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Sample records for acceleration deceleration effect

  1. 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 Section 56.19062 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating...

  2. 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 Section 57.19062 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating...

  3. Do ungulates accelerate or decelerate nitrogen cycling?

    USGS Publications Warehouse

    Singer, F.J.; Schoenecker, K.A.

    2003-01-01

    Nitrogen (N) is an essential nutrient for plants and animals, and N may be limiting in many western US grassland and shrubland ungulate winter ranges. Ungulates may influence N pools and they may alter N inputs and outputs (losses) to the ecosystem in a number of ways. In this paper we compare the ecosystem effects of ungulate herbivory in two western national parks, Rocky Mountain National Park (RMNP), Colorado, and Yellowstone National Park (YNP), Wyoming. We compare ungulate herbivory effects on N pools, N fluxes, N yields, and plant productivity in the context of the accelerating and decelerating nutrient cycling scenarios [Ecology 79 (1998) 165]. We concluded that the YNP grasslands fit the accelerating nutrient cycling scenario for ungulate herbivory: in response to grazing, grassland plant species abundance was largely unaltered, net annual aboveground primary productivity (NAPP) was stimulated (except during drought), consumption of key N-rich forages by ungulates was moderate and their abundance was sustained, soil N mineralization rates doubled, N pools increased, aboveground N yield increased, and N concentrations increased in most grassland plant species. Grazing in grasslands in RMNP resulted in no consistent detectable acceleration or deceleration of nutrient cycling. Grazing effects in short willow and aspen vegetation types in RMNP fit the decelerating nutrient cycling scenario of Ritchie et al. [Ecology 79 (1998) 165]. Key N-rich forages declined due to herbivory (willows, aspen, herbaceous vegetation). Aboveground production declined, soil N mineralization rates declined, N pools declined (NO3− pools were 30% that of ungrazed controls), and aboveground N yield declined. We believe that the higher ungulate densities and rates of plant consumption in RMNP, large declines in N-rich forage plants, and possibly a tendency of ungulates to move N from willow and aspen vegetation types to other types in RMNP, contributed to deceleration of nutrient

  4. Influence of angular acceleration-deceleration pulse shapes on regional brain strains.

    PubMed

    Yoganandan, Narayan; Li, Jianrong; Zhang, Jiangyue; Pintar, Frank A; Gennarelli, Thomas A

    2008-07-19

    Recognizing the association of angular loading with brain injuries and inconsistency in previous studies in the application of the biphasic loads to animal, physical, and experimental models, the present study examined the role of the acceleration-deceleration pulse shapes on region-specific strains. An experimentally validated two-dimensional finite element model representing the adult male human head was used. The model simulated the skull and falx as a linear elastic material, cerebrospinal fluid as a hydrodynamic material, and cerebrum as a linear viscoelastic material. The angular loading matrix consisted coronal plane rotation about a center of rotation that was acceleration-only (4.5 ms duration, 7.8 krad/s/s peak), deceleration-only (20 ms, 1.4 krad/s/s peak), acceleration-deceleration, and deceleration-acceleration pulses. Both biphasic pulses had peaks separated by intervals ranging from 0 to 25 ms. Principal strains were determined at the corpus callosum, base of the postcentral sulcus, and cerebral cortex of the parietal lobe. The cerebrum was divided into 17 regions and peak values of average maximum principal strains were determined. In all simulations, the corpus callosum responded with the highest strains. Strains were the least under all simulations in the lower parietal lobes. In all regions peak strains were the same for both monophase pulses suggesting that the angular velocity may be a better metric than peak acceleration or deceleration. In contrast, for the biphasic pulse, peak strains were region- and pulse-shape specific. Peak values were lower in both biphasic pulses when there was no time separation between the pulses than the corresponding monophase pulse. Increasing separation time intervals increased strains, albeit non-uniformly. Acceleration followed by deceleration pulse produced greater strains in all regions than the other form of biphasic pulse. Thus, pulse shape appears to have an effect on regional strains in the brain.

  5. Changes in Acceleration and Deceleration Capacity Throughout Professional Soccer Match-Play.

    PubMed

    Russell, Mark; Sparkes, William; Northeast, Jonny; Cook, Christian J; Love, Tom D; Bracken, Richard M; Kilduff, Liam P

    2016-10-01

    Russell, M, Sparkes, W, Northeast, J, Cook, CJ, Love, TD, Bracken, RM, and Kilduff, LP. Changes in acceleration and deceleration capacity throughout professional soccer match-play. J Strength Cond Res 30(10): 2839-2844, 2016-As the acceleration and deceleration demands of soccer are currently not well understood, this study aimed to profile markers of acceleration and deceleration capacity during professional soccer match-play. This within-player observational study required reserve team players from a Premier League club to wear 10-Hz Global Positioning System units throughout competitive matches played in the 2013-14 competitive season. Data are presented for players who completed 4 or more games during the season (n = 11), and variables are presented according to six 15-minute intervals (I1-6: 00:00-14:59 minutes, 15:00-29:59 minutes, 30:00-44:59 minutes, 45:00-59:59 minutes, 60:00-74:59 minutes, and 75:00-89:59 minutes, respectively). During I6, the distance covered (total, per minute, and at high intensity), number of sprints, accelerations (total and high intensity), decelerations (total and high intensity), and impacts were reduced compared with I1 (all p ≤ 0.05). The number of high-intensity impacts remained unchanged throughout match-play (p > 0.05). These findings indicate that high-intensity actions and markers of acceleration and deceleration capacity are reduced in the last 15 minutes of the normal duration of match-play. Such information can be used to increase the specificity of training programs designed for soccer players while also giving further insight in to the effects of 90 minutes of soccer-specific exercise. Interventions that seek to maintain the acceleration and deceleration capacity of players throughout the full duration of a soccer match warrant investigation.

  6. Study of Car Acceleration and Deceleration Characteristics at Dangerous Route FT050

    NASA Astrophysics Data System (ADS)

    Omar, N.; Prasetijo, J.; Daniel, B. D.; Abdullah, M. A. E.; Ismail, I.

    2018-04-01

    Individual vehicle acceleration and deceleration are important to generate vehicles speed profile. This study covered acceleration and deceleration characteristics of passenger car in Federal Route FT050 Jalan Batu Pahat-Ayer Hitam that was the top ranking dangerous road. Global Positioning System was used to record 10 cars speed to develop speed profile with clustering zone. At the acceleration manoeuver, the acceleration rate becomes lower as the drivers get near to desired speed. While, at deceleration manoeuver, vehicles with high speed needs more time to stop compare to low speed vehicle. This is because, the drivers need to accelerate more from zero speed to achieve desired speed and drivers need more distance and time to stop their vehicles. However, it was found out that 30% to 50% are driving in dangerous condition that was proven in clustering acceleration and deceleration speed profile. As conclusion, this excessive drivers are the factor that creating high risk in rear-end collision that inline FT050 as dangerous road in Malaysia

  7. 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.

  8. Position-Specific Acceleration and Deceleration Profiles in Elite Youth and Senior Soccer Players.

    PubMed

    Vigh-Larsen, Jeppe F; Dalgas, Ulrik; Andersen, Thomas B

    2018-04-01

    Vigh-Larsen, JF, Dalgas, U, and Andersen, TB. Position-specific acceleration and deceleration profiles in elite youth and senior soccer players. J Strength Cond Res 32(4): 1114-1122, 2018-The purpose of the study was to characterize and compare the position-specific activity profiles of young and senior elite soccer players with special emphasis put on accelerations and decelerations. Eight professional senior matches were tracked using the ZXY tracking system and analyzed for the number of accelerations and decelerations and running distances within different speed zones. Likewise, 4 U19 and 5 U17 matches were analyzed for comparison between youth and senior players. In senior players, the total distance (TD) was 10,776 ± 107 m with 668 ± 28 and 143 ± 10 m being high-intensity running (HIR) and sprinting, respectively. Number of accelerations and decelerations were 81 ± 2 and 84 ± 3, respectively, with central defenders performing the lowest and wide players the highest number. Declines were found between first and second halves for accelerations and decelerations (11 ± 3%), HIR (6 ± 4%), and TD (5 ± 1%), whereas sprinting distance did not differ. U19 players performed a higher number of accelerations, decelerations, and TD compared with senior players. In conclusion, differences in the number and distribution of accelerations and decelerations appeared between player positions, which is of importance when monitoring training and match loads and when prescribing specific training exercises. Furthermore, youth players performed as much high-intensity activities as senior players, indicating that this is not a discriminating physiological parameter between these players.

  9. 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.

  10. Accelerated and decelerated expansion in a causal dissipative cosmology

    NASA Astrophysics Data System (ADS)

    Cruz, Miguel; Cruz, Norman; Lepe, Samuel

    2017-12-01

    In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic equation of state (EoS) p =ω ρ , in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form ξ =ξ0ρ1 /2. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, cb. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for ω , ξ0, cb accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions d S /d t >0 (growth of the entropy) and d2S /d t2<0 (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations.

  11. Braking and Propulsive Impulses Increase with Speed during Accelerated and Decelerated Walking

    PubMed Central

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

    2011-01-01

    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 ten 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 to 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. PMID:21356590

  12. Asymmetric acceleration/deceleration dynamics in heart rate variability

    NASA Astrophysics Data System (ADS)

    Alvarez-Ramirez, J.; Echeverria, J. C.; Meraz, M.; Rodriguez, E.

    2017-08-01

    The heart rate variability (HRV) is an important physiological signal used either to assess the risk of cardiac death or to model the cardiovascular regulatory dynamics. Asymmetries in HRV data have been observed using 2D Poincare plots, which have been linked to a non-equilibrium operation of the cardiac autonomic system. This work further explores the presence of asymmetries but in the serial correlations of the dynamics of HRV data. To this end, detrended fluctuation analysis (DFA) was used to estimate the Hurst exponent both when the heart rate is accelerating and when it is decelerating. The analysis is conducted using data collected from subjects under normal sinus rhythm (NSR), congestive heart failure (CHF) and atrial fibrillation (AF) . For the NSR cases, it was found that correlations are stronger (p < 0 . 05) when the heart rate is accelerating than when it is decelerating over different scales in the range 20-40 beats. In contrast, the opposite behavior was detected for the CHF and AF patients. Possible links between asymmetric correlations in the dynamics and the mechanisms controlling the operation of the heart rate are discussed, as well as their implications for modeling the cardiovascular regulatory dynamics.

  13. 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 25more » 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.« less

  14. Multistage Zeeman decelerator for molecular-scattering studies

    NASA Astrophysics Data System (ADS)

    Cremers, Theo; Chefdeville, Simon; Janssen, Niek; Sweers, Edwin; Koot, Sven; Claus, Peter; van de Meerakker, Sebastiaan Y. T.

    2017-04-01

    We present a concept for a multistage Zeeman decelerator that is optimized particularly for applications in molecular beam scattering experiments. The decelerator consists of a series of alternating hexapoles and solenoids, that effectively decouple the transverse focusing and longitudinal deceleration properties of the decelerator. It can be operated in a deceleration and acceleration mode, as well as in a hybrid mode that makes it possible to guide a particle beam through the decelerator at constant speed. The deceleration features phase stability, with a relatively large six-dimensional phase-space acceptance. The separated focusing and deceleration elements result in an unequal partitioning of this acceptance between the longitudinal and transverse directions. This is ideal in scattering experiments, which typically benefit from a large longitudinal acceptance combined with narrow transverse distributions. We demonstrate the successful experimental implementation of this concept using a Zeeman decelerator consisting of an array of 25 hexapoles and 24 solenoids. The performance of the decelerator in acceleration, deceleration, and guiding modes is characterized using beams of metastable helium (3S ) atoms. Up to 60% of the kinetic energy was removed for He atoms that have an initial velocity of 520 m/s. The hexapoles consist of permanent magnets, whereas the solenoids are produced from a single hollow copper capillary through which cooling liquid is passed. The solenoid design allows for excellent thermal properties and enables the use of readily available and cheap electronics components to pulse high currents through the solenoids. The Zeeman decelerator demonstrated here is mechanically easy to build, can be operated with cost-effective electronics, and can run at repetition rates up to 10 Hz.

  15. Effects of drop acceleration and deceleration on particle capture in a cross-flow gravity tower at intermediate drop Reynolds numbers.

    PubMed

    Kumar, Anoop; Gupta, S K; Kale, S R

    2007-04-01

    Cross-flow gravity towers are particle scrubbing devices in which water is sprayed from the top into particle-laden flow moving horizontally. Models for predicting particle capture assume drops traveling at terminal velocity and potential flow (ReD > 1000) around it, however, Reynolds numbers in the intermediate range of 1 to 1000 are common in gravity towers. Drops are usually injected at velocities greater than their terminal velocities (as in nozzles) or from near rest (perforated tray) and they accelerate/decelerate to their terminal velocity in the tower. Also, the effects of intermediate drop Reynolds number on capture efficiency have been simulated for (a) drops at their terminal velocity and (b) drops accelerating/decelerating to their terminal velocity. Tower efficiency based on potential flow about the drop is 40%-50% greater than for 200 mm drops traveling at their terminal velocity. The corresponding values for 500 mm drops are about 10%-20%. The drop injection velocity is important operating parameter. Increase in tower efficiency by about 40% for particles smaller than 5 mm is observed for increase in injection velocity from 0 to 20 m/s for 200 and 500mm drops.

  16. Unsteady forces on a spherical particle accelerating or decelerating in an initially stagnant fluid

    NASA Astrophysics Data System (ADS)

    Keshav, Yashas Mudlapur Phaneesh

    Flows with particles play an important role in a number of engineering applications. These include trajectories of droplets in sprays in fuel-injected-reciprocating-piston and gas-turbine engines, erosion of materials due to particle impact on a surface, and deposition of materials on surfaces by impinging droplets or particles that could solidify or bond on impact. For these applications, it is important to understand the forces that act on the particles so that their trajectories could be predicted. Considerable work has been done on understanding the forces acting on spherical particles, where the Reynolds numbers (Rep) based on the particle diameter and the relative speed between the particle and the fluid is less than unity. When Rep is larger than unity and when the particle is accelerating or decelerating, the added-mass effect and the Basset forces are not well understood. In this study, time-accurate numerical simulations were performed to study laminar incompressible flow induced by a single non-rotating rigid spherical particle that is accelerated or decelerated at a constant rate in an initially stagnant fluid, where the unsteady flow about the spherical particle is resolved. The Rep studied range from 0.01 to 100, and the acceleration number (Ac), where A c is the square of the relative velocity between the particle and the fluid divided by the acceleration times the particle diameter studied was in the range 2.13x-7 < |Ac |< 21337. Results obtained show the added mass effect for Rep up to 100 has the same functional form as those based on potential theory where the Rep is infinite and creeping flow where Rep is less than unity. The Basset force, however, differs considerably from those under creeping flow conditions and depends on Rep and the acceleration number (Ac). A model was developed to provide the magnitude of the added-mass effect and the Basset force in the range of Rep and Ac studied. Results obtained also show the effect of unsteadiness to

  17. 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.

  18. The effect of the acceleration/deceleration trauma in angioid streaks: A pathogenic hypothesis.

    PubMed

    Fajardo Sánchez, J; Chau Ramos, C E; Mazagatos Used, P J; Aparicio Hernandez-Lastras, M J

    2016-09-01

    A 59-year-old male with acceleration/deceleration cranial trauma (ADT), caused by a car accident. After one month, he presented with loss of visual acuity in the right eye. A fluorescein angiography test was performed and it detected centrifugal hyperfluorescent lines from the optic nerve head, a characteristic compatible with the diagnosis of angioid streaks. The loss of visual acuity was demonstrated by the discovery of a juxtafoveal choroidal neovascular membrane (CNV). ADT can cause hyper-extension of the eyeball in its equator line, producing the rupture of fragile structures such as the Bruch membrane (MB) in patients with angioid streaks and the subsequent formation of CNV. Copyright © 2016 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

  19. Slip Ratio Estimation and Regenerative Brake Control for Decelerating Electric Vehicles without Detection of Vehicle Velocity and Acceleration

    NASA Astrophysics Data System (ADS)

    Suzuki, Toru; Fujimoto, Hiroshi

    In slip ratio control systems, it is necessary to detect the vehicle velocity in order to obtain the slip ratio. However, it is very difficult to measure this velocity directly. We have proposed slip ratio estimation and control methods that do not require the vehicle velocity with acceleration. In this paper, the slip ratio estimation and control methods are proposed without detecting the vehicle velocity and acceleration when it is decelerating. We carried out simulations and experiments by using an electric vehicle to verify the effectiveness of the proposed method.

  20. 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Effects of Vertical Direction and Aperture Size on the Perception of Visual Acceleration.

    PubMed

    Mueller, Alexandra S; González, Esther G; McNorgan, Chris; Steinbach, Martin J; Timney, Brian

    2016-02-06

    It is not well understood whether the distance over which moving stimuli are visible affects our sensitivity to the presence of acceleration or our ability to track such stimuli. It is also uncertain whether our experience with gravity creates anisotropies in how we detect vertical acceleration and deceleration. To address these questions, we varied the vertical extent of the aperture through which we presented vertically accelerating and decelerating random dot arrays. We hypothesized that observers would better detect and pursue accelerating and decelerating stimuli that extend over larger than smaller distances. In Experiment 1, we tested the effects of vertical direction and aperture size on acceleration and deceleration detection accuracy. Results indicated that detection is better for downward motion and for large apertures, but there is no difference between vertical acceleration and deceleration detection. A control experiment revealed that our manipulation of vertical aperture size affects the ability to track vertical motion. Smooth pursuit is better (i.e., with higher peak velocities) for large apertures than for small apertures. Our findings suggest that the ability to detect vertical acceleration and deceleration varies as a function of the direction and vertical extent over which an observer can track the moving stimulus. © The Author(s) 2016.

  2. 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.

  3. From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB

    SciTech Connect

    Giostri, R.; Santos, M. Vargas dos; Waga, I.

    2012-03-01

    We use type Ia supernovae (SN Ia) data in combination with recent baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) observations to constrain a kink-like parametrization of the deceleration parameter (q). This q-parametrization can be written in terms of the initial (q{sub i}) and present (q{sub 0}) values of the deceleration parameter, the redshift of the cosmic transition from deceleration to acceleration (z{sub t}) and the redshift width of such transition (τ). By assuming a flat space geometry, q{sub i} = 1/2 and adopting a likelihood approach to deal with the SN Ia data we obtain, at the 68%more » confidence level (C.L.), that: z{sub t} = 0.56{sup +0.13}{sub −0.10}, τ = 0.47{sup +0.16}{sub −0.20} and q{sub 0} = −0.31{sup +0.11}{sub −0.11} when we combine BAO/CMB observations with SN Ia data processed with the MLCS2k2 light-curve fitter. When in this combination we use the SALT2 fitter we get instead, at the same C.L.: z{sub t} = 0.64{sup +0.13}{sub −0.07}, τ = 0.36{sup +0.11}{sub −0.17} and q{sub 0} = −0.53{sup +0.17}{sub −0.13}. Our results indicate, with a quite general and model independent approach, that MLCS2k2 favors Dvali-Gabadadze-Porrati-like cosmological models, while SALT2 favors ΛCDM-like ones. Progress in determining the transition redshift and/or the present value of the deceleration parameter depends crucially on solving the issue of the difference obtained when using these two light-curve fitters.« less

  4. 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.

  5. The cost of transport of human running is not affected, as in walking, by wide acceleration/deceleration cycles.

    PubMed

    Minetti, Alberto E; Gaudino, Paolo; Seminati, Elena; Cazzola, Dario

    2013-02-15

    Although most of the literature on locomotion energetics and biomechanics is about constant-speed experiments, humans and animals tend to move at variable speeds in their daily life. This study addresses the following questions: 1) how much extra metabolic energy is associated with traveling a unit distance by adopting acceleration/deceleration cycles in walking and running, with respect to constant speed, and 2) how can biomechanics explain those metabolic findings. Ten males and ten females walked and ran at fluctuating speeds (5 ± 0, ± 1, ± 1.5, ± 2, ± 2.5 km/h for treadmill walking, 11 ± 0, ± 1, ± 2, ± 3, ± 4 km/h for treadmill and field running) in cycles lasting 6 s. Field experiments, consisting of subjects following a laser spot projected from a computer-controlled astronomic telescope, were necessary to check the noninertial bias of the oscillating-speed treadmill. Metabolic cost of transport was found to be almost constant at all speed oscillations for running and up to ±2 km/h for walking, with no remarkable differences between laboratory and field results. The substantial constancy of the metabolic cost is not explained by the predicted cost of pure acceleration/deceleration. As for walking, results from speed-oscillation running suggest that the inherent within-stride, elastic energy-free accelerations/decelerations when moving at constant speed work as a mechanical buffer for among-stride speed fluctuations, with no extra metabolic cost. Also, a recent theory about the analogy between sprint (level) running and constant-speed running on gradients, together with the mechanical determinants of gradient locomotion, helps to interpret the present findings.

  6. Decelerations of Parachute Opening Shock in Skydivers.

    PubMed

    Gladh, Kristofer; Lo Martire, Riccardo; Äng, Björn O; Lindholm, Peter; Nilsson, Jenny; Westman, Anton

    2017-02-01

    High prevalence of neck pain among skydivers is related to parachute opening shock (POS) exposure, but few investigations of POS deceleration have been made. Existing data incorporate equipment movements, limiting its representability of skydiver deceleration. This study aims to describe POS decelerations and compare human- with equipment-attached data. Wearing two triaxial accelerometers placed on the skydiver (neck-sensor) and equipment (rig-sensor), 20 participants made 2 skydives each. Due to technical issues, data from 35 skydives made by 19 participants were collected. Missing data were replaced using data substitution techniques. Acceleration axes were defined as posterior to anterior (+ax), lateral right (+ay), and caudal to cranial (+az). Deceleration magnitude [amax (G)] and jerks (G · s-1) during POS were analyzed. Two distinct phases related to skydiver positioning and acceleration direction were observed: 1) the x-phase (characterized by -ax, rotating the skydiver); and 2) the z-phase (characterized by +az, skydiver vertically oriented). Compared to the rig-sensor, the neck-sensor yielded lower amax (3.16 G vs. 6.96 G) and jerk (56.3 G · s-1 vs. 149.0 G · s-1) during the x-phase, and lower jerk (27.7 G · s-1 vs. 54.5 G · s-1) during the z-phase. The identified phases during POS should be considered in future neck pain preventive strategies. Accelerometer data differed, suggesting human-placed accelerometry to be more valid for measuring human acceleration.Gladh K, Lo Martire R, Äng BO, Lindholm P, Nilsson J, Westman A. Decelerations of parachute opening shock in skydivers. Aerosp Med Hum Perform. 2017; 88(2):121-127.

  7. Effects of deceleration and rate of deceleration on live seated human subjects

    DOT National Transportation Integrated Search

    1977-10-01

    This report describes the testing of live, seated human subjects to determine : the maximum deceleration and associated rate of change of deceleration (jerk) at : which the majority of potential users of automated guideway transportation (ACT) : syst...

  8. GDP-GTP exchange processes of G{alpha}i1 protein are accelerated/decelerated depending on the type and the concentration of added detergents.

    PubMed

    Kubota, Makoto; Tanaka, Takeshi; Kohno, Toshiyuki; Wakamatsu, Kaori

    2009-12-01

    Although detergents have been widely used in G-protein studies to increase solubility and stability of the protein, we noticed that detergents modulate the nucleotide-binding properties of G-proteins. Hence, we analysed the effects of detergents on guanine nucleotide exchange reactions of Galpha(i1). Lubrol PX, a non-ionic detergent, which has been widely used in nucleotide dissociation/binding assays, was found to accelerate both GDP dissociation and GTPgammaS binding from/to Galpha in parallel at above its critical micelle concentration (cmc). Sodium cholate, an anionic detergent, which have been used to extract G-proteins from animal tissues, decelerated and accelerated GDP dissociation below and above its cmc, respectively. Surprisingly, micellar cholate decelerated GTPgammaS binding, and the binding rate constant was decreased by three orders of magnitude in the presence of 2% cholate. These results demonstrate that the guanine nucleotide exchange reactions of Galpha(i1) are drastically modulated by detergents differently depending on the type and the state (monomeric or micellar) of the detergents and that dissociation of GDP from Galpha(i1) does not necessarily lead to immediate binding of GTP to Galpha(i1) in some cases. These effects of detergents on G-proteins must be taken into account in G-protein experiments.

  9. Brain sparing effect in growth-restricted fetuses is associated with decreased cardiac acceleration and deceleration capacities: a case-control study.

    PubMed

    Stampalija, T; Casati, D; Monasta, L; Sassi, R; Rivolta, M W; Muggiasca, M L; Bauer, A; Ferrazzi, E

    2016-11-01

    Phase rectified signal averaging (PRSA) is a new method of fetal heart rate variability (fHRV) analysis that quantifies the average acceleration (AC) and deceleration capacity (DC) of the heart. The aim of this study was to evaluate AC and DC of fHR [recorded by trans-abdominal fetal electrocardiogram (ta-fECG)] in relation to Doppler velocimetry characteristics of intrauterine growth restriction (IUGR). Prospective case-control study. Single third referral centre. IUGR (n = 66) between 25 and 40 gestational weeks and uncomplicated pregnancies (n = 79). In IUGR the nearest ta-fECG monitoring to delivery was used for PRSA analysis and Doppler velocimetry parameters obtained within 48 hours. AC and DC were computed at s = T = 9. The relation was evaluated between either AC or DC and Doppler velocimetry parameters adjusting for gestational age at monitoring, as well as the association between either AC or DC and IUGR with or without brain sparing. In IUGRs there was a significant association between either AC and DC and middle cerebral artery pulsatility index (PI; P = 0.01; P = 0.005), but the same was not true for uterine or umbilical artery PI (P > 0.05). Both IUGR fetuses with and without brain sparing had lower AC and DC than controls, but this association was stronger for IUGRs with brain sparing. Our study observed for the first time that AC and DC at PRSA analysis are associated with middle cerebral artery PI, but not with uterine or umbilical artery PI, and that there is a significant decrease of AC and DC in association with brain sparing in IUGR fetuses from 25 weeks of gestation to term. Brain sparing in IUGR fetuses is associated with decreased acceleration and deceleration capacities of the heart. © 2015 Royal College of Obstetricians and Gynaecologists.

  10. 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.

  11. 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.

  12. Decelerated medical education.

    PubMed

    McGrath, Brian; McQuail, Diane

    2004-09-01

    The aim of the study was to obtain information regarding the prevalence, structure, student characteristics and outcomes of formal decelerated medical education programs. A 13-item survey was mailed to all US medical schools examining characteristics of decelerated curricular programs. Responses were received from 77 schools (62% response). Some 24 (31%) indicated a formal decelerated option; 13 (57%) decelerate the first year while four (17%) decelerate year 1 or year 2. Participants may be selected before matriculation or after difficulty in 14 (61%) programs while four (17%) select only after encountering difficulty. Students may unilaterally choose deceleration in 10 (43%); 4.3% (0.1-12) of total matriculants were decelerated. The proportion of decelerated students identified as underrepresented minority (URM) was 37% (0-100), representing 10.5% (0-43) of total URM enrollment. Twelve (52%) programs do not provide unique support beyond deceleration. Standards for advancement are identical for decelerated and regular students in 17 schools (81%). In total, 10% (0-100) of decelerated students were dismissed within the last five years, representing 24% (0-90) of all dismissals. Few schools provided grade point average (GPA) or Medical College Admissions Test (MCAT) data but the limited responses indicate that many decelerated students are at risk for academic difficulty. It is concluded that decelerated curricular options are available at a significant number of US medical schools. Decelerated students comprise a small proportion of total enrollment but URM matriculants represent a disproportionate share of participants. Decelerated programs appear to be successful as measured by dismissal rates if one accepts attrition which exceeds that for regular MD students. Variation in dismissal rates is difficult to interpret given the lack of GPA and MCAT data. One half of all programs offer no additional support activities beyond deceleration. More data are needed to

  13. On the electrostatic deceleration of argon atoms in high Rydberg states by time-dependent inhomogeneous electric fields

    NASA Astrophysics Data System (ADS)

    Vliegen, E.; Merkt, F.

    2005-06-01

    Argon atoms in a pulsed supersonic expansion are prepared in selected Stark components of Rydberg states with effective principal quantum number in the range n* = 15-25. When traversing regions of inhomogeneous electric fields, these atoms get accelerated or decelerated depending on whether the Stark states are low- or high-field seeking states. Using a compact electrode design, which enables the application of highly inhomogeneous and time-dependent electric fields, the Rydberg atoms experience kinetic energy changes of up to 1.2 × 10-21 J (i.e. 60 cm-1 in spectroscopic units) in a single acceleration/deceleration stage of 3 mm length. The resulting differences in the velocities of the low- and high-field seeking states are large enough that the corresponding distributions of times of flight to the Rydberg particle detector are fully separated. As a result, efficient spectral searches of the Rydberg states best suited for acceleration/deceleration experiments are possible. Numerical simulations of the particle trajectories are used to analyse the time-of-flight distributions and to optimize the time dependence of the inhomogeneous electric fields. The decay of the Rydberg states by fluorescence, collisions and transitions induced by black-body radiation takes place on a timescale long enough not to interfere significantly with the deceleration during the first ~5 µs.

  14. 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.

  15. The crystal acceleration effect for cold neutrons

    SciTech Connect

    Braginetz, Yu. P., E-mail: aiver@pnpi.spb.ru; Berdnikov, Ya. A.; Fedorov, V. V., E-mail: vfedorov@pnpi.spb.ru

    A new mechanism of neutron acceleration is discussed and studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron-crystal interaction potential) for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal-neutron relative velocity. Therefore the neutrons enter into accelerated crystal with one neutron-crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to itsmore » homogeneity. So after passage through such a crystal neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.« less

  16. 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.

  17. Optimization of vehicle deceleration to reduce occupant injury risks in frontal impact.

    PubMed

    Mizuno, Koji; Itakura, Takuya; Hirabayashi, Satoko; Tanaka, Eiichi; Ito, Daisuke

    2014-01-01

    In vehicle frontal impacts, vehicle acceleration has a large effect on occupant loadings and injury risks. In this research, an optimal vehicle crash pulse was determined systematically to reduce injury measures of rear seat occupants by using mathematical simulations. The vehicle crash pulse was optimized based on a vehicle deceleration-deformation diagram under the conditions that the initial velocity and the maximum vehicle deformation were constant. Initially, a spring-mass model was used to understand the fundamental parameters for optimization. In order to investigate the optimization under a more realistic situation, the vehicle crash pulse was also optimized using a multibody model of a Hybrid III dummy seated in the rear seat for the objective functions of chest acceleration and chest deflection. A sled test using a Hybrid III dummy was carried out to confirm the simulation results. Finally, the optimal crash pulses determined from the multibody simulation were applied to a human finite element (FE) model. The optimized crash pulse to minimize the occupant deceleration had a concave shape: a high deceleration in the initial phase, low in the middle phase, and high again in the final phase. This crash pulse shape depended on the occupant restraint stiffness. The optimized crash pulse determined from the multibody simulation was comparable to that from the spring-mass model. From the sled test, it was demonstrated that the optimized crash pulse was effective for the reduction of chest acceleration. The crash pulse was also optimized for the objective function of chest deflection. The optimized crash pulse in the final phase was lower than that obtained for the minimization of chest acceleration. In the FE analysis of the human FE model, the optimized pulse for the objective function of the Hybrid III chest deflection was effective in reducing rib fracture risks. The optimized crash pulse has a concave shape and is dependent on the occupant restraint

  18. Enveloping Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Nock, Kerry T. (Inventor); Aaron, Kim M. (Inventor); McRonald, Angus D. (Inventor); Gates, Kristin L. (Inventor)

    2018-01-01

    An inflatable aerodynamic deceleration method and system is provided for use with an atmospheric entry payload. The inflatable aerodynamic decelerator includes an inflatable envelope and an inflatant, wherein the inflatant is configured to fill the inflatable envelope to an inflated state such that the inflatable envelope surrounds the atmospheric entry payload, causing aerodynamic forces to decelerate the atmospheric entry payload.

  19. 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.

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

    SciTech Connect

    Wang, L. F., E-mail: wang-lifeng@iapcm.ac.cn; Ye, W. H.; Liu, Jie

    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.

  1. Accelerated acidosis in response to variable fetal heart rate decelerations in chronically hypoxic ovine fetuses.

    PubMed

    Amaya, Kevin E; Matushewski, Brad; Durosier, L Daniel; Frasch, Martin G; Richardson, Bryan S; Ross, Michael G

    2016-02-01

    Due to limitations of technology, clinicians are typically unable to determine if human fetuses are normoxic or moderately, chronically hypoxic. Risk factors for chronic hypoxia include fetal growth restriction, which is associated with an increased incidence of oligohydramnios and thus a risk for umbilical cord occlusion (UCO) and variable fetal heart rate (FHR) decelerations. At delivery, fetal growth restriction infants (<3rd percentile) have nearly twice the incidence of low Apgar scores and umbilical pH <7.0. Despite the risks of oligohydramnios and intermittent UCO, there is little understanding of the acid/base responses rates of chronically hypoxic fetuses to variable FHR decelerations as might occur during human labor. We sought to compare the increase in base deficit (BD) among chronically hypoxic as compared to normoxic ovine fetuses in response to simulated mild, moderate, and severe variable FHR decelerations. Near-term ovine fetuses were chronically prepared with brachial artery catheters and an inflatable umbilical cuff occluder. Following a recovery period, normoxic (n = 9) and spontaneously hypoxic (n = 5) fetuses were identified (arterial O2 saturation ≤55%). Both animal groups underwent graded, 1-minute occlusions every 2.5 minutes with 1 hour of mild (∼30 beats/min [bpm] decrease from baseline), 1 hour of moderate (∼60 bpm decrease from baseline), and up to 2 hours of severe (∼90 bpm decrease from baseline) variable FHR decelerations until fetal arterial pH reached 7.00, when occlusions were stopped. Repetitive UCO resulted in development of acidosis (pH <7.0) in both groups. Hypoxic and normoxic fetuses demonstrated similar BD increases in response to both mild (0.39, interquartile range [IQR] 0.28-0.45 vs 0.26, IQR 0.01-0.30 mEq/L/10 min, P = .25) and severe (1.97, IQR 1.50-2.43 vs 1.51, IQR 0.97-2.45 mEq/L/10 min, P = .63) variable decelerations. However, moderate variable decelerations increased BD in hypoxic fetuses at 2.5 times the

  2. The impact of surfactants on Fe(III)-TAML-catalyzed oxidations by peroxides: accelerations, decelerations, and loss of activity.

    PubMed

    Banerjee, Deboshri; Apollo, Frank M; Ryabov, Alexander D; Collins, Terrence J

    2009-10-05

    Iron(III) complexes of tetraamidato macrocyclic ligands (TAMLs), [Fe{4-XC(6)H(3)-1,2-(NCOCMe(2)NCO)(2)CR(2)}(OH(2))](-), 1 (1 a: X = H, R = Me; 1 b: X = COOH, R = Me); 1 c: X = CONH(CH(2))(2)COOH, R = Me; 1 d: CONH(CH(2))(2)NMe(2), R = Me; 1 e: X = CONH(CH(2))(2)NMe(3) (+), R = Me; 1 f: X = H, R = F), have been tested as catalysts for the oxidative decolorization of Orange II and Sudan III dyes by hydrogen peroxide and tert-butyl hydroperoxide in the presence of micelles that are neutral (Triton X-100), positively charged (cetyltrimethylammonium bromide, CTAB), and negatively charged (sodium dodecyl sulfate, SDS). The previously reported mechanism of catalysis involves the formation of an oxidized intermediate from 1 and ROOH (k(I)) followed by dye bleaching (k(II)). The micellar effects on k(I) and k(II) have been separately studied and analyzed by using the Berezin pseudophase model of micellar catalysis. The largest micellar acceleration in terms of k(I) occurs for the 1 a-tBuOOH-CTAB system. At pH 9.0-10.5 the rate constant k(I) increased by approximately five times with increasing CTAB concentration and then gradually decreased. There was no acceleration at higher pH, presumably owing to the deprotonation of the axial water ligand of 1 a in this pH range. The k(I) value was only slightly affected by SDS (in the oxidation of Orange II), but was strongly decelerated by Triton X-100. No oxidation of the water-insoluble, hydrophobic dye Sudan III was observed in the presence of the SDS micelles. The k(II) value was accelerated by cationic CTAB micelles when the hydrophobic primary oxidant tert-butyl hydroperoxide was used. It is hypothesized that tBuOOH may affect the CTAB micelles and increase the binding of the oxidized catalysts. The tBuOOH-CTAB combination accelerated both of the catalysis steps k(I) and k(II).

  3. 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. Copyright © 2014 the authors 0270-6474/14/348488-11$15.00/0.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

    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. Hbar 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. Hbar 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.

  6. Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

    SciTech Connect

    Santos, M. Vargas dos; Reis, R.R.R.; Waga, I., E-mail: vargas@if.ufrj.br, E-mail: ribamar@if.ufrj.br, E-mail: ioav@if.ufrj.br

    2016-02-01

    We revisit the kink-like parametrization of the deceleration parameter q(z) [1], which considers a transition, at redshift z{sub t}, from cosmic deceleration to acceleration. In this parametrization the initial, at z >> z{sub t}, value of the q-parameter is q{sub i}, its final, z=−1, value is q{sub f} and the duration of the transition is parametrized by τ. By assuming a flat space geometry we obtain constraints on the free parameters of the model using recent data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and the Hubble parameter H(z). The use of H(z) data introducesmore » an explicit dependence of the combined likelihood on the present value of the Hubble parameter H{sub 0}, allowing us to explore the influence of different priors when marginalizing over this parameter. We also study the importance of the CMB information in the results by considering data from WMAP7, WMAP9 (Wilkinson Microwave Anisotropy Probe—7 and 9 years) and Planck 2015. We show that the contours and best fit do not depend much on the different CMB data used and that the considered new BAO data is responsible for most of the improvement in the results. Assuming a flat space geometry, q{sub i}=1/2 and expressing the present value of the deceleration parameter q{sub 0} as a function of the other three free parameters, we obtain z{sub t}=0.67{sup +0.10}{sub −0.08}, τ=0.26{sup +0.14}{sub −0.10} and q{sub 0}=−0.48{sup +0.11}{sub −0.13}, at 68% of confidence level, with an uniform prior over H{sub 0}. If in addition we fix q{sub f}=−1, as in flat ΛCDM, DGP and Chaplygin quartessence that are special models described by our parametrization, we get z{sub t}=0.66{sup +0.03}{sub −0.04}, τ=0.33{sup +0.04}{sub −0.04} and q{sub 0}=−0.54{sup +0.05}{sub −0.07}, in excellent agreement with flat ΛCDM for which τ=1/3. We also obtain for flat wCDM, another dark energy model described by our parametrization, the

  7. Stopping power: Effect of the projectile deceleration

    SciTech Connect

    Kompaneets, Roman, E-mail: kompaneets@mpe.mpg.de; 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 ismore » due to the protons.« less

  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. Designing cylindrical implosion experiments on NIF to study deceleration phase of Rayleigh-Taylor

    NASA Astrophysics Data System (ADS)

    Vazirani, N.; Kline, J. L.; Loomis, E.; Sauppe, J. P.; Palaniyappan, S.; Flippo, K.; Srinivasan, B.; Malka, E.; Bose, A.; Shvarts, D.

    2017-10-01

    The Rayleigh-Taylor (RT) hydrodynamic instability occurs when a lower density fluid pushes on a higher density fluid. This occurs in inertial confinement fusion (ICF) implosions at each of the capsule interfaces during the initial acceleration and the deceleration as it stagnates. The RT instabilities mix capsule material into the fusion fuel degrading the Deuterium-Tritium reactivity and ultimately play a key role in limiting target performance. While significant effort has focused on understanding RT at the outer capsule surface, little work has gone into understanding the inner surface RT instability growth during the deceleration phase. Direct measurements of the RT instability are difficult to make at high convergence in a spherical implosion. Here we present the design of a cylindrical implosion system for the National Ignition Facility for studying deceleration phase RT. We will discuss the experimental design, the estimated instability growth, and our outstanding concerns.

  10. Collective Deceleration: Toward a Compact Beam Dump

    SciTech Connect

    Wu, H.-C.; /Munich, Max Planck Inst. Quantenopt.; Tajima, T.

    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 themore » 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.« less

  11. C IV BROAD ABSORPTION LINE ACCELERATION IN SLOAN DIGITAL SKY SURVEY QUASARS

    SciTech Connect

    Grier, C. J.; Brandt, W. N.; Trump, J. R.

    2016-06-20

    We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ≈2.5–5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The C iv BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows amore » velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for 76 additional BAL troughs and find that the majority of BALs are stable to within about 3% of their mean velocities. The lack of widespread acceleration/deceleration could indicate that the gas producing most BALs is located at large radii from the central black hole and/or is not currently strongly interacting with ambient material within the host galaxy along our line of sight.« less

  12. Randomized trial of intermittent or continuous amnioinfusion for variable decelerations.

    PubMed

    Rinehart, B K; Terrone, D A; Barrow, J H; Isler, C M; Barrilleaux, P S; Roberts, W E

    2000-10-01

    To determine whether continuous or intermittent bolus amnioinfusion is more effective in relieving variable decelerations. Patients with repetitive variable decelerations were randomized to an intermittent bolus or continuous amnioinfusion. The intermittent bolus infusion group received boluses of 500 mL of normal saline, each over 30 minutes, with boluses repeated if variable decelerations recurred. The continuous infusion group received a bolus infusion of 500 mL of normal saline over 30 minutes and then 3 mL per minute until delivery occurred. The ability of the amnioinfusion to abolish variable decelerations was analyzed, as were maternal demographic and pregnancy outcome variables. Power analysis indicated that 64 patients would be required. Thirty-five patients were randomized to intermittent infusion and 30 to continuous infusion. There were no differences between groups in terms of maternal demographics, gestational age, delivery mode, neonatal outcome, median time to resolution of variable decelerations, or the number of times variable decelerations recurred. The median volume infused in the intermittent infusion group (500 mL) was significantly less than that in the continuous infusion group (905 mL, P =.003). Intermittent bolus amnioinfusion is as effective as continuous infusion in relieving variable decelerations in labor. Further investigation is necessary to determine whether either of these techniques is associated with increased occurrence of rare complications such as cord prolapse or uterine rupture.

  13. Predictive value of late decelerations for fetal acidemia in unselective low-risk pregnancies.

    PubMed

    Sameshima, Hiroshi; Ikenoue, Tsuyomu

    2005-01-01

    We evaluated the clinical significance of late decelerations (LD) of intrapartum fetal heart rate (FHR) monitoring to detect low pH (< 7.1) in low-risk pregnancies. We selected two secondary and two tertiary-level institutions where 10,030 women delivered. Among them, 5522 were low-risk pregnancies. The last 2 hours of FHR patterns before delivery were interpreted according to the guidelines of the National Institute of Child Health and Human Development. The correlation between the incidence of LD (occasional, < 50%; recurrent, > or = 50%) and severity (reduced baseline FHR accelerations and variability) of LD, and low pH (< 7.1) were evaluated. Statistical analyses included a contingency table with chi2 and the Fisher test, and one-way analysis of variance with the Bonferroni/Dunn test. In the 5522 low-risk pregnancies, 301 showed occasional LD and 99 showed recurrent LD. Blood gases and pH values deteriorated as the incidence of LD increased and as baseline accelerations or variability was decreased. Positive predictive value for low pH (< 7.1) was exponentially elevated from 0% at no deceleration, 1% in occasional LD, and > 50% in recurrent LD with no baseline FHR accelerations and reduced variability. In low-risk pregnancies, information on LD combined with acceleration and baseline variability enables us to predict the potential incidence of fetal acidemia.

  14. Impact accelerations

    NASA Technical Reports Server (NTRS)

    Vongierke, H. E.; Brinkley, J. W.

    1975-01-01

    The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

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

    DOE PAGES

    O’Shea, B. D.; Andonian, G.; Barber, S. K.; ...

    2016-09-14

    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 cmmore » 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. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.« less

  16. 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

  17. Preferential acceleration and magnetic field enhancement in plasmas with e{sup +}/e{sup −} beam injection

    SciTech Connect

    Huynh, Cong Tuan; Ryu, Chang-Mo, E-mail: ryu201@postech.ac.kr

    A theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e{sup +}/e{sup −} beam injection is presented. When the e{sup +}/e{sup −} 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{sup +} beam particles are preferentially accelerated, while the e{sup −} beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e{sup +}/e{sup −} plasma.more » 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{sup +}/e{sup −} beam injection.« less

  18. Deceleration-Limiting Roadway Barrier

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, P. James (Inventor)

    2006-01-01

    Roadway barrier system and method are disclosed for decelerating a moving vehicle in a controlled manner and for retaining the decelerated vehicle. A net or mesh of the roadway barrier system receives and captures the moving vehicle. The net or mesh is secured to anchors by energy absorbing straps. The energy absorbing straps deploy under a tensional load to decelerate the moving vehicle, the straps providing a controlled resistance to the tensional load over a predefined displacement or stroke to bring the moving vehicle to rest. Additional features include a sacrificial panel or sheet in front of the net that holds up the net or mesh while deflecting vehicles that collide only tangentially with the roadway barrier system.

  19. Turbulent pipe flows subjected to temporal decelerations

    NASA Astrophysics Data System (ADS)

    Jeong, Wongwan; Lee, Jae Hwa

    2016-11-01

    Direct numerical simulations of temporally decelerating turbulent pipe flows were performed to examine effects of temporal decelerations on turbulence. The simulations were started with a fully developed turbulent pipe flow at a Reynolds number, ReD =24380, based on the pipe radius (R) and the laminar centerline velocity (Uc 0). Three different temporal decelerations were imposed to the initial flow with f= | d Ub / dt | =0.00127, 0.00625 and 0.025, where Ub is the bulk mean velocity. Comparison of Reynolds stresses and turbulent production terms with those for steady flow at a similar Reynolds number showed that turbulence is highly intensified with increasing f due to delay effects. Furthermore, inspection of the Reynolds shear stress profiles showed that strong second- and fourth-quadrant Reynolds shear stresses are greatly increased, while first- and third-quadrant components are also increased. Decomposition of streamwise Reynolds normal stress with streamwise cutoff wavelength (λx) 1 R revealed that the turbulence delay is dominantly originated from delay of strong large-scale turbulent structures in the outer layer, although small-scale motions throughout the wall layer adjusted more rapidly to the temporal decelerations. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2014R1A1A2057031).

  20. Deceleration system for kinematic linkages of positioning

    NASA Astrophysics Data System (ADS)

    Stan, G.

    2017-08-01

    Flexible automation is used more and more in various production processes, so that both machining itself on CNC machine tools and workpiece handling means are performed through programming the needed working cycle. In order to obtain a successful precise positioning, each motion degree needs a certain deceleration before stopping at a programmed point. The increase of motion speed of moving elements within the manipulators structure depends directly on deceleration duty quality before the programmed stop. Proportional valves as well as servo-valves that can perform hydraulic decelerations are well known, but they feature several disadvantages, such as: high price, severe conditions for oil filtering and low reliability under industrial conditions. This work presents a new deceleration system that allows adjustment of deceleration slope according to actual conditions: inertial mass, speed etc. The new solution of hydraulic decelerator allows its integration to a position loop or its usage in case of positioning large elements that only perform fixed cycles. The results being obtained on the positioning accuracy of a linear axis using the new solution of the hydraulic decelerator are presented, too. The price of the new deceleration system is much lower compared to the price of proportional valves or servo-valves.

  1. Will there be again a transition from acceleration to deceleration in course of the dark energy evolution of the universe?

    NASA Astrophysics Data System (ADS)

    Pan, Supriya; Chakraborty, Subenoy

    2013-09-01

    In this work we consider the evolution of the interactive dark fluids in the background of homogeneous and isotropic FRW model of the universe. The dark fluids consist of a warm dark matter and a dark energy and both are described as perfect fluid with barotropic equation of state. The dark species interact non-gravitationally through an additional term in the energy conservation equations. An autonomous system is formed in the energy density spaces and fixed points are analyzed. A general expression for the deceleration parameter has been obtained and it is possible to have more than one zero of the deceleration parameter. Finally, vanishing of the deceleration parameter has been examined with some examples.

  2. Energy recapture through deceleration - regenerative braking in electric vehicles from a user perspective.

    PubMed

    Cocron, Peter; Bühler, Franziska; Franke, Thomas; Neumann, Isabel; Dielmann, Benno; Krems, Josef F

    2013-01-01

    We report results from a 1-year field study (N = 80) on user interactions with regenerative braking in electric vehicles. Designed to recapture energy in vehicles with electric powertrains, regenerative braking has an important influence on both the task of driving and energy consumption. Results from user assessments and data from onboard data loggers indicate that most drivers quickly learned to interact with the system, which was triggered via accelerator. Further, conventional braking manoeuvres decreased significantly as the majority of deceleration episodes could only be executed through regenerative braking. Still, some drivers reported difficulties when adapting to the system. These difficulties could be addressed by offering different levels of regeneration so that the intensity of the deceleration could be individually modified. In general, the system is trusted and regarded as a valuable tool for prolonging range. Regenerative braking in electric vehicles has direct implications for the driving task. We found that drivers quickly learn to use and accept a system, which is triggered via accelerator. For those reporting difficulties in the interaction, it appears reasonable to integrate options to customise or switch off the system.

  3. Continuous all-optical deceleration of molecular beams and demonstration with Rb atoms

    NASA Astrophysics Data System (ADS)

    Long, Xueping; Jayich, Andrew; Campbell, Wesley

    2017-04-01

    Ultracold samples of molecules are desirable for a variety of applications, such as many-body physics, precision measurement and quantum information science. However, the pursuit of ultracold molecules has achieved limited success: spontaneous emission into many different dark states makes it hard to optically decelerate molecules to trappable speed. We propose to address this problem with a general optical deceleration technique that exploits a pump-dump pulse pair from a mode-locked laser. A molecular beam is first excited by a counter-propagating ``pump'' pulse. The molecular beam is then driven back to the initial ground state by a co-propagating ``dump'' pulse via stimulated emission. The delay between the pump and dump pulse is set to be shorter than the excited state lifetimes in order to limit decays to dark states. We report progress benchmarking this stimulated force by accelerating a cold sample of neutral Rb atoms.

  4. Task-control of arousal and the effects of repeated unidirectional angular acceleration on human vestibular responses.

    DOT National Transportation Integrated Search

    1963-11-01

    Subjects were exposed to a 10-day habituation series of 200 CW accelerations in total darkness while performing attention-demanding tasks. Decelerations were sub-threshold. Preliminary and post-tests indicated that slow-phase nystagmus and duration o...

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Low Density Supersonic Decelerator Flight Dynamics Test-1 Flight Design and Targeting

    NASA Technical Reports Server (NTRS)

    Ivanov, Mark

    2015-01-01

    NASA's Low Density Supersonic Decelerator (LDSD) program was established to identify, develop, and eventually qualify to Test [i.e. Technology] Readiness Level (TRL) - 6 aerodynamic decelerators for eventual use on Mars. Through comprehensive Mars application studies, two distinct Supersonic Inflatable Aerodynamic Decelerator (SIAD) designs were chosen that afforded the optimum balance of benefit, cost, and development risk. In addition, a Supersonic Disk Sail (SSDS) parachute design was chosen that satisfied the same criteria. The final phase of the multi-tiered qualification process involves Earth Supersonic Flight Dynamics Tests (SFDTs) within environmental conditions similar to those that would be experienced during a Mars Entry, Descent, and Landing (EDL) mission. The first of these flight tests (i.e. SFDT-1) was completed on June 28, 2014 with two more tests scheduled for the summer of 2015 and 2016, respectively. The basic flight design for all the SFDT flights is for the SFDT test vehicle to be ferried to a float altitude of 120 kilo-feet by a 34 thousand cubic feet (Mcf) heavy lift helium balloon. Once float altitude is reached, the test vehicle is released from the balloon, spun-up for stability, and accelerated to supersonic speeds using a Star48 solid rocket motor. After burnout of the Star48 motor the vehicle decelerates to pre-flight selected test conditions for the deployment of the SIAD system. After further deceleration with the SIAD deployed, the SSDS parachute is then deployed stressing the performance of the parachute in the wake of the SIAD augmented blunt body. The test vehicle/SIAD/parachute system then descends to splashdown in the Pacific Ocean for eventual recovery. This paper will discuss the development of both the test vehicle and the trajectory sequence including design trade-offs resulting from the interaction of both engineering efforts. In addition, the SFDT-1 nominal trajectory design and associated sensitivities will be discussed

  10. EARTH’S ROTATIONAL DECELERATION: DETERMINATION OF TIDAL FRICTION INDEPENDENT OF TIMESCALES

    SciTech Connect

    Deines, Steven D.; Williams, Carol A., E-mail: steven.deines@gmail.com, E-mail: cw@math.usf.edu

    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, icemore » 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{sup −7} rad yr{sup −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.« less

  11. Responses to deceleration during car following: roles of optic flow, warnings, expectations, and interruptions.

    PubMed

    DeLucia, Patricia R; Tharanathan, Anand

    2009-12-01

    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 responses to deceleration during car following. With computer simulations of car-following scenes, university students pressed a button when the lead car decelerated. Both classes of information affected responses. Observers relied on discrete warnings when optic flow information was relatively less effective as determined by the lead car's headway and deceleration rate. This is consistent with DeLucia's (2008) conceptual framework of space perception that emphasized the importance of viewing distance and motion (and task). In Experiment 2, we measured responses to deceleration after a visual interruption. Scenes were designed to tease apart the role of expectations and optic flow. Responses mostly were consistent with optic flow information presented after the interruption rather than with putative mental expectations that were set up by the lead car's motion prior to the interruption. The theoretical implication of the present results is that responses to deceleration are based on multiple sources of information, including optical size, optical expansion rate and tau, and discrete warnings that are independent of optic flow. The practical implication is that in-vehicle collision-avoidance warning systems may be more useful when optic flow is less effective (e.g., slow deceleration rates), implicating a role for adaptive collision-warning systems. Copyright 2009 APA

  12. Finite Atwood Number Effects on Deceleration-Phase Instability in Room-Temperature Direct-Drive Implosions

    NASA Astrophysics Data System (ADS)

    Miller, S.; Knauer, J. P.; Radha, P. B.; Goncharov, V. N.

    2017-10-01

    Performance degradation in direct-drive inertial confinement fusion implosions can be caused by several effects, one of which is Rayleigh-Taylor (RT) instability growth during the deceleration phase. In room-temperature plastic target implosions, this deceleration-phase RT growth is enhanced by the density discontinuity and finite Atwood numbers at the fuel-pusher interface. For the first time, an experimental campaign at the Omega Laser Facility systematically varied the ratio of deuterium-to-tritium (D-to-T) within the DT gas fill to change the Atwood number. The goal of the experiment was to understand the effects of Atwood number variation on observables like apparent ion temperature, yield, and variations in areal density and bulk fluid motion, which lead to broadening of neutron spectra along different lines of sight. Simulations by the hydrodynamic codes LILAC and DRACO were used to study growth rates for different D-to-T ratios and identify observable quantities effected by Atwood number variation. Results from simulations and the experiment are presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  13. 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.

  14. Continuous centrifuge decelerator for polar molecules.

    PubMed

    Chervenkov, S; Wu, X; Bayerl, J; Rohlfes, A; Gantner, T; Zeppenfeld, M; Rempe, G

    2014-01-10

    Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, CH3F, CF3H, and CF3CCH, with input velocities of up to 200  m s(-1) to obtain beams with velocities below 15  m s(-1) and intensities of several 10(9)  mm(-2) s(-1). The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.

  15. A driving simulator study of driver performance on deceleration lanes.

    PubMed

    Calvi, A; Benedetto, A; De Blasiis, M R

    2012-03-01

    Deceleration lanes are important because they help drivers transition from high-speed lanes to low-speed ramps. Although they are designed to allow vehicles to depart the freeway safely and efficiently, many studies report high accident rates on exit ramps with the highest percentage of crashes taking place in deceleration lanes. This paper describes the results of a driving simulator study that focused on driving performance while approaching a divergence area and decelerating during the exiting maneuver. Three different traffic scenarios were simulated to analyze the influence of traffic volume on driving performance. Thirty drivers drove in the simulator in these scenarios while data on their lateral position, speed and deceleration were collected. Our results indicate there are considerable differences between the main assumptions of models generally used to design deceleration lanes and actual driving performance. In particular, diverging drivers begin to decelerate before arriving at the deceleration lane, causing interference with the main flow. Moreover, speeds recorded at the end of the deceleration lane exceed those for which the ramp's curves are designed; this creates risky driving conditions that could explain the high crash rates found in studies of exit ramps. Finally, statistical analyses demonstrate significant influences of traffic volume on some aspects of exiting drivers' performance: lower traffic volume results in elevated exiting speed and deceleration, and diverging drivers begin to decelerate earlier along the main lane when traffic volume is low. However, speeds at the end of the deceleration lane and the site of lane changing are not significantly influenced by traffic volume. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. 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.

  17. 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.

  18. 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. © 2010 Wiley-Liss, Inc.

  19. Flow Studies of Decelerators at Supersonic Speeds

    NASA Technical Reports Server (NTRS)

    1959-01-01

    Wind tunnel tests recorded the effect of decelerators on flow at various supersonic speeds. Rigid parachute models were tested for the effects of porosity, shroud length, and number of shrouds. Flexible model parachutes were tested for effects of porosity and conical-shaped canopy. Ribbon dive brakes on a missile-shaped body were tested for effect of tension cable type and ribbon flare type. The final test involved a plastic sphere on riser lines.

  20. Qualification flight tests of the Viking decelerator system.

    NASA Technical Reports Server (NTRS)

    Moog, R. D.; Bendura, R. J.; Timmons, J. D.; Lau, R. A.

    1973-01-01

    The Balloon Launched Decelerator Test (BLDT) series conducted at White Sands Missile Range (WSMR) during July and August of 1972 flight qualified the NASA Viking '75 decelerator system at conditions bracketing those expected for Mars. This paper discusses the decelerator system design requiremnts, compares the test results with prior work, and discusses significant considerations leading to successful qualification in earth's atmosphere. The Viking decelerator system consists of a single-stage mortar-deployed 53-foot nominal diameter disk-gap-band parachute. Full-scale parachutes were deployed behind a full-scale simulated Viking vehicle at Mach numbers from 0.47 to 2.18 and dynamic pressures from 6.9 to 14.6 psf. Analyses show that the system is qualified with sufficient margin to perform successfully for the Viking mission.

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

    PubMed

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

    2016-02-01

    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. 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. Mean (SD) shift PM2.5 exposure during welding was 0.47 (0.43) mg/m(3). 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/m(3) 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. There are short-term effects of metal particulates on AC and DC. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  2. Flow acceleration structure of Aurelia aurita: implications on propulsion

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Tae; Piper, Matthew; Chamorro, Leonardo P.

    2017-11-01

    The jetting and paddling mechanisms used by Aurelia aurita jellyfish allows for one of the most efficient propulsion among other metazoans. Characterization of the induced flow acceleration is critical to uncover distinctive patterns. We found four acceleration structures using 3D measurements of body and flow dynamics in Lagrangian frame of reference. Two intense structures occur near the bell margin and are generated by paddling; the other two around the center of the jellyfish and half magnitude are a result of jetting. Their interaction leads to the maximum flow velocity in the middle of the relaxation, where relatively straight flow trajectories occur. The jellyfish achieves an efficient relaxation by generating flow deceleration with minor body deceleration.

  3. Biodegradable Sonobuoy Decelerators

    DTIC Science & Technology

    2015-06-01

    material. Two materials studied were polyvinyl alcohol (PVOH) and polyhydroxyalkanoate (PHA). Single and multilayered PVOH films were evaluated as well...readiness point for technology transition. 15. SUBJECT TERMS biodegrade, decelerator, sonobuoy, polyvinyl alcohol, polyhydroxyalkanoate , marine...Center NGO non-governmental organizations NOAA National Oceanic and Atmospheric Administration PHA polyhydroxyalkanoate PIA Parachute Industry

  4. Modeling experiments on the deceleration and reactivation of Kangerlussuup Sermusa, West Greenland

    NASA Astrophysics Data System (ADS)

    Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.; Catania, G. A.

    2015-12-01

    Seasonal variations in outlet glacier velocity due to basal sliding are well-documented and typically involve acceleration early in the melt season due to enhanced sliding as a result of inefficient drainage of surface water reaching the bed. However, velocity observations from Kangerlussuup Sermusa (KS) in West Greenland contradict this pattern. Instead, ice velocity at KS shows no significant change in early spring compared with the previous winter. This sluggish response of the glacier to spring melt is often followed by an extreme, and short-lived, deceleration. For example, in August 2010, the lower 20 km of the trunk decelerated from about 1600 m a-1 to less than 250 m a-1; this event was followed by a rapid reactivation back to the previous velocity in less than 60 days. Available records since 2006 show that the sequence of steady spring velocity, followed by summer deceleration, and rapid fall reactivation occurs annually; however, the magnitudes of deceleration vary. In this regard, the response of KS to regional environmental forcings is unique compared to its neighboring glaciers. In this study, we investigate whether the unique behavior of KS can be explained by the interaction between changes in basal conditions and the local geometry of the glacier. We model the glacier flow by solving full-Stokes equations using the finite element method in the open-source FEniCS framework. Assuming isothermal ice within the lower trunk, we run experiments on the mechanical properties and boundary conditions of the glacier. These experiments include spatio-temporal changes in basal slipperiness, periodic melt-water influx to the bed, and ice viscosity variations due to changes in melt-water supply to the bed. We also conduct sensitivity analyses on the glacier flow with different ice geometries (e.g. thickness and surface slope) to investigate conditions under which we can produce the unique seasonal behavior of KS. Finally, we assess the impact of the combination

  5. Continuous all-optical deceleration of molecular beams

    NASA Astrophysics Data System (ADS)

    Jayich, Andrew; Chen, Gary; Long, Xueping; Wang, Anna; Campbell, Wesley

    2014-05-01

    A significant impediment to generating ultracold molecules is slowing a molecular beam to velocities where the molecules can be cooled and trapped. We report on progress toward addressing this issue with a general optical deceleration technique for molecular and atomic beams. We propose addressing the molecular beam with a pump and dump pulse sequence from a mode-locked laser. The pump pulse counter-propagates with respect to the beam and drives the molecules to the excited state. The dump pulse co-propagates and stimulates emission, driving the molecules back to the ground state. This cycle transfers 2 ℏk of momentum and can generate very large optical forces, not limited by the spontaneous emission lifetime of the molecule or atom. Importantly, avoiding spontaneous emission limits the branching to dark states. This technique can later be augmented with cooling and trapping. We are working towards demonstrating this optical force by accelerating a cold atomic sample.

  6. Rapid deceleration mode evaluation

    NASA Technical Reports Server (NTRS)

    Conners, Timothy R.; Nobbs, Steven G.; Orme, John S.

    1995-01-01

    Aircraft with flight capability above 1.4 normally have an RPM lockup or similar feature to prevent inlet buzz that would occur at low engine airflows. This RPM lockup has the effect of holding the engine thrust level at the intermediate power (maximum non-afterburning). For aircraft such as military fighters or supersonic transports, the need exists to be able to rapidly slow from supersonic to subsonic speeds. For example, a supersonic transport that experiences a cabin decompression needs to be able to slow/descend rapidly, and this requirement may size the cabin environmental control system. For a fighter, there may be a desire to slow/descend rapidly, and while doing so to minimize fuel usage and engine exhaust temperature. Both of these needs can be aided by achieving the minimum possible overall net propulsive force. As the intermediate power thrust levels of engines increase, it becomes even more difficult to slow rapidly from supersonic speeds. Therefore, a mode of the performance seeking control (PSC) system to minimize overall propulsion system thrust has been developed and tested. The rapid deceleration mode reduces the engine airflow consistent with avoiding inlet buzz. The engine controls are trimmed to minimize the thrust produced by this reduced airflow, and moves the inlet geometry to degrade the inlet performance. As in the case of the other PSC modes, the best overall performance (in this case the least net propulsive force) requires an integrated optimization of inlet, engine, and nozzle variables. This paper presents the predicted and measured results for the supersonic minimum thrust mode, including the overall effects on aircraft deceleration.

  7. 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.

  8. Impact-induced acceleration by obstacles

    NASA Astrophysics Data System (ADS)

    Corbin, N. A.; Hanna, J. A.; Royston, W. R.; Singh, H.; Warner, R. B.

    2018-05-01

    We explore a surprising phenomenon in which an obstruction accelerates, rather than decelerates, a moving flexible object. It has been claimed that the right kind of discrete chain falling onto a table falls faster than a free-falling body. We confirm and quantify this effect, reveal its complicated dependence on angle of incidence, and identify multiple operative mechanisms. Prior theories for direct impact onto flat surfaces, which involve a single constitutive parameter, match our data well if we account for a characteristic delay length that must impinge before the onset of excess acceleration. Our measurements provide a robust determination of this parameter. This supports the possibility of modeling such discrete structures as continuous bodies with a complicated constitutive law of impact that includes angle of incidence as an input.

  9. Principles and Design of a Zeeman–Sisyphus Decelerator for Molecular Beams

    PubMed Central

    Tarbutt, M. R.

    2016-01-01

    Abstract We explore a technique for decelerating molecules using a static magnetic field and optical pumping. Molecules travel through a spatially varying magnetic field and are repeatedly pumped into a weak‐field seeking state as they move towards each strong field region, and into a strong‐field seeking state as they move towards weak field. The method is time‐independent and so is suitable for decelerating both pulsed and continuous molecular beams. By using guiding magnets at each weak field region, the beam can be simultaneously guided and decelerated. By tapering the magnetic field strength in the strong field regions, and exploiting the Doppler shift, the velocity distribution can be compressed during deceleration. We develop the principles of this deceleration technique, provide a realistic design, use numerical simulations to evaluate its performance for a beam of CaF, and compare this performance to other deceleration methods. PMID:27629547

  10. 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.

  11. 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.

  12. Heart rate deceleration runs for postinfarction risk prediction.

    PubMed

    Guzik, Przemyslaw; Piskorski, Jaroslaw; Barthel, Petra; Bauer, Axel; Müller, Alexander; Junk, Nadine; Ulm, Kurt; Malik, Marek; Schmidt, Georg

    2012-01-01

    A method for counting episodes of uninterrupted beat-to-beat heart rate decelerations was developed. The method was set up and evaluated using 24-hour electrocardiogram Holter recordings of 1455 (training sample) and 946 (validation sample) postinfarction patients. During a median follow-up of 24 months, 70, 46, and 19 patients of the training sample suffered from total, cardiac, and sudden cardiac mortality, respectively. In the validation sample, these numbers were 39, 25, and 15. Episodes of consecutive beat-to-beat heart rate decelerations (deceleration runs [DRs]) were characterized by their length. Deceleration runs of 2 to 10 cycles were significantly less frequent in nonsurvivors. Multivariate model of DRs of 2, 4, and 8 cycles identified low-, intermediate-, and high-risk groups. In these groups of the training sample, the total mortalities were 1.8%, 6.1%, and 24%, respectively. In the validation sample, these numbers were 1.8%, 4.1%, and 21.9%. Infrequent DRs during 24-hour Holter indicate high risk of postinfarction mortality. Copyright © 2012 Elsevier Inc. All rights reserved.

  13. Rotary Wing Deceleration Use on Titan

    NASA Technical Reports Server (NTRS)

    Young, Larry A.; Steiner, Ted J.

    2011-01-01

    Rotary wing decelerator (RWD) systems were compared against other methods of atmospheric deceleration and were determined to show significant potential for application to a system requiring controlled descent, low-velocity landing, and atmospheric research capability on Titan. Design space exploration and down-selection results in a system with a single rotor utilizing cyclic pitch control. Models were developed for selection of a RWD descent system for use on Titan and to determine the relationships between the key design parameters of such a system and the time of descent. The possibility of extracting power from the system during descent was also investigated.

  14. Muscle activation patterns in acceleration-based phases during reach-to-grasp movement.

    PubMed

    Tokuda, Keisuke; Lee, Bumsuk; Shiihara, Yasufumi; Takahashi, Kazuhiro; Wada, Naoki; Shirakura, Kenji; Watanabe, Hideomi

    2016-11-01

    [Purpose] An earlier study divided reaching activity into characteristic phases based on hand velocity profiles. By synchronizing muscle activities and the acceleration profile, a phasing approach for reaching movement, based on hand acceleration profiles, was attempted in order to elucidate the roles of individual muscle activities in the different phases of the acceleration profile in reaching movements. [Subjects and Methods] Ten healthy volunteer subjects participated in this study. The aim was to electromyographically evaluate muscles around the shoulder, the upper trapezius, the anterior deltoid, the biceps brachii, and the triceps brachii, most of which have been used to evaluate arm motion, as well as the acceleration of the upper limb during simple reaching movement in the reach-to-grasp task. [Results] Analysis showed the kinematic trajectories of the acceleration during a simple biphasic profile of the reaching movement could be divided into four phases: increasing acceleration (IA), decreasing acceleration (DA), increasing deceleration (ID), and decreasing deceleration (DD). Muscles around the shoulder showed different activity patterns, which were closely associated with these acceleration phases. [Conclusion] These results suggest the important role of the four phases, derived from the acceleration trajectory, in the elucidation of the muscular mechanisms which regulate and coordinate the muscles around the shoulder in reaching movements.

  15. Summary of the First High-Altitude, Supersonic Flight Dynamics Test for the Low-Density Supersonic Decelerator Project

    NASA Technical Reports Server (NTRS)

    Clark, Ian G.; Adler, Mark; Manning, Rob

    2015-01-01

    NASA's Low-Density Supersonic Decelerator Project is developing and testing the next generation of supersonic aerodynamic decelerators for planetary entry. A key element of that development is the testing of full-scale articles in conditions relevant to their intended use, primarily the tenuous Mars atmosphere. To achieve this testing, the LDSD project developed a test architecture similar to that used by the Viking Project in the early 1970's for the qualification of their supersonic parachute. A large, helium filled scientific balloon is used to hoist a 4.7 m blunt body test vehicle to an altitude of approximately 32 kilometers. The test vehicle is released from the balloon, spun up for gyroscopic stability, and accelerated to over four times the speed of sound and an altitude of 50 kilometers using a large solid rocket motor. Once at those conditions, the vehicle is despun and the test period begins. The first flight of this architecture occurred on June 28th of 2014. Though primarily a shake out flight of the new test system, the flight was also able to achieve an early test of two of the LDSD technologies, a large 6 m diameter Supersonic Inflatable Aerodynamic Decelerator (SIAD) and a large, 30.5 m nominal diameter supersonic parachute. This paper summarizes this first flight.

  16. 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

  17. Numerical investigation on the effects of acceleration reversal times in Rayleigh-Taylor Instability with multiple reversals

    NASA Astrophysics Data System (ADS)

    Farley, Zachary; Aslangil, Denis; Banerjee, Arindam; Lawrie, Andrew G. W.

    2017-11-01

    An implicit large eddy simulation (ILES) code, MOBILE, is used to explore the growth rate of the mixing layer width of the acceleration-driven Rayleigh-Taylor instability (RTI) under variable acceleration histories. The sets of computations performed consist of a series of accel-decel-accel (ADA) cases in addition to baseline constant acceleration and accel-decel (AD) cases. The ADA cases are a series of varied times for the second acceleration reversal (t2) and show drastic differences in the growth rates. Upon the deceleration phase, the kinetic energy of the flow is shifted into internal wavelike patterns. These waves are evidenced by the examined differences in growth rate in the second acceleration phase for the set of ADA cases. Here, we investigate global parameters that include mixing width, growth rates and the anisotropy tensor for the kinetic energy to better understand the behavior of the growth during the re-acceleration period. Authors acknowledge financial support from DOE-SSAA (DE-NA0003195) and NSF CAREER (#1453056) awards.

  18. 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.

  19. 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.

  20. 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.

  1. The effect of the pressure on the deceleration parameter in inhomogeneous cosmological models

    NASA Astrophysics Data System (ADS)

    Vrba, David

    2012-07-01

    The cosmological parameters have been recently widely studied within inhomogeneous cosmological models. The investigation is usually done in the Lemaitre-Tolman-Bondi (LTB) metric, the spherically symmetric dust solution of Einstein equations. However only little attention has been paid to models with nonzero pressure. Recently it has been pointed out, that pressure gradients can have significant impact on the angular diameter distance redshift relation and it seems to be important to investigate how it effects other cosmological parameters. Here we investigate the influence of the pressure on the backreaction and consequently on the deceleration parameter using the inhomogeneous Lemaitre metric.

  2. Peculiar motions, accelerated expansion, and the cosmological axis

    NASA Astrophysics Data System (ADS)

    Tsagas, Christos G.

    2011-09-01

    Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large enough to give the false impression that the whole cosmos has recently entered an accelerating phase. Generally, peculiar velocities are also associated with dipolelike anisotropies, triggered by the fact that they introduce a preferred spatial direction. This implies that observers experiencing locally accelerated expansion, as a result of their own drift motion, may also find that the acceleration is maximized in one direction and minimized in the opposite. We argue that, typically, such a dipole anisotropy should be relatively small and the axis should probably lie fairly close to the one seen in the spectrum of the cosmic microwave background.

  3. Acceleration from short-duration blast

    NASA Astrophysics Data System (ADS)

    Ritzel, D. V.; Van Albert, S.; Sajja, V.; Long, J.

    2018-01-01

    The blast-induced motion of spheres has been studied experimentally where the shock wave is rapidly decaying during the period that quasi-steady acceleration would be developed in the case of a step-function shock wave as considered in most shock-tube studies. The motion of sphere models ranging from 39 to 251 mm in diameter and having a range of densities was assessed using the "free-flight" method in a simulator specially designed to replicate the decaying shock wave profile of spherical blast including negative phase and positive entropy gradient. A standardized blast-wave simulation of 125 kPa and 6-ms positive-phase duration was applied for all experiments. In all cases, there are three phases to the motion: a relatively low "kickoff" velocity from the shock diffraction, acceleration or deceleration during the positive duration, then deceleration through the negative phase and subsequent quiescent air. The unexpected deceleration of larger spheres after their kickoff velocity during the decaying yet high-speed flow of the blast wave seems associated with the persistence of a ring vortex on the downstream side of the sphere. The flow is entirely unsteady with initial forces dominated by the shock diffraction; therefore, the early motion of spheres under such conditions is not governed by quasi-steady drag as in classical aerodynamics. The work will help establish scaling rules for model studies of blast-induced motion relevant to improvised explosive devices, and preliminary results are shown for motion imparted to a human skull surrogate.

  4. Observations of the Coronal Mass Ejection with a Complex Acceleration Profile

    NASA Astrophysics Data System (ADS)

    Reva, A. A.; Kirichenko, A. S.; Ulyanov, A. S.; Kuzin, S. V.

    2017-12-01

    We study the coronal mass ejection (CME) with a complex acceleration profile. The event occurred on 2009 April 23. It had an impulsive acceleration phase, an impulsive deceleration phase, and a second impulsive acceleration phase. During its evolution, the CME showed signatures of different acceleration mechanisms: kink instability, prominence drainage, flare reconnection, and a CME–CME collision. The special feature of the observations is the usage of the TESIS EUV telescope. The instrument could image the solar corona in the Fe 171 Å line up to a distance of 2 {R}ȯ from the center of the Sun. This allows us to trace the CME up to the LASCO/C2 field of view without losing the CME from sight. The onset of the CME was caused by kink instability. The mass drainage occurred after the kink instability. The mass drainage played only an auxiliary role: it decreased the CME mass, which helped to accelerate the CME. The first impulsive acceleration phase was caused by the flare reconnection. We observed the two-ribbon flare and an increase of the soft X-ray flux during the first impulsive acceleration phase. The impulsive deceleration and the second impulsive acceleration phases were caused by the CME–CME collision. The studied event shows that CMEs are complex phenomena that cannot be explained with only one acceleration mechanism. We should seek a combination of different mechanisms that accelerate CMEs at different stages of their evolution.

  5. A study of the solar wind deceleration in the Earth's foreshock region

    NASA Technical Reports Server (NTRS)

    Zhang, T.-L.; Schwingenschuh, K.; Russell, C. T.

    1995-01-01

    Previous observations have shown that the solar wind is decelerated and deflected in the earth's upstream region populated by long-period waves. This deceleration is corelated with the 'diffuse' but not with the 'reflected' ion population. The speed of the solar wind may decrease tens of km/s in the foreshock region. The solar wind dynamic pressure exerted on the magnetopause may vary due to the fluctuation of the solar wind speed and density in the foreshock region. In this study, we examine this solar wind deceleration and determine how the solar wind deceleration varies in the foreshock region.

  6. Getting a grip on the transverse motion in a Zeeman decelerator

    SciTech Connect

    Dulitz, Katrin; Softley, Timothy P., E-mail: tim.softley@chem.ox.ac.uk; Motsch, Michael

    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 ismore » 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.« less

  7. 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

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

    PubMed

    Akbari, Nahid; Ramezankhani, Ali; Pazargadi, Mehrnoosh

    2013-07-01

    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. 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. 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 cascade model for presenting the

  9. A cell-based study on pedestrian acceleration and overtaking in a transfer station corridor

    NASA Astrophysics Data System (ADS)

    Ji, Xiangfeng; Zhou, Xuemei; Ran, Bin

    2013-04-01

    Pedestrian speed in a transfer station corridor is faster than usual and sometimes running can be found among some of them. In this paper, pedestrians are divided into two categories. The first one is aggressive, and the other is conservative. Aggressive pedestrians weaving their way through crowd in the corridor are the study object of this paper. During recent decades, much attention has been paid to the pedestrians' behavior, such as overtaking (also deceleration) and collision avoidance, and that continues in this paper. After sufficiently analyzing the characteristics of pedestrian flow in transfer station corridor, a cell-based model is presented in this paper, including the acceleration (also deceleration) and overtaking analysis. Acceleration (also deceleration) in a corridor is fixed according to Newton's Law and then speed calculated with a kinematic formula is discretized into cells based on the fuzzy logic. After the speed is updated, overtaking is analyzed based on updated speed and force explicitly, compared to rule-based models, which herein we call implicit ones. During the analysis of overtaking, a threshold value to determine the overtaking direction is introduced. Actually, model in this paper is a two-step one. The first step is to update speed, which is the cells the pedestrian can move in one time interval and the other is to analyze the overtaking. Finally, a comparison between the rule-based cellular automata, the model in this paper and data in HCM 2000 is made to demonstrate our model can be used to achieve reasonable simulation of acceleration (also deceleration) and overtaking among pedestrians.

  10. 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.

  11. Explaining the Supernova Data Without Accelerating Expansion

    NASA Astrophysics Data System (ADS)

    Stuckey, W. M.; McDevitt, T. J.; Silberstein, M.

    2012-10-01

    The 2011 Nobel Prize in Physics was awarded "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." However, it is not the case that the type Ia supernova data necessitates accelerating expansion. Since we do not have a successful theory of quantum gravity, we should not assume general relativity (GR) will survive unification intact, especially on cosmological scales where tests are scarce. We provide a simple example of how GR cosmology may be modified to produce a decelerating Einstein-de Sitter cosmology (EdS) that accounts for the Union2 Compilation data as well as the accelerating ΛCDM (EdS plus a cosmological constant).

  12. 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.

  13. Accelerated deforestation in the humid tropics from the 1990s to the 2000s

    NASA Astrophysics Data System (ADS)

    Kim, Do-Hyung; Sexton, Joseph O.; Townshend, John R.

    2015-05-01

    Using a consistent, 20 year series of high- (30 m) resolution, satellite-based maps of forest cover, we estimate forest area and its changes from 1990 to 2010 in 34 tropical countries that account for the majority of the global area of humid tropical forests. Our estimates indicate a 62% acceleration in net deforestation in the humid tropics from the 1990s to the 2000s, contradicting a 25% reduction reported by the United Nations Food and Agriculture Organization Forest Resource Assessment. Net loss of forest cover peaked from 2000 to 2005. Gross gains accelerated slowly and uniformly between 1990-2000, 2000-2005, and 2005-2010. However, the gains were overwhelmed by gross losses, which peaked from 2000 to 2005 and decelerated afterward. The acceleration of humid tropical deforestation we report contradicts the assertion that losses decelerated from the 1990s to the 2000s.

  14. Decelerating and Trapping Large Polar Molecules.

    PubMed

    Patterson, David

    2016-11-18

    Manipulating the motion of large polyatomic molecules, such as benzonitrile (C 6 H 5 CN), presents significant difficulties compared to the manipulation of diatomic molecules. Although recent impressive results have demonstrated manipulation, trapping, and cooling of molecules as large as CH 3 F, no general technique for trapping such molecules has been demonstrated, and cold neutral molecules larger than 5 atoms have not been trapped (M. Zeppenfeld, B. G. U. Englert, R. Glöckner, A. Prehn, M. Mielenz, C. Sommer, L. D. van Buuren, M. Motsch, G. Rempe, Nature 2012, 491, 570-573). In particular, extending Stark deceleration and electrostatic trapping to such species remains challenging. Here, we propose to combine a novel "asymmetric doublet state" Stark decelerator with recently demonstrated slow, cold, buffer-gas-cooled beams of closed-shell volatile molecules to realize a general system for decelerating and trapping samples of a broad range of volatile neutral polar prolate asymmetric top molecules. The technique is applicable to most stable volatile molecules in the 100-500 AMU range, and would be capable of producing trapped samples in a single rotational state and at a motional temperature of hundreds of mK. Such samples would immediately allow for spectroscopy of unprecedented resolution, and extensions would allow for further cooling and direct observation of slow intramolecular processes such as vibrational relaxation and Hertz-level tunneling dynamics. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Effect of electromagnetic field emitted by cellular phones on fetal heart rate patterns.

    PubMed

    Celik, Onder; Hascalik, Seyma

    2004-01-15

    The study was planned to determine the effects of electromagnetic fields produced by cellular phones on baseline fetal heart rate, acceleration and deceleration. Forty pregnant women undergoing non-stress test were admitted to the study. Non-stress test was obtained while the subjects were holding the CP on stand by mode and on dialing mode, each for 5 min. Similar recordings were taken while there were no phones around for 10 min. Electromagnetic fields produced by cellular phones do not cause any demonstrable affect in fetal heart rate, acceleration and deceleration.

  16. Beam deceleration for block-face scanning electron microscopy of embedded biological tissue.

    PubMed

    Ohta, Keisuke; Sadayama, Shoji; Togo, Akinobu; Higashi, Ryuhei; Tanoue, Ryuichiro; Nakamura, Kei-ichiro

    2012-04-01

    The beam deceleration (BD) method for scanning electron microscopes (SEM) also referred to as "retarding" was applied to back-scattered electron (BSE) imaging of the flat block face of a resin embedded biological specimen under low accelerating voltage and low beam current conditions. BSE imaging was performed with 0-4 kV of BD on en bloc stained rat hepatocyte. BD drastically enhanced the compositional contrast of the specimen and also improved the resolution at low landing energy levels (1.5-3 keV) and a low beam current (10 pA). These effects also functioned in long working distance observation, however, stage tilting caused uncorrectable astigmatism in BD observation. Stage tilting is mechanically required for a FIB/SEM, so we designed a novel specimen holder to minimize the unfavorable tilting effect. The FIB/SEM 3D reconstruction using the new holder showed a reasonable contrast and resolution high enough to analyze individual cell organelles and also the mitochondrial cristae structures (~5 nm) of the hepatocyte. These results indicate the advantages of BD for block face imaging of biological materials such as cells and tissues under low-voltage and low beam current conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Stability condition for the drive bunch in a collinear wakefield accelerator

    SciTech Connect

    Baturin, S. S.; Zholents, A.

    The beam breakup instability of the drive bunch in the structure-based collinear wakefield accelerator is considered and a stabilizing method is proposed. The method includes using the specially designed beam focusing channel, applying the energy chirp along the electron bunch, and keeping energy chirp constant during the drive bunch deceleration. A stability condition is derived that defines the limit on the accelerating field for the witness bunch.

  18. 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.

  19. Was There a Decelerating Past for the Universe?

    NASA Astrophysics Data System (ADS)

    John, Moncy V.

    2006-03-01

    Some analyzes of the apparent magnitude-redshift data of type Ia supernovas indicate that the suspected dark energy in the universe cannot be regarded as a cosmological constant of general relativistic origin or as the vacuum energy encountered in quantum field theories. If this is the case, our knowledge of the physical world remains deficient since no tested theory involves such a dark energy. Under this circumstance, an equation of state of the form p = wρ is not well-motivated and one is unable to use the Einstein equation in this case as well. I argue that the very method of analysing the data by assuming exotic energy densities with strange equations of state itself is misleading and the reasonable remaining option is to make a model-independent analysis of SNe data, without reference to the energy densities. In this basically kinematic approach, we limit ourselves to the observationally justifiable assumptions of homogeneity and isotropy, i.e., to the assumption that the universe has a RW metric. This cosmographic approach is historically the original one in cosmology. The analysis was performed by expanding the scale factor into a fifth-order polynomial, an assumption that can be further generalized to any order. The values obtained for the present expansion rates h, q0, r0 etc. are relevant, since any cosmological solution would ultimately need to explain them. Using this method, we address an important question relevant to cosmology: Was there a decelerating past for the universe? To answer this, the Bayes's probability theory is employed, which is the most appropriate tool for quantifying our knowledge when it changes through the acquisition of new data. The cosmographic approach helps to sort out models which were always accelerating from those which decelerated for at least some time in the period of interest. Bayesian model comparison technique is used to discriminate these rival hypotheses with the aid of recent releases of supernova data. It is

  20. 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.

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

    PubMed

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

    2016-01-01

    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. 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. 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). Both DC and AC of heart rate decreased in patients with hemispheric infarction, reflecting a decrease in both vagal and sympathetic modulation. Both DC and AC were correlated

  2. Viscous cosmology in new holographic dark energy model and the cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Singh, C. P.; Srivastava, Milan

    2018-03-01

    In this work, we study a flat Friedmann-Robertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to Λ CDM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ =ζ 0+ζ 1H, where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r-s and r-q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the Λ CDM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe.

  3. Flight investigation of manual and automatic VTOL decelerating instrument approaches and landings

    NASA Technical Reports Server (NTRS)

    Kelly, J. R.; Niessen, F. R.; Thibodeaux, J. J.; Yenni, K. R.; Garren, J. F., Jr.

    1974-01-01

    A flight investigation was undertaken to study the problems associated with manual and automatic control of steep, decelerating instrument approaches and landings under simulated instrument conditions. The study was conducted with a research helicopter equipped with a three-cue flight-director indicator. The scope of the investigation included variations in the flight-director control laws, glide-path angle, deceleration profile, and control response characteristics. Investigation of the automatic-control problem resulted in the first automated approach and landing to a predetermined spot ever accomplished with a helicopter. Although well-controlled approaches and landings could be performed manually with the flight-director concept, pilot comments indicated the need for a better display which would more effectively integrate command and situation information.

  4. Mode-Locked Deceleration of Molecular Beams: Physics with Ultracold Molecules

    DTIC Science & Technology

    2017-02-07

    AFRL-AFOSR-VA-TR-2017-0035 Mode-Locked Deceleration of Molecular Beams: Physics with Ultracold Molecules Wesley Campbell UNIVERSITY OF CALIFORNIA...REPORT TYPE Final 3. DATES COVERED (From - To) April 2013 - June 2016 4. TITLE AND SUBTITLE Mode-Locked Deceleration of Molecular Beams: Physics with...of Molecular Beams: Physics with Ultracold Molecules" P.I. Wesley C. Campbell Report Period: April 1, 2013- March 30, 2016 As a direct result of

  5. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Torus Mechanical Testing

    NASA Technical Reports Server (NTRS)

    Chen, Tony; Moholt, Matthew R.; Hudson, Larry D.

    2017-01-01

    The Armstrong Flight Research Center has performed loads testing of a series of developmental atmospheric entry decelerator structural components. Test setup hardware were designed and fabricated. In addition, test plan and checklist were developed for the consistent and efficient execution of the tests. Eight test articles were successfully tested in over one hundred test runs as test objectives were met. Test article buckling shapes and buckling loads were observed. Displacements and strains were also recorded as various load cases were applied. The test data was sent to Langley Research Center to help with the construction of the finite element model of the decelerator assembly.

  6. Gunshot residue particle velocity and deceleration.

    PubMed

    De Forest, Peter R; Martir, Kirby; Pizzola, Peter A

    2004-11-01

    The velocity of over 800 gunshot residue particles from eight different sources was determined using high speed stroboscopic photography (spark gap light source). These particles were found to have an average velocity of 500 to 600 ft per second. Many particles acquired considerably higher velocities. Thus, the particles have sufficient energy to embed themselves within certain nearby targets like skin or fabric. The relatively high velocity that the particles acquire explain the formation of stippling on skin in close proximity to a muzzle discharge. These findings also indicate little influence of air currents on particle behavior near the muzzle. The deceleration of less than 100 particles during a 100-microsecond interval was also calculated. The particles experienced rapid rates of deceleration which would explain why few particles are found in test firings beyond 3 ft from the muzzle of a discharged firearm. Because of their relatively high velocity, normal wind velocity would not be expected to significantly influence their motion near the muzzle.

  7. Inflatable Aerocapture Decelerators for Mars Orbiters

    NASA Technical Reports Server (NTRS)

    Brown, Glen J.; Lingard, J. Stephen; Darley, Matthew G.; Underwood, John C.

    2007-01-01

    A multi-disciplinary research program was recently completed, sponsored by NASA Marshall Space Flight Center, on the subject of aerocapture of spacecraft weighing up to 5 metric tons at Mars. Heavier spacecraft will require deployable drag area beyond the dimensional limits of current and planned launch fairings. This research focuses on the approach of lightweight inflatable decelerators constructed with thin films, using fiber reinforcement and having a temperature limitation of 500 C. Trajectory analysis defines trajectories for a range of low ballistic coefficients for which convective heat flux is compatible with the material set. Fluid-Structure Interaction (FSI) tools are expanded to include the rarified flow regime. Several non-symmetrical configurations are evaluated for their capability to develop lift as part of the necessary trajectory control strategy. Manufacturing technology is developed for 3-D stretch forming of polyimide films and for tailored fiber reinforcement of thin films. Finally, the mass of the decelerator is estimated and compared to the mass of a traditional rigid aeroshell.

  8. Balloon launched decelerator test program: Post-flight test report, BLDT vehicle AV-2, Viking 1975 project

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    The pertinent events concerned with the launch, float, and flight of balloon launched decelerator test vehicle AV-2 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 anomalies encounters during the mission is included.

  9. 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.

  10. Accelerating dark energy cosmological model in two fluids with hybrid scale factor

    NASA Astrophysics Data System (ADS)

    Mishra, B.; Sahoo, P. K.; Ray, Pratik P.

    In this paper, we have investigated the anisotropic behavior of the accelerating universe in Bianchi V spacetime in the framework of General Relativity (GR). The matter field we have considered is of two non-interacting fluids, i.e. the usual string fluid and dark energy (DE) fluid. In order to represent the pressure anisotropy, the skewness parameters are introduced along three different spatial directions. To achieve a physically realistic solutions to the field equations, we have considered a scale factor, known as hybrid scale factor, which is generated by a time-varying deceleration parameter. This simulates a cosmic transition from early deceleration to late time acceleration. It is observed that the string fluid dominates the universe at early deceleration phase but does not affect nature of cosmic dynamics substantially at late phase, whereas the DE fluid dominates the universe in present time, which is in accordance with the observations results. Hence, we analyzed here the role of two fluids in the transitional phases of universe with respect to time which depicts the reason behind the cosmic expansion and DE. The role of DE with variable equation of state parameter (EoS) and skewness parameters, is also discussed along with physical and geometrical properties.

  11. Generalized fractional diffusion equations for accelerating subdiffusion and truncated Lévy flights

    NASA Astrophysics Data System (ADS)

    Chechkin, A. V.; Gonchar, V. Yu.; Gorenflo, R.; Korabel, N.; Sokolov, I. M.

    2008-08-01

    Fractional diffusion equations are widely used to describe anomalous diffusion processes where the characteristic displacement scales as a power of time. For processes lacking such scaling the corresponding description may be given by diffusion equations with fractional derivatives of distributed order. Such equations were introduced in A. V. Chechkin, R. Gorenflo, and I. Sokolov [Phys. Rev. E 66, 046129 (2002)] for the description of the processes getting more anomalous in the course of time (decelerating subdiffusion and accelerating superdiffusion). Here we discuss the properties of diffusion equations with fractional derivatives of the distributed order for the description of anomalous relaxation and diffusion phenomena getting less anomalous in the course of time, which we call, respectively, accelerating subdiffusion and decelerating superdiffusion. For the former process, by taking a relatively simple particular example with two fixed anomalous diffusion exponents we show that the proposed equation effectively describes the subdiffusion phenomenon with diffusion exponent varying in time. For the latter process we demonstrate by a particular example how the power-law truncated Lévy stable distribution evolves in time to the distribution with power-law asymptotics and Gaussian shape in the central part. The special case of two different orders is characteristic for the general situation in which the extreme orders dominate the asymptotics.

  12. Time effect of erosion by solid particle impingement on ductile materials

    NASA Technical Reports Server (NTRS)

    Rao, P. V.; Buckley, D. H.

    1983-01-01

    Erosion and morphological studies of several metals and alloys eroded by normal impingement jets of spherical glass beads and angular crushed-glass erodent particles were conducted. Erosion morphology (the width, depth, and width-depth ratio of the pit) was studied in order to fully investigate the effect of time on erosion rate. The eroded surfaces were studied with a scanning electron microscope, and surface profiles were measured with a profilometer. A large amount of experimental data reported in the literature was also analyzed in order to understand the effect of variables such as the type of device, the erodent particle size and shape, the impact velocity, and the abrasive charge on erosion-rate-versus-time curves. In the present experiments the pit-width-versus-time or pit-depth-versus-time curves were similar to erosion-versus-time curves for glass-bead impingement. The pit-depth-rate-versus-time curves were similar to erosion-rate-versus-time curves for crushed-glass impingement. Analysis of experimental data with two forms of glass resulted in four types of erosion-rate-versus-time curves: (1) incubation, acceleration, and steady-state periods (type I), (2) incubation, acceleration, deceleration, and steady-state periods (type III), (3) incubation, acceleration, peak rate, and deceleration periods (type IV), and (4) incubation, acceleration, steady-state, and deceleration periods (type V).

  13. Before the Drop: Engineers Ready Supersonic Decelerator

    NASA Image and Video Library

    2014-05-21

    A saucer-shaped vehicle part of NASA Low-Density Supersonic Decelerator LDSD project designed to test interplanetary landing devices hangs on a tower in preparation for launch at the Pacific Missile Range Facility in Kauai, Hawaii.

  14. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried; Hipólito-Ricaldi, Wiliam S., E-mail: win_unac@hotmail.com, E-mail: hipolito@ceunes.ufes.br, E-mail: winfried.zimdahl@pq.cnpq.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 againstmore » 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.« less

  15. ACCELERATED FAILURE TIME MODELS PROVIDE A USEFUL STATISTICAL FRAMEWORK FOR AGING RESEARCH

    PubMed Central

    Swindell, William R.

    2009-01-01

    Survivorship experiments play a central role in aging research and are performed to evaluate whether interventions alter the rate of aging and increase lifespan. The accelerated failure time (AFT) model is seldom used to analyze survivorship data, but offers a potentially useful statistical approach that is based upon the survival curve rather than the hazard function. In this study, AFT models were used to analyze data from 16 survivorship experiments that evaluated the effects of one or more genetic manipulations on mouse lifespan. Most genetic manipulations were found to have a multiplicative effect on survivorship that is independent of age and well-characterized by the AFT model “deceleration factor”. AFT model deceleration factors also provided a more intuitive measure of treatment effect than the hazard ratio, and were robust to departures from modeling assumptions. Age-dependent treatment effects, when present, were investigated using quantile regression modeling. These results provide an informative and quantitative summary of survivorship data associated with currently known long-lived mouse models. In addition, from the standpoint of aging research, these statistical approaches have appealing properties and provide valuable tools for the analysis of survivorship data. PMID:19007875

  16. Accelerated failure time models provide a useful statistical framework for aging research.

    PubMed

    Swindell, William R

    2009-03-01

    Survivorship experiments play a central role in aging research and are performed to evaluate whether interventions alter the rate of aging and increase lifespan. The accelerated failure time (AFT) model is seldom used to analyze survivorship data, but offers a potentially useful statistical approach that is based upon the survival curve rather than the hazard function. In this study, AFT models were used to analyze data from 16 survivorship experiments that evaluated the effects of one or more genetic manipulations on mouse lifespan. Most genetic manipulations were found to have a multiplicative effect on survivorship that is independent of age and well-characterized by the AFT model "deceleration factor". AFT model deceleration factors also provided a more intuitive measure of treatment effect than the hazard ratio, and were robust to departures from modeling assumptions. Age-dependent treatment effects, when present, were investigated using quantile regression modeling. These results provide an informative and quantitative summary of survivorship data associated with currently known long-lived mouse models. In addition, from the standpoint of aging research, these statistical approaches have appealing properties and provide valuable tools for the analysis of survivorship data.

  17. Spectrum Evolution of Accelerating or Slowing down Soliton at its Propagation in a Medium with Gold Nanorods

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Lysak, Tatiana M.

    2018-04-01

    We investigate both numerically and analytically the spectrum evolution of a novel type soliton - nonlinear chirped accelerating or decelerating soliton - at a femtosecond pulse propagation in a medium containing noble nanoparticles. In our consideration, we take into account one- or two-photon absorption of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption. The chirped solitons are formed due to the trapping of laser radiation by the nanorods reshaping fronts, if a positive or negative phase-amplitude grating is induced by laser radiation. Accelerating or slowing down chirped soliton formation is accompanied by the soliton spectrum blue or red shift. To prove our numerical results, we derived the approximate analytical law for the spectrum maximum intensity evolution along the propagation coordinate, based on earlier developed approximate analytical solutions for accelerating and decelerating solitons.

  18. Physical condition for the slowing down of cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Zhang, Ming-Jian; Xia, Jun-Qing

    2018-04-01

    The possible slowing down of cosmic acceleration was widely studied. However, judgment on this effect in different dark energy parameterizations was very ambiguous. Moreover, the reason of generating these uncertainties was still unknown. In the present paper, we analyze the derivative of deceleration parameter q‧ (z) using the Gaussian processes. This model-independent reconstruction suggests that no slowing down of acceleration is presented within 95% C.L. from the Union2.1 and JLA supernova data. However, q‧ (z) from the observational H (z) data is a little smaller than zero at 95% C.L., which indicates that future H (z) data may have a potential to test this effect. From the evolution of q‧ (z), we present an interesting constraint on the dark energy and observational data. The physical constraint clearly solves the problem of why some dark energy models cannot produce this effect in previous work. Comparison between the constraint and observational data also shows that most of current data are not in the allowed regions. This implies a reason of why current data cannot convincingly measure this effect.

  19. 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.

  20. Use of induced acceleration to quantify the (de)stabilization effect of external and internal forces on postural responses.

    PubMed

    van Asseldonk, Edwin H F; Carpenter, Mark G; van der Helm, Frans C T; van der Kooij, Herman

    2007-12-01

    Due to the mechanical coupling between the body segments, it is impossible to see with the naked eye the causes of body movements and understand the interaction between movements of different body parts. The goal of this paper is to investigate the use of induced acceleration analysis to reveal the causes of body movements. We derive the analytical equations to calculate induced accelerations and evaluate its potential to study human postural responses to support-surface translations. We measured the kinematic and kinetic responses of a subject to sudden forward and backward translations of a moving platform. The kinematic and kinetics served as input to the induced acceleration analyses. The induced accelerations showed explicitly that the platform acceleration and deceleration contributed to the destabilization and restabilization of standing balance, respectively. Furthermore, the joint torques, coriolis and centrifugal forces caused by swinging of the arms, contributed positively to stabilization of the Center of Mass. It is concluded that induced acceleration analyses is a valuable tool in understanding balance responses to different kinds of perturbations and may help to identify the causes of movement in different pathologies.

  1. 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.

  2. Deformation and deceleration of coronal wave

    NASA Astrophysics Data System (ADS)

    Xue, Z. K.; Qu, Z. Q.; Yan, X. L.; Zhao, L.; Ma, L.

    2013-08-01

    Aims: We studied the kinematics and morphology of two coronal waves to better understand the nature and origin of coronal waves. Methods: Using multi-wavelength observations of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) and the Extreme Ultraviolet Imager (EUVI) on board the twin spacecraft Solar-TErrestrial RElations Observatory (STEREO), we present morphological and dynamic characteristics of consecutive coronal waves on 2011 March 24. We also show the coronal magnetic field based on the potential field source surface model. Results: This event contains several interesting aspects. The first coronal wave initially appeared after a surge-like eruption. Its front was changed and deformed significantly from a convex shape to a line-shaped appearance, and then to a concave configuration during its propagation to the northwest. The initial speeds ranged from 947 km s-1 to 560 km s-1. The first wave decelerated significantly after it passed through a filament channel. After the deceleration, the final propagation speeds of the wave were from 430 km s-1 to 312 km s-1. The second wave was found to appear after the first wave in the northwest side of the filament channel. Its wave front was more diffused and the speed was around 250 km s-1, much slower than that of the first wave. Conclusions: The deformation of the first coronal wave was caused by the different speeds along different paths. The sudden deceleration implies that the refraction of the first wave took place at the boundary of the filament channel. The event provides evidence that the first coronal wave may be a coronal MHD shock wave, and the second wave may be the apparent propagation of the brightenings caused by successive stretching of the magnetic field lines.

  3. 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.

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

    PubMed Central

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

    2016-01-01

    Abstract 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

  5. Separated-orbit bisected energy-recovered linear accelerator

    DOEpatents

    Douglas, David R.

    2015-09-01

    A separated-orbit bisected energy-recovered linear accelerator apparatus and method. The accelerator includes a first linac, a second linac, and a plurality of arcs of differing path lengths, including a plurality of up arcs, a plurality of downgoing arcs, and a full energy arc providing a path independent of the up arcs and downgoing arcs. The up arcs have a path length that is substantially a multiple of the RF wavelength and the full energy arc includes a path length that is substantially an odd half-integer multiple of the RF wavelength. Operation of the accelerator includes accelerating the beam utilizing the linacs and up arcs until the beam is at full energy, at full energy executing a full recirculation to the second linac using a path length that is substantially an odd half-integer of the RF wavelength, and then decelerating the beam using the linacs and downgoing arcs.

  6. Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

    SciTech Connect

    Bose, A., E-mail: abos@lle.rochester.edu; Woo, K. M.; Betti, R.

    2015-07-15

    The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of χ{sub Ω} ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

  7. Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

    SciTech Connect

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

    2015-07-02

    The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of ΧΩ ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

  8. 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

  9. Tragedy and delight: the ethics of decelerated ageing

    PubMed Central

    Gems, David

    2011-01-01

    Biogerontology is sometimes viewed as similar to other forms of biomedical research in that it seeks to understand and treat a pathological process. Yet the prospect of treating ageing is extraordinary in terms of the profound changes to the human condition that would result. Recent advances in biogerontology allow a clearer view of the ethical issues and dilemmas that confront humanity with respect to treating ageing. For example, they imply that organismal senescence is a disease process with a broad spectrum of pathological consequences in late life (causing or exascerbating cardiovascular disease, cancer, neurodegenerative disease and many others). Moreover, in laboratory animals, it is possible to decelerate ageing, extend healthy adulthood and reduce the age-incidence of a broad spectrum of ageing-related diseases. This is accompanied by an overall extension of lifespan, sometimes of a large magnitude. Discussions of the ethics of treating ageing sometimes involve hand-wringing about detrimental consequences (e.g. to society) of marked life extension which, arguably, would be a form of enhancement technology. Yet given the great improvements in health that decelerated ageing could provide, it would seem that the only possible ethical course is to pursue it energetically. Thus, decelerated ageing has an element of tragic inevitability: its benefits to health compel us to pursue it, despite the transformation of human society, and even human nature, that this could entail. PMID:21115537

  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. Effect of static shape deformation on aerodynamics and aerothermodynamics of hypersonic inflatable aerodynamic decelerator

    NASA Astrophysics Data System (ADS)

    Guo, Jinghui; Lin, Guiping; Bu, Xueqin; Fu, Shiming; Chao, Yanmeng

    2017-07-01

    The inflatable aerodynamic decelerator (IAD), which allows heavier and larger payloads and offers flexibility in landing site selection at higher altitudes, possesses potential superiority in next generation space transport system. However, due to the flexibilities of material and structure assembly, IAD inevitably experiences surface deformation during atmospheric entry, which in turn alters the flowfield around the vehicle and leads to the variations of aerodynamics and aerothermodynamics. In the current study, the effect of the static shape deformation on the hypersonic aerodynamics and aerothermodynamics of a stacked tori Hypersonic Inflatable Aerodynamic Decelerator (HIAD) is demonstrated and analyzed in detail by solving compressible Navier-Stokes equations with Menter's shear stress transport (SST) turbulence model. The deformed shape is obtained by structural modeling in the presence of maximum aerodynamic pressure during entry. The numerical results show that the undulating shape deformation makes significant difference to flow structure. In particular, the more curved outboard forebody surface results in local flow separations and reattachments in valleys, which consequently yields remarkable fluctuations of surface conditions with pressure rising in valleys yet dropping on crests while shear stress and heat flux falling in valleys yet rising on crests. Accordingly, compared with the initial (undeformed) shape, the corresponding differences of surface conditions get more striking outboard, with maximum augmentations of 379 pa, 2224 pa, and 19.0 W/cm2, i.e., 9.8%, 305.9%, and 101.6% for the pressure, shear stress and heat flux respectively. Moreover, it is found that, with the increase of angle of attack, the aerodynamic characters and surface heating vary and the aeroheating disparities are evident between the deformed and initial shape. For the deformable HIAD model investigated in this study, the more intense surface conditions and changed flight

  12. Older drivers and rapid deceleration events: Salisbury Eye Evaluation Driving Study.

    PubMed

    Keay, Lisa; Munoz, Beatriz; Duncan, Donald D; Hahn, Daniel; Baldwin, Kevin; Turano, Kathleen A; Munro, Cynthia A; Bandeen-Roche, Karen; West, Sheila K

    2013-09-01

    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 aged 67-87 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 monitoring system (DMS) was used to capture rapid deceleration events (RDEs), 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. 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

  14. Radially dependent angular acceleration of twisted light.

    PubMed

    Webster, Jason; Rosales-Guzmán, Carmelo; Forbes, Andrew

    2017-02-15

    While photons travel in a straight line at constant velocity in free space, the intensity profile of structured light may be tailored for acceleration in any degree of freedom. Here we propose a simple approach to control the angular acceleration of light. Using Laguerre-Gaussian modes as our twisted beams carrying orbital angular momentum, we show that superpositions of opposite handedness result in a radially dependent angular acceleration as they pass through a focus (waist plane). Due to conservation of orbital angular momentum, we find that propagation dynamics are complex despite the free-space medium: the outer part of the beam (rings) rotates in an opposite direction to the inner part (petals), and while the outer part accelerates, the inner part decelerates. We outline the concepts theoretically and confirm them experimentally. Such exotic structured light beams are topical due to their many applications, for instance in optical trapping and tweezing, metrology, and fundamental studies in optics.

  15. Obstetrics at Decisive Crossroads Regarding Pattern-Recognition of Fetal Heart Rate Decelerations: Scientific Principles and Lessons From Memetics.

    PubMed

    Sholapurkar, Shashikant L

    2018-04-01

    The survival of cardiotocography (CTG) as a tool for intrapartum fetal monitoring seems threatened somewhat unjustifiably and unwittingly despite the absence of better alternatives. Fetal heart rate (FHR) decelerations are center-stage (most important) in the interpretation of CTG with maximum impact on three-tier classification. The pattern-discrimination of FHR decelerations is inexorably linked to their nomenclature. Unscientific or flawed nomenclature of decelerations can explain the dysfunctional CTG interpretation leading to errors in detection of acidemic fetuses. There are three contrasting concepts about categorization of FHR decelerations: 1) all rapid decelerations (the vast majority) should be grouped as "variable" because they are predominantly due to cord-compression, 2) all decelerations are due to chemoreflex from fetal hypoxemia hence their timing is not important, and 3) FHR decelerations should be categorized into "early/late/variable" based primarily on their time relationship to contractions. These theoretical concepts are like memes (ideas/beliefs). Lessons from "memetics" are that the most popular, attractive or established beliefs may not necessarily be true, scientific, beneficial or even without harm. Decelerations coincident with contractions with trough corresponding to the peak of contractions cannot be explained by cord-compression or increasing hypoxia (from compromised uteroplacental perfusion, cord-compression or even cerebral hypoperfusion/anoxia purportedly conceivable from head-compression). Decelerations due to hypoxemia would be associated with delayed recovery of decelerations (lag phase). It is a scientific imperative to cast away disproven/falsified theories. Practices based on unscientific theories lead to patient harm. Clinicians should urgently adopt the categorization of FHR decelerations based primarily of the time relationship to contractions as originally proposed by Hon and Caldeyro-Barcia. This analytical review

  16. Obstetrics at Decisive Crossroads Regarding Pattern-Recognition of Fetal Heart Rate Decelerations: Scientific Principles and Lessons From Memetics

    PubMed Central

    Sholapurkar, Shashikant L.

    2018-01-01

    The survival of cardiotocography (CTG) as a tool for intrapartum fetal monitoring seems threatened somewhat unjustifiably and unwittingly despite the absence of better alternatives. Fetal heart rate (FHR) decelerations are center-stage (most important) in the interpretation of CTG with maximum impact on three-tier classification. The pattern-discrimination of FHR decelerations is inexorably linked to their nomenclature. Unscientific or flawed nomenclature of decelerations can explain the dysfunctional CTG interpretation leading to errors in detection of acidemic fetuses. There are three contrasting concepts about categorization of FHR decelerations: 1) all rapid decelerations (the vast majority) should be grouped as “variable” because they are predominantly due to cord-compression, 2) all decelerations are due to chemoreflex from fetal hypoxemia hence their timing is not important, and 3) FHR decelerations should be categorized into “early/late/variable” based primarily on their time relationship to contractions. These theoretical concepts are like memes (ideas/beliefs). Lessons from “memetics” are that the most popular, attractive or established beliefs may not necessarily be true, scientific, beneficial or even without harm. Decelerations coincident with contractions with trough corresponding to the peak of contractions cannot be explained by cord-compression or increasing hypoxia (from compromised uteroplacental perfusion, cord-compression or even cerebral hypoperfusion/anoxia purportedly conceivable from head-compression). Decelerations due to hypoxemia would be associated with delayed recovery of decelerations (lag phase). It is a scientific imperative to cast away disproven/falsified theories. Practices based on unscientific theories lead to patient harm. Clinicians should urgently adopt the categorization of FHR decelerations based primarily of the time relationship to contractions as originally proposed by Hon and Caldeyro-Barcia. This

  17. Effect of Peripheral μ-, δ-, and κ-Opioid Ligands on the Development of Tolerance to Ethanol-Induced Analgesia.

    PubMed

    Sudakov, S K; Alekseeva, E V; Nazarova, G A

    2017-06-01

    We studied the rate of development of tolerance to the ethanol-induced analgesia under the effect of μ-, δ-, and κ-opioid agonists and antagonists not crossing the blood-brain barrier and rapidly inactivated by gastric and duodenal proteolytic enzymes. Activation of gastric κ-opioid receptors eliminated the analgesic effect of ethanol and accelerated the development of tolerance to ethanol-induced analgesia. In contrast, activation of gastric μ-opioid receptors decelerated the development of this tolerance. Activation of gastric δ-opioid receptors produced no effect on examined tolerance. μ-Opioid receptor antagonist decelerated and δ-opioid receptor antagonist accelerated the development of tolerance to ethanol-induced analgesia. Thus, the state of gastric opioid receptors affects the manifestation of ethanol-induced analgesia and the development of tolerance to this effect.

  18. 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.

  19. Probing kinematics and fate of the Universe with linearly time-varying deceleration parameter

    NASA Astrophysics Data System (ADS)

    Akarsu, Özgür; Dereli, Tekin; Kumar, Suresh; Xu, Lixin

    2014-02-01

    The parametrizations q = q 0+ q 1 z and q = q 0+ q 1(1 - a/ a 0) (Chevallier-Polarski-Linder parametrization) of the deceleration parameter, which are linear in cosmic redshift z and scale factor a , have been frequently utilized in the literature to study the kinematics of the Universe. In this paper, we follow a strategy that leads to these two well-known parametrizations of the deceleration parameter as well as an additional new parametrization, q = q 0+ q 1(1 - t/ t 0), which is linear in cosmic time t. We study the features of this linearly time-varying deceleration parameter in contrast with the other two linear parametrizations. We investigate in detail the kinematics of the Universe by confronting the three models with the latest observational data. We further study the dynamics of the Universe by considering the linearly time-varying deceleration parameter model in comparison with the standard ΛCDM model. We also discuss the future of the Universe in the context of the models under consideration.

  20. Fetal heart rate deceleration detection using a discrete cosine transform implementation of singular spectrum analysis.

    PubMed

    Warrick, P A; Precup, D; Hamilton, E F; Kearney, R E

    2007-01-01

    To develop a singular-spectrum analysis (SSA) based change-point detection algorithm applicable to fetal heart rate (FHR) monitoring to improve the detection of deceleration events. We present a method for decomposing a signal into near-orthogonal components via the discrete cosine transform (DCT) and apply this in a novel online manner to change-point detection based on SSA. The SSA technique forms models of the underlying signal that can be compared over time; models that are sufficiently different indicate signal change points. To adapt the algorithm to deceleration detection where many successive similar change events can occur, we modify the standard SSA algorithm to hold the reference model constant under such conditions, an approach that we term "base-hold SSA". The algorithm is applied to a database of 15 FHR tracings that have been preprocessed to locate candidate decelerations and is compared to the markings of an expert obstetrician. Of the 528 true and 1285 false decelerations presented to the algorithm, the base-hold approach improved on standard SSA, reducing the number of missed decelerations from 64 to 49 (21.9%) while maintaining the same reduction in false-positives (278). The standard SSA assumption that changes are infrequent does not apply to FHR analysis where decelerations can occur successively and in close proximity; our base-hold SSA modification improves detection of these types of event series.

  1. 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.

  2. 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. © Georg Thieme Verlag KG Stuttgart · New York.

  3. 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.

  4. 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.

  5. Cardiac Deceleration in Newborns: Habituation, Dishabituation, and Offset Responses

    ERIC Educational Resources Information Center

    Adkinson, Cheryl D.; Berg, W. Keith

    1976-01-01

    A total of 20 neonates were presented with mild intensity blue or blue-green light during presentation of habituation and dishabituation stimuli. Orienting and defensive responses were measured by monitoring heart rate deceleration. (GO)

  6. Constraints on a generalized deceleration parameter from cosmic chronometers

    NASA Astrophysics Data System (ADS)

    Mamon, Abdulla Al

    2018-04-01

    In this paper, we have proposed a generalized parametrization for the deceleration parameter q in order to study the evolutionary history of the universe. We have shown that the proposed model can reproduce three well known q-parametrized models for some specific values of the model parameter α. We have used the latest compilation of the Hubble parameter measurements obtained from the cosmic chronometer (CC) method (in combination with the local value of the Hubble constant H0) and the Type Ia supernova (SNIa) data to place constraints on the parameters of the model for different values of α. We have found that the resulting constraints on the deceleration parameter and the dark energy equation of state support the ΛCDM model within 1σ confidence level at the present epoch.

  7. Validation of a computerized algorithm to quantify fetal heart rate deceleration area.

    PubMed

    Gyllencreutz, Erika; Lu, Ke; Lindecrantz, Kaj; Lindqvist, Pelle G; Nordstrom, Lennart; Holzmann, Malin; Abtahi, Farhad

    2018-05-16

    Reliability in visual cardiotocography interpretation is unsatisfying, which has led to development of computerized cardiotocography. Computerized analysis is well established for antenatal fetal surveillance, but has yet not performed sufficiently during labor. We aimed to investigate the capacity of a new computerized algorithm compared to visual assessment in identifying intrapartum fetal heart rate baseline and decelerations. Three-hundred-and-twelve intrapartum cardiotocography tracings with variable decelerations were analysed by the computerized algorithm and visually examined by two observers, blinded to each other and the computer analysis. The width, depth and area of each deceleration was measured. Four cases (>100 variable decelerations) were subject to in-depth detailed analysis. The outcome measures were bias in seconds (width), beats per minute (depth), and beats (area) between computer and observers by using Bland-Altman analysis. Interobserver reliability was determined by calculating intraclass correlation and Spearman rank analysis. The analysis (312 cases) showed excellent intraclass correlation (0.89-0.95) and very strong Spearman correlation (0.82-0.91). The detailed analysis of > 100 decelerations in 4 cases revealed low bias between the computer and the two observers; width 1.4 and 1.4 seconds, depth 5.1 and 0.7 beats per minute, and area 0.1 and -1.7 beats. This was comparable to the bias between the two observers; 0.3 seconds (width), 4.4 beats per minute (depth), and 1.7 beats (area). The intraclass correlation was excellent (0.90-0.98). A novel computerized algorithm for intrapartum cardiotocography analysis is as accurate as gold standard visual assessment with high correlation and low bias. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  8. Gauging the cosmic acceleration with recent type Ia supernovae data sets

    NASA Astrophysics Data System (ADS)

    Velten, Hermano; Gomes, Syrios; Busti, Vinicius C.

    2018-04-01

    We revisit a model-independent estimator for cosmic acceleration based on type Ia supernovae distance measurements. This approach does not rely on any specific theory for gravity, energy content, nor parametrization for the scale factor or deceleration parameter and is based on falsifying the null hypothesis that the Universe never expanded in an accelerated way. By generating mock catalogs of known cosmologies, we test the robustness of this estimator, establishing its limits of applicability. We detail the pros and cons of such an approach. For example, we find that there are specific counterexamples in which the estimator wrongly provides evidence against acceleration in accelerating cosmologies. The dependence of the estimator on the H0 value is also discussed. Finally, we update the evidence for acceleration using the recent UNION2.1 and Joint Light-Curve Analysis samples. Contrary to recent claims, available data strongly favor an accelerated expansion of the Universe in complete agreement with the standard Λ CDM model.

  9. 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.

  10. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-06-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

  11. 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.

  12. Cosmic transparency and acceleration

    NASA Astrophysics Data System (ADS)

    Holanda, R. F. L.; Pereira, S. H.; Jain, Deepak

    2018-01-01

    In this paper, by considering an absorption probability independent of photon wavelength, we show that current type Ia supernovae (SNe Ia) and gamma-ray burst (GRB) observations plus high-redshift measurements of the cosmic microwave background (CMB) radiation temperature support cosmic acceleration regardless of the transparent-universe assumption. Two flat scenarios are considered in our analyses: the Λ CDM model and a kinematic model. We consider τ (z )=2 ln (1 +z )ɛ, where τ (z ) denotes the opacity between an observer at z =0 and a source at z . This choice is equivalent to deforming the cosmic distance duality relation as DLDA-1=(1 +z )2+ɛ and, if the absorption probability is independent of photon wavelength, the CMB temperature evolution law is TCMB(z )=T0(1 +z )1+2 ɛ /3. By marginalizing on the ɛ parameter, our analyses rule out a decelerating universe at 99.99% C.L. for all scenarios considered. Interestingly, by considering only SNe Ia and GRBs observations, we obtain that a decelerated universe—indicated by ΩΛ≤0.33 and q0>0 —is ruled out around 1.5 σ C.L. and 2 σ C.L., respectively, regardless of the transparent-universe assumption.

  13. Figuring the Acceleration of the Simple Pendulum

    NASA Astrophysics Data System (ADS)

    Lieberherr, Martin

    2011-12-01

    The centripetal acceleration has been known since Huygens' (1659) and Newton's (1684) time.1,2 The physics to calculate the acceleration of a simple pendulum has been around for more than 300 years, and a fairly complete treatise has been given by C. Schwarz in this journal.3 But sentences like "the acceleration is always directed towards the equilibrium position" beside the picture of a swing on a circular arc can still be found in textbooks, as e.g. in Ref. 4. Vectors have been invented by Grassmann (1844)5 and are conveniently used to describe the acceleration in curved orbits, but acceleration is more often treated as a scalar with or without sign, as the words acceleration/deceleration suggest. The component tangential to the orbit is enough to deduce the period of the simple pendulum, but it is not enough to discuss the forces on the pendulum, as has been pointed out by Santos-Benito and A. Gras-Marti.6 A suitable way to address this problem is a nice figure with a catch for classroom discussions or homework. When I plotted the acceleration vectors of the simple pendulum in their proper positions, pictures as in Fig. 1 appeared on the screen. The endpoints of the acceleration vectors, if properly scaled, seemed to lie on a curve with a familiar shape: a cardioid. Is this true or just an illusion?

  14. Suppression of the chain nuclear fusion reaction based on the p+{sup 11}B reaction because of the deceleration of alpha particles

    SciTech Connect

    Shmatov, M. L., E-mail: M.Shmatov@mail.ioffe.ru

    2016-09-15

    It is shown that a rapid deceleration of alpha particles in matter of electron temperature up to 100 keV leads a strong suppression of the chain nuclear fusion reaction on the basis of the p+{sup 11}B reaction with the reproduction of fast protons in the α+{sup 11}B and n+{sup 10}B reactions. The statement that the chain nuclear fusion reaction based on the p+{sup 11}B reaction with an acceleration of {sup 11}B nuclei because of elastic alpha-particle scattering manifests itself in experiments at the PALS (Prague Asterix Laser System) facility is analyzed.

  15. Solar wind deceleration and MHD turbulence in the earth's foreshock region - ISEE 1 and 2 and IMP 8 observations

    NASA Technical Reports Server (NTRS)

    Bonifazi, C.; Moreno, G.; Russell, C. T.; Lazarus, A. J.; Sullivan, J. D.

    1983-01-01

    The interaction of the solar wind with ions backstreaming from the earth's bow shock is investigated using plasma and magnetic field measurements on ISEE 1 and 2 and IMP 8 at widely separated positions in the earth's foreshock. This technique separates temporal and spatial variations within the foreshock. It is found that the solar wind acceleration associated with backstreaming ions is correlated with the amplitude of the MHD turbulence, and that the largest decelerations are seen close to the bow shock. The density of the backstreaming ion beam is strongly correlated with distance from the shock, and decreases by about a factor of three in a distance of about 3R(e).

  16. 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.

  17. 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.

  18. Control of acceleration during sudden ankle supination in people with unstable ankles.

    PubMed

    Vaes, P; Van Gheluwe, B; Duquet, W

    2001-12-01

    Comparative study of differences in functional control during ankle supination in the standing position in matched stable and unstable ankles (ex post facto design). To document acceleration and deceleration during ankle supination in the standing position and to determine differences in control of supination perturbation between stable and unstable ankles. Repetitive ankle sprain can be explained by mechanical instability only in a minority of cases. Exercise therapy for ankle instability is based on clinical experience. Joint stability has not yet been measured in dynamic situations that are similar to the situations leading to a traumatic sprain. The process of motor control during accelerating ankle supination has not been adequately addressed in the literature. Patients with complaints of ankle instability (16 unstable ankles) and nonimpaired controls (18 stable ankles) were examined (N = 17 subjects, 10 women and 7 men). The average age was 23.7 +/- 5.0 years (range, 20-41 y). Control of supination speed was studied during 50 degrees of ankle supination in the standing position using accelerometry (total supination time and deceleration times) and electromyography (latency time). Timing of motor response was estimated by measuring electromechanical delay. The presence of an early, sudden, and presumably passive slowdown of ankle supination in the standing position was observed. Peroneal muscle motor response was detected before the end of the supination. Unstable ankles showed significantly shorter total supination time (109.3 ms versus 124.1 ms) and significantly longer latency time (58.9 ms versus 47.7 ms). Functional control in unstable ankles is less efficient in decelerating the ankle during the supination test procedures used in our study. Our conclusions are based on significantly faster total supination and significantly slower electromyogram response in unstable ankles. The results support the hypothesis that both decelerating the total supination

  19. Rapid deceleration-driven wetting transition during pendant drop deposition on superhydrophobic surfaces.

    PubMed

    Kwon, Hyuk-Min; Paxson, Adam T; Varanasi, Kripa K; Patankar, Neelesh A

    2011-01-21

    A hitherto unknown mechanism for wetting transition is reported. When a pendant drop settles upon deposition, there is a virtual "collision" where its center of gravity undergoes rapid deceleration. This induces a high water hammer-type pressure that causes wetting transition. A new phase diagram shows that both large and small droplets can transition to wetted states due to the new deceleration driven and the previously known Laplace mechanisms, respectively. It is explained how the attainment of a nonwetted Cassie-Baxter state is more restrictive than previously known.

  20. Rapid Deceleration-Driven Wetting Transition during Pendant Drop Deposition on Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Kwon, Hyuk-Min; Paxson, Adam T.; Varanasi, Kripa K.; Patankar, Neelesh A.

    2011-01-01

    A hitherto unknown mechanism for wetting transition is reported. When a pendant drop settles upon deposition, there is a virtual “collision” where its center of gravity undergoes rapid deceleration. This induces a high water hammer-type pressure that causes wetting transition. A new phase diagram shows that both large and small droplets can transition to wetted states due to the new deceleration driven and the previously known Laplace mechanisms, respectively. It is explained how the attainment of a nonwetted Cassie-Baxter state is more restrictive than previously known.

  1. Anticipating the effects of visual gravity during simulated self-motion: estimates of time-to-passage along vertical and horizontal paths.

    PubMed

    Indovina, Iole; Maffei, Vincenzo; Lacquaniti, Francesco

    2013-09-01

    By simulating self-motion on a virtual rollercoaster, we investigated whether acceleration cued by the optic flow affected the estimate of time-to-passage (TTP) to a target. In particular, we studied the role of a visual acceleration (1 g = 9.8 m/s(2)) simulating the effects of gravity in the scene, by manipulating motion law (accelerated or decelerated at 1 g, constant speed) and motion orientation (vertical, horizontal). Thus, 1-g-accelerated motion in the downward direction or decelerated motion in the upward direction was congruent with the effects of visual gravity. We found that acceleration (positive or negative) is taken into account but is overestimated in module in the calculation of TTP, independently of orientation. In addition, participants signaled TTP earlier when the rollercoaster accelerated downward at 1 g (as during free fall), with respect to when the same acceleration occurred along the horizontal orientation. This time shift indicates an influence of the orientation relative to visual gravity on response timing that could be attributed to the anticipation of the effects of visual gravity on self-motion along the vertical, but not the horizontal orientation. Finally, precision in TTP estimates was higher during vertical fall than when traveling at constant speed along the vertical orientation, consistent with a higher noise in TTP estimates when the motion violates gravity constraints.

  2. 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

  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. Amniotic fluid index predicts the relief of variable decelerations after amnioinfusion bolus.

    PubMed

    Spong, C Y; McKindsey, F; Ross, M G

    1996-10-01

    Our purpose was to determine whether intrapartum amniotic fluid index before amnioinfusion can be used to predict response to therapeutic amnioinfusion. Intrapartum patients (n = 85) with repetitive variable decelerations in fetal heart rate that necessitated amnioinfusion (10 ml/min for 60 minutes) underwent determination of amniotic fluid index before and after bolus amnioinfusion. The fetal heart tracing was scored (scorer blinded to amniotic fluid index values) for number and characteristics of variable decelerations before and 1 hour after initiation of amnioinfusion. The amnioinfusion was considered successful if it resulted in a decrease of > or = 50% in total number of variable decelerations or a decrease of > or = 50% in the rate of atypical or severe variable decelerations after administration of the bolus. Spontaneous vaginal births before completion of administration of the bolus (n = 18) were excluded from analysis. The probability of success of amnioinfusion in relation to amniotic fluid index was analyzed with the chi(2) test for progressive sequence. The mean amniotic fluid index before amnioinfusion was 6.2 +/- 3.3 cm. An amniotic fluid index of < or = 5 cm was present in 40% of patients (27/67), and an amniotic fluid index of < or = 8 cm was present in 72% of patients (48/67). The probability of success of amnioinfusion decreased with increasing amniotic fluid index before amnioinfusion (76% [16/21] when initial amniotic fluid index was 0 to 4 cm, 63% [17/27] when initial amniotic fluid index was 4 to 8 cm, 44% [7/16] when initial amniotic fluid index was 8 to 12 cm, and 33% [1/3] when initial amniotic fluid index was > 12 cm, p = 0.03). The incidence of nuchal cords or true umbilical cord knots increased in relation to amniotic fluid index before amnioinfusion. Amniotic fluid index before amnioinfusion can be used to predict the success of amnioinfusion for relief of variable decelerations in fetal heart rate. Failure of amnioinfusion at a high

  5. 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.

  6. Apparent cosmic acceleration from Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Dam, Lawrence H.; Heinesen, Asta; Wiltshire, David L.

    2017-11-01

    Parameters that quantify the acceleration of cosmic expansion are conventionally determined within the standard Friedmann-Lemaître-Robertson-Walker (FLRW) model, which fixes spatial curvature to be homogeneous. Generic averages of Einstein's equations in inhomogeneous cosmology lead to models with non-rigidly evolving average spatial curvature, and different parametrizations of apparent cosmic acceleration. The timescape cosmology is a viable example of such a model without dark energy. Using the largest available supernova data set, the JLA catalogue, we find that the timescape model fits the luminosity distance-redshift data with a likelihood that is statistically indistinguishable from the standard spatially flat Λ cold dark matter cosmology by Bayesian comparison. In the timescape case cosmic acceleration is non-zero but has a marginal amplitude, with best-fitting apparent deceleration parameter, q_{0}=-0.043^{+0.004}_{-0.000}. Systematic issues regarding standardization of supernova light curves are analysed. Cuts of data at the statistical homogeneity scale affect light-curve parameter fits independent of cosmology. A cosmological model dependence of empirical changes to the mean colour parameter is also found. Irrespective of which model ultimately fits better, we argue that as a competitive model with a non-FLRW expansion history, the timescape model may prove a useful diagnostic tool for disentangling selection effects and astrophysical systematics from the underlying expansion history.

  7. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    DOE PAGES

    Gessner, Spencer; Adli, Erik; Allen, James M.; ...

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m -1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

  8. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    PubMed Central

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-01-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m−1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations. PMID:27250570

  9. Accreting X-ray pulsar atmospheres heated by Coulomb deceleration of protons

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Harding, A. K.; Kirk, J. G.; Galloway, D. J.

    1983-01-01

    Results are presented from detailed self-consistent models of accreting magnetized neutron star atmospheres, heated by the gradual deceleration of infalling protons via Coulomb encounters. The temperature and density gradients are calculated assuming momentum and energy balance, coupled with the radiative transfer for two polarizations. The cyclotron resonance effects were treated approximately. These models are characterized by power-law energy spectra, with single pulses at higher frequencies and multiple pulses at lower ones for some aspect angles, as well as a phase-dependent spectral index.

  10. Rydberg Spectroscopy of Zeeman-Decelerated Beams of Metastable Helium Molecules

    NASA Astrophysics Data System (ADS)

    Jansen, Paul; Motsch, Michael; Sprecher, Daniel; Merkt, Frederic

    2014-06-01

    Having three and four electrons, respectively, He_2^+ and He_2 represent systems for which highly accurate ab-initio calculations might become feasible in the near future. With the goal of performing accurate measurements of the rovibrational energy-level structure of He_2^+ by Rydberg spectroscopy of He_2 and multichannel quantum-defect theory extrapolation techniques, we have produced samples of helium molecules in the a ^3Σu^+ state in supersonic beams with velocities tunable down to 100 m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator. The molecules are formed at an initial velocity of 500 m/s by striking a discharge in the pulsed expansion of helium gas from a reservoir kept at a cryogenic temperature of 10 K. Using rotationally-resolved PFI-ZEKE (pulsed-field-ionization zero-kinetic-energy) photoelectron spectroscopy, we have probed the rotational-state distribution of the molecules produced in the discharge and found vibrational levels up to ν" = 2 and rotational levels up to N"=21 to be populated. The molecular beam is coupled to a multistage Zeeman decelerator that employs pulsed inhomogeneous magnetic fields to further reduce the beam velocity. By measuring the quantum-state distribution of the decelerated sample using photoelectron and photoionization spectroscopy we observed no rotational or vibrational state-selectivity of the deceleration process, but found that one of the three spin-rotation components of the He_2 a ^3Σu^+ rotational levels is eliminated. W.-C. Tung, M. Pavanello, L. Adamowicz, J. Chem. Phys. 136, 104309 (2012). D. Sprecher, J. Liu, T. Krähenmann, M. Schäfer, and F. Merkt, J. Chem. Phys. 140, 064304 (2014). M. Motsch, P. Jansen, J. A. Agner, H. Schmutz, and F. Merkt, arXiv:1401.7774. N. Vanhaecke, U. Meier, M. Andrist, B. H. Meier, and F. Merkt, Phys. Rev. A 75, 031402(R) (2007).

  11. Effects of morphine and naloxone on feline colonic transit

    SciTech Connect

    Krevsky, B.; Libster, B.; Maurer, A.H.

    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 themore » other opioid receptors is inferred.« less

  12. 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.

  13. Parachute Decelerator System Performance During the Low Density Supersonic Decelerator Program's First Supersonic Flight Dynamics Test

    NASA Technical Reports Server (NTRS)

    Gallon, John C.; Clark, Ian G.; Witkowski, Allen

    2015-01-01

    During the first Supersonic Flight Dynamics Test (SFDT-1) for NASA's Low Density Supersonic Decelerator (LDSD) Program, the Parachute Decelerator System (PDS) was successfully tested. The main parachute in the PDS was a 30.5-meter supersonic Disksail parachute. The term Disksail is derived from the canopy's constructional geometry, as it combined the aspects of a ringsail and a flat circular round (disk) canopy. The crown area of the canopy contained the disk feature, as a large flat circular disk that extended from the canopy's vent down to the upper gap. From this upper gap to the skirt-band the canopy was constructed with characteristics of sails seen in a ringsail. There was a second lower gap present in this sail region. The canopy maintained a nearly 10x forebody diameter trailing distance with 1.7 Do suspension line lengths. During the test, the parachute was deployed at the targeted Mach and dynamic pressure. Although the supersonic Disksail parachute experienced an anomaly during the inflation process, the system was tested successfully in the environment it was designed to operate within. The nature of the failure seen originated in the disk portion of the canopy. High-speed and high-resolution imagery of the anomaly was captured and has been used to aid in the forensics of the failure cause. In addition to the imagery, an inertial measurement unit (IMU) recorded test vehicle dynamics and loadcells captured the bridle termination forces. In reviewing the imagery and load data a number of hypothesizes have been generated in an attempt to explain the cause of the anomaly.

  14. Holographic dark energy with linearly varying deceleration parameter and escaping big rip singularity of the Bianchi type-V universe

    NASA Astrophysics Data System (ADS)

    Sarkar, Sanjay

    2014-08-01

    The present work deals with the accretion of two minimally interacting fluids: dark matter and a hypothetical isotropic fluid as the holographic dark energy components onto black hole and wormhole in a spatially homogeneous and anisotropic Bianchi type-V universe. To obtain an exact solution of the Einstein's field equations, we use the assumption of linearly varying deceleration parameter. Solution describes effectively the actual acceleration and indicates a big rip type future singularity of the universe. We have studied the evolution of the mass of black hole and the wormhole embedded in this anisotropic universe in order to reproduce a stable universe protected against future-time singularity. It is observed that the accretion of these dark components leads to a gradual decrease and increase of black hole and wormhole mass respectively. Finally, we have found that contrary to our previous case (Sarkar in Astrophys. Space. Sci. 341:651, 2014a), the big rip singularity of the universe with a divergent Hubble parameter of this dark energy model may be avoided by a big trip.

  15. 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

  16. 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.

  17. Development of new platforms for hydrodynamic instability and asymmetry measurements in deceleration phase of indirectly-driven implosions on NIF

    NASA Astrophysics Data System (ADS)

    Pickworth, Louisa

    2017-10-01

    Hydrodynamic instabilities and asymmetries are a major obstacle in the quest to achieve ignition as they cause pre-existing capsule perturbations to grow and ultimately quench the fusion burn in experiments at the National Ignition Facility (NIF). This talk will review recent developments of the experimental platforms and techniques to measure high-mode instabilities and low-mode asymmetries in the deceleration phase of implosions. These new platforms provide a natural link between the acceleration-phase experiments and neutron performance of layered deuterium-tritium implosions. In one innovative technique, self-emission from the hot spot was enhanced with argon dopant to ``self-backlight'' the shell in-flight around peak compression. Experiments with pre-imposed 2-D perturbations measured instability growth factors, while experiments with 3-D, ``native-roughness'' perturbations measured shell integrity in the deceleration phase of implosions. In a complimentary technique, the inner surface of the shell, along with its low-mode asymmetries and high-mode perturbations were visualized in implosions using x-ray emission of a high-Z dopant added to the inner surface of the capsule. These new measurements were instrumental in revealing unexpected surprises and providing improved understanding of the role of instabilities and asymmetries on implosion performance. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  18. 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.

  19. Proposal of a calculation method to determine the structural components' contribution on the deceleration of a passenger compartment based on the energy-derivative method.

    PubMed

    Nagasaka, Kei; Mizuno, Koji; Ito, Daisuke; Saida, Naoya

    2017-05-29

    In car crashes, the passenger compartment deceleration significantly influences the occupant loading. Hence, it is important to consider how each structural component deforms in order to control the passenger compartment deceleration. In frontal impact tests, the passenger compartment deceleration depends on the energy absorption property of the front structures. However, at this point in time there are few papers describing the components' quantitative contributions on the passenger compartment deceleration. Generally, the cross-sectional force is used to examine each component's contribution to passenger compartment deceleration. However, it is difficult to determine each component's contribution based on the cross-sectional forces, especially within segments of the individual members itself such as the front rails, because the force is transmitted continuously and the cross-sectional forces remain the same through the component. The deceleration of a particle can be determined from the derivative of the kinetic energy. Using this energy-derivative method, the contribution of each component on the passenger compartment deceleration can be determined. Using finite element (FE) car models, this method was applied for full-width and offset impact tests. This method was also applied to evaluate the deceleration of the powertrain. The finite impulse response (FIR) coefficient of the vehicle deceleration (input) and the driver chest deceleration (output) was calculated from Japan New Car Assessment Program (JNCAP) tests. These were applied to the component's contribution on the vehicle deceleration in FE analysis, and the component's contribution to the deceleration of the driver's chest was determined. The sum of the contribution of each component coincides with the passenger compartment deceleration in all types of impacts; therefore, the validity of this method was confirmed. In the full-width impact, the contribution of the crush box was large in the initial phases

  20. Can superhorizon cosmological perturbations explain the acceleration of the universe?

    NASA Astrophysics Data System (ADS)

    Hirata, Christopher M.; Seljak, Uroš

    2005-10-01

    We investigate the recent suggestions by Barausse et al. and Kolb et al. that the acceleration of the universe could be explained by large superhorizon fluctuations generated by inflation. We show that no acceleration can be produced by this mechanism. We begin by showing how the application of Raychaudhuri equation to inhomogeneous cosmologies results in several “no go” theorems for accelerated expansion. Next we derive an exact solution for a specific case of initial perturbations, for which application of the Kolb et al. expressions leads to an acceleration, while the exact solution reveals that no acceleration is present. We show that the discrepancy can be traced to higher-order terms that were dropped in the Kolb et al. analysis. We proceed with the analysis of initial value formulation of general relativity to argue that causality severely limits what observable effects can be derived from superhorizon perturbations. By constructing a Riemann normal coordinate system on initial slice we show that no infrared divergence terms arise in this coordinate system. Thus any divergences found previously can be eliminated by a local rescaling of coordinates and are unobservable. We perform an explicit analysis of the variance of the deceleration parameter for the case of single-field inflation using usual coordinates and show that the infrared-divergent terms found by Barausse et al. and Kolb et al. cancel against several additional terms not considered in their analysis. Finally, we argue that introducing isocurvature perturbations does not alter our conclusion that the accelerating expansion of the universe cannot be explained by superhorizon modes.

  1. Ubiquinol-10 supplementation activates mitochondria functions to decelerate senescence in senescence-accelerated mice.

    PubMed

    Tian, Geng; Sawashita, Jinko; Kubo, Hiroshi; Nishio, Shin-ya; Hashimoto, Shigenari; Suzuki, Nobuyoshi; Yoshimura, Hidekane; Tsuruoka, Mineko; Wang, Yaoyong; Liu, Yingye; Luo, Hongming; Xu, Zhe; Mori, Masayuki; Kitano, Mitsuaki; Hosoe, Kazunori; Takeda, Toshio; Usami, Shin-ichi; Higuchi, Keiichi

    2014-06-01

    The present study was conducted to define the relationship between the anti-aging effect of ubiquinol-10 supplementation and mitochondrial activation in senescence-accelerated mouse prone 1 (SAMP1) mice. Here, we report that dietary supplementation with ubiquinol-10 prevents age-related decreases in the expression of sirtuin gene family members, which results in the activation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a major factor that controls mitochondrial biogenesis and respiration, as well as superoxide dismutase 2 (SOD2) and isocitrate dehydrogenase 2 (IDH2), which are major mitochondrial antioxidant enzymes. Ubiquinol-10 supplementation can also increase mitochondrial complex I activity and decrease levels of oxidative stress markers, including protein carbonyls, apurinic/apyrimidinic sites, malondialdehydes, and increase the reduced glutathione/oxidized glutathione ratio. Furthermore, ubiquinol-10 may activate Sirt1 and PGC-1α by increasing cyclic adenosine monophosphate (cAMP) levels that, in turn, activate cAMP response element-binding protein (CREB) and AMP-activated protein kinase (AMPK). These results show that ubiquinol-10 may enhance mitochondrial activity by increasing levels of SIRT1, PGC-1α, and SIRT3 that slow the rate of age-related hearing loss and protect against the progression of aging and symptoms of age-related diseases.

  2. Venus In Situ Explorer Mission design using a mechanically deployed aerodynamic decelerator

    NASA Astrophysics Data System (ADS)

    Smith, B.; Venkatapathy, E.; Wercinski, P.; Yount, B.; Prabhu, D.; Gage, P.; Glaze, L.; Baker, C.

    The Venus In Situ Explorer (VISE) Mission addresses the highest priority science questions within the Venus community outlined in the National Research Council's Decadal Survey. The heritage Venus atmospheric entry system architecture, a 45° sphere-cone rigid aeroshell with a carbon phenolic thermal protection system, may no longer be the preferred entry system architecture compared to other viable alternatives being explored at NASA. A mechanically-deployed aerodynamic decelerator, known as the Adaptive Deployable Entry and Placement Technology (ADEPT), is an entry system alternative that can provide key operational benefits and risk reduction compared to a rigid aeroshell. This paper describes a mission feasibility study performed with the objectives of identifying potential adverse interactions with other mission elements and establishing requirements on decelerator performance. Feasibility is assessed through a launch-to-landing mission design study where the Venus Intrepid Tessera Lander (VITaL), a VISE science payload designed to inform the Decadal Survey results, is repackaged from a rigid aeroshell into the ADEPT decelerator. It is shown that ADEPT reduces the deceleration load on VITaL by an order of magnitude relative to a rigid aeroshell. The more benign entry environment opens up the VISE mission design environment for increased science return, reduced risk, and reduced cost. The ADEPT-VITAL mission concept of operations is presented and details of the entry vehicle structures and mechanisms are given. Finally, entry aerothermal analysis is presented that defines the operational requirements for a revolutionary structural-TPS material employed by ADEPT: three-dimensionally woven carbon cloth. Ongoing work to mitigate key risks identified in this feasibility study is presented.

  3. Deceleration-driven wetting transition of "gently" deposited drops on textured hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Varanasi, Kripa; Kwon, Hyukmin; Paxson, Adam; Patankar, Neelesh

    2010-11-01

    Many applications of rough superhydrophobic surfaces rely on the presence of droplets in a Cassie state on the substrates. A well established understanding is that if sessile droplets are smaller than a critical size, then the large Laplace pressure induces wetting transition from a Cassie to a Wenzel state, i.e., the liquid impales the roughness grooves. Thus, larger droplets are expected to remain in the Cassie state. In this work we report a surprising wetting transition where even a "gentle" deposition of droplets on rough substrates lead to the transition of larger droplets to the Wenzel state. A hitherto unknown mechanism based on rapid deceleration is identified. It is found that modest amount of energy, during the deposition process, is channeled through rapid deceleration into high water hammer pressure which induces wetting transition. A new "phase" diagram is reported which shows that both large and small droplets can transition to Wenzel states due to the deceleration and Laplace mechanisms, respectively. This novel insight reveals for the first time that the attainment of a Cassie state is more restrictive than previous criteria based on the Laplace pressure transition mechanism.

  4. Velocity-tunable slow beams of cold O2 in a single spin-rovibronic state with full angular-momentum orientation by multistage Zeeman deceleration

    NASA Astrophysics Data System (ADS)

    Wiederkehr, A. W.; Schmutz, H.; Motsch, M.; Merkt, F.

    2012-08-01

    Cold samples of oxygen molecules in supersonic beams have been decelerated from initial velocities of 390 and 450 m s-1 to final velocities in the range between 150 and 280 m s-1 using a 90-stage Zeeman decelerator. (2 + 1) resonance-enhanced-multiphoton-ionization (REMPI) spectra of the 3sσ g 3Π g (C) ? two-photon transition of O2 have been recorded to characterize the state selectivity of the deceleration process. The decelerated molecular sample was found to consist exclusively of molecules in the J ‧‧ = 2 spin-rotational component of the X ? ground state of O2. Measurements of the REMPI spectra using linearly polarized laser radiation with polarization vector parallel to the decelerator axis, and thus to the magnetic-field vector of the deceleration solenoids, further showed that only the ? magnetic sublevel of the N‧‧ = 1, J ‧‧ = 2 spin-rotational level is populated in the decelerated sample, which therefore is characterized by a fully oriented total-angular-momentum vector. By maintaining a weak quantization magnetic field beyond the decelerator, the polarization of the sample could be maintained over the 5 cm distance separating the last deceleration solenoid and the detection region.

  5. A unique problem of muscle adaptation from weightlessness: The deceleration deficiency

    NASA Technical Reports Server (NTRS)

    Stauber, William T.

    1989-01-01

    Decelerator problems of the knee are emphasized since the lower leg musculature is known to atrophy in response to weightlessness. However, other important decelerator functions are served by the shoulder muscles, in particular the rotator cuff muscles. Problems in these muscles often result in tears and dislocations as seen in baseball pitchers. It is noteworthy that at least one device currently exists that can measure concentric and eccentric muscle loading including a submaximal simulated free weight exercise (i.e., force-controlled) and simultaneously record integrated EMG analysis appropriate for assessment of all muscle functional activities. Studies should be undertaken to provide information as to the performance of maximal and submaximal exercise in space travelers to define potential problems and provide rationale for prevention.

  6. Engineering design manual of parachute decelerator characteristics for space shuttle solid rocket booster recovery

    NASA Technical Reports Server (NTRS)

    Mansfield, D. L.

    1973-01-01

    The design criteria and characteristics of parachutes for recovery of the solid rocket boosters used with the space shuttle launch are presented. A computer program for analyzing the requirements of the parachute decelerators is described. The computer inputs for both the drogue and main parachute decelerators are; (1) parachute size, (2) deployment conditions, (3) inflation times, (4) reefing times, (5) mass properties, (6) spring properties, and (7) aerodynamic coefficients. Graphs of the parachute performance are included.

  7. Delivery Ring Lattice Modifications for Transitionless Deceleration

    SciTech Connect

    Johnstone, J. A.; Syphers, M. J.

    2016-10-09

    A portion of the remnant Tevatron program infrastruc- ture at Fermilab is being reconfigured to be used for the generation and delivery of proton and muon beams for new high-precision particle physics experiments. With the 8 GeV Booster as its primary source, the Mu2e exper- iment will receive 8.9 GeV/c bunched beam on target, after being stored and slow spilled from the Delivery Ring (DR) -- a refurbished debuncher ring from Tevatron anti- proton production. For the Muon g-2 experiment, the DR will be tuned for 3.1 GeV/c to capture muons off of a target before sending them to thismore » experiment's Storage Ring. The apertures in the beam transport systems are optimized for the large muon beams of this lower-energy experiment. In order to provide further flexibility in the operation of the DR for future possible low-energy, high- intensity particle physics experiments (REDTOP[1], for example) and detector development, investigations are underway into the feasibility of decelerating beams from its maximum kinetic energy of 8 GeV level to lower en- ergies, down to 1-2 GeV. In this paper we look at possi- ble lattice modifications to the DR to avoid a transition crossing during the deceleration process. Hardware re- quirements and other operational implications of this scheme will also be discussed.« less

  8. Rigging Test Bed Development for Validation of Multi-Stage Decelerator Extractions

    NASA Technical Reports Server (NTRS)

    Kenig, Sivan J.; Gallon, John C.; Adams, Douglas S.; Rivellini, Tommaso P.

    2013-01-01

    The Low Density Supersonic Decelerator project is developing new decelerator systems for Mars entry which would include testing with a Supersonic Flight Dynamics Test Vehicle. One of the decelerator systems being developed is a large supersonic ringsail parachute. Due to the configuration of the vehicle it is not possible to deploy the parachute with a mortar which would be the preferred method for a spacecraft in a supersonic flow. Alternatively, a multi-stage extraction process using a ballute as a pilot is being developed for the test vehicle. The Rigging Test Bed is a test venue being constructed to perform verification and validation of this extraction process. The test bed consists of a long pneumatic piston device capable of providing a constant force simulating the ballute drag force during the extraction events. The extraction tests will take place both inside a high-bay for frequent tests of individual extraction stages and outdoors using a mobile hydraulic crane for complete deployment tests from initial pack pull out to canopy extraction. These tests will measure line tensions and use photogrammetry to track motion of the elements involved. The resulting data will be used to verify packing and rigging as well, as validate models and identify potential failure modes in order to finalize the design of the extraction system.

  9. 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.

  10. Aerodynamic and Thermal Performance Characteristics of Supersonic-X Type Decelerators at Mach Number 8

    DTIC Science & Technology

    1977-02-01

    SUPERSONIC -X TYPE DECELERATORS AT MACH NUMBER 8 t’z.r I # I JJ’, o,. VON KARMAN GAS DYNAMICS FACILITY ARNOLD ENGINEERING DEVELOPMENT CENTER AIR FORCE...AERODYNAMIC AND THERMAL PERFORMANCE CHARACTERISTICS OF SUPERSONIC - X TYPE DECELERATORS AT MACH NUMBER 8 ’ 7 AU THORCs,: p ; J . D. Corce , ARO, Inc...pe r fo rmance cha rac t e r i s t i c s of model nylon, Kevlar 29, and Bisbenzimidazobenzophenanthroline Supersonic -X type parachutes behind a

  11. 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.

  12. 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.

  13. Underbody Blast Models of TBI Caused by Hyper-Acceleration and Secondary Head Impact

    DTIC Science & Technology

    2016-02-01

    discovery rate (FDR), which controls for the expected proportion of false rejected hypotheses. ANOVA was performed to evaluate the significance in gene...acceleration/deceleration11,27 and blast4,13 have also been designed for the purpose of evaluating coup-contrecoup and blast wave energies potentially... evaluation of different angles/ locations of the projectile impact to the surface of the rat head. Finally, pilot studies were conducted to provide further

  14. Long-term administration of pDC-Stimulative Lactococcus lactis strain decelerates senescence and prolongs the lifespan of mice.

    PubMed

    Sugimura, Tetsu; Jounai, Kenta; Ohshio, Konomi; Suzuki, Hiroaki; Kirisako, Takayoshi; Sugihara, Yoshihiko; Fujiwara, Daisuke

    2018-05-01

    The decline in immune function caused by aging increases the risk of infectious diseases, tumorigeneses and chronic inflammation, resulting in accelerating senescence. We previously reported a lactic acid bacteria, Lactococcus lactis strain Plasma (synonym of Lactococcus lactis subsp. lactis JCM 5805, Lc-Plasma), that stimulates plasmacytoid dendritic cells (pDCs), which play a crucial role in phylaxis from viral infection. In this study, we investigated the anti-aging effects of long-term oral administration of Lc-Plasma in a senescence-accelerated mouse strain, SAMP6. Mice given Lc-Plasma showed a significant improvement in survival rate at 82 weeks and a decreased senescence score as compared with control mice throughout this study. Anatomic analysis at 82 weeks revealed that the frequency of altered hepatocellular foci was significantly lower, and the incidence of other pathological findings in the liver and lungs tended to be lower in Lc-Plasma mice than in control mice. Transcription level of the IL-1β gene in lungs also tended to be lower in Lc-Plasma mice. Furthermore, the thinning of skin and age-related decrease in muscle mass were also significantly suppressed in the Lc-Plasma group as compared with the control group. Consistent with these phenotypic features, pDCs activity was significantly higher in Lc-Plasma mice than in control mice. In conclusion, long-term administration of Lc-Plasma can decelerate senescence and prolong lifespan via maintenance of the immune system due to activation of pDCs. Copyright © 2018 Elsevier B.V. All rights reserved.

  15. Ubiquinol-10 Supplementation Activates Mitochondria Functions to Decelerate Senescence in Senescence-Accelerated Mice

    PubMed Central

    Tian, Geng; Sawashita, Jinko; Kubo, Hiroshi; Nishio, Shin-ya; Hashimoto, Shigenari; Suzuki, Nobuyoshi; Yoshimura, Hidekane; Tsuruoka, Mineko; Wang, Yaoyong; Liu, Yingye; Luo, Hongming; Xu, Zhe; Mori, Masayuki; Kitano, Mitsuaki; Hosoe, Kazunori; Takeda, Toshio; Usami, Shin-ichi

    2014-01-01

    Abstract Aim: The present study was conducted to define the relationship between the anti-aging effect of ubiquinol-10 supplementation and mitochondrial activation in senescence-accelerated mouse prone 1 (SAMP1) mice. Results: Here, we report that dietary supplementation with ubiquinol-10 prevents age-related decreases in the expression of sirtuin gene family members, which results in the activation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a major factor that controls mitochondrial biogenesis and respiration, as well as superoxide dismutase 2 (SOD2) and isocitrate dehydrogenase 2 (IDH2), which are major mitochondrial antioxidant enzymes. Ubiquinol-10 supplementation can also increase mitochondrial complex I activity and decrease levels of oxidative stress markers, including protein carbonyls, apurinic/apyrimidinic sites, malondialdehydes, and increase the reduced glutathione/oxidized glutathione ratio. Furthermore, ubiquinol-10 may activate Sirt1 and PGC-1α by increasing cyclic adenosine monophosphate (cAMP) levels that, in turn, activate cAMP response element-binding protein (CREB) and AMP-activated protein kinase (AMPK). Innovation and Conclusion: These results show that ubiquinol-10 may enhance mitochondrial activity by increasing levels of SIRT1, PGC-1α, and SIRT3 that slow the rate of age-related hearing loss and protect against the progression of aging and symptoms of age-related diseases. Antioxid. Redox Signal. 20, 2606–2620 PMID:24124769

  16. 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.

  17. Correlation of arterial fetal base deficit and lactate changes with severity of variable heart rate decelerations in the near-term ovine fetus.

    PubMed

    Ross, Michael G; Jessie, Marquis; Amaya, Kevin; Matushewski, Brad; Durosier, L Daniel; Frasch, Martin G; Richardson, Bryan S

    2013-04-01

    Recent guidelines classify variable decelerations without detail as to degree of depth. We hypothesized that variable deceleration severity is highly correlated with fetal base deficit accumulation. Seven near-term fetal sheep underwent a series of graded umbilical cord occlusions resulting in mild (30 bpm decrease), moderate (60 bpm decrease), or severe (decrease of 90 bpm to baseline <70 bpm) variable decelerations at 2.5 minute intervals. Mild, moderate, and severe variable decelerations increased fetal base deficit (0.21 ± 0.03, 0.27 ± 0.03, and 0.54 ± 0.09 mEq/L per minute) in direct proportion to severity. During recovery, fetal base deficit cleared at 0.12 mEq/L per minute. In this model, ovine fetuses can tolerate repetitive mild and moderate variable decelerations with minimal change in base deficit and lactate. In contrast, repetitive severe variable decelerations may result in significant base deficit increases, dependent on frequency. Modified guideline differentiation of mild/moderate vs severe variable decelerations may aid in the interpretation of fetal heart rate tracings and optimization of clinical management paradigms. Copyright © 2013 Mosby, Inc. All rights reserved.

  18. Evaluation of the fetal state by automatic analysis of the heart rate. 2. Deceleration areas and umbilical artery blood pH.

    PubMed

    Tournaire, M; Sturbois, G; Ripoche, A; Le Houezec, R; Breart, G; Chavinie, J; Sureau, C

    1976-01-01

    Fetal heart rate (FHR) deceleration areas were studied to obtain by objective measurement of the FHR, their prognostic value of the new-born state. 1. There is a reasonably good correlation between FHR deceleration areas and UApH (Tab. II). Such a correlation was found by SHELLEY and TIPTON [6] for the whole deceleration area, and by TOURNAIRE et al. [10] for areas divided in a slightly different way. The correlation coefficients between FHR deceleration areas and Apgar score at 1 minute are within a close range of those of the FHR deceleration area and UApH (Tab. I and II). 2. According to the time relationship between deceleration areas and uterine contractions the best correlation coefficient was obtained surprisingly for total, followed by residual and then simultaneous areas. These results agree with those of SHELLEY and TIPTON [6] suggesting that in practice a simple measurement of the whole deceleration area, regardless of the uterine contractions is a sufficient method in evaluating FHR patterns. 3. The special purpose computer built by the BAUDELOCQUE research group can be used on-line, thus in clinical practice. It was not the case for the manual method [4] or the method using a large programmed computer [10]. 4 The evaluation of deceleration areas appears to have several advantages: 1. It provides objective measurements. 2. The unit used is independant of factors such as display speed or scale of the strip-chart. 3. The data is reduced: A few numbers replace the long descriptions of the usual clinical classifications.

  19. Exploratory field trial of motorcycle autonomous emergency braking (MAEB): Considerations on the acceptability of unexpected automatic decelerations.

    PubMed

    Savino, Giovanni; Pierini, Marco; Thompson, Jason; Fitzharris, Michael; Lenné, Michael G

    2016-11-16

    Autonomous emergency braking (AEB) acts to slow down a vehicle when an unavoidable impending collision is detected. In addition to documented benefits when applied to passenger cars, AEB has also shown potential when applied to motorcycles (MAEB). However, the feasibility of MAEB as practically applied to motorcycles in the real world is not well understood. In this study we performed a field trial involving 16 riders on a test motorcycle subjected to automatic decelerations, thus simulating MAEB activation. The tests were conducted along a rectilinear path at nominal speed of 40 km/h and with mean deceleration of 0.15 g (15% of full braking) deployed at random times. Riders were also exposed to one final undeclared brake activation with the aim of providing genuinely unexpected automatic braking events. Participants were consistently able to manage automatic decelerations of the vehicle with minor to moderate effort. Results of undeclared activations were consistent with those of standard runs. This study demonstrated the feasibility of a moderate automatic deceleration in a scenario of motorcycle travelling in a straight path, supporting the notion that the application of AEB on motorcycles is practicable. Furthermore, the proposed field trial can be used as a reference for future regulation or consumer tests in order to address safety and acceptability of unexpected automatic decelerations on a motorcycle.

  20. Analysis of Automobile Crash Test Data and Recommendations for Acquiring and Filtering Accelerometer Data

    DOT National Transportation Integrated Search

    1975-06-01

    An attempt is made to define the meaningful frequency content of occupant compartment deceleration data in order to establish effective filtering guidelines which will enhance the important features of the deceleration pulse. Acceleration and displac...

  1. Heart-rate deceleration predicting the determination of costly punishment: Implications for its involvement in cognitive effort expended in overriding self-interest.

    PubMed

    Osumi, Takahiro; Ohira, Hideki

    2016-11-01

    Previous studies have investigated which biological markers predict the decision to reject unfair monetary offers, termed costly punishment, in the ultimatum game (UG). One study showed that a phasic deceleratory response in heart rate (HR) is evoked in the responder more readily by offers that will be rejected than by offers that will be accepted. However, owing to the paucity of supporting evidence, it remains unclear whether and why HR deceleration can predict the decisions of UG responders. In this paper, we report two separate studies (Study 1 and Study 2) using modified versions of the UG to explore factors modulating HR deceleration. In Study 1, as well as unfair offers, fair offers induced greater HR deceleration when responders were forced to reject offers compared to when they were forced to accept offers. In Study 2, a high rejection rate for very unfair offers was sustained, regardless of the size of the offers, but HR deceleration was increased for unfair but large offers, relative to unfair, small offers. Moreover, HR deceleration was associated with the rejection of large offers. However, across the two studies, HR deceleration did not simply vary depending on unfairness. These findings support the possibility that HR decelerates as a function of cognitive load in determining costly punishment. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Unsteady flow over a decelerating rotating sphere

    NASA Astrophysics Data System (ADS)

    Turkyilmazoglu, M.

    2018-03-01

    Unsteady flow analysis induced by a decelerating rotating sphere is the main concern of this paper. A revolving sphere in a still fluid is supposed to slow down at an angular velocity rate that is inversely proportional to time. The governing partial differential equations of motion are scaled in accordance with the literature, reducing to the well-documented von Kármán equations in the special circumstance near the pole. Both numerical and perturbation approaches are pursued to identify the velocity fields, shear stresses, and suction velocity far above the sphere. It is detected that an induced flow surrounding the sphere acts accordingly to adapt to the motion of the sphere up to some critical unsteadiness parameters at certain latitudes. Afterward, the decay rate of rotation ceases such that the flow at the remaining azimuths starts revolving freely. At a critical unsteadiness parameter corresponding to s = -0.681, the decelerating sphere rotates freely and requires no more torque. At a value of s exactly matching the rotating disk flow at the pole identified in the literature, the entire flow field around the sphere starts revolving faster than the disk itself. Increasing values of -s almost diminish the radial outflow. This results in jet flows in both the latitudinal and meridional directions, concentrated near the wall region. The presented mean flow results will be useful for analyzing the instability features of the flow, whether of a convective or absolute nature.

  3. Application of energy derivative method to determine the structural components' contribution to deceleration in crashes.

    PubMed

    Nagasaka, Kei; Mizuno, Koji; Thomson, Robert

    2018-03-26

    For occupant protection, it is important to understand how a car's deceleration time history in crashes can be designed using efficient of energy absorption by a car body's structure. In a previous paper, the authors proposed an energy derivative method to determine each structural component's contribution to the longitudinal deceleration of a car passenger compartment in crashes. In this study, this method was extended to 2 dimensions in order to analyze various crash test conditions. The contribution of each structure estimated from the energy derivative method was compared to that from a conventional finite element (FE) analysis method using cross-sectional forces. A 2-dimensional energy derivative method was established. A simple FE model with a structural column connected to a rigid body was used to confirm the validity of this method and to compare with the result of cross-sectional forces determined using conventional analysis. Applying this method to a full-width frontal impact simulation of a car FE model, the contribution and the cross-sectional forces of the front rails were compared. In addition, this method was applied to a pedestrian headform FE simulation in order to determine the influence of the structural and inertia forces of the hood structures on the deceleration of the headform undergoing planar motion. In an oblique impact of the simple column and rigid body model, the sum of the contributions of each part agrees with the rigid body deceleration, which indicates the validity of the 2-dimensional energy derivative method. Using the energy derivative method, it was observed that each part of the column contributes to the deceleration of the rigid body by collapsing in the sequence from front to rear, whereas the cross-sectional force at the rear of the column cannot detect the continuous collapse. In the full-width impact of a car, the contributions of the front rails estimated in the energy derivative method was smaller than that using the

  4. 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.

  5. High gradient tests of metallic mm-wave accelerating structures

    DOE PAGES

    Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

    2017-05-10

    This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

  6. High gradient tests of metallic mm-wave accelerating structures

    SciTech Connect

    Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon

    This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

  7. Time-spatial drift of decelerating electromagnetic pulses.

    PubMed

    Nerukh, Alexander G; Nerukh, Dmitry A

    2013-07-15

    A time dependent electromagnetic pulse generated by a current running laterally to the direction of the pulse propagation is considered in paraxial approximation. It is shown that the pulse envelope moves in the time-spatial coordinates on the surface of a parabolic cylinder for the Airy pulse and a hyperbolic cylinder for the Gaussian. These pulses propagate in time with deceleration along the dominant propagation direction and drift uniformly in the lateral direction. The Airy pulse stops at infinity while the asymptotic velocity of the Gaussian is nonzero.

  8. Magnetized strange quark matter in f(R, T) gravity with bilinear and special form of time varying deceleration parameter

    NASA Astrophysics Data System (ADS)

    Sahoo, P. K.; Sahoo, Parbati; Bishi, Binaya K.; Aygün, Sezgin

    2018-04-01

    In this paper, we have studied homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type-I model with magnetized strange quark matter (MSQM) distribution and cosmological constant Λ in f(R, T) gravity where R is the Ricci scalar and T the trace of matter source. The exact solutions of the field equations are obtained under bilinear and special form of time varying deceleration parameter (DP). Firstly, we have considered two specific forms of bilinear DP with a single parameter of the form: q = α(1-t)/1+t and q = -αt/1+t, which leads to the constant or linear nature of the function based on the constant α. Second one is the special form of the DP as q = - 1 + β/1+aβ. From the results obtained here, one can observe that in the early universe magnetic flux has more effects and it reduces gradually in the later stage. For t → ∞, we get p → -Bc and ρ → Bc. The behaviour of strange quark matter along with magnetic epoch gives an idea of accelerated expansion of the universe as per the observations of the type Ia Supernovae.

  9. Anticipating the effects of gravity when intercepting moving objects: differentiating up and down based on nonvisual cues.

    PubMed

    Senot, Patrice; Zago, Myrka; Lacquaniti, Francesco; McIntyre, Joseph

    2005-12-01

    Intercepting an object requires a precise estimate of its time of arrival at the interception point (time to contact or "TTC"). It has been proposed that knowledge about gravitational acceleration can be combined with first-order, visual-field information to provide a better estimate of TTC when catching falling objects. In this experiment, we investigated the relative role of visual and nonvisual information on motor-response timing in an interceptive task. Subjects were immersed in a stereoscopic virtual environment and asked to intercept with a virtual racket a ball falling from above or rising from below. The ball moved with different initial velocities and could accelerate, decelerate, or move at a constant speed. Depending on the direction of motion, the acceleration or deceleration of the ball could therefore be congruent or not with the acceleration that would be expected due to the force of gravity acting on the ball. Although the best success rate was observed for balls moving at a constant velocity, we systematically found a cross-effect of ball direction and acceleration on success rate and response timing. Racket motion was triggered on average 25 ms earlier when the ball fell from above than when it rose from below, whatever the ball's true acceleration. As visual-flow information was the same in both cases, this shift indicates an influence of the ball's direction relative to gravity on response timing, consistent with the anticipation of the effects of gravity on the flight of the ball.

  10. Verification and Validation Testing of the Parachute Decelerator System Prior to the First Supersonic Flight Dynamics Test for the Low Density Supersonic Decelerator Program

    NASA Technical Reports Server (NTRS)

    Gallon, John C.; Witkowski, Allen

    2015-01-01

    The Parachute Decelerator System (PDS) is comprised of all components associated with the supersonic parachute and its associated deployment. During the Supersonic Flight Dynamics Test (SFDT), for the Low Density Supersonic Decelerators Program, the PDS was required to deploy the supersonic parachute in a defined fashion. The PDS hardware includes three major subsystems that must function together. The first subsystem is the Parachute Deployment Device (PDD), which acts as a modified pilot deployment system. It is comprised of a pyrotechnic mortar, a Kevlar ballute, a lanyard actuated pyrotechnic inflation aid, and rigging with its associated thermal protection material (TPS). The second subsystem is the supersonic parachute deployment hardware. This includes all of the parachute specific rigging that includes the parachute stowage can and the rigging including TPS and bridle stiffeners for bridle management during deployment. The third subsystem is the Supersonic Parachute itself, which includes the main parachute and deployment bags. This paper summarizes the verification and validation of the deployment process, from the initialization of the PDS system through parachute bag strip that was done prior to the first SFDT.

  11. LRS Bianchi type-I cosmological model with constant deceleration parameter in f(R,T) gravity

    NASA Astrophysics Data System (ADS)

    Bishi, Binaya K.; Pacif, S. K. J.; Sahoo, P. K.; Singh, G. P.

    A spatially homogeneous anisotropic LRS Bianchi type-I cosmological model is studied in f(R,T) gravity with a special form of Hubble's parameter, which leads to constant deceleration parameter. The parameters involved in the considered form of Hubble parameter can be tuned to match, our models with the ΛCDM model. With the present observed value of the deceleration parameter, we have discussed physical and kinematical properties of a specific model. Moreover, we have discussed the cosmological distances for our model.

  12. Review of NASA In-Space Propulsion Technology Program Inflatable Decelerator Investments

    NASA Technical Reports Server (NTRS)

    Richardson, E. H.; Mnk, M. M.; James, B. F.; Moon, S. A.

    2005-01-01

    The NASA In-Space Propulsion Technology (ISPT) Program is managed by the NASA Headquarters Science Mission Directorate and is implemented by the Marshall Space Flight Center in Huntsville, Alabama. The ISPT objective is to fund development of promising in-space propulsion technologies that can decrease flight times, decrease cost, or increase delivered payload mass for future science missions. Before ISPT will invest in a technology, the Technology Readiness Level (TRL) of the concept must be estimated to be at TRL 3. A TRL 3 signifies that the technical community agrees that the feasibility of the concept has been proven through experiment or analysis. One of the highest priority technology investments for ISPT is Aerocapture. The aerocapture maneuver uses a planetary atmosphere to reduce or alter the speed of a vehicle allowing for quick, propellantless (or using very little propellant) orbit capture. The atmosphere is used as a brake, transferring the energy associated with the vehicle's high speed into thermal energy. The ISPT Aerocapture Technology Area (ATA) is currently investing in the development of advanced lightweight ablative thermal protection systems, high temperature composite structures, and heat-flux sensors for rigid aeroshells. The heritage of rigid aeroshells extends back to the Apollo era and this technology will most likely be used by the first generation aerocapture vehicle. As a second generation aerocapture technology, ISPT is investing in three inflatable aerodynamic decelerator concepts for planetary aerocapture. They are: trailing ballute (balloon-parachute), attached afterbody ballute, and an inflatable aeroshell. ISPT also leverages the NASA Small Business Innovative Research Program for additional inflatable decelerator technology development. In mid-2004 ISPT requested an independent review of the three inflatable decelerator technologies funded directly by ISPT to validate the TRL and to identify technology maturation concerns. An

  13. Review of NASA In-Space Propulsion Technology Program Inflatable Decelerator Investments

    NASA Technical Reports Server (NTRS)

    Richardson, Erin H.; Munk, Michelle M.; James, Bonnie F.; Moon, Steve A.

    2005-01-01

    The NASA In-Space Propulsion Technology (ISPT) Program is managed by the NASA Headquarters Science Mission Directorate and is implemented by the Marshall Space Flight Center in Huntsville, Alabama. The ISPT objective is to fund development of promising in- space propulsion technologies that can decrease flight times, decrease cost, or increase delivered payload mass for future science missions. Before ISPT will invest in a technology, the Technology Readiness Level (TRL) of the concept must be estimated to be at TRL 3. A TRL 3 signifies that the technical community agrees that the feasibility of the concept has been proven through experiment or analysis. One of the highest priority technology investments for ISPT is Aerocapture. The aerocapture maneuver uses a planetary atmosphere to reduce or alter the speed of a vehicle allowing for quick, propellantless (or using very little propellant) orbit capture. The atmosphere is used as a brake, transferring the energy associated with the vehicle s high speed into thermal energy. The ISPT Aerocapture Technology Area (ATA) is currently investing in the development of advanced lightweight ablative thermal protection systems, high temperature composite structures, and heat-flux sensors for rigid aeroshells. The heritage of rigid aeroshells extends back to the Apollo era and this technology will most likely be used by the first generation aerocapture vehicle. As a second generation aerocapture technology, ISPT is investing in three inflatable aerodynamic decelerator concepts for planetary aerocapture. They are: trailing ballute (balloon-parachute), attached afterbody ballute, and an inflatable aeroshell. ISPT also leverages the NASA Small Business Innovative Research Program for additional inflatable decelerator technology development. In mid-2004 ISPT requested an independent review of the three inflatable decelerator technologies funded directly by ISPT to validate the TRL and to identify technology maturation concerns. An

  14. 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.

  15. 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

  16. 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.

  17. Singular F(R) cosmology unifying early- and late-time acceleration with matter and radiation domination era

    NASA Astrophysics Data System (ADS)

    Odintsov, S. D.; Oikonomou, V. K.

    2016-06-01

    We present some cosmological models which unify the late- and early-time acceleration eras with the radiation and the matter domination era, and we realize the cosmological models by using the theoretical framework of F(R) gravity. Particularly, the first model unifies the late- and early-time acceleration with the matter domination era, and the second model unifies all the evolution eras of our Universe. The two models are described in the same way at early and late times, and only the intermediate stages of the evolution have some differences. Each cosmological model contains two Type IV singularities which are chosen to occur one at the end of the inflationary era and one at the end of the matter domination era. The cosmological models at early times are approximately identical to the R 2 inflation model, so these describe a slow-roll inflationary era which ends when the slow-roll parameters become of order one. The inflationary era is followed by the radiation era and after that the matter domination era follows, which lasts until the second Type IV singularity, and then the late-time acceleration era follows. The models have two appealing features: firstly they produce a nearly scale invariant power spectrum of primordial curvature perturbations and a scalar-to-tensor ratio which are compatible with the most recent observational data and secondly, it seems that the deceleration-acceleration transition is crucially affected by the presence of the second Type IV singularity which occurs at the end of the matter domination era. As we demonstrate, the Hubble horizon at early times shrinks, as expected for an initially accelerating Universe, then during the matter domination era, it expands and finally after the Type IV singularity, the Hubble horizon starts to shrink again, during the late-time acceleration era. Intriguingly enough, the deceleration-acceleration transition, occurs after the second Type IV singularity. In addition, we investigate which F(R) gravity

  18. 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.

  19. Simulation of decelerating landing approaches on an externally blown flap STOL transport airplane

    NASA Technical Reports Server (NTRS)

    Grantham, W. D.; Nguyen, L. T.; Deal, P. L.

    1974-01-01

    A fixed-base simulator program was conducted to define the problems and methods for solution associated with performing decelerating landing approaches on a representative STOL transport having a high wing and equipped with an external-flow jet flap in combination with four high-bypass-ratio fan-jet engines. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom and the aerodynamic inputs were based on measured wind-tunnel data. The pilot's task was to capture the localizer and the glide slope and to maintain them as closely as possible while decelerating from an initial airspeed of 140 knots to a final airspeed of 75 knots, while under IFR conditions.

  20. 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.

  1. NOx profile around a signalized intersection of busy roadway

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Hwan; Lee, Seung-Bok; Woo, Sung Ho; Bae, Gwi-Nam

    2014-11-01

    The NOx pollution profile around a signalized intersection of a busy roadway was investigated to understand the effect of traffic control on urban air pollution. Traffic flow patterns were classified into three categories of quasi-cruising, a combination of deceleration and acceleration, and a combination of deceleration, idling, and acceleration. The spatial distribution of air pollution levels around an intersection could be represented as a quasi-normal distribution, whose peak height was aggravated by increased emissions due to transient driving patterns. The peak concentration of NOx around the signalized intersection for the deceleration, idling, and acceleration category was five times higher than that for the quasi-cruising category. Severe levels of NOx pollution tailed off approximately 400 m from the center of the intersection. Approximately 200-1000 ppb of additional NOx was observed when traffic was decelerating, idling, and accelerating within the intersection zone, resulting in high exposure levels for pedestrians around the intersection. We propose a fluctuating horizontal distribution of motor vehicle-induced air pollutants as a function of time.

  2. Abrupt deceleration of molecular evolution linked to the origin of arborescence in ferns.

    PubMed

    Korall, Petra; Schuettpelz, Eric; Pryer, Kathleen M

    2010-09-01

    Molecular rate heterogeneity, whereby rates of molecular evolution vary among groups of organisms, is a well-documented phenomenon. Nonetheless, its causes are poorly understood. For animals, generation time is frequently cited because longer-lived species tend to have slower rates of molecular evolution than their shorter-lived counterparts. Although a similar pattern has been uncovered in flowering plants, using proxies such as growth form, the underlying process has remained elusive. Here, we find a deceleration of molecular evolutionary rate to be coupled with the origin of arborescence in ferns. Phylogenetic branch lengths within the “tree fern” clade are considerably shorter than those of closely related lineages, and our analyses demonstrate that this is due to a significant difference in molecular evolutionary rate. Reconstructions reveal that an abrupt rate deceleration coincided with the evolution of the long-lived tree-like habit at the base of the tree fern clade. This suggests that a generation time effect may well be ubiquitous across the green tree of life, and that the search for a responsible mechanism must focus on characteristics shared by all vascular plants. Discriminating among the possibilities will require contributions from various biological disciplines,but will be necessary for a full appreciation of molecular evolution.

  3. Acceleration of black hole universe

    NASA Astrophysics Data System (ADS)

    Zhang, T. X.; Frederick, C.

    2014-01-01

    Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.

  4. New Kinematical Constraints on Cosmic Acceleration

    SciTech Connect

    Rapetti, David; Allen, Steve W.; Amin, Mustafa A.

    2007-05-25

    We present and employ a new kinematical approach to ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t)=1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for amore » late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t)=j, we measure q{sub 0}=-0.81 {+-} 0.14 and j=2.16 +0.81 -0.75, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible.« less

  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. Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies

    NASA Astrophysics Data System (ADS)

    Susoeff, A. R.; Hawke, R. S.; Morrison, J. J.; Dimonte, G.; Remington, B. A.

    1993-12-01

    An electromagnetic accelerator in the form of a linear electric motor (LEM) has been designed to achieve controlled acceleration profiles of a carriage containing hydrodynamically unstable fluids for the investigation of the development of turbulent mix. The Rayleigh-Taylor instability is investigated by accelerating two dissimilar density fluids using the LEM to achieve a wide variety of acceleration and deceleration profiles. The acceleration profiles are achieved by independent control of rail and augmentation currents. A variety of acceleration-time profiles are possible including: (1) constant, (2) impulsive and (3) shaped. The LEM and support structure are a robust design in order to withstand high loads with deflections and to mitigate operational vibration. Vibration of the carriage during acceleration could create artifacts in the data which would interfere with the intended study of the Rayleigh-Taylor instability. The design allows clear access for diagnostic techniques such as laser induced fluorescence radiography, shadowgraphs and particle imaging velocimetry. Electromagnetic modeling codes were used to optimize the rail and augmentation coil positions within the support structure framework. Results of contemporary studies for non-arcing sliding contact of solid armatures are used for the design of the driving armature and the dynamic electromagnetic braking system. A 0.6MJ electrolytic capacitor bank is used for energy storage to drive the LEM. This report will discuss a LEM design which will accelerate masses of up to 3kg to a maximum of about 3000g(sub o), where g(sub o) is accelerated due to gravity.

  7. From catastrophic acceleration to deceleration of liquid plugs in prewetted capillary tubes

    NASA Astrophysics Data System (ADS)

    Magniez, Juan; Baudoin, Michael; Zoueshtiagh, Farzam; Lemac/Lics Team

    2016-11-01

    Liquid/gas flows in capillaries are involved in a multitude of systems including flow in porous media, petroleum extraction, imbibition of paper or flows in pulmonary airways in pathological conditions. Liquid plugs, witch compose the biphasic flows, can have a dramatic impact on patients with pulmonary obstructive diseases, since they considerably alter the circulation of air in the airways and thus can lead to severe breathing difficulties. Here, the dynamics of liquid plugs in prewetted capillary tube is investigated experimentally and theoretically, with a particular emphasis on the role of the prewetting films and of the driving condition (constant flow rate, constant pressure). For both driving conditions, the plugs can either experience a continuous increase or decrease of their size. While this phenomenon is regular in the case of imposed flow rate, a constant pressure head can lead to a catastrophic acceleration of the plug and eventually its rupture or a dramatic increase of the plug size. A theoretical model is proposed to explain the transition between theses two regimes. These results give a new insight on the critical pressure required for airways obstruction and reopening. IEMN, International Laboratory LEMAC/LICS, UMR CNRS 8520, University of Lille.

  8. MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

    NASA Astrophysics Data System (ADS)

    Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

    2017-12-01

    Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

  9. 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.

  10. Whole-body γ-irradiation decelerates rat hepatocyte polyploidization.

    PubMed

    Ikhtiar, Adnan M

    2015-07-01

    To characterize hepatocyte polyploidization induced by intermediate dose of γ-ray. Male Wistar strain rats were whole-body irradiated (WBI) with 2 Gy of γ-ray at the age of 1 month, and 5-6 rats were sacrificed monthly at 0-25 months after irradiation. The nuclear DNA content of individual hepatocytes was measured by flow cytometry, then hepatocytes were classified into various ploidy classes. Survival percentage, after exposure up to the end of the study, did not indicate any differences between the irradiated groups and controls. The degree of polyploidization in hepatocytes of irradiated rats, was significantly lower than that for the control after 1 month of exposure, and it continued to be lower after up to 8 months. Thereafter, the degree of polyploidization in the irradiated group slowly returned to the control level when the irradiated rats reached the age of 10 months. Intermediate dose of ionizing radiation, in contrast to high doses, decelerate hepatocyte polyploidization, which may coincides with the hypothesis of the beneficial effects of low doses of ionizing radiation.

  11. Critical Imperative for the Reform of British Interpretation of Fetal Heart Rate Decelerations: Analysis of FIGO and NICE Guidelines, Post-Truth Foundations, Cognitive Fallacies, Myths and Occam's Razor.

    PubMed

    Sholapurkar, Shashikant L

    2017-04-01

    Cardiotocography (CTG) has disappointingly failed to show good predictability for fetal acidemia or neonatal outcomes in several large studies. A complete rethink of CTG interpretation will not be out of place. Fetal heart rate (FHR) decelerations are the most common deviations, benign as well as manifestation of impending fetal hypoxemia/acidemia, much more commonly than FHR baseline or variability. Their specific nomenclature is important (center-stage) because it provides the basic concepts and framework on which the complex "pattern recognition" of CTG interpretation by clinicians depends. Unfortunately, the discrimination of FHR decelerations seems to be muddled since the British obstetrics adopted the concept of vast majority of FHR decelerations being "variable" (cord-compression). With proliferation of confusing waveform criteria, "atypical variables" became the commonest cause of suspicious/pathological CTG. However, National Institute for Health and Care Excellence (NICE) (2014) had to disband the "typical" and "atypical" terminology because of flawed classifying criteria. This analytical review makes a strong case that there are major and fundamental framing and confirmation fallacies (not just biases) in interpretation of FHR decelerations by NICE (2014) and International Federation of Gynecology and Obstetrics (FIGO) (2015), probably the biggest in modern medicine. This "post-truth" approach is incompatible with scientific practice. Moreover, it amounts to setting oneself for failure. The inertia to change could be best described as "backfire effect". There is abundant evidence that head-compression (and other non-hypoxic mediators) causes rapid rather than shallow/gradual decelerations. Currently, the vast majority of decelerations are attributed to unproven cord compression underpinned by flawed disproven pathophysiological hypotheses. Their further discrimination based on abstract, random, trial and error criteria remains unresolved suggesting a

  12. Examining the cosmic acceleration with the latest Union2 supernova data

    NASA Astrophysics Data System (ADS)

    Li, Zhengxiang; Wu, Puxun; Yu, Hongwei

    2011-01-01

    In this Letter, by reconstructing the Om diagnostic and the deceleration parameter q from the latest Union2 Type Ia Supernova sample with and without the systematic error along with the baryon acoustic oscillation (BAO) and the cosmic microwave background (CMB), we study the cosmic expanding history, using the Chevallier-Polarski-Linder (CPL) parametrization. We obtain that Union2+BAO favor an expansion with a decreasing of the acceleration at z<0.3. However, once the CMB data is added in the analysis, the cosmic acceleration is found to be still increasing, indicating a tension between low redshift data and high redshift. In order to reduce this tension significantly, two different methods are considered and thus two different subsamples of Union2 are selected. We then find that two different subsamples+BAO+CMB give completely different results on the cosmic expanding history when the systematic error is ignored, with one suggesting a decreasing cosmic acceleration, the other just the opposite, although both of them alone with BAO support that the cosmic acceleration is slowing down. However, once the systematic error is considered, two different subsamples of Union2 along with BAO and CMB all favor an increasing of the present cosmic acceleration. Therefore a clear-cut answer on whether the cosmic acceleration is slowing down calls for more consistent data and more reliable methods to analyze them.

  13. An advanced technique for the prediction of decelerator system dynamics.

    NASA Technical Reports Server (NTRS)

    Talay, T. A.; Morris, W. D.; Whitlock, C. H.

    1973-01-01

    An advanced two-body six-degree-of-freedom computer model employing an indeterminate structures approach has been developed for the parachute deployment process. The program determines both vehicular and decelerator responses to aerodynamic and physical property inputs. A better insight into the dynamic processes that occur during parachute deployment has been developed. The model is of value in sensitivity studies to isolate important parameters that affect the vehicular response.

  14. A fast wind-farm boundary-layer model to investigate gravity wave effects and upstream flow deceleration

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2017-11-01

    Wind farm design and control often relies on fast analytical wake models to predict turbine wake interactions and associated power losses. Essential input to these models are the inflow velocity and turbulent intensity at hub height, which come from prior measurement campaigns or wind-atlas data. Recent LES studies showed that in some situations large wind farms excite atmospheric gravity waves, which in turn affect the upstream wind conditions. In the current study, we develop a fast boundary-layer model that computes the excitation of gravity waves and the perturbation of the boundary-layer flow in response to an applied force. The core of the model is constituted by height-averaged, linearised Navier-Stokes equations for the inner and outer layer, and the effect of atmospheric gravity waves (excited by the boundary-layer displacement) is included via the pressure gradient. Coupling with analytical wake models allows us to study wind-farm wakes and upstream flow deceleration in various atmospheric conditions. Comparison with wind-farm LES results shows excellent agreement in terms of pressure and boundary-layer displacement levels. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

  15. Electron Cloud Effects in Accelerators

    SciTech Connect

    Furman, M.A.

    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].

  16. BrainAGE score indicates accelerated brain aging in schizophrenia, but not bipolar disorder.

    PubMed

    Nenadić, Igor; Dietzek, Maren; Langbein, Kerstin; Sauer, Heinrich; Gaser, Christian

    2017-08-30

    BrainAGE (brain age gap estimation) is a novel morphometric parameter providing a univariate score derived from multivariate voxel-wise analyses. It uses a machine learning approach and can be used to analyse deviation from physiological developmental or aging-related trajectories. Using structural MRI data and BrainAGE quantification of acceleration or deceleration of in individual aging, we analysed data from 45 schizophrenia patients, 22 bipolar I disorder patients (mostly with previous psychotic symptoms / episodes), and 70 healthy controls. We found significantly higher BrainAGE scores in schizophrenia, but not bipolar disorder patients. Our findings indicate significantly accelerated brain structural aging in schizophrenia. This suggests, that despite the conceptualisation of schizophrenia as a neurodevelopmental disorder, there might be an additional progressive pathogenic component. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

  17. Deceleration of arginine kinase refolding by induced helical structures.

    PubMed

    Li, Hai-Long; Zhou, Sheng-Mei; Park, Daeui; Jeong, Hyoung Oh; Chung, Hae Young; Yang, Jun-Mo; Meng, Fan-Guo; Hu, Wei-Jiang

    2012-04-01

    Arginine kinase (AK) is a key metabolic enzyme for keeping energy balance in invertebrates. Therefore, regulation of the enzymatic activity and the folding studies of AK from the various invertebrates have been the focus of investigation. We studied the effects of helical structures by using hexafluoroisopropanol (HFIP) on AK folding. Folding kinetic studies showed that the folding rates of the urea-denatured AKs were significantly decelerated after being induced in various concentrations of HFIP. AK lost its activity completely at concentrations greater than 60%. The results indicated that the HFIP-induced helical structures in the denatured state play a negative role in protein folding, and the helical structures induced in 5% (v/v) HFIP act as the most effective barrier against AK taking its native structure. The computational docking simulations (binding energies for -2.19 kcal/mol for AutoDock4.2 and -20.47 kcal/mol for Dock6.3) suggested that HFIP interacts with the several important residues that are predicted by both programs. The excessively pre-organized helical structures not only hampered the folding process, but also ultimately brought about changes in the three-dimensional conformation and biological function of AK.

  18. 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.

  19. Tanning accelerators: prevalence, predictors of use, and adverse effects.

    PubMed

    Herrmann, Jennifer L; Cunningham, Rachel; Cantor, Alan; Elewski, Boni E; Elmets, Craig A

    2015-01-01

    Tanning accelerators are topical products used by indoor tanners to augment and hasten the tanning process. These products contain tyrosine, psoralens, and/or other chemicals. We sought to better define the population using accelerators, identify predictors of their use, and describe any related adverse effects. This cross-sectional study surveyed 200 indoor tanners about their tanning practices and accelerator use. Primary analysis compared accelerator users with nonusers with respect to questionnaire variables. Descriptive statistics and χ(2) contingency tables were applied to identify statistically significant variables. Of respondents, 53% used accelerators; 97% were female and 3% were male with a median age of 22 years (range: 19-67). Users were more likely to spray tan, tan frequently, and be addicted to tanning. Acne and rashes were more common in accelerator users. Adverse reactions to accelerators prevented their further use 31% of the time. A limited adult population was evaluated; exact accelerator ingredients were not examined. Tanning accelerator users are high-risk indoor tanners who tan more frequently and who are more likely addicted to tanning. Acne and rashes are more common with these products and act as only mild deterrents to continued use. Additional research should investigate accelerators' longer-term health effects. Copyright © 2014 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

  20. Tunnel flexibility effect on the ground surface acceleration response

    NASA Astrophysics Data System (ADS)

    Baziar, Mohammad Hassan; Moghadam, Masoud Rabeti; Choo, Yun Wook; Kim, Dong-Soo

    2016-09-01

    Flexibility of underground structures relative to the surrounding medium, referred to as the flexibility ratio, is an important factor that influences their dynamic interaction. This study investigates the flexibility effect of a box-shaped subway tunnel, resting directly on bedrock, on the ground surface acceleration response using a numerical model verified against dynamic centrifuge test results. A comparison of the ground surface acceleration response for tunnel models with different flexibility ratios revealed that the tunnels with different flexibility ratios influence the acceleration response at the ground surface in different ways. Tunnels with lower flexibility ratios have higher acceleration responses at short periods, whereas tunnels with higher flexibility ratios have higher acceleration responses at longer periods. The effect of the flexibility ratio on ground surface acceleration is more prominent in the high range of frequencies. Furthermore, as the flexibility ratio of the tunnel system increases, the acceleration response moves away from the free field response and shifts towards the longer periods. Therefore, the flexibility ratio of the underground tunnels influences the peak ground acceleration (PGA) at the ground surface, and may need to be considered in the seismic zonation of urban areas.

  1. 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.

  2. 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.

  3. Ion accelerator systems for high power 30 cm thruster operation

    NASA Technical Reports Server (NTRS)

    Aston, G.

    1982-01-01

    Two and three-grid accelerator systems for high power ion thruster operation were investigated. Two-grid translation tests show that over compensation of the 30 cm thruster SHAG grid set spacing the 30 cm thruster radial plasma density variation and by incorporating grid compensation only sufficient to maintain grid hole axial alignment, it is shown that beam current gains as large as 50% can be realized. Three-grid translation tests performed with a simulated 30 cm thruster discharge chamber show that substantial beamlet steering can be reliably affected by decelerator grid translation only, at net-to-total voltage ratios as low as 0.05.

  4. Modeling and Demonstrating Regenerative Braking of a Squirrel Cage Induction Motor with Various Deceleration Rates Using V by F Control

    DTIC Science & Technology

    2010-06-01

    DEMONSTRATING REGENERATIVE BRAKING OF A SQUIRREL CAGE INDUCTION MOTOR WITH VARIOUS DECELERATION RATES USING V BY F CONTROL by Billy J. Nytko...Regenerative Braking of a Squirrel Cage Induction Motor with Various Deceleration Rates Using V by F Control 6. AUTHOR(S) Billy J. Nytko 5. FUNDING...Naval Postgraduate School (NPS) to model regenerative braking to support energy conservation technologies and to improve the efficiencies within the

  5. Cosmic acceleration from matter-curvature coupling

    NASA Astrophysics Data System (ADS)

    Zaregonbadi, Raziyeh; Farhoudi, Mehrdad

    2016-10-01

    We consider f( {R,T} ) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory, the coupling energy-momentum tensor is not conserved. However, we mainly focus on a particular model that matter is minimally coupled to the geometry in the metric formalism and wherein, its coupling energy-momentum tensor is also conserved. We obtain the corresponding Raychaudhuri dynamical equation that presents the evolution of the kinematic quantities. Then for the chosen model, we derive the behavior of the deceleration parameter, and show that the coupling term can lead to an acceleration phase after the matter dominated phase. On the other hand, the curvature of the universe corresponds with the deviation from parallelism in the geodesic motion. Thus, we also scrutinize the motion of the free test particles on their geodesics, and derive the geodesic deviation equation in this modified theory to study the accelerating universe within the spatially flat FLRW background. Actually, this equation gives the relative accelerations of adjacent particles as a measurable physical quantity, and provides an elegant tool to investigate the timelike and the null structures of spacetime geometries. Then, through the null deviation vector, we find the observer area-distance as a function of the redshift for the chosen model, and compare the results with the corresponding results obtained in the literature.

  6. 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…

  7. Accelerating Universe from Gravitational Leakage into Extra Dimensions: Testing with Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Zhu, Zong-Hong; Alcaniz, Jailson S.

    2005-02-01

    There is mounting observational evidence that the expansion of our universe is undergoing an acceleration. A dark energy component has usually been invoked as the most feasible mechanism for the acceleration. However, it is desirable to explore alternative possibilities motivated by particle physics before adopting such an untested entity. In this work, we focus our attention on an acceleration mechanism arising from gravitational leakage into extra dimensions. We test this scenario with high-z Type Ia supernovae compiled by Tonry and coworkers and recent measurements of the X-ray gas mass fractions in clusters of galaxies published by Allen and coworkers. A combination of the two databases gives, at a 99% confidence level, Ωm=0.29+0.04-0.02, Ωrc=0.21+/-0.08, and Ωk=-0.36+0.31-0.35, indicating a closed universe. We then constrain the model using the test of the turnaround redshift, zq=0, at which the universe switches from deceleration to acceleration. We show that, in order to explain that acceleration happened earlier than zq=0=0.6 within the framework of gravitational leakage into extra dimensions, a low matter density, Ωm<0.27, or a closed universe is necessary.

  8. Thermal Design and Analysis of the Supersonic Flight Dynamics Test Vehicle for the Low Density Supersonic Decelerator Project

    NASA Technical Reports Server (NTRS)

    Mastropietro, A. J.; Pauken, Michael; Sunada, Eric; Gray, Sandria

    2013-01-01

    The thermal design and analysis of the experimental Supersonic Flight Dynamics Test (SFDT) vehicle is presented. The SFDT vehicle is currently being designed as a platform to help demonstrate key technologies for NASA's Low Density Supersonic Decelerator (LDSD) project. The LDSD project is charged by NASA's Office of the Chief Technologist (OCT) with the task of advancing the state of the art in Mars Entry, Descent, and Landing (EDL) systems by developing and testing three new technologies required for landing heavier payloads on Mars. The enabling technologies under development consist of a large 33.5 meter diameter Supersonic Ringsail (SSRS) parachute and two different types of Supersonic Inflatable Aerodynamic Decelerator (SIAD) devices - a robotic class, SIAD-R, that inflates to a 6 meter diameter torus, and an exploration class, SIAD-E, that inflates to an 8 meter diameter isotensoid. As part of the technology development effort, the various elements of the new supersonic decelerator system must be tested in a Mars-like environment. This is currently planned to be accomplished by sending a series of SFDT vehicles into Earth's stratosphere. Each SFDT vehicle will be lifted to a stable float altitude by a large helium carrier balloon. Once at altitude, the SFDT vehicles will be released from their carrier balloon and spun up via spin motors to provide trajectory stability. An onboard third stage solid rocket motor will propel each test vehicle to supersonic flight in the upper atmosphere. After main engine burnout, each vehicle will be despun and testing of the deceleration system will begin: first an inflatable decelerator will be deployed around the aeroshell to increase the drag surface area, and then the large parachute will be deployed to continue the deceleration and return the vehicle back to the Earth's surface. The SFDT vehicle thermal system must passively protect the vehicle structure and its components from cold temperatures experienced during the

  9. Coverage-dependent amplifiers of vegetation change on global water cycle dynamics

    NASA Astrophysics Data System (ADS)

    Feng, Huihui; Zou, Bin; Luo, Juhua

    2017-07-01

    The terrestrial water cycle describes the circulation of water worldwide from one store to another via repeated evapotranspiration (E) from land and precipitation (P) back to the surface. The cycle presents significant spatial variability, which is strongly affected by natural climate and anthropogenic influences. As one of the major anthropogenic influences, vegetation change unavoidably alters surface property and subsequent the terrestrial water cycle, while its contribution is yet difficult to isolate from the mixed influences. Here, we use satellite and in-situ datasets to identify the terrestrial water cycle dynamics in spatial detail and to evaluate the impact of vegetation change. Methodologically, the water cycle is identified by the indicator of difference between evapotranspiration and precipitation (E-P). Then the scalar form of the indicator's trend (ΔE + ΔP) is used for evaluating the dynamics of water cycle, with the positive value means acceleration and negative means deceleration. Then, the contributions of climate and vegetation change are isolated by the trajectory-based method. Our results indicate that 4 accelerating and 4 decelerating water cycles can be identified, affecting 42.11% of global land. The major water cycle type is characterized by non-changing precipitation and increasing evapotranspiration (PNO-EIN), which covers 20.88% of globally land. Vegetation change amplifies both accelerating and decelerating water cycles. It tends to intensify the trend of the decelerating water cycles, while climate change weakens the trend. In the accelerating water cycles, both vegetation and climate change present positive effect to intensify the trend. The effect of plant cover change varies with the coverage. In particular, vegetation change intensifies the water cycle in moderately vegetated regions (0.1 < NDVI < 0.6), but weakens the cycle in sparsely or highly vegetated regions (NDVI < 0.1 or 0.6 < NDVI < 0.8). In extremely vegetated regions

  10. Sternal fractures are frequent among polytraumatised patients following high deceleration velocities in a severe vehicle crash.

    PubMed

    Knobloch, K; Wagner, S; Haasper, C; Probst, C; Krettek, C; Vogt, P M; Otte, D; Richter, M

    2008-01-01

    Sternal fractures are a rare entity. We hypothesised that a sternal fracture is an indicator of injury severity following traffic accidents. Analysis of technical indicators of the collision, preclinical and clinical data of patients with sternal fractures from 1985 to 2004 among 42,055 injured patients assessed by an Accident Research Unit. Only 267/42,055 patients (0.64%) suffered a sternal fracture within the 20-year period. Soft tissue bruises are most often concomitant injuries (55%), followed by cervical spine injuries (23%), multiple rib fractures (14%) and lung injuries (12%). Eighteen percent of patients were polytraumatised, with 11.2% dying at the scene, 2.3% in hospital. Deceleration velocity (DeltaV) was significantly correlated with injury severity score (ISS, r2=0.92, y=0.408x-4.1573) as with maximal abbreviated injury scale (MAIS, r2=0.81). Patients suffering a sternal fracture being polytraumatised had significantly higher deceleration velocity (60+/-17km/h versus 37+/-16km/h [37.3+/-10.6mph versus 23+/-9.9mph], p=0.0001). Patients dying with a sternal fracture had a significant higher deceleration velocity (61km/h, 37.9mph) versus those surviving (38km/h, 23.6mph, p=0.0001). Regarding the vehicle type, the majority occurred after car accidents in 0.81% (251/31,183 patients), followed by 0.19% (5/2633 patients) driving motorbikes, and 0.11% (4/3258 patients) driving a truck. Only 13% of all passengers suffering a sternal fracture had an airbag on board (33/255 car/trucks), with an airbag malfunction in 18%. 22% were not admitted to hospital, 28% were admitted to a trauma ICU with a sternal fracture. In 1/5 of cases sternal fractures encountered in polytraumatised patients following significantly higher deceleration velocities during the crash. Typically car drivers without a functioning airbag suffer a sternal fracture.

  11. In situ observation of penetration process in silica aerogel: Deceleration mechanism of hard spherical projectiles

    NASA Astrophysics Data System (ADS)

    Niimi, Rei; Kadono, Toshihiko; Arakawa, Masahiko; Yasui, Minami; Dohi, Koji; Nakamura, Akiko M.; Iida, Yosuke; Tsuchiyama, Akira

    2011-02-01

    A large number of cometary dust particles were captured with low-density silica aerogels by NASA's Stardust Mission. Knowledge of the details of the capture mechanism of hypervelocity particles in silica aerogel is needed in order to correctly derive the original particle features from impact tracks. However, the mechanism has not been fully understood yet. We shot hard spherical projectiles of several different materials into silica aerogel of density 60 mg cm -3 and observed their penetration processes using an image converter or a high-speed video camera. In order to observe the deceleration of projectiles clearly, we carried out impact experiments at two velocity ranges; ˜4 km s -1 and ˜200 m s -1. From the movies we took, it was indicated that the projectiles were decelerated by hydrodynamic force which was proportional to v2 ( v: projectile velocity) during the faster penetration process (˜4 km s -1) and they were merely overcoming the aerogel crushing strength during the slower penetration process (˜200 m s -1). We applied these deceleration mechanisms for whole capture process to calculate the track length. Our model well explains the track length in the experimental data set by Burchell et al. (Burchell, M.J., Creighton, J.A., Cole, M.J., Mann, J., Kearsley, A.T. [2001]. Meteorit. Planet. Sci. 36, 209-221).

  12. Deceleration of the solar wind in the earth's 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's bow shock and associated waves is studied using a two-spacecraft technique. This deceleration depends on the solar wind bulk velocity; at low velocities (below 300 km/s) the velocity decrease is about 5 km/s, while at higher velocities (above 400 km/s) the decrease may be as large as 30 km/s. 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.

  13. Coiling, Entrainment, and Hydrodynamic Coupling of Decelerated Fluid Jets

    NASA Astrophysics Data System (ADS)

    Dombrowski, Christopher; Lewellyn, Braddon; Pesci, Adriana I.; Restrepo, Juan M.; Kessler, John O.; Goldstein, Raymond E.

    2005-10-01

    From algal suspensions to magma upwellings, one finds jets which exhibit complex symmetry-breaking instabilities as they are decelerated by their surroundings. We consider here a model system—a saline jet descending through a salinity gradient—which produces dynamics unlike those of standard momentum jets or plumes. The jet coils like a corkscrew within a conduit of viscously entrained fluid, whose upward recirculation braids the jet, and nearly confines transverse mixing to the narrow conduit. We show that the underlying jet structure and certain scaling relations follow from similarity solutions to the fluid equations and the physics of Kelvin-Helmholtz instabilities.

  14. Ice-sheet thinning and acceleration at Camp Century, Greenlan

    NASA Astrophysics Data System (ADS)

    Colgan, W. T.

    2017-12-01

    Camp Century, Greenland (77.18 °N, 61.12 °W, 1900 m), is located approximately 150 km inland from the ice-sheet margin in Northwest Greenland. In-situ and remotely-sensed measurements of ice-sheet elevation at Camp Century exhibit a thinning trend between 1964 and the present. A comparison of 1966 and 2017 firn density profiles indicates that a portion of this ice-sheet thinning is attributable to increased firn compaction rate. In-situ measurements of increasing ice surface velocity over the 1977-2017 period indicate that enhanced horizontal divergence of ice flux is also contributing to ice dynamic thinning at Camp Century. This apparent ice dynamic thinning could potentially result from a migrating local flow divide or decreasing effective ice viscosity. In a shorter-term context, observations of decadal-scale ice-sheet thinning and acceleration at Camp Century highlights underappreciated transience in inland ice form and flow during the satellite era. In a longer-term context, these multi-decadal observations contrast with inferences of millennial-scale ice-sheet thickening and deceleration at Camp Century.

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

    SciTech Connect

    Bogdanov, O. V., E-mail: bov@tpu.ru; 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 quantitymore » 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.« less

  16. Effect of knee flexion angle on ground reaction forces, knee moments and muscle co-contraction during an impact-like deceleration landing: implications for the non-contact mechanism of ACL injury.

    PubMed

    Podraza, Jeffery T; White, Scott C

    2010-08-01

    Investigating landing kinetics and neuromuscular control strategies during rapid deceleration movements is a prerequisite to understanding the non-contact mechanism of ACL injury. The purpose of this study was to quantify the effect of knee flexion angle on ground reaction forces, net knee joint moments, muscle co-contraction and lower extremity muscles during an impact-like, deceleration task. Ground reaction forces and knee joint moments were determined from video and force plate records of 10 healthy male subjects performing rapid deceleration single leg landings from a 10.5 cm height with different degrees of knee flexion at landing. Muscle co-contraction was based on muscle moments calculated from an EMG-to-moment processing model. Ground reaction forces and co-contraction indices decreased while knee extensor moments increased significantly with increased degrees of knee flexion at landing (all p<0.005). Higher ground reaction forces when landing in an extended knee position suggests they are a contributing factor in non-contact ACL injuries. Increased knee extensor moments and less co-contraction with flexed knee landings suggest that quadriceps overload may not be the primary cause of non-contact ACL injuries. The results bring into question the counterbalancing role of the hamstrings during dynamic movements. The soleus may be a valuable synergist stabilizing the tibia against anterior translation at landing. Movement strategies that lessen the propagation of reaction forces up the kinetic chain may help prevent non-contact ACL injuries. The relative interaction of all involved thigh and lower leg muscles, not just the quadriceps and hamstrings should be considered when interpreting non-contact ACL injury mechanisms. Copyright 2010 Elsevier B.V. All rights reserved.

  17. Comment on ;Acceleration of particles to high energy via gravitational repulsion in the Schwarzschild field; [Astropart. Phys. 86 (2017) 18-20

    NASA Astrophysics Data System (ADS)

    Spallicci, Alessandro D. A. M.

    2017-09-01

    Comments are due on a recent paper by McGruder III (2017) in which the author deals with the concept of gravitational repulsion in the context of the Schwarzschild-Droste solution. Repulsion (deceleration) for ingoing particles into a black hole is a concept proposed several times starting from Droste himself in 1916. It is a coordinate effect appearing to an observer at a remote distance from the black hole and when coordinate time is employed. Repulsion has no bearing and relation to the local physics of the black hole, and moreover it cannot be held responsible for accelerating outgoing particles. Thereby, the energy boost of cosmic rays cannot be produced by repulsion.

  18. Cylindrical effects on Richtmyer-Meshkov instability for arbitrary Atwood numbers in weakly nonlinear regime

    SciTech Connect

    Liu, W. H.; He, X. T.; LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088

    2012-07-15

    When an incident shock collides with a corrugated interface separating two fluids of different densities, the interface is prone to Richtmyer-Meshkov instability (RMI). Based on the formal perturbation expansion method as well as the potential flow theory, we present a simple method to investigate the cylindrical effects in weakly nonlinear RMI with the transmitted and reflected cylindrical shocks by considering the nonlinear corrections up to fourth order. The cylindrical results associated with the material interface show that the interface expression consists of two parts: the result in the planar system and that from the cylindrical effects. In the limit ofmore » the cylindrical radius tending to infinity, the cylindrical results can be reduced to those in the planar system. Our explicit results show that the cylindrical effects exert an inward velocity on the whole perturbed interface, regardless of bubbles or spikes of the interface. On the one hand, outgoing bubbles are constrained and ingoing spikes are accelerated for different Atwood numbers (A) and mode numbers k'. On the other hand, for ingoing bubbles, when |A|k'{sup 3/2} Less-Than-Or-Equivalent-To 1, bubbles are considerably accelerated especially at the small |A| and k'; otherwise, bubbles are decelerated. For outgoing spikes, when |A|k' Greater-Than-Or-Equivalent-To 1, spikes are dramatically accelerated especially at large |A| and k'; otherwise, spikes are decelerated. Furthermore, the cylindrical effects have a significant influence on the amplitudes of the ingoing spike and bubble for large k'. Thus, it should be included in applications where the cylindrical effects play a role, such as inertial confinement fusion ignition target design.« less

  19. Flight-test evaluation of STOL control and flight director concepts in a powered-lift aircraft flying curved decelerating approaches

    NASA Technical Reports Server (NTRS)

    Hindson, W. S.; Hardy, G. H.; Innis, R. C.

    1981-01-01

    Flight tests were carried out to assess the feasibility of piloted steep curved, and decelerating approach profiles in powered lift STOL aircraft. Several STOL control concepts representative of a variety of aircraft were evaluated in conjunction with suitably designed flight directions. The tests were carried out in a real navigation environment, employed special electronic cockpit displays, and included the development of the performance achieved and the control utilization involved in flying 180 deg turning, descending, and decelerating approach profiles to landing. The results suggest that such moderately complex piloted instrument approaches may indeed be feasible from a pilot acceptance point of view, given an acceptable navigation environment. Systems with the capability of those used in this experiment can provide the potential of achieving instrument operations on curved, descending, and decelerating landing approaches to weather minima corresponding to CTOL Category 2 criteria, while also providing a means of realizing more efficient operations during visual flight conditions.

  20. Continuous All-Optical Deceleration and Single-Photon Cooling of Molecular Beams

    DTIC Science & Technology

    2014-02-21

    PHYSICAL REVIEW A 89 , 023425 (2014) Continuous all-optical deceleration and single-photon cooling of molecular beams A. M. Jayich,1 A. C. Vutha,2 M...details including multilevel numerical simulations of strontium monohydride. These techniques are applicable to a large number of molecular species and...molecules that are considered difficult to directly laser cool—a class that includes many 1050-2947/2014/ 89 (2)/023425(8) 023425-1 ©2014 American

  1. 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

    2016-02-05

    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. Copyright © 2016, American Association for the Advancement of Science.

  2. Universe without dark energy: Cosmic acceleration from dark matter-baryon interactions

    NASA Astrophysics Data System (ADS)

    Berezhiani, Lasha; Khoury, Justin; Wang, Junpu

    2017-06-01

    Cosmic acceleration is widely believed to require either a source of negative pressure (i.e., dark energy), or a modification of gravity, which necessarily implies new degrees of freedom beyond those of Einstein gravity. In this paper we present a third possibility, using only dark matter (DM) and ordinary matter. The mechanism relies on the coupling between dark matter and ordinary matter through an effective metric. Dark matter couples to an Einstein-frame metric, and experiences a matter-dominated, decelerating cosmology up to the present time. Ordinary matter couples to an effective metric that depends also on the DM density, in such a way that it experiences late-time acceleration. Linear density perturbations are stable and propagate with arbitrarily small sound speed, at least in the case of "pressure" coupling. Assuming a simple parametrization of the effective metric, we show that our model can successfully match a set of basic cosmological observables, including luminosity distance, baryon acoustic oscillation measurements, angular-diameter distance to last scattering, etc. For the growth history of density perturbations, we find an intriguing connection between the growth factor and the Hubble constant. To get a growth history similar to the Λ CDM prediction, our model predicts a higher H0, closer to the value preferred by direct estimates. On the flip side, we tend to overpredict the growth of structures whenever H0 is comparable to the Planck preferred value. The model also tends to predict larger redshift-space distortions at low redshift than Λ CDM .

  3. Bianchi Type-I Anisotropic Dark Energy Model with Constant Deceleration Parameter

    NASA Astrophysics Data System (ADS)

    Pradhan, Anirudh; Amirhashchi, H.; Saha, Bijan

    2011-09-01

    A new dark energy model in anisotropic Bianchi type-I (B-I) space-time with time dependent equation of state (EoS) parameter and constant deceleration parameter has been investigated in the present paper. The Einstein's field equations have been solved by applying a variation law for generalized Hubble's parameter (Berman in Il Nuovo Cimento B 74:182, 1983) which generates two types of solutions, one is of power-law type and other is of the exponential form. The existing range of the dark energy EoS parameter ω for derived model is found to be in good agreement with the three recent observations (i) SNe Ia data (Knop et al. in Astrophys. J. 598:102, 2003), (ii) SNe Ia data collaborated with CMBR anisotropy and galaxy clustering statistics (Tegmark et al. in Astrophys. J. 606:702, 2004) and (iii) a combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type Ia supernovae and galaxy clustering (Hinshaw et al. in Astrophys. J. Suppl. Ser. 180:225, 2009 and Komatsu et al. in Astrophys. J. Suppl. Ser. 180:330, 2009). The cosmological constant Λ is found to be a decreasing function of time and it approaches a small positive value at the present epoch which is corroborated by results from recent supernovae Ia observations. It has also been suggested that the dark energy that explains the observed accelerating universe may arise due to the contribution to the vacuum energy of the EoS in a time dependent background. Geometric and kinematic properties of the model and the behaviour of the anisotropy of the dark energy have been carried out.

  4. 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)

  5. Amnioinfusion for relief of recurrent severe and moderate variable decelerations in labor.

    PubMed

    Regi, Annie; Alexander, Nancy; Jose, Ruby; Lionel, Jessie; Varghese, Lilly; Peedicayil, Abraham

    2009-05-01

    To determine whether intrapartum amnioinfusion (AI) relieves recurrent moderate and severe variable decelerations in laboring women with clear or grade I meconium-stained amniotic fluid and reduces cesarean section rate for fetal distress. A randomized controlled trial was conducted in labor unit of Christian Medical College Hospital, Vellore, India, between October 2003 and September 2004. Women were randomized to receive AI (group I) and not to receive it (group II). A total of 150 women (75 in each group) were included in the study. There was significant relief of variable decelerations in group I and no difference in overall cesarean section rate but significant reduction in cesarean section rate for fetal distress in group I, and significant reduction in cesarean section rate for fetal distress in nulliparous women of group I. Neonatal acidemia was also significantly reduced in the nulliparous women receiving AI. The duration of maternal postpartum hospital stay was significantly reduced in group I. There were no adverse maternal or neonatal outcomes. AI was a beneficial therapeutic intervention in women patients showing fetal distress in first stage of labor, and it reduced cesarean section for fetal distress and neonatal acidemia.

  6. Flow stagnation at Enceladus: The effects of neutral gas and charged dust

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Tokar, R. L.; Averkamp, T.; Gurnett, D. A.; Kurth, W. S.; Wang, Z.

    2012-06-01

    Enceladus is one of Saturn's most active moons. It ejects neutral gas and dust particles from its southern plumes with velocities of hundreds of meters per second. The interaction between the ejected material and the corotating plasma in Saturn's magnetosphere leads to flow deceleration in ways that remain to be understood. The most effective mechanism for the interaction between the corotating plasma and the neutral gas is charge exchange which replaces the hotter corotating ions with nearly stationary cold ions that are subsequently accelerated by the motional electric field. Dust particles in the plume can become electrically charged through electron absorption and couple to the plasma through the motional electric field. The objective of this study is to determine the level of flow deceleration associated with each of these processes using Cassini RPWS dust impact rates, Cassini Plasma Spectrometer (CAPS) plasma data, and 3-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations. Hybrid simulations show that the degree of flow deceleration by charged dust varies considerably with the spatial distribution of dust particles. Based on the RPWS observations of dust impacts during the E7 Cassini flyby of Enceladus, we have constructed a dust model consisting of multiple plumes. Using this model in the hybrid simulation shows that when the dust density is high enough for complete absorption of electrons at the point of maximum dust density, the corotating flow is decelerated by only a few km/s. This is not sufficient to account for the CAPS observation of flow stagnation in the interaction region. On the other hand, charge exchange with neutral gas plumes similar to the modeled dust plumes but with base (plume opening) densities of ˜109 cm-3 result in flow deceleration similar to that observed by CAPS. The results indicate that charge exchange with neutral gas is the dominant mechanism for flow deceleration at Enceladus.

  7. 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.

  8. Technology development for deployable aerodynamic decelerators at Mars

    NASA Astrophysics Data System (ADS)

    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. .

  9. Setting accelerated dissolution test for PLGA microspheres containing peptide, investigation of critical parameters affecting drug release rate and mechanism.

    PubMed

    Tomic, I; Vidis-Millward, A; Mueller-Zsigmondy, M; Cardot, J-M

    2016-05-30

    The objective of this study was development of accelerated in vitro release method for peptide loaded PLGA microspheres using flow-through apparatus and assessment of the effect of dissolution parameters (pH, temperature, medium composition) on drug release rate and mechanism. Accelerated release conditions were set as pH 2 and 45°C, in phosphate buffer saline (PBS) 0.02M. When the pH was changed from 2 to 4, diffusion controlled phases (burst and lag) were not affected, while release rate during erosion phase decreased two-fold due to slower ester bonds hydrolyses. Decreasing temperature from 45°C to 40°C, release rate showed three-fold deceleration without significant change in release mechanism. Effect of medium composition on drug release was tested in PBS 0.01M (200 mOsm/kg) and PBS 0.01M with glucose (380 mOsm/kg). Buffer concentration significantly affected drug release rate and mechanism due to the change in osmotic pressure, while ionic strength did not have any effect on peptide release. Furthermore, dialysis sac and sample-and-separate techniques were used, in order to evaluate significance of dissolution technique choice on the release process. After fitting obtained data to different mathematical models, flow-through method was confirmed as the most appropriate for accelerated in vitro dissolution testing for a given formulation. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Investigation of Microbunching Instabilities in Modern Recirculating Accelerators

    SciTech Connect

    Tsai, Cheng

    general linear beamline lattice including horizontal and vertical transport bending elements, and beam acceleration or deceleration. These featured generalizations are required for MBI analysis in recirculation accelerators. (2) Construction of CSR impedance models In addition to the steady-state CSR interaction, it has been found that the exit transient effect (or CSR drift) can even result in more serious MBI in high-brightness recirculation arcs. The onedimensional free-space CSR impedances, especially the exit transients, are derived. The steady-state CSR impedance is also extended to non-ultrarelativistic beam energy for MBI analysis of low-energy merger sections in recirculating accelerators. (3) Numerical implementation of the derived semi-analytical formulation This includes the development of a semi-analytical Vlasov solver for MBI analysis, and also benchmarking of the solver against massive particle tracking simulations. (4) Exploration of multistage amplification behavior of CSR microbunching development The CSR-induced MBI acts as an amplifier, which amplifies the sub-bunch modulation of a beam. The amplification is commonly quantified by the amplification gain. A beam transport system can be considered as a cascaded amplifier. Unlike the two-stage amplification of four-dipole bunch compressor chicanes employed in linacs, the recirculation arcs, which are usually constituted by several tens of bending magnets, show a distinguishing feature of up to six-stage microbunching amplification for our example arc lattices. That is, the maximal CSR amplification gain can be proportional to the peak bunch current up to sixth power. A method to compare lattice performance has been developed in terms of gain coefficients, which nearly depend on the lattice properties only. This method has also proven to be an effective way to quantify the current dependence of the maximal (5) Control of CSR MBI in multibend transport or recirculation arcs The existing mitigation schemes

  11. Ablative Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Laser-Accelerated Colliding Foils

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    In our experiments done on the Nike KrF laser, we study instability growth at shock-decelerated interfaces in planar colliding-foil experiments. We use streaked monochromatic (1.86 keV) x-ray face-on imaging diagnostics to measure the areal mass modulation growth caused by the instability. Higher x-ray energies up to 5.25 keV are used to follow the shock propagation as well as the 1D dynamics of the collision. While a laser-driven foil is accelerated towards the stationary low-density foam layer, an ablative RT instability develops. Having reached a high velocity, the foil hits the foam layer. The impact generates strong shocks in the plastic and in the foam. The reflected shock wave re-shocks the ablation front, its acceleration stops, and so does the observed RT growth. This is followed by areal mass oscillations due to the ablative RM instability and feedout mechanisms, of which the latter dominates.

  12. Effects of radial direction and eccentricity on acceleration perception.

    PubMed

    Mueller, Alexandra S; Timney, Brian

    2014-01-01

    Radial optic flow can elicit impressions of self-motion--vection--or of objects moving relative to the observer, but there is disagreement as to whether humans have greater sensitivity to expanding or to contracting optic flow. Although most studies agree there is an anisotropy in sensitivity to radial optic flow, it is unclear whether this asymmetry is a function of eccentricity. The issue is further complicated by the fact that few studies have examined how acceleration sensitivity is affected, even though observers and objects in the environment seldom move at a constant speed. To address these issues, we investigated the effects of direction and eccentricity on the ability to detect acceleration in radial optic flow. Our results indicate that observers are better at detecting acceleration when viewing contraction compared with expansion and that eccentricity has no effect on the ability to detect accelerating radial optic flow. Ecological interpretations are discussed.

  13. Acceleration effects in solid propellant rocket motors

    NASA Technical Reports Server (NTRS)

    Langhenry, M. T.

    1986-01-01

    The performance variations due to acceleration loads imposed on spinning solid propellant rocket motors are investigated. The four potentially most significant modes of acceleration-induced phenomena are identified from a study of the literature and modeled. The four modes are a mechanical mode which deals with deformations of the propellant and case: a thermodynamic mode which covers acceleration-induced combustion phenomena; a stress mode which covers the stressed propellant's effect on burn rate; and a gas dynamic mode which deals with changes in gas flow in the chamber and through the nozzle. Simplified models of each mode are developed or taken from the literature and are added to an internal ballistics evaluation computer program. The resulting analysis is the first to include all of the modes. In order to do this an original analysis of the mechanical and stress modes was necessary. However, the analysis shows that the stress mode is not important for the circular perforated grains studied. The other effects are shown to have a significant influence on solid rocket motor performance. The magnitude of the different mode effects are such that one may not be ignored over the others as has been done in the past. The results of the analysis are compared to published rocket motor data. The comparisons indicate an erosive burning effect that is a function of spin rate. A qualitative explanation of the erosive effect is presented.

  14. Pharmacology of saccadic eye movements in man. 1. Effects of the benzodiazepine receptor ligands midazolam and flumazenil.

    PubMed

    Ball, D M; Glue, P; Wilson, S; Nutt, D J

    1991-01-01

    A paradigm for assessing benzodiazepine receptor sensitivity was developed using intravenous midazolam in normal volunteers. After administration of incremental doses of midazolam, alterations in saccadic eye movement parameters and psychological self ratings were assessed. Significant changes included dose-dependent slowing of peak velocity, peak acceleration, peak deceleration, reduced saccade acceleration/deceleration ratio and saccade accuracy, and increased sedation self-ratings. Changes in saccade variables and sedation ratings were significantly correlated, and also correlated with plasma midazolam concentrations. No significant changes were seen in saccade latency or anxiety self-ratings. Pharmacological specificity of these changes was demonstrated by their reversal with the benzodiazepine antagonist flumazenil. This challenge paradigm appears to be a sensitive means of assessing benzodiazepine receptor function in man.

  15. 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.

  16. Effects of Shock and Turbulence Properties on Electron Acceleration

    NASA Astrophysics Data System (ADS)

    Qin, G.; Kong, F.-J.; Zhang, L.-H.

    2018-06-01

    Using test particle simulations, we study electron acceleration at collisionless shocks with a two-component model turbulent magnetic field with slab component including dissipation range. We investigate the importance of the shock-normal angle θ Bn, magnetic turbulence level {(b/{B}0)}2, and shock thickness on the acceleration efficiency of electrons. It is shown that at perpendicular shocks the electron acceleration efficiency is enhanced with the decrease of {(b/{B}0)}2, and at {(b/{B}0)}2=0.01 the acceleration becomes significant due to a strong drift electric field with long time particles staying near the shock front for shock drift acceleration (SDA). In addition, at parallel shocks the electron acceleration efficiency is increasing with the increase of {(b/{B}0)}2, and at {(b/{B}0)}2=10.0 the acceleration is very strong due to sufficient pitch-angle scattering for first-order Fermi acceleration, as well as due to the large local component of the magnetic field perpendicular to the shock-normal angle for SDA. On the other hand, the high perpendicular shock acceleration with {(b/{B}0)}2=0.01 is stronger than the high parallel shock acceleration with {(b/{B}0)}2=10.0, the reason might be the assumption that SDA is more efficient than first-order Fermi acceleration. Furthermore, for oblique shocks, the acceleration efficiency is small no matter whether the turbulence level is low or high. Moreover, for the effect of shock thickness on electron acceleration at perpendicular shocks, we show that there exists the bendover thickness, L diff,b. The acceleration efficiency does not noticeably change if the shock thickness is much smaller than L diff,b. However, if the shock thickness is much larger than L diff,b, the acceleration efficiency starts to drop abruptly.

  17. 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.

  18. Deceleration of free aqueous droplets skirting across the surface of a pool of the same fluid

    NASA Astrophysics Data System (ADS)

    Hale, Jacob; Akers, Caleb

    2014-11-01

    The non-coalescence of a free droplet atop a pool of the same fluid can be greatly enhanced when the drop has an initial horizontal velocity relative to the pool surface. The glancing impact and viscous interaction between the droplet and the pool impart a significant rotation to the droplet causing it to roll and thus entraining air between the two fluids. The translational speed of such a droplet is shown to decrease exponentially in time but with a time constant that increases linearly in time. This complex deceleration of the drop is in part due to the drop's rotational deceleration, visualized with suspended, neutrally buoyant microbeads. The observed motion is described in terms of viscous dissipation of the rotating drop and a viscous shear force between the droplet and bath.

  19. Deceleration, precooling, and multi-pass stopping of highly charged ions in Be{sup +} Coulomb crystals

    SciTech Connect

    Schmöger, L., E-mail: lisa.schmoeger@mpi-hd.mpg.de; Schwarz, M.; Versolato, O. O.

    2015-10-15

    Preparing highly charged ions (HCIs) in a cold and strongly localized state is of particular interest for frequency metrology and tests of possible spatial and temporal variations of the fine structure constant. Our versatile preparation technique is based on the generic modular combination of a pulsed ion source with a cryogenic linear Paul trap. Both instruments are connected by a compact beamline with deceleration and precooling properties. We present its design and commissioning experiments regarding these two functionalities. A pulsed buncher tube allows for the deceleration and longitudinal phase-space compression of the ion pulses. External injection of slow HCIs, specificallymore » Ar{sup 13+}, into the linear Paul trap and their subsequent retrapping in the absence of sympathetic cooling is demonstrated. The latter proved to be a necessary prerequisite for the multi-pass stopping of HCIs in continuously laser-cooled Be{sup +} Coulomb crystals.« less

  20. 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

  1. Effects of Mathematics Acceleration on Middle School Student Achievement

    ERIC Educational Resources Information Center

    Boysworth, Sylvia Elaine

    2010-01-01

    The researcher's purpose in the study was to evaluate the effectiveness of an Accelerated Mathematics Program (AMPS) for sixth and seventh grades, using the accelerative practice of curriculum telescoping in a rural school district in North Carolina. The mathematics achievement of students served in the locally developed Accelerated Mathematics…

  2. Projectile Combustion Effects on Ram Accelerator Performance

    NASA Astrophysics Data System (ADS)

    Chitale, Saarth Anjali

    University of Washington Abstract Projectile Combustion Effects on Ram Accelerator Performance Saarth Anjali Chitale Chair of the Supervisory Committee: Prof. Carl Knowlen William E. Boeing Department of Aeronautics and Astronautics The ram accelerator facility at the University of Washington is used to propel projectiles at supersonic velocities. This concept is similar to an air-breathing ramjet engine in that sub-caliber projectiles, shaped like the ramjet engine center-body, are shot through smooth-bore steel-walled tubes having an internal diameter of 38 mm. The ram accelerator propulsive cycles operate between Mach 2 to 10 and have the potential to accelerate projectile to velocities greater than 8 km/s. The theoretical thrust versus Mach number characteristics can be obtained using knowledge of gas dynamics and thermodynamics that goes into the design of the ram accelerator. The corresponding velocity versus distance profiles obtained from the test runs at the University of Washington, however, are often not consistent with the theoretical predictions after the projectiles reach in-tube Mach numbers greater than 4. The experimental velocities are typically greater than the expected theoretical predictions; which has led to the proposition that the combustion process may be moving up onto the projectile. An alternative explanation for higher than predicted thrust, which is explored here, is that the performance differences can be attributed to the ablation of the projectile body which results in molten metal being added to the flow of the gaseous combustible mixture around the projectile. This molten metal is assumed to mix uniformly and react with the gaseous propellant; thereby enhancing the propellant energy release and altering the predicted thrust-Mach characteristics. This theory predicts at what Mach number the projectile will first experience enhanced thrust and the corresponding velocity-distance profile. Preliminary results are in good agreement

  3. Magnetized string cosmological models of accelerated expansion of the Universe in f(R,T) theory of gravity

    NASA Astrophysics Data System (ADS)

    Pradhan, Anirudh; Jaiswal, Rekha

    A class of spatially homogeneous and anisotropic Bianchi-V massive string models have been studied in the modified f(R,T)-theory of gravity proposed by Harko et al. [Phys. Rev. D 84:024020, 2011] in the presence of magnetic field. For a specific choice of f(R,T)=f1(R) + f2(T), where f1(R) = ν1R and f2(T) = ν2T; ν1, ν2 being arbitrary parameters, solutions of modified gravity field equations have been generated. To find the deterministic solution of the field equations, we have considered the time varying deceleration parameter which is consistent with observational data of standard cosmology (SNIa, BAO and CMB). As a result to study the transit behavior of Universe, we consider a law of variation for the specifically chosen scale factor, which yields a time-dependent deceleration parameter comprising a class of models that depicts a transition of the Universe from the early decelerated phase to the recent accelerating phase. In this context, for the model of the Universe, the field equations are solved and corresponding cosmological aspects have been discussed. The Energy conditions in this modified gravity theory are also studied. Stability analysis of the solutions through cosmological perturbation is performed and it is concluded that the expanding solution is stable against the perturbation with respect to anisotropic spatial direction. Some physical and geometric properties of the models are also discussed.

  4. Late time acceleration of the 3-space in a higher dimensional steady state universe in dilaton gravity

    NASA Astrophysics Data System (ADS)

    Akarsu, Özgür; Dereli, Tekin

    2013-02-01

    We present cosmological solutions for (1+3+n)-dimensional steady state universe in dilaton gravity with an arbitrary dilaton coupling constant w and exponential dilaton self-interaction potentials in the string frame. We focus particularly on the class in which the 3-space expands with a time varying deceleration parameter. We discuss the number of the internal dimensions and the value of the dilaton coupling constant to determine the cases that are consistent with the observed universe and the primordial nucleosynthesis. The 3-space starts with a decelerated expansion rate and evolves into accelerated expansion phase subject to the values of w and n, but ends with a Big Rip in all cases. We discuss the cosmological evolution in further detail for the cases w = 1 and w = ½ that permit exact solutions. We also comment on how the universe would be conceived by an observer in four dimensions who is unaware of the internal dimensions and thinks that the conventional general relativity is valid at cosmological scales.

  5. LATTICES FOR HIGH-POWER PROTON BEAM ACCELERATION AND SECONDARY BEAM COLLECTION AND COOLING.

    SciTech Connect

    WANG, S.; WEI, J.; BROWN, K.

    2006-06-23

    Rapid cycling synchrotrons are used to accelerate high-intensity proton beams to energies of tens of GeV for secondary beam production. After primary beam collision with a target, the secondary beam can be collected, cooled, accelerated or decelerated by ancillary synchrotrons for various applications. In this paper, we first present a lattice for the main synchrotron. This lattice has: (a) flexible momentum compaction to avoid transition and to facilitate RF gymnastics (b) long straight sections for low-loss injection, extraction, and high-efficiency collimation (c) dispersion-free straights to avoid longitudinal-transverse coupling, and (d) momentum cleaning at locations of large dispersion with missing dipoles.more » Then, we present a lattice for a cooler ring for the secondary beam. The momentum compaction across half of this ring is near zero, while for the other half it is normal. Thus, bad mixing is minimized while good mixing is maintained for stochastic beam cooling.« less

  6. Deceleration of High-velocity Interstellar Photon Sails into Bound Orbits at α Centauri

    NASA Astrophysics Data System (ADS)

    Heller, René; Hippke, Michael

    2017-02-01

    At a distance of about 4.22 ly, it would take about 100,000 years for humans to visit our closest stellar neighbor Proxima Centauri using modern chemical thrusters. New technologies are now being developed that involve high-power lasers firing at 1 gram solar sails in near-Earth orbits, accelerating them to 20% the speed of light (c) within minutes. Although such an interstellar probe could reach Proxima 20 years after launch, without propellant to slow it down it would traverse the system within hours. Here we demonstrate how the stellar photon pressures of the stellar triple α Cen A, B, and C (Proxima) can be used together with gravity assists to decelerate incoming solar sails from Earth. The maximum injection speed at α Cen A to park a sail with a mass-to-surface ratio (σ) similar to graphene (7.6 × 10-4 gram m-2) in orbit around Proxima is about 13,800 km s-1 (4.6% c), implying travel times from Earth to α Cen A and B of about 95 years and another 46 years (with a residual velocity of 1280 km s-1) to Proxima. The size of such a low-σ sail required to carry a payload of 10 grams is about 105 m2 = (316 m)2. Such a sail could use solar photons instead of an expensive laser system to gain interstellar velocities at departure. Photogravitational assists allow visits of three stellar systems and an Earth-sized potentially habitable planet in one shot, promising extremely high scientific yields.

  7. Design considerations and test facilities for accelerated radiation effects testing

    NASA Technical Reports Server (NTRS)

    Price, W. E.; Miller, C. G.; Parker, R. H.

    1972-01-01

    Test design parameters for accelerated dose rate radiation effects tests for spacecraft parts and subsystems used in long term mission (years) are detailed. A facility for use in long term accelerated and unaccelerated testing is described.

  8. Nonlinear Monte Carlo model of superdiffusive shock acceleration with magnetic field amplification

    NASA Astrophysics Data System (ADS)

    Bykov, Andrei M.; Ellison, Donald C.; Osipov, Sergei M.

    2017-03-01

    Fast collisionless shocks in cosmic plasmas convert their kinetic energy flow into the hot downstream thermal plasma with a substantial fraction of energy going into a broad spectrum of superthermal charged particles and magnetic fluctuations. The superthermal particles can penetrate into the shock upstream region producing an extended shock precursor. The cold upstream plasma flow is decelerated by the force provided by the superthermal particle pressure gradient. In high Mach number collisionless shocks, efficient particle acceleration is likely coupled with turbulent magnetic field amplification (MFA) generated by the anisotropic distribution of accelerated particles. This anisotropy is determined by fast particle transport, making the problem strongly nonlinear and multiscale. Here, we present a nonlinear Monte Carlo model of collisionless shock structure with superdiffusive propagation of high-energy Fermi accelerated particles coupled to particle acceleration and MFA, which affords a consistent description of strong shocks. A distinctive feature of the Monte Carlo technique is that it includes the full angular anisotropy of the particle distribution at all precursor positions. The model reveals that the superdiffusive transport of energetic particles (i.e., Lévy-walk propagation) generates a strong quadruple anisotropy in the precursor particle distribution. The resultant pressure anisotropy of the high-energy particles produces a nonresonant mirror-type instability that amplifies compressible wave modes with wavelengths longer than the gyroradii of the highest-energy protons produced by the shock.

  9. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the gravitational-deceleration initiation of the phase transition of gas to a Bose condensate

    NASA Astrophysics Data System (ADS)

    Rivlin, L. A.

    2008-01-01

    A scenario of the experiment on the observation of the isothermal Bose condensation of cooled gas with increasing the concentration of atoms caused by the deceleration of a vertical atomic beam in the gravitational field resulting in a decrease in the phase transition critical temperature below the gas temperature is considered. Coherent phenomena accompanying the evolution of the Bose condensate during further beam deceleration are pointed out.

  10. 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 propagatesmore » 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.« less

  11. Assessment of zero gravity effects on space worker health and safety

    NASA Technical Reports Server (NTRS)

    1980-01-01

    One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

  12. The Differential Effect of Arm Movements during Gait on the Forward Acceleration of the Centre of Mass in Children with Cerebral Palsy and Typically Developing Children.

    PubMed

    Meyns, Pieter; Molenaers, Guy; Duysens, Jacques; Jonkers, Ilse

    2017-01-01

    Background: We aimed to study the contribution of upper limb movements to propulsion during walking in typically developing (TD) children ( n = 5) and children with hemiplegic and diplegic cerebral palsy (CP; n = 5 and n = 4, respectively). Methods: Using integrated three-dimensional motion capture data and a scaled generic musculoskeletal model that included upper limbs, we generated torque driven simulations of gait in OpenSim. Induced acceleration analyses were then used to determine the contributions of the individual actuators located at the relevant degrees of freedoms of the upper and lower limb joints to the forward acceleration of the COM at each time point of the gait simulation. The mean values of the contribution of the actuators of upper limbs, lower limbs, and gravity in different phases of the gait cycle were compared between the three groups. Findings: The results indicated a limited contribution of the upper limb actuators to COM forward acceleration compared to the contribution of lower limbs and gravity, in the three groups. In diplegic CP, the contribution of the upper limbs seemed larger compared to TD during the preswing and swing phases of gait. In hemiplegic CP, the unaffected arm seemed to contribute more to COM deceleration during (pre)swing, while the affected side contributed to COM acceleration. Interpretation: These findings suggest that in the presence of lower limb dysfunction, the contribution of the upper limbs to forward propulsion is altered, although they remain negligible compared to the lower limbs and gravity.

  13. Deceleration of Fusion–Fission Cycles Improves Mitochondrial Quality Control during Aging

    PubMed Central

    Meyer-Hermann, Michael; Osiewacz, Heinz D.

    2012-01-01

    Mitochondrial dynamics and mitophagy play a key role in ensuring mitochondrial quality control. Impairment thereof was proposed to be causative to neurodegenerative diseases, diabetes, and cancer. Accumulation of mitochondrial dysfunction was further linked to aging. Here we applied a probabilistic modeling approach integrating our current knowledge on mitochondrial biology allowing us to simulate mitochondrial function and quality control during aging in silico. We demonstrate that cycles of fusion and fission and mitophagy indeed are essential for ensuring a high average quality of mitochondria, even under conditions in which random molecular damage is present. Prompted by earlier observations that mitochondrial fission itself can cause a partial drop in mitochondrial membrane potential, we tested the consequences of mitochondrial dynamics being harmful on its own. Next to directly impairing mitochondrial function, pre-existing molecular damage may be propagated and enhanced across the mitochondrial population by content mixing. In this situation, such an infection-like phenomenon impairs mitochondrial quality control progressively. However, when imposing an age-dependent deceleration of cycles of fusion and fission, we observe a delay in the loss of average quality of mitochondria. This provides a rational why fusion and fission rates are reduced during aging and why loss of a mitochondrial fission factor can extend life span in fungi. We propose the ‘mitochondrial infectious damage adaptation’ (MIDA) model according to which a deceleration of fusion–fission cycles reflects a systemic adaptation increasing life span. PMID:22761564

  14. Association between vascular access creation and deceleration of estimated glomerular filtration rate decline in late-stage chronic kidney disease patients transitioning to end-stage renal disease.

    PubMed

    Sumida, Keiichi; Molnar, Miklos Z; Potukuchi, Praveen K; Thomas, Fridtjof; Lu, Jun Ling; Ravel, Vanessa A; Soohoo, Melissa; Rhee, Connie M; Streja, Elani; Yamagata, Kunihiro; Kalantar-Zadeh, Kamyar; Kovesdy, Csaba P

    2017-08-01

    Prior studies have suggested that arteriovenous fistula (AVF) or graft (AVG) creation may be associated with slowing of estimated glomerular filtration rate (eGFR) decline. It is unclear if this is attributable to the physiological benefits of a mature access on systemic circulation versus confounding factors. We examined a nationwide cohort of 3026 US veterans with advanced chronic kidney disease (CKD) transitioning to dialysis between 2007 and 2011 who had a pre-dialysis AVF/AVG and had at least three outpatient eGFR measurements both before and after AVF/AVG creation. Slopes of eGFR were estimated using mixed-effects models adjusted for fixed and time-dependent confounders, and compared separately for the pre- and post-AVF/AVG period overall and in patients stratified by AVF/AVG maturation. In all, 3514 patients without AVF/AVG who started dialysis with a catheter served as comparators, using an arbitrary 6-month index date before dialysis initiation to assess change in eGFR slopes. Of the 3026 patients with AVF/AVG (mean age 67 years, 98% male, 75% diabetic), 71% had a mature AVF/AVG at dialysis initiation. eGFR decline accelerated in the last 6 months prior to dialysis in patients with a catheter (median, from -6.0 to -16.3 mL/min/1.73 m2/year, P < 0.001), while a significant deceleration of eGFR decline was seen after vascular access creation in those with AVF/AVG (median, from -5.6 to -4.1 mL/min/1.73 m2/year, P < 0.001). Findings were independent of AVF/AVG maturation status and were robust in adjusted models. The creation of pre-dialysis AVF/AVG appears to be associated with eGFR slope deceleration and, consequently, may delay the onset of dialysis initiation in advanced CKD patients. Published by Oxford University Press on behalf of ERA-EDTA 2016. This work is written by US Government employees and is in the public domain in the US.

  15. Kinetics of the Shanghai Maglev: Kinematical Analysis of a Real "Textbook" Case of Linear Motion

    NASA Astrophysics Data System (ADS)

    Hsu, Tung

    2014-10-01

    A vehicle starts from rest at constant acceleration, then cruises at constant speed for a time. Next, it decelerates at a constant rate.… This and similar statements are common in elementary physics courses. Students are asked to graph the motion of the vehicle or find the velocity, acceleration, and distance traveled by the vehicle from a given graph.1 However, a "constant acceleration-constant velocity-constant deceleration" motion, which gives us an ideal trapezoidal shape in the velocity-time graph, is not common in everyday life. Driving a car or riding a bicycle for a short distance can be much more complicated. Therefore, it is interesting to take a look at a real case of "constant acceleration-constant velocity-constant deceleration" motion.

  16. Aerothermodynamic environment for a Titan probe with deployable decelerator

    NASA Technical Reports Server (NTRS)

    Green, M. J.; Swenson, B. L.; Balakrishnan, A.

    1985-01-01

    It is pointed out that further exploration of Titan, Saturn's largest moon, is of current interest to the scientific community, particularly from the standpoint of the organic chemical evolution of its atmosphere. For a suitable study of this Saturnian satellite, a mission involving a Titan atmospheric entry probe is to be conducted. The probe is to employ a deployable decelerator with the aim to allow scientific measurements in the haze layer. The present investigation is concerned with an assessment of the aerothermodynamic environment for the considered probe during its hypervelocity, low-Reynolds-number entry. Attention is given to the employed computational method, the Titan probe configuration, the Titan probe trajectory, the viscous-layer regime of the aerothermodynamic environment, and the incipient merged-layer regime.

  17. Instrumentation Development for Large Scale Hypersonic Inflatable Aerodynamic Decelerator Characterization

    NASA Technical Reports Server (NTRS)

    Swanson, Gregory T.; Cassell, Alan M.

    2011-01-01

    Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology is currently being considered for multiple atmospheric entry applications as the limitations of traditional entry vehicles have been reached. The Inflatable Re-entry Vehicle Experiment (IRVE) has successfully demonstrated this technology as a viable candidate with a 3.0 m diameter vehicle sub-orbital flight. To further this technology, large scale HIADs (6.0 8.5 m) must be developed and tested. To characterize the performance of large scale HIAD technology new instrumentation concepts must be developed to accommodate the flexible nature inflatable aeroshell. Many of the concepts that are under consideration for the HIAD FY12 subsonic wind tunnel test series are discussed below.

  18. 40 CFR Appendix I to Subpart B of... - Appendix I to Subpart B of Part 205

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Acceleration Test: Deceleration Test: Acceleration Test Run No. 1 2 3 4 5 dBA Left Right Highest RPM attained in End Zone Calculated Sound Pressure dBA Deceleration Test with Exhaust Brake Applied dBA Left Right Calculated Sound Pressure dBA TEST Personnel: (Name) Recorded By: Date:......... (Signature) Supervisor...

  19. 40 CFR Appendix I to Subpart B of... - Appendix I to Subpart B of Part 205

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...: Acceleration Test: Deceleration Test: Acceleration Test Run No. 1 2 3 4 5 dBA Left Right Highest RPM attained in End Zone Calculated Sound Pressure dBA Deceleration Test with Exhaust Brake Applied dBA Left Right Calculated Sound Pressure dBA TEST Personnel: (Name) Recorded By: Date:......... (Signature) Supervisor...

  20. Effects of Current Guides Destruction at Ultra-fast Acceleration of Macrobodies

    NASA Astrophysics Data System (ADS)

    Kataev, V. N.; Boriskin, A. S.; Golosov, S. N.; Demidov, V. A.; Klimashov, M. V.; Korolev, P. V.; Makartsev, G. F.; Pikar, A. S.; Russkov, A. S.; Shapovalov, E. V.; Shibitov, Yu. M.

    2006-08-01

    The paper is devoted to discussion of current guides destruction effects in different accelerators: thermal-electric and electro-magnetic rail accelerator at macrobodies acceleration value of 108-109 m/s2. Experimental results with thermal-electric accelerators powering from megajoule capacitor battery and helical magneto-cumulative generator MCG-100 at currents up to 3.5 MA are analyzed. The process of rails destruction at railgun at pressure magnetic field excess over the limit of metal fluidity is presented. Methods of efficiency coefficient increase of capacitive storage energy transmission to kinetic energy of accelerating body are discussed.

  1. Narrow bandwidth Laser-Plasma Accelerator driven Thomson photon source development

    NASA Astrophysics Data System (ADS)

    Geddes, C. G. R.; Tsai, H.-E.; Otero, G.; Liu, X.; van Tilborg, J.; Toth, Cs.; Vay, J.-L.; Lehe, R.; Schroeder, C. B.; Esarey, E.; Friedman, A.; Grote, D. P.; Leemans, W. P.

    2017-10-01

    Compact, high-quality photon sources at MeV energies can be provided by Thomson scattering of a laser from the electron beam of a Laser-Plasma Accelerator (LPA). Recent experiments and simulations demonstrate controllable LPAs in the energy range appropriate to MeV sources. Simulations indicate that high flux with narrow energy spread can be achieved via control of the scattering laser pulse shape and laser guiding, and that undesired background bremsstrahlung can be mitigated by plasma based deceleration of the electron beam after photon production. Construction of experiments and laser capabilities to combine these elements will be presented, along with initial operations, towards a compact photon source system. Work supported by US DOE NNSA DNN R&D and by Sc. HEP under contract DE-AC02-05CH11231.

  2. Deceleration processes of secondary electrons produced by a high-energy Auger electron in a biological context.

    PubMed

    Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi; Fujii, Kentaro; Watanabe, Ritsuko

    2016-11-01

    To simulate the deceleration processes of secondary electrons produced by a high-energy Auger electron in water, and particularly to focus on the spatial and temporal distributions of the secondary electron and the collision events (e.g. ionization, electronic excitation, and dissociative electron attachment) that are involved in the multiplication of lesions at sites of DNA damage. We developed a dynamic Monte Carlo code that considers the Coulombic force between an ejected electron and its parent cation produced by the Auger electron in water. Thus our code can simulate some return electrons to the parent cations. Using the code, we calculated to within the order of femtoseconds the temporal evolution of collision events, the mean energy, and the mean traveling distance (including its spatial probability distribution) of the electron at an ejected energy of 20 eV. Some of the decelerating electrons in water in the Coulombic field were attracted to the ionized atoms (cations) by the Coulombic force within hundreds of femtoseconds, although the force did not significantly enhance the number of ionization, electronic excitation, and dissociative electron attachment collision events leading to water radiolysis. The secondary electrons are decelerated in water by the Coulombic force and recombined to the ionized atoms (cations). Furthermore, the some return electrons might be prehydrated in water layer near the parent cation in DNA if the electrons might be emitted from the DNA. The prehydrated electron originated from the return electron might play a significant role in inducing DNA damage.

  3. 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.

  4. Reaction time to changes in the tempo of acoustic pulse trains.

    NASA Technical Reports Server (NTRS)

    Smith, R. P.; Warm, J. S.; Westendorf, D. H.

    1973-01-01

    Investigation of the ability of human observers to detect accelerations and decelerations in the rate of presentation of pulsed stimuli, i.e., changes in the tempo of acoustic pulse trains. Response times to accelerations in tempo were faster than to decelerations. Overall speed of response was inversely related to the pulse repetition rate.

  5. 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

  6. Slowing and cooling of heavy or light (even with a tiny electric dipole moment) polar molecules using a novel, versatile electrostatic Stark decelerator.

    PubMed

    Wang, Qin; Hou, Shunyong; Xu, Liang; Yin, Jianping

    2016-02-21

    To meet some demands for realizing precise measurements of an electric dipole moment of electron (eEDM) and examining cold collisions or cold chemical physics, we have proposed a novel, versatile electrostatic Stark decelerator with an array of true 3D electric potential wells, which are created by a series of horizontally-oriented, U-shaped electrodes with time-sequence controlling high voltages (± HV) and two guiding electrodes with a constant voltage. We have calculated the 2D electric field distribution, the Stark shifts of the four lowest rotational sub-levels of PbF molecules in the X1(2)Π1/2(v = 0) electronic and vibrational ground states as well as the population in the different rotational levels. We have discussed the 2D longitudinal and transverse phase-space acceptances of PbF molecules in our decelerator. Subsequently, we have simulated the dynamic processes of the decelerated PbF molecules using the 3D Monte-Carlo method, and have found that a supersonic PbF beam with a velocity of 300 m s(-1) can be efficiently slowed to about 5 m s(-1), which will greatly enhance the sensitivities to research a parity violation and measure an eEDM. In addition, we have investigated the dependences of the longitudinal velocity spread, longitudinal temperature and bunching efficiency on both the number of guiding stages and high voltages, and found that after bunching, a cold packet of PbF molecules in the J = 7/2, MΩ = -7/4 state with a longitudinal velocity spread of 0.69 m s(-1) (corresponding to a longitudinal temperature of 2.35 mK) will be produced by our high-efficient decelerator, which will generate a high energy-resolution molecular beam for studying cold collision physics. Finally, our novel decelerator can also be used to efficiently slow NO molecules with a tiny electric dipole moment (EDM) of 0.16 D from 315 m s(-1) to 28 m s(-1). It is clear that our proposed new decelerator has a good slowing performance and experimental feasibility as well as wide

  7. Ablation and deceleration of mass-driver launched projectiles for space disposal of nuclear wastes

    NASA Astrophysics Data System (ADS)

    Park, C.; Bowen, S. W.

    1981-01-01

    The energy cost of launching a projectile containing nuclear waste is two orders of magnitude lower with a mass driver than with a typical rocket system. A mass driver scheme will be feasible, however, only if ablation and deceleration are within certain tolerable limits. It is shown that if a hemisphere-cylinder-shaped projectile protected thermally with a graphite nose is launched vertically to attain a velocity of 17 km/sec at an altitude of 40 km, the mass loss from ablation during atmospheric flight will be less than 0.1 ton, provided the radius of the projectile is under 20 cm and the projectile's mass is of the order of 1 ton. The velocity loss from drag will vary from 0.4 to 30 km/sec, depending on the mass and radius of the projectile, the smaller velocity loss corresponding to large mass and small radius. Ablation is always within a tolerable range for schemes using a mass driver launcher to dispose of nuclear wastes outside the solar system. Deceleration can also be held in the tolerable range if the mass and diameter of the projectile are properly chosen.

  8. Deceleration of High-velocity Interstellar Photon Sails into Bound Orbits at α Centauri

    SciTech Connect

    Heller, René; Hippke, Michael, E-mail: heller@mps.mpg.de, E-mail: hippke@ifda.eu

    At a distance of about 4.22 ly, it would take about 100,000 years for humans to visit our closest stellar neighbor Proxima Centauri using modern chemical thrusters. New technologies are now being developed that involve high-power lasers firing at 1 gram solar sails in near-Earth orbits, accelerating them to 20% the speed of light ( c ) within minutes. Although such an interstellar probe could reach Proxima 20 years after launch, without propellant to slow it down it would traverse the system within hours. Here we demonstrate how the stellar photon pressures of the stellar triple α Cen A, B,more » and C (Proxima) can be used together with gravity assists to decelerate incoming solar sails from Earth. The maximum injection speed at α Cen A to park a sail with a mass-to-surface ratio ( σ ) similar to graphene (7.6 × 10{sup −4} gram m{sup −2}) in orbit around Proxima is about 13,800 km s{sup −1} (4.6% c ), implying travel times from Earth to α Cen A and B of about 95 years and another 46 years (with a residual velocity of 1280 km s{sup −1}) to Proxima. The size of such a low- σ sail required to carry a payload of 10 grams is about 10{sup 5} m{sup 2} = (316 m){sup 2}. Such a sail could use solar photons instead of an expensive laser system to gain interstellar velocities at departure. Photogravitational assists allow visits of three stellar systems and an Earth-sized potentially habitable planet in one shot, promising extremely high scientific yields.« less

  9. A Porcine Model of Traumatic Brain Injury via Head Rotational Acceleration

    PubMed Central

    Cullen, D. Kacy; Harris, James P.; Browne, Kevin D.; Wolf, John A; Duda, John E.; Meaney, David F.; Margulies, Susan S.; Smith, Douglas H.

    2017-01-01

    Unique from other brain disorders, traumatic brain injury (TBI) generally results from a discrete biomechanical event that induces rapid head movement. The large size and high organization of the human brain makes it particularly vulnerable to traumatic injury from rotational accelerations that can cause dynamic deformation of the brain tissue. Therefore, replicating the injury biomechanics of human TBI in animal models presents a substantial challenge, particularly with regard to addressing brain size and injury parameters. Here we present the historical development and use of a porcine model of head rotational acceleration. By scaling up the rotational forces to account for difference in brain mass between swine and humans, this model has been shown to produce the same tissue deformations and identical neuropathologies found in human TBI. The parameters of scaled rapid angular accelerations applied for the model reproduce inertial forces generated when the human head suddenly accelerates or decelerates in falls, collisions, or blunt impacts. The model uses custom-built linkage assemblies and a powerful linear actuator designed to produce purely impulsive nonimpact head rotation in different angular planes at controlled rotational acceleration levels. Through a range of head rotational kinematics, this model can produce functional and neuropathological changes across the spectrum from concussion to severe TBI. Notably, however, the model is very difficult to employ, requiring a highly skilled team for medical management, biomechanics, neurological recovery, and specialized outcome measures including neuromonitoring, neurophysiology, neuroimaging, and neuropathology. Nonetheless, while challenging, this clinically relevant model has proven valuable for identifying mechanisms of acute and progressive neuropathologies as well as for the evaluation of noninvasive diagnostic techniques and potential neuroprotective treatments following TBI. PMID:27604725

  10. The effect of accelerated aging on the wear of UHMWPE.

    PubMed

    Sakoda, H; Fisher, J; Lu, S; Buchanan, F

    2001-01-01

    Oxidative degradation of UHMWPE has been found to be a cause of elevated wear rate of the polymer in total joint replacement leading to failure of these devices. In order to evaluate long term stability of polymers, various accelerated aging methods have been developed. In this study, wear rates of shelf aged UHMWPE and "accelerated aged" UHMWPE were compared using a multi-directional pin-on-plate wear test machine in order to evaluate the effect of the accelerated aging on wear. Wear factors of the aged materials were found to depend on their density, which is a measure of oxidation level. Finally, accelerated aging was calibrated against shelf aging in terms of wear rate. Copyright 2001 Kluwer Academic Publishers

  11. Tunable inertia of chiral magnetic domain walls

    PubMed Central

    Torrejon, Jacob; Martinez, Eduardo; Hayashi, Masamitsu

    2016-01-01

    The time it takes to accelerate an object from zero to a given velocity depends on the applied force and the environment. If the force ceases, it takes exactly the same time to completely decelerate. A magnetic domain wall is a topological object that has been observed to follow this behaviour. Here we show that acceleration and deceleration times of chiral Neel walls driven by current are different in a system with low damping and moderate Dzyaloshinskii–Moriya exchange constant. The time needed to accelerate a domain wall with current via the spin Hall torque is much faster than the time it needs to decelerate once the current is turned off. The deceleration time is defined by the Dzyaloshinskii–Moriya exchange constant whereas the acceleration time depends on the spin Hall torque, enabling tunable inertia of chiral domain walls. Such unique feature of chiral domain walls can be utilized to move and position domain walls with lower current, key to the development of storage class memory devices. PMID:27882932

  12. Gait strategy changes with acceleration to accommodate the biomechanical constraint on push-off propulsion.

    PubMed

    Oh, Keonyoung; Baek, Juhyun; Park, Sukyung

    2012-11-15

    To maintain steady and level walking, push-off propulsion during the double support phase compensates for the energy loss through heel strike collisions in an energetically optimal manner. However, a large portion of daily gait activities also contains transient gait responses, such as acceleration or deceleration, during which the observed dominance of the push-off work or the energy optimality may not hold. In this study, we examined whether the push-off propulsion during the double support phase served as a major energy source for gait acceleration, and we also studied the energetic optimality of accelerated gait using a simple bipedal walking model. Seven healthy young subjects participated in the over-ground walking experiments. The subjects walked at four different constant gait speeds ranging from a self-selected speed to a maximum gait speed, and then they accelerated their gait from zero to the maximum gait speed using a self-selected acceleration ratio. We measured the ground reaction force (GRF) of three consecutive steps and the corresponding leg configuration using force platforms and an optical marker system, respectively, and we compared the mechanical work performed by the GRF during each single and double support phase. In contrast to the model prediction of an increase in the push-off propulsion that is proportional to the acceleration and minimizes the mechanical energy cost, the push-off propulsion was slightly increased, and a significant increase in the mechanical work during the single support phase was observed. The results suggest that gait acceleration occurs while accommodating a feasible push-off propulsion constraint. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Effective Teaching in Accelerated Learning Programs

    ERIC Educational Resources Information Center

    Boyd, Drick

    2004-01-01

    According to Wlodkowski (2003), "accelerated learning programs are one of the fastest growing transformations in higher education" (p. 5). The Center for the Study of Accelerated Learning at Regis University has documented at least 250 colleges or universities that offer accelerated learning programs for working adults. By definition, accelerated…

  14. Plate Speed-up and Deceleration during Continental Rifting: Insights from Global 2D Mantle Convection Models.

    NASA Astrophysics Data System (ADS)

    Brune, S.; Ulvrova, M.; Williams, S.

    2017-12-01

    The surface of the Earth is divided into a jigsaw of tectonic plates, some carrrying continents that disperse and aggregate through time, forming transient supercontinents like Pangea and Rodinia. Here, we study continental rifting using large-scale numerical simulations with self-consistent evolution of plate boundaries, where continental break-up emerges spontaneously due to slab pull, basal drag and trench suction forces.We use the StagYY convection code employing a visco-plastic rheology in a spherical annulus geometry. We consider an incompressible mantle under the Boussinesq approximation that is basally and internally heated.We show that continental separation follows a characteristic evolution with three distinctive phases: (1) A pre-rift phase that typically lasts for several hundreds of millions of years with tectonic quiescence in the suture and extensional stresses that are slowly building up. (2) A rift phase that further divides into a slow rift period of several tens of millions of years where stresses continuously increase followed by a rift acceleration period featuring an abrupt stress drop within several millions of years. The speed-up takes place before lithospheric break-up and therefore affects the structural architecture of the rifted margins. (3) The drifting phase with initially high divergence rates persists over tens of millions of years until the system adjust to new conditions and the spreading typically slows down.By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration within the second phase of rifting is compensated by enhanced convergence rates at subduction zones. This model outcome predicts enhanced subduction velocities, e.g. between North America and the Farallon plate during Central Atlantic rifting 200 My ago, or closure of potential back-arc basins such as in the proto-Andean ranges of South America

  15. The Effects of Training and Subject Reproducibility during Vertical Impact Acceleration

    DTIC Science & Technology

    2006-05-01

    configuration. Subjects were evaluated for reproducibility at 6, 8, and 10G with varying helmet weights. The head and sternum accelerations in the Z direction...helmet inertial properties, subject anthropometry, and the recorded head accelerations. The results from the study revealed no effect of training on the...Seat pan, seat cushion, sternum, and head accelerations were collected using an on-board data acquisition system, and neck loads were calculated to

  16. M2 ocean tide parameters and the deceleration of the moon's mean longitude from satellite orbit data

    NASA Technical Reports Server (NTRS)

    Felsentreger, T. L.; Marsh, J. G.; Williamson, R. G.

    1979-01-01

    An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

  17. Prenatal stress effects in a wild, long-lived primate: predictive adaptive responses in an unpredictable environment.

    PubMed

    Berghänel, Andreas; Heistermann, Michael; Schülke, Oliver; Ostner, Julia

    2016-09-28

    Prenatal maternal stress affects offspring phenotype in numerous species including humans, but it is debated whether these effects are evolutionarily adaptive. Relating stress to adverse conditions, current explanations invoke either short-term developmental constraints on offspring phenotype resulting in decelerated growth to avoid starvation, or long-term predictive adaptive responses (PARs) resulting in accelerated growth and reproduction in response to reduced life expectancies. Two PAR subtypes were proposed, acting either on predicted internal somatic states or predicted external environmental conditions, but because both affect phenotypes similarly, they are largely indistinguishable. Only external (not internal) PARs rely on high environmental stability particularly in long-lived species. We report on a crucial test case in a wild long-lived mammal, the Assamese macaque (Macaca assamensis), which evolved and lives in an unpredictable environment where external PARs are probably not advantageous. We quantified food availability, growth, motor skills, maternal caretaking style and maternal physiological stress from faecal glucocorticoid measures. Prenatal maternal stress was negatively correlated to prenatal food availability and led to accelerated offspring growth accompanied by decelerated motor skill acquisition and reduced immune function. These results support the 'internal PAR' theory, which stresses the role of stable adverse internal somatic states rather than stable external environments. © 2016 The Author(s).

  18. Methods to Determine the Deformation of the IRVE Hypersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Young, William R.

    2011-01-01

    Small resonant targets used in conjunction with a microwave reflectometer to determine the deformation of the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) during reentry are investigated. The reflectometer measures the distance to the targets and from this the HIAD deformation is determined. The HIAD is used by the Inflatable Reentry Vehicle Experiment (IRVE) which investigates the use of inflatable heat shields for atmospheric reentry. After several different microwave reflectometer systems were analyzed and compared it was determined that the most desirable for this application is the Frequency Doubling Target method.

  19. Comparative Assessment of Torso and Seat Mounted Restraint Systems using Manikins on the Vertical Deceleration Tower

    DTIC Science & Technology

    2017-03-01

    experimental effort involving a series of +z-axis impact tests was conducted on the 711th Human Performance Wing’s Vertical Deceleration Tower (VDT...parameters) and a JSF-styled ejection seat configuration (combined non -baseline test parameters) produced similar biodynamic response parameters for the LOIS...Photography .............................................................................. 12 6.0 EXPERIMENTAL DESIGN

  20. Gauss-Bonnet cosmology unifying late and early-time acceleration eras with intermediate eras

    NASA Astrophysics Data System (ADS)

    Oikonomou, V. K.

    2016-07-01

    In this paper we demonstrate that with vacuum F(G) gravity it is possible to describe the unification of late and early-time acceleration eras with the radiation and matter domination era. The Hubble rate of the unified evolution contains two mild singularities, so called Type IV singularities, and the evolution itself has some appealing features, such as the existence of a deceleration-acceleration transition at late times. We also address quantitatively a fundamental question related to modified gravity models description of cosmological evolution: Is it possible for all modified gravity descriptions of our Universe evolution, to produce a nearly scale invariant spectrum of primordial curvature perturbations? As we demonstrate, the answer for the F(G) description is no, since the resulting power spectrum is not scale invariant, in contrast to the F(R) description studied in the literature. Therefore, although the cosmological evolution can be realized in the context of vacuum F(G) gravity, the evolution is not compatible with the observational data, in contrast to the F(R) gravity description of the same cosmological evolution.

  1. 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.

  2. A 6% measurement of the Hubble parameter at z ∼0.45: direct evidence of the epoch of cosmic re-acceleration

    SciTech Connect

    Moresco, Michele; Cimatti, Andrea; Citro, Annalisa

    2016-05-01

    Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedentedmore » statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS, [1-3]) Data Release 9 to provide new constraints on the Hubble parameter H ( z ) using the cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent H ( z ) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ∼11–16% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6% accuracy constraint of H ( z = 0.4293) = 91.8 ± 5.3 km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring z {sub t} = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond—and including—the ΛCDM model.« less

  3. Compact two-beam push-pull free electron laser

    DOEpatents

    Hutton, Andrew [Yorktown, VA

    2009-03-03

    An ultra-compact free electron laser comprising a pair of opposed superconducting cavities that produce identical electron beams moving in opposite directions such that each set of superconducting cavities accelerates one electron beam and decelerates the other electron beam. Such an arrangement, allows the energy used to accelerate one beam to be recovered and used again to accelerate the second beam, thus, each electron beam is decelerated by a different structure than that which accelerated it so that energy exchange rather than recovery is achieved resulting in a more compact and highly efficient apparatus.

  4. Compliance control for a hydraulic bouncing system.

    PubMed

    Chen, Guangrong; Wang, Junzheng; Wang, Shoukun; Zhao, Jiangbo; Shen, Wei

    2018-05-17

    This paper is to reduce the contact impact, control the leg stiffness and bouncing height. Firstly, the combining position/force active compliance control was involved in the deceleration phase to decrease the impact force and improve the leg compliance capacity. Then a reasonable velocity control of cylinder was addressed to control the bouncing height to the given value in the acceleration phase. Due to the model uncertainties and disturbances in the deceleration and acceleration phase, a near inverse like controller with a proportional and differential control (PD) was added into the velocity control of acceleration phase to compensate the bouncing height control error. Finally, the effectiveness of proposed controller was validated by experiments. Experimental results showed the impact force could be reduced effectively and a significant bouncing height control performance could be achieved. The influences of initial energy, preload of spring and velocity of cylinder on the bouncing height were addressed as well. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  5. H0, q0 and the local velocity field. [Hubble and deceleration constants in Big Bang expansion

    NASA Technical Reports Server (NTRS)

    Sandage, A.; Tammann, G. A.

    1982-01-01

    An attempt is made to find a systematic deviation from linearity for distances that are under the control of the Virgo cluster, and to determine the value of the mean random motion about the systematic flow, in order to improve the measurement of the Hubble and the deceleration constants. The velocity-distance relation for large and intermediate distances is studied, and type I supernovae are calibrated relatively as distance indicators and absolutely to obtain a new value for the Hubble constant. Methods of determining the deceleration constant are assessed, including determination from direct measurement, mean luminosity density, virgocentric motion, and the time scale test. The very local velocity field is investigated, and a solution is preferred with a random peculiar radial velocity of very nearby field galaxies of 90-100 km/s, and a Virgocentric motion of the local group of 220 km/s, leading to an underlying expansion rate of 55, in satisfactory agreement with the global value.

  6. Plasma Radiation and Acceleration Effectiveness of CME-driven Shocks

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.; Schmidt, J. M.

    2008-05-01

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME- driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  7. Plasma radiation and acceleration effectiveness of CME-driven shocks

    NASA Astrophysics Data System (ADS)

    Schmidt, Joachim

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME-driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  8. Effects of acceleration rate on Rayleigh-Taylor instability in elastic-plastic materials

    NASA Astrophysics Data System (ADS)

    Banerjee, Arindam; Polavarapu, Rinosh

    2016-11-01

    The effect of acceleration rate in the elastic-plastic transition stage of Rayleigh-Taylor instability in an accelerated non-Newtonian material is investigated experimentally using a rotating wheel experiment. A non-Newtonian material (mayonnaise) was accelerated at different rates by varying the angular acceleration of a rotating wheel and growth patterns of single mode perturbations with different combinations of amplitude and wavelength were analyzed. Experiments were run at two different acceleration rates to compare with experiments presented in prior years at APS DFD meetings and the peak amplitude responses are captured using a high-speed camera. Similar to the instability acceleration, the elastic-plastic transition acceleration is found to be increasing with increase in acceleration rate for a given amplitude and wavelength. The experimental results will be compared to various analytical strength models and prior experimental studies using Newtonian fluids. Authors acknowledge funding support from Los Alamos National Lab subcontract(370333) and DOE-SSAA Grant (DE-NA0001975).

  9. Analysis on the time and frequency domains of the acceleration in front crawl stroke.

    PubMed

    Gil, Joaquín Madera; Moreno, Luis-Millán González; Mahiques, Juan Benavent; Muñoz, Víctor Tella

    2012-05-01

    The swimming involves accelerations and decelerations in the swimmer's body. Thus, the main objective of this study is to make a temporal and frequency analysis of the acceleration in front crawl swimming, regarding the gender and the performance. The sample was composed by 31 male swimmers (15 of high-level and 16 of low-level) and 20 female swimmers (11 of high-level and 9 of low-level). The acceleration was registered from the third complete cycle during eight seconds in a 25 meters maximum velocity test. A position transducer (200Hz) was used to collect the data, and it was synchronized to an aquatic camera (25Hz). The acceleration in the temporal (root mean square, minimum and maximum of the acceleration) and frequency (power peak, power peak frequency and spectral area) domains was calculated with Fourier analysis, as well as the velocity and the spectrums distribution in function to present one or more main peaks (type 1 and type 2). A one-way ANOVA was used to establish differences between gender and performance. Results show differences between genders in all the temporal domain variables (p<0.05) and only the Spectral Area (SA) in the frequency domain (p<0.05). Between gender and performance, only the Root Mean Square (RMS) showed differences in the performance of the male swimmers (p<0.05) and in the higher level swimmers, the Maximum (Max) and the Power Peak (PP) of the acceleration showed differences between both genders (p<0.05). These results confirms the importance of knowing the RMS to determine the efficiency of the swimmers regarding gender and performance level.

  10. Protective Effects of Hydroxychloroquine against Accelerated Atherosclerosis in Systemic Lupus Erythematosus

    PubMed Central

    Cauli, Alberto

    2018-01-01

    Cardiovascular (CV) morbidity and mortality are a challenge in management of patients with systemic lupus erythematosus (SLE). Higher risk of CV disease in SLE patients is mostly related to accelerated atherosclerosis. Nevertheless, high prevalence of traditional cardiovascular risk factors in SLE patients does not fully explain the increased CV risk. Despite the pathological bases of accelerated atherosclerosis are not fully understood, it is thought that this process is driven by the complex interplay between SLE and atherosclerosis pathogenesis. Hydroxychloroquine (HCQ) is a cornerstone in treatment of SLE patients and has been thought to exert a broad spectrum of beneficial effects on disease activity, prevention of damage accrual, and mortality. Furthermore, HCQ is thought to protect against accelerated atherosclerosis targeting toll-like receptor signaling, cytokine production, T-cell and monocyte activation, oxidative stress, and endothelial dysfunction. HCQ was also described to have beneficial effects on traditional CV risk factors, such as dyslipidemia and diabetes. In conclusion, despite lacking randomized controlled trials unambiguously proving the protection of HCQ against accelerated atherosclerosis and incidence of CV events in SLE patients, evidence analyzed in this review is in favor of its beneficial effect. PMID:29670462

  11. Critical Imperative for the Reform of British Interpretation of Fetal Heart Rate Decelerations: Analysis of FIGO and NICE Guidelines, Post-Truth Foundations, Cognitive Fallacies, Myths and Occam’s Razor

    PubMed Central

    Sholapurkar, Shashikant L.

    2017-01-01

    Cardiotocography (CTG) has disappointingly failed to show good predictability for fetal acidemia or neonatal outcomes in several large studies. A complete rethink of CTG interpretation will not be out of place. Fetal heart rate (FHR) decelerations are the most common deviations, benign as well as manifestation of impending fetal hypoxemia/acidemia, much more commonly than FHR baseline or variability. Their specific nomenclature is important (center-stage) because it provides the basic concepts and framework on which the complex “pattern recognition” of CTG interpretation by clinicians depends. Unfortunately, the discrimination of FHR decelerations seems to be muddled since the British obstetrics adopted the concept of vast majority of FHR decelerations being “variable” (cord-compression). With proliferation of confusing waveform criteria, “atypical variables” became the commonest cause of suspicious/pathological CTG. However, National Institute for Health and Care Excellence (NICE) (2014) had to disband the “typical” and “atypical” terminology because of flawed classifying criteria. This analytical review makes a strong case that there are major and fundamental framing and confirmation fallacies (not just biases) in interpretation of FHR decelerations by NICE (2014) and International Federation of Gynecology and Obstetrics (FIGO) (2015), probably the biggest in modern medicine. This “post-truth” approach is incompatible with scientific practice. Moreover, it amounts to setting oneself for failure. The inertia to change could be best described as “backfire effect”. There is abundant evidence that head-compression (and other non-hypoxic mediators) causes rapid rather than shallow/gradual decelerations. Currently, the vast majority of decelerations are attributed to unproven cord compression underpinned by flawed disproven pathophysiological hypotheses. Their further discrimination based on abstract, random, trial and error criteria remains

  12. Anisotropic Bianchi-V dark energy model under the new perspective of accelerated expansion of the universe in Brans-Dicke theory of gravitation

    NASA Astrophysics Data System (ADS)

    Jaiswal, Rekha; Zia, Rashid

    2018-04-01

    In this paper, we have proposed a cosmological model, which is consistent with the new findings of `The Supernova Cosmology project' headed by Saul Perlmutter, and the `High-Z Supernova Search team', headed by Brian Schimdt. According to these new findings, the universe is undergoing an expansion with an increasing rate, in contrast to the earlier belief that the rate of expansion is constant or the expansion is slowing down. We have considered spatially homogeneous and anisotropic Bianchi-V dark energy model in Brans-Dicke theory of gravitation. We have taken the scale factor a(t)=k t^α e^{β t} , which results into variable deceleration parameter (DP). The graph of DP shows a transition from positive to negative, which shows that universe has passed through the past decelerated expansion to the current accelerated expansion phase. In this context, we have also calculated and plotted various parameters and observed that these are in good agreement with physical and kinematic properties of the universe and are also consistent with recent observations.

  13. 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. (c) 2008 APA, all rights reserved

  14. A bridge between unified cosmic history by f( R)-gravity and BIonic system

    NASA Astrophysics Data System (ADS)

    Sepehri, Alireza; Capozziello, Salvatore; Setare, Mohammad Reza

    2016-04-01

    Recently, the cosmological deceleration-acceleration transition redshift in f( R) gravity has been considered in order to address consistently the problem of cosmic evolution. It is possible to show that the deceleration parameter changes sign at a given redshift according to observational data. Furthermore, a f( R) gravity cosmological model can be constructed in brane-antibrane system starting from the very early universe and accounting for the cosmological redshift at all phases of cosmic history, from inflation to late time acceleration. Here we propose a f( R) model where transition redshifts correspond to inflation-deceleration and deceleration-late time acceleration transitions starting froma BIon system. At the point where the universe was born, due to the transition of k black fundamental strings to the BIon configuration, the redshift is approximately infinity and decreases with reducing temperature (z˜ T2). The BIon is a configuration in flat space of a universe-brane and a parallel anti-universe-brane connected by a wormhole. This wormhole is a channel for flowing energy from extra dimensions into our universe, occurring at inflation and decreasing with redshift as z˜ T^{4+1/7}. Dynamics consists with the fact that the wormhole misses its energy and vanishes as soon as inflation ends and deceleration begins. Approaching two universe branes together, a tachyon is originated, it grows up and causes the formation of a wormhole. We show that, in the framework of f( R) gravity, the cosmological redshift depends on the tachyonic potential and has a significant decrease at deceleration-late time acceleration transition point (z˜ T^{2/3}). As soon as today acceleration approaches, the redshift tends to zero and the cosmological model reduces to the standard Λ CDM cosmology.

  15. Numerical and Experimental Investigation of the Effects of Acceleration Disturbances on Microgravity Experiments

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan

    2000-01-01

    Normal vibrational modes on large spacecraft are excited by crew activity, operating machinery, and other mechanical disturbances. Periodic engine burns for maintaining vehicle attitude and random impulse type disturbances also contribute to the acceleration environment of a Spacecraft. Accelerations from these vibrations (often referred to as g-jitter) are several orders of magnitude larger than the residual accelerations from atmospheric drag and gravity gradient effects. Naturally, the effects of such accelerations have been a concern to prospective experimenters wishing to take advantage of the microgravity environment offered by spacecraft operating in low Earth orbit and the topic has been studied extensively, both numerically and analytically. However, these studies have not produced a general theory that predicts the effects of multi-spectral periodic accelerations on a general class of experiments nor have they produced scaling laws that a prospective experimenter could use to assess how his/her experiment might be affected by this acceleration environment. Furthermore, there are no actual flight experimental data that correlates heat or mass transport with measurements of the periodic acceleration environment. The present investigation approaches this problem with carefully conducted terrestrial experiments and rigorous numerical modeling thereby providing comparative theoretical and experimental data. The modeling, it is hoped will provide a predictive tool that can be used for assessing experiment response to Spacecraft vibrations.

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

    PubMed Central

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

    2015-01-01

    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

  17. Magnet design for the splitter/combiner regions of CBETA, the Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator

    SciTech Connect

    Crittendon, J. A.; Burke, D. C.; Fuentes, Y. L.P.

    2017-01-06

    The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less

  18. Single event effects in high-energy accelerators

    NASA Astrophysics Data System (ADS)

    García Alía, Rubén; Brugger, Markus; Danzeca, Salvatore; Cerutti, Francesco; de Carvalho Saraiva, Joao Pedro; Denz, Reiner; Ferrari, Alfredo; Foro, Lionel L.; Peronnard, Paul; Røed, Ketil; Secondo, Raffaello; Steckert, Jens; Thurel, Yves; Toccafondo, Iacocpo; Uznanski, Slawosz

    2017-03-01

    The radiation environment encountered at high-energy hadron accelerators strongly differs from the environment relevant for space applications. The mixed-field expected at modern accelerators is composed of charged and neutral hadrons (protons, pions, kaons and neutrons), photons, electrons, positrons and muons, ranging from very low (thermal) energies up to the TeV range. This complex field, which is extensively simulated by Monte Carlo codes (e.g. FLUKA) is due to beam losses in the experimental areas, distributed along the machine (e.g. collimation points) and deriving from the interaction with the residual gas inside the beam pipe. The resulting intensity, energy distribution and proportion of the different particles largely depends on the distance and angle with respect to the interaction point as well as the amount of installed shielding material. Electronics operating in the vicinity of the accelerator will therefore be subject to both cumulative damage from radiation (total ionizing dose, displacement damage) as well as single event effects which can seriously compromise the operation of the machine. This, combined with the extensive use of commercial-off-the-shelf components due to budget, performance and availability reasons, results in the need to carefully characterize the response of the devices and systems to representative radiation conditions.

  19. 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.

  20. Beam dynamic simulation and optimization of the CLIC positron source and the capture linac

    SciTech Connect

    Bayar, C., E-mail: cafer.bayar@cern.ch; CERN, Geneva; Doebert, S., E-mail: Steffen.Doebert@cern.ch

    2016-03-25

    The CLIC Positron Source is based on the hybrid target composed of a crystal and an amorphous target. Simulations have been performed from the exit of the amorphous target to the end of pre-injector linac which captures and accelerates the positrons to an energy of 200 MeV. Simulations are performed by the particle tracking code PARMELA. The magnetic field of the AMD is represented in PARMELA by simple coils. Two modes are applied in this study. The first one is accelerating mode based on acceleration after the AMD. The second one is decelerating mode based on deceleration in the first acceleratingmore » structure. It is shown that the decelerating mode gives a higher yield for the e{sup +} beam in the end of the Pre-Injector Linac.« less

  1. Balloon launched decelerator test program: Post-test test report

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Balloon Launched Decelerator Test (BLDT) flights were conducted during the summer of 1972 over the White Sands Missile Range. The purpose of these tests was to qualify the Viking disk-gap band parachute system behind a full-scale simulator of the Viking Entry Vehicle over the maximum range of entry conditions anticipated in the Viking '75 soft landing on Mars. Test concerns centered on the ability of a minimum weight parachute system to operate without structural damage in the turbulent wake of the blunt-body entry vehicle (140 deg, 11.5 diameter cone). This is the first known instance of parachute operation at supersonic speeds in the wake of such a large blunt body. The flight tests utilized the largest successful balloon-payload weight combination known to get to high altitude (120kft) where rocket engines were employed to boost the test vehicle to supersonic speeds and dynamic pressures simulating the range of conditions on Mars.

  2. X-ray transitions studied for decelerated bare and H-like uranium ions at the ESR electron cooler

    NASA Astrophysics Data System (ADS)

    Gumberidze, A.; Stöhlker, Th.; Bednarz, G.; Beyer, H. F.; Bosch, F.; Cai, X.; Hagmann, S.; Klepper, O.; Kozhuharov, C.; Liesen, D.; Ma, X.; Mokler, P. H.; Sierpowski, D.; Stachura, Z.; Steck, M.; Toleikis, S.; Warczak, A.; Zou, Y.

    2003-05-01

    Here we report on X-ray spectra induced by spontaneous capture of free electrons into decelerated bare- and hydrogen-like uranium ions which we measured recently at the cooler section of the ESR storage ring. The most intense lines observed in spectra can be attributed to direct transition of electrons into the K shell of the projectile ions and to characteristic L → K (Lyα) transitions. Radiative recombination lines into the K shell of bare and H-like uranium can be exploited for measuring the two-electron contribution to the ground state binding energy in helium-like uranium. The goal is to probe for high-Z ions bound-state QED corrections which are of the order of α2. Besides the dominant characteristic L → K transitions, the strongly reduced Bremsstrahlung (due to the low cooler voltage applied to the decelerated ions) allowed us to observe for the very first time RR transitions into the L shell as well as the balmer radiation located at the low-energy part of the spectra.

  3. Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

    SciTech Connect

    Velikovich, A. L.; Schmit, P. F.

    Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

  4. Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Schmit, P. F.

    2015-12-01

    Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining the "instantaneous growth rate" are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].

  5. Seismic rupture and ground accelerations induced by CO 2 injection in the shallow crust

    DOE PAGES

    Cappa, Frédéric; Rutqvist, Jonny

    2012-09-01

    We present that because of the critically stressed nature of the upper crust, the injection of large volumes of carbon dioxide (CO 2) into shallow geological reservoirs can trigger seismicity and induce ground deformations when the injection increases the fluid pressure in the vicinity of potentially seismic faults. The increased fluid pressure reduces the strength against fault slip, allowing the stored elastic energy to be released in seismic events that can produce felt ground accelerations. Here, we seek to explore the likelihood ground motions induced by a CO 2 injection using hydromechanical modelling with multiphase fluid flow and dynamic rupture,more » including fault-frictional weakening. We extend the previous work of Cappa and Rutqvist, in which activation of a normal fault at critical stress may be possible for fast rupture nucleating by localized increase in fluid pressure and large decrease in fault friction. In this paper, we include seismic wave propagation generated by the rupture. For our assumed system and injection rate, simulations show that after a few days of injection, a dynamic fault rupture of few centimetres nucleates at the base of the CO 2 reservoir and grows bilaterally, both toward the top of the reservoir and outside. The rupture is asymmetric and affects a larger zone below the reservoir where the rupture is self-propagating (without any further pressure increase) as a result of fault-strength weakening. The acceleration and deceleration of the rupture generate waves and result in ground accelerations (~0.1–0.6 g) consistent with observed ground motion records. Finally, the maximum ground acceleration is obtained near the fault, and horizontal accelerations are generally markedly higher than vertical accelerations.« less

  6. Effects of a Mathematics Cognitive Acceleration Program on Student Achievement and Motivation

    ERIC Educational Resources Information Center

    Finau, Teukava; Treagust, David F.; Won, Mihye; Chandrasegaran, A. L.

    2018-01-01

    This paper presents the effects of a cognitive acceleration program in mathematics classes on Tongan students' achievements, motivation and self-regulation. Cognitive Acceleration in Mathematics Education (CAME) is a program developed at King's College and implemented worldwide with the aim of improving students' thinking skills, mathematics…

  7. 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

  8. Mission and Design Sensitivities for Human Mars Landers Using Hypersonic Inflatable Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    Polsgrove, Tara P.; Thomas, Herbert D.; Dwyer Ciancio, Alicia; Collins, Tim; Samareh, Jamshid

    2017-01-01

    Landing humans on Mars is one of NASA's long term goals. NASA's Evolvable Mars Campaign (EMC) is focused on evaluating architectural trade options to define the capabilities and elements needed to sustain human presence on the surface of Mars. The EMC study teams have considered a variety of in-space propulsion options and surface mission options. Understanding how these choices affect the performance of the lander will allow a balanced optimization of this complex system of systems problem. This paper presents the effects of mission and vehicle design options on lander mass and performance. Beginning with Earth launch, options include fairing size assumptions, co-manifesting elements with the lander, and Earth-Moon vicinity operations. Capturing into Mars orbit using either aerocapture or propulsive capture is assessed. For entry, descent, and landing both storable as well as oxygen and methane propellant combinations are considered, engine thrust level is assessed, and sensitivity to landed payload mass is presented. This paper focuses on lander designs using the Hypersonic Inflatable Aerodynamic Decelerators, one of several entry system technologies currently considered for human missions.

  9. Influence of maneuverability on helicopter combat effectiveness

    NASA Technical Reports Server (NTRS)

    Falco, M.; Smith, R.

    1982-01-01

    A computational procedure employing a stochastic learning method in conjunction with dynamic simulation of helicopter flight and weapon system operation was used to derive helicopter maneuvering strategies. The derived strategies maximize either survival or kill probability and are in the form of a feedback control based upon threat visual or warning system cues. Maneuverability parameters implicit in the strategy development include maximum longitudinal acceleration and deceleration, maximum sustained and transient load factor turn rate at forward speed, and maximum pedal turn rate and lateral acceleration at hover. Results are presented in terms of probability of skill for all combat initial conditions for two threat categories.

  10. Coupling and decoupling of the accelerating units for pulsed synchronous linear accelerator

    NASA Astrophysics Data System (ADS)

    Shen, Yi; Liu, Yi; Ye, Mao; Zhang, Huang; Wang, Wei; Xia, Liansheng; Wang, Zhiwen; Yang, Chao; Shi, Jinshui; Zhang, Linwen; Deng, Jianjun

    2017-12-01

    A pulsed synchronous linear accelerator (PSLA), based on the solid-state pulse forming line, photoconductive semiconductor switch, and high gradient insulator technologies, is a novel linear accelerator. During the prototype PSLA commissioning, the energy gain of proton beams was found to be much lower than expected. In this paper, the degradation of the energy gain is explained by the circuit and cavity coupling effect of the accelerating units. The coupling effects of accelerating units are studied, and the circuit topologies of these two kinds of coupling effects are presented. Two methods utilizing inductance and membrane isolations, respectively, are proposed to reduce the circuit coupling effects. The effectiveness of the membrane isolation method is also supported by simulations. The decoupling efficiency of the metal drift tube is also researched. We carried out the experiments on circuit decoupling of the multiple accelerating cavity. The result shows that both circuit decoupling methods could increase the normalized voltage.

  11. A prospective cohort study of fetal heart rate monitoring: deceleration area is predictive of fetal acidemia.

    PubMed

    Cahill, Alison G; Tuuli, Methodius G; Stout, Molly J; López, Julia D; Macones, George A

    2018-05-01

    Intrapartum electronic fetal monitoring is the most commonly used tool in obstetrics in the United States; however, which electronic fetal monitoring patterns predict acidemia remains unclear. This study was designed to describe the frequency of patterns seen in labor using modern nomenclature, and to test the hypothesis that visually interpreted patterns are associated with acidemia and morbidities in term infants. We further identified patterns prior to delivery, alone or in combination, predictive of acidemia and neonatal morbidity. This was a prospective cohort study of 8580 women from 2010 through 2015. Patients were all consecutive women laboring at ≥37 weeks' gestation with a singleton cephalic fetus. Electronic fetal monitoring patterns during the 120 minutes prior to delivery were interpreted in 10-minute epochs. Interpretation included the category system and individual electronic fetal monitoring patterns per the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria as well as novel patterns. The primary outcome was fetal acidemia (umbilical artery pH ≤7.10); neonatal morbidities were also assessed. Final regression models for acidemia adjusted for nulliparity, pregestational diabetes, and advanced maternal age. Area under the receiver operating characteristic curves were used to assess the test characteristics of individual models for acidemia and neonatal morbidity. Of 8580 women, 149 (1.7%) delivered acidemic infants. Composite neonatal morbidity was diagnosed in 757 (8.8%) neonates within the total cohort. Persistent category I, and 10-minute period of category III, were significantly associated with normal pH and acidemia, respectively. Total deceleration area was most discriminative of acidemia (area under the receiver operating characteristic curves, 0.76; 95% confidence interval, 0.72-0.80), and deceleration area with any 10 minutes of tachycardia had the greatest discriminative ability for neonatal

  12. The Longitudinal Stability of Flying Boats as Determined by Tests of Models in the NACA Tank II : Effect of Variations in Form of Hull on Longitudinal Stability

    NASA Technical Reports Server (NTRS)

    Olson, Roland E.; Truscott, Starr

    1942-01-01

    Data taken from tests at constant speed to establish trim limits of stability, tests at accelerated speeds to determine stable limits of center of gravity shift, and tests at decelerated speeds to obtain landing characteristics of several model hull forms were used to establish hull design effect on longitudinal stability of porpoising. Results show a reduction of dead rise angle as being the only investigated factor reducing low trim limit. Various methods of reducing afterbody interference increased upper trim limit

  13. 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…

  14. Computational and theoretical investigation of Mars's atmospheric impact on the descent module "Exomars-2018" under aerodynamic deceleration

    NASA Astrophysics Data System (ADS)

    Golomazov, M. M.; Ivankov, A. A.

    2016-12-01

    Methods for calculating the aerodynamic impact of the Martian atmosphere on the descent module "Exomars-2018" intended for solving the problem of heat protection of the descent module during aerodynamic deceleration are presented. The results of the investigation are also given. The flow field and radiative and convective heat exchange are calculated along the trajectory of the descent module until parachute system activation.

  15. Maternal deprivation decelerates postnatal morphological lung development of F344 rats.

    PubMed

    Hupa, Katharina Luise; Schmiedl, Andreas; Pabst, Reinhard; Von Hörsten, Stephan; Stephan, Michael

    2014-02-01

    Intensive medical care at premature born infants is often associated with separation of neonates from their mothers. Here, early artificial prolonged separation of rat pups from their dams (Maternal Deprivation, MD) was used to study potential impact on morphological lung maturation. Furthermore, we investigated the influence of an endogenous deficiency of the neuropeptide-cleaving dipeptidyl peptidase IV (DPP4), since the effects of MD are known to be partly mediated via neuropeptidergic effects, hypothesizing that MD will lead to a retardation of postnatal lung development, DPP4-dependendly. We used wild type and CD26/DPP4 deficient rats. For MD, the dam was placed each day into a separate cage for 2 h, while the pups remained in the nest on their own. Morphological lung maturation and cell proliferation at the postnatal days 7, 10, 14, and 21 were determined morphometrically. Maternally deprived wild types showed a retarded postnatal lung development compared with untreated controls in both substrains. During alveolarization, an increased thickness of alveolar septa and a decreased surface of septa about 50% were found. At the end of the morphological lung maturation, the surface of the alveolar septa was decreased at about 25% and the septal thickness remained increased about 20%. The proliferation rate was also decreased about 50% on day 14. However, the MD induced effects were less pronounced in DPP4-deficient rats, due to a significant deceleration already induced by DPP4-deficiency. Thus, MD as a model for postnatal stress experience influences remarkably postnatal development of rats, which is significantly modulated by the DPP4-system. Copyright © 2013 Wiley Periodicals, Inc.

  16. Passive and active plasma deceleration for the compact disposal of electron beams

    SciTech Connect

    Bonatto, A., E-mail: abonatto@lbl.gov; CAPES Foundation, Ministry of Education of Brazil, Brasília, DF 700040-020; Schroeder, C. B.

    2015-08-15

    Plasma-based decelerating schemes are investigated as compact alternatives for the disposal of high-energy beams (beam dumps). Analytical solutions for the energy loss of electron beams propagating in passive and active (laser-driven) schemes are derived. These solutions, along with numerical modeling, are used to investigate the evolution of the electron distribution, including energy chirp and total beam energy. In the active beam dump scheme, a laser-driver allows a more homogeneous beam energy extraction and drastically reduces the energy chirp observed in the passive scheme. These concepts could benefit applications requiring overall compactness, such as transportable light sources, or facilities operating atmore » high beam power.« less

  17. Bianchi type-I domain walls with negative constant deceleration parameter in Brans-Dicke theory

    NASA Astrophysics Data System (ADS)

    Katore, S. D.

    2011-04-01

    Bianchi type-I space-time is considered in the presence of a domain walls source in the scalar-tensor theory of gravitation proposed by Brans and Dicke (C.H. Brans and R.H. Dicke, Phys. Rev. 24, 925 (1961)). With the help of the special law of variation for Hubble's parameter proposed by Bermann (M.S. Berman, Nuovo Cimento B 74, 182 (1983)) a cosmological model with negative constant deceleration parameter is obtained in the presence of domain walls. Some physical properties of the model are also discussed.

  18. Effect of beta-blocker therapy on heart rate response in patients with hypertension and newly diagnosed untreated obstructive sleep apnea syndrome.

    PubMed

    Wolf, Jacek; Drozdowski, Jacek; Czechowicz, Krzysztof; Winklewski, Paweł J; Jassem, Ewa; Kara, Tomas; Somers, Virend K; Narkiewicz, Krzysztof

    2016-01-01

    Beta1-receptor antagonists (BBs) are commonly administered in the treatment of cardiovascular disease (CVD). The reported benefits of BB use in CVD patients with concomitant obstructive sleep apnea (OSA) may be limited by their impact on apnea-induced bradycardias. Therefore the aim of the study was to test the influence of BBs on periapneic heart rate (HR) fluctuations in hypertensive patients with newly-detected and untreated OSA. We studied 88 hypertensive patients (56 on BBs and 32 BB naive) with newly-diagnosed moderate-to-severe OSA who were free of major pulmonary comorbidities and did not require antiarrhythmic therapy. ECGs recorded during sleep were investigated for heart rate (HR) responses to apneas allowing to compare extreme HR accelerations and decelerations between the groups. Average sleep-time HR was comparable in BB-naive (BB-) and BB-treated (BB+) patients. Direct comparisons showed that HR decelerations were also similar in the two subgroups (53.8±9.6 vs. 54.4±7.8 bpm; P=0.78, for BB- and BB+, respectively) however, BBs blunted the OSA-induced HR accelerations (82.3±12.2 vs. 74.3±10.0; P=0.003). After adjusting for baseline HR and magnitude of desaturations, HR decelerations were more evident in BB-naive group whereas tachycardic responses remained blunted in the BB+ group. The incidence of ectopies and conduction abnormalities were comparable across two groups. Beta-blockers do not potentiate apnea-induced HR decelerations, attenuate apnea-induced increases in heart rate and do not influence incidence of ectopies and conduction abnormalities in patients with hypertension and moderate-to-severe, untreated OSA. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  19. Low External Workloads Are Related to Higher Injury Risk in Professional Male Basketball Games

    PubMed Central

    Caparrós, Toni; Casals, Martí; Solana, Álvaro; Peña, Javier

    2018-01-01

    The primary purpose of this study was to identify potential risk factors for sports injuries in professional basketball. An observational retrospective cohort study involving a male professional basketball team, using game tracking data was conducted during three consecutive seasons. Thirty-three professional basketball players took part in this study. A total of 29 time-loss injuries were recorded during regular season games, accounting for 244 total missed games with a mean of 16.26 ± 15.21 per player and season. The tracking data included the following variables: minutes played, physiological load, physiological intensity, mechanical load, mechanical intensity, distance covered, walking maximal speed, maximal speed, sprinting maximal speed, maximal speed, average offensive speed, average defensive speed, level one acceleration, level two acceleration, level three acceleration, level four acceleration, level one deceleration, level two deceleration, level three deceleration, level four deceleration, player efficiency rating and usage percentage. The influence of demographic characteristics, tracking data and performance factors on the risk of injury was investigated using multivariate analysis with their incidence rate ratios (IRRs). Athletes with less or equal than 3 decelerations per game (IRR, 4.36; 95% CI, 1.78-10.6) and those running less or equal than 1.3 miles per game (lower workload) (IRR, 6.42 ; 95% CI, 2.52-16.3) had a higher risk of injury during games (p < 0.01 in both cases). Therefore, unloaded players have a higher risk of injury. Adequate management of training loads might be a relevant factor to reduce the likelihood of injury according to individual profiles. Key points The number of decelerations and the total distance can be considered risk factors for injuries in professional basketball players. Unloaded players have greater risk of injury compared to players with higher accumulated external workload. Workload management should be

  20. Vestibular-ocular accommodation reflex in man

    NASA Technical Reports Server (NTRS)

    Clark, B.; Randle, R. J.; Stewart, J. D.

    1975-01-01

    Stimulation of the vestibular system by angular acceleration produces widespread sensory and motor effects. The present paper studies a motor effect which has not been reported in the literature, i.e., the influence of rotary acceleration of the body on ocular accommodation. The accommodation of 10 young men was recorded before and after a high-level deceleration to zero velocity following 30 sec of rotating. Accommodation was recorded continuously on an infrared optometer for 110 sec under two conditions: while the subjects observed a target set at the far point, and while they viewed the same target through a 0.3-mm pinhole. Stimulation by high-level rotary deceleration produced positive accommodation or a pseudomyopia under both conditions, but the positive accommodation was substantially greater and lasted much longer during fixation through the pinhole. It is hypothesized that this increase in accommodation is a result of a vestibular-ocular accommodation reflex.

  1. Does attention speed up processing? Decreases and increases of processing rates in visual prior entry.

    PubMed

    Tünnermann, Jan; Petersen, Anders; Scharlau, Ingrid

    2015-03-02

    Selective visual attention improves performance in many tasks. Among others, it leads to "prior entry"--earlier perception of an attended compared to an unattended stimulus. Whether this phenomenon is purely based on an increase of the processing rate of the attended stimulus or if a decrease in the processing rate of the unattended stimulus also contributes to the effect is, up to now, unanswered. Here we describe a novel approach to this question based on Bundesen's Theory of Visual Attention, which we use to overcome the limitations of earlier prior-entry assessment with temporal order judgments (TOJs) that only allow relative statements regarding the processing speed of attended and unattended stimuli. Prevalent models of prior entry in TOJs either indirectly predict a pure acceleration or cannot model the difference between acceleration and deceleration. In a paradigm that combines a letter-identification task with TOJs, we show that indeed acceleration of the attended and deceleration of the unattended stimuli conjointly cause prior entry. © 2015 ARVO.

  2. Controlling protein molecular dynamics: How to accelerate folding while preserving the native state

    NASA Astrophysics Data System (ADS)

    Jensen, Christian H.; Nerukh, Dmitry; Glen, Robert C.

    2008-12-01

    The dynamics of peptides and proteins generated by classical molecular dynamics (MD) is described by using a Markov model. The model is built by clustering the trajectory into conformational states and estimating transition probabilities between the states. Assuming that it is possible to influence the dynamics of the system by varying simulation parameters, we show how to use the Markov model to determine the parameter values that preserve the folded state of the protein and at the same time, reduce the folding time in the simulation. We investigate this by applying the method to two systems. The first system is an imaginary peptide described by given transition probabilities with a total folding time of 1μs. We find that only small changes in the transition probabilities are needed to accelerate (or decelerate) the folding. This implies that folding times for slowly folding peptides and proteins calculated using MD cannot be meaningfully compared to experimental results. The second system is a four residue peptide valine-proline-alanine-leucine in water. We control the dynamics of the transitions by varying the temperature and the atom masses. The simulation results show that it is possible to find the combinations of parameter values that accelerate the dynamics and at the same time preserve the native state of the peptide. A method for accelerating larger systems without performing simulations for the whole folding process is outlined.

  3. Low External Workloads Are Related to Higher Injury Risk in Professional Male Basketball Games.

    PubMed

    Caparrós, Toni; Casals, Martí; Solana, Álvaro; Peña, Javier

    2018-06-01

    The primary purpose of this study was to identify potential risk factors for sports injuries in professional basketball. An observational retrospective cohort study involving a male professional basketball team, using game tracking data was conducted during three consecutive seasons. Thirty-three professional basketball players took part in this study. A total of 29 time-loss injuries were recorded during regular season games, accounting for 244 total missed games with a mean of 16.26 ± 15.21 per player and season. The tracking data included the following variables: minutes played, physiological load, physiological intensity, mechanical load, mechanical intensity, distance covered, walking maximal speed, maximal speed, sprinting maximal speed, maximal speed, average offensive speed, average defensive speed, level one acceleration, level two acceleration, level three acceleration, level four acceleration, level one deceleration, level two deceleration, level three deceleration, level four deceleration, player efficiency rating and usage percentage. The influence of demographic characteristics, tracking data and performance factors on the risk of injury was investigated using multivariate analysis with their incidence rate ratios (IRRs). Athletes with less or equal than 3 decelerations per game (IRR, 4.36; 95% CI, 1.78-10.6) and those running less or equal than 1.3 miles per game (lower workload) (IRR, 6.42 ; 95% CI, 2.52-16.3) had a higher risk of injury during games (p < 0.01 in both cases). Therefore, unloaded players have a higher risk of injury. Adequate management of training loads might be a relevant factor to reduce the likelihood of injury according to individual profiles.

  4. The algorithm for duration acceleration of repetitive projects considering the learning effect

    NASA Astrophysics Data System (ADS)

    Chen, Hongtao; Wang, Keke; Du, Yang; Wang, Liwan

    2018-03-01

    Repetitive project optimization problem is common in project scheduling. Repetitive Scheduling Method (RSM) has many irreplaceable advantages in the field of repetitive projects. As the same or similar work is repeated, the proficiency of workers will be correspondingly low to high, and workers will gain experience and improve the efficiency of operations. This is learning effect. Learning effect is one of the important factors affecting the optimization results in repetitive project scheduling. This paper analyzes the influence of the learning effect on the controlling path in RSM from two aspects: one is that the learning effect changes the controlling path, the other is that the learning effect doesn't change the controlling path. This paper proposes corresponding methods to accelerate duration for different types of critical activities and proposes the algorithm for duration acceleration based on the learning effect in RSM. And the paper chooses graphical method to identity activities' types and considers the impacts of the learning effect on duration. The method meets the requirement of duration while ensuring the lowest acceleration cost. A concrete bridge construction project is given to verify the effectiveness of the method. The results of this study will help project managers understand the impacts of the learning effect on repetitive projects, and use the learning effect to optimize project scheduling.

  5. 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.

  6. Commnity Petascale Project for Accelerator Science And Simulation: Advancing Computational Science for Future Accelerators And Accelerator Technologies

    SciTech Connect

    Spentzouris, Panagiotis; /Fermilab; Cary, John

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors.« less

  7. Independent Orbiter Assessment (IOA): Assessment of the landing/deceleration (LDG/DEC) subsystem FMEA/CIL

    NASA Technical Reports Server (NTRS)

    Odonnell, R. A.; Weissinger, D.

    1988-01-01

    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 effort first completed an analysis of the Landing/Deceleration (LDG/DEC) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. This report documents the results of that comparison for the Orbiter LDG/DEC hardware. The IOA product for the LDG/DEC analysis consisted of 259 failure mode worksheets that resulted in 124 potential critical items being identified. Comparison was made to the NASA baseline which consisted of 267 FMEA's and 120 CIL items. This comparison produced agreement on all but 75 FMEA's which caused differences in 51 CIL items.

  8. Focused Attention, Heart Rate Deceleration, and Cognitive Development in Preterm and Full-Term Infants

    PubMed Central

    Petrie Thomas, Julianne H.; Whitfield, Michael F.; Oberlander, Tim F.; Synnes, Anne R.; Grunau, Ruth E.

    2012-01-01

    The majority of children who are born very preterm escape major impairment, yet more subtle cognitive and attention problems are very common in this population. Previous research has linked infant focused attention during exploratory play to later cognition in children born full-term and preterm. Infant focused attention can be indexed by sustained decreases in heart rate (HR). However there are no preterm studies that have jointly examined infant behavioral attention and concurrent HR response during exploratory play in relation to developing cognition. We recruited preterm infants free from neonatal conditions associated with major adverse outcomes, and further excluded infants with developmental delay (Bayley Mental Development Index [MDI < 70]) at 8 months corrected age (CA). During infant exploratory play at 8 months CA, focused attention and concurrent HR response were compared in 83 preterm infants (born 23–32 weeks gestational age [GA]) who escaped major impairment to 46 full-term infants. Focused attention and HR response were then examined in relation to Bayley MDI, after adjusting for neonatal risk. MDI did not differ by group, yet full-term infants displayed higher global focused attention ratings. Among the extremely preterm infants born <29 weeks, fewer days on mechanical ventilation, mean longest focus, and greater HR deceleration during focused attention episodes, accounted for 49% of adjusted variance in predicting concurrent MDI. There were no significant associations for later-born gestational age (29–32 weeks) or full-term infants. Among extremely preterm infants who escape major impairment, our findings suggest unique relationships between focused attention, HR deceleration, and developing cognition. PMID:22487941

  9. Influence of carbon monoxide poisoning on the fetal heart monitor tracing: a report of 3 cases.

    PubMed

    Towers, Craig V; Corcoran, Vincent A

    2009-03-01

    The diagnosis of carbon monoxide poisoning in the third trimester of pregnancy requires an index of suspicion, and the appearance of the fetal heart monitor tracing may help in this regard. Three cases of third-trimester acute carbon monoxide poisoning occurred. In each pregnancy, the fetal heart monitor tracing on admission was correlated with the maternal carboxyhemoglobin level, and how the pattern changed following the institution of therapy was analyzed. In all 3 cases, the initial fetal heart rate pattern demonstrated decreased variability with an elevated baseline and an absence of accelerations and decelerations. Within 45-90 minutes of treatment onset, the baseline fetal heart rate dropped by 20-40 beats per minute, the variability became moderate, and accelerations occurred. Absent accelerations with minimal variability, if caused by uteroplacental insufficiency, are usually preceded by recurrent decelerations. Absent accelerations with minimal variability in the absence of recurrent decelerations may suggest another cause, of which carbon monoxide intoxication can be added to the differential, especially since this disorder often has nonspecific clinical symptoms.

  10. 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

  11. Mission and Design Sensitivities for Human Mars Landers Using Hypersonic Inflatable Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    Polsgrove, Tara P.; Thomas, Herbert D.; Collins, Tim; Dwyer Cianciolo, Alicia; Samareh, Jamshid

    2017-01-01

    Landing humans on Mars is one of NASA's long term goals. The Evolvable Mars Campaign (EMC) is focused on evaluating architectural trade options to define the capabilities and elements needed for a sustainable human presence on the surface of Mars. The EMC study teams have considered a variety of in-space propulsion options and surface mission options. As we seek to better understand how these choices affect the performance of the lander, this work informs and influences requirements for transportation systems to deliver the landers to Mars and enable these missions. This paper presents the effects of mission and vehicle design options on lander mass and performance. Beginning with Earth launch, options include fairing size assumptions, co-manifesting other elements with the lander, and Earth-Moon vicinity operations. Capturing into Mars orbit using either aerocapture or propulsive capture is assessed. For entry, descent, and landing both storable as well as oxygen and methane propellant combinations are considered, engine thrust level is assessed, and sensitivity to landed payload mass is presented. This paper focuses on lander designs using the Hypersonic Inflatable Aerodynamic Decelerators (HIAD), one of several entry system technologies currently considered for human missions.

  12. A magnetic braking and sensing technique for deceleration and recovery of moving non-magnetic metallic particles

    NASA Astrophysics Data System (ADS)

    Cheng, David; Yoshinaka, Akio; Wu, Lawrence

    2018-05-01

    A magnetic braking and sensing technique developed as a potential alternative to assist with the non-contact deceleration and detection of explosively dispersed non-magnetic metallic particles is discussed. In order to verify the feasibility of such a technique and gain an understanding of how the underlying forces scale with particle size and velocity, a study was conducted whereby an aluminum particle moving along a spatially varying but time-invariant magnetic field was modeled and the corresponding experiment performed.

  13. Effects of Background Pressure on Relativistic Laser-Plasma Interaction Ion Acceleration

    NASA Astrophysics Data System (ADS)

    Peterson, Andrew; Orban, C.; Feister, S.; Ngirmang, G.; Smith, J. T.; Klim, A.; Frische, K.; Morrison, J.; Chowdhury, E.; Roquemore, W. M.

    2016-10-01

    Typically, ultra-intense laser-accelerated ion experiments are carried out under high-vacuum conditions and with a repetition rate up to several shots per day. Looking to the future there is a need to perform these experiments with a much larger repetition rate. A continuously flowing liquid target is more suitable than a solid target for this purpose. However liquids vaporize below their vapor pressure, and the experiment cannot be performed under high-vacuum conditions. The effects of this non-negligible high chamber pressure acceleration of charged particles is not yet well understood. We investigate this phenomena using Particle-in-Cell simulations, exploring the effect of the background pressure on the accelerated ion spectrum. Experiments in this regime are being performed at the Air Force Research Laboratory at Wright-Patterson Air Force Base. This research was sponsored by the Quantum and Non-Equilibrium Processes Division of the Air Force Office of Scientific Research, under the management of Dr. Enrique Parra, Program Manager and significant support from the DOD HPCMP Internship Program.

  14. Phasic heart rate responses and cardiac cycle time in auditory choice reaction time.

    PubMed

    van der Molen, M W; Somsen, R J; Orlebeke, J F

    1983-01-01

    This study investigated the cardiovascular-behavioral interaction under short and long stimulus interval conditions. In addition, the cardiovascular-behavioral interaction was studied as affected by cardiac cycle duration. Fourteen subjects performed a choice reaction time (RT) task employing a mixed speed-accuracy tradeoff design in which reactions were paced to coincide with a signal that occurs randomly at either 200 or 500 msec after the reaction stimulus. The preparatory interval between a warning stimulus and a lead-reaction stimulus complex was also varied (2 vs. 4.5 sec). Anticipatory deceleration occurred within the 4.5 sec interval but not in the 2 sec interval. The depth of anticipatory deceleration did not discriminate between fast and slow reactions; but an earlier shift from deceleration to acceleration was associated with fast reactions. The effect of stimulus timing relative to the R-wave of the electrocardiogram was also analysed. Meaningful stimuli tended to produce cardiac slowing as previously described in the literature. Early occurring stimuli prolong the cycle of their occurrence more than late occurring stimuli. The later prolong the subsequent cycle. Cardiac cycle time effects were absent for unattended stimuli. The results of anticipatory deceleration suggested that the depth of deceleration was regulated by time-uncertainty and speed-accuracy criterion.

  15. 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.

  16. Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

    SciTech Connect

    Velikovich, A. L.; Schmit, P. F.

    Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

  17. Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

    DOE PAGES

    Velikovich, A. L.; Schmit, P. F.

    2015-12-28

    Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

  18. Essential role of axonal VGSC inactivation in time-dependent deceleration and unreliability of spike propagation at cerebellar Purkinje cells

    PubMed Central

    2014-01-01

    Background The output of the neuronal digital spikes is fulfilled by axonal propagation and synaptic transmission to influence postsynaptic cells. Similar to synaptic transmission, spike propagation on the axon is not secure, especially in cerebellar Purkinje cells whose spiking rate is high. The characteristics, mechanisms and physiological impacts of propagation deceleration and infidelity remain elusive. The spike propagation is presumably initiated by local currents that raise membrane potential to the threshold of activating voltage-gated sodium channels (VGSC). Results We have investigated the natures of spike propagation and the role of VGSCs in this process by recording spikes simultaneously on the somata and axonal terminals of Purkinje cells in cerebellar slices. The velocity and fidelity of spike propagation decreased during long-lasting spikes, to which the velocity change was more sensitive than fidelity change. These time-dependent deceleration and infidelity of spike propagation were improved by facilitating axonal VGSC reactivation, and worsen by intensifying VGSC inactivation. Conclusion Our studies indicate that the functional status of axonal VGSCs is essential to influencing the velocity and fidelity of spike propagation. PMID:24382121

  19. An Anaylsis of Control Requirements and Control Parameters for Direct-Coupled Turbojet Engines

    NASA Technical Reports Server (NTRS)

    Novik, David; Otto, Edward W.

    1947-01-01

    Requirements of an automatic engine control, as affected by engine characteristics, have been analyzed for a direct-coupled turbojet engine. Control parameters for various conditions of engine operation are discussed. A hypothetical engine control is presented to illustrate the use of these parameters. An adjustable speed governor was found to offer a desirable method of over-all engine control. The selection of a minimum value of fuel flow was found to offer a means of preventing unstable burner operation during steady-state operation. Until satisfactory high-temperature-measuring devices are developed, air-fuel ratio is considered to be a satisfactory acceleration-control parameter for the attainment of the maximum acceleration rates consistent with safe turbine temperatures. No danger of unstable burner operation exists during acceleration if a temperature-limiting acceleration control is assumed to be effective. Deceleration was found to be accompanied by the possibility of burner blow-out even if a minimum fuel-flow control that prevents burner blow-out during steady-state operation is assumed to be effective. Burner blow-out during deceleration may be eliminated by varying the value of minimum fuel flow as a function of compressor-discharge pressure, but in no case should the fuel flow be allowed to fall below the value required for steady-state burner operation.

  20. Correlation of prefrontal cortical activation with changing vehicle speeds in actual driving: a vector-based functional near-infrared spectroscopy study

    PubMed Central

    Yoshino, Kayoko; Oka, Noriyuki; Yamamoto, Kouji; Takahashi, Hideki; Kato, Toshinori

    2013-01-01

    Traffic accidents occur more frequently during deceleration than during acceleration. However, little is known about the relationship between brain activation and vehicle acceleration because it has been difficult to measure the brain activation of drivers while they drive. In this study, we measured brain activation during actual driving using vector-based functional near-infrared spectroscopy. Subjects decelerated from 100 to 50 km/h (speed reduction task) and accelerated from 50 to 100 km/h (speed increase task) while driving on an expressway, in the daytime and at night. We examined correlations between average vehicle acceleration in each task and five hemodynamic indices: changes in oxygenated hemoglobin (ΔoxyHb), deoxygenated hemoglobin (ΔdeoxyHb), cerebral blood volume (ΔCBV), and cerebral oxygen exchange (ΔCOE); and the phase angle k (degrees) derived from the other hemoglobin (Hb) indices. ΔoxyHb and ΔCBV reflect changes in cerebral blood flow, whereas ΔdeoxyHb, ΔCOE, and k are related to variations in cerebral oxygen metabolism. Most of the resulting correlations with specific brain sites, for all the indices, appeared during deceleration rather than during acceleration. Faster deceleration resulted in greater increases in ΔdeoxyHb, ΔCOE, and k in the prefrontal cortex (r < −0.5, p < 0.01), in particular, in the frontal eye field, and at night, it also resulted in greater decreases in ΔoxyHb and ΔCBV in the prefrontal cortex and in the parietal lobe (r > 0.4, p < 0.01), suggesting oxygen metabolism associated with transient ischemic changes. Our results suggest that vehicle deceleration requires more brain activation, focused in the prefrontal cortex, than does acceleration. From the standpoint of the indices used, we found that simultaneous analysis of multiple hemodynamic indices was able to detect not only the blood flow components of hemodynamic responses, but also more localized frontal lobe activation involving oxygen metabolism. PMID

  1. 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…

  2. 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

  3. Effect of hypovolemia, infusion, and oral rehydration on gradual onset +Gz acceleration tolerance

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Brock, P. J.; Haines, R. F.; Rositano, S. A.; Montgomery, L. D.; Keil, L. C.

    1976-01-01

    The purpose of this study was to determine the effect of blood withdrawal, blood infusion, and oral fluid intake on +Gz tolerance at an acceleration rate of 0.5 G/min. Six healthy men aged 21-27 yr were centrifuged after the withdrawal of 400 ml of blood (hypovolemia) from each man; they were centrifuged again following blood infusion (Phase I). Three weeks later the men were accelerated after similar hypovolemia and again after consuming 800 ml of an isotonic NaCl drink (Phase II). Phase I hypovolemia resulted in a reduction in tolerance in all subjects from a mean control level of 6.42 + or - 0.35 min to 5.45 + or - 0.17 min (-15.1%, p less than 0.05). Both infusion and drinking returned tolerances to control levels. During acceleration there were significant (p less than 0.05) increases in plasma vasopressin levels to 35 pg/ml; these were not influenced appreciably by infusion or drinking. In all acceleration runs there was an obligatory shift (loss) of plasma volume and electrolytes, especially potassium, regardless of the experimental treatments. Oral rehydration is shown to be as effective as blood replacement in restoring +Gz acceleration tolerance decrements due to hypovolemia.

  4. Vestibular-ocular accommodation reflex in man.

    PubMed

    Clark, B R; Randle, R J; Stewart, J D

    1975-11-01

    Stimulation of the vestibular system by angular acceleration produces widespread sensory and motor effects. The present study was designed to study a motor effect which has not been reported in the literature, i.e., the influence of rotary acceleration of the body on ocular accommodation. The accommodation of 10 young men was recorded before and after a high-level deceleration to zero velocity following 30 s of rotation. Accommodation was recorded continuously on an infrared optometer for 110 s under two conditions; while the subjects observed a target set at the far point, and while they viewed the same target through a 0.3-mm pinhole. Stimulation by high-level rotary deceleration produced positive accommodation or a pseudomyopia under both conditions, but the positive accommodation was substantially greater and lasted much longer during fixation through the pinhole. It is hypothesized that this increase in accommodation is a result of a vestibular-ocular accommodation reflex.

  5. Landing Characteristics in Waves of Three Dynamic Models of Flying Boats

    NASA Technical Reports Server (NTRS)

    Benson, James M.; Havens, Robert F.; Woodward, David R.

    1947-01-01

    Powered models of three different flying boats were landed in oncoming wave of various heights and lengths. The resulting motions and acceleration were recorded to survey the effects of varying the trim at landing, the deceleration after landing, and the size of the waves. One of the models had an unusually long afterbody. The data for landing with normal rates of deceleration indicated that the most severe motions and accelerations were likely to occur at some period of the landing run subsequent to the initial impact. Landings made at abnormally low trims led to unusually severe bounces during the runout. The least severe landing occurred after a small lending when the model was rapidly decelerated at about 0.4 g in a simulation of the proposed use of braking devices. The severity of the landings increased with wave height and was at a maximum when the wave length was of the order of from one and one-half to twice the over-all length of the model. The models with afterbodies of moderate length frequently bounced clear of the water into a stalled attitude at speeds below flying speed. The model with the long afterbody had less tendency to bounce from the waves and consequently showed less severe accelerations during the landing run than the models with moderate lengths of afterbody.

  6. Female acceleration tolerance: effects of menstrual state and physical condition.

    PubMed

    Heaps, C L; Fischer, M D; Hill, R C

    1997-06-01

    The literature contains a paucity of information on female tolerance to high sustained acceleration. With women now flying high-performance aircraft, gender-specific factors that may affect female acceleration tolerance have become increasingly important. The purpose of this investigation was to determine how menstrual state and physical condition affect acceleration tolerance. We hypothesized the menstrual cycle would have no effect on acceleration tolerance and that a positive correlation would exist between physical fitness level and tolerance to high sustained acceleration. Centrifuge exposures on 8 female subjects consisted of a relaxed gradual-onset run (0.1 G.s-1) to the visual endpoint, a rapid-onset run (6 G.s-1) to +5 GZ for 15 s, and a +4.5 to +7 GZ simulated aerial combat maneuver (SACM) to physical exhaustion. Acceleration tolerance data were collected at onset of menstruation and 1, 2 and 3 weeks following the onset for two complete menstrual cycles. On separate days, body composition, anaerobic power output and peak oxygen uptake were determined. Retrospective data from 10 male subjects who had performed the +4.5 to +7 GZ SACM were analyzed and compared to these data. Analysis of variance revealed no significant difference in relaxed tolerance or SACM duration between the four selected menstrual cycle time points. Time-to-fatigue on the +4.5 to +7 GZ SACM was positively (p < or = 0.05) correlated with absolute fat-free mass (r = 0.87) and anaerobic power production (r = 0.76) in female subjects. However, when these variables were adjusted for total body mass, the significant correlations no longer existed. No correlation was found between SACM duration and absolute (L min-1) nor relative (ml.kg-1.min-1) aerobic fitness. Time-to-fatigue during the SACM was not significantly different between male and female subjects (250 +/- 97 and 246 +/- 149 s, respectively).

  7. Deceleration of probe beam by stage bias potential improves resolution of serial block-face scanning electron microscopic images.

    PubMed

    Bouwer, James C; Deerinck, Thomas J; Bushong, Eric; Astakhov, Vadim; Ramachandra, Ranjan; Peltier, Steven T; Ellisman, Mark H

    2017-01-01

    Serial block-face scanning electron microscopy (SBEM) is quickly becoming an important imaging tool to explore three-dimensional biological structure across spatial scales. At probe-beam-electron energies of 2.0 keV or lower, the axial resolution should improve, because there is less primary electron penetration into the block face. More specifically, at these lower energies, the interaction volume is much smaller, and therefore, surface detail is more highly resolved. However, the backscattered electron yield for metal contrast agents and the backscattered electron detector sensitivity are both sub-optimal at these lower energies, thus negating the gain in axial resolution. We found that the application of a negative voltage (reversal potential) applied to a modified SBEM stage creates a tunable electric field at the sample. This field can be used to decrease the probe-beam-landing energy and, at the same time, alter the trajectory of the signal to increase the signal collected by the detector. With decelerated low landing-energy electrons, we observed that the probe-beam-electron-penetration depth was reduced to less than 30 nm in epoxy-embedded biological specimens. Concurrently, a large increase in recorded signal occurred due to the re-acceleration of BSEs in the bias field towards the objective pole piece where the detector is located. By tuning the bias field, we were able to manipulate the trajectories of the  primary and secondary electrons, enabling the spatial discrimination of these signals using an advanced ring-type BSE detector configuration or a standard monolithic BSE detector coupled with a blocking aperture.

  8. Post-Flight Assessment of Low Density Supersonic Decelerator Flight Dynamics Test 2 Simulation

    NASA Technical Reports Server (NTRS)

    Dutta, Soumyo; Bowes, Angela L.; White, Joseph P.; Striepe, Scott A.; Queen, Eric M.; O'Farrel, Clara; Ivanov, Mark C.

    2016-01-01

    NASA's Low Density Supersonic Decelerator (LDSD) project conducted its second Supersonic Flight Dynamics Test (SFDT-2) on June 8, 2015. The Program to Optimize Simulated Trajectories II (POST2) was one of the flight dynamics tools used to simulate and predict the flight performance and was a major tool used in the post-flight assessment of the flight trajectory. This paper compares the simulation predictions with the reconstructed trajectory. Additionally, off-nominal conditions seen during flight are modeled in the simulation to reconcile the predictions with flight data. These analyses are beneficial to characterize the results of the flight test and to improve the simulation and targeting of the subsequent LDSD flights.

  9. Updates to Blast Injury Criteria Models for Nuclear Casualty Estimation

    DTIC Science & Technology

    2015-12-01

    the likelihood of blast-related injury use a two-step process. First, the maximum velocity obtained by the human body or secondary missile is determined...the human body . Secondary injuries are caused by missiles that are accelerated by the blast wave. Tertiary injuries are caused by the acceleration of...the human body and the ensuing deceleration. In this work, we focus on secondary and tertiary injuries. Because of the dramatic effects experienced

  10. 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.

  11. A New Estimator of the Deceleration Parameter from Galaxy Rotation Curves

    NASA Astrophysics Data System (ADS)

    van Putten, Maurice H. P. M.

    2016-06-01

    The nature of dark energy can be probed by the derivative Q={{dq}(z)/{dz}| }0 at redshift z = 0 of the deceleration parameter q(z). It is probably static if Q\\lt 1 or dynamic if Q\\gt 2.5, supporting ΛCDM or {{Λ }}=(1-q){H}2, respectively, where H denotes the Hubble parameter. We derive q=1-{(4π {a}0/{cH})}2, enabling a determination of q(z) by measuring Milgrom’s parameter, {a}0(z), in galaxy rotation curves, equivalent to the coefficient A in the Tully-Fisher relation {V}c4={{AM}}b between a rotation velocity V c and a baryonic mass M b . We infer that dark matter should be extremely light, with clustering limited to the size of galaxy clusters. The associated transition radius to non-Newtonian gravity can conceivably be probed in a freefall Cavendish-type experiment in space.

  12. Mechanically-Deployed Hypersonic Decelerator and Conformal Ablator Technologies for Mars Missions

    NASA Technical Reports Server (NTRS)

    Venkatapathy, Ethiraj; Wercinski, Paul F.; Beck, Robin A. S.; Hamm, Kenneth R.; Yount, Bryan C.; Makino, A.; Smith, B.; Gage, P.; Prabhu, D.

    2012-01-01

    The concept of a mechanically deployable hypersonic decelerator, developed initially for high mass (40 MT) human Mars missions, is currently funded by OCT for technology maturation. The ADEPT (Adaptive, Deployable Entry and Placement Technology) project has broad, game-changing applicability to in situ science missions to Venus, Mars, and the Outer Planets. Combined with maturation of conformal ablator technology (another current OCT investment), the two technologies provide unique low mass mission enabling capabilities otherwise not achievable by current rigid aeroshell or by inflatables. If this abstract is accepted, we will present results that illustrate the mission enabling capabilities of the mechanically deployable architecture for: (1) robotic Mars (Discovery or New Frontiers class) in the near term; (2) alternate approaches to landing MSL-class payloads, without the need for supersonic parachute or lifting entry, in the mid-term; and (3) Heavy mass and human missions to Mars in the long term.

  13. Mechanically-Deployed Hypersonic Decelerator and Conformal Ablator Technologies for Mars Missions

    NASA Technical Reports Server (NTRS)

    Venkatapathy, E.; Wercinski, P.; Prabhu, D.

    2012-01-01

    The concept of a mechanically deployable hypersonic decelerator, developed initially for high mass (approximately 40 MT) human Mars missions, is currently funded by OCT for technology maturation. The ADEPT (Adaptive, Deployable Entry and Placement Technology) project has broad, game-changing applicability to in situ science missions to Venus, Mars, and the Outer Planets. Combined with maturation of conformal ablator technology (another current OCT investment), the two technologies provide unique low-mass mission enabling capabilities otherwise not achievable by current rigid aeroshell or by inflatables. If this abstract is accepted, we will present results that illustrate the mission enabling capabilities of the mechanically deployable architecture for: (1) robotic Mars (Discovery or New Frontiers class) in the near term (2) alternate approaches to landing MSL-class payloads, without the need for supersonic parachute or lifting entry, in the mid-term and (3) Heavy mass and human missions to Mars in the long term.

  14. Accelerated Reader[R]: What Are the Lasting Effects on the Reading Habits of Middle School Students Exposed to Accelerated Reader[R] in Elementary Grades?

    ERIC Educational Resources Information Center

    Pavonetti, Linda M.; Brimmer, Kathryn M.; Cipielewski, James F.

    Promoted by effective advertising and disseminated by word of mouth, many schools have adopted Accelerated Reader[R] as a supplementary reading program or as their primary reading program. Accelerated Reader[R]'s philosophy is that by using the system, students are motivated to read more and better books. A study investigated whether seventh grade…

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

    SciTech Connect

    Tripathi, V. K., E-mail: tripathivipin@yahoo.co.in

    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-monomore » energy acceleration of ions. Multi-ion foils, e.g., diamond like carbon foil embedded with protons offer the possibility of suppressing RT instability.« less

  16. Social-emotional characteristics of gifted accelerated and non-accelerated students in the Netherlands.

    PubMed

    Hoogeveen, Lianne; van Hell, Janet G; Verhoeven, Ludo

    2012-12-01

    In the studies of acceleration conducted so far a multidimensional perspective has largely been neglected. No attempt has been made to relate social-emotional characteristics of accelerated versus non-accelerated students in perspective of environmental factors. In this study, social-emotional characteristics of accelerated gifted students in the Netherlands were examined in relation to personal and environmental factors. Self-concept and social contacts of accelerated (n = 148) and non-accelerated (n = 55) gifted students, aged 4 to 27 (M = 11.22, SD = 4.27) were measured. Self-concept and social contacts of accelerated and non-accelerated gifted students were measured using a questionnaire and a diary, and parents of these students evaluated their behavioural characteristics. Gender and birth order were studied as personal factors and grade, classroom, teachers' gender, teaching experience, and the quality of parent-school contact as environmental factors. The results showed minimal differences in the social-emotional characteristics of accelerated and non-accelerated gifted students. The few differences we found favoured the accelerated students. We also found that multiple grade skipping does not have negative effects on social-emotional characteristics, and that long-term effects of acceleration tend to be positive. As regards the possible modulation of personal and environmental factors, we merely found an impact of such factors in the non-accelerated group. The results of this study strongly suggest that social-emotional characteristics of accelerated gifted students and non-accelerated gifted students are largely similar. These results thus do not support worries expressed by teachers about the acceleration of gifted students. Our findings parallel the outcomes of earlier studies in the United States and Germany in that we observed that acceleration does not harm gifted students, not even in the case of multiple grade skipping. On the contrary, there is a

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. Prediction of secular acceleration of axial rotation of Mars

    NASA Astrophysics Data System (ADS)

    Barkin, Yu. V.

    2009-04-01

    northern direction to Taimyr peninsula. Thus the gravitational attraction of superfluous mass of the core (19 % from the Earth mass) causes secular asymmetric inversion tide [2] of fluids which effectively manages to be modeled by two points with variable masses. In the given work the attempt to construct a similar model of the directed secular redistribution of fluid masses of Mars from a southern hemisphere in northern is undertaken with the purpose of an explanation of observably tendencies in redistribution of masses between hemispheres and with the purpose of a prediction of the new phenomena in its rotary motion. The hypothetical assumption is made, that secular redistribution of fluid masses from a southern hemisphere in northern hemisphere of Mars mainly is determined by areocentric axis OP directed to the pole P with coordinates 570N, 820 E (as is known in this direction the centre of mass of Mars relatively the centre of a figure on 2.8 km is displaced). Material points with masses m2 and m1 settle down at poles of geocentric axis OP on a surface of Mars, and their masses change linearly in the time with velocities [5]: ṁ2 = 0.402 × 1015kg/yr and ṁ1 = 0.257 × 1015kg/yr. The given modeling characteristics correspond to prospective secular variations of coefficients of the second and third zonal harmonics of gravitational potential of Mars: J˙2= - 57.0 × 10-11 1/yr and ˙J3 = -4.94 × 10-11 1/yr, more less agreed for today with the data of observations (Dehant, private communication, 2008) [6]. Let's emphasize, that the discussed phenomena of asymmetry of hemispheres, intensity of inversion processes, and bipolarity and inversion of all structures of Mars much more expressive, than at the Earth. Therefore we in the right to expect the greater efficiency in application of geodynamic model and more significant secular effects in rotation of Mars in comparison with the Earth. The constructed model has allowed to estimate non-tidal acceleration of

  2. Design and Execution of the Hypersonic Inflatable Aerodynamic Decelerator Large-Article Wind Tunnel Experiment

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.

    2013-01-01

    The testing of 3- and 6-meter diameter Hypersonic Inflatable Aerodynamic Decelerator (HIAD) test articles was completed in the National Full-Scale Aerodynamics Complex 40 ft x 80 ft Wind Tunnel test section. Both models were stacked tori, constructed as 60 degree half-angle sphere cones. The 3-meter HIAD was tested in two configurations. The first 3-meter configuration utilized an instrumented flexible aerodynamic skin covering the inflatable aeroshell surface, while the second configuration employed a flight-like flexible thermal protection system. The 6-meter HIAD was tested in two structural configurations (with and without an aft-mounted stiffening torus near the shoulder), both utilizing an instrumented aerodynamic skin.

  3. Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

    NASA Astrophysics Data System (ADS)

    Mingming, SUN; Yanhui, JIA; Yongjie, HUANG; Juntai, YANG; Xiaodong, WEN; Meng, WANG

    2018-04-01

    In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process, a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 kW operation mode. Meanwhile, the fluid simulation method and particle-in-cell-Monte Carlo collision (PIC-MCC) method are adopted to simulate the ion extraction process according to the previous test results. The numerical calculation results are verified by the ion thruster performance test. The results show that after about 1.2 h operation, the hot gap between the screen grid and the accelerator grid reduce to 0.25–0.3 mm, while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium, and the hot gap is almost unchanged. In addition, the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value. Fluid simulation results show that the plasma density of the screen grid is in the range 6 × 1017–6 × 1018 m13 and displays a parabolic characteristic, while the electron temperature gradually increases along the axial direction. The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant. Meanwhile, the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap. The ion beam current has optimal perveance status without thermal deformation, and the intercepted current of the accelerator grid and the decelerator grid are 3.65 mA and 6.26 mA, respectively. Furthermore, under the effect of thermal deformation, the ion beam current has over-perveance status, and the intercepted current of the accelerator grid and the decelerator grid are 10.46 mA and 18.24 mA, respectively. Performance test

  4. A novel facility for reduced-gravity testing: A setup for studying low-velocity collisions into granular surfaces

    NASA Astrophysics Data System (ADS)

    Sunday, C.; Murdoch, N.; Cherrier, O.; Morales Serrano, S.; Valeria Nardi, C.; Janin, T.; Avila Martinez, I.; Gourinat, Y.; Mimoun, D.

    2016-08-01

    This work presents an experimental design for studying low-velocity collisions into granular surfaces in low-gravity. In the experiment apparatus, reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use of an Atwood machine, or a system of pulleys and counterweights. The starting height of the surface container and the initial separation distance between the projectile and surface are variable and chosen to accommodate collision velocities up to 20 cm/s and effective accelerations of ˜0.1 to 1.0 m/s2. Accelerometers, placed on the surface container and inside the projectile, provide acceleration data, while high-speed cameras capture the collision and act as secondary data sources. The experiment is built into an existing 5.5 m drop tower frame and requires the custom design of all components, including the projectile, surface sample container, release mechanism, and deceleration system. Data from calibration tests verify the efficiency of the experiment's deceleration system and provide a quantitative understanding of the performance of the Atwood system.

  5. A novel facility for reduced-gravity testing: A setup for studying low-velocity collisions into granular surfaces.

    PubMed

    Sunday, C; Murdoch, N; Cherrier, O; Morales Serrano, S; Valeria Nardi, C; Janin, T; Avila Martinez, I; Gourinat, Y; Mimoun, D

    2016-08-01

    This work presents an experimental design for studying low-velocity collisions into granular surfaces in low-gravity. In the experiment apparatus, reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use of an Atwood machine, or a system of pulleys and counterweights. The starting height of the surface container and the initial separation distance between the projectile and surface are variable and chosen to accommodate collision velocities up to 20 cm/s and effective accelerations of ∼0.1 to 1.0 m/s(2). Accelerometers, placed on the surface container and inside the projectile, provide acceleration data, while high-speed cameras capture the collision and act as secondary data sources. The experiment is built into an existing 5.5 m drop tower frame and requires the custom design of all components, including the projectile, surface sample container, release mechanism, and deceleration system. Data from calibration tests verify the efficiency of the experiment's deceleration system and provide a quantitative understanding of the performance of the Atwood system.

  6. Conceptual design of an intense positron source based on an LIA

    NASA Astrophysics Data System (ADS)

    Long, Ji-Dong; Yang, Zhen; Dong, Pan; Shi, Jin-Shui

    2012-04-01

    Accelerator based positron sources are widely used due to their high intensity. Most of these accelerators are RF accelerators. An LIA (linear induction accelerator) is a kind of high current pulsed accelerator used for radiography. A conceptual design of an intense pulsed positron source based on an LIA is presented in the paper. One advantage of an LIA is its pulsed power being higher than conventional accelerators, which means a higher amount of primary electrons for positron generations per pulse. Another advantage of an LIA is that it is very suitable to decelerate the positron bunch generated by bremsstrahlung pair process due to its ability to adjustably shape the voltage pulse. By implementing LIA cavities to decelerate the positron bunch before it is moderated, the positron yield could be greatly increased. These features may make the LIA based positron source become a high intensity pulsed positron source.

  7. 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

  8. The Role of Informal and Formal Leisure Activities in the Disablement Process

    ERIC Educational Resources Information Center

    Janke, Megan C.; Payne, Laura L.; Van Puymbroeck, Marieke

    2008-01-01

    The disablement process model has been used as a framework to investigate factors that accelerate or decelerate disablement among older adults. Although very little is known about the direct and moderating effects of involvement in leisure activities on the disablement process, research has suggested that participation in leisure activities may…

  9. Landing characteristics in waves of three dynamic models of flying boats

    NASA Technical Reports Server (NTRS)

    Benson, James M; Havens, Robert F; Woodward, David R

    1952-01-01

    Powered models of three different flying boats were landed in oncoming waves of various heights and lengths. The effects of varying the trim at landing, the deceleration after landing, and the size of the waves were determined. Data are presented on the motions and accelerations obtained during landings in rough water.

  10. An EMA analysis of the effect of increasing word length on consonant production in apraxia of speech: a case study.

    PubMed

    Bartle, Carly J; Goozée, Justine V; Murdoch, Bruce E

    2007-03-01

    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 using the AG-200 EMA system during word-initial consonant productions in one, two, and three syllable words. Significantly deviant articulatory parameters were recorded for each of the target consonants during one, two, and three syllables words. Word length effects were most evident during the release phase of target consonant productions. The results are discussed with respect to theories of speech motor control as they relate to AOS.

  11. 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, themore » 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.« less

  12. The Effect of Acceleration Sprint and Zig-zag Drill Combination to Increase Students’ Speed and Agility

    NASA Astrophysics Data System (ADS)

    Bana, O.; Mintarto, E.; Kusnanik, N. W.

    2018-01-01

    The purpose of this research is to analyze the following factors: (1) how far the effect of exercise acceleration sprint on the speed and agility (2) how much influence the zig-zag drill combination to the speed and agility (3) and is there any difference between the effects of exercise acceleration sprint and practice zig-zag drill combination of the speed and agility. This research is quantitative with quasi-experimental approach. The design of this study is matching only design.This study was conducted on 33 male students who take part in extracurricular and divided into 3 groups with 11 students in each group. Group 1 was given training of acceleration sprint, group 2 was given zig-zag training combination drills of conventional and exercises for group 3, for 8 weeks. The data collection was using sprint 30 meter to test the speed and agility t-test to test agility. Data were analyzed using t-test and analysis of variance. The conclusion of the research is (1) there is a significant effect of exercise acceleration sprint for the speed and agility, (2) there is a significant influence combination zig-zag drills, on speed and agility (3) and exercise acceleration sprint have more effect on the speed and agility.

  13. Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study

    PubMed Central

    Hsu, Hung-Yao

    2016-01-01

    Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies. PMID:28074178

  14. Study of the key factors affecting the triple grid lifetime of the LIPS-300 ion thruster

    NASA Astrophysics Data System (ADS)

    Mingming, SUN; Liang, WANG; Juntai, YANG; Xiaodong, WEN; Yongjie, HUANG; Meng, WANG

    2018-04-01

    In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster, the thermal deformation, upstream ion density and component lifetime of the grids are simulated with finite element analysis, fluid simulation and charged-particle tracing simulation methods on the basis of a 1500 h short lifetime test. The key factor affecting the lifetime of the triple grids in the LIPS-300 ion thruster is obtained and analyzed through the test results. The results show that ion sputtering erosion of the grids in 5 kW operation mode is greater than in the case of 3 kW. In 5 kW mode, the decelerator grid shows the most serious corrosion, the accelerator grid shows moderate corrosion, and the screen grid shows the least amount of corrosion. With the serious corrosion of the grids in 5 kW operation mode, the intercept current of the acceleration and deceleration grids increases substantially. Meanwhile, the cold gap between the accelerator grid and the screen grid decreases from 1 mm to 0.7 mm, while the cold gap between the accelerator grid and the decelerator grid increases from 1 mm to 1.25 mm after 1500 h of thruster operation. At equilibrium temperature with 5 kW power, the finite element method (FEM) simulation results show that the hot gap between the screen grid and the accelerator grid reduces to 0.2 mm. Accordingly, the hot gap between the accelerator grid and the decelerator grid increases to 1.5 mm. According to the fluid method, the plasma density simulated in most regions of the discharge chamber is 1 × 1018‑8 × 1018 m‑3. The upstream plasma density of the screen grid is in the range 6 × 1017‑6 × 1018 m‑3 and displays a parabolic characteristic. The charged particle tracing simulation method results show that the ion beam current without the thermal deformation of triple grids has optimal perveance status. The ion sputtering rates of the accelerator grid hole and the decelerator hole are 5.5 × 10‑14 kg s‑1 and

  15. Design of thermal neutron beam based on an electron linear accelerator for BNCT.

    PubMed

    Zolfaghari, Mona; Sedaghatizadeh, Mahmood

    2016-12-01

    An electron linear accelerator (Linac) can be used for boron neutron capture therapy (BNCT) by producing thermal neutron flux. In this study, we used a Varian 2300 C/D Linac and MCNPX.2.6.0 code to simulate an electron-photoneutron source for use in BNCT. In order to decelerate the produced fast neutrons from the photoneutron source, which optimize the thermal neutron flux, a beam-shaping assembly (BSA) was simulated. After simulations, a thermal neutron flux with sharp peak at the beam exit was obtained in the order of 3.09×10 8 n/cm 2 s and 6.19×10 8 n/cm 2 s for uranium and enriched uranium (10%) as electron-photoneutron sources respectively. Also, in-phantom dose analysis indicates that the simulated thermal neutron beam can be used for treatment of shallow skin melanoma in time of about 85.4 and 43.6min for uranium and enriched uranium (10%) respectively. Copyright © 2016. Published by Elsevier Ltd.

  16. The effect of cosmic-ray acceleration on supernova blast wave dynamics

    NASA Astrophysics Data System (ADS)

    Pais, M.; Pfrommer, C.; Ehlert, K.; Pakmor, R.

    2018-05-01

    Non-relativistic shocks accelerate ions to highly relativistic energies provided that the orientation of the magnetic field is closely aligned with the shock normal (quasi-parallel shock configuration). In contrast, quasi-perpendicular shocks do not efficiently accelerate ions. We model this obliquity-dependent acceleration process in a spherically expanding blast wave setup with the moving-mesh code AREPO for different magnetic field morphologies, ranging from homogeneous to turbulent configurations. A Sedov-Taylor explosion in a homogeneous magnetic field generates an oblate ellipsoidal shock surface due to the slower propagating blast wave in the direction of the magnetic field. This is because of the efficient cosmic ray (CR) production in the quasi-parallel polar cap regions, which softens the equation of state and increases the compressibility of the post-shock gas. We find that the solution remains self-similar because the ellipticity of the propagating blast wave stays constant in time. This enables us to derive an effective ratio of specific heats for a composite of thermal gas and CRs as a function of the maximum acceleration efficiency. We finally discuss the behavior of supernova remnants expanding into a turbulent magnetic field with varying coherence lengths. For a maximum CR acceleration efficiency of about 15 per cent at quasi-parallel shocks (as suggested by kinetic plasma simulations), we find an average efficiency of about 5 per cent, independent of the assumed magnetic coherence length.

  17. Anomalous acceleration of ions in a plasma accelerator with an anodic layer

    NASA Astrophysics Data System (ADS)

    V, M. BARDAKOV; S, D. IVANOV; A, V. KAZANTSEV; N, A. STROKIN; A, N. STUPIN; Binhao, JIANG; Zhenyu, WANG

    2018-03-01

    In a plasma accelerator with an anodic layer (PAAL), we discovered experimentally the effect of ‘super-acceleration’ of the bulk of the ions to energies W exceeding the energy equivalent to the discharge voltage V d. The E × B discharge was ignited in an environment of atomic argon and helium and molecular nitrogen. Singly charged argon ions were accelerated most effectively in the case of the largest discharge currents and pressure P of the working gas. Helium ions with W > eV d (e being the electron charge) were only recorded at maximum pressures. Molecular nitrogen was not accelerated to energies W > eV d. Anomalous acceleration is realized in the range of radial magnetic fields on the anode 2.8 × 10 -2 ≤ B rA ≤ 4 × 10 -2 T. It was also found analytically that the cathode of the accelerator can receive anomalously accelerated ions. In this case, the value of the potential in the anodic layer becomes higher than the anode potential, and the anode current exceeds some critical value. Numerical modeling in terms of the developed theory showed qualitative agreement between modeling data and measurements.

  18. Accelerated infliximab infusions for inflammatory bowel disease improve effectiveness.

    PubMed

    McConnell, John; Parvulescu-Codrea, Simona; Behm, Brian; Hill, Beth; Dunkle, Elizabeth; Finke, Karen; Snyder, Kathryn; Tuskey, Anne; Cox, Debbie; Woodward, Beth

    2012-10-06

    To study the safety and effectiveness associated with accelerated infliximab infusion protocols in patients with inflammatory bowel disease (IBD). Original protocols and infusion rates were developed for the administration of infliximab over 90-min and 60-min. Then the IBD patients on stable maintenance infliximab therapy were offered accelerated infusions. To be eligible for the study, patients needed a minimum of four prior infusions. An initial infusion of 90-min was given to each patient; those tolerating the accelerated infusion were transitioned to a 60-min infusion protocol at their next and all subsequent visits. Any patient having significant infusion reactions would be reverted to the standard 120-min protocol. A change in a patient's dose mandated a single 120-min infusion before accelerated infusions could be administered again. The University of Virginia Medical Center's Institutional Review Board approved this study. Fifty IBD patients treated with infliximab 5 mg/kg, 7.5 mg/kg and 10 mg/kg were offered accelerated infusions. Forty-six patients consented to participate in the study. Nineteen (41.3%) were female, five (10.9%) were African American and nine (19.6%) had ulcerative colitis. The mean age was 42.6 years old. Patients under age 18 were excluded. Ten patients used immunosuppressive drugs concurrently out of which six were taking azathioprine, three were taking 6-mercaptopurine and one was taking methotrexate. One of the 46 study patients used corticosteroid therapy for his IBD. Seventeen of the patients used prophylactic medications prior to receiving infusions; six patients received corticosteroids as pre-medication. Four patients had a history of distant transfusion reactions to infliximab. These reactions included shortness of breath, chest tightness, flushing, pruritus and urticaria. These patients all took prophylactic medications before receiving infusions. 46 patients (27 males and 19 females) received a total of fifty 90-min infusions

  19. Inverse Leidenfrost effect: self-propelling drops on a bath

    NASA Astrophysics Data System (ADS)

    Gauthier, Anais; van der Meer, Devaraj; Lohse, Detlef; Physics of Fluids Team

    2017-11-01

    When deposited on very hot solid, volatile drops can levitate over a cushion of vapor, in the so-called Leidenfrost state. This phenomenon can also be observed on a hot bath and similarly to the solid case, drops are very mobile due to the absence of contact with the substrate that sustains them. We discuss here a situation of ``inverse Leidenfrost effect'' where room-temperature drops levitate on a liquid nitrogen pool - the vapor is generated here by the bath sustaining the relatively hot drop. We show that the drop's movement is not random: the liquid goes across the bath in straight lines, a pattern only disrupted by elastic bouncing on the edges. In addition, the drops are initially self-propelled; first at rest, they accelerate for a few seconds and reach velocities of the order of a few cm/s, before slowing down. We investigate experimentally the parameters that affect their successive acceleration and deceleration, such as the size and nature of the drops and we discuss the origin of this pattern.

  20. PA1 Protein, a New Competitive Decelerator Acting at More than One Step to Impede Glucocorticoid Receptor-mediated Transactivation*

    PubMed Central

    Zhang, Zhenhuan; Sun, Yunguang; Cho, Young-Wook; Chow, Carson C.; Simons, S. Stoney

    2013-01-01

    Numerous cofactors modulate the gene regulatory activity of glucocorticoid receptors (GRs) by affecting one or more of the following three major transcriptional properties: the maximal activity of agonists (Amax), the potency of agonists (EC50), and the partial agonist activity of antisteroids (PAA). Here, we report that the recently described nuclear protein, Pax2 transactivation domain interaction protein (PTIP)-associated protein 1 (PA1), is a new inhibitor of GR transactivation. PA1 suppresses Amax, increases the EC50, and reduces the PAA of an exogenous reporter gene in a manner that is independent of associated PTIP. PA1 is fully active with, and strongly binds to, the C-terminal half of GR. PA1 reverses the effects of the coactivator TIF2 on GR-mediated gene induction but is unable to augment the actions of the corepressor SMRT. Analysis of competition assays between PA1 and TIF2 with an exogenous reporter indicates that the kinetic definition of PA1 action is a competitive decelerator at two sites upstream from where TIF2 acts. With the endogenous genes IGFBP1 and IP6K3, PA1 also represses GR induction, increases the EC50, and decreases the PAA. ChIP and re-ChIP experiments indicate that PA1 accomplishes this inhibition of the two genes via different mechanisms as follows: PA1 appears to increase GR dissociation from and reduce GR transactivation at the IGFBP1 promoter regions but blocks GR binding to the IP6K3 promoter. We conclude that PA1 is a new competitive decelerator of GR transactivation and can act at more than one molecularly defined step in a manner that depends upon the specific gene. PMID:23161582

  1. PA1 protein, a new competitive decelerator acting at more than one step to impede glucocorticoid receptor-mediated transactivation.

    PubMed

    Zhang, Zhenhuan; Sun, Yunguang; Cho, Young-Wook; Chow, Carson C; Simons, S Stoney

    2013-01-04

    Numerous cofactors modulate the gene regulatory activity of glucocorticoid receptors (GRs) by affecting one or more of the following three major transcriptional properties: the maximal activity of agonists (A(max)), the potency of agonists (EC(50)), and the partial agonist activity of antisteroids (PAA). Here, we report that the recently described nuclear protein, Pax2 transactivation domain interaction protein (PTIP)-associated protein 1 (PA1), is a new inhibitor of GR transactivation. PA1 suppresses A(max), increases the EC(50), and reduces the PAA of an exogenous reporter gene in a manner that is independent of associated PTIP. PA1 is fully active with, and strongly binds to, the C-terminal half of GR. PA1 reverses the effects of the coactivator TIF2 on GR-mediated gene induction but is unable to augment the actions of the corepressor SMRT. Analysis of competition assays between PA1 and TIF2 with an exogenous reporter indicates that the kinetic definition of PA1 action is a competitive decelerator at two sites upstream from where TIF2 acts. With the endogenous genes IGFBP1 and IP6K3, PA1 also represses GR induction, increases the EC(50), and decreases the PAA. ChIP and re-ChIP experiments indicate that PA1 accomplishes this inhibition of the two genes via different mechanisms as follows: PA1 appears to increase GR dissociation from and reduce GR transactivation at the IGFBP1 promoter regions but blocks GR binding to the IP6K3 promoter. We conclude that PA1 is a new competitive decelerator of GR transactivation and can act at more than one molecularly defined step in a manner that depends upon the specific gene.

  2. Validation of Finite-Element Models of Persistent-Current Effects in Nb 3Sn Accelerator Magnets

    DOE PAGES

    Wang, X.; Ambrosio, G.; Chlachidze, G.; ...

    2015-01-06

    Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnetmore » designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed.« less

  3. Community Petascale Project for Accelerator Science and Simulation: Advancing Computational Science for Future Accelerators and Accelerator Technologies

    SciTech Connect

    Spentzouris, P.; /Fermilab; Cary, J.

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors. ComPASS is in the first year of executing its plan to develop the next-generation HPC accelerator modeling tools. ComPASS aims to develop an integrated simulation environment that will utilize existing and new accelerator physics modules with petascale capabilities, by employing modern computing and solver technologies. The ComPASS vision is to deliver to accelerator scientists a virtual accelerator and virtual prototyping modeling environment, with the necessary multiphysics, multiscale capabilities. The plan for this development includes delivering accelerator modeling applications appropriate for each stage of the ComPASS software evolution. Such applications are already being used to address challenging problems in accelerator design and optimization. The Com

  4. Development of Velocity Guidance Assistance System by Haptic Accelerator Pedal Reaction Force Control

    NASA Astrophysics Data System (ADS)

    Yin, Feilong; Hayashi, Ryuzo; Raksincharoensak, Pongsathorn; Nagai, Masao

    This research proposes a haptic velocity guidance assistance system for realizing eco-driving as well as enhancing traffic capacity by cooperating with ITS (Intelligent Transportation Systems). The proposed guidance system generates the desired accelerator pedal (abbreviated as pedal) stroke with respect to the desired velocity obtained from ITS considering vehicle dynamics, and provides the desired pedal stroke to the driver via a haptic pedal whose reaction force is controllable and guides the driver in order to trace the desired velocity in real time. The main purpose of this paper is to discuss the feasibility of the haptic velocity guidance. A haptic velocity guidance system for research is developed on the Driving Simulator of TUAT (DS), by attaching a low-inertia, low-friction motor to the pedal, which does not change the original characteristics of the original pedal when it is not operated, implementing an algorithm regarding the desired pedal stroke calculation and the reaction force controller. The haptic guidance maneuver is designed based on human pedal stepping experiments. A simple velocity profile with acceleration, deceleration and cruising is synthesized according to naturalistic driving for testing the proposed system. The experiment result of 9 drivers shows that the haptic guidance provides high accuracy and quick response in velocity tracking. These results prove that the haptic guidance is a promising velocity guidance method from the viewpoint of HMI (Human Machine Interface).

  5. Inactivation of Plasma Membrane–Localized CDPK-RELATED KINASE5 Decelerates PIN2 Exocytosis and Root Gravitropic Response in Arabidopsis[C][W

    PubMed Central

    Rigó, Gábor; Ayaydin, Ferhan; Tietz, Olaf; Zsigmond, Laura; Kovács, Hajnalka; Páy, Anikó; Salchert, Klaus; Darula, Zsuzsanna; Medzihradszky, Katalin F.; Szabados, László; Palme, Klaus; Koncz, Csaba; Cséplő, Ágnes

    2013-01-01

    CRK5 is a member of the Arabidopsis thaliana Ca2+/calmodulin-dependent kinase-related kinase family. Here, we show that inactivation of CRK5 inhibits primary root elongation and delays gravitropic bending of shoots and roots. Reduced activity of the auxin-induced DR5–green fluorescent protein reporter suggests that auxin is depleted from crk5 root tips. However, no tip collapse is observed and the transcription of genes for auxin biosynthesis, AUXIN TRANSPORTER/AUXIN TRANSPORTER-LIKE PROTEIN (AUX/LAX) auxin influx, and PIN-FORMED (PIN) efflux carriers is unaffected by the crk5 mutation. Whereas AUX1, PIN1, PIN3, PIN4, and PIN7 display normal localization, PIN2 is depleted from apical membranes of epidermal cells and shows basal to apical relocalization in the cortex of the crk5 root transition zone. This, together with an increase in the number of crk5 lateral root primordia, suggests facilitated auxin efflux through the cortex toward the elongation zone. CRK5 is a plasma membrane–associated kinase that forms U-shaped patterns facing outer lateral walls of epidermis and cortex cells. Brefeldin inhibition of exocytosis stimulates CRK5 internalization into brefeldin bodies. CRK5 phosphorylates the hydrophilic loop of PIN2 in vitro, and PIN2 shows accelerated accumulation in brefeldin bodies in the crk5 mutant. Delayed gravitropic response of the crk5 mutant thus likely reflects defective phosphorylation of PIN2 and deceleration of its brefeldin-sensitive membrane recycling. PMID:23673979

  6. 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 particlemore » 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.« less

  7. Inhomogeneities in dusty universe — a possible alternative to dark energy?

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.

    2011-03-01

    There have been of late renewed debates on the role of inhomogeneities to explain the observed late acceleration of the universe. We have looked into the problem analytically with the help of the well known spherically symmetric but inhomogeneous Lemaitre-Tolman-Bondi(LTB) model generalised to higher dimensions. It is observed that in contrast to the claim made by Kolb et al. the presence of inhomogeneities as well as extra dimensions can not reverse the signature of the deceleration parameter if the matter field obeys the energy conditions. The well known Raychaudhuri equation also points to the same result. Without solving the field equations explicitly it can, however, be shown that although the total deceleration is positive everywhere nevertheless it does not exclude the possibility of having radial acceleration, even in the pure dust universe, if the angular scale factor is decelerating fast enough and vice versa. Moreover it is found that introduction of extra dimensions can not reverse the scenario. To the contrary it actually helps the decelerating process.

  8. 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

  9. Effect of Exercise Program Speed, Agility, and Quickness (SAQ) in Improving Speed, Agility, and Acceleration

    NASA Astrophysics Data System (ADS)

    Azmi, K.; Kusnanik, N. W.

    2018-01-01

    This study aimed to analyze the effect of speed, agility and quickness training program to increase in speed, agility and acceleration. This study was conducted at 26 soccer players and divided into 2 groups with 13 players each group. Group 1 was given SAQ training program, and Group 2 conventional training program for 8 weeks. This study used a quantitative approach with quasi-experimental method. The design of this study used a matching-only design. Data was collected by testing 30-meter sprint (speed), agility t-test (agility), and run 10 meters (acceleration) during the pretest and posttest. Furthermore, the data was analyzed using paired sample t-test and independent t-test. The results showed: that there was a significant effect of speed, agility and quickness training program in improving in speed, agility and acceleration. In summary, it can be concluded that the speed, agility and quickness training program can improve the speed, agility and acceleration of the soccer players.

  10. Astronaut mass measurement using linear acceleration method and the effect of body non-rigidity

    NASA Astrophysics Data System (ADS)

    Yan, Hui; Li, LuMing; Hu, ChunHua; Chen, Hao; Hao, HongWei

    2011-04-01

    Astronaut's body mass is an essential factor of health monitoring in space. The latest mass measurement device for the International Space Station (ISS) has employed a linear acceleration method. The principle of this method is that the device generates a constant pulling force, and the astronaut is accelerated on a parallelogram motion guide which rotates at a large radius to achieve a nearly linear trajectory. The acceleration is calculated by regression analysis of the displacement versus time trajectory and the body mass is calculated by using the formula m= F/ a. However, in actual flight, the device is instable that the deviation between runs could be 6-7 kg. This paper considers the body non-rigidity as the major cause of error and instability and analyzes the effects of body non-rigidity from different aspects. Body non-rigidity makes the acceleration of the center of mass (C.M.) oscillate and fall behind the point where force is applied. Actual acceleration curves showed that the overall effect of body non-rigidity is an oscillation at about 7 Hz and a deviation of about 25%. To enhance body rigidity, better body restraints were introduced and a prototype based on linear acceleration method was built. Measurement experiment was carried out on ground on an air table. Three human subjects weighing 60-70 kg were measured. The average variance was 0.04 kg and the average measurement error was 0.4%. This study will provide reference for future development of China's own mass measurement device.

  11. 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.

  12. Semiconductor acceleration sensor

    NASA Astrophysics Data System (ADS)

    Ueyanagi, Katsumichi; Kobayashi, Mitsuo; Goto, Tomoaki

    1996-09-01

    This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.

  13. The Influence of Passive Acceleration and Exercise+Acceleration on Work Capacity and Orthostasis

    NASA Technical Reports Server (NTRS)

    Simonson, S. R.; Cowell, S. A.; Stocks, J. M.; Biagini, H. W.; Vener, J. M.; Evetts, S. N.; Bailey, K. N.; Evans, J.; Knapp, C.; Greenleaf, J. E.

    1999-01-01

    The losses of aerobic power and orthostatic tolerance are significant effects of manned C) spaceflight that can negatively impact crew health and safety. Daily acceleration and aerobic training may ameliorate these effects. To determine the influence of passive intermittent +Gz acceleration (PA) training and active acceleration + interval exercise (AE) training on work 0 0 capacity and the acute (1 min) response to 70 deg head-up tilt, 6 men (X-Bar SD: age, 33 +/- 6 y; height, 178.3 +/- 4.6 cm; mass, 86.3 +/- 6.6 kg) participated in two 3-wk training protocols. It was hypothesized that PA and AE training would improve orthostatic tolerance and that the addition of aerobic conditioning, would not alter this effect.

  14. The effects of different concentrations of cocoa in the chocolate intaken by the mother on fetal heart rate.

    PubMed

    Buscicchio, Giorgia; Lorenzi, Sara; Tranquilli, Andrea Luigi

    2013-10-01

    To analyze the effects of different concentrations (30% and 80%) of cocoa on fetal heart rate (FHR). One hundred pregnant women with uncomplicated gestation, matched for age and parity, underwent computerized FHR recording before and after the consumption of 30 g of 30% and 80% cocoa chocolate. After 1 week, those who had received 30% were shifted to 80% and vice versa to have a crossover. Computerized cardiotocography parameters (contractions, fetal movements, baseline FHR, accelerations greater than 15 bpm for 15 s, number of decelerations, minutes of high variability, short term variability in ms) were recorded and expressed as mean and SD. The differences were tested for statistical significance using the paired t test, with the significance at p < 0.05. The percent change after chocolate intake for accelerations and short-term FHR variation was calculated. The number of fetal movements, accelerations, the duration of episodes of high variation and the short-term FHR variation were significantly higher (p < 0.0001) after 80% cocoa intake. After 30% cocoa chocolate intake, only the number of accelerations was significantly increased. The percent change of the number of accelerations and the short-term FHR variation were significantly higher after 80% cocoa chocolate maternal intake. Maternal intake of dark chocolate has a stimulating action on fetal reactivity. The effect is more marked with high concentrations (80%) of cocoa. This finding is likely due to the pharmacological action of theobromine, a methilxanthine present in cocoa.

  15. Sensitivity analysis of helicopter IMC decelerating steep approach and landing performance to navigation system parameters

    NASA Technical Reports Server (NTRS)

    Karmali, M. S.; Phatak, A. V.

    1982-01-01

    Results of a study to investigate, by means of a computer simulation, the performance sensitivity of helicopter IMC DSAL operations as a function of navigation system parameters are presented. A mathematical model representing generically a navigation system is formulated. The scenario simulated consists of a straight in helicopter approach to landing along a 6 deg glideslope. The deceleration magnitude chosen is 03g. The navigation model parameters are varied and the statistics of the total system errors (TSE) computed. These statistics are used to determine the critical navigation system parameters that affect the performance of the closed-loop navigation, guidance and control system of a UH-1H helicopter.

  16. Thermodynamic equilibrium with acceleration and the Unruh effect

    NASA Astrophysics Data System (ADS)

    Becattini, F.

    2018-04-01

    We address the problem of thermodynamic equilibrium with constant acceleration along the velocity field lines in a quantum relativistic statistical mechanics framework. We show that for a free scalar quantum field, after vacuum subtraction, all mean values vanish when the local temperature T is as low as the Unruh temperature TU=A /2 π where A is the magnitude of the acceleration four-vector. We argue that the Unruh temperature is an absolute lower bound for the temperature of any accelerated fluid at global thermodynamic equilibrium. We discuss the conditions of this bound to be applicable in a local thermodynamic equilibrium situation.

  17. Competing explanations for cosmic acceleration or why is the expansion of the universe accelerating?

    NASA Astrophysics Data System (ADS)

    Ishak, Mustapha

    2012-06-01

    For more than a decade, a number of cosmological observations have been indicating that the expansion of the universe is accelerating. Cosmic acceleration and the questions associated with it have become one of the most challenging and puzzling problems in cosmology and physics. Cosmic acceleration can be caused by (i) a repulsive dark energy pervading the universe, (ii) an extension to General Relativity that takes effect at cosmological scales of distance, or (iii) the acceleration may be an apparent effect due to the fact that the expansion rate of space-time is uneven from one region to another in the universe. I will review the basics of these possibilities and provide some recent results including ours on these questions.

  18. SciTech Connect

    Sairam, T., E-mail: sairamtvv@gmail.com; Bhatt, Pragya; Safvan, C. P.

    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.

  19. Optimality and oscillations near the edge of stability in the dynamics of autonomous vehicle platoons

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2013-09-01

    A model that includes the mechanical response of a vehicle to a demanded change in acceleration is analyzed to determine the string stability of a platoon of autonomous vehicles. The response is characterized by a first-order time constant τ and an explicit delay td. The minimum value of the acceleration feedback control gain is found from calculations of the velocity of vehicles following a lead vehicle that decelerates sharply from high speed to low speed. Larger values of ξ (in the stable range) give larger values of deceleration for vehicles in the platoon. Optimal operation is attained close to the minimum value of ξ for stability. Small oscillations are found after the main peak in deceleration for ξ in the stable region but near the transition to instability. A theory for predicting the frequency and amplitude of the oscillations is presented.

  20. Rapid Tachyphylaxis of the Glucagon-Like Peptide 1–Induced Deceleration of Gastric Emptying in Humans

    PubMed Central

    Nauck, Michael A.; Kemmeries, Guido; Holst, Jens J.; Meier, Juris J.

    2011-01-01

    OBJECTIVE Glucagon-like peptide (GLP)-1 lowers postprandial glycemia primarily through inhibition of gastric emptying. We addressed whether the GLP-1–induced deceleration of gastric emptying is subject to rapid tachyphylaxis and if so, how this would alter postprandial glucose control. RESEARCH DESIGN AND METHODS Nine healthy volunteers (25 ± 4 years old, BMI: 24.6 ± 4.7 kg/m2) were examined with intravenous infusion of GLP-1 (0.8 pmol · kg−1 . min−1) or placebo over 8.5 h. Two liquid mixed meals were administered at a 4-h interval. Gastric emptying was determined, and blood samples were drawn frequently. RESULTS GLP-1 decelerated gastric emptying significantly more after the first meal compared with the second meal (P = 0.01). This was associated with reductions in pancreatic polypeptide levels (marker of vagal activation) after the first but not the second meal (P < 0.05). With GLP-1, glucose concentrations declined after the first meal but increased after the second meal (P < 0.05). The GLP-1–induced reductions in postprandial insulin and C-peptide levels were stronger during the first meal course (P < 0.05). Likewise, glucagon levels were lowered by GLP-1 after the first meal but increased after the second test meal (P < 0.05). CONCLUSIONS The GLP-1–induced delay in gastric emptying is subject to rapid tachyphylaxis at the level of vagal nervous activation. As a consequence, postprandial glucose control by GLP-1 is attenuated after its chronic administration. PMID:21430088

  1. An externally oriented style of thinking as a moderator of responses to affective films in women.

    PubMed

    Davydov, Dmitry M; Luminet, Olivier; Zech, Emmanuelle

    2013-02-01

    This study was conducted to test the hypothesis that differences in alexithymia would moderate coupling in physiological and subjective-experiential responses to two affective films, which were shown to induce a common negative (sad) feeling, but to provoke different hyper- or hypo-arousal physiological responses (e.g., heart rate acceleration or deceleration) associated with antipathic or empathic context, respectively (Davydov et al., 2011). Only women were studied as persons showing more reactivity to sad films than men. Reactivity was evaluated for facial behavior, physiological arousal, and subjective experience. Some other affective and cognitive disposition factors (e.g., depression and defensiveness) were considered for evaluating their probable mediation of the alexithymia's effects. While subjective experience was not affected by alexithymia, high scorers on the externally-oriented thinking factor showed reduced physiological reactivity in both film conditions. These effects were mediated through different disposition factors: either low affectivity (low depressed mood), which mediated alexithymia's effect on hyper-arousal responses (e.g., decrease of heart rate acceleration), or impression management (other-deception), which mediated alexithymia's effect on hypo-arousal responses (e.g., decrease of heart rate deceleration). Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Effects of dimensionality on kinetic simulations of laser-ion acceleration in the transparency regime

    NASA Astrophysics Data System (ADS)

    Stark, D. J.; Yin, L.; Albright, B. J.; Guo, F.

    2017-05-01

    A particle-in-cell study of laser-ion acceleration mechanisms in the transparency regime illustrates how two-dimensional (2D) S and P simulations (laser polarization in and out of the simulation plane, respectively) capture different physics characterizing these systems, visible in their entirety often in cost-prohibitive three-dimensional (3D) simulations. The electron momentum anisotropy induced in the target by a laser pulse is dramatically different in the two 2D cases, manifested in differences in target expansion timescales, electric field strengths, and density thresholds for the onset of relativistically induced transparency. In particular, 2D-P simulations exhibit dramatically greater electron heating in the simulation plane, whereas 2D-S ones show a much more isotropic energy distribution, similar to 3D. An ion trajectory analysis allows one to isolate the fields responsible for ion acceleration and to characterize the acceleration regimes in time and space. The artificial longitudinal electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration into its dominant acceleration mechanism throughout the laser-plasma interaction, whereas 2D-S and 3D both have sizable populations accelerated preferentially during transparency.

  3. Effects of dimensionality on kinetic simulations of laser-ion acceleration in the transparency regime

    SciTech Connect

    Stark, David James; Yin, Lin; Albright, Brian James

    2017-05-03

    A particle-in-cell study of laser-ion acceleration mechanisms in the transparency regime illustrates how two-dimensional (2D) S and P simulations (laser polarization in and out of the simulation plane, respectively) capture different physics characterizing these systems, visible in their entirety in often cost-prohibitive three-dimensional (3D) simulations. The electron momentum anisotropy induced in the target by the laser pulse is dramatically different in the two 2D cases, manifested in differences in target expansion timescales, electric field strengths, and density thresholds for the onset of relativistically induced transparency. In particular, 2D-P simulations exhibit dramatically greater electron heating in the simulation plane, whereas 2D-Smore » ones show a much more isotropic energy distribution, similar to 3D. An ion trajectory analysis allows one to isolate the fields responsible for ion acceleration and to characterize the acceleration regimes in time and space. The artificial longitudinal electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration into its dominant acceleration mechanism throughout the laser-plasma interaction, whereas 2D-S and 3D both have sizable populations accelerated preferentially during transparency.« less

  4. Vertical dynamics of a single-span beam subjected to moving mass-suspended payload system with variable speeds

    NASA Astrophysics Data System (ADS)

    He, Wei

    2018-03-01

    This paper presents the vertical dynamics of a simply supported Euler-Bernoulli beam subjected to a moving mass-suspended payload system of variable velocities. A planar theoretical model of the moving mass-suspended payload system of variable speeds is developed based on several assumptions: the rope is massless and rigid, and its length keeps constant; the stiffness of the gantry beam is much greater than the supporting beam, and the gantry beam can be treated as a mass particle traveling along the supporting beam; the supporting beam is assumed as a simply supported Bernoulli-Euler beam. The model can be degenerated to consider two classical cases-the moving mass case and the moving payload case. The proposed model is verified using both numerical and experimental methods. To further investigate the effect of possible influential factors, numerical examples are conducted covering a range of parameters, such as variable speeds (acceleration or deceleration), mass ratios of the payload to the total moving load, and the pendulum lengths. The effect of beam flexibility on swing response of the payload is also investigated. It is shown that the effect of a variable speed is significant for the deflections of the beam. The accelerating movement tends to induce larger beam deflections, while the decelerating movement smaller ones. For accelerating or decelerating movements, the moving mass model may underestimate the deflections of the beam compared with the presented model; while for uniform motion, both the moving mass model and the moving mass-payload model lead to same beam responses. Furthermore, it is observed that the swing response of the payload is not sensitive to the stiffness of the beam for operational cases of a moving crane, thus a simple moving payload model can be employed in the swing control of the payload.

  5. 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.

  6. Idiopathic accelerated idioventricular rhythm or ventricular tachycardia originating from the right bundle branch: unusual type of ventricular arrhythmia.

    PubMed

    Chen, Minglong; Gu, Kai; Yang, Bing; Chen, Hongwu; Ju, Weizhu; Zhang, Fengxiang; Yang, Gang; Li, Mingfang; Lu, Xinzheng; Cao, Kejiang; Ouyang, Feifan

    2014-12-01

    Accelerated idioventricular rhythm (AIVR) or ventricular tachycardia (VT) originating from the right bundle branch (RBB) is rare and published clinical data on such arrhythmia are scarce. In this study, we will describe the clinical manifestations, diagnosis, and management of a cohort of patients with this novel arrhythmia. Eight patients (5 men; median age, 25 years) with RBB-AIVR/VT were consecutively enrolled in the study. Pharmacological testing, exercise treadmill testing, electrophysiological study, and catheter ablation were performed in the study patients, and ECG features were characterized. All RBB-AIVR/VTs were of typical left bundle-branch block morphology with atrioventricular dissociation. The arrhythmias, which demonstrated chronotropic variability, were often isorhythmic with sinus rhythm and were accelerated by physical exercise, stress, and intravenous isoprenaline infusion. The rate of RBB-AIVR/VT varied from 45 to 200 beats per minute. Two patients experienced syncope, and 3 had impaired left ventricular function. Metoprolol was proven to be the most effective drug to decelerate the arrhythmia rate and relieve symptoms. Electrophysiology study was performed in 5 patients and the earliest activation with a sharp RBB potential was localized in the mid or distal RBB area. Catheter ablation terminated the arrhythmia with subsequent RBB block morphology during sinus rhythm. During follow-up, patients' symptoms were controlled with normalization of left ventricular function either on metoprolol or by catheter ablation. RBB-AIVR/VT is an unusual type of ventricular arrhythmia. It can result in significant symptoms and depressed ventricular function and can be successfully treated with catheter ablation. © 2014 American Heart Association, Inc.

  7. Mechanisms of force and power production in unsteady ricochetal brachiation.

    PubMed

    Usherwood, James R; Larson, Susan G; Bertram, John E A

    2003-04-01

    Brachiators travel by swinging beneath handholds, and it is not obvious how these animals manage to accelerate and decelerate in a horizontal direction, especially when moving rapidly. Most previous analyses focused on brachiation in highly constrained laboratory conditions that induced steady-state locomotion. Emerging understanding of brachiation suggests that much of gibbon locomotory behavior and morphology must be considered within the context of the complexities of the natural environment: the forest canopy is three-dimensional, with high variation in handhold availability and properties. The goal of this paper is to quantify the active mechanisms by which gibbons can dynamically control their velocity. Force production and kinematics were analyzed from a white-handed gibbon Hylabates lar during ricochetal brachiation. Both the mechanisms of force production and power input may be inferred for accelerating and decelerating brachiation by combining force data with kinematics. Examples of steady-state, accelerating, and decelerating ricochetal brachiation are highlighted. Gibbons are able to produce net horizontal impulses by releasing early (resulting in a loss of potential energy, but an accelerating horizontal impulse) or delaying release (associated with an increase in potential energy, and a decelerating horizontal impulse). Torque about the shoulder, leg-lifting (or dropping), and elbow flexing (or straightening) are discussed as potential mechanisms for controlling energy within the brachiating system. Of these possibilities, leg-lifting and arm-flexing were observed as mechanisms of adding mechanical energy. Net energy loss, and substantial torques about the shoulder, were not observed. Copyright 2003 Wiley-Liss, Inc.

  8. 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.

  9. 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.

  10. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  11. Quantitative Approach to Failure Mode and Effect Analysis for Linear Accelerator Quality Assurance

    SciTech Connect

    O'Daniel, Jennifer C., E-mail: jennifer.odaniel@duke.edu; Yin, Fang-Fang

    Purpose: To determine clinic-specific linear accelerator quality assurance (QA) TG-142 test frequencies, to maximize physicist time efficiency and patient treatment quality. Methods and Materials: A novel quantitative approach to failure mode and effect analysis is proposed. Nine linear accelerator-years of QA records provided data on failure occurrence rates. The severity of test failure was modeled by introducing corresponding errors into head and neck intensity modulated radiation therapy treatment plans. The relative risk of daily linear accelerator QA was calculated as a function of frequency of test performance. Results: Although the failure severity was greatest for daily imaging QA (imaging vsmore » treatment isocenter and imaging positioning/repositioning), the failure occurrence rate was greatest for output and laser testing. The composite ranking results suggest that performing output and lasers tests daily, imaging versus treatment isocenter and imaging positioning/repositioning tests weekly, and optical distance indicator and jaws versus light field tests biweekly would be acceptable for non-stereotactic radiosurgery/stereotactic body radiation therapy linear accelerators. Conclusions: Failure mode and effect analysis is a useful tool to determine the relative importance of QA tests from TG-142. Because there are practical time limitations on how many QA tests can be performed, this analysis highlights which tests are the most important and suggests the frequency of testing based on each test's risk priority number.« less

  12. Flight Tests Results from Supersonic Deployment of an 18-Foot Diameter (5.49 meter) Towed Ballute Decelerator

    NASA Technical Reports Server (NTRS)

    Mayhue, Robert J.; Eckstrom, Clinton V.

    1969-01-01

    A ram-air-inflated, towed ballute decelerator having a maximum frontal diameter of 18 feet (5.49 meters) was deployed during free flight at a Mach number of 3.15 and a dynamic pressure of 38.5 lb/ft(exp 2) (1843.4 newtons/m(exp 2)). Deployment and extraction of the test ballute were normal but inflation stopped about 1 second after mortar firing and produced an average plateau drag force of 1500 pounds (6.7 kN) for about 1 second. Approximately 30 percent of expected total frontal area was obtained.

  13. 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.

  14. Measurements of Form and Frictional Drags over a Rough Topographic Bank

    DTIC Science & Technology

    2014-09-01

    processes, Topographic effects Unclassified Unclassified Unclassified UU 24 Hemantha Wijesekera (228) 688-4845 Reset I PAI!fElNTATION RELEASE...sea surface height associated with the sea surface slope resulting from rota- tional effects . Here barotropic pressure gradients associ- ated with...surface elevation are balanced by the Coriolis force; hTi(x, y, t) is the surface elevation resulting from accelerations/decelerations of flow over the

  15. Interobserver agreement in CTG interpretation using the 2015 FIGO guidelines for intrapartum fetal monitoring.

    PubMed

    Rei, Mariana; Tavares, Sara; Pinto, Pedro; Machado, Ana P; Monteiro, Sofia; Costa, Antónia; Costa-Santos, Cristina; Bernardes, João; Ayres-De-Campos, Diogo

    2016-10-01

    Visual analysis of cardiotocographic (CTG) tracings has been shown to be prone to poor intra- and interobserver agreement when several interpretation guidelines are used, and this may have an important impact on the technology's performance. The aim of this study was to evaluate agreement in CTG interpretation using the new 2015 FIGO guidelines on intrapartum fetal monitoring. A pre-existing database of intrapartum CTG tracings was used to sequentially select 151 cases acquired with a fetal electrode, with duration exceeding 60minutes, and signal loss less than 15%. These tracings were presented to six clinicians, three with more than 5 years' experience in the labor ward, and three with 5 or less years' experience. Observers were asked to evaluate tracings independently, to assess basic CTG features: baseline, variability, accelerations, decelerations, sinusoidal pattern, tachysystole, and to classify each tracing as normal, suspicious or pathologic, according to the 2015 FIGO guidelines on intrapartum fetal monitoring. Agreement between observers was evaluated using the proportions of agreement (Pa), with 95% confidence intervals (95%CI). A good interobserver agreement was found in the evaluation of most CTG features, but not bradycardia, reduced variability, saltatory pattern, absence of accelerations and absence of decelerations. For baseline classification Pa was 0.85 [0.82-0.90], for variability 0.82 [0.78-0.85], for accelerations 0.72 [0.68-0.75], for tachysystole 0.77 [0.74-0.81], for decelerations 0.92 [0.90-0.95], for variable decelerations 0.62 [0.58-0.65], for late decelerations 0.63 [0.59-0.66], for repetitive decelerations 0.73 [0.69-0.78], and for prolonged decelerations 0.81 [0.77-0.85]. For overall CTG classification, Pa were 0.60 [0.56-0.64], for classification as normal 0.67 [0.61-0.72], for suspicious 0.54 [0.48-0.60] and for pathologic 0.59 [0.51-0.66]. No differences in agreement according to the level of expertise were observed, except in the

  16. Gamma-Ray Burst Spectral Indices: Evidence for Deceleration of Synchrotron Shocks

    NASA Technical Reports Server (NTRS)

    Preece, R. D.; Briggs, M. S.; Giblin, T.; Mallozzi, R. S.; Pendleton, G. N.; Paciesas, W. S.; Band, D. L.

    2000-01-01

    The current scenario for gamma-ray bursts (GRBs) involves internal shocks for the prompt GRB emission phase and external shocks for the afterglow phase. Assuming synchrotron emission from energetic shocked electrons. GRB spectra observed with a low-energy power-law spectral index greater than -2/3 (for positive photon number indices E(sup alpha) indicate a problem with this model. The remaining spectra can test the synchrotron shock model prediction that the emission from a single distribution of electrons, cooling rapidly, is responsible for both the low-energy and high-energy power-low portions of the spectra. We find that the inferred relationship between the two spectral indices of observed GRB spectra is inconsistent with the constraints from the model, posing another problem for the synchrotron shock emission model. To overcome this problem, we describe a model where the average of -1, rather than the value of -3/2 predicted for cooling electrons. Situations where this might arise have been discussed in other contexts, and involve deceleration of the internal shocks during the GRB phase.

  17. Transition from AdS universe to DS universe in the BPP model

    NASA Astrophysics Data System (ADS)

    Kim, Wontae; Yoon, Myungseok

    2007-04-01

    It can be shown that in the BPP model the smooth phase transition from the asymptotically decelerated AdS universe to the asymptotically accelerated DS universe is possible by solving the modified semiclassical equations of motion. This transition comes from noncommutative Poisson algebra, which gives the constant curvature scalars asymptotically. The decelerated expansion of the early universe is due to the negative energy density with the negative pressure induced by quantum back reaction, and the accelerated late-time universe comes from the positive energy and the negative pressure which behave like dark energy source in recent cosmological models.

  18. Speed control with end cushion for high speed air cylinder

    DOEpatents

    Stevens, Wayne W.; Solbrig, Charles W.

    1991-01-01

    A high speed air cylinder in which the longitudinal movement of the piston within the air cylinder tube is controlled by pressurizing the air cylinder tube on the accelerating side of the piston and releasing pressure at a controlled rate on the decelerating side of the piston. The invention also includes a method for determining the pressure required on both the accelerating and decelerating sides of the piston to move the piston with a given load through a predetermined distance at the desired velocity, bringing the piston to rest safely without piston bounce at the end of its complete stroke.

  19. Deceleration-stats save much time during phototrophic culture optimization.

    PubMed

    Hoekema, Sebastiaan; Rinzema, Arjen; Tramper, Johannes; Wijffels, René H; Janssen, Marcel

    2014-04-01

    In case of phototrophic cultures, photobioreactor costs contribute significantly to the total operating costs. Therefore one of the most important parameters to be determined is the maximum biomass production rate, if biomass or a biomass associated product is the desired product. This is traditionally determined in time consuming series of chemostat cultivations. The goal of this work is to assess the experimental time that can be saved by applying the deceleration stat (D-stat) technique to assess the maximum biomass production rate of a phototrophic cultivation system, instead of a series of chemostat cultures. A mathematical model developed by Geider and co-workers was adapted in order to describe the rate of photosynthesis as a function of the local light intensity. This is essential for the accurate description of biomass productivity in phototrophic cultures. The presented simulations demonstrate that D-stat experiments executed in the absence of pseudo steady-state (i.e., the arbitrary situation that the observed specific growth rate deviates <5% from the dilution rate) can still be used to accurately determine the maximum biomass productivity of the system. Moreover, this approach saves up to 94% of the time required to perform a series of chemostat experiments that has the same accuracy. In case more information on the properties of the system is required, the reduction in experimental time is reduced but still significant. © 2013 Wiley Periodicals, Inc.

  20. Vestibular coriolis effect differences modeled with three-dimensional linear-angular interactions.

    PubMed

    Holly, Jan E

    2004-01-01

    The vestibular coriolis (or "cross-coupling") effect is traditionally explained by cross-coupled angular vectors, which, however, do not explain the differences in perceptual disturbance under different acceleration conditions. For example, during head roll tilt in a rotating chair, the magnitude of perceptual disturbance is affected by a number of factors, including acceleration or deceleration of the chair rotation or a zero-g environment. Therefore, it has been suggested that linear-angular interactions play a role. The present research investigated whether these perceptual differences and others involving linear coriolis accelerations could be explained under one common framework: the laws of motion in three dimensions, which include all linear-angular interactions among all six components of motion (three angular and three linear). The results show that the three-dimensional laws of motion predict the differences in perceptual disturbance. No special properties of the vestibular system or nervous system are required. In addition, simulations were performed with angular, linear, and tilt time constants inserted into the model, giving the same predictions. Three-dimensional graphics were used to highlight the manner in which linear-angular interaction causes perceptual disturbance, and a crucial component is the Stretch Factor, which measures the "unexpected" linear component.

  1. Advocating for Grade-Based Acceleration

    ERIC Educational Resources Information Center

    Guilbault, Keri M.

    2014-01-01

    Parents often struggle with the decision to accelerate their child and may worry about social and emotional issues, although research indicates positive effects on the social and emotional adjustment of carefully selected accelerants. As children's advocates, parents can work effectively with a school system to secure an appropriate academic…

  2. SciTech Connect

    Glascoe, E A; Zaug, J M; Burnham, A K

    The effect of pressure on the thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low to moderate pressures (i.e. between ambient pressure and 1 GPa) and decelerates the decomposition at higher pressures.more » The decomposition acceleration is attributed to pressure enhanced autocatalysis whereas the deceleration at high pressures is attributed pressure inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both {beta} and {delta} phase HMX are sensitive to pressure in the thermally induced decomposition kinetics.« less

  3. Pressure-dependent decomposition kinetics of the energetic material HMX up to 3.6 GPa.

    PubMed

    Glascoe, Elizabeth A; Zaug, Joseph M; Burnham, Alan K

    2009-12-03

    The effect of pressure on the global thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Global decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low-to-moderate pressures (i.e., between ambient pressure and 0.1 GPa) and decelerates the decomposition at higher pressures. The decomposition acceleration is attributed to pressure-enhanced autocatalysis, whereas the deceleration at high pressures is attributed to pressure-inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both the beta- and delta-polymorphs of HMX are sensitive to pressure in the thermally induced decomposition kinetics.

  4. Angular velocities, angular accelerations, and coriolis accelerations

    NASA Technical Reports Server (NTRS)

    Graybiel, A.

    1975-01-01

    Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.

  5. High-Resolution Spectroscopy of He{_2}^+ Using Rydberg-Series Extrapolation and Zeeman-Decelerated Supersonic Beams of Metastable He_2

    NASA Astrophysics Data System (ADS)

    Jansen, Paul; Semeria, Luca; Merkt, Frederic

    2016-06-01

    Having only three electrons, He{_2}^+ represents a system for which highly accurate ab initio calculations are possible. The latest calculations of rovibrational energies in He{_2}^+ do not include relativistic or QED corrections but claim an accuracy of 120 MHz We have performed high-resolution Rydberg spectroscopy of metastable He_2 molecules and employed multichannel-quantum-defect-theory extrapolation techniques to determine the rotational energy-level structure in the He{_2}^+ ion. To this end, we have produced samples of metastable helium molecules in supersonic beams with velocities tunable down to 100 m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator. The metastable He_2 molecules are excited to np Rydberg states using the frequency-doubled output of a pulse-amplified ring dye laser. Although the bandwidth of the laser system is too large to observe the reduction of the Doppler width resulting from deceleration, the deceleration greatly simplifies the spectral assignments because of its spin-rotational state selectivity. Our approach enabled us to determine the rotational structure of He_2 with an unprecedented accuracy of 18 MHz, to quantify the size of the relativistic and QED corrections by comparison with the results of Tung et al. and to precisely measure the rotational structure of the metastable state for comparison with the results of Focsa et al. Here, we present an extension of these measurements in which we have measured higher rotational intervals of He{_2}^+. In addition, we have replaced the pulsed UV laser by a cw UV laser and improved the resolution of the spectra by a factor of more than five. W.-C. Tung, M. Pavanello and L. Adamowicz, J. Chem. Phys. 136, 104309 (2012). P. Jansen, L. Semeria, L. Esteban Hofer, S. Scheidegger, J.A. Agner, H. Schmutz, and F. Merkt, Phys. Rev. Lett. 115, 133202 (2015). D. Sprecher, J. Liu, T. Krähenmann, M. Schäfer, and F. Merkt, J. Chem. Phys. 140, 064304 (2014). M

  6. 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).

  7. Comparing the Effects of Various Whole-Body Vibration Accelerations on Counter-Movement Jump Performance

    PubMed Central

    Bazett-Jones, David M.; Finch, Holmes W.; Dugan, Eric L.

    2008-01-01

    While it seems that whole body vibration (WBV) might be an effective modality to enhance physical performance, the proper prescription of WBV for performance enhancement remains unknown. The purpose of this study was to compare the immediate effect of various WBV accelerations on counter movement jump (CMJ) height, the duration of any effect, and differences between men and women. Forty-four participants (33 men, 11 women) participated in no less than four CMJ familiarization sessions and completed all vibration sessions. Participants performed a pre-test (three maximal CMJs), followed randomly by one of five WBV accelerations; 1g (no-WBV control), 2.16g, 2.80g, 4.87g, and 5.83g. Participants performed three maximal CMJs immediately, five, and 10 minutes following each 45 sec WBV session. The mean of the three performances was used and calculated as a percentage of the pre-vibration mean value. A Repeated Measures Analysis of Variance (ANOVA; acceleration x time x gender) model was used to analyze the data. The two-way interactions of acceleration-gender (p = 0.033) and time-gender (p = 0.050) were significant. Women performed significantly better following the 2.80g (p = 0.0064) and 5.83g (p = 0. 0125) WBV sessions compared to the 1g (control) session. Men, however, did not experience performance enhancing effects following any of the vibration sessions. While significant differences did not occur between time in either gender, the effects of the 45 sec WBV session in women were transient, lasting approximately five minutes. During the prescription of WBV, gender should be considered given that the results of this study seem to indicate that men and women respond differently to WBV. The results of this study suggest that WBV might be a useful modality as applied during the pre-competition warm-up. Key points WBV accelerations of 2.80g (40 Hz, 2-4 mm) and 5.83g (50 Hz, 4-6 mm) seem to elicit a performance enhancement effect following short-duration (45 sec

  8. Accelerator Technology Division annual report, FY 1989

    SciTech Connect

    Not Available

    1990-06-01

    This paper discusses: accelerator physics and special projects; experiments and injectors; magnetic optics and beam diagnostics; accelerator design and engineering; radio-frequency technology; accelerator theory and simulation; free-electron laser technology; accelerator controls and automation; and high power microwave sources and effects.

  9. Exploring the Inner Acceleration Region of Solar Wind: A Study Based on Coronagraphic UV and Visible Light Data

    NASA Astrophysics Data System (ADS)

    Bemporad, A.

    2017-09-01

    This work combined coronagraphic visible light (VL) and UV data to provide with an unprecedented view of the inner corona where the nascent solar wind is accelerated. The UV (H I Lyα) and VL (polarized brightness) images (reconstructed with SOHO/UVCS, LASCO, and Mauna Loa data) have been analyzed with the Doppler dimming technique to provide for the first time daily 2D images of the radial wind speed between 1 and 6 R ⊙ over 1 month of observations. Results show that both polar and equatorial regions are characterized at the base of the corona by plasma outflows at speeds > 100 km s-1. The plasma is then decelerated within ˜1.5 R ⊙ at the poles and ˜2.0 R ⊙ at the equator, where local minima of the expansion speeds are reached, and gently reaccelerated higher up, reaching speeds typical of fast and slow wind components. The mass flux is highly variable with latitude and time at the equator and more uniform and stable over the poles. The polar flow is asymmetric, with speeds above the south pole lower than those above the north pole. A correlation (anticorrelation) between the wind speed and its density is found below (above) ˜1.8 R ⊙. The 2D distribution of forces responsible for deceleration and reacceleration of solar wind is provided and interpreted in terms of Alfvén waves. These results provide a possible connection between small-scale outflows reported with other instruments at the base of the corona and bulk wind flows measured higher up.

  10. Ultrasound and polar homogeneous reactions.

    PubMed

    Tuulmets, A

    1997-04-01

    The effect of ultrasound on the rates of homogeneous heterolytic reactions not switched to a free radical pathway can be explained by the perturbation of the molecular organization of or the solvation in the reacting system. A quantitative analysis of the sonochemical acceleration on the basis of the microreactor concept was carried out. It was found that (1) the Diels-Alder reaction cannot be accelerated by ultrasound except when SET or free radical processes are promoted, (2) the rectified diffusion during cavitation cannot be responsible for the acceleration of reactions, and (3) the sonochemical acceleration of polar homogeneous reactions takes place in the bulk reaction medium. This implies the presence of a 'sound-field' sonochemistry besides the 'hot-spot' sonochemistry. The occurrence of a sonochemical deceleration effect can be predicted.

  11. Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Schmit, P. F.

    2015-11-01

    Bell-Plesset effects accounting for the time dependence of the radius, velocity and acceleration of the Rayleigh-Taylor-unstable surface are ubiquitous in the instability of spherical laser targets and magnetically driven cylindrical liners. We present an analytical model that, for an ideal incompressible fluid and small perturbation amplitudes, exactly accounts for the Bell-Plesset effects in finite-thickness targets and liners through acceleration and deceleration phases. We derive the time-dependent dispersion equations determining the ``instantaneous growth rate'' and demonstrate that by integrating this growth rate over time (the WKB approximation) we accurately evaluate the number of perturbation e-foldings during the acceleration phase. In the limit of the small target/liner thickness, we obtain the exact thin-shell perturbation equations and approximate thin-shell dispersion relations, generalizing the earlier results of Harris (1962), Ott (1972) and Bud'ko et al. (1989). This research was supported by the US DOE/NNSA (A.L.V.), and in part by appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering (P.F.S.), which is part of the Laboratory Directed Research and Development (LDRD) Program, Project No. 165746, and sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of Sandia National Laboratories under its U.S. Department of Energy Contract No. DE-AC04-94AL85000.

  12. Aeroelastic characteristics of a rapid prototype multi-material wind tunnel model of a mechanically deployable aerodynamic decelerator

    NASA Astrophysics Data System (ADS)

    Raskin, Boris

    Scaled wind tunnel models are necessary for the development of aircraft and spacecraft to simulate aerodynamic behavior. This allows for testing multiple iterations of a design before more expensive full-scale aircraft and spacecraft are built. However, the cost of building wind tunnel models can still be high because they normally require costly subtractive manufacturing processes, such as machining, which can be time consuming and laborious due to the complex surfaces of aerodynamic models. Rapid prototyping, commonly known as 3D printing, can be utilized to save on wind tunnel model manufacturing costs. A rapid prototype multi-material wind tunnel model was manufactured for this thesis to investigate the possibility of using PolyJet 3D printing to create a model that exhibits aeroelastic behavior. The model is of NASA's Adaptable Deployable entry and Placement (ADEPT) aerodynamic decelerator, used to decelerate a spacecraft during reentry into a planet's atmosphere. It is a 60° cone with a spherically blunted nose that consists of a 12 flexible panels supported by a rigid structure of nose, ribs, and rim. The novel rapid prototype multi-material model was instrumented and tested in two flow conditions. Quantitative comparisons were made of the average forces and dynamic forces on the model, demonstrating that the model matched expected behavior for average drag, but not Strouhal number, indicating that there was no aeroelastic behavior in this particular case. It was also noted that the dynamic properties (e.g., resonant frequency) associated with the mounting scheme are very important and may dominate the measured dynamic response.

  13. On Electron Hole Evolution in Inhomogeneous Plasmas

    NASA Astrophysics Data System (ADS)

    Kuzichev, I.; Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

    2017-12-01

    Electron holes (EHs) are the stationary localized non-linear structures in phase space existing due to an electron population trapp