Science.gov

Sample records for acceleration deceleration effect

  1. Accelerating, hyperaccelerating, and decelerating networks

    NASA Astrophysics Data System (ADS)

    Gagen, M. J.; Mattick, J. S.

    2005-07-01

    Many growing networks possess accelerating statistics where the number of links added with each new node is an increasing function of network size so the total number of links increases faster than linearly with network size. In particular, biological networks can display a quadratic growth in regulator number with genome size even while remaining sparsely connected. These features are mutually incompatible in standard treatments of network theory which typically require that every new network node possesses at least one connection. To model sparsely connected networks, we generalize existing approaches and add each new node with a probabilistic number of links to generate either accelerating, hyperaccelerating, or even decelerating network statistics in different regimes. Under preferential attachment for example, slowly accelerating networks display stationary scale-free statistics relatively independent of network size while more rapidly accelerating networks display a transition from scale-free to exponential statistics with network growth. Such transitions explain, for instance, the evolutionary record of single-celled organisms which display strict size and complexity limits.

  2. 30 CFR 56.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Maximum acceleration and deceleration. 56.19062... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  3. 30 CFR 57.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Maximum acceleration and deceleration. 57.19062... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  4. 30 CFR 57.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Maximum acceleration and deceleration. 57.19062... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  5. 30 CFR 57.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum acceleration and deceleration. 57.19062... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  6. 30 CFR 56.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Maximum acceleration and deceleration. 56.19062... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  7. 30 CFR 56.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Maximum acceleration and deceleration. 56.19062... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  8. 30 CFR 57.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Maximum acceleration and deceleration. 57.19062... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  9. 30 CFR 56.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Maximum acceleration and deceleration. 56.19062... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  10. 30 CFR 57.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Maximum acceleration and deceleration. 57.19062... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  11. 30 CFR 56.19062 - Maximum acceleration and deceleration.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum acceleration and deceleration. 56.19062... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking,...

  12. 40 CFR 1066.265 - Acceleration and deceleration verification.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Acceleration and deceleration...) AIR POLLUTION CONTROLS VEHICLE-TESTING PROCEDURES Dynamometer Specifications § 1066.265 Acceleration... ability to achieve targeted acceleration and deceleration rates. Paragraph (c) of this section...

  13. Stereoscopic camera and viewing systems with undistorted depth presentation and reduced or eliminated erroneous acceleration and deceleration perceptions, or with perceptions produced or enhanced for special effects

    NASA Technical Reports Server (NTRS)

    Diner, Daniel B. (Inventor)

    1991-01-01

    Methods for providing stereoscopic image presentation and stereoscopic configurations using stereoscopic viewing systems having converged or parallel cameras may be set up to reduce or eliminate erroneously perceived accelerations and decelerations by proper selection of parameters, such as an image magnification factor, q, and intercamera distance, 2w. For converged cameras, q is selected to be equal to Ve - qwl = 0, where V is the camera distance, e is half the interocular distance of an observer, w is half the intercamera distance, and l is the actual distance from the first nodal point of each camera to the convergence point, and for parallel cameras, q is selected to be equal to e/w. While converged cameras cannot be set up to provide fully undistorted three-dimensional views, they can be set up to provide a linear relationship between real and apparent depth and thus minimize erroneously perceived accelerations and decelerations for three sagittal planes, x = -w, x = 0, and x = +w which are indicated to the observer. Parallel cameras can be set up to provide fully undistorted three-dimensional views by controlling the location of the observer and by magnification and shifting of left and right images. In addition, the teachings of this disclosure can be used to provide methods of stereoscopic image presentation and stereoscopic camera configurations to produce a nonlinear relation between perceived and real depth, and erroneously produce or enhance perceived accelerations and decelerations in order to provide special effects for entertainment, training, or educational purposes.

  14. Acceleration and deceleration model of indirect drive ICF capsules

    NASA Astrophysics Data System (ADS)

    Saillard, Yves

    2006-12-01

    A general zero-dimensional modelling of implosion without thermonuclear reactions is presented, for standard indirectly driven capsules. It is not substantially a new theory, but new demonstrations and improvements of existing models. The model is derived directly from the gas dynamics conservation equations written in integral form for fluid domains with variable mass, in effect the whole non-ablated capsule, the hot spot and the dense shell. The necessary approximations which involve global or mean quantities are justifed theoretically and checked by comparisons with numerical simulations. Two different sets of approximations are developed, one for each of the acceleration and the deceleration phases of the implosion. An improved—in the sense that the time variation of the hohlraum temperature is fully taken into account as it is required for high gain capsules—rocket model is proposed for the acceleration phase. With further approximations, it gives the maximum implosion velocity and the initial capsule mass corresponding to a given final capsule mass, in terms of the initial outer deuterium-tritium radius and the maximum hohlraum temperature. For the deceleration phase, the present model gives an analytical solution for the time decrease in the implosion velocity up to stagnation. Assuming the invariance of PVγ for the different media considered—a property only approximately verified—this model defines the state of these mediums in deceleration and at stagnation, in terms of the mean entropy parameters, the capsule mass, the mean implosion velocity at the end of acceleration and the initial gas mass filling the shell. A simple ODE, which can be easily integrated numerically, is derived for the hot spot mass which depends on the heat conduction wave ablating the fuel from the inside. All the numerical coefficients presently involved in the model can be calculated from the EOS, opacities and heat conduction parameters, except for the value of the

  15. Acceleration and Deceleration of Coronal Mass Ejection (CME) Propagation

    NASA Astrophysics Data System (ADS)

    Shen, F.; Wu, S.; Feng, X. S.; Wu, C.

    2011-12-01

    A major challenge to the space weather forecasting community is accurate prediction of coronal mass ejections (CME) induced Shock Arrival Time (SAT) at Earth's environment. In order to improve the current accuracy, it is necessary to understand the physical processes of the acceleration and deceleration of the CME propagation in the heliosphere. We present a three-dimensional (3D) magnetohydrodynamic (MHD) simulation of the evolution of two interacting CMEs in a realistic ambient solar wind for the March 28-31, 2001 event. The forces which caused the acceleration and deceleration are analyzed in detail. The force which caused the acceleration are Lorenz force and pressure gradient and the forces which caused the deceleration are aerodynamic drag and the Sun's gravity. In addition the momentum exchange between the solar wind and the moving CMEs can cause acceleration and deceleration of the CME which are now analyzed. In this specific CME event (March 28-31, 2001), we also investigate the interactions of two CMEs causing the acceleration and deceleration of the CMEs.

  16. Free electron laser using Rf coupled accelerating and decelerating structures

    DOEpatents

    Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

    1984-01-01

    A free electron laser and free electron laser amplifier using beam transport devices for guiding an electron beam to a wiggler of a free electron laser and returning the electron beam to decelerating cavities disposed adjacent to the accelerating cavities of the free electron laser. Rf energy is generated from the energy depleted electron beam after it emerges from the wiggler by means of the decelerating cavities which are closely coupled to the accelerating cavities, or by means of a second bore within a single set of cavities. Rf energy generated from the decelerated electron beam is used to supplement energy provided by an external source, such as a klystron, to thereby enhance overall efficiency of the system.

  17. Is the brain's inertia for motor movements different for acceleration and deceleration?

    PubMed

    Adhikari, Bhim M; Quinn, Kristen M; Dhamala, Mukesh

    2013-01-01

    The brain's ability to synchronize movements with external cues is used daily, yet neuroscience is far from a full understanding of the brain mechanisms that facilitate and set behavioral limits on these sequential performances. This functional magnetic resonance imaging (fMRI) study was designed to help understand the neural basis of behavioral performance differences on a synchronizing movement task during increasing (acceleration) and decreasing (deceleration) metronome rates. In the MRI scanner, subjects were instructed to tap their right index finger on a response box in synchrony to visual cues presented on a display screen. The tapping rate varied either continuously or in discrete steps ranging from 0.5 Hz to 3 Hz. Subjects were able to synchronize better during continuously accelerating rhythms than in continuously or discretely decelerating rhythms. The fMRI data revealed that the precuneus was activated more during continuous deceleration than during acceleration with the hysteresis effect significant at rhythm rates above 1 Hz. From the behavioral data, two performance measures, tapping rate and synchrony index, were derived to further analyze the relative brain activity during acceleration and deceleration of rhythms. Tapping rate was associated with a greater brain activity during deceleration in the cerebellum, superior temporal gyrus and parahippocampal gyrus. Synchrony index was associated with a greater activity during the continuous acceleration phase than during the continuous deceleration or discrete acceleration phases in a distributed network of regions including the prefrontal cortex and precuneus. These results indicate that the brain's inertia for movement is different for acceleration and deceleration, which may have implications in understanding the origin of our perceptual and behavioral limits.

  18. Controllably accelerating and decelerating Airy–Bessel–Gaussian wave packets

    NASA Astrophysics Data System (ADS)

    Deng, Fu; Yu, Weihao; Deng, Dongmei

    2016-11-01

    By solving the (3  +  1)D free-space Schrödinger equation in polar coordinates analytically, we have investigated the propagation of 3D controllably accelerating and decelerating Airy–Bessel–Gaussian (CAiBG) wave packets, even CAiBG wave packets, odd CAiBG wave packets and the superposition of several CAiBG wave packets in free space. The CAiBG wave packets are constructed with the Airy pulses with initial velocity in temporal domain and the Bessel–Gaussian beams in space domain. Due to the initial velocity on Airy pulses, we can obtain decelerating and accelerating Airy–Bessel–Gaussian wave packets by selecting different initial velocities. Moreover, by superposing several CAiBG wave packets, we can obtain the rotating wave packets.

  19. Measurement of the Decelerating Wake in a Plasma Wakefield Accelerator

    SciTech Connect

    Blumenfeld, I.; Decker, F. J.; Hogan, M. J.; Ischebeck, R.; Iverson, R. H.; Kirby, N.; Siemann, R. H.; Walz, D. R.; Clayton, C. E.; Huang, C.; Joshi, C.; Lu, W.; Marsh, K. A.; Mori, W. B.; Zhou, M.; Katsouleas, T.; Muggli, P.; Oz, E.

    2009-01-22

    Recent experiments at SLAC have shown that high gradient acceleration of electrons is achievable in meter scale plasmas. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch lengths were varied systematically at constant charge. The effort to extract a measurement of the decelerating wake from the maximum energy loss of the electron beam is discussed.

  20. Stabilization of an axially moving accelerated/decelerated system via an adaptive boundary control.

    PubMed

    Liu, Yu; Zhao, Zhijia; He, Wei

    2016-09-01

    In this study, an adaptive boundary control is developed for vibration suppression of an axially moving accelerated/decelerated belt system. The dynamic model of the belt system is represented by partial-ordinary differential equations with consideration of the high acceleration/deceleration and unknown distributed disturbance. By utilizing adaptive technique and Lyapunov-based back stepping method, an adaptive boundary control is proposed for vibration suppression of the belt system, a disturbance observer is introduced to attenuate the effects of unknown boundary disturbance, the adaptive law is developed to handle parametric uncertainties and the S-curve acceleration/deceleration method is adopted to plan the belt׳s speed. With the proposed control scheme, the well-posedness and stability of the closed-loop system are mathematically demonstrated. Simulations are displayed to illustrate the effectiveness of the proposed control. PMID:27269191

  1. Leg joint function during walking acceleration and deceleration.

    PubMed

    Qiao, Mu; Jindrich, Devin L

    2016-01-01

    Although constant-average-velocity walking has been extensively studied, less is known about walking maneuvers that change speed. We investigated the function of individual leg joints when humans walked at a constant speed, accelerated or decelerated. We hypothesized that leg joints make different functional contributions to maneuvers. Specifically, we hypothesized that the hip generates positive mechanical work (acting like a "motor"), the knee generates little mechanical work (acting like a "strut"), and the ankle absorbs energy during the first half of stance and generates energy during the second half (consistent with "spring"-like function). We recorded full body kinematics and kinetics, used inverse dynamics to estimate net joint moments, and decomposed joint function into strut-, motor-, damper-, and spring-like components using indices based on net joint work. Although overall leg mechanics were primarily strut-like, individual joints did not act as struts during stance. The hip functioned as a power generating "motor," and ankle function was consistent with spring-like behavior. Even though net knee work was small, the knee did not behave solely as a strut but also showed motor-, and damper-like function. Acceleration involved increased motor-like function of the hip and ankle. Deceleration involved decreased hip motor-like function and ankle spring-like function and increased damping at the knee and ankle. Changes to joint mechanical work were primarily due to changes in joint angular displacements and not net moments. Overall, joints maintain different functional roles during unsteady locomotion.

  2. Periodic components of hand acceleration/deceleration impulses during telemanipulation

    SciTech Connect

    Draper, J.V.; Handel, S.

    1994-01-01

    Responsiveness is the ability of a telemanipulator to recreate user trajectories and impedance in time and space. For trajectory production, a key determinant of responsiveness is the ability of the system to accept user inputs, which are forces on the master handle generated by user hand acceleration/deceleration (a/d) impulses, and translate them into slave arm acceleration/deceleration. This paper presents observations of master controller a/d impulses during completion of a simple target acquisition task. Power spectral density functions (PSDF`s) calculated from hand controller a/d impulses were used to assess impulse waveform. The relative contributions of frequency intervals ranging up to 25 Hz for three spatially different versions of the task were used to determine which frequencies were most important. The highest relative power was observed in frequencies between 1 Hz and 6 Hz. The key frequencies related to task difficulty were in the range from 2 Hz to 8 Hz. the results provide clues to the source of the performance inhibition.

  3. Dynamic response of a poroelastic half-space to accelerating or decelerating trains

    NASA Astrophysics Data System (ADS)

    Cao, Zhigang; Boström, Anders

    2013-05-01

    The dynamic response of a fully saturated poroelastic half-space due to accelerating or decelerating trains is investigated by a semi-analytical method. The ground is modeled as a saturated poroelastic half-space and Biot's theory is applied to characterize the soil medium, taking the coupling effects between the soil skeleton and the pore fluid into account. A detailed track system is considered incorporating rails, sleepers and embankment, which are modeled as Euler-Bernoulli beams, an anisotropic Kirchhoff plate, and an elastic layer, respectively. The acceleration or deceleration of the train is simulated by properly choosing the time history of the train speed using Fourier transforms combined with Fresnel integrals in the transformed domain. The time domain results are obtained by the fast Fourier transform (FFT). It is found that the deceleration of moving trains can cause a significant increase to the ground vibrations as well as the excess pore water pressure responses at the train speed 200 km/h. Furthermore, the single-phase elastic soil model would underestimate the vertical displacement responses caused by both the accelerating and decelerating trains at the speed 200 km/h.

  4. Biases in the perception of self-motion during whole-body acceleration and deceleration

    PubMed Central

    Tremblay, Luc; Kennedy, Andrew; Paleressompoulle, Dany; Borel, Liliane; Mouchnino, Laurence; Blouin, Jean

    2013-01-01

    Several studies have investigated whether vestibular signals can be processed to determine the magnitude of passive body motions. Many of them required subjects to report their perceived displacements offline, i.e., after being submitted to passive displacements. Here, we used a protocol that allowed us to complement these results by asking subjects to report their introspective estimation of their displacement continuously, i.e., during the ongoing body rotation. To this end, participants rotated the handle of a manipulandum around a vertical axis to indicate their perceived change of angular position in space at the same time as they were passively rotated in the dark. The rotation acceleration (Acc) and deceleration (Dec) lasted either 1.5 s (peak of 60°/s2, referred to as being “High”) or 3 s (peak of 33°/s2, referred to as being “Low”). The participants were rotated either counter-clockwise or clockwise, and all combinations of acceleration and deceleration were tested (i.e., AccLow-DecLow; AccLow-DecHigh; AccHigh-DecLow; AccHigh-DecHigh). The participants’ perception of body rotation was assessed by computing the gain, i.e., ratio between the amplitude of the perceived rotations (as measured by the rotating manipulandum’s handle) and the amplitude of the actual chair rotations. The gain was measured at the end of the rotations, and was also computed separately for the acceleration and deceleration phases. Three salient findings resulted from this experiment: (i) the gain was much greater during body acceleration than during body deceleration, (ii) the gain was greater during High compared to Low accelerations and (iii) the gain measured during the deceleration was influenced by the preceding acceleration (i.e., Low or High). These different effects of the angular stimuli on the perception of body motion can be interpreted in relation to the consequences of body acceleration and deceleration on the vestibular system and on higher-order cognitive

  5. Modeling accelerated and decelerated drug release in terms of fractional release rate.

    PubMed

    Weiss, Michael

    2015-02-20

    The model of a proportional change in fractional dissolution rate was used to quantify influences on the vitro dissolution process. After fitting the original dissolution profile with an empirical model (inverse Gaussian distribution), acceleration and deceleration effects due to dissolution conditions or formulation parameters could be described by one parameter only. Acceleration of dissolution due to elevated temperature and deceleration by increasing the content of glyceryl monostearate in theophylline tablets are presented as examples. Likewise, this approach was applied to in vitro-in vivo correlation (IVIVC). It is shown that the model is appropriate when the plot of the in vivo versus in vivo times is nonlinear and can be described by a power function. The results demonstrate the utility of the model in dissolution testing and IVIVC assessment.

  6. Acceleration and deceleration of coronal mass ejections during propagation and interaction

    NASA Astrophysics Data System (ADS)

    Shen, Fang; Wu, S. T.; Feng, Xueshang; Wu, Chin-Chun

    2012-11-01

    A major challenge to the space weather forecasting community is accurate prediction of Coronal Mass Ejections (CMEs) induced Shock Arrival Time (SAT) at Earth's environment. In order to improve the current accuracy, one of the steps is to understand the physical processes of the acceleration and deceleration of a CME's propagation in the heliosphere. We employ our previous study of a three-dimensional (3D) magnetohydrodynamic (MHD) simulation for the evolution of two interacting CMEs in a realistic ambient solar wind during the period 28-31 March 2001 event to illustrate these acceleration and deceleration processes. The forces which caused the acceleration and deceleration are analyzed in detail. The forces which caused the acceleration are the magnetic pressure term of Lorentz force and pressure gradient. On the other hand, the forces which caused the deceleration are aerodynamic drag, the Sun's gravity and the tension of magnetic field. In addition the momentum exchange between the solar wind and the moving CMEs can cause acceleration and deceleration of the CME which are now analyzed. In this specific CME event 28-31 March 2001 we have analyzed those forces which cause acceleration and deceleration of CME with and without interaction with another CME. It shows that there are significant momentum changes between these two interacting CMEs to cause the acceleration and deceleration.

  7. Stopping power: Effect of the projectile deceleration

    SciTech Connect

    Kompaneets, Roman Ivlev, Alexei V.; Morfill, Gregor E.

    2014-11-15

    The stopping force is the force exerted on the projectile by its wake. Since the wake does not instantly adjust to the projectile velocity, the stopping force should be affected by the projectile deceleration caused by the stopping force itself. We address this effect by deriving the corresponding correction to the stopping force in the cold plasma approximation. By using the derived expression, we estimate that if the projectile is an ion passing through an electron-proton plasma, the correction is small when the stopping force is due to the plasma electrons, but can be significant when the stopping force is due to the protons.

  8. Comparison of hamstring-to-quadriceps ratio between accelerating and decelerating sections during squat exercise

    PubMed Central

    Yoo, Won-gyu

    2016-01-01

    [Purpose] The aim of this study was to compare hamstring-to-quadriceps ratio between the accelerating and decelerating sections for anterior cruciate ligament protection during squat exercise. [Subjects and Methods] Nine asymptomatic males were enrolled in this study. The hamstring (medial part) and quadriceps (rectus femoris) muscle activities during squat exercise were measured, and the squat exercises were classified into two sections (accelerating and decelerating) by using an accelerometer. [Results] The hamstring-to-quadriceps ratio was significantly higher in the decelerating section than in the accelerating section during the squat exercise. [Conclusion] Application of an increasing decelerating section strategy during the squat exercise can prevent damage in patients with a weakened anterior cruciate ligament due to sports activities. PMID:27799671

  9. Fast, transient cardiac accelerations and decelerations during fear conditioning in rats.

    PubMed

    Knippenberg, J M J; Barry, R J; Kuniecki, M J; van Luijtelaar, G

    2012-02-01

    The current study reports on a number of heart rate responses observed in rats subjected to a discriminatory Pavlovian fear conditioning procedure. Rats learned that a series of six auditory pips was followed by a footshock when presented alone, but not when the pip series was preceded by a visual safety signal. Each auditory pip in the series evoked a fast transient (<1s) cardiac deceleration. This was the case on both trials followed by shock and on trials not followed by shock. The onset of the safety light evoked a similar fast deceleration. We propose that these transient decelerations are similar to the human Evoked Cardiac Response 1 (ECR1), a brief modest deceleration evoked by simple sensory stimuli that is thought to reflect an early process of stimulus registration. Immediately following these pip-evoked decelerations, modest fast accelerations were observed. These accelerations were larger when the pip series was followed by shock than when it was not followed by shock. We propose a potential linkage between these accelerations and the human acceleratory ECR2 component, which is associated with more elaborate processing following stimulus registration; something likely to take place when the pip series predicts an aversive event. Both the ECR1- and ECR2-like responses were embedded within a slow, gradual heart rate increase across the entire pip series. This tonic increase was significantly larger on trials with footshock and is therefore probably associated with anticipatory fear of the upcoming shock. An additional special type of cardiac response was found to the first pip in the series not preceded by the safety signal; here, a much larger and more sustained deceleration was apparent. This response appears relatable to the prolonged deceleration reported in humans in response to aversive picture content. We discuss the cardiac responses found in rats in the current study in the context of heart rate responses known in the human literature.

  10. 40 CFR 1066.265 - Acceleration and deceleration verification.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... revolution frequency. If the dynamometer has no such function generator, set up a properly calibrated... to your dynamometer by identifying the roll-revolution frequency, f, in revolutions per second (or Hz... roll revolution. d roll = roll diameter, in inches. (2) Program the dynamometer to accelerate the...

  11. 40 CFR 1066.265 - Acceleration and deceleration verification.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... measuring roll revolution frequency. If the dynamometer has no such function generator, set up a properly... to your dynamometer by identifying the roll-revolution frequency, f, in revolutions per second (or Hz... roll revolution. d roll = roll diameter, in inches. (2) Program the dynamometer to accelerate the...

  12. The blast wave mitigation effects of a magnetogasdynamic decelerator

    SciTech Connect

    Baty, Roy S; Lundgren, Ronald G; Tucker, Don H

    2009-01-01

    This work computes shock wave jump functions for viscous blast waves propagating in a magnetogasdynamic decelerator. The decelerator is assumed to be a one-dimensional channel with sides that are perfect conductors. An electric field applied on the walls of the channel produces a magnetogasdynamic pump, which decelerates the flow field induced by a blast wave. The blast wave jump functions computed here are compared to magnetogasdynamic results for steady supersonic channel flow to quantify potential blast mitigation effects. Theoretical shock wave jump functions are also presented for inviscid blast waves propagating in a one-dimensional channel with an electromagnetic field.

  13. A pilot in the loop analysis of helicopter acceleration/deceleration maneuvers

    NASA Technical Reports Server (NTRS)

    Heffley, R. K.

    1982-01-01

    Helicopter flight acceleration/deceleration maneuvers are quantified and put to use in the fields of handling qualities, flight training and evaluation of simulator fidelity. The three specific cases include the normal speed change maneuver, the nap-of-the-Earth dash/quickstop, and the decelerating approach to hover. All of these maneuvers share common generic features in terms of pilot adaptation and mathematical description; yet each differs in terms of the essential feedback loop structure, implications for handling qualities requirements, and simulator fidelity criteria.

  14. Braking and propulsive impulses increase with speed during accelerated and decelerated walking.

    PubMed

    Peterson, Carrie L; Kautz, Steven A; Neptune, Richard R

    2011-04-01

    The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior-posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from 10 healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0-1.8 m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects' preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking.

  15. Mini acceleration and deceleration driving strategy to increase the operational time of flywheel hybrid module

    NASA Astrophysics Data System (ADS)

    Manaf, Muhammad Zaidan Abdul; Fakeruddin, Shafarul Hafidi; Zakaria, Mohamad Shukri; Saadun, Mohd Noor Asril; Hanafi, Mohd Hafidzal Mohd

    2015-05-01

    This paper presents a new driving strategy to increase the operational time of flywheel hybrid module. The flywheel hybrid module contains low cost mechanical parts which installed on the small motorcycle. Based on normal driving cycles characteristics, the Mini-AD driving strategy is develop. It is involved a series of short or mini acceleration cycle and short deceleration cycle on top of the normal driving cycles. The new strategy is simulated for flywheel hybrid module, aimed for acceleration phase only. Simulations show that the new driving strategy can increase the operational time of flywheel hybrid module up to 62.5%.

  16. Adiabatic Deceleration Effects on the Formation of Heavy Ion Charge Spectra in Interplanetary Space

    NASA Astrophysics Data System (ADS)

    Kartavykh, J. J.; Dröge, W.; Kovaltsov, G. A.; Ostryakov, V. M.

    2005-03-01

    We investigate the effects of interplanetary propagation on the energy dependence of the mean ionic charge of ~0.1 1 MeV/n iron observed during impulsive solar particle events at 1 AU. A Monte-Carlo approach is applied to solve the transport equation which takes into account spatial diffusion as well as convection and adiabatic deceleration. We find that interplanetary propagation results in a shift of charge spectra observed at 1 AU towards lower energies due to adiabatic deceleration. Taking the above effect into account, we compare predictions of our model of charge-consistent stochastic acceleration with recent ACE observations. A detailed analysis of two particle events shows that our model can give a consistent explanation of the observed iron charge and energy spectra, and allows one to put constraints on the temperature, density, and the acceleration and escape time scales in the acceleration region.

  17. Acceleration and deceleration phase nonlinear Rayleigh-Taylor growth at spherical interfaces

    SciTech Connect

    Clark, D S; Tabak, M

    2005-04-08

    The Layzer model for the nonlinear evolution of bubbles in the Rayleigh-Taylor instability has recently been generalized to the case of spherically imploding interfaces [D. S. Clark and M. Tabak, to appear, PRE (2005).]. The spherical case is more relevant to, e.g., inertial confinement fusion or various astrophysical phenomena when the convergence is strong or the perturbation wavelength is comparable to the interface curvature. Here, the model is further extended to the case of bubble growth during the deceleration (stagnation) phase of a spherical implosion and to the growth of spikes during both the acceleration and deceleration phases. Differences in the nonlinear growth rates for both bubbles and spikes are found when compared with planar results. The model predictions are verified by comparison with numerical hydrodynamics simulations.

  18. An analysis of spatially varying turbulent Prandtl number in a flow with local acceleration and deceleration

    NASA Astrophysics Data System (ADS)

    Jung, Eunbum; Lee, Wook; Kang, Seongwon; Iaccarino, Gianluca

    2015-11-01

    The turbulent Prandtl number (Prt) is an important parameter in turbulent flows used in many engineering models for heat transfer. In the present study, spatial variation of Prt in a wall-bounded turbulent flow is investigated using DNS. We derived a form of Prt applicable to a general flow configuration, using the least-square method in a manner consistent with the turbulent viscosity model in LES. For a flow subject to local acceleration and deceleration induced by the wall geometry, we performed a parametric study for the Reynolds number, Prandtl number and a geometric factor using DNS. A comparison of the data from DNS and RANS with a constant Prt indicates the potential of improved RANS predictions using the present variable Prt subject to the local flow field. Also, it is observed that the local pressure gradient has an important effect on the Prt field. From the flow statistics, a few flow variables showing higher correlations with Prt are identified. An elementary model for Prt is devised, and used for RANS prediction producing a more accurate prediction of the heat transfer rate. Corresponding author

  19. Acceleration{endash}deceleration process of thin foils confined in water and submitted to laser driven shocks

    SciTech Connect

    Romain, J.P.; Auroux, E.

    1997-08-01

    An experimental, numerical, and analytical study of the acceleration and deceleration process of thin metallic foils immersed in water and submitted to laser driven shocks is presented. Aluminum and copper foils of 20 to 120 {mu}m thickness, confined on both sides by water, have been irradiated at 1.06 {mu}m wavelength by laser pulses of {approximately}20ns duration, {approximately}17J energy, and {approximately}4GW/cm{sup 2} incident intensity. Time resolved velocity measurements have been made, using an electromagnetic velocity gauge. The recorded velocity profiles reveal an acceleration{endash}deceleration process, with a peak velocity up to 650 m/s. Predicted profiles from numerical simulations reproduce all experimental features, such as wave reverberations, rate of increase and decrease of velocity, peak velocity, effects of nature, and thickness of the foils. A shock pressure of about 2.5 GPa is inferred from the velocity measurements. Experimental points on the evolution of plasma pressure are derived from the measurements of peak velocities. An analytical description of the acceleration{endash}deceleration process, involving multiple shock and release waves reflecting on both sides of the foils, is presented. The space{endash}time diagrams of waves propagation and the successive pressure{endash}particle velocity states are determined, from which theoretical velocity profiles are constructed. All characteristics of experimental records and numerical simulations are well reproduced. The role of foil nature and thickness, in relation with the shock impedance of the materials, appears explicitly. {copyright} {ital 1997 American Institute of Physics.}

  20. The farthest known supernova: Support for an accelerating universeand a glimpse of the epoch of deceleration

    SciTech Connect

    Riess, Adam G.; Nugent, Peter E.; Schmidt, Brian P.; Tonry, John; Dickinson, Mark; Gilliland, Ronald L.; Thompson, Rodger I.; Budavari,Tamas; Casertano, Stefano; Evans, Aaron S.; Filippenko, Alexei V.; Livio,Mario; Sanders, David B.; Shapley, Alice E.; Spinrad, Hyron; Steidel,Charles C.; Stern, Daniel; Surace, Jason; Veilleux, Sylvain

    2001-04-01

    We present photometric observations of an apparent Type Iasupernova (SN Ia) at a redshift of approximately 1.7, the farthest SNobserved to date. The supernova, SN 1997, was discovered in a repeatobservation by the Hubble Space Telescope (HST) of the Hubble DeepField{North (HDF-N), and serendipitously monitored with NICMOS on HSTthroughout the Thompson et al. GTO campaign. The SN type can bedetermined from the host galaxy type: an evolved, red elliptical lackingenough recent star formation to provide a significant population ofcore-collapse supernovae. The classification is further supported bydiagnostics available from the observed colors and temporal behavior ofthe SN, both of which match a typical SN Ia. The photometric record ofthe SN includes a dozen flux measurements in the I, J, and H bandsspanning 35 days in the observed frame. The redshift derived from the SNphotometry, z = 1:7 plus or minus 0:1, is in excellent agreement with theredshift estimate of z = 1:65 plus or minus 0:15 derived from the U_300B_450 V_-606 I_814 J_110 J_125 H_160 H_165 K_s photometry of the galaxy.Optical and near-infrared spectra of the host provide a very tentativespectroscopic redshift of 1.755. Fits to observations of the SN provideconstraints for the redshift-distance relation of SNe Ia and a powerfultest of the current accelerating Universe hypothesis. The apparent SNbrightness is consistent with that expected in the decelerating phase ofthe preferred cosmological model, Omega_M approximately equal to 1/3;Omega_Lambda approximately equal to 2/3. It is inconsistent with greydust or simple luminosity evolution, candidate astrophysical effectswhich could mimic previous evidence for an accelerating Universe from SNeIa at z approximately equal to 0:5. We consider several sources ofpotential systematic error including gravitational lensing, supernovamisclassification, sample selection bias, and luminosity calibrationerrors. Currently, none of these effects alone appears likely

  1. Player Load, Acceleration, and Deceleration During Forty-Five Competitive Matches of Elite Soccer.

    PubMed

    Dalen, Terje; Ingebrigtsen, Jørgen; Ettema, Gertjan; Hjelde, Geir Havard; Wisløff, Ulrik

    2016-02-01

    The use of time-motion analysis has advanced our understanding of position-specific work rate profiles and the physical requirements of soccer players. Still, many of the typical soccer activities can be neglected, as these systems only examine activities measured by distance and speed variables. This study used triaxial accelerometer and time-motion analysis to obtain new knowledge about elite soccer players' match load. Furthermore, we determined acceleration/deceleration profiles of elite soccer players and their contribution to the players' match load. The data set includes every domestic home game (n = 45) covering 3 full seasons (2009, 2010, and 2011) for the participating team (Rosenborg FC), and includes 8 central defenders (n = 68), 9 fullbacks (n = 83), 9 central midfielders (n = 70), 7 wide midfielders (n = 39), and 5 attackers (A, n = 50). A novel finding was that accelerations contributed to 7-10% of the total player load for all player positions, whereas decelerations contributed to 5-7%. Furthermore, the results indicate that other activities besides the high-intensity movements contribute significantly to the players' total match workload. Therefore, motion analysis alone may underestimate player load because many high-intensity actions are without a change in location at the pitch or they are classified as low-speed activity according to current standards. This new knowledge may help coaches to better understand the different ways players achieve match load and could be used in developing individualized programs that better meet the "positional physical demands" in elite soccer.

  2. Canine fetal heart rate: do accelerations or decelerations predict the parturition day in bitches?

    PubMed

    Gil, E M U; Garcia, D A A; Giannico, A T; Froes, T R

    2014-10-15

    Ultrasonography is a safe and efficient technique for monitoring fetal development and viability. One of the most important and widely used parameters to verify fetal viability is the fetal heart rate (HR). In human medicine, the fetal HR normally oscillates during labor in transient accelerations and decelerations associated with uterine contractions. The present study investigated whether these variations also occur in canine fetuses and its relationship to parturition. A cohort study was conducted in 15 pregnant bitches undergoing two-dimensional high-resolution ultrasonographic examination during the 8th and 9th week of gestation. Fetal HR was assessed in M-mode for 5 minutes in each fetus in all bitches. In addition, the bitches were monitored for clinical signs of imminent parturition. Associations between the HR, antepartum time, and delivery characteristics were evaluated with a Poisson regression model. Fetal HR acceleration and deceleration occurred in canine fetuses and predicted the optimal time of parturition. These findings can help veterinarians and sonographers better understand this phenomenon in canine fetuses.

  3. Validity and reliability of GPS for measuring instantaneous velocity during acceleration, deceleration, and constant motion.

    PubMed

    Varley, Matthew C; Fairweather, Ian H; Aughey, Robert J

    2012-01-01

    In this study, we assessed the validity and reliability of 5 and 10 Hz global positioning systems (GPS) for measuring instantaneous velocity during acceleration, deceleration, and constant velocity while straight-line running. Three participants performed 80 running trials while wearing two GPS units each (5 Hz, V2.0 and 10 Hz, V4.0; MinimaxX, Catapult Innovations, Scoresby, VIC, Australia). The criterion measure used to assess GPS validity was instantaneous velocity recorded using a tripod-mounted laser. Validity was established using the standard error of the estimate (± 90% confidence limits). Reliability was determined using typical error (± 90% confidence limits, expressed as coefficient of variation) and Pearson's correlation. The 10 Hz GPS devices were two to three times more accurate than the 5 Hz devices when compared with a criterion value for instantaneous velocity during tasks completed at a range of velocities (coefficient of variation 3.1-11.3%). Similarly, the 10 Hz GPS units were up to six-fold more reliable for measuring instantaneous velocity than the 5 Hz units (coefficient of variation 1.9-6.0%). Newer GPS may provide an acceptable tool for the measurement of constant velocity, acceleration, and deceleration during straight-line running and have sufficient sensitivity for detecting changes in performance in team sport. However, researchers must account for the inherent match-to-match variation reported when using these devices.

  4. HUBBLE PARAMETER MEASUREMENT CONSTRAINTS ON THE COSMOLOGICAL DECELERATION-ACCELERATION TRANSITION REDSHIFT

    SciTech Connect

    Farooq, Omer; Ratra, Bharat E-mail: ratra@phys.ksu.edu

    2013-03-20

    We compile a list of 28 independent measurements of the Hubble parameter between redshifts 0.07 {<=} z {<=} 2.3 and use this to place constraints on model parameters of constant and time-evolving dark energy cosmologies. These H(z) measurements by themselves require a currently accelerating cosmological expansion at about, or better than, 3{sigma} confidence. The mean and standard deviation of the six best-fit model deceleration-acceleration transition redshifts (for the three cosmological models and two Hubble constant priors we consider) are z{sub da} = 0.74 {+-} 0.05, in good agreement with the recent Busca et al. determination of z{sub da} = 0.82 {+-} 0.08 based on 11 H(z) measurements between redshifts 0.2 {<=} z {<=} 2.3, almost entirely from baryon-acoustic-oscillation-like data.

  5. Effects of deceleration on the humoral antibody response in rats

    NASA Technical Reports Server (NTRS)

    Barone, R. P.; Caren, L. D.; Oyama, J.

    1985-01-01

    Effects of hypergravity, simulated by chronic centrifugation, followed by a return to normal G (deceleration) on the immune system of rats were investigated. Two groups of male rats (28 days at 2.1 G, and 3.1 G) were compared to the control group (1.0 G). The animals were immunized by i.p. injections of sheep red blood cells on days 29, 42, and 57, and bled on days 36, 47, and 62. While the centrifuged rats ate and gainedsignificantly less than the control rats, the antibody titers and the organ/body mass ratios for the adrenal glands, kidneys, lungs, heart, and thymus were unaffected by gravity exposures, as were the values of the hematocrit and the white blood cell counts. It is concluded that deceleration does not adversely affect these particular aspects of the immune system.

  6. Acceleration and deceleration of neutrons: From the phase modulation of a neutron wave to a neutron turbine with refracting prisms

    SciTech Connect

    Frank, A. I.

    2013-05-15

    The possibility of the acceleration and deceleration of neutrons undergoing diffraction at a moving grating is discussed. It is shown that, in contrast to phase {pi} gratings used at the present time, which form a discrete spectrum featuring a large number of lines, a grating that has a special profile may shift, under certain conditions, the entire spectrum of diffracted neutrons. A blazing grating of this type may be used in efficiently accelerating and decelerating neutrons. As the scale of the structure becomes larger, a description based on the idea of neutron-wave refraction at its elements becomes valid, a system of moving prims forming a 'neutron turbine,' which is also able to accelerate or decelerate neutrons, being a classical limit of this enlargement.

  7. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    NASA Astrophysics Data System (ADS)

    O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-09-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m-1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347+/-0.020 GeV m-1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320+/-17 MeV m-1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.

  8. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators.

    PubMed

    O'Shea, B D; Andonian, G; Barber, S K; Fitzmorris, K L; Hakimi, S; Harrison, J; Hoang, P D; Hogan, M J; Naranjo, B; Williams, O B; Yakimenko, V; Rosenzweig, J B

    2016-01-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m(-1)) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m(-1) using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m(-1). Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

  9. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    PubMed Central

    O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-01-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m−1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m−1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m−1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

  10. Applications of decelerated ions

    SciTech Connect

    Johnson, B.M.

    1985-03-01

    Many facilities whose sole purpose had been to accelerate ion beams are now becoming decelerators as well. The development and current status of accel-decel operations is reviewed here. Applications of decelerated ions in atomic physics experiments are discussed.

  11. The effects of "decelerated" rehabilitation following anterior cruciate ligament reconstruction on a hyperelastic female adolescent: a case study.

    PubMed

    Hardin, J A; Voight, M L; Blackburn, T A; Canner, G C; Soffer, S R

    1997-07-01

    Current concepts in postoperative anterior cruciate ligament (ACL) reconstruction management include participation in an "accelerated" rehabilitation program. There are no published reports examining the effects of accelerated or conservative rehabilitation on subjects with generalized ligamentous hyperelasticity. The purpose of this case study was to examine the effects of a conservative or "decelerated" rehabilitation program on the functional outcome of a hyperelastic female adolescent athlete following ACL reconstruction. The subject was a 15-year-old female basketball player who sustained a unilateral ACL tear and underwent subsequent ACL reconstruction using a patellar tendon autograft. The subject immediately began participation in a "decelerated" rehabilitation program in which the intensity and rate of progression was decelerated, emphasizing a prolonged period of maximum graft protection. Progress was objectively quantified with a battery of diagnosis-specific tests at scheduled intervals. Results at 52 weeks postoperative revealed normal range of motion, proprioception, balance, knee stability, quadriceps strength, hamstring strength, and subjective assessment values, and only a 4.0% deficit in functional scores. Our results suggest a "decelerated" rehabilitation program may be appropriate for the population with generalized ligamentous hyperelasticity by yielding excellent functional results without compromising the integrity of the graft and, ultimately, knee stability.

  12. Changes of deceleration and acceleration capacity of heart rate in patients with acute hemispheric ischemic stroke

    PubMed Central

    Xu, Yan-Hong; Wang, Xing-De; Yang, Jia-Jun; Zhou, Li; Pan, Yong-Chao

    2016-01-01

    Background and purpose Autonomic dysfunction is common after stroke, which is correlated with unfavorable outcome. Phase-rectified signal averaging is a newly developed technique for assessing cardiac autonomic function, by detecting sympathetic and vagal nerve activity separately through calculating acceleration capacity (AC) and deceleration capacity (DC) of heart rate. In this study, we used this technique for the first time to investigate the cardiac autonomic function of patients with acute hemispheric ischemic stroke. Methods A 24-hour Holter monitoring was performed in 63 patients with first-ever acute ischemic stroke in hemisphere and sinus rhythm, as well as in 50 controls with high risk of stroke. DC, AC, heart rate variability parameters, standard deviation of all normal-to-normal intervals (SDNN), and square root of the mean of the sum of the squares of differences between adjacent normal-to-normal intervals (RMSSD) were calculated. The National Institutes of Health Stroke Scale (NIHSS) was used to assess the severity of stroke. We analyzed the changes of DC, AC, SDNN, and RMSSD and also studied the correlations between these parameters and NIHSS scores. Results The R–R (R wave to R wave on electrocardiogram) intervals, DC, AC, and SDNN in the cerebral infarction group were lower than those in controls (P=0.003, P=0.002, P=0.006, and P=0.043), but the difference of RMSSD and the D-value and ratio between absolute value of AC (|AC|) and DC were not statistically significant compared with those in controls. The DC of the infarction group was significantly correlated with |AC|, SDNN, and RMSSD (r=0.857, r=0.619, and r=0.358; P=0.000, P=0.000, and P=0.004). Correlation analysis also showed that DC, |AC|, and SDNN were negatively correlated with NIHSS scores (r=−0.279, r=−0.266, and r=−0.319; P=0.027, P=0.035, and P=0.011). Conclusion Both DC and AC of heart rate decreased in patients with hemispheric infarction, reflecting a decrease in both vagal

  13. Evaluation of acceleration and deceleration cardiac processes using phase-rectified signal averaging in healthy and idiopathic dilated cardiomyopathy subjects.

    PubMed

    Bas, Rosana; Vallverdú, Montserrat; Valencia, Jose F; Voss, Andreas; de Luna, Antonio Bayés; Caminal, Pere

    2015-02-01

    The aim of the present study was to investigate the suitability of the Phase-Rectified Signal Averaging (PRSA) method for improved risk prediction in cardiac patients. Moreover, this technique, which separately evaluates acceleration and deceleration processes of cardiac rhythm, allows the effect of sympathetic and vagal modulations of beat-to-beat intervals to be characterized. Holter recordings of idiopathic dilated cardiomyopathy (IDC) patients were analyzed: high-risk (HR), who suffered sudden cardiac death (SCD) during the follow-up; and low-risk (LR), without any kind of cardiac-related death. Moreover, a control group of healthy subjects was analyzed. PRSA indexes were analyzed, for different time scales T and wavelet scales s, from RR series of 24 h-ECG recordings, awake periods and sleep periods. Also, the behavior of these indexes from simulated data was analyzed and compared with real data results. Outcomes demonstrated the PRSA capacity to significantly discriminate healthy subjects from IDC patients and HR from LR patients on a higher level than traditional temporal and spectral measures. The behavior of PRSA indexes agrees with experimental evidences related to cardiac autonomic modulations. Also, these parameters reflect more regularity of the autonomic nervous system (ANS) in HR patients. PMID:25585858

  14. An investigation of accelerating mode and decelerating mode constant-momentum mass spectrometry and their application to a residual gas analyzer

    NASA Technical Reports Server (NTRS)

    Ng, Y. S.

    1977-01-01

    A theoretical analysis of constant momentum mass spectrometry was made. A maximum resolving power for the decelerating mode constant momentum mass spectrometer was shown theoretically to exist for a beam of ions of known energy. A vacuum system and an electron beam ionization source was constructed. Supporting electronics for a residual gas analyzer were built. Experimental investigations of various types of accelerating and decelerating impulsive modes of a constant momentum mass spectrometer as applied to a residual gas analyzer were made. The data indicate that the resolving power for the decelerating mode is comparable to that of the accelerating mode.

  15. Short-term metal particulate exposures decrease cardiac acceleration and deceleration capacities in welders: a repeated-measures panel study

    PubMed Central

    Cavallari, Jennifer M; Fang, Shona C; Lu, Chensheng; Lin, Xihong; Mittleman, Murray A; Christiani, David C

    2016-01-01

    Objective Acceleration (AC) and deceleration (DC) capacities measure heart rate variability during speeding up and slowing down of the heart, respectively. We investigated associations between AC and DC with occupational short-term metal PM2.5 exposures. Methods A panel of 48 male welders had particulate matter less than 2.5 microns in diameter (PM2.5) exposure measurements over 4–6 h repeated over 5 sampling periods between January 2010 and June 2012. We simultaneously obtained continuous recordings of digital ECG using a Holter monitor. We analysed ECG data in the time domain to obtain hourly AC and DC. Linear mixed models were used to assess the associations between hourly PM2.5 exposure and each of hourly AC and DC, controlling for age, smoking status, active smoking, exposure to secondhand smoke, season/time of day when ECG reading was obtained and baseline AC or DC. We also ran lagged exposure response models for each successive hour up to 3 h after onset of exposure. Results Mean (SD) shift PM2.5 exposure during welding was 0.47 (0.43) mg/m3. Significant exposure–response associations were found for AC and DC with increased PM2.5 exposure. In our adjusted models without any lag between exposure and response, a 1 mg/m3 increase of PM2.5 was associated with a decrease of 1.46 (95% CI 1.00 to 1.92) ms in AC and a decrease of 1.00 (95% CI 0.53 to 1.46) ms in DC. The effect of PM2.5 on AC and DC was maximal immediately postexposure and lasted 1 h following exposure. Conclusions There are short-term effects of metal particulates on AC and DC. PMID:26644456

  16. Evaluation of the Acceleration and Deceleration Phase-Rectified Slope to Detect and Improve IUGR Clinical Management

    PubMed Central

    Tagliaferri, Salvatore; Fanelli, Andrea; Esposito, Giuseppina; Esposito, Francesca Giovanna; Magenes, Giovanni; Signorini, Maria Gabriella; Campanile, Marta; Martinelli, Pasquale

    2015-01-01

    Objective. This study used a new method called Acceleration (or Deceleration) Phase-Rectified Slope, APRS (or DPRS) to analyze computerized Cardiotocographic (cCTG) traces in intrauterine growth restriction (IUGR), in order to calculate acceleration- and deceleration-related fluctuations of the fetal heart rate, and to enhance the prediction of neonatal outcome. Method. Cardiotocograms from a population of 59 healthy and 61 IUGR fetuses from the 30th gestation week matched for gestational age were included. APRS and DPRS analysis was compared to the standard linear and nonlinear cCTG parameters. Statistical analysis was performed through the t-test, ANOVA test, Pearson correlation test and receiver operator characteristic (ROC) curves (p < 0, 05). Results. APRS and DPRS showed high performance to discriminate between Healthy and IUGR fetuses, according to gestational week. A linear correlation with the fetal pH at birth was found in IUGR. The area under the ROC curve was 0.865 for APRS and 0.900 for DPRS before the 34th gestation week. Conclusions. APRS and DPRS could be useful in the identification and management of IUGR fetuses and in the prediction of the neonatal outcome, especially before the 34th week of gestation. PMID:26779279

  17. Transverse stability in a Stark decelerator

    SciTech Connect

    Meerakker, Sebastiaan Y. T. van de; Bethlem, Hendrick L.; Vanhaecke, Nicolas; Meijer, Gerard

    2006-02-15

    The concept of phase stability in a Stark decelerator ensures that polar molecules can be accelerated, guided, or decelerated without loss; molecules within a certain position and velocity interval are kept together throughout the deceleration process. In this paper the influence of the transverse motion on phase stability in a Stark decelerator is investigated. For typical deceleration experiments--i.e., for high values of the phase angle {phi}{sub 0}--the transverse motion considerably enhances the region in phase space for which phase stable deceleration occurs. For low values of {phi}{sub 0}, however, the transverse motion reduces the acceptance of a Stark decelerator and unstable regions in phase space appear. These effects are quantitatively explained in terms of a coupling between the longitudinal and transverse motion. The predicted longitudinal acceptance of a Stark decelerator is verified by measurements on a beam of OH (X {sup 2}{pi}{sub 3/2},J=3/2) radicals passing through a Stark decelerator.

  18. A review of trend models applied to sea level data with reference to the "acceleration-deceleration debate"

    NASA Astrophysics Data System (ADS)

    Visser, Hans; Dangendorf, Sönke; Petersen, Arthur C.

    2015-06-01

    Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. This has motivated a number of authors to search for already existing accelerations in observations, which would be, if present, vital for coastal protection planning purposes. No scientific consensus has been reached yet as to how a possible acceleration could be separated from intrinsic climate variability in sea level records. This has led to an intensive debate on its existence and, if absent, also on the general validity of current future projections. Here we shed light on the controversial discussion from a methodological point of view. To do so, we provide a comprehensive review of trend methods used in the community so far. This resulted in an overview of 30 methods, each having its individual mathematical formulation, flexibilities, and characteristics. We illustrate that varying trend approaches may lead to contradictory acceleration-deceleration inferences. As for statistics-oriented trend methods, we argue that checks on model assumptions and model selection techniques yield a way out. However, since these selection methods all have implicit assumptions, we show that good modeling practices are of importance too. We conclude at this point that (i) several differently characterized methods should be applied and discussed simultaneously, (ii) uncertainties should be taken into account to prevent biased or wrong conclusions, and (iii) removing internally generated climate variability by incorporating atmospheric or oceanographic information helps to uncover externally forced climate change signals.

  19. Decelerated and linear eaters: effect of eating rate on food intake and satiety.

    PubMed

    Zandian, Modjtaba; Ioakimidis, Ioannis; Bergh, Cecilia; Brodin, Ulf; Södersten, Per

    2009-02-16

    Women were divided into those eating at a decelerated or linear rate. Eating rate was then experimentally increased or decreased by asking the women to adapt their rate of eating to curves presented on a computer screen and the effect on food intake and satiety was studied. Decelerated eaters were unable to eat at an increased rate, but ate the same amount of food when eating at a decreased rate as during the control condition. Linear eaters ate more food when eating at an increased rate, but less food when eating at a decreased rate. Decelerated eaters estimated their level of satiety lower when eating at an increased rate but similar to the control condition when eating at a decreased rate. Linear eaters estimated their level of satiety similar to the control level despite eating more food at an increased rate and higher despite eating less food at a decreased rate. The cumulative satiety curve was fitted to a sigmoid curve both in decelerated and linear eater under all conditions. Linear eaters rated their desire to eat and estimated their prospective intake lower than decelerated eaters and scored higher on a scale for restrained eating. It is suggested that linear eaters have difficulty maintaining their intake when eating rate is dissociated from its baseline level and that this puts them at risk of developing disordered eating. It is also suggested that feedback on eating rate can be used as an intervention to treat eating disorders.

  20. Redshift-Drift as a Test for Discriminating Between Decelerating Inhomogeneous and Accelerating Universe Models

    NASA Astrophysics Data System (ADS)

    Mishra, Priti; Célérier, Marie-Noëlle Singh, Tejinder P.

    2015-01-01

    Exact inhomogeneous solutions of Einstein's equations have been used in the literature to build models reproducing the cosmological data without dark energy. However, owing to the degrees of freedom pertaining to these models, it is necessary to get rid of the degeneracy often exhibited by the problem of distinguishing between them and accelerating universe models. We give an overview of redshift drift in inhomogeneous cosmologies, and explain how it serves to this purpose. One class of models which fits the data is the Szekeres Swiss-cheese class where non-spherically symmetric voids exhibit a typical size of about 400 Mpc. We present our calculation of the redshift drift in this model, and compare it with the results obtained by other authors for alternate scenarios.

  1. Accelerators/decelerators of achieving universal access to sexual and reproductive health services: a case study of Iranian health system

    PubMed Central

    2013-01-01

    Background At the 1994 International Conference on Population and Development (ICPD), held in Cairo, the global community agreed to the goal of achieving universal access to sexual and reproductive health (SRH) and rights by 2015. This research explores the accelerators and decelerators of achieving universal access to the sexual and reproductive health targets and accordingly makes some suggestions. Method We have critically reviewed the latest national reports and extracted the background data on each SRH indicator. The key stakeholders, both national and international, were visited and interviewed at two sites. A total of 55 in-depth interviews were conducted with religious leaders, policy-makers, senior managers, senior academics, and health care managers. Six focus-group discussions were also held among health care providers. The study was qualitative in nature. Results Obstacles on the road to achieving universal access to SRH can be viewed from two perspectives. One gap exists between current achievements and the targets. The other gap arises due to age, marital status, and residency status. The most recently observed trends in the indicators of the universal access to SRH shows that the achievements in the “unmet need for family planning” have been poor. Unmet need for family planning could directly be translated to unwanted pregnancies and unwanted childbirths; the former calls for sexual education to underserved people, including adolescents; and the latter calls for access to safe abortion. Local religious leaders have not actively attended international goal-setting programs. Therefore, they usually do not presume a positive attitude towards these goals. Such negative attitudes seem to be the most important factors hindering the progress towards universal access to SRH. Lack of international donors to fund for SRH programs is also another barrier. In national levels both state and the society are interactively playing their roles. We have used a

  2. Aerocapture Inflatable Decelerator (AID)

    NASA Technical Reports Server (NTRS)

    Reza, Sajjad

    2007-01-01

    Forward Attached Inflatable Decelerators, more commonly known as inflatable aeroshells, provide an effective, cost efficient means of decelerating spacecrafts by using atmospheric drag for aerocapture or planetary entry instead of conventional liquid propulsion deceleration systems. Entry into planetary atmospheres results in significant heating and aerodynamic pressures which stress aeroshell systems to their useful limits. Incorporation of lightweight inflatable decelerator surfaces with increased surface-area footprints provides the opportunity to reduce heat flux and induced temperatures, while increasing the payload mass fraction. Furthermore, inflatable aeroshell decelerators provide the needed deceleration at considerably higher altitudes and Mach numbers when compared with conventional rigid aeroshell entry systems. Inflatable aeroshells also provide for stowage in a compact space, with subsequent deployment of a large-area, lightweight heatshield to survive entry heating. Use of a deployable heatshield decelerator not only enables an increase in the spacecraft payload mass fraction and but may also eliminate the need for a spacecraft backshell and cruise stage. This document is the viewgraph slides for the paper's presentation.

  3. Higher-order resonances in a Stark decelerator

    SciTech Connect

    Meerakker, Sebastiaan Y.T. van de; Bethlem, Hendrick L.; Vanhaecke, Nicolas; Meijer, Gerard

    2005-05-15

    The motion of polar molecules can be controlled by time-varying inhomogeneous electric fields. In a Stark decelerator, this is exploited to select a fraction of a molecular beam that is accelerated, transported, or decelerated. Phase stability ensures that the selected bunch of molecules is kept together throughout the deceleration process. In this paper an extended description of phase stability in a Stark decelerator is given, including higher-order effects. This analysis predicts a wide variety of resonances that originate from the spatial and temporal periodicity of the electric fields. These resonances are experimentally observed using a beam of OH ({sup 2}{pi}{sub 3/2},v=0,J=3/2) radicals passing through a Stark decelerator.

  4. Motional, isotope and quadratic Stark effects in Rydberg-Stark deceleration and electric trapping of H and D

    NASA Astrophysics Data System (ADS)

    Hogan, S. D.; Seiler, Ch; Merkt, F.

    2013-02-01

    Hydrogen and deuterium Rydberg atoms, initially moving at velocities of 600 and 560 m s-1, respectively, in pulsed supersonic beams, have been decelerated and electrostatically trapped following adiabatic 90° deflection from their initial axis of propagation to minimize collisions with the trailing edge of the gas pulses. The time evolution of the potential energy surfaces, over which the atoms undergoing deceleration travel during the trap-loading process, is analogous to that of a moving electrodynamic trap. It has been studied in the laboratory-fixed frame of reference and in the continuously moving frame of reference defined by the instantaneous position of the electric-field minimum around which the atoms are located. The importance of the quadratic Stark effect in the deceleration of samples in Rydberg states with principal quantum numbers above 35 has also been investigated by comparison of experimental results with predictions resulting from the numerical calculation of particle trajectories. The data presented for deuterium atoms represent the first application of Rydberg-Stark deceleration and trapping for this atom. Comparison of the rate of loss of n = 30 H and D atoms from the trap enables one to conclude that it is not affected by the particle dynamics during deceleration and trap loading.

  5. Deceleration Orbit Improvements

    SciTech Connect

    Church, M.

    1991-04-26

    During the accelerator studies period of 12/90-1/91 much study time was dedicated to improving the E760 deceleration ramps. 4 general goals were in mind: (1) Reduce the relative orbit deviations from the nominal reference orbit as much as possible. This reduces the potential error in the orbit length calculation - which is the primary source of error in the beam energy calculation. (2) Maximize the transverse apertures. This minimizes beam loss during deceleration and during accidental beam blow-ups. (3) Measure and correct lattice parameters. Knowledge of {gamma}{sub T}, {eta}, Q{sub h}, Q{sub v}, and the dispersion in the straight sections allows for a more accurate energy calculation and reliable SYNCH calculations. (4) Minimize the coupling. This allows one to discern between horizontal and vertical tunes.

  6. Cell cycle of primitive hematopoietic progenitors decelerated in senescent mice is reactively accelerated after 2-Gy whole-body irradiation

    PubMed Central

    Tsuboi, Isao; Kuramoto, Kazunao; Kusunoki, Yoichiro; Inoue, Tohru

    2016-01-01

    Aging is considered to be a functional retardation of continuous xenobiotic responses over a lifetime after the developmental period; thus, the effects of ionizing radiation over a lifetime may be somewhat accounted for by a modifier of aging effects. This study was conducted to evaluate the possible/synergic effects of radiation during aging by determining cell-cycle parameters of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs), such as the percent of cells in cycling, the generation doubling time, and the cumulative cycling-cell fraction, by bromodeoxyuridine-ultraviolet assay, which enables the determination of their cycling capacity in vivo. Colony-forming progenitor cells, such as colony-forming unit (CFU)-granulocyte/macrophage (GM), CFU in the spleen on day 9 (CFU-S9), and CFU-S on day 13 (CFU-S13) for mature, less mature, and immature HPCs, respectively, were evaluated in young and old mice (6 weeks and 21 months of age, respectively) with or without 2-Gy whole-body irradiation and a 4-week recovery period. Then, cell-cycle parameters were evaluated and compared. As a result, the generation doubling time of all types of HPC was prolonged by the irradiation in both young and old mouse groups, except that of CFU-S13 in old mice, which showed acceleration of the cell cycle following the irradiation. In addition, only CFU-S13 in irradiated old mice showed a significant increase in the cumulative cycling-cell-fraction ratio. Significant changes due to the effects of aging and irradiation on HPCs were observed only in the immature HPCs, i.e., the cell cycle of immature HPCs was suppressed by aging without irradiation and was, in contrast, accelerated as the cells recovered from radiation-induced damage. This suggests that the mechanisms of peripheral blood recovery after 2-Gy whole-body irradiation are markedly different between young and old mice, although 21-month-old mice showed almost the same level of recovery as the young mice. PMID

  7. Differential longitudinal changes in cortical thickness, surface area and volume across the adult life span: regions of accelerating and decelerating change.

    PubMed

    Storsve, Andreas B; Fjell, Anders M; Tamnes, Christian K; Westlye, Lars T; Overbye, Knut; Aasland, Hilde W; Walhovd, Kristine B

    2014-06-18

    Human cortical thickness and surface area are genetically independent, emerge through different neurobiological events during development, and are sensitive to different clinical conditions. However, the relationship between changes in the two over time is unknown. Additionally, longitudinal studies have almost invariably been restricted to older adults, precluding the delineation of adult life span trajectories of change in cortical structure. In this longitudinal study, we investigated changes in cortical thickness, surface area, and volume after an average interval of 3.6 years in 207 well screened healthy adults aged 23-87 years. We hypothesized that the relationships among metrics are dynamic across the life span, that the primary contributor to cortical volume reductions in aging is cortical thinning, and that magnitude of change varies with age and region. Changes over time were seen in cortical area (mean annual percentage change [APC], -0.19), thickness (APC, -0.35), and volume (APC, -0.51) in most regions. Volume changes were primarily explained by changes in thickness rather than area. A negative relationship between change in thickness and surface area was found across several regions, where more thinning was associated with less decrease in area, and vice versa. Accelerating changes with increasing age was seen in temporal and occipital cortices. In contrast, decelerating changes were seen in prefrontal and anterior cingulate cortices. In conclusion, a dynamic relationship between cortical thickness and surface area changes exists throughout the adult life span. The mixture of accelerating and decelerating changes further demonstrates the importance of studying these metrics across the entire adult life span. PMID:24948804

  8. Differential longitudinal changes in cortical thickness, surface area and volume across the adult life span: regions of accelerating and decelerating change.

    PubMed

    Storsve, Andreas B; Fjell, Anders M; Tamnes, Christian K; Westlye, Lars T; Overbye, Knut; Aasland, Hilde W; Walhovd, Kristine B

    2014-06-18

    Human cortical thickness and surface area are genetically independent, emerge through different neurobiological events during development, and are sensitive to different clinical conditions. However, the relationship between changes in the two over time is unknown. Additionally, longitudinal studies have almost invariably been restricted to older adults, precluding the delineation of adult life span trajectories of change in cortical structure. In this longitudinal study, we investigated changes in cortical thickness, surface area, and volume after an average interval of 3.6 years in 207 well screened healthy adults aged 23-87 years. We hypothesized that the relationships among metrics are dynamic across the life span, that the primary contributor to cortical volume reductions in aging is cortical thinning, and that magnitude of change varies with age and region. Changes over time were seen in cortical area (mean annual percentage change [APC], -0.19), thickness (APC, -0.35), and volume (APC, -0.51) in most regions. Volume changes were primarily explained by changes in thickness rather than area. A negative relationship between change in thickness and surface area was found across several regions, where more thinning was associated with less decrease in area, and vice versa. Accelerating changes with increasing age was seen in temporal and occipital cortices. In contrast, decelerating changes were seen in prefrontal and anterior cingulate cortices. In conclusion, a dynamic relationship between cortical thickness and surface area changes exists throughout the adult life span. The mixture of accelerating and decelerating changes further demonstrates the importance of studying these metrics across the entire adult life span.

  9. Deceleration of neutral molecules in macroscopic traveling traps

    SciTech Connect

    Osterwalder, Andreas; Meek, Samuel A.; Hammer, Georg; Haak, Henrik; Meijer, Gerard

    2010-05-15

    A decelerator is presented where polar neutral molecules are guided and decelerated using the principle of traveling electric potential wells, such that molecules are confined in stable three-dimensional traps throughout. We compare this decelerator with that of Scharfenberg et al. [Phys. Rev. A 79, 023410 (2009)] and we show that the current decelerator provides a substantially larger phase-space acceptance, even at higher acceleration. The mode of operation is described and experimentally demonstrated by guiding and decelerating CO molecules.

  10. Analytic wave model of Stark deceleration dynamics

    SciTech Connect

    Gubbels, Koos; Meijer, Gerard; Friedrich, Bretislav

    2006-06-15

    Stark deceleration relies on time-dependent inhomogeneous electric fields which repetitively exert a decelerating force on polar molecules. Fourier analysis reveals that such fields, generated by an array of field stages, consist of a superposition of partial waves with well-defined phase velocities. Molecules whose velocities come close to the phase velocity of a given wave get a ride from that wave. For a square-wave temporal dependence of the Stark field, the phase velocities of the waves are found to be odd-fraction multiples of a fundamental phase velocity {lambda}/{tau}, with {lambda} and {tau} the spatial and temporal periods of the field. Here we study explicitly the dynamics due to any of the waves as well as due to their mutual perturbations. We first solve the equations of motion for the case of single-wave interactions and exploit their isomorphism with those for the biased pendulum. Next we analyze the perturbations of the single-wave dynamics by other waves and find that these have no net effect on the phase stability of the acceleration or deceleration process. Finally, we find that a packet of molecules can also ride a wave which results from an interference of adjacent waves. In this case, small phase stability areas form around phase velocities that are even-fraction multiples of the fundamental velocity. A detailed comparison with classical trajectory simulations and with experiment demonstrates that the analytic 'wave model' encompasses all the longitudinal physics encountered in a Stark decelerator.

  11. A transition from a decelerated to an accelerated phase of the universe expansion from the simplest non-trivial polynomial function of T in the f(R,T) formalism

    NASA Astrophysics Data System (ADS)

    Moraes, P. H. R. S.; Ribeiro, G.; Correa, R. A. C.

    2016-07-01

    In this work we present cosmological solutions from the simplest non-trivial polynomial function of T in f(R,T) theory of gravity, with R and T standing for the Ricci scalar and trace of the energy-momentum tensor, respectively. Although such an approach yields a highly non-linear differential equation for the scale factor, we show that it is possible to obtain analytical solutions for the cosmological parameters. For some values of the free parameters, the model is able to predict a transition from a decelerated to an accelerated expansion of the universe and the values of the deceleration parameter agree with observation.

  12. Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot Performance

    NASA Technical Reports Server (NTRS)

    Creer, Brent Y.; Smedal, Harald A.; Wingrove, Rodney C.

    1960-01-01

    A research program the general objective of which was to measure the effects of various sustained accelerations on the control performance of pilots, was carried out on the Aviation Medical Acceleration Laboratory centrifuge, U.S. Naval Air Development Center, Johnsville, PA. The experimental setup consisted of a flight simulator with the centrifuge in the control loop. The pilot performed his control tasks while being subjected to acceleration fields such as might be encountered by a forward-facing pilot flying an atmosphere entry vehicle. The study was divided into three phases. In one phase of the program, the pilots were subjected to a variety of sustained linear acceleration forces while controlling vehicles with several different sets of longitudinal dynamics. Here, a randomly moving target was displayed to the pilot on a cathode-ray tube. For each combination of acceleration field and vehicle dynamics, pilot tracking accuracy was measured and pilot opinion of the stability and control characteristics was recorded. Thus, information was obtained on the combined effects of complexity of control task and magnitude and direction of acceleration forces on pilot performance. These tests showed that the pilot's tracking performance deteriorated markedly at accelerations greater than about 4g when controlling a lightly damped vehicle. The tentative conclusion was also reached that regardless of the airframe dynamics involved, the pilot feels that in order to have the same level of control over the vehicle, an increase in the vehicle dynamic stability was required with increases in the magnitudes of the acceleration impressed upon the pilot. In another phase, boundaries of human tolerance of acceleration were established for acceleration fields such as might be encountered by a pilot flying an orbital vehicle. A special pilot restraint system was developed to increase human tolerance to longitudinal decelerations. The results of the tests showed that human tolerance

  13. Beam Breakup Effects in Dielectric Based Accelerators

    SciTech Connect

    Schoessow, P.; Kanareykin, A.; Jing, C.; Kustov, A.; Altmark, A.; Power, J. G.; Gai, W.

    2009-01-22

    The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.

  14. The degree of heart rate asymmetry is crucial for the validity of the deceleration and acceleration capacity indices of heart rate: A model-based study.

    PubMed

    Pan, Qing; Zhou, Gongzhan; Wang, Ruofan; Yu, Yihua; Li, Feng; Fang, Luping; Yan, Jing; Ning, Gangmin

    2016-09-01

    The deceleration capacity (DC) and acceleration capacity (AC) of heart rate are a pair of indices used for evaluating the autonomic nervous system (ANS). We assessed the role of heart rate asymmetry (HRA) in defining the relative performance of DC and AC using a mathematical model, which is able to generate a realistic RR interval (RRI) time series with controlled ANS states. The simulation produced a set of RRI series with random sympathetic and vagal activities. The multi-scale DCs and ACs were computed from the RRI series, and the correlation of DC and AC with the ANS functions was analyzed to evaluate the performance of the indices. In the model, the HRA level was modified by changing the inspiration/expiration (I/E) ratio to examine the influence of HRA on the performances of DC and AC. The results show that on the conventional scales (T=1, s=2), an HRA level above 50% results in a stronger association of DC with the ANS, compared with AC. On higher scales (T=4, s=6), there was no HRA and DC showed a similar performance to AC for all I/E ratios. The data suggest that the HRA level determines which of DC or AC is the optimal index for expressing ANS functions. Future clinical applications of DC and AC should be accompanied by an HRA analysis to provide a better index for assessing ANS. PMID:27392228

  15. Modulational effects in accelerators

    SciTech Connect

    Satogata, T.

    1997-12-01

    We discuss effects of field modulations in accelerators, specifically those that can be used for operational beam diagnostics and beam halo control. In transverse beam dynamics, combined effects of nonlinear resonances and tune modulations influence diffusion rates with applied tune modulation has been demonstrated. In the longitudinal domain, applied RF phase and voltage modulations provide mechanisms for parasitic halo transport, useful in slow crystal extraction. Experimental experiences with transverse tune and RF modulations are also discussed.

  16. Effects of acceleration on gait measures in three horse gaits.

    PubMed

    Nauwelaerts, Sandra; Zarski, Lila; Aerts, Peter; Clayton, Hilary

    2015-05-01

    Animals switch gaits according to locomotor speed. In terrestrial locomotion, gaits have been defined according to footfall patterns or differences in center of mass (COM) motion, which characterizes mechanisms that are more general and more predictive than footfall patterns. This has generated different variables designed primarily to evaluate steady-speed locomotion, which is easier to standardize in laboratory conditions. However, in the ecology of an animal, steady-state conditions are rare and the ability to accelerate, decelerate and turn is essential. Currently, there are no data available that have tested whether COM variables can be used in accelerative or decelerative conditions. This study used a data set of kinematics and kinetics of horses using three gaits (walk, trot, canter) to evaluate the effects of acceleration (both positive and negative) on commonly used gait descriptors. The goal was to identify variables that distinguish between gaits both at steady state and during acceleration/deceleration. These variables will either be unaffected by acceleration or affected by it in a predictable way. Congruity, phase shift and COM velocity angle did not distinguish between gaits when the dataset included trials in unsteady conditions. Work (positive and negative) and energy recovery distinguished between gaits and showed a clear relationship with acceleration. Hodographs are interesting graphical representations to study COM mechanics, but they are descriptive rather than quantitative. Force angle, collision angle and collision fraction showed a U-shaped relationship with acceleration and seem promising tools for future research in unsteady conditions.

  17. Aerocapture Inflatable Decelerator for Planetary Entry

    NASA Technical Reports Server (NTRS)

    Reza, Sajjad; Hund, Richard; Kustas, Frank; Willcockson, William; Songer, Jarvis; Brown, Glen

    2007-01-01

    Forward Attached Inflatable Decelerators, more commonly known as inflatable aeroshells, provide an effective, cost efficient means of decelerating spacecrafts by using atmospheric drag for aerocapture or planetary entry instead of conventional liquid propulsion deceleration systems. Entry into planetary atmospheres results in significant heating and aerodynamic pressures which stress aeroshell systems to their useful limits. Incorporation of lightweight inflatable decelerator surfaces with increased surface-area footprints provides the opportunity to reduce heat flux and induced temperatures, while increasing the payload mass fraction. Furthermore, inflatable aeroshell decelerators provide the needed deceleration at considerably higher altitudes and Mach numbers when compared with conventional rigid aeroshell entry systems. Inflatable aeroshells also provide for stowage in a compact space, with subsequent deployment of a large-area, lightweight heatshield to survive entry heating. Use of a deployable heatshield decelerator enables an increase in the spacecraft payload mass fraction and may eliminate the need for a spacecraft backshell.

  18. Visual acceleration detection - Effect of sign and motion orientation

    NASA Technical Reports Server (NTRS)

    Calderone, Jack B.; Kaiser, Mary K.

    1989-01-01

    Thresholds for the detection of constant acceleration and deceleration of a discrete object moving along horizontal and vertical axes were studied. A staircase methodology was used to determine thresholds for three average velocities (0.7, 1.2, and 1.7 deg/sec). Thresholds, expressed as the proportion of velocity change, did not differ significantly among the average velocities; thus, a consistent Weber-like fraction is suggested by the data. Furthermore, there was an interaction between the axis of motion (horizontal or vertical) and the sign of the velocity change (acceleration or deceleration): accelerations were easier to detect along the vertical axis, decelerations along the horizontal axis.

  19. Photorefractive deceleration of light pulses

    NASA Astrophysics Data System (ADS)

    Sturman, B.; Podivilov, E.; Gorkunov, M.

    2008-04-01

    We theoretically study the effect of light deceleration in photorefractive nonlinear media. This includes consideration of different types of the photorefractive nonlinear response, different wave interaction schemes, and an analysis of the influence of the input parameters, such as the input temporal pulse width and the coupling strength, on the output pulse characteristics: the time delay, the propagation velocity, the amplification factor, and the output width. We show that photorefractive light deceleration has numerous advantages over other known techniques. It works already at low intensities, at room temperature, and within wide spectral ranges and offers a vast variety of handles for manipulating light pulses. An analogy with the light deceleration method based on the quantum effect of electromagnetically induced transparency in ultracold resonant gases is also considered.

  20. Phase stability in a multistage Zeeman decelerator

    SciTech Connect

    Wiederkehr, A. W.; Hogan, S. D.; Merkt, F.

    2010-10-15

    The phase stability of a multistage Zeeman decelerator is analyzed by numerical particle-trajectory simulations and experimental measurements. A one-dimensional model of the phase stability in multistage Stark deceleration [Bethlem et al., Phys. Rev. Lett. 84, 5744 (2000)] has been adapted to multistage Zeeman deceleration and compared with one- and three-dimensional particle-trajectory simulations, including the analysis of the effect of finite switch-on and -off times of the deceleration pulses. The comparison reveals that transverse effects in the decelerator lead to a considerable reduction of the phase-space acceptance at low values of the phase angle and an enhancement at high values. The optimal combinations of phase angles and currents with which a preset amount of kinetic energy can be removed from atoms and molecules in a pulsed supersonic beam using a multistage decelerator are determined by simulation. Quantitative analysis of the phase-space acceptance within a given volume reveals that for our decelerator (8 {mu}s switch-off time) optimal conditions are achieved for values of the phase angle between 45 deg. and 55 deg. This conclusion is examined and confirmed by experimental measurements using deuterium atoms. Alternative approaches to generate optimal deceleration pulse sequences, such as the implementation of evolutionary algorithms or the use of higher-order modes of the decelerator, are discussed.

  1. Earth's Decelerating Tectonic Plates

    SciTech Connect

    Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P

    2008-08-22

    Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.

  2. Acceleration or deceleration of self-motion by the Marangoni effect

    NASA Astrophysics Data System (ADS)

    Matsuda, Yui; Suematsu, Nobuhiko J.; Kitahata, Hiroyuki; Ikura, Yumihiko S.; Nakata, Satoshi

    2016-06-01

    We investigated the water-depth dependence of the self-motion of a camphor disk and camphor boat. With increasing water depth, the speed of motion of the camphor disk increased, but that of the camphor boat decreased in an annular one-dimensional system. We discussed the difference in the water-depth dependence of the speed of the camphor objects in relation to Marangoni flow. We concluded that Marangoni flow, which became stronger with increasing the water depth, positively and negatively affected the speed of the disk and boat, respectively.

  3. Low Density Supersonic Decelerator Parachute Decelerator System

    NASA Technical Reports Server (NTRS)

    Gallon, John C.; Clark, Ian G.; Rivellini, Tommaso P.; Adams, Douglas S.; Witkowski, Allen

    2013-01-01

    The Low Density Supersonic Decelerator Project has undertaken the task of developing and testing a large supersonic ringsail parachute. The parachute under development is intended to provide mission planners more options for parachutes larger than the Mars Science Laboratory's 21.5m parachute. During its development, this new parachute will be taken through a series of tests in order to bring the parachute to a TRL-6 readiness level and make the technology available for future Mars missions. This effort is primarily focused on two tests, a subsonic structural verification test done at sea level atmospheric conditions and a supersonic flight behind a blunt body in low-density atmospheric conditions. The preferred method of deploying a parachute behind a decelerating blunt body robotic spacecraft in a supersonic flow-field is via mortar deployment. Due to the configuration constraints in the design of the test vehicle used in the supersonic testing it is not possible to perform a mortar deployment. As a result of this limitation an alternative deployment process using a ballute as a pilot is being developed. The intent in this alternate approach is to preserve the requisite features of a mortar deployment during canopy extraction in a supersonic flow. Doing so will allow future Mars missions to either choose to mortar deploy or pilot deploy the parachute that is being developed.

  4. Multistage Zeeman deceleration

    NASA Astrophysics Data System (ADS)

    Wiederkehr, A. W.; Hogan, S. D.; Andrist, M.; Schmutz, H.; Lambilotte, B.; Merkt, F.

    2009-05-01

    In recent years multistage Zeeman deceleration of open shell atoms and molecules has been developed as a possible method to produce cold (< 1 K) samples for applications in precision spectroscopy and studies of cold reactive collisions [1-7]. This contribution will present the strategy followed at ETH Zurich which relies on (i) the generation of strong magnetic field pulses (> 2 T) with rise and fall times of only a few microseconds, (ii) the deceleration and loading of samples into quadrupole magnetic traps, (iii) 3D particle trajectory simulations of the complete deceleration and trapping processes, and (iv) comparison of the simulations with measurements of the velocity and spatial distributions of the decelerated and trapped samples. The four generations of Zeeman deceleration and trapping devices developed in our group will be presented and compared using results obtained with different samples. [0pt] [1] N. Vanhaecke et al., Phys. Rev. A 75, 031402(R)(2007).[0pt] [2] S. D. Hogan et al., Phys. Rev. A 76, 023412 (2007).[0pt] [3] E. Narevicius et al., New. J. Phys. 9, 358 (2007).[0pt] [4] E. Narevicius et al., Phys. Rev. Lett. 100, 093003 (2008).[0pt] [5] E. Narevicius et al., Phys. Rev. A 77, 051401(R) (2008).[0pt] [6] S. D. Hogan et al., J. Phys. B 41, 081005 (2008).[0pt] [7] S. D. Hogan et al., Phys. Rev. Lett. 101, 143001 (2008).

  5. Electron Cloud Effects in Accelerators

    SciTech Connect

    Furman, M.A.

    2012-11-30

    Abstract We present a brief summary of various aspects of the electron-cloud effect (ECE) in accelerators. For further details, the reader is encouraged to refer to the proceedings of many prior workshops, either dedicated to EC or with significant EC contents, including the entire ?ECLOUD? series [1?22]. In addition, the proceedings of the various flavors of Particle Accelerator Conferences [23] contain a large number of EC-related publications. The ICFA Beam Dynamics Newsletter series [24] contains one dedicated issue, and several occasional articles, on EC. An extensive reference database is the LHC website on EC [25].

  6. Parameterizing the Deceleration Parameter

    NASA Astrophysics Data System (ADS)

    Pavón, D.; Duran, I.; Del Campo, S.; Herrera, R.

    2015-01-01

    We propose and constrain with the latest observational data three parameterizations of the deceleration parameter, valid from the matter era to the far future. They are well behaved and do not diverge at any redshift. On the other hand, they are model independent in the sense that in constructing them the only assumption made was that the Universe is homogeneous and isotropic at large scales.

  7. Deceleration efficiencies of shrub windbreaks in a wind tunnel

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoxu; Zou, Xueyong; Zhou, Na; Zhang, Chunlai; Shi, Sha

    2015-03-01

    Artemisia and Salix are dominant shrub species for windbreaks in arid areas of China, and they show similar features to shrubs in other arid areas of the world. We compared the mean velocity fields and shelter effects of two shrub windbreaks with different layouts. For a single plant of Artemisia, the higher the free airflow velocity is, the more the wind velocity around two sides of the plant increases. The velocity gradient around a single plant of Salix is smaller than that around an Artemisia plant due to the difference in the plant shapes. Seven new velocity zones in the horizontal direction appear when airflow passes through an Artemisia windbreak, including four deceleration zones and three acceleration zones. The mean velocity field that is affected by a Salix windbreak can be divided into a deceleration zone in the front, an acceleration zone above, a vortex zone behind and a restoration zone downwind of the vortex zone. Shelter effects of the shrub windbreaks vary with the wind velocity and are influenced by the construct of the windbreaks. Shrub windbreaks that have a complex construction have better shelter effects than simple ones. The shelter effects of plant windbreaks are also influenced by the growth features of the plants. Considering the plant characteristics and the shelter effects of Salix and Artemisia windbreaks, it is optimal to plant these two windbreaks together in a sand-control system. This research is intended to be useful for sand movement control in arid areas.

  8. Aerodynamic Decelerators for Planetary Exploration: Past, Present, and Future

    NASA Technical Reports Server (NTRS)

    Cruz, Juna R.; Lingard, J. Stephen

    2006-01-01

    In this paper, aerodynamic decelerators are defined as textile devices intended to be deployed at Mach numbers below five. Such aerodynamic decelerators include parachutes and inflatable aerodynamic decelerators (often known as ballutes). Aerodynamic decelerators play a key role in the Entry, Descent, and Landing (EDL) of planetary exploration vehicles. Among the functions performed by aerodynamic decelerators for such vehicles are deceleration (often from supersonic to subsonic speeds), minimization of descent rate, providing specific descent rates (so that scientific measurements can be obtained), providing stability (drogue function - either to prevent aeroshell tumbling or to meet instrumentation requirements), effecting further aerodynamic decelerator system deployment (pilot function), providing differences in ballistic coefficients of components to enable separation events, and providing height and timeline to allow for completion of the EDL sequence. Challenging aspects in the development of aerodynamic decelerators for planetary exploration missions include: deployment in the unusual combination of high Mach numbers and low dynamic pressures, deployment in the wake behind a blunt-body entry vehicle, stringent mass and volume constraints, and the requirement for high drag and stability. Furthermore, these aerodynamic decelerators must be qualified for flight without access to the exotic operating environment where they are expected to operate. This paper is an introduction to the development and application of aerodynamic decelerators for robotic planetary exploration missions (including Earth sample return missions) from the earliest work in the 1960s to new ideas and technologies with possible application to future missions. An extensive list of references is provided for additional study.

  9. Psychological effects of thought acceleration.

    PubMed

    Pronin, Emily; Jacobs, Elana; Wegner, Daniel M

    2008-10-01

    Six experiments found that manipulations that increase thought speed also yield positive affect. These experiments varied in both the methods used for accelerating thought (i.e., instructions to brainstorm freely, exposure to multiple ideas, encouragement to plagiarize others' ideas, performance of easy cognitive tasks, narration of a silent video in fast-forward, and experimentally controlled reading speed) and the contents of the thoughts that were induced (from thoughts about money-making schemes to thoughts of five-letter words). The results suggested that effects of thought speed on mood are partially rooted in the subjective experience of thought speed. The results also suggested that these effects can be attributed to the joy-enhancing effects of fast thinking (rather than only to the joy-killing effects of slow thinking). This work is inspired by observations of a link between "racing thoughts" and euphoria in cases of clinical mania, and potential implications of that observed link are discussed.

  10. Low-temperature M =3 flow deceleration by Lorentz force

    NASA Astrophysics Data System (ADS)

    Nishihara, Munetake; Rich, J. William; Lempert, Walter R.; Adamovich, Igor V.; Gogineni, Sivaram

    2006-08-01

    This paper presents results of cold magnetohydrodynamic (MHD) flow deceleration experiments using repetitively pulsed, short pulse duration, high voltage discharge to produce ionization in M =3 nitrogen and air flows in the presence of transverse direct current electric field and transverse magnetic field. MHD effect on the flow is detected from the flow static pressure measurements. Retarding Lorentz force applied to the flow produces a static pressure increase of up to 17%-20%, while accelerating force of the same magnitude results in static pressure increase of up to 5%-7%. The measured static pressure changes are compared with modeling calculations using quasi-one-dimensional MHD flow equations. Comparison of the experimental results with the modeling calculations shows that the retarding Lorentz force increases the static pressure rise produced by Joule heating of the flow, while the accelerating Lorentz force reduces the pressure rise. The effect is produced for two possible combinations of the magnetic field and transverse current directions producing the same Lorentz force direction (both for accelerating and retarding force). This demonstrates that the observed static pressure change is indeed due to the MHD interaction, and not due to Joule heating of the flow in the crossed discharge. No discharge polarity effect on the static pressure was detected in the absence of the magnetic field. The fraction of the discharge input power going into Joule heat in nitrogen and dry air, inferred from the present experiments, is low, α =0.1, primarily because energy remains frozen in the vibrational energy mode of nitrogen. This result provides first direct evidence of cold supersonic flow deceleration by Lorentz force.

  11. Low-temperature M=3 flow deceleration by Lorentz force

    SciTech Connect

    Nishihara, Munetake; Rich, J. William; Lempert, Walter R.; Adamovich, Igor V.; Gogineni, Sivaram

    2006-08-15

    This paper presents results of cold magnetohydrodynamic (MHD) flow deceleration experiments using repetitively pulsed, short pulse duration, high voltage discharge to produce ionization in M=3 nitrogen and air flows in the presence of transverse direct current electric field and transverse magnetic field. MHD effect on the flow is detected from the flow static pressure measurements. Retarding Lorentz force applied to the flow produces a static pressure increase of up to 17%-20%, while accelerating force of the same magnitude results in static pressure increase of up to 5%-7%. The measured static pressure changes are compared with modeling calculations using quasi-one-dimensional MHD flow equations. Comparison of the experimental results with the modeling calculations shows that the retarding Lorentz force increases the static pressure rise produced by Joule heating of the flow, while the accelerating Lorentz force reduces the pressure rise. The effect is produced for two possible combinations of the magnetic field and transverse current directions producing the same Lorentz force direction (both for accelerating and retarding force). This demonstrates that the observed static pressure change is indeed due to the MHD interaction, and not due to Joule heating of the flow in the crossed discharge. No discharge polarity effect on the static pressure was detected in the absence of the magnetic field. The fraction of the discharge input power going into Joule heat in nitrogen and dry air, inferred from the present experiments, is low, {alpha}=0.1, primarily because energy remains frozen in the vibrational energy mode of nitrogen. This result provides first direct evidence of cold supersonic flow deceleration by Lorentz force.

  12. Physics at CERN’s Antiproton Decelerator

    NASA Astrophysics Data System (ADS)

    Hori, M.; Walz, J.

    2013-09-01

    The Antiproton Decelerator (AD) facility of CERN began operation in 1999 to serve experiments for studies of CPT invariance by precision laser and microwave spectroscopy of antihydrogen (Hbar ) and antiprotonic helium (pbar He) atoms. The first 12 years of AD operation saw cold Hbar synthesized by overlapping clouds of positrons (e+) and antiprotons (pbar ) confined in magnetic Penning traps. Cold Hbar was also produced in collisions between Rydberg positronium (Ps) atoms and pbar . Ground-state Hbar was later trapped for up to ˜1000 s in a magnetic bottle trap, and microwave transitions excited between its hyperfine levels. In the pbar He atom, deep ultraviolet transitions were measured to a fractional precision of (2.3-5)×10-9 by sub-Doppler two-photon laser spectroscopy. From this the antiproton-to-electron mass ratio was determined as M/me=1836.1526736(23), which agrees with the p value known to a similar precision. Microwave spectroscopy of pbar He yielded a measurement of the pbar magnetic moment with a precision of 0.3%. More recently, the magnetic moment of a single pbar confined in a Penning trap was measured with a higher precision, as μ=-2.792845(12)μ in nuclear magnetons. Other results reviewed here include the first measurements of the energy loss (-dE/dx) of 1-100 keV pbar traversing conductor and insulator targets; the cross sections of low-energy (<10 keV) pbar ionizing atomic and molecular gas targets; and the cross sections of 5 MeV pbar annihilating on various target foils via nuclear collisions. The biological effectiveness of pbar beams destroying cancer cells was measured as a possible method for radiological therapy. New experiments under preparation attempt to measure the gravitational acceleration of Hbar or synthesize H. Several other future experiments will also be briefly described.

  13. Collective Deceleration: Toward a Compact Beam Dump

    SciTech Connect

    Wu, H.-C.; Tajima, T.; Habs, D.; Chao, A.W.; Meyer-ter-Vehn, J.; /Munich, Max Planck Inst. Quantenopt.

    2011-11-28

    With the increasing development of laser accelerators, the electron energy is already beyond GeV and even higher in near future. Conventional beam dump based on ionization or radiation loss mechanism is cumbersome and costly, also has radiological hazards. We revisit the stopping power of high-energy charged particles in matter and discuss the associated problem of beam dump from the point of view of collective deceleration. The collective stopping length in an ionized gas can be several orders of magnitude shorter than the Bethe-Bloch and multiple electromagnetic cascades stopping length in solid. At the mean time, the tenuous density of the gas makes the radioactivation negligible. Such a compact and non-radioactivating beam dump works well for short and dense bunches, which is typically generated from laser wakefield accelerator.

  14. Automated Fetal Heart Rate Analysis in Labor: Decelerations and Overshoots

    SciTech Connect

    Georgieva, A. E.; Payne, S. J.; Moulden, M.; Redman, C. W. G.

    2010-10-25

    Electronic fetal heart rate (FHR) recording is a standard way of monitoring fetal health in labor. Decelerations and accelerations usually indicate fetal distress and normality respectively. But one type of acceleration may differ, namely an overshoot that may atypically reflect fetal stress. Here we describe a new method for detecting decelerations, accelerations and overshoots as part of a novel system for computerized FHR analysis (OxSyS). There was poor agreement between clinicians when identifying these FHR features visually, which precluded setting a gold standard of interpretation. We therefore introduced 'modified' Sensitivity (SE deg.) and 'modified' Positive Predictive Value (PPV deg.) as appropriate performance measures with which the algorithm was optimized. The relation between overshoots and fetal compromise in labor was studied in 15 cases and 15 controls. Overshoots showed promise as an indicator of fetal compromise. Unlike ordinary accelerations, overshoots cannot be considered to be reassuring features of fetal health.

  15. Automated Fetal Heart Rate Analysis in Labor: Decelerations and Overshoots

    NASA Astrophysics Data System (ADS)

    Georgieva, A. E.; Payne, S. J.; Moulden, M.; Redman, C. W. G.

    2010-10-01

    Electronic fetal heart rate (FHR) recording is a standard way of monitoring fetal health in labor. Decelerations and accelerations usually indicate fetal distress and normality respectively. But one type of acceleration may differ, namely an overshoot that may atypically reflect fetal stress. Here we describe a new method for detecting decelerations, accelerations and overshoots as part of a novel system for computerized FHR analysis (OxSyS). There was poor agreement between clinicians when identifying these FHR features visually, which precluded setting a gold standard of interpretation. We therefore introduced `modified' Sensitivity (SE°) and `modified' Positive Predictive Value (PPV°) as appropriate performance measures with which the algorithm was optimized. The relation between overshoots and fetal compromise in labor was studied in 15 cases and 15 controls. Overshoots showed promise as an indicator of fetal compromise. Unlike ordinary accelerations, overshoots cannot be considered to be reassuring features of fetal health.

  16. Accelerated School Programmes: Assessing Their Effectiveness.

    ERIC Educational Resources Information Center

    Gaziel, Haim

    2001-01-01

    Examines the effectiveness of Accelerated School Programs (ASPs) on the basis of a study of four comprehensive schools in Israel. Assesses the influence of ASPs upon internal school processes, such as school goals, structures, and cultures, as perceived by school staff. Determines the project's impact on staff and parents' attitudes, and examines…

  17. Acceleration in Linear and Circular Motion

    ERIC Educational Resources Information Center

    Kellington, S. H.; Docherty, W.

    1975-01-01

    Describes the construction of a simple accelerometer and explains its use in demonstrating acceleration, deceleration, constant speed, measurement of acceleration, acceleration and the inclined plane and angular and radial acceleration. (GS)

  18. Combining Magnetic and Electric Sails for Interstellar Deceleration

    NASA Astrophysics Data System (ADS)

    Perakis, Nikolaos; Hein, Andreas M.

    2016-07-01

    The main benefit of an interstellar mission is to carry out in-situ measurements within a target star system. To allow for extended in-situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technologys shortcomings: A magnetic sail is more effective at higher velocities than the electric sail and vice versa. It is demonstrated that using both sails sequentially outperforms using only the magnetic or electric sail for various mission scenarios and velocity ranges, at a constant total spacecraft mass. For example, for decelerating from 5% c, to interplanetary velocities, a spacecraft with both sails needs about 29 years, whereas the electric sail alone would take 35 years and the magnetic sail about 40 years with a total spacecraft mass of 8250 kg. Furthermore, it is assessed how the combined deceleration system affects the optimal overall mission architecture for different spacecraft masses and cruising speeds. Future work would investigate how operating both systems in parallel instead of sequentially would affect its performance. Moreover, uncertainties in the density of interstellar matter and sail properties need to be explored.

  19. Reduction of Effective Acceleration to Microgravity Levels

    NASA Technical Reports Server (NTRS)

    Downey, James P.

    2000-01-01

    Acceleration due to earth's gravity causes buoyancy driven convection and sedimentation in solutions. In addition. pressure gradients occur as a function of the height within a liquid column. Hence gravity effects both equilbria conditions and phase transitions as a result of hydrostatic pressure gradients. The affect of gravity on the rate of heat and man transfer in solutal processes can be particularly important in polymer processing due to the high sensitivity of polymeric materials to processing conditions. The term microgravity has been coined to describe an environment in which the affects of gravitational acceleration am greatly reduced. It may seem odd to talk in term of reducing the effects of gravitational acceleration since gravitational attraction is a basic property of matter. However, die presence of gravity on in situ processing or measurements can be negated by achieving conditions in which the laboratory, or more specifically the container of the experimental materials, a subjected to the same acceleration as the materials themselves. With regard to the laboratory reference frame, there is virtually no force on the experimental solutions. This is difficult to achieve but can be done. A short review of Newtonian physics provides an explanation on both how processes we affected by gravity and how microgravity conditions are achieved. The fact that fluids deform when subject to a force bid solids do not indicates that solids have a structure able to exert an opposing force that negates an externally applied force. Liquids deform when a force is applied, indicating that a liquid structure cannot completely negate an applied force. Just how easily a liquid resists deformation is related to its viscosity. Spaceflight provides an environment in which the laboratory reference frame i.e. the spacecraft and all the equipment therein an experiencing virtually identical forces. There is no solid foundation underneath such a laboratory, so the laboratory

  20. HIAD-2 (Hypersonic Inflatable Aerodynamic Decelerator)

    NASA Video Gallery

    The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project is a disruptive technology that will accommodate the atmospheric entry of heavy payloads to planetary bodies such as Mars. HIAD over...

  1. A scheme for reducing deceleration-phase Rayleigh-Taylor growth in inertial confinement fusion implosions

    NASA Astrophysics Data System (ADS)

    Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

    2016-05-01

    It is demonstrated that the growth of acceleration-phase instabilities in inertial confinement fusion implosions can be controlled, especially in the high-foot implosions [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility. However, the excessive growth of the deceleration-phase instabilities can still destroy the hot spot ignition. A scheme is proposed to retard the deceleration-phase Rayleigh-Taylor instability growth by shock collision near the waist of the inner shell surface. Two-dimensional radiation hydrodynamic simulations confirm the improved deceleration-phase hot spot stability properties without sacrificing the fuel compression.

  2. Stability of a Shock-Decelerated Ablation Front

    SciTech Connect

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

    2009-08-21

    Experimental study of a shock-decelerated ablation front is reported. A planar solid plastic target is accelerated by a laser across a vacuum gap and collides with a lower-density plastic foam layer. While the target is accelerated, a fast Rayleigh-Taylor (RT) growth of the seeded single-mode perturbation at the ablation front is observed. After the collision, the velocity of the ablation front is seen to remain constant. The reshock quenches the RT growth but does not trigger any Richtmyer-Meshkov growth at the ablation front, which is shown to be consistent with both theory and simulations.

  3. Tidal deceleration of the moon's mean motion

    NASA Technical Reports Server (NTRS)

    Cheng, M. K.; Eanes, R. J.; Tapley, B. D.

    1992-01-01

    The secular change in the mean motion of the moon, n, caused by the tidal dissipation in the ocean and solid earth is due primarily to the effect of the diurnal and semidiurnal tides. The long-period ocean tides produce an increase in n, but the effects are only 1 percent of the diurnal and semidiurnal ocean tides. In this investigation, expressions for these effects are obtained by developing the tidal potential in the ecliptic reference system. The computation of the amplitude of equilibrium tide and the phase corrections is also discussed. The averaged tidal deceleration of the moon's mean motion, n, from the most recent satellite ocean tide solutions is -25.25 +/- 0.4 arcseconds/sq century. The value for n inferred from the satellite-determined ocean-tide solution is in good agreement with the value obtained from the analysis of 20 years of lunar laser-ranging observations.

  4. Universe acceleration in brane world models

    NASA Astrophysics Data System (ADS)

    Chiou-Lahanas, C.; Diamandis, G. A.; Georgalas, B. C.

    2014-05-01

    We examine the cosmology induced on a brane moving in the background of a five-dimensional black hole, solution of the string effective action. The evolution, determined by the Israel junction conditions is found to be compatible with an accelerating universe with the present day acceleration coming after a decelerating phase. The possible species of the energy-momentum tensor, localized on the brane, for these solutions to be valid are discussed.

  5. Effect of clenching with a mouthguard on head acceleration during heading of a soccer ball.

    PubMed

    Narimatsu, Keishiro; Takeda, Tomotaka; Nakajima, Kazunori; Konno, Michiyo; Ozawa, Takamitsu; Ishigami, Keiichi

    2015-01-01

    Concussions are acceleration-deceleration injuries that occur when biomechanical forces are transmitted to the cerebral tissues. By limiting acceleration of the head, enhanced cervical muscle activity derived from clenching with a mouthguard (MG) may reduce the incidence or severity of concussions following impact. The purpose of this study was to investigate the effect of voluntary clenching with a proper MG on acceleration of the head during "heading" of a soccer ball. Eleven male high school soccer players (mean age, 16.8 years) participated in the study. Each player was given a customized MG. An automated soccer machine was used to project the ball at the participants at a constant speed. The participants headed the ball under 3 different oral conditions: drill 1, heading freely performed without instruction and without the MG; drill 2, heading performed as the subject was instructed to clench the masseter muscles tightly while not wearing the MG; drill 3, heading performed as the subject was instructed to clench tightly while wearing the MG. Each participant repeated each drill 5 times. Linear acceleration of the head was measured with a 3-axis accelerometer. Activity of the masseter and sternocleidomastoid muscles was measured by wireless electromyography. Weak masseter and sternocleidomastoid muscle activity was observed during drill 1. After the soccer players had been instructed to clench their masseter muscles (drills 2 and 3), statistically significant decreases in head acceleration and increases in masseter and sternocleidomastoid muscle activity were observed (P < 0.05; paired t test). The effect was stronger when the players wore the MG. Dentists should encourage soccer players to habitually clench while wearing a proper mouthguard to strengthen cervical muscle resistance as a way to mitigate the damage caused by heading.

  6. Multistage Zeeman deceleration of metastable neon

    SciTech Connect

    Wiederkehr, Alex W.; Motsch, Michael; Hogan, Stephen D.; Andrist, Markus; Schmutz, Hansjuerg; Lambillotte, Bruno; Agner, Josef A.; Merkt, Frederic

    2011-12-07

    A supersonic beam of metastable neon atoms has been decelerated by exploiting the interaction between the magnetic moment of the atoms and time-dependent inhomogeneous magnetic fields in a multistage Zeeman decelerator. Using 91 deceleration solenoids, the atoms were decelerated from an initial velocity of 580 m/s to final velocities as low as 105 m/s, corresponding to a removal of more than 95% of their initial kinetic energy. The phase-space distribution of the cold, decelerated atoms was characterized by time-of-flight and imaging measurements, from which a temperature of 10 mK was obtained in the moving frame of the decelerated sample. In combination with particle-trajectory simulations, these measurements allowed the phase-space acceptance of the decelerator to be quantified. The degree of isotope separation that can be achieved by multistage Zeeman deceleration was also studied by performing experiments with pulse sequences generated for {sup 20}Ne and {sup 22}Ne.

  7. DECELERATING RELATIVISTIC TWO-COMPONENT JETS

    SciTech Connect

    Meliani, Z.; Keppens, R. E-mail: Rony.Keppens@wis.kuleuven.b

    2009-11-10

    Transverse stratification is a common intrinsic feature of astrophysical jets. There is growing evidence that jets in radio galaxies consist of a fast low-density outflow at the jet axis, surrounded by a slower, denser, extended jet. The inner and outer jet components then have a different origin and launching mechanism, making their effective inertia, magnetization, associated energy flux, and angular momentum content different as well. Their interface will develop differential rotation, where disruptions may occur. Here we investigate the stability of rotating, two-component relativistic outflows typical for jets in radio galaxies. For this purpose, we parametrically explore the long-term evolution of a transverse cross section of radially stratified jets numerically, extending our previous study where a single, purely hydrodynamic evolution was considered. We include cases with poloidally magnetized jet components, covering hydro and magnetohydrodynamic (MHD) models. With grid-adaptive relativistic MHD simulations, augmented with approximate linear stability analysis, we revisit the interaction between the two jet components. We study the influence of dynamically important poloidal magnetic fields, with varying contributions of the inner component jet to the total kinetic energy flux of the jet, on their non-linear azimuthal stability. We demonstrate that two-component jets with high kinetic energy flux and inner jet effective inertia which is higher than the outer jet effective inertia are subject to the development of a relativistically enhanced, rotation-induced Rayleigh-Taylor-type instability. This instability plays a major role in decelerating the inner jet and the overall jet decollimation. This novel deceleration scenario can partly explain the radio source dichotomy, relating it directly to the efficiency of the central engine in launching the inner jet component. The FRII/FRI transition could then occur when the relative kinetic energy flux of the

  8. Magnetic circuit for hall effect plasma accelerator

    NASA Technical Reports Server (NTRS)

    Manzella, David H. (Inventor); Jacobson, David T. (Inventor); Jankovsky, Robert S. (Inventor); Hofer, Richard (Inventor); Peterson, Peter (Inventor)

    2009-01-01

    A Hall effect plasma accelerator includes inner and outer electromagnets, circumferentially surrounding the inner electromagnet along a thruster centerline axis and separated therefrom, inner and outer magnetic conductors, in physical connection with their respective inner and outer electromagnets, with the inner magnetic conductor having a mostly circular shape and the outer magnetic conductor having a mostly annular shape, a discharge chamber, located between the inner and outer magnetic conductors, a magnetically conducting back plate, in magnetic contact with the inner and outer magnetic conductors, and a combined anode electrode/gaseous propellant distributor, located at a bottom portion of the discharge chamber. The inner and outer electromagnets, the inner and outer magnetic conductors and the magnetically conducting back plate form a magnetic circuit that produces a magnetic field that is largely axial and radially symmetric with respect to the thruster centerline.

  9. Microwave Stark decelerator for polar molecules

    SciTech Connect

    Enomoto, Katsunari; Momose, Takamasa

    2005-12-15

    We propose a method to decelerate polar molecules from a beam using a microwave field. A moving standing wave of a microwave electric field causes an ac Stark shift to polar molecules and decelerates them. The method is applicable to polar molecules in rotational ground states and can be used to directly load a microwave trap. Numerical simulations are presented indicating large phase-space acceptance volume.

  10. A large-acceptance beam-deceleration module for retrofitting into ion-source beam lines

    NASA Astrophysics Data System (ADS)

    Hijazi, H.; Meyer, F. W.

    2013-03-01

    We describe a large-acceptance deceleration module capable of decelerating large-emittance full-intensity ion beams typical of ECR ion sources to very low energies with high efficiency. The deceleration module is designed to permit convenient retrofitting into an existing beam line to replace, e.g., the first Faraday cup after magnetic analysis of the beam extracted from the ion source. For starting energies of 10 keV, and incident ion currents as large as 300 μA, deceleration efficiencies have been measured to be greater than 80% for final energies as low as 70 eV. The decelerated beam intensity can be monitored either by insertion of a beam catcher floating at the final deceleration voltage or from the current to the exit grid itself, with suitable correction applied for the grid transparency factor. The behavior of the deceleration optics was modeled using SIMION, incorporating the effects of intra-beam space charge repulsion. We describe a recent application of this deceleration module to study near-surface He bubble and blister formation of a W target heated to 1250 K and irradiated with a 98 eV He ion beam with a flux of ˜1016 cm-2 s-1.

  11. Zeeman-Sisyphus Deceleration of Molecular Beams

    NASA Astrophysics Data System (ADS)

    Fitch, Noah; Tarbutt, Mike

    2016-05-01

    Ultracold molecules are useful for testing fundamental physics and studying strongly-interacting quantum systems. One production method is via direct laser cooling in a magneto-optical trap (MOT). In this endeavor, one major challenge is to produce molecules below the MOT capture velocity. Established molecular beam deceleration techniques are poorly suited because they decelerate only a small fraction of a typical molecular pulse. Direct laser cooling is a natural choice, but is also problematic due to transverse heating and the associated molecule loss. I will present a new technique that we are developing, which we call Zeeman-Sisyphus deceleration and which shows great promise for preparing molecular beams for MOT loading. This technique decelerates molecules using a linear array of permanent magnets, along with lasers that periodically optically pump molecules between weak and strong-field seeking quantum states. Being time-independent, this method is well-suited for temporally extended molecular beams. Simultaneous deceleration and transverse guiding makes this approach attractive as an alternative to direct laser cooling. I will present our development of the Zeeman-Sisyphus decelerator and its application to a molecular MOT of CaF and an ultracold fountain of YbF.

  12. Rindler effect for a nonuniformly accelerating observer

    SciTech Connect

    Zhu Jian-yang; Bao Aidong; Zhao Zheng

    1995-10-01

    Both the Klein-Gordon equation and the Dirac equation are dealt with in the generalized Rindler space-time of a nonuniformly accelerating observer. Making use of a new method and introducing a tortoise-type coordinate transformation, it is proved that there exist an event horizon and thermal radiation depending on time in the space-time. The Hawking-Unruh temperature is proportional to the variable acceleration.

  13. 17 CFR 230.461 - Acceleration of effective date.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., readable, and in compliance with the plain English requirements of Rule 421(d) of Regulation C (17 CFR 230... 17 Commodity and Securities Exchanges 2 2011-04-01 2011-04-01 false Acceleration of effective date... RULES AND REGULATIONS, SECURITIES ACT OF 1933 Filings; Fees; Effective Date § 230.461 Acceleration...

  14. 17 CFR 230.461 - Acceleration of effective date.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., readable, and in compliance with the plain English requirements of Rule 421(d) of Regulation C (17 CFR 230... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Acceleration of effective date... RULES AND REGULATIONS, SECURITIES ACT OF 1933 Filings; Fees; Effective Date § 230.461 Acceleration...

  15. 17 CFR 230.461 - Acceleration of effective date.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ..., readable, and in compliance with the plain English requirements of Rule 421(d) of Regulation C (17 CFR 230... 17 Commodity and Securities Exchanges 2 2012-04-01 2012-04-01 false Acceleration of effective date... RULES AND REGULATIONS, SECURITIES ACT OF 1933 Filings; Fees; Effective Date § 230.461 Acceleration...

  16. 17 CFR 230.461 - Acceleration of effective date.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., readable, and in compliance with the plain English requirements of Rule 421(d) of Regulation C (17 CFR 230... 17 Commodity and Securities Exchanges 3 2014-04-01 2014-04-01 false Acceleration of effective date... RULES AND REGULATIONS, SECURITIES ACT OF 1933 Filings; Fees; Effective Date § 230.461 Acceleration...

  17. 17 CFR 230.461 - Acceleration of effective date.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., readable, and in compliance with the plain English requirements of Rule 421(d) of Regulation C (17 CFR 230... 17 Commodity and Securities Exchanges 2 2013-04-01 2013-04-01 false Acceleration of effective date... RULES AND REGULATIONS, SECURITIES ACT OF 1933 Filings; Fees; Effective Date § 230.461 Acceleration...

  18. Rocket Sled Propelled Testing of a Supersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Meacham, Michael B.; Kennett, Andrew; Townsend, Derik J.; Marti, Benjamin

    2013-01-01

    Decelerators (IADs) have traditionally been tested in wind tunnels. As the limitations of these test facilities are reached, other avenues must be pursued. The IAD being tested is a Supersonic IAD (SIAD), which attaches just aft of the heatshield around the perimeter of an entry body. This 'attached torus' SIAD is meant to improve the accuracy of landing for robotic class missions to Mars and allow for potentially increased payloads. The SIAD Design Verification (SDV) test aims to qualify the SIAD by applying a targeted aerodynamic load to the vehicle. While many test architectures were researched, a rocket sled track was ultimately chosen to be the most cost effective way to achieve the desired dynamic pressures. The Supersonic Naval Ordnance Research Track (SNORT) at the Naval Air Warfare Center Weapons Division (NAWCWD) China Lake is a four mile test track, traditionally used for warhead and ejection seat testing. Prior to SDV, inflatable drag bodies have been tested on this particular track. Teams at Jet Propulsion Laboratory (JPL) and NAWCWD collaborate together to design and fabricate one of the largest sleds ever built. The SDV sled is comprised of three individual sleds: a Pusher Sled which holds the solid booster rockets, an Item Sled which supports the test vehicle, and a Camera Sled that is pushed in front for in-situ footage and measurements. The JPL-designed Test Vehicle has a full-scale heatshield shape and contains all instrumentation and inflation systems necessary to inflate and test a SIAD. The first campaign that is run at SNORT tested all hardware and instrumentation before the SIAD was ready to be tested. For each of the three tests in this campaign, the number of rockets and top speed was increased and the data analyzed to ensure the hardware is safe at the necessary accelerations and aerodynamic loads.

  19. Deimination of the myelin basic protein decelerates its proteasome-mediated metabolism.

    PubMed

    Kuzina, E S; Kudriaeva, A A; Glagoleva, I S; Knorre, V D; Gabibov, A G; Belogurov, A A

    2016-07-01

    Deimination of myelin basic protein (MBP) by peptidylarginine deiminase (PAD) prevents its binding to the proteasome and decelerates its degradation by the proteasome in mammalian cells. Potential anticancer drug tetrazole analogue of chloramidine 2, at concentrations greater than 1 µM inhibits the enzymatic activity of PAD in vitro. The observed acceleration of proteasome hydrolysis of MBP to antigenic peptides in the presence of PAD inhibitor may increase the efficiency of lesion of the central nervous system by cytotoxic lymphocytes in multiple sclerosis. We therefore suggest that clinical trials and the introduction of PAD inhibitors in clinical practice for the treatment of malignant neoplasms should be performed only after a careful analysis of their potential effect on the induction of autoimmune neurodegeneration processes. PMID:27599511

  20. Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.

    PubMed

    Laschinsky, Lydia; Baumann, Michael; Beyreuther, Elke; Enghardt, Wolfgang; Kaluza, Malte; Karsch, Leonhard; Lessmann, Elisabeth; Naumburger, Doreen; Nicolai, Maria; Richter, Christian; Sauerbrey, Roland; Schlenvoigt, Hans-Peter; Pawelke, Jörg

    2012-01-01

    The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

  1. Accelerated expansion in bosonic and fermionic 2D cosmologies with quantum effects

    NASA Astrophysics Data System (ADS)

    Samojeden, L. L.; Kremer, G. M.; Devecchi, F. P.

    2009-07-01

    In this work we analyze the effects produced by bosonic and fermionic constituents, including quantum corrections, in two-dimensional (2D) cosmological models. We focus on a gravitational theory related to the Callan-Giddings-Harvey-Strominger model, to simulate the dynamics of a young, spatially lineal, universe. The cosmic substratum is formed by an inflaton field plus a matter component, sources of the 2D gravitational field; the degrees of freedom also include the presence of a dilaton field. We show that this combination permits, among other scenarios, the simulation of a period of inflation, that would be followed by a (bosonic/fermionic)-matter-dominated era. We also analyse how quantum effects contribute to the destiny of the expansion, given the fact that in 2D we have a consistent (renormalizable) quantum theory of gravity. The dynamical behavior of the system follows from the solution of the gravitational-field equations, the (Klein-Gordon and Dirac) equations for the sources and the dilaton-field equation. Consistent (accelerated) regimes are present among the solutions of the 2D equations; the results depend strongly on the initial conditions used for the dilaton field. In the particular case where fermions are included as matter fields a transition to a decelerated expansion is possible, something that does not happen in the exclusively bosonic case.

  2. Deceleration in advance in the Nagel-Schreckenberg traffic flow model

    NASA Astrophysics Data System (ADS)

    Li, Xin-Gang; Gao, Zi-You; Jia, Bin; Jiang, Rui

    2009-05-01

    Based on the Nagel-Schreckenberg model, we study the impact of deceleration in advance on the dynamics of traffic flow. In the process of deceleration in advance, the effect of reaction delay and the effect of expectation are considered respectively. The traffic flow properties are studied by analyzing the fundamental diagram, spatio-temporal patterns, distance headway distribution and car accidents. The simulation results show that reaction delay brings complex traffic flow patterns and expectation makes the serious car accidents rarely happen.

  3. The effect of stochastic re-acceleration on the energy spectrum of shock-accelerated protons

    SciTech Connect

    Afanasiev, Alexandr; Vainio, Rami; Kocharov, Leon

    2014-07-20

    The energy spectra of particles in gradual solar energetic particle (SEP) events do not always have a power-law form attributed to the diffusive shock acceleration mechanism. In particular, the observed spectra in major SEP events can take the form of a broken (double) power law. In this paper, we study the effect of a process that can modify the power-law spectral form produced by the diffusive shock acceleration: the stochastic re-acceleration of energetic protons by enhanced Alfvénic turbulence in the downstream region of a shock wave. There are arguments suggesting that this process can be important when the shock propagates in the corona. We consider a coronal magnetic loop traversed by a shock and perform Monte Carlo simulations of interactions of shock-accelerated protons with Alfvén waves in the loop. The wave-particle interactions are treated self-consistently, so the finiteness of the available turbulent energy is taken into account. The initial energy spectrum of particles is taken to be a power law. The simulations reveal that the stochastic re-acceleration leads either to the formation of a spectrum that is described in a wide energy range by a power law (although the resulting power-law index is different from the initial one) or to a broken power-law spectrum. The resulting spectral form is determined by the ratio of the energy density of shock-accelerated protons to the wave energy density in the shock's downstream region.

  4. Holographic dark energy and late cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Pavón, Diego

    2007-06-01

    It has been persuasively argued that the number of effective degrees of freedom of a macroscopic system is proportional to its area rather than to its volume. This entails interesting consequences for cosmology. Here we present a model based on this 'holographic principle' that accounts for the present stage of accelerated expansion of the Universe and significantly alleviates the coincidence problem also for non-spatially flat cosmologies. Likewise, we comment on a recently proposed late transition to a fresh decelerated phase.

  5. Effect of gasoline octane quality on vehicle acceleration performance

    SciTech Connect

    Not Available

    1991-07-01

    A study was conducted under the auspices of the Coordinating Research Council, Inc. (CRC) to assess the potential effects of gasoline octane quality on vehicle acceleration performance. Twelve participating laboratories, representing both the oil and the automotive industries, tested a total of 182 vehicles as part of the 1989 CRC Octane Number Requirement Survey. The vehicles consisted of 78 with electronic knock control systems and 104 without. All testing was performed using the 1989/1990 CRC FBRU fuel series. The results showed that acceleration performance of vehicles with knock sensors was significantly affected by gasoline octane quality. Octane effects on acceleration performance were most pronounced at maximum-throttle (detent) conditions and at octane levels below the vehicles' octane requirements; however, some knock-sensor vehicles did show improved acceleration performance with fuels at octane levels above the octane number requirement. Acceleration performance in non-knock sensor vehicles was unaffected by octane quality.

  6. Safer Roadside Crash Walls Would Limit Deceleration

    NASA Technical Reports Server (NTRS)

    Schneider, William C.; Locke, James P.

    2003-01-01

    The figure depicts the aspects of a proposed deceleration-limiting design for crash walls at the sides of racetracks and highways. The proposal is intended to overcome the disadvantages of both rigid barriers and kinetic-energy-absorbing barriers of prior design. Rigid barriers can keep high-speed crashing motor vehicles from leaving roadways and thereby prevent injury to nearby persons and objects, but they can also subject the occupants of the vehicles to deceleration levels high enough to cause injury or death. Kinetic-energy-absorbing barriers of prior design reduce deceleration levels somewhat, but are not designed to soften impacts optimally; moreover, some of them allow debris to bounce back onto roadways or onto roadside areas, and, in cases of glancingly incident vehicles, some of them can trap the vehicles in such a manner as to cause more injury than would occur if the vehicles were allowed to skid along the rigid barriers. The proposed crash walls would (1) allow tangentially impacting vehicles to continue sliding along the racetrack without catching them, (2) catch directly impacting vehicles to prevent them from injuring nearby persons and objects, and (3) absorb kinetic energy in a more nearly optimum way to limit decelerations to levels that human occupants could survive.

  7. Ionization and pulse lethargy effects in inverse Cherenkov accelerators

    SciTech Connect

    Sprangle, P.; Hubbard, R.F.,; Hafizi, B.,

    1997-05-01

    Ionization processes limit the accelerating gradient and place an upper limit on the pulse duration of the electromagnetic driver in the inverse Cherenkov accelerator (ICA). Group velocity slippage, i.e., pulse lethargy, on the other hand, imposes a lower limit on the pulse duration. These limits are obtained for two ICA configurations in which the electromagnetic driver (e.g., laser or millimeter wave source) is propagated in a waveguide that is (i) lined with a dielectric material or (ii) filled with a neutral gas. In either configuration the electromagnetic driving field is guided and has an axial electric field with phase velocity equal to the speed of light in vacuum, c. The intensity of the driver in the ICA, and therefore the acceleration gradient, is limited by tunneling and collisional ionization effects. Partial ionization of the dielectric liner or gas can lead to significant modification of the dispersive properties of the waveguide, altering the phase velocity of the accelerating field and causing particle slippage, thus disrupting the acceleration process. An additional limitation on the pulse duration is imposed since the group velocity of the driving pulse is less than c and the pulse slips behind the accelerated electrons. Hence for sufficiently short pulses the electrons outrun the pulse, terminating the acceleration. Limitations on the driver pulse duration and accelerating gradient, due to ionization and pulse lethargy, are estimated for the two ICA configurations. Maximum accelerating gradients and pulse durations are presented for a 10 {mu}m, 1 mm, and 1 cm wavelength electromagnetic driver. The combination of ionization and pulse lethargy effects impose severe limitations on the maximum energy gain in inverse Cherenkov accelerators. {copyright} {ital 1997} {ital The American Physical Society}

  8. Transient acceleration in f(T) gravity

    NASA Astrophysics Data System (ADS)

    Qi, Jing-Zhao; Yang, Rong-Jia; Zhang, Ming-Jian; Liu, Wen-Biao

    2016-02-01

    Recently an f(T) gravity based on the modification of teleparallel gravity was proposed to explain the accelerated expansion of the universe. We use observational data from type Ia supernovae, baryon acoustic oscillations, and cosmic microwave background to constrain this f(T) theory and reconstruct the effective equation of state and the deceleration parameter. We obtain the best-fit values of parameters and find an interesting result that the constrained f(T) theory allows for the accelerated Hubble expansion to be a transient effect.

  9. Effects of horizontal acceleration on human visual acuity and stereopsis.

    PubMed

    Horng, Chi-Ting; Hsieh, Yih-Shou; Tsai, Ming-Ling; Chang, Wei-Kang; Yang, Tzu-Hung; Yauan, Chien-Han; Wang, Chih-Hung; Kuo, Wu-Hsien; Wu, Yi-Chang

    2015-01-01

    The effect of horizontal acceleration on human visual acuity and stereopsis is demonstrated in this study. Twenty participants (mean age 22.6 years) were enrolled in the experiment. Acceleration from two different directions was performed at the Taiwan High-Speed Rail Laboratory. Gx and Gy (< and >0.1 g) were produced on an accelerating platform where the subjects stood. The visual acuity and stereopsis of the right eye were measured before and during the acceleration. Acceleration <0.1 g in the X- or Y-axis did not affect dynamic vision and stereopsis. Vision decreased (mean from 0.02 logMAR to 0.25 logMAR) and stereopsis declined significantly (mean from 40 s to 60.2 s of arc) when Gx > 0.1 g. Visual acuity worsened (mean from 0.02 logMAR to 0.19 logMAR) and poor stereopsis was noted (mean from 40 s to 50.2 s of arc) when Gy > 0.1 g. The effect of acceleration from the X-axis on the visual system was higher than that from the Y-axis. During acceleration, most subjects complained of ocular strain when reading. To our knowledge, this study is the first to report the exact levels of visual function loss during Gx and Gy. PMID:25607601

  10. Effects of horizontal acceleration on human visual acuity and stereopsis.

    PubMed

    Horng, Chi-Ting; Hsieh, Yih-Shou; Tsai, Ming-Ling; Chang, Wei-Kang; Yang, Tzu-Hung; Yauan, Chien-Han; Wang, Chih-Hung; Kuo, Wu-Hsien; Wu, Yi-Chang

    2015-01-19

    The effect of horizontal acceleration on human visual acuity and stereopsis is demonstrated in this study. Twenty participants (mean age 22.6 years) were enrolled in the experiment. Acceleration from two different directions was performed at the Taiwan High-Speed Rail Laboratory. Gx and Gy (< and >0.1 g) were produced on an accelerating platform where the subjects stood. The visual acuity and stereopsis of the right eye were measured before and during the acceleration. Acceleration <0.1 g in the X- or Y-axis did not affect dynamic vision and stereopsis. Vision decreased (mean from 0.02 logMAR to 0.25 logMAR) and stereopsis declined significantly (mean from 40 s to 60.2 s of arc) when Gx > 0.1 g. Visual acuity worsened (mean from 0.02 logMAR to 0.19 logMAR) and poor stereopsis was noted (mean from 40 s to 50.2 s of arc) when Gy > 0.1 g. The effect of acceleration from the X-axis on the visual system was higher than that from the Y-axis. During acceleration, most subjects complained of ocular strain when reading. To our knowledge, this study is the first to report the exact levels of visual function loss during Gx and Gy.

  11. Effects of Horizontal Acceleration on Human Visual Acuity and Stereopsis

    PubMed Central

    Horng, Chi-Ting; Hsieh, Yih-Shou; Tsai, Ming-Ling; Chang, Wei-Kang; Yang, Tzu-Hung; Yauan, Chien-Han; Wang, Chih-Hung; Kuo, Wu-Hsien; Wu, Yi-Chang

    2015-01-01

    The effect of horizontal acceleration on human visual acuity and stereopsis is demonstrated in this study. Twenty participants (mean age 22.6 years) were enrolled in the experiment. Acceleration from two different directions was performed at the Taiwan High-Speed Rail Laboratory. Gx and Gy (< and >0.1 g) were produced on an accelerating platform where the subjects stood. The visual acuity and stereopsis of the right eye were measured before and during the acceleration. Acceleration <0.1 g in the X- or Y-axis did not affect dynamic vision and stereopsis. Vision decreased (mean from 0.02 logMAR to 0.25 logMAR) and stereopsis declined significantly (mean from 40 s to 60.2 s of arc) when Gx > 0.1 g. Visual acuity worsened (mean from 0.02 logMAR to 0.19 logMAR) and poor stereopsis was noted (mean from 40 s to 50.2 s of arc) when Gy > 0.1 g. The effect of acceleration from the X-axis on the visual system was higher than that from the Y-axis. During acceleration, most subjects complained of ocular strain when reading. To our knowledge, this study is the first to report the exact levels of visual function loss during Gx and Gy. PMID:25607601

  12. Cerebrolysin Accelerates Metamorphosis and Attenuates Aging-Accelerating Effect of High Temperature in Drosophila Melanogaster

    PubMed Central

    Navrotskaya, V.; Vorobyova, L.; Sharma, H.; Muresanu, D.; Summergrad, P.

    2015-01-01

    Cerebrolysin® (CBL) is a neuroprotective drug used for the treatment of neurodegenerative diseases. CBL’s mechanisms of action remain unclear. Involvement of tryptophan (TRP)–kynurenine (KYN) pathway in neuroprotective effect of CBL might be suggested considering that modulation of KYN pathway of TRP metabolism by CBL, and protection against eclosion defect and prolongation of life span of Drosophila melanogaster with pharmacologically or genetically-induced down-regulation of TRP conversion into KYN. To investigate possible involvement of TRP–KYN pathway in mechanisms of neuroprotective effect of CBL, we evaluated CBL effects on metamorphosis and life span of Drosophila melanogaster maintained at 23 °C and 28 °C ambient temperature. CBL accelerated metamorphosis, exerted strong tendency (p = 0.04) to prolong life span in female but not in male flies, and attenuated aging-accelerating effect of high (28 °C) ambient temperature in both female and male flies. Further research of CBL effects on metamorphosis and resistance to aging-accelerating effect of high temperature might offer new insights in mechanisms of its neuroprotective action and expand its clinical applications. PMID:25798213

  13. Earth’s Rotational Deceleration: Determination of Tidal Friction Independent of Timescales

    NASA Astrophysics Data System (ADS)

    Deines, Steven D.; Williams, Carol A.

    2016-04-01

    This paper determines Earth's rotational deceleration without relying on atomic or ephemeris timescales. Earth's rotation defines the civil time standard called Universal Time (UT). Our previous paper did not examine tidal friction in depth when analyzing the timescale divergence between UT and International Atomic Time (TAI). We examine all available paleontological fossils and deposits for the direct measurements of Earth's past rotation rates, because that record includes all contributing effects. We examine paleontological reports that date Earth's rotation rate using corals, bivalves, brachiopods, rhythmites, and stromatolites. Contributions that vary Earth's moment of inertia, such as continental plate drifts, coastline changes, ice age formations, and viscous glacial rebounds, are superimposed with the secular deceleration. The average deceleration of Earth's rotation rate from all available fossil data is found to be (5.969 ± 1.762) × 10-7 rad yr-2. Our value is 99.8% of the total rotational deceleration determined by Christodoulidis et al., who used artificial satellite data, and our value is 96.6% of the expected tidal friction value obtained by Stephenson and Morrison. Taking the derivative of conserved angular momentum, the predicted lunar orbital deceleration caused by the average rotational deceleration corresponds closely to lunar models. When evaluating the significant time gaps between UT and TAI, Earth's rotational deceleration is a minor contributing factor. Also, the secular deceleration rate is necessary to correctly date ancient astronomical events. We strongly encourage that more ocean paleontological evidence be found to supplement the record to separate the many periodic variations embedded in these data.

  14. Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

    NASA Astrophysics Data System (ADS)

    Thopan, P.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.

    2015-12-01

    In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

  15. Plasma acceleration using a radio frequency self-bias effect

    NASA Astrophysics Data System (ADS)

    Rafalskyi, D.; Aanesland, A.

    2015-06-01

    In this work plasma acceleration using a RF self-bias effect is experimentally studied. The experiments are conducted using a novel plasma accelerator system, called Neptune, consisting of an inductively coupled plasma source and a RF-biased set of grids. The plasma accelerator can operate in a steady state mode, producing a plasma flow with separately controlled plasma flux and velocity without any magnetic configuration. The operating pressure at the source output is as low as 0.2 mTorr and can further be decreased. The ion and electron flows are investigated by measuring the ion and electron energy distribution functions both space resolved and with different orientations with respect to the flow direction. It is found that the flow of electrons from the source is highly anisotropic and directed along the ion flow and this global flow of accelerated plasma is well localized in the plasma transport chamber. The maximum flux is about 7.5.1015 ions s-1 m-2 (at standard conditions) on the axis and decreasing to almost zero at a radial distances of more than 15 cm from the flow axis. Varying the RF acceleration voltage in the range 20-350 V, the plasma flow velocity can be changed between 10 and 35 km/s. The system is prospective for different technology such as space propulsion and surface modification and also interesting for fundamental studies for space-related plasma simulations and investigation of the dynamo effect using accelerated rotating plasmas.

  16. Estimates of effects of residual acceleration on USML-1 experiments

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.

    1995-01-01

    The purpose of this study effort was to develop analytical models to describe the effects of residual accelerations on the experiments to be carried on the first U.S. Microgravity Lab mission (USML-1) and to test the accuracy of these models by comparing the pre-flight predicted effects with the post-flight measured effects. After surveying the experiments to be performed on USML-1, it became evident that the anticipated residual accelerations during the USML-1 mission were well below the threshold for most of the primary experiments and all of the secondary (Glovebox) experiments and that the only set of experiments that could provide quantifiable effects, and thus provide a definitive test of the analytical models, were the three melt growth experiments using the Bridgman-Stockbarger type Crystal Growth Furnace (CGF). This class of experiments is by far the most sensitive to low level quasi-steady accelerations that are unavoidable on space craft operating in low earth orbit. Because of this, they have been the drivers for the acceleration requirements imposed on the Space Station. Therefore, it is appropriate that the models on which these requirements are based are tested experimentally. Also, since solidification proceeds directionally over a long period of time, the solidified ingot provides a more or less continuous record of the effects from acceleration disturbances.

  17. Regulating the infrared by mode matching: A massless scalar in expanding spaces with constant deceleration

    SciTech Connect

    Janssen, T. M.; Prokopec, T.

    2011-04-15

    In this paper we consider a massless scalar field, with a possible coupling {xi} to the Ricci scalar in a D dimensional Friedmann-Lemaitre-Robertson-Walker space-time with a constant deceleration parameter q={epsilon}-1, {epsilon}=-H/H{sup 2}. Correlation functions for the Bunch-Davies vacuum of such a theory have long been known to be infrared divergent for a wide range of values of {epsilon}. We resolve these divergences by explicitly matching the space-time under consideration to a space-time without infrared divergencies. Such a procedure ensures that all correlation functions with respect to the vacuum in the space-time of interest are infrared finite. In this newly defined vacuum we construct the coincidence limit of the propagator and as an example calculate the expectation value of the stress-energy tensor. We find that this approach gives both in the ultraviolet and in the infrared satisfactory results. Moreover, we find that, unless the effective mass due to the coupling to the Ricci scalar {xi}R is negative, quantum contributions to the energy density always dilute away faster, or just as fast, as the background energy density. Therefore, quantum backreaction is insignificant at the one-loop order, unless {xi}R is negative. Finally we compare this approach with known results where the infrared is regulated by placing the Universe in a finite box. In an accelerating universe, the results are qualitatively the same, provided one identifies the size of the Universe with the physical Hubble radius at the time of the matching. In a decelerating universe, however, the two schemes give different late time behavior for the quantum stress-energy tensor. This happens because in this case the length scale at which one regulates the infrared becomes sub-Hubble at late times.

  18. The influence of large-scale structures on entrainment in a decelerating transient turbulent jet revealed by large eddy simulation

    NASA Astrophysics Data System (ADS)

    Hu, Bing; Musculus, Mark P. B.; Oefelein, Joseph C.

    2012-04-01

    To provide a better understanding of the fluid mechanical mechanisms governing entrainment in decelerating jets, we performed a large eddy simulation (LES) of a transient air jet. The ensemble-averaged LES calculations agree well with the available measurements of centerline velocity, and they reveal a region of increased entrainment that grows as it propagates downstream during deceleration. Within the temporal and spatial domains of the simulation, entrainment during deceleration temporarily increases by roughly a factor of two over that of the quasi-steady jet, and thereafter decays to a level lower than the quasi-steady jet. The LES results also provide large-structure flow details that lend insight into the effects of deceleration on entrainment. The simulations show greater growth and separation of large vortical structures during deceleration. Ambient fluid is engulfed into the gaps between the large-scale structures, causing large-scale indentations in the scalar jet boundary. The changes in the growth and separation of large structures during deceleration are attributed to changes in the production and convection of vorticity. Both the absolute and normalized scalar dissipation rates decrease during deceleration, implying that changes in small-scale mixing during deceleration do not play an important role in the increased entrainment. Hence, the simulations predict that entrainment in combustion devices may be controlled by manipulating the fuel-jet boundary conditions, which affect structures at large scales much more than at small scales.

  19. Patterns of Rapid Deceleration Observed at Two Tidewater Outlet Glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Stearns, L. A.; Catania, G. A.; Bartholomaus, T.; Sutherland, D.; Nash, J. D.; Shroyer, E.; Byers, L. C.; Rosenau, R.; Fried, M.; Felikson, D.; Walker, R. T.; Carroll, D.

    2015-12-01

    Flow speeds of Greenland outlet glaciers play an important role in modulating ice sheet mass balance. Flow variability is dictated by how outlet glaciers respond to unknown or poorly constrained perturbations in their boundary conditions; identifying the physical processes controlling outlet glacier flow variability is key to improving models of ice sheet evolution. In this study, we use satellite remote sensing data, in situ observations, and numerical models to explore the boundary conditions that control the unique flow behavior of two West Greenland outlet glaciers. Kangerdlugssup Sermerssua (KS) and Kangilerngata Sermia (KGS), exhibit seasonal flow variability that is anti-correlated with surrounding glaciers. Both glaciers decelerate in the spring when meltwater becomes available. The seasonal deceleration is usually on the order of 10% the annual average speed, and lasts ~2 months. During high melt years, the deceleration is highly exaggerated (~80% of the annual average), causing a near shutdown of glacier flow along the lower 20 km of the trunk. For example, in 2010 KS decelerated from its average speed of ~2000 m/yr to 250 m/yr; the deceleration and the acceleration back to its average speed took roughly 2 months. Force balance analyses show that both glaciers have anomalously low driving stress and basal drag values. We hypothesize that glaciers with low basal drag are particularly sensitive to variations in subglacial water. The discrete decelerations and reactivation of these two unique glacier systems allow us to analyze the complicated evolution of subglacial hydrologic systems and their interaction with ice velocity and force components.

  20. Nuclear effects in atmospheric and accelerator neutrino experiments

    SciTech Connect

    Chauhan, S.; Athar, M. Sajjad; Singh, S. K.

    2010-11-24

    We have studied the nuclear medium effects in the neutrino (antineutrino) induced interactions in nuclei at intermediate energy region. We have applied this study to calculate the event rates for atmospheric and accelerator neutrino experiments. The study of the nuclear effects has been done for the quasielastic lepton production and the charged current incoherent and coherent pion production processes.

  1. Nonthermal effects of acceleration in the resonance interaction between two uniformly accelerated atoms

    NASA Astrophysics Data System (ADS)

    Rizzuto, Lucia; Lattuca, Margherita; Marino, Jamir; Noto, Antonio; Spagnolo, Salvatore; Zhou, Wenting; Passante, Roberto

    2016-07-01

    We study the resonance interaction between two uniformly accelerated identical atoms, one excited and the other in the ground state, prepared in a correlated (symmetric or antisymmetric) state and interacting with the scalar field or the electromagnetic field in the vacuum state. In this case (resonance interaction), the interatomic interaction is a second-order effect in the atom-field coupling. We separate the contributions of vacuum fluctuations and radiation reaction to the resonance energy shift of the system, and show that only radiation reaction contributes, while Unruh thermal fluctuations do not affect the resonance interaction. We also find that beyond a characteristic length scale related to the atomic acceleration, nonthermal effects in the radiation-reaction contribution change the distance dependence of the resonance interaction. Finally, we find that previously unidentified features appear, compared with the scalar field case, when the interaction with the electromagnetic field is considered, as a consequence of the peculiar nature of the vacuum quantum noise of the electromagnetic field in a relativistically accelerated background.

  2. Laser-assisted Stark deceleration of polar diatomic molecules in the Χ1Σ state

    NASA Astrophysics Data System (ADS)

    Huang, Yunxia; Xu, Shuwu; Yang, Xiaohua

    2016-07-01

    The traditional Stark deceleration method is difficult to apply in chemically stable polar diatomic molecules in their ground (Χ1Σ) state because the Χ1Σ state normally experiences little Stark shift and the rovibronic ground level is mostly high-field-seeking. To solve this problem, we propose a laser-assisted Stark deceleration scheme to decelerate such molecules in the present paper. Our results show that, owing to the transverse bunching effect of the applied red-detuning laser beam, the molecules of the high-field-seeking level |J = 0, M = 0> in the Χ1Σ state can be effectively decelerated. Furthermore, the present scheme is more effective because the interaction between the molecules and the combined fields can produce the pseudo-first-order Stark effect, and thus increase the depth of the effective potential. Compared to those molecules in the low-field-seeking state |J = 1, MΩ = ‑1> in the usual electrostatic Stark deceleration, a higher molecular density and lower velocity can be achieved under an equivalent initial phase angle.

  3. Laser-assisted Stark deceleration of polar diatomic molecules in the Χ1Σ state

    NASA Astrophysics Data System (ADS)

    Huang, Yunxia; Xu, Shuwu; Yang, Xiaohua

    2016-07-01

    The traditional Stark deceleration method is difficult to apply in chemically stable polar diatomic molecules in their ground (Χ1Σ) state because the Χ1Σ state normally experiences little Stark shift and the rovibronic ground level is mostly high-field-seeking. To solve this problem, we propose a laser-assisted Stark deceleration scheme to decelerate such molecules in the present paper. Our results show that, owing to the transverse bunching effect of the applied red-detuning laser beam, the molecules of the high-field-seeking level |J = 0, M = 0> in the Χ1Σ state can be effectively decelerated. Furthermore, the present scheme is more effective because the interaction between the molecules and the combined fields can produce the pseudo-first-order Stark effect, and thus increase the depth of the effective potential. Compared to those molecules in the low-field-seeking state |J = 1, MΩ = -1> in the usual electrostatic Stark deceleration, a higher molecular density and lower velocity can be achieved under an equivalent initial phase angle.

  4. High Altitude Supersonic Decelerator Test Vehicle

    NASA Technical Reports Server (NTRS)

    Cook, Brant T.; Blando, Guillermo; Kennett, Andrew; Von Der Heydt, Max; Wolff, John Luke; Yerdon, Mark

    2013-01-01

    The Low Density Supersonic Decelerator (LDSD) project is tasked by NASA's Office of the Chief Technologist (OCT) to advance the state of the art in Mars entry and descent technology in order to allow for larger payloads to be delivered to Mars at higher altitudes with better accuracy. The project will develop a 33.5 m Do Supersonic Ringsail (SSRS) parachute, 6m attached torus, robotic class Supersonic Inflatable Aerodynamic Decelerator (SIAD-R), and an 8 m attached isotensoid, exploration class Supersonic Inflatable Aerodynamic Decelerator (SIAD-E). The SSRS and SIAD-R should be brought to TRL-6, while the SIAD-E should be brought to TRL-5. As part of the qualification and development program, LDSD must perform a Mach-scaled Supersonic Flight Dynamics Test (SFDT) in order to demonstrate successful free flight dynamic deployments at Mars equivalent altitude, of all three technologies. In order to perform these tests, LDSD must design and build a test vehicle to deliver all technologies to approximately 180,000 ft and Mach 4, deploy a SIAD, free fly to approximately Mach 2, deploy the SSRS, record high-speed and high-resolution imagery of both deployments, as well as record data from an instrumentation suite capable of characterizing the technology induced vehicle dynamics. The vehicle must also be recoverable after splashdown into the ocean under a nominal flight, while guaranteeing forensic data protection in an off nominal catastrophic failure of a test article that could result in a terminal velocity, tumbling water impact.

  5. Decelerating cosmologies are de-scramblers

    NASA Astrophysics Data System (ADS)

    Carney, Daniel; Fischler, Willy

    2015-08-01

    Stationary observers in static spacetimes see falling objects spread exponen-tially fast, or fast-scramble, near event horizons. We generalize this picture to arbitrary cosmological horizons. We give examples of exponential fast-scrambling and power-law scrambling and "de-scrambling" as charges propagate freely near a horizon. In particular we show that when the universe is decelerating, information hidden behind the apparent horizon is de-scrambled as it re-enters the view of the observer. In contrast to the de Sitter case, the power-law scaling suggests that the microscopic dynamics of the horizon are local.

  6. The water entry of decelerating spheres

    NASA Astrophysics Data System (ADS)

    Aristoff, Jeffrey M.; Truscott, Tadd T.; Techet, Alexandra H.; Bush, John W. M.

    2010-03-01

    We present the results of a combined experimental and theoretical investigation of the vertical impact of low-density spheres on a water surface. Particular attention is given to characterizing the sphere dynamics and the influence of its deceleration on the shape of the resulting air cavity. A theoretical model is developed which yields simple expressions for the pinch-off time and depth, as well as the volume of air entrained by the sphere. Theoretical predictions compare favorably with our experimental observations, and allow us to rationalize the form of water-entry cavities resulting from the impact of buoyant and nearly buoyant spheres.

  7. The water entry of decelerating spheres

    NASA Astrophysics Data System (ADS)

    Aristoff, Jeffrey; Truscott, Tadd; Techet, Alexandra; Bush, John

    2009-11-01

    We present the results of a combined experimental and theoretical investigation of the vertical impact of low-density spheres on a water surface. Particular attention is given to characterizing the sphere dynamics and the influence of its deceleration on the shape of the resulting air cavity. A theoretical model is developed that yields simple expressions for the pinch-off time and depth. Theoretical predictions compare favorably with our experimental observations, and allow us to rationalize the form of water-entry cavities resulting from the impact of buoyant and nearly buoyant spheres.

  8. Detachment of secondary dendrite arm in a directionally solidified Sn-Ni peritectic alloy under deceleration growth condition

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-06-01

    In order to better understand the detachment mechanism of secondary dendrite arm during peritectic solidification, the detachment of secondary dendrite arm from the primary dendrite arms in directionally solidified Sn-36at.%Ni peritectic alloys is investigated at different deceleration rates. Extensive detachment of secondary dendrite arms from primary stem is observed below peritectic reaction temperature TP. And an analytical model is established to characterize the detachment process in terms of the secondary dendrite arm spacing λ2, the root radius of detached arms and the specific surface area (SV) of dendrites. It is found that the detachment mechanism is caused by not only curvature difference between the tips and roots of secondary branches, but also that between the thicker secondary branches and the thinner ones. Besides, this detachment process is significantly accelerated by the temperature gradient zone melting (TGZM) effect during peritectic solidification. It is demonstrated that the reaction constant (f) which is used to characterize the kinetics of peritectic reaction is crucial for the determination of the detachment process. The value of f not only changes with growth rate but also with solidification time at a given deceleration rate. In conclusion, these findings help the better understanding of the detachment mechanism.

  9. Detachment of secondary dendrite arm in a directionally solidified Sn-Ni peritectic alloy under deceleration growth condition

    PubMed Central

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-01-01

    In order to better understand the detachment mechanism of secondary dendrite arm during peritectic solidification, the detachment of secondary dendrite arm from the primary dendrite arms in directionally solidified Sn-36at.%Ni peritectic alloys is investigated at different deceleration rates. Extensive detachment of secondary dendrite arms from primary stem is observed below peritectic reaction temperature TP. And an analytical model is established to characterize the detachment process in terms of the secondary dendrite arm spacing λ2, the root radius of detached arms and the specific surface area (SV) of dendrites. It is found that the detachment mechanism is caused by not only curvature difference between the tips and roots of secondary branches, but also that between the thicker secondary branches and the thinner ones. Besides, this detachment process is significantly accelerated by the temperature gradient zone melting (TGZM) effect during peritectic solidification. It is demonstrated that the reaction constant (f) which is used to characterize the kinetics of peritectic reaction is crucial for the determination of the detachment process. The value of f not only changes with growth rate but also with solidification time at a given deceleration rate. In conclusion, these findings help the better understanding of the detachment mechanism. PMID:27270334

  10. Detachment of secondary dendrite arm in a directionally solidified Sn-Ni peritectic alloy under deceleration growth condition.

    PubMed

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-01-01

    In order to better understand the detachment mechanism of secondary dendrite arm during peritectic solidification, the detachment of secondary dendrite arm from the primary dendrite arms in directionally solidified Sn-36at.%Ni peritectic alloys is investigated at different deceleration rates. Extensive detachment of secondary dendrite arms from primary stem is observed below peritectic reaction temperature TP. And an analytical model is established to characterize the detachment process in terms of the secondary dendrite arm spacing λ2, the root radius of detached arms and the specific surface area (SV) of dendrites. It is found that the detachment mechanism is caused by not only curvature difference between the tips and roots of secondary branches, but also that between the thicker secondary branches and the thinner ones. Besides, this detachment process is significantly accelerated by the temperature gradient zone melting (TGZM) effect during peritectic solidification. It is demonstrated that the reaction constant (f) which is used to characterize the kinetics of peritectic reaction is crucial for the determination of the detachment process. The value of f not only changes with growth rate but also with solidification time at a given deceleration rate. In conclusion, these findings help the better understanding of the detachment mechanism. PMID:27270334

  11. Effects of chronic acceleration on body composition

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.

    1982-01-01

    Studies of the centrifugation of adult rats showed an unexpected decrease in the mass of fat-free muscle and bone, in spite of the added load induced by centrifugation. It is suggested that the lower but constant fat-free body mass was probably regulated during centrifugation. Rats placed in weightless conditions for 18.5 days gave indirect but strong evidence that the muscle had increased in mass. Other changes in the rats placed in weightless conditions included a smaller fraction of skeletal mineral, a smaller fraction of water in the total fat-free body, and a net shift of fluid from skin to viscera. Adult rats centrifuged throughout the post-weaning growth period exhibited smaller masses of bone and central nervous system (probably attributable to slower growth of the total body), and a larger mass of skin than controls at 1 G. Efforts at simulating the effects of weightlessness or centrifugation on the body composition of rats by regimens at terrestrial gravity were inconclusive.

  12. How Can People Be so Good at Intercepting Accelerating Objects if They Are so Poor at Visually Judging Acceleration?

    PubMed Central

    Rodriguez, Inés Abalo; Muñoz, Victor Estal; Schootemeijer, Sabine; Mahieu, Yannick; Veerkamp, Kirsten; Zandbergen, Marit; van der Zee, Tim; Smeets, Jeroen BJ

    2016-01-01

    People are known to be very poor at visually judging acceleration. Yet, they are extremely proficient at intercepting balls that fall under gravitational acceleration. How is this possible? We previously found that people make systematic errors when trying to tap on targets that move with different constant accelerations or decelerations on interleaved trials. Here, we show that providing contextual information that indicates how the target will decelerate on the next trial does not reduce such errors. Such errors do rapidly diminish if the same deceleration is present on successive trials. After observing several targets move with a particular acceleration or deceleration without attempting to tap on them, participants tapped as if they had never experienced the acceleration or deceleration. Thus, people presumably deal with acceleration when catching or hitting a ball by compensating for the errors that they made on preceding attempts. PMID:27482367

  13. Ground motions and its effects in accelerator design

    SciTech Connect

    Fischer, G.E.

    1984-07-01

    This lecture includes a discussion of types of motion, frequencies of interest, measurements at SLAC, some general comments regarding local sources of ground motion at SLAC, and steps that can be taken to minimize the effects of ground motion on accelerators. (GHT)

  14. Ecological causes of decelerating diversification in carnivoran mammals.

    PubMed

    Machac, Antonin; Storch, David; Wiens, John J

    2013-08-01

    Clade diversification is a central topic in macroevolutionary studies. Recently, it has been shown that diversification rates appear to decelerate over time in many clades. What causes this deceleration remains unclear, but it has been proposed that competition for limited resources between sympatric, ecologically similar species slows diversification. Employing carnivoran mammals as a model system, we test this hypothesis using a comprehensive time-calibrated phylogeny. We also explore several conceptually related explanations including limited geographic area and limited rates of niche evolution. We find that diversification slowdowns are strong in carnivorans. Surprisingly, these slowdowns are independent of geographic range overlap between related species and are also decoupled from rates of niche evolution, suggesting that slowdowns are unrelated to competition and niche filling. When controlling for the effects of clade diversity, diversification slowdowns appear independent of geographic area. There is a significant effect of clade diversity on diversification slowdowns, but simulations show that this relationship may arise as a statistical artifact (i.e., greater clade diversity increases the ability of the gamma statistic to refute constant diversification). Overall, our results emphasize the need to test hypotheses about the causes of diversification slowdowns with ecological data, rather than assuming ecological processes from phylogenies alone.

  15. Ecological causes of decelerating diversification in carnivoran mammals.

    PubMed

    Machac, Antonin; Storch, David; Wiens, John J

    2013-08-01

    Clade diversification is a central topic in macroevolutionary studies. Recently, it has been shown that diversification rates appear to decelerate over time in many clades. What causes this deceleration remains unclear, but it has been proposed that competition for limited resources between sympatric, ecologically similar species slows diversification. Employing carnivoran mammals as a model system, we test this hypothesis using a comprehensive time-calibrated phylogeny. We also explore several conceptually related explanations including limited geographic area and limited rates of niche evolution. We find that diversification slowdowns are strong in carnivorans. Surprisingly, these slowdowns are independent of geographic range overlap between related species and are also decoupled from rates of niche evolution, suggesting that slowdowns are unrelated to competition and niche filling. When controlling for the effects of clade diversity, diversification slowdowns appear independent of geographic area. There is a significant effect of clade diversity on diversification slowdowns, but simulations show that this relationship may arise as a statistical artifact (i.e., greater clade diversity increases the ability of the gamma statistic to refute constant diversification). Overall, our results emphasize the need to test hypotheses about the causes of diversification slowdowns with ecological data, rather than assuming ecological processes from phylogenies alone. PMID:23888862

  16. Magnetohydrodynamic Effects in Propagating Relativistic Ejecta: Reverse Shock and Magnetic Acceleration

    NASA Technical Reports Server (NTRS)

    Mizuno, Y.; Nishikawa, K.I.; Zhang, B.; Giacomazzo, B.; Hardee, P.E.; Nagataki, S.; Hartmann, D.H.

    2008-01-01

    We solve the Riemann problem for the deceleration of arbitrarily magnetized relativistic ejecta injected into a static unmagnetized medium. We find that for the same initial Lorentz factor, the reverse shock becomes progressively weaker with increasing magnetization s (the Poynting-to-kinetic energy flux ratio), and the shock becomes a rarefaction wave when s exceeds a critical value, sc, defined by the balance between the magnetic pressure in the ejecta and the thermal pressure in the forward shock. In the rarefaction wave regime, we find that the rarefied region is accelerated to a Lorentz factor that is significantly larger than the initial value. This acceleration mechanism is due to the strong magnetic pressure in the ejecta.

  17. The effect of assisted and resisted sprint training on acceleration and velocity in Division IA female soccer athletes.

    PubMed

    Upton, David E

    2011-10-01

    This investigation evaluated the effects of a 4-week, 12-session training program using resisted sprint training (RST), assisted sprint training (AST), and traditional sprint training (TST) on maximal velocity and acceleration in National Collegiate Athletic Association (NCAA) Division IA female soccer athletes (n = 27). The subjects, using their respective training modality, completed 10 maximal effort sprints of 20 yd (18.3 m) followed by a 20-yd (18.3 m) deceleration to jog. Repeated measures multivariate analyses of variance and analyses of variance demonstrated significant (p < 0.001) 3-way interactions (time × distance × group) and 2-way interactions (time × group), respectively, for both velocity and acceleration. Paired t-tests demonstrated that maximum 40-yd (36.6-m) velocity increased significantly in both the AST (p < 0.001) and RST (p < 0.05) groups, with no change in the TST group. Five-yard (4.6-m), 15-yd (13.7 m), 5- to 15-yd (4.6- to 13.7-m) acceleration increased significantly (p < 0.01) in the AST group and did not change in the RST and TST groups. Fifteen- to 25-yd (13.7- to 22.9-m) acceleration increased significantly (p < 0.01) in the RST group, decreased significantly (p < 0.01) in the AST group, and was unchanged in the TST group. Twenty-five to 40-yd (22.9- to 36.6-m) acceleration increased significantly (p < 0.05) in the RST group and remained unchanged in the AST and TST groups. It is purposed that the increased 5-yd (4.6-m) and 15-yd (13.7-m) accelerations were the result of enhanced neuromuscular facilitation in response to the 12-session supramaximal training protocol. Accordingly, it is suggested that athletes participating in short distance acceleration events (i.e., ≤15 yd; ≤13.7 m) use AST protocols, whereas athletes participating in events that require greater maximum velocity (i.e., >15 yd; > 13.7 m) should use resisted sprint training protocols.

  18. Plasma acceleration using a radio frequency self-bias effect

    SciTech Connect

    Rafalskyi, D.; Aanesland, A.

    2015-06-15

    In this work plasma acceleration using a RF self-bias effect is experimentally studied. The experiments are conducted using a novel plasma accelerator system, called Neptune, consisting of an inductively coupled plasma source and a RF-biased set of grids. The plasma accelerator can operate in a steady state mode, producing a plasma flow with separately controlled plasma flux and velocity without any magnetic configuration. The operating pressure at the source output is as low as 0.2 mTorr and can further be decreased. The ion and electron flows are investigated by measuring the ion and electron energy distribution functions both space resolved and with different orientations with respect to the flow direction. It is found that the flow of electrons from the source is highly anisotropic and directed along the ion flow and this global flow of accelerated plasma is well localized in the plasma transport chamber. The maximum flux is about 7.5·10{sup 15} ions s{sup −1} m{sup −2} (at standard conditions) on the axis and decreasing to almost zero at a radial distances of more than 15 cm from the flow axis. Varying the RF acceleration voltage in the range 20–350 V, the plasma flow velocity can be changed between 10 and 35 km/s. The system is prospective for different technology such as space propulsion and surface modification and also interesting for fundamental studies for space-related plasma simulations and investigation of the dynamo effect using accelerated rotating plasmas.

  19. Polymer enrichment decelerates surfactant membranes near interfaces

    NASA Astrophysics Data System (ADS)

    Lipfert, F.; Frielinghaus, H.; Holderer, O.; Mattauch, S.; Monkenbusch, M.; Arend, N.; Richter, D.

    2014-04-01

    Close to a planar surface, lamellar structures are imposed upon otherwise bulk bicontinuous microemulsions. Thermally induced membrane undulations are modified by the presence of the rigid interface. While it has been shown that a pure membrane's dynamics are accelerated close to the interface, we observed nearly unchanged relaxation rates for membranes spiked with large amphiphilic diblock copolymers. An increase of the polymer concentration by a factor of 2-3 for the first and second surfactant membrane layers was observed. We interpret the reduced relaxation times as the result of an interplay between the bending rigidity and the characteristic distance of the first surfactant membrane to the rigid interface, which causes the hydrodynamic and steric interface effects described in Seifert's theory. The influence of these effects on decorated membranes yields a reduction of the frequencies and an amplification of the amplitudes of long-wavelength undulations, which are in accordance to our experimental findings.

  20. Supersonic Decelerator on 'Right Track' for Future Mars Missions

    NASA Video Gallery

    Project Manager, Mark Adler, and Principal Investigator, Ian Clark describe the innovative testing being conducted by the Low Density Supersonic Decelerator (LDSD) project. Combining very large sup...

  1. Hydrodynamic Scaling of the Deceleration-Phase Rayleigh-Taylor Instability for Inertial Confinement Fusion Implosions

    NASA Astrophysics Data System (ADS)

    Bose, A.; Betti, R.; Woo, K.; Nora, R.

    2014-10-01

    Hydrodynamic equivalence and ignition theory allow for the extrapolation of OMEGA experiments to ignition-scale implosions. The yield-over-clean (YOC = measured yield/1-D yield) depicts the effect of hydro-instabilities on inertial confinement fusion implosions. A 2-D study of the deceleration-phase Rayleigh-Taylor instability (RTI) is carried out to assess the YOC scaling with target size at varying nonuniformity levels. The deceleration-phase ablative RTI is mitigated by the hot-spot thermal and radiation transport, which do not scale hydro-equivalently. Scaling of the thermal conduction shows that hot-spot ablation velocity is higher on OMEGA than on the National Ignition Facility (NIF), resulting in higher RTI growth factors on the NIF. Radiation emitted in the hot-spot makes the implosion nearly hydro-equivalent by increasing the density gradient scale length on the NIF. Thermal conduction and radiation both are nonscalable physics in the deceleration phase, with complementary impacts the scaling of deceleration-phase RTI. Analytic and numerical study of the deceleration-phase RTI on OMEGA and NIF-scale targets show that YOCNIF ~ YOCΩ considering identical laser imprinting and normalized ice roughness levels. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786.

  2. Flight-Path Characteristics for Decelerating From Supercircular Speed

    NASA Technical Reports Server (NTRS)

    Luidens, Roger W.

    1961-01-01

    Characteristics of the following six flight paths for decelerating from a supercircular speed are developed in closed form: constant angle of attack, constant net acceleration, constant altitude" constant free-stream Reynolds number, and "modulated roll." The vehicles were required to remain in or near the atmosphere, and to stay within the aerodynamic capabilities of a vehicle with a maximum lift-drag ratio of 1.0 and within a maximum net acceleration G of 10 g's. The local Reynolds number for all the flight paths for a vehicle with a gross weight of 10,000 pounds and a 600 swept wing was found to be about 0.7 x 10(exp 6). With the assumption of a laminar boundary layer, the heating of the vehicle is studied as a function of type of flight path, initial G load, and initial velocity. The following heating parameters were considered: the distribution of the heating rate over the vehicle, the distribution of the heat per square foot over the vehicle, and the total heat input to the vehicle. The constant G load path at limiting G was found to give the lowest total heat input for a given initial velocity. For a vehicle with a maximum lift-drag ratio of 1.0 and a flight path with a maximum G of 10 g's, entry velocities of twice circular appear thermo- dynamically feasible, and entries at velocities of 2.8 times circular are aerodynamically possible. The predominant heating (about 85 percent) occurs at the leading edge of the vehicle. The total ablated weight for a 10,000-pound-gross-weight vehicle decelerating from an initial velocity of twice circular velocity is estimated to be 5 percent of gross weight. Modifying the constant G load flight path by a constant-angle-of-attack segment through a flight- to circular-velocity ratio of 1.0 gives essentially a "point landing" capability but also results in an increased total heat input to the vehicle.

  3. A piloted simulator investigation of helicopter precision decelerating approaches to hover to determine single-pilot IFR /SPIFR/ requirements

    NASA Technical Reports Server (NTRS)

    Phatak, A. V.; Peach, L. L., Jr.; Hess, R. A.; Ross, V. L.; Hall, G. W.; Gerdes, R. M.

    1979-01-01

    The results of single-pilot instrument flight rules (SPIFR) experiments conducted on the NASA-Ames V/STOLAND simulator are presented. Several factors having a significant impact on requirements for helicopter SPIFR decelerating, steep approaches to landing are considered: (1) approach weather conditions, (2) flight path geometry, (3) deceleration guidance law, (4) level of stability and command augmentation, (5) cockpit display sophistication, (6) accuracy of navigation aids, and (7) helipad lighting and visual aids. Particular emphasis is placed on the relative effects of deceleration profile, control augmentation, and flight director parameters on pilot performance, workload, and opinion rating. Problems associated with the development of a pilot acceptance analytical methodology are outlined.

  4. Holocene deceleration of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    MacGregor, Joseph A.; Colgan, William T.; Fahnestock, Mark A.; Morlighem, Mathieu; Catania, Ginny A.; Paden, John D.; Gogineni, S. Prasad

    2016-02-01

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet’s radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet’s dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  5. Photogrammetry of a Hypersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Kushner, Laura Kathryn; Littell, Justin D.; Cassell, Alan M.

    2013-01-01

    In 2012, two large-scale models of a Hypersonic Inflatable Aerodynamic decelerator were tested in the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. One of the objectives of this test was to measure model deflections under aerodynamic loading that approximated expected flight conditions. The measurements were acquired using stereo photogrammetry. Four pairs of stereo cameras were mounted inside the NFAC test section, each imaging a particular section of the HIAD. The views were then stitched together post-test to create a surface deformation profile. The data from the photogram- metry system will largely be used for comparisons to and refinement of Fluid Structure Interaction models. This paper describes how a commercial photogrammetry system was adapted to make the measurements and presents some preliminary results.

  6. Holocene deceleration of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Colgan, William T; Fahnestock, Mark A; Morlighem, Mathieu; Catania, Ginny A; Paden, John D; Gogineni, S Prasad

    2016-02-01

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry. PMID:26912699

  7. Compact disposal of high-energy electron beams using passive or laser-driven plasma decelerating stage

    SciTech Connect

    Bonatto, A.; Schroeder, C. B.; Vay, J. -L.; Geddes, C. R.; Benedetti, C.; Esarey and, E.; Leemans, W. P.

    2014-07-13

    A plasma decelerating stage is investigated as a compact alternative for the disposal of high-energy beams (beam dumps). This could benefit the design of laser-driven plasma accelerator (LPA) applications that require transportability and or high-repetition-rate operation regimes. Passive and laser-driven (active) plasma-based beam dumps are studied analytically and with particle-in-cell (PIC) simulations in a 1D geometry. Analytical estimates for the beam energy loss are compared to and extended by the PIC simulations, showing that with the proposed schemes a beam can be efficiently decelerated in a centimeter-scale distance.

  8. Accumulation and Effects of Stray Electrons in IFE Accelerators

    NASA Astrophysics Data System (ADS)

    Cohen, R. H.; Molvik, A. W.; Vay, J. L.

    2002-11-01

    Stray electrons can be introduced in positive-charge accelerators for heavy ion fusion (or other applications) as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary-electron emission. Electron accumulation is impacted by the ion beam potential, accelerating fields, multipole magnetic fields used for beam focus, and the pulse duration. We present electron particle orbit studies and estimates showing the various dependences. We also present ion simulations with prescribed random electron neutralization to elucidate electron effects on ion beam quality. Finally we contrast electron effects to be expected on the proposed Integrated Beam Experiment (IBX) with those for the High-Current Experiment (HCX), and discuss ways to measure these differences.

  9. Transverse effects in plasma wakefield acceleration at FACET - Simulation studies

    SciTech Connect

    Adli, E.; Hogan, M.; Frederico, J.; Litos, M. D.; An, W.; Mori, W.

    2012-12-21

    We investigate transverse effects in the plasma-wakefield acceleration experiments planned and ongoing at FACET. We use PIC simulation tools, mainly QuickPIC, to simulate the interaction of the drive electron beam and the plasma. In FACET a number of beam dynamics knobs, including dispersion and bunch length knobs, can be used to vary the beam transverse characteristics in the plasma. We present simulation results and the status of the FACET experimental searches.

  10. The drag characteristics of several airships determined by deceleration tests

    NASA Technical Reports Server (NTRS)

    Thompson, F L; Kirschbaum, H W

    1932-01-01

    This report presents the results of deceleration tests conducted for the purpose of determining the drag characteristics of six airships. The tests were made with airships of various shapes and sizes belonging to the Army, the Navy, and the Goodyear-Zeppelin Corporation. Drag coefficients for the following airships are shown: Army TC-6, TC-10, and TE-2; Navy Los Angeles and ZMC-2; Goodyear Puritan. The coefficients vary from about 0.045 for the small blunt airships to 0.023 for the relatively large slender Los Angeles. This variation may be due to a combination of effects, but the most important of these is probably the effect of length-diameter ratio.

  11. Two-dimensional descent through a compressible atmosphere: Sequential deceleration of an unpowered load

    NASA Astrophysics Data System (ADS)

    Silverman, M. P.

    2010-02-01

    Equations, based on Rayleigh's drag law valid for high Reynolds number, are derived for two-dimensional motion through a compressible atmosphere in isentropic equilibrium, such as characterizes the Earth's troposphere. Solutions yield horizontal and vertical displacement, velocity, and acceleration as a function of altitude and ground-level temperature. An exact analytical solution to the equations linearized in the aero-thermodynamic parameter is given; in general the equations must be solved numerically. The theory, applied to the unpowered fall of a large aircraft stabilized to flat descent by symmetrical, sequential deployment of horizontal and vertical decelerators, shows that such an aircraft can be brought down with mean peak deployment and impact decelerations below 10g.

  12. Lightweight, variable solidity knitted parachute fabric. [for aerodynamic decelerators

    NASA Technical Reports Server (NTRS)

    Matthews, F. R., Jr.; White, E. C. (Inventor)

    1973-01-01

    A parachute fabric for aerodynamic decelerator applications is described. The fabric will permit deployment of the decelerator at high altitudes and low density conditions. The fabric consists of lightweight, highly open, circular knitted parachute fabric with ribbon-like yarns to assist in air deflection.

  13. Modified hydraulic braking system limits angular deceleration to safe values

    NASA Technical Reports Server (NTRS)

    Briggs, R. S.; Council, M.; Green, P. M.

    1966-01-01

    Conventional spring actuated, hydraulically released, fail-safe disk braking system is modified to control the angular deceleration of a massive antenna. The hydraulic system provides an immediate preset pressure to the spring-loaded brake shoes and holds it at this value to decelerate the antenna at the desired rate.

  14. Generation of the sedimentation potential by rapid deceleration of a fluid jet

    NASA Astrophysics Data System (ADS)

    Park, Han Jung; Tang, Ziyao; Diebold, Gerald; University of Tennessee at Chattanooga Team; Brown University Team

    2015-04-01

    The sedimentation potential refers to the generation of a voltage in an ionic or colloidal solution as a result of motion of the ions or colloidal particles relative to the surrounding fluid. In the case of colloidal suspensions, where the density of the colloidal particles differs from that of the fluid, the effect of a body force on the suspension, generated typically either in a centrifuge or the earth's gravitational field, is to give different motion to the charged particles and the fluid, producing a distortion of the normally spherical counter charge distribution around the colloidal particles. As a result of the opposing charges attached to the particles and in the double layer in the surrounding fluid, dipoles are generated at the sites of the particles, which add to give a macroscopic voltage in the fluid. Experiments reported here show that the sedimentation potential can be generated by the rapid deceleration of a jet of colloid at a rigid surface where, again, the differential acceleration of the particles and fluid gives rise to a voltage. The voltages between a conducting surface and a metallic tube used to form the jet are found to have large signal-to-noise ratios.

  15. Speed Profiles for Deceleration Guidance During Rollout and Turnoff (ROTO)

    NASA Technical Reports Server (NTRS)

    Barker, L. Keith; Hankins, Walter W., III; Hueschen, Richard M.

    1999-01-01

    Two NASA goals are to enhance airport safety and to improve capacity in all weather conditions. This paper contributes to these goals by examining speed guidance profiles to aid a pilot in decelerating along the runway to an exit. A speed profile essentially tells the pilot what the airplane's speed should be as a function of where the airplane is on the runway. While it is important to get off the runway as soon as possible (when striving to minimize runway occupancy time), the deceleration along a speed profile should be constrained by passenger comfort. Several speed profiles are examined with respect to their maximum decelerations and times to reach exit speed. One profile varies speed linearly with distance; another has constant deceleration; and two related nonlinear profiles delay maximum deceleration (braking) to reduce time spent on the runway.

  16. Performance Limiting Effects in X-Band Accelerators

    SciTech Connect

    Wang, Faya; Adolphsen, Chris; Nantista, Christopher; /SLAC

    2012-06-11

    Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating has been associated with breakdown for many years; however, there have been no experiments that clearly separate field and heating effects on the breakdown rate. Recently, such experiments have been performed at SLAC with both standing-wave and traveling-wave structures. These experiments have demonstrated that pulsed heating is limiting the gradient. Nevertheless the X-band structures breakdown studies show damage to the iris surfaces in locations of high electric field rather than of high magnetic field after thousands of breakdowns. It is not yet clear how the relative roles of electric field, magnetic field, and heating factor into the damage caused by rf breakdown. Thus, a dual-moded cavity has been designed to better study the electric field, magnetic field, and pulsed heating effects on breakdown damage.

  17. Effects of changing from non-accelerated to accelerated MRI for follow-up in brain atrophy measurement.

    PubMed

    Leung, Kelvin K; Malone, Ian M; Ourselin, Sebastien; Gunter, Jeffrey L; Bernstein, Matt A; Thompson, Paul M; Jack, Clifford R; Weiner, Michael W; Fox, Nick C

    2015-02-15

    Stable MR acquisition is essential for reliable measurement of brain atrophy in longitudinal studies. One attractive recent advance in MRI is to speed up acquisition using parallel imaging (e.g. reducing volumetric T1-weighted acquisition scan times from around 9 to 5 min). In some studies, a decision to change to an accelerated acquisition may have been deliberately taken, while in others repeat scans may occasionally be accidentally acquired with an accelerated acquisition. In ADNI, non-accelerated and accelerated scans were acquired in the same scanning session on each individual. We investigated the impact on brain atrophy as measured by k-means normalized boundary shift integral (KN-BSI) and deformation-based morphometry when changing from non-accelerated to accelerated MRI acquisitions over a 12-month interval using scans of 422 subjects from ADNI. KN-BSIs were calculated using both a non-accelerated baseline scan and non-accelerated 12-month scans (i.e. consistent acquisition), and a non-accelerated baseline scan and an accelerated 12-month scan (i.e. changed acquisition). Fluid-based non-rigid registration was also performed on those scans to estimate the brain atrophy rate. We found that the effect on KN-BSI and fluid-based non-rigid registration depended on the scanner manufacturer. For KN-BSI, in Philips and Siemens scanners, the change had very little impact on the measured atrophy rate (increase of 0.051% in Philips and -0.035% in Siemens from consistent acquisition to changed acquisition), whereas, in GE, the change caused a mean reduction of 0.65% in the brain atrophy rate. This is likely due to the difference in tissue contrast between gray matter and cerebrospinal fluid in the non-accelerated and accelerated scans in GE, which uses IR-FSPGR instead of MP-RAGE. For fluid-based non-rigid registration, the change caused a mean increase of 0.29% in the brain atrophy rate in the changed acquisition compared with consistent acquisition in Philips

  18. Multi-dimensional effects in radiation pressure acceleration of ions

    SciTech Connect

    Tripathi, V. K.

    2015-07-31

    A laser carries momentum. On reflection from an ultra-thin overdense plasma foil, it deposits recoil momentum on the foil, i.e. exerts radiation pressure on the foil electrons and pushes them to the rear. The space charge field thus created takes the ions along, accelerating the electron-ion double layer as a single unit. When the foil has surface ripple, of wavelength comparable to laser wavelength, the radiation pressure acts non-uniformly on the foil and the perturbation grows as Reyleigh-Taylor (RT) instability as the foil moves. The finite spot size of the laser causes foil to bend. These effects limit the quasi-mono energy acceleration of ions. Multi-ion foils, e.g., diamond like carbon foil embedded with protons offer the possibility of suppressing RT instability.

  19. Development flight tests of the Viking decelerator system.

    NASA Technical Reports Server (NTRS)

    Murrow, H. N.; Eckstrom, C. V.; Henke, D. W.

    1973-01-01

    Significant aspects of a low altitude flight test phase of the overall Viking decelerator system development are given. This test series included nine aircraft drop tests that were conducted at the Joint Parachute Test Facility, El Centro, California, between September 1971 and May 1972. The test technique and analytical planning method utilized to best simulate loading conditions in a low density environment are presented and some test results are shown to assess their adequacy. Performance effects relating to suspension line lengths of 1.7 D sub o with different canopy loadings are noted. System hardware developments are described, in particular the utilization of a fabric deployment mortar cover which remained attached to the parachute canopy. Finally, the contribution of this test series to the overall program is assessed.

  20. ELECTRON CLOUD EFFECTS IN HIGH INTENSITY PROTON ACCELERATORS.

    SciTech Connect

    WEI,J.; MACEK,R.J.

    2002-04-14

    One of the primary concerns in the design and operation of high-intensity proton synchrotrons and accumulators is the electron cloud and associated beam loss and instabilities. Electron-cloud effects are observed at high-intensity proton machines like the Los Alamos National Laboratory's PSR and CERN's SPS, and investigated experimentally and theoretically. In the design of next-generation high-intensity proton accelerators like the Spallation Neutron Source ring, emphasis is made in minimizing electron production and in enhancing Landau damping. This paper reviews the present understanding of the electron-cloud effects and presents mitigation measures.

  1. Educating to manage the accelerated change environment effectively: Part 2.

    PubMed

    Menix, K D

    2001-01-01

    Without appropriate educational preparation, nurse managers may not have the competencies to manage accelerated change effectively. Part 1 of this two-part series provided the condensed findings from an extensive review of nursing, business, and higher education literature. Part 2 describes the results of a Delphi study whereby baccalaureate-prepared nurse manager experts and nurse educator experts in baccalaureate nursing programs validated what linear and nonlinear change management concepts they believed were relevant in managing change in today's dynamic environment. Staff development educators and administrators, as organizational change agents, can use the validated concepts to develop educational offerings to promote effective change management. PMID:12759940

  2. Suppressing Parasitic Effects in a Long Dielectric Wakefield Accelerator

    SciTech Connect

    Shchegolkov, Dmitry; Simakov, Evgenya Ivanovna; Jing, Chunguang; Li, Chen; Zholents, Alexander A.; Power, John G.

    2014-08-27

    Dielectric wakefield acceleration is a promising concept for increasing the accelerating gradient above the limits of conventional accelerators. Although superior gradients are reported in short dielectric wakefield accelerator tubes, problems arise when it comes to efficiency and multi-meter long interaction lengths. Here we discuss possible issues and provide some solutions backed by simulations.

  3. Responses to Deceleration during Car Following: Roles of Optic Flow, Warnings, Expectations, and Interruptions

    ERIC Educational Resources Information Center

    DeLucia, Patricia R.; Tharanathan, Anand

    2009-01-01

    More than 25% of accidents are rear-end collisions. It is essential to identify the factors that contribute to such collisions. One such factor is a driver's ability to respond to the deceleration of the car ahead. In Experiment 1, we measured effects of optic flow information and discrete visual and auditory warnings (brake lights, tones) on…

  4. Rotary-Wing Decelerators for Probe Descent Through the Atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Young, Larry A.; Briggs, Geoffrey; Aiken, Edwin; Pisanich, Greg

    2005-01-01

    An innovative concept is proposed for atmospheric entry probe deceleration, wherein one or more deployed rotors (in autorotation or wind-turbine flow states) on the aft end of the probe effect controlled descent. This concept is particularly oriented toward probes intended to land safely on the surface of Venus. Initial work on design trade studies is discussed.

  5. The effects of acceleration forces on night vision.

    PubMed

    Tipton, D A; Marko, A R; Ratino, D A

    1984-03-01

    The effects of Gy and Gz acceleration forces on cone-type mesopic vision threshold values are examined. An experiment has been conducted on the Dynamic Environment Simulator, a three-axis human centrifuge, to reproduce an acceleration environment in a simulated night-flight combat situation. Acceleration environments studied were levels of +1 Gz, + 1Gy, +1.4 Gz, +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz. A visual task was performed which determined 20/50 visual acuity illumination threshold values. Physiological parameters recorded were arterial oxygen saturation (SaO2) by ear oximetry, heart rate, and visual acuity threshold values. There were 10 male subjects, all members of the United States Air Force. Their ages ranged from 25-39 years (mean +/- S.D., 29.1 +/- 4.3). Results were zero means obtained by self-pairing with +1 Gz controls. Analysis was done by self-pairing, two-tailed t test. Results showed no significant shift in luminance threshold values at +1 Gy or +1.4 Gz, and significant increases in luminance thresholds at the 0.01 level for +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz.

  6. The Stability of Decelerating Shocks Revisited

    NASA Astrophysics Data System (ADS)

    Kushnir, Doron; Waxman, Eli; Shvarts, Dov

    2005-11-01

    We present a new method for analyzing the global stability of the Sedov-von Neumann-Taylor self-similar solutions, describing the asymptotic behavior of spherical decelerating shock waves expanding into ideal gas with density ~r-ω. Our method allows one to overcome the difficulties associated with the nonphysical divergences of the solutions at the origin. We show that while the growth rates of global modes derived by previous analyses are accurate in the large-wavenumber (small-wavelength) limit, they do not correctly describe the small-wavenumber behavior for small values of the adiabatic index γ. Our method furthermore allows one to analyze the stability properties of the flow at early times, when the flow deviates significantly from the asymptotic self-similar behavior. We find that at this stage the perturbation growth rates are larger than those obtained for unstable asymptotic solutions at similar γ, ω. Our results reduce the discrepancy that exists between theoretical predictions and experimental results.

  7. Decelerating Mature Adipocyte Dedifferentiation by Media Composition.

    PubMed

    Huber, Birgit; Kluger, Petra J

    2015-12-01

    The establishment of adipose tissue test systems is still a major challenge in the investigation of cellular and molecular interactions responsible for the pathogenesis of inflammatory diseases involving adipose tissue. Mature adipocytes are mainly involved in these pathologies, but rarely used in vitro, due to the lack of an appropriate culture medium which inhibits dedifferentiation and maintains adipocyte functionality. In our study, we showed that Dulbecco's Modified Eagle's Medium/Ham's F-12 with 10% fetal calf serum (FCS) reported for the culture of mature adipocytes favors dedifferentiation, which was accompanied by a high glycerol release, a decreasing release of leptin, and a low expression of the adipocyte marker perilipin A, but high expression of CD73 after 21 days. Optimized media containing FCS, biotin, pantothenate, insulin, and dexamethasone decelerated the dedifferentiation process. These cells showed a lower lipolysis rate, a high level of leptin release, as well as a high expression of perilipin A. CD73-positive dedifferentiated fat cells were only found in low quantity. In this work, we showed that mature adipocytes when cultured under optimized conditions could be highly valuable for adipose tissue engineering in vitro. PMID:26228997

  8. Hypersonic Inflatable Aerodynamic Decelerator Ground Test Development

    NASA Technical Reports Server (NTRS)

    Del Corso, Jospeh A.; Hughes, Stephen; Cheatwood, Neil; Johnson, Keith; Calomino, Anthony

    2015-01-01

    Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology readiness levels have been incrementally matured by NASA over the last thirteen years, with most recent support from NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). Recently STMD GCDP has authorized funding and support through fiscal year 2015 (FY15) for continued HIAD ground developments which support a Mars Entry, Descent, and Landing (EDL) study. The Mars study will assess the viability of various EDL architectures to enable a Mars human architecture pathfinder mission planned for mid-2020. At its conclusion in November 2014, NASA's first HIAD ground development effort had demonstrated success with fabricating a 50 W/cm2 modular thermal protection system, a 400 C capable inflatable structure, a 10-meter scale aeroshell manufacturing capability, together with calibrated thermal and structural models. Despite the unquestionable success of the first HIAD ground development effort, it was recognized that additional investment was needed in order to realize the full potential of the HIAD technology capability to enable future flight opportunities. The second HIAD ground development effort will focus on extending performance capability in key technology areas that include thermal protection system, lifting-body structures, inflation systems, flight control, stage transitions, and 15-meter aeroshell scalability. This paper presents an overview of the accomplishments under the baseline HIAD development effort and current plans for a follow-on development effort focused on extending those critical technologies needed to enable a Mars Pathfinder mission.

  9. Effect of Exercise Training and +Gz Acceleration Training on Men

    NASA Technical Reports Server (NTRS)

    Greenleaf, John E.; Simonson, Shawn R.; Stocks, Jodie M.; Evans, Joyce; Knapp, Charles F.; Cowell, Stephenie A.; Pemberton, Kendra N.; Wilson, Heather W.; Vener, Jamie M.; Evetts, Simon N.

    2001-01-01

    Countermeasures for reduction in work capacity (maximal oxygen uptake and strength) during spaceflight and enhanced orthostatic intolerance during re-entry, landing and egress from the return vehicle are continuing problems. The purpose for this study was to test the hypothesis that passive-acceleration training; supine, interval, exercise plus acceleration training and exercise combined with acceleration training would improve orthostatic tolerance in ambulatory men; and that addition of the aerobic exercise conditioning would not alter this improved tolerance from that of passive-acceleration training. Seven men (24-38 yr) underwent "Passive" training on the Ames human-powered centrifuge (HPC) for 30 min, "Exercise" training on the cycle ergometer with constant +Gz acceleration; and "Combined" exercise training at 40% to 90% of the HPC +Gz(max) exercise level. Maximal supine exercise loads increased significant (P<0.05) by 8.3% (Passive), 12.6% (Exercise), and by 15.4% (Combined) after training, but their post-training maximal oxygen uptakes and maximal heart rates were unchanged. Maximal time to fatigue (endurance) was unchanged with Passive was increased (P<0.05) with Exercise and Combined training. Thus, the exercise in the Exercise and Combined training Phases resulted in greater maximal loads and endurance without effect on maximal oxygen uptake or heart rate. There was a 4% to 6% increase (P<0.05) in all four quadriceps muscle volumes (right and left) after post-Combined training. Resting pre-tilt heart rate was elevated by 12.9% (P<0.05) only after Passive training suggesting that the exercise training attenuated the HR response. Plasma volume (% Delta) was uniformly decreased by 8% to 14% (P<0.05) at tilt-tolerance pre- vs. post-training indicating essentially no effect of training on the level of hypovolemia. Post-training tilt-tolerance time and heart rate were increased (P<0.05) only with Passive training by 37.8% and by 29.1%, respectively. Thus

  10. Independent Orbiter Assessment (IOA): Analysis of the landing/deceleration subsystem

    NASA Technical Reports Server (NTRS)

    Compton, J. M.; Beaird, H. G.; Weissinger, W. D.

    1987-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Landing/Deceleration Subsystem hardware. The Landing/Deceleration Subsystem is utilized to allow the Orbiter to perform a safe landing, allowing for landing-gear deploy activities, steering and braking control throughout the landing rollout to wheel-stop, and to allow for ground-handling capability during the ground-processing phase of the flight cycle. Specifically, the Landing/Deceleration hardware consists of the following components: Nose Landing Gear (NLG); Main Landing Gear (MLG); Brake and Antiskid (B and AS) Electrical Power Distribution and Controls (EPD and C); Nose Wheel Steering (NWS); and Hydraulics Actuators. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Due to the lack of redundancy in the Landing/Deceleration Subsystems there is a high number of critical items.

  11. Effect of re-acceleration on cosmic ray components

    NASA Technical Reports Server (NTRS)

    Stephens, S. A.; Golden, R. L.

    1989-01-01

    Reacceleration of cosmic rays in interstellar space has been studied in detail in order to examine the behavior of the ratios of secondary to primary nuclei in cosmic radiation. It is found that modest acceleration in a confinement region, where particles escape more freely at high energies, provides a better fit to the observed data. The effect of reacceleration on the spectral shape of proton and helium components of cosmic rays has been studied. The examination of two different models has shown that reacceleration provides a poor fit to the observed proton data.

  12. On the deceleration of Fanaroff-Riley Class I jets: mass loading by stellar winds

    NASA Astrophysics Data System (ADS)

    Perucho, M.; Martí, J. M.; Laing, R. A.; Hardee, P. E.

    2014-06-01

    Jets in low-luminosity radio galaxies are known to decelerate from relativistic speeds on parsec scales to mildly or subrelativistic speeds on kiloparsec scales. Several mechanisms have been proposed to explain this effect, including strong reconfinement shocks and the growth of instabilities (both leading to boundary-layer entrainment) and mass loading from stellar winds or molecular clouds. We have performed a series of axisymmetric simulations of the early evolution of jets in a realistic ambient medium to probe the effects of mass loading from stellar winds using the code RATPENAT. We study the evolution of Fanaroff-Riley Class I (FR I) jets, with kinetic powers Lj ˜ 1041-1044 erg s-1, within the first 2 kpc of their evolution, where deceleration by stellar mass loading should be most effective. Mass entrainment rates consistent with present models of stellar mass loss in elliptical galaxies produce deceleration and effective decollimation of weak FR I jets within the first kiloparsec. However, powerful FR I jets are not decelerated significantly. In those cases where the mass loading is important, the jets show larger opening angles and decollimate at smaller distances, but the overall structure and dynamics of the bow shock are similar to those of unloaded jets with the same power and thrust. According to our results, the flaring observed on kiloparsec scales is initiated by mass loading in the weaker FR I jets and by reconfinement shocks or the growth of instabilities in the more powerful jets. The final mechanism of decollimation and deceleration is always the development of disruptive pinching modes.

  13. A divergence-free parametrization of deceleration parameter for scalar field dark energy

    NASA Astrophysics Data System (ADS)

    Al Mamon, Abdulla; Das, Sudipta

    2016-01-01

    In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy (DE). We have considered a phenomenological parametrization of the deceleration parameter q(z) and from this, we have reconstructed the equation-of-state (EoS) for DE ωϕ(z). This divergence-free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the DE EoS given by Barboza and Alcaniz [see E. M. Barboza and J. S. Alcaniz, Phys. Lett. B 666 (2008) 415]. Using the combination of datasets (Type Ia Supernova (SN Ia) + Hubble + baryonic acoustic oscillations/cosmic microwave background (BAO/CMB)), we have constrained the transition redshift zt (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of zt. We have also compared the reconstructed results of q(z) and ωϕ(z) and have found that the results are compatible with a ΛCDM universe if we consider SN Ia + Hubble data, but inclusion of BAO/CMB data makes q(z) and ωϕ(z) incompatible with ΛCDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

  14. Aerodynamic Models for the Low Density Supersonic Decelerator (LDSD) Test Vehicles

    NASA Technical Reports Server (NTRS)

    Van Norman, John W.; Dyakonov, Artem; Schoenenberger, Mark; Davis, Jody; Muppidi, Suman; Tang, Chun; Bose, Deepak; Mobley, Brandon; Clark, Ian

    2016-01-01

    An overview of aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign test vehicle is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a helium balloon, then accelerating the TV to Mach 4 and 53 km altitude with a solid rocket motor. Test flights conducted in June of 2014 (SFDT-1) and 2015 (SFDT-2) each successfully delivered a 6 meter diameter decelerator (SIAD-R) to test conditions and several seconds of flight, and were successful in demonstrating the SFDT flight system concept and SIAD-R technology. Aerodynamic models and uncertainties developed for the SFDT campaign are presented, including the methods used to generate them and their implementation within an aerodynamic database (ADB) routine for flight simulations. Pre- and post-flight aerodynamic models are compared against reconstructed flight data and model changes based upon knowledge gained from the flights are discussed. The pre-flight powered phase model is shown to have a significant contribution to off-nominal SFDT trajectory lofting, while coast and SIAD phase models behaved much as predicted.

  15. 5.0 Aerodynamic and Propulsive Decelerator Systems

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.; Powell, Richard; Masciarelli, James; Brown, Glenn; Witkowski, Al; Guernsey, Carl

    2005-01-01

    Contents include the following: Introduction. Capability Breakdown Structure. Decelerator Functions. Candidate Solutions. Performance and Technology. Capability State-of-the-Art. Performance Needs. Candidate Configurations. Possible Technology Roadmaps. Capability Roadmaps.

  16. Design, manufacture, and testing of the Armstrong Hall drop tower decelerator

    NASA Astrophysics Data System (ADS)

    Ocampo, Jaime Andres

    A decelerator was needed for the Armstrong Hall Microgravity tower. Three designs were considered as concepts and the one chosen was an airbag. The airbag is 5 feet tall and 4.5 feet in diameter due to floor constraints. The deceleration was controlled by designing the vent system to provide the needed vent area as a function of time. This dynamics vent area controls the rate at which volume is expelled from the airbag. The volume expelled depends on the pressure inside the airbag, thus, a direct relation between the vent area and the deceleration profile was determined. The airbag and associated infrastructure was designed, manufactured, and tested. This system includes an airbag with a cushion on top to prevent wear, cart and rails, a drop package, and a latch and release system. More than forty tests were done with different drop height and drop weight combinations culminating in three drops of 200 lbs from the third floor. The drop weight was varied by adjusting the water level in a plastic barrel in the drop package. Pressure measurements inside the bag and vent were taken using two pressure transducers. The pressure transducers sampled the pressure at one of the exit vents and at the center of the bottom of the airbag. The signals were low-pass filtered for noise and scaled for pressure. The pressure traces were processed to find the mean deceleration. The deceleration was found to be independent of drop weight, only depending on drop height. The traces were also integrated to find a momentum per unit area. This value was then compared to the momentum of the drop package. From these two results an effective impact area can be found. It was found that the cushion not only reduced wear but also increased the effective impact area substantially. This increase in area reduced the value of the mean deceleration by reducing the pressure inside the airbag. The airbag proved to work well for the drops, decelerating the package and preventing a direct hit with the

  17. Mutagenic effect of accelerated heavy ions on bacterial cells

    NASA Astrophysics Data System (ADS)

    Boreyko, A. V.; Krasavin, E. A.

    2011-11-01

    The heavy ion accelerators of the Joint Institute for Nuclear Research were used to study the regularities and mechanisms of formation of different types of mutations in prokaryote cells. The induction of direct (lac-, ton B-, col B) mutations for Esherichia coli cells and reverse his- → His+ mutations of Salmonella typhimurium, Bacillus subtilis cells under the action of radiation in a wide range of linear energy transfer (LET) was studied. The regularities of formation of gene and structural (tonB trp-) mutations for Esherichia coli bacteria under the action of accelerated heavy ions were studied. It was demonstrated that the rate of gene mutations as a function of the dose under the action of Γ rays and accelerated heavy ions is described by linear-quadratic functions. For structural mutations, linear "dose-effect" dependences are typical. The quadratic character of mutagenesis dose curves is determined by the "interaction" of two independent "hitting" events in the course of SOS repair of genetic structures. The conclusion made was that gene mutations under the action of accelerated heavy ions are induced by δ electron regions of charged particle tracks. The methods of SOS chromotest, SOS lux test, and λ prophage induction were used to study the regularities of SOS response of cells under the action of radiations in a wide LET range. The following proposition was substantiated: the molecular basis for formation of gene mutations are cluster single-strand DNA breaks, and that for structural mutations, double-strand DNA breaks. It was found out that the LET dependence of the relative biological efficiency of accelerated ions is described by curves with a local maximum. It was demonstrated that the biological efficiency of ionizing radiations with different physical characteristics on cells with different genotype, estimated by the lethal action, induction of gene and deletion mutations, precision excision of transposons, is determined by the specific

  18. Vacuum laser-driven acceleration by two slits-truncated Bessel beams

    SciTech Connect

    Li, D.; Imasaki, K.

    2005-08-29

    An approach of vacuum acceleration by two laser Bessel beams is presented in this letter. With elaborate arrangement, the two Bessel beams are truncated by a set of special annular slits to form consecutive acceleration field in the electron traveling direction. Therefore, the electron of a certain initial energy can be accelerated in the whole interaction region without experiencing deceleration even though the phase-slippage occurs. Furthermore, the Bessel beam can provide a rather long distance for the effective interaction between the electron and the laser field due to its 'diffraction-free' property, resulting in improvement of the energy exchange.

  19. Effect of dilute acid on the accelerated weathering of wood

    SciTech Connect

    Williams, R.S.

    1988-02-01

    Western red cedar (Thuja plicata) specimens were soaked in acid solutions to determine the effect of acid conditions (such as low pH fog) on the weathering of wood. Daily 1-hour soaking in dilute sulfurous, sulfuric, or nitric acid (pH 2.0, 2.5, 3.0, 3.5, or 4.0) increased the rate of accelerated (xenon arc) weathering of the specimens compared to controls soaked in distilled/deionized water. Weathering was manifested as the erosion rate of the wood surface and was determined gravimetrically be fitting the weight loss over time to a linear model. This method detected significant differences between acid-treated specimens and untreated controls within 300 hours of accelerated weathering. The erosion rate was dependent on the acid type and pH. Sulfurous acid treatment caused the fastest rate of erosion, followed by sulfuric then nitric acid. None of the acids affected the erosion rate at pH 3.5 or above. Below this threshold, the rate of erosion increased as the hydrogen ion concentration increased. Sugar analysis of residues from the acids and the distilled water used to soak the wood indicated acid-dependent degradation of polysaccharides.

  20. Ion effects in future circular and linear accelerators

    SciTech Connect

    Raubenheimer, T.O.

    1995-05-01

    In this paper, the author discusses ion effects relevant to future storage rings and linear colliders. The author first reviews the conventional ion effects observed in present storage rings and then discusses how these effects will differ in the next generation of rings and linacs. These future accelerators operate in a new regime because of the high current long bunch trains and the very small transverse beam emittances. Usually, storage rings are designed with ion clearing gaps to prevent ion trapping between bunch trains or beam revolutions. Regardless, ions generated within a single bunch train can have significant effects. The same is true in transport lines and linacs, where typical vacuum pressures are relatively high. Amongst other effects, the author addresses the tune spreads due to the ions and the resulting filamentation which can severely limit emittance correction techniques in future linear colliders, the bunch-to-bunch coupling due to the ions which can cause a multi-bunch instability with fast growth rates, and the betatron coupling and beam halo creation which limit the vertical emittance and beam lifetimes.

  1. Acceleration of positrons by a relativistic electron beam in the presence of quantum effects

    SciTech Connect

    Niknam, A. R.; Aki, H.; Khorashadizadeh, S. M.

    2013-09-15

    Using the quantum magnetohydrodynamic model and obtaining the dispersion relation of the Cherenkov and cyclotron waves, the acceleration of positrons by a relativistic electron beam is investigated. The Cherenkov and cyclotron acceleration mechanisms of positrons are compared together. It is shown that growth rate and, therefore, the acceleration of positrons can be increased in the presence of quantum effects.

  2. Deceleration of Antiprotons in Support of Antiproton Storage/Utilization Research

    SciTech Connect

    Howe, Steven D.; Jackson, Gerald P.; Pearson, J. Boise; Lewis, Raymond A.

    2005-02-06

    Antimatter has the highest energy density known to mankind. Many concepts have been studied that use antimatter for propulsion. All of these concepts require the development of high density storage. H-bar Technologies, under contract with the NASA Marshall Space Flight Center, has undertaken the first step toward development of high density storage. Demonstration of the ability to store antiprotons in a Penning Trap provides the technology to pursue research in alternative storage methods that may lead to eventually to high density concepts. H-bar Technologies has undertaken research activity on the detailed design and operations required to decelerate and redirect the Fermi National Accelerator Laboratory (FNAL) antiproton beam to lay the groundwork for a source of low energy antiprotons. We have performed a detailed assessment of an antiproton deceleration scheme using the FNAL Main Injector, outlining the requirements to significantly and efficiently lower the energy of antiprotons. This task shall require a combination of: theoretical/computation simulations, development of specialized accelerator controls programming, modification of specific Main Injector hardware, and experimental testing of the modified system. Testing shall be performed to characterize the system with a goal of reducing the beam momentum from 8.9 GeV/c to a level of 1 GeV/c or less. We have designed an antiproton degrader system that will integrate with the FNAL decelerated/transferred beam. The degrader shall be designed to maximize the number of low energy antiprotons with a beam spot sized for acceptance by the Mark I test hardware.

  3. Quasi-gravitational Effect in the Accelerating Universe

    NASA Astrophysics Data System (ADS)

    Harutyunian, H. A.

    2016-09-01

    The possibility of measuring of the accelerated expansion rate at any point of our Universe is considered. It is argued that as the only reference frame in the Universe expanding with acceleration can serve the cosmological horizon - the most distant sphere belonging the observable Universe. All the points of this sphere represent the initial point coincided with the observer's local point at the beginning of time. And at the present the observer moves away from all that points. Simple calculations show that the acceleration of the observer with respect to the cosmological horizon is very small and numerically equal to the Pioneers' anomalous acceleration.

  4. Low energy highly charged ion beam facility at Inter University Accelerator Centre: Measurement of the plasma potential and ion energy distributions

    SciTech Connect

    Sairam, T. Bhatt, Pragya; Safvan, C. P.; Kumar, Ajit; Kumar, Herendra

    2015-11-15

    A deceleration lens coupled to one of the beam lines of the electron cyclotron resonance based low energy beam facility at Inter University Accelerator Centre is reported. This system is capable of delivering low energy (2.5 eV/q–1 keV/q) highly charged ion beams. The presence of plasma potential hinders the measurements of low energies (<50 eV), therefore, plasma potential measurements have been undertaken using a retarding plate analyzer in unison with the deceleration assembly. The distributions of the ion energies have been obtained and the effect of different source parameters on these distributions is studied.

  5. Accelerating quantum instanton calculations of the kinetic isotope effects

    SciTech Connect

    Karandashev, Konstantin; Vaníček, Jiří

    2015-11-21

    Path integral implementation of the quantum instanton approximation currently belongs among the most accurate methods for computing quantum rate constants and kinetic isotope effects, but its use has been limited due to the rather high computational cost. Here, we demonstrate that the efficiency of quantum instanton calculations of the kinetic isotope effects can be increased by orders of magnitude by combining two approaches: The convergence to the quantum limit is accelerated by employing high-order path integral factorizations of the Boltzmann operator, while the statistical convergence is improved by implementing virial estimators for relevant quantities. After deriving several new virial estimators for the high-order factorization and evaluating the resulting increase in efficiency, using ⋅H{sub α} + H{sub β}H{sub γ} → H{sub α}H{sub β} + ⋅ H{sub γ} reaction as an example, we apply the proposed method to obtain several kinetic isotope effects on CH{sub 4} + ⋅ H ⇌ ⋅ CH{sub 3} + H{sub 2} forward and backward reactions.

  6. [Accelerating effects of immobilized anthanquinone on the anaerobic biodegradation].

    PubMed

    Guo, Jian-bo; Zhou, Ji-ti; Wang, Dong; Tian, Cun-ping; Wang, Ping; Wang, Jing; Salah, Uddin; Li, Li-hua

    2006-10-01

    The accelerating effect of anthanquinone as a redox mediator in the bio-decolorization was conducted. Decolorization of azo dyes was carried out experimentally using the salt-tolerant bacteria under immobilized anthanquinone and high salt conditions. Anthnaquinone used as a redox mediator was able to increase the decolorization rate of wastewater containing azo dyes, and was immobilized by entrapment in calcium alginate (CA), polyvinyl alcohol (PVA)-H3BO3, polyvinyl alcohol (PVA)-calcium alginate (CA) and agar, respectively. The effects of various operating conditions such as anthnaquinone bead number and dissolved oxygen on microbial decolorization were investigated experimentally. At the same time, immobilized anthanquinone was tested to assess the effects on the change of the oxidation-reduction potential (ORP) values during the decolorization processes. High decolorization rate was obtained in the presence of 200 anthnaquinone immobilization beads at 30 degrees C, which increased 1.5-2 fold, in comparison with the control of free-anthanquinone. The oxidation-reduction potential (ORP) values stabilized around -260 to approximately -265 mV after 6 hours anoxic conditions, which lowered ORP values around -10 to approximately -15 mV by anthanquinone. The reusability of the anthnaquinone immobilization beads was evaluated with repeated-bacth decolorization experiments. After four repeated experiments, the decolorization rate of calcium alginate (CA) immobilized anthnaquinone retained over 90% of their original activity.

  7. Dark Energy Models in f( R, T) Theory with Variable Deceleration Parameter

    NASA Astrophysics Data System (ADS)

    Mishra, R. K.; Chand, Avtar; Pradhan, Anirudh

    2016-02-01

    In this communication we have investigated Bianchi type-II dark energy (DE) cosmological models with and without presence of magnetic field in modified f( R, T) gravity theory as proposed by Harko et al. (Phys. Rev. D, 84, 024020, 2011). The exact solution of the field equations is obtained by setting the deceleration parameter q as a time function along with suitable assumption the scale factor a(t)= [sinh(α t)]^{{1/n}}, α and n are positive constant. We have obtained a class of accelerating and decelerating DE cosmological models for different values of n and α. The present study believes that the mysterious dark energy is the main responsible force for accelerating expansion of the universe. For our constructed models the DE candidates cosmological constant (Λ) and the EoS parameter ( ω) both are found to be time varying quantities. The cosmological constant Λ is very large at early time and approaches to a small positive value at late time whereas the EoS parameters is found small negative at present time. Physical and kinematical properties of the models are discussed with the help of pictorial representations of the parameters. We have observed that our constructed models are compatible with recent cosmological observations.

  8. Trapping cold molecules and atoms: Simultaneous magnetic deceleration and trapping of cold molecular Oxygen with Lithium atoms

    NASA Astrophysics Data System (ADS)

    Akerman, Nitzan; Karpov, Michael; Segev, Yair; Bibelink, Natan; Narevicius, Julia; Narevicius, Edvardas

    2016-05-01

    Cooling molecules to the ultra-cold regime remains a major challenge in the growing field of cold molecules. The molecular internal degrees of freedom complicate the effort of direct application of laser cooling. An alternative and general path towards ultra-cold molecules relies on sympathetic cooling via collisions with laser-cooled atoms. Here, we demonstrate the first step towards application of sympathetic cooling by co-trapping of molecular Oxygen with Lithium atoms in a magnetic trap at a temperature of 300 mK. Our experiment begins with a pulsed supersonic beam which is a general source for cold high-flux atomic and molecular beams. Although the supersonic expansion efficiently cools the beam to temperatures below 1K, it also accelerates the beam to high mean velocities. We decelerate a beam of O2 in a moving magnetic trap decelerator from 375 m/s to a stop. We entrained the molecular beam with Li atoms by laser ablation prior to deceleration. The deceleration ends with loading the molecules and atoms into a static quadrupole trap, which is generated by two permanent magnets. We estimate 109 trapped molecules with background limited lifetime of 0.6 Sec. Our achievement enables application of laser cooling on the Li atoms in order to sympathetically cool the O2.

  9. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Astrophysics Data System (ADS)

    Singh, N.; Schunk, R. W.; Sojka, J. J.

    1982-09-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  10. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Technical Reports Server (NTRS)

    Singh, N.; Schunk, R. W.; Sojka, J. J.

    1982-01-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  11. Some effects of acceleration in man and chimpanzees. [gravitational effects

    NASA Technical Reports Server (NTRS)

    Wood, E. H.; Sass, D. J.; Ritman, E. L.; Greenleaf, J. F.; Coulam, C. M.; Nathan, D.; Nolan, E. C.

    1977-01-01

    Early physiologic experiments using dogs and humans in centrifuges are reviewed. Because of the close similarity between the shape and dimensions of the thoraces of chimpanzees and humans, the former were used to obtain roentgenograms and photokymographic recordings of multiple physiologic variables before and during exposure to +5.8 Gy to study the effects of changes in the gravitational-inertial force environment on the cardiovascular and pulmonary systems during long duration space flight. A computer-controlled sciscanning system was used to obtain a two dimensional map of the amount of radiation emanating from the dorsal and ventricle surfaces after insertion of radioactive microspheres in the right ventricle. By using four different batches of microspheres tagged with isotopes of different energies, the spatial distribution of pulmonary blood flow under four conditions was determined.

  12. Preferential acceleration and magnetic field enhancement in plasmas with e+/e- beam injection

    NASA Astrophysics Data System (ADS)

    Huynh, Cong Tuan; Ryu, Chang-Mo

    2016-03-01

    A theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e+/e- beam injection is presented. When the e+/e- beams are injected into a plasma, current filaments are formed. The beam particles are accelerated or decelerated depending on the types of current filaments in which they are trapped. It is found that in the electron/ion ambient plasma, the e+ beam particles are preferentially accelerated, while the e- beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e+/e- plasma. We also find that the particle momentum decrease can explain the magnetic field increase during the development of Weibel/filamentation instability. Supporting simulation results of particle acceleration/deceleration and magnetic field enhancement are presented. Our findings can be applied to a wide range of astrophysical plasmas with the e+/e- beam injection.

  13. Accelerator Stewardship Test Facility Program - Elliptical Twin Cavity for Accelerator Applications

    SciTech Connect

    Hutton, Andrew; Areti, Hari

    2015-08-01

    Funding is being requested pursuant to the proposals entitled Elliptical Twin Cavity for Accelerator Applications that was submitted and reviewed through the Portfolio Analysis and Management System (PAMS). The PAMS proposal identifier number is 0000219731. The proposed new type of superconducting cavity, the Elliptical Twin Cavity, is capable of accelerating or decelerating beams in two separate beam pipes. This configuration is particularly effective for high-current, low energy electron beams that will be used for bunched beam cooling of high-energy protons or ions. Having the accelerated beam physically separated from the decelerated beam, but interacting with the same RF mode, means that the low energy beam from the gun can be injected into to the superconducting cavity without bends enabling a small beam emittance to be maintained. A staff engineer who has been working with non-standard complicated cavity structures replaces the senior engineer (in the original budget) who is moving on to be a project leader. This is reflected in a slightly increased engineer time and in reduced costs. The Indirect costs for FY16 are lower than the previous projection. As a result, there is no scope reduction.

  14. Modal Test of Six-Meter Hypersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Abraham, Nijo; Buehrle, Ralph; Templeton, Justin; Lindell, Mike; Hancock, Sean M.

    2014-01-01

    A modal test was performed on the six-meter Hypersonic Inflatable Aerodynamic Decelerator (HIAD) test article to gain a firm understanding of the dynamic characteristics of the unloaded structure within the low frequency range. The tests involved various configurations of the HIAD to understand the influence of the tri-torus, the varying pressure within the toroids and the influence of straps. The primary test was conducted utilizing an eletrodynamic shaker and the results were verified using a step relaxation technique. The analysis results show an increase in the structure's stiffness with respect to increasing pressure. The results also show the rise of coupled modes with the tri-torus configurations. During the testing activity, the attached straps exhibited a behavior that is similar to that described as fuzzy structures in the literature. Therefore extensive tests were also performed by utilizing foam to mitigate these effects as well as understand the modal parameters of these fuzzy sub structures. Results are being utilized to update the finite element model of the six-meter HIAD and to gain a better understanding of the modeling of complex inflatable structures.

  15. Effects of radiation reaction in relativistic laser acceleration

    SciTech Connect

    Hadad, Y.; Labun, L.; Rafelski, J.; Elkina, N.; Klier, C.; Ruhl, H.

    2010-11-01

    The goal of this paper is twofold: to explore the response of classical charges to electromagnetic force at the level of unity in natural units and to establish a criterion that determines physical parameters for which the related radiation-reaction effects are detectable. In pursuit of this goal, the Landau-Lifshitz equation is solved analytically for an arbitrary (transverse) electromagnetic pulse. A comparative study of the radiation emission of an electron in a linearly polarized pulse for the Landau-Lifshitz equation and for the Lorentz force equation reveals the radiation-reaction-dominated regime, in which radiation-reaction effects overcome the influence of the external fields. The case of a relativistic electron that is slowed down by a counterpropagating electromagnetic wave is studied in detail. We further show that when the electron experiences acceleration of order unity, the dynamics of the Lorentz force equation, the Landau-Lifshitz equation and the Lorentz-Abraham-Dirac equation all result in different radiation emission that could be distinguished in experiment. Finally, our analytic and numerical results are compared with those appearing in the literature.

  16. Effect of gravitational acceleration, hypokinesia and hypodynamia on the structure of the intestinal vascular bed

    NASA Technical Reports Server (NTRS)

    Nikitin, M. V.

    1980-01-01

    A series of experiments comparing single and combined effects of hypokinesia and gravitational acceleration on morphology of intestinal blood vessels are discussed. Results indicate that hypokinesia has a whole body nonspecific effect reflected even in an organ whose activity shows little or no change due to hypokinesia. In early hypokinetic stages blood redistribution caused anorexia, intestinal atonia, and secretory disruption. Destructive changes from further exposure include aneurisms, varicoses, extravascular movement of blood elements, and vascular wall muscle fiber degeneration. The effect of acceleration is greatest in the ventrodorsal direction. Changes due to acceleration then hypokinesia are like those due to hypokinesia alone; changes due to acceleration before and after hypokinesia are like those due to acceleration. Adaptation raises acceleration tolerance but the effects do not survive four-week hypokinesia.

  17. Interacting Dark Fluid in Anisotropic Universe with Dynamical Deceleration Parameter

    NASA Astrophysics Data System (ADS)

    Adhav, K. S.; Bokey, V. D.; Bansod, A. S.; Munde, S. L.

    2016-10-01

    In this paper we have studied the anisotropic and homogeneous Bianchi Type-I and V universe filled with Interacting Dark Matter and Holographic Dark Energy. The solutions of field equations are obtained for both models under the assumption of linearly varying deceleration parameter which yields dynamical deceleration parameter. It has been observed that the anisotropy of expansion dies out very quickly (soon after inflation) in both models (B-I, B-V). The physical and geometrical parameters for the both models have been obtained and discussed in details.

  18. Interacting Dark Fluid in Anisotropic Universe with Dynamical Deceleration Parameter

    NASA Astrophysics Data System (ADS)

    Adhav, K. S.; Bokey, V. D.; Bansod, A. S.; Munde, S. L.

    2016-06-01

    In this paper we have studied the anisotropic and homogeneous Bianchi Type-I and V universe filled with Interacting Dark Matter and Holographic Dark Energy. The solutions of field equations are obtained for both models under the assumption of linearly varying deceleration parameter which yields dynamical deceleration parameter. It has been observed that the anisotropy of expansion dies out very quickly (soon after inflation) in both models (B-I, B-V). The physical and geometrical parameters for the both models have been obtained and discussed in details.

  19. Drag Characteristics of Several Towed Decelerator Models at Mach 3

    NASA Technical Reports Server (NTRS)

    Miserentino, Robert; Bohon, Herman L.

    1970-01-01

    An investigation has been made to determine the possibility of using toroid-membrane and wide-angle conical shapes as towed decelerators. Parameter variations were investigated which might render toroid-membrane models and wide-angle- cone models stable without loss of the high drag coefficients obtainable with sting-mounted models. The parameters varied included location of center of gravity, location of the pivot between the towline and the model, and configuration modifications of the aft end as the addition of a corner radius and the addition of a skirt. The toroid membrane can be made into a stable towed decelerator with a suitable configuration modification of the aft end.

  20. Modeling Electron-Cloud Effects in Heavy-Ion Accelerators

    SciTech Connect

    Cohen, R H; Friedman, A; Lund, S M; Molvik, A W; Lee, E P; Azevedo, T; Vay, J; Stoltz, P; Veitzer, S

    2004-09-21

    Stray electrons can arise in positive-ion accelerators for heavy ion fusion or other applications as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary- electron emission. We summarize results from several studies undertaken in conjunction with an effort to develop a self-consistent modeling capability: (1) Calculation of the electron cloud produced by electron desorption from computed beam-ion loss, which illustrates the importance of retaining ion reflection at the walls; (2) Simulation of the effect of specified electron cloud distributions on ion beam dynamics; and (3) analysis of an instability associated with a resonance between the beam-envelope ''breathing'' mode and the electron perturbation. We also report first results from a long-timestep algorithm for electron dynamics, which holds promise for efficient simultaneous solution of electron and ion dynamics. One conclusion from study (2) is that heavy-ion beams are surprisingly robust to electron clouds, compared to a priori expectations.

  1. A class of effective field theory models of cosmic acceleration

    SciTech Connect

    Bloomfield, Jolyon K.; Flanagan, Éanna É. E-mail: eef3@cornell.edu

    2012-10-01

    We explore a class of effective field theory models of cosmic acceleration involving a metric and a single scalar field. These models can be obtained by starting with a set of ultralight pseudo-Nambu-Goldstone bosons whose couplings to matter satisfy the weak equivalence principle, assuming that one boson is lighter than all the others, and integrating out the heavier fields. The result is a quintessence model with matter coupling, together with a series of correction terms in the action in a covariant derivative expansion, with specific scalings for the coefficients. After eliminating higher derivative terms and exploiting the field redefinition freedom, we show that the resulting theory contains nine independent free functions of the scalar field when truncated at four derivatives. This is in contrast to the four free functions found in similar theories of single-field inflation, where matter is not present. We discuss several different representations of the theory that can be obtained using the field redefinition freedom. For perturbations to the quintessence field today on subhorizon lengthscales larger than the Compton wavelength of the heavy fields, the theory is weakly coupled and natural in the sense of t'Hooft. The theory admits a regime where the perturbations become modestly nonlinear, but very strong nonlinearities lie outside its domain of validity.

  2. Accelerated life testing effects on CMOS microcircuit characteristics

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The 250 C, 200C and 125C accelerated tests are described. The wear-out distributions from the 250 and 200 C tests were used to estimate the activation energy between the two test temperatures. The duration of the 125 C test was not sufficient to bring the test devices into the wear-out region. It was estimated that, for the most complex of the three devices types, the activation energy between 200 C and 125 C should be at least as high as that between 250 C and 200 C. The practicality of the use of high temperature for the accelerated life tests from the point of view of durability of equipment is assessed. Guidlines for the development of accelerated life-test conditions are proposed. The use of the silicon nitride overcoat to improve the high temperature accelerated life-test characteristics of CMOS microcircuits is described.

  3. [Cumulative effect of Coriolis acceleration on coronary hemodynamics].

    PubMed

    Lapaev, E V; Bednenko, V S

    1985-01-01

    Time-course variations in coronary circulation and cardiac output were measured in 29 healthy test subjects who performed tests with a continuous cumulation of Coriolis accelerations and in 12 healthy test subjects who were exposed to Coriolis accelerations combined with acute hypoxia. Adaptive changes in coronary circulation were seen. It is recommended to monitor coronary circulation during vestibulometric tests as part of medical expertise of the flying personnel.

  4. Preliminary results of velocities and deceleration of aluminum, magnesium, zirconium, tantalum, pyrofuze, and titanium particles burning in steam. Contractor report, December 1984-May 1985

    SciTech Connect

    Kol, J.; Chozev, Y.; Berger, M.

    1985-07-01

    The energy released by metals burning in steam has several important applications including torpedo propulsion, nuclear reactor safety, underwater vehicles, underwater ordnance, etc. For investigation of shaped-charge performance, velocities and decelerations of the burning particles are important parameters that can be used for aerodynamic drag studies as well as for studies of different burning mechanisms. Wires of various metals were exploded in a steam atmosphere. The metals investigated were aluminum, magnesium, tantalum, zirconium, pyrofuze, and titanium. Exploding wires generated numerous hot, small particles. Using high-speed photography, velocities and decelerations were measured. Typical results are as follows: aluminum particles initial velocity 26 + or - 0.74 m/s and deceleration of 8075 m/sq. s zirconium (ejected from 1 mm diameter wire) particles initial velocity is from 5 to 11 + or - 0.47 m/s and deceleration is from 200 to 635 m/sq. s; zirconium (ejected from 0.127 mm diameter wire) particles initial velocity is from 1.25 to 1.6 + or - 0.47 m/s and acceleration 16 m/sq. s; magnesium particles initial velocity from 27 to 34 + or - 0.43 m/s and deceleration from 3300 to 6750 m/sq. s; tantalum (ejected from 1 mm diameter wire) particles initial velocity is 5.9 + or - 0.74 m/s; pyrofuze (ejected from 0.5 mm diameter wire) particles initial velocity is from 1.25 to 1.6 + or - 0.74 m/s and deceleration from 3700 to acceleration of 200 m/sq. s; titanium titanium (ejected from 0.127 mm diameter wire) particles initial velocity is 0.6 + or - 0.43 m/s and acceleration of 15 m/sq. s.

  5. Structural Verification and Modeling of a Tension Cone Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Tanner, Christopher L.; Cruz, Juan R.; Braun, Robert D.

    2010-01-01

    Verification analyses were conducted on membrane structures pertaining to a tension cone inflatable aerodynamic decelerator using the analysis code LS-DYNA. The responses of three structures - a cylinder, torus, and tension shell - were compared against linear theory for various loading cases. Stress distribution, buckling behavior, and wrinkling behavior were investigated. In general, agreement between theory and LS-DYNA was very good for all cases investigated. These verification cases exposed the important effects of using a linear elastic liner in membrane structures under compression. Finally, a tension cone wind tunnel test article is modeled in LS-DYNA for which preliminary results are presented. Unlike data from supersonic wind tunnel testing, the segmented tension shell and torus experienced oscillatory behavior when subjected to a steady aerodynamic pressure distribution. This work is presented as a work in progress towards development of a fluid-structures interaction mechanism to investigate aeroelastic behavior of inflatable aerodynamic decelerators.

  6. Effects of angular acceleration on man - Choice reaction time using visual and rotary motion information

    NASA Technical Reports Server (NTRS)

    Clark, B.; Stewart, J. D.

    1974-01-01

    This experiment was concerned with the effects of rotary acceleration on choice reaction time (RTc) to the motion of a luminous line on a cathode-ray tube. Specifically, it compared the (RTc) to rotary acceleration alone, visual acceleration alone, and simultaneous, double stimulation by both rotary and visual acceleration. Thirteen airline pilots were rotated about an earth-vertical axis in a precision rotation device while they observed a vertical line. The stimuli were 7 rotary and visual accelerations which were matched for rise time. The pilot responded as quickly as possible by displacing a vertical controller to the right or left. The results showed a decreasing (RTc) with increasing acceleration for all conditions, while the (RTc) to rotary motion alone was substantially longer than for all other conditions. The (RTc) to the double stimulation was significantly longer than that for visual acceleration alone.

  7. Effect of acceleration rate on automatic transmission shift-speeds for two 1979 Novas. Technical report

    SciTech Connect

    Jones, R.

    1980-01-01

    Variations in acceleration rates will result in variations in vehicle fuel economy. If typical vehicle acceleration rates are distributed in the same manner as the accelerations are distributed on the EPA test cycles, or if the vehicle operational characteristics do not significantly change with acceleration rate, then results from the EPA cycles should be representative of average vehicle use. However, if vehicle operational characteristics change with changing acceleration rates, and if vehicle accelerations in consumer use are not distributed in the same manner as the accelerations of the EPA test cycle, then significant differences between EPA estimated fuel economy and actual vehicle fuel consumption may result. One vehicle characteristic which often changes with acceleration rate is the transmission shift speed for vehicles with automatic transmissions. To determine the effects of acceleration rates on transmission shift speeds, EPA recently conducted a short test sequence on two vehicles with automatic transmissions. These tests determined the relation between vehicle acceleration rate and transmission shift speed for acceleration rates from 1 to 6 mph/sec.

  8. Acceleration in Elementary School: Using Propensity Score Matching to Estimate the Effects on Academic Achievement

    ERIC Educational Resources Information Center

    Kretschmann, Julia; Vock, Miriam; Lüdtke, Oliver

    2014-01-01

    Using German data, we examined the effects of one specific type of acceleration--grade skipping--on academic performance. Prior research on the effects of acceleration has suffered from methodological restrictions, especially due to a lack of appropriate comparison groups and a priori measurements. For this reason, propensity score matching was…

  9. Enhancing trappable antiproton populations through deceleration and frictional cooling

    SciTech Connect

    Zolotorev, Max; Sessler, Andrew; Penn, Gregory; Wurtele, Jonathan S.; Charman, Andrew E.

    2012-03-20

    CERN currently delivers antiprotons for trapping experiments with the Antiproton Decelerator (AD), which slows the antiprotons down to about 5 MeV.This energy is currently too high for direct trapping, and thick foils are used to slow down the beam to energies which can be trapped.To allow further deceleration to $\\sim 100 \\;\\mbox{keV}$, CERN is initiating the construction of ELENA,consisting of a ring which will combine RF deceleration and electron cooling capabilities. We describe a simple frictionalcooling scheme that can serve to provide significantly improved trapping efficiency, either directly from the AD or first usinga standard deceleration mechanism (induction linac or RFQ). This scheme could be implemented in a short time.The device itself is short in length, uses accessible voltages, and at reasonable cost could serve in the interim beforeELENA becomes operational, or possibly in lieu of ELENA for some experiments. Simple theory and simulations provide a preliminary assessment of theconcept and its strengths and limitations, and highlight important areas for experimental studies, in particular to pin down the level of multiplescattering for low-energy antiprotons. We show that the frictional cooling scheme can provide a similar energy spectrum to that of ELENA,but with higher transverse emittances.

  10. Effects of Spatial Gradients on Electron Runaway Acceleration

    NASA Technical Reports Server (NTRS)

    MacNeice, Peter; Ljepojevic, N. N.

    1996-01-01

    The runaway process is known to accelerate electrons in many laboratory plasmas and has been suggested as an acceleration mechanism in some astrophysical plasmas, including solar flares. Current calculations of the electron velocity distributions resulting from the runaway process are greatly restricted because they impose spatial homogeneity on the distribution. We have computed runaway distributions which include consistent development of spatial gradients in the energetic tail. Our solution for the electron velocity distribution is presented as a function of distance along a finite length acceleration region, and is compared with the equivalent distribution for the infinitely long homogenous system (i.e., no spatial gradients), as considered in the existing literature. All these results are for the weak field regime. We also discuss the severe restrictiveness of this weak field assumption.

  11. Coriolis effects are principally caused by gyroscopic angular acceleration.

    PubMed

    Isu, N; Yanagihara, M; Mikuni, T; Koo, J

    1994-07-01

    A cause of nausea evoked by cross-coupled rotation (termed Coriolis stimulus) was determined. Subjects were provided with two types of cross-coupled rotations: neck-forward flexion (Neck Flx) and upper body-forward flexion (Body Flx) during horizontal whole body rotation at a constant angular velocity. These Coriolis stimuli were given alternatively in an experimental sequence, and the severity of the nausea they evoked was compared by the subjects. The results indicated that the same quality of nausea was evoked by a slightly higher angular velocity during Body Flx (100.5 degrees/s) than during Neck Flx (90 degrees/s). While Body Flx generated Coriolis linear acceleration several times larger than Neck Flx, both the stimuli generated a similar magnitude of gyroscopic angular acceleration in this condition. Therefore, it was inferred that the nausea evoked by a Coriolis stimulus is principally caused by gyroscopic angular acceleration.

  12. Phase Stable Net Acceleration of Electrons From a Two-Stage Optical Accelerator

    SciTech Connect

    Sears, Christopher M.S.; Colby, Eric; England, R.J.; Ischebeck, Rasmus; McGuinness, Christopher; Nelson, Janice; Noble, Robert; Siemann, Robert H.; Spencer, James; Walz, Dieter; Plettner, Tomas; Byer, Robert L.; /Stanford U., Phys. Dept.

    2011-11-11

    In this article we demonstrate the net acceleration of relativistic electrons using a direct, in-vacuum interaction with a laser. In the experiment, an electron beam from a conventional accelerator is first energy modulated at optical frequencies in an inverse-free-electron-laser and bunched in a chicane. This is followed by a second stage optical accelerator to obtain net acceleration. The optical phase between accelerator stages is monitored and controlled in order to scan the accelerating phase and observe net acceleration and deceleration. Phase jitter measurements indicate control of the phase to {approx}13{sup o} allowing for stable net acceleration of electrons with lasers.

  13. Oscillation Amplitude Growth for a Decelerating Object with Constant Pitch Damping

    NASA Technical Reports Server (NTRS)

    Schoenenberger, Mark; Queen, Eric M.; Litton, Daniel

    2006-01-01

    The equations governing the deceleration and oscillation of a blunt body moving along a planar trajectory are re-expressed in the form of the Euler-Cauchy equation. An analytic solution of this equation describes the oscillation amplitude growth and frequency dilation with time for a statically stable decelerating body with constant pitch damping. The oscillation histories for several constant pitch damping values, predicted by the solution of the Euler-Cauchy equation are compared to POST six degree-of-freedom (6-DoF) trajectory simulations. The simulations use simplified aerodynamic coefficients matching the Euler-Cauchy approximations. Agreement between the model predictions and simulation results are excellent. Euler-Cauchy curves are also fit through nonlinear 6-DoF simulations and ballistic range data to identify static stability and pitch damping coefficients. The model os shown to closely fit through the data points and capture the behavior of the blunt body observed in simulation and experiment. The extracted coefficients are in reasonable agreement with higher fidelity, nonlinear parameter identification results. Finally, a nondimensional version of the Euler-Cauchy equation is presented and shown to be a simple and effective tool for designing dynamically scaled experiments for decelerating blunt capsule flight.

  14. Gas cooled fast reactor control rod drive mechanism deceleration unit. Test program

    SciTech Connect

    Wagner, T.H.

    1981-10-01

    This report presents the results of the airtesting portion of the proof-of-principle testing of a Control Rod Scram Deceleration Device developed for use in the Gas Cooled Fast Reactor (GCFR). The device utilizes a grooved flywheel to decelerate the translating assembly (T/A). Two cam followers on the translating assembly travel in the flywheel grooves and transfer the energy of the T/A to the flywheel. The grooves in the flywheel are straight for most of the flywheel length. Near the bottom of the T/A stroke the grooves are spiraled in a decreasing slope helix so that the cam followers accelerate the flywheel as they transfer the energy of the falling T/A. To expedite proof-of-principle testing, some of the materials used in the fabrication of certain test article components were not prototypic. With these exceptions the concept appears to be acceptable. The initial test of 300 scrams was completed with only one failure and the failure was that of a non-prototypic cam follower outer sleeve material.

  15. Accelerated life testing effects on CMOS microcircuit characteristics

    NASA Technical Reports Server (NTRS)

    1980-01-01

    This report covers the time period from May 1976 to December 1979 and encompasses the three phases of accelerated testing: Phase 1, the 250 C testing; Phase 2, the 200 C testing; and Phase 3, the 125 C testing. The duration of the test in Phase 1 and Phase 2 was sufficient to take the devices into the wear out region. The wear out distributions were used to estimate the activation energy between the 250 C and the 200 C test temperatures. The duration of the 125 C test, 20,000 hours, was not sufficient to bring the test devices into the wear out region; consequently the third data point at 125 C for determining the consistency of activation energy could not be obtained. It was estimated that, for the most complex of the three device types, the activation energy between 200 C and 125 C should be at least as high as that between 250 C and 200 C. The practicality of the use of high temperature for the accelerated life tests from the point of view of durability of equipment was assessed. Guidelines for the development of accelerated life test conditions were proposed. The use of the silicon nitride overcoat to improve the high temperature accelerated life test characteristics of CMOS microcircuits was explored in Phase 4 of this study and is attached as an appendix to this report.

  16. Accelerated life testing effects on CMOS microcircuit characteristics

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Accelerated life tests were performed on CMOS microcircuits to predict their long term reliability. The consistency of the CMOS microcircuit activation energy between the range of 125 C to 200 C and the range 200 C to 250 C was determined. Results indicate CMOS complexity and the amount of moisture detected inside the devices after testing influences time to failure of tested CMOS devices.

  17. Decelerating Environmentally Destructive Lawn-Walking

    ERIC Educational Resources Information Center

    Hayes, Steven C.; Cone, John D.

    1977-01-01

    Three general strategies were used to generate six interventions to decrease lawn walking in a park. While none of the three strategies appeared generally superior, some interventions were more effective than others. Another intervention, designed independently by professional planners, was also evaluated and shown to increase lawn walking…

  18. The effect of initial temperature on flame acceleration and deflagration-to-detonation transition phenomenon

    SciTech Connect

    Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.; Finfrock, C.; Gerlach, L.; Tagawa, H.; Malliakos, A.

    1998-05-01

    The High-Temperature Combustion Facility at BNL was used to conduct deflagration-to-detonation transition (DDT) experiments. Periodic orifice plates were installed inside the entire length of the detonation tube in order to promote flame acceleration. The orifice plates are 27.3-cm-outer diameter, which is equivalent to the inner diameter of the tube, and 20.6-cm-inner diameter. The detonation tube length is 21.3-meters long, and the spacing of the orifice plates is one tube diameter. A standard automobile diesel engine glow plug was used to ignite the test mixture at one end of the tube. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in DDT corresponded to the mixture whose detonation cell size, {lambda}, was equal to the inner diameter of the orifice plate, d (e.g., d/{lambda}=1). The only exception was in the dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/{lambda} equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 mIs and then decelerated to below 2 mIs. By maintaining the first 6.1 meters of the vessel at the ignition end at 400K, and the rest of the vessel at 650K, the DDT limit was reduced to 9.5 percent hydrogen (d/{lambda}=4.2). This observation indicates that the d/{lambda}=1 DDT limit criteria provides a necessary condition but not a sufficient one for the onset of DDT in obstacle laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the point of detonation initiation, referred to as the run-up distance, was found to be a function of both the hydrogen mole fraction

  19. Effects of the acceleration vector on transient burning rate of an aluminized solid propellant.

    NASA Technical Reports Server (NTRS)

    Northam, G. B.

    1971-01-01

    Experimental results concerning the transient burning-rate augmentation of a 16% aluminum polybutadiene acrylic acid (PBAA) propellant burned in a 2-in. web motor at pressure levels from 300 to 1200 psia with centrifugal accelerations from 0 to 140 g. The orientation of the acceleration vector was varied to determine its effect on the transient burning rate. The burning-rate augmentation was strongly dependent on (1) acceleration level, (2) propellant distance burned (or burn time), and (3) orientation of the acceleration vector with respect to the burning surface. This transient rate augmentation resulted from the retention of molten metallic residue on the burning surface by the normal acceleration loading. The presence of the residue altered the combustion zone heat transfer and caused increased localized burning rates, as evidenced by the pitted propellant surfaces that were observed from extinction tests conducted at various acceleration levels.

  20. Static and dynamic characteristics of angular velocity and acceleration transducers based on optical tunneling effect

    NASA Astrophysics Data System (ADS)

    Busurin, V. I.; Korobkov, V. V.; Htoo Lwin, Naing; Tuan, Phan Anh

    2016-08-01

    Theoretical and experimental analysis of quasi-linear conversion function of angular velocity and acceleration microoptoelectromechnical (MOEM) transducers based on optical tunneling effect (OTE) are conducted. Equivalent oscillating circuit is developed and dynamic characteristics of angular velocity and acceleration MOEM-transducers are investigated.

  1. Mechanism of Isoflavone Aglycone's Effect on Cognitive Performance of Senescence-Accelerated Mice

    ERIC Educational Resources Information Center

    Yang, Hong; Jin, Guifang; Ren, Dongdong; Luo, Sijing; Zhou, Tianhong

    2011-01-01

    This study investigated the effect of isoflavone aglycone (IA) on the learning and memory performance of senescence-accelerated mice, and explored its neural protective mechanism. Results showed that SAM-P/8 senescence-accelerated mice treated with IA performed significantly better in the Y-maze cognitive test than the no treatment control (P less…

  2. Acceleration of passive tracers in compressible turbulent flow.

    PubMed

    Yang, Yantao; Wang, Jianchun; Shi, Yipeng; Xiao, Zuoli; He, X T; Chen, Shiyi

    2013-02-01

    In compressible turbulence at high Reynolds and Mach numbers, shocklets emerge as a new type of flow structure in addition to intense vortices as in incompressible turbulence. Using numerical simulation of compressible homogeneous isotropic turbulence, we conduct a Lagrangian study to explore the effects of shocklets on the dynamics of passive tracers. We show that shocklets cause very strong intermittency and short correlation time of tracer acceleration. The probability density function of acceleration magnitude exhibits a -2.5 power-law scaling in the high compression region. Through a heuristic model, we demonstrate that this scaling is directly related to the statistical behavior of strong negative velocity divergence, i.e., the local compression. Tracers experience intense acceleration near shocklets, and most of them are decelerated, usually with large curvatures in their trajectories.

  3. Effect of Accelerator in Green Synthesis of Silver Nanoparticles

    PubMed Central

    Darroudi, Majid; Ahmad, Mansor Bin; Abdullah, Abdul Halim; Ibrahim, Nor Azowa; Shameli, Kamyar

    2010-01-01

    Silver nanoparticles (Ag-NPs) were successfully synthesized in the natural polymeric matrix. Silver nitrate, gelatin, glucose, and sodium hydroxide have been used as silver precursor, stabilizer, reducing agent, and accelerator reagent, respectively. This study investigated the role of NaOH as the accelerator. The resultant products have been confirmed to be Ag-NPs using powder X-ray diffraction (PXRD), UV-vis spectroscopy, and transmission electron microscopy (TEM). The colloidal sols of Ag-NPs obtained at different volumes of NaOH show strong and different surface plasmon resonance (SPR) peaks, which can be explained from the TEM images of Ag-NPs and their particle size distribution. Compared with other synthetic methods, this work is green, rapid, and simple to use. The newly prepared Ag-NPs may have many potential applications in chemical and biological industries. PMID:21152307

  4. Accelerated life testing effects on CMOS microcircuit characteristics, phase 1

    NASA Technical Reports Server (NTRS)

    Maximow, B.

    1976-01-01

    An accelerated life test of sufficient duration to generate a minimum of 50% cumulative failures in lots of CMOS devices was conducted to provide a basis for determining the consistency of activation energy at 250 C. An investigation was made to determine whether any thresholds were exceeded during the high temperature testing, which could trigger failure mechanisms unique to that temperature. The usefulness of the 250 C temperature test as a predictor of long term reliability was evaluated.

  5. Halting eternal acceleration with an effective negative cosmological constant

    NASA Astrophysics Data System (ADS)

    Cardone, V. F.; Cardenas, R. P.; Leyva Nodal, Y.

    2008-07-01

    In order to solve the problem of eternal acceleration, a model has been recently proposed including both a negative cosmological constant Λ and a scalar field evolving under the action of an exponential potential. We further explore this model by contrasting it against the Hubble diagram of type Ia supernovae, the gas mass fraction in galaxy clusters and the acoustic peak and shift parameters. It turns out that the model is able to fit this large dataset quite well so that we conclude that a negative Λ is indeed allowed and could represent a viable mechanism to halt eternal acceleration. In order to avoid problems with theoretical motivations for both a negative Λ term and the scalar field, we reconstruct the gravity Lagrangian f(R) of a fourth-order theory of gravity predicting the same dynamics (scale factor and Hubble parameter) as the starting model. We thus end up with a f(R) theory able to both fit the data and solve the problem of eternal acceleration without the need of unusual negative Λ and ad hoc scalar fields.

  6. Optimizing the Stark-decelerator beamline for the trapping of cold molecules using evolutionary strategies

    SciTech Connect

    Gilijamse, Joop J.; Kuepper, Jochen; Hoekstra, Steven; Vanhaecke, Nicolas; Meerakker, Sebastiaan Y. T. van de; Meijer, Gerard

    2006-06-15

    We demonstrate feedback control optimization for the Stark deceleration and trapping of neutral polar molecules using evolutionary strategies. In a Stark-decelerator beamline, pulsed electric fields are used to decelerate OH radicals and subsequently store them in an electrostatic trap. The efficiency of the deceleration and trapping process is determined by the exact timings of the applied electric field pulses. Automated optimization of these timings yields an increase of 40% of the number of trapped OH radicals.

  7. Physiological Effects of Acceleration Observed During a Centrifuge Study of Pilot Performance

    NASA Technical Reports Server (NTRS)

    Smedal, Harald A.; Creer, Brent Y.; Wingrove, Rodney C.

    1960-01-01

    An investigation was conducted by the National Aeronautics and Space Administration, Ames Research Center, and the Naval Air Development Center, Aviation Medical Acceleration Laboratory, to study the effects of acceleration on pilot performance and to obtain some meaningful data for use in establishing tolerance to acceleration levels. The flight simulator used in the study was the Johnsville centrifuge operated as a closed loop system. The pilot was required to perform a control task in various sustained acceleration fields typical of those that Might be encountered by a pilot flying an entry vehicle in which he is seated in a forward-facing position. A special restraint system was developed and designed to increase the pilot's tolerance to these accelerations. The results of this study demonstrated that a well-trained subject, such as a test pilot, can adequately carry out a control task during moderately high accelerations for prolonged periods of time. The maximum levels of acceleration tolerated were approximately 6 times that of gravity for approximately 6 minutes, and varied slightly with the acceleration direction. The tolerance runs were in each case terminated by the subject. In all but two instances, the cause was extreme fatigue. On two occasions the subject terminated the run when he "grayed out." Although there were subjective and objective findings involving the visual and cardiovascular systems, the respiratory system yielded the more critical limiting factors. It would appear that these limiting factors were less severe during the "eyeballs-out" accelerations when compared with the "eyeballs-in" accelerations. These findings are explained on the basis of the influence that the inertial forces of acceleration have on the mechanics of respiration. A condensed version of this report was presented at the Annual Meeting of the Aerospace Medical Association, Miami Beach, May 5-11, 1960, in a paper entitled "Ability of Pilots to Perform a Control Task in

  8. A Method of Simulating Fluid Structure Interactions for Deformable Decelerators

    NASA Astrophysics Data System (ADS)

    Gidzak, Vladimyr Mykhalo

    A method is developed for performing simulations that contain fluid-structure interactions between deployable decelerators and a high speed compressible flow. The problem of coupling together multiple physical systems is examined with discussion of the strength of coupling for various methods. A non-monolithic strongly coupled option is presented for fluid-structure systems based on grid deformation. A class of algebraic grid deformation methods is then presented with examples of increasing complexity. The strength of the fluid-structure coupling is validated against two analytic problems, chosen to test the time dependent behavior of structure on fluid interactions, and of fluid on structure interruptions. A one-dimentional material heating model is also validated against experimental data. Results are provided for simulations of a wind tunnel scale disk-gap-band parachute with comparison to experimental data. Finally, a simulation is performed on a flight scale tension cone decelerator, with examination of time-dependent material stress, and heating.

  9. Development and Testing of a New Family of Supersonic Decelerators

    NASA Technical Reports Server (NTRS)

    Clark, Ian G.; Adler, Mark; Rivellini, Tommaso P.

    2013-01-01

    The state of the art in Entry, Descent, and Landing systems for Mars applications is largely based on technologies developed in the late 1960's and early 1970's for the Viking Lander program. Although the 2011 Mars Science Laboratory has made advances in EDL technology, these are predominantly in the areas of entry (new thermal protection systems and guided hypersonic flight) and landing (the sky crane architecture). Increases in entry mass, landed mass, and landed altitude beyond MSL capabilities will require advances predominantly in the field of supersonic decelerators. With this in mind, a multi-year program has been initiated to advance three new types of supersonic decelerators that would enable future large-robotic and human-precursor class missions to Mars.

  10. An electrostatic deceleration lens for highly charged ions.

    PubMed

    Rajput, J; Roy, A; Kanjilal, D; Ahuja, R; Safvan, C P

    2010-04-01

    The design and implementation of a purely electrostatic deceleration lens used to obtain beams of highly charged ions at very low energies is presented. The design of the lens is such that it can be used with parallel as well as diverging incoming beams and delivers a well focused low energy beam at the target. In addition, tuning of the final energy of the beam over a wide range (1 eV/q to several hundred eV/q, where q is the beam charge state) is possible without any change in hardware configuration. The deceleration lens was tested with Ar(8+), extracted from an electron cyclotron resonance ion source, having an initial energy of 30 keV/q and final energies as low as 70 eV/q have been achieved.

  11. Aero-Structural Assessment of an Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Sheta, Essam F.; Venugopalan, Vinod; Tan, X. G.; Liever, Peter A.; Habchi, Sami D.

    2010-01-01

    NASA is conducting an Entry, Descent and Landing Systems Analysis (EDL-SA) Study to determine the key technology development projects that should be undertaken for enabling the landing of large payloads on Mars for both human and robotic missions. Inflatable Aerodynamic Decelerators (IADs) are one of the candidate technologies. A variety of EDL architectures are under consideration. The current effort is conducted for development and simulations of computational framework for inflatable structures.

  12. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Technology Development Overview

    NASA Technical Reports Server (NTRS)

    Hughes, Stephen J.; Cheatwood, F. McNeil; Calomino, Anthony M.; Wright, Henry S.; Wusk, Mary E.; Hughes, Monica F.

    2013-01-01

    The successful flight of the Inflatable Reentry Vehicle Experiment (IRVE)-3 has further demonstrated the potential value of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This technology development effort is funded by NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). This paper provides an overview of a multi-year HIAD technology development effort, detailing the projects completed to date and the additional testing planned for the future.

  13. Space shuttle program solid rocket booster decelerator subsystem

    NASA Technical Reports Server (NTRS)

    Barnard, J. W.

    1985-01-01

    The recovery of the Solid Rocket Boosters presented a major challenge. The SRB represents the largest payload ever recovered and presents the added complication that it is continually emitting hot gases and burning particles of insulation and other debris. Some items, such as portions of the nozzle, are large enough to burn through the nylon parachute material. The SRB Decelerator Subsystem program was highly successful in that no SRB has been lost as a result of inadequate performance of the DSS.

  14. Falkner-Skan flow of a magnetic-Carreau fluid past a wedge in the presence of cross diffusion effects

    NASA Astrophysics Data System (ADS)

    Raju, C. S. K.; Sandeep, N.

    2016-08-01

    Heat and mass transfer in the Falkner-Skan flow of a Carreau fluid past a wedge is investigated numerically. In most of the existing studies thermal radiation is linear. Due to the prominent importance of the various industrial applications, in this study we considered the nonlinear thermal radiation along with cross diffusion effects for the heat and mass transfer controlling process. Numerical results are presented graphically as well as in tabular form by enforcing Runge-Kutta and Newton's methods. We also validated the present results by comparing with the published results and found favourable agreement. We presented solutions for the flow separation, decelerating and accelerating cases. We observed that the thermal and concentration boundary layers are non-uniform for the flow separation, decelerating and accelerating cases. For industrial needs, we analysed the heat and mass transfer rates of the accelerating, decelerating and flow separation cases and found that the heat transfer rate is high in the accelerating case when compared with the decelerating case. From this we can conclude that the decelerating flow over a wedge is very useful for cooling applications.

  15. Physiological constraints on deceleration during the aerocapture of manned vehicles

    NASA Technical Reports Server (NTRS)

    Lyne, J. E.

    1992-01-01

    The peak deceleration load allowed for aerobraking of manned vehicles is a critical parameter in planning future excursions to Mars. However, considerable variation exists in the limits used by various investigators. The goal of this study was to determine the most appropriate level for this limit. Methods: Since previous U.S. space flights have been limited to 84 days duration, Soviet flight results were examined. Published details of Soviet entry trajectories were not available. However, personal communication with Soviet cosmonauts suggested that peak entry loads of 5-6 G had been encountered upon return from 8 months in orbit. Soyuz entry capsule's characteristics were established and the capsule's entry trajectory was numerically calculated. The results confirm a peak load of 5 to 6 G. Results: Although the Soviet flights were of shorter duration than expected Mars missions, evidence exists that the deceleration experience is applicable. G tolerance has been shown to stabilize after 1 to 3 months in space if adequate countermeasures are used. The calculated Soyuz deceleration histories are graphically compared with those expected for Mars aerobraking. Conclusions: Previous spaceflight experience supports the use of a 5 G limit for the aerocapture of a manned vehicle at Mars.

  16. Modified Rindler acceleration as a nonlinear electromagnetic effect

    NASA Astrophysics Data System (ADS)

    Halilsoy, M.; Gurtug, O.; Mazharimousavi, S. H.

    2015-08-01

    The model proposed originally by Mannheim and Kazanas for fitting the shapes of galactic rotation curves has recently been considered by Grumiller to describe gravity of a central object at large distances. Herein we employ the same geometry within the context of nonlinear electrodynamics (NED). Pure electrical NED model is shown to generate the novel Rindler acceleration term in the metric which explains anomalous behaviors of test particles/satellites. Remarkably a pure magnetic model of NED yields flat rotation curves that may account for the missing dark matter. Weak and strong energy conditions are satisfied in such models of NED.

  17. Some experimental observations on circulating currents in a crossed field plasma accelerator

    NASA Technical Reports Server (NTRS)

    Jedlicka, J.; Haacker, J.

    1971-01-01

    Experiments on a thermally ionized argon plasma suggest that applying a Lorentz force by means of orthogonal electric and magnetic fields to an electrically conducting fluid flow imposes necessary but not sufficient conditions for acceleration. There are, in fact, many combinations of current and magnetic field which cause decelerations of the fluid. The deceleration arises from a retarding force which may be larger than the applied Lorentz force. The retarding force causing the deceleration is a consequence of currents circulating completely within the fluid. These currents arise from differences in velocity between the central and wall regions of the duct which interact with the imposed magnetic field to produce differences in induced voltages. The observed physical effects of the circulating currents cause a loss in velocity in the central region of the duct, an increase in thermal energy in the sidewall region, and little change in thermal energy near the electrode wall region. For similar velocity profiles, the adverse effects appear to be related to the product of electrical conductivity and velocity, and performance as an accelerator appears to be controlled by the Hoffman loading parameter (i.e., the ratio of the applied to the induced currents).

  18. Effects of cosmic acceleration on black hole thermodynamics

    NASA Astrophysics Data System (ADS)

    Mandal, Abhijit; Biswas, Ritabrata

    2015-05-01

    Direct local impacts of cosmic acceleration upon a black hole are matters of interest. Babichev et al. had published before that the Friedmann equations which are prevailing the part of fluid filled up in the universe to lead (or to be very specific, `dominate') the other constituents of universe and are forcing the universe to undergo present-day accelerating phase (or to lead to violate the strong energy condition and latter the week energy condition), will themselves tell that the rate of change of mass of the central black hole due to such exotic fluid's accretion will essentially shrink the mass of the black hole. But this is a global impact indeed. The local changes in the space time geometry next to the black hole can be analysed from a modified metric governing the surrounding space time of a black hole. A charged de Sitter black hole solution encircled by quintessence field is chosen for this purpose. Different thermodynamic quantities are analysed for different values of quintessence equation of state parameter, ω q . Specific jumps in the nature of the thermodynamic space near to the quintessence or phantom barrier are noted and physically interpreted as far as possible. Nature of phase transitions and the situations at which these transitions are taking place are also explored. It is determined that before quintessence starts to work () it was preferable to have a small unstable black hole followed by a large stable one. But in quintessence (), black holes are destined to be unstable large ones pre-quelled by stable/unstable small/intermediate mass black holes.

  19. Effects of cosmic acceleration on black hole thermodynamics

    NASA Astrophysics Data System (ADS)

    Mandal, Abhijit

    2016-07-01

    Direct local impacts of cosmic acceleration upon a black hole are matters of interest. Babichev et. al. had published before that the Friedmann equations which are prevailing the part of fluid filled up in the universe to lead (or to be very specific, `dominate') the other constituents of universe and are forcing the universe to undergo present-day accelerating phase (or to lead to violate the strong energy condition and latter the week energy condition), will themselves tell that the rate of change of mass of the central black hole due to such exotic fluid's accretion will essentially shrink the mass of the black hole. But this is a global impact indeed. The local changes in the space time geometry next to the black hole can be analysed from a modified metric governing the surrounding space time of a black hole. A charged deSitter black hole solution encircled by quintessence field is chosen for this purpose. Different thermodynamic parameters are analysed for different values of quintessence equation of state parameter, ω_q. Specific jumps in the nature of the thermodynamic space near to the quintessence or phantom barrier are noted and physically interpreted as far as possible. Nature of phase transitions and the situations at which these transitions are taking place are also explored. It is determined that before quintessence starts to work (ω_q=-0.33>-1/3) it was preferable to have a small unstable black hole followed by a large stable one. But in quintessence (-1/3>ω_q>-1), black holes are destined to be unstable large ones pre-quelled by stable/ unstable small/ intermediate mass black holes.

  20. An investigation into the effectiveness of smartphone experiments on students’ conceptual knowledge about acceleration

    NASA Astrophysics Data System (ADS)

    Mazzella, Alessandra; Testa, Italo

    2016-09-01

    This study is a first attempt to investigate effectiveness of smartphone-based activities on students’ conceptual understanding of acceleration. 143 secondary school students (15-16 years old) were involved in two types of activities: smartphone- and non-smartphone activities. The latter consisted in data logging and ‘cookbook’ activities. For the sake of comparison, all activities featured the same phenomena, i.e., the motion on an inclined plane and pendulum oscillations. A pre-post design was adopted, using open questionnaires as probes. Results show only weak statistical differences between the smartphone and non-smartphone groups. Students who followed smartphone activities were more able to design an experiment to measure acceleration and to correctly describe acceleration in a free fall motion. However, students of both groups had many difficulties in drawing acceleration vector along the trajectory of the studied motion. Results suggest that smartphone-based activities may be effective substitutes of traditional experimental settings and represent a valuable aid for teachers who want to implement laboratory activities at secondary school level. However, to achieve a deeper conceptual understanding of acceleration, some issues need to be addressed: what is the reference system of the built-in smartphone sensor; relationships between smartphone acceleration graphs and experimental setup; vector representation of the measured acceleration.

  1. Out on a limb: The differential effect of substrate diameter on acceleration capacity in Anolis lizards.

    PubMed

    Vanhooydonck, Bieke; Herrel, Anthony; Irschick, Duncan J

    2006-11-01

    We investigated how substrate diameter affects acceleration performance in three Anolis lizard species (A. sagrei, A. carolinensis and A. valencienni), representing three different ecomorphs (trunk-ground, trunk-crown, and twig, respectively). We did so by measuring maximal acceleration capacity of the three species on a broad and narrow dowel. In addition to acceleration capacity, we quantified maximal sprint speed on both dowels. Both acceleration capacity and sprint speed are affected by substrate diameter, but the way in which they are, differs among species. Acceleration capacity in the trunk-ground anole, A. sagrei, was least affected by dowel diameter, whereas it was greatly reduced on the narrow dowel in the twig anole, A. valencienni. Sprint speed on the narrow dowel, however, was reduced to the greatest extent in the fastest running species, A. sagrei, whereas sprint speed was hardly affected by dowel diameter in the slow A. valencienni. The differential effect of dowel diameter on maximal acceleration capacity cannot be explained by differences in the timing of reaching maximal acceleration, but may be due to interspecific differences in the relative positioning of the limbs on the different dowels. The differential effect of dowel diameter on sprint speed, on the other hand, may be based on interspecific differences in the relative contribution of subsequent acceleratory bouts to maximal sprint speed on the broad and narrow dowel.

  2. An investigation into the effectiveness of smartphone experiments on students’ conceptual knowledge about acceleration

    NASA Astrophysics Data System (ADS)

    Mazzella, Alessandra; Testa, Italo

    2016-09-01

    This study is a first attempt to investigate effectiveness of smartphone-based activities on students’ conceptual understanding of acceleration. 143 secondary school students (15–16 years old) were involved in two types of activities: smartphone- and non-smartphone activities. The latter consisted in data logging and ‘cookbook’ activities. For the sake of comparison, all activities featured the same phenomena, i.e., the motion on an inclined plane and pendulum oscillations. A pre-post design was adopted, using open questionnaires as probes. Results show only weak statistical differences between the smartphone and non-smartphone groups. Students who followed smartphone activities were more able to design an experiment to measure acceleration and to correctly describe acceleration in a free fall motion. However, students of both groups had many difficulties in drawing acceleration vector along the trajectory of the studied motion. Results suggest that smartphone-based activities may be effective substitutes of traditional experimental settings and represent a valuable aid for teachers who want to implement laboratory activities at secondary school level. However, to achieve a deeper conceptual understanding of acceleration, some issues need to be addressed: what is the reference system of the built-in smartphone sensor; relationships between smartphone acceleration graphs and experimental setup; vector representation of the measured acceleration.

  3. Effect of electromagnetic pulse transverse inhomogeneity on ion acceleration by radiation pressure

    SciTech Connect

    Lezhnin, K. V.; Kamenets, F. F.; Beskin, V. S.; Kando, M.; Esirkepov, T. Zh.; Bulanov, S. V.

    2015-03-15

    During ion acceleration by radiation pressure, a transverse inhomogeneity of an electromagnetic pulse leads to an off-axis displacement of the irradiated target, limiting the achievable ion energy. This effect is analytically described within the framework of a thin foil target model and with particle-in-cell simulations showing that the maximum energy of the accelerated ions decreases as the displacement from the axis of the target's initial position increases. The results obtained can be applied to the optimization of ion acceleration by the laser radiation pressure with mass-limited targets.

  4. Effect of the plasma piston size on the efficiency of the electrodynamic acceleration of a body

    NASA Astrophysics Data System (ADS)

    Drobyshevskii, E. M.; Rozov, S. I.; Zhukov, B. G.; Kurakin, R. O.; Sokolov, V. M.

    1991-01-01

    The objective of the experiments reported here was to investigate the effect of the size of the plasma piston on velocity saturation during the electrodynamic acceleration of a body in rail-gun accelerators. An analysis of the results suggests that the observed decrease of the efficiency of the accelerating action of an expanded plasma piston is associated with the increased permeability of the piston with respect to the gas enclosed between the piston and the body. This conclusion is consistent with the concept of the plasma piston as a combination of merging and separating arc channels.

  5. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried; Hipólito-Ricaldi, Wiliam S. E-mail: hipolito@ceunes.ufes.br

    2012-04-01

    According to the standard ΛCDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

  6. Advanced High-Temperature Flexible TPS for Inflatable Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    DelCorso, Joseph A.; Cheatwood, F. McNeil; Bruce, Walter E., III; Hughes, Stephen J.; Calomino, Anthony M.

    2011-01-01

    Typical entry vehicle aeroshells are limited in size by the launch vehicle shroud. Inflatable aerodynamic decelerators allow larger aeroshell diameters for entry vehicles because they are not constrained to the launch vehicle shroud diameter. During launch, the hypersonic inflatable aerodynamic decelerator (HIAD) is packed in a stowed configuration. Prior to atmospheric entry, the HIAD is deployed to produce a drag device many times larger than the launch shroud diameter. The large surface area of the inflatable aeroshell provides deceleration of high-mass entry vehicles at relatively low ballistic coefficients. Even for these low ballistic coefficients there is still appreciable heating, requiring the HIAD to employ a thermal protection system (TPS). This TPS must be capable of surviving the heat pulse, and the rigors of fabrication handling, high density packing, deployment, and aerodynamic loading. This paper provides a comprehensive overview of flexible TPS tests and results, conducted over the last three years. This paper also includes an overview of each test facility, the general approach for testing flexible TPS, the thermal analysis methodology and results, and a comparison with 8-foot High Temperature Tunnel, Laser-Hardened Materials Evaluation Laboratory, and Panel Test Facility test data. Results are presented for a baseline TPS layup that can withstand a 20 W/cm2 heat flux, silicon carbide (SiC) based TPS layup, and polyimide insulator TPS layup. Recent work has focused on developing material layups expected to survive heat flux loads up to 50 W/cm2 (which is adequate for many potential applications), future work will consider concepts capable of withstanding more than 100 W/cm2 incident radiant heat flux. This paper provides an overview of the experimental setup, material layup configurations, facility conditions, and planned future flexible TPS activities.

  7. A micrometeoroid deceleration and capture experiment: Conceptual experiment design description

    NASA Technical Reports Server (NTRS)

    Wolfe, J. H.; Ballard, R. W.; Carle, G. C.; Bunch, T. E.

    1986-01-01

    The preliminary conceptual design for a cosmic dust collector is described. For the case of low Earth orbit (LEO), dust particles enter the collector through the collimator at a few volts negative potential due to charging in the ionosphere, at a velocity of 1 to 50 km/sec. The particles then pass through an electron stream and are charged to about 1 KV negative (regardless of incoming polarity). The 1 KV negatively charged particle then passes through three sensing grids coupled to charge sensitive preamps (CSP). The comparison of the two pulses provided by S(1) and S(2) are utilized by the microprocessor to determine the charge, q, on the particle (pulse amplitude) and its velocity, v (by time of flight). The third sensing grid, S(3), is kept at about 20 KV negative so that the dust particle will now be decelerated in passing from S(2) (zero potential) to S(3). S(3) is capacitively coupled to its CSP and the pulse from S(3) is utilized by the microprocessor to determine the particle's energy, E, and therefore its mass, m (again by time of flight) by comparison with the pulses from S(1) and S(2). The microprocessor can now precisely program the high-voltage switching network for the proper timing in the grounding of the successive deceleration grids. As determined by the microprocessor, each successive deceleration grid is grounded just after the dust particle passes, thus reducing the particle's energy by the amount q*100 KV at each stage. The microprocessor also determines at which stage the particle will fall below a certain critical energy where all remaining grids remain unswitched so that the particle will drift to the collector. The collector is kept at about 100V positive and is covered with gold foil to eliminate contamination and is removable for subsequent return to earth for detailed analysis.

  8. Voltage stress effects on microcircuit accelerated life test failure rates

    NASA Technical Reports Server (NTRS)

    Johnson, G. M.

    1976-01-01

    The applicability of Arrhenius and Eyring reaction rate models for describing microcircuit aging characteristics as a function of junction temperature and applied voltage was evaluated. The results of a matrix of accelerated life tests with a single metal oxide semiconductor microcircuit operated at six different combinations of temperature and voltage were used to evaluate the models. A total of 450 devices from two different lots were tested at ambient temperatures between 200 C and 250 C and applied voltages between 5 Vdc and 15 Vdc. A statistical analysis of the surface related failure data resulted in bimodal failure distributions comprising two lognormal distributions; a 'freak' distribution observed early in time, and a 'main' distribution observed later in time. The Arrhenius model was shown to provide a good description of device aging as a function of temperature at a fixed voltage. The Eyring model also appeared to provide a reasonable description of main distribution device aging as a function of temperature and voltage. Circuit diagrams are shown.

  9. Collisions of Small Drops in a Turbulent Flow. Part II: Effects of Flow Accelerations.

    NASA Astrophysics Data System (ADS)

    Pinsky, M. B.; Khain, A. P.

    2004-08-01

    The effects of Lagrangian acceleration on collision efficiency and collision kernels of small cloud droplets in a turbulent flow are investigated using the results of the recent laboratory experiments by La Porta et al., conducted under high Reλ flow of pronounced intermittency. The effect of Lagrangian accelerations on drop collisions has been found to be significant, namely, for drop pairs, containing a drop collector exceeding 10 μm in radius, collision efficiency, and collision kernels increase by up to 25% and 40%, respectively, at dissipation rates of 200 cm2 s-3 typical of weak cumulus clouds. In well-developed deep cumulus clouds, the increase attains the factor of 2.5 and 5, respectively, at typical dissipation rates of 1000 cm2 s-3. The effect of Lagrangian accelerations is mainly caused by the increase in the collision efficiency that is highly sensitive even to weak variations of interdrop relative velocity. The increase in the swept volume is responsible only for a fraction of the overall increase in the collision kernel.The effect of intermittency of a turbulent flow manifests itself in two aspects: (i) an increase in variance of Lagrangian accelerations with an increase in Reλ, and (ii) the formation of a specific shape of the probability distribution function (PDF) characterized by a sharp maximum and elongated tail. The increase in variance of Lagrangian accelerations leads to an increase in the collision rate between droplets. The effect of the PDF shape on the collision rate is studied by comparing the magnitudes of collision efficiencies (and kernels) obtained in case of the non-Gaussian PDF with those obtained using the Gaussian PDF of the same acceleration variation. The utilization of the Gaussian PDF leads to a slight (about 10% 15%) overestimation of the values of the collision efficiency and collision kernel. Thus, the effect of intermittency on drop collisions related to high values of PDF flatness has been found to be insignificant

  10. Effect of polarization and focusing on laser pulse driven auto-resonant particle acceleration

    SciTech Connect

    Sagar, Vikram; Sengupta, Sudip; Kaw, Predhiman

    2014-04-15

    The effect of laser polarization and focusing is theoretically studied on the final energy gain of a particle in the Auto-resonant acceleration scheme using a finite duration laser pulse with Gaussian shaped temporal envelope. The exact expressions for dynamical variables viz. position, momentum, and energy are obtained by analytically solving the relativistic equation of motion describing particle dynamics in the combined field of an elliptically polarized finite duration pulse and homogeneous static axial magnetic field. From the solutions, it is shown that for a given set of laser parameters viz. intensity and pulse length along with static magnetic field, the energy gain by a positively charged particle is maximum for a right circularly polarized laser pulse. Further, a new scheme is proposed for particle acceleration by subjecting it to the combined field of a focused finite duration laser pulse and static axial magnetic field. In this scheme, the particle is initially accelerated by the focused laser field, which drives the non-resonant particle to second stage of acceleration by cyclotron Auto-resonance. The new scheme is found to be efficient over two individual schemes, i.e., auto-resonant acceleration and direct acceleration by focused laser field, as significant particle acceleration can be achieved at one order lesser values of static axial magnetic field and laser intensity.

  11. Ares I First Stage Booster Deceleration System: An Overview

    NASA Technical Reports Server (NTRS)

    King, Ron; Hengel, John E.; Wolf, Dean

    2009-01-01

    In 2005, the Congressional NASA Authorization Act enacted a new space exploration program, the "Vision for Space Exploratien". The Constellation Program was formed to oversee the implementation of this new mission. With an intent not simply to support the International Space Station, but to build a permanent outpost on the Moon and then travel on to explore ever more distant terrains, the Constellation Program is supervising the development of a brand new fleet of launch vehicles, the Ares. The Ares lineup will include two new launch vehicles: the Ares I Crew Launch Vehicle and the Ares V Cargo Launch Vehicle. A crew exploration vehicle, Orion, will be launched on the Ares I. It will be capable of docking with the Space Station, the lunar lander, Altair, and the Earth Departure Stage of Ares V. The Ares V will be capable of lifting both large-scale hardware and the Altair into space. The Ares First Stage Team is tasked with developing the propulsion system necessary to liftoff from the Earth and loft the entire Ares vehicle stack toward low Earth orbit. The Ares I First Stage booster is a 12-foot diameter, five-segment, reusable solid rocket booster derived from the Space Shuttle's four segment reusable solid rocket booster (SRB). It is separated from the Upper Stage through the use of a Deceleration Subsystem (DSS). Booster Tumble Motors are used to induce the pitch tumble following separation from the Upper Stage. The spent Ares I booster must be recoverable using a parachute deceleration system similar to that of the Shuttle SRB heritage system. Since Ares I is much heavier and reenters the Earth's atmosphere from a higher altitude at a much higher velocity than the SRB, all of the parachutes must be redesigned to reliably meet the operational requisites of the new launch vehicles. This paper presents an overview of this new booster deceleration system. It includes comprehensive detail of the parachute deceleration system, its design and deployment sequences

  12. Effects of treadmill running and fatigue on impact acceleration in distance running.

    PubMed

    García-Pérez, José Antonio; Pérez-Soriano, Pedro; Llana Belloch, Salvador; Lucas-Cuevas, Angel Gabriel; Sánchez-Zuriaga, Daniel

    2014-09-01

    The effects of treadmill running on impact acceleration were examined together with the interaction between running surface and runner's fatigue state. Twenty recreational runners (11 men and 9 women) ran overground and on a treadmill (at 4.0 m/s) before and after a fatigue protocol consisting of a 30-minute run at 85% of individual maximal aerobic speed. Impact accelerations were analysed using two lightweight capacitive uniaxial accelerometers. A two-way repeated-measure analysis of variance showed that, in the pre-fatigue condition, the treadmill running decreased head and tibial peak impact accelerations and impact rates (the rate of change of acceleration), but no significant difference was observed between the two surfaces in shock attenuation. There was no significant difference in acceleration parameters between the two surfaces in the post-fatigue condition. There was a significant interaction between surface (treadmill and overground) and fatigue state (pre-fatigue and post-fatigue). In particular, fatigue when running overground decreased impact acceleration severity, but it had no such effect when running on the treadmill. The effects of treadmill running and the interaction need to be taken into account when interpreting the results of studies that use a treadmill in their experimental protocols, and when prescribing physical exercise. PMID:25325770

  13. Effects of treadmill running and fatigue on impact acceleration in distance running.

    PubMed

    García-Pérez, José Antonio; Pérez-Soriano, Pedro; Llana Belloch, Salvador; Lucas-Cuevas, Angel Gabriel; Sánchez-Zuriaga, Daniel

    2014-09-01

    The effects of treadmill running on impact acceleration were examined together with the interaction between running surface and runner's fatigue state. Twenty recreational runners (11 men and 9 women) ran overground and on a treadmill (at 4.0 m/s) before and after a fatigue protocol consisting of a 30-minute run at 85% of individual maximal aerobic speed. Impact accelerations were analysed using two lightweight capacitive uniaxial accelerometers. A two-way repeated-measure analysis of variance showed that, in the pre-fatigue condition, the treadmill running decreased head and tibial peak impact accelerations and impact rates (the rate of change of acceleration), but no significant difference was observed between the two surfaces in shock attenuation. There was no significant difference in acceleration parameters between the two surfaces in the post-fatigue condition. There was a significant interaction between surface (treadmill and overground) and fatigue state (pre-fatigue and post-fatigue). In particular, fatigue when running overground decreased impact acceleration severity, but it had no such effect when running on the treadmill. The effects of treadmill running and the interaction need to be taken into account when interpreting the results of studies that use a treadmill in their experimental protocols, and when prescribing physical exercise.

  14. Untangling the Effect of Head Acceleration on Brain Responses to Blast Waves.

    PubMed

    Mao, Haojie; Unnikrishnan, Ginu; Rakesh, Vineet; Reifman, Jaques

    2015-12-01

    Multiple injury-causing mechanisms, such as wave propagation, skull flexure, cavitation, and head acceleration, have been proposed to explain blast-induced traumatic brain injury (bTBI). An accurate, quantitative description of the individual contribution of each of these mechanisms may be necessary to develop preventive strategies against bTBI. However, to date, despite numerous experimental and computational studies of bTBI, this question remains elusive. In this study, using a two-dimensional (2D) rat head model, we quantified the contribution of head acceleration to the biomechanical response of brain tissues when exposed to blast waves in a shock tube. We compared brain pressure at the coup, middle, and contre-coup regions between a 2D rat head model capable of simulating all mechanisms (i.e., the all-effects model) and an acceleration-only model. From our simulations, we determined that head acceleration contributed 36-45% of the maximum brain pressure at the coup region, had a negligible effect on the pressure at the middle region, and was responsible for the low pressure at the contre-coup region. Our findings also demonstrate that the current practice of measuring rat brain pressures close to the center of the brain would record only two-thirds of the maximum pressure observed at the coup region. Therefore, to accurately capture the effects of acceleration in experiments, we recommend placing a pressure sensor near the coup region, especially when investigating the acceleration mechanism using different experimental setups.

  15. Effects of Accelerated Aging on Fiber Damage Thresholds

    SciTech Connect

    Setchell, R.E.

    1999-02-15

    internal defects. Damage characteristics obtained from fibers subjected to each of these aging environments were compared to results from fresh fibers tested under identical conditions. A surprising result was that internal damage was not observed in any of the tested fibers. Only breakdown at the fiber entrance face and catastrophic damage at both end faces were observed. Fiber end faces were not sealed during the accelerated aging environments, and thresholds at these faces were significantly lower in the aged fibers. However, most fibers transmitted relatively high pulse energies before damaging, and a large fraction never damaged before we reached the limits of our test laser. The absence of any observable affect on internal damage thresholds is encouraging, but the current results do not rule out the possibility that some other approach to accelerated aging could reveal a growth mechanism for internal defects.

  16. Balloon launched decelerator test program: Post-flight test report, BLDT vehicle AV-3, Viking 1975 project

    NASA Technical Reports Server (NTRS)

    Dickinson, D.; Hicks, F.; Schlemmer, J.; Michel, F.; Moog, R. D.

    1973-01-01

    The pertinent events concerned with the launch, float, and flight of balloon launched decelerator test vehicle AV-3 are discussed. The performance of the decelerator system is analyzed. Data on the flight trajectory and decelerator test points at the time of decelerator deployment are provided. A description of the time history of vehicle events and anaomalies encounters during the mission is included.

  17. Production of clinically useful positron emitter beams during carbon ion deceleration.

    PubMed

    Lazzeroni, M; Brahme, A

    2011-03-21

    In external beam radiation therapy, radioactive beams offer the best clinical solution to simultaneously treat and in vivo monitor the dose delivery and tumor response using PET or PET-CT imaging. However, difficulties mainly linked to the low production efficiency have so far limited their use. This study is devoted to the analysis of the production of high energy (11)C fragments, preferably by projectile fragmentation of a stable monodirectional and monoenergetic primary (12)C beam in different absorbing materials (decelerators) in order to identify the optimal elemental composition. The study was performed using the Monte Carlo code SHIELD-HIT07. The track length and fluence of generated secondary particles were scored in a uniform absorber of 300 cm length and 10 cm radius, divided into slices of 1 cm thickness. The (11)C fluence build-up and mean energy variation with increasing decelerator depth are presented. Furthermore, the fluence of the secondary (11)C beam was studied as a function of its mean energy and the corresponding remaining range in water. It is shown that the maximum (11)C fluence build-up is high in compounds where the fraction by weight of hydrogen is high, being the highest in liquid hydrogen. Furthermore, a cost effective alternative solution to the single medium initially envisaged is presented: a two-media decelerator that comprises a first liquid hydrogen section followed by a second decelerating section made of a hydrogen-rich material, such as polyethylene (C(2)H(4)). The purpose of the first section is to achieve a fast initial (11)C fluence build-up, while the second section is primarily designed to modulate the mean energy of the generated (11)C beam in order to reach the tumor depth. Finally, it was demonstrated that, if the intensity of the primary (12)C beam can be increased by an order of magnitude, a sufficient intensity of the secondary (11)C beam is achieved for therapy and subsequent therapeutic PET imaging sessions. Such an

  18. Production of clinically useful positron emitter beams during carbon ion deceleration

    NASA Astrophysics Data System (ADS)

    Lazzeroni, M.; Brahme, A.

    2011-03-01

    In external beam radiation therapy, radioactive beams offer the best clinical solution to simultaneously treat and in vivo monitor the dose delivery and tumor response using PET or PET-CT imaging. However, difficulties mainly linked to the low production efficiency have so far limited their use. This study is devoted to the analysis of the production of high energy 11C fragments, preferably by projectile fragmentation of a stable monodirectional and monoenergetic primary 12C beam in different absorbing materials (decelerators) in order to identify the optimal elemental composition. The study was performed using the Monte Carlo code SHIELD-HIT07. The track length and fluence of generated secondary particles were scored in a uniform absorber of 300 cm length and 10 cm radius, divided into slices of 1 cm thickness. The 11C fluence build-up and mean energy variation with increasing decelerator depth are presented. Furthermore, the fluence of the secondary 11C beam was studied as a function of its mean energy and the corresponding remaining range in water. It is shown that the maximum 11C fluence build-up is high in compounds where the fraction by weight of hydrogen is high, being the highest in liquid hydrogen. Furthermore, a cost effective alternative solution to the single medium initially envisaged is presented: a two-media decelerator that comprises a first liquid hydrogen section followed by a second decelerating section made of a hydrogen-rich material, such as polyethylene (C2H4). The purpose of the first section is to achieve a fast initial 11C fluence build-up, while the second section is primarily designed to modulate the mean energy of the generated 11C beam in order to reach the tumor depth. Finally, it was demonstrated that, if the intensity of the primary 12C beam can be increased by an order of magnitude, a sufficient intensity of the secondary 11C beam is achieved for therapy and subsequent therapeutic PET imaging sessions. Such an increase in the

  19. EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators

    NASA Astrophysics Data System (ADS)

    Bingham, Robert

    2009-02-01

    by Chen et al where the driver, instead of being a laser, is a whistler wave known as the magnetowave plasma accelerator. The application to electron--positron plasmas that are found around pulsars is studied in the paper by Shukla, and to muon acceleration by Peano et al. Electron wakefield experiments are now concentrating on control and optimisation of high-quality beams that can be used as drivers for novel radiation sources. Studies by Thomas et al show that filamentation has a deleterious effect on the production of high quality mono-energetic electron beams and is caused by non-optimal choice of focusing geometry and/or electron density. It is crucial to match the focusing with the right plasma parameters and new types of plasma channels are being developed, such as the magnetically controlled plasma waveguide reported by Froula et al. The magnetic field provides a pressure profile shaping the channel to match the guiding conditions of the incident laser, resulting in predicted electron energies of 3GeV. In the forced laser-wakefield experiment Fang et al show that pump depletion reduces or inhibits the acceleration of electrons. One of the earlier laser acceleration concepts known as the beat wave may be revived due to the work by Kalmykov et al who report on all-optical control of nonlinear focusing of laser beams, allowing for stable propagation over several Rayleigh lengths with pre-injected electrons accelerated beyond 100 MeV. With the increasing number of petawatt lasers, attention is being focused on different acceleration regimes such as stochastic acceleration by counterpropagating laser pulses, the relativistic mirror, or the snow-plough effect leading to single-step acceleration reported by Mendonca. During wakefield acceleration the leading edge of the pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake while the trailing edge of the laser pulse undergoes frequency up-shift. This is commonly known

  20. Long-Term Effectiveness of Accelerated Hepatitis B Vaccination Schedule in Drug Users

    PubMed Central

    Shah, Dimpy P.; Grimes, Carolyn Z.; Nguyen, Anh T.; Lai, Dejian

    2015-01-01

    Objectives. We demonstrated the effectiveness of an accelerated hepatitis B vaccination schedule in drug users. Methods. We compared the long-term effectiveness of accelerated (0–1–2 months) and standard (0–1–6 months) hepatitis B vaccination schedules in preventing hepatitis B virus (HBV) infections and anti-hepatitis B (anti-HBs) antibody loss during 2-year follow-up in 707 drug users (HIV and HBV negative at enrollment and completed 3 vaccine doses) from February 2004 to October 2009. Results. Drug users in the accelerated schedule group had significantly lower HBV infection rates, but had a similar rate of anti-HBs antibody loss compared with the standard schedule group over 2 years of follow-up. No chronic HBV infections were observed. Hepatitis C positivity at enrollment and age younger than 40 years were independent risk factors for HBV infection and antibody loss, respectively. Conclusions. An accelerated vaccination schedule was more preferable than a standard vaccination schedule in preventing HBV infections in drug users. To overcome the disadvantages of a standard vaccination schedule, an accelerated vaccination schedule should be considered in drug users with low adherence. Our study should be repeated in different cohorts to validate our findings and establish the role of an accelerated schedule in hepatitis B vaccination guidelines for drug users. PMID:25880946

  1. The effect of summation of contraction on acceleration signals in human skeletal muscle.

    PubMed

    Ohta, Yoichi; Shima, Norihiro; Yabe, Kyonosuke

    2010-10-01

    The purpose of this study was to determine the effects of summation of contraction on acceleration signals in human skeletal muscle. The torque parameters of dorsiflexion and acceleration signals in the tibialis anterior muscle were measured during evoked isometric contractions. In an examination of two-pulse trains with different inter-pulse intervals, the torque and accelerometer responses to inter-pulse intervals of 10-100 ms were recorded. In an investigation of the effects of different numbers of stimuli, the torque and accelerometer responses to 1-8 pulses with a constant inter-pulse interval of 10 ms were recorded. The present study found that there was a difference in acceleration amplitude between the single-pulse and two-pulse trains with an inter-pulse interval of 10 ms but not two-pulse trains with an inter-pulse interval of 20 ms or more. In the investigation of different numbers of stimuli, we found a similar MMG amplitude across 2-8 pulses. Moreover, we observed that the maximal time to the peak acceleration signal was approximately 27 ms. In a comparison of torque parameters with acceleration signals, the present study clearly shows that acceleration amplitude is poorly correlated to changes in force parameters when the inter-pulse interval or the number of stimuli are increased. These results suggest that the absence of associated changes in acceleration peak is due to the long interval for the subsequent pulses relative to the time at which acceleration peak is achieved ( approximately 27 ms). These findings will provide useful information concerning the method for assessing summation of contraction with an accelerometer.

  2. Hydrodynamic Scaling of the Deceleration-Phase Rayleigh-Taylor Instability

    NASA Astrophysics Data System (ADS)

    Bose, A.; Nora, R.; Woo, K.; Betti, R.

    2013-10-01

    A 2-D study of the deceleration-phase Rayleigh-Taylor (RT) growth is carried out to assess how the yield-over-clean (YOC) varies in hydro-equivalent implosions. Hydro-equivalent implosions exhibit equal implosion velocity, adiabat, and laser intensity. The YOC indicates the effects of hydrodynamic instabilities on inertial fusion capsule implosions. While the classical RT instability follows the laws of hydrodynamic similarity (the same growth factor for hydro-equivalent implosions), the effects of ablation and thermal transport in the hot spot cause a deviation from similarity. We present analytic and numerical calculations of the RT growth factors in hydro-equivalent implosions with target sizes varying from typical OMEGA to NIF-scale targets. Theoretical scaling suggests that the deceleration-phase Atwood number and ablation velocity is different for OMEGA and the NIF, yielding growth factors that are dependent on the target size. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).

  3. Decelerated invasion and waning-moon patterns in public goods games with delayed distribution.

    PubMed

    Szolnoki, Attila; Perc, Matjaž

    2013-05-01

    We study the evolution of cooperation in the spatial public goods game, focusing on the effects that are brought about by the delayed distribution of goods that accumulate in groups due to the continuous investments of cooperators. We find that intermediate delays enhance network reciprocity because of a decelerated invasion of defectors, who are unable to reap the same high short-term benefits as they do in the absence of delayed distribution. Long delays, however, introduce a risk because the large accumulated wealth might fall into the wrong hands. Indeed, as soon as the curvature of a cooperative cluster turns negative, the engulfed defectors can collect the heritage of many generations of cooperators and by doing so start a waning-moon pattern that nullifies the benefits of decelerated invasion. Accidental meeting points of growing cooperative clusters may also act as triggers for the waning-moon effect, thus linking the success of cooperators with their propensity to fail in a rather bizarre way. Our results highlight that "investing in the future" is a good idea only if that future is sufficiently near and not likely to be burdened by inflation. PMID:23767662

  4. Overview of the Mars Science Laboratory Parachute Decelerator Subsystem

    NASA Technical Reports Server (NTRS)

    Sengupta, Anita; Steltzner, Adam; Witkowski, Al; Rowan, Jerry; Cruz, Juan

    2007-01-01

    In 2010 the Mars Science Laboratory (MSL) mission will deliver NASA's largest and most capable rover to the surface of Mars. MSL will explore previously unattainable landing sites due to the implementation of a high precision Entry, Descent, and Landing (EDL) system. The parachute decelerator subsystem (PDS) is an integral prat of the EDL system, providing a mass and volume efficient some of aerodynamic drag to decelerate the entry vehicle from Mach 2 to subsonic speeds prior to final propulsive descent to the sutface. The PDS for MSL is a mortar deployed 19.7m Viking type Disk-Gap-Band (DGB) parachute; chosen to meet the EDL timeline requirements and to utilize the heritage parachute systems from Viking, Mars Pathfinder, Mars Exploration Rover, and Phoenix NASA Mars Lander Programs. The preliminary design of the parachute soft goods including materials selection, stress analysis, fabrication approach, and development testing will be discussed. The preliminary design of mortar deployment system including mortar system sizing and performance predictions, gas generator design, and development mortar testing will also be presented.

  5. The challenges of integrating instrumentation with inflatable aerodynamic decelerators

    NASA Astrophysics Data System (ADS)

    Swanson, Gregory T.; Cassell, Alan M.; Hughes, Stephen J.; Johnson, R. Keith; Calomino, Anthony M.

    New Entry, Decent, and Landing (EDL) technologies are being explored to facilitate the landing of high mass vehicles. Current EDL technologies are limited due to mass and volume constraints dictated by launch vehicle fairings. Therefore, past and present technologies are now being considered to provide a mass and volume efficient solution, including Inflatable Aerodynamic Decelerators (IADs). To better define the instrumentation challenges posed by IAD technology development, a survey was conducted to identify valuable measurements for ground and flight testing of the flexible materials and structures used in their design. From this survey many sensing technologies and systems were explored specific to the stacked torus IAD, resulting in a down-selection to the most viable prospects. The majority of these systems, including wireless data acquisition, were then rapid prototyped and evaluated during component level testing to determine the best integration techniques specific to a 3m and 6m diameter stacked toroid IAD. Each sensing system was then integrated in support of the Hypersonic Inflatable Aerodynamic Decelerator ground test campaign. In this paper these IAD instrumentation systems are described along with their challenges in comparison to traditional rigid aeroshell systems. Requirements resulting from the survey are listed and instrumentation integration techniques and data acquisition are discussed.

  6. Estimating Mass of Inflatable Aerodynamic Decelerators Using Dimensionless Parameters

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.

    2011-01-01

    This paper describes a technique for estimating mass for inflatable aerodynamic decelerators. The technique uses dimensional analysis to identify a set of dimensionless parameters for inflation pressure, mass of inflation gas, and mass of flexible material. The dimensionless parameters enable scaling of an inflatable concept with geometry parameters (e.g., diameter), environmental conditions (e.g., dynamic pressure), inflation gas properties (e.g., molecular mass), and mass growth allowance. This technique is applicable for attached (e.g., tension cone, hypercone, and stacked toroid) and trailing inflatable aerodynamic decelerators. The technique uses simple engineering approximations that were developed by NASA in the 1960s and 1970s, as well as some recent important developments. The NASA Mars Entry and Descent Landing System Analysis (EDL-SA) project used this technique to estimate the masses of the inflatable concepts that were used in the analysis. The EDL-SA results compared well with two independent sets of high-fidelity finite element analyses.

  7. Temperature effects on snapping performance in the common snapper Chelydra serpentina (Reptilia, Testudines).

    PubMed

    Vervust, Bart; Brecko, Jonathan; Herrel, Anthony

    2011-01-01

    Studies on the effect of temperature on whole-animal performance traits other than locomotion are rare. Here we investigate the effects of temperature on the performance of the turtle feeding apparatus in a defensive context. We measured bite force and the kinematics of snapping in the Common Snapping Turtle (Chelydra serpentina) over a wide range of body temperatures. Bite force performance was thermally insensitive over the broad range of temperatures typically experienced by these turtles in nature. In contrast, neck extension (velocity, acceleration, and deceleration) and jaw movements (velocity, acceleration, and deceleration) showed clear temperature dependence with peak acceleration and deceleration capacity increasing with increasing temperatures. Our results regarding the temperature dependence of defensive behavior are reflected by the ecology and overall behavior of this species. These data illustrate the necessity for carefully controlling T(b) when carrying out behavioral and functional studies on turtles as temperature affects the velocity, acceleration, and deceleration of jaw and neck extension movements. More generally, these data add to the limited but increasing number of studies showing that temperature may have important effects on feeding and defensive performance in ectotherms. PMID:21137093

  8. Bell-Plesset effects for an accelerating interface with contiguous density gradients

    SciTech Connect

    Amendt, P

    2005-12-20

    A Plesset-type treatment [J. Appl. Phys. 25, 96 (1954)] is used to assess the effects of contiguous density gradients at an accelerating spherical classical interface on Rayleigh-Taylor and Bell-Plesset perturbation growth. Analytic expressions are obtained that describe enhanced Rayleigh-Taylor instability growth from contiguous density gradients aligned with the acceleration and which increase the effective Atwood number of the perturbed interface. A new pathway for geometric amplification of surface perturbations on an accelerating interface with contiguous density gradients is identified. A resonance condition between the density-gradient scalelength and the radius of the interface is also predicted based on a linearized analysis of Bernoulli's equation, potentially leading to enhanced perturbation growth. Comparison of the analytic treatment with detailed two-dimensional single-mode growth-factor simulations shows good agreement for low-mode numbers where the effects of spherical geometry are most manifested.

  9. An EMA Analysis of the Effect of Increasing Word Length on Consonant Production in Apraxia of Speech: A Case Study

    ERIC Educational Resources Information Center

    Bartle, Carly J.; Goozee, Justine V.; Murdoch, Bruce E.

    2007-01-01

    The effect of increasing word length on the articulatory dynamics (i.e. duration, distance, maximum acceleration, maximum deceleration, and maximum velocity) of consonant production in acquired apraxia of speech was investigated using electromagnetic articulography (EMA). Tongue-tip and tongue-back movement of one apraxic patient was recorded…

  10. On the Origin of Fanaroff-Riley Classification of Radio Galaxies: Deceleration of Supersonic Radio Lobes

    NASA Astrophysics Data System (ADS)

    Kawakatu, Nozomu; Kino, Motoki; Nagai, Hiroshi

    2009-06-01

    We argue that the origin of "FRI/FRII dichotomy"—the division between Fanaroff-Riley class I (FRI) with subsonic lobes and class II (FRII) radio sources with supersonic lobes is sharp in the radio-optical luminosity plane (Owen-White diagram)—can be explained by the deceleration of advancing radio lobes. The deceleration is caused by the growth of the effective cross-sectional area of radio lobes. We derive the condition in which an initially supersonic lobe turns into a subsonic lobe, combining the ram pressure equilibrium between the hot spots and the ambient medium with the relation between "the hot spot radius" and "the linear size of radio sources" obtained from the radio observations. We find that the dividing line between the supersonic lobes and subsonic ones is determined by the ratio of the jet power L j to the number density of the ambient matter at the core radius of the host galaxy \\bar{n}_a. It is also found that the maximal ratio of (L_j/\\bar{n}_a) exists and its value resides in (L_j/\\bar{n}_a)_max≈ 10^{44-47} erg s^{-1} cm^{3}, taking into account considerable uncertainties. This suggests that the maximal value (L_j/\\bar{n}_a)_max separates between FRIs and FRIIs.

  11. Angular distribution of Cherenkov radiation from relativistic heavy ions taking into account deceleration in the radiator

    SciTech Connect

    Bogdanov, O. V. Fiks, E. I.; Pivovarov, Yu. L.

    2012-09-15

    Numerical methods are used to study the dependence of the structure and the width of the angular distribution of Vavilov-Cherenkov radiation with a fixed wavelength in the vicinity of the Cherenkov cone on the radiator parameters (thickness and refractive index), as well as on the parameters of the relativistic heavy ion beam (charge and initial energy). The deceleration of relativistic heavy ions in the radiator, which decreases the velocity of ions, modifies the condition of structural interference of the waves emitted from various segments of the trajectory; as a result, a complex distribution of Vavilov-Cherenkov radiation appears. The main quantity is the stopping power of a thin layer of the radiator (average loss of the ion energy), which is calculated by the Bethe-Bloch formula and using the SRIM code package. A simple formula is obtained to estimate the angular distribution width of Cherenkov radiation (with a fixed wavelength) from relativistic heavy ions taking into account the deceleration in the radiator. The measurement of this width can provide direct information on the charge of the ion that passes through the radiator, which extends the potentialities of Cherenkov detectors. The isotopic effect (dependence of the angular distribution of Vavilov-Cherenkov radiation on the ion mass) is also considered.

  12. Forced unsteady deceleration of a turbulent boundary layer from a temporal perspective

    NASA Technical Reports Server (NTRS)

    Brereton, G. J.

    1992-01-01

    The behavior of a turbulent boundary layer which has been subjected to a local ramp-like deceleration in the external velocity field, which leads to forced separation, has been studied experimentally. The data of this study are re-interpreted in light of more recent findings concerning the temporal nature of boundary layer turbulence in the presence of forced unsteady shear. In particular, the robustness of the near-wall turbulent motions to organized deformation is recognized. Their resilence during unsteady shearing action promotes continued efficient turbulent mixing and rapid redistribution of turbulent kinetic energy during forced transients. In aerodynamic problems, the rapid nature of the adjustment of the turbulence field to a new temporal boundary condition necessitates equally rapid remedial measures to be taken if means of control/prevention of forced unsteady separation are to be deployed to maximum effect. This requirement suggests exploration of the use of simple, real-time statistical forecasting techniques, based upon time-series analysis of easily-measurable features of the flow, to help assure timely deployment of mechanisms of boundary-layer control. This paper focuses upon the nature of turbulence in boundary layers undergoing forced deceleration which would lead to separation. A preliminary form of a forecasting model is presented and evaluated. Using observations of the previous two large eddies passing a detector, it forecasts the behavior of the future large eddy rather well.

  13. Three-dimensional hydrodynamics of the deceleration stage in inertial confinement fusion

    SciTech Connect

    Weber, C. R. Clark, D. S.; Cook, A. W.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Marinak, M. M.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.; Thomas, C. A.

    2015-03-15

    The deceleration stage of inertial confinement fusion implosions is modeled in detail using three-dimensional simulations designed to match experiments at the National Ignition Facility. In this final stage of the implosion, shocks rebound from the center of the capsule, forming the high-temperature, low-density hot spot and slowing the incoming fuel. The flow field that results from this process is highly three-dimensional and influences many aspects of the implosion. The interior of the capsule has high-velocity motion, but viscous effects limit the range of scales that develop. The bulk motion of the hot spot shows qualitative agreement with experimental velocity measurements, while the variance of the hot spot velocity would broaden the DT neutron spectrum, increasing the inferred temperature by 400–800 eV. Jets of ablator material are broken apart and redirected as they enter this dynamic hot spot. Deceleration stage simulations using two fundamentally different rad-hydro codes are compared and the flow field is found to be in good agreement.

  14. Effect of Reprocessing and Accelerated Weathering on Impact-Modified Recycled Blend

    NASA Astrophysics Data System (ADS)

    Ramesh, V.; Mohanty, Smita; Biswal, Manoranjan; Nayak, Sanjay K.

    2015-12-01

    Recovery of recycled polycarbonate, acrylonitrile butadiene styrene, high-impact polystyrene, and its blends from waste electrical and electronic equipment plastics products properties were enhanced by the addition of virgin polycarbonate and impact modifier. The optimized blend formulation was processed through five cycles, at processing temperature, 220-240 °C and accelerated weathering up to 700 h. Moreover, the effect of reprocessing and accelerated weathering in the physical properties of the modified blends was investigated by mechanical, thermal, rheological, and morphological studies. The results show that in each reprocessing cycle, the tensile strength and impact strength decreased significantly and the similar behavior has been observed from accelerated weathering. Subsequently, the viscosity decreases and this decrease becomes the effect of thermal and photo-oxidative degradation. This can be correlated with FTIR analysis.

  15. Effect of relativistic acceleration on localized two-mode Gaussian quantum states

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mehdi; Lorek, Krzysztof; Checińska, Agata; Smith, Alexander R. H.; Mann, Robert B.; Dragan, Andrzej

    2016-06-01

    We study how an arbitrary Gaussian state of two localized wave packets, prepared in an inertial frame of reference, is described by a pair of uniformly accelerated observers. We explicitly compute the resulting state for arbitrarily chosen proper accelerations of the observers and independently tuned distance between them. To do so, we introduce a generalized Rindler frame of reference and analytically derive the corresponding state transformation as a Gaussian channel. Our approach provides several new insights into the phenomenon of vacuum entanglement such as the highly nontrivial effect of spatial separation between the observers including sudden death of entanglement. We also calculate the fidelity of the two-mode channel for nonvacuum Gaussian states and obtain bounds on classical and quantum capacities of a single-mode channel. Our framework can be directly applied to any continuous variable quantum information protocol in which the effects of acceleration or gravity cannot be neglected.

  16. Effects of fibers on the color change and stability of resin composites after accelerated aging.

    PubMed

    Tuncdemir, Ali Riza; Aykent, Filiz

    2012-01-01

    Composite resins were reinforced with glass and polyethylene fibers in this study, and the effect of fiber reinforcement on the color change of composite resins was investigated. After accelerated aging, the effect of fiber reinforcement on the color stability of composite resins was also examined. There were three experimental groups (n=12 disks per group): non-fiber-reinforced composite (non-FRC control), polyethylene fiber (Ribbond-THM)-reinforced composite, and glass fiber (everstick NET)-reinforced composite. According to the critical remarks of color change of National Bureau of Standarts (NSB), glass fiber-reinforced anterior composites showed trace color change and polyethylene-fiber reinforced composites showed slight color change before accelerated aging. After accelerated aging, both control and fiber-reinforced composite groups showed noticeable color change. It was concluded that both the types of fiber reinforcement and composite resin influenced the color change of fiber-reinforced composite resins.

  17. Technology Development for Deployable Aerodynamic Decelerators at Mars

    NASA Technical Reports Server (NTRS)

    Masciarelli, James P.

    2002-01-01

    Parachutes used for Mars landing missions are only certified for deployment at Mars behind blunt bodies flying at low angles of attack, Mach numbers up to 2.2, and dynamic pressures of up to 800 Pa. NASA is currently studying entry vehicle concepts for future robotic missions to Mars that would require parachutes to be deployed at higher Mach numbers and dynamic pressures. This paper demonstrates the need for expanding the parachute deployment envelope, and describes a three-phase technology development activity that has been initiated to address the need. The end result of the technology development program will be a aerodynamic decelerator system that can be deployed at Mach numbers of up to 3.1 and dynamic pressures of up to 1400 Pa.

  18. Impact Accelerations of Barefoot and Shod Running.

    PubMed

    Thompson, M; Seegmiller, J; McGowan, C P

    2016-05-01

    During the ground contact phase of running, the body's mass is rapidly decelerated resulting in forces that propagate through the musculoskeletal system. The repetitive attenuation of these impact forces is thought to contribute to overuse injuries. Modern running shoes are designed to reduce impact forces, with the goal to minimize running related overuse injuries. Additionally, the fore/mid foot strike pattern that is adopted by most individuals when running barefoot may reduce impact force transmission. The aim of the present study was to compare the effects of the barefoot running form (fore/mid foot strike & decreased stride length) and running shoes on running kinetics and impact accelerations. 10 healthy, physically active, heel strike runners ran in 3 conditions: shod, barefoot and barefoot while heel striking, during which 3-dimensional motion analysis, ground reaction force and accelerometer data were collected. Shod running was associated with increased ground reaction force and impact peak magnitudes, but decreased impact accelerations, suggesting that the midsole of running shoes helps to attenuate impact forces. Barefoot running exhibited a similar decrease in impact accelerations, as well as decreased impact peak magnitude, which appears to be due to a decrease in stride length and/or a more plantarflexed position at ground contact. PMID:26837933

  19. Effect of accelerated weathering on surface chemistry of modified wood

    NASA Astrophysics Data System (ADS)

    Temiz, Ali; Terziev, Nasko; Eikenes, Morten; Hafren, Jonas

    2007-04-01

    In this study, the effects of UV-light irradiation and water spray on colour and surface chemistry of scots pine sapwood samples were investigated. The specimens were treated with chromated copper arsenate (CCA), a metal-free propiconazol-based formulation, chitosan, furfuryl alcohol and linseed and tall oils. The weathering experiment was performed by cycles of 2 h UV-light irradiation followed by water spray for 18 min. The changes at the surface of the weathered samples were characterised by Fourier transform infrared spectroscopy (FT-IR); colour characterizations were performed by measuring CIELab parameters. The results show that all treatment methods except chitosan treatment provided lower colour changes than the control groups after 800 h exposure in weathering test cycle, but differences between chitosan and control were also small. The lowest colour changes were found on linseed oil (full cell process) and CCA treated wood. FT-IR results show that oil treatment (linseed and tall oil) decreased the intensities of a lignin specific peak (1500-1515 cm -1). Absorption band changes at 1630-1660 cm -1 were reduced by all treatments.

  20. Biological Effectiveness of Accelerated Protons for Chromosome Exchanges.

    PubMed

    George, Kerry A; Hada, Megumi; Cucinotta, Francis A

    2015-01-01

    We have investigated chromosome exchanges induced in human cells by seven different energies of protons (5-2500 MeV) with LET values ranging from 0.2 to 8 keV/μm. Human lymphocytes were irradiated in vitro and chromosome damage was assessed using three-color fluorescence in situ hybridization chromosome painting in chemically condensed chromosomes collected during the first cell division post irradiation. The relative biological effectiveness (RBE) was calculated from the initial slope of the dose-response curve for chromosome exchanges with respect to low dose and low dose-rate γ-rays (denoted as RBEmax), and relative to acute doses of γ-rays (denoted as RBEγAcute). The linear dose-response term was similar for all energies of protons, suggesting that the decrease in LET with increasing proton energy was balanced by the increase in dose from the production of nuclear secondaries. Secondary particles increase slowly above energies of a few hundred megaelectronvolts. Additional studies of 50 g/cm(2) aluminum shielded high-energy proton beams showed minor differences compared to the unshielded protons and lower RBE values found for shielded in comparison to unshielded beams of 2 or 2.5 GeV. All energies of protons produced a much higher percentage of complex-type chromosome exchanges when compared to acute doses of γ-rays. The implications of these results for space radiation protection and proton therapy are discussed. PMID:26539409

  1. Salt Effect Accelerates Site-Selective Cysteine Bioconjugation

    PubMed Central

    2016-01-01

    Highly efficient and selective chemical reactions are desired. For small molecule chemistry, the reaction rate can be varied by changing the concentration, temperature, and solvent used. In contrast for large biomolecules, the reaction rate is difficult to modify by adjusting these variables because stringent biocompatible reaction conditions are required. Here we show that adding salts can change the rate constant over 4 orders of magnitude for an arylation bioconjugation reaction between a cysteine residue within a four-residue sequence (π-clamp) and a perfluoroaryl electrophile. Biocompatible ammonium sulfate significantly enhances the reaction rate without influencing the site-specificity of π-clamp mediated arylation, enabling the fast synthesis of two site-specific antibody–drug conjugates that selectively kill HER2-positive breast cancer cells. Computational and structure–reactivity studies indicate that salts may tune the reaction rate through modulating the interactions between the π-clamp hydrophobic side chains and the electrophile. On the basis of this understanding, the salt effect is extended to other bioconjugation chemistry, and a new regioselective alkylation reaction at π-clamp cysteine is developed. PMID:27725962

  2. Biological Effectiveness of Accelerated Protons for Chromosome Exchanges

    PubMed Central

    George, Kerry A.; Hada, Megumi; Cucinotta, Francis A.

    2015-01-01

    We have investigated chromosome exchanges induced in human cells by seven different energies of protons (5–2500 MeV) with LET values ranging from 0.2 to 8 keV/μm. Human lymphocytes were irradiated in vitro and chromosome damage was assessed using three-color fluorescence in situ hybridization chromosome painting in chemically condensed chromosomes collected during the first cell division post irradiation. The relative biological effectiveness (RBE) was calculated from the initial slope of the dose–response curve for chromosome exchanges with respect to low dose and low dose-rate γ-rays (denoted as RBEmax), and relative to acute doses of γ-rays (denoted as RBEγAcute). The linear dose–response term was similar for all energies of protons, suggesting that the decrease in LET with increasing proton energy was balanced by the increase in dose from the production of nuclear secondaries. Secondary particles increase slowly above energies of a few hundred megaelectronvolts. Additional studies of 50 g/cm2 aluminum shielded high-energy proton beams showed minor differences compared to the unshielded protons and lower RBE values found for shielded in comparison to unshielded beams of 2 or 2.5 GeV. All energies of protons produced a much higher percentage of complex-type chromosome exchanges when compared to acute doses of γ-rays. The implications of these results for space radiation protection and proton therapy are discussed. PMID:26539409

  3. Untangling the Effect of Head Acceleration on Brain Responses to Blast Waves.

    PubMed

    Mao, Haojie; Unnikrishnan, Ginu; Rakesh, Vineet; Reifman, Jaques

    2015-12-01

    Multiple injury-causing mechanisms, such as wave propagation, skull flexure, cavitation, and head acceleration, have been proposed to explain blast-induced traumatic brain injury (bTBI). An accurate, quantitative description of the individual contribution of each of these mechanisms may be necessary to develop preventive strategies against bTBI. However, to date, despite numerous experimental and computational studies of bTBI, this question remains elusive. In this study, using a two-dimensional (2D) rat head model, we quantified the contribution of head acceleration to the biomechanical response of brain tissues when exposed to blast waves in a shock tube. We compared brain pressure at the coup, middle, and contre-coup regions between a 2D rat head model capable of simulating all mechanisms (i.e., the all-effects model) and an acceleration-only model. From our simulations, we determined that head acceleration contributed 36-45% of the maximum brain pressure at the coup region, had a negligible effect on the pressure at the middle region, and was responsible for the low pressure at the contre-coup region. Our findings also demonstrate that the current practice of measuring rat brain pressures close to the center of the brain would record only two-thirds of the maximum pressure observed at the coup region. Therefore, to accurately capture the effects of acceleration in experiments, we recommend placing a pressure sensor near the coup region, especially when investigating the acceleration mechanism using different experimental setups. PMID:26458125

  4. Accelerated expansion through interaction

    SciTech Connect

    Zimdahl, Winfried

    2009-05-01

    Interactions between dark matter and dark energy with a given equation of state are known to modify the cosmic dynamics. On the other hand, the strength of these interactions is subject to strong observational constraints. Here we discuss a model in which the transition from decelerated to accelerated expansion of the Universe arises as a pure interaction phenomenon. Various cosmological scenarios that describe a present stage of accelerated expansion, like the {lambda}CDM model or a (generalized) Chaplygin gas, follow as special cases for different interaction rates. This unifying view on the homogeneous and isotropic background level is accompanied by a non-adiabatic perturbation dynamics which can be seen as a consequence of a fluctuating interaction rate.

  5. The Effects of Two Different Reading Acceleration Training Programs on Improving Reading Skills of Second Graders

    ERIC Educational Resources Information Center

    Nevo, Einat; Brande, Sigalit; Shaul, Shelley

    2016-01-01

    It has been well established that poor reading skills in the first grades of primary school can lead to poor reading skills in all coming years. A reading acceleration program (RAP) known to improve reading skills in adults and children with and without reading difficulties (RD) was tested for its effect on children in second grade with standard…

  6. Procedure of practical exercise with students on the pathogenic effect of accelerations on the organism

    NASA Technical Reports Server (NTRS)

    Tyrtyshnikov, I. M.; Tarasenko, L. M.

    1980-01-01

    The effects of acceleration alone and coupled with administration of either aminazine (chlorpromazine- a sedative) or caffeine (a stimulant) on the development of kinetoses in mice were studied. The problem is presented as a method to teach students and to demonstrate the role of the nervous factor in the development of kinetosis.

  7. Microbunching Instability Effect Studies and Laser Heater Optimization for the SPARX FEL Accelerator

    SciTech Connect

    Vaccarezza, C.; Chiadroni, E.; Ferrario, M.; Giannessi, L.; Quattromini, M.; Ronsivalle, C.; Venturini, C.; Migliorati, M.; Dattoli, G.

    2010-05-23

    The effects of microbunching instability for the SPARX accelerator have been analyzed by means of numerical simulations. The laser heater counteracting action has been addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.

  8. The Effects of Acceleration on High-Ability Learners: A Meta-Analysis

    ERIC Educational Resources Information Center

    Steenbergen-Hu, Saiying; Moon, Sidney M.

    2011-01-01

    Current empirical research about the effects of acceleration on high-ability learners' academic achievement and social-emotional development were synthesized using meta-analytic techniques. A total of 38 primary studies conducted between 1984 and 2008 were included. The results were broken down by developmental level (P-12 and postsecondary) and…

  9. Accelerated Reader Can Be an Effective Tool to Encourage and Bolster Student Reading

    ERIC Educational Resources Information Center

    Solley, Kathryn

    2011-01-01

    Accelerated Reader's impact on student reading achievement has been debated in educational circles for some time. The effectiveness of this tool to motivate students and build reading comprehension depends on its usage and the training provided to teachers using it. In its training seminars, Renaissance Learning stresses that AR is to be used as a…

  10. Accelerating Teacher Effectiveness: Lessons Learned from Two Decades of New Teacher Induction

    ERIC Educational Resources Information Center

    Moir, Ellen

    2009-01-01

    This article describes 10 lessons learned from two decades of new teacher induction. These include: (1) A new teacher induction program requires a systemwide commitment to teacher development; (2) Induction programs accelerate new teacher effectiveness; (3) Standards-based formative assessment tools document impact; (4) Induction programs build a…

  11. Accelerated Degree Completion Programs: The Effects of Core Professors in Nontraditional Higher Education

    ERIC Educational Resources Information Center

    Gadd, Dale Fredrick

    2012-01-01

    Nontraditional Accelerated Degree Completion Programs (ADCPs) became popular in the 1980s at many private, higher education institutions, and involved cohort groups facilitated by core or major professors. There has been little research addressing the effectiveness of a core-professor or multiple-professor approach within ADCPs, or research on how…

  12. Life in the Fast Lane: Effects of Early Grade Acceleration on High School and College Outcomes

    ERIC Educational Resources Information Center

    McClarty, Katie Larsen

    2015-01-01

    Research has repeatedly demonstrated the positive effects of acceleration for gifted and talented students. This study expands the literature by not only evaluating the impact of early grade skipping on high school and college outcomes but also examining the role of postacceleration opportunities on subsequent performance. Using a representative…

  13. Effects of Early Acceleration of Students in Mathematics on Taking Advanced Mathematics Coursework in High School

    ERIC Educational Resources Information Center

    Ma, Xin

    2010-01-01

    Based on data from the Longitudinal Study of American Youth (LSAY), students were classified into high-, middle-, and low-ability students. The effects of early acceleration in mathematics on the most advanced mathematics coursework (precalculus and calculus) in high school were examined in each category. Results showed that although early…

  14. Accelerated Reader and Its Effect on Fifth-Grade Students' Reading Comprehension

    ERIC Educational Resources Information Center

    Nichols, Jan Shelton

    2013-01-01

    Schools in the United States have been using the Accelerated Reader (AR) program since the mid-1980s. A search of the literature related to the effectiveness of the AR program revealed that many of the studies were conducted more than a decade ago, and a large number of those studies failed to utilize a control group to provide comparative data.…

  15. Effect of Body Acceleration on Pulsatile Flow of Micropolar Fluid through an Irregular Arterial Stenosis

    NASA Astrophysics Data System (ADS)

    Abdullah, Ilyani; Amin, Norsarahaida

    2008-01-01

    The present study deals with the effect of body acceleration together with surface irregularities on blood flow in artery. Prolonged exposure to high level unintended acceleration may cause serious health problems in the cardiovascular system. The situations like riding in vehicles, flying in airplanes and fast body movements during sport activities can lead to the impairment of certain physiological functions. A micropolar model of blood flow through an irregular arterial stenosis is considered. The governing equations involving unsteady nonlinear two-dimensional partial differential equations are solved employing finite difference scheme. Computational results on the velocity profiles and the flow characteristics are presented.

  16. Effects of propellant composition variables on acceleration-induced burning-rate augmentation of solid propellants

    NASA Technical Reports Server (NTRS)

    Northam, G. B.

    1972-01-01

    This work was conducted to define further the effects of propellant composition variables on the acceleration-induced burning rate augmentation of solid propellants. The rate augmentation at a given acceleration was found to be a nonlinear inverse function of the reference burning rate and not controlled by binder or catalyst type at a given reference rate. A nonaluminized propellant and a low rate double-base propellant exhibited strong transient rate augmentation due to surface pitting resulting from the retention of hot particles on the propellant surface.

  17. Degradation of entanglement between two accelerated parties: Bell states under the Unruh effect

    NASA Astrophysics Data System (ADS)

    Richter, Benedikt; Omar, Yasser

    2015-08-01

    We study the entanglement of families of Unruh modes in the Bell states | Φ±>=1 / √{2 }(|00 > ±|11 >) and | Ψ±>=1 / √{2 }(|01 > ±|10 >) shared by two accelerated observers and find fundamental differences in the robustness of entanglement against acceleration for these states. States Ψ± are entangled for all finite accelerations, whereas, due to the Unruh effect, states Φ± lose their entanglement for finite accelerations. This is true for Bell states of two bosonic modes, as well as for Bell states of a bosonic and a fermionic mode. Furthermore, there are also differences in the degradation of entanglement for Bell states of fermionic modes. We reveal the origin of these distinct characteristics of entanglement degradation and discuss the role that is played by particle statistics. Our studies suggest that the behavior of entanglement in accelerated frames strongly depends on the occupation patterns of the constituent states, whose superposition constitutes the entangled state, where especially states Φ± and Ψ± exhibit distinct characteristics regarding entanglement degradation. Finally, we point out possible implications of hovering over a black hole for these states.

  18. Effect of water load in human body systems upon tolerance to +Gz acceleration.

    PubMed

    Gembicka, D

    1989-01-01

    A possible improvement of +Gz acceleration tolerance, obtained in human subjects through administering specific volumes of water, viz. 7, 14 and 21 ml/kg body weight, to be drunk immediately before centrifuge examination in order to increase the volume of plasma, thus increasing the circulating blood volume, was the starting-point for this work. Two hundred healthy male subjects, aged 19.9 +/- 0.9, were classified in 4 main groups and 2 supplementary groups for examination. It was found that the water intake in volumes of 14 ml/kg body weight produced a significant mean increase in the acceleration tolerance of 0.8 G, and that of 21 ml/kg body weight improved acceleration tolerance by 1.1 G on the average. The increase tolerance to acceleration was maintained throughout a period of about 30 minutes (for 14 ml/kg body weight) up to approximately 50 minutes (for 21 ml/kg body weight). The favourable effect of water load in the body systems upon +Gz acceleration tolerance was probably due to the increase of plasma volume (by 5.24% and 6.98% for 14 and 21 ml/kg body weight, respectively). PMID:2485611

  19. Effect of accelerated aging on the viscoelastic properties of a medical grade silicone.

    PubMed

    Mahomed, Aziza; Hukins, David W L; Kukureka, Stephen N

    2015-01-01

    The viscoelastic properties of cylinders (diameter 5 mm, height 2.2 ± 0.2 mm) of Nagor silicone elastomer of medium hardness, were investigated before and after the specimens had undergone accelerated aging in saline solution at 70°C for 38, 76 and 114 days (to simulate aging at 37°C, for 1, 2 and 3 years, respectively). All sets of specimens were immersed in physiological saline solution at 37°C during testing and the properties were measured using dynamic mechanical analysis (DMA). A sinusoidal cyclic compression of 40 N ± 5 N was applied over a frequency range, f, of 0.02-25 Hz. Values of the storage, E', and loss, E″, moduli were found to depend on f; the dependence of E' or E″ on the logarithm (base 10) of f was represented by a second-order polynomial. After accelerated aging, the E' and E″ values did not increase significantly (p<0.05). Furthermore, scanning electron microscopy (SEM) showed that accelerated aging did not affect the surface morphology of silicone. Attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR) showed that accelerated aging had a negligible effect on the surface chemical structures of the material. Differential scanning calorimetry (DSC) showed no changes to the bulk properties of silicone, following accelerated aging.

  20. Simulation analysis for effects of bone loss on acceleration tolerance of human lumbar vertebra

    NASA Astrophysics Data System (ADS)

    Ma, Honglei; Zhang, Feng; Zhu, Yu; Xiao, Yanhua; Wazir, Abrar

    2014-02-01

    The purpose of the present study was to analyze and predict the changes in acceleration tolerance of human vertebra as a result of bone loss caused by long-term space flight. A human L3-L4 vertebra FEM model was constructed, in which the cancellous bone was separated, and surrounding ligaments were also taken into account. The simulation results demonstrated that bone loss has more of an effect on the acceleration tolerance in x-direction. The results serve to aid in the creation of new acceleration tolerance standards, ensuring astronauts return home safely after long-term space flight. This study shows that more attention should be focused on the bone degradation of crew members and to create new protective designs for space capsules in the future.

  1. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    SciTech Connect

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current, 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.

  2. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    DOE PAGES

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current,more » 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.« less

  3. Effect of the degree of hill slope on acute downhill running velocity and acceleration.

    PubMed

    Ebben, William P; Davies, Joseph A; Clewien, Rustin W

    2008-05-01

    This study analyzes the effects of hill slope on acute overspeed running. This study considers both acceleration and supramaximal velocity. Forty-four athletes ran 40-yard sprints, on 5 different hill slopes, ranging from 2.1 degrees to 6.9 degrees . Forty-yard sprint times and 10-yard split times were recorded using the Brower Timing System Speedtrap II. Analysis reveals that 40-yard and 10-yard sprints performed on hill slopes of approximately 5.8 degrees were optimal compared to flatland running and the other slopes assessed. Sprinting on a 5.8 degrees slope increased the subjects' maximal speed by 7.09% +/- 3.66% and increased the subjects' acceleration by 6.54% +/- 1.56%. Strength and conditioning professionals who train athletes for speed should develop and use overspeed hills or platforms with slopes of approximately 5.8 degrees in order to maximize acute sprinting velocity and acceleration.

  4. Effects of fore-aft body mass distribution on acceleration in dogs.

    PubMed

    Walter, Rebecca M; Carrier, David R

    2011-05-15

    The ability of a quadruped to apply propulsive ground reaction forces (GRF) during rapid acceleration may be limited by muscle power, foot traction or the ability to counteract the nose-up pitching moment due to acceleration. Because the biomechanics of acceleration change, both throughout the stride cycle and over subsequent strides as velocity increases, the factors limiting propulsive force production may also change. Depending on which factors are limiting during each step, alterations in fore-aft body mass distribution may either increase or decrease the maximum propulsive GRF produced. We analyzed the effects of experimental alterations in the fore-aft body mass distribution of dogs as they performed rapid accelerations. We measured the changes in trunk kinematics and GRF as dogs accelerated while carrying 10% body mass in saddlebags positioned just in front of the shoulder girdle or directly over the pelvic girdle. We found that dogs applied greater propulsive forces in the initial hindlimb push-off and first step by the lead forelimb in both weighted conditions. During these steps dogs appear to have been limited by foot traction. For the trailing forelimb, propulsive forces and impulses were reduced when dogs wore caudally placed weights and increased when dogs wore cranially placed weights. This is consistent with nose-up pitching or avoidance thereof having limited propulsive force production by the trailing forelimb. By the second stride, the hindlimbs appear to have been limited by muscle power in their ability to apply propulsive force. Adding weights decreased the propulsive force they applied most in the beginning of stance, when limb retractor muscles were active in supporting body weight. These results suggest that all three factors: foot traction, pitching of the body, and muscle power play roles in limiting quadrupedal acceleration. Digging in to the substrate with claws or hooves appears to be necessary for maximizing propulsion in the initial

  5. Shock acceleration of energetic particles in corotating interaction regions in the solar wind

    SciTech Connect

    Fisk, L.A.; Lee, M.A.

    1980-04-15

    A simple shock model for the acceleration of energetic particles in corotating interaction regions (CIRs) in the solar wind is presented. Particles are accelerated at the forward and reverse shocks which bound the CIR by being compressed between the shock fronts and magnetic irregularities upstream from the shocks, or by being compressed between upstream irregularities and those downstream from the shocks. Particles also suffer adiabatic deceleration in the expanding solar wind, an effect not included in previous shock models for acceleration in CIRs. The model is able to account for the observed exponential spectra at Earth, the observed behavior of the spectra with radial distance, the observed radial gradients in the intensity, and the observed differences in the intensity and spectra at the forward and reverse shocks.

  6. Accelerated simulation study of space charge effects in quadrupole ion traps using GPU techniques.

    PubMed

    Xiong, Xingchuang; Xu, Wei; Fang, Xiang; Deng, Yulin; Ouyang, Zheng

    2012-10-01

    Space charge effects play important roles in the performance of various types of mass analyzers. Simulation of space charge effects is often limited by the computation capability. In this study, we evaluate the method of using graphics processing unit (GPU) to accelerate ion trajectory simulation. Simulation using GPU has been compared with multi-core central processing unit (CPU), and an acceleration of about 390 times have been obtained using a single computer for simulation of up to 10(5) ions in quadrupole ion traps. Characteristics of trapped ions can be investigated at detailed levels within a reasonable simulation time. Space charge effects on the trapping capacities of linear and 3D ion traps, ion cloud shapes, ion motion frequency shift, mass spectrum peak coalescence effects between two ion clouds of close m/z are studied with the ion trajectory simulation using GPU.

  7. State-to-state inelastic scattering of Stark-decelerated OH radicals with Ar atoms.

    PubMed

    Scharfenberg, Ludwig; Kłos, Jacek; Dagdigian, Paul J; Alexander, Millard H; Meijer, Gerard; van de Meerakker, Sebastiaan Y T

    2010-09-28

    The Stark deceleration method exploits the concepts of charged particle accelerator physics to produce molecular beams with a tunable velocity. These tamed molecular beams offer interesting perspectives for precise crossed beam scattering studies as a function of the collision energy. The method has advanced sufficiently to compete with state-of-the-art beam methods that are used for scattering studies throughout. This is demonstrated here for the scattering of OH radicals (X(2)Pi(3/2), J = 3/2, f) with Ar atoms, a benchmark system for the scattering of open-shell molecules with atoms. Parity-resolved integral state-to-state inelastic scattering cross sections are measured at collision energies between 80 and 800 cm(-1). The threshold behavior and collision energy dependence of 13 inelastic scattering channels is accurately determined. Excellent agreement is obtained with the cross sections predicted by close-coupling scattering calculations based on the most accurate ab initio OH + Ar potential energy surfaces to date. PMID:20657906

  8. Direct spectroscopic observation of ion deceleration accompanying laser plasma-wall interaction

    NASA Astrophysics Data System (ADS)

    Renner, O.; Krouský, E.; Liska, R.; Šmíd, M.; Larroche, O.; Dalimier, E.; Rosmej, F. B.

    2010-08-01

    Interactions of plasma jets with solid surfaces are extensively studied in context with development of future fusion devices. In experiments carried out on the iodine laser system PALS, the energetic ions were produced at double-foil Al/Mg targets irradiated by one or two counter-propagating laser beams. The plasma jets from the rear surface of the laser-exploded Al foil streamed towards the Mg target representing the wall preheated by the action of the high-energy photons, particle and/or laser beams. Instead of being trapped by the cold secondary-target material, the forward-accelerated Al ions collided with the counter-propagating matter ejected from the wall. The environmental conditions in near-wall plasmas were analyzed with the high-resolution x-ray spectroscopy and temporally-resolved x-ray imaging. The deceleration of the incident Al ions in the near-wall region was directly observed and quantitatively characterized via Doppler shifts of the J-satellite from the Al Lya spectral group. The interaction scenario was modelled using the 2D arbitrary Lagrangian Eulerian hydrocode PALE and the multifluid code MULTIF.

  9. Apparent and average accelerations of the Universe

    SciTech Connect

    Bolejko, Krzysztof; Andersson, Lars E-mail: larsa@math.miami.edu

    2008-10-15

    In this paper we consider the relation between the volume deceleration parameter obtained within the Buchert averaging scheme and the deceleration parameter derived from supernova observation. This work was motivated by recent findings that showed that there are models which despite having {Lambda} = 0 have volume deceleration parameter q{sup vol}<0. This opens the possibility that back-reaction and averaging effects may be used as an interesting alternative explanation to the dark energy phenomenon. We have calculated q{sup vol} in some Lemaitre-Tolman models. For those models which are chosen to be realistic and which fit the supernova data, we find that q{sup vol}>0, while those models which we have been able to find which exhibit q{sup vol}<0 turn out to be unrealistic. This indicates that care must be exercised in relating the deceleration parameter to observations.

  10. Femtosecond laser detection of Stark-decelerated and trapped methylfluoride molecules

    NASA Astrophysics Data System (ADS)

    Meng, Congsen; van der Poel, Aernout P. P.; Cheng, Cunfeng; Bethlem, Hendrick L.

    2015-08-01

    We demonstrate deceleration and trapping of methylfluoride (CH3F ) molecules in the low-field-seeking component of the J =1 ,K =1 state using a combination of a conventional Stark decelerator and a traveling wave decelerator. The methylfluoride molecules are detected by nonresonant multiphoton ionization using a femtosecond laser. Subsequent mass and velocity selection of the produced ions enables us to eliminate most background signal resulting from thermal gas in our vacuum chamber. This detection method can be applied to virtually any molecule, thereby enhancing the scope of molecules that can be Stark decelerated. Methylfluoride is so far the heaviest and most complex molecule that has been decelerated to rest. Typically we trap 2 ×104 CH3F molecules at a peak density of 4.5 ×107 cm-3 and a temperature of 40 mK.

  11. Effectiveness of breakpoint chlorination to reduce accelerated chemical chloramine decay in severely nitrified bulk waters.

    PubMed

    Bal Krishna, K C; Sathasivan, Arumugam; Kastl, George

    2014-12-01

    Rectifying the accelerated chloramine decay after the onset of nitrification is a major challenge for water utilities that employ chloramine as a disinfectant. Recently, the evidence of soluble microbial products (SMPs) accelerating chloramine decay beyond traditionally known means was reported. After the onset of nitrification, with an intention to inactivate nitrifying bacteria and thus maintaining disinfectant residuals, breakpoint chlorination followed by re-chloramination is usually practiced by water utilities. However, what actually breakpoint chlorination does beyond known effects is not known, especially in light of the new finding of SMPs. In this study, experiments were conducted using severely nitrified chloraminated water samples (chloramine residuals <0.5 mg Cl2 L−1, nitrite residuals >0.1 mg N L−1 and an order of magnitude higher chloramine decay rate compared to normal decay) obtained from two laboratory scale systems operated by feeding natural organic matter (NOM) containing and NOM free waters. Results showed that the accelerated decay of chloramine as a result of SMPs can be eliminated by spiking higher free chlorine residuals (about 0.92 ± 0.03 to 1.16 ± 0.12 mg Cl2 L−1) than the stoichiometric requirement for breakpoint chlorination and nitrite oxidation. Further, accelerated initial chlorine decay showed chlorine preferentially reacts with nitrite and ammonia before destroying SMPs. This study, clearly demonstrated there is an additional demand from SMPs that needs to be satisfied to effectively recover disinfection residuals in subsequent re-chloramination. PMID:25461936

  12. Biological effectiveness of accelerated particles for the induction of chromosome damage: track structure effects.

    PubMed

    George, Kerry A; Hada, Megumi; Chappell, Lori; Cucinotta, Francis A

    2013-07-01

    We have investigated how radiation quality affects the induction of chromosomal aberrations in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated high charge and energy (HZE) particles including oxygen, neon, silicon, titanium and iron. Chromosome damage was assessed using three-color FISH chromosome painting in chemically induced premature chromosome condensation samples collected at first cell division after irradiation. The LET values for these particles ranged from 30 to 195 keV/μm, and their energies ranged from about 55 MeV/u to more than 1,000 MeV/u. The 89 and 142 MeV/u neon particles produced the most simple-type reciprocal exchanges per unit dose. For complex-type exchanges, 64 MeV/u neon and 450 MeV/u iron were equally effective and induced the greatest amount of complex damage. Track structure models predict that at a fixed value of LET, particles with lower charge number (Z) will have a higher biological effectiveness compared to particles with a higher Z, and that a saturation cross section will be observed for different radiation qualities. Our results are consistent with model expectations within the limitation of experimental error, and provide the most extensive data that have been reported on the radiation quality dependences of chromosomal aberrations. PMID:23692480

  13. The effect of buccal corticotomy on accelerating orthodontic tooth movement of maxillary canine

    PubMed Central

    Jahanbakhshi, Mohammad Reza; Motamedi, Ali Mohammad Kalantar; Feizbakhsh, Masoud; Mogharehabed, Ahmad

    2016-01-01

    Background: Selective alveolar corticotomy is defined as an intentional injury to cortical bone. This technique is an effective means of accelerating orthodontic tooth movement. The aim of this study is to evaluate the effect of buccal corticotomy in accelerating maxillary canine retraction. Materials and Methods: The sample in this clinical trial study consisted of 15 adult female patients with therapeutic need for extraction of maxillary first premolars and maximum canine retraction. By use of split-mouth design, at the time of premolars extraction, buccal corticotomy was performed around the maxillary first premolar, randomly on one side of maxilla, and the other side was reserved as the control side. Canine retraction was performed by use of friction – less mechanic with simple vertical loop. Every 2 weeks, distance between canines and second premolars was measured until complete space closure. The velocity of space closure was calculated to evaluate the effect of this technique in accelerating orthodontic tooth movement. The obtained data were statistically analyzed using independent t-test, and the significance was set at 0.05. Results: The rate of canine retraction was significantly higher on the corticotomy side than the control side by an average of 1.8 mm/month versus 1.1 mm/month in the corticotomy side and control side, respectively (P < 0.001). Conclusion: Based on result of this study, corticotomy can accelerates the rate of orthodontic tooth movement about two times faster than conventional orthodontics and it is significant in early stages after surgical porsedure. Therefore Buccal corticotomy is a useful adjunct technique for accelerating orthodontic tooth movement. PMID:27605986

  14. Evolution of morphology in UHMWPE following accelerated aging: the effect of heating rates.

    PubMed

    Kurtz, S M; Pruitt, L A; Crane, D J; Edidin, A A

    1999-07-01

    Accelerated aging methods are used to evaluate the oxidative stability of UHMWPE components for total joint replacements. In this study, we traced the evolution of the crystalline morphology during accelerated thermal aging of UHMWPE in air with the intent of explaining previous, counterintuitive heating rate effects. GUR4150HP extruded rod stock material was machined into miniature (0.5 mm thick) specimens that were either gamma irradiated in air or in nitrogen (27 +/- 3 kGy) or left unirradiated (control). Accelerated aging in an air furnace (at 80 degrees C, atmospheric pressure) was performed on half of the test samples at a heating rate of 0.1 degrees C/min and at 5 degrees C/min for the remaining half. Although the initial heating rate, as measured by changes in density, did influence the absolute degradation rate by up to 214%, the heating rate effect did not appear to influence the relative ranking of UHMWPE in terms of its oxidative stability. The heating rate effect is more consistent with a kinetic mechanism of the oxidation process than it is with a previously hypothesized diffusion mechanism. UHMWPE morphology, as characterized using a transmission electron microscope (TEM), demonstrated considerable rearrangement of the crystalline regions as a result of the accelerated aging. The stacking of the lamellae observed after accelerated aging was not consistent with the morphology of naturally aged UHMWPE components. The observed differences in crystalline morphology likely result from the enhanced mobility of the polymer chains due to thermal aging and may be analogous to an annealing process.

  15. The effect of buccal corticotomy on accelerating orthodontic tooth movement of maxillary canine

    PubMed Central

    Jahanbakhshi, Mohammad Reza; Motamedi, Ali Mohammad Kalantar; Feizbakhsh, Masoud; Mogharehabed, Ahmad

    2016-01-01

    Background: Selective alveolar corticotomy is defined as an intentional injury to cortical bone. This technique is an effective means of accelerating orthodontic tooth movement. The aim of this study is to evaluate the effect of buccal corticotomy in accelerating maxillary canine retraction. Materials and Methods: The sample in this clinical trial study consisted of 15 adult female patients with therapeutic need for extraction of maxillary first premolars and maximum canine retraction. By use of split-mouth design, at the time of premolars extraction, buccal corticotomy was performed around the maxillary first premolar, randomly on one side of maxilla, and the other side was reserved as the control side. Canine retraction was performed by use of friction – less mechanic with simple vertical loop. Every 2 weeks, distance between canines and second premolars was measured until complete space closure. The velocity of space closure was calculated to evaluate the effect of this technique in accelerating orthodontic tooth movement. The obtained data were statistically analyzed using independent t-test, and the significance was set at 0.05. Results: The rate of canine retraction was significantly higher on the corticotomy side than the control side by an average of 1.8 mm/month versus 1.1 mm/month in the corticotomy side and control side, respectively (P < 0.001). Conclusion: Based on result of this study, corticotomy can accelerates the rate of orthodontic tooth movement about two times faster than conventional orthodontics and it is significant in early stages after surgical porsedure. Therefore Buccal corticotomy is a useful adjunct technique for accelerating orthodontic tooth movement.

  16. The effect of flow acceleration on the cyclic variation of blood echogenicity under pulsatile flow.

    PubMed

    Huang, Chih-Chung; Liao, Chen-Chih; Lee, Po-Yang; Shih, Cho-Chiang

    2013-04-01

    It has been shown that the echogenicity of blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. In general, the echogenicity of flowing whole blood increases during the early systole phase and then reduces to a minimum at late diastole. While it has been postulated that this cyclic variation is associated with the dynamics of erythrocyte aggregation, the mechanisms underlying this increasing echogenicity with flow velocity remain uncertain. The effect of flow acceleration has also been proposed as an explanation for this phenomenon, but no specific experiments have been conducted to test this hypothesis. In addition, the influence of ultrasonic attenuation on the cyclic variation of echogenicity requires clarification. In the present study, a Couette flow system was designed to simulate blood flowing with different acceleration patterns, and the flow velocity, attenuation, and backscattering coefficient were measured synchronously from 20%- and 40%-hematocrit porcine whole blood and erythrocyte suspensions using 35-MHz ultrasound transducers. The results showed ultrasonic attenuation exerted only minor effects on the echogenicity of blood under pulsatile flow conditions. Cyclic variations of echogenicity were clearly observed for whole blood with a hematocrit of 40%, but no variations were apparent for erythrocyte suspensions. The echogenicity did not appear to be enhanced when instantaneous acceleration was applied to flowing blood in any case. These findings show that flow acceleration does not promote erythrocyte aggregation, even when a higher peak velocity is applied to the blood. Comparison of the results obtained with different accelerations revealed that the cyclic variation in echogenicity observed during pulsatile blood flow may be jointly attributable to the effect of shear rate and the distribution of erythrocyte on aggregation.

  17. EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators

    NASA Astrophysics Data System (ADS)

    Bingham, Robert

    2009-02-01

    by Chen et al where the driver, instead of being a laser, is a whistler wave known as the magnetowave plasma accelerator. The application to electron--positron plasmas that are found around pulsars is studied in the paper by Shukla, and to muon acceleration by Peano et al. Electron wakefield experiments are now concentrating on control and optimisation of high-quality beams that can be used as drivers for novel radiation sources. Studies by Thomas et al show that filamentation has a deleterious effect on the production of high quality mono-energetic electron beams and is caused by non-optimal choice of focusing geometry and/or electron density. It is crucial to match the focusing with the right plasma parameters and new types of plasma channels are being developed, such as the magnetically controlled plasma waveguide reported by Froula et al. The magnetic field provides a pressure profile shaping the channel to match the guiding conditions of the incident laser, resulting in predicted electron energies of 3GeV. In the forced laser-wakefield experiment Fang et al show that pump depletion reduces or inhibits the acceleration of electrons. One of the earlier laser acceleration concepts known as the beat wave may be revived due to the work by Kalmykov et al who report on all-optical control of nonlinear focusing of laser beams, allowing for stable propagation over several Rayleigh lengths with pre-injected electrons accelerated beyond 100 MeV. With the increasing number of petawatt lasers, attention is being focused on different acceleration regimes such as stochastic acceleration by counterpropagating laser pulses, the relativistic mirror, or the snow-plough effect leading to single-step acceleration reported by Mendonca. During wakefield acceleration the leading edge of the pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake while the trailing edge of the laser pulse undergoes frequency up-shift. This is commonly known

  18. THE DECELERATION OF NEBULAR SHELLS IN EVOLVED PLANETARY NEBULAE

    SciTech Connect

    Pereyra, Margarita; Richer, Michael G.; Lopez, Jose Alberto E-mail: richer@astrosen.unam.mx

    2013-07-10

    We have selected a group of 100 evolved planetary nebulae (PNe) and study their kinematics based upon spatially-resolved, long-slit, echelle spectroscopy. The data have been drawn from the San Pedro Martir Kinematic Catalogue of PNe. The aim is to characterize in detail the global kinematics of PNe at advanced stages of evolution with the largest sample of homogenous data used to date for this purpose. The results reveal two groups that share kinematics, morphology, and photo-ionization characteristics of the nebular shell and central star luminosities at the different late stages under study. The typical flow velocities we measure are usually larger than seen in earlier evolutionary stages, with the largest velocities occurring in objects with very weak or absent [N II] {lambda}6584 line emission, by all indications the least evolved objects in our sample. The most evolved objects expand more slowly. This apparent deceleration during the final stage of PNe evolution is predicted by hydrodynamical models, but other explanations are also possible. These results provide a template for comparison with the predictions of theoretical models.

  19. High-Speed Schlieren Movies of Decelerators at Supersonic Speeds

    NASA Technical Reports Server (NTRS)

    1960-01-01

    High-Speed Schlieren Movies of Decelerators at Supersonic Speeds. Tests were conducted on several types of porous parachutes, a paraglider, and a simulated retrorocket. Mach numbers ranged from 1.8-3.0, porosity from 20-80 percent, and camera speeds from 1680-3000 feet per second (fps) in trials with porous parachutes. Trials of reefed parachutes were conducted at Mach number 2.0 and reefing of 12-33 percent at camera speeds of 600 fps. A flexible parachute with an inflatable ring in the periphery of the canopy was tested at Reynolds number 750,000 per foot, Mach number 2.85, porosity of 28 percent, and camera speed of 36oo fps. A vortex-ring parachute was tested at Mach number 2.2 and camera speed of 3000 fps. The paraglider, with a sweepback of 45 degrees at an angle of attack of 45 degrees was tested at Mach number 2.65, drag coefficient of 0.200, and lift coefficient of 0.278 at a camera speed of 600 fps. A cold air jet exhausting upstream from the center of a bluff body was used to simulate a retrorocket. The free-stream Mach number was 2.0, free-stream dynamic pressure was 620 lb/sq ft, jet-exit static pressure ratio was 10.9, and camera speed was 600 fps. [Entire movie available on DVD from CASI as Doc ID 20070030973. Contact help@sti.nasa.gov

  20. Estimating the Collapse Pressure of an Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Baginski, Frank E.; Brakke, Kenneth A.; Cruz, Juan R.

    2013-01-01

    The collapse pressure of an inflatable membrane is the minimum differential pressure which will sustain a specific desired shape under an applied load. In this paper, we present a method for estimating the collapse pressure of a tension-cone inflatable aerodynamic decelerator (IAD) that is subject to a static aerodynamic load. The IAD surface is modeled as an elastic membrane. For a given aerodynamic load and sufficiently high torus differential pressure, the IAD assumes a stable axisymmetric equilibrium shape. When the torus pressure is reduced sufficiently, the symmetric equilibrium state becomes unstable and we define this instance to be the critical pressure Pcr. In this paper, we will compare our predicted critical torus pressure with the corresponding observed torus collapse pressure (OTCP) for fifteen tests that were conducted by the third author and his collaborators at the NASA Glenn Research Center 10x10 Supersonic Wind Tunnel in April 2008. One of the difficulties with these types of comparisons is establishing the instance of torus collapse and determining the OTCP from quantities measured during the experiment. In many cases, torus collapse is gradual and the OTCP is not well-defined. However, in eight of the fifteen wind tunnel tests where the OTCP is well-defined, we find that the average of the relative differences (Pcr - OTCP/Pcr) was 8.9%. For completeness, we will also discuss the seven tests where the observed torus collapse pressure is not well-defined.

  1. Durability of organobentonite-amended liner for decelerating chloroform transport.

    PubMed

    He, Shichong; Zhu, Lizhong

    2016-04-01

    Chloroform is added to landfill for suppressing methane generation, which however may transport through landfill liners and lead to contamination of groundwater. To decelerate chloroform transport, the enhanced sorption ability of clay liners following organobentonite addition was tested. In this study, we used batch sorption to evaluate sorption capacity of chloroform to organobentonite, followed by column tests and model simulations for assessing durability of different liners. Results show that adding 10% CTMAB-bentonite (organobentonite synthesized using cetyltrimethylammonium bromide) increased the duration of a bentonite liner by 88.5%. CTMAB-bentonite consistently showed the highest sorption capacity (Qm) among six typical organobentonites under various environmental conditions. The removal rate of chloroform by CTMAB-bentonite was 3.6-23 times higher than that by natural soils. According to the results derived by model simulation, a 70-cm 10% CTMAB-bentonite liner exhibited much better durability than a 100-cm compact clay liner (CCL) and natural bentonite liner evidenced by the delayed and lower peak of eluent concentration. A minimum thickness of 65.8 cm of the 10% CTMAB-bentonite liner could completely sorb the chloroform in a 100-m-high landfill. The 10% CTMAB-bentonite liner exhibiting much better durability has the promise for reducing environmental risk of chloroform in landfill.

  2. Extremely Energetic Outflow and Decelerated Expansion in W49N

    NASA Astrophysics Data System (ADS)

    Liu, Tie; Kim, Kee-Tae; Wu, Yuefang; Li, Di; Lee, Chang-Won; De Pree, Christopher G.; Qin, Sheng-Li; Wang, Ke; Tatematsu, Ken'ichi; Zhang, Qizhou; Mardones, Diego; Liu, Sheng-Yuan; Cho, Se-Hyung

    2015-09-01

    W49N is a mini-starburst in the Milky Way and is thus an ideal laboratory for high-mass star formation studies. Due to its large distance ({11.1}-0.7+0.9 kpc), the kinematics inside and between the dense molecular clumps in W49N are far from well-understood. The Submillimeter Array observations resolved the continuum emission into two clumps. The molecular line observation of SO2 ({28}{4,24}-{28}{3,25}) suggests that the two clumps have a velocity difference of ˜7 km s-1. The eastern clump is very close to two radio sources “G1” and “G2,” and the western clump coincides with a radio source “B.” The HCN (3-2) line reveals an extremely energetic outflow, which is among the most energetic molecular outflows in the Milky Way. This is the first report of high-velocity molecular outflow detection in W49N. The outflow jet might be in precession, which could account for the distribution, velocity, and rotation of water maser spots. Three absorption systems are identified in {{HCO}}+ (3-2) spectra. The absorption features are blueshifted with respect to the emission of SO2 ({28}{4,24}-{28}{3,25}) lines, indicating that a cold layer is expanding in front of the warm gas. Further analysis indicates that the expansion is decelerated from the geometric expansion centers.

  3. Flexible Thermal Protection System Development for Hypersonic Inflatable Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    DelCorso, Joseph A.; Bruce, Walter E., III; Hughes, Stephen J.; Dec, John A.; Rezin, Marc D.; Meador, Mary Ann B.; Guo, Haiquan; Fletcher, Douglas G.; Calomino, Anthony M.; Cheatwood, McNeil

    2012-01-01

    The Hypersonic Inflatable Aerodynamic Decelerators (HIAD) project has invested in development of multiple thermal protection system (TPS) candidates to be used in inflatable, high downmass, technology flight projects. Flexible TPS is one element of the HIAD project which is tasked with the research and development of the technology ranging from direct ground tests, modelling and simulation, characterization of TPS systems, manufacturing and handling, and standards and policy definition. The intent of flexible TPS is to enable large deployable aeroshell technologies, which increase the drag performance while significantly reducing the ballistic coefficient of high-mass entry vehicles. A HIAD requires a flexible TPS capable of surviving aerothermal loads, and durable enough to survive the rigors of construction, handling, high density packing, long duration exposure to extrinsic, in-situ environments, and deployment. This paper provides a comprehensive overview of key work being performed within the Flexible TPS element of the HIAD project. Included in this paper is an overview of, and results from, each Flexible TPS research and development activity, which includes ground testing, physics-based thermal modelling, age testing, margins policy, catalysis, materials characterization, and recent developments with new TPS materials.

  4. Fuel Cavity Asymmetry at the Onset of Deceleration in ICF

    NASA Astrophysics Data System (ADS)

    Shah, Rahul C.; Wysocki, F. J.; Glebov, V.; Hakel, P.; Joshi, T.; Kagan, G.; Mancini, R. C.; Murphy, T. J.; Stoeckl, C.; Yaakobi, B.; Benage, J. F.

    2014-10-01

    In ICF, the impact on symmetry of low mode drive non-uniformity is amplified by high convergence. Measurements have shown low mode areal density variation, however, direct impact of low modes on fuel volume has remained undemonstrated. We suggest our images provide first evidence of symmetry loss at the fuel-shell interface. The experiments use direct-drive spherical implosions (Omega). The inner 100 nm layer of the plastic shell is doped with diagnostic Ti to obtain information about interface position, temperature and density. Measurement is made at onset of deceleration at which time nuclear yield rate (NTD) and time resolved (SSCA) spectrum both are in agreement with 1-D prediction. Spectrally resolved images are obtained using the Multiple Monochromatic Imager, which combines a pinhole array with x-ray dispersive mirror and gated detector. Angle averaging of the limb-brightened image data also shows agreement with the 1D calculation. However, the 2D image shows ~20% brightness variations over modes 2-10. These modulations are discussed in context of predicted variations of interface position.

  5. Effects of Different Backpack Loads in Acceleration Transmission during Recreational Distance Walking

    PubMed Central

    Lucas-Cuevas, Angel G.; Pérez-Soriano, Pedro; Bush, Michael; Crossman, Aaron; Llana, Salvador; Cortell-Tormo, Juan M.; Pérez-Turpin, José A.

    It is well established nowadays the benefits that physical activity can have on the health of individuals. Walking is considered a fundamental method of movement and using a backpack is a common and economical manner of carrying load weight. Nevertheless, the shock wave produced by the impact forces when carrying a backpack can have detrimental effects on health status. Therefore, the aim of this study was to investigate differences in the accelerations placed on males and females whilst carrying different loads when walking. Twenty nine sports science students (16 males and 13 females) participated in the study under 3 different conditions: no weight, 10% and 20% body weight (BW) added in a backpack. Accelerometers were attached to the right shank and the centre of the forehead. Results showed that males have lower accelerations than females both in the head (2.62 ± 0.43G compared to 2.83 + 0.47G) and shank (1.37 ± 0.14G compared to 1.52 ± 0.15G; p<0.01). Accelerations for males and females were consistent throughout each backpack condition (p>0.05). The body acts as a natural shock absorber, reducing the amount of force that transmits through the body between the foot (impact point) and head. Anthropometric and body mass distribution differences between males and females may result in women receiving greater impact acceleration compared to men when the same load is carried. PMID:24146708

  6. High-energy, laser accelerator for electrons using the inverse Cherenkov effect

    SciTech Connect

    Fontana, J.R.; Pantell, R.H.

    1983-08-01

    A laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas. The laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time. Expressions are obtained relating the overall energy transfer to total laser power and wavelength, and to gas index and interaction length. With laser powers now available, energy increments of tens of GeV are possible. For comparative purposes, a related alternative scheme involving electrons in vacuum and evanescent laser fields is also analyzed. It is found that the method applies particularly well to adding energy to the electron bunches produced by large microwave accelerators, as collision effects are less troublesome at high injection energies.

  7. Parallel Computation of Intergrated Electronmagnetic, Thermal and Structural Effects for Accelerator Cavities

    SciTech Connect

    Akcelik, V.; Candel, A.; Kabel, A.; Lee, L-Q.; Li, Z.; Ng, C-K.; Xiao, L.; Ko, K.

    2008-07-02

    The successful operation of accelerator cavities has to satisfy both rf and mechanical requirements. It is highly desirable that electromagnetic, thermal and structural effects such as cavity wall heating and Lorentz force detuning in superconducting rf cavities can be addressed in an integrated analysis. Based on the SLAC parallel finite-element code infrastructure for electromagnetic modeling, a novel multi-physics analysis tool has been developed to include additional thermal and mechanical effects. The parallel computation enables virtual prototyping of accelerator cavities on computers, which would substantially reduce the cost and time of a design cycle. The multi-physics tool is applied to the LCLS rf gun for electromagnetic, thermal and structural analyses.

  8. Parallel Computation of Integrated Electromagnetic, Thermal and Structural Effects for Accelerator Cavities

    SciTech Connect

    Akcelik, V.; Candel, A.E.; Kabel, A.C.; Ko, K.; Lee, L.; Li, Z.; Ng, C.K.; Xiao, L.; /SLAC

    2011-11-02

    The successful operation of accelerator cavities has to satisfy both rf and mechanical requirements. It is highly desirable that electromagnetic, thermal and structural effects such as cavity wall heating and Lorentz force detuning in superconducting rf cavities can be addressed in an integrated analysis. Based on the SLAC parallel finite-element code infrastructure for electromagnetic modeling, a novel multi-physics analysis tool has been developed to include additional thermal and mechanical effects. The parallel computation enables virtual prototyping of accelerator cavities on computers, which would substantially reduce the cost and time of a design cycle. The multi-physics tool is applied to the LCLS rf gun for electromagnetic, thermal and structural analyses.

  9. The myths and physiology surrounding intrapartum decelerations: the critical role of the peripheral chemoreflex.

    PubMed

    Lear, Christopher A; Galinsky, Robert; Wassink, Guido; Yamaguchi, Kyohei; Davidson, Joanne O; Westgate, Jenny A; Bennet, Laura; Gunn, Alistair J

    2016-09-01

    A distinctive pattern of recurrent rapid falls in fetal heart rate, called decelerations, are commonly associated with uterine contractions during labour. These brief decelerations are mediated by vagal activation. The reflex triggering this vagal response has been variably attributed to a mechanoreceptor response to fetal head compression, to baroreflex activation following increased blood pressure during umbilical cord compression, and/or a Bezold-Jarisch reflex response to reduced venous return from the placenta. Although these complex explanations are still widespread today, there is no consistent evidence that they are common during labour. Instead, the only mechanism that has been systematically investigated, proven to be reliably active during labour and, crucially, capable of producing rapid decelerations is the peripheral chemoreflex. The peripheral chemoreflex is triggered by transient periods of asphyxia that are a normal phenomenon associated with all uterine contractions. This should not cause concern as the healthy fetus has a remarkable ability to adapt to these repeated but short periods of asphyxia. This means that the healthy fetus is typically not at risk of hypotension and injury during uncomplicated labour even during repeated brief decelerations. The physiologically incorrect theories surrounding decelerations that ignore the natural occurrence of repeated asphyxia probably gained widespread support to help explain why many babies are born healthy despite repeated decelerations during labour. We propose that a unified and physiological understanding of intrapartum decelerations that accepts the true nature of labour is critical to improve interpretation of intrapartum fetal heart rate patterns. PMID:27328617

  10. Effects of morphine and naloxone on feline colonic transit

    SciTech Connect

    Krevsky, B.; Libster, B.; Maurer, A.H.; Chase, B.J.; Fisher, R.S.

    1989-01-01

    The effects of endogenous and exogenous opioid substances on feline colonic transit were evaluated using colonic transit scintigraphy. Naloxone accelerated emptying of the cecum and ascending colon, and filling of the transverse colon. Endogenous opioid peptides thus appear to play a significant role in the regulation of colonic transit. At a moderate dose of morphine cecum and ascending colon transit was accelerated, while at a larger dose morphine had no effect. Since naloxone, a relatively nonspecific opioid antagonist, and morphine, a principally mu opioid receptor agonist, both accelerate proximal colonic transit, a decelerating role for at least one of the other opioid receptors is inferred.

  11. The effect of helmet liner density upon acceleration and local contact forces during bicycle helmet impacts

    NASA Astrophysics Data System (ADS)

    Smith, Terrance Alan

    In order to address the need to monitor local contact forces during head impacts, a custom transducer was designed to monitor local force distribution patterns on an ISO size E magnesium headform concurrently with linear acceleration measures from an accelerometer located at the center of gravity of the headform. The response characteristics of the transducer were found to be predictable and acceptable given the limitations of high speed data collection in a confined environment. During bicycle helmet testing, the output from the transducer was also found to be sensitive to ventilation openings and ventilation channels located on the underside of the helmet liner. The effect of helmet liner density upon local contact forces and headform acceleration was evaluated using an identical bicycle helmet model fabricated in four different helmet liner densities. The study found that peak headform acceleration and peak local contact sensor force values were significantly lower for the low density helmet liners when compared to the highest density of helmet liners during low to moderate energy impacts. During the high energy impact tests against the hemispherical anvil, the lower density helmets bottomed out, resulting in high local contact forces and high peak headform acceleration values relative to the higher density helmets. These results suggest that a tradeoff does exist in terms of the protection offered by low density helmets at low to moderate energy impacts compared to the performance of higher density helmets during the higher energy impacts. The study also found that a poor correlation exists between peak headform acceleration and local contact force suggesting that future head protection standards should include evaluation of the load distribution characteristics of the helmet.

  12. Acceleration Tolerance: Effect of Exercise, Acceleration Training; Bed Rest and Weightlessness Deconditioning. A Compendium of Research (1950-1996)

    NASA Technical Reports Server (NTRS)

    Chou, J. L.; McKenzie, M. A.; Stad, N. J.; Barnes, P. R.; Jackson, C. G. R.; Ghiasvand, F.; Greenleaf, J. E.

    1997-01-01

    This compendium includes abstracts and annotations of clinical observations and of more basic studies involving physiological mechanisms concerning interaction of acceleration, training and deconditioning. If the author's abstract or summary was appropriate, it was included. In other cases a more detailed annotation of the paper was prepared under the subheadings Purpose, Methods, Results, and Conclusions. Author and keyword indices are provided, plus an additional selected bibliography of related work and of those papers received after the volume was prepared for publication. This volume includes material published from 1950-1996.

  13. Early Acceleration of Mathematics Students and its Effect on Growth in Self-esteem: A Longitudinal Study

    NASA Astrophysics Data System (ADS)

    Ma, Xin

    2002-11-01

    The Longitudinal Study of American Youth (LSAY) database was employed to examine the educational practice of early acceleration of students of mathematics on the development of their self-esteem across the entire secondary grade levels. Students were classified into three different academic categories (gifted, honors, and regular). Results indicated that, in terms of the development of their self-esteem, gifted students benefited from early acceleration, honors students neither benefited nor were harmed by early acceleration, and regular students were harmed by early acceleration. Early acceleration in mathematics promoted significant growth in self-esteem among gifted male students and among gifted, honors, and regular minority students. When students were accelerated, schools showed similar average growth in self-esteem among gifted students and regular students and a large effect of general support for mathematics on the average growth in self-esteem among honors students.

  14. Flame acceleration and DDT in channels with obstacles: Effect of obstacle spacing

    SciTech Connect

    Gamezo, Vadim N.; Oran, Elaine S.; Ogawa, Takanobu

    2008-10-15

    We study flame acceleration and deflagration-to-detonation transition (DDT) in obstructed channels using 2D reactive Navier-Stokes numerical simulations. The energy release rate for the stoichiometric hydrogen-air mixture is modeled by one-step Arrhenius kinetics. Computations performed for channels with symmetrical and staggered obstacle configurations show two main effects of obstacle spacing S. First, more obstacles per unit length create more perturbations that increase the flame surface area more quickly, and therefore the flame speed grows faster. Second, DDT occurs more easily when the obstacle spacing is large enough for Mach stems to form between obstacles. These two effects are responsible for three different regimes of flame acceleration and DDT observed in simulations: (1) Detonation is ignited when a Mach stem formed by the diffracting shock reflecting from the side wall collides with an obstacle, (2) Mach stems do not form, and the detonation is not ignited, and (3) Mach stems do not form, but the leading shock becomes strong enough to ignite a detonation by direct collision with the top of an obstacle. Regime 3 is observed for small S and involves multiple isolated detonations that appear between obstacles and play a key role in final stages of flame and shock acceleration. For Regime 1 and staggered obstacle configurations, we observe resonance phenomena that significantly reduce the DDT time when S/2 is comparable to the channel width. Effects of imposed symmetry and stochasticity on DDT phenomena are also considered. (author)

  15. Effects of prolonged acceleration with or without clinostat rotation on seedlings of Arabidopsis thaliana (L.) Heynh

    NASA Technical Reports Server (NTRS)

    Brown, A. H.; Dahl, A. O.; Loercher, L.

    1974-01-01

    Three 21-day tests of the effects of chronic centrifugation were carried out on populations of Arabidopsis thaliana. In addition to 1 g the resultant g-forces tested were: 2,4,6,8,16, and 20 g. Observed end points included gross morphological characters such as size of plant organs and, at the other extreme, features of sub-cellular structure and ultrastructure. Plants were grown on banks of clinostats. The acceleration vector was directed either parallel with the plants' axes or transverse to the axes. Plant responses to chronic axial acceleration and to transverse acceleration with clinostated plants were determined. From the data obtained it was possible in some cases: (1) to determine the g-functions of specific plant developmental characters; (2) to extrapolate those functions to the hypothetical value at zero g in order to predict (tentatively) the morphology of a plant grown in space, (3) to describe morphological effects of clinostat rotation, (4) to determine which of those effects was influenced by the prevailing g-force, and (5) to put to direct test the assumption that clinostat rotation nullifies or compensates for the influence of gravity.

  16. Effects of pulse duration and areal density on ultrathin foil acceleration

    SciTech Connect

    Zhang Xiaomei; Shen Baifei; Ji Liangliang; Wang Fengchao; Wen Meng; Wang Wenpeng; Xu Jiancai; Yu Yahong

    2010-06-15

    The influence of laser pulse duration and areal density of target in the interaction of a circularly polarized pulse with an ultrathin overdense foil is investigated. One-dimensional particle-in-cell simulation shows that with an appropriate laser-pulse rising front, the light pressure acceleration regime is effective even though the thin foil is transparent. As the laser intensity evolves, three stages in the acceleration process can be identified: at first the total reflection of the laser pulse, followed by partial reflection, and then near total reflection again due to the Doppler effect. The influences of the rising front of laser pulse and areal density of the ultrathin foil are investigated. It is found that an optimal laser pulse rising front exists for obtaining high (saturation) ion energy with the same laser energy within a short time. An optimal areal density also exists for obtaining the highest energy. For the same laser pulse, a higher areal density or a higher density with same areal density is more appropriate for obtaining a stationary state for making light pressure acceleration mechanism more effective.

  17. Cosmic acceleration and Brans-Dicke theory

    SciTech Connect

    Sharif, M. Waheed, S.

    2012-10-15

    We study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this, we take the FRW universe model with a viscous fluid (without potential) and the Bianchi type-I universe model with a barotropic fluid (with and without a potential). We evaluate the deceleration parameter and the Brans-Dicke parameter to explore cosmic acceleration. It is concluded that accelerated expansion of the universe can also be achieved for higher values of the Brans-Dicke parameter in some cases.

  18. The impact of interplanetary transport on the charge spectra of heavy ions accelerated in solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Kartavykh, Y. Y.; Dröge, W.; Kovaltsov, G. A.; Ostryakov, V. M.

    2006-01-01

    The effect of interplanetary propagation on the energy dependence of the iron mean ionic charge of solar cosmic rays is investigated. The diffusion convection transport equation is solved numerically making use of a Monte-Carlo approach. The interplanetary propagation results in a shift of charge spectra towards lower energies due to adiabatic deceleration which becomes stronger as the particles’ scattering mean free path decreases. Taking the above effect into account, we compare predictions of our model of charge-consistent stochastic acceleration with recent ACE observations. A detailed analysis of two particle events shows that our model can give a consistent explanation of the observed iron charge and energy spectra, and allows to put constrains on the temperature, density, and the acceleration and escape time scales in the acceleration region.

  19. State-of-the-Art Study for High-speed Deceleration and Stabilization Devices

    NASA Technical Reports Server (NTRS)

    Alexander, W. C.; Lau, R. A.

    1966-01-01

    Documented aerodynamic deployable decelerator performance data above Mach 1. 0 is presented. The state of the art of drag and stability characteristics for reentry and recovery applications is defined for a wide range of decelerator configurations. Structural and material data and other design information also are presented. Emphasis is given to presentation of basic aero, thermal, and structural design data, which points out basic problem areas and voids in existing technology. The basic problems and voids include supersonic "buzzing" of towed porous decelerators in the wake of the forebody, the complete lack of dynamic stability data, and the general lack of aerothermal data at speeds above Mach 5.

  20. Accelerating coordination in temporal networks by engineering the link order

    NASA Astrophysics Data System (ADS)

    Masuda, Naoki

    2016-02-01

    Social dynamics on a network may be accelerated or decelerated depending on which pairs of individuals in the network communicate early and which pairs do later. The order with which the links in a given network are sequentially used, which we call the link order, may be a strong determinant of dynamical behaviour on networks, potentially adding a new dimension to effects of temporal networks relative to static networks. Here we study the effect of the link order on linear coordination (i.e., synchronisation) dynamics. We show that the coordination speed considerably depends on specific orders of links. In addition, applying each single link for a long time to ensure strong pairwise coordination before moving to a next pair of individuals does not often enhance coordination of the entire network. We also implement a simple greedy algorithm to optimise the link order in favour of fast coordination.

  1. Deceleration and electrostatic trapping of hydrogen Rydberg molecules

    NASA Astrophysics Data System (ADS)

    Hogan, Stephen

    2009-05-01

    Recent progress in the development of methods by which to decelerate and manipulate the translational motion of Rydberg atoms in the gas phase using static and time-varying inhomogeneous electric fields [1] has led to the experimental realization of Rydberg atom optics elements including a lens [2], a mirror [3] and two- and three-dimensional traps [4,5]. These experiments exploit the very large electric dipole moments associated with Rydberg Stark states, and have demonstrated the possibility to stop a seeded, pulsed, supersonic beam of atomic hydrogen traveling with an initial velocity of 700 ms-1 within 2 mm and only ˜5 μs using electric fields of a few kVcm-1. We have now extended these techniques to manipulate the translational motion of molecular hydrogen, for applications in precision spectroscopy and in studies of molecular collisions at low temperature or with a high degree of control over collision energies. The results of recent experiments in which we have been able to load hydrogen Rydberg molecules into a three-dimensional electrostatic traps will be summarized. These experiments have relied upon the preparation of nonpenetrating (l>=3) Rydberg-Stark states, with principal quantum number in the range n=20-30, using circularly polarized laser radiation. The rate of decay of these states in the trap has been determined providing, for the first time, experimental information on the predissociation of nonpenetrating molecular Rydberg states.[4pt] [1] S. R. Procter et al., Chem. Phys. Lett., 374, 667 (2003).[0pt] [2] E. Vliegen et al., Eur. Phys. J. D, 40, 73 (2006).[0pt] [3] E. Vliegen and F. Merkt, Phys. Rev. Lett., 97, 033002 (2006).[0pt] [4] E. Vliegen et al., Phys. Rev. A, 76, 023405 (2007).[0pt] [5] S. D. Hogan and F. Merkt, Phys. Rev. Lett., 100, 043001 (2008).

  2. Sediment identification using free fall penetrometer acceleration-time histories

    NASA Astrophysics Data System (ADS)

    Mulukutla, Gopal K.; Huff, Lloyd C.; Melton, Jeffrey S.; Baldwin, Kenneth C.; Mayer, Larry A.

    2011-09-01

    Knowledge of physical properties of near-surface sediments is an important requirement for many studies of the seafloor. Dynamic or Free Fall Penetrometers (FFP), instrumented with accelerometers, are widely used to assess the mechanical properties of the sediment by deriving penetration resistance from the deceleration response of the probe as it impacts and embeds the seabed. Other field investigations, a priori knowledge or a very basic description of the type of sediment (such as a description of the sediment as soft, medium or hard) derived from studying the deceleration response (accelerometer-time histories) are used for sediment identification prior to the application of an appropriate strength determination model. In many cases this information is site-specific and in others the penetration resistance is overestimated due to the dilatory effects observed in sediment with an undetected grain fraction. In this study variables affecting a dynamic penetrometer-sediment interaction system are identified. Using data from field investigations and literature we found a relationship among five variables: peak acceleration, embedment depth, total embedment time, velocity of impact and grain size. This is used to formulate a sediment identification model. The model accounts for variables that may vary widely within one deployment and it can be applied to other FFPs with different physical characteristics (such as a different mass or size). This may lead to the increased use of FFP as a deployment tool for rapid in situ characterization of the seafloor.

  3. Diaphragm opening effects on shock wave formation and acceleration in a rectangular cross section channel

    NASA Astrophysics Data System (ADS)

    Pakdaman, S. A.; Garcia, M.; Teh, E.; Lincoln, D.; Trivedi, M.; Alves, M.; Johansen, C.

    2016-03-01

    Shock wave formation and acceleration in a high-aspect ratio cross section shock tube were studied experimentally and numerically. The relative importance of geometric effects and diaphragm opening time on shock formation are assessed. The diaphragm opening time was controlled through the use of slit-type (fast opening time) and petal-type (slow opening time) diaphragms. A novel method of fabricating the petal-type diaphragms, which results in a consistent burst pressure and symmetric opening without fragmentation, is presented. High-speed schlieren photography was used to visualize the unsteady propagation of the lead shock wave and trailing gas dynamic structures. Surface-mounted pressure sensors were used to capture the spatial and temporal development of the pressure field. Unsteady Reynolds-Averaged Navier-Stokes simulation predictions using the shear-stress-transport turbulence model are compared to the experimental data. Simulation results are used to explain the presence of high-frequency pressure oscillations observed experimentally in the driver section as well as the cause of the initial acceleration and subsequent rapid decay of shock velocity measured along the top and bottom channel surfaces. A one-dimensional theoretical model predicting the effect of the finite opening time of the diaphragm on the rate of driver depressurization and shock acceleration is proposed. The model removes the large amount of empiricism that accompanies existing models published in the literature. Model accuracy is assessed through comparisons with experiments and simulations. Limitations of and potential improvements in the model are discussed.

  4. In vitro cytotoxicity of maxillofacial silicone elastomers: effect of accelerated aging.

    PubMed

    Bal, Bilge Turhan; Yilmaz, Handan; Aydin, Cemal; Karakoca, Seçil; Yilmaz, Sükran

    2009-04-01

    The purpose of this in vitro study was to evaluate the cytotoxicity of three maxillofacial silicone elastomers at 24, 48, and 72 h on L-929 cells and to determine the effect of accelerated aging on the cytotoxicity of these silicone elastomers. Disc-shaped test samples of maxillofacial silicone elastomers (Cosmesil, Episil, Multisil) were fabricated according to manufacturers' instructions under aseptic conditions. Samples were then divided into three groups: (1) not aged; (2) aged for 150 h with an accelerated weathering tester; and (3) aged for 300 h. Then the samples were placed in Dulbecco's Modified Eagle Medium/Ham's F12 (DMEM/F12) for 24, 48, and 72 h. After the incubation periods, cytotoxicity of the extracts to cultured fibroblasts (L-929) was measured by MTT assay. The degree of cytotoxicity of each sample was determined according to the reference value represented by the cells with a control (culture without sample). Statistical significance was determined by repeated measurement ANOVA (p < 0.01) followed by Duncan's test (p < 0.05). All test materials in each group demonstrated high survival rates in MTT assay (Episil; 93.84%, Multisil; 88.30%, Cosmesil; 87.50%, respectively); however, in all groups, Episil material demonstrated significantly higher cell survival rate after each of the experimental incubation periods (p < 0.05). Accelerated aging for 150 and 300 h had no significant effect on the biocompatibility of maxillofacial silicone elastomers tested (p > 0.05).

  5. Investigation of Beam Loading Effects for the Neutrino Factory Muon Accelerator

    SciTech Connect

    J. Pozimski,M. Aslaninejad,C. Bontoiu,S. Berg,Alex Bogacz

    2010-05-01

    The International design study (IDS) study showed that a Neutrino Factory [1] seems to be the most promising candidate for the next phase of high precision neutrino oscillation experiments. One part of the increased precision is due to the fact that in a Neutrino Factory the decay of muons produces a neutrino beam with narrow energy distribution and divergence. The effect of beam loading on the energy distribution of the muon beam in the Neutrino Factory decay rings has been investigated numerically. The simulations have been performed using the baseline accelerator design including cavities for different number of bunch trains and bunch train timing. A detailed analysis of the beam energy distribution expected is given together with a discussion of the energy spread produced by the gutter acceleration in the FFAG and the implications for the neutrino oscillation experiments will be presented.

  6. The effect of external magnetic field on plasma acceleration in electromagnetic railgun channel

    NASA Astrophysics Data System (ADS)

    Bobashev, S. V.; Zhukov, B. G.; Kurakin, R. O.; Ponyaev, S. A.; Reznikov, B. I.

    2016-03-01

    We have studied the effect of an external magnetic field on the dynamics of a free plasma piston (PP) accelerated without solid striker armature in an electromagnetic railgun channel filled with various gases (argon or helium). It is established that, as the applied magnetic field grows, the velocity of a shock wave generated by PP in the channel increases. The experimental results are compared to a theoretical model that takes into account the gas pressure force behind the shock wave and the drag force that arises when erosion mass entering the channel is partly entrained by the accelerated plasma. The results of model calculations are in satisfactory agreement with experimental data. The discrepancy somewhat increases with the applied field, but the maximum deviation still does not exceed 20%.

  7. Acceleration effects observed in optical data taken in Spacelab 3 FES

    NASA Technical Reports Server (NTRS)

    Trolinger, James; Lal, Ravindra; Ruff, Rudy

    1990-01-01

    Optical instrumentation in the Fluids Experiment System (FES) is briefly described. Samples of the data produced by the schlieren and holography systems during the Spacelab 3 flight are then presented with some of the holographic interferometry data being presented for the first time. Acceleration effects that can be observed in these data are discussed and the potential for using them as a basis for measurement is explored. This includes the tracking of deliberately introduced tracer particles and density gradients in the FES, the analysis of the existing concentration gradients, and a new fiber optic G-meter concept. Finally, some of the plans for acceleration measurement in the upcoming International Microgravity-1/FES are described.

  8. Focal spot motion of linear accelerators and its effect on portal image analysis.

    PubMed

    Sonke, Jan-Jakob; Brand, Bob; van Herk, Marcel

    2003-06-01

    The focal spot of a linear accelerator is often considered to have a fully stable position. In practice, however, the beam control loop of a linear accelerator needs to stabilize after the beam is turned on. As a result, some motion of the focal spot might occur during the start-up phase of irradiation. When acquiring portal images, this motion will affect the projected position of anatomy and field edges, especially when low exposures are used. In this paper, the motion of the focal spot and the effect of this motion on portal image analysis are quantified. A slightly tilted narrow slit phantom was placed at the isocenter of several linear accelerators and images were acquired (3.5 frames per second) by means of an amorphous silicon flat panel imager positioned approximately 0.7 m below the isocenter. The motion of the focal spot was determined by converting the tilted slit images to subpixel accurate line spread functions. The error in portal image analysis due to focal spot motionwas estimated by a subtraction of the relative displacement of the projected slit from the relative displacement of the field edges. It was found that the motion of the focal spot depends on the control system and design of the accelerator. The shift of the focal spot at the start of irradiation ranges between 0.05-0.7 mm in the gun-target (GT) direction. In the left-right (AB) direction the shift is generally smaller. The resulting error in portal image analysis due to focal spotmotion ranges between 0.05-1.1 mm for a dose corresponding to two monitor units (MUs). For 20 MUs, the effect of the focal spot motion reduces to 0.01-0.3 mm. The error in portal image analysis due to focal spot motion can be reduced by reducing the applied dose rate.

  9. Detection of linear ego-acceleration from optic flow.

    PubMed

    Festl, Freya; Recktenwald, Fabian; Yuan, Chunrong; Mallot, Hanspeter A

    2012-07-20

    Human observers are able to estimate various ego-motion parameters from optic flow, including rotation, translational heading, time-to-collision (TTC), time-to-passage (TTP), etc. The perception of linear ego-acceleration or deceleration, i.e., changes of translational velocity, is less well understood. While time-to-passage experiments indicate that ego-acceleration is neglected, subjects are able to keep their (perceived) speed constant under changing conditions, indicating that some sense of ego-acceleration or velocity change must be present. In this paper, we analyze the relation of ego-acceleration estimates and geometrical parameters of the environment using simulated flights through cylindrical and conic (narrowing or widening) corridors. Theoretical analysis shows that a logarithmic ego-acceleration parameter, called the acceleration rate ρ, can be calculated from retinal acceleration measurements. This parameter is independent of the geometrical layout of the scene; if veridical ego-motion is known at some instant in time, acceleration rate allows updating of ego-motion without further depth-velocity calibration. Results indicate, however, that subjects systematically confuse ego-acceleration with corridor narrowing and ego-deceleration with corridor widening, while veridically judging ego-acceleration in straight corridors. We conclude that judgments of ego-acceleration are based on first-order retinal flow and do not make use of acceleration rate or retinal acceleration.

  10. Accelerating a Mechanically Driven anti-Woodward-Hoffmann Ring Opening with a Polymer Lever Arm Effect.

    PubMed

    Wang, Junpeng; Kouznetsova, Tatiana B; Niu, Zhenbin; Rheingold, Arnold L; Craig, Stephen L

    2015-12-01

    Mechanical forces have previously been used to drive reactions along pathways that violate the orbital symmetry effects captured in the Woodward-Hoffmann rules. Here, we show that a polymer "lever arm effect" can provide a mechanical advantage in accelerating the symmetry forbidden disrotatory ring opening of benzocyclobutene (BCB). Addition of an α-E-alkene to the BCB mechanophore drops the force required to induce reactions on the ∼0.1 s time scale of single-molecule force spectroscopy experiments from 1370 to 920 pN.

  11. Paraelectric gas flow accelerator

    NASA Technical Reports Server (NTRS)

    Sherman, Daniel M. (Inventor); Wilkinson, Stephen P. (Inventor); Roth, J. Reece (Inventor)

    2001-01-01

    A substrate is configured with first and second sets of electrodes, where the second set of electrodes is positioned asymmetrically between the first set of electrodes. When a RF voltage is applied to the electrodes sufficient to generate a discharge plasma (e.g., a one-atmosphere uniform glow discharge plasma) in the gas adjacent to the substrate, the asymmetry in the electrode configuration results in force being applied to the active species in the plasma and in turn to the neutral background gas. Depending on the relative orientation of the electrodes to the gas, the present invention can be used to accelerate or decelerate the gas. The present invention has many potential applications, including increasing or decreasing aerodynamic drag or turbulence, and controlling the flow of active and/or neutral species for such uses as flow separation, altering heat flow, plasma cleaning, sterilization, deposition, etching, or alteration in wettability, printability, and/or adhesion.

  12. Relationship between Lower Limb Angular Kinematic Variables and the Effectiveness of Sprinting during the Acceleration Phase

    PubMed Central

    Konieczny, Grzegorz; Winiarski, Sławomir; Rokita, Andrzej

    2016-01-01

    The ability to reach a high running velocity over a short distance is essential to a high playing performance in team games. The aim of this study was to determine the relationship between running time over a 10-meter section of a 30-meter sprint along a straight line and changes in the angle and angular velocity that were observed in the ankle, knee, and hip joints. The possible presence may help to optimize motion efficiency during acceleration sprint phase. Eighteen girls involved in team sports were examined in the study. The Fusion Smart Speed System was employed for running time measurements. The kinematic data were recorded using the Noraxon MyoMotion system. Statistically significant relationships were found between running time over a 10-meter section and the kinematic variables of hip and ankle joints. An excessively large flexion in hip joints might have an unfavorable effect on running time during the acceleration phase. Furthermore, in order to minimize running time during the acceleration phase, stride should be maintained along a line (a straight line) rather than from side to side. It is also necessary to ensure an adequate range of motion in the hip and ankle joints with respect to the sagittal axis. PMID:27516724

  13. Effect of Driver Impedance on Dense Plasma Focus Z-Pinch Neutron Yield and Beam Acceleration

    NASA Astrophysics Data System (ADS)

    Sears, J.; Link, A.; Ellsworth, J.; Falabella, S.; Rusnak, B.; Tang, V.; Schmidt, A.; Welch, D.

    2014-10-01

    We explore the effect of driver characteristics on dense plasma focus (DPF) neutron yield and beam acceleration using particle-in-cell (PIC) simulations of a kJ-scale DPF. Our PIC simulations are fluid for the run-down phase and transition to fully kinetic for the pinch phase. The anode-cathode boundary is driven by a circuit model of the capacitive driver, including system inductance, the load of the railgap switches, the guard resistors, and the coaxial transmission line parameters. Simulations are benchmarked to measurements of a table top kJ DPF experiment with neutron yield measured with He3-based detectors. Simulated neutron yield scales approximately with the fourth power of peak current, I4. We also probe the accelerating fields by measuring the acceleration of a 4 MeV deuteron beam and by measuring the DPF self-generated beam energy distribution, finding gradients higher than 50 MV/m. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (11-ERD-063) at LLNL.

  14. The Effect of Large Scale Magnetic Turbulence on the Acceleration of Electrons by Perpendicular Collisionless Shocks

    NASA Astrophysics Data System (ADS)

    Guo, F.; Giacalone, J.

    2009-12-01

    We investigate electron acceleration at collisionless shocks propagating into an upstream plasma containing large-scale magnetic fluctuations in the direction normal to the mean field. We treat electrons as test particles, and integrate their trajectories numerically, in a time dependent electromagnetic field which is determined from a two-dimensional hybrid (kinetic ions, fluid electron) simulation. We find the large-scale magnetic fluctuations effect the electrons in a number of ways leading to efficient and rapid energization at the shock front. Since the electrons move freely along the magnetic field lines, the large scale field line meandering allows the fast-moving electrons to cross the shock front multiple times, leading to efficient acceleration. Ripples in the shock front occurring at various scales will also contribute to the acceleration by mirroring electrons back and forth between them. The downstream spectrum is broadened, with a power-law like tail at high energies up to 200-300 times of the original energy. It is also shown that the spatial distribution of energetic electrons appears to be similar to in-situ observations (e.g. Bale 1999; Simnett 2005). The study may be important in understanding observations of energetic electrons in planetary bow shocks and interplanetary shocks, and explaining herringbone structures in type II solar radio bursts.

  15. Electron Acceleration by Cascading Reconnection in the Solar Corona. I. Magnetic Gradient and Curvature Drift Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2015-12-01

    We investigate the electron acceleration by magnetic gradient and curvature drift effects in cascading magnetic reconnection of a coronal current sheet via a test particle method in the framework of the guiding center approximation. After several Alfvén transit times, most of the electrons injected at the current sheet are still trapped in the magnetic islands. A small fraction of the injected electrons precipitate into the chromosphere. The acceleration of trapped electrons is dominated by the magnetic curvature drifts, which change the parallel momentum of the electron, and appears to be more efficient than the acceleration of precipitating electrons, which is dominated by the perpendicular momentum change caused by the magnetic gradient drifts. With the resulting trapped energetic electron distribution, the corresponding hard X-ray (HXR) radiation spectra are calculated using an optically thin Bremsstrahlung model. Trapped electrons may explain flare loop top HXR emission as well as the observed bright spots along current sheets trailing coronal mass ejections. The asymmetry of precipitating electrons with respect to the polarity inversion line may contribute to the observed asymmetry of footpoint emission.

  16. ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. I. MAGNETIC GRADIENT AND CURVATURE DRIFT EFFECTS

    SciTech Connect

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2015-12-10

    We investigate the electron acceleration by magnetic gradient and curvature drift effects in cascading magnetic reconnection of a coronal current sheet via a test particle method in the framework of the guiding center approximation. After several Alfvén transit times, most of the electrons injected at the current sheet are still trapped in the magnetic islands. A small fraction of the injected electrons precipitate into the chromosphere. The acceleration of trapped electrons is dominated by the magnetic curvature drifts, which change the parallel momentum of the electron, and appears to be more efficient than the acceleration of precipitating electrons, which is dominated by the perpendicular momentum change caused by the magnetic gradient drifts. With the resulting trapped energetic electron distribution, the corresponding hard X-ray (HXR) radiation spectra are calculated using an optically thin Bremsstrahlung model. Trapped electrons may explain flare loop top HXR emission as well as the observed bright spots along current sheets trailing coronal mass ejections. The asymmetry of precipitating electrons with respect to the polarity inversion line may contribute to the observed asymmetry of footpoint emission.

  17. Relationship between Lower Limb Angular Kinematic Variables and the Effectiveness of Sprinting during the Acceleration Phase.

    PubMed

    Struzik, Artur; Konieczny, Grzegorz; Stawarz, Mateusz; Grzesik, Kamila; Winiarski, Sławomir; Rokita, Andrzej

    2016-01-01

    The ability to reach a high running velocity over a short distance is essential to a high playing performance in team games. The aim of this study was to determine the relationship between running time over a 10-meter section of a 30-meter sprint along a straight line and changes in the angle and angular velocity that were observed in the ankle, knee, and hip joints. The possible presence may help to optimize motion efficiency during acceleration sprint phase. Eighteen girls involved in team sports were examined in the study. The Fusion Smart Speed System was employed for running time measurements. The kinematic data were recorded using the Noraxon MyoMotion system. Statistically significant relationships were found between running time over a 10-meter section and the kinematic variables of hip and ankle joints. An excessively large flexion in hip joints might have an unfavorable effect on running time during the acceleration phase. Furthermore, in order to minimize running time during the acceleration phase, stride should be maintained along a line (a straight line) rather than from side to side. It is also necessary to ensure an adequate range of motion in the hip and ankle joints with respect to the sagittal axis. PMID:27516724

  18. Investigation of the effect of high +Gz accelerations on human cardiac function.

    PubMed

    Jamshidi, M; Ahmadian, M T

    2013-11-01

    This study investigates the effect of body acceleration on human cardiac function. Finite element analysis is conducted to simulate geometrical and mechanical properties of human heart. Heart geometrical modeling in three-dimension is performed by segmentation of cardiac MRI images. The nonlinear mechanical behavior of myocardium is modeled by Mooney-Rivlin, Polynomial, Ogden and Yeoh hyperelastic material models. Stress-strain curves of myocardial tissue are obtained from experimental compression tests on bovine heart samples. The experimental results are employed for the evaluation of material coefficients by the nonlinear least squares method. Among hyperelastic models, the Yeoh model presents the best fit with experimental stress-strain curve and is used for finite element simulation of heart tissue. Obtained material coefficients are implemented into the constructed heart model and nonlinear finite element analysis is performed for different levels of acceleration in upward direction of vertical axis of body during the rapid filling phase of cardiac cycle. Based on the finite element analysis, ventricular volume change, stress and deformation of heart model are evaluated. It is revealed that when the body is subjected to high accelerations, structural changes in the heart reduce blood supply to body up to 7.2% at +6G.

  19. Mitigation of ground motion effects in linear accelerators via feed-forward control

    NASA Astrophysics Data System (ADS)

    Pfingstner, J.; Artoos, K.; Charrondiere, C.; Janssens, St.; Patecki, M.; Renier, Y.; Schulte, D.; Tomás, R.; Jeremie, A.; Kubo, K.; Kuroda, S.; Naito, T.; Okugi, T.; Tauchi, T.; Terunuma, N.

    2014-12-01

    Ground motion is a severe problem for many particle accelerators, since it excites beam oscillations, which decrease the beam quality and create beam-beam offset (at colliders). Orbit feedback systems can only compensate ground motion effects at frequencies significantly smaller than the beam repetition rate. In linear colliders, where the repetition rate is low, additional counter measures have to be put in place. For this reason, a ground motion mitigation method based on feed-forward control is presented in this paper. It has several advantages compared to other techniques (stabilization systems and intratrain feedback systems) such as cost reduction and potential performance improvement. An analytical model is presented that allows the derivation of hardware specification and performance estimates for a specific accelerator and ground motion model. At the Accelerator Test Facility (ATF2), ground motion sensors have been installed to verify the feasibility of important parts of the mitigation strategy. In experimental studies, it has been shown that beam excitations due to ground motion can be predicted from ground motion measurements on a pulse-to-pulse basis. Correlations of up to 80% between the estimated and measured orbit jitter have been observed. Additionally, an orbit jitter source was identified and has been removed, which halved the orbit jitter power at ATF2 and shows that the feed-forward scheme is also very useful for the detection of installation issues. We believe that the presented mitigation method has the potential to reduce costs and improve the performance of linear colliders and potentially other linear accelerators.

  20. Numerical simulations of Hall-effect plasma accelerators on a magnetic-field-aligned mesh.

    PubMed

    Mikellides, Ioannis G; Katz, Ira

    2012-10-01

    The ionized gas in Hall-effect plasma accelerators spans a wide range of spatial and temporal scales, and exhibits diverse physics some of which remain elusive even after decades of research. Inside the acceleration channel a quasiradial applied magnetic field impedes the current of electrons perpendicular to it in favor of a significant component in the E×B direction. Ions are unmagnetized and, arguably, of wide collisional mean free paths. Collisions between the atomic species are rare. This paper reports on a computational approach that solves numerically the 2D axisymmetric vector form of Ohm's law with no assumptions regarding the resistance to classical electron transport in the parallel relative to the perpendicular direction. The numerical challenges related to the large disparity of the transport coefficients in the two directions are met by solving the equations on a computational mesh that is aligned with the applied magnetic field. This approach allows for a large physical domain that extends more than five times the thruster channel length in the axial direction and encompasses the cathode boundary where the lines of force can become nonisothermal. It also allows for the self-consistent solution of the plasma conservation laws near the anode boundary, and for simulations in accelerators with complex magnetic field topologies. Ions are treated as an isothermal, cold (relative to the electrons) fluid, accounting for the ion drag in the momentum equation due to ion-neutral (charge-exchange) and ion-ion collisions. The density of the atomic species is determined using an algorithm that eliminates the statistical noise associated with discrete-particle methods. Numerical simulations are presented that illustrate the impact of the above-mentioned features on our understanding of the plasma in these accelerators.

  1. Effects of Frequency and Motion Paradigm on Perception of Tilt and Translation During Periodic Linear Acceleration

    NASA Technical Reports Server (NTRS)

    Beaton, K. H.; Holly, J. E.; Clement, G. R.; Wood, Scott J.

    2009-01-01

    Previous studies have demonstrated an effect of frequency on the gain of tilt and translation perception. Results from different motion paradigms are often combined to extend the stimulus frequency range. For example, Off-Vertical Axis Rotation (OVAR) and Variable Radius Centrifugation (VRC) are useful to test low frequencies of linear acceleration at amplitudes that would require impractical sled lengths. The purpose of this study was to compare roll-tilt and lateral translation motion perception in 12 healthy subjects across four paradigms: OVAR, VRC, sled translation and rotation about an earth-horizontal axis. Subjects were oscillated in darkness at six frequencies from 0.01875 to 0.6 Hz (peak acceleration equivalent to 10 deg, less for sled motion below 0.15 Hz). Subjects verbally described the amplitude of perceived tilt and translation, and used a joystick to indicate the direction of motion. Consistent with previous reports, tilt perception gain decreased as a function of stimulus frequency in the motion paradigms without concordant canal tilt cues (OVAR, VRC and Sled). Translation perception gain was negligible at low stimulus frequencies and increased at higher frequencies. There were no significant differences between the phase of tilt and translation, nor did the phase significantly vary across stimulus frequency. There were differences in perception gain across the different paradigms. Paradigms that included actual tilt stimuli had the larger tilt gains, and paradigms that included actual translation stimuli had larger translation gains. In addition, the frequency at which there was a crossover of tilt and translation gains appeared to vary across motion paradigm between 0.15 and 0.3 Hz. Since the linear acceleration in the head lateral plane was equivalent across paradigms, differences in gain may be attributable to the presence of linear accelerations in orthogonal directions and/or cognitive aspects based on the expected motion paths.

  2. Numerical simulations of Hall-effect plasma accelerators on a magnetic-field-aligned mesh.

    PubMed

    Mikellides, Ioannis G; Katz, Ira

    2012-10-01

    The ionized gas in Hall-effect plasma accelerators spans a wide range of spatial and temporal scales, and exhibits diverse physics some of which remain elusive even after decades of research. Inside the acceleration channel a quasiradial applied magnetic field impedes the current of electrons perpendicular to it in favor of a significant component in the E×B direction. Ions are unmagnetized and, arguably, of wide collisional mean free paths. Collisions between the atomic species are rare. This paper reports on a computational approach that solves numerically the 2D axisymmetric vector form of Ohm's law with no assumptions regarding the resistance to classical electron transport in the parallel relative to the perpendicular direction. The numerical challenges related to the large disparity of the transport coefficients in the two directions are met by solving the equations on a computational mesh that is aligned with the applied magnetic field. This approach allows for a large physical domain that extends more than five times the thruster channel length in the axial direction and encompasses the cathode boundary where the lines of force can become nonisothermal. It also allows for the self-consistent solution of the plasma conservation laws near the anode boundary, and for simulations in accelerators with complex magnetic field topologies. Ions are treated as an isothermal, cold (relative to the electrons) fluid, accounting for the ion drag in the momentum equation due to ion-neutral (charge-exchange) and ion-ion collisions. The density of the atomic species is determined using an algorithm that eliminates the statistical noise associated with discrete-particle methods. Numerical simulations are presented that illustrate the impact of the above-mentioned features on our understanding of the plasma in these accelerators. PMID:23214706

  3. Interlaboratory study of the ion source memory effect in 36Cl accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Pavetich, Stefan; Akhmadaliev, Shavkat; Arnold, Maurice; Aumaître, Georges; Bourlès, Didier; Buchriegler, Josef; Golser, Robin; Keddadouche, Karim; Martschini, Martin; Merchel, Silke; Rugel, Georg; Steier, Peter

    2014-06-01

    Understanding and minimization of contaminations in the ion source due to cross-contamination and long-term memory effect is one of the key issues for accurate accelerator mass spectrometry (AMS) measurements of volatile elements. The focus of this work is on the investigation of the long-term memory effect for the volatile element chlorine, and the minimization of this effect in the ion source of the Dresden accelerator mass spectrometry facility (DREAMS). For this purpose, one of the two original HVE ion sources at the DREAMS facility was modified, allowing the use of larger sample holders having individual target apertures. Additionally, a more open geometry was used to improve the vacuum level. To evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison had been initiated. The long-term memory effect of the four Cs sputter ion sources at DREAMS (two sources: original and modified), ASTER (Accélérateur pour les Sciences de la Terre, Environnement, Risques) and VERA (Vienna Environmental Research Accelerator) had been investigated by measuring samples of natural 35Cl/37Cl-ratio and samples highly-enriched in 35Cl (35Cl/37Cl ∼ 999). Besides investigating and comparing the individual levels of long-term memory, recovery time constants could be calculated. The tests show that all four sources suffer from long-term memory, but the modified DREAMS ion source showed the lowest level of contamination. The recovery times of the four ion sources were widely spread between 61 and 1390 s, where the modified DREAMS ion source with values between 156 and 262 s showed the fastest recovery in 80% of the measurements.

  4. Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial.

    PubMed

    Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare

    2014-01-01

    Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies. PMID:24497947

  5. Biochar Decelerates Soil Organic Nitrogen Cycling but Stimulates Soil Nitrification in a Temperate Arable Field Trial

    PubMed Central

    Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare

    2014-01-01

    Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50–80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies. PMID:24497947

  6. The effects of resisted sprint training on acceleration performance and kinematics in soccer, rugby union, and Australian football players.

    PubMed

    Spinks, Christopher D; Murphy, Aron J; Spinks, Warwick L; Lockie, Robert G

    2007-02-01

    Acceleration is a significant feature of game-deciding situations in the various codes of football. However little is known about the acceleration characteristics of football players, the effects of acceleration training, or the effectiveness of different training modalities. This study examined the effects of resisted sprint (RS) training (weighted sled towing) on acceleration performance (0-15 m), leg power (countermovement jump [CMJ], 5-bound test [5BT], and 50-cm drop jump [50DJ]), gait (foot contact time, stride length, stride frequency, step length, and flight time), and joint (shoulder, elbow, hip, and knee) kinematics in men (N = 30) currently playing soccer, rugby union, or Australian football. Gait and kinematic measurements were derived from the first and second strides of an acceleration effort. Participants were randomly assigned to 1 of 3 treatment conditions: (a) 8-week sprint training of two 1-h sessions x wk(-1) plus RS training (RS group, n = 10), (b) 8-week nonresisted sprint training program of two 1-h sessions x wk(-1) (NRS group, n = 10), or (c) control (n = 10). The results indicated that an 8-week RS training program (a) significantly improves acceleration and leg power (CMJ and 5BT) performance but is no more effective than an 8-week NRS training program, (b) significantly improves reactive strength (50DJ), and (c) has minimal impact on gait and upper- and lower-body kinematics during acceleration performance compared to an 8-week NRS training program. These findings suggest that RS training will not adversely affect acceleration kinematics and gait. Although apparently no more effective than NRS training, this training modality provides an overload stimulus to acceleration mechanics and recruitment of the hip and knee extensors, resulting in greater application of horizontal power.

  7. Effects of Prenatal Irradiation with an Accelerated Heavy-Ion Beam on Postnatal Development in Rats

    NASA Astrophysics Data System (ADS)

    Wang, B.; Murakami, M.; Eguchi-Kasai, K.; Nojima, K.; Shang, Y.; Tanaka, K.; Fujita, K.; Coffigny, H.; Hayata, I.

    Effects on postnatal neurophysiological development in offspring were studied following exposure of pregnant Wistar rats to accelerated neon-ion beams with a LET value of about 30 keV mu m at a dose range from 0 1 Gy to 2 0Gy on the 15th day of gestation The age at which four physiologic markers appeared and five reflexes were acquired was examined prior to weaning Gain in body weight was monitored until the offspring were 3 months old Male offspring were evaluated as young adults using two behavioral tests The effects of X-rays at 200 kVp measured for the same biological end points were studied for comparison Our previous study on carbon-ion beams with a LET value of about 13 keV mu m was also cited to elucidate a possible LET-related effect For most of the endpoints at early age significant alteration was even observed in offspring prenatally received 0 1 Gy of accelerated neon ions while neither X rays nor carbon-ions under the same dose resulted in such a significant alteration compared to that from the sham-irradiated dams All offspring whose mothers received 2 0 Gy died prior to weaning Offspring from dams irradiated with accelerated neon ions generally showed higher incidences of prenatal death and preweaning mortality markedly delayed accomplishment in their physiological markers and reflexes and gain in body weight compared to those exposed to X-rays or carbon ions at doses of 0 1 to 1 5 Gy Significantly reduced ratios of main organ weight to body weight at postnatal ages of 30 60 and 90 days were also observed

  8. Transverse space charge effect calculation in the Synergia accelerator modeling toolkit

    SciTech Connect

    Okonechnikov, Konstantin; Amundson, James; Macridin, Alexandru; /Fermilab

    2009-09-01

    This paper describes a transverse space charge effect calculation algorithm, developed in the context of accelerator modeling toolkit Synergia. The introduction to the space charge problem and the Synergia modeling toolkit short description are given. The developed algorithm is explained and the implementation is described in detail. As a result of this work a new space charge solver was developed and integrated into the Synergia toolkit. The solver showed correct results in comparison to existing Synergia solvers and delivered better performance in the regime where it is applicable.

  9. Transient particle acceleration in strongly magnetized neutron stars. II - Effects due to a dipole field geometry

    NASA Technical Reports Server (NTRS)

    Fatuzzo, Marco; Melia, Fulvio

    1991-01-01

    Sheared Alfven waves generated by nonradial crustal disturbances above the polar cap of a strongly magnetized neutron star induce an electric field component parallel to B. An attempt is made to determine the manner in which the strong radial dependence of B affects the propagation of these sheared Alfven waves, and whether this MHD process is still an effective particle accelerator. It is found that although the general field equation is quite complicated, a simple wavelike solution can still be obtained under the conditions of interest for which the Alfven phase velocity decouples from the wave equation. The results may be applicable to gamma-ray burst sources.

  10. The role of boronic acids in accelerating condensation reactions of α-effect amines with carbonyls.

    PubMed

    Gillingham, Dennis

    2016-08-10

    A broad palette of bioconjugation reactions are available for chemical biologists, but an area that still requires investigation is high-rate constant reactions. These are indispensable in certain applications, particularly for in vivo labelling. Appropriately positioned boronic acids accelerate normally sluggish Schiff base condensations of α-effect nucleophiles by five orders of magnitude - providing a new entry to the rare set of reactions that have a rate constant above 100 M(-1) s(-1) under physiological conditions. I summarize here a number of recent reports, including work from my own group, and outline a mechanistic picture that explains the differing behaviour of seemingly similar substrate classes.

  11. The Effects of Ambulatory Accelerations on the Stability of a Magnetically Suspended Impeller for an Implantable Blood Pump.

    PubMed

    Paul, Gordon; Rezaienia, Mohammed Amin; Rahideh, Akbar; Munjiza, Ante; Korakianitis, Theodosios

    2016-09-01

    This article describes the effects of ambulatory accelerations on the stability of a magnetically suspended impeller for use in implantable blood pumps. A magnetic suspension system is developed to control the radial position of a magnetic impeller using coils in the pump casing. The magnitude and periodicity of ambulatory accelerations at the torso are measured. A test rig is then designed to apply appropriate accelerations to the suspension system. Accelerations from 0 to 1 g are applied to the suspended impeller with ambulatory periodicity while the radial position of the impeller and power consumption of the suspension system are monitored. The test is carried out with the impeller suspended in air, water, and a glycerol solution to simulate the viscosity of blood. A model is developed to investigate the effects of the radial magnetic suspension system and fluid damping during ambulatory accelerations. The suspension system reduces the average displacement of the impeller suspended in aqueous solutions within its casing to 100 µm with a power consumption of below 2 W during higher magnitude ambulatory accelerations (RMS magnitude 0.3 g). The damping effect of the fluid is also examined and it is shown that buoyancy, rather than drag, is the primary cause of the damping at the low displacement oscillations that occur during the application of ambulatory accelerations to such a suspension system. PMID:27401117

  12. Effects of working memory and reading acceleration training on improving working memory abilities and reading skills among third graders.

    PubMed

    Nevo, Einat; Breznitz, Zvia

    2014-01-01

    Working memory (WM) plays a crucial role in supporting learning, including reading. This study investigated the influence of reading acceleration and WM training programs on improving reading skills and WM abilities. Ninety-seven children in third grade were divided into three study groups and one control group. The three study groups each received a different combination of two training programs: only reading acceleration, WM followed by reading acceleration, and reading acceleration followed by WM. All training programs significantly improved reading skills and WM abilities. Compared with the control group, the group trained with only the reading acceleration program improved word accuracy, whereas the groups trained with a combination of reading and WM programs improved word and pseudo-word fluency. The reading-acceleration-alone group and the WM-program-followed-by-reading-acceleration group improved phonological complex memory. We conclude that a training program that combines a long reading acceleration program and a short WM program is the most effective for improving the abilities most related to scholastic achievement.

  13. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  14. Is the Universe's Acceleration Eternal?

    NASA Astrophysics Data System (ADS)

    Bean, Rachel; Magueijo, Joao; Barrow, John

    2002-12-01

    We present a new interpretation of recent observations suggesting that the expansion of the Universe has recently started to accelerate. First we introduce a cosmological model with a minimally coupled quintessence field driven by a potential motivated by M-theory. We find that late-time acceleration does not have to lead to the usual predictions of perpetual acceleration. The model allows another broad class of scenarios in which today's acceleration is a transient phenomenon which is succeeded by a return to matter domination and decelerating expansion. Quintessence scenarios provide a simple explanation for the observed acceleration of the Universe. Yet, explaining why acceleration did not start a long time ago remains a challenge. The idea that the transition from radiation to matter domination played a dynamical role in triggering acceleration has been put forward in various guises. We, secondly, propose a simple dilaton-derived quintessence model in which temporary vacuum domination is naturally triggered by the radiation to matter transition. In this model Einstein's gravity is preserved but quintessence couples non-minimally to the cold dark matter, but not to "visible" matter. Such couplings have been attributed to the dilaton in the low-energy limit of string theory beyond tree level.

  15. Radiation reaction effect on laser driven auto-resonant particle acceleration

    SciTech Connect

    Sagar, Vikram; Sengupta, Sudip; Kaw, P. K.

    2015-12-15

    The effects of radiation reaction force on laser driven auto-resonant particle acceleration scheme are studied using Landau-Lifshitz equation of motion. These studies are carried out for both linear and circularly polarized laser fields in the presence of static axial magnetic field. From the parametric study, a radiation reaction dominated region has been identified in which the particle dynamics is greatly effected by this force. In the radiation reaction dominated region, the two significant effects on particle dynamics are seen, viz., (1) saturation in energy gain by the initially resonant particle and (2) net energy gain by an initially non-resonant particle which is caused due to resonance broadening. It has been further shown that with the relaxation of resonance condition and with optimum choice of parameters, this scheme may become competitive with the other present-day laser driven particle acceleration schemes. The quantum corrections to the Landau-Lifshitz equation of motion have also been taken into account. The difference in the energy gain estimates of the particle by the quantum corrected and classical Landau-Lifshitz equation is found to be insignificant for the present day as well as upcoming laser facilities.

  16. Effect of accelerated carbonation and zero valent iron on metal leaching from bottom ash.

    PubMed

    Nilsson, M; Andreas, L; Lagerkvist, A

    2016-05-01

    . The effects of Fe(0) addition can be related to binding of the studied elements to newly formed iron oxides. The effects of Fe(0) addition were often more distinct at pH values between 7 and 9, which indicates that a single treatment with only Fe addition would be less effective and a combined treatment is recommended. The pHstat results showed that accelerated carbonation in combination with Fe(0)(0) addition widens the pH range for low solubility of about one unit for several of the studied elements. This indicates that pre-treating the bottom ash with a combination of accelerated carbonation and Fe(0) addition makes the leaching properties of the ash less sensitive to pH changes that may occur during reuse. All in all, the addition of Fe(0) in combination with carbonation could be an effective pre-treatment method for decreasing the mobility of potentially harmful components in bottom ash. PMID:26786400

  17. Effect of accelerated carbonation and zero valent iron on metal leaching from bottom ash.

    PubMed

    Nilsson, M; Andreas, L; Lagerkvist, A

    2016-05-01

    . The effects of Fe(0) addition can be related to binding of the studied elements to newly formed iron oxides. The effects of Fe(0) addition were often more distinct at pH values between 7 and 9, which indicates that a single treatment with only Fe addition would be less effective and a combined treatment is recommended. The pHstat results showed that accelerated carbonation in combination with Fe(0)(0) addition widens the pH range for low solubility of about one unit for several of the studied elements. This indicates that pre-treating the bottom ash with a combination of accelerated carbonation and Fe(0) addition makes the leaching properties of the ash less sensitive to pH changes that may occur during reuse. All in all, the addition of Fe(0) in combination with carbonation could be an effective pre-treatment method for decreasing the mobility of potentially harmful components in bottom ash.

  18. Nonlinear dynamics of autonomous vehicles with limits on acceleration

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2014-07-01

    The stability of autonomous vehicle platoons with limits on acceleration and deceleration is determined. If the leading-vehicle acceleration remains within the limits, all vehicles in the platoon remain within the limits when the relative-velocity feedback coefficient is equal to the headway time constant [k=1/h]. Furthermore, if the sensitivity α>1/h, no collisions occur. String stability for small perturbations is assumed and the initial condition is taken as the equilibrium state. Other values of k and α that give stability with no collisions are found from simulations. For vehicles with non-negligible mechanical response, simulations indicate that the acceleration-feedback-control gain might have to be dynamically adjusted to obtain optimal performance as the response time changes with engine speed. Stability is demonstrated for some perturbations that cause initial acceleration or deceleration greater than the limits, yet do not cause collisions.

  19. Analytical model of the ablative Rayleigh-Taylor instability in the deceleration phase

    SciTech Connect

    Sanz, J.; Betti, R.

    2005-04-15

    A sharp boundary model for the deceleration phase of imploding capsules in inertial confinement fusion, in both direct and indirect drive, has been developed. The model includes heat conduction, local {alpha}-particle energy deposition, and shell compressibility effects. A differential equation for the temporal evolution of the modal amplitude interface is obtained. It is found that the {alpha}-particle energy has a strong influence on the evolution of the low l modes, via the compressibility of the shell. The modes are damped by vorticity convection, fire polishing, and {alpha}-particle energy deposition. The existence of a cutoff l number arises from the high blow of velocity into the hot region (rocket effect) if density gradient scale length effects are taken into account at the interface. The differential equation for the modal amplitude is used as a postprocessor to the results of 1D-SARA code [J. J. Honrubia, J. Quant. Spectrosc. Radiat. Transfer. 49, 491 (1993)] in a typical capsule for indirect-drive ignition designed on the National Ignition Facility. It is found that modes with l>180 are completely stabilized. The results are in agreement with two-dimensional simulations.

  20. Properties of acceleration sites in active regions as derived from heavy ion charge states

    NASA Astrophysics Data System (ADS)

    Kartavykh, Y.; Dröge, W.; Klecker, B.; Möbius, E.; Popecki, M.; Mason, G.; Krucker, S.

    Charge states of heavy ions in solar energetic particle SEP events are determined by both the plasma conditions in the acceleration region and propagation effects The steep increase of the ionic charge of heavy ions as observed in all 3He- and Fe-rich SEP events suggests that stripping in a dense environment in the low corona is important in all these events The observed charge states and energy spectra of iron ions are used to infer the plasma conditions in the acceleration region by modelling the observations with a combined acceleration and propagation model that includes charge stripping acceleration coulomb losses and recombination in the corona and interplanetary propagation The interplanetary propagation includes anisotropic pitch-angle scattering on magnetic irregularities as well as magnetic focusing convection and adiabatic deceleration in the expanding solar wind To accurately derive the value of the scattering mean free path of particles the intensity profiles and anisotropy data from ACE and Wind spacecraft were used The comparison of the deduced parameters of the acceleration region with coronal density profiles shows that the acceleration of these ions takes place in closed magnetic structures in the low corona

  1. Effect of epithalon on the incidence of chromosome aberrations in senescence-accelerated mice.

    PubMed

    Rosenfeld, S V; Togo, E F; Mikheev, V S; Popovich, I G; Khavinson, V Kh; Anisimov, V N

    2002-03-01

    The incidence of chromosome aberrations in bone marrow cells of 12-month-old SAMP-1 female mice characterized by accelerated aging was 1.8 times higher than in wild-type SAMR-1 females and 2.2 times higher than in SHR females of the same age. Treatment with Epithalon (Ala-Glu-Asp-Gly) starting from the age of 2 months decreased the incidence of chromosome aberrations in SAMP-1, SAMR-1, and SHR mice by 20%, 30.1%, and 17.9%, respectively, compared to age-matched controls (p<0.05). Treatment with melatonin (given with drinking water in a dose of 20 mg/liter in night hours) had no effect on the incidence of chromosome aberrations in SHR mice. These data indicate antimutagenic effect of Epithalon, which probably underlies the geroprotective effect of this peptide. PMID:12360351

  2. Passive Thermal Control for the Low Density Supersonic Decelerator (LDSD) Test Vehicle Spin Motors Sub-System

    NASA Technical Reports Server (NTRS)

    Redmond, Matthew; Mastropietro, A. J.; Pauken, Michael; Mobley, Brandon

    2014-01-01

    Future missions to Mars will require improved entry, descent, and landing (EDL) technology over the Viking-heritage systems which recently landed the largest payload to date, the 900 kg Mars Science Laboratory. As a result, NASA's Low Density Supersonic Decelerator (LDSD) project is working to advance the state of the art in Mars EDL systems by developing and testing three key technologies which will enable heavier payloads and higher altitude landing sites on the red planet. These technologies consist of a large 33.5 m diameter Supersonic Disk Sail (SSDS) parachute and two different Supersonic Inflatable Aerodynamic Decelerator (SIAD) devices - a robotic class that inflates to a 6 m diameter torus (SIAD-R), and an exploration class that inflates to an 8 m diameter isotensoid (SIADE). All three technologies will be demonstrated on test vehicles at high earth altitudes in order to simulate the Mars EDL environment. Each vehicle will be carried to altitude by a large helium balloon, released, spun up using spin motors to stabilize the vehicle's trajectory, and accelerated to supersonic speeds using a large solid rocket motor. The vehicle will then be spun down using another set of spin motors, and will deploy either the SIAD-R or SIAD-E, followed by the SSDS parachute until the vehicle lands in the ocean. Component level testing and bounding analysis are used to ensure the survival of system components in extreme thermal environments and predict temperatures throughout the flight. This paper presents a general description of the thermal testing, model correlation, and analysis of the spin motor passive thermal control sub-system to maintain spin motor performance, prescribed vehicle trajectory, and structural integrity of the test vehicle. The spin motor subsystem is predicted to meet its requirements with margin.

  3. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Technology Development Overview

    NASA Technical Reports Server (NTRS)

    Hughes, Stephen J.; Cheatwood, F. McNeil; Calomino, Anthony M.; Wright, Henry S.

    2013-01-01

    The successful flight of the Inflatable Reentry Vehicle Experiment (IRVE)-3 has further demonstrated the potential value of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This technology development effort is funded by NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). This paper provides an overview of a multi-year HIAD technology development effort, detailing the projects completed to date and the additional testing planned for the future. The effort was divided into three areas: Flexible Systems Development (FSD), Mission Advanced Entry Concepts (AEC), and Flight Validation. FSD consists of a Flexible Thermal Protection Systems (FTPS) element, which is investigating high temperature materials, coatings, and additives for use in the bladder, insulator, and heat shield layers; and an Inflatable Structures (IS) element which includes manufacture and testing (laboratory and wind tunnel) of inflatable structures and their associated structural elements. AEC consists of the Mission Applications element developing concepts (including payload interfaces) for missions at multiple destinations for the purpose of demonstrating the benefits and need for the HIAD technology as well as the Next Generation Subsystems element. Ground test development has been pursued in parallel with the Flight Validation IRVE-3 flight test. A larger scale (6m diameter) HIAD inflatable structure was constructed and aerodynamically tested in the National Full-scale Aerodynamics Complex (NFAC) 40ft by 80ft test section along with a duplicate of the IRVE-3 3m article. Both the 6m and 3m articles were tested with instrumented aerodynamic covers which incorporated an array of pressure taps to capture surface pressure distribution to validate Computational Fluid Dynamics (CFD) model predictions of surface pressure distribution. The 3m article also had a duplicate IRVE-3 Thermal Protection System (TPS) to test in addition to testing with the

  4. No effects of lifelong creatine supplementation on sarcopenia in senescence-accelerated mice (SAMP8).

    PubMed

    Derave, Wim; Eijnde, Bert O; Ramaekers, Monique; Hespel, Peter

    2005-08-01

    Oral creatine supplementation can acutely ameliorate skeletal muscle function in older humans, but its value in the prevention of sarcopenia remains unknown. We evaluated the effects of lifelong creatine supplementation on muscle mass and morphology, contractility, and metabolic properties in a mouse model of muscle senescence. Male senescence-accelerated mice (SAMP8) were fed control or creatine-supplemented (2% of food intake) diet from the age of 10 to 60 wk. Soleus and extensor digitorum longus muscles were tested for in vitro contractile properties, creatine content, and morphology at weeks 25 and 60. Both muscle types showed reduced phosphocreatine content at week 60 that could not be prevented by creatine. Accordingly, age-associated decline in muscle mass and contractility was not influenced by treatment. Aged soleus muscles had fewer and smaller fast-twitch glycolytic fibers irrespective of treatment received. It is concluded that lifelong creatine supplementation is no effective strategy to prevent sarcopenia in senescence-accelerated mice. PMID:15727953

  5. Geometric effects on quantum transport of ultracold atoms in optical lattices: Quantum acceleration and flat band

    NASA Astrophysics Data System (ADS)

    Chien, Chih-Chun; Metcalf, Mekena; di Ventra, Massimiliano; Chern, Gia-Wei

    2015-05-01

    The realizations of interesting optical lattices for ultracold atoms provide opportunities for investigating geometric effects on many-body physics. Thesquare, triangular, honeycomb, kagome lattices, and other geometries have been experimentally demonstrated. When the atoms are driven out of equilibrium by manipulations of the density or trapping potential, their quantum transport can be monitored and fundamental questions regarding transport in isolated systems can be addressed unambiguously. We found that the propagation velocity of the matter wave representing the flowing atoms can be accelerated by tuning the lattice geometry. This acceleration is a pure quantum effect because no shorter path is created as the geometry changes. For lattice geometries supporting a dispersionless flat band, the localized atoms in the flat band do not participate in transport but interfere with the mobile atoms. We found a generic insulating phase exhibiting a density jump in the profile that can be dynamically generated. Interesting spatial patterns may emerge if those flat-band lattices are manipulated, and an analogue of geometric frustration in quantum transport will be presented.

  6. Do altered energy metabolism or spontaneous locomotion ‘mediate’ decelerated senescence?

    PubMed Central

    Arum, Oge; Dawson, John Alexander; Smith, Daniel Larry; Kopchick, John J; Allison, David B; Bartke, Andrzej

    2015-01-01

    That one or multiple measures of metabolic rate may be robustly associated with, or possibly even causative of, the progression of aging-resultant phenotypes such as lifespan is a long-standing, well-known mechanistic hypothesis. To broach this hypothesis, we assessed metabolic function and spontaneous locomotion in two genetic and one dietary mouse models for retarded aging, and subjected the data to mediation analyses to determine whether any metabolic or locomotor trait could be identified as a mediator of the effect of any of the interventions on senescence. We do not test the hypothesis of causality (which would require some experiments), but instead test whether the correlation structure of certain variables is consistent with one possible pathway model in which a proposed mediating variable has a causal role. Results for metabolic measures, including oxygen consumption and respiratory quotient, failed to support this hypothesis; similar negative results were obtained for three behavioral motion metrics. Therefore, our mediation analyses did not find support that any of these correlates of decelerated senescence was a substantial mediator of the effect of either of these genetic alterations (with or without caloric restriction) on longevity. Further studies are needed to relate the examined phenotypic characteristics to mechanisms of aging and control of longevity. PMID:25720347

  7. Accelerated carbonation of different size fractions of MSW IBA and the effect on leaching.

    PubMed

    Lin, Wenlin Yvonne; Heng, Kim Soon; Sun, Xiaolong; Wang, Jing-Yuan

    2015-07-01

    Accelerated carbonation has been studied as a treatment method for MSW IBA, and the main advantage is that it can shorten the treatment duration from months to days, compared to natural weathering. This study investigated the effect of accelerated carbonation on different size fractions of IBA collected from two incineration plants in Singapore. The different size fractions were ground to <425μm to minimise the influence of morphological difference on carbonation efficiency from that of chemical and mineralogical differences. Total element content was carried out for IBA collected from both incineration plants and the different size fractions. XRD was also used to analyse the mineralogical composition of IBA. Results showed that the degree of carbonation decreased as the size increased, which in turn corresponded to decreasing total Ca content and portlandite phase. The leaching behaviour of Pb, Zn, Cu, Cr and soluble constituents like DOC, Cl(-), and SO4(2-) were evaluated. It was found that carbonation resulted in the reduction of leaching of most constituents, except Cl(-) and SO4(2-). The reduction in leaching after carbonation can be attributed to the decrease in pH and formation of secondary minerals, rather than the precipitation of calcite. The research also suggested that since the leaching of soluble constituents from untreated IBA is mainly from the fine fractions and the fine fractions are more reactive to accelerated carbonation, size separation is beneficial in improving the carbonation efficiency and reducing the volume of IBA that needs to be treated, which can potentially reduce the treatment cost of IBA.

  8. Gamma radiation and magnetic field mediated delay in effect of accelerated ageing of soybean.

    PubMed

    Kumar, Mahesh; Singh, Bhupinder; Ahuja, Sumedha; Dahuja, Anil; Anand, Anjali

    2015-08-01

    Soybean seeds were exposed to gamma radiation (0.5, 1, 3 and 5 kGy), static magnetic field (50, 100 and 200 mT) and a combination of gamma radiation and magnetic energy (0.5 kGy + 200 mT and 5 kGy + 50 mT) and stored at room temperature for six months. These seeds were later subjected to accelerated ageing treatment at 42 °C temperature and 95-100 % relative humidity and were compared for various physical and biochemical characteristics between the untreated and the energized treatments. Energy treatment protected the quality of stored seeds in terms of its protein and oil content . Accelerated aging conditions, however, affected the oil and protein quantity and quality of seed negatively. Antioxidant enzymes exhibited a decline in their activity during aging while the LOX activity, which reflects the rate of lipid peroxidation, in general, increased during the aging. Gamma irradiated (3 and 5 kGy) and magnetic field treated seeds (100 and 200 mT) maintained a higher catalase and ascorbate peroxidase activity which may help in efficient scavenging of deleterious free radical produced during the aging. Aging caused peroxidative changes to lipids, which could be contributed to the loss of oil quality. Among the electromagnetic energy treatments, a dose of 1-5 kGy of gamma and 100 mT, 200 mT magnetic field effectively slowed the rate of biochemical degradation and loss of cellular integrity in seeds stored under conditions of accelerated aging and thus, protected the deterioration of seed quality. Energy combination treatments did not yield any additional protection advantage. PMID:26243899

  9. On the compressibility effect in test particle acceleration by magnetohydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    González, C. A.; Dmitruk, P.; Mininni, P. D.; Matthaeus, W. H.

    2016-08-01

    The effect of compressibility in a charged particle energization by magnetohydrodynamic (MHD) fields is studied in the context of test particle simulations. This problem is relevant to the solar wind and the solar corona due to the compressible nature of the flow in those astrophysical scenarios. We consider turbulent electromagnetic fields obtained from direct numerical simulations of the MHD equations with a strong background magnetic field. In order to explore the flow compressibility effect over the particle dynamics, we performed different numerical experiments: an incompressible case and two weak compressible cases with Mach number M = 0.1 and M = 0.25. We analyze the behavior of protons and electrons in those turbulent fields, which are well known to form aligned current sheets in the direction of the guide magnetic field. What we call protons and electrons are test particles with scales comparable to (for protons) and much smaller than (for electrons) the dissipative scale of MHD turbulence, maintaining the correct mass ratio m e / m i . For these test particles, we show that compressibility enhances the efficiency of proton acceleration, and that the energization is caused by perpendicular electric fields generated between currents sheets. On the other hand, electrons remain magnetized and display an almost adiabatic motion, with no effect of compressibility observed. Another set of numerical experiments takes into account two fluid modifications, namely, electric field due to Hall effect and electron pressure gradient. We show that the electron pressure has an important contribution to electron acceleration allowing highly parallel energization. In contrast, no significant effect of these additional terms is observed for the protons.

  10. Prototype rf cavity for the HISTRAP accelerator

    SciTech Connect

    Mosko, S.W.; Dowling, D.T.; Olsen, D.K.

    1989-01-01

    HISTRAP, a proposed synchrotron-cooling-storage ring designed to both accelerate and decelerate very highly charged very heavy ions for atomic physics research, requires an rf accelerating system to provide /+-/2.5 kV of peak accelerating voltage per turn while tuning through a 13.5:1 frequency range in a fraction of a second. A prototype half-wave, single gap rf cavity with biased ferrite tuning was built and tested over a continuous tuning range of 200 kHz through 2.7 MHz. Initial test results establish the feasibility of using ferrite tuning at the required rf power levels. The resonant system is located entirely outside of the accelerator's 15cm ID beam line vacuum enclosure except for a single rf window which serves as an accelerating gap. Physical separation of the cavity and the beam line permits in situ vacuum baking of the beam line at 300/degree/C.

  11. Development of a new large balloon launch technique for the low density supersonic decelerator project

    NASA Astrophysics Data System (ADS)

    Ball, Danny

    D. Ball1 and 2 E. Klein 1,2 Columbia Scientific Balloon Facility Danny.Ball@csbf.nasa.gov/Fax 903-723-8068 Erich.Klein@csbf.nasa.gov/Fax 903-723-8068 Scientific balloon flights have served for decades as a unique and cost effective platform for conducting world class space science and for developing and testing new technologies for exploration. These technologies have ranged from detector development to in situ testing of unique cutting edge space systems. The Earth’s stratosphere is an analog to Mars’s atmosphere and provides as close to an in situ environment to test a reentry system. Previous in situ tests for a Mars reentry system were a series of drop tests that were conducted from stratospheric balloon flights in 2004 to test a NASA Mars subsonic parachute entry design. In 2014 and 2015 a series of balloon flights to test a Mars prototype reentry system are planned. The JPL Mars Science Laboratory’s Low Density Supersonic Decelerator (LDSD) effort is intended to test the system by flying different new drag devices on three tests, at full scale and at supersonic speeds, high in Earth’s stratosphere, simulating entry into the atmosphere of Mars. To start the tests, the system must be first lofted to the stratosphere via a large high altitude balloon. NASA has been launching high altitude balloons to support science for many years, but with LDSD there are unique challenges with performing the test and lofting the test system to the stratosphere. The test involves launching a Star 48 Motor on a balloon to a set float altitude, orienting the payload, and then releasing the system from the balloon to start the test where the rocket motor is ignited to accelerate the test system to supersonic speeds. Safety is a significant driver in the development process for all phases of any balloon launch operation. Because a rocket motor is part of the payload to be launched, the balloon launching operations for the LDSD project have required a completely fresh look to

  12. Development of a new large balloon launch technique for the low density supersonic decelerator project

    NASA Astrophysics Data System (ADS)

    Ball, Danny

    D. Ball1 and 2 E. Klein 1,2 Columbia Scientific Balloon Facility Danny.Ball@csbf.nasa.gov/Fax 903-723-8068 Erich.Klein@csbf.nasa.gov/Fax 903-723-8068 Scientific balloon flights have served for decades as a unique and cost effective platform for conducting world class space science and for developing and testing new technologies for exploration. These technologies have ranged from detector development to in situ testing of unique cutting edge space systems. The Earth’s stratosphere is an analog to Mars’s atmosphere and provides as close to an in situ environment to test a reentry system. Previous in situ tests for a Mars reentry system were a series of drop tests that were conducted from stratospheric balloon flights in 2004 to test a NASA Mars subsonic parachute entry design. In 2014 and 2015 a series of balloon flights to test a Mars prototype reentry system are planned. The JPL Mars Science Laboratory’s Low Density Supersonic Decelerator (LDSD) effort is intended to test the system by flying different new drag devices on three tests, at full scale and at supersonic speeds, high in Earth’s stratosphere, simulating entry into the atmosphere of Mars. To start the tests, the system must be first lofted to the stratosphere via a large high altitude balloon. NASA has been launching high altitude balloons to support science for many years, but with LDSD there are unique challenges with performing the test and lofting the test system to the stratosphere. The test involves launching a Star 48 Motor on a balloon to a set float altitude, orienting the payload, and then releasing the system from the balloon to start the test where the rocket motor is ignited to accelerate the test system to supersonic speeds. Safety is a significant driver in the development process for all phases of any balloon launch operation. Because a rocket motor is part of the payload to be launched, the balloon launching operations for the LDSD project have required a completely fresh look to

  13. Workshop on Solar Activity, Solar Wind, Terrestrial Effects, and Solar Acceleration

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A summary of the proceedings from the workshop are presented. The areas covered were solar activity, solar wind, terrestrial effects, and solar acceleration. Specific topics addressed include: (1) solar cycle manifestations, both large and small scale, as well as long-term and short-term changes, including transients such as flares; (2) sources of solar wind, as identified by interplanetary observations including coronal mass ejections (CME's) or x-ray bright points, and the theory for and evolution of large-scale and small-scale structures; (3) magnetosphere responses, as observed by spacecraft, to variable solar wind and transient energetic particle emissions; and (4) origin and propagation of solar cosmic rays as related to solar activity and terrestrial effects, and solar wind coronal-hole relationships and dynamics.

  14. Effects of UV on power degradation of photovoltaic modules in combined acceleration tests

    NASA Astrophysics Data System (ADS)

    Ngo, Trang; Heta, Yushi; Doi, Takuya; Masuda, Atsushi

    2016-05-01

    UV exposure and other factors such as high/low temperature, humidity and mechanical stress have been reported to degrade photovoltaic (PV) module materials. By focusing on the combined effects of UV stress and moisture on PV modules, two new acceleration tests of light irradiation and damp heat (DH) were designed and conducted. The effects of UV exposure were validated through a change in irradiation time (UV dosage) and a change of the light irradiation side (glass side vs backsheet side) in the UV-preconditioned DH and cyclic sequential tests, respectively. The chemical corrosion of finger electrodes in the presence of acetic acid generated from ethylene vinyl acetate used as an encapsulant was considered to be the main origin of degradation. The module performance characterized by electroluminescence images was confirmed to correlate with the measured acetic acid concentration and Ag finger electrode resistance.

  15. The slingshot effect: A possible new laser-driven high energy acceleration mechanism for electrons

    SciTech Connect

    Fiore, Gaetano; Fedele, Renato; Angelis, Umberto de

    2014-11-15

    We show that under appropriate conditions the impact of a very short and intense laser pulse onto a plasma causes the expulsion of surface electrons with high energy in the direction opposite to the one of the propagations of the pulse. This is due to the combined effects of the ponderomotive force and the huge longitudinal field arising from charge separation (“slingshot effect”). The effect should also be present with other states of matter, provided the pulse is sufficiently intense to locally cause complete ionization. An experimental test seems to be feasible and, if confirmed, would provide a new extraction and acceleration mechanism for electrons, alternative to traditional radio-frequency-based or laser-wake-field ones.

  16. TURBULENT HEATING OF THE DISTANT SOLAR WIND BY INTERSTELLAR PICKUP PROTONS IN A DECELERATING FLOW

    SciTech Connect

    Isenberg, Philip A.; Smith, Charles W.; Matthaeus, William H.; Richardson, John D.

    2010-08-10

    Previous models of solar wind heating by interstellar pickup proton-driven turbulence have assumed that the wind speed is a constant in heliocentric radial position. However, the same pickup process, which is taken to provide the turbulent energy, must also decelerate the wind. In this paper, we extend our phenomenological turbulence model to include variable wind speed, and then incorporate the deceleration due to interstellar pickup protons into the model. We compare the model results with plasma and field data from Voyager 2, taking this opportunity to present an extended and improved data set of proton core temperature, magnetic field fluctuation intensity, and correlation length along the Voyager trajectory. A particular motivation for including the solar wind deceleration in this model is the expectation that a slower wind would reduce the resulting proton core temperature in the region beyond {approx}60 AU, where the previous model predictions were higher than the observed values. However, we find instead that the deceleration of the steady-state wind increases the energy input to the turbulence, causing even higher temperatures in that region. The increased heating is shown to result from the larger values of the ratio of Alfven speed to solar wind speed that develop in the decelerating wind.

  17. Getting a grip on the transverse motion in a Zeeman decelerator

    SciTech Connect

    Dulitz, Katrin; Softley, Timothy P.; Motsch, Michael; Vanhaecke, Nicolas

    2014-03-14

    Zeeman deceleration is an experimental technique in which inhomogeneous, time-dependent magnetic fields generated inside an array of solenoid coils are used to manipulate the velocity of a supersonic beam. A 12-stage Zeeman decelerator has been built and characterized using hydrogen atoms as a test system. The instrument has several original features including the possibility to replace each deceleration coil individually. In this article, we give a detailed description of the experimental setup, and illustrate its performance. We demonstrate that the overall acceptance in a Zeeman decelerator can be significantly increased with only minor changes to the setup itself. This is achieved by applying a rather low, anti-parallel magnetic field in one of the solenoid coils that forms a temporally varying quadrupole field, and improves particle confinement in the transverse direction. The results are reproduced by three-dimensional numerical particle trajectory simulations thus allowing for a rigorous analysis of the experimental data. The findings suggest the use of a modified coil configuration to improve transverse focusing during the deceleration process.

  18. Subclinical decelerations during developing hypotension in preterm fetal sheep after acute on chronic lipopolysaccharide exposure

    PubMed Central

    Lear, Christopher A.; Davidson, Joanne O.; Galinsky, Robert; Yuill, Caroline A.; Wassink, Guido; Booth, Lindsea C.; Drury, Paul P.; Bennet, Laura; Gunn, Alistair J.

    2015-01-01

    Subclinical (shallow) heart rate decelerations occur during neonatal sepsis, but there is limited information on their relationship with hypotension or whether they occur before birth. We examined whether subclinical decelerations, a fall in fetal heart rate (FHR) that remained above 100 bpm, were associated with hypotension in preterm fetal sheep exposed to lipopolysaccharide (LPS). Chronically-instrumented fetal sheep at 0.7 gestation received continuous low-dose LPS infusions (n = 15, 100 ng/kg over 24 h, followed by 250 ng/kg/24 h for 96 h) or saline (n = 8). Boluses of 1 μg LPS or saline were given at 48 and 72 h. FHR variability (FHRV) was calculated, and sample asymmetry was used to assess the severity and frequency of decelerations. Low-dose LPS infusion did not affect FHR. After the first LPS bolus, 7 fetuses remained normotensive, while 8 developed hypotension (a fall in mean arterial blood pressure of ≥5 mmHg). Developing hypotension was associated with subclinical decelerations, with a corresponding increase in sample asymmetry and FHRV (p < 0.05). The second LPS bolus was associated with similar but attenuated changes in FHR and blood pressure (p < 0.05). In conclusion, subclinical decelerations are not consistently seen during prenatal exposure to LPS, but may be a useful marker of developing inflammation-related hypotension before birth. PMID:26537688

  19. Subclinical decelerations during developing hypotension in preterm fetal sheep after acute on chronic lipopolysaccharide exposure.

    PubMed

    Lear, Christopher A; Davidson, Joanne O; Galinsky, Robert; Yuill, Caroline A; Wassink, Guido; Booth, Lindsea C; Drury, Paul P; Bennet, Laura; Gunn, Alistair J

    2015-01-01

    Subclinical (shallow) heart rate decelerations occur during neonatal sepsis, but there is limited information on their relationship with hypotension or whether they occur before birth. We examined whether subclinical decelerations, a fall in fetal heart rate (FHR) that remained above 100 bpm, were associated with hypotension in preterm fetal sheep exposed to lipopolysaccharide (LPS). Chronically-instrumented fetal sheep at 0.7 gestation received continuous low-dose LPS infusions (n = 15, 100 ng/kg over 24 h, followed by 250 ng/kg/24 h for 96 h) or saline (n = 8). Boluses of 1 μg LPS or saline were given at 48 and 72 h. FHR variability (FHRV) was calculated, and sample asymmetry was used to assess the severity and frequency of decelerations. Low-dose LPS infusion did not affect FHR. After the first LPS bolus, 7 fetuses remained normotensive, while 8 developed hypotension (a fall in mean arterial blood pressure of ≥5 mmHg). Developing hypotension was associated with subclinical decelerations, with a corresponding increase in sample asymmetry and FHRV (p < 0.05). The second LPS bolus was associated with similar but attenuated changes in FHR and blood pressure (p < 0.05). In conclusion, subclinical decelerations are not consistently seen during prenatal exposure to LPS, but may be a useful marker of developing inflammation-related hypotension before birth. PMID:26537688

  20. The effects of height and distance on the force production and acceleration in martial arts strikes.

    PubMed

    Bolander, Richard P; Neto, Osmar Pinto; Bir, Cynthia A

    2009-11-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key PointsIt has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints.A strike at head level is less effective than a strike at chest level for developing force and transferring momentum.Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact.The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique.

  1. The Effects of Height and Distance on the Force Production and Acceleration in Martial Arts Strikes

    PubMed Central

    Bolander, Richard P.; Neto, Osmar Pinto; Bir, Cynthia A.

    2009-01-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key Points It has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints. A strike at head level is less effective than a strike at chest level for developing force and transferring momentum. Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact. The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique. PMID:24474886

  2. The effects of height and distance on the force production and acceleration in martial arts strikes.

    PubMed

    Bolander, Richard P; Neto, Osmar Pinto; Bir, Cynthia A

    2009-11-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key PointsIt has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints.A strike at head level is less effective than a strike at chest level for developing force and transferring momentum.Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact.The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique. PMID:24474886

  3. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  4. Can Accelerators Accelerate Learning?

    SciTech Connect

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-10

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ)[1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  5. Backreaction and the Unruh effect: New insights from exact solutions of uniformly accelerated detectors

    SciTech Connect

    Lin, S.-Y.; Hu, B. L.

    2007-09-15

    Using nonperturbative results obtained recently for a uniformly accelerated Unruh-DeWitt detector, we discover new features in the dynamical evolution of the detector's internal degree of freedom, and identified the Unruh effect derived originally from time-dependent perturbation theory as operative in the ultraweak coupling and ultrahigh acceleration limits. The mutual interaction between the detector and the field engenders entanglement between them, and tracing out the field leads to a mixed state of the detector even for a detector at rest in Minkowski vacuum. Our findings based on this exact solution show clearly the differences from the ordinary result where the quantum field's backreaction is ignored in that the detector no longer behaves like a perfect thermometer. From a calculation of the evolution of the reduced density matrix of the detector, we find that the transition probability from the initial ground state over an infinitely long duration of interaction derived from time-dependent perturbation theory is existent in the exact solution only in transient under special limiting conditions corresponding to the Markovian regime. Furthermore, the detector at late times never sees an exact Boltzmann distribution over the energy eigenstates of the free detector, thus in the non-Markovian regime covering a wider range of parameters the Unruh temperature cannot be identified inside the detector.

  6. A new look at liming as an approach to accelerate recovery from acidic deposition effects.

    PubMed

    Lawrence, Gregory B; Burns, Douglas A; Riva-Murray, Karen

    2016-08-15

    Acidic deposition caused by fossil fuel combustion has degraded aquatic and terrestrial ecosystems in North America for over four decades. The only management option other than emissions reductions for combating the effects of acidic deposition has been the application of lime to neutralize acidity after it has been deposited on the landscape. For this reason, liming has been a part of acid rain science from the beginning. However, continued declines in acidic deposition have led to partial recovery of surface water chemistry, and the start of soil recovery. Liming is therefore no longer needed to prevent further damage, so the question becomes whether liming would be useful for accelerating recovery of systems where improvement has lagged. As more is learned about recovering ecosystems, it has become clear that recovery rates vary with watershed characteristics and among ecosystem components. Lakes appear to show the strongest recovery, but recovery in streams is sluggish and recovery of soils appears to be in the early stages. The method in which lime is applied is therefore critical in achieving the goal of accelerated recovery. Application of lime to a watershed provides the advantage of increasing Ca availability and reducing or preventing mobilization of toxic Al, an outcome that is beneficial to both terrestrial and aquatic ecosystems. However, the goal should not be complete neutralization of soil acidity, which is naturally produced. Liming of naturally acidic areas such as wetlands should also be avoided to prevent damage to indigenous species that rely on an acidic environment. PMID:27092419

  7. A new look at liming as an approach to accelerate recovery from acidic deposition effects

    USGS Publications Warehouse

    Lawrence, Gregory B.; Burns, Douglas A.; Murray, Karen

    2016-01-01

    Acidic deposition caused by fossil fuel combustion has degraded aquatic and terrestrial ecosystems in North America for over four decades. The only management option other than emissions reductions for combating the effects of acidic deposition has been the application of lime to neutralize acidity after it has been deposited on the landscape. For this reason, liming has been a part of acid rain science from the beginning. However, continued declines in acidic deposition have led to partial recovery of surface water chemistry, and the start of soil recovery. Liming is therefore no longer needed to prevent further damage, so the question becomes whether liming would be useful for accelerating recovery of systems where improvement has lagged. As more is learned about recovering ecosystems, it has become clear that recovery rates vary with watershed characteristics and among ecosystem components. Lakes appear to show the strongest recovery, but recovery in streams is sluggish and recovery of soils appears to be in the early stages. The method in which lime is applied is therefore critical in achieving the goal of accelerated recovery. Application of lime to a watershed provides the advantage of increasing Ca availability and reducing or preventing mobilization of toxic Al, an outcome that is beneficial to both terrestrial and aquatic ecosystems. However, the goal should not be complete neutralization of soil acidity, which is naturally produced. Liming of naturally acidic areas such as wetlands should also be avoided to prevent damage to indigenous species that rely on an acidic environment.

  8. Effect of prolonged bedrest and plus Gz acceleration on peripheral visual response time

    NASA Technical Reports Server (NTRS)

    Haines, R. F.

    1973-01-01

    Peripheral visual response time changes during +G sub z acceleration following fourteen days of bedrest are considered as well as what effect prolonged bedrest has upon this response. Eighteen test lights, placed 10 deg are apart along the horizontal meridian of the subject's field of view, were presented in a random sequence. The subject was instructed to press a button as soon as a light appeared. Response time testing occurred periodically during bedrest and continuously during centrifugation testing. The results indicate that: (1) mean response time is significantly longer to stimuli imaged in the far periphery than to stimuli imaged closer to the line of sight; (2) mean response time at each stimulus position tends to be longer at plateau g than during the preacceleration baseline period; (3) mean response time tends to lengthen as the g level is increased; (4) peripheral visual response time during +G sub x acceleration at 2, 3.2, and 3.8 g was not a reliable advanced indicator that blackout was going to occur; and (5) the subject's field of view collapsed rapidly just before blackout. Bedrest data showed that the distribution of response times to stimuli imaged across the subject's horizontal retinal meridian remained remarkably constant from day to day during both the bedrest and recovery periods.

  9. A new look at liming as an approach to accelerate recovery from acidic deposition effects.

    PubMed

    Lawrence, Gregory B; Burns, Douglas A; Riva-Murray, Karen

    2016-08-15

    Acidic deposition caused by fossil fuel combustion has degraded aquatic and terrestrial ecosystems in North America for over four decades. The only management option other than emissions reductions for combating the effects of acidic deposition has been the application of lime to neutralize acidity after it has been deposited on the landscape. For this reason, liming has been a part of acid rain science from the beginning. However, continued declines in acidic deposition have led to partial recovery of surface water chemistry, and the start of soil recovery. Liming is therefore no longer needed to prevent further damage, so the question becomes whether liming would be useful for accelerating recovery of systems where improvement has lagged. As more is learned about recovering ecosystems, it has become clear that recovery rates vary with watershed characteristics and among ecosystem components. Lakes appear to show the strongest recovery, but recovery in streams is sluggish and recovery of soils appears to be in the early stages. The method in which lime is applied is therefore critical in achieving the goal of accelerated recovery. Application of lime to a watershed provides the advantage of increasing Ca availability and reducing or preventing mobilization of toxic Al, an outcome that is beneficial to both terrestrial and aquatic ecosystems. However, the goal should not be complete neutralization of soil acidity, which is naturally produced. Liming of naturally acidic areas such as wetlands should also be avoided to prevent damage to indigenous species that rely on an acidic environment.

  10. Effects of different polishing methods on color stability of resin composites after accelerated aging.

    PubMed

    Sirin Karaarslan, Emine; Bulbul, Mehmet; Yildiz, Esma; Secilmis, Asli; Sari, Fatih; Usumez, Aslihan

    2013-01-01

    The purpose of this study was to evaluate the effect of polishing procedures on the color stability of different types of composites after aging. Forty disk-shaped specimens (Ø10×2 mm) were prepared for each composite resin type (an ormocer, a packable, a nanohybrid, and a microhybrid) for a total of 160 specimens. Each composite group was divided into four subgroups according to polishing method (n=10): control (no finishing and polishing), polishing disk, polishing wheel, and glaze material. Color parameters (L*, a*, and b*) and surface roughness were measured before and after accelerated aging. Of the polishing methods, glazed specimens showed the lowest color change (∆E*), ∆L*, and ∆b* values (p<0.05). Of the composite resins, the microhybrid composite showed the lowest ∆E* value, whereas the ormocer showed the highest (p<0.05). For all composite types, the surface roughness of their control groups decreased after aging (p<0.05). In conclusion, all composite resins showed color changes after accelerated aging, with the use of glaze material resulting in the lowest color change.

  11. Accelerating oscillatory fronts in a nonlinear sonic vacuum with strong nonlocal effects.

    PubMed

    Gendelman, O V; Zolotarevskiy, V; Savin, A V; Bergman, L A; Vakakis, A F

    2016-03-01

    We describe and explore accelerating oscillatory fronts in sonic vacua with nonlocal interactions. As an example, a chain of particles oscillating in the plane and coupled by linear springs, with fixed ends, is considered. When one end of this system is harmonically excited in the transverse direction, one observes accelerated propagation of the excitation front, accompanied by an almost monochromatic oscillatory tail. Position of the front obeys the scaling law l(t) ∼ t(4/3). The frequency of the oscillatory tail remains constant, and the wavelength scales as λ ∼ t(1/3). These scaling laws result from the nonlocal effects; we derive them analytically (including the scaling coefficients) from a continuum approximation. Moreover, a certain threshold excitation amplitude is required in order to initiate the front propagation. The initiation threshold is evaluated on the basis of a simplified discrete model, further reduced to a completely integrable nonlinear system. Given their simplicity, nonlinear sonic vacua of the type considered herein should be common in periodic lattices. PMID:27078353

  12. The Interaction of Motor Performance and Psycho-Physiological Effects During Acceleration to Hypergravity

    NASA Astrophysics Data System (ADS)

    Guardiera, Simon; Schneider, Stefan

    2008-06-01

    Several studies reported that human motor performance is impaired during acceleration to hypergravity. While physiological explanations (e.g. vestibular activity) are widely discussed, psycho-physiological reasons (e.g. stress) are less considered. The present study therefore evaluates the interaction between psycho-physiological effects and motor performance in hypergravity. Eleven subjects performed a manual tracking task. Additionally, stress hormone concentration, EEG and subjective mood were evaluated. All measurements were performed in normal (+1Gz), and in (or directly after) three times gravitational acceleration (+3Gz). Motor performance decreased, while all determined stress hormone concentrations increased in +3Gz. EEG analysis revealed an increase of brain cortical activity in right frontal lobe in +3Gz. Subjective mood decreased due to +3Gz. Our data confirm, that motor performance is decreased in hypergravity, whereas an increase in psychophysiological stress markers could be obtained. We conclude that psycho-physiological changes have to be regarded as a possible explanation for deficits in motor performance in hypergravity.

  13. Three-grid accelerator system for an ion propulsion engine

    NASA Technical Reports Server (NTRS)

    Brophy, John R. (Inventor)

    1994-01-01

    An apparatus is presented for an ion engine comprising a three-grid accelerator system with the decelerator grid biased negative of the beam plasma. This arrangement substantially reduces the charge-exchange ion current reaching the accelerator grid at high tank pressures, which minimizes erosion of the accelerator grid due to charge exchange ion sputtering, known to be the major accelerator grid wear mechanism. An improved method for life testing ion engines is also provided using the disclosed apparatus. In addition, the invention can also be applied in materials processing.

  14. Resonant ion acceleration by plasma jets: Effects of jet breaking and the magnetic-field curvature.

    PubMed

    Artemyev, A V; Vasiliev, A A

    2015-05-01

    In this paper we consider resonant ion acceleration by a plasma jet originating from the magnetic reconnection region. Such jets propagate in the background magnetic field with significantly curved magnetic-field lines. Decoupling of ion and electron motions at the leading edge of the jet results in generation of strong electrostatic fields. Ions can be trapped by this field and get accelerated along the jet front. This mechanism of resonant acceleration resembles surfing acceleration of charged particles at a shock wave. To describe resonant acceleration of ions, we use adiabatic theory of resonant phenomena. We show that particle motion along the curved field lines significantly influences the acceleration rate. The maximum gain of energy is determined by the particle's escape from the system due to this motion. Applications of the proposed mechanism to charged-particle acceleration in the planetary magnetospheres and the solar corona are discussed. PMID:26066269

  15. Flight Dynamics of an Aeroshell Using an Attached Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.; Schoenenberger, Mark; Axdahl, Erik; Wilhite, Alan

    2009-01-01

    An aeroelastic analysis of the behavior of an entry vehicle utilizing an attached inflatable aerodynamic decelerator during supersonic flight is presented. The analysis consists of a planar, four degree of freedom simulation. The aeroshell and the IAD are assumed to be separate, rigid bodies connected with a spring-damper at an interface point constraining the relative motion of the two bodies. Aerodynamic forces and moments are modeled using modified Newtonian aerodynamics. The analysis includes the contribution of static aerodynamic forces and moments as well as pitch damping. Two cases are considered in the analysis: constant velocity flight and planar free flight. For the constant velocity and free flight cases with neutral pitch damping, configurations with highly-stiff interfaces exhibit statically stable but dynamically unstable aeroshell angle of attack. Moderately stiff interfaces exhibit static and dynamic stability of aeroshell angle of attack due to damping induced by the pitch angle rate lag between the aeroshell and IAD. For the free-flight case, low values of both the interface stiffness and damping cause divergence of the aeroshell angle of attack due to the offset of the IAD drag force with respect to the aeroshell center of mass. The presence of dynamic aerodynamic moments was found to influence the stability characteristics of the vehicle. The effect of gravity on the aeroshell angle of attack stability characteristics was determined to be negligible for the cases investigated.

  16. Aerodynamic Interactions of Propulsive Deceleration and Reaction Control System Jets on Mars-Entry Aeroshells

    NASA Astrophysics Data System (ADS)

    Alkandry, Hicham

    Future missions to Mars, including sample-return and human-exploration missions, may require alternative entry, descent, and landing technologies in order to perform pinpoint landing of heavy vehicles. Two such alternatives are propulsive deceleration (PD) and reaction control systems (RCS). PD can slow the vehicle during Mars atmospheric descent by directing thrusters into the incoming freestream. RCS can provide vehicle control and steering by inducing moments using thrusters on the hack of the entry capsule. The use of these PD and RCS jets, however, involves complex flow interactions that are still not well understood. The fluid interactions induced by PD and RCS jets for Mars-entry vehicles in hypersonic freestream conditions are investigated using computational fluid dynamics (CFD). The effects of central and peripheral PD configurations using both sonic and supersonic jets at various thrust conditions are examined in this dissertation. The RCS jet is directed either parallel or transverse to the freestream flow at different thrust conditions in order to examine the effects of the thruster orientation with respect to the center of gravity of the aeroshell. The physical accuracy of the computational method is also assessed by comparing the numerical results with available experimental data. The central PD configuration decreases the drag force acting on the entry capsule due to a shielding effect that prevents mass and momentum in the hypersonic freestream from reaching the aeroshell. The peripheral PD configuration also decreases the drag force by obstructing the flow around the aeroshell and creating low surface pressure regions downstream of the PD nozzles. The Mach number of the PD jets, however, does not have a significant effect on the induced fluid interactions. The reaction control system also alters the flowfield, surface, and aerodynamic properties of the aeroshell, while the jet orientation can have a significant effect on the control effectiveness

  17. Improving rate capability and decelerating voltage decay of Li-rich layered oxide cathodes via selenium doping to stabilize oxygen

    NASA Astrophysics Data System (ADS)

    Ma, Quanxin; Li, Ruhong; Zheng, Rujuan; Liu, Yuanlong; Huo, Hua; Dai, Changsong

    2016-11-01

    To improve the rate performance and decelerate the voltage decay of Li-rich layered oxide cathode materials, a series of cathode materials Li1.2[Mn0.7Ni0.2Co0.1]0.8-xSexO2 (x = 0, 0.07, 0.14 and 0.21) was synthesized via co-precipitation. Based on the characterization results, it can be concluded that uniform Se6+ doping can improve the degree of crystallinity of Li2MnO3, resulting in a better ordering of atoms in the transition metal layer of this type of cathode materials. In the electrochemical experiments, compared to un-doped samples, one of the Se doped samples (LLMO-Se0.14) exhibited a longer sloping region and shorter potential plateau in the initial charge curves, a larger first coulombic efficiency (ca. 77%), better rate capability (178 mAhm g-1 at 10 C) and higher mid-point voltage (MPV) retention (ca. 95%) after 100 cycles. These results prove that Se doping can effectively improve the rate capability and decelerate the voltage decay process of these cathode materials during cycling via suppressing the oxidation process of O2- to O2 and curbing a layered-to-spinel phase transformation. The above-mentioned functions of Se doping are probably due to the higher bonding energy of Sesbnd O than that of Mnsbnd O.

  18. The effects of gait time and trunk acceleration ratio during stair climbing in old-old adult females.

    PubMed

    Shin, Sun-Shil; Yoo, Won-Gyu

    2016-07-01

    [Purpose] This study investigated the effects of gait time and trunk acceleration ratio in old-old adult females during stair climbing. [Subjects and Methods] Twenty-five older adult females who were able to walk independently volunteered for this study and were categorized into two age groups (older adults or old-old adults). Gait time and trunk acceleration ratio were measured using an accelerometer during stair climbing. [Results] Gait time and trunk acceleration ratio when climbing stairs were significantly higher in the old-old age group than in the older adults group. [Conclusions] These findings suggest that old-old females have decreased upper trunk control. In addition, gait time and the trunk acceleration ratio during stair climbing are useful clinical markers for predicting function and balance control ability in old-old elderly populations. PMID:27512256

  19. Resonant absorption effects induced by polarized laser light irradiating thin foils in the TNSA regime of ion acceleration

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Badziak, J.; Rosinski, M.; Zaras-Szydlowska, A.; Pfeifer, M.; Torrisi, A.

    2016-04-01

    Thin foils were irradiated by short pulsed lasers at intensities of 1016-19W/cm2 in order to produce non-equilibrium plasmas and ion acceleration from the target-normal-sheath-acceleration (TNSA) regime. Ion acceleration in forward direction was measured by SiC detectors and ion collectors used in the time-of-flight configuration. Laser irradiations were employed using p-polarized light at different incidence angles with respect to the target surface and at different focal distances from the target surface. Measurements demonstrate that resonant absorption effects, due to the plasma wave excitations, enhance the plasma temperature and the ion acceleration with respect to those performed without to use of p-polarized light. Dependences of the ion flux characteristics on the laser energy, wavelength, focal distance and incidence angle will be reported and discussed.

  20. The effects of gait time and trunk acceleration ratio during stair climbing in old-old adult females

    PubMed Central

    Shin, Sun-Shil; Yoo, Won-Gyu

    2016-01-01

    [Purpose] This study investigated the effects of gait time and trunk acceleration ratio in old-old adult females during stair climbing. [Subjects and Methods] Twenty-five older adult females who were able to walk independently volunteered for this study and were categorized into two age groups (older adults or old-old adults). Gait time and trunk acceleration ratio were measured using an accelerometer during stair climbing. [Results] Gait time and trunk acceleration ratio when climbing stairs were significantly higher in the old-old age group than in the older adults group. [Conclusions] These findings suggest that old-old females have decreased upper trunk control. In addition, gait time and the trunk acceleration ratio during stair climbing are useful clinical markers for predicting function and balance control ability in old-old elderly populations. PMID:27512256

  1. An assessment of the contamination acquired by IDPs during atmospheric deceleration

    NASA Technical Reports Server (NTRS)

    Flynn, George J.

    1994-01-01

    The E-layer of the terrestrial mesosphere, between 80 and 110 km altitude, is derived from meteoric ablation. Concentrations of Na and Fe, contributed by meteoric vapor, have been monitored in the mesosphere, and both individual meteors and average concentration profiles have been measured. Individual interplanetary dust particles (IDP's) entering the earth's atmosphere must pass through the mesospheric layers rich in meteoric volatile elements. Limits on the extent to which individual IDP's can be contaminated by meteoric volatile elements during deceleration in the upper atmosphere can be established by considering the extreme cases: the direct passage of an IDP through a meteoric vapor trail or the passage of an IDP through the mesospheric layer rich in meteoric volatiles. It appears the interaction of IDP's with meteoric vapor during deceleration in the upper atmosphere does not produce significant contamination of IDP's as they decelerate in the upper atmosphere.

  2. Simultaneous, Unsteady PIV and Photogrammetry Measurements of a Tension-Cone Decelerator in Subsonic Flow

    NASA Technical Reports Server (NTRS)

    Schairer, Edward T.; Heineck, James T.; Walker, Louise Ann; Kushner, Laura Kathryn; Zilliac, Gregory

    2010-01-01

    This paper describes simultaneous, synchronized, high-frequency measurements of both unsteady flow in the wake of a tension-cone decelerator in subsonic flow (by PIV) and the unsteady shape of the decelerator (by photogrammetry). The purpose of these measurements was to develop the test techniques necessary to validate numerical methods for computing fluid-structure interactions of flexible decelerators. A critical need for this effort is to map fabric surfaces that have buckled or wrinkled so that code developers can accurately represent them. This paper describes a new photogrammetric technique that performs this measurement. The work was done in support of the Entry, Descent, and Landing discipline within the Supersonics Project of NASA s Fundamental Aeronautics Program.

  3. A switched ring Stark decelerator for both light and heavy polar molecules

    NASA Astrophysics Data System (ADS)

    Hou, Shunyong; Wang, Qin; Deng, Lianzhong; Yin, Jianping

    2016-03-01

    There is increasing interest in cold heavy polar molecular species for their applications in fundamental physics, such as the tests of the electron’s electric dipole moment. Here we propose a switched ring Stark decelerator suitable for slowing both light and heavy polar molecules. Two typical polar molecular species, ND3 and 205TlF, are employed to test the feasibility of our scheme with the help of trajectory calculation. Our proposed scheme is found to share many advantages with the state-of-the-art traveling wave decelerator, yet with relatively simple electronics and flexible operation modes. Sub-millikelvin molecular samples can be conveniently obtained in our decelerator using a combined operation mode. These monochromatic beams are ideal starting points for precise studies of molecular collision, cold chemistry and high-resolution spectroscopy.

  4. Deceleration of the solar wind in the Earth foreshock region: ISEE 2 and IMP 8 observations

    NASA Technical Reports Server (NTRS)

    Bonifazi, C.; Moreno, G.; Lazarus, A. J.; Sullivan, J. D.

    1980-01-01

    The deceleration of the solar wind in the region of the interplanetary space filled by ions backstreaming from the Earth bow shock was studied using a two spacecraft technique. This deceleration, which is correlated with the "diffuse" but not with the "reflected" ion population, depends on the solar wind bulk velocity: at low velocities (below 300 km/sec) the velocity decrease is about 5 km/sec, while at higher velocities (above 400 km/sec) the decrease may be as large as 30 km/sec. Along with this deceleration, the solar wind undergoes a deflection of about 1 deg away from the direction of the Earth bow shock. The energy balance shows that the kinetic energy loss far exceeds the thermal energy which is possibly gained by the solar wind, therefore, at least part of this energy must go into waves and/or into the backstreaming ions.

  5. Comparison of Analysis with Test for Static Loading of Two Hypersonic Inflatable Aerodynamic Decelerator Concepts

    NASA Technical Reports Server (NTRS)

    Lyle, Karen H.

    2015-01-01

    Acceptance of new spacecraft structural architectures and concepts requires validated design methods to minimize the expense involved with technology demonstration via flight-testing. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) architectures are attractive for spacecraft deceleration because they are lightweight, store compactly, and utilize the atmosphere to decelerate a spacecraft during entry. However, designers are hesitant to include these inflatable approaches for large payloads or spacecraft because of the lack of flight validation. This publication summarizes results comparing analytical results with test data for two concepts subjected to representative entry, static loading. The level of agreement and ability to predict the load distribution is considered sufficient to enable analytical predictions to be used in the design process.

  6. Post-Flight Aerodynamic and Aerothermal Model Validation of a Supersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Tang, Chun; Muppidi, Suman; Bose, Deepak; Van Norman, John W.; Tanimoto, Rebekah; Clark, Ian

    2015-01-01

    NASA's Low Density Supersonic Decelerator Program is developing new technologies that will enable the landing of heavier payloads in low density environments, such as Mars. A recent flight experiment conducted high above the Hawaiian Islands has demonstrated the performance of several decelerator technologies. In particular, the deployment of the Robotic class Supersonic Inflatable Aerodynamic Decelerator (SIAD-R) was highly successful, and valuable data were collected during the test flight. This paper outlines the Computational Fluid Dynamics (CFD) analysis used to estimate the aerodynamic and aerothermal characteristics of the SIAD-R. Pre-flight and post-flight predictions are compared with the flight data, and a very good agreement in aerodynamic force and moment coefficients is observed between the CFD solutions and the reconstructed flight data.

  7. Preliminary Structural Sensitivity Study of Hypersonic Inflatable Aerodynamic Decelerator Using Probabilistic Methods

    NASA Technical Reports Server (NTRS)

    Lyle, Karen H.

    2014-01-01

    Acceptance of new spacecraft structural architectures and concepts requires validated design methods to minimize the expense involved with technology validation via flighttesting. This paper explores the implementation of probabilistic methods in the sensitivity analysis of the structural response of a Hypersonic Inflatable Aerodynamic Decelerator (HIAD). HIAD architectures are attractive for spacecraft deceleration because they are lightweight, store compactly, and utilize the atmosphere to decelerate a spacecraft during re-entry. However, designers are hesitant to include these inflatable approaches for large payloads or spacecraft because of the lack of flight validation. In the example presented here, the structural parameters of an existing HIAD model have been varied to illustrate the design approach utilizing uncertainty-based methods. Surrogate models have been used to reduce computational expense several orders of magnitude. The suitability of the design is based on assessing variation in the resulting cone angle. The acceptable cone angle variation would rely on the aerodynamic requirements.

  8. Hall Effects on Mhd Flow Past an Accelerated Plate with Heat Transfer

    NASA Astrophysics Data System (ADS)

    Sundarnath, J. K.; Muthucumarswamy, R.

    2015-02-01

    Hall current and rotation on an MHD flow past an accelerated horizontal plate relative to a rotating fluid, in the presence of heat transfer has been analyzed. The effects of the Hall parameter, Hartmann number, rotation parameter (non-dimensional angular velocity), Grashof's number and Prandtl number on axial and transverse velocity profiles are presented graphically. It is found that with the increase in the Hartmann number, the axial and transverse velocity components increase in a direction opposite to that of obtained by increasing the Hall parameter and rotation parameter. Also, when Ω=M2m /(1 + m2 ) , it is observed that the transverse velocity component vanishes and axial velocity attains a maximum value.

  9. GPU-accelerated computational tool for studying the effectiveness of asteroid disruption techniques

    NASA Astrophysics Data System (ADS)

    Zimmerman, Ben J.; Wie, Bong

    2016-10-01

    This paper presents the development of a new Graphics Processing Unit (GPU) accelerated computational tool for asteroid disruption techniques. Numerical simulations are completed using the high-order spectral difference (SD) method. Due to the compact nature of the SD method, it is well suited for implementation with the GPU architecture, hence solutions are generated at orders of magnitude faster than the Central Processing Unit (CPU) counterpart. A multiphase model integrated with the SD method is introduced, and several asteroid disruption simulations are conducted, including kinetic-energy impactors, multi-kinetic energy impactor systems, and nuclear options. Results illustrate the benefits of using multi-kinetic energy impactor systems when compared to a single impactor system. In addition, the effectiveness of nuclear options is observed.

  10. Big Data and Comparative Effectiveness Research in Radiation Oncology: Synergy and Accelerated Discovery

    PubMed Central

    Trifiletti, Daniel M.; Showalter, Timothy N.

    2015-01-01

    Several advances in large data set collection and processing have the potential to provide a wave of new insights and improvements in the use of radiation therapy for cancer treatment. The era of electronic health records, genomics, and improving information technology resources creates the opportunity to leverage these developments to create a learning healthcare system that can rapidly deliver informative clinical evidence. By merging concepts from comparative effectiveness research with the tools and analytic approaches of “big data,” it is hoped that this union will accelerate discovery, improve evidence for decision making, and increase the availability of highly relevant, personalized information. This combination offers the potential to provide data and analysis that can be leveraged for ultra-personalized medicine and high-quality, cutting-edge radiation therapy. PMID:26697409

  11. Track Structure and the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

    NASA Technical Reports Server (NTRS)

    George, K.; Hada, M.; Chappell, L.; Cucinotta, F. A.

    2011-01-01

    Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to195 keV/micron. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons.

  12. Effect of ball size on player reaction and racket acceleration during the tennis volley.

    PubMed

    Andrew, D P S; Chow, J W; Knudson, D V; Tillman, M D

    2003-03-01

    The purpose of this study was to examine the effect of ball size on reaction time (from ball projection to initial racket movement), movement time (from ball projection to ball-racket impact), mean rectified acceleration and vibration frequency of the racket during the impact phase (100 ms duration after ball-racket impact) of the tennis volley. Twenty-nine beginning to intermediate level tennis players performed volleys under 18 experimental conditions including variations in lateral contact location (forehand and backhand), ball type (Penn oversize, Wilson oversize, regular size), and ball speed (fast, medium, slow). A ball machine was shielded so that the subjects could not predict the ball trajectory before it was released from the machine. Outcome measures were determined using a miniature uni-axial accelerometer and a Photogate timing device. ANOVA with repeated measures and Tukey's post hoc tests were used in statistical analyses (p < .025). The reaction times for the fast speed were significantly shorter than the corresponding times for the slow speed and the reaction times for the forehand volley were significantly shorter than that of the backhand volley. The significant interaction in movement time between ball speed and ball type indicates that the benefits of the larger ball (to slow the game down) increase as the ball speed increases. No significant effect of ball type or ball speed, or interactions were found on mean rectified acceleration and vibration frequency. These results suggest that oversized balls would not cause an increased load to the hitting arm while executing a tennis volley. PMID:12801215

  13. Solar Wind Acceleration: Modeling Effects of Turbulent Heating in Open Flux Tubes

    NASA Astrophysics Data System (ADS)

    Woolsey, Lauren N.; Cranmer, Steven R.

    2014-06-01

    We present two self-consistent coronal heating models that determine the properties of the solar wind generated and accelerated in magnetic field geometries that are open to the heliosphere. These models require only the radial magnetic field profile as input. The first code, ZEPHYR (Cranmer et al. 2007) is a 1D MHD code that includes the effects of turbulent heating created by counter-propagating Alfven waves rather than relying on empirical heating functions. We present the analysis of a large grid of modeled flux tubes (> 400) and the resulting solar wind properties. From the models and results, we recreate the observed anti-correlation between wind speed at 1 AU and the so-called expansion factor, a parameterization of the magnetic field profile. We also find that our models follow the same observationally-derived relation between temperature at 1 AU and wind speed at 1 AU. We continue our analysis with a newly-developed code written in Python called TEMPEST (The Efficient Modified-Parker-Equation-Solving Tool) that runs an order of magnitude faster than ZEPHYR due to a set of simplifying relations between the input magnetic field profile and the temperature and wave reflection coefficient profiles. We present these simplifying relations as a useful result in themselves as well as the anti-correlation between wind speed and expansion factor also found with TEMPEST. Due to the nature of the algorithm TEMPEST utilizes to find solar wind solutions, we can effectively separate the two primary ways in which Alfven waves contribute to solar wind acceleration: 1) heating the surrounding gas through a turbulent cascade and 2) providing a separate source of wave pressure. We intend to make TEMPEST easily available to the public and suggest that TEMPEST can be used as a valuable tool in the forecasting of space weather, either as a stand-alone code or within an existing modeling framework.

  14. Effects of vestibular rotatory accelerations on covert attentional orienting in vision and touch.

    PubMed

    Figliozzi, Francesca; Guariglia, Paola; Silvetti, Massimo; Siegler, Isabelle; Doricchi, Fabrizio

    2005-10-01

    Peripheral vestibular organs feed the central nervous system with inputs favoring the correct perception of space during head and body motion. Applying temporal order judgments (TOJs) to pairs of simultaneous or asynchronous stimuli presented in the left and right egocentric space, we evaluated the influence of leftward and rightward vestibular rotatory accelerations given around the vertical head-body axis on covert attentional orienting. In a first experiment, we presented visual stimuli in the left and right hemifield. In a second experiment, tactile stimuli were presented to hands lying on their anatomical side or in a crossed position across the sagittal body midline. In both experiments, stimuli were presented while normal subjects suppressed or did not suppress the vestibulo-ocular response (VOR) evoked by head-body rotation. Independently of VOR suppression, visual and tactile stimuli presented on the side of rotation were judged to precede simultaneous stimuli presented on the side opposite the rotation. When limbs were crossed, attentional facilitatory effects were only observed for stimuli presented to the right hand lying in the left hemispace during leftward rotatory trials with VOR suppression. This result points to spatiotopic rather than somatotopic influences of vestibular inputs, suggesting that cross-modal effects of these inputs on tactile ones operate on a representation of space that is updated following arm crossing. In a third control experiment, we demonstrated that temporal prioritization of stimuli presented on the side of rotation was not determined by response bias linked to spatial compatibility between the directions of rotation and the directional labels used in TOJs (i.e., "left" or "right" first). These findings suggest that during passive rotatory head-body accelerations, covert attention is shifted toward the direction of rotation and the direction of the fast phases of the VOR.

  15. An accelerator-based neutron microbeam system for studies of radiation effects

    PubMed Central

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A.; Bigelow, Alan W.; Akselrod, Mark S.; Sykora, Jeff G.; Brenner, David J.

    2011-01-01

    A novel neutron microbeam is being developed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The RARAF microbeam facility has been used for studies of radiation bystander effects in mammalian cells for many years. Now a prototype neutron microbeam is being developed that can be used for bystander effect studies. The neutron microbeam design here is based on the existing charged particle microbeam technology at the RARAF. The principle of the neutron microbeam is to use the proton beam with a micrometre-sized diameter impinging on a very thin lithium fluoride target system. From the kinematics of the 7Li(p,n)7Be reaction near the threshold of 1.881 MeV, the neutron beam is confined within a narrow, forward solid angle. Calculations show that the neutron spot using a target with a 17-µm thick gold backing foil will be <20 µm in diameter for cells attached to a 3.8-µm thick propylene-bottomed cell dish in contact with the target backing. The neutron flux will roughly be 2000 per second based on the current beam setup at the RARAF singleton accelerator. The dose rate will be about 200 mGy min−1. The principle of this neutron microbeam system has been preliminarily tested at the RARAF using a collimated proton beam. The imaging of the neutron beam was performed using novel fluorescent nuclear track detector technology based on Mg-doped luminescent aluminum oxide single crystals and confocal laser scanning fluorescent microscopy. PMID:21131327

  16. Effects of resisted sprint training on acceleration in professional rugby union players.

    PubMed

    West, Daniel J; Cunningham, Dan J; Bracken, Richard M; Bevan, Huw R; Crewther, Blair T; Cook, Christian J; Kilduff, Liam P

    2013-04-01

    The use of weighted sled towing as a training tool to improve athlete acceleration has received considerable attention; however, its effectiveness for developing acceleration is equivocal. This study compared the effects of combined weighted sled towing and sprint training against traditional sprint training on 10 and 30 m speed in professional rugby union players (n = 20). After baseline testing of 10 and 30 m speed, participants were assigned to either the combined sled towing and sprint training (SLED) or traditional sprint training (TRAD) groups, matched for 10-m sprint times. Each group completed 2 training sessions per week for 6 weeks, with performance reassessed post-training. Both training programmes improved participants' 10 and 30 m speed (p < 0.001), but the performance changes (from pre to post) in 10 m (SLED -0.04 ± 0.01 vs. TRAD -0.02 ± 0.01 seconds; p < 0.001) and 30 m (SLED -0.10 ± 0.03 vs. TRAD -0.05 ± 0.03 seconds; p = 0.003) sprint times were significantly greater in the SLED training group. Similarly, the percent change within the SLED group for the 10 m (SLED -2.43 ± 0.67 vs. TRAD -1.06 ± 0.80 seconds; p = 0.003) and 30 m (SLED -2.46 ± 0.63 vs. TRAD -1.15 ± 0.72 seconds; p = 0.003) tests were greater than the TRAD group. In conclusion, sprint training alone or combined with weighted sled towing can improve 10 and 30 m sprint times; however, the latter training method promoted greater improvements in a group of professional rugby players.

  17. Effect of ball size on player reaction and racket acceleration during the tennis volley.

    PubMed

    Andrew, D P S; Chow, J W; Knudson, D V; Tillman, M D

    2003-03-01

    The purpose of this study was to examine the effect of ball size on reaction time (from ball projection to initial racket movement), movement time (from ball projection to ball-racket impact), mean rectified acceleration and vibration frequency of the racket during the impact phase (100 ms duration after ball-racket impact) of the tennis volley. Twenty-nine beginning to intermediate level tennis players performed volleys under 18 experimental conditions including variations in lateral contact location (forehand and backhand), ball type (Penn oversize, Wilson oversize, regular size), and ball speed (fast, medium, slow). A ball machine was shielded so that the subjects could not predict the ball trajectory before it was released from the machine. Outcome measures were determined using a miniature uni-axial accelerometer and a Photogate timing device. ANOVA with repeated measures and Tukey's post hoc tests were used in statistical analyses (p < .025). The reaction times for the fast speed were significantly shorter than the corresponding times for the slow speed and the reaction times for the forehand volley were significantly shorter than that of the backhand volley. The significant interaction in movement time between ball speed and ball type indicates that the benefits of the larger ball (to slow the game down) increase as the ball speed increases. No significant effect of ball type or ball speed, or interactions were found on mean rectified acceleration and vibration frequency. These results suggest that oversized balls would not cause an increased load to the hitting arm while executing a tennis volley.

  18. Effect of energy density on color stability in dental resin composites under accelerated aging.

    PubMed

    Zamarripa, Eliezer; Ancona, Adriana L; D'Accorso, Norma B; Macchi, Ricardo L; Abate, Pablo F

    2008-01-01

    The effects of the energy density that is used for polymerization on properties of dental resin composites are well known. However, few studies relate color stability to this factor. The aim of this study was to assess color changes (deltaE*), in vitro, in terms of accelerated aging under UV exposure of specimens prepared with different energy densities. Four commercial dental resin composites were included in the study. Thirty six specimens were prepared for each one of them, following the procedure established by ISO 4049 Standard, and assigned to three groups: A (3.75 J/cm2), B (9 J/cm2), C (24 J/cm2). Each group was further subdivided into four subgroups: 1 (no aging), 2 (500 hours aging), 3 (1000 hours aging) and 4 (1500 hours aging). The results were analyzed by means of ANOVA and Tukey's test (alpha = 0.05) to determine the effect of the factors. Correlation was performed in order to determine the possible relationship among variables. Energy density is not a significant factor in color stability. However aging is directly proportional to color changes. deltaE* depends on filler size; hybrid material presented deltaE* of 2.1(0.5), 2.4(0.6) and 3.3(0.3) at 500, 1000 and 1500 hours of accelerated aging respectively, and nanofilled material showed deltaE* of 3.0(0.6), 4.5(1.2) and 5.9(0.6) at the same times respectively. It can be concluded that deltaE* does not depend on energy density; however other factors are involved in color change. Further studies in this area are warranted.

  19. Formation and nonlinear dynamics of the squeezed state of a helical electron beam with additional deceleration

    SciTech Connect

    Egorov, E. N. Koronovskii, A. A.; Kurkin, S. A.; Hramov, A. E.

    2013-11-15

    Results of numerical simulations and analysis of the formation and nonlinear dynamics of the squeezed state of a helical electron beam in a vircator with a magnetron injection gun as an electron source and with additional electron deceleration are presented. The ranges of control parameters where the squeezed state can form in such a system are revealed, and specific features of the system dynamics are analyzed. It is shown that the formation of a squeezed state of a nonrelativistic helical electron beam in a system with electron deceleration is accompanied by low-frequency longitudinal dynamics of the space charge.

  20. Autophase gyroresonance decelerator of electron beams (a gyrodecelerator) - Relativistic nonlinear theory

    NASA Astrophysics Data System (ADS)

    Zhurakhovskii, V. A.

    1987-04-01

    The feasibility of using an autophasing principle for the deceleration of electron beams and the amplification of electromagnetic waves in the gyroresonance mode is considered with reference to the design of TWTs and free-electron lasers. Profiling of the magnetostatic field induction provides for the phase constancy of the resonant force of a synchronous electron which is decelerated for a long time by an undecelerated wave together with a cloud of charged particles that pulsates around this electron. A computer analysis showed an average efficiency of 85 percent for a relativistic autophase gyrodecelerator-amplifier with an initially monovelocity electron beam.

  1. The Mars Exploration Rovers Entry Descent and Landing and the Use of Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    Steltzner, Adam; Desai, Prasun; Lee, Wayne; Bruno, Robin

    2003-01-01

    The Mars Exploration Rovers (MER) project, the next United States mission to the surface of Mars, uses aerodynamic decelerators in during its entry, descent and landing (EDL) phase. These two identical missions (MER-A and MER-B), which deliver NASA s largest mobile science suite to date to the surface of Mars, employ hypersonic entry with an ablative energy dissipating aeroshell, a supersonic/subsonic disk-gap-band parachute and an airbag landing system within EDL. This paper gives an overview of the MER EDL system and speaks to some of the challenges faced by the various aerodynamic decelerators.

  2. The effect of viscosity on steady transonic flow with a nodal solution topology

    NASA Technical Reports Server (NTRS)

    Owocki, Stanley P.; Zank, Gary P.

    1991-01-01

    The effect of viscosity on a steady, transonic flow for which the inviscid limit has a nodal solution topology near the critical point is investigated. For the accelerating case, viscous solutions tend to repel each other, so that a very delicate choice of initial conditions is required to prevent them from diverging. Only the two critical solutions extend to arbitrarily large distances into both the subsonic and supersonic flows. For the decelerating case, the solutions tend to attract, and so an entire two-parameter family of solutions now extends over large distances. The general effect of viscosity on the solution degeneracy of a nodal topology is thus to reduce or limit it for the accelerating case and to enhance it for the decelerating case. The astrophysical implications of these findings are addressed.

  3. Role of the Russell-McPherron Effect in the Acceleration of Relativistic Electrons

    NASA Technical Reports Server (NTRS)

    McPherron, R. L.; Baker, D. N.; Crooker, N. U.

    2010-01-01

    While it is well known that high fluxes of relativistic electrons in the Earth's radiation belts are associated with high-speed solar wind and its heightened geoeffectiveness,less known is the fact that the Russell McPherron(R M) effect strongly controls whether or not a given high-speed stream is geoffective. To test whether it then follows that the R M effect also strongly controls fluxes of relativistic electrons, we perform a superposed epoch analysis across corotating interaction regions (CIR) keyed on the interfaces between slow and fast wind. A total of 394 stream interfaces were identified in the years 1994-2006. Equinoctial interfaces were separated into four classes based on the R-M effect,that is, whether the solar wind on either side of the interface was either(geo)effective (E) or ineffective (I) depending on season and the polarity of the interplanetary magnetic field (IMF). Four classes of interface identified as II, IE, EI,and EE are possible. The classes IE and EI correspond to CIRs with polarity changes indicating passage through the heliospheric current sheet. To characterize the behavior of solar wind and magnetospheric variables, we produced maps of dynamic cumulative probability distribution functions (cdfs) as a function of time over 10-day intervals centered on the interfaces. These reveal that effective high-speed streams have geomagnetic activity nearly twice as strong as ineffective streams and electron fluxes a factor of 12 higher. In addition they show that an effective low-speed stream increases the flux of relativistic electrons before the interface so that an effective to ineffective transition results in lower fluxes after the interface.We conclude that the R-M effect plays a major role in organizing and sustaining a sequence of physical processes responsible for the acceleration of relativistic electrons.

  4. ACE3P Computations of Wakefield Coupling in the CLIC Two-Beam Accelerator

    SciTech Connect

    Candel, Arno; Li, Z.; Ng, C.; Rawat, V.; Schussman, G.; Ko, K.; Syratchev, I.; Grudiev, A.; Wuensch, W.; /CERN

    2010-10-27

    The Compact Linear Collider (CLIC) provides a path to a multi-TeV accelerator to explore the energy frontier of High Energy Physics. Its novel two-beam accelerator concept envisions rf power transfer to the accelerating structures from a separate high-current decelerator beam line consisting of power extraction and transfer structures (PETS). It is critical to numerically verify the fundamental and higher-order mode properties in and between the two beam lines with high accuracy and confidence. To solve these large-scale problems, SLAC's parallel finite element electromagnetic code suite ACE3P is employed. Using curvilinear conformal meshes and higher-order finite element vector basis functions, unprecedented accuracy and computational efficiency are achieved, enabling high-fidelity modeling of complex detuned structures such as the CLIC TD24 accelerating structure. In this paper, time-domain simulations of wakefield coupling effects in the combined system of PETS and the TD24 structures are presented. The results will help to identify potential issues and provide new insights on the design, leading to further improvements on the novel CLIC two-beam accelerator scheme.

  5. Field Operations Program Chevrolet S-10 (Lead-Acid) Accelerated Reliability Testing - Final Report

    SciTech Connect

    J. Francfort; J. Argueta; M. Wehrey; D. Karner; L. Tyree

    1999-07-01

    This report summarizes the Accelerated Reliability testing of five lead-acid battery-equipped Chevrolet S-10 electric vehicles by the US Department of Energy's Field Operations Program and the Program's testing partners, Electric Transportation Applications (ETA) and Southern California Edison (SCE). ETA and SCE operated the S-10s with the goal of placing 25,000 miles on each vehicle within 1 year, providing an accelerated life-cycle analysis. The testing was performed according to established and published test procedures. The S-10s' average ranges were highest during summer months; changes in ambient temperature from night to day and from season-to-season impacted range by as much as 10 miles. Drivers also noted that excessive use of power during acceleration also had a dramatic effect on vehicle range. The spirited performance of the S-10s created a great temptation to inexperienced electric vehicle drivers to ''have a good time'' and to fully utilize the S-10's acceleration capability. The price of injudicious use of power is greatly reduced range and a long-term reduction in battery life. The range using full-power accelerations followed by rapid deceleration in city driving has been 20 miles or less.

  6. Radiative damping in plasma-based accelerators

    NASA Astrophysics Data System (ADS)

    Kostyukov, I. Yu.; Nerush, E. N.; Litvak, A. G.

    2012-11-01

    The electrons accelerated in a plasma-based accelerator undergo betatron oscillations and emit synchrotron radiation. The energy loss to synchrotron radiation may seriously affect electron acceleration. The electron dynamics under combined influence of the constant accelerating force and the classical radiation reaction force is studied. It is shown that electron acceleration cannot be limited by radiation reaction. If initially the accelerating force was stronger than the radiation reaction force, then the electron acceleration is unlimited. Otherwise the electron is decelerated by radiative damping up to a certain instant of time and then accelerated without limits. It is shown that regardless of the initial conditions the infinite-time asymptotic behavior of an electron is governed by a self-similar solution providing that the radiative damping becomes exactly equal to 2/3 of the accelerating force. The relative energy spread induced by the radiative damping decreases with time in the infinite-time limit. The multistage schemes operating in the asymptotic acceleration regime when electron dynamics is determined by the radiation reaction are discussed.

  7. Accelerator Technology Division

    NASA Astrophysics Data System (ADS)

    1992-04-01

    In fiscal year (FY) 1991, the Accelerator Technology (AT) division continued fulfilling its mission to pursue accelerator science and technology and to develop new accelerator concepts for application to research, defense, energy, industry, and other areas of national interest. This report discusses the following programs: The Ground Test Accelerator Program; APLE Free-Electron Laser Program; Accelerator Transmutation of Waste; JAERI, OMEGA Project, and Intense Neutron Source for Materials Testing; Advanced Free-Electron Laser Initiative; Superconducting Super Collider; The High-Power Microwave Program; (Phi) Factory Collaboration; Neutral Particle Beam Power System Highlights; Accelerator Physics and Special Projects; Magnetic Optics and Beam Diagnostics; Accelerator Design and Engineering; Radio-Frequency Technology; Free-Electron Laser Technology; Accelerator Controls and Automation; Very High-Power Microwave Sources and Effects; and GTA Installation, Commissioning, and Operations.

  8. Accelerating effect of hydroxylamine and hydrazine on nitrogen removal rate in moving bed biofilm reactor.

    PubMed

    Zekker, Ivar; Kroon, Kristel; Rikmann, Ergo; Tenno, Toomas; Tomingas, Martin; Vabamäe, Priit; Vlaeminck, Siegfried E; Tenno, Taavo

    2012-09-01

    In biological nitrogen removal, application of the autotrophic anammox process is gaining ground worldwide. Although this field has been widely researched in last years, some aspects as the accelerating effect of putative intermediates (mainly N₂H₄ and NH₂OH) need more specific investigation. In the current study, experiments in a moving bed biofilm reactor (MBBR) and batch tests were performed to evaluate the optimum concentrations of anammox process intermediates that accelerate the autotrophic nitrogen removal and mitigate a decrease in the anammox bacteria activity using anammox (anaerobic ammonium oxidation) biomass enriched on ring-shaped biofilm carriers. Anammox biomass was previously grown on blank biofilm carriers for 450 days at moderate temperature 26.0 (±0.5) °C by using sludge reject water as seeding material. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. With addition of 1.27 and 1.31 mg N L⁻¹ of each NH₂OH and N₂H₄, respectively, into the MBBR total nitrogen (TN) removal efficiency was rapidly restored after inhibitions by NO₂⁻. Various combinations of N₂H₄, NH₂OH, NH₄⁺, and NO₂⁻ were used as batch substrates. The highest total nitrogen (TN) removal rate with the optimum N₂H₄ concentration (4.38 mg N L⁻¹) present in these batches was 5.43 mg N g⁻¹ TSS h⁻¹, whereas equimolar concentrations of N₂H₄ and NH₂OH added together showed lower TN removal rates. Intermediates could be applied in practice to contribute to the recovery of inhibition-damaged wastewater treatment facilities using anammox technology.

  9. Weak turbulence cascading effects in the acceleration and heating of ions in the solar wind

    SciTech Connect

    Moya, P. S.; Viñas, A. F.; Navarro, R.; Muñoz, V.; Valdivia, J. A.

    2014-02-01

    We study the wave-particle interaction and the evolution of electromagnetic waves propagating through a solar-wind-like plasma composed of cold electrons, isotropic protons, and a small portion of drifting anisotropic He{sup +2} (T {sub α} = 6 T {sub ∥α}) and O{sup +6} (T {sub O} = 11 T {sub ∥O}) ions as suggested in Gomberoff and Valdivia and Gomberoff et al., using two approaches. First, we use quasilinear kinetic theory to study the energy transfer between waves and particles, with the subsequent acceleration and heating of ions. Second, 1.5 D (one spatial dimension and three dimensions in velocity space) hybrid numerical simulations are performed to investigate the fully nonlinear evolution of this wave-particle interaction. Numerical results of both approaches show that the temperatures of all species evolve anisotropically, consistent with the time-dependent wave-spectrum energy. In a cascade effect, we observe the emergence of modes at frequencies higher than those initially considered, peaking at values close to the resonance frequencies of O{sup +6} ions (ω ∼ Ω {sub cO}) and He{sup +2} ions (ω ∼ Ω {sub cα}), being the peak due to O{sup +6} ions about three times bigger than the peak associated with He{sup +2} ions. Both the heating of the plasma and the energy cascade were more efficient in the nonlinear analysis than in the quasilinear one. These results suggest that this energy cascade mechanism may participate in the acceleration and heating of the solar wind plasma close to the Sun during fast streams associated with coronal holes.

  10. Effects of weighted sled towing with heavy versus light load on sprint acceleration ability.

    PubMed

    Kawamori, Naoki; Newton, Robert U; Hori, Naruhiro; Nosaka, Kazunori

    2014-10-01

    Weighted sled towing is used by athletes to improve sprint acceleration ability. The typical coaching recommendation is to use relatively light loads, as excessively heavy loads are hypothesized to disrupt running mechanics and be detrimental to sprint performance. However, this coaching recommendation has not been empirically tested. This study compared the effects of weighted sled towing with 2 different external loads on sprint acceleration ability. Twenty-one physically active men were randomly allocated to heavy- (n = 10) or light-load weighted sled towing (n = 11) groups. All subjects participated in 2 training sessions per week for 8 weeks. The subjects in the heavy and light groups performed weighted sled towing using external loads that reduced sprint velocity by approximately 30 and 10%, respectively. Before and after the training, the subjects performed a 10-m sprint test, in which split time was measured at 5 and 10 m from the start. The heavy group significantly improved both the 5- and 10-m sprint time by 5.7 ± 5.7 and 5.0 ± 3.5%, respectively (P < 0.05), whereas only 10-m sprint time was improved significantly by 3.0 ± 3.5% (P < 0.05) in the light group. No significant differences were found between the groups in the changes in 5-m and 10-m sprint time from pre- to posttraining. These results question the notion that training loads that induce greater than 10% reduction in sprint velocity would negatively affect sprint performance and point out the potential benefit of using a heavier load for weighted sled towing.

  11. The Effectiveness of Rambutan (Nephelium lappaceum L.) Extract in Stabilization of Sunflower Oil under Accelerated Conditions.

    PubMed

    Mei, Winne Sia Chiaw; Ismail, Amin; Esa, Norhaizan Mohd; Akowuah, Gabriel Akyirem; Wai, Ho Chun; Seng, Yim Hip

    2014-05-09

    The oxidative properties of sunflower oil supplemented with rambutan extract, (crude extract and its fractionated fraction, SF II) in comparison with synthetic antioxidant were investigated. The supplemented sunflower oils were stored under accelerated conditions for 24 days at 60 °C. For every 6-day interval, the oxidative properties of the supplemented sunflower oil were evaluated based on the following tests, namely peroxide value, p-anisidine value, Thiobarbituric Acid Reactive Substances (TBARS) assay, iodine value and free fatty acids. The total oxidation (TOTOX) values were also calculated based on the peroxide values and p-anisidine values. Rambutan extract is a potential source of antioxidant. The oxidative activities of the extracts at all concentrations were significantly (p < 0.05) higher than the control. Generally, the partially fractionated fraction was more effective than the crude extract. With a 2-year storage period at ambient temperature, the fractionated fraction of the extract, SF II at 300 ppm, was observed to work more effectively than the synthetic antioxidant, t-Tocopherol, and it possessed a protective effect comparable with butylatedhydrioxynanisole (BHA). Therefore, rambutan extract could be used as a potential alternative source of antioxidant in the oil industry or other fat-based products to delay lipid oxidation.

  12. The Effectiveness of Rambutan (Nephelium lappaceum L.) Extract in Stabilization of Sunflower Oil under Accelerated Conditions

    PubMed Central

    Mei, Winne Sia Chiaw; Ismail, Amin; Mohd. Esa, Norhaizan; Akowuah, Gabriel Akyirem; Wai, Ho Chun; Seng, Yim Hip

    2014-01-01

    The oxidative properties of sunflower oil supplemented with rambutan extract, (crude extract and its fractionated fraction, SF II) in comparison with synthetic antioxidant were investigated. The supplemented sunflower oils were stored under accelerated conditions for 24 days at 60 °C. For every 6-day interval, the oxidative properties of the supplemented sunflower oil were evaluated based on the following tests, namely peroxide value, p-anisidine value, Thiobarbituric Acid Reactive Substances (TBARS) assay, iodine value and free fatty acids. The total oxidation (TOTOX) values were also calculated based on the peroxide values and p-anisidine values. Rambutan extract is a potential source of antioxidant. The oxidative activities of the extracts at all concentrations were significantly (p < 0.05) higher than the control. Generally, the partially fractionated fraction was more effective than the crude extract. With a 2-year storage period at ambient temperature, the fractionated fraction of the extract, SF II at 300 ppm, was observed to work more effectively than the synthetic antioxidant, t-Tocopherol, and it possessed a protective effect comparable with butylatedhydrioxynanisole (BHA). Therefore, rambutan extract could be used as a potential alternative source of antioxidant in the oil industry or other fat-based products to delay lipid oxidation. PMID:26784877

  13. Sucrose accelerates flower opening and delays senescence through a hormonal effect in cut lily flowers.

    PubMed

    Arrom, Laia; Munné-Bosch, Sergi

    2012-06-01

    Sugars are generally used to extend the vase life of cut flowers. Such beneficial effects have been associated with an improvement of water relations and an increase in available energy for respiration by floral tissues. In this study we aimed at evaluating to what extent (i) endogenous levels of sugars in outer and inner tepals, androecium and gynoecium are altered during opening and senescence of lily flowers; (ii) sugar levels increase in various floral tissues after sucrose addition to the vase solution; and (iii) sucrose addition alters the hormonal balance of floral tissues. Results showed that endogenous glucose levels increased during flower opening and decreased during senescence in all floral organs, while sucrose levels increased in outer and inner tepals and the androecium during senescence. Sucrose treatment accelerated flower opening, and delayed senescence, but did not affect tepal abscission. Such effects appeared to be exerted through a specific increase in the endogenous levels of sucrose in the gynoecium and of glucose in all floral tissues. The hormonal balance was altered in the gynoecium as well as in other floral tissues. Aside from cytokinin and auxin increases in the gynoecium; cytokinins, gibberellins, abscisic acid and salicylic acid levels increased in the androecium, while abscisic acid decreased in outer tepals. It is concluded that sucrose addition to the vase solution exerts an effect on flower opening and senescence by, among other factors, altering the hormonal balance of several floral tissues.

  14. Opportunities for TeV Laser Acceleration

    SciTech Connect

    Kando, M.; Kiriyama, H.; Koga, J.K.; Bulanov, S.; Chao, A.W.; Esirkepov, T.; Hajima, R.; Tajima, T.; /JAERI, Kyoto

    2008-06-02

    A set of ballpark parameters for laser, plasma, and accelerator technologies that define for electron energies reaching as high as TeV are identified. These ballpark parameters are carved out from the fundamental scaling laws that govern laser acceleration, theoretically suggested and experimentally explored over a wide range in the recent years. In the density regime on the order of 10{sup 16} cm{sup -3}, the appropriate laser technology, we find, matches well with that of a highly efficient high fluence LD driven Yb ceramic laser. Further, the collective acceleration technique applies to compactify the beam stoppage stage by adopting the beam-plasma wave deceleration, which contributes to significantly enhance the stopping power and energy recovery capability of the beam. Thus we find the confluence of the needed laser acceleration parameters dictated by these scaling laws and the emerging laser technology. This may herald a new technology in the ultrahigh energy frontier.

  15. Opportunities for TeV Laser Acceleration

    SciTech Connect

    Kando, M.; Kiriyama, H.; Koga, J. K.; Bulanov, S.; Esirkepov, T.; Hajima, R.; Tajima, T.; Chao, A. W.

    2008-06-24

    A set of ballpark parameters for laser, plasma, and accelerator technologies that define for electron energies reaching as high as TeV are identified. These ballpark parameters are carved out from the fundamental scaling laws that govern laser acceleration, theoretically suggested and experimentally explored over a wide range in the recent years. In the density regime on the order of 10{sup 16} cm{sup -3}, the appropriate laser technology, we find, matches well with that of a highly efficient high fluence LD driven Yb ceramic laser. Further, the collective acceleration technique applies to compactify the beam stoppage stage by adopting the beam-plasma wave deceleration, which contributes to significantly enhance the stopping power and energy recovery capability of the beam. Thus we find the confluence of the needed laser acceleration parameters dictated by these scaling laws and the emerging laser technology. This may herald a new technology in the ultrahigh energy frontier.

  16. High efficiency ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, G.

    1981-01-01

    An ion accelerator system that successfully combines geometrical and electrostatic focusing principles is presented. This accelerator system uses thin, concave, multiple-hole, closely spaced graphite screen and focusing grids which are coupled to single slot accelerator and decelerator grids to provide high ion extraction efficiency and good focusing. Tests with the system showed a substantial improvement in ion beam current density and collimation as compared with a Pierce electrode configuration. Durability of the thin graphite screen and focusing grids has been proven, and tests are being performed to determine the minimum screen and focusing grid spacing and thickness required to extract the maximum reliable beam current density. Compared with present neutral beam injector accelerator systems, this one has more efficient ion extraction, easier grid alignment, easier fabrication, a less cumbersome design, and the capacity to be constructed in a modular fashion. Conceptual neutral beam injector designs using this modular approach have electrostatic beam deflection plates downstream of each module.

  17. Effect of resistivity on the Rayleigh-Taylor instability in an accelerated plasma

    SciTech Connect

    Castillo, J.L. ); Huerta, M.A. )

    1993-11-01

    We study the Rayleigh-Taylor instability in finite-conductivity accelerated plasma arcs of the type found in electromagnetic rail launchers. For a plasma of length [ital l], acceleration [ital a], and thermal speed [ital v][sub [ital T

  18. Nuclear Effects of Supernova-Accelerated Cosmic Rays on Early Solar System Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Meyer, B. S.; The, L.-S.; Johnson, J.

    2008-03-01

    The solar system apparently formed in the neighborhood of massive stars. Supernova explosions of these stars accelerate cosmic rays to 100s of TeVs. These cosmic rays could accelerate the beta decay of certain radioactive species in meteorite parent bodies.

  19. Deceleration of single-stranded DNA passing through a nanopore using a nanometre-sized bead structure

    PubMed Central

    Goto, Yusuke; Haga, Takanobu; Yanagi, Itaru; Yokoi, Takahide; Takeda, Ken-ichi

    2015-01-01

    DNA sequencing with a solid-state nanopore requires a reduction of the translocation speeds of single-stranded DNA (ssDNA) over 10 μs/base. In this study, we report that a nanometre-sized bead structure constructed around a nanopore can reduce the moving speed of ssDNA to 270 μs/base by adjusting the diameter of the bead and its surface chemical group. This decelerating effect originates from the strong interaction between ssDNA and the chemical group on the surface of the bead. This nanostructure was simply prepared by dip coating in which a substrate with a nanopore was immersed in a silica bead solution and then dried in an oven. As compared with conventional approaches, our novel method is less laborious, simpler to perform and more effective in reducing ssDNA translocation speed. PMID:26559466

  20. Deceleration of single-stranded DNA passing through a nanopore using a nanometre-sized bead structure

    NASA Astrophysics Data System (ADS)

    Goto, Yusuke; Haga, Takanobu; Yanagi, Itaru; Yokoi, Takahide; Takeda, Ken-Ichi

    2015-11-01

    DNA sequencing with a solid-state nanopore requires a reduction of the translocation speeds of single-stranded DNA (ssDNA) over 10 μs/base. In this study, we report that a nanometre-sized bead structure constructed around a nanopore can reduce the moving speed of ssDNA to 270 μs/base by adjusting the diameter of the bead and its surface chemical group. This decelerating effect originates from the strong interaction between ssDNA and the chemical group on the surface of the bead. This nanostructure was simply prepared by dip coating in which a substrate with a nanopore was immersed in a silica bead solution and then dried in an oven. As compared with conventional approaches, our novel method is less laborious, simpler to perform and more effective in reducing ssDNA translocation speed.

  1. Does Missing Classes Decelerate Student Exam Performance Progress? Empirical Evidence and Policy Implications

    ERIC Educational Resources Information Center

    Lin, Tin-Chun

    2014-01-01

    A total of 389 business students in undergraduate introductory microeconomics classes in spring 2007, 2009, and 2011, and fall 2012 participated in an exam performance progress study. Empirical evidence suggested that missing classes decelerates and hampers high-performing students' exam performance progress. Nevertheless, the evidence does…

  2. Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) Plume Induced Environment Modelling

    NASA Technical Reports Server (NTRS)

    Mobley, B. L.; Smith, S. D.; Van Norman, J. W.; Muppidi, S.; Clark, I

    2016-01-01

    Provide plume induced heating (radiation & convection) predictions in support of the LDSD thermal design (pre-flight SFDT-1) Predict plume induced aerodynamics in support of flight dynamics, to achieve targeted freestream conditions to test supersonic deceleration technologies (post-flight SFDT-1, pre-flight SFDT-2)

  3. Loss of CAR promotes migration and proliferation of HaCaT cells, and accelerates wound healing in rats via Src-p38 MAPK pathway

    PubMed Central

    Su, Linlin; Fu, Lanqing; Li, Xiaodong; Zhang, Yue; Li, Zhenzhen; Wu, Xue; Li, Yan; Bai, Xiaozhi; Hu, Dahai

    2016-01-01

    The coxsackie and adenovirus receptor (CAR) is a cell adhesion molecule mostly localized to cell-cell contacts in epithelial and endothelial cells. CAR is known to regulate tumor progression, however, its physiological role in keratinocyte migration and proliferation, two essential steps in re-epithelialization during wound healing, has less been investigated. Here we showed that CAR was predominantly expressed in the epidermis of human skin, CAR knockdown by RNAi significantly accelerated HaCaT cell migration and proliferation. In addition, knockdown of CAR in vitro increased p-Src, p-p38, and p-JNK protein levels; however, Src inhibitor PP2 prevented the increase of p-Src and p-p38 induced by CAR RNAi, but not p-JNK, and decelerated cell migration and proliferation. More intriguingly, in vivo CAR RNAi on the skin area surrounding the wounds on rat back visually accelerated wound healing and re-epithelialization process, while treatment with PP2 or p38 inhibitor SB203580 obviously inhibited these effects. By contrast, overexpressing CAR in HaCaT cells significantly decelerated cell migration and proliferation. Above results demonstrate that suppression of CAR could accelerate HaCaT cell migration and proliferation, and promote wound healing in rat skin, probably via Src-p38 MAPK pathway. CAR thus might serve as a novel therapeutic target for facilitating wound healing. PMID:26804208

  4. Effects of Testosterone Treatment on Synaptic Plasticity and Behavior in Senescence Accelerated Mice.

    PubMed

    Jian-xin, Jia; Cheng-li, Cui; Song, Wei; Yan, Xu-sheng; Huo, Dong-sheng; Wang, He; Yang, Zhan-jun

    2015-01-01

    Learning and memory are known to be influenced by circulating sex steroidal hormones and these behavioral processes are diminished in aging. Thus, the aim of this study was to examine the mechanism underlying testosterone-induced effects on cognitive performance in the senescence accelerated mouse P8 (SAMP8) model. Treatment with testosterone (T) as evidenced by the Morris water maze test produced a significantly shorter escape latency and reduced path length to reach the platform compared to the control (C). No significant differences were noted in mean swim speed among all groups. During the probe trials, the T group spent a significantly greater percent of time in the target quadrant and improved the number of platform crossings. Flutamide (F), an antiandrogen, significantly inhibited the effects of T on behavioral and memory performances indicators. Following Nissl staining, the number of intact pyramidal cells was markedly elevated in the treated mice, and this effect was blocked by F. Immunohistochemistry and Western blot analysis showed that the expression levels of NMDAR1, SYN, and p-CREC/CREB protein levels were significantly increased in the T group, while F inhibited the T-mediated effects. Western blot analysis showed that there were no significant differences in the expression levels of SYN, p-CREC/CREB, and NMDAR1 between C, F, and F + T groups. Reverse-transcription polymerase chain reaction (RT-PCR) analysis showed that the mRNA expression levels of NMDAR1 and SYN were significantly increased in T-administered mice, while F inhibited the T-mediated effects. Data suggest that the T-mediated increase in SYN expression levels resulted in improvement in behavioral performances and learning, which may involve stimulation of central nervous system androgen receptors (AR). PMID:26529502

  5. Removal of boron from wastewater by the hydroxyapatite formation reaction using acceleration effect of ammonia.

    PubMed

    Yoshikawa, Eishi; Sasaki, Atsushi; Endo, Masatoshi

    2012-10-30

    The mechanism was discussed for the removal of boron by the hydroxyapatite (HAp) formation reaction using Ca(OH)(2) and (NH(4))(2)HPO(4) in room temperature. Time required to remove boron was 20 min by adding Ca(OH)(2) and (NH(4))(2)HPO(4) for the remaining boron to below 1mg/L. The removal rate of boron was controlled by the HAp precipitate formation and the presence of ammonia. From the XRD patterns and SEM images, HAp could be confirmed in the precipitate product. The reaction between borate ions and calcium hydroxide was accelerated by dehydration with ammonia; the borate-calcium hydroxide compound coprecipitated with resulting HAp. Although the removal of boron decreased in the presence of sulfate, phosphate, and aluminum, these effects could be prevented by adding excess Ca(OH)(2). Interference of fluoride ions was eliminated by adding Al(3+). Sodium alpha-olefin sulfonate was the most effective coagulant for HAp precipitation. The proposed boron removal method has several advantages about treating time and ability of boron removal. The method was successfully applied to the real hot spring wastewater.

  6. Effect of an Additional, Parallel Capacitor on Pulsed Inductive Plasma Accelerator Performance

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Sivak, Amy D.; Balla, Joseph V.

    2011-01-01

    A model of pulsed inductive plasma thrusters consisting of a set of coupled circuit equations and a one-dimensional momentum equation has been used to study the effects of adding a second, parallel capacitor into the system. The equations were nondimensionalized, permitting the recovery of several already-known scaling parameters and leading to the identification of a parameter that is unique to the particular topology studied. The current rise rate through the inductive acceleration coil was used as a proxy measurement of the effectiveness of inductive propellant ionization since higher rise rates produce stronger, potentially better ionizing electric fields at the coil face. Contour plots representing thruster performance (exhaust velocity and efficiency) and current rise rate in the coil were generated numerically as a function of the scaling parameters. The analysis reveals that when the value of the second capacitor is much less than the first capacitor, the performance of the two-capacitor system approaches that of the single-capacitor system. In addition, as the second capacitor is decreased in value the current rise rate can grow to be twice as great as the rise rate attained in the single capacitor case.

  7. The effect of accelerated ageing on performance properties of addition type silicone biomaterials.

    PubMed

    Stathi, K; Tarantili, P A; Polyzois, G

    2010-05-01

    The UV-protection provided to addition type silicone elastomers by various colorants, such as conventional dry earth pigments, as well as the so called "functional or reactive" pigments, was investigated. Moreover, the effect of a UV light absorber and a silica filler was also explored. Under the experimental parameters of this work, the exposure of silicone to UV radiation resulted in some changes of the IR absorbance, thermal decomposition after 400 degrees C, T(g) and tensile properties, whereas the storage modulus of samples was not affected. The obtained spectroscopic data, as well as the results of TGA and storage modulus, were interpreted by assuming that chain scission takes place during aging, whereas the improvement of tensile strength allows the hypothesis of a post-curing process, initiated by UV radiation. Therefore, the increase of T(g) could partly be due to the above reason and, furthermore, to the contribution of a rearrangement of chain fragments within the free volume of the elastomeric material. Regarding the evaluation of various coloring agents used in this work, the obtained results show that dry pigments are more sensitive to accelerated ageing conditions in comparison with functional liquid pigments. Moreover, the hydrophobic character of silicone matrix is enhanced, with the addition of this type pigments because of the vinyl functional silanes groups present in their chemical structure. Finally, it should be noted that the incorporation of silica nanofiller did not seem to prevent the silicone elastomer from degradation upon UV irradiation, but showed a significant reinforcing effect.

  8. Effects of thin-film accelerated carbonation on steel slag leaching.

    PubMed

    Baciocchi, R; Costa, G; Polettini, A; Pomi, R

    2015-04-01

    This paper discusses the effects of accelerated carbonation on the leaching behaviour of two types of stainless steel slags (electric arc furnace and argon oxygen decarburisation slag). The release of major elements and toxic metals both at the natural pH and at varying pH conditions was addressed. Geochemical modelling of the eluates was used to theoretically describe leaching and derive information about mineralogical changes induced by carbonation. Among the investigated elements, Ca and Si were most appreciably affected by carbonation. A very clear effect of carbonation on leaching was observed for silicate phases; geochemical modelling indicated that the Ca/Si ratio of Ca-controlling minerals shifted from ∼ 1 for the untreated slag to 0.5-0.67 for the carbonated samples, thus showing that the carbonation process left some residual Ca-depleted silicate phases while the extracted Ca precipitated in the form of carbonate minerals. For toxic metals the changes in leaching induced by carbonation appeared to be mainly related to the resulting pH changes, which were as high as ∼ 2 orders of magnitude upon carbonation. Depending on the specific shape of the respective solubility curves, the extent of leaching of toxic metals from the slag was differently affected by carbonation.

  9. Removal of boron from wastewater by the hydroxyapatite formation reaction using acceleration effect of ammonia.

    PubMed

    Yoshikawa, Eishi; Sasaki, Atsushi; Endo, Masatoshi

    2012-10-30

    The mechanism was discussed for the removal of boron by the hydroxyapatite (HAp) formation reaction using Ca(OH)(2) and (NH(4))(2)HPO(4) in room temperature. Time required to remove boron was 20 min by adding Ca(OH)(2) and (NH(4))(2)HPO(4) for the remaining boron to below 1mg/L. The removal rate of boron was controlled by the HAp precipitate formation and the presence of ammonia. From the XRD patterns and SEM images, HAp could be confirmed in the precipitate product. The reaction between borate ions and calcium hydroxide was accelerated by dehydration with ammonia; the borate-calcium hydroxide compound coprecipitated with resulting HAp. Although the removal of boron decreased in the presence of sulfate, phosphate, and aluminum, these effects could be prevented by adding excess Ca(OH)(2). Interference of fluoride ions was eliminated by adding Al(3+). Sodium alpha-olefin sulfonate was the most effective coagulant for HAp precipitation. The proposed boron removal method has several advantages about treating time and ability of boron removal. The method was successfully applied to the real hot spring wastewater. PMID:22981286

  10. Older Drivers and Rapid Deceleration Events: Salisbury Eye Evaluation Driving Study

    PubMed Central

    Keay, Lisa; Munoz, Beatriz; Duncan, Donald D; Hahn, Daniel; Baldwin, Kevin; Turano, Kathleen A; Munro, Cynthia A; Bandeen-Roche, Karen; West, Sheila K

    2012-01-01

    Drivers who rapidly change speed while driving may be more at risk for a crash. We sought to determine the relationship of demographic, vision, and cognitive variables with episodes of rapid decelerations during five days of normal driving in a cohort of older drivers. In the Salisbury Eye Evaluation Driving Study, 1425 older drivers ages 67 to 87 were recruited from the Maryland Motor Vehicle Administration’s rolls for licensees in Salisbury, Maryland. Participants had several measures of vision tested: visual acuity, contrast sensitivity, visual fields, and the attentional visual field. Participants were also tested for various domains of cognitive function including executive function, attention, psychomotor speed, and visual search. A custom created Driving Monitor System (DMS) was used to capture rapid deceleration events (RDE), defined as at least 350 milli-g deceleration, during a five day period of monitoring. The rate of RDE per mile driven was modeled using a negative binomial regression model with an offset of the logarithm of the number of miles driven. We found that 30% of older drivers had one or more RDE during a five day period, and of those, about 1/3 had four or more. The rate of RDE per mile driven was highest for those drivers driving <59 miles during the 5-day period of monitoring. However, older drivers with RDE’s were more likely to have better scores in cognitive tests of psychomotor speed and visual search, and have faster brake reaction time. Further, greater average speed and maximum speed per driving segment was protective against RDE events. In conclusion, contrary to our hypothesis, older drivers who perform rapid decelerations tend to be more “fit”, with better measures of vision and cognition compared to those who do not have events of rapid deceleration. PMID:22742775

  11. Effect of low temperature baking on the RF properties of niobium superconducting cavities for particle accelerators

    SciTech Connect

    Gianluigi Ciovati

    2004-03-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some ''anomalous'' losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low temperature (100 C-150 C) ''in situ'' bake under ultra-high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from ''anomalous'' losses (so-called ''Q-drop'') without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37 K-280 K and resonant frequency shift between 6 K-9.3 K provide information about the surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with Nuclear Reaction Analysis (NRA). The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models

  12. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2016-08-01

    We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.

  13. Experimental demonstration of wakefield effects in a THz planar diamond accelerating structure

    SciTech Connect

    Antipov, S.; Jing, C.; Kanareykin, A.; Butler, J. E.; Yakimenko, V.; Fedurin, M.; Kusche, K.; Gai, W.

    2012-03-26

    We have directly measured THz wakefields induced by a subpicosecond, intense relativistic electron bunch in a diamond loaded accelerating structure via the wakefield acceleration method. We present here the beam test results from the diamond based structure. Diamond has been chosen for its high breakdown threshold and unique thermoconductive properties. Fields produced by a leading (drive) beam were used to accelerate a trailing (witness) electron bunch, which followed the drive bunch at a variable distance. The energy gain of a witness bunch as a function of its separation from the drive bunch describes the time structure of the generated wakefield.

  14. The effect of electrode material on the motion of a plasma piston in rail accelerators

    NASA Astrophysics Data System (ADS)

    Bobashev, S. V.; Zhukov, B. G.; Kurakin, R. O.; Ponyaev, S. A.; Reznikov, B. I.

    2015-10-01

    The acceleration of a plasma piston in the channels of rail accelerators with copper and graphite electrodes is studied experimentally. It is found that the plasma velocity is reduced by 15-20% (at equal discharge currents) when graphite electrodes are used instead of copper ones. This may be attributed to an increase in the erosion graphite mass that is drawn into motion by the plasma piston. It is concluded based on the interpretation of the obtained data that the current flow in the channels of rail accelerators is governed at high plasma speeds by the processes of thermoautoelectron emission.

  15. A Mixed Method Study of the Effectiveness of the Accelerated Reader Program on Middle School Students' Reading Achievement and Motivation

    ERIC Educational Resources Information Center

    Huang, SuHua

    2012-01-01

    The mixed-method explanatory research design was employed to investigate the effectiveness of the Accelerated Reader (AR) program on middle school students' reading achievement and motivation. A total of 211 sixth to eighth-grade students provided quantitative data by completing an AR Survey. Thirty of the 211 students were randomly selected to…

  16. Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame

    SciTech Connect

    Vay, J.-L.; Geddes, C. G. R.; Cormier-Michel, E.; Grote, D. P.

    2010-09-21

    Laser driven plasma accelerators promise much shorter particle accelerators but their development requires detailed simulations that challenge or exceed current capabilities. We report the first direct simulations of stages up to 1 TeV from simulations using a Lorentz boosted calculation frame resulting in a million times speedup, thanks to a frame boost as high as gamma = 1300. Effects of the hyperbolic rotation in Minkowski space resulting from the frame boost on the laser propagation in the plasma is shown to be key in the mitigation of a numerical instability that was limiting previous attempts.

  17. Effect of disinfection and accelerated ageing on dimensional stability and detail reproduction of a facial silicone with nanoparticles.

    PubMed

    Pesqueira, A A; Goiato, M C; Dos Santos, D M; Haddad, M F; Moreno, A

    2012-05-01

    The aim of the present study was to evaluate the effect of disinfection and accelerated ageing on the dimensional stability and detail reproduction of a facial silicone with different types of nanoparticle. A total of 60 specimens were fabricated with Silastic MDX 4-4210 silicone and they were divided into three groups: colourless and pigmented with nanoparticles (make-up powder and ceramic powder). Half of the specimens of each group were disinfected with Efferdent tablets and half with neutral soap for 60 days. Afterwards, all specimens were subjected to accelerated ageing. Both dimensional stability and detail reproduction tests were performed after specimen fabrication (initial period), after chemical disinfection, and after accelerated ageing periods (252, 504 and 1008 hours). The dimensional stability test was conducted using AutoCAD software, while detail reproduction was analysed using a stereoscope magnifying glass. Dimensional stability values were statistically evaluated by analysis of variance (ANOVA) followed by Tukey's test (p < 0.01). Detail reproduction results were compared using a score. Chemical disinfection and also accelerated ageing affected the dimensional stability of the facial silicone with statistically significant results. The silicone's detail reproduction was not affected by these two factors regardless of nanoparticle type, disinfection and accelerated ageing.

  18. Development of a two-beam high-current ion accelerator based on Doppler effect. Final report (1994)

    SciTech Connect

    Ivanov, B.I.; Yegorov, A.M.

    1995-03-01

    This Final Report presents the results of work accomplished in accordance with the Scope of Work to the Purchase Order No 4596310. The amount of works includes the following items: 1. Start of the manufacture of the Experimental Accelerating Stand (EAS)-the section for proton acceleration from 5 MeV to 8 MeV, in which RF fields are excited by an electron beam at the anomalous Doppler effect. 2. Theoretical investigation and computer simulation of field excitation and ion acceleration in the EAS. Under item 1, the EAS manufacturing is begun. To present time, a pedestal for the EAS and a stainless steel vacuum chamber for RF resonator are made (length of the chamber is about 180 cm, diameter is about 40 cm). Besides, parts of the EAS resonator with the acceleration structure are manufactured, and its assembly is begun. Under item 2, it is realized three works: calculation of increment and frequency shift of the EAS resonator excited by electron beam, calculation of the solenoid for creation of magnetic field with required spatial distribution, and theoretical investigation and computer simulation of ion acceleration in the EAS. 14 figs., 16 refs.

  19. Effect of disinfection and accelerated ageing on dimensional stability and detail reproduction of a facial silicone with nanoparticles.

    PubMed

    Pesqueira, A A; Goiato, M C; Dos Santos, D M; Haddad, M F; Moreno, A

    2012-05-01

    The aim of the present study was to evaluate the effect of disinfection and accelerated ageing on the dimensional stability and detail reproduction of a facial silicone with different types of nanoparticle. A total of 60 specimens were fabricated with Silastic MDX 4-4210 silicone and they were divided into three groups: colourless and pigmented with nanoparticles (make-up powder and ceramic powder). Half of the specimens of each group were disinfected with Efferdent tablets and half with neutral soap for 60 days. Afterwards, all specimens were subjected to accelerated ageing. Both dimensional stability and detail reproduction tests were performed after specimen fabrication (initial period), after chemical disinfection, and after accelerated ageing periods (252, 504 and 1008 hours). The dimensional stability test was conducted using AutoCAD software, while detail reproduction was analysed using a stereoscope magnifying glass. Dimensional stability values were statistically evaluated by analysis of variance (ANOVA) followed by Tukey's test (p < 0.01). Detail reproduction results were compared using a score. Chemical disinfection and also accelerated ageing affected the dimensional stability of the facial silicone with statistically significant results. The silicone's detail reproduction was not affected by these two factors regardless of nanoparticle type, disinfection and accelerated ageing. PMID:22428808

  20. An accelerating cosmology without dark energy

    SciTech Connect

    Steigman, G.; Santos, R.C.; Lima, J.A.S. E-mail: cliviars@astro.iag.usp.br

    2009-06-01

    The negative pressure accompanying gravitationally-induced particle creation can lead to a cold dark matter (CDM) dominated, accelerating Universe (Lima et al. 1996 [1]) without requiring the presence of dark energy or a cosmological constant. In a recent study, Lima et al. 2008 [2] (LSS) demonstrated that particle creation driven cosmological models are capable of accounting for the SNIa observations [3] of the recent transition from a decelerating to an accelerating Universe, without the need for Dark Energy. Here we consider a class of such models where the particle creation rate is assumed to be of the form Γ = βH+γH{sub 0}, where H is the Hubble parameter and H{sub 0} is its present value. The evolution of such models is tested at low redshift by the latest SNe Ia data provided by the Union compilation [4] and at high redshift using the value of z{sub eq}, the redshift of the epoch of matter — radiation equality, inferred from the WMAP constraints on the early Integrated Sachs-Wolfe (ISW) effect [5]. Since the contributions of baryons and radiation were ignored in the work of LSS, we include them in our study of this class of models. The parameters of these more realistic models with continuous creation of CDM are constrained at widely-separated epochs (z{sub eq} ≈ 3000 and z ≈ 0) in the evolution of the Universe. The comparison of the parameter values, (β, γ), determined at these different epochs reveals a tension between the values favored by the high redshift CMB constraint on z{sub eq} from the ISW and those which follow from the low redshift SNIa data, posing a potential challenge to this class of models. While for β = 0 this conflict is only at ∼< 2σ, it worsens as β increases from zero.