations irrespective of estrus cycles might have strengthened the pair bond. Molecular and paleontological dating indicates that CLCA existed 6 Mya, and early hominin fossils show that they were bipeds, indicating that humanization from CLCA occurred rapidly. A single mutation in animals with scalp hair is known to induce hairless phenotype (ectodermal dysplasia). Bipedalism and hairlessness are disadvantageous traits; only those who could survive trials and tribulations in cooperation with family members must have been able to evolve as humans. PMID:22404045

  17. Dielectric Analysis for the Spherical and Rodlike Micelle Aggregates Formed from a Gemini Surfactant: Driving Forces of Micellization and Stability of Micelles.

    PubMed

    Wang, Shanshan; Zhao, Kongshuang

    2016-08-01

    The self-aggregation behavior of Gemini surfactant 12-2-12 (ethanediyl-1,2-bis(dimethyldodecylammonium bromide)) in water was investigated by dielectric relaxation spectroscopy (DRS) over a frequency range from 40 Hz to 110 MHz. Dielectric determination shows that well-defined spherical micelles formed when the concentration of the surfactant was above a critical micelle concentration CMC1 of 3 mM and rodlike micelles formed above CMC2, 16 mM. The formation mechanism of the spherical micelles and their transition mechanism to clubbed micelles were proposed by calculating the degree of counterion binding of the micelles. The interactions between the head groups and the hydrophobic chains of the surfactant led to the formation of the micelles, whereas the transition is mainly attributed to the interaction among the hydrophobic chains. By analyzing the dielectric relaxation observed at about 10(7) Hz based on the interface polarization theory, the permittivity and conductivity of micelle aggregates (spherical and clubbed) and volume fraction of micelles were calculated theoretically as well as the electrical properties of the solution medium. Furthermore, we also calculated the electrokinetic parameters of the micelle particle surface, surface conductivity, surface charge density, and zeta potential, using the relaxation parameters and phase parameters. On the basis of these results, the balance of forces controlling morphological transitions, interfacial electrokinetic properties, and the stability of the micelle aggregates was discussed. PMID:27396495

  18. Protein-protein interfaces from cytochrome c oxidase I evolve faster than nonbinding surfaces, yet negative selection is the driving force.

    PubMed

    Aledo, Juan Carlos; Valverde, Héctor; Ruíz-Camacho, Manuel; Morilla, Ian; López, Francisco Demetrio

    2014-01-01

    Respiratory complexes are encoded by two genomes (mitochondrial DNA [mtDNA] and nuclear DNA [nDNA]). Although the importance of intergenomic coadaptation is acknowledged, the forces and constraints shaping such coevolution are largely unknown. Previous works using cytochrome c oxidase (COX) as a model enzyme have led to the so-called "optimizing interaction" hypothesis. According to this view, mtDNA-encoded residues close to nDNA-encoded residues evolve faster than the rest of positions, favoring the optimization of protein-protein interfaces. Herein, using evolutionary data in combination with structural information of COX, we show that failing to discern the effects of interaction from other structural and functional effects can lead to deceptive conclusions such as the "optimizing hypothesis." Once spurious factors have been accounted for, data analysis shows that mtDNA-encoded residues engaged in contacts are, in general, more constrained than their noncontact counterparts. Nevertheless, noncontact residues from the surface of COX I subunit are a remarkable exception, being subjected to an exceptionally high purifying selection that may be related to the maintenance of a suitable heme environment. We also report that mtDNA-encoded residues involved in contacts with other mtDNA-encoded subunits are more constrained than mtDNA-encoded residues interacting with nDNA-encoded polypeptides. This differential behavior cannot be explained on the basis of predicted thermodynamic stability, as interactions between mtDNA-encoded subunits contribute more weakly to the complex stability than those interactions between subunits encoded by different genomes. Therefore, the higher conservation observed among mtDNA-encoded residues involved in intragenome interactions is likely due to factors other than structural stability. PMID:25359921

  19. Protein–Protein Interfaces from Cytochrome c Oxidase I Evolve Faster than Nonbinding Surfaces, yet Negative Selection Is the Driving Force

    PubMed Central

    Aledo, Juan Carlos; Valverde, Héctor; Ruíz-Camacho, Manuel; Morilla, Ian; López, Francisco Demetrio

    2014-01-01

    Respiratory complexes are encoded by two genomes (mitochondrial DNA [mtDNA] and nuclear DNA [nDNA]). Although the importance of intergenomic coadaptation is acknowledged, the forces and constraints shaping such coevolution are largely unknown. Previous works using cytochrome c oxidase (COX) as a model enzyme have led to the so-called “optimizing interaction” hypothesis. According to this view, mtDNA-encoded residues close to nDNA-encoded residues evolve faster than the rest of positions, favoring the optimization of protein–protein interfaces. Herein, using evolutionary data in combination with structural information of COX, we show that failing to discern the effects of interaction from other structural and functional effects can lead to deceptive conclusions such as the “optimizing hypothesis.” Once spurious factors have been accounted for, data analysis shows that mtDNA-encoded residues engaged in contacts are, in general, more constrained than their noncontact counterparts. Nevertheless, noncontact residues from the surface of COX I subunit are a remarkable exception, being subjected to an exceptionally high purifying selection that may be related to the maintenance of a suitable heme environment. We also report that mtDNA-encoded residues involved in contacts with other mtDNA-encoded subunits are more constrained than mtDNA-encoded residues interacting with nDNA-encoded polypeptides. This differential behavior cannot be explained on the basis of predicted thermodynamic stability, as interactions between mtDNA-encoded subunits contribute more weakly to the complex stability than those interactions between subunits encoded by different genomes. Therefore, the higher conservation observed among mtDNA-encoded residues involved in intragenome interactions is likely due to factors other than structural stability. PMID:25359921

  20. Non-additive Empirical Force Fields for Short-Chain Linear Alcohols: Methanol to Butanol. Hydration Free Energetics and Kirkwood-Buff Analysis Using Charge Equilibration Models

    PubMed Central

    Zhong, Yang; Patel, Sandeep

    2010-01-01

    Building upon the nonadditive electrostatic force field for alcohols based on the CHARMM charge equilibration (CHEQ) formalism, we introduce atom-pair specific solute-solvent Lennard-Jones (LJ) parameters for alcohol-water interaction force fields targeting improved agreement with experimental hydration free energies of a series of small molecule linear alcohols as well as ab initio water-alcohol geometries and energetics. We consider short-chain, linear alcohols from methanol to butanol as they are canonical small-molecule organic model compounds to represent the hydroxyl chemical functionality for parameterizing biomolecular force fields for proteins. We discuss molecular dynamics simulations of dilute aqueous solutions of methanol and ethanol in TIP4P-FQ water, with particular discussion of solution densities, structure defined in radial distribution functions, electrostatic properties (dipole moment distributions), hydrogen bonding patterns of water, as well as a Kirkwood-Buff (KB) integral analysis. Calculation of the latter provides an assessment of how well classical force fields parameterized to at least semi-quantitatively match experimental hydration free energies capture the microscopic structures of dilute alcohol solutions; the latter translate into macroscopic thermodynamic properties through the application of KB analysis. We find that the CHEQ alcohol force fields of this work semi-quantitatively match experimental KB integrals for methanol and ethanol mole fractions of 0.1 and 0.2. The force field combination qualitatively captures the concentration dependence of the alcohol-alcohol and water-water KB integrals, but due to inadequacies in the representation of the microscopic structures in such systems (which cannot be parameterized in any systematic fashion), a priori quantitative description of alcohol-water KB integrals remains elusive. PMID:20687517

  1. Intra-Articular Fms-Like Tyrosine Kinase 3 Ligand Expression Is a Driving Force in Induction and Progression of Arthritis

    PubMed Central

    Dehlin, Mats; Bokarewa, Maria; Rottapel, Robert; Foster, Simon J.; Magnusson, Mattias; Dahlberg, Leif E.; Tarkowski, Andrej

    2008-01-01

    Background One of the hallmarks of rheumatoid arthritis (RA) is hyperplasia and inflammation of the synovial tissue being characterized by in situ occurrence of highly differentiated leukocytes. Fms-like tyrosine kinase 3 (Flt3) has a crucial role in hematopoiesis, regulation of cell proliferation, differentiation and apoptosis. Typically, Flt3 is expressed on early myeloid and lymphoid progenitors and is activated by its soluble ligand (Flt3-L). The highly differentiated cellular pattern in the synovium of the RA patients made us hypothesize that Flt3-L, with its ability to induce proliferation and differentiation, could be of importance in induction and/or progression of arthritis. Methodology/Principal Findings To investigate occurrence of Flt3-L in RA we have measured its levels in matched serum and synovial fluid samples from 130 patients and 107 controls. To analyse the pro-inflammatory role of Flt3-L, we continuously overexpressed this protein locally in healthy mouse joints using homologous B-cell line transfected with Flt3-L gene. Additionally, recombinant Flt3-L was instillated intra-articularly in combination with peptidoglycans, a Toll Like Receptor 2-ligand with stong arthritogenic properties. Our results show significantly higher levels of Flt3-L in the synovial fluid as compared to serum levels in RA subjects (p = 0.0001). In addition, RA synovial fluid levels of Flt-3-L were significantly higher than these obtained from synovial fluids originating from non-inflammatory joint diseases (p = 0.022). Intra-articular administration of B-cell line transfected with Flt3-L gene resulted in highly erosive arthritis while inoculation of the same B-cell line without hyperexpression of Flt3-L did not induce erosivity and only in a minority of cases caused synovial proliferation! Flt3-ligand potentiated peptidoglycan induced arthritis as compared to mice injected with peptidoglycan alone (p<0.05). Conclusions/Significance Our findings indicate that Flt3

  2. Molecular diversity of Chickpea chlorotic dwarf virus in Sudan: high rates of intra-species recombination - a driving force in the emergence of new strains.

    PubMed

    Kraberger, Simona; Kumari, Safaa G; Hamed, Abdelmagid A; Gronenborn, Bruno; Thomas, John E; Sharman, Murray; Harkins, Gordon W; Muhire, Brejnev M; Martin, Darren P; Varsani, Arvind

    2015-01-01

    In Sudan Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus, family Geminiviridae) is an important pathogen of pulses that are grown both for local consumption, and for export. Although a few studies have characterised CpCDV genomes from countries in the Middle East, Africa and the Indian subcontinent, little is known about CpCDV diversity in any of the major chickpea production areas in these regions. Here we analyse the diversity of 146 CpCDV isolates characterised from pulses collected across the chickpea growing regions of Sudan. Although we find that seven of the twelve known CpCDV strains are present within the country, strain CpCDV-H alone accounted for ∼73% of the infections analysed. Additionally we identified four new strains (CpCDV-M, -N, -O and -P) and show that recombination has played a significant role in the diversification of CpCDV, at least in this region. Accounting for observed recombination events, we use the large amounts of data generated here to compare patterns of natural selection within protein coding regions of CpCDV and other dicot-infecting mastrevirus species. PMID:25444941

  3. Ammonium as a Driving Force of Plant Diversity and Ecosystem Functioning: Observations Based on 5 Years' Manipulation of N Dose and Form in a Mediterranean Ecosystem

    PubMed Central

    Dias, Teresa; Clemente, Adelaide; Martins-Loução, Maria Amélia; Sheppard, Lucy; Bobbink, Roland; Cruz, Cristina

    2014-01-01

    Enhanced nitrogen (N) availability is one of the main drivers of biodiversity loss and degradation of ecosystem functions. However, in very nutrient-poor ecosystems, enhanced N input can, in the short-term, promote diversity. Mediterranean Basin ecosystems are nutrient-limited biodiversity hotspots, but no information is available on their medium- or long-term responses to enhanced N input. Since 2007, we have been manipulating the form and dose of available N in a Mediterranean Basin maquis in south-western Europe that has low ambient N deposition (<4 kg N ha−1 yr−1) and low soil N content (0.1%). N availability was modified by the addition of 40 kg N ha−1 yr−1 as a 1∶1 NH4Cl to (NH4)2SO4 mixture, and 40 and 80 kg N ha−1 yr−1 as NH4NO3. Over the following 5 years, the impacts on plant composition and diversity (richness and evenness) and some ecosystem characteristics (soil extractable N and organic matter, aboveground biomass and % of bare soil) were assessed. Plant species richness increased with enhanced N input and was more related to ammonium than to nitrate. Exposure to 40 kg NH4+-N ha−1 yr−1 (alone and with nitrate) enhanced plant richness, but did not increase aboveground biomass; soil extractable N even increased under 80 kg NH4NO3-N ha−1 yr−1 and the % of bare soil increased under 40 kg NH4+-N ha−1 yr−1. The treatment containing less ammonium, 40 kg NH4NO3-N ha−1 yr−1, did not enhance plant diversity but promoted aboveground biomass and reduced the % of bare soil. Data suggest that enhanced NHy availability affects the structure of the maquis, which may promote soil erosion and N leakage, whereas enhanced NOx availability leads to biomass accumulation which may increase the fire risk. These observations are relevant for land use management in biodiverse and fragmented ecosystems such as the maquis, especially in conservation areas. PMID:24695101

  4. An analysis of the daily precipitation variability in the Himalayan orogen using a statistical parameterisation and its potential in driving landscape evolution models with stochastic climatic forcing

    NASA Astrophysics Data System (ADS)

    Deal, Eric; Braun, Jean

    2015-04-01

    parameters. We also demonstrate over what spatial and temporal scales this parameterisation applies and is stable. Applying the parameterisation over the Himalayan orogen reveals large-scale strike-perpendicular gradients in precipitation variability in addition to the long observed strike-perpendicular gradient in precipitation magnitude. This observation, combined with the theoretical work mentioned above, suggests that variability is an integral part of the interaction between climate and erosion. References Bras, R. L., & Tucker, G. E. (2000). A stochastic approach to modeling the role of rainfall variability in drainage basin evolution. Water Resources Research, 36(7), 1953-1964. doi:10.1029/2000WR900065 Lague, D. (2005). Discharge, discharge variability, and the bedrock channel profile. Journal of Geophysical Research, 110(F4), F04006. doi:10.1029/2004JF000259

  5. Shapiro steps for skyrmion motion on a washboard potential with longitudinal and transverse ac drives

    NASA Astrophysics Data System (ADS)

    Reichhardt, C.; Reichhardt, C. J. Olson

    2015-12-01

    We numerically study the behavior of two-dimensional skyrmions in the presence of a quasi-one-dimensional sinusoidal substrate under the influence of externally applied dc and ac drives. In the overdamped limit, when both dc and ac drives are aligned in the longitudinal direction parallel to the direction of the substrate modulation, the velocity-force curves exhibit classic Shapiro step features when the frequency of the ac drive matches the washboard frequency that is dynamically generated by the motion of the skyrmions over the substrate, similar to previous observations in superconducting vortex systems. In the case of skyrmions, the additional contribution to the skyrmion motion from a nondissipative Magnus force shifts the location of the locking steps to higher dc drives, and we find that the skyrmions move at an angle with respect to the direction of the dc drive. For a longitudinal dc drive and a perpendicular or transverse ac drive, the overdamped system exhibits no Shapiro steps; however, when a finite Magnus force is present, we find pronounced transverse Shapiro steps along with complex two-dimensional periodic orbits of the skyrmions in the phase-locked regimes. Both the longitudinal and transverse ac drives produce locking steps whose widths oscillate with increasing ac drive amplitude. We examine the role of collective skyrmion interactions and find that additional fractional locking steps occur for both longitudinal and transverse ac drives. At higher skyrmion densities, the system undergoes a series of dynamical order-disorder transitions, with the skyrmions forming a moving solid on the phase locking steps and a fluctuating dynamical liquid in regimes between the steps.

  6. [Using the 'Driving Force - Pressure - State - Exposure - Effects - Action' (DPSEEA) model of the World Health Organization (WHO) for the analysis of risks related to the use of pesticides in agricultural activities in the state of Rio de Janeiro].

    PubMed

    Araújo-Pinto, Mariana de; Peres, Frederico; Moreira, Josino Costa

    2012-06-01

    This paper seeks to apply the DPSEEA model (WHO) to identify major health risks to rural workers and the environment associated with the intensive use of pesticides in the State of Rio de Janeiro, based on an analysis of official public documents and a review of the (national and international) literature. It emphasizes the two main representative branches of agriculture in the state: family farming in the mountain region and the monoculture of sugarcane in the flatlands. Results show that the bulk of the determinants identified in the DPSEEA Matrix are related to deficiencies in actions for monitoring and surveillance of pesticide use, as well as a lack of technical assistance provided by the Public Sector in Rio de Janeiro State. Most of the actions developed in the state address the effects of pesticide exposure and, to a lesser extent, exposure to these chemicals, failing to focus on the higher levels of the matrix (such as driving forces and pressure). These are considered, by several authors, as the most appropriate when tackling the complex and systemic issues, such as the scope of this paper. By means of this study, an attempt was made to enable the application of the DPSEEA Model to assist in environmental and occupational health surveillance initiatives. PMID:22699645

  7. The community as a driving force.

    PubMed

    1993-12-01

    A Workshop on Effective Strategies for Sustainable Community-based Family Planning (FP) and Maternal and Child Health (MCH) was held on October 14-23, 1993, as part of an Asian regional project focusing on women. Bangladesh, China, Laos, Nepal, the Philippines, and Viet Nam were represented at the workshop. The program introduced participants to effective community participation strategies in FP and MCH in Indonesia and allowed for the exchange of information. The UN Population Fund expressed support and encouragement for the exchange and recognition of Indonesia's government support for efforts at regional exchanges. Indonesia established integrated service posts or "Posyandu" in villages during the 1980s for women volunteers as health advocates. FP/MCH was later integrated in these health posts. The service posts aim to reduce infant mortality and maternal mortality through growth monitoring of children aged under five years, provision of FP, nutrition services for pregnant mothers, immunization, and monitoring of high-risk pregnancies. Trained volunteers and community people are aides to either government personnel or nongovernmental (NGO) workers. The Indonesian government FP program evolved from a program "for" the people, to "with" the people, and finally "by" the people. Fees for contraception, which are still below retail prices, are being introduced as a means of achieving sustainability. The government trains doctors and midwives in FP. NGOs such as Yayasan Kusuma Buana (YKB) in Jakarta provide a mix of quality services. YKB is active in promoting awareness of FP. Community outreach is achieved through mothers' classes, urban Posyandu services, and training of traditional birth attendants. The Indonesian Planned Parenthood Association maintains self-reliance programs in FP/MCH. Day-care centers and youth counseling centers are used in promoting FP/MCH. YKB methods were demonstrated for workshop participants (posters used in local shops and awareness activities for school health programs). Workshop participants were exposed to many activities in FP/MCH. Participants learned the importance of government commitment and the importance of people's acceptance that FP is necessary for improving the quality of life. PMID:12287329

  8. Refiners respond to strategic driving forces

    SciTech Connect

    Gonzalez, R.G.

    1996-05-01

    Better days should lie ahead for the international refining industry. While political unrest, lingering uncertainty regarding environmental policies, slowing world economic growth, over capacity and poor image will continue to plague the industry, margins in most areas appear to have bottomed out. Current margins, and even modestly improved margins, do not cover the cost of capital on certain equipment nor provide the returns necessary to achieve reinvestment economics. Refiners must determine how to improve the financial performance of their assets given this reality. Low margins and returns are generally characteristic of mature industries. Many of the business strategies employed by emerging businesses are no longer viable for refiners. The cost-cutting programs of the `90s have mainly been realized, leaving little to be gained from further reduction. Consequently, refiners will have to concentrate on increasing efficiency and delivering higher value products to survive. Rather than focusing solely on their competition, companies will emphasize substantial improvements in their own operations to achieve financial targets. This trend is clearly shown by the growing reliance on benchmarking services.

  9. Collaboration: The Driving Force for Success

    ERIC Educational Resources Information Center

    Rourke, James; Boone, Elizabeth

    2008-01-01

    Nestled in the mountains and surrounded by Christmas tree farms, Ashe County Middle School is a small, rural school in the far northwest corner of North Carolina. Recognized nationally for its fine academic and co-curricular programs, the school prepares students for high school and real-life situations by teaching important concepts, essential…

  10. Inflammation: a driving force speeds cancer metastasis

    PubMed Central

    Wu, Yadi; Zhou, Binhua P.

    2013-01-01

    It has been increasingly recognized that tumor microenvironment plays an important role in carcinogenesis. Inflammatory component is present and contributes to tumor proliferation, angiogenesis, metastasis, and resistance to hormonal and chemotherapy. This review highlights the role of inflammation in the tumor metastasis. We focus on the function of proinflammatory factors, particularly cytokines during tumor metastasis. Understanding of the mechanisms by which inflammation contributes to metastasis will lead to innovative approach for treating cancer. PMID:19770594

  11. Corporate Universities: Driving Force of Knowledge Innovation

    ERIC Educational Resources Information Center

    Rademakers, Martijn

    2005-01-01

    Purpose: This paper aims to explain the rapid emergence of corporate universities on the basis of fundamental developments presently shaping the economy and society on a world-wide scale. Design/methodology/approach: Four key forms of innovation are identified and combined with the corporate university concept. The paper explains why corporate…

  12. The drive-wise project: driving simulator training increases real driving performance in healthy older drivers

    PubMed Central

    Casutt, Gianclaudio; Theill, Nathan; Martin, Mike; Keller, Martin; Jäncke, Lutz

    2014-01-01

    Background: Age-related cognitive decline is often associated with unsafe driving behavior. We hypothesized that 10 active training sessions in a driving simulator increase cognitive and on-road driving performance. In addition, driving simulator training should outperform cognitive training. Methods: Ninety-one healthy active drivers (62–87 years) were randomly assigned to one of three groups: (1) a driving simulator training group, (2) an attention training group (vigilance and selective attention), or (3) a control group. The main outcome variables were on-road driving and cognitive performance. Seventy-seven participants (85%) completed the training and were included in the analyses. Training gains were analyzed using a multiple regression analysis with planned orthogonal comparisons. Results: The driving simulator-training group showed an improvement in on-road driving performance compared to the attention-training group. In addition, both training groups increased cognitive performance compared to the control group. Conclusion: Driving simulator training offers the potential to enhance driving skills in older drivers. Compared to the attention training, the simulator training seems to be a more powerful program for increasing older drivers' safety on the road. PMID:24860497

  13. SCM-Forcing Data

    DOE Data Explorer

    Xie, Shaocheng; Tang,Shuaiqi; Zhang,Yunyan; Zhang,Minghua

    2016-07-01

    Single-Column Model (SCM) Forcing Data are derived from the ARM facility observational data using the constrained variational analysis approach (Zhang and Lin 1997 and Zhang et al., 2001). The resulting products include both the large-scale forcing terms and the evaluation fields, which can be used for driving the SCMs and Cloud Resolving Models (CRMs) and validating model simulations.

  14. Metal band drives in spacecraft mechanisms

    NASA Technical Reports Server (NTRS)

    Maus, Daryl

    1993-01-01

    Transmitting and changing the characteristics of force and stroke is a requirement in nearly all mechanisms. Examples include changing linear to rotary motion, providing a 90 deg change in direction, and amplifying stroke or force. Requirements for size, weight, efficiency and reliability create unique problems in spacecraft mechanisms. Flexible metal band and cam drive systems provide powerful solutions to these problems. Band drives, rack and pinion gears, and bell cranks are compared for effectiveness. Band drive issues are discussed including materials, bend radius, fabrication, attachment and reliability. Numerous mechanisms are shown which illustrate practical applications of band drives.

  15. Mental workload and driving

    PubMed Central

    Paxion, Julie; Galy, Edith; Berthelon, Catherine

    2014-01-01

    The aim of this review is to identify the most representative measures of subjective and objective mental workload in driving, and to understand how the subjective and objective levels of mental workload influence the performance as a function of situation complexity and driving experience, i.e., to verify whether the increase of situation complexity and the lack of experience increase the subjective and physiological levels of mental workload and lead to driving performance impairments. This review will be useful to both researchers designing an experimental study of mental workload and to designers of drivers’ training content. In the first part, we will broach the theoretical approach with two factors of mental workload and performance, i.e., situation complexity and driving experience. Indeed, a low complex situation (e.g., highways), or conversely a high complex situation (e.g., town) can provoke an overload. Additionally, performing the driving tasks implies producing a high effort for novice drivers who have not totally automated the driving activity. In the second part, we will focus on subjective measures of mental workload. A comparison of questionnaires usually used in driving will allow identifying the most appropriate ones as a function of different criteria. Moreover, we will review the empirical studies to verify if the subjective level of mental workload is high in simple and very complex situations, especially for novice drivers compared to the experienced ones. In the third part, we will focus on physiological measures. A comparison of physiological indicators will be realized in order to identify the most correlated to mental workload. An empirical review will also take the effect of situation complexity and experience on these physiological indicators into consideration. Finally, a more nuanced comparison between subjective and physiological measures will be established from the impact on situation complexity and experience. PMID:25520678

  16. Dementia and driving

    MedlinePlus

    ... not drive at times of the day when traffic is heaviest. Do not drive when the weather is bad. Do not drive long distances. Drive only on roads the person is used to. Caregivers should try to lessen ...

  17. Parallel RF force driven by the inhomogeneity of power absorption in magnetized plasma.

    PubMed

    Gao, Zhe; Chen, Jiale; Fisch, Nathaniel J

    2013-06-01

    A nonlinear parallel force can be exerted through the inhomogeneity of rf resonant absorption in a magnetized plasma. While providing no integrated force over a plasma volume, this force can redistribute momentum parallel to the magnetic field. Because flows and currents parallel to the magnetic field encounter different resistances, this redistribution can play a large role, in addition to the role played by the direct absorption of parallel momentum. For nearly perpendicular propagating waves in a tokamak plasma, this additional force is expected to affect significantly the toroidal rf-driven current and the toroidal flow drive. PMID:25167505

  18. Camshaft driving device for internal combustion engine

    SciTech Connect

    Ebesu, H.

    1988-06-14

    A camshaft driving device for use in a double overhead cam type internal combustion engine having a cylinder block, an upper deck formed at an upper portion of the cylinder block, a cylinder head disposed on the cylinder block, a driving shaft rotatably mounted at a lower portion of the cylinder block, and a pair of camshafts rotatably mounted at an upper portion of the cylinder head, is described comprising: driving force transmitting endless chain members engaging in the reduction gear means for transmitting a driving force from the driving shaft to the pair of camshaft through the reduction gear means. The camshaft driving device further including chain tensioners for tightening the chain, a nozzle means for supplying a lubricating oil to the driving force chain members on the side of the drive shaft and an oil guide wall formed immediately above the sprocket of the transmitting portion of the reduction gear means at a lower end portion of the journal boss and lapping thereover both in the radial direction and in the axial direction of the driving shaft. A mounting boss for mounting the reduction gear means thereon is formed on the upper deck of the cylinder block.

  19. A mechanism for the dynamo terms to sustain closed-flux current, including helicity balance, by driving current which crosses the magnetic field

    SciTech Connect

    Jarboe, T. R.; Nelson, B. A.; Sutherland, D. A.

    2015-07-15

    An analysis of imposed dynamo current drive (IDCD) [T.R. Jarboe et al., Nucl. Fusion 52 083017 (2012)] reveals: (a) current drive on closed flux surfaces seems possible without relaxation, reconnection, or other flux-surface-breaking large events; (b) the scale size of the key physics may be smaller than is often computationally resolved; (c) helicity can be sustained across closed flux; and (d) IDCD current drive is parallel to the current which crosses the magnetic field to produce the current driving force. In addition to agreeing with spheromak data, IDCD agrees with selected tokamak data.

  20. Stochastically forced zonal flows

    NASA Astrophysics Data System (ADS)

    Srinivasan, Kaushik

    This thesis investigates the dynamics of multiple zonal jets, that spontaneously emerge on the barotropic beta-plane, driven by a homogenous and rapidly decorrelating forcing and damped by bottom drag. Decomposing the barotropic vorticity equation into the zonal-mean and eddy equations, and neglecting the eddy-eddy interactions, defines the quasi-linear (QL) system. Numerical solution of the QL system shows zonal jets with length scales comparable to jets obtained by solving the nonlinear (NL) system. Starting with the QL system, one can construct a deterministic equation for the evolution of the two-point single-time correlation function of the vorticity, from which one can obtain the Reynolds stress that drives the zonal mean flow. This deterministic system has an exact nonlinear solution, which is a homogenous eddy field with no jets. When the forcing is also isotropic in space, we characterize the linear stability of this jetless solution by calculating the critical stability curve in the parameter space and successfully comparing this analytic result with numerical solutions of the QL system. But the critical drag required for the onset of NL zonostrophic instability is up to a factor of six smaller than that for QL zonostrophic instability. The constraint of isotropic forcing is then relaxed and spatially anisotropic forcing is used to drive the jets. Meridionally drifting jets are observed whenever the forcing breaks an additional symmetry that we refer to as mirror, or reflexional symmetry. The magnitude of drift speed in our results shows a strong variation with both mu and beta: while the drift speed decreases almost linearly with decreasing mu, it actually increases as beta decreases. Similar drifting jets are also observed in QL, with the same direction (i.e. northward or southward) and similar magnitude as NL jet-drift. Starting from the laminar solution, and assuming a mean-flow that varies slowly with reference to the scale of the eddies, we obtain

  1. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction. PMID:12364804

  2. NGSI student activities in open source information analysis in support of the training program of the U.S. DOE laboratories for the entry into force of the additional protocol

    SciTech Connect

    Sandoval, M Analisa; Uribe, Eva C; Sandoval, Marisa N; Boyer, Brian D; Stevens, Rebecca S

    2009-01-01

    In 2008 a joint team from Los Alamos National Laboratory (LANL) and Brookhaven National Laboratory (BNL) consisting of specialists in training of IAEA inspectors in the use of complementary access activities formulated a training program to prepare the U.S. Doe laboratories for the entry into force of the Additional Protocol. As a major part of the support of the activity, LANL summer interns provided open source information analysis to the LANL-BNL mock inspection team. They were a part of the Next Generation Safeguards Initiative's (NGSI) summer intern program aimed at producing the next generation of safeguards specialists. This paper describes how they used open source information to 'backstop' the LANL-BNL team's effort to construct meaningful Additional Protocol Complementary Access training scenarios for each of the three DOE laboratories, Lawrence Livermore National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory.

  3. Magnetostrictive direct drive motors

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1992-01-01

    A new rare earth alloy, Terfenol-D, combines low frequency operation and extremely high energy density with high magnetostriction. Its material properties make it suitable as a drive element for actuators requiring high output torque. The high strains, the high forces and the high controllability of Terfenol alloys provide a powerful and challenging basis for new ways to generate motion in actuators. Two prototypes of motors using Terfenol-D rods were developed at NASA Goddard. The basic principles of operation are provided of the motor along with other relevant details. A conceptual design of a torque limiting safety clutch/brake under development is illustrated. Also, preliminary design drawings of a linear actuator using Terfenol-D is shown.

  4. QUICK RELEASABLE DRIVE

    DOEpatents

    Dickson, J.J.

    1958-07-01

    A quick releasable mechanical drive system suitable for use in a nuclear reactor is described. A small reversible motor positions a control rod by means of a worm and gear speed reducer, a magnetic torque clutch, and a bell crank. As the control rod is raised to the operating position, a heavy coil spring is compressed. In the event of an emergency indicated by either a''scram'' signal or a power failure, the current to the magnetic clutch is cut off, thereby freeing the coil spring and the bell crank positioner from the motor and speed reduction gearing. The coil spring will immediately act upon the bell crank to cause the insertion of the control rod. This arrangement will allow the slow, accurate positioning of the control rod during reactor operation, while providing an independent force to rapidly insert the rod in the event of an emergency.

  5. Piezoresistive cantilever force-clamp system

    SciTech Connect

    Park, Sung-Jin; Petzold, Bryan C.; Pruitt, Beth L.; Goodman, Miriam B.

    2011-04-15

    We present a microelectromechanical device-based tool, namely, a force-clamp system that sets or ''clamps'' the scaled force and can apply designed loading profiles (e.g., constant, sinusoidal) of a desired magnitude. The system implements a piezoresistive cantilever as a force sensor and the built-in capacitive sensor of a piezoelectric actuator as a displacement sensor, such that sample indentation depth can be directly calculated from the force and displacement signals. A programmable real-time controller operating at 100 kHz feedback calculates the driving voltage of the actuator. The system has two distinct modes: a force-clamp mode that controls the force applied to a sample and a displacement-clamp mode that controls the moving distance of the actuator. We demonstrate that the system has a large dynamic range (sub-nN up to tens of {mu}N force and nm up to tens of {mu}m displacement) in both air and water, and excellent dynamic response (fast response time, <2 ms and large bandwidth, 1 Hz up to 1 kHz). In addition, the system has been specifically designed to be integrated with other instruments such as a microscope with patch-clamp electronics. We demonstrate the capabilities of the system by using it to calibrate the stiffness and sensitivity of an electrostatic actuator and to measure the mechanics of a living, freely moving Caenorhabditis elegans nematode.

  6. Piezoresistive cantilever force-clamp system

    PubMed Central

    Park, Sung-Jin; Petzold, Bryan C.; Goodman, Miriam B.; Pruitt, Beth L.

    2011-01-01

    We present a microelectromechanical device-based tool, namely, a force-clamp system that sets or “clamps” the scaled force and can apply designed loading profiles (e.g., constant, sinusoidal) of a desired magnitude. The system implements a piezoresistive cantilever as a force sensor and the built-in capacitive sensor of a piezoelectric actuator as a displacement sensor, such that sample indentation depth can be directly calculated from the force and displacement signals. A programmable real-time controller operating at 100 kHz feedback calculates the driving voltage of the actuator. The system has two distinct modes: a force-clamp mode that controls the force applied to a sample and a displacement-clamp mode that controls the moving distance of the actuator. We demonstrate that the system has a large dynamic range (sub-nN up to tens of μN force and nm up to tens of μm displacement) in both air and water, and excellent dynamic response (fast response time, <2 ms and large bandwidth, 1 Hz up to 1 kHz). In addition, the system has been specifically designed to be integrated with other instruments such as a microscope with patch-clamp electronics. We demonstrate the capabilities of the system by using it to calibrate the stiffness and sensitivity of an electrostatic actuator and to measure the mechanics of a living, freely moving Caenorhabditis elegans nematode. PMID:21529009

  7. EPS forces in Bacillus subtilis biofilms

    NASA Astrophysics Data System (ADS)

    Zhang, Wenbo; Angelini, Thomas; Tsai, Shih-Ming; Nixon, Ryan

    2014-03-01

    Bacteria have evolved to congregate in complex communities known as biofilms. The structure that holds a biofilm together is a matrix called extracellular polymeric substance (EPS). It has been observed in previous studies that EPS up-regulation occurs when the nutrient levels fall below a threshold concentration; this increase in EPS concentration produces an osmotic pressure that forces the colony to spread outward. This osmotic pressure may drive nutrient uptake, but the stresses generated by the EPS matrix has never been measured. Here we present measurements of the forces exerted by a biofilm on its supporting substrate and on its fluid nutrients. In our experiments, we use a technique analogous to traction force microscopy to measure strain in agar nutrient substrates imposed by Bacillus subtilis biofilms. By running additional test to measure the permeability and elastic modulus of the agar, we can estimate the pressure generated by the biofilm.

  8. The Energetics of Motivated Cognition: A Force-Field Analysis

    ERIC Educational Resources Information Center

    Kruglanski, Arie W.; Belanger, Jocelyn J.; Chen, Xiaoyan; Kopetz, Catalina; Pierro, Antonio; Mannetti, Lucia

    2012-01-01

    A force-field theory of motivated cognition is presented and applied to a broad variety of phenomena in social judgment and self-regulation. Purposeful cognitive activity is assumed to be propelled by a "driving force" and opposed by a "restraining force". "Potential" driving force represents the maximal amount of energy an individual is prepared…

  9. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique

    PubMed Central

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field. PMID:26418550

  10. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique.

    PubMed

    Pichardo, Samuel; Silva, Rafael R C; Rubel, Oleg; Curiel, Laura

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field. PMID:26418550

  11. Force measurements during vibration testing

    SciTech Connect

    Smallwood, D.O.; Coleman, R.G.

    1993-12-31

    Experimental measurements of force into a ``rigid`` test item representing a typical system level vibration test were conducted to evaluate several methods of force measurements. The methods evaluated included: (1) Direct measurement with force gages between the test item and the fixturing; (2) Measurement of the force at the shaker/fixture interface and correcting the force required to drive the fixturing using two methods, (a) mass subtraction and (b) SWAT (sum of weighted accelerations technique), (3) Force deduced from voltage and current needed to drive the test item. All of the methods worked over a limited frequency range of five to a few hundred Hertz. The widest bandwidth was achieved with force at the shaker/fixture interface with SWAT corrections and from the voltage and current measurements.

  12. Direct Cytoskeleton Forces Cause Membrane Softening in Red Blood Cells

    PubMed Central

    Rodríguez-García, Ruddi; López-Montero, Iván; Mell, Michael; Egea, Gustavo; Gov, Nir S.; Monroy, Francisco

    2015-01-01

    Erythrocytes are flexible cells specialized in the systemic transport of oxygen in vertebrates. This physiological function is connected to their outstanding ability to deform in passing through narrow capillaries. In recent years, there has been an influx of experimental evidence of enhanced cell-shape fluctuations related to metabolically driven activity of the erythroid membrane skeleton. However, no direct observation of the active cytoskeleton forces has yet been reported to our knowledge. Here, we show experimental evidence of the presence of temporally correlated forces superposed over the thermal fluctuations of the erythrocyte membrane. These forces are ATP-dependent and drive enhanced flickering motions in human erythrocytes. Theoretical analyses provide support for a direct force exerted on the membrane by the cytoskeleton nodes as pulses of well-defined average duration. In addition, such metabolically regulated active forces cause global membrane softening, a mechanical attribute related to the functional erythroid deformability. PMID:26083919

  13. [Driving licenses and medical fitness].

    PubMed

    Sénéchal, Antoine; Manaouil, Cécile

    2015-09-01

    The Highway Code requires that any vehicle driver is constantly in a state and in position of performing easily and without delay all the maneuvers required of them. What about a vehicle driver suffering from a medical condition that does not allow it to meet the requirements of the Highway Code? While it may seem obvious that some diseases irrefutably presumed inability to drive, the regulatory authority had to answer a number of questions. What people should be subject to medical control of driving ability? What constitutes control? Who may be responsible for this control? The government, through a decree dated 17 July 2012 relating to medical control of driving ability, came to ask a new legal framework in this area meets all of these issues. In addition, a decree of 31 July 2012 came to specify the implementation rules for monitoring medical fitness to drive. PMID:25900083

  14. Exposure to Movie Reckless Driving in Early Adolescence Predicts Reckless, but Not Inattentive Driving

    PubMed Central

    Kostermans, Evelien; Stoolmiller, Mike; de Leeuw, Rebecca N. H.; Engels, Rutger C. M. E.; Sargent, James D.

    2014-01-01

    Objective We examine the association between exposure to depictions of reckless driving in movies and unsafe driving, modeling inattentive and reckless driving as separate outcomes. Methods Data were obtained by telephone from 1,630 US adolescents aged 10 to 14 years at baseline who were drivers at a survey 6 years later. Exposure to movie reckless driving was measured based on movies seen from a randomly selected list of 50 movie titles that had been content coded for reckless driving among characters. Associations were tested with inattentive and reckless driving behaviors in the subsequent survey–controlling for baseline age, sex, socioeconomic status, parental education, school performance, extracurricular activities, daily television and video/computer game exposure, number of movies watched per week, self-regulation and sensation seeking. Results Exposure to movie reckless driving was common, with approximately 10% of movie characters having driven recklessly. Confirmatory factor analysis revealed a significant distinction between items tapping reckless and inattentive driving at the 6th wave. Age and exposure to movie reckless driving at baseline were directly associated with wave-6 reckless (but not inattentive) driving. Additionally, growth in sensation seeking mediated a prospective relation between the total number of movies watched per week at baseline and reckless driving, independent of exposure to movie reckless driving. Males and high sensation seekers reported lower seatbelt usage and more reckless driving, whereas lower self-regulation predicted inattentive driving. Discussion In this study, exposure to movie reckless driving during early adolescence predicted adolescents’ reckless driving, suggesting a direct modeling effect. Other aspects of movies were also associated with reckless driving, with that association mediated through growth in sensation seeking. Predictors of reckless driving were different from predictors of inattentive driving

  15. Camshaft driving system for internal combustion engine

    SciTech Connect

    Hiroshima, K.A.

    1987-06-23

    This patent describes camshaft driving system for a double overhead camshaft engine cylinder rows extend parallel to the crankshaft of the engine. The second cylinder row is rearwardly displaced from the first cylinder row in the axial direction of the crankshaft so that vacant spaces are formed respectively behind the first cylinder row and in front of the second cylinder row. All the pistons in the cylinders of the first and second cylinder rows are connected to the crankshaft and a pair of camshafts for driving the intake and exhaust valves are provided in the cylinder head of each cylinder row to extend in the direction of the crankshaft. The camshaft driving system comprises a timing pulley provided on one of the intake and exhaust camshafts of each cylinder row to rotate together with the camshaft; A crank pulley is driven by the crankshaft; A first driving force transmission means transmits rotation of the crank pulley to the timing pulleys of the first and second cylinder rows; a second driving force transmission means transmits rotation of the timing pulley of the first cylinder row to the other of the camshafts of the first cylinder row; and a third driving force transmission means transmits rotation of the timing pulley of the second cylinder row to the other of the camshafts of the second cylinder row. The second driving force transmission means is disposed in the vacant space behind the first cylinder row and the third driving force transmission means is disposed in the vacant space in front of the second cylinder row.

  16. Extended Driving Impairs Nocturnal Driving Performances

    PubMed Central

    Sagaspe, Patricia; Taillard, Jacques; Åkerstedt, Torbjorn; Bayon, Virginie; Espié, Stéphane; Chaumet, Guillaume; Bioulac, Bernard; Philip, Pierre

    2008-01-01

    Though fatigue and sleepiness at the wheel are well-known risk factors for traffic accidents, many drivers combine extended driving and sleep deprivation. Fatigue-related accidents occur mainly at night but there is no experimental data available to determine if the duration of prior driving affects driving performance at night. Participants drove in 3 nocturnal driving sessions (3–5am, 1–5am and 9pm–5am) on open highway. Fourteen young healthy men (mean age [±SD] = 23.4 [±1.7] years) participated Inappropriate line crossings (ILC) in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were measured. Compared to the short (3–5am) driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 (95% CI, 1.1 to 6.0; P<.05) for the intermediate (1–5am) driving session and by 4.0 (CI, 1.7 to 9.4; P<.001) for the long (9pm–5am) driving session. Compared to the reference session (9–10pm), the incidence rate ratio of inappropriate line crossings were 6.0 (95% CI, 2.3 to 15.5; P<.001), 15.4 (CI, 4.6 to 51.5; P<.001) and 24.3 (CI, 7.4 to 79.5; P<.001), respectively, for the three different durations of driving. Self-rated fatigue and sleepiness scores were both positively correlated to driving impairment in the intermediate and long duration sessions (P<.05) and increased significantly during the nocturnal driving sessions compared to the reference session (P<.01). At night, extended driving impairs driving performances and therefore should be limited. PMID:18941525

  17. Crossflow force transducer. [LMFBR

    SciTech Connect

    Mulcahy, T M

    1982-05-01

    A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related.

  18. Electrical drive for automobile

    SciTech Connect

    Fobbs, H.

    1980-09-16

    Electrical apparatus for driving an automobile is described that is comprised of a dc motor operationally connected to the rear axle through a drive shaft with the motor energized from storage batteries and recharged from alternators coupled to the drive shaft adjacent a clutch at the rear end of the automobile through an auxiliary drive shaft.

  19. Coaxial Redundant Drives

    NASA Technical Reports Server (NTRS)

    Brissette, R.

    1983-01-01

    Harmonic drives allow redundancy and high out put torque in small package. If main drive fails, standby drive takes over and produces torque along same axis as main drive. Uses include power units in robot for internal pipeline inspection, manipulators in deep submersible probes or other applications in which redundancy protects against costly failures.

  20. Dynamics and control of instrumented harmonic drives

    NASA Technical Reports Server (NTRS)

    Kazerooni, H.; Ellis, S. R. (Principal Investigator)

    1995-01-01

    Since torque in harmonic drives is transmitted by a pure couple, harmonic drives do not generate radial forces and therefore can be instrumented with torque sensors without interference from radial forces. The installation of torque sensors on the stationary component of harmonic drives (the Flexipline cup in this research work) produce backdrivability needed for robotic and telerobotic compliant maneuvers. Backdrivability of a harmonic drive, when used as torque increaser, means that the output shaft can be rotated via finite amount of torque. A high ratio harmonic drive is non-backdrivable because its output shaft cannot be turned by applying a torque on it. This article first develops the dynamic behavior of a harmonic drive, in particular the non-backdrivability, in terms of a sensitivity transfer function. The instrumentation of the harmonic drive with torque sensor is then described. This leads to a description of the control architecture which allows modulation of the sensitivity transfer function within the limits established by the closed-loop stability. A set of experiments on an active hand controller, powered by a DC motor coupled to an instrumented harmonic drive, is given to exhibit this method's limitations.

  1. 75 FR 6643 - U.S. Air Force Academy Board of Visitors; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-10

    ... Force Academy (USAFA) Board of Visitors (BoV) will meet in Harmon Hall, 2304 Cadet Drive, Suite 3300 at... covered by subsection (c)(6) of 5 U.S.C. 552b. Public attendance at the open portions of this USAFA BoV... of the meeting room. In addition, any member of the public wishing to provide input to the USAFA...

  2. Electric drive motors for industrial robots

    NASA Astrophysics Data System (ADS)

    Fichtner, K.

    1985-04-01

    In robotized industrial plants it is possible to use electric motors in the technological process and also for control, assembly, transport, testing, and measurements. Particularly suitable for these applications are permanent-magnet d.c. motors. A new special series was developed for industrial robots with hinge joints in kinematic pairs. The complete drive includes thyristors or transistor controls with regulators and, if necessary, a line transformer as well as a servomotor with tachometer and odometer for speed, current, and position control. The drive is coupled to a robot tong through mechanical torque and force converters. In addition to a 0 to 4000 rpm speed regulation, without wobble at low speeds, and a high torque-to-weight ratio for repetitive short-time heavy duty, these low-inertia motors develop high starting and accelerating torques over the entire speed range. They operate from a 1 to O 220 V a.c. line through a rectifier. The motors are totally enclosed, or of open construction for better ventilation. Their windings have class F insulation for operation at ambient temperatures up to 40 C.

  3. Solar array drive system

    NASA Technical Reports Server (NTRS)

    Berkopec, F. D.; Sturman, J. C.; Stanhouse, R. W.

    1976-01-01

    A solar array drive system consisting of a solar array drive mechanism and the corresponding solar array drive electronics is being developed. The principal feature of the solar array drive mechanism is its bidirectional capability which enables its use in mechanical redundancy. The solar array drive system is of a widely applicable design. This configuration will be tested to determine its acceptability for generic mission sets. Foremost of the testing to be performed is the testing for extended duration.

  4. Quantification of Staphylococcus aureus adhesion forces on various dental restorative materials using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Merghni, Abderrahmen; Kammoun, Dorra; Hentati, Hajer; Janel, Sébastien; Popoff, Michka; Lafont, Frank; Aouni, Mahjoub; Mastouri, Maha

    2016-08-01

    In the oral cavity dental restorative biomaterials can act as a reservoir for infection with opportunistic Staphylococcus aureus pathogen, which can lead to the occurrence of secondary caries and treatment failures. Our aim was to evaluate the adhesion forces by S. aureus on four dental restorative biomaterials and to correlate this finding to differences in specific surface characteristics. Additionally, the influence of salivary conditioning films in exerted adhesion forces was investigated. The substrate hydrophobicity was measured by goniometer and the surface free energy was calculated using the equilibrium advancing contact angle values of water, formamide, and diiodomethane on the tested surfaces. The surface roughness was determined using atomic force microscope (AFM). Additionally, cell force spectroscopy was achieved to quantify the forces that drive cell-substrate interactions. S. aureus bacterium exerted a considerable adhesion forces on various dental restorative materials, which decreased in the presence of saliva conditioning film. The influence of the surface roughness and free energy in initial adhesion appears to be more important than the effect of hydrophobicity, either in presence or absence of saliva coating. Hence, control of surface properties of dental restorative biomaterials is of crucial importance in preventing the attachment and subsequent the biofilm formation.

  5. Repulsive force actuated rotary micromirror

    NASA Astrophysics Data System (ADS)

    He, Siyuan; Ben Mrad, Ridha

    2004-09-01

    In this paper, a novel repulsive force based rotary micromirror is proposed. A repulsive force is produced in the rotary micromirror and the mirror plate is pushed up and away from the substrate. Therefore the rotation angle of the micromirror is not limited to the space underneath the mirror plate and thus the "pull-in" effect is completely circumvented. The novel rotary micromirror can achieve a large rotation angle with a large mirror plate. In addition the novel micromirror has a very simple structure and can be fabricated by standard surface micromachining technology. Numerical simulation is used to verify the working principle of the novel micromirror. A prototype of the novel rotary micromirror is fabricated by a commercially available surface microfabrication process called MUMPs. The prototype has a mirror size of 300μm x 300μm. The experimental measurements show that the prototype can achieve a mechanical rotation of 2.25 degrees (an optical angle of 4.5 degrees) at a driving voltage of 170 volts. A conventional surface micromachined attractive force based rotary micromirror of the same size can only achieve an angle of 0.1~0.2 degree.

  6. Bottlebrush Polymer Additives for Binary Polymer Blends

    NASA Astrophysics Data System (ADS)

    Mah, Hui Zhen; Afzali, Pantea; Phan, Hanh; Qi, Luqing; Pesek, Stacy; Verduzco, Rafael; Stein, Gila

    Bottlebrush polymers are highly branched polymers that have been used in applications such as self-assembling photonics, drug delivery and stimuli-responsive surface coatings. However, they have not been widely studied as compatibilizers for polymer blends. In this study, bottlebrush polymers with poly(styrene-r-methyl methacrylate) side chains were used as additives for thin film blends of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The blends were heated above the glass transition temperature to drive phase separation, and the resulting morphology was characterized with atomic force microscopy and optical microscopy. Outcomes were compared with PS/PMMA blends that contain conventional compatibilizers such as linear random copolymers of poly(styrene-r-methyl methacrylate) and diblock PS-PMMA copolymers. The bottlebrush additive accumulates at the PS/PMMA interface and drives the formation of vesicle-like droplets that assemble into longer chains. The continuity of the chains depends on the blend composition, where a network structure is achieved close to the critical composition. This unusual microstructure was not observed with the other additives, and may be a consequence of preferential wetting of the bottlebrush by the PS phase.

  7. Control rod drive for reactor shutdown

    DOEpatents

    McKeehan, Ernest R.; Shawver, Bruce M.; Schiro, Donald J.; Taft, William E.

    1976-01-20

    A means for rapidly shutting down or scramming a nuclear reactor, such as a liquid metal-cooled fast breeder reactor, and serves as a backup to the primary shutdown system. The control rod drive consists basically of an in-core assembly, a drive shaft and seal assembly, and a control drive mechanism. The control rod is driven into the core region of the reactor by gravity and hydraulic pressure forces supplied by the reactor coolant, thus assuring that common mode failures will not interfere with or prohibit scramming the reactor when necessary.

  8. Future hard disk drive systems

    NASA Astrophysics Data System (ADS)

    Wood, Roger

    2009-03-01

    This paper briefly reviews the evolution of today's hard disk drive with the additional intention of orienting the reader to the overall mechanical and electrical architecture. The modern hard disk drive is a miracle of storage capacity and function together with remarkable economy of design. This paper presents a personal view of future customer requirements and the anticipated design evolution of the components. There are critical decisions and great challenges ahead for the key technologies of heads, media, head-disk interface, mechanics, and electronics.

  9. Driving and neurodegenerative diseases.

    PubMed

    Uc, Ergun Y; Rizzo, Matthew

    2008-09-01

    The proportion of elderly people in the general population is rising, resulting in greater numbers of drivers with neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. These neurodegenerative disorders impair cognition, visual perception, and motor function, leading to reduced driver fitness and greater crash risk. Yet neither medical diagnosis nor age alone is reliable enough to predict driver safety or crashes or to revoke the driving privileges of these individuals. Driving research utilizes tools such as questionnaires about driving habits and history, driving simulators, standardized road tests utilizing instrumented vehicles, and state driving records. Research challenges include outlining the evolution of driving safety, understanding the mechanisms of driving impairment, and developing a reliable and efficient standardized test battery for prediction of driver safety in neurodegenerative disorders. This information will enable healthcare providers to advise their patients with neurodegenerative disorders with more certainty, affect policy, and help develop rehabilitative measures for driving. PMID:18713573

  10. Gear bearing drive

    NASA Technical Reports Server (NTRS)

    Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  11. Combination spindle-drive system for high precision machining

    DOEpatents

    Gerth, Howard L.

    1977-07-26

    A combination spindle-drive is provided for fabrication of optical quality surface finishes. Both the spindle-and-drive utilize the spindle bearings for support, thereby removing the conventional drive-means bearings as a source of vibration. An airbearing spindle is modified to carry at the drive end a highly conductive cup-shaped rotor which is aligned with a stationary stator to produce torque in the cup-shaped rotor through the reaction of eddy currents induced in the rotor. This arrangement eliminates magnetic attraction forces and all force is in the form of torque on the cup-shaped rotor.

  12. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1987-01-01

    The driving and driven members of a magnetic drive are separated by en enlarged gap to provide clearance for a conduit or other member. Flux pins in the gap maintain the torque transmitting capability of the drive. The spacing between two of the flux pins is increased to provide space for the conduit.

  13. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1989-01-01

    The driving (30) and driven (32) members of a magnetic drive (20) are separated by an enlarged gap (35) to provide clearance for a conduit (23) or other member. Flux pins (40) in the gap (35) maintain the torque transmitting capability of the drive (20). The spacing between two of the flux pins is increased to provide space for the conduit (23).

  14. Sequential Dependencies in Driving

    ERIC Educational Resources Information Center

    Doshi, Anup; Tran, Cuong; Wilder, Matthew H.; Mozer, Michael C.; Trivedi, Mohan M.

    2012-01-01

    The effect of recent experience on current behavior has been studied extensively in simple laboratory tasks. We explore the nature of sequential effects in the more naturalistic setting of automobile driving. Driving is a safety-critical task in which delayed response times may have severe consequences. Using a realistic driving simulator, we find…

  15. Grieving while Driving

    ERIC Educational Resources Information Center

    Rosenblatt, Paul C.

    2004-01-01

    Secondary analysis of data from 84 people in 2 interview studies shows that some bereaved people grieve actively while driving. The grief can be intense, even years after a death. Grief while driving may erupt spontaneously or be set off by a wide range of reminders. Some bereaved people seem to save their grieving for times when they drive,…

  16. Configuring NIF for direct drive experiments

    SciTech Connect

    Eimerl, D.; Rothenberg, J.; Key, M.

    1995-07-11

    The National Ignition Facility (NIF) is a proposed 1.8 MJ laser facility for carrying out experiments in inertial confinement fusion, currently designed for indirect drive experiments. The direct drive approach is being pursued at the 30 kJ Omega facility at the University of Rochester. In this paper we discuss the modifications to the NIF laser that would be required for both indirect and direct drive experiments. A primary concern is the additional cost of adding direct drive capability to the facility.

  17. Food additives

    MedlinePlus

    Food additives are substances that become part of a food product when they are added during the processing or making of that food. "Direct" food additives are often added during processing to: Add nutrients ...

  18. Electric versus hydraulic drives

    SciTech Connect

    Not Available

    1983-01-01

    This volume records the proceedings of a conference organised by the Engineering Manufacturing Industries Division of the Institution of Mechanical Engineers. Topics considered include high performance position control - a review of the current state of developments; hydrostatic drives - present and future; electric drives - present and future trends; electrical and hydraulic drives for heavy industrial robots; the development of an electro-mechanical tilt system for the advanced passenger train; industrial hydraulic ring mains - effective or efficient. the comparison of performance of servo feed-drive systems; overhead crane drives; the future of d.c. servodrives; the choice of actuator for military systems; linear electro-hydraulic actuators; and actuation for industrial robots.

  19. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  20. Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Chia; Kramer, Corinne M.; Chen, Christopher S.; Reich, Daniel H.

    2012-02-01

    In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 μm were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells’ traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.

  1. Forced wetting and hydrodynamic assist

    NASA Astrophysics Data System (ADS)

    Blake, Terence D.; Fernandez-Toledano, Juan-Carlos; Doyen, Guillaume; De Coninck, Joël

    2015-11-01

    Wetting is a prerequisite for coating a uniform layer of liquid onto a solid. Wetting failure and air entrainment set the ultimate limit to coating speed. It is well known in the coating art that this limit can be postponed by manipulating the coating flow to generate what has been termed "hydrodynamic assist," but the underlying mechanism is unclear. Experiments have shown that the conditions that postpone air entrainment also reduce the apparent dynamic contact angle, suggesting a direct link, but how the flow might affect the contact angle remains to be established. Here, we use molecular dynamics to compare the outcome of steady forced wetting with previous results for the spontaneous spreading of liquid drops and apply the molecular-kinetic theory of dynamic wetting to rationalize our findings and place them on a quantitative footing. The forced wetting simulations reveal significant slip at the solid-liquid interface and details of the flow immediately adjacent to the moving contact line. Our results confirm that the local, microscopic contact angle is dependent not simply only on the velocity of wetting but also on the nature of the flow that drives it. In particular, they support an earlier suggestion that during forced wetting, an intense shear stress in the vicinity of the contact line can assist surface tension forces in promoting dynamic wetting, thus reducing the velocity-dependence of the contact angle. Hydrodynamic assist then appears as a natural consequence of wetting that emerges when the contact line is driven by a strong and highly confined flow. Our theoretical approach also provides a self-consistent model of molecular slip at the solid-liquid interface that enables its magnitude to be estimated from dynamic contact angle measurements. In addition, the model predicts how hydrodynamic assist and slip may be influenced by liquid viscosity and solid-liquid interactions.

  2. Prediction and analysis of variable reluctance stepmotor drive systems

    NASA Astrophysics Data System (ADS)

    Pulle, D. W. J.

    1982-01-01

    A relationship between the electric terminal parameters and output/input power is derived for conventional doubly-salient synchronous machines and extended to include the variable reluctance motor. The advantages and limitations of the drive-schemes are shown in Blondel diagrams and torque speed curves. A general method for obtaining a quantitative assessment of drive-schemes is developed by the introduction of so-called performance figures, related to the output power and efficiency. From this method applied to four drive schemes, it is concluded that severe performance degradation is the result of using a forging resistance in a drive-scheme. A forced decay unipolar chopper drive is presented.

  3. Drill drive mechanism

    DOEpatents

    Dressel, Michael O.

    1979-01-01

    A drill drive mechanism is especially adapted to provide both rotational drive and axial feed for a drill of substantial diameter such as may be used for drilling holes for roof bolts in mine shafts. The drill shaft is made with a helical pattern of scroll-like projections on its surface for removal of cuttings. The drill drive mechanism includes a plurality of sprockets carrying two chains of drive links which are arranged to interlock around the drill shaft with each drive link having depressions which mate with the scroll-like projections. As the chain links move upwardly or downwardly the surfaces of the depressions in the links mate with the scroll projections to move the shaft axially. Tangs on the drive links mate with notch surfaces between scroll projections to provide a means for rotating the shaft. Projections on the drive links mate together at the center to hold the drive links tightly around the drill shaft. The entire chain drive mechanism is rotated around the drill shaft axis by means of a hydraulic motor and gear drive to cause rotation of the drill shaft. This gear drive also connects with a differential gearset which is interconnected with a second gear. A second motor is connected to the spider shaft of the differential gearset to produce differential movement (speeds) at the output gears of the differential gearset. This differential in speed is utilized to drive said second gear at a speed different from the speed of said gear drive, this speed differential being utilized to drive said sprockets for axial movement of said drill shaft.

  4. Nanonet Force Microscopy for Measuring Cell Forces.

    PubMed

    Sheets, Kevin; Wang, Ji; Zhao, Wei; Kapania, Rakesh; Nain, Amrinder S

    2016-07-12

    The influence of physical forces exerted by or felt by cells on cell shape, migration, and cytoskeleton arrangement is now widely acknowledged and hypothesized to occur due to modulation of cellular inside-out forces in response to changes in the external fibrous environment (outside-in). Our previous work using the non-electrospinning Spinneret-based Tunable Engineered Parameters' suspended fibers has revealed that cells are able to sense and respond to changes in fiber curvature and structural stiffness as evidenced by alterations to focal adhesion cluster lengths. Here, we present the development and application of a suspended nanonet platform for measuring C2C12 mouse myoblast forces attached to fibers of three diameters (250, 400, and 800 nm) representing a wide range of structural stiffness (3-50 nN/μm). The nanonet force microscopy platform measures cell adhesion forces in response to symmetric and asymmetric external perturbation in single and cyclic modes. We find that contractility-based, inside-out forces are evenly distributed at the edges of the cell, and that forces are dependent on fiber structural stiffness. Additionally, external perturbation in symmetric and asymmetric modes biases cell-fiber failure location without affecting the outside-in forces of cell-fiber adhesion. We then extend the platform to measure forces of (1) cell-cell junctions, (2) single cells undergoing cyclic perturbation in the presence of drugs, and (3) cancerous single-cells transitioning from a blebbing to a pseudopodial morphology. PMID:27410747

  5. Downward Slope Driving Control for Electric Powered Wheelchair Based on Capacitor Regenerative Brake

    NASA Astrophysics Data System (ADS)

    Seki, Hirokazu; Takahashi, Yoshiaki

    This paper describes a novel capacitor regenerative braking control scheme of electric powered wheelchairs for efficient driving on downward slopes. An electric powered wheelchair, which generates the driving force by electric motors, is expected to be widely used as a mobility support system for elderly people and disabled people; however the energy efficiency has to be further improved because it is driven only by battery energy. This study proposes a capacitor regenerative braking circuit and two types of velocity control schemes with variable duty ratio. The proposed regenerative braking circuit is based on the step-up/down circuit with additional resistance and connects right and left motors in series in order to obtain a larger braking power. Some driving experiments on a practical downward slope show the effectiveness of the proposed control system.

  6. Relativistic Linear Restoring Force

    ERIC Educational Resources Information Center

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  7. 15. TYPE H, BUILDING #321451 BREENE DRIVE, INTERIOR, FIRST FLOOR, ...

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

    15. TYPE H, BUILDING #321-451 BREENE DRIVE, INTERIOR, FIRST FLOOR, LIVING ROOM, SOUTHEAST VIEW. - Wright-Patterson Air Force Base, Brick Officers' Quarters, Types G & H, Area A, Dayton, Montgomery County, OH

  8. 16. TYPE H, BUILDING #321451 BREENE DRIVE, INTERIOR, SECOND FLOOR, ...

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

    16. TYPE H, BUILDING #321-451 BREENE DRIVE, INTERIOR, SECOND FLOOR, HALLWAY, BEDROOM AND HALLWAY, NORTH VIEW. - Wright-Patterson Air Force Base, Brick Officers' Quarters, Types G & H, Area A, Dayton, Montgomery County, OH

  9. 14. TYPE H, BUILDING #321451 BREENE DRIVE, INTERIOR, FIRST FLOOR, ...

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

    14. TYPE H, BUILDING #321-451 BREENE DRIVE, INTERIOR, FIRST FLOOR, LIVING ROOM, EAST VIEW. - Wright-Patterson Air Force Base, Brick Officers' Quarters, Types G & H, Area A, Dayton, Montgomery County, OH

  10. 17. View of Mercury Avenue from Apollo Drive, looking north ...

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

    17. View of Mercury Avenue from Apollo Drive, looking north at E-wing - Offutt Air Force Base, Strategic Air Command Headquarters & Command Center, Headquarters Building, 901 SAC Boulevard, Bellevue, Sarpy County, NE

  11. 15. Threequarter view of Gwing from intersection of Apollo Drive ...

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

    15. Three-quarter view of G-wing from intersection of Apollo Drive and Mercury Avenue, looking northwest - Offutt Air Force Base, Strategic Air Command Headquarters & Command Center, Headquarters Building, 901 SAC Boulevard, Bellevue, Sarpy County, NE

  12. Superluminal warp drive

    NASA Astrophysics Data System (ADS)

    González-Díaz, Pedro F.

    2007-09-01

    In this Letter we consider a warp drive spacetime resulting from that suggested by Alcubierre when the spaceship can only travel faster than light. Restricting to the two dimensions that retains most of the physics, we derive the thermodynamic properties of the warp drive and show that the temperature of the spaceship rises up as its apparent velocity increases. We also find that the warp drive spacetime can be exhibited in a manifestly cosmological form.

  13. Sensing mode atomic force microscope

    DOEpatents

    Hough, Paul V. C.; Wang, Chengpu

    2003-01-01

    An atomic force microscope utilizes a pulse release system and improved method of operation to minimize contact forces between a probe tip affixed to a flexible cantilever and a specimen being measured. The pulse release system includes a magnetic particle affixed proximate the probe tip and an electromagnetic coil. When energized, the electromagnetic coil generates a magnetic field which applies a driving force on the magnetic particle sufficient to overcome adhesive forces exhibited between the probe tip and specimen. The atomic force microscope includes two independently displaceable piezo elements operable along a Z-axis. A controller drives the first Z-axis piezo element to provide a controlled approach between the probe tip and specimen up to a point of contact between the probe tip and specimen. The controller then drives the first Z-axis piezo element to withdraw the cantilever from the specimen. The controller also activates the pulse release system which drives the probe tip away from the specimen during withdrawal. Following withdrawal, the controller adjusts the height of the second Z-axis piezo element to maintain a substantially constant approach distance between successive samples.

  14. Diabetes and driving.

    PubMed

    Inkster, B; Frier, B M

    2013-09-01

    The principal safety concern for driving for people treated with insulin or insulin secretagogues is hypoglycaemia, which impairs driving performance. Other complications, such as those causing visual impairment and peripheral neuropathy, are also relevant to medical fitness to drive. Case control studies have suggested that drivers with diabetes pose a modestly increased but acceptable and measurable risk of motor vehicle accidents compared to non-diabetic drivers, but many studies are limited and of poor quality. Factors which have been shown to increase driving risk include previous episodes of severe hypoglycaemia, previous hypoglycaemia while driving, strict glycaemic control (lower HbA1c) and absence of blood glucose monitoring before driving. Impaired awareness of hypoglycaemia may be counteracted by frequent blood glucose testing. The European Union Third directive on driving (2006) has necessitated changes in statutory regulations for driving licences for people with diabetes in all European States, including the UK. Stricter criteria have been introduced for Group 1 vehicle licences while those for Group 2 licences have been relaxed. Insulin-treated drivers can now apply to drive Group 2 vehicles, but in the UK must meet very strict criteria and be assessed by an independent specialist to be issued with a 1-year licence. PMID:23350766

  15. ATP drives direct photosynthetic production of 1-butanol in cyanobacteria

    PubMed Central

    Lan, Ethan I.; Liao, James C.

    2012-01-01

    While conservation of ATP is often a desirable trait for microbial production of chemicals, we demonstrate that additional consumption of ATP may be beneficial to drive product formation in a nonnatural pathway. Although production of 1-butanol by the fermentative coenzyme A (CoA)-dependent pathway using the reversal of β-oxidation exists in nature and has been demonstrated in various organisms, the first step of the pathway, condensation of two molecules of acetyl-CoA to acetoacetyl-CoA, is thermodynamically unfavorable. Here, we show that artificially engineered ATP consumption through a pathway modification can drive this reaction forward and enables for the first time the direct photosynthetic production of 1-butanol from cyanobacteria Synechococcus elongatus PCC 7942. We further demonstrated that substitution of bifunctional aldehyde/alcohol dehydrogenase (AdhE2) with separate butyraldehyde dehydrogenase (Bldh) and NADPH-dependent alcohol dehydrogenase (YqhD) increased 1-butanol production by 4-fold. These results demonstrated the importance of ATP and cofactor driving forces as a design principle to alter metabolic flux. PMID:22474341

  16. Proceedings of the international conference on maglev and linear drives

    SciTech Connect

    Not Available

    1986-01-01

    This book contains papers presented at a conference on Maglev and linear drives. Topics covered include: Development of superconducting magnets for the Canadian electrodynamic Maglev vehicle; Power supply system to drive HSST - Expo '86; and Thrust and levitation force characteristics of linear synchronous motors.

  17. Viscous damping and spring force in periodic perforated planar microstructures when the Reynolds’ equation cannot be applied

    PubMed Central

    Homentcovschi, Dorel; Miles, Ronald N.

    2010-01-01

    A model of squeeze-film behavior is developed based on Stokes’ equations for viscous, compressible isothermal flows. The flow domain is an axisymmetrical, unit cell approximation of a planar, periodic, perforated microstructure. The model is developed for cases when the lubrication approximation cannot be applied. The complex force generated by vibrations of the diaphragm driving the flow has two components: the damping force and the spring force. While for large frequencies the spring force dominates, at low (acoustical) frequencies the damping force is the most important part. The analytical approach developed here yields an explicit formula for both forces. In addition, using a finite element software package, the damping force is also obtained numerically. A comparison is made between the analytic result, numerical solution, and some experimental data found in the literature, which validates the analytic formula and provides compelling arguments about its value in designing microelectomechanical devices. PMID:20329828

  18. Nuclear forces

    SciTech Connect

    Machleidt, R.

    2013-06-10

    These lectures present an introduction into the theory of nuclear forces. We focus mainly on the modern approach, in which the forces between nucleons emerge from low-energy QCD via chiral effective field theory.

  19. Food additives.

    PubMed

    Berglund, F

    1978-01-01

    The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI

  20. Reading Text While Driving

    PubMed Central

    Horrey, William J.; Hoffman, Joshua D.

    2015-01-01

    Objective In this study, we investigated how drivers adapt secondary-task initiation and time-sharing behavior when faced with fluctuating driving demands. Background Reading text while driving is particularly detrimental; however, in real-world driving, drivers actively decide when to perform the task. Method In a test track experiment, participants were free to decide when to read messages while driving along a straight road consisting of an area with increased driving demands (demand zone) followed by an area with low demands. A message was made available shortly before the vehicle entered the demand zone. We manipulated the type of driving demands (baseline, narrow lane, pace clock, combined), message format (no message, paragraph, parsed), and the distance from the demand zone when the message was available (near, far). Results In all conditions, drivers started reading messages (drivers’ first glance to the display) before entering or before leaving the demand zone but tended to wait longer when faced with increased driving demands. While reading messages, drivers looked more or less off road, depending on types of driving demands. Conclusions For task initiation, drivers avoid transitions from low to high demands; however, they are not discouraged when driving demands are already elevated. Drivers adjust time-sharing behavior according to driving demands while performing secondary tasks. Nonetheless, such adjustment may be less effective when total demands are high. Application This study helps us to understand a driver’s role as an active controller in the context of distracted driving and provides insights for developing distraction interventions. PMID:25850162

  1. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2012

    2012-01-01

    The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

  2. Full-Height Magneto-Optic Rewritable Disk Drive

    NASA Astrophysics Data System (ADS)

    Murakami, Teruo; Ando, Hideo; Yana, Magasumi

    1989-05-01

    1 , 2 A magneto optic (MO) rewritable disk drive has been put to practical use. The ISO standardization activity on a 130 mm rewritable disk is in its final stage and it will be standardized in 1989. An MO disk drive must he equipped with bias magnetic field generating functions in addition to the same characteristics as that of a write once read many (WORM) disk drive. The key factor for the broad acceptance of MO disk drives by users is that they conform to the ISO standard and that the drive size is of such a widely adopted size as that of a magnetic disk drive.

  3. Nonlinear resonances and antiresonances of a forced sonic vacuum.

    PubMed

    Pozharskiy, D; Zhang, Y; Williams, M O; McFarland, D M; Kevrekidis, P G; Vakakis, A F; Kevrekidis, I G

    2015-12-01

    We consider a harmonically driven acoustic medium in the form of a (finite length) highly nonlinear granular crystal with an amplitude- and frequency-dependent boundary drive. Despite the absence of a linear spectrum in the system, we identify resonant periodic propagation whereby the crystal responds at integer multiples of the drive period and observe that this can lead to local maxima of transmitted force at its fixed boundary. In addition, we identify and discuss minima of the transmitted force ("antiresonances") between these resonances. Representative one-parameter complex bifurcation diagrams involve period doublings and Neimark-Sacker bifurcations as well as multiple isolas (e.g., of period-3, -4, or -5 solutions entrained by the forcing). We combine them in a more detailed, two-parameter bifurcation diagram describing the stability of such responses to both frequency and amplitude variations of the drive. This picture supports a notion of a (purely) "nonlinear spectrum" in a system which allows no sound wave propagation (due to zero sound speed: the so-called sonic vacuum). We rationalize this behavior in terms of purely nonlinear building blocks: apparent traveling and standing nonlinear waves. PMID:26764846

  4. Nonlinear resonances and antiresonances of a forced sonic vacuum

    NASA Astrophysics Data System (ADS)

    Pozharskiy, D.; Zhang, Y.; Williams, M. O.; McFarland, D. M.; Kevrekidis, P. G.; Vakakis, A. F.; Kevrekidis, I. G.

    2015-12-01

    We consider a harmonically driven acoustic medium in the form of a (finite length) highly nonlinear granular crystal with an amplitude- and frequency-dependent boundary drive. Despite the absence of a linear spectrum in the system, we identify resonant periodic propagation whereby the crystal responds at integer multiples of the drive period and observe that this can lead to local maxima of transmitted force at its fixed boundary. In addition, we identify and discuss minima of the transmitted force ("antiresonances") between these resonances. Representative one-parameter complex bifurcation diagrams involve period doublings and Neimark-Sacker bifurcations as well as multiple isolas (e.g., of period-3, -4, or -5 solutions entrained by the forcing). We combine them in a more detailed, two-parameter bifurcation diagram describing the stability of such responses to both frequency and amplitude variations of the drive. This picture supports a notion of a (purely) "nonlinear spectrum" in a system which allows no sound wave propagation (due to zero sound speed: the so-called sonic vacuum). We rationalize this behavior in terms of purely nonlinear building blocks: apparent traveling and standing nonlinear waves.

  5. Nonlinear resonances and antiresonances of a forced sonic vacuum

    DOE PAGESBeta

    Pozharskiy, D.; Zhang, Y.; Williams, M. O.; McFarland, D. M.; Kevrekidis, P. G.; Vakakis, A. F.; Kevrekidis, I. G.

    2015-12-23

    We consider a harmonically driven acoustic medium in the form of a (finite length) highly nonlinear granular crystal with an amplitude- and frequency-dependent boundary drive. Despite the absence of a linear spectrum in the system, we identify resonant periodic propagation whereby the crystal responds at integer multiples of the drive period and observe that this can lead to local maxima of transmitted force at its fixed boundary. In addition, we identify and discuss minima of the transmitted force (“antiresonances”) between these resonances. Representative one-parameter complex bifurcation diagrams involve period doublings and Neimark-Sacker bifurcations as well as multiple isolas (e.g., ofmore » period-3, -4, or -5 solutions entrained by the forcing). We combine them in a more detailed, two-parameter bifurcation diagram describing the stability of such responses to both frequency and amplitude variations of the drive. This picture supports a notion of a (purely) “nonlinear spectrum” in a system which allows no sound wave propagation (due to zero sound speed: the so-called sonic vacuum). As a result, we rationalize this behavior in terms of purely nonlinear building blocks: apparent traveling and standing nonlinear waves.« less

  6. Nonlinear resonances and antiresonances of a forced sonic vacuum

    SciTech Connect

    Pozharskiy, D.; Zhang, Y.; Williams, M. O.; McFarland, D. M.; Kevrekidis, P. G.; Vakakis, A. F.; Kevrekidis, I. G.

    2015-12-23

    We consider a harmonically driven acoustic medium in the form of a (finite length) highly nonlinear granular crystal with an amplitude- and frequency-dependent boundary drive. Despite the absence of a linear spectrum in the system, we identify resonant periodic propagation whereby the crystal responds at integer multiples of the drive period and observe that this can lead to local maxima of transmitted force at its fixed boundary. In addition, we identify and discuss minima of the transmitted force (“antiresonances”) between these resonances. Representative one-parameter complex bifurcation diagrams involve period doublings and Neimark-Sacker bifurcations as well as multiple isolas (e.g., of period-3, -4, or -5 solutions entrained by the forcing). We combine them in a more detailed, two-parameter bifurcation diagram describing the stability of such responses to both frequency and amplitude variations of the drive. This picture supports a notion of a (purely) “nonlinear spectrum” in a system which allows no sound wave propagation (due to zero sound speed: the so-called sonic vacuum). As a result, we rationalize this behavior in terms of purely nonlinear building blocks: apparent traveling and standing nonlinear waves.

  7. A new class of high force, low-voltage, compliant actuation system

    SciTech Connect

    RODGERS,M. STEVEN; KOTA,SRIDHAR; HETRICK,JOEL; LI,ZHE; JENSEN,BRIAN D.; KRYGOWSKI,THOMAS W.; MILLER,SAMUEL L.; BARNES,STEPHEN MATTHEW; BURG,MICHAEL STANLEY

    2000-04-10

    Although many actuators employing electrostatic comb drives have been demonstrated in a laboratory environment, widespread acceptance in mass produced microelectromechanical systems (MEMS) may be limited due to issues associated with low drive force, large real estate demands, high operating voltages, and reliability concerns due to stiction. On the other hand, comb drives require very low drive currents, offer predictable response, and are highly compatible with the fabrication technology. The expand the application space and facilitate the widespread deployment of self-actuated MEMS, a new class of advanced actuation systems has been developed that maintains the highly desirable aspects of existing components, while significantly diminishing the issues that could impede large scale acceptance. In this paper, the authors will present low-voltage electrostatic actuators that offer a dramatic increase in force over conventional comb drive designs. In addition, these actuators consume only a small fraction of the chip area previously used, yielding significant gains in power density. To increase the stroke length of these novel electrostatic actuators, the authors have developed highly efficient compliant stroke amplifiers. The coupling of compact, high-force actuators with fully compliant displacement multipliers sets a new paradigm for highly integrated microelectromechanical systems.

  8. Piezoelectric drive circuit

    DOEpatents

    Treu, C.A. Jr.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

  9. Piezoelectric drive circuit

    DOEpatents

    Treu, Jr., Charles A.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

  10. Dual drive actuators

    NASA Technical Reports Server (NTRS)

    Packard, D. T.

    1982-01-01

    A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically.

  11. Design of traction drives

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Zaretsky, E. V.

    1985-01-01

    Traction drives are among the simplest of all speed-changing mechanisms. Because of their simplicity and their ability to smoothly and continuously adjust speed, they are excellent choices for many drive system applications. They have been used in industrial service for more than 100 years. Today's traction drives have power capacities which rival the best gear and belt drives due to modern traction fluids and highly fatigue-resistant bearing steels. This report summarizes methods to analyze and size traction drives. Lubrication principles, contact kinematics, stress, fatigue life, and performance prediction methods are presented. The effects of the lubricant's traction characteristics on life and power loss are discussed. An example problem is given which illustrates the effects of spin on power loss. Loading mechanism design and the design of nonlubricated friction wheels and rings are also treated.

  12. Neural substrates of driving behaviour

    PubMed Central

    Spiers, Hugo J.; Maguire, Eleanor A.

    2007-01-01

    Driving a vehicle is an indispensable daily behaviour for many people, yet we know little about how it is supported by the brain. Given that driving in the real world involves the engagement of many cognitive systems that rapidly change to meet varying environmental demands, identifying its neural basis presents substantial problems. By employing a unique combination of functional magnetic resonance imaging (fMRI), an accurate interactive virtual simulation of a bustling central London (UK) and a retrospective verbal report protocol, we surmounted these difficulties. We identified different events that characterise the driving process on a second by second basis and the brain regions that underlie them. Prepared actions such as starting, turning, reversing and stopping were associated with a common network comprised of premotor, parietal and cerebellar regions. Each prepared action also recruited additional brain areas. We also observed unexpected hazardous events such as swerving and avoiding collisions that were associated with activation of lateral occipital and parietal regions, insula, as well as a more posterior region in the medial premotor cortex than prepared actions. By contrast, planning future actions and monitoring fellow road users were associated with activity in superior parietal, lateral occipital cortices and the cerebellum. The anterior pre-SMA was also recruited during action planning. The right lateral prefrontal cortex was specifically engaged during the processing of road traffic rules. By systematically characterising the brain dynamics underlying naturalistic driving behaviour in a real city, our findings may have implications for how driving competence is considered in the context of neurological damage. PMID:17412611

  13. A friction regulation hybrid driving method for backward motion restraint of the smooth impact drive mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Chen, Dong; Cheng, Tinghai; He, Pu; Lu, Xiaohui; Zhao, Hongwei

    2016-08-01

    The smooth impact drive mechanism (SIDM) is a type of piezoelectric actuator that has been developed for several decades. As a kind of driving method for the SIDM, the traditional sawtooth (TS) wave is always employed. The kinetic friction force during the rapid contraction stage usually results in the generation of a backward motion. A friction regulation hybrid (FRH) driving method realized by a composite waveform for the backward motion restraint of the SIDM is proposed in this paper. The composite waveform is composed of a sawtooth driving (SD) wave and a sinusoidal friction regulation (SFR) wave which is applied to the rapid deformation stage of the SD wave. A prototype of the SIDM was fabricated and its output performance under the excitation of the FRH driving method and the TS wave driving method was tested. The results indicate that the backward motion can be restrained obviously using the FRH driving method. Compared with the driving effect of the TS wave, the backward rates of the prototype in forward and reverse motions are decreased by 83% and 85%, respectively.

  14. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  15. Phosphazene additives

    SciTech Connect

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  16. Magnetic drive system for a new centrifugal rotary blood pump.

    PubMed

    Hilton, Andrew; Tansley, Geoff

    2008-10-01

    The purpose of this investigation was to design a novel magnetic drive and bearing system for a new centrifugal rotary blood pump (CRBP). The drive system consists of two components: (i) permanent magnets within the impeller of the CRBP; and (ii) the driving electromagnets. Orientation of the magnets varies from axial through to 60 degrees included out-lean (conical configuration). Permanent magnets replace the electromagnet drive to allow easier characterization. The performance characteristics tested were the axial force of attraction between the stator and rotor at angles of rotational alignment, Ø, and the corresponding torque at those angles. The drive components were tested for various magnetic cone angles, theta. The test was repeated for three backing conditions: (i) non-backed; (ii) steel-cupped; and (iii) steel plate back-iron, performed on an Instron tensile testing machine. Experimental results were expanded upon through finite element and boundary element analysis (BEM). The force/torque characteristics were maximal for a 12-magnet configuration at 0 degree cone angle with steel-back iron (axial force = 60 N, torque = 0.375 Nm). BEM showed how introducing a cone angle increases the radial restoring force threefold while not compromising axial bearing force. Magnets in the drive system may be orientated not only to provide adequate coupling to drive the CRBP, but to provide significant axial and radial bearing forces capable of withstanding over 100 m/s(2) shock excitation on the impeller. Although the 12 magnet 0 degree (theta) configuration yielded the greatest force/torque characteristic, this was seen as potentially unattractive as this magnetic cone angle yielded poor radial restoring force characteristics. PMID:18959665

  17. Magnetostrictive Roller-Drive Stepping Motor

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1993-01-01

    Proposed motor based on magnetostrictive effect provides stepped angular motion with angular increments of order of 100 microradians. Driven to repeat stepping cycle rapidly enough to achieve maximum speed of about 20 rpm, provides torque an order of magnitude greater than electric motors, and brakes itself when power turned off. Magnetostrictive rods in electromagnet coils push against drive plate, causing it to rotate slightly. This slight rotation jams conical rollers between cam surfaces on outer drive ring and split drum, so rollers transmit rotation to drum. Suitable for precise, high-torque, fail-safe-braking, direct drive of robot joint, without bulk and weight of additional brake mechanism and gear train.

  18. Vision and Driving

    PubMed Central

    Owsley, Cynthia; McGwin, Gerald

    2010-01-01

    Driving is the primary means of personal travel in many countries and is relies heavily on vision for its successful execution. Research over the past few decades has addressed the role of vision in driver safety (motor vehicle collision involvement) and in driver performance (both on-road and using interactive simulators in the laboratory). Here we critically review what is currently known about the role of various aspects of visual function in driving. We also discuss translational research issues on vision screening for licensure and re-licensure and rehabilitation of visually impaired persons who want to drive. PMID:20580907

  19. Redundant motor drive system

    NASA Technical Reports Server (NTRS)

    Calvert, J. A. (Inventor)

    1980-01-01

    A drive system characterized by a base supporting a pair of pillars arranged in spaced parallelism, a shaft extended between and supported by the pillars for rotation about the longitudinal axis thereof, a worm gear affixed to the shaft and supported in coaxial relation therewith is described. A bearing housing of a sleeve like configuration is concentrically related to the shaft and is supported thereby for free rotation. A first and a second quiescent drive train, alternatively activatable, is provided for imparting rotation into said bearing housing. Each of the drive trains is characterized by a selectively energizable motor connected to a spur gear.

  20. The Test Drive

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at NASA's Jet Propulsion Laboratory shows engineers rehearsing the sol 133 (June 8, 2004) drive into 'Endurance' crater by NASA's Mars Exploration Rover Opportunity. Engineers and scientists have recreated the martian surface and slope the rover will encounter using a combination of bare and thinly sand-coated rocks, simulated martian 'blueberries' and a platform tilted at a 25-degree angle. The results of this test convinced engineers that the rover was capable of driving up and down a straight slope before it attempted the actual drive on Mars.

  1. Dementia and driving

    MedlinePlus

    ... getting more dangerous include: Getting lost on familiar roads Reacting more slowly in traffic Driving too slowly ... attention to traffic signs Taking chances on the road Drifting into other lanes Getting more agitated in ...

  2. Drive program documentation

    NASA Technical Reports Server (NTRS)

    Graham, S.

    1979-01-01

    The program description and user's guide for the Downlist Requirement Integrated Verification and Evaluation (DRIVE) program is provided. The program is used to compare existing telemetry downlist files with updated downlist requirements.

  3. Safe driving for teens

    MedlinePlus

    ... drivers. Do not use cell phones for talking, texting, or email when you are driving. Mobile phones ... pull off of the road before answering or texting. Other tips include: Avoid putting on makeup while ...

  4. Labs drive the arms race

    SciTech Connect

    DeWitt, H.E.

    1984-11-01

    The conviction of laboratory managers that high technology can provide safety and national security in a dangerous world and that technological solutions are paramount over political solutions has been a major driving force in perpetuating the nuclear arms race. The credo in the laboratories appears to be that there are never enough designs of nuclear weapons for deterrence so that there is always a need to develop such new ideas as the nuclear-pumped X-ray laser as a defense against energy missiles. The author outlines several alternative steps, including the ratification and reaffirmation of arms control treaties, negotiations, and a halt to the Star Wars program. A central point is to stop nuclear weapons testing. 7 references.

  5. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett Lee; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-09-19

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  6. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2007-02-27

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  7. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-07-11

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  8. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2006-10-10

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  9. Common drive unit

    NASA Technical Reports Server (NTRS)

    Ellis, R. C.; Fink, R. A.; Moore, E. A.

    1987-01-01

    The Common Drive Unit (CDU) is a high reliability rotary actuator with many versatile applications in mechanism designs. The CDU incorporates a set of redundant motor-brake assemblies driving a single output shaft through differential. Tachometers provide speed information in the AC version. Operation of both motors, as compared to the operation of one motor, will yield the same output torque with twice the output speed.

  10. Self-driving carsickness.

    PubMed

    Diels, Cyriel; Bos, Jelte E

    2016-03-01

    This paper discusses the predicted increase in the occurrence and severity of motion sickness in self-driving cars. Self-driving cars have the potential to lead to significant benefits. From the driver's perspective, the direct benefits of this technology are considered increased comfort and productivity. However, we here show that the envisaged scenarios all lead to an increased risk of motion sickness. As such, the benefits this technology is assumed to bring may not be capitalised on, in particular by those already susceptible to motion sickness. This can negatively affect user acceptance and uptake and, in turn, limit the potential socioeconomic benefits that this emerging technology may provide. Following a discussion on the causes of motion sickness in the context of self-driving cars, we present guidelines to steer the design and development of automated vehicle technologies. The aim is to limit or avoid the impact of motion sickness and ultimately promote the uptake of self-driving cars. Attention is also given to less well known consequences of motion sickness, in particular negative aftereffects such as postural instability, and detrimental effects on task performance and how this may impact the use and design of self-driving cars. We conclude that basic perceptual mechanisms need to be considered in the design process whereby self-driving cars cannot simply be thought of as living rooms, offices, or entertainment venues on wheels. PMID:26446454

  11. Parkinson disease and driving

    PubMed Central

    Classen, Sherrilene; Uc, Ergun Y.

    2012-01-01

    ABSTRACT The growing literature on driving in Parkinson disease (PD) has shown that driving is impaired in PD compared to healthy comparison drivers. PD is a complex neurodegenerative disorder leading to motor, cognitive, and visual impairments, all of which can affect fitness to drive. In this review, we examined studies of driving performance (on-road tests and simulators) in PD for outcome measures and their predictors. We searched through various databases and found 25 (of 99) primary studies, all published in English. Using the American Academy of Neurology criteria, a study class of evidence was assigned (I–IV, I indicating the highest level of evidence) and recommendations were made (Level A: predictive or not; B: probably predictive or not; C: possibly predictive or not; U: no recommendations). From available Class II and III studies, we identified various cognitive, visual, and motor measures that met different levels of evidence (usually Level B or C) with respect to predicting on-road and simulated driving performance. Class I studies reporting Level A recommendations for definitive predictors of driving performance in drivers with PD are needed by policy makers and clinicians to develop evidence-based guidelines. PMID:23150533

  12. Hydraulic drive system prevents backlash

    NASA Technical Reports Server (NTRS)

    Acord, J. D.

    1965-01-01

    Hydraulic drive system uses a second drive motor operating at reduced torque. This exerts a relative braking action which eliminates the normal gear train backlash that is intolerable when driving certain heavy loads.

  13. Family Influences and Unconscious Drives.

    ERIC Educational Resources Information Center

    English, Fanita

    2001-01-01

    Drives for survival, expression, and quiescence influence early human development and continue to influence career development throughout life. Turmoil may arise when a drive conflicts with others or is suppressed by other drives. (SK)

  14. 77 FR 34025 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-08

    ... INFORMATION: ] Addition On 4/132012 (77 FR 22289-22290), the Committee for Purchase From People Who Are Blind... & Development Center (ERDC), Construction Engineering Research Lab (CERL), 2902 Newmark Drive, Champaign, IL. AT & T Building, 3001 Newmark Drive, Champaign, IL. NPA: The Chicago Lighthouse for People Who Are...

  15. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2010

    2010-01-01

    The labor force is the number of people aged 16 or older who are either working or looking for work. It does not include active-duty military personnel or institutionalized people, such as prison inmates. Quantifying this total supply of labor is a way of determining how big the economy can get. Labor force participation rates vary significantly…

  16. One Force

    NASA Astrophysics Data System (ADS)

    Kotas, Ronald R.

    2002-04-01

    There is only one entity that can extend force and couple through space; and it should be apparent that Electromagnetism is that entity. In the cases of the nuclear strong force and the nuclear weak force, this is the same fundamental Electromagnetism manifesting itself in two different ways in the nucleus. It remains the same basic Electromagnetism. On the other hand, General Relativity fails to produce force at a distance, fails the Cavendish experiment, and does not allow an apple to fall to the ground. The result shows there is only Electromagnetism that functions through physical nature providing gravity, actions in the nucleus, as well as all other physical actions universally, including Gravity and Gravitation. There are many direct proofs of this, the same proofs as in NUCLEAR QUANTUM GRAVITATION. In contrast, General Relativity plainly relies on fallacy abstract and incoherent proofs; proofs which have now been mostly disproved. In the past it was deemed necessary by some to have an "ether" to propagate Electromagnetic waves. The fallacy concept of time space needs "space distortions" in order to cause gravity. However, Electromagnetic gravity does not have this problem. Clearly there is only ONE FORCE that causes Gravity, Electromagnetism, the Nuclear Strong Force, and the Nuclear Weak Force, and that ONE FORCE is Electromagnetism.

  17. Modulating Brain Oscillations to Drive Brain Function

    PubMed Central

    Thut, Gregor

    2014-01-01

    Do neuronal oscillations play a causal role in brain function? In a study in this issue of PLOS Biology, Helfrich and colleagues address this long-standing question by attempting to drive brain oscillations using transcranial electrical current stimulation. Remarkably, they were able to manipulate visual perception by forcing brain oscillations of the left and right visual hemispheres into synchrony using oscillatory currents over both hemispheres. Under this condition, human observers more often perceived an inherently ambiguous visual stimulus in one of its perceptual instantiations. These findings shed light on the mechanisms underlying neuronal computation. They show that it is the neuronal oscillations that drive the visual experience, not the experience driving the oscillations. And they indicate that synchronized oscillatory activity groups brain areas into functional networks. This points to new ways for controlled experimental and possibly also clinical interventions for the study and modulation of brain oscillations and associated functions. PMID:25549340

  18. Friction drive characterization breadboard: test results

    NASA Astrophysics Data System (ADS)

    Sedghi, B.; Lucuix, C.; Tortolani, J. M.; Brunetto, E.; Delrez, C.; Gabriel, E.

    2010-07-01

    The drive and bearing technologies have a major impact on the static and dynamic performance of steerable structures such as telescope and dome. Merging drive and bearing system into friction drive mechanical devices (bogie) can reduce the complexity and cost of the design. In the framework of ELT design study (European FP6) a breadboard test setup was realized to test and evaluate the static and dynamic behavior of such bogies. In this paper some of the characterization test results are presented. Characterization of the bogies and the setup structure in the frequency domain, quantification and measure of the most important parameters of the friction forces, the control of the bogies and the tracking performance of the test setup are among the main results discussed in this paper.

  19. Electric vehicle drive train components

    SciTech Connect

    Silver, F.

    1994-12-31

    Power Control Systems has developed a family of electric vehicle drive systems that range from 65 horsepower through 300 horse power. These propulsion systems support vehicle applications ranging from light cars and pickups to buses and trucks weighing as much as 40,000 lbs (18,400 kg). These robust systems are designed specifically for automotive applications including safety, electromagnetic emissions, and environment ruggedness. Dolphin Drive Systems are very flexible. Their inverter controllers are programmable and can be provided as stand alone components matched to customer specified motors. A selection of pre-calibrated systems including motor and inverter/controller can be provided. Accessory tools are also available for customer self programming. Dolphin Drive Systems provide precision control of AC induction motors providing excellent torque-speed performance usually eliminating the need for multistage transmissions. In addition, they are very efficient over a wide speed/torque range. This provides for excellent power management over a variety of continuous speed and stop and go applications.

  20. Driving Competence in Mild Dementia with Lewy Bodies: In Search of Cognitive Predictors Using Driving Simulation

    PubMed Central

    Yamin, Stephanie; Stinchcombe, Arne; Gagnon, Sylvain

    2015-01-01

    Driving is a multifactorial behaviour drawing on multiple cognitive, sensory, and physical systems. Dementia is a progressive and degenerative neurological condition that impacts the cognitive processes necessary for safe driving. While a number of studies have examined driving among individuals with Alzheimer's disease, less is known about the impact of Dementia with Lewy Bodies (DLB) on driving safety. The present study compared simulated driving performance of 15 older drivers with mild DLB with that of 21 neurologically healthy control drivers. DLB drivers showed poorer performance on all indicators of simulated driving including an increased number of collisions in the simulator and poorer composite indicators of overall driving performance. A measure of global cognitive function (i.e., the Mini Mental State Exam) was found to be related to the overall driving performance. In addition, measures of attention (i.e., Useful Field of View, UFOV) and space processing (Visual Object and Space Perception, VOSP, Test) correlated significantly with a rater's assessment of driving performance. PMID:26713169

  1. Base drive for paralleled inverter systems

    NASA Technical Reports Server (NTRS)

    Nagano, S. (Inventor)

    1980-01-01

    In a paralleled inverter system, a positive feedback current derived from the total current from all of the modules of the inverter system is applied to the base drive of each of the power transistors of all modules, thereby to provide all modules protection against open or short circuit faults occurring in any of the modules, and force equal current sharing among the modules during turn on of the power transistors.

  2. A high-fidelity harmonic drive model.

    SciTech Connect

    Preissner, C.; Royston, T. J.; Shu, D.

    2012-01-01

    In this paper, a new model of the harmonic drive transmission is presented. The purpose of this work is to better understand the transmission hysteresis behavior while constructing a new type of comprehensive harmonic drive model. The four dominant aspects of harmonic drive behavior - nonlinear viscous friction, nonlinear stiffness, hysteresis, and kinematic error - are all included in the model. The harmonic drive is taken to be a black box, and a dynamometer is used to observe the input/output relations of the transmission. This phenomenological approach does not require any specific knowledge of the internal kinematics. In a novel application, the Maxwell resistive-capacitor hysteresis model is applied to the harmonic drive. In this model, sets of linear stiffness elements in series with Coulomb friction elements are arranged in parallel to capture the hysteresis behavior of the transmission. The causal hysteresis model is combined with nonlinear viscous friction and spectral kinematic error models to accurately represent the harmonic drive behavior. Empirical measurements are presented to quantify all four aspects of the transmission behavior. These measurements motivate the formulation of the complete model. Simulation results are then compared to additional measurements of the harmonic drive performance.

  3. Modeling of Passive Forces of Machine Tool Covers

    NASA Astrophysics Data System (ADS)

    Kolar, Petr; Hudec, Jan; Sulitka, Matej

    The passive forces acting against the drive force are phenomena that influence dynamical properties and precision of linear axes equipped with feed drives. Covers are one of important sources of passive forces in machine tools. The paper describes virtual evaluation of cover passive forces using the cover complex model. The model is able to compute interaction between flexible cover segments and sealing wiper. The result is deformation of cover segments and wipers which is used together with measured friction coefficient for computation of cover total passive force. This resulting passive force is dependent on cover position. Comparison of computational results and measurement on the real cover is presented in the paper.

  4. [Daytime sleepiness and driving behaviour].

    PubMed

    Mathis, Johannes; Schreier, David

    2014-11-01

    Daytime sleepiness is reported by 10-15 % within the general population of industrialised countries. According to federal statistics in Switzerland, only ~1.5 % of motor vehicle crashes are caused by excessive daytime sleepiness, which is in sharp contrast to the scientific literature, indicating a figure of 10 to 30 %. This is most likely related to the difficulty to detect the underlying sleepiness by police officers and their low awareness of this cause in case of car accidents. As a consequence of this massively reduced figure, the real problem is underestimated and countermeasures as well as examinations of drivers at fault are inadequately realised in our country. The risk factors for sleepiness induced accidents are young age, male sex, driving at night or long distances and a number of diseases or sedative drugs. The most prevalent cause of sleepiness related accidents is the behaviourally induced sleep insufficiency syndrome or irregular sleep-wake rhythm in otherwise healthy subjects. Disease related sleepiness which may also cause motor vehicle accidents must be managed by physicians. In the diagnostic work-up sedative drugs, medical causes of sleepiness or tiredness as well as primary sleep-wake disorders must be considered. The most important duty of the treating physician, in addition to correct diagnosis and treatment, is to inform the affected patient of his or her responsibility not to drive while sleepy, about the theoretical legal consequences in case of an accident and about efficient countermeasures such as stopping in a rest area, drinking coffee, and taking a nap. For legal reasons, this information must be written in the patient's notes. Professional drivers suffering from sleep apnoea syndrome or other disorders with excessive daytime sleepiness, or private drivers who have already experienced a sleepiness induced accident, should be referred to a sleep-wake-centre for objective assessment of their sleepiness in the maintenance of

  5. Improved linear ultrasonic motor performance with square-wave based driving-tip trajectory

    NASA Astrophysics Data System (ADS)

    Le, Adam Y.; Mills, James K.; Benhabib, Beno

    2015-03-01

    This paper proposes the application of a non-sinusoidal periodic excitation voltage to induce a near-square-wave driving tip trajectory in linear ultrasonic motors (LUSMs). A square-wave-based trajectory can deliver superior frictional force to the moving stage in the forward stroke of the driving tip motion and reduced frictional force during the return stroke. This would reduce lost power in the periodic driving tip motion, thereby, increasing the output force and power of the LUSM. An implementation procedure is suggested to achieve the near-square-wave driving tip trajectory. The proposed approach is illustrated through realistic finite-element-based simulations using a bimodal LUSM configuration.

  6. Force sensor

    DOEpatents

    Grahn, Allen R.

    1993-01-01

    A force sensor and related method for determining force components. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  7. Force sensor

    DOEpatents

    Grahn, A.R.

    1993-05-11

    A force sensor and related method for determining force components is described. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  8. Alcohol policies and impaired driving in the United States: Effects of driving- vs. drinking-oriented policies

    PubMed Central

    Xuan, Ziming; Blanchette, Jason G.; Nelson, Toben F.; Heeren, Timothy C.; Nguyen, Thien H.; Naimi, Timothy S.

    2015-01-01

    Aims To test the hypotheses that stronger policy environments are associated with less impaired driving and that driving-oriented and drinking-oriented policy subgroups are independently associated with impaired driving. Design State-level data on 29 policies in 50 states from 2001–2009 were used as lagged exposures in generalized linear regression models to predict self-reported impaired driving. Setting Fifty United States and Washington, D.C. Participants A total of 1,292,245 adults (≥ 18 years old) biennially from 2002–2010. Measures Alcohol Policy Scale scores representing the alcohol policy environment were created by summing policies weighted by their efficacy and degree of implementation by state-year. Past-30-day alcohol-impaired driving from 2002–2010 was obtained from the Behavioral Risk Factor Surveillance System surveys. Findings Higher Alcohol Policy Scale scores are strongly associated with lower state-level prevalence and individual-level risk of impaired driving. After accounting for driving-oriented policies, drinking-oriented policies had a robust independent association with reduced likelihood of impaired driving. Reduced binge drinking mediates the relationship between drinking-oriented policies and impaired driving, and driving-oriented policies reduce the likelihood of impaired driving among binge drinkers. Conclusions Efforts to reduce alcohol-impaired driving should focus on reducing excessive drinking in addition to preventing driving among those who are impaired. PMID:26925185

  9. Driving Anger and Driving Behavior in Adults with ADHD

    ERIC Educational Resources Information Center

    Richards, Tracy L.; Deffenbacher, Jerry L.; Rosen, Lee A.; Barkley, Russell A.; Rodricks, Trisha

    2006-01-01

    Objective: This study assesses whether anger in the context of driving is associated with the negative driving outcomes experienced by individuals with ADHD. Method: ADHD adults (n = 56) complete measures of driving anger, driving anger expression, angry thoughts behind the wheel, and aggressive, risky, and crash-related behavior. Results are…

  10. Driving anger in Malaysia.

    PubMed

    Sullman, Mark J M; Stephens, Amanda N; Yong, Michelle

    2014-10-01

    The present study examined the types of situations that cause Malaysian drivers to become angry. The 33-item version of the driver anger scale (Deffenbacher et al., 1994) was used to investigate driver anger amongst a sample of 339 drivers. Confirmatory factor analysis showed that the fit of the original six-factor model (discourtesy, traffic obstructions, hostile gestures, slow driving, illegal driving and police presence), after removing one item and allowing three error pairs to covary, was satisfactory. Female drivers reported more anger, than males, caused by traffic obstruction and hostile gestures. Age was also negatively related to five (discourtesy, traffic obstructions, hostile gestures, slow driving and police presence) of the six factors and also to the total DAS score. Furthermore, although they were not directly related to crash involvement, several of the six forms of driving anger were significantly related to the crash-related conditions of: near misses, loss of concentration, having lost control of a vehicle and being ticketed. Overall the pattern of findings made in the present research were broadly similar to those from Western countries, indicating that the DAS is a valid measure of driving anger even among non-European based cultures. PMID:24863369

  11. [Drug use and driving].

    PubMed

    Lemaire-Hurtel, Anne-Sophie; Goullé, Jean-Pierre; Alvarez, Jean-Claude; Mura, Patrick; Verstraete, Alain G

    2015-10-01

    Some drugs are known to impair driving because they can change the vision or hearing, and/or disrupt the intellectual or motor abilities: impaired vigilance, sedation, disinhibition effect, the coordination of movement disorders and the balance. The doctor during prescribing and the pharmacist during deliverance of drug treatment should inform their patients of the potential risks of drugs on driving or operating machinery. The driver has direct responsibility, who hired him and him alone, to follow the medical advice received. The pictograms on the outer packaging of medicinal products intended to classify substances according to their risk driving: The driver can whether to observe simple precautions (level one "be prudent"), or follow the advice of a health professional (level two "be very careful"), or if it is totally not drive (level three "danger caution: do not drive"). This classification only evaluates the intrinsic danger of drugs but not the individual variability. Medicines should be taken into account also the conditions for which the medication is prescribed. It is important to inform the patient on several points. PMID:25956300

  12. Universal power transistor base drive control unit

    DOEpatents

    Gale, A.R.; Gritter, D.J.

    1988-06-07

    A saturation condition regulator system for a power transistor is disclosed which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition. 2 figs.

  13. Universal power transistor base drive control unit

    DOEpatents

    Gale, Allan R.; Gritter, David J.

    1988-01-01

    A saturation condition regulator system for a power transistor which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition.

  14. Ceramic vane drive joint

    DOEpatents

    Smale, Charles H.

    1981-01-01

    A variable geometry gas turbine has an array of ceramic composition vanes positioned by an actuating ring coupled through a plurality of circumferentially spaced turbine vane levers to the outer end of a metallic vane drive shaft at each of the ceramic vanes. Each of the ceramic vanes has an end slot of bow tie configuration including flared end segments and a center slot therebetween. Each of the vane drive shafts has a cross head with ends thereof spaced with respect to the sides of the end slot to define clearance for free expansion of the cross head with respect to the vane and the cross head being configured to uniformly distribute drive loads across bearing surfaces of the vane slot.

  15. U.S. DRIVE

    SciTech Connect

    2012-03-16

    U.S. DRIVE, which stands for United States Driving Research and Innovation for Vehicle efficiency and Energy sustainability, is an expanded government-industry partnership among the U.S. Department of Energy; USCAR, representing Chrysler Group LLC, Ford Motor Company and General Motors; Tesla Motors; five energy companies – BP America, Chevron Corporation, ConocoPhillips, ExxonMobil Corporation, and Shell Oil Products US; two utilities – Southern California Edison and Michigan-based DTE Energy; and the Electric Power Research Institute (EPRI). The U.S. DRIVE mission is to accelerate the development of pre-competitive and innovative technologies to enable a full range of affordable and clean advanced light-duty vehicles, as well as related energy infrastructure.

  16. Sensing mode atomic force microscope

    DOEpatents

    Hough, Paul V.; Wang, Chengpu

    2004-11-16

    An atomic force microscope is described having a cantilever comprising a base and a probe tip on an end opposite the base; a cantilever drive device connected to the base; a magnetic material coupled to the probe tip, such that when an incrementally increasing magnetic field is applied to the magnetic material an incrementally increasing force will be applied to the probe tip; a moveable specimen base; and a controller constructed to obtain a profile height of a specimen at a point based upon a contact between the probe tip and a specimen, and measure an adhesion force between the probe tip and the specimen by, under control of a program, incrementally increasing an amount of a magnetic field until a release force, sufficient to break the contact, is applied. An imaging method for atomic force microscopy involving measuring a specimen profile height and adhesion force at multiple points within an area and concurrently displaying the profile and adhesion force for each of the points is also described. A microscope controller is also described and is constructed to, for a group of points, calculate a specimen height at a point based upon a cantilever deflection, a cantilever base position and a specimen piezo position; calculate an adhesion force between a probe tip and a specimen at the point by causing an incrementally increasing force to be applied to the probe tip until the probe tip separates from a specimen; and move the probe tip to a new point in the group.

  17. Sensing mode atomic force microscope

    DOEpatents

    Hough, Paul V. C.; Wang, Chengpu

    2006-08-22

    An atomic force microscope is described having a cantilever comprising a base and a probe tip on an end opposite the base; a cantilever drive device connected to the base; a magnetic material coupled to the probe tip, such that when an incrementally increasing magnetic field is applied to the magnetic material an incrementally increasing force will be applied to the probe tip; a moveable specimen base; and a controller constructed to obtain a profile height of a specimen at a point based upon a contact between the probe tip and a specimen, and measure an adhesion force between the probe tip and the specimen by, under control of a program, incrementally increasing an amount of a magnetic field until a release force, sufficient to break the contact, is applied. An imaging method for atomic force microscopy involving measuring a specimen profile height and adhesion force at multiple points within an area and concurrently displaying the profile and adhesion force for each of the points is also described. A microscope controller is also described and is constructed to, for a group of points, calculate a specimen height at a point based upon a cantilever deflection, a cantilever base position and a specimen piezo position; calculate an adhesion force between a probe tip and a specimen at the point by causing an incrementally increasing force to be applied to the probe tip until the probe tip separates from a specimen; and move the probe tip to a new point in the group.

  18. How are Inner Hair Cells Stimulated? Evidence for multiple mechanical drives

    PubMed Central

    Guinan, John J.

    2013-01-01

    Recent studies indicate that the gap over outer hair cells (OHCs) between the reticular lamina (RL) and the tectorial membrane (TM) varies cyclically during low-frequency sounds. Variation in the RL-TM gap produces radial fluid flow in the gap that can drive inner hair cell (IHC) stereocilia. Analysis of RL-TM gap changes reveals three IHC drives in addition to classic SHEAR. For upward basilar-membrane (BM) motion, IHC stereocilia are deflected in the excitatory direction by SHEAR and OHC-MOTILITY, but in the inhibitory direction by TM-PUSH and CILIA-SLANT. Upward BM motion causes OHC somatic contraction which tilts the RL, compresses the RL-TM gap over IHCs and expands the RL-TM gap over OHCs, thereby producing an outward (away from the IHCs) radial fluid flow which is the OHC-MOTILITY drive. For upward BM motion, the force that moves the TM upward also compresses the RL-TM gap over OHCs causing inward radial flow past IHCs which is the TM-PUSH drive. Motions that produce large tilting of OHC stereocilia squeeze the supra-OHC RL-TM gap and caused inward radial flow past IHCs which is the CILIA-SLANT drive. Combinations of these drives explain: (1) the reversal at high sound levels of auditory nerve (AN) initial peak (ANIP) responses to clicks, and medial olivocochlear (MOC) inhibition of ANIP responses below, but not above, the ANIP reversal, (2) dips and phase reversals in AN responses to tones in cats and chinchillas, (3) hypersensitivity and phase reversals in tuning-curve tails after OHC ablation, and (4) MOC inhibition of tail-frequency AN responses. The OHC-MOTILITY drive provides another mechanism, in addition to BM motion amplification, that uses active processes to enhance the output of the cochlea. The ability of these IHC drives to explain previously anomalous data provides strong, although indirect, evidence that these drives are significant and presents a new view of how the cochlea works at frequencies below 3 kHz. PMID:22959529

  19. Test bed with force-measuring crank for static and dynamic investigations on cycling by means of functional electrical stimulation.

    PubMed

    Gföhler, M; Angeli, T; Eberharter, T; Lugner, P; Mayr, W; Hofer, C

    2001-06-01

    Cycling by means of functional electrical stimulation (FES) is an attractive training method for individuals with paraplegia. The physiological benefits of FES are combined with the psychological incentive of independent locomotion. In addition, cycling has the advantage in that the generated muscle forces are converted into drive power with relatively high efficiency compared to other means of locomotion, e.g., walking. For the design of an appropriate cycling device and the development of optimal stimulation patterns, it has to be investigated how the geometry for FES cycling, influenced by individual parameters of the FES-generated drive torques and the magnitude of variations among subjects with paraplegia, can be optimized. This study shows the design of a freely adjustable test bed with additional motor drive which allows static and dynamic measurements of force components and drive torque at the crank. Furthermore, the influence of geometry and various individual parameters on FES pedaling can be tested for each subject individually. A pedal path realized by a three-bar linkage that was optimized according to preliminary simulations further increases leg cycling efficiency. Safety precautions avoid injuries in case of excessive forces, e.g., spasms. Test results illustrate the application of the test bed and measurement routines. A test series with four paraplegic test persons showed that the presented static and dynamic measurement routines allow to provide optimal stimulation patterns for individual paraplegic subjects. While pedaling with these optimal stimulation patterns only negligible negative active drive torques, due to active muscle forces, were applied to the crank and sufficient drive power was generated to power a cycle independently. PMID:11474970

  20. LCLS Injector Drive Laser

    SciTech Connect

    Dowell, D.H.; Castro, J.; Emma, P.; Frisch, J.; Gilevich, A.; Hays, G.; Hering, P.; Limborg-Deprey, C.; Loos, H.; Miahnahri, A.; White, W.; /SLAC

    2007-11-02

    Requirements for the LCLS injector drive laser present significant challenges to the design of the system. While progress has been demonstrated in spatial shape, temporal shape, UV generation and rep-rate, a laser that meets all of the LCLS specifications simultaneously has yet to be demonstrated. These challenges are compounded by the stability and reliability requirements. The drive laser and transport system has been installed and tested. We will report on the current operational state of the laser and plans for future improvements.