Sample records for internal forces

  1. Internal forces during object manipulation

    PubMed Central

    Gao, Fan; Latash, Mark L.; Zatsiorsky, Vladimir M.

    2010-01-01

    Internal force is a set of contact forces that does not disturb object equilibrium. The elements of the internal force vector cancel each other and, hence, do not contribute to the resultant (manipulation) force acting on the object. The mathematical independence of the internal and manipulation forces allows for their independent (decoupled) control realized in robotic manipulators. To examine whether in humans internal force is coupled with the manipulation force and what grasping strategy the performers utilize, the subjects (n=6) were instructed to make cyclic arm movements with a customized handle. Six combinations of handle orientation and movement direction were tested. These involved: parallel manipulations (1) VV task (vertical orientation and vertical movement) and (2) HH task (horizontal orientation and horizontal movement); orthogonal manipulations (3) VH task (vertical orientation and horizontal movement) and (4) HV task (horizontal orientation and vertical movement); and diagonal manipulations (5) DV task (diagonal orientation and vertical movement) and (6) DH task (diagonal orientation and horizontal movement). Handle weight (from 3.8 to 13.8 N), and movement frequency (from 1 to 3 Hz) were systematically changed. The analysis was performed at the thumb-virtual finger level (VF, an imaginary finger that produces a wrench equal to the sum of wrenches produced by all the fingers). At this level, the forces of interest could be reduced to the internal force and internal moment. During the parallel manipulations, the internal (grip) force was coupled with the manipulation force (producing object acceleration) and the thumb-VF forces increased or decreased in phase: the thumb and VF worked in synchrony to grasp the object more strongly or more weakly. During the orthogonal manipulations, the thumb-VF forces changed out of phase: the plots of the internal force vs. object acceleration resembled an inverted letter V. The HV task was the only task where the relative phase (coupling) between the normal forces of the thumb and VF depended on oscillation frequency. During the diagonal manipulations, the coupling was different in the DV and DH tasks. A novel observation of substantial internal moments is described: the moments produced by the normal finger forces were counterbalanced by the moments produced by the tangential forces such that the resultant moments were close to zero. Implications of the findings for the notion of grasping synergies are discussed. PMID:15912369

  2. On the work of internal forces

    NASA Astrophysics Data System (ADS)

    Güémez, J.; Fiolhais, M.; Brito, L.

    2015-07-01

    We discuss the role of the internal forces and how their work changes the energy of a system. We illustrate the contribution of the internal work to the variation of the system’s energy, using a pure mechanical example, a thermodynamical system and an example from electromagnetism. We emphasize that internal energy variations related to the work of the internal forces should be pinpointed in the classroom and placed on the same footing as other internal energy variations such as those caused by temperature changes or by chemical reactions.

  3. 77 FR 29899 - Safety Zone; International Special Operations Forces Week Capability Exercise, Seddon Channel...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-21

    ...International Special Operations Forces Week Capability Exercise, Seddon Channel...International Special Operations Forces Week Capability Exercise. The exercise is scheduled...International Special Operations Forces Week Capability Exercise is scheduled to...

  4. 47 CFR 2.100 - International regulations in force.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.100 International regulations in force. The ITU Radio Regulations,...

  5. 47 CFR 2.100 - International regulations in force.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.100 International regulations in force. The ITU Radio Regulations,...

  6. 47 CFR 2.100 - International regulations in force.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.100 International regulations in force. The ITU Radio Regulations,...

  7. 47 CFR 2.100 - International regulations in force.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.100 International regulations in force. The ITU Radio Regulations,...

  8. 47 CFR 2.100 - International regulations in force.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.100 International regulations in force. The ITU Radio Regulations ,...

  9. Joining Forces: The Case of Alliant International University

    ERIC Educational Resources Information Center

    Leslie, Heather

    2013-01-01

    Mergers and acquisitions are a prevalent force in higher education as more colleges and universities are joining forces to expand resources, enhance missions, or prevent closures. This study examines the merger of Alliant University (formerly California School of Professional Psychology) with United States International University to create what…

  10. Forcing, feedback and internal variability in global temperature trends.

    PubMed

    Marotzke, Jochem; Forster, Piers M

    2015-01-29

    Most present-generation climate models simulate an increase in global-mean surface temperature (GMST) since 1998, whereas observations suggest a warming hiatus. It is unclear to what extent this mismatch is caused by incorrect model forcing, by incorrect model response to forcing or by random factors. Here we analyse simulations and observations of GMST from 1900 to 2012, and show that the distribution of simulated 15-year trends shows no systematic bias against the observations. Using a multiple regression approach that is physically motivated by surface energy balance, we isolate the impact of radiative forcing, climate feedback and ocean heat uptake on GMST--with the regression residual interpreted as internal variability--and assess all possible 15- and 62-year trends. The differences between simulated and observed trends are dominated by random internal variability over the shorter timescale and by variations in the radiative forcings used to drive models over the longer timescale. For either trend length, spread in simulated climate feedback leaves no traceable imprint on GMST trends or, consequently, on the difference between simulations and observations. The claim that climate models systematically overestimate the response to radiative forcing from increasing greenhouse gas concentrations therefore seems to be unfounded. PMID:25631444

  11. Internal flows and force matrices in axial flow inducers

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Abhijit

    1994-01-01

    Axial flow inducers such as those used in high speed rocket engine turbopumps are subject to complex internal flows and fluid-induced lateral and rotordynamic forces. An investigation of these internal flows was conducted using boundary layer flow visualization on the blades, hub and housing of unshrouded and shrouded inducers. Results showed that the blade boundary layer flows have strong radial components at off-design conditions and remain attached to the blade surface at all flow coefficients tested. The origin of upstream swirling backflow was found to be at the discharge plane of the inducer. In addition, flow reversal was observed at the suction side blade tip near the leading edge in a shrouded inducer. Re-entry of the hub boundary layer flow, a downstream backflow, into the blade passage area was observed at flow coefficients below design. For unshrouded inducers the radially outward flow near the blade tip mixed with the leakage flow to form the upstream backflow. The lateral and rotordynamic forces acting on an inducer due to an imposed whirl motion was also investigated at various flow coefficients. It was found that the rotordynamic force data at various whirl frequency ratios does not allow a normal quadratic fit; consequently the conventional inertial, stiffness and damping coefficients cannot be obtained and a definite whirl ratio describing the instability region does not result. Application of an actuator disk theory proved to be inaccurate in estimating the rotordynamic tangential force in a non-whirling inducer. The effect of upstream and downstream flow distortions on the rotordynamic and lateral forces on an inducer were studied. It was found that at flow coefficients below design, large lateral forces occurred in the presence of a downstream asymmetry. Results of inlet distortion experiments show that a strong inlet shear causes a significant increase in the lateral force. Cavitation was found to have important consequences for fluid-induced rotordynamic forces. These forces become destabilizing for both forward and reverse whirl. Decreasing cavitation numbers caused an increase in the magnitudes of the destabilizing forces.

  12. Forcing of oceanic mean flows by dissipating internal tides

    NASA Astrophysics Data System (ADS)

    Grisouard, Nicolas; Buhler, Oliver

    2012-11-01

    We present a theoretical study of the effective mean force exerted on an oceanic mean flow due to the presence of small-amplitude internal waves that are forced by a barotropic tide flowing over a topography and are also subject to dissipation. Although the details of our computation are quite different, we recover the main action-at-a-distance result familiar from atmospheric wave-mean interaction theory, namely that the effective mean force that is felt by the mean flow is located in regions of wave dissipation, and not necessarily near the topographic wave source. Specifically, using a perturbation series in small wave amplitude, we compute the three-dimensional leading-order wave field using a Green's function approach, derive an explicit expression for the leading-order effective mean force at the next order within the framework of generalized Lagrangian-mean theory, discuss in detail the range of situations in which a strong, secularly growing mean-flow response can be expected, and finally compute the effective mean force numerically in a number of illustrative examples with simple topographies. Financial support under the United States National Science Foundation grants NSF/OCE 1024180 and NSF/DMS 1009213 is gratefully acknowledged.

  13. Internal force control with no object motion in compliant robotic grasps M. Malvezzi and D. Prattichizzo

    E-print Network

    Siena, Università di

    Internal force control with no object motion in compliant robotic grasps M. Malvezzi and D of internal forces implies the motion of the manipulated object. This paper deals with this issue and studies the structural conditions for the control of internal forces which do not involve any motion of the grasped

  14. Integrals of Motion for Planar Multi-Body Formations with Internal Forces

    E-print Network

    Peck, Mason A.

    Integrals of Motion for Planar Multi-Body Formations with Internal Forces Michael C. Norman of such a force potentially complicates the analysis of these systems, inte- grals of motion still exist, AIAA Member. 1 of 19 Integrals of Motion for Planar Multi-Body Formations with Internal Forces #12;~q

  15. Foot Forces during Treadmill Exercise on the International Space Station

    NASA Technical Reports Server (NTRS)

    Cavanagh, Peter R.; Rice, Andrea J.; Maender, Christian C.; Gopalakrishnan, Raghavan; Genc, Kerim O.; Kuklis, Matthew

    2006-01-01

    Exercise has been the primary countermeasure to combat musculoskeletal changes during the approximately 6 month missions to the International Space Station (ISS). However, these countermeasures have not been successful in preventing loss of bone mineral density in the spine and hip of astronauts. We examined lower extremity loading during typical bouts of on-orbit exercise performed by 4 ISS crew members on the ISS treadmill (TVIS) and during locomotor activities on earth (1g). In-shoe forces were monitored at 128Hz using force-measuring insoles placed inside the shoes of the exercising crewmember, stored temporarily on Flash cards, and down-linked via satellite for analysis. Custom software extracted peak forces from up to 30 minutes of locomotor activity. All on-orbit loading conditions for walking and running resulted in peak forces and impact loading rates that were significantly less than those measured in 1g. Typical single leg loads on-orbit in walking and running were 0.860 plus or minus 0.04 body weights (BW) and 1.339 plus or minus 0.07 BW compared to 1.2 plus or minus 0.036 BW and 2.36 plus or minus 0.07 BW in 1g BW respectively. These results indicate that typical exercise on the ISS treadmill does not generate 1g-like loading conditions. This may be partly responsible for the loss of bone mineral density that has been observed in these and other crew members. Since on-orbit treadmill exercise requires a restraining load to return the crew member to the treadmill surface, more studies are required to enable comfortable full body weight loading to be applied.

  16. International Reference Ionosphere (IRI): Task Force Activity 2000

    NASA Technical Reports Server (NTRS)

    Bilitza, D.

    2000-01-01

    The annual IRI Task Force Activity was held at the Abdus Salam International Center for Theoretical Physics in Trieste, Italy from July 10 to July 14. The participants included J. Adeniyi (University of Ilorin, Nigeria), D. Bilitza (NSSDC/RITSS, USA), D. Buresova (Institute of Atmospheric Physics, Czech Republic), B. Forte (ICTP, Italy), R. Leitinger (University of Graz, Austria), B. Nava (ICTP, Italy), M. Mosert (University National Tucuman, Argentina), S. Pulinets (IZMIRAN, Russia), S. Radicella (ICTP, Italy), and B. Reinisch (University of Mass. Lowell, USA). The main topic of this Task Force Activity was the modeling of the topside ionosphere and the development of strategies for modeling of ionospheric variability. Each day during the workshop week the team debated a specific modeling problem in the morning during informal presentations and round table discussions of all participants. Ways of resolving the specific modeling problem were devised and tested in the afternoon in front of the computers of the ICTP Aeronomy and Radiopropagation Laboratory using ICTP s computer networks and internet access.

  17. Foot forces during exercise on the International Space Station.

    PubMed

    Genc, K O; Gopalakrishnan, R; Kuklis, M M; Maender, C C; Rice, A J; Bowersox, K D; Cavanagh, P R

    2010-11-16

    Long-duration exposure to microgravity has been shown to have detrimental effects on the human musculoskeletal system. To date, exercise countermeasures have been the primary approach to maintain bone and muscle mass and they have not been successful. Up until 2008, the three exercise countermeasure devices available on the International Space Station (ISS) were the treadmill with vibration isolation and stabilization (TVIS), the cycle ergometer with vibration isolation and stabilization (CEVIS), and the interim resistance exercise device (iRED). This article examines the available envelope of mechanical loads to the lower extremity that these exercise devices can generate based on direct in-shoe force measurements performed on the ISS. Four male crewmembers who flew on long-duration ISS missions participated in this study. In-shoe forces were recorded during activities designed to elicit maximum loads from the various exercise devices. Data from typical exercise sessions on Earth and on-orbit were also available for comparison. Maximum on-orbit single-leg loads from TVIS were 1.77 body weight (BW) while running at 8mph. The largest single-leg forces during resistance exercise were 0.72 BW during single-leg heel raises and 0.68 BW during double-leg squats. Forces during CEVIS exercise were small, approaching only 0.19 BW at 210W and 95RPM. We conclude that the three exercise devices studied were not able to elicit loads comparable to exercise on Earth, with the exception of CEVIS at its maximal setting. The decrements were, on average, 77% for walking, 75% for running, and 65% for squats when each device was at its maximum setting. Future developments must include an improved harness to apply higher gravity replacement loads during locomotor exercise and the provision of greater resistance exercise capability. The present data set provides a benchmark that will enable future researchers to judge whether or not the new generation of exercise countermeasures recently added to the ISS will address the need for greater loading. PMID:20728086

  18. Internal Forces during Static Prehension: Effects of Age and Grasp Configuration

    PubMed Central

    Solnik, Stanislaw; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2014-01-01

    We studied effects of healthy aging on three components of the internal force vector during static prehensile tasks. Young and older subjects held an instrumented handle using a five-digit prismatic grasp under different digit configurations and external torques. Across digit configurations, older subjects showed larger internal normal (grip) and tangential (load-resisting) digit force components and larger internal moment of force. In contrast to earlier reports, safety margin values were not higher in the older subjects. The results show that the increased grip force in older persons is a specific example of a more general age-related problem reflected in the generation of large internal force vectors in prehensile tasks. It is possible that the higher internal forces increase the apparent stiffness of the “hand+handle” system and, hence, contribute to its stability. This strategy, however, may be maladaptive, energetically wasteful, and inefficient in ensuring safety of hand-held objects. PMID:24650078

  19. Foot forces during typical days on the international space station.

    PubMed

    Cavanagh, P R; Genc, K O; Gopalakrishnan, R; Kuklis, M M; Maender, C C; Rice, A J

    2010-08-10

    Decreased bone mineral density (BMD) in astronauts returning from long-duration spaceflight missions has been well documented, but the altered mechanical loading environment experienced by the musculoskeletal system, which may contribute to these changes, has not been well characterized. The current study describes the loading environment of the lower extremity (LE) during typical days on the International Space Station (ISS) compared to similar data for the same individuals living on Earth. Data from in-shoe force measurements are also used as input to the enhanced daily load stimulus (EDLS) model to determine the mechanical "dose" experienced by the musculoskeletal system and to associate this dose with changes in BMD. Four male astronauts on approximately 6-month missions to the ISS participated in this study. In-shoe forces were recorded using capacitance-based insoles during entire typical working days both on Earth and on-orbit. BMD estimates from the hip and spine regions were obtained from dual energy X-ray absorptiometry (DXA) pre- and post-flight. Measurable loading was recorded for only 30% of the time assigned for exercise. In-shoe forces during treadmill walking and running on the ISS were reduced by 25% and 46%, respectively, compared to similar activities on Earth. Mean on-orbit LE loads varied from 0.20 to 1.3 body weight (BW) during resistance exercise and were approximately 0.10 BW during bicycle ergometry. Application of the EDLS model showed a mean decrease of 25% in the daily load experienced by the LE. BMD decreased by 0.71% and 0.83% per month during their missions in the femoral neck and lumbar spine, respectively. Our findings support the conclusion that the measured ISS exercise durations and/or loading were insufficient to provide the loading stimulus required to prevent bone loss. Future trials with EDLS values closer to 100% of Earth values will offer a true test of exercise as a countermeasure to on-orbit bone loss. PMID:20462584

  20. A simple estimation of the force exerted by internal solitons on cylindrical piles

    Microsoft Academic Search

    Shuqun Cai; Shengan Wang; Xiaomin Long

    2006-01-01

    Internal solitons can bring about strong force on the oil drilling platform and pipeline at sea, which causes severe threat to the ocean engineering. Cai et al. (2003) introduced Morison's empirical formula, modal separation method and regression analyses to estimate the forces exerted by internal soliton on cylindrical piles. However, this method is very complicated and it requires some observational

  1. The Virtual Linkage: A Model for Internal Forces in Multi-Grasp Manipulation

    Microsoft Academic Search

    David Williams; Oussama Khatib

    1993-01-01

    We propose a model to characterize internal forcesand moments during multi-grasp manipulation. Theproposed approach is based on construction of a physicalmodel, called the virtual linkage, which is a closedchain mechanism that represents the object being manipulated.Forces and moments applied at the grasppoints of this linkage cause joint forces and torquesat its actuators. When these actuators are subjectedto the opposing forces

  2. The dynamics of internal wave resonance in periodically forced narrow basins

    NASA Astrophysics Data System (ADS)

    Boegman, Leon; Ivey, Gregory N.

    2012-11-01

    Laboratory experiments were conducted to determine the steady state internal wave response of a periodically forced, density-stratified, basin characterized by both horizontal and vertical length scales and a known seiche period. The system was two-layer stratified and was subjected to periodic forcing over a wide frequency range. The forcing amplitude and ratio of the forcing frequency (?f) to horizontal mode one (H1) internal seiche frequency (?1) governed the system response. For ?f > ?1, higher-mode internal seiches were observed; for?f < ?1, a nonresonant forced H1 internal seiche was observed; and for ?f ? ?1, a resonant H1 internal seiche was observed. For this resonant regime, progressive nonlinear internal waves (NLIWs) formed upon the H1 seiche. When the NLIWs amplitudes were large, Kelvin-Helmholtz instabilities grew within the wave troughs, leading to significant diapycnal mixing within the basin interior. Resonant amplification was most pronounced for small forcing amplitudes because weakly forced waves have the most potential for growth prior to energy flux to NLIWs and ultimate turbulent dissipation and mixing. This observation suggests that each mode has a maximum energy density that, when exceeded, leads to a nonlinear energy cascade. The resonant wave response was modeled as a driven underdamped harmonic oscillator, where the damping coefficient was interpreted as the sum of the effects of mixing and dissipation.

  3. Minimizing distortion and internal forces in truss structures by simulated annealing

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.; Padula, Sharon L.

    1990-01-01

    Inaccuracies in the length of members and the diameters of joints of large space structures may produce unacceptable levels of surface distortion and internal forces. Here, two discrete optimization problems are formulated, one to minimize surface distortion (DSQRMS) and the other to minimize internal forces (FSQRMS). Both of these problems are based on the influence matrices generated by a small-deformation linear analysis. Good solutions are obtained for DSQRMS and FSQRMS through the use of a simulated annealing heuristic.

  4. Reflections on a Seminal Force in International Accounting

    ERIC Educational Resources Information Center

    Cascini, Karen T.

    2007-01-01

    Accounting is a manifestation of several important environmental factors within a country, including economic, educational and political, and, as such, is evolutionary in accordance with those changing social structures. Because of the major impact that international accounting has had on countries' internal accounting systems, it is important to…

  5. Internal Versus SST-Forced Atmospheric Variability as Simulated by an Atmospheric General Circulation Model

    Microsoft Academic Search

    Ali Harzallah; Robert Sadourny

    1995-01-01

    The variability of atmospheric flow is analyzed by separating it into an internal part due to atmospheric dynamics only and an external (or forced) part due to the variability of sea surface temperature forcing. The two modes of variability are identified by performing an ensemble of seven independent long-term simulations of the atmospheric response to observed SST (1970-1988) with the

  6. Effects of internal flow and viscosity ratio on measurements of dynamic forces between deformable drops.

    PubMed

    Edwards, Scott A; Carnie, Steven L; Manor, Ofer; Chan, Derek Y C

    2009-04-01

    A model that has been shown to give very accurate predictions of dynamic forces between deformable emulsion drops and bubbles is used to quantify the effects of internal flow and viscosity ratio on the hydrodynamic interaction in such systems. The results demonstrate that direct force measurement using an atomic force microscope can readily differentiate whether the interfaces of drops of different viscosities respond as immobile (no-slip) or fully mobile (no tangential shear stress) boundaries. PMID:19708135

  7. Instinctual Affective Forces in the Internalization Process: Contributions of Hans Loewald.

    ERIC Educational Resources Information Center

    Dean, Anne L.

    1994-01-01

    Focuses on the role of instinctual and affective forces in internalization, a process identified by Piaget and Vygotsky as the primary mechanism underlying the development of higher mental structures and functions. Discusses the theory of contemporary psychoanalyst Hans Loewald, who shares Piaget's and Vygotsky's emphasis on internalization but…

  8. Foot forces during exercise on the International Space Station

    Microsoft Academic Search

    K. O. Genc; R. Gopalakrishnan; M. M. Kuklis; C. C. Maender; A. J. Rice; K. D. Bowersox; P. R. Cavanagh

    2010-01-01

    Long-duration exposure to microgravity has been shown to have detrimental effects on the human musculoskeletal system. To date, exercise countermeasures have been the primary approach to maintain bone and muscle mass and they have not been successful. Up until 2008, the three exercise countermeasure devices available on the International Space Station (ISS) were the treadmill with vibration isolation and stabilization

  9. Foot forces during typical days on the international space station

    Microsoft Academic Search

    P. R. Cavanagh; K. O. Genc; R. Gopalakrishnan; M. M. Kuklis; C. C. Maender; A. J. Rice

    2010-01-01

    Decreased bone mineral density (BMD) in astronauts returning from long-duration spaceflight missions has been well documented, but the altered mechanical loading environment experienced by the musculoskeletal system, which may contribute to these changes, has not been well characterized. The current study describes the loading environment of the lower extremity (LE) during typical days on the International Space Station (ISS) compared

  10. Forced convective heat transfer in channels with internal longitudinal fins

    E-print Network

    Ong, Liang Eng

    1987-01-01

    Chairman of Advisory Committee: Dr. S. C. Lau A computational study is conducted to examine the fully developed laminar flow and heat transfer characteristics in a parallel plate channel with internal, longitudinal fins. The fins are integrally attached... exchangers, include the detailed rv distributions of the velocity in the flow cross section; the distributions of the temperature in the finned channel wall and the flow; the distributions of the local heat flux on the exposed channel wall and fin...

  11. Anomalies of ac driven solitary waves with internal modes: Nonparametric resonances induced by parametric forces

    E-print Network

    Niurka R. Quintero; Angel Sanchez; Franz G. Mertens

    2001-07-19

    We study the dynamics of kinks in the $\\phi^4$ model subjected to a parametric ac force, both with and without damping, as a paradigm of solitary waves with internal modes. By using a collective coordinate approach, we find that the parametric force has a non-parametric effect on the kink motion. Specifically, we find that the internal mode leads to a resonance for frequencies of the parametric driving close to its own frequency, in which case the energy of the system grows as well as the width of the kink. These predictions of the collective coordinate theory are verified by numerical simulations of the full partial differential equation. We finally compare this kind of resonance with that obtained for non-parametric ac forces and conclude that the effect of ac drivings on solitary waves with internal modes is exactly the opposite of their character in the partial differential equation.

  12. Externally Forced and Internal Variability in Ensemble Climate Simulations of the Maunder Minimum

    Microsoft Academic Search

    Masakazu Yoshimori; Thomas F. Stocker; Christoph C. Raible; Manuel Renold

    2005-01-01

    The response of the climate system to natural, external forcing during the Maunder Minimum (ca. A.D. 1645 1715) is investigated using a comprehensive climate model. An ensemble of six transient simulations is produced in order to examine the relative importance of externally forced and internally generated variability. The simulated annual Northern Hemisphere and zonal-mean near-surface air temperature agree well with

  13. Rapid generation of high-frequency internal waves beneath a wind and wave forced oceanic surface mixed layer

    E-print Network

    Smith, Jerome A.

    Rapid generation of high-frequency internal waves beneath a wind and wave forced oceanic surface-frequency internal waves generated by Langmuir motions over stratified water may be an important source of turbulent the wind) generates high- frequency internal waves in the stratified fluid below. The internal waves evolve

  14. Simulating the winter North Atlantic Oscillation: the roles of internal variability and greenhouse gas forcing

    Microsoft Academic Search

    T. J. Osborn

    2004-01-01

    Analysis of simulations with seven coupled climate models demonstrates that the observed variations in the winter North Atlantic Oscillation (NAO), particularly the increase from the 1960s to the 1990s, are not compatible with either the internally generated variability nor the response to increasing greenhouse gas forcing simulated by these models. The observed NAO record can be explained by a combination

  15. Ultrasonic imaging of internal vibration of soft tissue under forced vibration

    Microsoft Academic Search

    YOSHIKI YAMAKOSHI; JUNICHI SATO; TAKUSO SATO

    1990-01-01

    An imaging system that can display both the amplitude and phase maps of internal vibration in soft tissues for forced low-frequency vibration is described. In this method, low-frequency sinusoidal vibration of frequency under several hundred hertz is applied from the surface of the sample and the resulting movement in it is measured from the Doppler frequency shift of the simultaneously

  16. International Dimensions of the University of Alberta. Report of the Senate Task Force.

    ERIC Educational Resources Information Center

    Alberta Univ., Edmonton.

    This report, written by the University of Alberta (Canada) Senate Task Force, was created to facilitate discussion and propose actions to facilitate internationalization of the campus. The report reviews how the university's current activities and strengths might be leveraged to enhance its international stature. It examines a multitude of factors…

  17. Force

    NSDL National Science Digital Library

    Mrs. Brownie

    2010-04-07

    Instructions: This is a webquest designed to help students understand force. It is specifically meant to teach the idea that the greater the force applied to an object the greater the change in speed or direction of the object depending on the mass. This is also known as Newton's Second Law of Motion. Lets Learn about Force! For this project your students will understand force. They will use Newton's second law to solve the problem presented. UT Core Curriculum: Science 3rd Grade. Standard 3- Students will understand the relationship between the force applied to an object and resulting motion of the ...

  18. Spatial solution to the problem of the effect of internal frictional forces in pressing low plasticity bodies

    Microsoft Academic Search

    N. M. Savel'ev; A. N. Savel'ev

    1970-01-01

    direction. In order to establish the effect of the internal friction forces on the individual elements of the article being pressed, equations have been proposed [4, 5] which enable us to determine the change in the stresses over the height of the article, taking into account the internal friction forces, but without taking into account the changes in the cross

  19. Perturbation analysis of internal balancing for lightly damped mechanical systems with gyroscopic and circulatory forces

    NASA Technical Reports Server (NTRS)

    Blelloch, P. A.; Mingori, D. L.; Wei, J. D.

    1987-01-01

    Approximate expressions are developed for internally balanced singular values corresponding to the modes of mechanical systems with gyroscopic forces, light damping, and small circulatory forces. A brief overview is first given of the balanced realization model reduction method, including a discussion of recent work. The models considered are defined, and a perturbation analysis is used to show that the modal representation becomes asymptotically balanced as damping reduces to zero. The approximate balanced singular values are calculated, and a simple example of a flexible, dual-spin spacecraft is given as an illustration of the results.

  20. Internal versus SST-forced atmospheric variability as simulated by an atmospheric general circulation model

    SciTech Connect

    Harzallah, A.; Sadourny, R. [Laboratoire de Meteorologie Dynamique du CNRS Ecole Normale Superieure, Paris (France)] [Laboratoire de Meteorologie Dynamique du CNRS Ecole Normale Superieure, Paris (France)

    1995-03-01

    The variability of atmospheric flow is analyzed by separating it into an internal part due to atmospheric dynamics only and an external (or forced) part due to the variability of sea surface temperature forcing. The two modes of variability are identified by performing an ensemble of seven independent long-term simulations of the atmospheric response to observed SST (1970-1988) with the LMD atmospheric general circulation model. The forced variability is defined from the analysis of the ensemble mean and the internal variability from the analysis of deviations from the ensemble mean. Emphasis is put on interannual variability of sea level pressure and 500-hPa geopotential height for the Northern Hemisphere winter. In view of the large systematic errors related to the relatively small number of realizations, unbiased variance estimators have been developed. Although statistical significance is not reached in some extratropical regions, large significant extratropical responses are found at the North Pacific-Alaska sector for SLP and over western Canada and the Aleutians for 500-hPa geopotential height. The influence of SST variations on internal variability is also examined by using a 7-year simulation using the climatological SST seasonal cycle. It is found that interannual SST changes strongly influence the geographical distribution of internal variability; in particular, it tends to increase it over oceans. EOF decompositions, showing that the model realistically simulates the leading observed variability modes. The geographical structure of internal variability patterns is found to be similar to that of total variability, although similar modes tend to evolve rather differently in time. The zonally symmetric seesaw dominates the internal variability for both observed and climatologically prescribed SST. 46 refs., 15 figs., 3 tabs.

  1. The bacteriophage ?29 portal motor can package DNA against a large internal force

    NASA Astrophysics Data System (ADS)

    Smith, Douglas E.; Tans, Sander J.; Smith, Steven B.; Grimes, Shelley; Anderson, Dwight L.; Bustamante, Carlos

    2001-10-01

    As part of the viral infection cycle, viruses must package their newly replicated genomes for delivery to other host cells. Bacteriophage ?29 packages its 6.6-µm long, double-stranded DNA into a 42×54nm capsid by means of a portal complex that hydrolyses ATP. This process is remarkable because entropic, electrostatic and bending energies of the DNA must be overcome to package the DNA to near-crystalline density. Here we use optical tweezers to pull on single DNA molecules as they are packaged, thus demonstrating that the portal complex is a force-generating motor. This motor can work against loads of up to 57pN on average, making it one of the strongest molecular motors reported to date. Movements of over 5µm are observed, indicating high processivity. Pauses and slips also occur, particularly at higher forces. We establish the force-velocity relationship of the motor and find that the rate-limiting step of the motor's cycle is force dependent even at low loads. Notably, the packaging rate decreases as the prohead is filled, indicating that an internal force builds up to ~50pN owing to DNA confinement. Our data suggest that this force may be available for initiating the ejection of the DNA from the capsid during infection.

  2. Interactions between internal forces, body stiffness, and fluid environment in a neuromechanical model of lamprey swimming.

    PubMed

    Tytell, Eric D; Hsu, Chia-Yu; Williams, Thelma L; Cohen, Avis H; Fauci, Lisa J

    2010-11-16

    Animal movements result from a complex balance of many different forces. Muscles produce force to move the body; the body has inertial, elastic, and damping properties that may aid or oppose the muscle force; and the environment produces reaction forces back on the body. The actual motion is an emergent property of these interactions. To examine the roles of body stiffness, muscle activation, and fluid environment for swimming animals, a computational model of a lamprey was developed. The model uses an immersed boundary framework that fully couples the Navier-Stokes equations of fluid dynamics with an actuated, elastic body model. This is the first model at a Reynolds number appropriate for a swimming fish that captures the complete fluid-structure interaction, in which the body deforms according to both internal muscular forces and external fluid forces. Results indicate that identical muscle activation patterns can produce different kinematics depending on body stiffness, and the optimal value of stiffness for maximum acceleration is different from that for maximum steady swimming speed. Additionally, negative muscle work, observed in many fishes, emerges at higher tail beat frequencies without sensory input and may contribute to energy efficiency. Swimming fishes that can tune their body stiffness by appropriately timed muscle contractions may therefore be able to optimize the passive dynamics of their bodies to maximize peak acceleration or swimming speed. PMID:21037110

  3. Redesigning residency training in internal medicine: the consensus report of the Alliance for Academic Internal Medicine Education Redesign Task Force.

    PubMed

    Meyers, Frederick J; Weinberger, Steven E; Fitzgibbons, John P; Glassroth, Jeffrey; Duffy, F Daniel; Clayton, Charles P

    2007-12-01

    Because of numerous criticisms of the content and structure of residency training, redesigning graduate medical education (GME) has become a high priority for the internal medicine community. From 2005 to 2007, the leadership of the internal medicine community, working under the auspices of the Alliance for Academic Internal Medicine Education Redesign Task Force, developed six recommendations it will pursue to improve residency education: (1) focus education around a "core" of internal medicine, which provides the framework for both the structure and content of residents' educational experiences, (2) fully adopt competency-based evaluation and advancement, which will enhance training by focusing on individual learners' needs, (3) allow for increased, resident-centered education beyond the internal medicine core, because different types of practice require customized knowledge and skills, (4) improve ambulatory training by providing patient-centered longitudinal care that addresses the conflict between inpatient and outpatient responsibilities, (5) use new faculty models that emphasize the creation of a core faculty, and (6) align institutional and programmatic resources with the goals of redesign, balancing the clinical mission of the institution with the educational goals of residency training. Adoption of these recommendations will require significant efforts, including pilot projects, faculty development, changes in accreditation requirements, and modifications of GME funding systems. Opportunities are ample for individual programs to develop creative approaches based on the framework for educational redesign outlined in this article, and for these educational and clinical redesign initiatives to work hand-in-hand for the benefit of patients, faculty, trainees, and institutions. PMID:18046131

  4. Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers

    SciTech Connect

    Goodzeit, C.L.; Anerella, M.D.; Ganetis, G.L.

    1988-01-01

    An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effect in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation. 13 figs., 1 tab.

  5. Foraging at the Edge of Chaos: Internal Clock versus External Forcing

    NASA Astrophysics Data System (ADS)

    Nicolis, S. C.; Fernández, J.; Pérez-Penichet, C.; Noda, C.; Tejera, F.; Ramos, O.; Sumpter, D. J. T.; Altshuler, E.

    2013-06-01

    Activity rhythms in animal groups arise both from external changes in the environment, as well as from internal group dynamics. These cycles are reminiscent of physical and chemical systems with quasiperiodic and even chaotic behavior resulting from “autocatalytic” mechanisms. We use nonlinear differential equations to model how the coupling between the self-excitatory interactions of individuals and external forcing can produce four different types of activity rhythms: quasiperiodic, chaotic, phase locked, and displaying over or under shooting. At the transition between quasiperiodic and chaotic regimes, activity cycles are asymmetrical, with rapid activity increases and slower decreases and a phase shift between external forcing and activity. We find similar activity patterns in ant colonies in response to varying temperature during the day. Thus foraging ants operate in a region of quasiperiodicity close to a cascade of transitions leading to chaos. The model suggests that a wide range of temporal structures and irregularities seen in the activity of animal and human groups might be accounted for by the coupling between collectively generated internal clocks and external forcings.

  6. Binaries Traveling through a Gaseous Medium: Dynamical Drag Forces and Internal Torques

    NASA Astrophysics Data System (ADS)

    Sánchez-Salcedo, F. J.; Chametla, Raul O.

    2014-10-01

    Using time-dependent linear theory, we investigate the morphology of the gravitational wake induced by a binary, whose center of mass moves at velocity {\\boldsymbol {V}}_cm against a uniform background of gas. For simplicity, we assume that the components of the binary are on circular orbits about their common center of mass. The consequences of dynamical friction is twofold. First, gas dynamical friction may drag the center of mass of the binary and cause the binary to migrate. Second, drag forces also induce a braking torque, which causes the orbits of the components of the binary to shrink. We compute the drag forces acting on one component of the binary due to the gravitational interaction with its own wake. We show that the dynamical friction force responsible for decelerating the center of mass of the binary is smaller than it is in the point-mass case because of the loss of gravitational focusing. We show that the braking internal torque depends on the Mach numbers of each binary component about their center of mass, and also on the Mach number of the center of mass of the binary. In general, the internal torque decreases with increasing the velocity of the binary relative to the ambient gas cloud. However, this is not always the case. We also mention the relevance of our results to the period distribution of binaries.

  7. Forces

    NSDL National Science Digital Library

    The representation depicts what forces are and how they can change the motion and shape of objects in an animated slide show. This resource also includes an interactive test and review of the material, and can be downloaded for offline use.

  8. Research priorities and plans for the International Space Station-results of the 'REMAP' Task Force.

    PubMed

    Kicza, M; Erickson, K; Trinh, E

    2003-01-01

    Recent events in the International Space Station (ISS) Program have resulted in the necessity to re-examine the research priorities and research plans for future years. Due to both technical and fiscal resource constraints expected on the International Space Station, it is imperative that research priorities be carefully reviewed and clearly articulated. In consultation with OSTP and the Office of Management and budget (OMB), NASA's Office of Biological and Physical Research (OBPR) assembled an ad-hoc external advisory committee, the Biological and Physical Research Maximization and Prioritization (REMAP) Task Force. This paper describes the outcome of the Task Force and how it is being used to define a roadmap for near and long-term Biological and Physical Research objectives that supports NASA's Vision and Mission. Additionally, the paper discusses further prioritizations that were necessitated by budget and ISS resource constraints in order to maximize utilization of the International Space Station. Finally, a process has been developed to integrate the requirements for this prioritized research with other agency requirements to develop an integrated ISS assembly and utilization plan that maximizes scientific output. PMID:14649263

  9. Research priorities and plans for the International Space Station-results of the 'REMAP' Task Force

    NASA Technical Reports Server (NTRS)

    Kicza, M.; Erickson, K.; Trinh, E.

    2003-01-01

    Recent events in the International Space Station (ISS) Program have resulted in the necessity to re-examine the research priorities and research plans for future years. Due to both technical and fiscal resource constraints expected on the International Space Station, it is imperative that research priorities be carefully reviewed and clearly articulated. In consultation with OSTP and the Office of Management and budget (OMB), NASA's Office of Biological and Physical Research (OBPR) assembled an ad-hoc external advisory committee, the Biological and Physical Research Maximization and Prioritization (REMAP) Task Force. This paper describes the outcome of the Task Force and how it is being used to define a roadmap for near and long-term Biological and Physical Research objectives that supports NASA's Vision and Mission. Additionally, the paper discusses further prioritizations that were necessitated by budget and ISS resource constraints in order to maximize utilization of the International Space Station. Finally, a process has been developed to integrate the requirements for this prioritized research with other agency requirements to develop an integrated ISS assembly and utilization plan that maximizes scientific output. c2003 American Institute of Aeronautics and Astronautics. Published by Elsevier Science Ltd. All rights reserved.

  10. Topography and Mechanical Property Mapping of International Simple Glass Surfaces with Atomic Force Microscopy

    SciTech Connect

    Hopf, Juliane [ORNL; Pierce, Eric M [ORNL

    2014-01-01

    Quantitative Nanomechanical Peak Force (PF-QNM) TappingModeTM atomic force microscopy measurements are presented for the first time on polished glass surfaces. The PF-QNM technique allows for topography and mechanical property information to be measured simultaneously at each pixel. Results for the international simple glass which represents a simplified version of SON68 glass suggests an average Young s modulus of 78.8 15.1 GPa is within the experimental error of the modulus measured for SON68 glass (83.6 2 GPa) with conventional approaches. Application of the PF-QNM technique will be extended to in situ glass corrosion experiments with the goal of gaining atomic-scale insights into altered layer development by exploiting the mechanical property differences that exist between silica gel (e.g., altered layer) and pristine glass surface.

  11. International PV QA Task Force's proposed comparative rating system for PV modules

    NASA Astrophysics Data System (ADS)

    Wohlgemuth, John; Kurtz, Sarah

    2014-10-01

    The International PV Quality Assurance Task Force is developing a rating system that provides comparative information about the relative durability of PV modules. Development of accelerated stress tests that can provide such comparative information is seen as a major step toward being able to predict PV module service life. This paper will provide details of the ongoing effort to determine the format of such an overall module rating system. The latest proposal is based on using three distinct climate zones as defined in IEC 60721-2-1 for two different mounting systems. Specific stresses beyond those used in the qualification tests are being developed for each of the selected climate zones.

  12. The forced flow cooled coils for the International Energy Agency Large Coil Task

    SciTech Connect

    Young, J.L.; Heyne, C.J.; Komarek, P.; Krauth, H.; Marinucci, C.; Vecsey, G.

    1982-01-01

    The purpose of the International Energy Agency ''Large Coil Task'' is stated and its design described and illustrated. The general design philosophy is defined: to develop coil designs which would meet the performance requirements of the LCT while demonstrating the applicability of these designs for future fusion requirements. The major elements of the three conductors and three coil designs are illustrated. Voltage capability, thermal stability and cryogenic requirements are described. Five advantages of forced cooled magnet systems are listed and the potential for future coils are projected.

  13. Transport and mixing by internal waves in stellar interiors: effect of the Coriolis force

    E-print Network

    S. Mathis; J. -P. Zahn

    2007-06-16

    We briefly recall the physical background of the transport of angular momentum and the mixing of chemicals inside stellar radiation zones and its importance for stellar evolution. Then, we describe its present modeling, its successes and its weaknesses. Next, we introduce the new theoretical developments that allow us to treat in a self-consistent way the effect of the Coriolis force on the low-frequencies internal waves and its consequences for the transport processes. This research is aimed at improving the modeling of stellar interiors in the perspective of future astero and helioseismology missions such as COROT and GOLF-NG.

  14. Long term changes of East Asian Summer Monsoon: Internal variability versus external forcing

    NASA Astrophysics Data System (ADS)

    Zhou, Tianjun

    2015-04-01

    The Asian Summer Monsoon (ASM) system exhibits considerable variability on decadal and inter-decadal time scales. For example, since the late 1970s, the East Asian Summer Monsoon circulation has exhibited a weakening tendency. Following the weakened monsoon circulation, there was a trend toward increasing drought in North China but excessive rainfall in South China along the Yangtze River valley. The drought in North China is concurrent with the declining rainfall over the northern Gangetic Plain of India, suggesting that the long-term trends of monsoon rainfall in these vast domains should be forced by same mechanisms. This weakening tendency of ASM from the late 1970s to the end of the 20th century has been of great concern to the climate research community (see Zhou et al. 2009 for a review). However, recent studies found that the ASM circulation has been recovering since the early 1990s. How to understand the earlier and recent decadal changes of ASM has been of great concern to both greater society and climate research community. Both the trends and long-term decadal variability of ASM have been attributed to increased aerosol/dust loadings, or increased greenhouse gas emissions, or internal variability such as the Pacific Decadal Oscillation (PDO) / Inter-decadal Pacific Oscillation (IPO). In this presentation, a review of our current understanding of the contributions of internal variability such as the PDO/IPO and external forcing agents such as greenhouse gases and anthropogenic aerosols will be given

  15. 14th International Congress on Antiphospholipid Antibodies Task Force report on obstetric antiphospholipid syndrome.

    PubMed

    de Jesus, Guilherme R; Agmon-Levin, Nancy; Andrade, Carlos A; Andreoli, Laura; Chighizola, Cecilia B; Porter, T Flint; Salmon, Jane; Silver, Robert M; Tincani, Angela; Branch, D Ware

    2014-08-01

    Pregnancy morbidity is one of the clinical manifestations used for classification criteria of antiphospholipid syndrome (APS). During the 14th International Congress on Antiphospholipid Antibodies (aPL), a Task Force with internationally-known experts was created to carry out a critical appraisal of the literature available regarding the association of aPL with obstetric manifestations present in actual classification criteria (recurrent early miscarriage, fetal death, preeclampsia and placental insufficiency) and the quality of the evidence that treatment(s) provide benefit in terms of avoiding recurrent adverse obstetric outcomes. The association of infertility with aPL and the effectiveness of the treatment of patients with infertility and positive aPL was also investigated. This report presents current knowledge and limitations of published studies regarding pregnancy morbidity, infertility and aPL, identifying areas that need better investigative efforts and proposing how critical flaws could be avoided in future studies, as suggested by participants of the Task Force. Except for fetal death, there are limitations in the quality of the data supporting the association of aPL with obstetric complications included in the current APS classification criteria. Recommended treatments for all pregnancy morbidity associated to APS also lack well-designed studies to confirm its efficacy. APL does not seem to be associated with infertility and treatment does not improve the outcomes in infertile patients with aPL. In another section of the Task Force, Dr. Jane Salmon reviewed complement-mediated inflammation in reproductive failure in APS, considering new therapeutic targets to obstetric APS (Ob APS). PMID:24650941

  16. Reliability of forced internal rotation and active internal rotation to assess lateral instability of the biceps pulley

    PubMed Central

    ARRIGONI, PAOLO; ROSE, GIACOMO DELLE; D’AMBROSI, RICCARDO; ROTUNDO, GIORGIO; CAMPAGNA, VINCENZO; PIRANI, PIERGIORGIO; PANASCÌ, MANLIO; PETRICCIOLI, DARIO; BERTONE, CELESTE; GRASSO, ANDREA; LATTE, CARMINE; COSTA, ALBERTO; VIOLA, GINO; DE GIORGI, SILVANA; PANELLA, ANTONELLO; PADUA, ROBERTO; BECCARINI, ALESSANDRO; SALCHER, BARBARA; OLIVIERI, MATTEO; MUGNAINI, MARCO; PANNONE, ANTONELLO; CEOLDO, CHIARA; LONGO, UMILE GIUSEPPE; DENARO, VINCENZO; CERCIELLO, SIMONE; PANNI, ALFREDO SCHIAVONE; AVANZI, PAOLO; ZORZI, CLAUDIO; RAGONE, VINCENZA; CASTAGNA, ALESSANDRO; RANDELLI, PIETRO

    2015-01-01

    Purpose the aim of this study was to investigate the relationship between positive painful forced internal rotation (FIR) and lateral pulley instability in the presence of a pre-diagnosed posterosuperior cuff tear. The same investigation was conducted for painful active internal rotation (AIR). Methods a multicenter prospective study was conducted in a series of patients scheduled to undergo arthroscopic posterosuperior cuff repair. Pain was assessed using a visual analog scale (VAS) and the Disabilities of the Arm, Shoulder and Hand questionnaire (DASH) was administered. The VAS score at rest, DASH score, and presence/absence of pain on FIR and AIR were recorded and their relationships with lesions of the lateral pulley, cuff tear patterns and shape of lesions were analyzed. Results the study population consisted of 115 patients (mean age: 55.1 years) recruited from 12 centers. The dominant arm was affected in 72 cases (62.6%). The average anteroposterior extension of the lesion was 1.61 cm. The mean preoperative VAS and DASH scores were 6.1 and 41.8, respectively. FIR and AIR were positive in 94 (81.7%) and 85 (73.9%) cases, respectively. The lateral pulley was compromised in 50 cases (43.4%). Cuff tears were partial articular in 35 patients (30.4%), complete in 61 (53%), and partial bursal in 19 (16.5%). No statistical correlation between positive FIR or AIR and lateral pulley lesions was detected. Positive FIR and AIR were statistically associated with complete lesions. Negative FIR was associated with the presence of partial articular tears. Conclusions painful FIR in the presence of a postero-superior cuff tear does not indicate lateral pulley instability. When a cuff tear is suspected, positive FIR and AIR are suggestive of full-thickness tear patterns while a negative FIR suggests a partial articular lesion. Level of evidence: level I, validating cohort study with good reference standards. PMID:26151035

  17. 2013 International Society for Clinical Densitometry Position Development Conference: Task Force on Normative Databases.

    PubMed

    Watts, Nelson B; Leslie, William D; Foldes, A Joseph; Miller, Paul D

    2013-01-01

    Following the standard protocol for development of Official Positions for the International Society for Clinical Densitometry, the Expert Panel heard the report and recommendations from the Task Force on Normative Databases; using the RAND methodology, agreement was reached on the following statements: 1. Manufacturers should continue to use their own databases for the lumbar spine as the reference standard for T-scores. 2. Manufacturers should continue to use National Health and Nutrition Examination Survey III data as the reference standard for femoral neck and total hip T-scores. 3. If local reference data are available, they should be used to calculate only Z-scores but not T-scores. 4. A uniform Caucasian (non-race adjusted) female reference database should be used to calculate T-scores for men of all ethnic groups. PMID:24076161

  18. Late Pliocene to Pleistocene sensitivity of the Greenland Ice Sheet in response to external forcing and internal feedbacks

    Microsoft Academic Search

    Sebastian J. Koenig; Robert M. Deconto; David Pollard

    2011-01-01

    The timing and nature of ice sheet variations on Greenland over the last ˜5 million years remain largely uncertain. Here, we use a coupled climate-vegetation-ice sheet model to determine the climatic sensitivity of Greenland to combined sets of external forcings and internal feedbacks operating on glacial-interglacial timescales. In particular, we assess the role of atmospheric pCO2, orbital forcing, and vegetation

  19. Late Pliocene to Pleistocene sensitivity of the Greenland Ice Sheet in response to external forcing and internal feedbacks

    Microsoft Academic Search

    Sebastian J. Koenig; Robert M. DeConto; David Pollard

    The timing and nature of ice sheet variations on Greenland over the last ?5 million years remain largely uncertain. Here,\\u000a we use a coupled climate-vegetation-ice sheet model to determine the climatic sensitivity of Greenland to combined sets of\\u000a external forcings and internal feedbacks operating on glacial-interglacial timescales. In particular, we assess the role of\\u000a atmospheric pCO2, orbital forcing, and vegetation dynamics

  20. 14th International Congress on Antiphospholipid Antibodies: task force report on antiphospholipid syndrome treatment trends.

    PubMed

    Erkan, Doruk; Aguiar, Cassyanne L; Andrade, Danieli; Cohen, Hannah; Cuadrado, Maria J; Danowski, Adriana; Levy, Roger A; Ortel, Thomas L; Rahman, Anisur; Salmon, Jane E; Tektonidou, Maria G; Willis, Rohan; Lockshin, Michael D

    2014-06-01

    Antiphospholipid Syndrome (APS) is characterized by vascular thrombosis and/or pregnancy morbidity occurring in patients with persistent antiphospholipid antibodies (aPL). The primary objective of the APS Treatment Trends Task Force, created as part of the 14th International Congress on aPL, was to systematically review the potential future treatment strategies for aPL-positive patients. The task force chose as future clinical research directions: a) determining the necessity for controlled clinical trials in venous thromboembolism with the new oral direct thrombin or anti-factor Xa inhibitors pending the results of the ongoing rivaroxaban in APS (RAPS) trial, and designing controlled clinical trials in other forms of thrombotic APS; b) systematically analyzing the literature as well as aPL/APS registries, and creating specific registries for non-warfarin/heparin anticoagulants; c) increasing recruitment for an ongoing primary thrombosis prevention trial, and designing secondary thrombosis and pregnancy morbidity prevention trials with hydroxychloroquine; d) determining surrogate markers to select patients for statin trials; e) designing controlled studies with rituximab and other anti-B-cell agents; f) designing mechanistic and clinical studies with eculizumab and other complement inhibitors; and g) chemically modifying peptide therapy to improve the half-life and minimize immunogenicity. The report also includes recommendations for clinicians who consider using these agents in difficult-to-manage aPL-positive patients. PMID:24468415

  1. Internally displaced "victims of armed conflict" in Colombia: the trajectory and trauma signature of forced migration.

    PubMed

    Shultz, James M; Garfin, Dana Rose; Espinel, Zelde; Araya, Ricardo; Oquendo, Maria A; Wainberg, Milton L; Chaskel, Roberto; Gaviria, Silvia L; Ordóñez, Anna E; Espinola, Maria; Wilson, Fiona E; Muñoz García, Natalia; Gómez Ceballos, Angela Milena; Garcia-Barcena, Yanira; Verdeli, Helen; Neria, Yuval

    2014-10-01

    While conflict-induced forced migration is a global phenomenon, the situation in Colombia, South America, is distinctive. Colombia has ranked either first or second in the number of internally displaced persons for 10 years, a consequence of decades of armed conflict compounded by high prevalence of drug trafficking. The displacement trajectory for displaced persons in Colombia proceeds through a sequence of stages: (1) pre-expulsion threats and vulnerability, (2) expulsion, (3) migration, (4) initial adaptation to relocation, (5) protracted resettlement (the end point for most forced migrants), and, rarely, (6) return to the community of origin. Trauma signature analysis, an evidence-based method that elucidates the physical and psychological consequences associated with exposures to harm and loss during disasters and complex emergencies, was used to identify the psychological risk factors and potentially traumatic events experienced by conflict-displaced persons in Colombia, stratified across the phases of displacement. Trauma and loss are experienced differentially throughout the pathway of displacement. PMID:25135775

  2. A photoelastic and strain-gauge analysis of interface force transmission of internal-cone implants.

    PubMed

    Akça, Kivanç; Cehreli, Murat C

    2008-08-01

    The objective of this study was to compare force transmissions in the peri-implant bone region of implants with various conical implant-abutment mating designs. Photoelastic models of solitary Bicon, Astra Tech, and synOcta and monoblock ITI implants were fabricated. Static vertical and 20-degree oblique forces of 75 N were applied on the implants in separate loading cases, and the generation of isochromatic fringes was observed and photographed in the field of a circular polariscope. Three-element strain gauges were bonded on the models in close proximity to the implants. Under the same loading protocol, the strain-gauge signals were digitized by a data-acquisition system and displayed on a computer using corresponding software at a sample rate of 10 kHz, and the principal strains were calculated. Isochromatic fringe orders around ITI and Astra Tech implants were similar at the collar region and slightly higher than around the Bicon implant under both loading conditions. Strains around the Bicon implant were lower than those around all implants tested under vertical loading (P < .05), whereas the strains around both ITI implants were similar and lower than those around the Astra Tech implant (P < .05). Under oblique loading, strains around both ITI implants were higher than those around other implants tested (P < .05). However, these differences do not seem to have any clinical relevance. Internal-cone implants have similar interface force transfer characteristics that resemble a one-part implant. To reduce stresses in the peri-implant region, implant diameter may be more effective than the type of implant. PMID:18717378

  3. Systematic Attribution of Observed Southern Hemispheric Circulation Trends to External Forcing and Internal Variability

    NASA Astrophysics Data System (ADS)

    Franzke, Christian; O'Kane, Terence; Monselesan, Didier; Risbey, James; Horenko, Illia

    2015-04-01

    A critical question in the global warming debate concerns the causes of the observed trends of the Southern Hemisphere (SH) atmospheric circulation over recent decades. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included observational forcing data or have mixed external forcing with indices of internal climate variability impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the winter and early spring when mid-latitude blocking is most active and stratospheric ozone plays no role. Here we systematically attribute the secular trends over the recent decades using a non-stationary clustering method applied to both reanalysis and observational forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing summer SH circulation trends, we show observational evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that seasonal effects are likely crucial in understanding the causes of the secular trends.

  4. Systematic attribution of observed southern hemispheric circulation trends to external forcing and internal variability

    NASA Astrophysics Data System (ADS)

    Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.

    2015-04-01

    A critical question in the global warming debate concerns the causes of the observed trends of the Southern Hemisphere (SH) atmospheric circulation over recent decades. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included observational forcing data or have mixed external forcing with indices of internal climate variability impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the austral winter and early spring when mid-latitude blocking is most active and stratospheric ozone should not a play a role. Here we systematically attribute the secular trends over the recent decades using a non-stationary clustering method applied to both reanalysis and observational forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing austral summer SH circulation trends, we show observational evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that effects from all seasons are likely crucial in understanding the causes of the secular trends.

  5. Forced-air warming design: evaluation of intake filtration, internal microbial buildup, and airborne-contamination emissions.

    PubMed

    Reed, Mike; Kimberger, Oliver; McGovern, Paul D; Albrecht, Mark C

    2013-08-01

    Forced-air warming devices are effective for the prevention of surgical hypothermia. However, these devices intake nonsterile floor-level air, and it is unknown whether they have adequate filtration measures to prevent the internal buildup or emission of microbial contaminants. We rated the intake filtration efficiency of a popular current-generation forced-air warming device (Bair Hugger model 750, Arizant Healthcare) using a monodisperse sodium chloride aerosol in the laboratory. We further sampled 23 forced-air warming devices (same model) in daily hospital use for internal microbial buildup and airborne-contamination emissions via swabbing and particle counting. Laboratory testing found the intake filter to be 63.8% efficient. Swabbing detected microorganisms within 100% of the forced-air warming blowers sampled, with isolates of coagulase-negative staphylococci, mold, and micrococci identified. Particle counting showed 96% of forced-air warming blowers to be emitting significant levels of internally generated airborne contaminants out of the hose end. These findings highlight the need for upgraded intake filtration, preferably high-efficiency particulate air filtration (99.97% efficient), on current-generation forced-air warming devices to reduce contamination buildup and emission risks. PMID:24133849

  6. Depression and elevation internal solitary waves in a two-layer fluid and their forces on cylindrical piles

    NASA Astrophysics Data System (ADS)

    Xu, Zhenhua; Yin, Baoshu; Yang, Hongwei; Qi, Jifeng

    2012-07-01

    Both large amplitude depression and elevation internal solitary waves (ISWs) were observed on the continental shelf of the northwest South China Sea (SCS) during the Wenchang Internal Wave Experiment. In this study, we investigate the characteristics of depression and elevation ISWs based on comparisons between observational results and internal wave theories. It is suggested that the large amplitude depression wave is better represented by the extended Korteweg-de Vries (EKdV) theory than by the KdV model, whereas the large amplitude elevation wave is in better agreement with the KdV equation than with the EKdV theory. Wave-induced forces on a supposed small-diameter cylindrical pile by depression and elevation waves are also estimated using the internal wave theory and Morison formula. The wave-induced force by elevation ISWs is rarely reported in the literature. It is found that the force induced by the elevation wave differs significantly from that by the depression wave, and the elevation wave generally produces greater force on the pile in the lower water column than the depression wave. These results show that ISWs in the study area can present a serious threat to ocean engineering structures, and should not be ignored in the design of oil platforms and ocean operations.

  7. Occupational identity status development, gender comparisons, and internal-external control in first-year air force cadets

    Microsoft Academic Search

    Marie Dellas; Louise P. Jernigan

    1987-01-01

    This study of cadets at the United States Air Force Academy during their first six months assessed the pattern of developmental changes in occupational identity status for males and females, examined the relationship of internal-external control to identity statuses, and discussed the data in terms of Erikson's proposals and factors involved in gender differences in identity development. More than half

  8. Electro-elastic fields of piezoelectric materials with an elliptic hole under uniform internal shearing forces

    NASA Astrophysics Data System (ADS)

    Du, Yanliang; Liu, Shuhong; Duan, Shijie; Li, Yanqiang

    2013-05-01

    The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant's principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields inside and outside the elliptic hole are considered.

  9. Optimum rib size to enhance forced convection in a horizontal triangular duct with ribbed internal surfaces

    NASA Astrophysics Data System (ADS)

    Luo, D. D.; Leung, C. W.; Chan, T. L.

    2004-09-01

    The optimum rib size to enhance heat transfer had been proposed through an experimental investigation on the forced convection of a fully developed turbulent flow in an air-cooled horizontal equilateral triangular duct fabricated on its internal surfaces with uniformly spaced square ribs. Five different rib sizes (B) of 5 mm, 6 mm, 7 mm, 7.9 mm and 9 mm, respectively, were used in the present investigation, while the separation (S) between the center lines of two adjacent ribs was kept at a constant of 57 mm. The experimental triangular ducts were of the same axial length (L) of 1050 mm and the same hydraulic diameter (D) of 44 mm. Both the ducts and the ribs were fabricated with duralumin. For every experimental set-up, the entire inner wall of the duct was heated uniformly while the outer wall was thermally insulated. From the experimental results, a maximum average Nusselt number of the triangular duct was observed at the rib size of 7.9 mm (i.e. relative rib size B/D = 0.1795 ). Considering the pressure drop along the triangular duct, it was found to increase almost linearly with the rib size. Non-dimensional expressions had been developed for the determination of the average Nusselt number and the average friction factor of the equilateral triangular ducts with ribbed internal surfaces. The developed equations were valid for a wide range of Reynolds numbers of 4,000 < Re D < 23,000 and relative rib sizes of 0.11 ?slant frac{B} {D} ?slant 0.21 under steady-state condition.

  10. Internal variability, external forcing and climate trends in multi-decadal AGCM ensembles

    NASA Astrophysics Data System (ADS)

    Bracco, Annalisa; Kucharski, Fred; Kallummal, Rameshan; Molteni, Franco

    2004-11-01

    An atmospheric general circulation model of intermediate complexity is used to investigate the origin and structure of the climate change in the second half of the twentieth century. The variability of the atmospheric flow is considered as a superposition of an internal part, due to intrinsic dynamical variability, and an external part, due to the variations of the sea surface temperature (SST) forcing. The two components are identified by performing a 50-member ensemble of atmospheric simulations with prescribed, observed SSTs in the period 1949 2002. The large number of realizations allows the estimation of statistics of the atmospheric variability with a high confidence level. The analysis performed focuses on interdecadal and interannual variability of 500 hPa geopotential height in the Northern Hemisphere (NH) during winter. The model reproduces well the structure of the observed trend (defined as the difference in the two 25-year intervals 1977 2001 and 1952 1976), particularly in the Pacific region, and about half of the amplitude of the signal. The trend in 500 hPa height projects mainly onto the second empirical orthogonal function (EOF), both in the observations and in the model ensemble. However, differences between the modelled and the observed variability are found in the pattern of the second EOF in the Atlantic sector. SST changes associated with the El Niño southern oscillation (ENSO) are responsible for about 50% of the signal of the 500 hPa height trend in the Pacific. A second 50-member ensemble is used to evaluate the sensitivity of interdecadal variability to an increase in CO2 optical depth compatible with observed concentration changes. In this second experiment, the simulated trend includes a statistically significant contribution from the positive phase of the Arctic oscillation (AO). Such a contribution is also found in observations. Furthermore, the additional CO2 forcing accounts for part of the NH trend in near-surface temperature, and brings the zonal-mean temperature changes in the stratosphere and upper-troposphere closer to observations.

  11. Force-induced melting of DNA--evidence for peeling and internal melting from force spectra on short synthetic duplex sequences.

    PubMed

    Bosaeus, Niklas; El-Sagheer, Afaf H; Brown, Tom; Åkerman, Björn; Nordén, Bengt

    2014-07-01

    Overstretching of DNA occurs at about 60-70 pN when a torsionally unconstrained double-stranded DNA molecule is stretched by its ends. During the transition, the contour length increases by up to 70% without complete strand dissociation. Three mechanisms are thought to be involved: force-induced melting into single-stranded DNA where either one or both strands carry the tension, or a B-to-S transition into a longer, still base-paired conformation. We stretch sequence-designed oligonucleotides in an effort to isolate the three processes, focusing on force-induced melting. By introducing site-specific inter-strand cross-links in one or both ends of a 64 bp AT-rich duplex we could repeatedly follow the two melting processes at 5 mM and 1 M monovalent salt. We find that when one end is sealed the AT-rich sequence undergoes peeling exhibiting hysteresis at low and high salt. When both ends are sealed the AT sequence instead undergoes internal melting. Thirdly, the peeling melting is studied in a composite oligonucleotide where the same AT-rich sequence is concatenated to a GC-rich sequence known to undergo a B-to-S transition rather than melting. The construct then first melts in the AT-rich part followed at higher forces by a B-to-S transition in the GC-part, indicating that DNA overstretching modes are additive. PMID:24838568

  12. Force-induced melting of DNA—evidence for peeling and internal melting from force spectra on short synthetic duplex sequences

    PubMed Central

    Bosaeus, Niklas; El-Sagheer, Afaf H.; Brown, Tom; Åkerman, Björn; Nordén, Bengt

    2014-01-01

    Overstretching of DNA occurs at about 60–70 pN when a torsionally unconstrained double-stranded DNA molecule is stretched by its ends. During the transition, the contour length increases by up to 70% without complete strand dissociation. Three mechanisms are thought to be involved: force-induced melting into single-stranded DNA where either one or both strands carry the tension, or a B-to-S transition into a longer, still base-paired conformation. We stretch sequence-designed oligonucleotides in an effort to isolate the three processes, focusing on force-induced melting. By introducing site-specific inter-strand cross-links in one or both ends of a 64 bp AT-rich duplex we could repeatedly follow the two melting processes at 5 mM and 1 M monovalent salt. We find that when one end is sealed the AT-rich sequence undergoes peeling exhibiting hysteresis at low and high salt. When both ends are sealed the AT sequence instead undergoes internal melting. Thirdly, the peeling melting is studied in a composite oligonucleotide where the same AT-rich sequence is concatenated to a GC-rich sequence known to undergo a B-to-S transition rather than melting. The construct then first melts in the AT-rich part followed at higher forces by a B-to-S transition in the GC-part, indicating that DNA overstretching modes are additive. PMID:24838568

  13. Probing Membrane Order and Topography in Supported Lipid Bilayers by Combined Polarized Total Internal Reflection Fluorescence-Atomic Force Microscopy

    PubMed Central

    Oreopoulos, John; Yip, Christopher M.

    2009-01-01

    Determining the local structure, dynamics, and conformational requirements for protein-protein and protein-lipid interactions in membranes is critical to understanding biological processes ranging from signaling to the translocating and membranolytic action of antimicrobial peptides. We report here the application of a combined polarized total internal reflection fluorescence microscopy-in situ atomic force microscopy platform. This platform's ability to image membrane orientational order was demonstrated on DOPC/DSPC/cholesterol model membranes containing the fluorescent membrane probe, DiI-C20 or BODIPY-PC. Spatially resolved order parameters and fluorophore tilt angles extracted from the polarized total internal reflection fluorescence microscopy images were in good agreement with the topographical details resolved by in situ atomic force microscopy, portending use of this technique for high-resolution characterization of membrane domain structures and peptide-membrane interactions. PMID:19254557

  14. Measurements of coupling losses in superconducting cable-in-conduit conductors affected by internal transverse electromagnetic-forces

    Microsoft Academic Search

    F. Sumiyoshi; S. Kawabata; K. Matsuyama; T. Kawashima; T. Mito; K. Takahata; T. Satow; J. Yamamoto; Y. Kanai; T. Yamamoto; K. Nakamoto

    1996-01-01

    In order to elucidate the dependence of the internal electromagnetic-forces on the interstrand coupling loss in superconducting cable-in-conduit conductors, we develop a new measuring system. This system enables us to measure the coupling loss of large scale conductors with transport current of 20 kA and the transverse magnetic field of 3.22 T bias in the wide frequency range of the

  15. Confining forces

    E-print Network

    Dirk Rollmann; David E. Miller

    2015-05-26

    We discuss the forces on the internal constituents of the hadrons based on the bag model. The ground state of the hadrons forms a color singlet so that the effects of the colored internal states are neutralized. From the breaking of the dilatation and conformal symmetries under the strong interactions the corresponding currents are not conserved. These currents give rise to the forces changing the motion of the internal particles which causes confinement.

  16. A method to estimate the forces exerted by internal solitons on cylindrical piles

    Microsoft Academic Search

    Shuqun Cai; Xiaomin Long; Zijun Gan

    2003-01-01

    Internal soliton is the large amplitude wave existing in the pycnocline, induced by internal tide in the condition of special bottom topography. During its propagation process, the induced disturbance can bring about strong convergence of sea water and sudden strong current (wave-induced-current), which can cause severe threat to the ocean engineering structures, such as oil drilling platform and pipeline. In

  17. Non-contact internal-MMIC measurement using scanning force probing

    Microsoft Academic Search

    C. J. Falkingham; I. H. Edwards; G. E. Bridges

    2000-01-01

    A non-contacting probe capable of internal vector measurements of MMICs is presented. Accurate internal amplitude and phase measurements can be made with micrometer spatial resolution, <1 fF loading and without the need to depassivate the circuit. A 10 GHz bandwidth probe is presented

  18. International Education: A Force for Peace and Cross-Cultural Understanding?

    ERIC Educational Resources Information Center

    Brown, Lorraine

    2009-01-01

    This paper discusses the notion that the international sojourn has the potential to transform sojourners into cultural mediators who carry the power to improve global relations. A year-long ethnographic study of the adjustment experiences of international postgraduate students in England revealed a universal early enthusiasm for cross-cultural…

  19. The Peaceful Uses of Military Forces. Praeger Special Studies in International Politics and Public Affairs.

    ERIC Educational Resources Information Center

    Hanning, Hugh

    This study of the peaceful uses of military forces (PUMF) offers a compendium of information and principles for the planning and conduct of such PUMF activities as meeting disaster or emergency relief situations, education and training, and economic and social projects. The provision of training opportunities by the military is a means of…

  20. INTERNAL FORCED iquid or gas flow through pipes or ducts is commonly used in heating and

    E-print Network

    Ghajar, Afshin J.

    to flow by a fan or pump through a flow section that is sufficiently long to accomplish the desired heat Transitional Flow in Tubes* An important design problem in industrial heat exchangers arises when flow inside or ducts is commonly used in heating and cooling applications. The fluid in such applications is forced

  1. Development of a new physics-based internal coordinate mechanics force field and its application to protein loop modeling.

    PubMed

    Arnautova, Yelena A; Abagyan, Ruben A; Totrov, Maxim

    2011-02-01

    We report the development of internal coordinate mechanics force field (ICMFF), new force field parameterized using a combination of experimental data for crystals of small molecules and quantum mechanics calculations. The main features of ICMFF include: (a) parameterization for the dielectric constant relevant to the condensed state (? = 2) instead of vacuum, (b) an improved description of hydrogen-bond interactions using duplicate sets of van der Waals parameters for heavy atom-hydrogen interactions, and (c) improved backbone covalent geometry and energetics achieved using novel backbone torsional potentials and inclusion of the bond angles at the C(?) atoms into the internal variable set. The performance of ICMFF was evaluated through loop modeling simulations for 4-13 residue loops. ICMFF was combined with a solvent-accessible surface area solvation model optimized using a large set of loop decoys. Conformational sampling was carried out using the biased probability Monte Carlo method. Average/median backbone root-mean-square deviations of the lowest energy conformations from the native structures were 0.25/0.21 Å for four residues loops, 0.84/0.46 Å for eight residue loops, and 1.16/0.73 Å for 12 residue loops. To our knowledge, these results are significantly better than or comparable with those reported to date for any loop modeling method that does not take crystal packing into account. Moreover, the accuracy of our method is on par with the best previously reported results obtained considering the crystal environment. We attribute this success to the high accuracy of the new ICM force field achieved by meticulous parameterization, to the optimized solvent model, and the efficiency of the search method. PMID:21069716

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  3. A pendulum-driven cart via internal force and static friction

    Microsoft Academic Search

    Hongyi Li; Katsuhisa Furuta; Felix L. Chernousko

    2005-01-01

    In this paper, a pendulum driven cart is built using Lego robot parts. It consists of a cart with four passive wheels and a pendulum mounted on top of the cart. A DC motor is attached to the hinge joint between the cart and the pendulum which cart swing forward and backward. The cart motion is generated using its internal

  4. Turbofan forced mixer-nozzle internal flowfield. Volume 1: A benchmark experimental study

    NASA Technical Reports Server (NTRS)

    Paterson, R. W.

    1982-01-01

    An experimental investigation of the flow field within a model turbofan forced mixer nozzle is described. Velocity and thermodynamic state variable data for use in assessing the accuracy and assisting the further development of computational procedures for predicting the flow field within mixer nozzles are provided. Velocity and temperature data suggested that the nozzle mixing process was dominated by circulations (secondary flows) of a length scale on the order the lobe dimensions which were associated with strong radial velocities observed near the lobe exit plane. The 'benchmark' model mixer experiment conducted for code assessment purposes is discussed.

  5. Joining forces: Collaborating internationally to deliver high-quality, online postgraduate education in pain management

    PubMed Central

    Devonshire, Elizabeth; Siddall, Philip J

    2011-01-01

    The effective management of pain is a complex and costly global issue, requiring a range of innovative educational strategies to enable culturally appropriate and high-quality health care provision. In response to this issue, the Pain Management Research Institute at the University of Sydney (Sydney, Australia) has established several strategic alliances with other overseas universities to deliver online postgraduate education in pain management. The present article discusses the rationale for joining forces, and the approach adopted in creating and maintaining these alliances. It also provides insights into the benefits, challenges and opportunities associated with collaborative educational initiatives of this nature, from institutional, academic and student perspectives. PMID:22184549

  6. Forcing level effect of internal acoustic excitation on the improvement of airfoil performance

    Microsoft Academic Search

    F. B. Hsiao; R. C. Chang; R. N. Shyu

    1990-01-01

    The effects of internal acoustic excitation on the leading edge separated boundary layers and the aerodynamic performance over an airfoil of NACA 63(3)-018 cross section are examined as a function of excitation amplitude and frequency. Tests are conducted in an open-type suction wind tunnel at the Reynolds number of 300,000. Experimental results indicate that the flow separation is suppressed at

  7. The mechanism of force generation in myosin: a disorder-to-order transition, coupled to internal structural changes.

    PubMed Central

    Thomas, D. D.; Ramachandran, S.; Roopnarine, O.; Hayden, D. W.; Ostap, E. M.

    1995-01-01

    We propose a molecular mechanism of force generation in muscle, based primarily on site-specific spectroscopic probe studies of myosin heads in contracting muscle fibers and myofibrils. Electron paramagnetic resonance (EPR) and time-resolved phosphorescence anisotropy (TPA) of probes attached to SH1 (Cys 707, in the catalytic domain of the head) have consistently shown that most myosin heads in contracting muscle are dynamically disordered, undergoing large-amplitude rotations in the microsecond time range. Some of these disordered heads are bound to actin, especially in the early (weak-binding, preforce) phase of the ATPase cycle. The small ordered population (10-20%) is rigidly oriented precisely as in rigor, with no other distinct angle observed in contraction or in the presence of intermediate states trapped by nucleotide analogs. These results are not consistent with the classical model in which the entire head undergoes a 45 degree transition between two distinct orientations. Therefore, it has been proposed that the catalytic domain of the myosin head has only one stereospecific (rigor-like) actin-binding angle, and that the head's internal structure changes during force generation, causing the distal light-chain-binding domain to rotate. To test this model, we have performed EPR and TPA studies of probes attached to regulatory light chains (RLCs) in rabbit and scallop myofibrils and fibers. The RLC results confirm the predominance of dynamic (microsecond) rotational disorder in both relaxation and contraction, and show that the different mechanisms of calcium regulation in the two muscles produce different rotational dynamics. In rabbit myofibrils, RLC probes are more dynamically disordered than SH1 probes, especially in rigor and contraction,indicating that the light-chain-binding domain undergoes rotational motions relative to the catalytic domain when myosin heads interact with actin. An SH1-bound spin label, which is sensitive to myosin's internal dynamics, resolves three distinct conformations during contraction, and time-resolved EPR shows that these transitions are coupled to specific steps in the ATPase cycle. We propose that force is generated during contraction by a disorder-to-order transition, in which myosin heads first attach weakly to actin in a nonstereospecific mode characterized by large-scale dynamic disorder, then undergo at least two conformational transitions involving large-scale structural (rotational) changes within the head, culminating in a highly ordered strong-binding state that bears force. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 PMID:7787056

  8. The mechanism of force generation in myosin: a disorder-to-order transition, coupled to internal structural changes.

    PubMed

    Thomas, D D; Ramachandran, S; Roopnarine, O; Hayden, D W; Ostap, E M

    1995-04-01

    We propose a molecular mechanism of force generation in muscle, based primarily on site-specific spectroscopic probe studies of myosin heads in contracting muscle fibers and myofibrils. Electron paramagnetic resonance (EPR) and time-resolved phosphorescence anisotropy (TPA) of probes attached to SH1 (Cys 707, in the catalytic domain of the head) have consistently shown that most myosin heads in contracting muscle are dynamically disordered, undergoing large-amplitude rotations in the microsecond time range. Some of these disordered heads are bound to actin, especially in the early (weak-binding, preforce) phase of the ATPase cycle. The small ordered population (10-20%) is rigidly oriented precisely as in rigor, with no other distinct angle observed in contraction or in the presence of intermediate states trapped by nucleotide analogs. These results are not consistent with the classical model in which the entire head undergoes a 45 degree transition between two distinct orientations. Therefore, it has been proposed that the catalytic domain of the myosin head has only one stereospecific (rigor-like) actin-binding angle, and that the head's internal structure changes during force generation, causing the distal light-chain-binding domain to rotate. To test this model, we have performed EPR and TPA studies of probes attached to regulatory light chains (RLCs) in rabbit and scallop myofibrils and fibers. The RLC results confirm the predominance of dynamic (microsecond) rotational disorder in both relaxation and contraction, and show that the different mechanisms of calcium regulation in the two muscles produce different rotational dynamics. In rabbit myofibrils, RLC probes are more dynamically disordered than SH1 probes, especially in rigor and contraction,indicating that the light-chain-binding domain undergoes rotational motions relative to the catalytic domain when myosin heads interact with actin. An SH1-bound spin label, which is sensitive to myosin's internal dynamics, resolves three distinct conformations during contraction, and time-resolved EPR shows that these transitions are coupled to specific steps in the ATPase cycle. We propose that force is generated during contraction by a disorder-to-order transition, in which myosin heads first attach weakly to actin in a nonstereospecific mode characterized by large-scale dynamic disorder, then undergo at least two conformational transitions involving large-scale structural (rotational) changes within the head, culminating in a highly ordered strong-binding state that bears force. PMID:7787056

  9. Cookery method and end-point temperature can affect the Warner–Bratzler shear force, cooking loss, and internal cooked color of beef longissimus steaks

    Microsoft Academic Search

    J. W. S. Yancey; M. D. Wharton; J. K. Apple

    2011-01-01

    Steaks from 60 beef ribeye rolls were used to test the interactive effects of cookery method and end-point temperature on Warner–Bratzler shear force (WBSF) and internal cooked color. Pairs of longissimus thoracis (LT) steaks were assigned to combinations of 3 different end-point temperatures and 5 cookery methods. The forced-air convection oven (FAC) required the longest time and produced the reddest

  10. Lobe Shifting in the Gulf of Papua: Internal or External Forcing?

    NASA Astrophysics Data System (ADS)

    Johnstone, E. A.; Driscoll, N. W.; Slingerland, R.; Milliman, J. D.; Babcock, J.

    2007-12-01

    Recently acquired CHIRP data from the Gulf of Papua (GoP) reveals that the modern clinoform is inherently three- dimensional across a variety of scales. Three depositional lobes are identified in the mid-shelf region of the GoP; a central lobe that is downlapped by younger northern and southern lobes. While the depocenter shift and infilling of available accommodation within the central lobe appears to be predominantly controlled by depositional processes and stacking patterns (autocyclic forces), the marked shift in deposition away from the central lobe to the northern and southern lobes (~60-80 km) is difficult to explain by depositional processes alone. The northern and southern lobes downlap onto the central lobe with no evidence of interfingering, which suggests an abrupt shift in the loci of deposition away from the central lobe. Radiocarbon dates from the youngest units in the central lobe suggest this shift occurred after 2 ka and thus it is difficult to invoke eustatic sea level fluctuations to explain this marked shift in deposition. Sediment rerouting or oceanographic changes may account for this dramatic shift in the depositional lobes. High-resolution mapping of the three dimensional architecture of shelf building clinothems has provided new insight into sediment dispersal systems that is the critical first step to determine whether GoP lobe switching is a stochastic (autocyclic) or externally driven (allocyclic) process.

  11. Treating rheumatoid arthritis to target: recommendations of an international task force

    PubMed Central

    Smolen, Josef S; Aletaha, Daniel; Bijlsma, Johannes W J; Breedveld, Ferdinand C; Boumpas, Dimitrios; Burmester, Gerd; Combe, Bernard; Cutolo, Maurizio; de Wit, Maarten; Dougados, Maxime; Emery, Paul; Gibofsky, Alan; Gomez-Reino, Juan Jesus; Haraoui, Boulos; Kalden, Joachim; Keystone, Edward C; Kvien, Tore K; McInnes, Iain; Martin-Mola, Emilio; Montecucco, Carlomaurizio; Schoels, Monika; van der Heijde, Desirée

    2010-01-01

    Background Aiming at therapeutic targets has reduced the risk of organ failure in many diseases such as diabetes or hypertension. Such targets have not been defined for rheumatoid arthritis (RA). Objective To develop recommendations for achieving optimal therapeutic outcomes in RA. Methods A task force of rheumatologists and a patient developed a set of recommendations on the basis of evidence derived from a systematic literature review and expert opinion; these were subsequently discussed, amended and voted upon by >60 experts from various regions of the world in a Delphi-like procedure. Levels of evidence, strength of recommendations and levels of agreement were derived. Results The treat-to-target activity resulted in 10 recommendations. The treatment aim was defined as remission with low disease activity being an alternative goal in patients with long-standing disease. Regular follow-up (every 1–3 months during active disease) with appropriate therapeutic adaptation to reach the desired state within 3 to a maximum of 6 months was recommended. Follow-up examinations ought to employ composite measures of disease activity which include joint counts. Additional items provide further details for particular aspects of the disease. Levels of agreement were very high for many of these recommendations (?9/10). Conclusion The 10 recommendations are supposed to inform patients, rheumatologists and other stakeholders about strategies to reach optimal outcomes of RA based on evidence and expert opinion. PMID:20215140

  12. Screening for adolescent idiopathic scoliosis: an information statement by the scoliosis research society international task force

    PubMed Central

    2013-01-01

    Background Routine screening of scoliosis is a controversial subject and screening efforts vary greatly around the world. Methods Consensus was sought among an international group of experts (seven spine surgeons and one clinical epidemiologist) using a modified Delphi approach. The consensus achieved was based on careful analysis of a recent critical review of the literature on scoliosis screening, performed using a conceptual framework of analysis focusing on five main dimensions: technical, clinical, program, cost and treatment effectiveness. Findings A consensus was obtained in all five dimensions of analysis, resulting in 10 statements and recommendations. In summary, there is scientific evidence to support the value of scoliosis screening with respect to technical efficacy, clinical, program and treatment effectiveness, but there insufficient evidence to make a statement with respect to cost effectiveness. Scoliosis screening should be aimed at identifying suspected cases of scoliosis that will be referred for diagnostic evaluation and confirmed, or ruled out, with a clinically significant scoliosis. The scoliometer is currently the best tool available for scoliosis screening and there is moderate evidence to recommend referral with values between 5 degrees and 7 degrees. There is moderate evidence that scoliosis screening allows for detection and referral of patients at an earlier stage of the clinical course, and there is low evidence suggesting that scoliosis patients detected by screening are less likely to need surgery than those who did not have screening. There is strong evidence to support treatment by bracing. Interpretation This information statement by an expert panel supports scoliosis screening in 4 of the 5 domains studied, using a framework of analysis which includes all of the World Health Organisation criteria for a valid screening procedure. PMID:24171910

  13. Effect of soil–bridge interaction on the magnitude of internal forces in integral abutment bridge components due to live load effects

    Microsoft Academic Search

    Murat Dicleli; Semih Erhan

    2010-01-01

    In this study, the effect of soil–bridge interaction on the magnitude of the internal forces in integral abutment bridge (IAB) components due to live load effects is studied. For this purpose, structural models of typical IABs are built by including and excluding the effect of backfill and foundation soil. Analyses of the models are then conducted under an AASHTO live

  14. Eruption triggering of giant magma bodies by internal versus external forcing: A rhyolite-MELTS study

    NASA Astrophysics Data System (ADS)

    Carley, T. L.; Gualda, G. A.; Ghiorso, M. S.; Miller, C. F.

    2012-12-01

    Silicic volcanism, particularly supereruptions, raises questions about the mechanisms by which magma bodies destabilize and erupt. Are external events necessary to initiate an eruption of a large silicic system, or is possible for internal processes (crystallization, volatile exsolution) to destabilize a system and drive it to erupt? If external triggers are critically important to prompting eruption, are all felsic magma bodies equally prone to erupt? To respond to these questions, we use rhyolite-MELTS (Gualda et al. 2012) to investigate the pre-eruptive chemical evolution and the resultant changes to physical properties of giant (super-eruptive) felsic magma bodies. Simulations are conducted using pumice and glass compositions from the Peach Spring (Southwestern USA) and the Bishop (California USA) Tuffs, two giant high-silica rhyolite deposits. In our simulations, we vary initial pressure (150-350 MPa in 50 MPa intervals), volatile content (initial water ranging from 1-7 wt. %), mode of crystallization (equilibrium vs. fractional), and rheology of the magma reservoir (isobaric vs. isochoric vs. transitional). We run simulations through as much of the crystallization interval as possible, but focus on the first ~50 wt. % crystallization, most relevant for volcanic systems. In all simulations, we observe near-invariant behavior when the system becomes saturated in quartz, two feldspars and a fluid phase, from which point crystallization is essentially isothermal. Prior to the near-invariant, crystallization leads to gradual changes in bulk properties (e.g., < 1% volume decrease over 50 °C), which effectively results in modest pressure changes within the magma body (i.e., ~10 MPa). Upon reaching the near-invariant, the bulk properties change abruptly (e.g., > 5% volume increase in 0.1 °C), causing significant overpressurization of the magma body. The magnitude of this overpressurization (i.e. 10s to 100s of MPa depending on system conditions) is sufficient to exceed the yield strength of the country rocks, effectively making eruption possible independent of any external triggers. Our simulations reveal that the Peach Spring and Bishop Tuff magmatic systems represent two contrasting types of behavior. In the Bishop case, only ~5-25 wt.% of crystallization over a short temperature interval (~30 °C cooling) is needed to reach near-invariant behavior, making it plausible that crystallization led to eruption without external triggers. This is consistent with the lack of evidence for interaction of Bishop magma with mafic magmas. In the Peach Spring case, 30-70 wt. % crystallization over a much longer temperature interval (~60-130 °C cooling) is needed for the system to reach the near-invariant. Given that Peach Spring pumice and fiamme are characterized by <30 wt. % crystals, it seems unlikely that crystallization alone led to eruption, suggesting the action of an external trigger in promoting eruption. This is consistent with evidence for significant heating and mush remobilization preserved in intracaldera Peach Spring rocks. Our results show that phase-equilibria constrains whether a magma system is likely to destabilize itself and erupt as a result of overpressurization by closed-system crystallization and volatile exsolution.

  15. A total internal reflection ellipsometry and atomic force microscopy study of interactions between Proteus mirabilis lipopolysaccharides and antibodies.

    PubMed

    Gle?ska-Olender, J; S?k, S; Dworecki, K; Kaca, W

    2015-07-01

    Specific antigen-antibody interactions play a central role in the human immune system. The objective of this paper is to detect immune complexes using label-free detection techniques, that is, total internal reflection ellipsometry (TIRE) and atomic force microscopy (AFM)-based topography and recognition imaging. Interactions of purified rabbit immunoglobulin G (IgG) antibodies with bacterial endotoxins (Proteus mirabilis S1959 O3 lipopolysaccharides) were studied. Lipopolysaccharide was adsorbed on gold surface for TIRE. In the AFM imaging experiments, LPS was attachment to the PEG linker (AFM tip modification). The mica surface was covered by IgG. In TIRE, the optical parameters ? and ? change when a complex is formed. It was found that even highly structured molecules, such as IgG antibodies (anti-O3 LPS rabbit serum), preserve their specific affinity to their antigens (LPS O3). LPS P. mirabilis O3 response of rabbit serum anti-O3 was also tested by topography and recognition imaging. Both TIRE and AFM techniques were recruited to check for possible detection of antigen-antibody recognition event. The presented data allow for determination of interactions between a variety of biomolecules. In future research, this technique has considerable potential for studying a wide range of antigen-antibody interactions and its use may be extended to other biomacromolecular systems. PMID:25854960

  16. Force Dependent Internalization of Magnetic Nanoparticles Results in Highly Loaded Endothelial Cells for Use as Potential Therapy Delivery Vectors

    PubMed Central

    MacDonald, Cristin; Barbee, Kenneth

    2015-01-01

    Purpose To investigate the kinetics, mechanism and extent of MNP loading into endothelial cells and the effect of this loading on cell function. Methods MNP uptake was examined under field on/off conditions, utilizing varying magnetite concentration MNPs. MNP-loaded cell viability and functional integrity was assessed using metabolic respiration, cell proliferation and migration assays. Results MNP uptake in endothelial cells significantly increased under the influence of a magnetic field versus non-magnetic conditions. Larger magnetite density of the MNPs led to a higher MNP internalization by cells under application of a magnetic field without compromising cellular respiration activity. Two-dimensional migration assays at no field showed that higher magnetite loading resulted in greater cell migration rates. In a three-dimensional migration assay under magnetic field, the migration rate of MNP-loaded cells was more than twice that of unloaded cells and was comparable to migration stimulated by a serum gradient. Conclusions Our results suggest that endothelial cell uptake of MNPs is a force dependent process. The in vitro assays determined that cell health is not adversely affected by high MNP loadings, allowing these highly magnetically responsive cells to be potentially beneficial therapy (gene, drug or cell) delivery systems. PMID:22234617

  17. A review of a method for dynamic load distribution, dynamical modeling, and explicit internal force control when two manipulators mutually lift and transport a rigid body object

    SciTech Connect

    Unseren, M.A.

    1997-04-20

    The paper reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restrict the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system.

  18. Organization of the United States International Communications Industry. Appendix. Report of the Panel on Satellites and Other Long-Haul Transmission Modes of the National Academy of Engineering. President's Task Force on Communications Policy. Staff Paper Two.

    ERIC Educational Resources Information Center

    Rostow, Eugene V.

    A staff paper to the President's Task Force on Communications Policy reviews the organization of the American international communications industries and recommends a consolidation of the competing international carriers. Particularly emphasized is the competition and division of ownership between the two technologies involved in international…

  19. PREFACE: NC-AFM 2006: Proceedings of the 9th International Conference on Non-contact Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Tomitori, Masahiko; Onishi, Hiroshi

    2007-02-01

    The advent of scanning probe microscopy (SPM) in the 1980s has significantly promoted nanoscience and nanotechnology. In particular, non-contact atomic force microscopy (NC-AFM), one of the SPM family, has unique capabilities with high spatial resolution for nanoscale measurements in vacuum, air and liquids. In the last decade we have witnessed the rapid progress of NC-AFM with improved performance and increasing applications. A series of NC-AFM international conferences have greatly contributed to this field. Initiated in Osaka in 1998, the NC-AFM meeting has been followed by annual conferences at Pontresina, Hamburg, Kyoto, Montreal, Dingle, Seattle and Bad Essen. The 9th conference was held in Kobe, Japan, 16-20 July 2006. This special issue of Nanotechnology contains the outstanding contributions of the conference. During the meeting delegates learnt about a number of significant advances. Topics covered atomic resolution imaging of metals, semiconductors, insulators, ionic crystals, oxides, molecular systems, imaging of biological materials in various environments and novel instrumentation. Work also included the characterization of electronic and magnetic properties, tip and cantilever fabrication and characterization, atomic distinction based on analysis of tip-sample interaction, atomic scale manipulation, fabrication of nanostructures using NC-AFM, and related theories and simulations. We are greatly impressed by the increasing number of applications, and convinced that NC-AFM and related techniques are building a bridge to a future nano world, where quantum phenomena will dominate and nano devices will be realized. In addition, a special session on SPM road maps was held as a first trial in the field, where the future prospects of SPM were discussed enthusiastically. The overall success of the NC-AFM 2006 conference was due to the efforts of many individuals and groups with respect to scientific and technological progress, as well as the international exchange among participants. We hope that all of the participants enjoyed the activities of the conference and the town of Kobe. We are indebted to the members of the international steering committee and the local organizing committee for this successful conference. The operation of conference business by the Kobe Convention and Visitors Association, and by the staff in Professor Morita's lab in Osaka University, and Professor Onishi's lab in Kobe University, is greatly acknowledged. We would like to express our sincere gratitude to the 167th committee on Nano-probe Technology of Japan Society for the Promotion of Science, Nanotechnology Researchers Network Center of Japan, Foundation Advanced Technology Institute, Tsutomu Nakauchi Foundation, and all of the exhibitors at the conference for their financial support. The funding from Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, is greatly appreciated and enabled these proceedings to be published by IOP Publishing (IOP). We also thank the editorial staff of IOP for their professional work in publishing this special issue.

  20. The contribution of internal climate variability and anthropogenic forcing to Pacific Ocean regional sea level variability over altimetry era and 21st century.

    NASA Astrophysics Data System (ADS)

    Palanisamy, Hindumathi; Meyssignac, Benoit; Cazenave, Anny; Delcroix, Thierry; Salas Y Melia, David

    2015-04-01

    From recently published studies, it is not yet clear whether the sea level spatial trend patterns of the Pacific Ocean observed by satellite altimetry over 20 years are mostly due to internal climate variability or if some anthropogenic fingerprint is already detectable. A number of recent studies have shown that the removal of the signal corresponding to the Pacific Decadal Oscillation (PDO)/ Interdecadal Pacific Oscillation (IPO) from the observed altimetry sea level data over 1993-2010/12 results in some significant residual trend pattern in the western tropical Pacific. It has thus been suggested that the PDO/IPO-related internal climate variability alone cannot account for all of the observed trend patterns in the western tropical Pacific and that the residual signal could be the fingerprint of the anthropogenic forcing. In this study, we investigate if there is any other internal climate variability signal still present in the residual trend pattern after the removal of IPO contribution. We show that subtraction of the IPO contribution to sea level trends does not totally remove the internal variability, leaving significant non-linear internal climatic modes like El Niño Southern Oscillation (ENSO). In addition, by making use of 21 CMIP5 coupled climate models, we study the contribution of anthropogenic forcing and internal climate variability to the Pacific Ocean regional sea level variability over 1993- 2012, and show that the anthropogenic sea level fingerprint in the tropical Pacific is yet not detectable. Over the 21st century, the anthropogenic signal does not dominate the internal variability in the tropical Pacific.

  1. PREFACE: NC-AFM 2005: Proceedings of the 8th International Conference on Non-Contact Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Reichling, M.; Mikosch, W.

    2006-04-01

    The 8th International Conference on Non-Contact Atomic Force Microscopy, held in Bad Essen, Germany, from 15?18th August 2005, attracted a record breaking number of participants presenting excellent contributions from a variety of scientific fields. This clearly demonstrated the high level of activity and innovation present in the community of NC-AFM researchers and the continuous growth of the field. The strongest ever participation of companies for a NC-AFM meeting is a sign for the emergence of new markets for the growing NC-AFM community; and the high standard of the products presented at the exhibition, many of them brand-new developments, reflected the unbroken progress in technology. The development of novel technologies and the sophistication of known techniques in research laboratories and their subsequent commercialization is still a major driving force for progress in this area of nanoscience. The conference was a perfect demonstration of how progress in the development of enabling technologies can readily be transcribed into basic research yielding fundamental insight with an impact across disciplines. The NC-AFM 2005 scientific programme was based on five cornerstones, each representing an area of vivid research and scientific progress. Atomic resolution imaging on oxide surfaces, which has long been a vision for the catalysis community, appears to be routine in several laboratories and after a period of demonstrative experiments NC-AFM now makes unique contributions to the understanding of processes in surface chemistry. These capabilities also open up new routes for the analysis of clusters and molecules deposited on dielectric surfaces where resolution limits are pushed towards the single atom level. Atomic precision manipulation with the dynamic AFM left the cradle of its infancy and flourishes in the family of bottom-up fabrication nanotechnologies. The systematic development of established and the introduction of new concepts of contrast formation allow the highly resolved measurement of a number of physical properties far beyond the determination of surface topography. The development of techniques allowing atomic resolution dynamic mode imaging in liquids pushes the door open for an atomic precision analysis of biological samples under physiological conditions. In each of these fields, the conference demonstrated cutting-edge results and also provided perspectives for the next steps on the roadmap of NC-AFM towards the development of its full extent. The conference in Bad Essen was made possible by the continuous dedication of the local management and we are most grateful to Frauke Riemann, Joachim Fontaine and the members of the supporting team for the smooth organization. We gratefully appreciate the financial support of the exhibitors, namely Anfatec, HALCYONICS, JEOL, LOT-Oriel, NanoMagnetics, NT-MDT, Omicron, Schaefer Technology, SURFACE, UNISOKU and the local sponsors which enabled us to provide free participation at the conference for ten promising young researchers who had submitted excellent contributions. It was a great pleasure for us to continue our most successful collaboration with Nanotechnology as our partner for the proceedings publication and we would like to thank Ian Forbes and the publishing team for the professional handling of the peer review and all production matters.

  2. Internal vs. external forcing in shallow marine diatreme formation: A case study from the Iblean Mountains (SE-Sicily, Central Mediterranean)

    NASA Astrophysics Data System (ADS)

    Suiting, Ines; Schmincke, Hans-Ulrich

    2009-10-01

    A model of diatreme evolution in a shallow marine setting is based on a multi-disciplinary analysis of diatremes in the Iblean Mountains (Sicily). The approach includes stratigraphic, volcanological, structural, petrologic and compositional data. We invoke a complex interplay of internal (rapid ascent and pyroclastic fragmentation of a volatile (CO 2)-rich nephelinitic magma at depth) and external factors. These comprise hydroclastic explosions due to near-surface interaction of the rising particle/volatile mixture with seawater and water-saturated lime mud. Other external factors contributing to diatreme formation include regional and local tectonics (graben formation in pull-apart motion) combined with lateral pipe enlargement by bedrock-spalling and radial block subsidence into the diatreme pipe. We suggest that fragmentation of volatile-rich magma due to internal eruption forcing was fundamental in the formation of the Iblean shallow marine diatremes. Internal and external factors may act to a variable degree, however, during diatreme evolution in general.

  3. Part-time careers in academic internal medicine: a report from the association of specialty professors part-time careers task force on behalf of the alliance for academic internal medicine.

    PubMed

    Linzer, Mark; Warde, Carole; Alexander, R Wayne; Demarco, Deborah M; Haupt, Allison; Hicks, Leroi; Kutner, Jean; Mangione, Carol M; Mechaber, Hilit; Rentz, Meridith; Riley, Joanne; Schuster, Barbara; Solomon, Glen D; Volberding, Paul; Ibrahim, Tod

    2009-10-01

    To establish guidelines for more effectively incorporating part-time faculty into departments of internal medicine, a task force was convened in early 2007 by the Association of Specialty Professors. The task force used informal surveys, current literature, and consensus building among members of the Alliance for Academic Internal Medicine to produce a consensus statement and a series of recommendations. The task force agreed that part-time faculty could enrich a department of medicine, enhance workforce flexibility, and provide high-quality research, patient care, and education in a cost-effective manner. The task force provided a series of detailed steps for operationalizing part-time practice; to do so, key issues were addressed, such as fixed costs, malpractice insurance, space, cross-coverage, mentoring, career development, productivity targets, and flexible scheduling. Recommendations included (1) increasing respect for work-family balance, (2) allowing flexible time as well as part-time employment, (3) directly addressing negative perceptions about part-time faculty, (4) developing policies to allow flexibility in academic advancement, (5) considering part-time faculty as candidates for leadership positions, (6) encouraging granting agencies, including the National Institutes of Health and Veterans Administration, to consider part-time faculty as eligible for research career development awards, and (7) supporting future research in "best practices" for incorporating part-time faculty into academic departments of medicine. PMID:19881429

  4. Driving force-dependent block by internal Ba(2+) on the Kir2.1 channel: Mechanistic insight into inward rectification.

    PubMed

    Hsieh, Chi-Pan; Kuo, Chung-Chin; Huang, Chiung-Wei

    2015-07-01

    The Kir2.1 channel is characterized by strong inward rectification; however, the mechanism of the steep voltage dependence near the equilibrium potential remains to be investigated. Here, we studied the internal Ba(2+) block of the Kir2.1 channel expressed in Xenopus oocytes. We showed that the driving force and thus the K(+) ion flux significantly influenced the apparent affinity of the block by internal Ba(2+). Kinetic analysis revealed that the binding rate shifted with the driving force and changed steeply near the equilibrium point, either in the presence or absence of the transmembrane electrical field. The unbinding rate was determined by the intrinsic affinity of the site. Mutagenesis studies revealed that the high-affinity binding site for Ba(2+) was located near T141 at the internal entrance of the selectivity filter. The steep change of the blocking affinity near the equilibrium potential may result from the flux-coupling effect in the single-file, multi-ion cytoplasmic pore. PMID:25913355

  5. The Role of Internal Models in Motion Planning and Control: Evidence from Grip Force Adjustments during Movements

    E-print Network

    Flanagan, Randy

    . The manipulandum was attached to two servo-controlled linear motors used to create inertial and vis- cous loads of an internal model of the motor apparatus in planning and controlling arm movements. In particular, we tested movement on which the load depends. We suggest this pre- diction is based on an internal model of the motor

  6. Monitoring analysis of internal forces and deformation of the retaining structure for deep subway station foundation pit in silty sand

    Microsoft Academic Search

    Zhang Zhong-miao; Fang Kai; Wu Zu-fu

    2010-01-01

    In this paper the horizontal displacements of diaphragm wall, axial forces of steel struts and surface settlements for different stages in different zones are compared by analyzing the monitoring data of a deep subway station foundation pit support structure in Hangzhou. The results shows that the rate of deformation of the diaphragm wall increases during the excavation near the bottom

  7. International Journal of Machine Tools & Manufacture 39 (1999) 17171731 Indirect cutting force measurement in multi-axis

    E-print Network

    Kim, Jongwon

    1999-01-01

    current signals of servo motors. A Kalman filter disturbance observer and an artificial neural network: Milling; Cutting force; In-process measurement; Kalman filter; Artificial neural network 1. Introduction, fragility to overload, inherent measurement stroke limit, intricate wiring harnesses within the machining

  8. COMPUTER MODEL FOR THE PREDICTION OF THE IMPACT FORCE INDUCED BY PISTON SLAP IN INTERNAL COMBUSTION ENGINES

    Microsoft Academic Search

    Alessandro Ruggiero; Adolfo Senatore

    This paper introduces a computer model for the investigations about the piston dynamic behaviour of a traditional slider-crank mechanism, focusing on the impact force between piston skirt and cylinder wall, responsible of the piston slap phenom- ena. The code allows analysing the effect of the geometric parameters, lubricant proper- ties and engine operating conditions on the piston slap. The model

  9. Understanding the Programmatic and Contextual Forces That Influence Participation in a Government-Sponsored International Student-Mobility Program

    ERIC Educational Resources Information Center

    Perna, Laura W.; Orosz, Kata; Jumakulov, Zakir; Kishkentayeva, Marina; Ashirbekov, Adil

    2015-01-01

    Although prior research establishes the forces that "push" and "pull" students to participate in foreign study, the transferability of findings from earlier studies is limited by the absence of theoretical grounding. In addition, relatively little is known about how a government-sponsored student mobility program promotes…

  10. Climate forcing Climate forcing

    E-print Network

    MacKinnon, Jennifer

    on Climate Change (IPCC), honored with the 2007 Nobel Peace Prize.6 Summary for Policymakers CHANGESClimate forcing #12;Climate forcing External forcing for earth's climate includes earth orbit tectonics (plate motion) greenhouse gases (to the extent that they are not part of the climate system itself

  11. Speaker-External versus Speaker-Internal Forces on Utterance Form: Do Cognitive Demands Override Threats to Referential Success?

    ERIC Educational Resources Information Center

    Lane, Liane Wardlow; Ferreira, Victor S.

    2008-01-01

    To what extent do speaker-external communicative pressures versus speaker-internal cognitive pressures affect utterance form? Four experiments measured speakers' references to privately known (i.e., privileged) objects when naming mutually known (i.e., common ground) objects. Although speaker-external communicative pressures demanded that speakers…

  12. Can International Large-Scale Assessments Inform a Global Learning Goal? Insights from the Learning Metrics Task Force

    ERIC Educational Resources Information Center

    Winthrop, Rebecca; Simons, Kate Anderson

    2013-01-01

    In recent years, the global community has developed a range of initiatives to inform the post-2015 global development agenda. In the education community, International Large-Scale Assessments (ILSAs) have an important role to play in advancing a global shift in focus to access plus learning. However, there are a number of other assessment tools…

  13. Influence of forced internal air circulation on airflow distribution and heat transfer in a gas double-dynamic solid-state fermentation bioreactor.

    PubMed

    Chen, Hongzhang; Qin, Lanzhi; Li, Hongqiang

    2014-02-01

    Internal air circulation affects the temperature field distribution in a gas double-dynamic solid-state fermentation bioreactor (GDSFB). To enhance heat transfer through strengthening internal air circulation in a GDSFB, we put an air distribution plate (ADP) into the bioreactor and studied the effects of forced internal air circulation on airflow, heat transfer, and cellulase activity of Trichoderma viride L3. Results showed that ADP could help form a steady and uniform airflow distribution, and with gas-guide tubes, air reversal was formed inside the bioreactor, thus resulting in a smaller temperature difference between medium and air by enhancing convective heat transfer inside the bioreactor. Using an ADP of 5.35 % aperture ratio caused a 1 °C decrease in the average temperature difference during the solid-state fermentation process of T. viride L3. Meanwhile, the cellulase activity of T. viride L3 increased by 13.5 %. The best heat-transfer effect was attained when using an ADP of 5.35 % aperture ratio and setting the fan power to 125 V (4.81 W) in the gas double-dynamic solid-state fermentation (GDSF) process. An option of suitable aperture ratio and fan power may be conducive to ADPs' industrial amplification. PMID:24347160

  14. Turbofan forced mixer-nozzle internal flowfield. Volume 3: A computer code for 3-D mixing in axisymmetric nozzles

    NASA Technical Reports Server (NTRS)

    Kreskovsky, J. P.; Briley, W. R.; Mcdonald, H.

    1982-01-01

    A finite difference method is developed for making detailed predictions of three dimensional subsonic turbulent flow in turbofan lobe mixers. The governing equations are solved by a forward-marching solution procedure which corrects an inviscid potential flow solution for viscous and thermal effects, secondary flows, total pressure distortion and losses, internal flow blockage and pressure drop. Test calculations for a turbulent coaxial jet flow verify that the turbulence model performs satisfactorily for this relatively simple flow. Lobe mixer flows are presented for two geometries typical of current mixer design. These calculations included both hot and cold flow conditions, and both matched and mismatched Mach number and total pressure in the fan and turbine streams.

  15. Magnetoelectric Ponderomotive Force

    NASA Astrophysics Data System (ADS)

    Brechet, Sylvain D.; Roulet, Alexandre; Ansermet, Jean-Philippe

    2013-08-01

    The dynamics of a system consisting of a matter continuum with a weak linear magnetoelectric coupling interacting with electromagnetic fields is examined on a local scale in a nonrelativistic limit. A consistent expression for the internal energy of the system is derived. The internal energy density and the continuity equation for the momentum lead to the derivation of ponderomotive forces. A nonuniform magnetoelectric coupling generates a "magnetoelectric" ponderomotive force that could be distinguished from the purely electric or magnetic ponderomotive forces by applying alternating electric and magnetic fields at distinct frequencies.

  16. Data mining of external and internal forcing of fluvial systems for catchment management: A case study on the Red River (Song Hong), Vietnam

    NASA Astrophysics Data System (ADS)

    Schmitt, Rafael; Bizzi, Simone; Castelletti, Andrea

    2013-04-01

    The understanding of river hydromorphological processes has been recognized in the last decades as a priority of modern catchment management, since interactions of natural and anthropogenic forces within the catchment drives fluvial geomorphic processes, which shape physical habitat, affect river infrastructures and influence freshwater ecological processes. The characterization of river hydromorphological features is commonly location and time specific and highly resource demanding. Therefore, its routine application at regional or national scales and the assessment of spatio-temporal changes as reaction to internal and external disturbances is rarely feasible at present. Information ranging from recently available high-resolution remote-sensing data (such as DEM), historic data such as land use maps or aerial photographs and monitoring networks of flow and rainfall, open up novel and promising capacity for basin-wide understanding of dominant hydromorphological drivers. Analysing the resulting multiparametric data sets in their temporal and spatial dimensions requires sophisticated data mining tools to exploit the potential of this information. We propose a novel framework that allows for the quantitative assessment of multiparametric data sets to identify classes of channel reaches characterized by similar geomorphic drivers using remote-sensing data and monitoring networks available in the catchment. This generic framework was applied to the Red River (Song Hong) basin, the second largest basin (87,800 sq.km) in Vietnam. Besides its economic importance, the river is experiencing severe river bed incisions due to recent construction of new dams in the upstream part of the catchment and sand mining in the surrounding of the capital city Hanoi. In this context, characterized by an high development rate, current efforts to increase water productivity and minimize impacts on the fluvial systems by means of focused infrastructure and management measures require a thorough understanding of the fluvial system and, in particular, basin-wide assessment of resilience to human-induced change. . The framework proposed has allowed producing high-dimensional samples of spatially distributed geomorphic drivers at catchment scale while integrating recent and historic point records for the Red River basin. This novel dataset has been then analysed using self-organizing maps (SOM) an artificial neural network model in combination with fuzzy clustering. The above framework is able to identify non-trivial correlations in driving forces and to derive a fuzzy classification at reach scale which represents continuities and discontinuities in the river systems. The use of the above framework allowed analyzing the spatial distribution of geomorphic features at catchment scale, revealing patterns of similarities and dissimilarities within the catchment and allowing a classification of river reaches characterized by similar geomorphic drivers, fluvial processes and response to external forcing. The paper proposes an innovative and promising technique to produce hydromorphological classifications at catchment scale integrating historical and recent available high resolution data. The framework aims at opening the way to a more structured organization and analyses of recently available information on river geomorphic features, so far often missing or rarely exploited. This approach poses the basis to produce efficient databases of river geomorphic features and processes related to natural and anthropogenic drivers. That is a necessity in order to enhance our understanding of the internal and external forces which drive fluvial systems, to assess the resilience and dynamic of river landscapes and to develop the more efficient river management strategies of the future.

  17. A review of a method for dynamic load distribution, dynamic modeling, and explicit internal force control when two serial link manipulators mutually lift and transport a rigid body object

    SciTech Connect

    Unseren, M.A.

    1997-09-01

    The report reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restricts the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system.

  18. International International

    E-print Network

    Puglisi, Joseph

    Egon Zehnder International Egon Zehnder International Egon Zehnder International #12;I. ID info and qualifications Strategies for navigating a difficult job market Anything else? #12;Biographical Information Planning, Bayer HealthCare Pharmaceuticals · Senior Manager Business the Life Sciences Practice Group

  19. The ``Phantom'' Force1

    Microsoft Academic Search

    A. S. Herschel

    1878-01-01

    IT might be supposed that permanent and entirely local or ``internal'' force-pairs of this kind acting on innumerable material couplets in a system would so disturb the individual energies of their motions that no general conclusion as to the total change of energy during the progress of such a system's motion could be drawn; but the simple law that impulses

  20. Air Force

    NSDL National Science Digital Library

    Merkle

    2011-10-22

    The students will engage in an open inquiry developing an experiment pertaining to unbalanced forces. The students will create an experiment and test their hypothesis. Content Statement: Tell me if an unbalanced force affects speed, direction or both.

  1. 32 CFR 536.104 - Current agreements in force.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 3 2013-07-01 2013-07-01 false Current agreements in force. 536.104 Section 536...Under International Agreements § 536.104 Current agreements in force. Current listings of known agreements in force are also...

  2. Forces and motion

    NSDL National Science Digital Library

    Ted Latham

    2002-01-01

    In this activity, students will understand the following (1) gravity is the force of attraction that causes objects to fall toward the center of the earth, (2) air resistance, or air friction, can slow down the acceleration of a falling object, (3) the area 'fronting the wind' affects the amount of air resistance a falling object encounters, (4) terminal speed is the speed at which the downward pull of gravity is balanced by the equal and upward opposing force of air resistance for a falling object. This would be a suitable activity for small groups. Copyright 2005 International Technology Education Association

  3. Dam Forces

    NSDL National Science Digital Library

    Integrated Teaching and Learning Program and Laboratory,

    Students learn how the force of water helps determine the size and shape of dams. They use clay to build models of four types of dams, and observe the force of the water against each type. They conclude by deciding which type of dam they, as Splash Engineering engineers, will design for Thirsty County.

  4. Unbalanced Forces

    NSDL National Science Digital Library

    The representation describes the effect of unbalanced forces on objects at rest and objects in motion in an animated slide show. This resource also includes an interactive test and review of the material. The slide show is accessed through a link marked "Unbalanced Forces" on the resource page, and the entire resource is downloadable, allowing users to run the slide show offline.

  5. Social force model for pedestrian dynamics

    Microsoft Academic Search

    Dirk Helbing; Péter Molnár

    1995-01-01

    It is suggested that the motion of pedestrians can be described as if they would be subject to ``social forces.'' These ``forces'' are not directly exerted by the pedestrians' personal environment, but they are a measure for the internal motivations of the individuals to perform certain actions (movements). The corresponding force concept is discussed in more detail and can also

  6. Force sensor

    DOEpatents

    Grahn, Allen R. (Salt Lake City, UT)

    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. Internal combustion engine

    SciTech Connect

    Kurek, W.; Startek, A.

    1989-02-14

    A crankless internal combustion engine is described comprising: a cylinder; a piston slidably disposed for rectilinear reciprocal movement within the cylinder; a continuous internally facing force transfer means pivotally mounted to the piston; a drive shaft; a drive means keyed to the drive shaft and internally adjacent to the force transfer means, a portion of the drive means engaging a portion of the force transfer means; the drive means and/or the force transfer means being shaped in accordance with the variable forces applied to the piston during rectilinear reciprocal movement of the piston within the cylinder; and means for guiding the force transfer means such that the drive means cooperatively associates with the force transfer means to convert the rectilinear movement of the piston into rotary movement of the drive shaft.

  9. Casimir forces

    E-print Network

    S. Reynaud; A. Lambrecht

    2014-10-10

    The present notes are organized as the lectures given at the Les Houches Summer School "Quantum Optics and Nanophotonics" in August 2013. The first section contains an introduction and a description of the current state-of-the-art for Casimir force measurements and their comparison with theory. The second and third sections are a pedagogical presentation of the main features of the theory of Casimir forces for 1-dimensional model systems and for mirrors in 3-dimensional space.

  10. Physlet Force Concept Inventory: Forces

    NSDL National Science Digital Library

    Wolfgang Christian

    A large truck breaks down out on the road and receives a push back into town by a small compact car as shown in the animation. Learners are to answer questions regarding forces exerted by the two vehicles.

  11. On Force Regulation Strategies in Predictable Environments

    PubMed Central

    Kolesnikov, Maxim; Piovesan, Davide; Lynch, Kevin M.; Mussa-Ivaldi, Ferdinando A.

    2015-01-01

    This paper is focused on investigating force regulation strategies employed by human central nervous system (CNS). The mechanism responsible for force control is extremely important in people’s lives, but not yet well understood. We formulate the general model of force regulation and identify several possible control strategies. An experimental approach is used to determine which of the force control strategies could actually be used by the CNS. Obtained results suggest that the force regulation process involves not only the pure force controller, but also a coupled motion controller, relying on the internal model of the environment. PMID:22255236

  12. From local force-flux relationships to internal dissipations and their impact on heat engine performance: The illustrative case of a thermoelectric generator

    NASA Astrophysics Data System (ADS)

    Apertet, Y.; Ouerdane, H.; Goupil, C.; Lecoeur, Ph.

    2013-08-01

    We present an in-depth analysis of the sometimes understated role of the principle of energy conservation in linear irreversible thermodynamics. Our case study is that of a thermoelectric generator (TEG), which is a heat engine of choice in irreversible thermodynamics, owing to the coupling between the electrical and heat fluxes. We show why Onsager's reciprocal relations must be considered locally and how internal dissipative processes emerge from the extension of these relations to a global scale: The linear behavior of a heat engine at the local scale is associated with a dissipation process that must partake in the global energy balance. We discuss the consequences of internal dissipations on the so-called efficiency at maximum power, in the light of our comparative analyses of exoreversibility and endoreversibility on the one hand and of two classes of heat engines, autonomous and periodically driven, on the other hand. Finally, basing our analysis on energy conservation, we also discuss recent works which claim the possibility to overcome the traditional boundaries on efficiency imposed by finite-time thermodynamics in thermoelectric systems with broken time-reversal symmetry; this we do by introducing a “thermal” thermopower and an “electrical” thermopower which permits an analysis of the thermoelectric response of the TEG considering a possible dissymmetry between the electrical/thermal and the thermal/electrical couplings.

  13. Forces Lab

    NSDL National Science Digital Library

    This set of online simulations shows the forces that may be at work on geologic structures or on man-made structures during an earthquake. Users can see examples of compression, tension, bending, and torsion. Each simulation also features a link to a photo of a real-life example.

  14. Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.

    PubMed

    LaFrance, W Curt; Baker, Gus A; Duncan, Rod; Goldstein, Laura H; Reuber, Markus

    2013-11-01

    An international consensus group of clinician-researchers in epilepsy, neurology, neuropsychology, and neuropsychiatry collaborated with the aim of developing clear guidance on standards for the diagnosis of psychogenic nonepileptic seizures (PNES). Because the gold standard of video electroencephalography (vEEG) is not available worldwide, or for every patient, the group delineated a staged approach to PNES diagnosis. Using a consensus review of the literature, this group evaluated key diagnostic approaches. These included: history, EEG, ambulatory EEG, vEEG/monitoring, neurophysiologic, neurohumoral, neuroimaging, neuropsychological testing, hypnosis, and conversation analysis. Levels of diagnostic certainty were developed including possible, probable, clinically established, and documented diagnosis, based on the availability of history, witnessed event, and investigations, including vEEG. The aim and hope of this report is to provide greater clarity about the process and certainty of the diagnosis of PNES, with the intent to improve the care for people with epilepsy and nonepileptic seizures. PMID:24111933

  15. Forced Migration Review

    NSDL National Science Digital Library

    Published tri-annually since January 1998, the Forced Migration Review (FMR) is the in-house journal of the Refugee Studies Centre at the University of Oxford. The journal (and its online edition made available on this site) is published in English, Arabic, and Spanish, and "provides the humanitarian community with a practice-oriented forum for debate on issues facing refugees and internally displaced people in order to improve policy and practice." From the site, visitors can browse through single articles or complete issues of the journal all the way back to 1998. Many of the issues are dedicated to a single theme, including recent issues which have been titled When does internal displacement end? and Reproductive health for displaced people: Investing in the future. The site also provides ample information on submitting articles to the journal, material on the current editorial board, and the themes for upcoming issues. Rounding out the site is a collection of related links for consideration, organized into topics such as international law, reproductive health and forced migration research institutes and centers.

  16. Elasticity, structure, and relaxation of extended proteins under force

    E-print Network

    Berne, Bruce J.

    perspective, it is still unclear how applied force affects internal diffusion of a polypeptide along greatly enhances internal friction along the end-to- end coordinate with a power law dependence (12

  17. Centrifuges and inertial shear forces.

    PubMed

    van Loon, Jack J W A; Folgering, Erik H T E; Bouten, Carlijn V C; Smit, Theo H

    2004-03-01

    Centrifuges are often used in biological studies for 1 x g control samples in space flight microgravity experiments as well as in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces may contribute as much as 99% to the total force acting on the cells or tissues. The inertial shear force artifact should be dealt with for future experiment hardware development for Shuttle and the International Space Station (ISS) as well as for the interpretation of previous spaceflight and on-ground research data. PMID:16145797

  18. The effect of force feedback delay on stiffness perception and grip force modulation during tool-mediated interaction with elastic force fields.

    PubMed

    Leib, Raz; Karniel, Amir; Nisky, Ilana

    2015-05-01

    During interaction with objects, we form an internal representation of their mechanical properties. This representation is used for perception and for guiding actions, such as in precision grip, where grip force is modulated with the predicted load forces. In this study, we explored the relationship between grip force adjustment and perception of stiffness during interaction with linear elastic force fields. In a forced-choice paradigm, participants probed pairs of virtual force fields while grasping a force sensor that was attached to a haptic device. For each pair, they were asked which field had higher level of stiffness. In half of the pairs, the force feedback of one of the fields was delayed. Participants underestimated the stiffness of the delayed field relatively to the nondelayed, but their grip force characteristics were similar in both conditions. We analyzed the magnitude of the grip force and the lag between the grip force and the load force in the exploratory probing movements within each trial. Right before answering which force field had higher level of stiffness, both magnitude and lag were similar between delayed and nondelayed force fields. These results suggest that an accurate internal representation of environment stiffness and time delay was used for adjusting the grip force. However, this representation did not help in eliminating the bias in stiffness perception. We argue that during performance of a perceptual task that is based on proprioceptive feedback, separate neural mechanisms are responsible for perception and action-related computations in the brain. PMID:25717155

  19. 1. Forces and thermostats 1 Irreversibility time scale

    E-print Network

    a system is modeled as an aggregate of molecules interacting via conservative forces. A corresponding1. Forces and thermostats 1 Irreversibility time scale G.Gallavotti I.N.F.N. Roma 1, Fisica Roma1 language, for a system subject to internal conservative forces in­ teracting with ``external'' thermostats

  20. 75 FR 34438 - Defense Science Board Task Force on Trends and Implications of Climate Change for National and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-17

    ...Science Board Task Force on Trends and Implications of Climate Change for National and International Security AGENCY: Department...Science Board Task Force on Trends and Implications of Climate Change for National and International Security will meet...

  1. 75 FR 43944 - Defense Science Board; Task Force on Trends and Implications of Climate Change for National and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ...Science Board; Task Force on Trends and Implications of Climate Change for National and International Security AGENCY: Department...Science Board Task Force on Trends and Implications of Climate Change for National and International Security will meet...

  2. Internationalization, market forces and domestic sectoral institutionalization

    Microsoft Academic Search

    Murat Hakan Altintas; Demetris Vrontis; Hans Ruediger Kaufmann; Ilan Alon

    2011-01-01

    Purpose – The purpose of this paper is to investigate the influence of micro-environmental international entrepreneurship and the macro-environmental market forces on domestic institutionalization of the industrial sector. In doing so, the paper examines the moderating effect of the degree of internationalization on the relationship between domestic market forces and domestic sectoral institutionalization. Design\\/methodology\\/approach – Based upon the creation of

  3. Forced vs unforced drivers of Atlantic SST variability - linking forced role to magnitude of aerosol forcing

    NASA Astrophysics Data System (ADS)

    Booth, B.; Dunstone, N.; Halloran, P. R.; Andrews, T.; Bellouin, N.; Martin, E. R.

    2014-12-01

    Historical variations in North Atlantic SSTs have been a key driver of regional climate change - linked to drought frequency in the Sahel, Amazon and American Mid-West, rainfall and heat waves in Europe and frequency of Atlantic tropical storms. Traditionally these SST variations were deemed to arise from internally generated ocean variability. We present results from recent studies (Booth et al, 2012, Dunstone, 2013) that identify a mechanism via which volcanic and industrial aerosols could explain a large fraction of observed Atlantic variability, and its associated climate impacts. This work has prompted a lot of subsequent discussion about the relative contribution of ocean generated and external forced variability in the Atlantic. Here we present new results, that extend this earlier work, by looking at forced variability in the CMIP5 modelling context. This provides new insights into the potential externally forced role aerosols may play in the real world. CMIP5 models that represent aerosol-cloud interactions tend to have stronger correlations to observed variations in SSTs, but disagree on the magnitude of forced variability that they explain. We can link this contribution to the magnitude of aerosol forcing in each of these models - a factor that is both dependent on the aerosol parameterisation and the representation of boundary layer cloud in this region. This suggests that whether aerosols have played a larger or smaller role in historical Atlantic variability is tied to whether aerosols have a larger or smaller aerosol forcing (particularly indirect) in the real world. This in turn suggests that benefits of reducing current aerosol uncertainty are likely to extend beyond better estimates of global forcing, to providing a clearer picture of the past aerosol driven role in historical regional climate change.

  4. Efficacy of climate forcings

    Microsoft Academic Search

    J. Hansen; M. Sato; R. Ruedy; L. Nazarenko; A. Lacis; G. A. Schmidt; G. Russell; I. Aleinov; M. Bauer; S. Bauer; N. Bell; B. Cairns; V. Canuto; M. Chandler; Y. Cheng; A. Del Genio; G. Faluvegi; E. Fleming; A. Friend; T. Hall; C. Jackman; M. Kelley; N. Kiang; D. Koch; J. Lean; J. Lerner; K. Lo; S. Menon; R. Miller; P. Minnis; T. Novakov; V. Oinas; Ja. Perlwitz; Ju. Perlwitz; D. Rind; A. Romanou; D. Shindell; P. Stone; S. Sun; N. Tausnev; D. Thresher; B. Wielicki; T. Wong; M. Yao; S. Zhang

    2005-01-01

    We use a global climate model to compare the effectiveness of many climate forcing agents for producing climate change. We find a substantial range in the “efficacy” of different forcings, where the efficacy is the global temperature response per unit forcing relative to the response to CO2 forcing. Anthropogenic CH4 has efficacy ?110%, which increases to ?145% when its indirect

  5. Intermolecular Forces (Netorials)

    NSDL National Science Digital Library

    Intermolecular Forces: this is a resource in the collection "Netorials". In this resource there is a review of Lewis structures, molecular geometry, electronegativity, or molecular polarity. After that, you can learn about the forces of attraction that exist between molecules. This module explores London forces and dipole-dipole forces (including hydrogen bonds). The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

  6. Magnetic microposts as an approach to apply forces to living cells

    E-print Network

    Chen, Christopher S.

    Magnetic microposts as an approach to apply forces to living cells Nathan J. Sniadecki*, Alexandre, 2007) Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via

  7. DISPOSITIF ELECTROMECANIQUE POUR APPLICATION DE FAIBLES ELECTRO-MECHANICAL DEVICE FOR GENERATING SMALL FORCES

    E-print Network

    Paris-Sud XI, Université de

    DISPOSITIF ELECTROMECANIQUE POUR APPLICATION DE FAIBLES FORCES ELECTRO-MECHANICAL DEVICE FOR GENERATING SMALL FORCES N-E. Khélifa CNAM/LNE : Laboratoire Commun de Métrologie 61, rue du Landy, 93210 la forces. En effet, aucune réalisation de force inférieure à 1 Newton, raccordée au système international d

  8. Physicists' Forced Migrations under Hitler

    NASA Astrophysics Data System (ADS)

    Beyerchen, Alan

    2011-03-01

    When the Nazis came to power in early 1933 they initiated formal and informal measures that forced Jews and political opponents from public institutions such as universities. Some physicists retired and others went into industry, but most emigrated. International communication and contact made emigration a viable option despite the desperate economic times in the Great Depression. Another wave of emigrations followed the annexation of Austria in 1938. Individual cases as well as general patterns of migration and adaptation to new environments will be examined in this presentation. One important result of the forced migrations was that many of the physicists expelled under Hitler played important roles in strengthening physics elsewhere, often on the Allied side in World War II.

  9. Forces in general relativity

    NASA Astrophysics Data System (ADS)

    Ridgely, Charles T.

    2010-07-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced by an observer in general coordinates. The general force is then applied to the local co-moving coordinate system of a uniformly accelerating observer, leading to an expression of the inertial force experienced by the observer. Next, applying the general force in Schwarzschild coordinates is shown to lead to familiar expressions of the gravitational force. As a more complex demonstration, the general force is applied to an observer in Boyer-Lindquist coordinates near a rotating, Kerr black hole. It is then shown that when the angular momentum of the black hole goes to zero, the force on the observer reduces to the force on an observer held stationary in Schwarzschild coordinates. As a final consideration, the force on an observer moving in rotating coordinates is derived. Expressing the force in terms of Christoffel symbols in rotating coordinates leads to familiar expressions of the centrifugal and Coriolis forces on the observer. It is envisioned that the techniques presented herein will be most useful to graduate level students, as well as those undergraduate students having experience with general relativity and tensor analysis.

  10. Citizen groups: a creative force

    SciTech Connect

    Stoel, T.

    1981-02-01

    The role of citizen groups is as important as that of government agencies when it comes to environmental policy in a democracy. These groups spend little money, yet they have initiated the major US environmental legislation of the past two decades. They are a recent, but effective, force in developing countries even though adversarial approaches are not often appropriate. The methods used by US environmental groups range from lobbying to confrontation in court. Groups outside the US tend to use consensus in democracies and information gathering in developing countries. While the groups' primary concerns are national in scope, international awareness and cooperation are growing. (DCK)

  11. THE INTERNATIONAL CRIMINAL COURT

    Microsoft Academic Search

    HÅKAN FRIMAN

    2004-01-01

    The statute of the International Criminal Court is now in force and the court has begun its first investigations. Other conflicts and more investigations are being considered. The first investigations in the DRC and Uganda are based on these states referring crimes committed on their own territory to the court, an unexpected development. Such a move has been encouraged by

  12. Forces in the Atmosphere

    NSDL National Science Digital Library

    John Nielsen-Gammon

    1996-01-01

    This undergraduate meteorology tutorial is about understanding the forces that cause the motion of air, producing winds and changes of weather. It discusses how these forces tend to balance each other, and how they produce the wind.

  13. Aerodynamic Lifting Force.

    ERIC Educational Resources Information Center

    Weltner, Klaus

    1990-01-01

    Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)

  14. Forces in One Dimension

    NSDL National Science Digital Library

    The representation depicts the relationship between frictional and applied forces for a variety of objects in an interactive simulation. As the user manipulates objects, charts show the resulting forces and depict position, velocity, and acceleration vs. time.

  15. Fluid force transducer

    DOEpatents

    Jendrzejczyk, Joseph A. (Warrenville, IL)

    1982-01-01

    An electrical fluid force transducer for measuring the magnitude and direction of fluid forces caused by lateral fluid flow, includes a movable sleeve which is deflectable in response to the movement of fluid, and a rod fixed to the sleeve to translate forces applied to the sleeve to strain gauges attached to the rod, the strain gauges being connected in a bridge circuit arrangement enabling generation of a signal output indicative of the magnitude and direction of the force applied to the sleeve.

  16. Forces in General Relativity

    ERIC Educational Resources Information Center

    Ridgely, Charles T.

    2010-01-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…

  17. Debunking Coriolis Force Myths

    ERIC Educational Resources Information Center

    Shakur, Asif

    2014-01-01

    Much has been written and debated about the Coriolis force. Unfortunately, this has done little to demystify the paradoxes surrounding this fictitious force invoked by an observer in a rotating frame of reference. It is the purpose of this article to make another valiant attempt to slay the dragon of the Coriolis force! This will be done without…

  18. Turkish Students' Force Meanings

    ERIC Educational Resources Information Center

    Menekse, Muhsin; Clark, Douglas B.; Ozdemir, Gokhan; D'angelo, Cynthia; Scheligh, Sharon

    2009-01-01

    What are Turkish pre, elementary, middle, and high school students' force ideas? And, how do Turkish students' non-normative force ideas differ or be similar to the well-known force misconceptions reported in the literature? Students have false and persistent beliefs about the physical world and they struggle with challenging misconceptions based…

  19. The Missing Climate Forcing

    Microsoft Academic Search

    J. Hansen; M. Sato; A. Lacis; R. Ruedy

    1997-01-01

    Observed climate change is consistent with radiative forcings on several time scales for which the dominant forcings are known, ranging from the few years after a large volcanic eruption to glacial-to-interglacial changes. In the period with most detailed data, 1979 to the present, climate observations contain clear signatures of both natural and anthropogenic forcings. But in the full period since

  20. Operating internationally

    SciTech Connect

    Seeley, R.S.

    1994-02-01

    When Enron Power Corp. took over a 28 MW power facility at the former US Naval base in Subic Bay, the Philippines, the company was required to employ 139 people to run the plant. This large labor force was necessary not because of the plant's operational needs, but because of local labor practices and unemployment pressures. Independent power companies have become all too familiar with the high cost and complexity of developing projects in emerging international markets. Some of the most significant issues involve taxation, unfamiliar legal systems, changing regulations, and foreign investment restrictions. In addition, questions about currency exchange, national credit worthiness, and political stability add to the difficulty of international development. However, one of the most daunting challenges centers not on development, but on long-term operations and maintenance (O M). A key concern is finding qualified labor. Most developers and O M companies agree that local people should run the plant, with the top person, or persons, thoroughly trained in the developer's company philosophy.

  1. Force Concept Inventory: Forces and Speed

    NSDL National Science Digital Library

    Wolfgang Christian

    A rocket drifts sideways in outer space from point "a" to point "b" as shown in the animations. The rocket is subject to no outside forces. Starting at position "b", the rockets's engine is turned on and produces a constant thrust (force on the rocket) at right angles to the line "ab". The constant thrust is maintained until the rocket reaches a point "c" in space. At point "c" the rocket's engine is turned off and the thrust immediately drops to zero.

  2. Force Concept Inventory: Forces and Speed

    NSDL National Science Digital Library

    Wolfgang Christian

    A rocket drifts sideways in outer space from point "a" to point "b" as shown in the animations. The rocket is subject to no outside forces. Starting at position "b", the rockets's engine is turned on and produces a constant thrust (force on the rocket) at right angles to the line "ab". The constant thrust is maintained until the rocket reaches a point "c" in space.

  3. Efficacy of climate forcings

    NASA Astrophysics Data System (ADS)

    Hansen, J.; Sato, M.; Ruedy, R.; Nazarenko, L.; Lacis, A.; Schmidt, G. A.; Russell, G.; Aleinov, I.; Bauer, M.; Bauer, S.; Bell, N.; Cairns, B.; Canuto, V.; Chandler, M.; Cheng, Y.; Del Genio, A.; Faluvegi, G.; Fleming, E.; Friend, A.; Hall, T.; Jackman, C.; Kelley, M.; Kiang, N.; Koch, D.; Lean, J.; Lerner, J.; Lo, K.; Menon, S.; Miller, R.; Minnis, P.; Novakov, T.; Oinas, V.; Perlwitz, Ja.; Perlwitz, Ju.; Rind, D.; Romanou, A.; Shindell, D.; Stone, P.; Sun, S.; Tausnev, N.; Thresher, D.; Wielicki, B.; Wong, T.; Yao, M.; Zhang, S.

    2005-09-01

    We use a global climate model to compare the effectiveness of many climate forcing agents for producing climate change. We find a substantial range in the "efficacy" of different forcings, where the efficacy is the global temperature response per unit forcing relative to the response to CO2 forcing. Anthropogenic CH4 has efficacy ˜110%, which increases to ˜145% when its indirect effects on stratospheric H2O and tropospheric O3 are included, yielding an effective climate forcing of ˜0.8 W/m2 for the period 1750-2000 and making CH4 the largest anthropogenic climate forcing other than CO2. Black carbon (BC) aerosols from biomass burning have a calculated efficacy ˜58%, while fossil fuel BC has an efficacy ˜78%. Accounting for forcing efficacies and for indirect effects via snow albedo and cloud changes, we find that fossil fuel soot, defined as BC + OC (organic carbon), has a net positive forcing while biomass burning BC + OC has a negative forcing. We show that replacement of the traditional instantaneous and adjusted forcings, Fi and Fa, with an easily computed alternative, Fs, yields a better predictor of climate change, i.e., its efficacies are closer to unity. Fs is inferred from flux and temperature changes in a fixed-ocean model run. There is remarkable congruence in the spatial distribution of climate change, normalized to the same forcing Fs, for most climate forcing agents, suggesting that the global forcing has more relevance to regional climate change than may have been anticipated. Increasing greenhouse gases intensify the Hadley circulation in our model, increasing rainfall in the Intertropical Convergence Zone (ITCZ), Eastern United States, and East Asia, while intensifying dry conditions in the subtropics including the Southwest United States, the Mediterranean region, the Middle East, and an expanding Sahel. These features survive in model simulations that use all estimated forcings for the period 1880-2000. Responses to localized forcings, such as land use change and heavy regional concentrations of BC aerosols, include more specific regional characteristics. We suggest that anthropogenic tropospheric O3 and the BC snow albedo effect contribute substantially to rapid warming and sea ice loss in the Arctic. As a complement to a priori forcings, such as Fi, Fa, and Fs, we tabulate the a posteriori effective forcing, Fe, which is the product of the forcing and its efficacy. Fe requires calculation of the climate response and introduces greater model dependence, but once it is calculated for a given amount of a forcing agent it provides a good prediction of the response to other forcing amounts.

  4. Faking It: Coriolis Force

    NSDL National Science Digital Library

    This lesson will help students understand what the Coriolis force is, and what effects it has on objects in motion. Students will be able to describe and explain the Coriolis force, and compare and contrast conditions under which the Coriolis force has a significant impact on objects in motion with conditions under which the influence of the Coriolis force is negligible. Portions of this lesson are based on a webpage called "Bad Coriolis", a resource devoted to correcting misconceptions about the Coriolis force and other natural phenomena.

  5. Forces in molecules.

    PubMed

    Hernández-Trujillo, Jesús; Cortés-Guzmán, Fernando; Fang, De-Chai; Bader, Richard F W

    2007-01-01

    Chemistry is determined by the electrostatic forces acting within a collection of nuclei and electrons. The attraction of the nuclei for the electrons is the only attractive force in a molecule and is the force responsible for the bonding between atoms. This is the attractive force acting on the electrons in the Ehrenfest force and on the nuclei in the Feynman force, one that is countered by the repulsion between the electrons in the former and by the repulsion between the nuclei in the latter. The virial theorem relates these forces to the energy changes resulting from interactions between atoms. All bonding, as signified by the presence of a bond path, has a common origin in terms of the mechanics determined by the Ehrenfest, Feynman and virial theorems. This paper is concerned in particular with the mechanics of interaction encountered in what are classically described as 'nonbonded interactions'--are atoms that 'touch' bonded or repelling one another? PMID:17328425

  6. Effect of climate sensitivity on the response to volcanic forcing

    Microsoft Academic Search

    T. M. L. Wigley; C. M. Ammann; B. D. Santer; S. C. B. Raper

    2005-01-01

    The results from 16 coupled atmosphere\\/ocean general circulation model (AOGCM) simulations are used to reduce internally generated noise and to obtain an improved estimate of the underlying response of 20th century global mean temperature to volcanic forcing. An upwelling diffusion energy balance model (UD EBM) with the same forcing and the same climate sensitivity as the AOGCM is then used

  7. Glenohumeral contact forces in reversed anatomy shoulder replacement

    Microsoft Academic Search

    Milad Masjedi; Garth R. Johnson

    2010-01-01

    A major requirement to design an implant is to develop our understanding of the applied internal forces during everyday activities. In the absence of any basic apparatus for measuring forces directly, it is essential to rely on modelling. The major aim of this study was therefore to understand the biomechanical function of subjects with the reversed anatomy Bayley?Walker prosthesis, using

  8. Position And Force Control For Multiple-Arm Robots

    NASA Technical Reports Server (NTRS)

    Hayati, Samad A.

    1988-01-01

    Number of arms increased without introducing undue complexity. Strategy and computer architecture developed for simultaneous control of positions of number of robot arms manipulating same object and of forces and torques that arms exert on object. Scheme enables coordinated manipulation of object, causing it to move along assigned trajectory and be subjected to assigned internal forces and torques.

  9. The value of a certified quality management system: the perception of internal developers

    Microsoft Academic Search

    K. Robinson; P. Simmons

    1996-01-01

    There is growing interest among internal information technology (IT) departments in implementing a certified quality management system (QMS). This paper examines the forces that have influenced organizations that supply development services to adopt QMS models and explores the relevance of these forces to internal IT developers. The perceptions of internal developers regarding the value of QMS in addressing these forces

  10. Do novel gravitational environments alter the grip-force/load-force coupling at the fingertips?

    PubMed

    White, Olivier; McIntyre, Joseph; Augurelle, Anne-Sophie; Thonnard, Jean-Louis

    2005-06-01

    In this experiment we examined the coupling between grip force and load force observed during cyclic vertical arm movements with a hand-held object, performed in different gravitational environments. Six subjects highly experienced in parabolic flight participated in this study. They had to continuously move a cylindrical object up and down in the different gravity fields (1g, 1.8 g and 0 g) induced by parabolic flights. The imposed movement frequency was 1 Hz, the object mass was either 200 or 400 g, the amplitude of movement was either 20 or 40 cm and an additional mass of 200 g could be wound around the forearm. Each subject performed the task during 15 consecutive parabolas. The coordination between the grip force normal to the surface and the tangential load force was examined in nine loading conditions. We observed that the same normal grip force was used for equivalent loads generated by changes of mass, gravity or acceleration despite the fact that these loads required different motor commands to move the arm. Moreover, our results suggest that the gravitational and inertial components of the load are treated adequately and independently by the internal models used to predictively control the required grip force. These results indicate that the forward internal models used to control precision grip take into account the dynamic characteristics of the upper limb, the object and the environment to predict the object's acceleration and, in turn, the load force acting at the fingertips. PMID:15635455

  11. Tactical force protection

    NASA Astrophysics Data System (ADS)

    Stockel, Eugene; Moneyhun, Jon C.

    2004-09-01

    The need for enhanced tactical force protection capabilities is evidenced from our recent experiences in Iraq and Afghanistan and occurs wherever U.S. Forces maintain a forward presence in a potentially hostile environment. Levels of force protection proficiency vary widely from combat units whose mission is to close with and destroy the enemy to combat support/combat service support units performing maintenance and logistics functions. We must provide force protection capabilities that are not only good enough to get the job done, but affordable for the entire force. Addressing the force protection challenge requires an investment in research and development to deliver affordable, scalable, modular and sustainable force protection equipment. This can be accomplished through an evolutionary acquisition strategy of capability upgrades in the near, mid and far-terms that leverage the Army's investments in unmanned ground sensors (UGS), unmanned ground vehicles (UGV) and surveillance radar and imaging technology. This approach addresses the field's immediate tactical force protection requirements, while working towards full integration with the Future Combat System. Futuristic Tactical Force Protection will consist of a fully integrated system of systems architecture that will include UGVs, UGS and Unmanned Aerial Vehicles (UAVs) that are networked with the Future Force.

  12. Forces and Interactions

    NSDL National Science Digital Library

    Although the purist will state that there are four forces, when explaining observed phenomena at the nanoscale it is very useful to include interactions such as ionic and covalent bonding, hydrogen bonds, Brownian motion, van der Waals forces, thermal vibration, rotation , adhesive and cohesive forces and subcategories of these interactions. Often, the effect of what is observed at any scale (macroscale to nanoscale) is dependent upon the priorities of these forces. For example the interaction between planets is driven by the gravitational force because of the large mass of the objects, The strength of the interaction of planets due to the electrostatic forces exists, but is very small -- overshadowed by the gravitational forces. The opposite is often true at the nanoscale, atoms and molecules are significantly impacted by electrostatic forces - and because of the small mass, minimally impacted by gravitational attraction. So it is just a matter of which force or interaction is the top interaction for any given situation. These modules use many different activities which allow students to evaluate the priority of different forces and interactions with different materials and at different scales.

  13. Air Force Link

    NSDL National Science Digital Library

    Appropriately enough, this website is "dedicated to the men and women who made the U.S. Air Force what it is today." As an official website of the United States Air Force, the Air Force Link Heritage website presents a wide range of materials that detail the history of this division of the Armed Forces. Here visitors will find a "This Week in History" feature which presents summary details of important events in the organization's past, such as the dates of important test flights and important air battles. Within the "Categories" area, visitors can delve into Air Force history. Neatly divided into decades, each section allows visitors to view photographs of important persons in the Air Force during the period, along with documents that relate various aspects of the group's history. Finally, the site also contains a set of links to other useful sites, such as the American Airpower Heritage Museum and the National Museum of Naval Aviation.

  14. Coulomb force as an entropic force

    SciTech Connect

    Wang Tower [Center for High-Energy Physics, Peking University, Beijing 100871 (China)

    2010-05-15

    Motivated by Verlinde's theory of entropic gravity, we give a tentative explanation to the Coulomb's law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb's law, the Poisson equation, and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics.

  15. Coulomb force as an entropic force

    NASA Astrophysics Data System (ADS)

    Wang, Tower

    2010-05-01

    Motivated by Verlinde’s theory of entropic gravity, we give a tentative explanation to the Coulomb’s law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb’s law, the Poisson equation, and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics.

  16. Coulomb Force as an Entropic Force

    E-print Network

    Tower Wang

    2010-05-17

    Motivated by Verlinde's theory of entropic gravity, we give a tentative explanation to Coulomb's law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb's law, the Poisson equation and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics.

  17. Casimir forces between spheres

    E-print Network

    James Babington

    2009-11-13

    We discuss the calculation of Casimir forces between a collection of $N$-dielectric spheres. This is done by evaluating directly the force on a sphere constructed from a stress tensor, rather than an interaction energy. Two and three body forces between the spheres are evaluated for setups of two and three sphere systems respectively. An approximate large-$N$ limit is also obtained for the functional dependence on the number of spheres.

  18. 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…

  19. Directional shear force microscopy

    SciTech Connect

    Burns, A. R.; Carpick, R. W.

    2001-01-15

    We describe a technique, based on shear force microscopy, that allows one to detect shear forces in a chosen direction at the nanometer scale. The lateral direction of an oscillating probe tip is determined by selecting which of the four quadrants are excited on the piezo driver. The shear forces depend directly on this lateral direction if structural anisotropies are present, as confirmed with polydiacetylene monolayers.

  20. A Possible Unification Model for All Basic Forces

    E-print Network

    Wu Yue-Liang; Zhou Guang-Zhao

    1998-12-22

    A unification model for strong, electromagnetic, weak and gravitational forces is proposed. The tangent space of ordinary coordinate 4-dimensional spacetime is a submanifold of an 14-dimensional internal spacetime spanned by four frame fields. The unification of the standard model with gravity is governed by gauge symmetry in the internal spacetime.

  1. Forces in yeast flocculation

    NASA Astrophysics Data System (ADS)

    El-Kirat-Chatel, Sofiane; Beaussart, Audrey; Vincent, Stéphane P.; Abellán Flos, Marta; Hols, Pascal; Lipke, Peter N.; Dufrêne, Yves F.

    2015-01-01

    In the baker's yeast Saccharomyces cerevisiae, cell-cell adhesion (``flocculation'') is conferred by a family of lectin-like proteins known as the flocculin (Flo) proteins. Knowledge of the adhesive and mechanical properties of flocculins is important for understanding the mechanisms of yeast adhesion, and may help controlling yeast behaviour in biotechnology. We use single-molecule and single-cell atomic force microscopy (AFM) to explore the nanoscale forces engaged in yeast flocculation, focusing on the role of Flo1 as a prototype of flocculins. Using AFM tips labelled with mannose, we detect single flocculins on Flo1-expressing cells, showing they are widely exposed on the cell surface. When subjected to force, individual Flo1 proteins display two distinct force responses, i.e. weak lectin binding forces and strong unfolding forces reflecting the force-induced extension of hydrophobic tandem repeats. We demonstrate that cell-cell adhesion bonds also involve multiple weak lectin interactions together with strong unfolding forces, both associated with Flo1 molecules. Single-molecule and single-cell data correlate with microscale cell adhesion behaviour, suggesting strongly that Flo1 mechanics is critical for yeast flocculation. These results favour a model in which not only weak lectin-sugar interactions are involved in yeast flocculation but also strong hydrophobic interactions resulting from protein unfolding.

  2. Force, mass and acceleration

    Microsoft Academic Search

    Phil Dalrymple; Richard Griffiths

    2005-01-01

    Force, mass and acceleration are everyday words but often used inaccurately. Force is a physical influence, which when applied to an object causes it to accelerate in the direction from which it was applied. Mass is the amount of matter in an object and is expressed in kilograms. Acceleration is the rate of change of velocity of an object in

  3. Multivariate Force of Mortality

    E-print Network

    Rao, Arni S R Srinivasa

    2011-01-01

    We introduce bi-variate and multivariate force of mortality functions. The pattern of mortality in a population is one of the strong influencing factors in determining the life expectancies at various ages in the population. Multiple reasons behind declining forces of mortality could be studied using the proposed functions.

  4. Elementary Particles and Forces.

    ERIC Educational Resources Information Center

    Quigg, Chris

    1985-01-01

    Discusses subatomic particles (quarks, leptons, and others) revealed by higher accelerator energies. A connection between forces at this subatomic level has been established, and prospects are good for a description of forces that encompass binding atomic nuclei. Colors, fundamental interactions, screening, camouflage, electroweak symmetry, and…

  5. Force Modulator System

    Microsoft Academic Search

    Redmond Clark

    2009-01-01

    Many metal parts manufacturers use large metal presses to shape sheet metal into finished products like car body parts, jet wing and fuselage surfaces, etc. These metal presses take sheet metal and - with enormous force - reshape the metal into a fully formed part in a manner of seconds. Although highly efficient, the forces involved in forming metal parts

  6. Forces in Molecules

    Microsoft Academic Search

    R. P. Feynman

    1939-01-01

    Formulas have been developed to calculate the forces in a molecular system directly, rather than indirectly through the agency of energy. This permits an independent calculation of the slope of the curves of energy vs. position of the nuclei, and may thus increase the accuracy, or decrease the labor involved in the calculation of these curves. The force on a

  7. Conservative entropic forces

    NASA Astrophysics Data System (ADS)

    Visser, Matt

    2011-10-01

    Entropic forces have recently attracted considerable attention as ways to reformulate, retrodict, and perhaps even "explain" classical Newtonian gravity from a rather specific thermodynamic perspective. In this article I point out that if one wishes to reformulate classical Newtonian gravity in terms of an entropic force, then the fact that Newtonian gravity is described by a conservative force places significant constraints on the form of the entropy and temperature functions. (These constraints also apply to entropic reinterpretations of electromagnetism, and indeed to any conservative force derivable from a potential.) The constraints I will establish are sufficient to present real and significant problems for any reasonable variant of Verlinde's entropic gravity proposal, though for technical reasons the constraints established herein do not directly impact on either Jacobson'sor Padmanabhan's versions of entropic gravity. In an attempt to resolve these issues, I will extend the usual notion of entropic force to multiple heat baths with multiple "temperatures" and multiple "entropies".

  8. The effect of shear force on ink transfer in gravure offset printing

    Microsoft Academic Search

    Taik-Min Lee; Seung-Hyun Lee; Jae-Ho Noh; Dong-Soo Kim; Sangki Chun

    2010-01-01

    This paper asserts that shear force plays an important role in the printing mechanism of gravure offset line printing. To that end, a theoretical printing model showing shear force dependence on the printing angle is proposed. The decrement of the internal angle between the printing direction and the pattern-line direction increases shear force, thereby enhancing the amount of transferred ink

  9. Turbomachinery rotor forces

    NASA Technical Reports Server (NTRS)

    Arndt, Norbert

    1988-01-01

    The fluid-induced forces, both steady and unsteady, acting upon an impeller of a centrifugal pump, and impeller blade-diffuser vane interaction in centrifugal pumps with vaned radial diffusers were evaluated experimentally and theoretically. Knowledge of the steady and unsteady forces, and the associated rotordynamic coefficients are required to effectively model the rotor dynamics of the High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). These forces and rotordynamic coefficients were investigated using different impellers in combination with volutes and vaned diffusers, and axial inducers. These rotor forces are global. Local forces and pressures are also important in impeller-diffuser interaction, for they may cause cavitation damage and even vane failures. Thus, in a separate investigation, impeller wake, and impeller blade and diffuser vane pressure measurements were made. The nature of the rotordynamic forces is discussed, the experimental facility is described, and the measurements of unsteady forces and pressure are reported together with a brief and incomplete attempt to calculate these flows.

  10. Linearly Forced Isotropic Turbulence

    NASA Technical Reports Server (NTRS)

    Lundgren, T. S.

    2003-01-01

    Stationary isotropic turbulence is often studied numerically by adding a forcing term to the Navier-Stokes equation. This is usually done for the purpose of achieving higher Reynolds number and longer statistics than is possible for isotropic decaying turbulence. It is generally accepted that forcing the Navier-Stokes equation at low wave number does not influence the small scale statistics of the flow provided that there is wide separation between the largest and smallest scales. It will be shown, however, that the spectral width of the forcing has a noticeable effect on inertial range statistics. A case will be made here for using a broader form of forcing in order to compare computed isotropic stationary turbulence with (decaying) grid turbulence. It is shown that using a forcing function which is directly proportional to the velocity has physical meaning and gives results which are closer to both homogeneous and non-homogeneous turbulence. Section 1 presents a four part series of motivations for linear forcing. Section 2 puts linear forcing to a numerical test with a pseudospectral computation.

  11. Potential of Average Force in a Plasma

    Microsoft Academic Search

    O. Theimer; P. Kepple

    1966-01-01

    The potential of average force W1,2qq' experienced by a charge q' at a distance|r1-r2| from a charge q is calculated from the Bogoliubov-Born-Green-Kirkwood-Yvon equations of classical statistical mechanics without linearization or equivalent approximations. Diverging integrals are eliminated by the condition that bound-particle states with negative internal energy, e.g., atoms, be excluded from the partition function. The 3-particle distribution functions required

  12. Trends of measured climate forcing agents

    PubMed Central

    Hansen, James E.; Sato, Makiko

    2001-01-01

    The growth rate of climate forcing by measured greenhouse gases peaked near 1980 at almost 5 W/m2 per century. This growth rate has since declined to ?3 W/m2 per century, largely because of cooperative international actions. We argue that trends can be reduced to the level needed for the moderate “alternative” climate scenario (?2 W/m2 per century for the next 50 years) by means of concerted actions that have other benefits, but the forcing reductions are not automatic “co-benefits” of actions that slow CO2 emissions. Current trends of climate forcings by aerosols remain very uncertain. Nevertheless, practical constraints on changes in emission levels suggest that global warming at a rate +0.15 ± 0.05°C per decade will occur over the next several decades. PMID:11752424

  13. Cytotoxic Ribonucleases: The Dichotomy of Coulombic Forces†

    PubMed Central

    Johnson, R. Jeremy; Chao, Tzu-Yuan; Lavis, Luke D.; Raines, Ronald T.

    2010-01-01

    Cells tightly regulate their contents. Still, nonspecific Coulombic interactions between cationic molecules and anionic membrane components can lead to adventitious endocytosis. Here, we characterize this process in a natural system. To do so, we create variants of human pancreatic ribonuclease (RNase 1) that differ in net molecular charge. By conjugating a small-molecule latent fluorophore to these variants and using flow cytometry, we are able to determine the kinetic mechanism for RNase 1 internalization into live human cells. We find that internalization increases with solution concentration and is not saturable. Internalization also increases with time to a steady-state level, which varies linearly with molecular charge. In contrast, the rate constant for internalization (t1/2 = 2 h) is independent of charge. We conclude that internalization involves an extracellular equilibrium complex between the cationic proteins and abundant anionic cell-surface molecules, followed by rate-limiting internalization. The enhanced internalization of more cationic variants of RNase 1 is, however, countered by their increased affinity for the cytosolic ribonuclease inhibitor protein, which is anionic. Thus, Coulombic forces mediate extracellular and intracellular equilibria in a dichotomous manner that both endangers cells and defends them from the potentially lethal enzymatic activity of ribonucleases. PMID:17705507

  14. On the 5D Extra-Force according to Basini Capozziello Ponce De Leon Formalism and five important features: Kar Sinha Gravitational Bending of Light, Chung Freese Superluminal Behaviour, Maartens Clarkson Black Strings, experimental measures of Extra Dimensions on board International Space Station (ISS) and the existence of the Particle Z due to a higher dimensional spacetime

    NASA Astrophysics Data System (ADS)

    Loup, Fernando

    2006-10-01

    We use the Conformal Metric as described in Kar Sinha work on Gravitational Bending of Light in a 5 D Spacetime to recompute the equations of the 5 D Force in Basini Capozziello Ponce De Leon Formalism and we arrive at a result that possesses some advantages. The equations of the Extra Force as proposed by Ponce De Leon are now more elegant in Conformal Formalism and many algebraic terms can be simplified or even suppressed. Also we recompute the Kar Sinha Gravitational Bending of Light affected by the presence of the Extra Dimension and analyze the Superluminal Chung Freese Features of this Formalism describing the advantages of the Chung Freese BraneWorld when compared to other Superluminal spacetime metrics (e.g. Warp Drive) and we describe why the Extra Dimension is invisible and how the Extra Dimension could be made visible at least in theory. We also examine the Maartens Clarkson Black Holes in 5 D (Black Strings) coupled to massive Kaluza Klein graviton modes predicted by Extra Dimensions theories and we study experimental detection of Extra Dimensions on-board LIGO and LISA Space Telescopes. We also propose the use of International Space Station (ISS) to measure the additional terms (resulting from the presence of Extra Dimensions) in the Kar Sinha Gravitational Bending of Light in Outer Space to verify if we really lives in a Higher Dimensional Spacetime. Also we demonstrate that Particle Z can only exist if the 5 D spacetime exists.

  15. Forced Migration Projects

    NSDL National Science Digital Library

    The Forced Migration Projects (FMP), operating under the auspices of the Open Society Institute (OSI), monitor developments in the Americas, the former Yugoslavia, and the former Soviet Union to identify the social, political, and economic conditions that cause the forced dislocations of people. This Website provides background information about the projects as well as full-text access to several FMP publications including The Forced Migration Monitor, a series of special reports on refugees and migration, recent news and articles on germane issues, and FM Alert, an electronic bulletin service. In addition, the site compiles a list of refugee-related links and hosts a discussion forum.

  16. Motional Casimir force

    E-print Network

    Marc-Thierry Jaekel; Serge Reynaud

    2001-01-16

    We study the situation where two point like mirrors are placed in the vacuum state of a scalar field in a two-dimensional spacetime. Describing the scattering upon the mirrors by transmittivity and reflectivity functions obeying unitarity, causality and high frequency transparency conditions, we compute the fluctuations of the Casimir forces exerted upon the two motionless mirrors. We use the linear response theory to derive the motional forces exerted upon one mirror when it moves or when the other one moves. We show that these forces may be resonantly enhanced at the frequencies corresponding to the cavity modes. We interpret them as the mechanical consequence of generation of squeezed fields.

  17. Forced marriage, forced sex: the perils of childhood for girls.

    PubMed

    Ouattara, M; Sen, P; Thomson, M

    1998-11-01

    A recently formed interagency Forum on the Rights of Girls and Women in Marriage is investigating the widespread problem of nonconsensual marriage and forced sex and advocating for legislative and policy initiatives. This article reviews three research projects in this area: research by Anti-Slavery International on child marriage in parts of West Africa, an investigation by Save the Children of children's views of early marriage, and research conducted by CHANGE on women's resistance to domestic violence in Calcutta, India. Girls who marry before 15 years of age are more likely to be illiterate than their older counterparts, more likely to be dowry payment brides, less likely to come into contact with development projects, have higher rates of infant mortality, and are most vulnerable to sexual violence. In many cases, intercourse is initiated before the girl begins to menstruate. Although adult women also face sexual violence within marriage, this problem is all the more traumatic for girls who lack any information about sexuality. Sex with girls below a certain age is usually covered by rape legislation, but, in countries such as India, this is mitigated by the religiously defined personal laws. The absence of adequate legal and policy action frameworks to deal with the rights of girls, coupled with the lack of sanctions against these abuses, comprise state complicity and neglect of duty under international law to this vulnerable group. PMID:12294409

  18. Plasma igniter for internal-combustion engines

    NASA Technical Reports Server (NTRS)

    Breshears, R. R.; Fitzgerald, D. J.

    1978-01-01

    Hot ionized gas (plasma) ignites air/fuel mixture in internal combustion engines more effectively than spark. Electromagnetic forces propel plasma into combustion zone. Combustion rate is not limited by flame-front speed.

  19. Motion and force control for multiple cooperative manipulators

    NASA Technical Reports Server (NTRS)

    Wen, John T.; Kreutz, Kenneth

    1989-01-01

    The motion and force control of multiple robot arms manipulating a commonly held object is addressed. A general control paradigm that decouples the motion and force control problems is introduced. For motion control, there are three natural choices: (1) joint torques, (2) arm-tip force vectors, and (3) the acceleration of a generalized coordinate. Choice (1) allows a class of relatively model-independent control laws by exploiting the Hamiltonian structure of the open-loop system; (2) and (3) require the full model information but produce simpler problems. To resolve the nonuniqueness of the joint torques, two methods are introduced. If the arm and object models are available, the allocation of the desired end-effector control force to the joint actuators can be optimized; otherwise the internal force can be controlled about some set point. It is shown that effective force regulation can be achieved even if little model information is available.

  20. 76 FR 45311 - International Joint Commission Public Hearings on Binational Management of Lake of the Woods and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-28

    ...of Lake of the Woods and Rainy River Watershed The International Joint Commission...International Lake of the Woods and Rainy River Watershed Task Force (Task Force). The Task...international Lake of the Woods and Rainy River watershed. Task Force recommendations...

  1. Relativistic linear restoring force

    NASA Astrophysics Data System (ADS)

    Clark, D.; Franklin, J.; Mann, N.

    2012-09-01

    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: dp/dt or dp/d?. Either formulation recovers Hooke’s law in the non-relativistic limit. In addition to these two forces, we introduce a form of retardation appropriate for the description of a linear (in displacement) force arising from the interaction of a pair of particles with a relativistic field. The procedure is akin to replacing Coulomb’s law in electromagnetism with a retarded form (the first correction in the full relativistic case). This retardation leads to the expected oscillation, but with amplitude growth in both its relativistic and non-relativistic incarnations.

  2. Causal reasoning with forces.

    PubMed

    Wolff, Phillip; Barbey, Aron K

    2015-01-01

    Causal composition allows people to generate new causal relations by combining existing causal knowledge. We introduce a new computational model of such reasoning, the force theory, which holds that people compose causal relations by simulating the processes that join forces in the world, and compare this theory with the mental model theory (Khemlani et al., 2014) and the causal model theory (Sloman et al., 2009), which explain causal composition on the basis of mental models and structural equations, respectively. In one experiment, the force theory was uniquely able to account for people's ability to compose causal relationships from complex animations of real-world events. In three additional experiments, the force theory did as well as or better than the other two theories in explaining the causal compositions people generated from linguistically presented causal relations. Implications for causal learning and the hierarchical structure of causal knowledge are discussed. PMID:25653611

  3. Motion and Forces

    NSDL National Science Digital Library

    Houghton Mifflin Science

    This self-contained module on motion and forces includes a range of fun activities that students can perform in the classroom and at home with family members. They impart important concepts such as observation, identification, measurement, and differentiation.

  4. Strategic forces briefing

    SciTech Connect

    Bing, G.; Chrzanowski, P.; May, M.; Nordyke, M.

    1989-04-06

    The Strategic Forces Briefing'' is our attempt, accomplished over the past several months, to outline and highlight the more significant strategic force issues that must be addressed in the near future. Some issues are recurrent: the need for an effective modernized Triad and a constant concern for force survivability. Some issues derive from arms control: the Strategic Arms Reduction Talks (SALT) are sufficiently advanced to set broad numerical limits on forces, but not so constraining as to preclude choices among weapon systems and deployment modes. Finally, a new administration faced with serious budgetary problems must strive for the most effective strategic forces limited dollars can buy and support. A review of strategic forces logically begins with consideration of the missions the forces are charged with. We begin the briefing with a short review of targeting policy and implementation within the constraints of available unclassified information. We then review each element of the Triad with sections on SLBMs, ICBMs, and Air-Breathing (bomber and cruise missile) systems. A short section at the end deals with the potential impact of strategic defense on offensive force planning. We consider ABM, ASAT, and air defense; but we do not attempt to address the technical issues of strategic defense per se. The final section gives a brief overview of the tritium supply problem. We conclude with a summary of recommendations that emerge from our review. The results of calculation on the effectiveness of various weapon systems as a function of cost that are presented in the briefing are by Paul Chrzanowski.

  5. Force-Measuring Clamp

    NASA Technical Reports Server (NTRS)

    Nunnelee, Mark (Inventor)

    2004-01-01

    A precision clamp that accurately measures force over a wide range of conditions is described. Using a full bridge or other strain gage configuration. the elastic deformation of the clamp is measured or detected by the strain gages. Thc strain gages transmit a signal that corresponds to the degree of stress upon the clamp. Thc strain gage signal is converted to a numeric display. Calibration is achieved by ero and span potentiometers which enable accurate measurements by the force-measuring clamp.

  6. Optical ``Bernoulli'' forces

    NASA Astrophysics Data System (ADS)

    Movassagh, Ramis; Johnson, Steven

    2015-03-01

    By Bernoulli's law, an increase in the relative speed of a fluid around a body is accompanies by a decrease in the pressure. Therefore, a rotating body in a fluid stream experiences a force perpendicular to the motion of the fluid because of the unequal relative speed of the fluid across its surface. It is well known that light has a constant speed irrespective of the relative motion. Does a rotating body immersed in a stream of photons experience a Bernoulli-like force? We show that, indeed, a rotating dielectric cylinder experiences such a lateral force from an electromagnetic wave. In fact, the sign of the lateral force is the same as that of the fluid-mechanical analogue as long as the electric susceptibility is positive (? >?0), but for negative-susceptibility materials (e.g. metals) we show that the lateral force is in the opposite direction. Because these results are derived from a classical electromagnetic scattering problem, Mie-resonance enhancements that occur in other scattering phenomena also enhance the lateral force. [This talk is based on Phys. Rev. A 88, 023829 (2013).] Supported in part by the U.S. Army Research Office under contract W911NF-13-D-0001.

  7. The missing climate forcing

    PubMed Central

    Hansen, J.; Sato, M.; Lacis, A.; Ruedy, R.

    1997-01-01

    Observed climate change is consistent with radiative forcings on several time-scales for which the dominant forcings are known, ranging from the few years after a large volcanic eruption to glacial-to-interglacial changes. In the period with most detailed data, 1979 to the present, climate observations contain clear signatures of both natural and anthropogenic forcings. But in the full period since the industrial revolution began, global warming is only about half of that expected due to the principal forcing, increasing greenhouse gases. The direct radiative effect of anthropogenic aerosols contributes only little towards resolving this discrepancy. Unforced climate variability is an unlikely explanation. We argue on the basis of several lines of indirect evidence that aerosol effects on clouds have caused a large negative forcing, at least -1 Wm-2, which has substantially offset greenhouse warming. The tasks of observing this forcing and determining the microphysical mechanisms at its basis are exceptionally difficult, but they are essential for the prognosis of future climate change.

  8. Van der Waals Forces

    NASA Astrophysics Data System (ADS)

    Parsegian, V. Adrian

    2006-03-01

    This should prove to be the definitive work explaining van der Waals forces, how to calculate them and take account of their impact under any circumstances and conditions. These weak intermolecular forces are of truly pervasive impact, and biologists, chemists, physicists and engineers will profit greatly from the thorough grounding in these fundamental forces that this book offers. Parsegian has organized his book at three successive levels of mathematical sophistication, to satisfy the needs and interests of readers at all levels of preparation. The Prelude and Level 1 are intended to give everyone an overview in words and pictures of the modern theory of van der Waals forces. Level 2 gives the formulae and a wide range of algorithms to let readers compute the van der Waals forces under virtually any physical or physiological conditions. Level 3 offers a rigorous basic formulation of the theory. Author is among the most highly respected biophysicists Van der Waals forces are significant for a wide range of questions and problems in the life sciences, chemistry, physics, and engineering, ranging up to the macro level No other book that develops the subject vigorously, and this book also makes the subject intuitively accessible to students who had not previously been mathematically sophisticated enough to calculate them

  9. Future trends in international migration to Europe.

    PubMed

    Verhaeren, R

    1993-01-01

    The author discusses future trends in international migration to Europe, with a focus on the impact of the economic situation on labor force needs and resources. Aspects considered include changes in foreign direct investments, changes in the size of the European labor market, and the potential emigration of the labor force in underdeveloped countries. PMID:12287572

  10. International social development and counter-development

    Microsoft Academic Search

    Mark Lusk

    2010-01-01

    International development theory and practice tend to emphasize the importance of optimizing development inputs such as capital, infrastructure, and expertise. Equally important in the success of development is the mitigation of counter-development forces such as corruption, rent-seeking, terrorism and organized crime. This article presents a development model that incorporates those forces that impede development.

  11. Coordination of Contact Forces During Multifinger Static Prehension

    PubMed Central

    Martin, Joel R.; Latash, Mark L.

    2011-01-01

    This study investigated the effects of modifying contact finger forces in one direction—normal or tangential—on the entire set of the contact forces, while statically holding an object. Subjects grasped a handle instrumented with finger force-moment sensors, maintained it at rest in the air, and then slowly: (1) increased the grasping force, (2) tried to spread fingers apart, and (3) tried to squeeze fingers together. Analysis was mostly performed at the virtual finger (VF) level (the VF is an imaginable finger that generates the same force and moment as the four fingers combined). For all three tasks there were statistically significant changes in the VF normal and tangential forces. For finger spreading/squeezing the tangential force neutral point was located between the index and middle fingers. We conclude that the internal forces are regulated as a whole, including adjustments in both normal and tangential force, instead of only a subset of forces (normal or tangential). The effects of such factors as EFFORT and TORQUE were additive; their interaction was not statistically significant, thus supporting the principle of superposition in human prehension. PMID:21576716

  12. Lingual force detection system.

    PubMed

    Sangave, Amit; Manuccia, Thomas; Kay, Matthew; Zderic, Vesna

    2008-01-01

    The tongue is an organ of great significance in the processes of both swallowing and speech. Any disorder of the tongue's function (dysphagia, lateral sclerosis), with regard especially to the forces it produces, can drastically impair an individual by leaving them unable to swallow or talk. Up to this point, few systems have been created to quantitatively measure tongue force. Here we describe development of a new device that measures and outputs tongue force and endurance at six strategically positioned points in the mouth. Two mouth guards were fitted with six (three per guard) thin, highly sensitive sensors that independently output tongue force at each location. To ensure proper sensor readings, that is, reliable contact between the tongue and the sensor, each sensor was placed between a hard backing plate of stainless steel and a pliable puck constructed from silicone rubber. Forces were output to a computer using National Instruments' ELVIS system and a novel user friendly interface created using NI's LabVIEW. The proposed system can be utilized as a first step in diagnosis and treatment planning for speech rehabilitation and therapy. In future studies, collected data will be compared with control data (obtained previously from healthy volunteers) to diagnose potential tongue weakness and pinpoint its location in the mouth (whether unilateral or diffuse). PMID:19163801

  13. Chiral drag force

    E-print Network

    Rajagopal, Krishna

    2015-01-01

    We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks and in that they are proportional to the coefficient of the axial anomaly. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a frame in which there is no local ...

  14. Police use of force and the cumulative force factor

    Microsoft Academic Search

    Ross Wolf; Charlie Mesloh; Mark Henych; L. Frank Thompson

    2009-01-01

    Purpose – This paper aims to build on and contribute to earlier studies on use of force by the police, and examines both officer and suspect force levels during altercations. Design\\/methodology\\/approach – Prior attempts to study non-lethal force have only recently begun to examine the multiple levels of force that may be used within a single encounter, advocating the use

  15. Schooling, Labor-Force Quality, and the Growth of Nations

    Microsoft Academic Search

    Eric A. Hanushek; Dennis D. Kimko

    2000-01-01

    Direct measures of labor-force quality from international mathematics and science test scores are strongly related to growth. Indirect specification tests are generally consistent with a causal link: direct spending on schools is unrelated to student performance differences; the estimated growth effects of improved labor-force quality hold when East Asian countries are excluded; and, finally, home-country quality differences of immigrants are

  16. Linear force device

    NASA Technical Reports Server (NTRS)

    Clancy, John P.

    1988-01-01

    The object of the invention is to provide a mechanical force actuator which is lightweight and manipulatable and utilizes linear motion for push or pull forces while maintaining a constant overall length. The mechanical force producing mechanism comprises a linear actuator mechanism and a linear motion shaft mounted parallel to one another. The linear motion shaft is connected to a stationary or fixed housing and to a movable housing where the movable housing is mechanically actuated through actuator mechanism by either manual means or motor means. The housings are adapted to releasably receive a variety of jaw or pulling elements adapted for clamping or prying action. The stationary housing is adapted to be pivotally mounted to permit an angular position of the housing to allow the tool to adapt to skewed interfaces. The actuator mechanisms is operated by a gear train to obtain linear motion of the actuator mechanism.

  17. Forces and Graphing

    NSDL National Science Digital Library

    2014-09-18

    Use this activity to explore forces acting on objects, practice graphing experimental data, and introduce the algebra concepts of slope and intercept of a line. A wooden 2 x 4 beam is set on top of two scales. Students learn how to conduct an experiment by applying loads at different locations along the beam, recording the exact position of the applied load and the reaction forces measured by the scales at each end of the beam. In addition, students analyze the experiment data with the use of a chart and a table, and model/graph linear equations to describe relationships between independent and dependent variables.

  18. Dynamically Forced Fog

    NSDL National Science Digital Library

    2014-09-14

    Fog frequently forms in response to dynamically forced changes in the boundary layer. This module examines dynamically forced fog in the coastal and marine environment, focusing on advection fog, steam fog, and west coast type fog. The focus of the module is on the boundary layer evolution of air parcels as they traverse trajectories over land and water. The module also examines mesoscale effects that impact the distribution of fog and low-level stratus over short distances. A general discussion of forecast products and methodologies concludes the module.

  19. Assessing internal stress evolution in unsaturated soils

    Microsoft Academic Search

    Majdi Abou Najm; Rabi H. Mohtar; Jason Weiss; Erik Braudeau

    2009-01-01

    Internal stresses in soils evolve as a result of the various interactions among soil particles and the pore fluids in response to natural or human-induced activities. Whether attributed to suction, structure, or the various physicochemical forces that may develop, assessing the internal stresses in soils has been an active area of research in soil science and engineering. This paper presents

  20. Intermolecular Forces: A Jigsaw Activity

    NSDL National Science Digital Library

    Boise State Edu.

    2011-09-20

    This jigsaw activity is designed as a cooperative learning activity used to introduce the idea of intermolecular forces. Intermolecular forces are the types of attractive forces that occur between molecules in a solid, liquid, or gas. Each force causes different physical properties of matter. Each member of the group will become an expert on one type of force and then teach the rest of the group.

  1. Finite element modeling and experimentation of bone drilling forces

    NASA Astrophysics Data System (ADS)

    Lughmani, W. A.; Bouazza-Marouf, K.; Ashcroft, I.

    2013-07-01

    Bone drilling is an essential part of many orthopaedic surgery procedures, including those for internal fixation and for attaching prosthetics. Estimation and control of bone drilling forces are critical to prevent drill breakthrough, excessive heat generation, and mechanical damage to the bone. This paper presents a 3D finite element (FE) model for prediction of thrust forces experienced during bone drilling. The model incorporates the dynamic characteristics involved in the process along with the accurate geometrical considerations. The average critical thrust forces and torques obtained using FE analysis, for set of machining parameters are found to be in good agreement with the experimental results.

  2. Drag force scaling for penetration into granular media

    E-print Network

    H. Katsuragi; D. J. Durian

    2013-05-16

    Impact dynamics is measured for spherical and cylindrical projectiles of many different densities dropped onto a variety non-cohesive granular media. The results are analyzed in terms of the material-dependent scaling of the inertial and frictional drag contributions to the total stopping force. The inertial drag force scales similar to that in fluids, except that it depends on the internal friction coefficient. The frictional drag force scales as the square-root of the density of granular medium and projectile, and hence cannot be explained by the combination of granular hydrostatic pressure and Coulomb friction law. The combined results provide an explanation for the previously-observed penetration depth scaling.

  3. The Force of Ideas

    ERIC Educational Resources Information Center

    Ascher, Carol

    2005-01-01

    "The Force of Ideas" describes a little-known aspect of both educational history and Viennese psychoanalysis during the interwar years: the movement for psychoanalytic pedagogy. The author traces her father's own story, beginning with his application to the Vienna Psychoanalytic Society for training as a psychoanalytic pedagogue, as a way to…

  4. Direct Aerosol Forcing Uncertainty

    DOE Data Explorer

    Mccomiskey, Allison

    Understanding sources of uncertainty in aerosol direct radiative forcing (DRF), the difference in a given radiative flux component with and without aerosol, is essential to quantifying changes in Earth's radiation budget. We examine the uncertainty in DRF due to measurement uncertainty in the quantities on which it depends: aerosol optical depth, single scattering albedo, asymmetry parameter, solar geometry, and surface albedo. Direct radiative forcing at the top of the atmosphere and at the surface as well as sensitivities, the changes in DRF in response to unit changes in individual aerosol or surface properties, are calculated at three locations representing distinct aerosol types and radiative environments. The uncertainty in DRF associated with a given property is computed as the product of the sensitivity and typical measurement uncertainty in the respective aerosol or surface property. Sensitivity and uncertainty values permit estimation of total uncertainty in calculated DRF and identification of properties that most limit accuracy in estimating forcing. Total uncertainties in modeled local diurnally averaged forcing range from 0.2 to 1.3 W m-2 (42 to 20%) depending on location (from tropical to polar sites), solar zenith angle, surface reflectance, aerosol type, and aerosol optical depth. The largest contributor to total uncertainty in DRF is usually single scattering albedo; however decreasing measurement uncertainties for any property would increase accuracy in DRF. Comparison of two radiative transfer models suggests the contribution of modeling error is small compared to the total uncertainty although comparable to uncertainty arising from some individual properties.

  5. Forced Spring Systems

    NSDL National Science Digital Library

    Moore, Lang

    Created by Lang Moore and David Smith for the Connected Curriculum Project, the purpose of this module is to explore the effects of an external driving force on a simple linear oscillator, damped or undamped. This is one within a much larger set of learning modules hosted by Duke University.

  6. Orbital Forces: Teacher Page

    NSDL National Science Digital Library

    This activity demonstates orbital motions and forces using a tennis ball swung by a ribbon (this activity should be done outside). The Teacher Page contains background information, tennis ball preparation instructions, and wrap up information. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

  7. Orbital Forces: Student Page

    NSDL National Science Digital Library

    This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

  8. Measuring Your Force

    ERIC Educational Resources Information Center

    Gee, David E.

    2005-01-01

    This article talks about the force behind education leaders. With all the challenges facing public education today, it is difficult to remain focused and to remember why one chartered this particular leadership course. Perhaps someone respected encouraged one to take this path long ago. Perhaps this kind of service to the nation and its future…

  9. Direct Aerosol Forcing Uncertainty

    SciTech Connect

    Mccomiskey, Allison

    2008-01-15

    Understanding sources of uncertainty in aerosol direct radiative forcing (DRF), the difference in a given radiative flux component with and without aerosol, is essential to quantifying changes in Earth's radiation budget. We examine the uncertainty in DRF due to measurement uncertainty in the quantities on which it depends: aerosol optical depth, single scattering albedo, asymmetry parameter, solar geometry, and surface albedo. Direct radiative forcing at the top of the atmosphere and at the surface as well as sensitivities, the changes in DRF in response to unit changes in individual aerosol or surface properties, are calculated at three locations representing distinct aerosol types and radiative environments. The uncertainty in DRF associated with a given property is computed as the product of the sensitivity and typical measurement uncertainty in the respective aerosol or surface property. Sensitivity and uncertainty values permit estimation of total uncertainty in calculated DRF and identification of properties that most limit accuracy in estimating forcing. Total uncertainties in modeled local diurnally averaged forcing range from 0.2 to 1.3 W m-2 (42 to 20%) depending on location (from tropical to polar sites), solar zenith angle, surface reflectance, aerosol type, and aerosol optical depth. The largest contributor to total uncertainty in DRF is usually single scattering albedo; however decreasing measurement uncertainties for any property would increase accuracy in DRF. Comparison of two radiative transfer models suggests the contribution of modeling error is small compared to the total uncertainty although comparable to uncertainty arising from some individual properties.

  10. The fifth force

    SciTech Connect

    Fischbach, E.; Sudarsky, D.; Szafer, A.; Talmadge, C.; Aronson, S.H.

    1986-01-01

    We present a phenomenological description of the ''fifth force'' which focuses on the implications of the existing data from satellite and geophysical measurements of gravity, the Eoetvoes experiment, decays into hyperphotons, and the energy-dependence of the K/sup 0/ - anti K/sup 0/ parameters.

  11. ``Force,'' ontology, and language

    NASA Astrophysics Data System (ADS)

    Brookes, David T.; Etkina, Eugenia

    2009-06-01

    We introduce a linguistic framework through which one can interpret systematically students’ understanding of and reasoning about force and motion. Some researchers have suggested that students have robust misconceptions or alternative frameworks grounded in everyday experience. Others have pointed out the inconsistency of students’ responses and presented a phenomenological explanation for what is observed, namely, knowledge in pieces. We wish to present a view that builds on and unifies aspects of this prior research. Our argument is that many students’ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term “force” as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

  12. Investigation of Calibrating Force Transducer Using Sinusoidal Force

    SciTech Connect

    Zhang Li [School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing (China); Key Laboratory for Metrology, Changcheng Institute of Metrology and Measurement (CIMM), Beijing 100095 (China); Wang Yu; Zhang Lizhe [Key Laboratory for Metrology, Changcheng Institute of Metrology and Measurement (CIMM), Beijing 100095 (China)

    2010-05-28

    Sinusoidal force calibration method was studied several years before at Physikalisch-Technische Bundesanstalt (PTB). A similar dynamic force calibration system is developed at Changcheng Institute of Metrology and Measurement (CIMM). It uses electro-dynamic shakers to generate dynamic force in the range from 1 N to 20 kN, and heterodyne laser interferometers are used for acceleration measurement. The force transducer to be calibrated is mounted on the shaker, and a mass block is screwed on the top of force transducer, the sinusoidal forces realized by accelerated load masses are traceable to acceleration and mass according to the force definition. The methods of determining Spatial-dependent acceleration on mass block and measuring the end mass of force transducer in dynamic force calibration are discussed in this paper.

  13. ENGINEERING INTERNATIONAL

    E-print Network

    University of Technology, Sydney

    COURSE GUIDE 2013 UTS: ENGINEERING INTERNATIONAL UNDERGRADUATE w w w.eng.uts.edu.au #12;2 / ENGINEERING IN AUSTRALIA Internationally, Australian universities have a reputation for high quality research developed close links with many international institutions, particularly in Asia. ENGINEERING IN SYDNEY

  14. Enhancement of photon intensity in forced coupled quantum wells inside a semiconductor microcavity

    NASA Astrophysics Data System (ADS)

    Eleuch, Hichem; Prasad, Awadhesh; Rotter, Ingrid

    2013-02-01

    We study numerically the photon emission from a semiconductor microcavity containing N?2 quantum wells under the influence of a periodic external forcing. The emission is determined by the interplay between external forcing and internal interaction between the wells. While the external forcing synchronizes the periodic motion, the internal interaction destroys it. The nonlinear term of the Hamiltonian supports the synchronization. The numerical results show a jump of the photon intensity to very large values at a certain critical value of the external forcing when the number of quantum wells is not too large. We discuss the dynamics of the system across this transition.

  15. Diamagnetic force on a flux tube

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1983-01-01

    The diamagnetic force on a straight flux tube is elucidated. The case when the flux tube has a circular cross section is considered, and the result is generalized to the case of noncircular cross section. The result shows that when the external magnetic field is uniform, the diamagnetic force is simply equal to the vector multiplication of the internal conduction current and the external magnetic field. It is independent of the size and shape of the cross section of the flux tube. This is analogous to the Kutta-Joukowski theorem that the aerodynamic lift force is proportional to the vector multiplication of the unperturbed flow velocity and the circulation around the airfoil. When the external magnetic field is nonuniform, the diamagnetic force has an additional contribution which is proportional to the gradient of magnetic pressure and to the volume of the flux tube. The constant of proportionality, which is shown to be equal to two for a circular cross section, indicates the enhancement of the nonuniformity of the external magnetic field in the vicinity of the periphery by the polarization current.

  16. Exploring Sources of Variation in Studies of Knowledge Structure Coherence: Comparing Force Meanings and Force Meaning Consistency across Two Turkish Cities

    ERIC Educational Resources Information Center

    Clark, Douglas B.; Menekse, Muhsin; Ozdemir, Gokhan; D'Angelo, Cynthis M.; Price Schleigh, Sharon

    2014-01-01

    Substantial variation has been observed across an international series of studies examining the consistency of students' explanations of force and the most common meanings of force apparent in those explanations. On the surface, the variations among studies might be attributed to differences at the national level, but the studies also…

  17. Air Force Historical Research Agency

    NSDL National Science Digital Library

    This Website from the US Air Force provides a brief description of the overall holdings of the agency, which are comprised of over "70,000,000 pages devoted to the history of the service, and represent the world's largest and most valuable organized collection of documents on US military aviation." The site also supplies detailed descriptions of the personal papers of Air Force members held by the agency and gives bibliographic information on 200 historical studies conducted by the agency on topics of Air Force history. Also included here are a substantive account of Air Force involvement in the Korean War; an online text on Air Force heraldry; detailed descriptions of the Air Force's force structure from 1939 to the present, giving an accounting of the types and quantities of different crafts held by the Force; and more information about Air Force organization and unit history.

  18. Force Feedback Joystick

    NASA Technical Reports Server (NTRS)

    1997-01-01

    I-FORCE, a computer peripheral from Immersion Corporation, was derived from virtual environment and human factors research at the Advanced Displays and Spatial Perception Laboratory at Ames Research Center in collaboration with Stanford University Center for Design Research. Entrepreneur Louis Rosenberg, a former Stanford researcher, now president of Immersion, collaborated with Dr. Bernard Adelstein at Ames on studies of perception in virtual reality. The result was an inexpensive way to incorporate motors and a sophisticated microprocessor into joysticks and other game controllers. These devices can emulate the feel of a car on the skid, a crashing plane, the bounce of a ball, compressed springs, or other physical phenomenon. The first products incorporating I-FORCE technology include CH- Products' line of FlightStick and CombatStick controllers.

  19. Force Modulator System

    SciTech Connect

    Redmond Clark

    2009-04-30

    Many metal parts manufacturers use large metal presses to shape sheet metal into finished products like car body parts, jet wing and fuselage surfaces, etc. These metal presses take sheet metal and - with enormous force - reshape the metal into a fully formed part in a manner of seconds. Although highly efficient, the forces involved in forming metal parts also damage the press itself, limit the metals used in part production, slow press operations and, when not properly controlled, cause the manufacture of large volumes of defective metal parts. To date, the metal-forming industry has not been able to develop a metal-holding technology that allows full control of press forces during the part forming process. This is of particular importance in the automotive lightweighting efforts under way in the US automotive manufacturing marketplace. Metalforming Controls Technology Inc. (MC2) has developed a patented press control system called the Force Modulator that has the ability to control these press forces, allowing a breakthrough in stamping process control. The technology includes a series of hydraulic cylinders that provide controlled tonnage at all points in the forming process. At the same time, the unique cylinder design allows for the generation of very high levels of clamping forces (very high tonnages) in very small spaces; a requirement for forming medium and large panels out of HSS and AHSS. Successful production application of these systems testing at multiple stamping operations - including Ford and Chrysler - has validated the capabilities and economic benefits of the system. Although this technology has been adopted in a number of stamping operations, one of the primary barriers to faster adoption and application of this technology in HSS projects is system cost. The cost issue has surfaced because the systems currently in use are built for each individual die as a custom application, thus driving higher tooling costs. This project proposed to better marry the die-specific Force Modulator technology with stamping presses in the form of a press cushion. This system would be designed to operate the binder ring for multiple parts, thus cutting the per-die cost of the technology. This study reports the results of technology field application. This project produced the following conclusions: (1) The Force Modulator system is capable of operating at very high tempos in the stamping environment; (2) The company can generate substantial, controlled holding tonnage (binder ring pressure) necessary to hold high strength steel parts for proper formation during draw operations; (3) A single system can be designed to operate with a family of parts, thus significantly reducing the per-die cost of a FM system; (4) High strength steel parts made with these systems appear to show significant quality improvements; (5) The amounts of steel required to make these parts is typically less than the amounts required with traditional blank-holding technologies; and (6) This technology will aid in the use of higher strength steels in auto and truck production, thus reducing weight and improving fuel efficiency.

  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 an approximate equation for the vorticity correlation function that is then solved perturbatively. The Reynolds stress of the pertubative solution can then be expressed as a function of the mean-flow and its y-derivatives. In particular, it is shown that as long as the forcing breaks mirror-symmetry, the Reynolds stress has a wave-like term, as a result of which the mean-flow is governed by a dispersive wave equation. In a separate study, Reynolds stress induced by an anisotropically forced unbounded Couette flow with uniform shear gamma, on a beta-plane, is calculated in conjunction with the eddy diffusivity of a co-evolving passive tracer. The flow is damped by linear drag on a time scale mu--1. The stochastic forcing is controlled by a parameter alpha, that characterizes whether eddies are elongated along the zonal direction (alpha < 0), the meridional direction (alpha > 0) or are isotropic (alpha = 0). The Reynolds stress varies linearly with alpha and non-linearly and non-monotonically with gamma; but the Reynolds stress is independent of beta. For positive values of alpha, the Reynolds stress displays an "anti-frictional" effect (energy is transferred from the eddies to the mean flow) and a frictional effect for negative values of alpha. With gamma = beta =0, the meridional tracer eddy diffusivity is v'2/(2mu), where v' is the meridional eddy velocity. In general, beta and gamma suppress the diffusivity below v'2/(2mu).

  1. Resonant forcing and instabilities of inertial waves

    NASA Astrophysics Data System (ADS)

    Cebron, D.; Le Bars, M.

    2012-12-01

    The flows in fluid layers of planets and moons are of major interest because they imply first order consequences for their internal dynamics and orbital evolutions. Indeed, internal flows create torques on solid layers and induce energy dissipation. Moreover, internal flows are directly responsible for the generation of magnetic fields, either by induction of an existing background magnetic field or by excitation of a self-sustained dynamo. Finally, planetary heat fluxes are also directly linked to flows in fluid layers, which can act as thermal blankets for stably stratified configurations, or as efficient heat flux conveyers in the case of convective flows. Planetary fluid layers are subject to body rotation, which implies that inertial waves can propagate through them. Usually damped by viscosity, these waves can, however, be excited by longitudinal libration, precession, and tides, which are harmonic mechanical forcings of azimuthal periodicity m=0, 1, and 2, respectively. In previous studies, it has been shown that the dynamics of a fluid layer is completely modified when the forcing resonates with an inertial wave. In addition to these direct forcings, inertial waves can also form triadic resonances, leading to parametric inertial instabilities. For instance, the so-called precssional inertial instability can be excited by precession, and the elliptical instability can be excited by tides in non-synchronized bodies and by librations in synchronized ones. These different inertial mechanisms are discussed in the framework of the Earth's liquid core. In particular, we take the presence of the solid inner core into account in our analysis, showing the possible strong influence of its motion on the flows driven by these inertial resonances. For instance, we show and quantify for the first time the possible excitation of an elliptical instability by an ellipsoidal inner core rotating or oscillating in a spherical surrounding liquid core. We also present some new inertial instabilities possibly directly excited by the solid inner core motions.

  2. Atomic force microscope cantilever calibration device for quantified force metrology at micro- or nano-scale regime: the nano force calibrator (NFC)

    NASA Astrophysics Data System (ADS)

    Kim, Min-Seok; Choi, Jae-Hyuk; Park, Yon-Kyu; Kim, Jong-Ho

    2006-10-01

    Motivated by emerging needs for accurate force measurements in the nanotechnology and biophysics areas, we present an atomic force microscope (AFM) cantilever calibration system, the 'nano force calibrator' (NFC), consisting of a microbalance and a precision translation stage. Calibration using the NFC has proved to be a reliable and accurate method through a series of experiments with a commercial piezoresistive AFM cantilever. In these experiments, linearity, repeatability and reproducibility of measurements were investigated along with the effects of calibration conditions, such as orientation of the cantilever and temperature. Uncertainty analysis shows that the stiffness and force sensitivity are determined to be 3.385 N m-1 and 0.6490 µN ?-1, which are traceable to the Système International d'Unités (SI units). The relative standard uncertainties of both the stiffness and sensitivity are approximately 0.4% or conservatively 0.5%.

  3. Exploring Forces: Static Electricity

    NSDL National Science Digital Library

    2014-06-18

    In this activity, learners investigate what happens when you build up static electricity on plastic balls. Learners discover that electrostatic forces cause smaller balls to suspend in a tube, while larger balls fall to the bottom. This activity shows learners that size can affect the way a material behaves. This activity is a great way to talk about how different things behave at the nanoscale.

  4. Atomic Force Microscopy

    NSDL National Science Digital Library

    This site features a video lecture on Atomic Force Microscopy (AFM) by Prof. Arvind Raman of Purdue University that discusses the historical development, instrumentation and operational principles of various AFM modes. The lecture is accompanied by power point slides with clear illustrative graphics. The basics are provided in the application examples with advantages and limitation discussed. This would be a useful site to those interested in learning AFM.

  5. Displacements that null forces

    Microsoft Academic Search

    M. Griffis; C. Crane; J. Duffy

    1991-01-01

    Experimental results indicate that the inner product defined by stiffness does in fact provide the correct force-error nulling directions along which to move a robotic end-effector. These directions, which are defined as the twists of compliance, form the [K]-orthogonal complement to the twists of freedom of a partially constrained gripper (where the matrix [K] describes the stiffness of the robot

  6. Modified entropic force

    NASA Astrophysics Data System (ADS)

    Gao, Changjun

    2010-04-01

    The theory of statistical thermodynamics tells us the equipartition law of energy does not hold in the limit of very low temperatures. It is found the Debye model is very successful in explaining the experimental results for most of the solid objects. Motivated by this fact, we modify the entropic force formula which is proposed very recently. Since the Unruh temperature is proportional to the strength of the gravitational field, so the modified entropic force formula is an extension of the Newtonian gravity to the weak field. On the contrary, general relativity extends Newtonian gravity to the strong field case. Corresponding to Debye temperature, there exists a Debye acceleration gD. It is found the Debye acceleration is gD=10-15Nkg-1. This acceleration is very much smaller than the gravitational acceleration 10-4Nkg-1 which is felt by Neptune and the gravitational acceleration 10-10Nkg-1 felt by the Sun. Therefore, the modified entropic force can be very well approximated by the Newtonian gravity in the Solar System and in the Galaxy. With this Debye acceleration, we find the current cosmic speeding up can be explained without invoking any kind of dark energy.

  7. Modified entropic force

    SciTech Connect

    Gao Changjun [National Astronomical Observatories, Chinese Academy of Sciences, Key Laboratory of Optical Astronomy, NAOC, CAS, Beijing, 100012 and Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China)

    2010-04-15

    The theory of statistical thermodynamics tells us the equipartition law of energy does not hold in the limit of very low temperatures. It is found the Debye model is very successful in explaining the experimental results for most of the solid objects. Motivated by this fact, we modify the entropic force formula which is proposed very recently. Since the Unruh temperature is proportional to the strength of the gravitational field, so the modified entropic force formula is an extension of the Newtonian gravity to the weak field. On the contrary, general relativity extends Newtonian gravity to the strong field case. Corresponding to Debye temperature, there exists a Debye acceleration g{sub D}. It is found the Debye acceleration is g{sub D}=10{sup -15} N kg{sup -1}. This acceleration is very much smaller than the gravitational acceleration 10{sup -4} N kg{sup -1} which is felt by Neptune and the gravitational acceleration 10{sup -10} N kg{sup -1} felt by the Sun. Therefore, the modified entropic force can be very well approximated by the Newtonian gravity in the Solar System and in the Galaxy. With this Debye acceleration, we find the current cosmic speeding up can be explained without invoking any kind of dark energy.

  8. Atomic force microscopy and chemical force microscopy of microbial cells

    Microsoft Academic Search

    Yves F Dufrêne

    2008-01-01

    Over the past years, atomic force microscopy (AFM) has emerged as a powerful tool for imaging the surface of microbial cells with nanometer resolution, and under physiological conditions. Moreover, chemical force microscopy (CFM) and single-molecule force spectroscopy have enabled researchers to map chemical groups and receptors on cell surfaces, providing valuable insight into their structure–function relationships. Here, we present protocols

  9. Tuning the interaction forces in tapping mode atomic force microscopy

    Microsoft Academic Search

    Robert W. Stark; Georg Schitter; Andreas Stemmer

    2003-01-01

    The driving frequency is a key parameter to determine the tip-sample interaction forces in tapping mode atomic force microscopy (AFM). By adjusting the driving frequency slightly above the resonance frequency stable imaging with net attractive forces can be achieved almost independently from the quality factor of the cantilever. A reduction of the driving frequency below the resonance leads to a

  10. Forces in atomic force microscopy in air and water

    Microsoft Academic Search

    A. L. Weisenhorn; P. K. Hansma; T. R. Albrecht; C. F. Quate

    1989-01-01

    A new atomic force microscope, which combines a microfabricated cantilever with an optical lever detection system, now makes it possible to measure the absolute force applied by a tip on a surface. This absolute force has been measured as a function of distance (the position of the surface) in air and water over a range of 600 nm. In the

  11. Forces in atomic force microscopy in air and water

    Microsoft Academic Search

    A. L. Weisenhorn; P. K. Hansma; T. R. Albrecht; C. F. Quate

    1989-01-01

    A new atomic force microscope, which combines a microfabricated cantilever with an optical lever detection system, now makes it possible to measure the absolute force applied by a tip on a surface. This absolute force has been measured as a function of distance (=position of the surface) in air and water over a range of 600 nm. In the absolute

  12. Magnetic microposts as an approach to apply forces to living cells.

    PubMed

    Sniadecki, Nathan J; Anguelouch, Alexandre; Yang, Michael T; Lamb, Corinne M; Liu, Zhijun; Kirschner, Stuart B; Liu, Yaohua; Reich, Daniel H; Chen, Christopher S

    2007-09-11

    Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction. PMID:17804810

  13. Forced unfolding of single-chain polymeric nanoparticles.

    PubMed

    Hosono, Nobuhiko; Kushner, Aaron M; Chung, Jaeyoon; Palmans, Anja R A; Guan, Zhibin; Meijer, E W

    2015-06-01

    Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) is applied to single-chain polymeric nanoparticles (SCPNs) to acquire information about the internal folding structure of SCPNs and inherent kinetic parameters of supramolecular self-assembling motifs embedded into the SCPNs. The SCPNs used here are polyacrylate-based polymers carrying 2-ureido-4-[1H]-pyrimidinone (UPy) or benzene-1,3,5-tricarboxamide (BTA) pendants that induce an intramolecular chain collapse into nanoparticles consisting of one polymer chain only via internal supramolecular cross-linking. The SCPN is stretched by an AFM cantilever to unfold mechanically, which allows measuring of force-extension profiles of the SCPNs. Consecutive peaks observed in the force profiles are attributed to rupture events of self-assembled UPy/BTA units in the SCPNs. The force profiles have been analyzed statistically for a series of polymers with different UPy/BTA incorporation densities. The results provide insights into the internal conformation of SCPNs, where the folding structure can be changed with the incorporation density of UPy/BTA. In addition, dynamic loading rate analysis allows the determination of kinetic parameters of BTA self-assembly, which has not been accessible by any other method. This study offers a rational tool for understanding the folding structure, kinetics, and pathway of two series of SCPNs. PMID:25946315

  14. The Lord's Resistance Army and Forced Conscription in Northern Uganda

    Microsoft Academic Search

    Patrick Vinck Phuong N. Pham; Eric Stover

    2008-01-01

    On 13 October 2005, the International Criminal Court unsealed warrants of arrest for five senior leaders of the Lord's Resistance Army (LRA) for the forced conscription of children and other war crimes in northern Uganda. We compiled a database of 25,231 children and youth who had been registered by receptions centers in northern Uganda after their return from the LRA.

  15. Silk Fiber Mechanics from Multiscale Force Distribution Analysis Murat Cetinkaya,

    E-print Network

    Gräter, Frauke

    Silk Fiber Mechanics from Multiscale Force Distribution Analysis Murat Cetinkaya, Senbo Xiao, Bernd the molecular determinants for the extreme toughness of spider silk fibers. Our bottom-up computational approach of the internal strain distribution and load-carrying motifs in silk fibers on scales of both molecular

  16. CONTROL FORCE CHANGE DUE TO ADAPTATON OF FORWARD MODEL IN

    E-print Network

    Shadmehr, Reza

    CONTROL FORCE CHANGE DUE TO ADAPTATON OF FORWARD MODEL IN HUMAN MOTOR CONTROL by Tie Wang A thesis of the human motor adaptive controller. The concept of internal model, a system for predicting behavior of the controlled movements, is divided into a forward and an inverse model. The existence and learning ability

  17. Demonstrating and Calculating Electrostatic Forces

    NSDL National Science Digital Library

    Rosen, Robert

    This lesson plan from the Beacon Learning Center educates students on the topic of demonstrating and calculating electrostatic forces. The lesson focuses on how electrostatic forces exist between charged objects. Florida state educational standards which the experiment exemplifies are included.

  18. Understanding Forces: What's the Problem?

    ERIC Educational Resources Information Center

    Kibble, Bob

    2006-01-01

    Misconceptions about forces are very common and seem to arise from everyday experience and use of words. Ways to improve students' understanding of forces, as used in recent a IOP CD-Rom, are discussed here.

  19. BIOCHEMISTRY: Force Signaling in Biology

    NSDL National Science Digital Library

    J. Christof (Technische Universität München; Physik Department)

    2009-06-05

    Knowledge of the effect of forces on processes in the body, such as muscle contraction, cell locomotion and division, or transport processes, has been limited. This perspective discusses new research into the effect of forces on protein conformation and function.

  20. Gait alterations to effectively reduce hip contact forces.

    PubMed

    Wesseling, Mariska; de Groote, Friedl; Meyer, Christophe; Corten, Kristoff; Simon, Jean-Pierre; Desloovere, Kaat; Jonkers, Ilse

    2015-07-01

    Patients with hip pathology present alterations in gait which have an effect on joint moments and loading. In knee osteoarthritic patients, the relation between medial knee contact forces and the knee adduction moment are currently being exploited to define gait retraining strategies to effectively reduce pain and disease progression. However, the relation between hip contact forces and joint moments has not been clearly established. Therefore, this study aims to investigate the effect of changes in hip and pelvis kinematics during gait on internal hip moments and contact forces which is calculated using muscle driven simulations. The results showed that frontal plane kinetics have the largest effect on hip contact forces. Given the high correlation between the change in hip adduction moment and contact force at initial stance (R(2) ?=?0.87), this parameter can be used to alter kinematics and predict changes in contact force. At terminal stance the hip adduction and flexion moment can be used to predict changes in contact force (R(2) ?=?0.76). Therefore, gait training that focuses on decreasing hip adduction moments, a wide base gait pattern, has the largest potential to reduce hip contact forces. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1094-1102, 2015. PMID:25676535

  1. Force fluctuations in bead packs.

    PubMed

    Liu, C H; Nagel, S R; Schecter, D A; Coppersmith, S N; Majumdar, S; Narayan, O; Witten, T A

    1995-07-28

    Experimental observations and numerical simulations of the large force inhomogeneities present in stationary bead packs are presented. Forces much larger than the mean occurred but were exponentially rare. An exactly soluble model reproduced many aspects of the experiments and simulations. In this model, the fluctuations in the force distribution arise because of variations in the contact angles and the constraints imposed by the force balance on each bead in the pile. PMID:17842361

  2. Lateral Casimir Force beyond the Proximity-Force Approximation

    SciTech Connect

    Rodrigues, Robson B.; Neto, Paulo A. Maia [Instituto de Fisica, UFRJ, CP 68528, Rio de Janeiro, RJ, 21941-972 (Brazil); Lambrecht, Astrid; Reynaud, Serge [Laboratoire Kastler Brossel, CNRS, ENS, Universite Pierre et Marie Curie case 74, Campus Jussieu, F-75252 Paris Cedex 05 (France)

    2006-03-17

    We argue that the appropriate variable to study a nontrivial geometry dependence of the Casimir force is the lateral component of the Casimir force, which we evaluate between two corrugated metallic plates outside the validity of the proximity-force approximation. The metallic plates are described by the plasma model, with arbitrary values for the plasma wavelength, the plate separation, and the corrugation period, the corrugation amplitude remaining the smallest length scale. Our analysis shows that in realistic experimental situations the proximity-force approximation overestimates the force by up to 30%.

  3. Ground reaction forces during treadmill running in microgravity.

    PubMed

    De Witt, John K; Ploutz-Snyder, Lori L

    2014-07-18

    Astronauts perform treadmill exercise during long-duration space missions to counter the harmful effects of microgravity exposure upon bone, muscle, and cardiopulmonary health. When exercising in microgravity, astronauts wear a harness and bungee system that provides forces that maintain attachment to the treadmill. Typical applied forces are less than body weight. The decreased gravity-replacement force could result in differences in ground-reaction force at a given running speed when compared to those achieved in normal gravity, which could influence the adaptive response to the performed exercise. Seven astronauts (6 m/1 f) who completed approximately 6-month missions on the International Space Station (ISS) completed a preflight (1G) and multiple in-flight (0G) data collection sessions. Ground-reaction forces were measured during running at speeds of 8.0 kph and greater on an instrumented treadmill in the lab and on the ISS. Ground-reaction forces in 0G were less than in 1G for a given speed depending upon the gravity-replacement force, but did increase with increased speed and gravity-replacement force. Ground-reaction forces attained in 1G during slower running could be attained by increasing running speed and/or increasing gravity-replacement forces in 0G. Loading rates in 1G, however, could not be replicated in 0G. While current gravity-replacement force devices are limited in load delivery magnitude, we recommend increasing running speeds to increase the mechanical loads applied to the musculoskeletal system during 0G treadmill exercise, and to potentially increase exercise session efficiency. PMID:24835563

  4. Atomic force microscopy and spectroscopy

    Microsoft Academic Search

    Yongho Seo; Wonho Jhe

    2008-01-01

    Since it was invented by Binnig et al in 1986, atomic force microscopy (AFM) has played a crucial role in nano-scale science and technology. AFM is a microscopic technique imaging a surface topography by using attractive and repulsive interaction forces between a few atoms attached at a tip on a cantilever and a sample. In the case of attractive forces,

  5. Single electron tunneling force microscopy

    Microsoft Academic Search

    Ezra Barrus Bussmann

    2006-01-01

    The development and first application of a new scanning probe microscopy technique is described. This technique, called single-electron tunneling force microscopy (SETFM), is used to image and to perform spectroscopy of individual localized electronic states in completely nonconducting oxide surfaces. The SETFM detects single-electron tunneling events between a metallized atomic force microscope probe and individual electronic states by electrostatic force

  6. Proper forcing remastered Giorgio Venturi

    E-print Network

    Viale, Matteo

    Proper forcing remastered Giorgio Venturi (joint work with Boban Velickovic) Scuola Normale Superiore di Pisa Universit´e Paris Diderot - Paris 7 Giorgio Venturi (SNS) Proper forcing remastered 1 / 12, P)-strongly generic condition q. Giorgio Venturi (SNS) Proper forcing remastered 2 / 12 #12

  7. Low temperature friction force microscopy

    Microsoft Academic Search

    Christopher Gregory Dunckle

    2010-01-01

    The application of friction force techniques within atomic force microscopy (AFM) allows for direct measurements of friction forces at a sliding, single-asperity interface. The temperature dependence of such single-asperity contacts provides key insight into the comparative importance of dissipative mechanisms that result in dry sliding friction. A variable temperature (VT), ultrahigh vacuum (UHV) AFM was used with an interface consisting

  8. Air Force ROTC Detachment 165

    E-print Network

    Li, Mo

    Air Force ROTC Detachment 165 2011 OPEN HOUSE We will be opening our doors on the evening of April would like more information on the Air Force ROTC program at Georgia Tech and our crosstown recruiting@afrotc.gatech.edu 404-894-7386 Air Force ROTC Detachment 165 The Georgia Institute of Technology

  9. Future Air Force Tactical Communications

    Microsoft Academic Search

    D. Brick; F. Ellersick

    1980-01-01

    During the 1980's, many improvements will be made in the Air Force's ability to communicate in a battlefield environment. Programs like JTIDS, SEEK TALK, TRI-TAC, and the Ground Mobile Forces satellite communications terminals will improve the security, jam resistance, connectivity, and capacity of today's Air Force tactical communications. Even after these programs have been implemented, however, some important problem areas

  10. Constructing Force-Closure Grasps

    Microsoft Academic Search

    Van-duc Nguyen

    1988-01-01

    This paper presents fast and simple algorithms for directly constructing force-closure grasps based on the shape of the grasped object. The synthesis of force-closure grasps finds in dependent regions of contact for the fingertips, such that the motion of the grasped object is totally constrained. A force- closure grasp implies equilibrium grasps exist. In the reverse direction, we show that

  11. Internal resorption

    PubMed Central

    Mohan, Ravi Prakash Sasankoti; Verma, Sankalp; Singh, Udita; Agarwal, Neha

    2013-01-01

    Internal resorption is a relatively rare resorption of dentine, which starts in the pulpal cavity either in the pulpal chamber or in the root canal and destroys surrounding dental hard tissues. The initiating factor in internal root resorption is thought to be trauma or chronic pulpal inflammation, but other aetiological factors have also been suggested. The prognosis for treatment of small lesions of internal resorption is good. However, if the tooth structure is greatly weakened and perforation has occurred, the prognosis is poor and tooth extraction must be considered. In this article we report a rare case of internal resorption in a 26-year-old male patient. PMID:23845670

  12. Nonequilibrium forces between neutral atoms mediated by a quantum field

    SciTech Connect

    Behunin, Ryan O. [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Hu, Bei-Lok [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States)

    2010-08-15

    We study forces between two neutral atoms, modeled as three-dimensional harmonic oscillators, arising from mutual influences mediated by an electromagnetic field but not from their direct interactions. We allow as dynamical variables the center-of-mass motion of the atom, its internal degrees of freedom, and the quantum field treated relativistically. We adopt the method of nonequilibrium quantum field theory which can provide a first-principles, systematic, and unified description including the intrinsic and induced dipole fluctuations. The inclusion of self-consistent back-actions makes possible a fully dynamical description of these forces valid for general atom motion. In thermal equilibrium we recover the known forces--London, van der Waals, and Casimir-Polder--between neutral atoms in the long-time limit. We also reproduce a recently reported force between atoms when the system is out of thermal equilibrium at late times. More noteworthy is the discovery of the existence of a type of (or identification of the source of some known) interatomic force which we call the ''entanglement force,'' originating from the quantum correlations of the internal degrees of freedom of entangled atoms.

  13. Interfacial force sensor with force-feedback control

    SciTech Connect

    Joyce, S.A.; Houston, J.E.; Smith, B.K.

    1990-01-01

    A new interfacial force microscope capable of measuring the forces between two surfaces over the entire range of surface separations, up to contact, has been developed. The design is centered around a differential capacitance displacement sensor where the common capacitor plate is supported by torsion bars. A force-feedback control system balances the interfacial forces at the sensor, maintaining the common capacitor plate at its rest position. This control eliminates the instability which occurs with the conventional cantilever-based force sensors when the attractive force gradient exceeds the mechanical stiffness of the cantilever. The ability to measure interfacial forces at surface separations smaller than this instability point using the feedback control is demonstrated. 11 refs., 3 figs.

  14. Causal Entropic Forces

    NASA Astrophysics Data System (ADS)

    Wissner-Gross, A. D.; Freer, C. E.

    2013-04-01

    Recent advances in fields ranging from cosmology to computer science have hinted at a possible deep connection between intelligence and entropy maximization, but no formal physical relationship between them has yet been established. Here, we explicitly propose a first step toward such a relationship in the form of a causal generalization of entropic forces that we find can cause two defining behaviors of the human “cognitive niche”—tool use and social cooperation—to spontaneously emerge in simple physical systems. Our results suggest a potentially general thermodynamic model of adaptive behavior as a nonequilibrium process in open systems.

  15. forced-migration-history

    NSDL National Science Digital Library

    This new, UK-based, moderated mailing list serves as a forum for discussions on population displacements in 20th-century European history, "and to explore the inter-relationship of forced migration/resettlement/repatriation with nationalism, state formation and the construction of social identities." While the moderators believe that most of the subscribers will be involved in migration studies, history, geography, demography, and anthropology or sociology, scholars from other fields and different geographical and historical time periods are most welcome. Users will find archived messages and subscription information at the site.

  16. Atomic Force Microscope

    SciTech Connect

    Day, R.D.; Russell, P.E.

    1988-12-01

    The Atomic Force Microscope (AFM) is a recently developed instrument that has achieved atomic resolution imaging of both conducting and non- conducting surfaces. Because the AFM is in the early stages of development, and because of the difficulty of building the instrument, it is currently in use in fewer than ten laboratories worldwide. It promises to be a valuable tool for obtaining information about engineering surfaces and aiding the .study of precision fabrication processes. This paper gives an overview of AFM technology and presents plans to build an instrument designed to look at engineering surfaces.

  17. Bisensory force feedback in telerobotics

    NASA Astrophysics Data System (ADS)

    Williams, Lorraine E. P.

    2001-11-01

    Effectively controlling a robot remotely to perform a desired task---teleoperation---offers benefits in improving human safety, reducing workload, providing location accessibility, and in convenience. Because these benefits become more evident under the extreme environmental conditions of space operations, NASA Johnson Space Center has been actively researching the usage of and improvements in teleoperations. Teleoperator task performance has been shown to improve with the addition of sensory feedback. In particular, providing force-feedback to a human operator, has been shown to decrease task completion times and lessen potentially damaging contact forces between the slave robot and its target work environment. We summarize the design, development, and usage of a human interface system built to provide position control as well as both kinesthetic and visual six-axis force-feedback displays to a human teleoperator of a remote manipulator. The system developed is utilized as an experimentation platform evaluating the merit of providing force feedback through both kinesthetic (muscular position and force) and substituted visual displays on a typical space operations task utilizing an anthropomorphic slave robot called "Robonaut". Teleoperator performance of a drill task is measured under four different display scenarios: no force display, visual force display, kinesthetic, and both. Task completion times and contact forces are measured, and subjective questionnaire responses collected. Our results indicate lower maximum force/torque, lower cumulative force/torque, and a greater task consistency with any type of feedback, with no significant differences in task completion time. Cumulative force/torque was reduced between 46--51% with visually substituted force feedback, 69--81% with kinesthetic feedback and 63--92% with both forms of feedback. Maximum force/torque variance between subjects was reduced between 61--90% with any type of force display, indicating improved consistency. Maximum contact force/torque was reduced 23% in the visual case, and between 27--43% for kinesthetic and both cases.

  18. Air Force Technology

    NSDL National Science Digital Library

    Although designed for professional contractors, this site offers an interesting diversion for the technophile or armchair general. Provided by Net Resources International, the site contains a host of professional information, including industry organizations, exhibitions, and conferences, and a company index. However, general users will be most interested in the current projects and equipment catalog sections, which offer specifications and photos of a large number of interesting gadgets and vehicles.

  19. Updates on Force Limiting Improvements

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Scharton, Terry

    2013-01-01

    The following conventional force limiting methods currently practiced in deriving force limiting specifications assume one-dimensional translation source and load apparent masses: Simple TDOF model; Semi-empirical force limits; Apparent mass, etc.; Impedance method. Uncorrelated motion of the mounting points for components mounted on panels and correlated, but out-of-phase, motions of the support structures are important and should be considered in deriving force limiting specifications. In this presentation "rock-n-roll" motions of the components supported by panels, which leads to a more realistic force limiting specifications are discussed.

  20. FLOW VISUALIZATION OF FORCED AND NATURAL CONVECTION IN INTERNAL CAVITIES

    EPA Science Inventory

    This research project will focus efforts on developing techniques to model fluid flow in spent nuclear fuel canisters. One treatment technique is to inject gases which react with spent fuels into storage canisters, preventing the occurrence of pyrophoric reactions. The primary go...

  1. Permeability of continental crust influenced by internal and external forcing

    Microsoft Academic Search

    S. A. R OJSTACZER; S. E. IN; GEB RIT

    The permeability of continental crust is so highly variable that it is often considered to defy systematic character- ization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability-depth rela- tions) on a very large scale? Here we argue that large-scale crustal

  2. International Curriculums.

    ERIC Educational Resources Information Center

    Neal, Larry L.

    This workshop presentation on international curriculums in the field of parks, recreation, leisure, cultural services, and travel/tourism comments that the literature is replete with articles addressing what the field is about, but not about curriculum issues, models, and structure. It reports an international survey of 12 college educators…

  3. International development

    E-print Network

    Sussex, University of

    ) in International Development and a Language (one from French, Italian or Spanish) BA (Hons) in Anthropology for details Related subjects Anthropology (p36), Geography (p83), International relations (p90) A levels, with at least 20 in Listening, 19 in Reading, 21 in Speaking and 23 in Writing. For alternative English language

  4. International english

    SciTech Connect

    Amador, M.

    1990-01-01

    This paper is a presentation to the International Professional Communication Conference on International English. Presidence is taken from the Royal Society of London in 1667 to purify and simplify the English language. Because English has become the most spoken language in the world, the case in herein made to make it plainer and more easily learned. Technical communications is stressed. (FSD).

  5. Internalized activities

    Microsoft Academic Search

    Jean-Christophe Buisson; Jean-Charles Quinton

    2010-01-01

    This paper argues that interactive mental processes in humans have a natural tendency to replay internally and cyclically, a typical example being the tunes that run ‘in our head’ for hours. The existence of these ‘internalized activities’ may be shown by both simple introspection and neurological experiments, which also reveal that they occur in all sensory modalities and involve everything

  6. Force reflecting hand controller

    NASA Technical Reports Server (NTRS)

    Mcaffee, Douglas A. (inventor); Snow, Edward R. (inventor); Townsend, William T. (inventor)

    1993-01-01

    A universal input device for interfacing a human operator with a slave machine such as a robot or the like includes a plurality of serially connected mechanical links extending from a base. A handgrip is connected to the mechanical links distal from the base such that a human operator may grasp the handgrip and control the position thereof relative to the base through the mechanical links. A plurality of rotary joints is arranged to connect the mechanical links together to provide at least three translational degrees of freedom and at least three rotational degrees of freedom of motion of the handgrip relative to the base. A cable and pulley assembly for each joint is connected to a corresponding motor for transmitting forces from the slave machine to the handgrip to provide kinesthetic feedback to the operator and for producing control signals that may be transmitted from the handgrip to the slave machine. The device gives excellent kinesthetic feedback, high-fidelity force/torque feedback, a kinematically simple structure, mechanically decoupled motion in all six degrees of freedom, and zero backlash. The device also has a much larger work envelope, greater stiffness and responsiveness, smaller stowage volume, and better overlap of the human operator's range of motion than previous designs.

  7. Forces Stabilizing Proteins

    PubMed Central

    Pace, C. Nick; Scholtz, J. Martin; Grimsley, Gerald R.

    2014-01-01

    The goal of this article is to summarize what has been learned about the major forces stabilizing proteins since the late 1980s when site-directed mutagenesis became possible. The following conclusions are derived from experimental studies of hydrophobic and hydrogen bonding variants. 1. Based on studies of 138 hydrophobic interaction variants in 11 proteins, burying a –CH2– group on folding contributes 1.1 ± 0.5 kcal/mol to protein stability. 2. The burial of nonpolar side chains contributes to protein stability in two ways: first, a term that depends on the removal of the side chains from water and, more importantly, the enhanced London dispersion forces that result from the tight packing in the protein interior. 3. Based on studies of 151 hydrogen bonding variants in 15 proteins, forming a hydrogen bond on folding contributes 1.1 ± 0.8 kcal/mol to protein stability. 4. The contribution of hydrogen bonds to protein stability is strongly context dependent. 5. Hydrogen bonds by side chains and peptide groups make similar contributions to protein stability. 6. Polar group burial can make a favorable contribution to protein stability even if the polar group is not hydrogen bonded. 7. Hydrophobic interactions and hydrogen bonds both make large contributions to protein stability. PMID:24846139

  8. Controlling Casimir forces using heterostructures

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, Raul; Villarreal, Carlos; Cocoletzi, Gregorio H.

    2001-03-01

    Recent precise measurements of Casimir forces, the influence they may have in the performance of micro electromechanical systems (MEMS) and the possibility of using Casimir forces to drive MEMS, has prompted a renew interest in studying these forces. In this work we present a study on how Casimir forces can be enhanced or inhibited using heterostructures. The system we consider consists of two parallel slabs separated by a distance s. Each slab is an heterostructure made of alternate layers of different materials (metals and/or dielectrics). Depending on the composition of the heterostructure, we show that it is possible to inhibit or enhance the Casimir force between the slabs while keeping the separation s constant. Furthermore, the Casimir forces can be change by the presence of surface-plasmon modes when we consider metallic materials. Our calculations are based on a variation of the Lifshitz formalism for Casimir forces.

  9. Theory of rapid force spectroscopy

    PubMed Central

    Bullerjahn, Jakob T.; Sturm, Sebastian; Kroy, Klaus

    2014-01-01

    In dynamic force spectroscopy, single (bio-)molecular bonds are actively broken to assess their range and strength. At low loading rates, the experimentally measured statistical distributions of rupture forces can be analysed using Kramers’ theory of spontaneous unbinding. The essentially deterministic unbinding events induced by the extreme forces employed to speed up full-scale molecular simulations have been interpreted in mechanical terms, instead. Here we start from a rigorous probabilistic model of bond dynamics to develop a unified systematic theory that provides exact closed-form expressions for the rupture force distributions and mean unbinding forces, for slow and fast loading protocols. Comparing them with Brownian dynamics simulations, we find them to work well also at intermediate pulling forces. This renders them an ideal companion to Bayesian methods of data analysis, yielding an accurate tool for analysing and comparing force spectroscopy data from a wide range of experiments and simulations. PMID:25079911

  10. Pressure, Force, Muscles and Massage

    NSDL National Science Digital Library

    BEGIN:VCARD VERSION:2.1 FN:Kristin Shields N:Shields; Kristin ORG:Vanden High School REV:2005-04-12 END:VCARD

    1995-06-30

    The human body is constantly being subjected to external forces. The relation between force and pressure is straightforward. The more force exerted, the greater the pressure, but the effect of area on pressure is somewhat more subtle. Through the process of massage students apply their understanding of forces and pressures to enhance the relaxation of their lab partner's forearm. A proper understanding of the concept of pressure is essential to an understanding of most areas of physiology. This activity provides students with a feeling for what pressure is and how it is related to force and area. Students determine the pressure exerted on the bottoms of their feet under a variety of circumstances. In each case, the force exerted is body weight. But the area over which that force is exerted differs, depending on whether one is standing on two feet, one foot or tiptoe (one-foot.)

  11. Equivalent linearization of nonlinear forces

    NASA Astrophysics Data System (ADS)

    Meng, Guang; Xue, Zhongqing

    1987-07-01

    A method used for equivalent linearization of the two orthogonal squeeze-film forces is extended here to the general case of n degrees of freedom and n components of nonlinear forces, and the expressions for equivalent linear coefficients are derived. Nonlinear forces can be linearized by the methods of Fourier expansion, active and reactive powers, or mean-square error. The n components of nonlinear forces can all be expressed formally as the sum of an average force, a linear spring force, and a linear damping force. This paper also gives a flow chart for calculating the steady-state responses of a nonlinear system with many degrees of freedom, using the method of equivalent linearization. The resulting saving in computation time is demonstrated by a numerical example of a flexible rotor-bearing system with a noncentralized squeeze-film damper.

  12. 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.

  13. Comparison between static maximal force and handbrake pulling force.

    PubMed

    Chateauroux, E; Wang, X

    2012-01-01

    The measurement of maximum pulling force is important not only for specifying force limit of industrial workers but also for designing controls requiring high force. This paper presents a comparison between maximal static handbrake pulling force (FST) and force exerted during normal handbrake pulling task (FDY). These forces were measured for different handle locations and subject characteristics. Participants were asked to pull a handbrake on an adjustable car mock-up as they would do when parking their own car, then to exert a force as high as possible on the pulled handbrake. Hand pulling forces were measured using a six-axes force sensor. 5 fixed handbrake positions were tested as well as a neutral handbrake position defined by the subject. FST and FDY were significantly correlated. Both were found to be dependent on handbrake position, age and gender. As expected, women and older subjects exerted lower forces. FST was significantly higher than FDY. The ratio FmR (FDY divided by FST) was also analyzed. Women showed higher FmR than men meaning that the task required a higher amount of muscle capability for women. FmR was also influenced by handbrake location. These data will be useful for handbrake design. PMID:22316898

  14. Potential Fields as an External Force and Algorithmic Improvements in Deformable Models

    Microsoft Academic Search

    Andrés Caro; Pablo G. Rodríguez; Eva Cernadas; Teresa Antequera; M. L. Duran

    2003-01-01

    Deformable Models are extensively used as a Pattern Recognition technique. They are curves defined within an image domain that can be moved under the influence of internal and external forces. Some trade-offs of standard deformable models algorithms are the selection of image energy function (external force), the location of initial snake and the attraction of contour points to local energy

  15. Generalized heteroclinic cycles forced by the spherical symmetry in the GEOFLOW experiment framework

    Microsoft Academic Search

    Ph. Beltrame; Ch. Egbers; V. Travnikov; M. Gellert

    2004-01-01

    Microgravity experiments of thermal convection under a central force field are important to understand of large scale astro- and geophysical motions. The ``GeoFlow'' experiment on the International Space Station (ISS) aims at simulating the spherical Rayleigh-Bénard problem: thermal convection in the gap between two concentric, possible rotating, spheres. A central symmetric force field, similar to the gravity field acting on

  16. The Training Environment Of The Irish Defence Forces:Integrated Training, Bullying and Sexual Harassment

    Microsoft Academic Search

    Tom Clonan

    2000-01-01

    The training environment of the Irish Defence Forces: integrated training and bullying in the workplace In this chapter I will refer to recruit and cadet training within the defence forces in light of international trends in integrated training. Following the consideration of ‘commitment’ in terms of numbers of women recruited to the organisation in chapter five, this chapter assesses the

  17. PERSONAL EXPOSURE TO JP-8 JET FUEL VAPORS AND EXHAUST AT AIR FORCE BASES

    EPA Science Inventory

    JP-8 jet fuel (similar to commercial/international jet A-1 fuel) is the standard military fuel for all types of vehicles, including the U.S. Air Force aircraft inventory. As such, JP-8 presents the most common chemical exposure in the Air Force, particularly for flight and gro...

  18. Chin force in violin playing.

    PubMed

    Obata, Satoshi; Kinoshita, Hiroshi

    2012-06-01

    Force generated between the left mandible of violinists and the chinrest of the violin was examined using a force-sensing chinrest developed in this study. A strain-gauge force sensor was built, and it was fixed between the violin's top plate and a chin cup. Fifteen professional/amateur violinists held the violin statically, played musical scales with different sound properties and sounding techniques, as well as an excerpt from a Max Bruch concerto. Peak and mean forces were evaluated for each task. In a separate experiment, lateral movement of the lower teeth due to different levels of voluntary chin force exertion was measured. Static holding forces observed were 15 and 22 N with and without the help of the left hand, respectively. Peak force increased from 16 N at soft dynamics to 20 N at strong dynamics during scales. The force further increased to 29 N with the use of vibrato technique and 35 N during shifts. Tempo and hand position did not affect the force. Playing a Bruch concerto induced a mean peak force of 52 N, ranging from 31 to 82 N among the violinists. The developed force-sensing chinrest could accurately record the generated chin force. Typical chin force to stabilize the violin during ordinary musical performance was less than 30 N, but it could momentarily exceed 50 N when technically demanding musical pieces were performed. The lateral shift of the mandible was fairly small (<0.4 mm) even with high chin-force exertion, possibly due to clenching of the molars. PMID:21952980

  19. Mass effects and internal space geometry in triatomic reaction dynamics

    SciTech Connect

    Yanao, Tomohiro; Koon, Wang S.; Marsden, Jerrold E. [Control and Dynamical Systems, MC 107-81, California Institute of Technology, Pasadena, California 91125 (United States)

    2006-05-15

    The effect of the distribution of mass in triatomic reaction dynamics is analyzed using the geometry of the associated internal space. Atomic masses are appropriately incorporated into internal coordinates as well as the associated non-Euclidean internal space metric tensor after a separation of the rotational degrees of freedom. Because of the non-Euclidean nature of the metric in the internal space, terms such as connection coefficients arise in the internal equations of motion, which act as velocity-dependent forces in a coordinate chart. By statistically averaging these terms, an effective force field is deduced, which accounts for the statistical tendency of geodesics in the internal space. This force field is shown to play a crucial role in determining mass-related branching ratios of isomerization and dissociation dynamics of a triatomic molecule. The methodology presented can be useful for qualitatively predicting branching ratios in general triatomic reactions, and may be applied to the study of isotope effects.

  20. Trends of measured climate forcing agents

    NASA Astrophysics Data System (ADS)

    Hansen, James E.; Sato, Makiko

    2001-12-01

    * National Aeronautics and Space Administration, Goddard Institute for Space Studies, New York, NY 10025; and Center for Climate Systems Research, Columbia University Earth Institute, New York, NY 10025 Contributed by James E. Hansen, October 16, 2001 The growth rate of climate forcing by measured greenhouse gases peaked near 1980 at almost 5 W/m2 per century. This growth rate has since declined to 3 W/m2 per century, largely because of cooperative international actions. We argue that trends can be reduced to the level needed for the moderate "alternative" climate scenario (?2 W/m2 per century for the next 50 years) by means of concerted actions that have other benefits, but the forcing reductions are not automatic "co-benefits" of actions that slow CO2 emissions. Current trends of climate forcings by aerosols remain very uncertain. Nevertheless, practical constraints on changes in emission levels suggest that global warming at a rate +0.15 ± 0.05°C per decade will occur over the next several decades.

  1. Nonlinear dynamics and force spectroscopy in dynamic atomic force microscopy

    Microsoft Academic Search

    Shuiqing Hu

    2007-01-01

    As one branch of atomic force microscopy (AFM), dynamic atomic force microscopy (Dynamic AFM) uses a resonating probe with frequency (FM-AFM) or amplitude modulation (AM-AFM) to measure sample topography and material properties of nanostructures with nanometer resolution. Under the influence of tip-sample interaction forces, the dynamics of the probe become highly nonlinear and can affect the imaging stability and interaction

  2. Imaging viscoelasticity by force modulation with the atomic force microscope

    PubMed Central

    Radmacher, M.; Tillmann, R. W.; Gaub, H. E.

    1993-01-01

    Force modulation and phase sensitive detection was used to image soft surfaces with the atomic force microscope. This force modulation microscopy allows the simultaneous recording of images of the surface profile, the storage modulus, and the loss modulus of the sample. A theoretical treatment of the elastic tip-sample interaction is given. As examples, images of Langmuir-Blodgett films of a polymeric amphiphile and of a structured fatty acid are presented. ImagesFIGURE 6FIGURE 7FIGURE 8 PMID:19431876

  3. Force Limit System

    NASA Technical Reports Server (NTRS)

    Pawlik, Ralph; Krause, David; Bremenour, Frank

    2011-01-01

    The Force Limit System (FLS) was developed to protect test specimens from inadvertent overload. The load limit value is fully adjustable by the operator and works independently of the test system control as a mechanical (non-electrical) device. When a test specimen is loaded via an electromechanical or hydraulic test system, a chance of an overload condition exists. An overload applied to a specimen could result in irreparable damage to the specimen and/or fixturing. The FLS restricts the maximum load that an actuator can apply to a test specimen. When testing limited-run test articles or using very expensive fixtures, the use of such a device is highly recommended. Test setups typically use electronic peak protection, which can be the source of overload due to malfunctioning components or the inability to react quickly enough to load spikes. The FLS works independently of the electronic overload protection.

  4. Vector Piezoresponse Force Microscopy

    SciTech Connect

    Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Jesse, Stephen [ORNL; Shin, Junsoo [ORNL; Baddorf, Arthur P [ORNL; Gupta, P. [Lehigh University, Bethlehem, PA; Jain, H. [Lehigh University, Bethlehem, PA; Williams, D. B. [Lehigh University, Bethlehem, PA; Gruverman, A. [North Carolina State University

    2006-01-01

    A novel approach for nanoscale imaging and characterization of the orientation dependence of electromechanical properties - vector piezoresponse force microscopy (Vector PFM) - is described. The relationship between local electromechanical response, polarization, piezoelectric constants, and crystallographic orientation is analyzed in detail. The image formation mechanism in vector PFM is discussed. Conditions for complete three-dimensional (3D) reconstruction of the electromechanical response vector and evaluation of the piezoelectric constants from PFM data are set forth. The developed approach can be applied to crystallographic orientation imaging in piezoelectric materials with a spatial resolution below 10 nm. Several approaches for data representation in 2D-PFM and 3D-PFM are presented. The potential of vector PFM for molecular orientation imaging in macroscopically disordered piezoelectric polymers and biological systems is discussed.

  5. Electricity: The Mysterious Force

    NSDL National Science Digital Library

    2008-01-01

    This document examines the mysterious force of electricity. The reading will focus on the physical properties of electricity and discuss topics such as (1) The Atom of Carbon, (2) Static electricity, (3) Magnets are special, (4) Magnetic fields can produce electricity, (5) Batteries produce electricity, (6) Electricity travels in circuits, (7) Secondary energy source, (8) Making electricity, (9) Moving electricity from power plants to homes, (10) Fuels that make electricity, (11) Fossil fuel power plants, (12) Nuclear power plants, (13) Hydropower plants, (14) What's a Watt, and (15) Cost of electricity. The document also depicts illustrations of a bar magnet, turbine generator, transporting electricity, U.S. electricity production, peak demand, and energy efficiency. This resource is structured as an informational booklet to supplement your energy activities or to generate discussion questions.

  6. Deep atomic force microscopy

    SciTech Connect

    Barnard, H.; Drake, B.; Randall, C.; Hansma, P. K. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)] [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

    2013-12-15

    The Atomic Force Microscope (AFM) possesses several desirable imaging features including the ability to produce height profiles as well as two-dimensional images, in fluid or air, at high resolution. AFM has been used to study a vast selection of samples on the scale of angstroms to micrometers. However, current AFMs cannot access samples with vertical topography of the order of 100 ?m or greater. Research efforts have produced AFM scanners capable of vertical motion greater than 100 ?m, but commercially available probe tip lengths are still typically less than 10 ?m high. Even the longest probe tips are below 100 ?m and even at this range are problematic. In this paper, we present a method to hand-fabricate “Deep AFM” probes with tips of the order of 100 ?m and longer so that AFM can be used to image samples with large scale vertical topography, such as fractured bone samples.

  7. Deep atomic force microscopy

    PubMed Central

    Barnard, H.; Drake, B.; Randall, C.; Hansma, P. K.

    2013-01-01

    The Atomic Force Microscope (AFM) possesses several desirable imaging features including the ability to produce height profiles as well as two-dimensional images, in fluid or air, at high resolution. AFM has been used to study a vast selection of samples on the scale of angstroms to micrometers. However, current AFMs cannot access samples with vertical topography of the order of 100 ?m or greater. Research efforts have produced AFM scanners capable of vertical motion greater than 100 ?m, but commercially available probe tip lengths are still typically less than 10 ?m high. Even the longest probe tips are below 100 ?m and even at this range are problematic. In this paper, we present a method to hand-fabricate “Deep AFM” probes with tips of the order of 100 ?m and longer so that AFM can be used to image samples with large scale vertical topography, such as fractured bone samples. PMID:24387435

  8. Deep atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Barnard, H.; Drake, B.; Randall, C.; Hansma, P. K.

    2013-12-01

    The Atomic Force Microscope (AFM) possesses several desirable imaging features including the ability to produce height profiles as well as two-dimensional images, in fluid or air, at high resolution. AFM has been used to study a vast selection of samples on the scale of angstroms to micrometers. However, current AFMs cannot access samples with vertical topography of the order of 100 ?m or greater. Research efforts have produced AFM scanners capable of vertical motion greater than 100 ?m, but commercially available probe tip lengths are still typically less than 10 ?m high. Even the longest probe tips are below 100 ?m and even at this range are problematic. In this paper, we present a method to hand-fabricate "Deep AFM" probes with tips of the order of 100 ?m and longer so that AFM can be used to image samples with large scale vertical topography, such as fractured bone samples.

  9. Observations of Internal Tides on the Oregon Continental Slope KIM I. MARTINI, MATTHEW H. ALFORD, AND ERIC KUNZE

    E-print Network

    Observations of Internal Tides on the Oregon Continental Slope KIM I. MARTINI, MATTHEW H. ALFORD A complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs neap tides, during which the proportions of the locally and remotely forced internal tides vary

  10. Interpretation and use of FRAX in clinical practice - position paper of the International Osteoporosis Foundation and the International Society for Clinical Densitometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The International Osteoporosis Foundation (IOF) and the International Society for Clinical Densitometry (ISCD) appointed a joint Task Force to develop resource documents in order to make recommendations on how to improve FRAX and better inform clinicians who use FRAX. The Task Force met in November...

  11. 22 CFR 130.3 - Armed forces.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 2010-04-01 2010-04-01 false Armed forces. 130.3 Section 130.3 Foreign Relations...CONTRIBUTIONS, FEES AND COMMISSIONS § 130.3 Armed forces. Armed forces means the army, navy, marine, air force,...

  12. 22 CFR 130.3 - Armed forces.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 2011-04-01 2011-04-01 false Armed forces. 130.3 Section 130.3 Foreign Relations...CONTRIBUTIONS, FEES AND COMMISSIONS § 130.3 Armed forces. Armed forces means the army, navy, marine, air force,...

  13. 22 CFR 130.3 - Armed forces.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 2012-04-01 2012-04-01 false Armed forces. 130.3 Section 130.3 Foreign Relations...CONTRIBUTIONS, FEES AND COMMISSIONS § 130.3 Armed forces. Armed forces means the army, navy, marine, air force,...

  14. 22 CFR 130.3 - Armed forces.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 2013-04-01 2013-04-01 false Armed forces. 130.3 Section 130.3 Foreign Relations...CONTRIBUTIONS, FEES AND COMMISSIONS § 130.3 Armed forces. Armed forces means the army, navy, marine, air force,...

  15. International Geology

    ERIC Educational Resources Information Center

    Hoover, Linn

    1977-01-01

    Briefly discusses recent international programs in various areas of geology, including land-use problems, coping with geological hazards, and conserving the environment while searching for energy and mineral resources. (MLH)

  16. Transparency International

    NSDL National Science Digital Library

    Transparency International (TI) is a non-governmental organization concerned with "increasing governmental accountability and curbing both international and national corruption." Best known for its Corruption Perceptions Index (see the February 26, 1998 Scout Report for Business and Economics), Transparency International also offers a host of other corruption-related resources, including the TI Bribers's Pay Survey and TI Bribers's Pay Index, two resources on bribe-paying in international trade; an anti-corruption directory which serves as a reference guide to efforts in central and eastern European countries to support anti-corruption programs; working papers; and other publications. Also worthy of note is TI's ten-point program directed at pressuring the World Bank Organization to help strengthen its anti-corruption programs. The layout of the TI Website is somewhat confusing, but most of the organization's research efforts can be found in the Info Centre.

  17. International Migration

    NSDL National Science Digital Library

    This Website, Push and Pull Factors of International Migration, features background and preliminary research data from a joint project of Eurostat and The Netherlands Interdisciplinary Demographic Institute the goal of which is to "improve understanding of the direct and indirect causes and mechanisms of international migration to the European Union from an internationally comparative perspective. The project is an effort to respond to the fact that "international migration flows have increased in magnitude and complexity over the past decades." Separate sections of the site provide information on the aim, objectives, and approach of the project; the research design; as well as a summary of first results on recent migration, migration motives, migration networks, and migration intentions; and further bibliographic and Web-based resources. The project is under the auspices of the Commission of the European Communities.

  18. The Science of Spring Force

    NSDL National Science Digital Library

    AMPS GK-12 Program,

    Students use data acquisition equipment to learn about force and displacement in regard to simple and complex machines. In the engineering world, materials and systems are tested by applying forces and measuring the resulting displacements. The relationship between the force applied on a material, and its resulting displacement, is a distinct property of the material, which is measured in order to evaluate the material for correct use in structures and machines.

  19. Collision forces for compliant projectiles

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.

    1990-01-01

    Force histories resulting from the impact of compliant projectiles were determined experimentally. A long instrumented rod was used as the target, and the impact force was calculated directly from the measured strain response. Results from a series of tests on several different sized impactors were used to define four dimensionless parameters that determine, for a specified impactor velocity and size, the amplitude, duration, shape, and impulse of the impact force history.

  20. MEMS Bragg grating force sensor.

    PubMed

    Reck, Kasper; Thomsen, Erik V; Hansen, Ole

    2011-09-26

    We present modeling, design, fabrication and characterization of a new type of all-optical frequency modulated MEMS force sensor based on a mechanically amplified double clamped waveguide beam structure with integrated Bragg grating. The sensor is ideally suited for force measurements in harsh environments and for remote and distributed sensing and has a measured sensitivity of -14 nm/N, which is several times higher than what is obtained in conventional fiber Bragg grating force sensors. PMID:21996861

  1. INTERNATIONAL universidad

    E-print Network

    Cardeñosa, Jesús

    ACTIVITIES 8.7. SPORTS 8.8. TRAVEL GRANTS 8.9. LIBRARIES AND COMPUTER LOANS 8.10. WI-FI ON CAMPUS 8.11. COIE IN MADRID 9.6 DISCOUNT CARDS 9.6.1. UPM STUDENT ID CARD 9.6.2. YOUTH CARD (CARNÉ JOVEN) 9.6.3. ISIC: INTERNATIONAL STUDENT IDENTITY CARD. 9.6.4. FIYTO (International Federation of Youth Travel Organisations) 9

  2. Forced convection and subcooled flow boiling heat transfer in asymmetrically heated ducts of T-section

    Microsoft Academic Search

    Hosny Z. Abou-Ziyan

    2004-01-01

    This paper presents the results of an experimental investigation of heat transfer from the heated bottom side of tee cross-section ducts to an internally flowing fluid. The idea of this work is derived from the cooling of critical areas in the cylinder heads of internal combustion engines. Fully developed single phase forced convection and subcooled flow boiling heat transfer data

  3. Are Mathematics and Science Test Scores Good Indicators of Labor-Force Quality?

    ERIC Educational Resources Information Center

    Chen, Shiu-Sheng; Luoh, Ming-Ching

    2010-01-01

    Using data from the Programme for International Student Assessment (PISA) and the Trends in International Mathematics and Science Study (TIMSS), we investigate the link between test scores (mathematics and science) and cross-country income differences. We would like to know whether test scores are good indicators of labor-force quality. The…

  4. 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.

  5. Coriolis Force on Your Arms

    NASA Astrophysics Data System (ADS)

    Johns, Robert

    2003-12-01

    The Coriolis force is a sideward force that acts on a rotating object as it moves toward or away from the center of rotation. It is important to long-range artillery and the formation of tornados, but we seldom experience this force on a human scale, unless we play on a merry-go-round or similar apparatus. This note describes a simple activity that lets us see the effect of the Coriolis force on our outstretched arms as they fall down to our sides while we rotate.

  6. Force As A Momentum Current

    SciTech Connect

    Munera, Hector A. [International Center for Physics (CIF, Centro Internacional de Fisica), Apartado 4948, Bogota (Colombia)

    2010-07-28

    Advantages of a neo-Cartesian approach to classical mechanics are noted. If conservation of linear momentum is the fundamental principle, Newton's three laws become theorems. A minor paradox in static Newtonian mechanics is identified, and solved by reinterpreting force as a current of momentum. Contact force plays the role of a mere midwife in the exchange of momentum; however, force cannot be eliminated from physics because it provides the numerical value for momentum current. In this sense, in a neo-Cartesian formulation of mechanics the concept of force becomes strengthened rather than weakened.

  7. Climate forcing by stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew; Hansen, James; Sato, Makiko

    1992-01-01

    It is illustrated how climate forcing by stratospheric aerosols depends on aerosol properties. The climate forcing is a function of aerosols size distribution, but the size dependence can be described well by a single parameter: the area-weighted mean radius, r(eff). If r(eff) is greater than about 2 microns, the global average greenhouse effect of the aerosols exceeds the albedo effect, causing a surface heating. The aerosol climate forcing is less sensitive to other characteristics of the size distribution, the aerosol composition, and the altitude of the aerosols. Thus stratospheric aerosol forcing can be defined accurately from measurements of aerosol extinction over a broad wavelength range.

  8. Adding Value to Force Diagrams: Representing Relative Force Magnitudes

    ERIC Educational Resources Information Center

    Wendel, Paul

    2011-01-01

    Nearly all physics instructors recognize the instructional value of force diagrams, and this journal has published several collections of exercises to improve student skill in this area. Yet some instructors worry that too few students perceive the conceptual and problem-solving utility of force diagrams, and over recent years a rich variety of…

  9. Stability of Trilateral Forces: II, Large Symmetric Force

    SciTech Connect

    Canavan, G.H.

    1998-09-17

    For large symmetric offensive forces, as for small, at few weapons per missile all forces are reserved, costs are constant, and configurations are stable. At many weapons permissile, no weapons are reserved, first strike costs decrease, fractionation is attractive, and stability degrades. These results a due to symmetries that would not be degraded by additional symmetric opponents.

  10. Bacterial adhesion force quantification by fluidic force microscopy

    NASA Astrophysics Data System (ADS)

    Potthoff, Eva; Ossola, Dario; Zambelli, Tomaso; Vorholt, Julia A.

    2015-02-01

    Quantification of detachment forces between bacteria and substrates facilitates the understanding of the bacterial adhesion process that affects cell physiology and survival. Here, we present a method that allows for serial, single bacterial cell force spectroscopy by combining the force control of atomic force microscopy with microfluidics. Reversible bacterial cell immobilization under physiological conditions on the pyramidal tip of a microchanneled cantilever is achieved by underpressure. Using the fluidic force microscopy technology (FluidFM), we achieve immobilization forces greater than those of state-of-the-art cell-cantilever binding as demonstrated by the detachment of Escherichia coli from polydopamine with recorded forces between 4 and 8 nN for many cells. The contact time and setpoint dependence of the adhesion forces of E. coli and Streptococcus pyogenes, as well as the sequential detachment of bacteria out of a chain, are shown, revealing distinct force patterns in the detachment curves. This study demonstrates the potential of the FluidFM technology for quantitative bacterial adhesion measurements of cell-substrate and cell-cell interactions that are relevant in biofilms and infection biology.Quantification of detachment forces between bacteria and substrates facilitates the understanding of the bacterial adhesion process that affects cell physiology and survival. Here, we present a method that allows for serial, single bacterial cell force spectroscopy by combining the force control of atomic force microscopy with microfluidics. Reversible bacterial cell immobilization under physiological conditions on the pyramidal tip of a microchanneled cantilever is achieved by underpressure. Using the fluidic force microscopy technology (FluidFM), we achieve immobilization forces greater than those of state-of-the-art cell-cantilever binding as demonstrated by the detachment of Escherichia coli from polydopamine with recorded forces between 4 and 8 nN for many cells. The contact time and setpoint dependence of the adhesion forces of E. coli and Streptococcus pyogenes, as well as the sequential detachment of bacteria out of a chain, are shown, revealing distinct force patterns in the detachment curves. This study demonstrates the potential of the FluidFM technology for quantitative bacterial adhesion measurements of cell-substrate and cell-cell interactions that are relevant in biofilms and infection biology. Electronic supplementary information (ESI) available: Video S1. Detachment of a S. pyogenes cell chain from glass substrate. The cantilever is approached on the outermost adherent cell of a chain and four bacteria were then sequentially detached. The sequential cell detachment suddenly stopped after four bacteria. This possibly occurred because bacteria-glass interactions became too strong or the maximal probe retraction was reached. The cells spontaneously detached from the cantilever flipping back on the surface. Fig. S1. (A) Adhesion force-distance and (B) adhesion force-detaching work correlation of E.coli on PLL for setpoints of 1 and 10 nN. Circle: 1 nN setpoint, square: 10 nN. See DOI: 10.1039/c4nr06495j

  11. Elementary Implantable Force Sensor

    PubMed Central

    Wachs, Rebecca A.; Ellstein, David; Drazan, John; Healey, Colleen P.; Uhl, Richard L.; Connor, Kenneth A.

    2014-01-01

    Implementing implantable sensors which are robust enough to maintain long term functionality inside the body remains a significant challenge. The ideal implantable sensing system is one which is simple and robust; free from batteries, telemetry, and complex electronics. We have developed an elementary implantable sensor for orthopaedic smart implants. The sensor requires no telemetry and no batteries to communicate wirelessly. It has no on-board signal conditioning electronics. The sensor itself has no electrical connections and thus does not require a hermetic package. The sensor is an elementary L-C resonator which can function as a simple force transducer by using a solid dielectric material of known stiffness between two parallel Archimedean coils. The operating characteristics of the sensors are predicted using a simplified, lumped circuit model. We have demonstrated sensor functionality both in air and in saline. Our preliminary data indicate that the sensor can be reasonably well modeled as a lumped circuit to predict its response to loading. PMID:24883335

  12. Report of the Fermilab ILC Citizens' Task Force

    SciTech Connect

    None

    2008-06-01

    Fermi National Accelerator Laboratory convened the ILC Citizens' Task Force to provide guidance and advice to the laboratory to ensure that community concerns and ideas are included in all public aspects of planning and design for a proposed future accelerator, the International Linear Collider. In this report, the members of the Task Force describe the process they used to gather and analyze information on all aspects of the proposed accelerator and its potential location at Fermilab in northern Illinois. They present the conclusions and recommendations they reached as a result of the learning process and their subsequent discussions and deliberations. While the Task Force was charged to provide guidance on the ILC, it became clear during the process that the high cost of the proposed accelerator made a near-term start for the project at Fermilab unlikely. Nevertheless, based on a year of extensive learning and dialogue, the Task Force developed a series of recommendations for Fermilab to consider as the laboratory develops all successor projects to the Tevatron. The Task Force recognizes that bringing a next-generation particle physics project to Fermilab will require both a large international effort and the support of the local community. While the Task Force developed its recommendations in response to the parameters of a future ILC, the principles they set forth apply directly to any large project that may be conceived at Fermilab, or at other laboratories, in the future. With this report, the Task Force fulfills its task of guiding Fermilab from the perspective of the local community on how to move forward with a large-scale project while building positive relationships with surrounding communities. The report summarizes the benefits, concerns and potential impacts of bringing a large-scale scientific project to northern Illinois.

  13. Teaching International Law: Concepts in International Relations

    ERIC Educational Resources Information Center

    Starbird, Caroline; Pettit, Jenny; Singleton, Laurel

    2004-01-01

    This book is designed to introduce students to public international law. Topics covered include international public organizations, such as the United Nations and World Trade Organization, international courts, international human rights law, international trade law, and international environmental law. The goal of each study is to examine how…

  14. International Programs and Services International Programs

    E-print Network

    Stephens, Graeme L.

    International Programs and Services _______________ 1.5 Page 1 International Programs and Services OFFICE OF INTERNATIONAL PROGRAMS Offices in Laurel Hall (970) 491-5917 www.international.colostate.edu James A. Cooney, Vice Provost for International Affairs The Office of International Programs acts

  15. International Programs and Services International Programs

    E-print Network

    Collett Jr., Jeffrey L.

    International Programs and Services International Programs and Services OFFICE OF INTERNATIONAL PROGRAMS Offices in Laurel Hall (970) 491-5917 international.colostate.edu James A. Cooney, Vice Provost for International Affairs The Office of International Programs acts as a catalyst for ideas that bring about

  16. Optical forces in nanoplasmonic systems: how do they work, what can they be useful for?

    PubMed

    Raziman, T V; Wolke, R J; Martin, O J F

    2015-01-01

    In this article, we share our vision for a future nanofactory, where plasmonic trapping is used to control the different manufacturing steps associated with the transformation of initial nanostructures to produce complex compounds. All the different functions existing in a traditional factory can be translated at the nanoscale using the optical forces produced by plasmonic nanostructures. A detailed knowledge of optical forces in plasmonic nanostructures is however essential to design such a nanofactory. To this end, we review the numerical techniques for computing optical forces on nanostructures immersed in a strong optical field and show under which conditions approximate solutions, like the dipole approximation, can be used in a satisfactory manner. Internal optical forces on realistic plasmonic antennas are investigated and the reconfiguration of a Fano-resonant plasmonic system using such internal forces is also studied in detail. PMID:25743413

  17. Force optimized recoil control system

    NASA Astrophysics Data System (ADS)

    Townsend, P. E.; Radkiewicz, R. J.; Gartner, R. F.

    1982-05-01

    Reduction of the recoil force of high rate of fire automatic guns was proven effective. This system will allow consideration of more powerful guns for use in both helicopter and armored personnel carrier applications. By substituting the large shock loads of firing guns with a nearly constant force, both vibration and fatigue problems that prevent mounting of powerful automatic guns is eliminated.

  18. Force optimized recoil control system

    Microsoft Academic Search

    P. E. Townsend; R. J. Radkiewicz; R. F. Gartner

    1982-01-01

    Reduction of the recoil force of high rate of fire automatic guns was proven effective. This system will allow consideration of more powerful guns for use in both helicopter and armored personnel carrier applications. By substituting the large shock loads of firing guns with a nearly constant force, both vibration and fatigue problems that prevent mounting of powerful automatic guns

  19. System Funding Task Force Report.

    ERIC Educational Resources Information Center

    Hale, Toussaint L., Jr.

    The System Funding Task Force (SFTF) of the Illinois Community College Board was formed to review the recommendations and framework for modifying the state's funding plan developed by the Board's President's Council. This report presents the SFTF's review of the Council's findings and presents the Task Force's own recommendations for funding.…

  20. Simplified Relativistic Force Transformation Equation.

    ERIC Educational Resources Information Center

    Stewart, Benjamin U.

    1979-01-01

    A simplified relativistic force transformation equation is derived and then used to obtain the equation for the electromagnetic forces on a charged particle, calculate the electromagnetic fields due to a point charge with constant velocity, transform electromagnetic fields in general, derive the Biot-Savart law, and relate it to Coulomb's law.…

  1. Climate forcing by stratospheric aerosols

    Microsoft Academic Search

    Andrew Lacis; James Hansen; Makiko Sato

    1992-01-01

    We illustrate how climate forcing by stratospheric aerosols depends on aerosol properties. The climate forcing is a function of aerosol size distribution, but the size dependence can be described well by a single parameter: the area-weighted mean radius, reff.If reff is greater than about 2 ?m, the global average greenhouse effect of the aerosols exceeds the albedo effect, causing a

  2. Physics 2000: Electric Force Fields

    NSDL National Science Digital Library

    This page illustrates and describes electric fields and forces through a simulation. The explanation is given in the form of a conversation between two people. There is also a simple simulation which helps understand the concept better. This web page is part of a tutorial that introduces electric forces and fields.

  3. The Forced Hard Spring Equation

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2006-01-01

    Through numerical investigations, various examples of the Duffing type forced spring equation with epsilon positive, are studied. Since [epsilon] is positive, all solutions to the associated homogeneous equation are periodic and the same is true with the forcing applied. The damped equation exhibits steady state trajectories with the interesting…

  4. Ecosystem Task Force Meeting Minutes

    E-print Network

    New Hampshire, University of

    Ecosystem Task Force Meeting Minutes Date: April 28, 2011 Title of Meeting: Monthly Meeting. A focus on planning helps ground the Task Force because of the complexity of ecosystems. UNH-862-0785 sustainability.info@unh.edu http://www.sustainableunh.unh.edu/ #12;3.1. Ecosystem work has no defined parameters

  5. Kollisionsdetektion fr Force-Feedback-

    E-print Network

    Zachmann, Gabriel

    algorithm!) § Penetration volume offers a new approach to computing haptic forces Inner Sphere Trees triangles § 1 kHz simulation rate § Pentium IV 3GHz (3 years old) Force on haptic device Inner Sphere Trees Benchmark Protosphere Conclusion Results: Quality Benchmark VPS IST Color code = intensity of frequency

  6. Grasp force control in telemanipulation

    NASA Technical Reports Server (NTRS)

    Wiker, Steven F.; Duffie, Neil A.

    1992-01-01

    This paper presents two experiments which focus upon the issue of grasp force control in telemanipulation. The first experiment examines the ability to control and stabilize master-controller grasp force during a 30-s compensatory tracking task under different levels of master controller digit mass, friction, and backlash. The second experiment explores the potential for substituting tactile feedback in lieu of direct force-feedback to gage and control remote grasp force. Results show that subjects were better able to control force when mass and friction levels were increased. Even when perceptual gains between tactile and direct force feedback displays were matched, force reflection produced better grasp control. The lack of backlash effects and improvements in performance with direct force reflection in comparison to tactile feedback are attributable to reflexive short-loop adjustment of grasp tension afforded by the muscle's length-tension control system. The criterion of acceptable operator performance, dependent upon both the quality of the transmission of control commands and feedback, and the response of the remote device, is discussed.

  7. Fifth Force from Fifth Dimension

    Microsoft Academic Search

    F. Dahia; E. M. Monte; C. Romero

    2003-01-01

    We investigate the dynamics of particles moving in a spacetime augmented by one extra dimension in the context of the induced matter theory of gravity. We examine the appearance of a fifth force as an effect caused by the extra dimension and discuss two different approaches to the fifth force formalism. We then give two simple examples of application of

  8. Traffic Safety Task Force Report

    E-print Network

    1 Traffic Safety Task Force Report September 2012 November Board of Trustees Meeting - Academic Paul Denton ­ OSUPD Traffic Safety Task Force Members 2 A special thanks goes to Jaime Pujol, College Hetrick, a master's in city and regional planning student, for his studies of pedestrian and cyclist

  9. The Electrodeless Lorentz Force Thruster

    Microsoft Academic Search

    Thomas Weber; Brian Nelson; Richard Milroy; David Kirtley; John Slough

    2009-01-01

    The Electrodeless Lorentz Force (ELF) thruster is a novel plasma thruster under development at MSNW and the University of Washington which utilizes Rotating Magnetic Field (RMF) current drive technology to ionize a neutral gas and drive an azimuthal current to form a Field Reversed Configuration (FRC) plasmoid in a diverging magnetic field. The magnetic gradient imparts a net force to

  10. Hebrew as a Binding Force.

    ERIC Educational Resources Information Center

    Fischler, Ben-Zion

    1990-01-01

    The role of the Hebrew language as a cohesive force and the history of modern Hebrew instruction are chronicled. It is proposed that despite the scattering of its speakers and periods of use only as a literary or business language, Hebrew has been a binding force for the Jewish people. It was with considerable struggle that Hebrew gained…

  11. Intermolecular Forces: Solids and Liquids

    NSDL National Science Digital Library

    General chemistry WebCT exam/quiz questions. The Intermolecular Forces: Solids and Liquids topic covers the forces that exist between atoms and molecules in solids and liquids, and how these affect properties such as boiling point, conductivity, and lattice energy.

  12. Retarded Dispersion Forces Between Molecules

    Microsoft Academic Search

    A. D. McLachlan

    1963-01-01

    The frequency-dependent susceptibility of the molecules and of the electromagnetic field is used to calculate the force between two molecules at zero temperature. The field susceptibility at imaginary frequency, which is the Laplace transform of the retarded potentials, is found from the commutation relations, otherwise we do not need quantum field theory. A method of `images' gives the force between

  13. Potential Wave Drift Force Simplified

    Microsoft Academic Search

    G. Burns; S. Liu

    1983-01-01

    Morison's equation has the advantage of simplicity, and has been used extensively to determine wave forces on small diameter members of offshore platforms. For larger members the inertia coefficient of the Morison equation is replaced by a modified coefficient derived from diffraction theory to calculate first order wave forces. Linear wave analysis is not sufficient for compliant structures such as

  14. Language Learning in International Schools: Has This Become a Business?

    Microsoft Academic Search

    Lalima Jenckes

    International schools are unique as they have grown into a dynamic educational force both locally and globally in recent decades. These schools originally started in the early 1900s to serve children of armed forces personnel and diplomats overseas. Teachers were initially recruited from amongst the available transient parent body to provide an education similar to that which the students would

  15. Incipient Sediment Movement by Shoaling Internal Gravity Waves

    Microsoft Academic Search

    D. A. Cacchione; J. B. Southard

    1974-01-01

    criterion for incipient movement of bottom sediment by shoaling internal waves by equating moments due to fluid force and gravity force acting on an exposed bed particle. Comparison of predicted conditions of incipient sediment movement with mean sediment sizes actually present on the continental shelf and continental slope southeast of New England indicates that shoreward propagation of relatively high frequency

  16. Inertial shear forces and the use of centrifuges in gravity research. What is the proper control?

    PubMed

    van Loon, Jack J; Folgering, Erik H; Bouten, Carlijn V; Veldhuijzen, J Paul; Smit, Theo H

    2003-06-01

    Centrifuges are used for 1 x g controls in space flight microgravity experiments and in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces contribute significantly to the total force acting on the cells or tissues. The inertial shear force artifact should be dealt with for future experiment hardware development for Shuttle and the International Space Station (ISS) as well as for the interpretation of previous space-flight and on-ground research data. PMID:12929238

  17. Gene regulation by mechanical forces

    NASA Technical Reports Server (NTRS)

    Oluwole, B. O.; Du, W.; Mills, I.; Sumpio, B. E.

    1997-01-01

    Endothelial cells are subjected to various mechanical forces in vivo from the flow of blood across the luminal surface of the blood vessel. The purpose of this review was to examine the data available on how these mechanical forces, in particular cyclic strain, affect the expression and regulation of endothelial cell function. Studies from various investigators using models of cyclic strain in vitro have shown that various vasoactive mediators such as nitric oxide and prostacyclin are induced by the effect of mechanical deformation, and that the expression of these mediators may be regulated at the transcription level by mechanical forces. There also seems to be emerging evidence that endothelial cells may also act as mechanotransducers, whereby the transmission of external forces induces various cytoskeletal changes and second messenger cascades. Furthermore, it seems these forces may act on specific response elements of promoter genes.

  18. Air Force satellite position management

    NASA Astrophysics Data System (ADS)

    Davis, R.

    1985-03-01

    The Space Act of 1958 identified the Department of Defense as responsible for conducting military operations in space. Subsequently, the United States Air Force was assigned to act as the DOD's executive agent for space. In addition, the Air Force is responsible for acquisition and launch of DOD space systems. Within the Air Force, space related roles and activities have been delegated to several subordinate organizations and agencies. The roles and responsibilities of agencies are still evolving. The Air Force has designated the Air Force System Command's Space Division as its office of primary responsibility for satellite position management. Spacecraft program offices at Space Division are required by regulation to include position management planning in both prelaunch and orbital phases of spacecraft development and operation.

  19. Globalization and the Growth of International Educational Testing and National Assessment

    ERIC Educational Resources Information Center

    Kamens, David H.; McNeely, Connie L.

    2010-01-01

    In this article, the authors develop an argument about the global forces that have led to the explosive growth of national educational assessment and international testing. In particular, the authors argue that the international acceptance of testing comes from key ideological forces in the world polity that are associated with the accelerating…

  20. International vision and strategy for drug regulatory authority: the PMDA's international vision.

    PubMed

    Tominaga, Toshiyoshi; Ando, Yuki; Kondo, Tatsuya

    2012-09-01

    The past several years saw various countries' drug regulatory authorities (DRAs) internationalizing their activities in response to the rapid globalization of pharmaceutical affairs. This is the second surge of internationalization, coming after the first in the 1990s, when the International Conference on Harmonisation (ICH) and the Global Harmonization Task Force were founded. For maximum effect, a DRA needs to carefully strategize its international activities. The significance of international master plans is discussed in relation to the recently published International Vision of Japan's Pharmaceuticals and Medical Devices Agency (PMDA). PMID:22871996

  1. Atomic Force Microscope Operation

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation (large file)

    This animation is a scientific illustration of the operation of NASA's Phoenix Mars Lander's Atomic Force Microscope, or AFM. The AFM is part of Phoenix's Microscopy, Electrochemistry, and Conductivity Analyzer, or MECA.

    The AFM is used to image the smallest Martian particles using a very sharp tip at the end of one of eight beams.

    The beam of the AFM is set into vibration and brought up to the surface of a micromachined silicon substrate. The substrate has etched in it a series of pits, 5 micrometers deep, designed to hold the Martian dust particles.

    The microscope then maps the shape of particles in three dimensions by scanning them with the tip.

    At the end of the animation is a 3D representation of the AFM image of a particle that was part of a sample informally called 'Sorceress.' The sample was delivered to the AFM on the 38th Martian day, or sol, of the mission (July 2, 2008).

    The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate.

    A Martian particle only one micrometer, or one millionth of a meter, across is held in the upper left pit.

    The rounded particle shown at the highest magnification ever seen from another world is a particle of the dust that cloaks Mars. Such dust particles color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars' distinctive red soil.

    The AFM was developed by a Swiss-led consortium, with Imperial College London producing the silicon substrate that holds sampled particles.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  2. Motion and force control of multiple robotic manipulators

    NASA Technical Reports Server (NTRS)

    Wen, John T.; Kreutz-Delgado, Kenneth

    1992-01-01

    This paper addresses the motion and force control problem of multiple robot arms manipulating a cooperatively held object. A general control paradigm is introduced which decouples the motion and force control problems. For motion control, different control strategies are constructed based on the variables used as the control input in the controller design. There are three natural choices; acceleration of a generalized coordinate, arm tip force vectors, and the joint torques. The first two choices require full model information but produce simple models for the control design problem. The last choice results in a class of relatively model independent control laws by exploiting the Hamiltonian structure of the open loop system. The motion control only determines the joint torque to within a manifold, due to the multiple-arm kinematic constraint. To resolve the nonuniqueness of the joint torques, two methods are introduced. If the arm and object models are available, an optimization can be performed to best allocate the desired and effector control force to the joint actuators. The other possibility is to control the internal force about some set point. It is shown that effective force regulation can be achieved even if little model information is available.

  3. Experimental Investigation of Forces Produced by Misaligned Steel Rollers

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy; DellaCorte, Christopher; Dube, Michael

    2010-01-01

    The International Space Station (ISS) Solar Alpha Rotary Joint (SARJ) uses a roller-based mechanism for positioning of the solar arrays. The forces and moments that develop at the roller interfaces are influenced by the design including the kinematic constraints and the lubrication condition. To help understand the SARJ operation, a set of dedicated experiments were completed using roller pairs. Of primary interest was to measure the axial force directed along the axis of rotation of the roller as a function of shaft misalignment. The conditions studied included dry and clean surfaces; one surface plated by a gold film, and greased surfaces. For the case of a bare 440C roller against a nitrided 15-5 roller without lubrication, the axial force can be as great as 0.4 times the normal load for a shaft angle of 0.5 deg. Such a magnitude of force on a roller in the SARJ mechanism would cause roller tipping and contact pressures much greater than anticipated by the designers. For the case of a bare 440C roller against a nitrided 15-5 roller with grease lubrication, the axial force does not exceed about 0.15 times the normal load even for the largest misalignment angles tested. Gold films provided good lubrication for the short duration testing reported herein. Grease lubrication limited the magnitude of the axial force to even smaller magnitudes than was achieved with the gold films. The experiments demonstrate the critical role of good lubrication for the SARJ mechanism.

  4. Experimental Investigation of Forces Produced by Misaligned Steel Rollers

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy; DellaCorte, Christopher; Dube, Michael

    2010-01-01

    The International Space Station Solar Alpha Rotary Joint (SARJ) uses a roller-based mechanism for positioning of the solar arrays. The forces and moments that develop at the roller interfaces are influenced by the design including the kinematic constraints and the lubrication condition. To help understand the SARJ operation, a set of dedicated experiments were completed using roller pairs. Of primary interest was to measure the axial force directed along the axis of rotation of the roller as a function of shaft misalignment. The conditions studied included dry and clean surfaces; one surface plated by a gold film, and greased surfaces. For the case of a bare 440C roller against a nitrided 15-5 roller without lubrication, the axial force can be as great as 0.4 times the normal load for a shaft angle of 0.5 degree. Such a magnitude of force on a roller in the SARJ mechanism would cause roller tipping and contact pressures much greater than anticipated by the designers. For the case of a bare 440C roller against a nitrided 15-5 roller with grease lubrication, the axial force does not exceed about 0.15 times the normal load even for the largest misalignment angles tested. Gold films provided good lubrication for the short duration testing reported herein. Grease lubrication limited the magnitude of the axial force to even smaller magnitudes than was achieved with the gold films. The experiments demonstrate the critical role of good lubrication for the SARJ mechanism.

  5. Internal Medicine

    PubMed Central

    Bouland, Daniel L.; Doram, Keith

    1994-01-01

    The Council on Scientific Affairs of the California Medical Association presents the following inventory of items of progress in internal medicine. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, and scholars to stay abreast of these items of progress in internal medicine that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another. The items of progress listed below were selected by the Advisory Panel to the Section on Internal Medicine of the California Medical Association, and the summaries were prepared under its direction. PMID:8191758

  6. Rolling Contact Force Energy Reconstruction

    NASA Astrophysics Data System (ADS)

    BRACCIALI, A.; CASCINI, G.

    2000-09-01

    Knowledge of the forces at the wheel-rail contact is fundamental to estimate the consequences in terms of noise and vibration. The traditional use of strain gauges mounted on the wheel web and axle is not capable of determining the high-frequency content of the contact force. Measurements made on the rail are characterized by the spatial variability of input-output transfer functions which makes it difficult to estimate the contact force by simple inversion of the point frequency response function. In this study the problem of rolling contact force reconstruction has been approached through the following steps: (i) the track has been characterized precisely for a finite length by the analysis of the time series of several impacts supplied with an instrumented hammer by using an ARMAX model that proved to be capable of modelling the vertical dynamics of the rail up to 5 kHz; (ii) the response of the rail has been simulated with a random force acting on the system, and the variability of the transfer function has been taken into account by distributing the force on adjacent elements; (iii) the simulated response has been compared with the rail acceleration measured for the passage of several trains; (iv) the wheel-rail contact force has been estimated with a closed-loop algorithm. It has thus been possible to reconstruct the13octave power spectrum of contact forces with a simple and stable iterative procedure. Forces reconstructed from different sensors were found to be practically the same for a given wheel; forces from nominally similar wheels are statistically examined and partial results of comparisons made on different rolling stock are shown.

  7. Forces on laboratory model dredge cutterhead 

    E-print Network

    Young, Dustin Ray

    2010-07-14

    ???? = Vertical cutting force (F#ca represents cavitating) lb Fv = Cutting force perpendicular to swing direction and perpendicular to axis of excavating element lb ????1?? = Shear force along x-axis lb vii Units ????1?? = Shear force along y... - pcavitation = Cavitation pore pressure psi R = Resultant force of N and S lb r = Cutterhead radius in Re = Reynolds Number - ?water = Water density lb/ft3 S = Shear force of cutting blade due to sand lb ??? = Average tangential cutterhead force...

  8. Rotary internal combustion engine

    SciTech Connect

    Murray, J.L.

    1993-07-20

    A multi bank power plant is described comprising at least a first and a second rotary internal combustion engine connectable together in series, each of the engines comprising: a housing; a cam track internally disposed within the housing and adapted to receive a cam follower; an engine block disposed within the housing and rotatable about a central axis; an output shaft extending axially from each the engine block, each output shaft being coaxial with the other; means for coupling the output shafts together so that the output shafts rotate together in the same direction at the same speed; at least one radially arranged cylinder assembly on each block, each cylinder assembly including a cylinder having a longitudinal axis extending generally radially outwardly from the rotational axis of the block, the cylinder including means defining an end wall, a piston member disposed within the cylinder and adapted to reciprocate within the cylinder; a combustion chamber, means permitting periodic introduction of air and fuel into the combustion chamber, means for causing combustion of a compressed mixture of air and fuel within the combustion chamber, means permitting periodic exhaust of products of combustion of air and fuel from the combustion chamber, and means for imparting forces and motions of the piston within the cylinder to and from the cam track, the means comprising a cam follower operatively connected to the piston; wherein the cam track includes at least a first segment and at least a second segment thereof, the first segment having a generally positive slope wherein the segment has a generally increasing radial distance from the rotational axis of the engine block whereby as a piston moves outwardly in a cylinder on a power stroke while the cam follower is in radial register with the cam track segment, the reactive force of the respective cam follower against the cam track segment acts in a direction tending to impart rotation to the engine block.

  9. Climate forcing by anthropogenic aerosols.

    PubMed

    Charlson, R J; Schwartz, S E; Hales, J M; Cess, R D; Coakley, J A; Hansen, J E; Hofmann, D J

    1992-01-24

    Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes. PMID:17842894

  10. Gravity and Orbits: Gravitational Force

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2006-11-01

    This Science Object is the second of three Science Objects in the Gravity and Orbits SciPack. It investigates the variables that influence gravitational forces acting on objects. Mass is a measure of the amount of matter that makes up an object (regardless of where that object is located) and weight is a measure of the gravitational force acting on an object. The strength of the gravitational force between masses is proportional to the product of the masses and inversely proportional to the square of the distance between them. Gravity will cause all objects at the same distance from Earth's surface to fall toward Earth with the same acceleration regardless of their mass. Learning Outcomes:? Identify variables that affect the strength of the gravitational force acting between any two objects.? Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.? Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.? Provide a quantitative description of the relationship between distance and gravitational force. ? Provide a qualitative description of the inverse square relationship.? Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored.

  11. Elbow and wrist joint contact forces during occupational pick and place activities.

    PubMed

    Chadwick, E K; Nicol, A C

    2000-05-01

    A three-dimensional, mathematical model of the elbow and wrist joints, including 15 muscle units, 3 ligaments and 4 joint forces, has been developed. A new strain gauge transducer has been developed to measure functional grip forces. The device measures radial forces divided into six components and forces of up to 250N per segment can be measured with an accuracy of +/-1%. Ten normal volunteers were asked to complete four tasks representing occupational activities, during which time their grip force was monitored. Together with kinematic information from the six-camera Vicon data, the moment effect of these loads at the joints was calculated. These external moments are assumed to be balanced by the internal moments, generated by the muscles, passive soft tissue and bone contact. The effectiveness of the body's internal structures in generating joint moments was assessed by studying the geometry of a simplified model of the structures, where information about the lines of action and moment arms of muscles, tendons and ligaments is contained. The assumption of equilibrium between these external and internal joint moments allows formulation of a set of equations from which muscle and joint forces can be calculated. A two stage, linear optimisation routine minimising the overall muscle stress and the sum of the joint forces has been used to overcome the force-sharing problem. Humero-ulnar forces of up to 1600N, humero-radial forces of up to 800N and wrist joint forces of up to 2800N were found for moderate level activity. The model was validated by comparison with other studies. PMID:10708780

  12. Force reconstruction from tapping mode force microscopy experiments

    NASA Astrophysics Data System (ADS)

    Payam, Amir F.; Martin-Jimenez, Daniel; Garcia, Ricardo

    2015-05-01

    Fast, accurate, and robust nanomechanical measurements are intensely studied in materials science, applied physics, and molecular biology. Amplitude modulation force microscopy (tapping mode) is the most established nanoscale characterization technique of surfaces for air and liquid environments. However, its quantitative capabilities lag behind its high spatial resolution and robustness. We develop a general method to transform the observables into quantitative force measurements. The force reconstruction algorithm has been deduced on the assumption that the observables (amplitude and phase shift) are slowly varying functions of the tip–surface separation. The accuracy and applicability of the method is validated by numerical simulations and experiments. The method is valid for liquid and air environments, small and large free amplitudes, compliant and rigid materials, and conservative and non-conservative forces.

  13. Force reconstruction from tapping mode force microscopy experiments.

    PubMed

    Payam, Amir F; Martin-Jimenez, Daniel; Garcia, Ricardo

    2015-05-01

    Fast, accurate, and robust nanomechanical measurements are intensely studied in materials science, applied physics, and molecular biology. Amplitude modulation force microscopy (tapping mode) is the most established nanoscale characterization technique of surfaces for air and liquid environments. However, its quantitative capabilities lag behind its high spatial resolution and robustness. We develop a general method to transform the observables into quantitative force measurements. The force reconstruction algorithm has been deduced on the assumption that the observables (amplitude and phase shift) are slowly varying functions of the tip-surface separation. The accuracy and applicability of the method is validated by numerical simulations and experiments. The method is valid for liquid and air environments, small and large free amplitudes, compliant and rigid materials, and conservative and non-conservative forces. PMID:25876817

  14. International Telecommunication

    E-print Network

    Carle, Georg

    Telecommunication Union Lannion, France, 10-12 September 2008 2 Contents Motivation and concept Methodology, 10-12 September 2008 4 Human perception abilities are naturally binaural. Has this been exploited such as head or the body movements due to changes in the acoustic delays and echoes. Concept #12;International

  15. INTERNATIONAL SCHOLARSHIPS

    E-print Network

    INTERNATIONAL STUDENT SCHOLARSHIPS scholarships.curtin.edu.auMake tomorrow better. Curtin Scholarships #12;WHAT IS A CURTIN SCHOLARSHIP? A SCHOLARSHIP AT CURTIN CAN OFFER YOU GREAT OPPORTUNITIES to complete university studies but face financial difficulties. Our scholarships range from one-off cash

  16. International Entomology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pests and diseases of plants in agriculture are a shared international problem. Yet some of the very places that pest invaders come from often lack the institutional structure and organization necessary to help in understanding the biology of the pest or disease. Strengthening entomology by stimulat...

  17. INTERNATIONAL UNDERGRADUATE

    E-print Network

    University of Technology, Sydney

    .CHANGE.DO #12;ITALY SWITZERLAND GERMANY FRANCE SPAIN CANADA (QUEBEC) LATINO USA MEXICO CHILE COLOMBIA ARGENTINA MAJOR > Argentina > Canada (Quebec) > Chile > China > Colombia > France > Germany > Italy > Japan BLUCHER Bachelor of Arts in Communication (Journalism), Bachelor of Arts in International Studies (China

  18. INTERNATIONAL COMPETITION

    E-print Network

    Borissova, Daniela

    and animal diversity, cultural traditions and lifestyle of the people occupying them. This world of rareTHIRD INTERNATIONAL COMPETITION "Karst under protection ­ gift for the future generations" This competition is organized by the National Institute of Geophysics, Geodesy and Geography at the Bulgarian

  19. IEEE Computer Society Task Force on Cluster Computing

    NSDL National Science Digital Library

    The TFCC is an international forum promoting cluster computing research and education. It participates in helping to set up and promote technical standards in this area. The Task Force is concerned with issues related to the design, analysis, development and implementation of cluster-based systems. Of particular interest are: cluster hardware technologies, distributed environments, application tools and utilities, as well as the development and optimisation of cluster-based applications.

  20. Forces Applied by Cilia Measured on Explants from Mucociliary Tissue

    PubMed Central

    Teff, Zvi; Priel, Zvi; Gheber, Levi A.

    2007-01-01

    Forces applied by intact mucus-propelling cilia were measured for the first time that we know of using a combined atomic force microscopy (AFM) and electrooptic system. The AFM probe was dipped into a field of beating cilia and its time-dependent deflection was recorded as it was struck by the cilia while the electrooptic system simultaneously and colocally measured the frequency to ensure that no perturbation was induced by the AFM probe. Using cilia from frog esophagus, we measured forces of ?0.21 nN per cilium during the effective stroke. This value, together with the known internal structure of these cilia, leads to the conclusion that most dynein arms along the length of the axoneme contribute to the effective stroke of these cilia. PMID:17142280

  1. Drag force scaling for penetration into granular media.

    PubMed

    Katsuragi, Hiroaki; Durian, Douglas J

    2013-05-01

    Impact dynamics is measured for spherical and cylindrical projectiles of many different densities dropped onto a variety non-cohesive granular media. The results are analyzed in terms of the material-dependent scaling of the inertial and frictional drag contributions to the total stopping force. The inertial drag force scales similar to that in fluids, except that it depends on the internal friction coefficient. The frictional drag force scales as the square-root of the density of granular medium and projectile, and hence cannot be explained by the combination of granular hydrostatic pressure and Coulomb friction law. The combined results provide an explanation for the previously observed penetration depth scaling. PMID:23767531

  2. Fluid of Janus molecules between two walls: the solvation force.

    PubMed

    Patrykiejew, A; Soko?owski, S; Soko?owska, Z; Ilnytskyi, Ja

    2013-12-14

    We apply a density functional theory to calculate the solvation force in the system involving Janus particles confined between two planar walls. Janus particles are modeled as spheres composed of attractive and repulsive parts and their orientation is described by the vectors representing internal degrees of freedom. We consider the cases of pores with identical walls, as well as the pores with competing walls (the so-called Janus-like pores). The density functional approach we employ combines fundamental measure theory with a mean-field approximation for the anisotropic interparticle interaction. We study how the solvation force and the orientational structure of confined particles depend on the competition between the surface field and the interactions between confined molecules and on the parameters of the model such as temperature and density. It is shown that the anisotropic interaction between the confined molecules and the character of the walls significantly influence the solvation force. PMID:24329086

  3. Variational treatment of electrostatic interaction force in atomic force microscopy

    Microsoft Academic Search

    E. Shmoylova; A. Dorfmann; S. Potapenko

    2008-01-01

    .  In this paper we introduce the mathematical model for the electrostatic interaction force between an atomic force microscope\\u000a (AFM) tip and a sample surface. We formulate the electrostatic potential problem in Sobolev spaces and find the corresponding\\u000a weak solution in terms of the integral potential, which can be approximated numerically by generalized Fourier series and\\u000a used to find the interaction

  4. Forces on the Human Molecule

    NSDL National Science Digital Library

    Worcester Polytechnic Institute

    2013-01-01

    In this physical activity, two lines of learners link hands and arms to model a beam subject to various loading schemes. They discover how inter-atomic forces react to the five fundamental load types that can act on structures: tension, compression, shear, bending, and torsion. This activity can be used as an introduction to these forces or as review. Note: The description refers to learners as "molecules of steel" and their arms being the bonds between them. Since steel is an alloy of multiple elements, each learner would represent an atom and their arms are the inter-atomic forces which join them.

  5. Roller Coaster G-Forces

    NSDL National Science Digital Library

    Henderson, Tom

    This page, created by Tom Henderson of Glenbrook South High School, features an animated image and a discussion of the forces involved in going through a looping coaster. This page is fairly simplistic, but it does provides links to other helpful physics resources. Some of these include lesson plans discussing the subjects of: acceleration, net force and acceleration, free body diagrams, weightlessness, circular motion and tangential velocity, circular motion and acceleration, the centripetal force requirement and amusement park physics. All together, this is a nice resource for an upper high school to lower undergraduate level course in basic physics.

  6. Fluid forces on circular cylinders

    E-print Network

    Dean, Robert G

    1956-01-01

    of the inert1sl coefficient, C Tba ~ority of investidations of flu14 forces on e cylindrical obp?tt bove been associated with forces which resulted face surface wataa' waves. These results bove been anslyaad to yield values of C& snd C+ by tm approaches..., Tba eerhtest snd s~ aetbN4 of ~lysis wes to choose a tine in the weve history when either tha boriaontal particle velocity or boriaon- tal particle acceleration wae theareAically aero. The entire aessured force at this tiae was than attributed...

  7. Internal seiche dynamics in Lake Geneva

    Microsoft Academic Search

    U. Lemmin; C. H. Mortimer; E. Bäuerle

    2005-01-01

    We analyzed season-long water level records at 12 stations around the Lake of Geneva (local name Leman) for evidence of internal seiches modified by Coriolis force and compared the results with predictions from a two-layer numerical model with real bottom topography for typical wind situations. Results are also compared with those obtained from current and temperature measurements in the lake.

  8. Revised 12.VI.2003 Tenth International Congress

    E-print Network

    Revised 12.VI.2003 Tenth International Congress on Sound and Vibration 7--10 July 2003 · Stockholm question by pointing out that this dynamically induced tension tends to oppose the fluid the drag forces at the flagpole; and · from the fluid side, we can analyze the flow field, or measure

  9. Collaborative International Education: Reaching across Borders

    ERIC Educational Resources Information Center

    Hilgers, Michael G.; Flachsbart, Barry B.; Elrod, Cassandra C.

    2012-01-01

    Purpose: As international boundaries fade and financial pressures increase, universities are redefining the norm in educational models. The move from a synchronous classroom to a blended classroom or a completely asynchronous environment has forced faculty to be creative in delivery while overcoming complexities in the associated infrastructure.…

  10. Forces in atomic force microscopy in air and water

    NASA Astrophysics Data System (ADS)

    Weisenhorn, A. L.; Hansma, P. K.; Albrecht, T. R.; Quate, C. F.

    1989-06-01

    A new atomic force microscope, which combines a microfabricated cantilever with an optical lever detection system, now makes it possible to measure the absolute force applied by a tip on a surface. This absolute force has been measured as a function of distance (the position of the surface) in air and water over a range of 600 nm. In the absolute force versus distance curves there are two transitions from touching the surface to a total release in air caused by van der Waals interaction and surface tension. One transition is due to lifting off the surface; the other is due to lifting out of an adsorbed layer on the surface. In water there is just one transition due to lifting off the surface. There is also a transition in air and water when the totally released tip is pulled down to touch the surface as the surface and tip are brought together. Based on the force versus distance curves, a procedure is proposed to set the lowest possible imaging force. It can now be as low as 10 to the -9th N or less in water and 10 to the -7th N in air.

  11. Calibration of frictional forces in atomic force microscopy

    SciTech Connect

    Ogletree, D.F.; Carpick, R.W.; Salmeron, M. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1996-09-01

    The atomic force microscope can provide information on the atomic-level frictional properties of surfaces, but reproducible quantitative measurements are difficult to obtain. Parameters that are either unknown or difficult to precisely measure include the normal and lateral cantilever force constants (particularly with microfabricated cantilevers), the tip height, the deflection sensor response, and the tip structure and composition at the tip-surface contact. We present an {ital in} {ital situ} experimental procedure to determine the response of a cantilever to lateral forces in terms of its normal force response. This procedure is quite general. It will work with any type of deflection sensor and does not require the knowledge or direct measurement of the lever dimensions or the tip height. In addition, the shape of the tip apex can be determined. We also discuss a number of specific issues related to force and friction measurements using optical lever deflection sensing. We present experimental results on the lateral force response of commercially available V-shaped cantilevers. Our results are consistent with estimates of lever mechanical properties using continuum elasticity theory. {copyright} {ital 1996 American Institute of Physics.}

  12. Resultant of Forces (Addition of vectors)

    NSDL National Science Digital Library

    Walter Fendt

    The representation is a java applet demonstrating the combination of multiple force vectors on a body into a single resultant force vector. The user can vary the number of single forces, change the sizes and directions of these forces and determine the total force exerted on the body.

  13. U.S.Air Force Advanced Power

    E-print Network

    U.S.Air Force Advanced Power Technology Office (APTO) U.S.Air Force Advanced Power Technology - Electric Drive U.S.Air Force Advanced PowerTechnology Office Our Customers TheWarfighter Homeland Defense of technological developments. U.S.Air Force Advanced PowerTechnology Office "Center of Excellence" for Air Force

  14. International women's magazines in China: Global and local perspectives

    Microsoft Academic Search

    Kavita Karan; Yang Feng

    2009-01-01

    Unlike other global media products that are imported from overseas, international women's magazines in China are published via licensing agreements or joint ventures with local companies. These ownership patterns allow local editions of international women's magazines to negotiate the tensions and contradictions between the global players and local publishers. Given the influence of cultural and commercial forces in different economic

  15. International Education Hubs: Collaboration for Competitiveness and Sustainability

    ERIC Educational Resources Information Center

    Knight, Jane

    2014-01-01

    This chapter focuses on the development of education hubs, a recent phenomenon in international higher education. Three models of hubs are examined in relation to the forces, risks, and opportunities of globalization and how local and international collaborations are essential for both global competitiveness and sustainability.

  16. Internal wave excitation by vertically-oscillating bodies

    E-print Network

    Flynn, Morris R.

    Internal wave excitation by vertically-oscillating bodies Morris R. Flynn , Kristjan Onu & Bruce R Internal gravity waves (IGW) are ubiquitous features of stably-stratified flow. Two types of IGW://www.taylor.math.ualberta.ca/bruce/ ­ p.2/38 #12;IGW in the environment Mountain Wave radiation Wind Wave breaking Drag force Atmosphere

  17. Direct detection of intermolecular forces by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Skulason, Hjalti

    The phenomenon of adhesion appears in various applications of everyday life, ranging from PostIt Notes(TM) and Scotch Tape(TM), to the assembly of aircraft and space shuttles. However, adhesion on the molecular scale is fundamentally different from the adhesion that we experience in the macroscopic world. While macroscopic objects require special adhesives or glues to bind them together, microscale and nanoscale objects and molecules commonly have a high affinity to adhere to each other. A detailed description of intermolecular forces is therefore of key importance in order to understand a wide range of phenomena, ranging from macroscopic properties of materials to molecular recognition. Two key aspects of the atomic force microscope (AFM), namely its sensitivity to sub-nanoNewton forces and its very sharp probe, offer the opportunity to measure interactions between very small numbers of molecules. Through chemical tailoring of both substrates and AFM probes with self-assembled monolayers (SAMs), measurements of forces acting between specific functional groups can be measured. Furthermore, the force required to rupture a single chemical bond can be obtained by a detailed analysis of the histograms of rupture forces. A new model was derived to examine the relationship between the various experimental variables and the shape of histograms of rupture forces when discrete chemical bonds are formed between the AFM probe and substrate. Calculations based on the model demonstrated that in measurements aimed at detecting single bond rupture forces, strict limits are put on the size of the AFM probe, the relative magnitude of the interfacial energies and the bond formation probability. These results were used in two experimental systems where the single bond rupture force was successfully measured: (i) the abstraction of a single Au-S complex from an Au coated AFM probe; and (ii) the rupture of a single charge-transfer (CT) complex between tetramethylphenylenediamine (TMPD) and tetracyanoquinodimethane (TCNQ). Measurements involving only one molecule at a time were conducted using polymer chains chemically grafted to the AFM probe and substrate. In these measurements, the effect of the solvent on the elasticity of the poly-ethylene-propylene oligomers was directly observed in the force-elongation profile.

  18. Chemical force microscopy of microcontact-printed self-assembled monolayers by pulsed-force-mode atomic force microscopy

    Microsoft Academic Search

    Yoh Okabe; Manabu Furugori; Yuki Tani; Uichi Akiba; Masamichi Fujihira

    2000-01-01

    A novel chemically sensitive imaging mode based on adhesive force detection by previously developed pulsed-force-mode atomic force microscopy (PFM-AFM) is presented. PFM-AFM enables simultaneous imaging of surface topography and adhesive force between tip and sample surfaces. Since the adhesive forces are directly related to interaction between chemical functional groups on tip and sample surfaces, we combined the adhesive force mapping

  19. Physlet Force Concept Inventory: Gravity

    NSDL National Science Digital Library

    Wolfgang Christian

    A boy throws a steel ball straight up. Consider the motion of the ball only after it has left the boy's hand but before it touches the ground, and assume that the forces exerted by the air are negligible.

  20. Investigating Forces: Balloon car activity

    NSDL National Science Digital Library

    This is a guided inquiry-based lab that investigates forces exerted on a group of student-designed and engineered "balloon cars". Each group of students is then challenged to build a "balloon car" that travels a maximum distance.

  1. Extra force in brane worlds

    NASA Astrophysics Data System (ADS)

    Youm, Donam

    2000-10-01

    By carefully analyzing the geodesic motion of a test particle in the bulk of brane worlds, we identify an extra force which is recognized in a spacetime of one lower dimension as a nongravitational force acting on the particle. Such extra force acts on the particle in such a way that the conventional particle mechanics in one lower dimension is violated, thereby hinting at the higher-dimensional origin of embedded spacetime in the brane world scenario. We obtain the explicit equations describing the motion of the bulk test particle as observed in one lower dimension for general gravitating configurations in brane worlds and identify the extra nongravitational force acting on the particle measured in one lower dimension.

  2. Molecular Force Spectroscopy on Cells

    NASA Astrophysics Data System (ADS)

    Liu, Baoyu; Chen, Wei; Zhu, Cheng

    2015-04-01

    Molecular force spectroscopy has become a powerful tool to study how mechanics regulates biology, especially the mechanical regulation of molecular interactions and its impact on cellular functions. This force-driven methodology has uncovered a wealth of new information of the physical chemistry of molecular bonds for various biological systems. The new concepts, qualitative and quantitative measures describing bond behavior under force, and structural bases underlying these phenomena have substantially advanced our fundamental understanding of the inner workings of biological systems from the nanoscale (molecule) to the microscale (cell), elucidated basic molecular mechanisms of a wide range of important biological processes, and provided opportunities for engineering applications. Here, we review major force spectroscopic assays, conceptual developments of mechanically regulated kinetics of molecular interactions, and their biological relevance. We also present current challenges and highlight future directions.

  3. Models agree on forced response pattern of precipitation and temperature extremes

    NASA Astrophysics Data System (ADS)

    Fischer, Erich; Sedlacek, Jan; Hawkins, Ed; Knutti, Reto

    2015-04-01

    Model projections of heavy precipitation and temperature extremes include large uncertainties. We demonstrate that the disagreement between individual simulations primarily arises from internal variability, whereas models agree remarkably well on the forced signal, the change in the absence of internal variability. Agreement is high on the spatial pattern of the forced heavy precipitation response showing an intensification over most land regions, in particular Eurasia and North America. The forced response of heavy precipitation is even more robust than that of annual mean precipitation. Likewise, models agree on the forced response pattern of hot extremes showing the greatest intensification over mid-latitudinal land regions. Thus, confidence in the forced changes of temperature and precipitation extremes in response to a certain warming is high. Although in reality internal variability will be superimposed on that pattern, it is the forced response that determines the changes in temperature and precipitation extremes in a risk perspective. Reference: Fischer, E.M., J. Sedlá?ek, E. Hawkins and R. Knutti, 2014: Models agree on forced response pattern of precipitation and temperature extremes, Geophys. Res. Lett., 10.1002/2014GL062018.

  4. Thermomagnetic Force in Polyatomic Gases 

    E-print Network

    Larchez, M. E.; Adair, Thomas W.

    1971-01-01

    . Since then extensive investigations have been conducted on these field effects [now called Senftleben-Beenakker (SB}effects] in nu- merous gases. A comprehensive review and bib- liography of the experimental and theoretical work in this field can... in place were identical to those made without it. IV. DISCUSSION OF RESULTS The thermomagnetic-force effect reported here may be compared to the Senftleben-Beenakker (SB) effect. The force effect approaches a maxi- mum as a universal function of H...

  5. Forced motion near black holes

    SciTech Connect

    Gair, Jonathan R. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Flanagan, Eanna E. [Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853 (United States); Drasco, Steve [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-14476 Golm (Germany); Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 (United States); California Polytechnic State University, San Luis Obispo, California 93405 (United States); Hinderer, Tanja [Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 (United States); Babak, Stanislav [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-14476 Golm (Germany)

    2011-02-15

    We present two methods for integrating forced geodesic equations in the Kerr spacetime. The methods can accommodate arbitrary forces. As a test case, we compute inspirals caused by a simple drag force, mimicking motion in the presence of gas. We verify that both methods give the same results for this simple force. We find that drag generally causes eccentricity to increase throughout the inspiral. This is a relativistic effect qualitatively opposite to what is seen in gravitational-radiation-driven inspirals, and similar to what others have observed in hydrodynamic simulations of gaseous binaries. We provide an analytic explanation by deriving the leading order relativistic correction to the Newtonian dynamics. If observed, an increasing eccentricity would thus provide clear evidence that the inspiral was occurring in a nonvacuum environment. Our two methods are especially useful for evolving orbits in the adiabatic regime. Both use the method of osculating orbits, in which each point on the orbit is characterized by the parameters of the geodesic with the same instantaneous position and velocity. Both methods describe the orbit in terms of the geodesic energy, axial angular momentum, Carter constant, azimuthal phase, and two angular variables that increase monotonically and are relativistic generalizations of the eccentric anomaly. The two methods differ in their treatment of the orbital phases and the representation of the force. In the first method, the geodesic phase and phase constant are evolved together as a single orbital phase parameter, and the force is expressed in terms of its components on the Kinnersley orthonormal tetrad. In the second method, the phase constants of the geodesic motion are evolved separately and the force is expressed in terms of its Boyer-Lindquist components. This second approach is a direct generalization of earlier work by Pound and Poisson [A. Pound and E. Poisson, Phys. Rev. D 77, 044013 (2008).] for planar forces in a Schwarzschild background.

  6. Is Gravity an Entropic Force?

    E-print Network

    Shan Gao

    2011-07-16

    The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde's example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde's argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.

  7. Extending Bell's Model: How Force Transducer Stiffness Alters Measured Unbinding Forces and Kinetics of Molecular Complexes

    E-print Network

    Van Vliet, Krystyn J.

    Extending Bell's Model: How Force Transducer Stiffness Alters Measured Unbinding Forces Forced unbinding of complementary macromolecules such as ligand-receptor complexes can reveal energetic dissociation events, disparities in measured unbinding force FR among these methods lead to marked variation

  8. The Community College of the Air Force

    ERIC Educational Resources Information Center

    Kaapke, Lyle D.; Wojciechowske, William A.

    1977-01-01

    The Community College of the Air Force is unique as a postsecondary occupational education institution because it integrates Air Force technical education and civilian-related education into programs which are totally responsive to the Air Force community. (JG)

  9. The influence of catch trials on the consolidation of motor memory in force field adaptation tasks.

    PubMed

    Focke, Anne; Stockinger, Christian; Diepold, Christina; Taubert, Marco; Stein, Thorsten

    2013-01-01

    In computational neuroscience it is generally accepted that human motor memory contains neural representations of the physics of the musculoskeletal system and the objects in the environment. These representations are called "internal models". Force field studies, in which subjects have to adapt to dynamic perturbations induced by a robotic manipulandum, are an established tool to analyze the characteristics of such internal models. The aim of the current study was to investigate whether catch trials during force field learning could influence the consolidation of motor memory in more complex tasks. Thereby, the force field was more than double the force field of previous studies (35 N·s/m). Moreover, the arm of the subjects was not supported. A total of 46 subjects participated in this study and performed center-out movements at a robotic manipulandum in two different force fields. Two control groups learned force field A on day 1 and were retested in the same force field on day 3 (AA). Two test groups additionally learned an interfering force field B (= -A) on day 2 (ABA). The difference between the two test and control groups, respectively, was the absence (0%) or presence (19%) of catch trials, in which the force field was turned-off suddenly. The results showed consolidation of force field A on day 3 for both control groups. Test groups showed no consolidation of force field A (19% catch trials) and even poorer performance on day 3 (0% catch trials). In conclusion, it can be stated that catch trials seem to have a positive effect on the performance on day 3 but do not trigger a consolidation process as shown in previous studies that used a lower force field viscosity with supported arm. These findings indicate that the results of previous studies in which less complex tasks were analyzed, cannot be fully transferred to more complex tasks. Moreover, the effects of catch trials in these situations are insufficiently understood and further research is needed. PMID:23898319

  10. The influence of catch trials on the consolidation of motor memory in force field adaptation tasks

    PubMed Central

    Focke, Anne; Stockinger, Christian; Diepold, Christina; Taubert, Marco; Stein, Thorsten

    2013-01-01

    In computational neuroscience it is generally accepted that human motor memory contains neural representations of the physics of the musculoskeletal system and the objects in the environment. These representations are called “internal models”. Force field studies, in which subjects have to adapt to dynamic perturbations induced by a robotic manipulandum, are an established tool to analyze the characteristics of such internal models. The aim of the current study was to investigate whether catch trials during force field learning could influence the consolidation of motor memory in more complex tasks. Thereby, the force field was more than double the force field of previous studies (35 N·s/m). Moreover, the arm of the subjects was not supported. A total of 46 subjects participated in this study and performed center-out movements at a robotic manipulandum in two different force fields. Two control groups learned force field A on day 1 and were retested in the same force field on day 3 (AA). Two test groups additionally learned an interfering force field B (= ?A) on day 2 (ABA). The difference between the two test and control groups, respectively, was the absence (0%) or presence (19%) of catch trials, in which the force field was turned-off suddenly. The results showed consolidation of force field A on day 3 for both control groups. Test groups showed no consolidation of force field A (19% catch trials) and even poorer performance on day 3 (0% catch trials). In conclusion, it can be stated that catch trials seem to have a positive effect on the performance on day 3 but do not trigger a consolidation process as shown in previous studies that used a lower force field viscosity with supported arm. These findings indicate that the results of previous studies in which less complex tasks were analyzed, cannot be fully transferred to more complex tasks. Moreover, the effects of catch trials in these situations are insufficiently understood and further research is needed. PMID:23898319

  11. International Programs International Student and Advising Services

    E-print Network

    Escher, Christine

    supervisor or hiring manager, please submit to International Student Advising and Services (ISAS) and allow (print): Immediate Supervisor/Hiring Manager Contact Phone #: Immediate Supervisor/Hiring ManagerInternational Programs International Student and Advising Services Oregon State University

  12. GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1029/, Rapid generation of high-frequency internal waves beneath a

    E-print Network

    MacKinnon, Jennifer

    -frequency internal waves beneath a wind and wave forced oceanic surface mixed-layer Jeff A. Polton,1 Jerome A. Smith,1 Jennifer A. MacKinnon,1 and Andr´es E. Tejada-Mart´inez2 High-frequency internal waves generated-frequency internal waves in the stratified fluid below. The internal waves evolve such that their vector phase

  13. Resonant Generation of Internal Waves on a Model Continental Slope H. P. Zhang, B. King, and Harry L. Swinney

    E-print Network

    Texas at Austin. University of

    Resonant Generation of Internal Waves on a Model Continental Slope H. P. Zhang, B. King, and Harry that of internal waves. Fluid motion with a velocity an order of magnitude larger than that of the forcing occurs interior called internal waves. In a nonrotating stratified fluid (Coriolis parameter f 0), internal waves

  14. Sensorimotor memory and grip force control: does grip force anticipate a self-produced weight change when drinking with a straw from a cup?

    PubMed

    Nowak, Dennis A; Hermsdörfer, Joachim

    2003-11-01

    We examined whether self-generated weight changes are anticipated by adequate grip force adjustments when repeatedly lifting an instrumented manipulandum. Subjects lifted a cup filled with 500 mL of water prior to and following drinking two portions of water with a straw without touching it. One half of the subjects drank from and lifted an uncovered cup receiving constant visual information about its filling level and the other half of the subjects drank from a covered cup without such visual feedback. During the lifts immediately following the drinking procedures, grip force scaling was erroneously programmed for the heavier weight of the preceding lift as was obvious from an inadequately high rate of grip force development. Vision had only a minor influence on the rate of grip force increase. The influence of vision on the scaling of peak grip force was more pronounced. More accurate force scaling was obtained with an increasing number of lifts performed under each weight condition, indicating an ongoing force adjustment process probably based on sensory feedback. We conclude that self-generation of a change in the weight of an object to be lifted is not, in itself, sufficient to elicit a predictive grip force output. Rather, accurate feedback information associated with the self-generated weight change is essential to update internal models related to the mechanical object properties. This assumption was confirmed in pilot experiments; when subjects lifted the cup after having poured water from it, they accurately scaled their fingertip force to the self-produced weight change. Here, direct sensory feedback from the grasping fingers could signal the weight change and update internal models while pouring water from the cup. Our data support the hypothesis that the sensorimotor system planning and processing predictive fingertip force can operate independently of higher-level cognitive and perceptual systems. PMID:14656338

  15. Any time the magnitude of the force applied to a muscle exceeds that produced by the muscle, it will lengthen.

    E-print Network

    Lindstedt, Stan

    Ritchie (1). They connected two stationary cycle ergometers back-to-back with a single chain-moving pedals. Because the internal resistance of the device was low, the same force was being applied by both that a tiny female resisting the movement of the pedals (in this case, Bigland) could easily exert more force

  16. Evaluation of the Second Global Soil Wetness Project soil moisture simulations: 2. Sensitivity to external meteorological forcing

    Microsoft Academic Search

    Zhichang Guo; Paul A. Dirmeyer; Zeng-Zhen Hu; Xiang Gao; Mei Zhao

    2006-01-01

    The quality of meteorological forcing data has a strong impact on the simulation of the land surface component of the hydrological cycle. In this paper, the sensitivity of soil moisture simulations to combinations of different external meteorological forcing and vegetation parameters supplied by the International Satellite Land-Surface Climatology Project (ISLSCP) Initiative II (II2) as part of the Second Global Soil

  17. Control of Grasping Force by Detecting Stick\\/Slip Distribution at the Curved Surface of an Elastic Finger

    Microsoft Academic Search

    Takashi Maeno; Shinichi Hiromitsu; Takashi Kawai

    2000-01-01

    A method for controlling the grasping force when an object is grasped by artificial elastic fingers is proposed. First, the relationship between the stick area and the internal strain distribution of the finger is calculated using FE (finite element) analysis. Based on this relationship, a method is proposed for controlling the grasping force by decreasing the increasing ratio of the

  18. Method of Calibrating a Force Balance

    NASA Technical Reports Server (NTRS)

    Parker, Peter A. (Inventor); Rhew, Ray D. (Inventor); Johnson, Thomas H. (Inventor); Landman, Drew (Inventor)

    2015-01-01

    A calibration system and method utilizes acceleration of a mass to generate a force on the mass. An expected value of the force is calculated based on the magnitude and acceleration of the mass. A fixture is utilized to mount the mass to a force balance, and the force balance is calibrated to provide a reading consistent with the expected force determined for a given acceleration. The acceleration can be varied to provide different expected forces, and the force balance can be calibrated for different applied forces. The acceleration may result from linear acceleration of the mass or rotational movement of the mass.

  19. Integration of contractile forces during tissue invagination

    E-print Network

    Martin, Adam C.

    Contractile forces generated by the actomyosin cytoskeleton within individual cells collectively generate tissue-level force during epithelial morphogenesis. During Drosophila mesoderm invagination, pulsed actomyosin ...

  20. International migration: a global challenge.

    PubMed

    Martin, P; Widgren, J

    1996-04-01

    Trends in international migration are presented in this multiregional analysis. Seven of the world's wealthiest countries have about 33% of the world's migrant population, but under 16% of the total world population. Population growth in these countries is substantially affected by the migrant population. The migration challenge is external and internal. The external challenge is to balance the need for foreign labor and the commitment to human rights for those migrants seeking economic opportunity and political freedom. The internal challenge is to assure the social adjustment of immigrants and their children and to integrate them into society as citizens and future leaders. Why people cross national borders and how migration flows are likely to evolve over the next decades are explained. This report also presents some ways that countries can manage migration or reduce the pressures which force people to migrate. It is recommended that receiving nations control immigration by accelerating global economic growth and reducing wars and human rights violations. This report examines the impact of immigration on international trade, aid, and direct intervention policies. Although migration is one of the most important international economic issues, it is not coordinated by an international group. The European experience indicates that it is not easy to secure international cooperation on issues that affect national sovereignty. It is suggested that countries desiring control of their borders should remember that most people never cross national borders to live or work in another country, that 50% of the world's migrants move among developing countries, and that countries can shift from being emigration to immigration countries. The author suggests that sustained reductions in migration pressure are a better alternative than the "quick fixes" that may invite the very much feared mass and unpredictable movements. PMID:12320315

  1. SI traceable calibration of an instrumented indentation sensor spring constant using electrostatic force.

    PubMed

    Chung, Koo-Hyun; Scholz, Stefan; Shaw, Gordon A; Kramar, John A; Pratt, Jon R

    2008-09-01

    We present a measurement scheme for creating reference electrostatic forces that are traceable to the International System of Units. This scheme yields reference forces suitable for calibrating the force sensitivity of instrumented indentation machines and atomic force microscopes. Forces between 10 and 200 muN were created and expressed in terms of the voltage, length, and capacitance between a pair of interacting electrodes. The electrodes comprised an electrically conductive sphere mounted as a tip on an instrumented indentation sensor, and a planar counterelectrode fixed to a sample stage in close proximity to the sphere. For comparison, we applied mechanical forces of similar magnitudes, first using deadweights and then using a reference force sensor. The deflection of the sensor due to the various applied forces was measured using an interferometer. A spring constant for the sensor was computed from the observed records of force versus displacement. Each procedure yielded a relative standard uncertainty of approximately 1%; however, the electrostatic technique is scalable and could provide traceable reference forces as small as a few hundred piconewtons, a range far below anything yet achieved using deadweights. PMID:19044452

  2. Stationary Apparatus Would Apply Forces of Walking to Feet

    NASA Technical Reports Server (NTRS)

    Hauss, Jessica; Wood, John; Budinoff, Jason; Correia, Michael; Albrecht, Rudolf

    2006-01-01

    A proposed apparatus would apply controlled cyclic forces to both feet for the purpose of preventing the loss of bone density in a human subject whose bones are not subjected daily to the mechanical loads of normal activity in normal Earth gravitation. The apparatus was conceived for use by astronauts on long missions in outer space; it could also be used by bedridden patients on Earth, including patients too weak to generate the necessary forces by their own efforts. The apparatus (see figure) would be a modified version of a bicycle-like exercise machine, called the cycle ergometer with vibration isolation system (CEVIS), now aboard the International Space Station. Attached to each CEVIS pedal would be a computer-controlled stress/ vibration exciter connected to the heel portion of a special-purpose pedal. The user would wear custom shoes that would amount to standard bicycle shoes equipped with cleats for secure attachment of the balls of the feet to the special- purpose pedals. If possible, prior to use of the apparatus, the human subject would wear a portable network of recording accelerometers, while walking, jogging, and running. The information thus gathered would be fed to the computer, wherein it would be used to make the exciters apply forces and vibrations closely approximating the forces and vibrations experienced by that individual during normal exercise. It is anticipated that like the forces applied to bones during natural exercise, these artificial forces would stimulate the production of osteoblasts (bone-forming cells), as needed to prevent or retard loss of bone mass. In addition to helping to prevent deterioration of bones, the apparatus could be used in treating a person already suffering from osteoporosis. For this purpose, the magnitude of the applied forces could be reduced, if necessary, to a level at which weak hip and leg bones would still be stimulated to produce osteoblasts without exposing them to the full stresses of walking and thereby risking fracture.

  3. Match your sales force structure to your business life cycle.

    PubMed

    Zoltners, Andris A; Sinha, Prabhakant; Lorimer, Sally E

    2006-01-01

    Although companies devote considerable time and money to managing their sales forces, few focus much thought on how the structure of the sales force needs to change over the life cycle of a product or a business. However, the organization and goals of a sales operation have to evolve as businesses start up, grow, mature, and decline if a company wants to keep winning the race for customers. Specifically, firms must consider and alter four factors over time: the differing roles that internal salespeople and external selling partners should play, the size of the sales force, its degree of specialization, and how salespeople apportion their efforts among different customers, products, and activities. These variables are critical because they determine how quickly sales forces respond to market opportunities, they influence sales reps' performance, and they affect companies' revenues, costs, and profitability. In this article, the authors use timeseries data and cases to explain how, at each stage, firms can best tackle the relevant issues and get the most out of their sales forces. During start-up, smart companies focus on how big their sales staff should be and on whether they can depend upon selling partners. In the growth phase, they concentrate on getting the sales force's degree of specialization and size right. When businesses hit maturity, companies should better allocate existing resources and hire more general-purpose salespeople. Finally, as organizations go into decline, wise sales leaders reduce sales force size and use partners to keep the business afloat for as long as possible. PMID:16846191

  4. RESEARCH ARTICLE Schlieren measurements of internal waves in non-Boussinesq

    E-print Network

    Sutherland, Bruce

    RESEARCH ARTICLE Schlieren measurements of internal waves in non-Boussinesq fluids H. A. Clark Æ forcing in Boussinesq stratified fluids. Here we present measurements of internal waves generated the generation of internal gravity waves by a monochromatic source have been restricted to small amplitude

  5. 1 Copyright 2009 by ASME Proceedings of the ASME 2009 International Design Engineering Technical Conferences &

    E-print Network

    Williams II, Robert L.

    1 Copyright © 2009 by ASME Proceedings of the ASME 2009 International Design Engineering Technical goal of those models is to predict the internal and external forces during a regular walking cycle with internal variables in the robotic structure. The next sections give an overview of the simplified models

  6. Experimental observation of a strong mean flow induced by internal gravity waves Guilhem Bordes,1, a)

    E-print Network

    Paris-Sud XI, Université de

    Experimental observation of a strong mean flow induced by internal gravity waves Guilhem Bordes,1 mean flow induced by internal gravity waves. A wave beam is forced at the lateral boundary of a tank fluids support the existence of anisotropic dispersive waves, called internal gravity waves, which play

  7. Transparency International

    NSDL National Science Digital Library

    With headquarters in Berlin, Transparency International (TI) is an international non-governmental organization dedicated to combating corruption in its many guises across the world. As their website notes, TI â??focuses on prevention and reforming systemsâ?. With a well-designed and rather elegant homepage, visitors will find much to admire here. The top of the homepage provides access to their â??In Focusâ? feature, which draws attention to some of TIâ??s more recent work, such as the Global Corruption Report for 2006. Below this feature, visitors will find links to recent news stories dealing with corruption, such as the recent Kenyan government scandal and anti-corruption initiatives in West Africa. Visitors can also utilize the â??Corruption: Learn About itâ? area, as it contains FAQs on corruption, and a number of indices, such as the global corruption barometer as well as a number of regional surveys. For pragmatic material, one need to look no further than their â??How to Fight Corruptionâ? section, which contains an anti-corruption handbook and a set of business principles for countering bribery.

  8. ACCION International

    NSDL National Science Digital Library

    Part of the ongoing debate about the process of globalization throughout both the developed and developing world is that a good deal of the world's population continues to grow poorer and poorer while a number of international transnational corporations continue to increase their share of the world's assets. There have been a number of efforts to combat poverty in the developing world, including the highly publicized and generally well-received efforts of the Grameen Bank in Bangladesh. One such nonprofit program that has successfully been transplanted from the developing world to the developed world is the ACCION International program of microlending. On its homepage, visitors can learn about the organization's various programs designed to raise people out of poverty through microlending, and also read some key statistics behind its work. For those looking for more detailed information, there is also a publications area, where visitors may download works on topic such as the sustainability of such programs and various "how to" manuals for microentrepreneurs. Many of the publications are available at no charge, and a number of them are also available in Spanish. Finally, visitors may also sign up to receive the ACCION e-News as well.

  9. Internal Audit Who is Internal Audit?

    E-print Network

    Michel, Robert G.

    Process? Research audit area Determine criteria Notify auditee Assess risk Plan audit Refine scopeInternal Audit Who is Internal Audit? Internal Auditors (UConn employees) and external experts who augment internal audit capabilities External auditors include Federal, State and independent auditors

  10. INTERNATIONAL STUDENT SURVEY INTERNATIONAL STUDENT SURVEY

    E-print Network

    INTERNATIONAL STUDENT SURVEY OCT 2010 1 SO L I D U MPE- internati- ona l s INTERNATIONAL STUDENT SURVEY SUMMARY AND RESULTS OCTOBER 2010 au AARHUS UNIVERSITET #12;Aarhus universitet International Centre;INTERNATIONAL STUDENT SURVEY OCT 2010 3 Introduction Survey Objectives

  11. Quantitative force measurements with intermodulation atomic force microscopy

    Microsoft Academic Search

    Daniel Platz; Daniel Forchheimer; Carsten Hutter; Erik Tholén; David Haviland

    2011-01-01

    Dynamic atomic force microscopy (dynamic AFM) is a key tool for surface characterization on the nanoscale. Operation close to a cantilever resonance increases sensitivity and allows for the measurement of the phase of the cantilever response. This phase is traditionally interpreted as a measure of the energy dissipation due to the tip-sample interaction. However, a full understanding of dissipative processes

  12. Measured forces and displacements of integrated force arrays

    Microsoft Academic Search

    Scott Goodwin-Johansson; Stephen M. Bobbio; Charles Bartlett; Nadeem Eleyan; James Jacobson; Joseph Mancusi; Lindsey Yadon; Christian Ball; Thomas D. Dubois; William Palmer; David Vellenga; Farid M. Tranjan

    1995-01-01

    IFAs are MEMS actuators which are powered by the electrostatic forces between the plates of many microscopic deformable capacitors arranged in monolithic arrays. IFAs are fabricated using standard techniques of VLSI electronics. The IFAs reported here resemble thin, flexible plastic membranes 10 mm long and either 1 or 3 mm wide, which contain from 75,000 to 200,000 cells. They are

  13. The Forces Behind Cell Movement

    PubMed Central

    Ananthakrishnan, Revathi; Ehrlicher, Allen

    2007-01-01

    Cell movement is a complex phenomenon primarily driven by the actin network beneath the cell membrane, and can be divided into three general components: protrusion of the leading edge of the cell, adhesion of the leading edge and deadhesion at the cell body and rear, and cytoskeletal contraction to pull the cell forward. Each of these steps is driven by physical forces generated by unique segments of the cytoskeleton. This review examines the specific physics underlying these phases of cell movement and the origins of the forces that drive locomotion. PMID:17589565

  14. LABORATORY I ELECTRIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    LABORATORY I ELECTRIC FIELDS AND FORCES Lab I - 1 The most fundamental forces are characterized as "action-at-a-distance". This means that an object can exert a force on another object that is not in contact with it. You have already learned about the gravitational force, which is of this type. You

  15. Force and motion Science teaching unit

    E-print Network

    Berzins, M.

    Force and motion Science teaching unit #12;Disclaimer The Department for Children, Schools and motion #12;#12;© Crown copyright 2008 1The National Strategies | Secondary Force and motion 00094-2008DVD-EN Contents Force and motion 3 Lift-off activity: Remember forces? 7 Lesson 1: Identifying and representing

  16. Titan Tusk Force Student Engagement Report

    E-print Network

    de Lijser, Peter

    Titan Tusk Force Student Engagement Report FY 2008-2009 Mission Statement The mission of Titan Tusk Force is to develop a strong sense of campus unity, pride and identity with CSUF. Titan Tusk Force, Incorporated here at California State University, Fullerton. Program Overview Titan Tusk Force (TTF) functions

  17. Titan Tusk Force Student Engagement Report

    E-print Network

    de Lijser, Peter

    Titan Tusk Force Student Engagement Report FY 2009-2010 Mission Statement The mission of Titan Tusk Force is to develop a strong sense of campus unity, pride and identity with CSUF. Titan Tusk Force, Incorporated here at California State University, Fullerton. Program Overview Titan Tusk Force (TTF) functions

  18. Titan Tusk Force Student Engagement Report

    E-print Network

    de Lijser, Peter

    Titan Tusk Force Student Engagement Report FY 2011-2012 Mission Statement The mission of Titan Tusk Force is to develop a strong sense of campus unity, pride and identity with CSUF. Titan Tusk Force, Incorporated here at California State University, Fullerton. Program Overview Titan Tusk Force (TTF) functions

  19. Titan Tusk Force Student Engagement Report

    E-print Network

    de Lijser, Peter

    Titan Tusk Force Student Engagement Report FY 2010-2011 Mission Statement The mission of Titan Tusk Force is to develop a strong sense of campus unity, pride and identity with CSUF. Titan Tusk Force, Incorporated here at California State University, Fullerton. Program Overview Titan Tusk Force (TTF) functions

  20. The effect of occlusal forces on restorations.

    PubMed

    Larson, Thomas D

    2014-09-01

    This review will focus on the effect occlusal forces, both normal masticatory force and paranormal bruxing and clenching force, have on various restorative materials and their interaction with the teeth through a variety of bonding mechanisms. Salient physical properties of each of the materials will be reviewed, as well as the effect occlusal force has on restoration durability. PMID:25318197

  1. The effect of occlusal forces on restorations.

    PubMed

    Larson, Thomas D

    2012-01-01

    This review will focus on the effect occlusal forces, both normal masticatory force and paranormal bruxing and clenching force, have on various restorative materials and their interaction with the teeth through a variety of bonding mechanisms. Salient physical properties of each of the materials will be reviewed, as well as the effect occlusal force has on restoration durability. PMID:23346657

  2. America's Changing Work Force: Statistics in Brief.

    ERIC Educational Resources Information Center

    American Association of Retired Persons, Washington, DC.

    This booklet provides information about the demographics of the changing work force. It offers an at-a-glance profile of workers age 45 and older and considers likely changes in the work force of the future. The document includes topics such as the composition of the work force of today and tomorrow by age and sex, labor force participation rates,…

  3. Climate Forcings in the Industrial Era

    Microsoft Academic Search

    James E. Hansen; Makiko Sato; Andrew Lacis; Reto Ruedy; Ina Tegen; Elaine Matthews

    1998-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence

  4. Probing protein-protein interactions by dynamic force correlated spectroscopy (FCS)

    E-print Network

    V. Barsegov; D. Thirumalai

    2005-09-05

    We develop a formalism for single molecule dynamic force spectroscopy to map the energy landscape of protein-protein complex ($P_1$$P_2$). The joint distribution $P(\\tau_1,\\tau_2)$ of unbinding lifetimes $\\tau_1$ and $\\tau_2$ measurable in a compression-tension cycle, which accounts for the internal relaxation dynamics of the proteins under tension, shows that the histogram of $\\tau_1$ is not Poissonian. The theory is applied to the forced unbinding of protein $P_1$, modeled as a wormlike chain, from $P_1$$P_2$. We propose a new class of experiments which can resolve the effect of internal protein dynamics on the unbinding lifetimes.

  5. Population commission discusses international migration.

    PubMed

    1997-01-01

    At the 30th session of the Commission on Population and Development during February 24-28, 1997, international migration was the main topic, with special linkages between migration and development and on gender issues and the family. New and emerging issues were also considered. Members stressed the need for more reliable data on migration, the direction of migrants flows, and the characteristics of migrants. The Commission requested a task force on basic social services to hold a technical symposium of experts on international migration in 1998. Its chair, Dr. Nafis Sadik, said that migration issues should based on the reality of choice not on coercive measures or quotas. Almost half of the migrants globally are women. The Commission was given a new impetus by the International Conference on Population and Development held at Cairo in 1994. Migration pressures intensified in the second half of the 1980s and in the early 1990s, creating areas of concern: the negative impact of short-term migration on working conditions in host countries; migration pressures emanating from climatic change; the protection of migrant women and their children; the right of receiving countries to regulate access to their territory; the adverse consequences of forced migration; the situation of persons whose asylum claims have been rejected; the trafficking in women and children, prostitution and coercive adoption; and the sudden and massive arrival of refugees in need of international protection. The 1998 session of the Commission will feature the theme of health and mortality, with special emphasis on the linkages between health and development and on gender and age. PMID:12292475

  6. Role of uterine forces in intrauterine device embedment, perforation, and expulsion

    PubMed Central

    Goldstuck, Norman D; Wildemeersch, Dirk

    2014-01-01

    Background The purpose of this study was to examine factors that could help reduce primary perforation during insertion of a framed intrauterine device (IUD) and to determine factors that contribute in generating enough uterine muscle force to cause embedment and secondary perforation of an IUD. The objective was also to evaluate the main underlying mechanism of IUD expulsion. Methods We compared known IUD insertion forces for “framed” devices with known perforation forces in vitro (hysterectomy specimens) and known IUD removal forces and calculated a range of possible intrauterine forces using pressure and surface area. These were compared with known perforation forces. Results IUD insertion forces range from 1.5 N to 6.5 N. Removal forces range from 1 N to 5.8 N and fracture forces from 8.7 N to 30 N depending upon device. Measured perforation forces are from 20 N to 54 N, and calculations show the uterus is capable of generating up to 50 N of myometrial force depending on internal pressure and surface area. Conclusion Primary perforation with conventional framed IUDs may occur if the insertion pressure exceeds the perforation resistance of the uterine fundus. This is more likely to occur if the front end of the inserter/IUD is narrow, the passage through the cervix is difficult, and the procedure is complex. IUD embedment and secondary perforation and IUD expulsion may be due to imbalance between the size of the IUD and that of the uterine cavity, causing production of asymmetrical uterine forces. The uterine muscle seems capable of generating enough force to cause an IUD to perforate the myometrium provided it is applied asymmetrically. A physical theory for IUD expulsion and secondary IUD perforation is given. PMID:25143756

  7. Force and Motion: Newton's Third Law

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2006-11-01

    This Science Object is the last of four Science Objects in the Force and Motion SciPack. It provides a conceptual and real-world understanding of Newton's Third Law of Motion, addressing common misconceptions associated with this law. Whenever one object exerts a force on another, an equal amount of force is exerted back on it. These equal and opposite forces are exerted simultaneously on the objects involved. Learning Outcomes:? Explain that when object A exerts a force on object B, object B exerts an equal and opposite force back on object A, regardless of the masses or motion of either object.? Identify the force that B applies on A, given a force that A applies on B.? Recognize that these forces are exerted simultaneously.? Apply this concept in a variety of situations. ? Use Newton's third law to explain how an inanimate object can exert a force on another object.

  8. Climate forcings of past droughts in the Czech Lands

    NASA Astrophysics Data System (ADS)

    Mikšovský, Ji?í; Trnka, Miroslav; Brázdil, Rudolf

    2015-04-01

    Frequency and intensity of local droughts is governed by a complex interaction of diverse processes, originating from internal dynamics of the climate system as well as its responses to external forcings. Separating and quantifying the effects of individual drought-inducing agents is a nontrivial task, often approached via statistical methods. In this presentation, we employ multiple linear regression to identify components attributable to various forcing factors, both external (solar irradiance, volcanic activity, anthropogenic greenhouse gases and aerosols) and internal (NAO, ENSO, AMO), in the monthly series of selected drought indices (PDSI, Z-index, SPI, SPEI) calculated for the territory of the recent Czech Republic during the 1883-2010 period. Moving block bootstrap is used for evaluation of the statistical significance of the results. Our analysis, carried out for drought index series characterizing a country-wide average as well as ten individual locations, suggests presence of a distinct component correlated with anthropogenic forcing (driven largely by the increasing concentrations of greenhouse gases) in the temperature-sensitive drought indices (PDSI, Z-index, SPEI). There are also indications of an influence of major volcanic eruptions in some of the Czech drought series, whereas variations of solar activity do not seem to leave a significant imprint. Of the major oscillatory modes in the climate system, North Atlantic Oscillation can be linked to a relatively strong component in most of the drought characteristics. Effects of ENSO, while generally weaker and scattered, are also detectable. No significant relation to Atlantic Multidecadal Oscillation phase was found.

  9. Mesoscale Eddy - Internal Wave Coupling:

    NASA Astrophysics Data System (ADS)

    Polzin, K. L.

    2012-12-01

    The issue of internal wave--mesoscale eddy interactions is revisited. Direct estimates of energy transfer from the Local Dynamics Experiment of the PolyMode field program (Polzin, 2010 JPO) return viscosity estimates of ? h \\cong 50 m2 s-1 and ? v + (f2)/(N^2) Kh \\cong 2.5×10-3 m2 s-1. These estimates indicate that mesoscale eddy-internal wave interactions may play an O(1) role in the mesoscale eddy energy budget as dissipation and the internal wave budget as a source. Radiation balance equation formulations for this coupling (Müller 1976, JFM) are examined. In these formulations permanent transfer of energy and internal wave pseudomomentum for mesoscale eddy potential vorticity is enabled by nonlinearity in the wavefield. Revision of radiation balance equation formulations to account for non-local effects returns predictions of ? h \\cong 50-100 m2 s-1 and ? v + (f2)/(N^2) Kh \\cong -1×10-3 to 4×10-3 m2 s-1. The prediction for the effective vertical viscosity is sensitive to how internal wave energy is distributed in the spectral domain with negative values appropriate to the Garrett and Munk spectrum and positive values appropriate to the background spectrum in the LDE area. Geographic scalings in terms of latitude, stratification and mesoscale eddy variability will be described. The process described here is best interpreted as an amplifier of a pre-existing or externally forced finite amplitude wavefield rather than the spontaneous imbalance of a linear field. Energy, pseudomomentum and vorticity can be transfered from the slow manifold (geostrophically balanced motions) to the fast manifold (internal gravity waves) via linear wave propagation in asymmetric background flows, but that transfer is reversible. The permanent transfer is accomplished by nonlinearity on the fast manifold.

  10. Good Research Practices for Comparative Effectiveness Research: Approaches to Mitigate Bias and Confounding in the Design of Nonrandomized Studies of Treatment Effects Using Secondary Data Sources: The International Society for Pharmacoeconomics and Outcomes Research Good Research Practices for Retrospective Database Analysis Task Force Report—Part II

    Microsoft Academic Search

    Emily Cox; Bradley C. Martin; Tjeerd Van Staa; Edeltraut Garbe; Uwe Siebert; Michael L. Johnson

    2009-01-01

    ObjectivesThe goal of comparative effectiveness analysis is to examine the relationship between two variables, treatment, or exposure and effectiveness or outcome. Unlike data obtained through randomized controlled trials, researchers face greater challenges with causal inference with observational studies. Recognizing these challenges, a task force was formed to develop a guidance document on methodological approaches to addresses these biases.

  11. Understanding how uncertainty in the forcing irradiances impacts simulations of snow

    NASA Astrophysics Data System (ADS)

    Lapo, Karl E.

    Snowmelt in mountains is an important part of the water and energy cycles and provides water for 1/6th of the world's population. The downwelling irradiances are the primary drivers of this melt, however, they are rarely observed. The use of estimated irradiances, few observations, lack of evaluation of alternative sources of data, and the unique climate of mountain environments all lead to substantial uncertainties in the radiative fluxes used to force simulations of snow. The net irradiance of snow is determined by external forcing irradiances, the downwelling irradiances, and by the upwelling irradiances, which are functions of the internal model feedbacks. Errors in the forcing irradiances can be masked by errors in the internal processes that control the outgoing irradiances. The impact of uncertainties in the forcing irradiances for simulations of snow is evaluated in a series of idealized modeling experiment that split into two parts: 1) understanding errors in the forcing irradiances alone and 2) understanding the feedback and compensation between errors in the forcing irradiances and the internal processes that control the outgoing irradiances. In the forcing irradiances, it is shown that longwave biases of magnitude greater than 20 Wm-2 and shortwave biases of magnitude greater than 40 Wm-2, typical of methods for estimating irradiances in complex terrain, have substantial impacts on simulated snow water equivalent (SWE) and the simulated energy balance across a range of mountain climates. Random noise in the forcing irradiances has a negligible effect on modeled snowmelt and energy balance. The exception is warmer sites, which were found to be sensitive to nearly all errors in the forcing irradiances. The internal processes that control the outgoing fluxes can significantly impact the net irradiance of the snow. Two processes are explored: 1) albedo parameterization that controls the reflected shortwave irradiance and 2) the turbulence parameterization that controls the outgoing longwave irradiance through the surface temperature. Tuning of albedo parameters, an approach typically taken in modeling set-ups, can completely compensate for biases in the forcing irradiances when evaluating model performance using SWE. Varying turbulent flux parameters was found to have a much smaller impact on simulated snowmelt than albedo parameters---calling the role of the stability feedback into question. However, the surface temperature does depend strongly on the turbulence scheme selected. Finally, the application of these results is shown for a variety of mountain environments and methods. In general, the uncertainty in the albedo terms is larger than the uncertainty in the forcing irradiance terms. The structure of errors in the forcing irradiances is either uniform offsets that do not vary substantially throughout the year or shorter punctuated periods where the irradiance values are substantially different.

  12. Lorentz Force Accelerator Technology Investigated

    NASA Technical Reports Server (NTRS)

    Pencil, Eric J.; LaPointe, Michael R.; Arrington, Lynn A.; Kamhawi, Hani; Benson, Scott W.; Hoskins, W. Andrew

    2004-01-01

    The NASA Glenn Research Center is developing Lorenz force accelerators (LFAs) for a wide variety of space applications. These range from the precision control of formation-flying spacecraft to the primary propulsion system for very high power interplanetary spacecraft. The specific thruster technologies being addressed are pulsed plasma thrusters (PPT) and magnetoplasmadynamic (MPD) thrusters.

  13. 8, 50915135, 2008 Radiative forcing

    E-print Network

    Paris-Sud XI, Université de

    on the NOx removal efficiency from the aircraft emission regions by large scale transport. 1 IntroductionACPD 8, 5091­5135, 2008 Radiative forcing from particle emissions by future supersonic aircraft G from particle emissions by future supersonic aircraft G. Pitari 1 , D. Iachetti 1 , E. Mancini 1 , V

  14. Electromagnetic forces in photonic crystals

    Microsoft Academic Search

    M. I. Antonoyiannakis; J. B. Pendry

    1999-01-01

    We have developed a general methodology for computing electromagnetic (EM) fields and forces in matter, based on solving the macroscopic Maxwell's equations numerically in real space and adopting the time-averaged Maxwell stress tensor formalism. We can treat both dielectric and metallic systems characterized by a local frequency-dependent dielectric function, and of any size and geometry in principle. In this paper,

  15. Dynamic atomic force microscopy methods

    Microsoft Academic Search

    Ricardo Garc??a; Rubén Pérez

    2002-01-01

    In this report we review the fundamentals, applications and future tendencies of dynamic atomic force microscopy (AFM) methods. Our focus is on understanding why the changes observed in the dynamic properties of a vibrating tip that interacts with a surface make possible to obtain molecular resolution images of membrane proteins in aqueous solutions or to resolve atomic-scale surface defects in

  16. Forces Seeking to Control Education

    ERIC Educational Resources Information Center

    Male, George A.

    1977-01-01

    It is very difficult to know who controls such educational agencies as the home, television, the churches, youth groups, and factories. Control of the schools shifts a little bit daily among such forces as social class, American business, the sexes, teachers, administrators, racial and ethnic groups, the citizenry, the courts, and the young. (JM)

  17. LABORATORY I FORCES AND EQUILIBRIUM

    E-print Network

    Minnesota, University of

    LABORATORY I FORCES AND EQUILIBRIUM Lab I -1 In biological systems, most objects of interest system. OBJECTIVES: After successfully completing this laboratory, you should be able to: · Determine and 6), and chapter 15 (section 4). It is likely that you will be doing some of these laboratory

  18. Electric and Magnetic Forces: Electromagnetism

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2008-10-30

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the last of three Science Objects in the Electric and Magnetic Forces SciPack.

  19. Force10 P10 Evaluation

    SciTech Connect

    Allen, J; Goldstone, R; Instenes, S; Lawver, B

    2007-06-08

    The lack of an acceptable intrusion monitoring solution limits the deployment of 10GE (10 Gigabit-per-second Ethernet) technology across the LLNL's unclassified network infrastructure. The desire to operate at 10GE motivates us to evaluate the functionality and performance of a 10GE intrusion monitoring solution, the Force10 P10.

  20. Security force effectiveness and technology

    Microsoft Academic Search

    Seaton

    1988-01-01

    No one would propose ineffective security forces. Applied technology always has, as its purpose, to increase effectiveness. Evidence exists, however, that poorly conceived or executed technological solutions can actually do more harm than good. The author argues for improved human factor considerations in physical security applied technology -- especially in the area of security console operations.

  1. Dynamic properties of force fields

    NASA Astrophysics Data System (ADS)

    Vitalini, F.; Mey, A. S. J. S.; Noé, F.; Keller, B. G.

    2015-02-01

    Molecular-dynamics simulations are increasingly used to study dynamic properties of biological systems. With this development, the ability of force fields to successfully predict relaxation timescales and the associated conformational exchange processes moves into focus. We assess to what extent the dynamic properties of model peptides (Ac-A-NHMe, Ac-V-NHMe, AVAVA, A10) differ when simulated with different force fields (AMBER ff99SB-ILDN, AMBER ff03, OPLS-AA/L, CHARMM27, and GROMOS43a1). The dynamic properties are extracted using Markov state models. For single-residue models (Ac-A-NHMe, Ac-V-NHMe), the slow conformational exchange processes are similar in all force fields, but the associated relaxation timescales differ by up to an order of magnitude. For the peptide systems, not only the relaxation timescales, but also the conformational exchange processes differ considerably across force fields. This finding calls the significance of dynamic interpretations of molecular-dynamics simulations into question.

  2. The forced turbulent wall jet

    Microsoft Academic Search

    Y. Katz; E. Horev; I. Wygnanski

    1992-01-01

    Results of an experimental and theoretical investigation of the effects of external 2D excitation on the plane turbulent wall jet are presented. Measurements of the streamwise component of velocity were made throughout the flow field for a variety of imposed frequencies and amplitudes. Two methods of forcing are used: one global, imposed on the entire jet by pressure fluctuations in

  3. Autoresonances with a damping force

    NASA Astrophysics Data System (ADS)

    Higaki, H.; Abo, Y.; Ito, K.; Okamoto, H.; Gomberoff, K.

    2015-06-01

    A single particle equation of motion for an autoresonance with a damping force is evaluated with simple numerical calculations. The obtained results show a clear deviation from the standard threshold amplitude dependence on the sweep rate. It tends to be a constant for the smaller sweep rate.

  4. Radiative Forcing from Carbonaceous Emissions

    NASA Astrophysics Data System (ADS)

    Fatima, H.; Sharma, O.; Upadhyaya, H.

    2011-12-01

    Black Carbon particles are emitted as primary particles from incomplete combustion process, such as fossil fuel and biomass burning. Organic carbon particles are released in the atmosphere both from primary emissions and secondary emission of gaseous compounds via condensation or gas phase oxidation of hydrocarbons. Black carbon aerosols absorb the solar radiation and induce positive forcing whereas organic matter aerosols reflect solar radiation and produce negative forcing. Direct radiative forcing at the top of the atmosphere (TOA) for black carbon aerosols from these two inventories comes out to be +0.33 W/m2 (GEIA) and +0.14 W/m2 (Bond et al. 2004) respectively. However, for organic matter aerosols, it is simulated as -0.44 W/m2 for GEIA and -0.11 W/m2 with the inventory of Bond et al. (2004). In the present study we have compared the annual global burden, aerosol optical depth (AOD) and direct radiative forcing of carbonaceous aerosols using two emission inventories with the help of the general circulation model of the Laboratoire de Météorologie Dynamique (LMD). Normalised difference plots clearly show that with GEIA inventory model simulates generally higher values carbonaceous aerosols which are far superior in some parts of the globe in comparison to the BOND emission inventory.

  5. Fifth force from fifth dimension

    Microsoft Academic Search

    P. S. Wesson; B. Mashhoon; H. Liu; W. N. Sajko

    1999-01-01

    If the world has more than four dimensions, but is still described by a theory like general relativity, there are (small) modifications to the conservation laws and dynamics. Using a novel coordinate system, we examine a 5D space and isolate a fifth force which in principle is measurable. In general, the detection of departures from conventional dynamics is a way

  6. Thought experiments on gravitational forces

    NASA Astrophysics Data System (ADS)

    Lynden-Bell, D.; Katz, Joseph

    2014-03-01

    Large contributions to the near closure of the Universe and to the acceleration of its expansion are due to the gravitation of components of the stress-energy tensor other than its mass density. To familiarize astronomers with the gravitation of these components we conduct thought experiments on gravity, analogous to the real experiments that our forebears conducted on electricity. By analogy to the forces due to electric currents we investigate the gravitational forces due to the flows of momentum, angular momentum and energy along a cylinder. Under tension the gravity of the cylinder decreases but the `closure' of the 3-space around it increases. When the cylinder carries a torque the flow of angular momentum along it leads to a novel helical interpretation of Levi-Civita's external metric and a novel relativistic effect. Energy currents give gravomagnetic effects in which parallel currents repel and antiparallel currents attract, though such effects must be added to those of static gravity. The gravity of beams of light give striking illustrations of these effects and a re-derivation of light bending via the gravity of the light itself. Faraday's experiments lead us to discuss lines of force of both gravomagnetic and gravity fields. A serious conundrum arises if Landau and Lifshitz's definition of gravitational force is adopted.

  7. Complex Forces Affect China's Biodiversity

    E-print Network

    CHAPTER 24 Complex Forces Affect China's Biodiversity Jianguo Liu Center for Systems Integration and Sustainability, Michigan State University, MI, USA INTRODUCTION Global biodiversity continues along a trajectory of the most biodiversity-rich countries in the world (Liu and Raven, 2010; Ministry of Environmental

  8. Nuclear Force from String Theory

    E-print Network

    Koji Hashimoto; Tadakatsu Sakai; Shigeki Sugimoto

    2010-03-09

    We compute nuclear force in a holographic model of QCD on the basis of a D4-D8 brane configuration in type IIA string theory. Repulsive core of nucleons is quite important in nuclear physics, but its origin has not been well-understood in strongly-coupled QCD. We find that string theory via gauge/string duality deduces this repulsive core at short distance between nucleons. Since baryons in the model are realized as solitons given by Yang-Mills instanton configuration on flavor D8-branes, ADHM construction of two instantons probes well the nucleon interaction at short scale, which provides the nuclear force quantitatively. We obtain, as well as a tensor force, a central force which is strongly repulsive as suggested in experiments and lattice results. In particular, the nucleon-nucleon potential V(r) (as a function of the distance) scales as 1/r^2, which is peculiar to the holographic model. We compare our results with one-boson exchange model using the nucleon-nucleon-meson coupling obtained in our previous paper (arXiv:0806.3122).

  9. Forced-Flow Evaporative Cooler

    NASA Technical Reports Server (NTRS)

    Ellis, Wilbert E.; Niggemann, Richard E.

    1987-01-01

    Evaporative cooler absorbs heat efficiently under unusual gravitational conditions by using centrifugal force and vapor vortexes to maintain good thermal contact between heat-transfer surface and vaporizable coolant. System useful for cooling electronic or other equipment under low gravity encountered in spacecraft or under multiple-gravity conditions frequently experienced in high-performance airplanes.

  10. Plotting shear-flow forces

    NASA Technical Reports Server (NTRS)

    Furuike, T.; Long, J. C.

    1979-01-01

    Structural analysts can use computer program to study shear-flow and in-plane forces characteristic of quadrilateral panels subjected to different loading conditions. Digital outputs are presented for engineers and management, with various options to allow bulk of data to be analyzed quickly.

  11. Intermolecular Forces for Polyatomic Molecules

    Microsoft Academic Search

    Taro Kihara

    1967-01-01

    Part I is a review of papers dealing with the convex-core potential (sometimes called the Kihara potential) of intermolecular forces, which is a useful mathematical model for the interaction between polyatomic molecules in gases. For molecular crystals electric multipoles of the molecules often play a decisive role in the crystal structures. This fact is demonstrated in Part II by use

  12. Force of an actin spring

    NASA Astrophysics Data System (ADS)

    Shin, Jennifer; Mahadevan, L.; Matsudaira, Paul

    2003-03-01

    The acrosomal process of the horseshoe crab sperm is a novel mechanochemical molecular spring that converts its elastic stain energy to mechanical work upon the chemical activation by Ca2+. Twisted and bent, the initial state of the acrosomal bundle features a high degree of complexity in its structure and the energy is believed to be stored in the highly strained actin filaments as an elastic potential energy. When activated, the bundle relaxes from the coil of the highly twisted and bent filaments to its straight conformation at a mean velocity of 15um/s. The mean extension velocity increases dramatically from 3um/s to 27um/s when temperature of the medium is changed from 9.6C to 32C (respective viscosities of 1.25-0.75cp), yet it exhibits a very weak dependence on changes in the medium viscosity (1cp-33cp). These experiments suggest that the uncoiling of the actin spring should be limited not by the viscosity of the medium but by the unlatching events of involved proteins at a molecular level. Unlike the viscosity-limited processes, where force is directly related to the rate of the reaction, a direct measurement is required to obtain the spring force of the acrosomal process. The extending acrosomal bundle is forced to push against a barrier and its elastic buckling response is analyzed to measure the force generated during the uncoiling.

  13. The Forced Soft Spring Equation

    ERIC Educational Resources Information Center

    Fay, T. H.

    2006-01-01

    Through numerical investigations, this paper studies examples of the forced Duffing type spring equation with [epsilon] negative. By performing trial-and-error numerical experiments, the existence is demonstrated of stability boundaries in the phase plane indicating initial conditions yielding bounded solutions. Subharmonic boundaries are…

  14. Effective Forces Between Colloidal Particles

    NASA Technical Reports Server (NTRS)

    Tehver, Riina; Banavar, Jayanth R.; Koplik, Joel

    1999-01-01

    Colloidal suspensions have proven to be excellent model systems for the study of condensed matter and its phase behavior. Many of the properties of colloidal suspensions can be investigated with a systematic variation of the characteristics of the systems and, in addition, the energy, length and time scales associated with them allow for experimental probing of otherwise inaccessible regimes. The latter property also makes colloidal systems vulnerable to external influences such as gravity. Experiments performed in micro-ravity by Chaikin and Russell have been invaluable in extracting the true behavior of the systems without an external field. Weitz and Pusey intend to use mixtures of colloidal particles with additives such as polymers to induce aggregation and form weak, tenuous, highly disordered fractal structures that would be stable in the absence of gravitational forces. When dispersed in a polarizable medium, colloidal particles can ionize, emitting counterions into the solution. The standard interaction potential in these charged colloidal suspensions was first obtained by Derjaguin, Landau, Verwey and Overbeek. The DLVO potential is obtained in the mean-field linearized Poisson-Boltzmann approximation and thus has limited applicability. For more precise calculations, we have used ab initio density functional theory. In our model, colloidal particles are charged hard spheres, the counterions are described by a continuum density field and the solvent is treated as a homogeneous medium with a specified dielectric constant. We calculate the effective forces between charged colloidal particles by integrating over the solvent and counterion degrees of freedom, taking into account the direct interactions between the particles as well as particle-counterion, counterion-counterion Coulomb, counterion entropic and correlation contributions. We obtain the effective interaction potential between charged colloidal particles in different configurations. We evaluate two- and three-body forces in the bulk as well as study the influence of soft walls. We qualitatively explain the effects of the walls on the forces and demonstrate that many-body effects are negligible in our system. With adjustments in the parameters, the DLVO pair-potential can describe the results quantitatively. Besides electrostatic interactions, entropic depletion effects that arise from (hard-core) exclusion play an important role in determining the behavior of multi-component colloidal suspensions. A standard theory for depletion forces is due to Asakura and Oosawa and is based on the ideal gas approximation. To go beyond this approximation, we have studied entropic forces in molecular dynamics simulations of systems of hard spheres (the effects of the solvent have been ignored). The effective depletion forces for these systems can be found either from equilibrium distribution functions or from direct momentum transfer calculations. Our results obtained by either method show qualitative differences from the Asakura-Oosawa forces, indicating a longer range, higher value at contact and most importantly a more complicated structure, comprising of several maxima and minima. Our calculations include the determination of effective forces between two spheres, a hard sphere and a wall, and the behavior of a hard sphere near a step-edge and a corner. We also demonstrate that such entropic forces do not necessarily satisfy pairwise additivity.

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

    NASA Astrophysics Data System (ADS)

    Güntürkün, Ula?

    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.

  16. High-resolution noncontact atomic force microscopy.

    PubMed

    Pérez, Rubén; García, Ricardo; Schwarz, Udo

    2009-07-01

    Progress in nanoscience and nanotechnology requires tools that enable the imaging and manipulation of matter at the atomic and molecular scale. During the last two decades or so, scanning probe-based techniques have proven to be particularly versatile in this regard. Among the various probe-based approaches, atomic force microscopy (AFM) stands out in many ways, including the total number of citations and the breadth of possible applications, ranging from materials characterization to nanofabrication and biological studies. However, while nanometer scale operation in different environments became routine, atomic resolution imaging remained elusive for a long time. The reason for this initial deficiency was that contact with the sample blunts atomically sharp tips, which are mandatory for successful atomic resolution imaging. This problem was overcome in the mid-1990s with the introduction of noncontact atomic force microscopy (NC-AFM), which represents a version of AFM where the cantilever is oscillated close to the sample surface without actually 'touching' it. This allows the preservation of the atomic sharpness of the tip while interaction-induced changes in the cantilever's resonance frequency are used to quantify the tip-sample distance. Since then, progress has been steady and includes the development of commercial instruments as well as the addition of many new capabilities beyond imaging, such as the identification and manipulation of individual atoms. A series of annual international conferences, starting in Osaka in 1998, have contributed significantly to this outstanding performance. The program of the most recent conference from this series, held in Madrid on 15-19 September 2008, reflects the maturity of this field, with an increasing number of groups developing strong activities that involve novel approaches and applications covering areas well beyond the original vacuum-based imaging. In this special issue of Nanotechnology we present a selection of original papers authored by many of the leading groups in the field with the goal of providing a well-balanced overview on the state-of-the-art in this rapidly evolving field. These papers, many of which are based on notable presentations given during the Madrid conference, feature highlights such as (1) the development of sophisticated force spectroscopy procedures that are able to map the complete 3D tip-sample force field on different surfaces; (2) the considerable resolution improvement of Kelvin probe force microscopy (reaching, in some cases, the atomic scale), which is accompanied by a thorough, quantitative understanding of the contrast observed; (3) the perfecting of atomic resolution imaging on insulating substrates, which helps reshape our microscopic understanding of surface properties and chemical activity of these surfaces; (4) the description of instrumental and methodological developments that pave the way to the atomic-scale characterization of magnetic and electronic properties of nanostructures, and last but not least (5) the extension of dynamic imaging modes to high-resolution operation in liquids, ultimately achieving atomic resolution. The latter developments are already having a significant impact in the highly competitive field of biological imaging under physiological conditions. This special issue of Nanotechnology would not have been possible without the highly professional support from Nina Couzin, Amy Harvey, Alex Wotherspoon and the entire Nanotechnology team at IOP Publishing. We are thankful for their help in pushing this project forward. We also thank the authors who have contributed their excellent original articles to this issue, the referees whose comments have helped make the issue an accurate portrait of this rapidly moving field, and the entire NC-AFM community that continues to drive NC-AFM to new horizons. PMID:19531843

  17. A physically?based treatment of elemental carbon optics: Implications for global direct forcing of aerosols

    Microsoft Academic Search

    Mark Z. Jacobson

    2000-01-01

    To date, global models of direct radiative forcing have treated elemental carbon (EC) as completely externally mixed or well-mixed internally. No global study has treated EC as a core in an internal mixture. It is hypothesized that the well-mixed treatment is unphysical and reality lies between the externally-mixed and core treatments. It is also suggested, but not proven, that most

  18. Effect of the Capillary Force on Force Measurements in Submerged Micromanipulations

    E-print Network

    Boyer, Edmond

    Effect of the Capillary Force on Force Measurements in Submerged Micromanipulations Mourad Nourine of liquid surface tension on force measurement in submerged micromanipulations. On the one hand. On the other hand, the reduction of the surface force, and adhesion forces in a submerged medium could

  19. Measurement of Dynamical Forces between Deformable Drops Using the Atomic Force Microscope. I. Theory

    E-print Network

    Chan, Derek Y C

    Measurement of Dynamical Forces between Deformable Drops Using the Atomic Force Microscope. I forces between two moving liquid drops in solution using an atomic force microscope (AFM). The drop sizes, interfacial tension, and approach velocities used in the experiments are in a regime where surface forces

  20. Dynamic Surface Force Measurement. 2. Friction and the Atomic Force Microscope

    E-print Network

    Attard, Phil

    Dynamic Surface Force Measurement. 2. Friction and the Atomic Force Microscope Phil Attard* Ian of force measurement with the atomic force microscope are analyzed in detail. The effective spring constant of the piezoelectric drive motor and position detector used in the atomic force microscope. It is shown that hysteresis

  1. Haptic TeachingHaptic Teaching using Opposite Force Presentationusing Opposite Force Presentation

    E-print Network

    Tachi, Susumu

    motion and forces model motion and force FFEE are recorded. Theare recorded. The haptic deviceHaptic TeachingHaptic Teaching using Opposite Force Presentationusing Opposite Force Presentation a new haptic teaching method, in which the haptic device produces force that isthe haptic device

  2. The Forces Between Polyatomic Molecules. I. Long-Range Forces

    Microsoft Academic Search

    H. C. Longuet-Higgins; L. Salem

    1961-01-01

    It is known that the electrostatic long-range forces between two molecules are `locally additive' in the sense that the first-order interaction energy between molecules bearing charges or permanent multipole moments may be written as a double integral over pairs of points, one in each molecule. In this paper we examine the second-order interaction energy, which comprises polarization and dispersion terms,

  3. Numerical studies of a plasma diode with external forcing

    NASA Astrophysics Data System (ADS)

    Rekaa, V. L.; Pécseli, H. L.; Trulsen, J. K.

    2012-08-01

    With reference to laboratory Q-machine studies we analyze the dynamics of a plasma diode under external forcing. Assuming a strong axial magnetic field, the problem is analyzed in one spatial dimension by a particle-in-cell code. The cathode is assumed to be operated in electron rich conditions, supplying an abundance of electrons. We compare different forcing schemes with the results obtained by solving the van der Pol equation. In one method of forcing we apply an oscillation in addition to the DC end plate bias and consider both amplitude and frequency variations. An alternative method of perturbation consists of modelling an absorbing grid at some internal position. Also in this case we can have a constant frequency with varying amplitude or alternatively an oscillation with chirped frequency but constant amplitude. We find that the overall features of the forced van der Pol equation are recovered, but the details in the plasma response need more attention to the harmonic responses, requiring extensions of the model equation. The analysis is extended by introducing collisional effects, where we emphasize charge exchange collisions of ions, since these processes usually have the largest cross sections and give significant modifications of the diode performance. In particular we find a reduction in oscillator frequency, although a linear scaling of the oscillation time with the system length remains also in this case.

  4. Sound propagation and force chains in granular materials

    E-print Network

    Eli T. Owens; Karen E. Daniels

    2010-12-17

    Granular materials are inherently heterogeneous, leading to challenges in formulating accurate models of sound propagation. In order to quantify acoustic responses in space and time, we perform experiments in a photoelastic granular material in which the internal stress pattern (in the form of force chains) is visible. We utilize two complementary methods, high-speed imaging and piezoelectric transduction, to provide particle-scale measurements of both the amplitude and speed of an acoustic wave in the near-field regime. We observe that the wave amplitude is on average largest within particles experiencing the largest forces, particularly in those chains radiating away from the source, with the force-dependence of this amplitude in qualitative agreement with a simple Hertzian-like model of particle contact area. In addition, we are able to directly observe rare transient force chains formed by the opening and closing of contacts during propagation. The speed of the leading edge of the pulse is in quantitative agreement with predictions for one-dimensional chains, while the slower speed of the peak response suggests that it contains waves which have travelled over multiple paths even within just this near-field region. These effects highlight the importance of particle-scale behaviors in determining the acoustical properties of granular materials.

  5. Sound propagation and force chains in granular materials

    NASA Astrophysics Data System (ADS)

    Owens, E. T.; Daniels, K. E.

    2011-06-01

    Granular materials are inherently heterogeneous, leading to challenges in formulating accurate models of sound propagation. In order to quantify acoustic responses in space and time, we perform experiments in a photoelastic granular material in which the internal stress pattern (in the form of force chains) is visible. We utilize two complementary methods, high-speed imaging and piezoelectric transduction, to provide particle-scale measurements of both the amplitude and speed of an acoustic wave in the near-field regime. We observe that the wave amplitude is on average largest within particles experiencing the largest forces, particularly in those chains radiating away from the source, with the force-dependence of this amplitude in qualitative agreement with a simple Hertzian-like model of particle contact area. In addition, we are able to directly observe rare transiently strong force chains formed by the opening and closing of contacts during propagation. The speed of the leading edge of the pulse is in agreement with the speed of a one-dimensional chain, while the slower speed of the peak response suggests that it contains waves which have travelled over multiple paths even within just this near-field region. These effects highlight the importance of particle-scale behaviors in determining the acoustical properties of granular materials.

  6. Numerical studies of a plasma diode with external forcing

    SciTech Connect

    Rekaa, V. L.; Pecseli, H. L. [Department of Physics, University of Oslo, Box 1048 Blindern, N-0316 Oslo (Norway); Trulsen, J. K. [Institute of Theoretical Astrophysics, University of Oslo, Box 1029 Blindern, N-0315 Oslo (Norway)

    2012-08-15

    With reference to laboratory Q-machine studies we analyze the dynamics of a plasma diode under external forcing. Assuming a strong axial magnetic field, the problem is analyzed in one spatial dimension by a particle-in-cell code. The cathode is assumed to be operated in electron rich conditions, supplying an abundance of electrons. We compare different forcing schemes with the results obtained by solving the van der Pol equation. In one method of forcing we apply an oscillation in addition to the DC end plate bias and consider both amplitude and frequency variations. An alternative method of perturbation consists of modelling an absorbing grid at some internal position. Also in this case we can have a constant frequency with varying amplitude or alternatively an oscillation with chirped frequency but constant amplitude. We find that the overall features of the forced van der Pol equation are recovered, but the details in the plasma response need more attention to the harmonic responses, requiring extensions of the model equation. The analysis is extended by introducing collisional effects, where we emphasize charge exchange collisions of ions, since these processes usually have the largest cross sections and give significant modifications of the diode performance. In particular we find a reduction in oscillator frequency, although a linear scaling of the oscillation time with the system length remains also in this case.

  7. Force interactions in laparoscopic simulations: haptic rendering of soft tissues.

    PubMed

    Basdogan, C; Ho, C H; Srinivasan, M A; Small, S D; Dawson, S L

    1998-01-01

    Research in the area of computer assisted surgery and surgical simulation has mainly focused on developing 3D geometrical models of the human body from 2D medical images, visualization of internal structures for educational and preoperative surgical planning purposes, and graphical display of soft tissue behavior in real time. Conveying to the surgeon the touch and force sensations with the use of haptic interfaces has not been investigated in detail. We have developed a set of haptic rendering algorithms for simulating "surgical instrument--soft tissue" interactions. Although the focus of the study is the development of algorithms for simulation of laparoscopic procedures, the developed techniques are also useful in simulating other medical procedures involving touch and feel of soft tissues. The proposed force-reflecting soft tissue models are in various fidelities and have been developed to simulate the behavior of elastically deformable objects in virtual environments. The developed algorithms deal directly with geometry of anatomical organs, surface and compliance characteristics of tissues, and the estimation of appropriate reaction forces to convey to the user a feeling of touch and force sensations. PMID:10180581

  8. Tidally-forced flow in a rotating, stratified, shoaling basin

    NASA Astrophysics Data System (ADS)

    Winters, Kraig B.

    2015-06-01

    Baroclinic flow of a rotating, stratified fluid in a parabolic basin is computed in response to barotropic tidal forcing using the nonlinear, non-hydrostatic, Boussinesq equations of motion. The tidal forcing is derived from an imposed, boundary-enhanced free-surface deflection that advances cyclonically around a central amphidrome. The tidal forcing perturbs a shallow pycnocline, sloshing it up and down over the shoaling bottom. Nonlinearities in the near-shore internal tide produce an azimuthally independent 'set-up' of the isopycnals that in turn drives an approximately geostrophically balanced, cyclonic, near-shore, sub-surface jet. The sub-surface cyclonic jet is an example of a slowly evolving, nearly balanced flow that is excited and maintained solely by forcing in the fast, super-inertial frequency band. Baroclinic instability of the nearly balanced jet and subsequent interactions between eddies produce a weak transfer of energy back into the inertia-gravity band as swirling motions with super-inertial vorticity stir the stratified fluid and spontaneously emit waves. The sub-surface cyclonic jet is similar in many ways to the poleward flows observed along eastern ocean boundaries, particularly the California Undercurrent. It is conjectured that such currents may be driven by the surface tide rather than by winds and/or along-shore pressure gradients.

  9. Electrostatic force-feedback force sensor incorporated in an ultrahigh vacuum force microscope

    NASA Astrophysics Data System (ADS)

    Yakimov, V.; Erlandsson, R.

    2000-01-01

    A force sensor based on a fiber-optic interferometric displacement transducer incorporated in an ultrahigh vacuum atomic force microscope is described. The operation of the sensor is based on balancing the tip-sample interfacial force using an electrostatic actuator. The electrodes of the actuator are formed by the grounded W cantilever and the metallized end facet of the optical fiber used by the interferometer. Chemical reduction of Ag by a wet chemical method is used for metal coating of the fiber end. A special masking procedure is used to obtain a window hole in the metal coating at the position of the fiber core to allow for optical beam output. Using a window instead of a semitransparent metal film allows us to save the low-finesse characteristics of the interferometer which facilitates the calibration of cantilever displacement. The performance of the sensor is discussed and exemplified by experimental results from force-separation measurements on the W-Au system in ultrahigh vacuum.

  10. Wrist action affects precision grip force.

    PubMed

    Werremeyer, M M; Cole, K J

    1997-07-01

    When moving objects with a precision grip, fingertip forces normal to the object surface (grip force) change in parallel with forces tangential to the object (load force). We investigated whether voluntary wrist actions can affect grip force independent of load force, because the extrinsic finger muscles cross the wrist. Grip force increased with wrist angular speed during wrist motion in the horizontal plane, and was much larger than the increased tangential load at the fingertips or the reaction forces from linear acceleration of the test object. During wrist flexion the index finger muscles in the hand and forearm increased myoelectric activity; during wrist extension this myoelectric activity increased little, or decreased for some subjects. The grip force maxima coincided with wrist acceleration maxima, and grip force remained elevated when subjects held the wrist in extreme flexion or extension. Likewise, during isometric wrist actions the grip force increased even though the fingertip loads remained constant. A grip force "pulse" developed that increased with wrist force rate, followed by a static grip force while the wrist force was sustained. Subjects could not suppress the grip force pulse when provided visual feedback of their grip force. We conclude that the extrinsic hand muscles can be recruited to assist the intended wrist action, yielding higher grip-load ratios than those employed with the wrist at rest. This added drive to hand muscles overcame any loss in muscle force while the extrinsic finger flexors shortened during wrist flexion motion. During wrist extension motion grip force increases apparently occurred from eccentric contraction of the extrinsic finger flexors. The coactivation of hand closing muscles with other wrist muscles also may result in part from a general motor facilitation, because grip force increased during isometric knee extension. However, these increases were related weakly to the knee force. The observed muscle coactivation, from all sources, may contribute to grasp stability. For example, when transporting grasped objects, upper limb accelerations simultaneously produce inertial torques at the wrist that must be resisted, and inertial loads at the fingertips from the object that must be offset by increased grip force. The muscle coactivation described here would cause similarly timed pulses in the wrist force and grip force. However, grip-load coupling from this mechanism would not contribute much to grasp stability when small wrist forces are required, such as for slow movements or when the object's total resistive load is small. PMID:9242279

  11. Multistage Force Amplification of Piezoelectric Stacks

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing (Inventor); Siochi, Emilie J. (Inventor); Zuo, Lei (Inventor); Jiang, Xiaoning (Inventor); Kang, Jin Ho (Inventor)

    2015-01-01

    Embodiments of the disclosure include an apparatus and methods for using a piezoelectric device, that includes an outer flextensional casing, a first cell and a last cell serially coupled to each other and coupled to the outer flextensional casing such that each cell having a flextensional cell structure and each cell receives an input force and provides an output force that is amplified based on the input force. The apparatus further includes a piezoelectric stack coupled to each cell such that the piezoelectric stack of each cell provides piezoelectric energy based on the output force for each cell. Further, the last cell receives an input force that is the output force from the first cell and the last cell provides an output apparatus force In addition, the piezoelectric energy harvested is based on the output apparatus force. Moreover, the apparatus provides displacement based on the output apparatus force.

  12. The Engineering of Optical Conservative Force

    E-print Network

    Du, Junjie; Ding, Kun; Du, Guiqiang; Lin, Zhifang; Chan, C T; Ng, Jack

    2015-01-01

    Optical forces have been fruitfully applied in a broad variety of areas that not only span the traditional scientific fields such as physics, chemistry, and biology, but also in more applied fields. It is customary and useful to split the optical force into the (conservative) gradient force and the (non-conservative) scattering and absorption force. These forces are different in attributes. The ability to tailor them will open great potential in fundamental optics and practical applications. Here, we present an analytical and a numerical approach to calculate these forces, and, with these tools, we create a fairly general class of 2D conservative optical force field. In general, particles immersed in an optical force do not obey equilibrium statistical mechanics, making the analysis complicated. With conservative forces, these issues are resolved.

  13. Constraints on stable equilibria with fluctuation-induced forces

    E-print Network

    Rahi, Sahand Jamal; Emig, Thorsten

    2009-01-01

    We examine whether fluctuation-induced forces can lead to stable levitation. First, we analyze a collection of classical objects at finite temperature that contain fixed and mobile charges, and show that any arrangement in space is unstable to small perturbations in position. This extends Earnshaw's theorem for electrostatics by including thermal fluctuations of internal charges. Quantum fluctuations of the electromagnetic field are responsible for Casimir/van der Waals interactions. Neglecting permeabilities, we find that any equilibrium position of items subject to such forces is also unstable if the permittivities of all objects are higher or lower than that of the enveloping medium; the former being the generic case for ordinary materials in vacuum.

  14. Constraints on stable equilibria with fluctuation-induced forces

    E-print Network

    Sahand Jamal Rahi; Mehran Kardar; Thorsten Emig

    2009-11-27

    We examine whether fluctuation-induced forces can lead to stable levitation. First, we analyze a collection of classical objects at finite temperature that contain fixed and mobile charges, and show that any arrangement in space is unstable to small perturbations in position. This extends Earnshaw's theorem for electrostatics by including thermal fluctuations of internal charges. Quantum fluctuations of the electromagnetic field are responsible for Casimir/van der Waals interactions. Neglecting permeabilities, we find that any equilibrium position of items subject to such forces is also unstable if the permittivities of all objects are higher or lower than that of the enveloping medium; the former being the generic case for ordinary materials in vacuum.

  15. Constraints on Stable Equilibria with Fluctuation-Induced (Casimir) Forces

    NASA Astrophysics Data System (ADS)

    Rahi, Sahand Jamal; Kardar, Mehran; Emig, Thorsten

    2010-08-01

    We examine whether fluctuation-induced forces can lead to stable levitation. First, we analyze a collection of classical objects at finite temperature that contain fixed and mobile charges and show that any arrangement in space is unstable to small perturbations in position. This extends Earnshaw’s theorem for electrostatics by including thermal fluctuations of internal charges. Quantum fluctuations of the electromagnetic field are responsible for Casimir or van der Waals interactions. Neglecting permeabilities, we find that any equilibrium position of items subject to such forces is also unstable if the permittivities of all objects are higher or lower than that of the enveloping medium, the former being the generic case for ordinary materials in vacuum.

  16. Constraints on stable equilibria with fluctuation-induced (Casimir) forces.

    PubMed

    Rahi, Sahand Jamal; Kardar, Mehran; Emig, Thorsten

    2010-08-13

    We examine whether fluctuation-induced forces can lead to stable levitation. First, we analyze a collection of classical objects at finite temperature that contain fixed and mobile charges and show that any arrangement in space is unstable to small perturbations in position. This extends Earnshaw's theorem for electrostatics by including thermal fluctuations of internal charges. Quantum fluctuations of the electromagnetic field are responsible for Casimir or van der Waals interactions. Neglecting permeabilities, we find that any equilibrium position of items subject to such forces is also unstable if the permittivities of all objects are higher or lower than that of the enveloping medium, the former being the generic case for ordinary materials in vacuum. PMID:20868024

  17. Constraints on Stable Equilibria with Fluctuation-Induced (Casimir) Forces

    SciTech Connect

    Rahi, Sahand Jamal; Kardar, Mehran [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Emig, Thorsten [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Laboratoire de Physique Theorique et Modeles Statistiques, CNRS UMR 8626, Batiment 100, Universite Paris-Sud, 91405 Orsay cedex (France)

    2010-08-13

    We examine whether fluctuation-induced forces can lead to stable levitation. First, we analyze a collection of classical objects at finite temperature that contain fixed and mobile charges and show that any arrangement in space is unstable to small perturbations in position. This extends Earnshaw's theorem for electrostatics by including thermal fluctuations of internal charges. Quantum fluctuations of the electromagnetic field are responsible for Casimir or van der Waals interactions. Neglecting permeabilities, we find that any equilibrium position of items subject to such forces is also unstable if the permittivities of all objects are higher or lower than that of the enveloping medium, the former being the generic case for ordinary materials in vacuum.

  18. Radation force on a relativistic plasma and the Eddington limit

    SciTech Connect

    O'Dell, S.L.

    1981-02-01

    The Thomson-scattering radiation force on a hot isotropic exceeds that on a cold one by a factor of (2/3<(..gamma beta..)/sup 2/>+1), where ..gamma.. = (1-..beta../sup 2/)/sup -1/2/ is the electron Lorentz factor. This excess force results from the anisotropic loss of internal energy. Consequently, a relativistic plasma with <..gamma../sup 2/>>>5/2, when exposed to an anisotropic radiation field, acts as a rocket-a ''Compton rocket'', Compton rockets quite likely play a role in the more exotic astronomical objects (quasars, blazars, Seyfert nuclei, compact galactic X-ray sources, etc.), which appear to operate within a few orders of magnitude of the (classical) Thomson-scattering Eddington limit.

  19. Mingei International Museum

    NSDL National Science Digital Library

    Mingei is Japanese for "art of the people" and is used to describe everyday items that are also wonderful arts and crafts. The arts of daily lives are represented at the Mingei International Museum, but the museum doesn't only highlight the everyday art of the Japanese, as there is art from cultures and countries around the world and from historic and contemporary artists. Visitors can see many of the objects in their digital form on their website. The artist in the current exhibition "Sonabai: Another Way of Seeing", is clay sculptor Sonabai Rajawar, and there are also some selections from four artists who studied under Rajawar. Her clay animals are whimsical, yet were born of her forced isolation in rural India for 15 years. She has since been honored in India and around the world. There are several other exhibitions visitors can view online, along with a calendar of events, a place to sign up for the museum's newsletter, and additional links to past and future exhibits.

  20. A tense situation: forcing tumour progression

    PubMed Central

    Butcher, Darci T.; Alliston, Tamara; Weaver, Valerie M.

    2009-01-01

    Cells within tissues are continuously exposed to physical forces including hydrostatic pressure, shear stress, and compression and tension forces. Cells dynamically adapt to force by modifying their behaviour and remodelling their microenvironment. They also sense these forces through mechanoreceptors and respond by exerting reciprocal actomyosin- and cytoskeletal-dependent cell-generated force by a process termed ‘mechanoreciprocity’. Loss of mechanoreciprocity has been shown to promote the progression of disease, including cancer. Moreover, the mechanical properties of a tissue contribute to disease progression, compromise treatment and might also alter cancer risk. Thus, the changing force that cells experience needs to be considered when trying to understand the complex nature of tumorigenesis. PMID:19165226